From: Rob Bamford [mailto:rbamford@ndep.nv.gov] 

Sent: Tuesday, August 24, 2010 7:36 PM

To: 'French.Chuck@epamail.epa.gov'; Branscome, Marvin R.

Subject: pre-treatment cost docs & projects

Hello gentlemen,

Here's some info on pre-treatment NvMACT projects and cost. Of note, the 

Queenstake document was not an application, but has technical data and my 

handwriting on one of the pages notes the project estimated cost. Queenstake was 

required to submit a plan under the consent decree as opposed to a NvMACT

application.

Hope this helps,

-Rob

See attached documents:

Queenstake ore dryer.pdf

NMCP Application AC 4-6.pdf

Goldstrike_NvMACT_Autoclave1-3_08102010.pdf

Goldquarry pre-heater.pdf

Rob Bamford

Supervisor, Nevada Mercury Control 

Program

Nevada Division of Environmental 

Protection

Bureau of Air Quality Planning

Phone: 775-687-9330

Cell: 775-315-3655

Fax: 775-687-6396

E-mail: rbamford@ndep.nv.gov








Nevada Mercury Control Program 

Application for Minor Modification: 

Systems 66C and 66D, Autoclave Circuits 3 and 4 

BARRICK GOLDSTRIKE MINES INC.

June 2010
Page 1 

Table of Contents

General Information ........................................................................................................... Page 2 

APPLICATION

Mercury Operating Permit to Construct Application Cover Page ......................................Page 3 

General Company Information ..........................................................................................Page 4 

-General Company Information Form and Application Information (4 Pages) 

Additional Forms

Mercury Unit Application Form ................................................................................ Appendix 1 

- Section 1A: System 66C, TU4.016, Autoclave Circuit 3, Autoclave #4 .............................. 3 

- Section 2A: System 66C, TU4.016, Autoclave Circuit 3, Autoclave #4 .............................. 3 

- Section 3A: System 66C, TU4.016, Autoclave Circuit 3, Autoclave #4 .............................. 4 

- Section 1B: System 66D, TU4.017, Autoclave Circuit 3, Autoclave #5 .............................. 5 

- Section 2B: System 66D, TU4.017, Autoclave Circuit 3, Autoclave #5 .............................. 5 

- Section 3B: System 66D, TU4.017, Autoclave Circuit 3, Autoclave #5 .............................. 6 

- Section 1C: System 66D, TU4.018, Autoclave Circuit 4, Autoclave #6.............................. 7 

- Section 2C: System 66D, TU4.018, Autoclave Circuit 4, Autoclave #6.............................. 7 

- Section 3C: System 66D, TU4.018, Autoclave Circuit 4, Autoclave #6.............................. 8 

- Section 4: System 66C & 66D, TU4.016 – TU4.018, Autoclave Circuits 3 & 4, 

Autoclaves #4 - #6............................................................................................................................... 9 

- Section 5: System 66C & 66D, TU4.016 – TU4.018, Autoclave Circuits 3 & 4, 

Autoclaves #4 - #6............................................................................................................................. 10

- Section 6: System 66C & 66D, TU4.016 – TU4.018, Autoclave Circuits 3 & 4, 

Autoclaves #4 - #6............................................................................................................................. 11

- Section 7: System 66C & 66D, TU4.016 – TU4.018, Autoclave Circuits 3 & 4, 

Autoclaves #4 - #6............................................................................................................................. 12

Monitoring/Testing Plan ............................................................................................ Appendix 2

Nevada MACT (NvMACT) Analysis ........................................................................ Appendix 3 

De minimis emissions Request .................................................................................. Appendix 4 

Application Certification ........................................................................................... Appendix 5 
Page 2 

State of Nevada 

 Division of Environmental Protection 

 Bureau of Air Pollution Control 

APPLICATION FOR 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Please return to: Nevada Division of Environmental Protection 

 Bureau of Air Pollution Control, Permitting Branch 

 901 South Stewart Street 

 Carson City, Nevada 89701-5249 

 (775) 687-9350 FAX (775) 687-6396 

General Information

• This application is available from the Bureau of Air Pollution Control in a Microsoft Word file, or on the 

internet at http://www.ndep.nv.gov/bapc. All information required in the application may be computer 

generated and submitted to the Bureau on compact disk(s) or DVD(s). In addition, one printed copy must be 

submitted. 

• All information required by the “General Company Information” and by the relevant forms in the Appendices 

 must be completed. 

• The application filing fee required by NAC 445B.3689 must be submitted with the completed application. 

Checks must be made payable to: “Nevada State Treasurer, Environmental Protection”. 

• This application packet shall be used for Tier 1, Tier 2 thermal units that emit mercury, for construction of 

new thermal units that emit mercury, for de minimis designation and construction and installation projects for 

thermal units that emit mercury at new and existing stationary sources. 

• An application for a mercury operating permit to construct must be signed by a responsible official, as 

defined in Section NAC 445B.297.1. The certification/signature page is contained in Appendix 5. 

• All items in the application must be addressed. If an item does not apply, please indicate so with “N/A” or 

similar notation in the appropriate blank. All other information must be provided. Incomplete applications 

will be returned to the responsible official. 

 
Page 3 

Application 

for 

Mercury Air Quality 

Operating Permit to 

Construct 
Page 4 

GENERAL COMPANY INFORMATION

All applicants shall complete each item or explain in the space provided why no information is needed. Please specify 

"N/A" (Not Applicable) if necessary. The application will be returned to the applicant if it is deemed incomplete. 

1. COMPANY NAME AND ADDRESS THAT ARE TO APPEAR ON THE OPERATING PERMIT

[NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Barrick Goldstrike Mines Inc. 

 (Name) 

 P.O. Box 29 

 (Address) 

 Elko NV 89803

 (City) (State) (Zip Code) 

2. Owner's Name and Address [NAC 445B.295.1]: 

 Barrick Gold Corporation 

 (Name) 

 BCE Place, Canada Trust Tower, Suite 3700.161 Bay Street, P.O. Box 212 

 (Address) 

 Toronto Ontario M5J2S1 

 (City) (State) (Zip Code) 

3. Source Name and Mailing Address, if different from #1 [NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Same as #1 

 (Name) 

 

 (Address) 

 

 (City) (State) (Zip Code) 

4. Physical Location of Stationary Source [NAC 445B.3671.2 and NAC 445B.3681.7]: (if no physical 

address, describe location, e.g., 4 miles south of I-80 at xx Interchange) 

 27 miles north of Carlin, Nevada, off state route 766 

Township(s) * Range(s) * Section(s) * 

* Sections 1 through 4, T35N, R49E; Sections 12 through 15, 21 through 28, and 33 through 36, T36N, R49E; 

Sections 7 through 9, 16 through 21, and 28 through 32, T36N, R50E, MDB&M (HA61) 

5. Responsible Official Name, Title and Address [NAC 445B.295.1]: 

 Joseph Giraudo Environmental Manager

 (Name) (Title) 

 Same as #1

 (Address) 

 

 (City) (State) (Zip Code) 

(775) 778-8140 (775) 778-8262 jgiraudo@barrick.com 

 (Telephone #) (FAX #) (E-mail address) 
Page 5 

GENERAL COMPANY INFORMATION (CONTINUED)

6. Plant Manager or Other Appropriate Contact [NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Carly Keeney Environmental Engineer

 (Name) (Title) 

 Same as #1 

 (Address) 

 

 (City) (State) (Zip Code) 

(775) 778-8157 (775) 778-8262 ckeeney@barrick.com 

 (Telephone #) (FAX #) (E-mail address) 

7. If records required under the operating permit will be kept at a location other than the source, specify that 

location [NAC 445B.3671.5 and NAC 445B.3681]. 

N/A. Records will be kept on site. 

 (Name) 

 

(Address) 

 

 (City) (State) (Zip Code) 
Page 6 

APPLICATION INFORMATION 

8. This application is submitted for (please check appropriate box below): 

Phase 1 Application

 Tier 1 Unit(s) – Please provide the following:

 a. An identification and description of any equipment for control of mercury emissions from all 

existing thermal units that emit mercury, including any presumptive NvMACT controls. In 

addition to the identification and description, please complete Section 5 of the Mercury Unit 

application form in Appendix 1. A separate Mercury Unit application form is required for each 

thermal unit that emits mercury. [NAC 445B.3673.1] 

 b. A proposed monitoring plan for each thermal unit that emits mercury consistent with the 

requirements of NAC 445B.3673.2(a). Include the plan in Appendix 2. 

 c. For each requested mercury early reduction credit, the additional controls that are proposed to be 

implemented to reduce mercury emissions. [NAC 445B.3671.6] 

 Tier 2 Unit(s) – Please provide the following: 

 a. An identification and description of any equipment for control of mercury emissions from all 

existing thermal units that emit mercury, including any presumptive NvMACT controls. In 

addition to the identification and description, please complete Section 5 of the Mercury Unit 

application form in Appendix 1. A separate Mercury Unit application form is required for each 

thermal unit that emits mercury. [Section 33.1 of amended NAC 445B] 

 b. A proposed monitoring plan for each thermal unit that emits mercury consistent with the 

requirements of Section 33.2(b) of amended NAC 445B. Include the plan in Appendix 2. 

Phase 2 Application

 Tier 1 or Tier 2 Unit(s) – Please provide the following: 

 a. A proposed monitoring plan consistent with the requirements of NAC 445B.3675.2. Include the 

plan in Appendix 2. 

 b. The NvMACT analysis for each thermal unit that emits mercury consistent with the requirements of 

NAC 445B.3675.1. Include the analysis in Appendix 3. 

New or Modified Thermal Unit that Emits Mercury

 a. Please provide the NvMACT analysis for each thermal unit that emits mercury consistent with the 

requirements of NAC 445B.3681.6. Include the analysis in Appendix 3. 

Request for De Minimis Designation

 a. For a request for determination of de minimis mercury emissions, include a de minimis 

demonstration in Appendix 4. De minimis status is considered for each thermal unit. 

Demonstration must be at the individual unit level, but include cumulative impact of all de minimis 

units at a facility. [NAC 445B.3613 and NAC 445B.3657.3] 

 b. De minimis demonstration must include, at a minimum: identification of the proposed thermal unit, 

a process description, location, unit manufacturer, unit model, serial number and fuel type used (or 

specify if electric). Identify if any exhaust stacks are shared and if mercury emission controls are 

utilized. [NAC 445B.295] 

 c. Include potential to emit values based on unit operation at maximum design capacity at 8,760 hours 

per year. Supply laboratory test results, performance stack test results and calculations 

implemented to calculate potential to emit mercury emissions. Include a thorough discussion of 

any assumptions. [NAC 445B.295] 

 d. Identify under what Air Quality Operating Permit the proposed units are contained and if the 

proposed units are designated as “insignificant” or “non-permitted items.” [NAC 445B.295] 
Page 7 

APPLICATION INFORMATION (CONTINUED)

9. The application must also contain: 

 a. An identification of each thermal unit that emits mercury. In addition to the identification of each 

thermal unit that emits mercury, please complete Section 1 of the Mercury Unit application form in 

Appendix 1. Complete a separate Mercury Unit application form for each thermal unit that emits 

mercury. [NAC 445B.3671.2 and NAC 445B.3681.2] 

 b. A description of the production rates, operating schedules, fuels, fuel use and raw materials to be used 

for each thermal unit that emits mercury. In addition to the description, please complete Sections 2 

and 3 of the Mercury Unit application form in Appendix 1. Complete a separate Mercury Unit 

application form for each thermal unit that emits mercury. [NAC 445B.3671.3 and NAC 445B.3681] 

 c. Limitations on the operation of stationary source or thermal unit that emits mercury or any work 

practices which may affect mercury emissions from the thermal unit that emits mercury. Use Sections 

4 and 5 of the Mercury Unit application form in Appendix 1. Complete a separate Mercury Unit 

application form for each thermal unit that emits mercury. [NAC 445B.3671.4 and NAC 

445B.3681.4] 

 d. Requested emissions limits. Use Section 7 of the Mercury Unit application form in Appendix 1. 

Complete a separate Mercury Unit application form for each thermal unit that emits mercury. [NAC 

445B.3671.7 and NAC 445B.3681.7] 

11. Will the construction occur in more than one phase? Yes No 

 If the construction will occur in more than one phase, please provide the projected date of the commencement 

for each phase of construction (include additional phases if necessary): [NAC 445B.3687] 

Phase 1: 

Phase 2: 

Phase 3: 

12. For Application Submittal:

Please remove the cover page, Table of Contents and General Information page. Submit the remainder of the 

application packet as your formal application. This should consist of, at a minimum, the Mercury Operating 

Permit to Construct Application cover page, the general Company Information and Application Information, 

and any applicable Appendices. 
Appendix 1, Page 1

Appendix 1 

THERMAL MERCURY 

EMITTING UNIT 

APPLICATION FORM 
Appendix 1, Page 2

Instructions 

PLEASE RESPOND SEPARATELY TO ITEMS 1 through 7 FOR EACH EMISSION UNIT, as 

appropriate. Each emission unit at the stationary source must be identified by completion of the application 

form contained in this appendix. The forms may be duplicated for as many thermal mercury emission units 

as needed. Complete all applicable attachments (Appendix 1) included in this application package [NAC 

445B.295]. 

Section 1. Equipment Description: Describe the processes and products by SIC, including any associated 

with an alternative operating scenario identified in this application, model number, manufacture 

date, dimensions and UTM coordinates. 

Section 2. Design Rate/Operating Parameters: Describe all production rates, operating schedules and 

materials used in the process. 

Section 3. Fuel Usage: Describe all fuels and fuel usage. 

Section 4. Pollution Control Equipment/Exhaust Stack Parameters: Identify and describe all air pollution 

 control equipment. 

Section 5. Work Practice Standards: provide information on limitations on the operation or any standards 

for work practices which affect emissions for all regulated air pollutants. [NAC 445B.295.5] 

Section 6. Compliance Monitoring Devices and Activities: Identify and describe any equipment for the 

control of air pollution and any devices or activities for monitoring compliance with emission 

limitations. 

Section 7. Requested Emission Limits: Provide the requested emission limits for each emission unit. 

Include the emission rates of total mercury . The emission rates must be described in pounds per 

hour and pounds per year and any other units of measure for mercury emissions as may be 

proposed. 

Alternative Operating Scenarios: Complete a separate application form for each emission unit having an 

alternative operating scenario. (A common example of an alternative operating scenario is a steam boiler that 

utilizes natural gas as the primary fuel, but may combust diesel fuel as an alternate fuel source). Please 

check the box in the upper right hand corner of each application form for emission units requesting an 

alternative operating scenario. Additionally, for each emission unit application form requesting an alternative 

operating scenario: 

1. Define each alternative operating scenario; 

2. Provide an alternative monitoring plan for each unit, for which an alternative operating scenario is 

requested, in Appendix 2, if different from the monitoring plan provided for the primary operating 

scenario. Contemporaneous log entries must be provided every time the source changes from one 

scenario to another. 
Appendix 1, Page 3

System 66C, TU4.016 (Autoclave Circuit 3, Autoclave #4)

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Check here if this is an 

alternative operating scenario

Section 1A - Equipment Description

a. Type of equipment System 66C, TU4.016 (Autoclave Circuit 3, Autoclave #4)

b. Standard Industrial Classification (SIC) Code 1041 

c. Manufacturer of equipment Eaton 

d. Model number not specified Serial number not specified *Equip. number not specified

e. Date equipment manufactured: 1992

f. UTM Coordinates 4,536,011 meters N; 554,734 meters E; Zone 11 

(Please specify NAD 27 or NAD 83 ; Method used to obtain coordinates: ) 

g. Basic equipment dimensions (feet): L not specified W not specified H not specified 

*The equipment number is the facility's own numbering system for this piece of equipment. 

Section 2A - Design Rate/Operating Parameters 

a. Maximum design capacity (tons per hour) 200

b. Requested operating rate (tons per hour)* 

c. Requested operating time: (time of day)* to 

 

 Hours per day 0-24 Days per year 365, 8,760 hr/yr

d. Batch load or charge weight (tons) (if applicable) N/A 

e. Total hours required to process batch or charge (if applicable) N/A 

f. Maximum operating rate (tons per year) not specified 

g. Requested operating rate (tons per year)* 

f. Type of material processed ore

*Note: Please complete if other than the maximum design capacity (tons per hour and tons per year) and/or the maximum hours of 

operation (24 hours per day, 8,760 hours per year) are being requested. The permit will be limited to these values. 
Appendix 1, Page 4

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66C - TU4.016 

Section 3A - Fuel Usage / Heat Source

Electric Unit □

Type of Fuel Amount Used Per 

Hour 

Heat Content 

(specify in Btus) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

( % by 

weight) 

Trace 

Elements 

(% by 

weight) 

Oil- Specify 

Type(s) 

 none gallons N/A N/A N/A N/A 

 none gallons N/A N/A N/A N/A 

Gasoline none gallons N/A N/A N/A N/A 

Propane none cubic feet N/A N/A N/A N/A 

Natural Gas none cubic feet N/A N/A N/A N/A 

*Waste Oil none gallons N/A N/A N/A N/A 

Other none N/A N/A N/A N/A 

Type of 

Coal 

Fuel 

Amount 

Used 

Per 

Hour 

(tons) 

Heat 

Content 

(specify 

in 

BTUs) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

(% by 

weight) 

Trace 

Elements 

(% by 

weight) 

Percent 

moisture 

Percent 

volatile 

matter 

Percent 

fixed 

carbon 

Coal - 

Specify 

Type(s) 

 

none N/A N/A N/A N/A N/A N/A N/A N/A 

 

If more than one type of fuel is combusted, under this operating scenario please specify primary fuel and percentage on a 

maximum hourly and annual basis (if fuel blending is the primary fuel, identify percentages of each fuel blended). Attach 

additional information to this form if necessary. 

*Firing of waste oil will require multi metals test to insure fuel is non-hazardous. 
Appendix 1, Page 5

System 66D, TU4.017 (Autoclave Circuit 3, Autoclave #5)

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Check here if this is an 

alternative operating scenario

Section 1B - Equipment Description

a. Type of equipment System 66D, TU4.017 (Autoclave Circuit 3, Autoclave #5) 

b. Standard Industrial Classification (SIC) Code 1041 

c. Manufacturer of equipment Eaton 

d. Model number not specified Serial number not specified *Equip. number not specified

e. Date equipment manufactured: 1992

f. UTM Coordinates 4,536,011 meters N; 554,734 meters E; Zone 11 

(Please specify NAD 27 or NAD 83 ; Method used to obtain coordinates: ) 

g. Basic equipment dimensions (feet): L not specified W not specified H not specified 

*The equipment number is the facility's own numbering system for this piece of equipment. 

Section 2B - Design Rate/Operating Parameters 

a. Maximum design capacity (tons per hour) 200 

b. Requested operating rate (tons per hour)* 

c. Requested operating time: (time of day)* to 

 

 Hours per day 0-24 Days per year 365, 8,760 hr/yr

d. Batch load or charge weight (tons) (if applicable) N/A 

e. Total hours required to process batch or charge (if applicable) N/A 

f. Maximum operating rate (tons per year) not specified 

g. Requested operating rate (tons per year)* 

f. Type of material processed ore

*Note: Please complete if other than the maximum design capacity (tons per hour and tons per year) and/or the maximum hours of 

operation (24 hours per day, 8,760 hours per year) are being requested. The permit will be limited to these values. 
Appendix 1, Page 6

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66D - TU4.017 

Section 3B - Fuel Usage / Heat Source

Electric Unit □

Type of Fuel Amount Used Per 

Hour 

Heat Content 

(specify in Btus) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

( % by 

weight) 

Trace 

Elements 

(% by 

weight) 

Oil- Specify 

Type(s) 

 none gallons N/A N/A N/A N/A 

 none gallons N/A N/A N/A N/A 

Gasoline none gallons N/A N/A N/A N/A 

Propane none cubic feet N/A N/A N/A N/A 

Natural Gas none cubic feet N/A N/A N/A N/A 

*Waste Oil none gallons N/A N/A N/A N/A 

Other none N/A N/A N/A N/A 

Type of 

Coal 

Fuel 

Amount 

Used 

Per 

Hour 

(tons) 

Heat 

Content 

(specify 

in 

BTUs) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

(% by 

weight) 

Trace 

Elements 

(% by 

weight) 

Percent 

moisture 

Percent 

volatile 

matter 

Percent 

fixed 

carbon 

Coal - 

Specify 

Type(s) 

 

none N/A N/A N/A N/A N/A N/A N/A N/A 

 

If more than one type of fuel is combusted, under this operating scenario please specify primary fuel and percentage on a 

maximum hourly and annual basis (if fuel blending is the primary fuel, identify percentages of each fuel blended). Attach 

additional information to this form if necessary. 

*Firing of waste oil will require multi metals test to insure fuel is non-hazardous. 
Appendix 1, Page 7

System 66D, TU4.018 (Autoclave Circuit 4, Autoclave #6)

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Check here if this is an 

alternative operating scenario

Section 1C - Equipment Description

a. Type of equipment System 66D, TU4.018 (Autoclave Circuit 4, Autoclave #6) 

b. Standard Industrial Classification (SIC) Code 1041 

c. Manufacturer of equipment Eaton 

d. Model number not specified Serial number not specified *Equip. number not specified

e. Date equipment manufactured: 1992

f. UTM Coordinates 4,536,011 meters N; 554,734 meters E; Zone 11 

(Please specify NAD 27 or NAD 83 ; Method used to obtain coordinates: ) 

g. Basic equipment dimensions (feet): L not specified W not specified H not specified 

*The equipment number is the facility's own numbering system for this piece of equipment. 

Section 2C - Design Rate/Operating Parameters 

a. Maximum design capacity (tons per hour) 200 

b. Requested operating rate (tons per hour)* 

c. Requested operating time: (time of day)* to 

 

 Hours per day 0-24 Days per year 365, 8,760 hr/yr

d. Batch load or charge weight (tons) (if applicable) N/A 

e. Total hours required to process batch or charge (if applicable) N/A 

f. Maximum operating rate (tons per year) not specified 

g. Requested operating rate (tons per year)* 

f. Type of material processed ore

*Note: Please complete if other than the maximum design capacity (tons per hour and tons per year) and/or the maximum hours of 

operation (24 hours per day, 8,760 hours per year) are being requested. The permit will be limited to these values. 
Appendix 1, Page 8

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66D - TU4.018 

Section 3C - Fuel Usage / Heat Source 

Electric Unit □

Type of Fuel Amount Used Per 

Hour 

Heat Content 

(specify in Btus) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

( % by 

weight) 

Trace 

Elements 

(% by 

weight) 

Oil- Specify 

Type(s) 

 none gallons N/A N/A N/A N/A 

 none gallons N/A N/A N/A N/A 

Gasoline none gallons N/A N/A N/A N/A 

Propane none cubic feet N/A N/A N/A N/A 

Natural Gas none cubic feet N/A N/A N/A N/A 

*Waste Oil none gallons N/A N/A N/A N/A 

Other none N/A N/A N/A N/A 

Type of 

Coal 

Fuel 

Amount 

Used 

Per 

Hour 

(tons) 

Heat 

Content 

(specify 

in 

BTUs) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

(% by 

weight) 

Trace 

Elements 

(% by 

weight) 

Percent 

moisture 

Percent 

volatile 

matter 

Percent 

fixed 

carbon 

Coal - 

Specify 

Type(s) 

 

none N/A N/A N/A N/A N/A N/A N/A N/A 

 

If more than one type of fuel is combusted, under this operating scenario please specify primary fuel and percentage on a 

maximum hourly and annual basis (if fuel blending is the primary fuel, identify percentages of each fuel blended). Attach 

additional information to this form if necessary. 

*Firing of waste oil will require multi metals test to insure fuel is non-hazardous. 
Appendix 1, Page 9

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: Systems 66C & 66D - TU4.016-TU4.018 (Autoclaves #4 - #6 share a common stack) 

Section 4 - Pollution Control Equipment/Exhaust Stack Parameters (this section must be 

completed)

-Complete for emissions exhausting through a stack, chimney or vent: (baghouse, wet scrubber, cyclone, 

sulfur impregnated carbon filter, uncontrolled stack, etc.) 

 Control #1 Control #2 

Type of Control 

(See Note 1) 

existing: venturi wet dust scrubber 

proposed: secondary venturi 

scrubber, scrubber mist eliminator, 

gas cooling tower, condenser, wet gas 

separator, carbon filter 

Pollutant(s) Controlled particulates and mercury

Manufacturer existing: Hosokawa 

proposed: TBD 

Manufacturer's 

Guarantee (see Note 2) N/A 

Stack height (feet from 

ground level) 100 

Stack inside diameter 

(feet) 4.5 

Temperature (°F) at 

design capacity approximately 110 

Stack exit velocity (feet 

per second) approximately 17 

Gas volume flow rate: 

Actual cubic feet per minute approximately 16,200 

Gas volume flow rate: 

Dry standard cubic feet per 

minute

approximately 11,820 

Unusual stack characteristics (e.g. raincap, 

horizontal discharge)

N/A 

Note 1: Specify "uncontrolled" if no pollution control device is installed. 

Note 2: Manufacturer's guarantee of control efficiency must be attached to this form. 
Appendix 1, Page 10

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: Systems 66C & 66D - TU4.016-TU4.018 (Autoclaves #4 - #6 share a common stack) 

Section 5 - Identify and Describe Work Practice Standards, Etc. (attach additional pages if necessary 

(Eg., 1. Baghouse housing and bags will be inspected weekly for holes/leaks.) 

Work Practices: 

Primary Venturi Wet Dust Scrubbers: 

(a) The pressure drop across each primary venturi wet dust scrubber will be maintained at or below 70 inches of 

water, based on a 1-hour period. 

(b) The water flow rate to each primary venturi wet dust scrubber will be maintained at or above 50 gallons per 

minute, based on a 1-hour period. 

Secondary Venturi Scrubber: 

(a) The pressure drop across the secondary venturi scrubber will be maintained within the manufacturer’s 

specified range, based on a 1-hour period. 

(b) The water flow rate to the secondary venturi scrubber will be maintained at or above the manufacturer’s 

specified range, based on a 1-hour period. 

Cooling Tower: 

(a) The pressure drop across the gas cooling tower will be maintained within the manufacturer’s specified range, 

based on a 1-hour period. 

(b) The water flow rate to the gas cooling tower will be maintained at or above the manufacturer’s specified 

range, based on a 1-hour period. 

Condenser: 

(a) The condenser outlet exhaust temperature will be maintained at or below 58° Fahrenheit, based on a 1-hour 

period. 

Carbon Adsorption Bed: 

(a) Sulfur-impregnated carbon from the carbon adsorption filter will be replaced in accordance with the 

following schedule: 

(i) Conduct an initial sampling of the sulfur-impregnated carbon within 90 days after commencement of 

operation under this permit. A representative sample shall be taken and analyzed. The sample location 

will be recorded. Using this sample, the percentage of mercury by weight shall be calculated. Sampling 

will continue quarterly, at the same sample depth location, until 70% of the carbon loading capacity of 

20% by weight is reached. Upon reaching 70% of the carbon loading capacity of 20% by weight, 

sampling of the carbon will occur monthly until 75% of the carbon loading capacity of 20% by weight is 

reached. The carbon will be replaced with an equivalent performing sulfur-impregnated carbon no later 

than 30 days after reaching 75% of the carbon loading capacity of 20% by weight. The required 

mercury analysis shall be performed utilizing one of the following methods: 

1. EPA method 6020-Inductively Coupled Plasma-Mass Spectrometry; 

2. EPA method 7471B- Mercury in Solid or Semisolid Waste (Manual Cold-Vapor Technique); or 

3. An alternative test method as approved by the Director. 

(b) A halogen impregnated carbon may be used in place of the sulfur impregnated carbon upon approval by the 

Director. Halogen carbon will follow the same sampling and change-out schedule as sulfur-impregnated 

carbon.
Appendix 1, Page 11

Section 6 - Identify and Describe Compliance Monitoring Devices or Activities (attach additional 

pages if necessary) 

(Eg., Emissions from this unit will be monitored by CEMS for mercury.) 

Monitoring and Recordkeeping: 

(a) The pressure drop across each primary venturi scrubber will be monitored and recorded once, during each 

day of operation. 

(b) The water flow rate to each primary venturi scrubber will be monitored and recorded once, during each day 

of operation. 

(c) The pressure drop across the secondary venturi scrubber will be monitored and recorded once, during each 

day of operation. 

(d) The water flow rate to the secondary venturi scrubber will be monitored and recorded once, during each day 

of operation. 

(e) The pressure drop across the gas cooling tower will be monitored and recorded once, during each day of 

operation. 

(f) The water flow rate to the gas cooling tower will be monitored and recorded once during each day of 

operation. 

(g) The condenser outlet exhaust temperature will be monitored and recorded once, during each day of 

operation. 

(h) The percentage of mercury by weight on the carbon in the carbon adsorption filter will be monitored and 

recorded quarterly until reaching 70% of the carbon loading capacity of 20%, and then monthly until 

reaching 75% percent of the carbon loading capacity of 20%. 

Testing Requirements: 

Annual Testing

Before the conclusion of the calendar year, Permittee shall conduct and record a Method 29 (or alternative test method 

approved by the Director) compliance test for the mercury on the exhaust stack of TU4.016 through TU4.018. 

Annual Reporting

The Permittee shall: 

1. Report the mercury co-product on an annual basis. 

2. Report the mercury emissions on an annual basis which must be based on mercury emissions test data. 

 
Appendix 1, Page 12

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: Systems 66C & 66D - TU4.016-TU4.018 (Autoclaves #4 - #6 share a common stack) 

Section 7 - Proposed Emission Rates

Pollutant Potential to 

Emit 

(pounds/hour*)

Potential to Emit 

(tons/year) 

Calculation (including reference or emissions 

tests) on Which Emissions Information is Based 

(attach supporting information including dates 

of tests/methods, if necessary) 

Total Mercury (all 

forms) 

Total Mercury 

(alternative emissions 

limitations) 

7.8 x 10-5 gr/dscf See Appendix 3, Page 19 for calculations 

 

*Note: In addition to lb/hr, alternative emissions limitations (e.g., lb/MMBtu, ppm, grains/dscf) may be requested by the applicant. If alternative 

emissions limitations are requested, please clearly describe the units in column 2 above. Use additional lines, as needed. 
Appendix 2, Page 1

Appendix 2 

Monitoring Plan 

For Each: 

(Check Appropriate Box) 

 Phase 1, Tier 1; 

 Phase 1, Tier 2; 

 Phase 2; or 

 New or Modified 

Thermal Mercury Emitting Unit 
Air Pollution Equipment: 

(a) Exhaust gases from TU4.016 through TU4.018 (System 66, Autoclaves 4, 5 and 6) shall be ducted to a control 

system consisting of: 

a. Primary venturi wet dust scrubber 

b. Secondary venturi wet dust scrubber 

c. Gas cooling tower 

d. Condenser 

e. Carbon adsorption bed 

(b) Stack Parameters 

a. Height: 100 Feet 

b. Diameter: 4.5 Feet 

c. Stack Temperature: 110°F 

d. Flow: Approximately 16,200 ACFM 

e. Units TU4.016 through TU4.018 are ducted to a single stack. 

Operating Requirements: 

(a) Limitations of operation 

a. Mercury emissions from TU4.016 through TU4.018 shall not exceed 7.8 x 10-5 gr/dscf. 

b. Hours 

i. TU4.016 through TU4.018 may operate 24 hours per day 

ii. TU4.016 through TU4.018 may operate 8,760 hours per calendar year. 

Work Practices: 

Primary Venturi Wet Dust Scrubbers: 

(a) The pressure drop across each primary venturi wet dust scrubber will be maintained at or below 70 inches of 

water, based on a 1-hour period. 

(b) The water flow rate to each primary venturi wet dust scrubber will be maintained at or above 50 gallons per 

minute, based on a 1-hour period. 

Secondary Venturi Scrubber: 

(a) The pressure drop across the secondary venturi scrubber will be maintained within the manufacturer’s specified 

range, based on a 1-hour period. 

(b) The water flow rate to the secondary venturi scrubber will be maintained at or above the manufacturer’s 

specified range, based on a 1-hour period. 

Gas Cooling Tower: 

(a) The pressure drop across the gas cooling tower will be maintained within the manufacturer’s specified range, 

based on a 1-hour period. 

(b) The water flow rate to the gas cooling tower will be maintained at or above the manufacturer’s specified range, 

based on a 1-hour period. 

Condenser: 

(a) The condenser outlet exhaust temperature will be maintained at or below 58° Fahrenheit, based on a 1-hour 

period. 

Carbon Adsorption Bed: 

(a) Sulfur-impregnated carbon from the carbon adsorption filter will be replaced in accordance with the following 

schedule: 

(i) Conduct an initial sampling of the sulfur-impregnated carbon within 90 days after commencement of 

operation under this permit. A representative sample shall be taken and analyzed. The sample location 

will be recorded. Using this sample, the percentage of mercury by weight shall be calculated. Sampling will 

continue quarterly, at the same sample location, until 70% of the carbon loading capacity of 20% by weight 

is reached. Upon reaching 70% of the carbon loading capacity of 20% by weight, sampling of the carbon 

will occur monthly until 75% of the carbon loading capacity of 20% by weight is reached. The carbon will 

be replaced with an equivalent performing sulfur-impregnated carbon no later than 30 days after reaching 

75% of the carbon loading capacity of 20% by weight. The required mercury analysis shall be performed 
utilizing one of the following methods: 

1. EPA method 6020-Inductively Coupled Plasma-Mass Spectrometry; 

2. EPA method 7471B- Mercury in Solid or Semisolid Waste (Manual Cold-Vapor Technique); or 

3. An alternative test method as approved by the Director. 

(b) A halogen impregnated carbon may be used in place of the sulfur impregnated carbon upon approval by the 

Director. Halogen carbon will follow the same sampling and change-out schedule as sulfur-impregnated carbon. 

Monitoring and Recordkeeping: 

(a) The pressure drop across each primary venturi scrubber will be monitored and recorded once during each day 

of operation. 

(b) The water flow rate to each primary venturi scrubber will be monitored and recorded once during each day of 

operation. 

(c) The pressure drop across the secondary venturi scrubber will be monitored and recorded once during each day 

of operation. 

(d) The water flow rate to the secondary venturi scrubber will be monitored and recorded once during each day of 

operation. 

(e) The pressure drop across the gas cooling tower cooling tower will be monitored and recorded once during each 

day of operation. 

(f) The water flow rate to the gas cooling tower will be monitored and recorded once during each day of operation. 

(g) The condenser outlet exhaust temperature will be monitored and recorded once during each day of operation. 

(h) The percentage of mercury by weight on the carbon in the carbon adsorption filter will be monitored and 

recorded quarterly until reaching 70% of the carbon loading capacity of 20%, and then monthly until reaching 

75% percent of the carbon loading capacity of 20%. 

Testing Requirements: 

Annual Testing

Before the conclusion of the calendar year, Permittee shall conduct and record a Method 29 (or alternative test method 

approved by the Director) compliance test for the mercury on the exhaust stack of TU4.016 through TU4.018. 

Annual Reporting

The Permittee shall: 

1. Report the mercury co-product on an annual basis. 

2. Report the mercury emissions on an annual basis which must be based on mercury emissions test data. 
Appendix 3, Page 1

Appendix 3 

Nevada MACT Analysis 

For Each: 

(Check Appropriate Box) 

 Phase 2; 

 New or Modified; or 

 Not Applicable 

Thermal Mercury Emitting Unit 
Appendix 3, Page 2 

CONTENTS Page

BARRICK GOLDSTRIKE MINES, INC. (GOLDSTRIKE) NVMACT ANALYSIS FOR THE AUTOCLAVES..................................... 3

Introduction................................................................................................................................................................................... 3

Source Description ....................................................................................................................................................................... 3

Part I – Existing Similar Thermal Units..................................................................................................................................... 6

Mercury Controls...............................................................................................................................................6

Wet Scrubbers................................................................................................................................................6

Work Practices ..................................................................................................................................................8

Mercury Emissions............................................................................................................................................8

Mercury Control Costs....................................................................................................................................10

Non-Air Quality Health and Environmental Impacts and Energy Requirements............................................11

Part II – Other Controls and/or Work Practices...................................................................................................................... 12

Other Mercury Control Options......................................................................................................................12

Boliden Norzinc...........................................................................................................................................12

Selenium Scrubbers .....................................................................................................................................13

Wet Electrostatic Precipitators.....................................................................................................................13

Activated Carbon Filters..............................................................................................................................13

Activated Carbon Injection..........................................................................................................................14

Selenium Filters...........................................................................................................................................14

Condensers...................................................................................................................................................15

Other Work Practices......................................................................................................................................16

Part III - Proposed NvMACT .................................................................................................................................................. 17

Mercury Controls and Work Practices............................................................................................................17

Mercury Emissions..........................................................................................................................................19

Mercury Control Costs....................................................................................................................................19

Non-Air Quality Health and Environmental Impacts and Energy Requirements............................................20 

Appendix A - General Arrangement ........................................................................................................................................... 22

Appendix B - Piping and Instrumentation Diagrams................................................................................................................... 32

Appendix C - Process Flow Diagrams........................................................................................................................................ 36

Appendix D - Process Design Criteria........................................................................................................................................ 52

ENDNOTES.................................................................................................................................................................................... 69

Tables 

Table 3.1: Autoclave Stack Testing Mercury Emissions Summary.................................................................................................. 9 

Table 3.2: Autoclave Stack Test Mercury Speciation .................................................................................................................... 10 

Table 3.3: Goldstrike Alkaline Source Test Mercury Emissions .................................................................................................... 19 

Table 3.4: Estimated Capitol and Operating Costs for the New Autoclave Mercury Off-Gas Control System .............................. 20 

Figures 

Figure 3.1: Existing Autoclave Circuit Process Flow Diagram......................................................................................................... 4 

Figure 3.2: Existing Autoclave Circuit Emission Controls ................................................................................................................ 5 

Figure 3.3: Rectangular Throat Venturi Scrubber............................................................................................................................ 7 

Figure 3.4: Mercury Saturation Pressure Curve ............................................................................................................................ 15 

Figure 3.5: Proposed Autoclave Circuit Emission Controls ........................................................................................................... 18 
Appendix 3, Page 3 

BARRICK GOLDSTRIKE MINES, INC. (GOLDSTRIKE) NVMACT 

ANALYSIS FOR THE AUTOCLAVES 

Introduction 

Barrick Goldstrike Mines Inc. (Goldstrike) operates six autoclaves which vent to four stacks. The 

autoclaves are used to oxidize sulfide ore under pressure using steam and oxygen. Historically, 

Goldstrike has used acidic autoclaving to process the sulfide ore; however, due to the changing ore 

characteristics, Goldstrike plans to operate three autoclaves (Autoclaves 4 though 6) in an alkaline mode 

of operation in the future. Recent mercury stack test data indicates that the mercury emissions from 

processing ore under alkaline conditions are higher than the emissions from acidic autoclaving. (Testing 

was authorized by NDEP pursuant to NAC 445B.232.) 

Per NAC 445B.3681.6, a Nevada Maximum Achievable Control Technology (NvMACT) analysis is 

required to be conducted for new or modified thermal units that emit mercury as a part of the application 

for a revision to a mercury operating permit to construct. The NvMACT analysis provided herein 

addresses all the requirements of NAC 445B.3681.6. 

Source Description 

In the autoclave circuit, sulfide ore is oxidized (see Figure 3.1). Sulfide ore slurry from the wet grinding 

mills is first thickened in thickener tanks. The slurry is then acidulated with sulfuric acid in acidulation 

tanks. Sulfide ore slurry from the acidulation tanks is pre-heated and then oxidized in the autoclaves 

with pressure, steam, and oxygen. Currently, the off-gas from each autoclave passes through a dedicated 

venturi scrubber before being released to the atmosphere (the exhaust from Autoclaves 2 and 3 and 

Autoclaves 5 and 6 are ducted together downstream of the venturi scrubbers for a total of four stacks) 

(see Figure 3.2). When the gas exits the venturi scrubber it is saturated with water. 
Appendix 3, Page 4 

Figure 3.1: Existing Autoclave Circuit Process Flow Diagram 

STEAM

GENERATION

PLANT

TO ATMOSPHERE

SLURRY

COOLER

SURGE

TANKS

FLASH

TANKS

SLURRY

COOLERS

STEAM

AUTOCLAVES

AIR LIQUIDE

OXYGEN PLANT

O2

S2.015 - S2.020

SPLASH

CONDENSERS

COOLING

TOWERS

WATER

ORE

FROM WET GRINDING PROCESS

TO CIL TANKS

SLAKED LIME

LIME

SLAKERS

HEAT

PRE

OXIDATION

THICKENERS

TO

ATMOSPHERE

WET

SCRUBBERS

TO RECLAIM WATER TANK

SULFURIC

ACID

TANKS

ACIDULATION

TANKS

NEUTRALIZATION

TANKS

FLOW OF GOLD

LEGEND:

MINOR FLOW

WATER
Appendix 3, Page 5 

Figure 3.2: Existing Autoclave Circuit Emission Controls 

Autoclave #1

S2.015

Autoclave #1

Venturi

Scrubber

Autoclave #3

S2.017

Autoclave #2

S2.016

Autoclave #2

Venturi

Scrubber

Autoclave #3

Venturi

Scrubber

To Atmosphere

(Stack #2)

To Atmosphere

(Stack #1)

Autoclave #4

S2.018

Autoclave #4

Venturi

Scrubber

Autoclave #6

S2.020

Autoclave #5

S2.019

Autoclave #5

Venturi

Scrubber

Autoclave #6

Venturi

Scrubber

To Atmosphere

(Stack #4)

To Atmosphere

(Stack #3)
Appendix 3, Page 6 

NvMACT Analysis 

Part I – Existing Similar Thermal Units 

Part I of this NvMACT analysis provides a list of the similar existing thermal units used for precious 

metal mining and describes the controls and work practices used to reduce mercury emissions. All 

information required by NAC 445B.3681, as described below, is provided herein: 

NAC 445B.3681 New or modified thermal unit that emits mercury: Contents of required application. 

 6.(b) Sets forth a list of similar thermal units that emit mercury which are used for precious metal mining that 

includes, without limitation: 

 (1) Any methods or technologies to control mercury emissions which are associated with the thermal units that 

emit mercury; 

 (2) The level of mercury emissions associated with each method or technology to control mercury emissions 

from the thermal units that emit mercury; 

 (3) The design for each method or technology to control mercury emissions from the thermal units that emit 

mercury; 

 (4) Costs associated with reductions of mercury emissions as a result of each method or technology to control 

mercury emissions from the thermal units that emit mercury; 

 (5) Costs associated with energy for each method or technology to control mercury emissions from the thermal 

that emit mercury; and 

 (6) Consistent with section 112(d)(2) of the Act, any nonair quality health and environmental impacts and 

energy requirements for each method or technology to control mercury emissions from the thermal units that 

emit mercury. 

Mercury Controls 

An examination of the Nevada Mercury Control Program (NMCP) Phase-2 Applications1 showed that 

there is only one other precious metal mining facility in Nevada with an existing autoclave circuit. At 

both Goldstrike and Newmont Twin Creeks, the existing control for these thermal units is venturi wet 

scrubbers. 

Wet Scrubbers 

All of the existing autoclaves employ a venturi scrubber as an off-gas control. The venturi scrubbers are 

installed primarily to control particulate emissions. Wet scrubbers may control oxidized mercury,2 as this 

form of mercury is soluble in the scrubber water, and elemental mercury, if the scrubber exhaust 

temperature is decreased to below the mercury saturation temperature. 

Venturi wet scrubbers control particulates, including particulate mercury, through impaction, diffusion, 

interception, and/or adsorption of the pollutant onto droplets of liquid.3 Venturi scrubbers use a 

converging then diverging flow channel such that the area of the channel decreases then increases along 
Appendix 3, Page 7 

the length of the channel. The narrowest area is called the throat. As the exhaust gas enters the venturi 

scrubber, the decrease in area causes the gas velocity and turbulence to increase. The scrubbing water is 

injected either slightly upstream of or directly into the throat section. As the scrubbing solution is 

injected, the turbulence in the throat causes it to atomize, which improves gas-liquid contact.3 After 

passing through the throat, the gas-liquid mixture decelerates and causes additional particle-droplet 

impacts and agglomeration of the droplets. Before the gas exits the scrubber, the liquid droplets are 

separated from the gas in an entrainment section.3 

As the gas passes through the venturi scrubber, there is a drop in pressure. For venturi scrubbers in 

general, the greater the pressure drop, the higher the particulate control efficiency. However, for 

autoclaves, the temperature and pressure of the autoclave itself is maintained by limiting the release of 

steam and off-gas. Therefore, when the gas flow passing through the scrubber is low, there is low 

pressure drop across the scrubber. 

The liquid to gas ratio also affects venturi scrubber efficiency. There must be sufficient liquid injected 

into the scrubber to allow for coverage over the throat area and to create sufficient collection targets. 

After an optimal point, adding excess liquid to a scrubber does not increase the particulate control 

efficiency. The liquid to gas ratio for wet scrubbers typically ranges from 4 to 20 gallons per 1,000 actual 

cubic feet (gal/kacf).4 A diagram of a typical venturi scrubber is provided as Figure 3.2. 

Figure 3.3: Rectangular Throat Venturi Scrubber5
Appendix 3, Page 8 

Work Practices 

Work practices associated with autoclaves and venturi scrubbers include monitoring of the autoclave 

throughput and monitoring the venturi scrubber flow rate and pressure drop. Autoclaves operate under 

pressure and are ducted such that all the exhaust is vented through the venturi scrubber. Total exhaust 

flow, and emissions, are limited by limiting the release of steam and off-gas to the venturi scrubber as 

previously discussed. 

Mercury Emissions 

The actual mercury emissions from the autoclaves at precious metal mining facilities in Nevada were 

obtained from stack tests.6 Table 3.1 provides the pound-per-hour (lb/hr) emission rate as well as the 

mercury concentration data for autoclaves. 
Table 3.1: Autoclave Stack Testing Mercury Emissions Summary

Emissions Hg Conc.

Mine Unit Control lb/hr gr/dscf Test Infoa

Twin Creeks Mine Phase I & II Autoclave Venturi Scrubber 1.16E-01 1.12E-03 10/21/1997

Autoclave Venturi Scrubber 5.77E-02 1.29E-03 6/22/1998

Autoclave Venturi Scrubber 1.53E-02 6.57E-04 1/27/2001

Phase I Autoclave Venturi Scrubber 8.25E-02 1.27E-03 10/4/2005

Phase I Autoclave Venturi Scrubber 3.87E-02 5.81E-04 10/4/2005

Phase I Autoclave Venturi Scrubber 5.26E-02 9.68E-04 6/13/2007

Phase I Autoclave Venturi Scrubber 4.34E-02 8.37E-04 6/13/2007

Phase I Autoclave Venturi Scrubber 6.55E-02 1.02E-03 6/15/2007

Phase I Autoclave Venturi Scrubber 6.62E-02 1.15E-03 6/15/2007

Phase II Autoclave Venturi Scrubber 3.30E-02 6.06E-04 6/16/2007

Phase II Autoclave Venturi Scrubber 2.54E-02 4.23E-04 6/16/2007

Phase I Autoclave Venturi Scrubber 8.47E-02 1.72E-03 8/18/2008

Phase II Autoclave Venturi Scrubber 3.30E-02 6.73E-04 8/21/2008

Barrick Goldstrike Mine Autoclave 1 Venturi Scrubber 6.63E-03 3.05E-04 8/28/1990

Autoclave 1 Venturi Scrubber 2.30E-03 1.40E-04 7/10/1991

Autoclave 2 & 3 Venturi Scrubber 1.23E-03 2.01E-05 9/17/1992

Autoclave 4 Venturi Scrubber 1.13E-03 1.37E-04 5/2/2006

Autoclave 4 Venturi Scrubber 2.87E-03 2.63E-04 5/3/2006

Autoclave 4 Venturi Scrubber 1.07E-03 6.20E-05 7/23/2009

Autoclave 5 & 6 Venturi Scrubber 1.17E-03 3.65E-05 7/24/2009

Autoclave 2 & 3 Venturi Scrubber 8.63E-04 2.55E-05 7/28/2009

Autoclave 1 Venturi Scrubber 7.13E-04 5.92E-05 7/29/2009

a

 Obtained from the Nevada Mercury Control Program (NMCP) Mercury Emission Management System (MEMS) database.

Appendix 3, Page 8
Appendix 3, Page 10 

Ontario Hydro Method (OHM) stack test reports provided mercury speciation data for the autoclaves at 

Goldstrike. Flue-gas Absorbent Mercury Speciation (FAMS) test data was available for Newmont Twin 

Creeks. For all these autoclaves, the test data is representative of an autoclave controlled by a venturi wet 

scrubber. The mercury speciation data is provided in Table 3.2. 

Table 3.2: Autoclave Stack Test Mercury Speciation7,8,9

Mine Source Controls 

Elemental

Mercury 

Oxidized 

Mercury 

Particulate

Mercury 

Goldstrike Autoclave 1 Venturi Scrubber 92.8% 5.1% 2.2% 

 Autoclave 2 & 3 Venturi Scrubber 69.8% 23.3% 6.9% 

 Autoclave 4 Venturi Scrubber 78.1% 8.3% 13.6% 

 Autoclave 5 & 6 Venturi Scrubber 66.4% 26.8% 6.7% 

Twin Creeks Phase I Autoclave Venturi Scrubber 97.9% 1.6% 0.5% 

Average 81.0% 13.0% 6.0% 

As shown by Table 3.2, a majority of the emissions from the existing autoclaves is in the form of 

elemental mercury (81 percent on average). A smaller percentage of the emissions is oxidized mercury 

(13 percent on average) and the remaining smallest percentage of emissions is particulate mercury (6 

percent on average). 

Mercury Control Costs 

The Phase-2 Applications submitted by precious metal mining facilities in Nevada provided estimated 

total installed costs for the existing mercury controls for autoclaves. According to Newmont Twin 

Creek’s Phase-2 Application, the total installed costs of their venturi scrubbers for Autoclaves 1 and 2 

were $347,000 and $364,000 in 2007 dollars, respectively. The annual operating and maintenance costs 

were not provided. 

Annual utility costs represent the cost of the energy required for each of the control technologies. Venturi 

scrubbers require energy for the pumps that circulate scrubber solution through the system. Due to the 

fact that autoclaves are pressurized, the venturi scrubbers do not require a fan to push the exhaust 

through the scrubbers. According to the EPA Control Cost Manual, for a typical venturi scrubber with a 

liquid flow rate of 10 gallons per minute (gpm), a pressure of 20 pounds per square inch gauge (psig), 

and a pressure drop of 15 inches of water gauge (in. H2O g), the water pump energy requirement is 

estimated to be 0.233 horsepower per thousand cubic feet per minute (hp/1,000 cfm).3 Assuming 24 

hours per day and 7 days per week operation and an electricity cost of 9 cents per kilowatt-hour (kW-hr), 

the annual utility cost of a venturi scrubber with a gas flow rate of 30,000 acfm is approximately $4,000. 
Appendix 3, Page 11 

Non-Air Quality Health and Environmental Impacts and Energy Requirements 

For autoclaves, the typical venturi scrubber installation uses process water as the scrubbing solution. 

This results in non-air quality health and environmental impacts from the discharge of the scrubbing 

solution. Venturi scrubbers also cause non-air quality health and environmental impacts from the 

increased energy consumption due to the scrubber water pump. For a typical venturi scrubber with a gas 

flow rate of 30,000 acfm, the energy requirement is estimated at 46,000 kW-hr/yr. 
Appendix 3, Page 12 

Part II – Other Controls and/or Work Practices 

This part of the NvMACT analysis examines other control options and/or work practices that are not 

currently employed on existing autoclaves. (See Part I.) 

Other Mercury Control Options 

In addition to the mercury technologies employed at existing autoclaves at precious metal mining 

facilities in Nevada, other mercury control options for autoclaves have been examined. These control 

technologies include: 

• Boliden Norzinc, 

• selenium scrubbers, 

• wet electrostatic precipitators (ESPs), 

• activated carbon filters 

• activated carbon injection, 

• selenium filters, and 

• condensers. 

Boliden Norzinc 

In the Boliden Norzinc process, a mercuric chloride solution reacts with the elemental mercury in the offgas to form a mercurous chloride precipitate, known as calomel, which is settled and recovered. This 

reaction occurs in a packed column. Once the solid is removed, the wash solution can be recirculated. A 

portion of the precipitate can be used to regenerate the mercuric chloride solution using chlorine gas.10 

The rest of the calomel is sent off site for reclamation. The Boliden Norzinc process uses the following 

reaction: 

HgCl2(sol’n) + Hg(gas) → 2HgCl(solid)

The Boliden Norzinc process is installed at Goldstrike’s roasters, which have a gas stream with high 

mercury content. The Boliden Norzinc process can achieve outlet concentrations of 0.03 to 0.05 mg/Nm3. 

Because these outlet concentrations are similar to the outlet mercury concentrations from the autoclaves, 

the Boliden Norzinc process would not be expected to provide significant additional mercury control. 

The ideal operating temperature for the Boliden Norzinc process is 104 ̊F. As shown in Table 3.1, the 

average outlet temperature for autoclaves is approximately 190 ̊F, and would therefore require gas 

stream cooling before control by the Boliden Norzinc process. The cooling of the saturated gas stream 

would require significant energy input, as energy is required to both condense the water and cool the gas 

stream. At the Goldstrike autoclaves, over 100 MMBtu/hr would be required to cool the combined gas 

stream to 100 ̊F. 
Appendix 3, Page 13 

The Boliden Norzinc process has not been applied to an existing autoclave at precious metal mining 

facilities in Nevada. Thus, there is no basis for assessing its performance in such an application given the 

dissimilarities between the autoclaving process (and its characteristic emission stream) and those 

units/emission streams where Boliden Norzinc has been applied. In addition, this technology requires a 

significant capital investment and results in increased wastewater (process water containing chloride 

ions) and solid waste (calomel). 

Selenium Scrubbers 

Selenium scrubbers use selenium or a selenium compound within a scrubber to react with the elemental 

mercury in the off-gas to form mercuric selenide (HgSe). Mercuric selenide has a lower vapor pressure 

than other common mercury compounds which allows for mercury capture. The mercuric selenide is 

removed in a sludge separation circuit, which requires a thickener and HgSe reclamation. Sulfuric acid, 

at concentrations between 10 and 60 percent, is used as the wash solution for the process. 

Selenium scrubbers are appropriate for gas streams with high mercury loading. The outlet 

concentrations from this process are typically higher than the concentrations achieved from the Boliden 

Norzinc process discussed above. Selenium scrubbers are not widely used due to the low removal 

efficiencies as well as the expensive reagent and reclamation requirements. 

Wet Electrostatic Precipitators 

Wet electrostatic precipitators (ESPs) use electrostatic charges to move particulates from a gas stream 

onto a collection surface. The electric field is created through electrodes that are maintained at a high 

voltage. Wash water is used to clean the particulates from the collection plates.10 Wet ESPs are designed 

for saturated gas streams and have a maximum operating temperature of 170 to 190 ̊F. Wet ESPs will 

collect dust, fumes, aerosol mist, and liquid droplets from a gas stream; however they do not provide any 

effective control of oxidized or elemental mercury.10 Therefore, gaseous elemental and oxidized 

mercury, which is a majority of autoclave mercury emissions, will not be controlled. The particulate 

mercury is already controlled by the existing venturi scrubber. 

Activated Carbon Filters 

Carbon adsorption filters use activated carbon particles to adsorb mercury from the gas stream. 

Adsorption occurs when gas molecules are passed through a bed of solid particles, and the gas molecules 

migrate from the gas stream to the surface of the solids where they are held by physical attraction.11 

Carbon impregnated with elemental sulfur increases the adsorption efficiency of the beds due to the 

mercury reacting with the sulfur to form mercury sulfide (HgS). Mercury sulfide has a lower vapor 

pressure than elemental mercury and is more readily removed.10 

Activated carbon beds control all types of mercury: particulate bound, oxidized, and elemental. The 

mercury in the gas stream is adsorbed to the carbon and collected as carbon loaded with mercury. Once 

the carbon reaches adsorptive capacity, it is replaced, and the spent carbon is reclaimed. Monitoring of 

the carbon bed mercury content is performed to ensure that the mercury loading does not exceed the 
Appendix 3, Page 14 

value recommended by the manufacturer. For activated carbon beds, the typical carbon loading capacity 

is approximately 20 percent (or more) mercury by weight.12,13 Carbon mercury loading can be monitored 

directly, or the mercury concentration in the exhaust at the outlet of the carbon bed can be monitored to 

ensure the effectiveness of the carbon adsorber. 

Some factors that can affect carbon bed adsorption efficiency include residence time of the gas in the 

carbon bed, bed temperature, and carbon particle size. Longer residence times, lower bed temperature, 

and smaller carbon particle sizes increase the mercury removal efficiency of the carbon bed.10 The gas 

flow rate, bed size, and mass of the carbon in the bed influence the residence time of the gas in the carbon 

bed. A lower flow rate and larger carbon bed with more carbon mass increases the residence time.10

The possibility of controlling the autoclaves at Goldstrike with carbon adsorption technology was 

investigated. The exhaust streams from the existing Venturi scrubbers would have to be cooled and have 

the water removed before entering a carbon bed. Excessive water collection in a carbon filter will reduce 

control efficiency. Water can enter the pore structure of the carbon and block active adsorption sites, 

reducing the surface area available for mercury collection. The application of activated carbon 

technology for controlling mercury emissions from the autoclaves when operating in an alkaline mode is 

discussed further below in Part III. 

Activated Carbon Injection 

Activated carbon injection is similar to activated carbon filters in that activated carbon particles are used 

to adsorb mercury from the gas stream. With carbon injection, the carbon particles are injected directly 

into the gas stream where they adsorb mercury and are then collected in downstream particulate controls 

such as baghouses, wet scrubbers, or wet ESPs. As with activated carbon filters, the control effectiveness 

of activated carbon injection will be limited if water enters the activated adsorption sites. There is no 

precedent for using the carbon injection technology on gas streams with high moisture content as in the 

case of the Goldstrike autoclaves. In addition, the control efficiency for carbon injection is typically lower 

than for carbon beds. Therefore, the appropriate application of the activated carbon technology for 

autoclaves is a carbon adsorption filter. 

Selenium Filters 

Selenium filters are similar to selenium scrubbers in that they use selenium to react with the elemental 

mercury in the gas stream to form mercuric selenide. Selenium filters use a selenium impregnated 

porous carrier structure which is housed in a cylindrical tower. The selenium filter’s maximum operating 

temperature is approximately 250 ̊F. The filters require a dry gas stream because water will degrade the 

filter media. This provides a significant limitation to its application for the Goldstrike autoclaves. The 

typical filter carrying capacity is between 10 and 15 percent mercury by weight. 

There are only a few installations of selenium filters in the world, primarily in Sweden, and there is no 

operating data from these applications. Selenium filters are expensive to produce and to regenerate. 
Appendix 3, Page 15 

There is no basis to believe that selenium filters would provide a better alternative than activated carbon. 

In addition, there is some concern that the filters cause selenium air emissions. 

Condensers 

Condensers control mercury by cooling a gas stream and causing the elemental mercury to condense. In 

order for condensation to occur with a drop in temperature, the gas stream must be saturated with 

mercury vapor. Mercury saturation is determined by the mercury saturation pressure curve as shown 

below. 

Figure 3.4: Mercury Saturation Pressure Curve14

Based on recent stack tests of alkaline autoclaving at Goldstrike (authorized by NDEP pursuant to NAC 

445B.232), the concentration of mercury in the exhaust stream ranged from 1.14x10-3 to 3.00x10-3 gr/dscf. 

This concentration is below the mercury saturation concentration even if the gas stream is cooled to 70 ̊F. 

(The saturated mercury concentration at 70 ̊F is approximately 6.8x10-3 gr/dscf.14) However, at the 

maximum mercury concentration (6.8x10-3 gr/dscf), the exhaust stream would be close to saturated if it 

was cooled to 70 ̊F and therefore, mercury condensation may be an effective control technology for the 

autoclaves at Goldstrike, when operating in the alkaline mode. 

0.000

0.005

0.010

0.015

0.020

0.025

0.030

30 50 70 90 110 130 150 170 190

Temperature (F)

Vapor Pressure (kPa)
Appendix 3, Page 16 

Other Work Practices 

There are no process changes or material substitutions that can be instituted to reduce mercury emissions 

from autoclaves. (All work practice options are discussed in Part I). Mercury is present in the ore 

currently being mined and will be present during the mine life. 
Appendix 3, Page 17 

Part III - Proposed NvMACT

Per NAC 445B.3681.6(a), the applicant must propose “standards, methods of control or other limitations to be 

applied to the thermal unit for the reduction of mercury emissions that the applicant deems sufficient for the 

Director to determine to be NvMACT for the thermal unit that emits mercury.” Therefore, the NvMACT 

proposed in this part follows the criteria that are required by the Director pursuant to NAC 

445B.3683.2(b). All items considered in this NvMACT analysis are checked in the criteria list provided 

below: 

NAC 445B.3683 Review of and action on application for new or modified thermal unit that emits mercury. 

2.(b) Make a determination of NvMACT for the thermal unit that emits mercury in which the Director shall consider the 

following for each thermal unit that emits mercury: 

 (1) The maximum degree of reduction of mercury emissions that is achievable for the thermal unit after 

considering: 

(I) The cost of achieving such a reduction; and 

(II) Consistent with section 112(d)(2) of the Act, any nonair quality health and environmental impacts and 

energy requirements for each method or technology to control mercury emissions from the thermal unit 

that emits mercury to implement the NvMACT. 

 (2) The measures that reduce the volume or eliminate mercury emissions through process changes, substitution 

of materials or any other modifications. 

 (3) The enclosure of systems or processes to eliminate mercury emissions. 

 (4) The collection, capture or treatment of mercury emissions. 

 (5) The design, equipment, work practice or operational standards of the thermal unit that emits mercury, 

including, without limitation, the requirements for training and certification of operators of the thermal unit 

that emits mercury. 

 (6) The differences in the age, remaining operating life and configurations of similar thermal units that emit 

mercury. The Director may also consider the differences in the concentration of mercury in the ore, size and 

any other relevant factors of the similar thermal units that emit mercury. 

Mercury Controls and Work Practices 

Based on the existing control technologies and work practices described in Part I and the additional 

control technology options described in Part II, Goldstrike proposes that adding a secondary venturi 

scrubber, a scrubber mist eliminator, a gas cooling tower, a condenser, a wet gas separator, and a carbon 

filter downstream of the existing Autoclave 4 through 6 venturi scrubbers and the following work 

practices are NvMACT. These work practices include: 

• monitoring the autoclave throughput, 

• maintaining the flow rate and pressure drop within the manufacturer’s recommended operating 

range for all venturi scrubbers, 
Appendix 3, Page 18 

• maintaining the flow rate and pressure drop of the cooling tower within the manufacturer’s 

recommended operating range, 

• maintaining the outlet temperature of the condenser within the manufacturer’s recommended 

operating range, 

• collecting condensed mercury from the condenser as a co-product, and 

• replacing the carbon in the new carbon filter prior to exceeding the maximum loading as 

recommended by the manufacturer. 

A flow diagram of the proposed NvMACT control system is provided in Figure 3.5. Please see 

Appendices A through D for the general arrangement, piping and instrumentation diagrams, process 

flow diagrams, and process design criteria. 

Figure 3.5: Proposed Autoclave Circuit Emission Controls 

The Goldstrike Autoclaves can process a total of 1,130 tons of ore per hour (130 tons/hr for Autoclave 1 

and 200 tons/hr each for Autoclaves 2 - 6) and can operate 8,760 hours per year, each. 

Autoclave #4

S2.018

Secondary

Venturi

Scrubber

Scrubber

Mist

Eliminator

Gas

Cooling

Tower

Condenser Wet Gas

Separator

Carbon

Filter

Booster

Fan

Autoclave #4

Primary

Venturi

Scrubber

Autoclave #6

S2.020

Autoclave #5

S2.019

Autoclave #5

Primary

Venturi

Scrubber

Autoclave #6

Primary

Venturi

Scrubber

To Atmosphere

(Stack #3)

Autoclave #1

S2.015

Autoclave #1

Venturi

Scrubber

Autoclave #3

S2.017

Autoclave #2

S2.016

Autoclave #2

Venturi

Scrubber

Autoclave #3

Venturi

Scrubber

To Atmosphere

(Stack #2)

To Atmosphere

(Stack #1)
Appendix 3, Page 19 

The engineering for the new autoclave mercury off-gas control project has not been completed. However, 

preliminary design specifications and cost data have been obtained from Aker Solutions. Based on this 

preliminary data, the carbon adsorption filter will contain 40,000 pounds of activated sulfur-impregnated 

carbon. The new controls are designed so that the exhaust flow rate through the carbon filters is expected 

to be approximately 15,500 acfm and the residence time to be approximately 4 seconds. For activated 

carbon filters, the typical carbon loading capacity is approximately 20 percent (or more) mercury by 

weight. 

A new venturi scrubber, scrubber mist eliminator, gas cooling tower, condenser, and wet gas separator 

will be installed upstream of the carbon filter to cool the gas stream and remove mercury and condensate 

from the gas stream. 

Mercury Emissions 

The proposed NvMACT performance standard for the autoclave 4 through 6 common stack is 7.8 x 10-5

grains per dry standard cubic foot (gr/dscf). This standard was estimated based on the recent mercury 

source tests performed in March 2010 at the Goldstrike autoclaves while processing ore under alkaline 

conditions. (Testing was authorized by NDEP pursuant to NAC 445B.232.) The concentration was 

calculated from the maximum average concentration (two run avg.) of the aforementioned Goldstrike 

alkaline source tests (provided in Table 3.3) plus three standard deviations, targeting 98% control. This 

calculation method accounts for limited test data as well as stack testing and operational variability. 

Table 3.3: Goldstrike Alkaline Source Test Mercury Emissions 

Run #1 Run #2 Run #1 Run #2 Run #1 Run #2 Run #1 Run #2 Run #1 Run #2 

Total 

Mercury 

(gr/dscf)

2.80 x 10-3 2.37 x 10-3 2.91 x 10-3 2.66 x 10-3 2.87 x 10-3 2.73 x 10-3 3.00 x 10-3 1.14 x 10-3 2.16 x 10-3 1.99 x 10-3 

Two Run 

Avg. 

(gr/dscf) 

2.59 x 10-3 2.79 x 10-3 2.80 x 10-3 2.07 x 10-3 2.08 x 10-3

Mercury Control Costs 

Estimated capitol and operating costs for the new autoclave mercury off-gas control system are provided 

in Table 3.4. 
Appendix 3, Page 20 

Table 3.4: Estimated Capitol and Operating Costs for the New Autoclave Mercury Off-Gas Control 

System 

Item Description Cost Basis 

Capitol Costs 

Engineering Costs $ 3,506,350 2010 estimate 

Material Costs $ 13,219,950 2010 estimate

Labor Costs $ 11,583,070 2010 estimate 

Barrick Project Support $ 977,500 2010 estimate 

Total Capitol Costs $ 29,286,870 2010 estimate 

Operating Costs 

Operating Labor (4 operators at $90,000/yr) $ 360,000 Per year 

Maintenance Labor (1 maintenance at $90,000/yr) $ 90,000 Per year 

Maintenance Supplies $ 533,774 Per year 

Utilities ($0.08/kW-hr) $ 911,129 Per year 

Consumables (replacement carbon, reagents and flocculants, 

cooling tower treatment chemical) $ 251,550 Per year 

Total Operating Costs $ 2,146,453 Per year 

The proposed control technologies and work practices require energy for the venturi scrubber variable 

throat, venturi scrubber/scrubber mist eliminator pump, gas cooling tower pump, condensate pump, 

effluent pump, refrigeration unit, booster fan, cooling tower fans, cooling tower pumps, humidity control 

heater, and transformer. The maximum annual estimate of total energy required for these units, 

assuming 24 hours per day and 7 days per week operation is 11,389,107 kilowatt-hours per year (kWhr/yr). As shown in Table 3.5, assuming an electricity cost of 8 cents per kW-hr, the total energy cost is 

$911,129 per year. 

Before the sulfur-impregnated carbon in the carbon filter reaches the maximum carbon loading capacity 

(approximately 20 percent mercury by weight), it will need to be replaced. The new carbon and each 

carbon replacement will cost approximately $82,800 per replacement. In addition, disposal costs of spent 

carbon are approximately $2.50 per pound of carbon15 or $100,000 per replacement. 

The proposed new control technologies are expected to last the remaining life of the mine. 

Non-Air Quality Health and Environmental Impacts and Energy Requirements 

Non-air quality health, environmental, and energy impacts are associated with the collection of 

particulates and mercury condensates from the venturi scrubber, gas cooling tower, and condenser. 

Furthermore, the shipping and reclamation of the spent carbon and elemental mercury has non-air 

quality health, environmental, and energy impacts. Due to additional controls on this system, overall 

emissions of regulated pollutants (PM, SO2, H2S) are expected to decrease. 
Appendix 3, Page 21 

In addition, better control of mercury emissions from these sources decreases the opportunity of mercury 

exposure for Goldstrike personnel and contractors performing work in the autoclave areas. 

The cooling towers also have non-air quality health, environmental, and energy impacts from the 

recirculation of water. To counteract the non-air quality health and environmental impacts associated, 

chemicals are added to the water to prevent the growth of harmful bacteria. Additionally, because of the 

pumping requirements for the recirculation of water through the cooling towers energy impacts are also 

associated with this aspect of the project. 

Furthermore, condensation of the steam from the autoclaves which is currently being evaporated will 

increase Goldstrike’s water balance. All water condensed must be treated and reused to offset the 

additional water input. 

Goldstrike’s energy requirements will increase as a result of this project. Operation of the new autoclave 

off-gas mercury control system will require 11,389,107 kW-hr/yr. 

Installation of these controls allows for an extended life of the autoclave facility, which in turn maintains 

job availability for Goldstrike personnel. Without these controls, the autoclaves would be shut down at 

the end of 2010. 
Appendix 3, Page 22 

Appendix A 

GENERAL 

ARRANGEMENT 
Copyrighted page/s removed. Copyrighted material is not available in 

Regulations.gov since it may not be reproduced without consent of 

the copyright holder. 

Contact the EPA Docket Center’s Public Reading Room to view 

or receive a copy of this document. 

Requests for copies may be made as follows: 

In person/writing: 

Environmental Protection Agency, Docket Center 

1301 Constitution Ave NW, 2822T, Room 3334 

Washington, DC. 20004 

Telephone: 

202-566-1744 

Fax: 

202-566- 9744 

Email: 

docket-customerservice@epa.gov 
Appendix 3, Page 32 

Appendix B 

PIPING AND 

INSTRUMENTATION 

DIAGRAMS 
Copyrighted page/s removed. Copyrighted material is not available in 

Regulations.gov since it may not be reproduced without consent of 

the copyright holder. 

Contact the EPA Docket Center’s Public Reading Room to view 

or receive a copy of this document. 

Requests for copies may be made as follows: 

In person/writing: 

Environmental Protection Agency, Docket Center 

1301 Constitution Ave NW, 2822T, Room 3334 

Washington, DC. 20004 

Telephone: 

202-566-1744 

Fax: 

202-566- 9744 

Email: 

docket-customerservice@epa.gov 
Appendix 3, Page 36 

Appendix C 

PROCESS FLOW 

DIAGRAMS 
Copyrighted page/s removed. Copyrighted material is not available in 

Regulations.gov since it may not be reproduced without consent of 

the copyright holder. 

Contact the EPA Docket Center’s Public Reading Room to view 

or receive a copy of this document. 

Requests for copies may be made as follows: 

In person/writing: 

Environmental Protection Agency, Docket Center 

1301 Constitution Ave NW, 2822T, Room 3334 

Washington, DC. 20004 

Telephone: 

202-566-1744 

Fax: 

202-566- 9744 

Email: 

docket-customerservice@epa.gov 
Appendix 3, Page 52 

Appendix D 

PROCESS DESIGN 

CRITERIA 
Copyrighted page/s removed. Copyrighted material is not available in 

Regulations.gov since it may not be reproduced without consent of 

the copyright holder. 

Contact the EPA Docket Center’s Public Reading Room to view 

or receive a copy of this document. 

Requests for copies may be made as follows: 

In person/writing: 

Environmental Protection Agency, Docket Center 

1301 Constitution Ave NW, 2822T, Room 3334 

Washington, DC. 20004 

Telephone: 

202-566-1744 

Fax: 

202-566- 9744 

Email: 

docket-customerservice@epa.gov 
Appendix 3, Page 59 

ENDNOTES 

1 Nevada Division of Environmental Protection, Bureau of Air Quality Planning. Nevada Mercury 

Control Program (NMCP) - NvMACT Clearinghouse. Phase-2 Applications. 2008. 

http://ndep.nv.gov/BAQP/hg/clearinghouse.html 

2 Rong Yan et al. “Bench-scale experimental evaluation of carbon performance on mercury 

vapour adsorption.” Fuel. Vol. 83, No. 17-18, 2004, p. 2402. 

3 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Control Cost 

Manual, 6th ed. U.S. EPA Office of Air Quality Planning and Standards. Research Triangle Park, North 

Carolina. 2003. Section 6, Chapter 2 – Wet Scrubbers for Particulate Matter. 

4 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Training Institute 

(APTI) SI:412C Scrubber Systems Operation Review. Lesson 2, 1998. 

5 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Training Institute 

(APTI)SI:412C Scrubber Systems Operation Review. 1998. Lesson 3. 

6 Nevada Division of Environmental Protection, Bureau of Air Quality Planning. Nevada Mercury 

Control Program (NMCP) - NvMACT Clearinghouse. Mercury Emissions Management System (MEMS). 2010. 

http://www.ndep.nv.gov/baqp/search 

7 Nevada Division of Environmental Protection, Bureau of Air Pollution Control. Precious Metals 

Mining Mercury Air Emissions Questionnaires. 2006. 

8 2006 OHM Test Data for Tier-1 Units. Nevada Mercury Control Program (NMCP) Data Site. 

http://ndep.nv.gov/bapc/mercury/. 

9 TRC Environmental Corp. Final Report - Emissions Compliance Demonstration for Systems 18, 19, 

61, and 66 (Class I Operating Permit No. AP1041-0739.01) - September 2007. September 2, 2007. 

10 Booz Allen & Hamilton Inc. Report prepared for U.S. EPA Region 9. Mercury Mass Balance and 

Emission Factor Estimates for Gold Ore Processing Facilities (Draft), U.S. EPA Region 9. January 14, 2001. 

11 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Control Cost 

Manual, 6th ed. U.S. EPA Office of Air Quality Planning and Standards. Research Triangle Park, North 

Carolina. 2002. Section 3.1, Chapter 1 – Carbon Adsorbers. 

12 Scotia International of Nevada, Inc. Product Bulletin COL-IS 60 Coal Based Activated Carbon 

Impregnated with Sulfur. 

13 Michael G. Klett, Russell C. Maxwell, and Michael D. Rutkowski. Parsons Infrastructure and 

Technology Group Inc. Report prepared for the United States Department of Energy National Energy 

Technology Laboratory. The Cost of Mercury Removal in an IGCC Plant Final Report. September 2002. 
Appendix 3, Page 60 

 

14 Taylor and Francis Group. CRC Handbook of Chemistry and Physics, 86th Ed. New York. 2005, p. 

6-126. 

15 Kemp, Joe. Environmental Engineer, Barrick Goldstrike Mines, Inc. [Communication with E. 

Steen, Air Sciences Inc.]. October 1, 2007. 
Appendix 4, Page 1

Appendix 4 

Request for de minimis 

Emissions Determination 

Thermal Mercury Emitting Unit 

 
Appendix 5, Page 1

Appendix 5 

APPLICATION 

CERTIFICATION 

The responsible official must sign and date the application certification found in Appendix 5. If the 

application is signed by a person other than the responsible official, as defined in NAC 445B.156, the 

application will be returned as incomplete. 

Note: According to NAC 445B.156, Responsible Official means: 

1. For a corporation: 

 (a) A president; 

 (b) A vice president in charge of a principal business function; 

 (c) A secretary; 

 (d) A treasurer; or 

 (e) An authorized representative of such a person who is responsible for the overall operation of 

the facility and who is designated in writing by the officer of the corporation and approved in 

advance by the director. 

2. For a partnership or sole proprietorship: a general partner or the proprietor, respectively. 

3. For a municipality or a state, federal or other public agency: a ranking elected official or a principal 

executive officer, including, for a federal agency, a chief executive officer who has 

responsibility for the overall operations of a principal geographic unit of the agency. 

4. For an affected source: the designated representative or his alternate, as defined in 42 U.S. C. § 

7651 a (26). 

Nevada Mercury 

Control Program 

Operating Permit to 

Construct 

Autoclaves 1 through 3 

PREPARED FOR: 

BARRICK GOLDSTRIKE MINES 

INC.

PREPARED BY: 

AIR SCIENCES INC. 

PROJECT NO. 59-43-80 

AUGUST 2010 
Page 1 

Table of Contents

General Information ........................................................................................................... Page 2 

APPLICATION

Mercury Operating Permit to Construct Application Cover Page ...................................... Page 3 

General Company Information .......................................................................................... Page 4

-General Company Information Form and Application Information (4 Pages) 

Additional Forms

Mercury Unit Application Form ................................................................................ Appendix 1 

System 66A, TU4.013, Autoclave Circuit 1, Autoclave #1 ................................................................................ 3

System 66B, TU4.014-TU4.015, Autoclave Circuit 2, Autoclaves #2 & #3 ...................................................... 8

Monitoring/Testing Plan ............................................................................................ Appendix 2 

Nevada MACT (NvMACT) Analysis ........................................................................ Appendix 3 

De minimis emissions Request .................................................................................. Appendix 4 

Application Certification ........................................................................................... Appendix 5 
Page 2 

State of Nevada 

 Division of Environmental Protection 

 Bureau of Air Pollution Control 

APPLICATION FOR 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Please return to: Nevada Division of Environmental Protection 

 Bureau of Air Pollution Control, Permitting Branch 

 901 South Stewart Street 

 Carson City, Nevada 89701-5249 

 (775) 687-9350 FAX (775) 687-6396 

General Information

 This application is available from the Bureau of Air Pollution Control in a Microsoft Word file, or on the 

internet at http://www.ndep.nv.gov/bapc. All information required in the application may be computer 

generated and submitted to the Bureau on compact disk(s) or DVD(s). In addition, one printed copy must be 

submitted. 

 All information required by the “General Company Information” and by the relevant forms in the Appendices 

 must be completed. 

 The application filing fee required by NAC 445B.3689 must be submitted with the completed application. 

Checks must be made payable to: “Nevada State Treasurer, Environmental Protection”. 

 This application packet shall be used for Tier 1, Tier 2 thermal units that emit mercury, for construction of 

new thermal units that emit mercury, for de minimis designation and construction and installation projects for 

thermal units that emit mercury at new and existing stationary sources. 

 An application for a mercury operating permit to construct must be signed by a responsible official, as 

defined in Section NAC 445B.297.1. The certification/signature page is contained in Appendix 5. 

 All items in the application must be addressed. If an item does not apply, please indicate so with “N/A” or 

similar notation in the appropriate blank. All other information must be provided. Incomplete applications 

will be returned to the responsible official. 

 
Page 3 

Application 

for 

Mercury Air Quality 

Operating Permit to 

Construct 
Page 4 

GENERAL COMPANY INFORMATION

All applicants shall complete each item or explain in the space provided why no information is needed. Please specify 

"N/A" (Not Applicable) if necessary. The application will be returned to the applicant if it is deemed incomplete. 

1. COMPANY NAME AND ADDRESS THAT ARE TO APPEAR ON THE OPERATING PERMIT

[NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Barrick Goldstrike Mines Inc. 

 (Name) 

 P.O. Box 29 

 (Address) 

 Elko NV 89803 

 (City) (State) (Zip Code) 

2. Owner's Name and Address [NAC 445B.295.1]: 

 Barrick Gold Corporation 

 (Name) 

 BCE Place, Canada Trust Tower, Suite 3700, 161 Bay Street, P.O. Box 212 

 (Address) 

 Toronto Ontario M5J2S1 

 (City) (State) (Zip Code) 

3. Source Name and Mailing Address, if different from #1 [NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Same as #1 

 (Name) 

 

 (Address) 

 

 (City) (State) (Zip Code) 

4. Physical Location of Stationary Source [NAC 445B.3671.2 and NAC 445B.3681.7]: (if no physical 

address, describe location, e.g., 4 miles south of I-80 at xx Interchange) 

 27 miles north of Carlin, off State Route 766 

Township(s) * Range(s) * Section(s) * 

* Sections 1 through 4, T35N, R49E; Sections 12 through 15, 21 through 28, and 33 through 36, T36N, R49E; 

Sections 7 through 9, 16 through 21, and 28 through 32, T36N, R50E, MDB&M (HA 61) 

5. Responsible Official Name, Title and Address [NAC 445B.295.1]: 

 Joseph Giraudo Environmental Manager 

 (Name) (Title) 

 Same as #1 

 (Address) 

 

 (City) (State) (Zip Code) 

(775) 778 - 8140 (775) 778 - 8262 jgiraudo@barrick.com 

 (Telephone #) (FAX #) (E-mail address) 
Page 5 

GENERAL COMPANY INFORMATION (CONTINUED)

6. Plant Manager or Other Appropriate Contact [NAC 445B.3671.1 and NAC 445B.3681.1]: 

 Carly Keeney Environmental Engineer 

 (Name) (Title) 

 Same as #1 

 (Address) 

 

 (City) (State) (Zip Code) 

(775) 778 - 8157 (775) 778 - 8262 ckeeney@barrick.com 

 (Telephone #) (FAX #) (E-mail address) 

 

7. If records required under the operating permit will be kept at a location other than the source, specify that 

location [NAC 445B.3671.5 and NAC 445B.3681]. 

 N/A. Records will be kept on site. 

 (Name) 

 

(Address) 

 

 (City) (State) (Zip Code) 
Page 6 

APPLICATION INFORMATION 

8. This application is submitted for (please check appropriate box below): 

Phase 1 Application

 Tier 1 Unit(s) – Please provide the following: 

 a. An identification and description of any equipment for control of mercury emissions from all 

existing thermal units that emit mercury, including any presumptive NvMACT controls. In 

addition to the identification and description, please complete Section 5 of the Mercury Unit 

application form in Appendix 1. A separate Mercury Unit application form is required for each 

thermal unit that emits mercury. [NAC 445B.3673.1] 

 b. A proposed monitoring plan for each thermal unit that emits mercury consistent with the 

requirements of NAC 445B.3673.2(a). Include the plan in Appendix 2. 

 c. For each requested mercury early reduction credit, the additional controls that are proposed to be 

implemented to reduce mercury emissions. [NAC 445B.3671.6] 

 Tier 2 Unit(s) – Please provide the following: 

 a. An identification and description of any equipment for control of mercury emissions from all 

existing thermal units that emit mercury, including any presumptive NvMACT controls. In 

addition to the identification and description, please complete Section 5 of the Mercury Unit 

application form in Appendix 1. A separate Mercury Unit application form is required for each 

thermal unit that emits mercury. [Section 33.1 of amended NAC 445B] 

 b. A proposed monitoring plan for each thermal unit that emits mercury consistent with the 

requirements of Section 33.2(b) of amended NAC 445B. Include the plan in Appendix 2. 

Phase 2 Application

 Tier 1 or Tier 2 Unit(s) – Please provide the following: 

 a. A proposed monitoring plan consistent with the requirements of NAC 445B.3675.2. Include the 

plan in Appendix 2. 

 b. The NvMACT analysis for each thermal unit that emits mercury consistent with the requirements of 

NAC 445B.3675.1. Include the analysis in Appendix 3. 

New or Modified Thermal Unit that Emits Mercury

 a. Please provide the NvMACT analysis for each thermal unit that emits mercury consistent with the 

requirements of NAC 445B.3681.6. Include the analysis in Appendix 3. 

Request for De Minimis Designation

 a. For a request for determination of de minimis mercury emissions, include a de minimis 

demonstration in Appendix 4. De minimis status is considered for each thermal unit. 

Demonstration must be at the individual unit level, but include cumulative impact of all de minimis 

units at a facility. [NAC 445B.3613 and NAC 445B.3657.3] 

 b. De minimis demonstration must include, at a minimum: identification of the proposed thermal unit, 

a process description, location, unit manufacturer, unit model, serial number and fuel type used (or 

specify if electric). Identify if any exhaust stacks are shared and if mercury emission controls are 

utilized. [NAC 445B.295] 

 c. Include potential to emit values based on unit operation at maximum design capacity at 8,760 hours 

per year. Supply laboratory test results, performance stack test results and calculations 

implemented to calculate potential to emit mercury emissions. Include a thorough discussion of 

any assumptions. [NAC 445B.295] 

 d. Identify under what Air Quality Operating Permit the proposed units are contained and if the 

proposed units are designated as “insignificant” or “non-permitted items.” [NAC 445B.295] 
Page 7 

APPLICATION INFORMATION (CONTINUED)

9. The application must also contain: 

 a. An identification of each thermal unit that emits mercury. In addition to the identification of each 

thermal unit that emits mercury, please complete Section 1 of the Mercury Unit application form in 

Appendix 1. Complete a separate Mercury Unit application form for each thermal unit that emits 

mercury. [NAC 445B.3671.2 and NAC 445B.3681.2] 

 b. A description of the production rates, operating schedules, fuels, fuel use and raw materials to be used 

for each thermal unit that emits mercury. In addition to the description, please complete Sections 2 

and 3 of the Mercury Unit application form in Appendix 1. Complete a separate Mercury Unit 

application form for each thermal unit that emits mercury. [NAC 445B.3671.3 and NAC 445B.3681] 

 c. Limitations on the operation of stationary source or thermal unit that emits mercury or any work 

practices which may affect mercury emissions from the thermal unit that emits mercury. Use Sections 

4 and 5 of the Mercury Unit application form in Appendix 1. Complete a separate Mercury Unit 

application form for each thermal unit that emits mercury. [NAC 445B.3671.4 and NAC 

445B.3681.4] 

 d. Requested emissions limits. Use Section 7 of the Mercury Unit application form in Appendix 1. 

Complete a separate Mercury Unit application form for each thermal unit that emits mercury. [NAC 

445B.3671.7 and NAC 445B.3681.7] 

11. Will the construction occur in more than one phase? Yes No 

 If the construction will occur in more than one phase, please provide the projected date of the commencement 

for each phase of construction (include additional phases if necessary): [NAC 445B.3687] 

Phase 1: 

Phase 2: 

Phase 3: 

12. For Application Submittal:

Please remove the cover page, Table of Contents and General Information page. Submit the remainder of the 

application packet as your formal application. This should consist of, at a minimum, the Mercury Operating 

Permit to Construct Application cover page, the general Company Information and Application Information, 

and any applicable Appendices. 
Appendix 1, Page 1 

Appendix 1 

THERMAL MERCURY 

EMITTING UNIT 

APPLICATION FORM 
Appendix 1, Page 2 

Instructions 

PLEASE RESPOND SEPARATELY TO ITEMS 1 through 7 FOR EACH EMISSION UNIT, as 

appropriate. Each emission unit at the stationary source must be identified by completion of the application 

form contained in this appendix. The forms may be duplicated for as many thermal mercury emission units 

as needed. Complete all applicable attachments (Appendix 1) included in this application package [NAC 

445B.295]. 

Section 1. Equipment Description: Describe the processes and products by SIC, including any associated 

with an alternative operating scenario identified in this application, model number, manufacture 

date, dimensions and UTM coordinates. 

Section 2. Design Rate/Operating Parameters: Describe all production rates, operating schedules and 

materials used in the process. 

Section 3. Fuel Usage: Describe all fuels and fuel usage. 

Section 4. Pollution Control Equipment/Exhaust Stack Parameters: Identify and describe all air pollution 

 control equipment. 

Section 5. Work Practice Standards: provide information on limitations on the operation or any standards 

for work practices which affect emissions for all regulated air pollutants. [NAC 445B.295.5] 

Section 6. Compliance Monitoring Devices and Activities: Identify and describe any equipment for the 

control of air pollution and any devices or activities for monitoring compliance with emission 

limitations. 

Section 7. Requested Emission Limits: Provide the requested emission limits for each emission unit. 

Include the emission rates of total mercury . The emission rates must be described in pounds per 

hour and pounds per year and any other units of measure for mercury emissions as may be 

proposed. 

Alternative Operating Scenarios: Complete a separate application form for each emission unit having an 

alternative operating scenario. (A common example of an alternative operating scenario is a steam boiler that 

utilizes natural gas as the primary fuel, but may combust diesel fuel as an alternate fuel source). Please 

check the box in the upper right hand corner of each application form for emission units requesting an 

alternative operating scenario. Additionally, for each emission unit application form requesting an alternative 

operating scenario: 

1. Define each alternative operating scenario; 

2. Provide an alternative monitoring plan for each unit, for which an alternative operating scenario is 

requested, in Appendix 2, if different from the monitoring plan provided for the primary operating 

scenario. Contemporaneous log entries must be provided every time the source changes from one 

scenario to another. 
Appendix 1, Page 3 

System 66A, TU4.013, Autoclave Circuit 1, Autoclave #1

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Check here if this is an 

alternative operating scenario

Section 1 - Equipment Description

a. Type of equipment System 66A, TU4.013, Autoclave Circuit 1, Autoclave #1 

b. Standard Industrial Classification (SIC) Code 1041 

c. Manufacturer of equipment Eaton 

d. Model number not specified Serial number not specified *Equip. number not specified

e. Date equipment manufactured: not specified

f. UTM Coordinates 4,536,042 meters N; 554,723 meters E; Zone 11 

(Please specify NAD 27 or NAD 83 ; Method used to obtain coordinates: AutoCAD file overlay onto USGS map)

g. Basic equipment dimensions (feet): L N/A W N/A H N/A 

*The equipment number is the facility's own numbering system for this piece of equipment. 

Section 2 - Design Rate/Operating Parameters 

a. Maximum design capacity (tons per hour) 130 

b. Requested operating rate (tons per hour)* 

c. Requested operating time: (time of day)* to 

 

 Hours per day 0-24 Days per year 365, 8,760 hr/yr

d. Batch load or charge weight (tons) (if applicable) N/A 

e. Total hours required to process batch or charge (if applicable) N/A 

f. Maximum operating rate (tons per year) not specified 

g. Requested operating rate (tons per year)* 

f. Type of material processed ore

*Note: Please complete if other than the maximum design capacity (tons per hour and tons per year) and/or the maximum hours of 

operation (24 hours per day, 8,760 hours per year) are being requested. The permit will be limited to these values. 
Appendix 1, Page 4 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66A - TU4.013 

Section 3 - Fuel Usage / Heat Source

Electric Unit 

Type of Fuel Amount Used Per 

Hour 

Heat Content 

(specify in Btus) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

( % by 

weight) 

Trace 

Elements 

(% by 

weight) 

Oil- Specify 

Type(s) 

 none gallons N/A N/A N/A N/A 

 none gallons N/A N/A N/A N/A 

Gasoline none gallons N/A N/A N/A N/A 

Propane none cubic feet N/A N/A N/A N/A 

Natural Gas none cubic feet N/A N/A N/A N/A 

*Waste Oil none gallons N/A N/A N/A N/A 

Other none N/A N/A N/A N/A 

Type of 

Coal 

Fuel 

Amount 

Used 

Per 

Hour 

(tons) 

Heat 

Content 

(specify 

in 

BTUs) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

(% by 

weight) 

Trace 

Elements 

(% by 

weight) 

Percent 

moisture 

Percent 

volatile 

matter 

Percent 

fixed 

carbon 

Coal - 

Specify 

Type(s) 

 

none N/A N/A N/A N/A N/A N/A N/A N/A 

 

If more than one type of fuel is combusted, under this operating scenario please specify primary fuel and percentage on a 

maximum hourly and annual basis (if fuel blending is the primary fuel, identify percentages of each fuel blended). Attach 

additional information to this form if necessary. 

*Firing of waste oil will require multi metals test to insure fuel is non-hazardous. 
Appendix 1, Page 5 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66A - TU4.013 

Section 4 - Pollution Control Equipment/Exhaust Stack Parameters (this section must be 

completed)

-Complete for emissions exhausting through a stack, chimney or vent: (baghouse, wet scrubber, cyclone, 

sulfur impregnated carbon filter, uncontrolled stack, etc.) 

 Control #1* Control #2 

Type of Control 

(See Note 1) venturi wet dust scrubber 

Pollutant(s) Controlled particulates and mercury 

Manufacturer Ducon 

Manufacturer's 

Guarantee (see Note 2) N/A 

Stack height (feet from 

ground level) 100 

Stack inside diameter 

(feet) 3.67 

Temperature (°F) at 

design capacity 223 

Stack exit velocity (feet 

per second) 9.97 

Gas volume flow rate: 

Actual cubic feet per minute 6,330 

Gas volume flow rate: 

Dry standard cubic feet per 

minute

1,395** 

Unusual stack characteristics (e.g. raincap, 

horizontal discharge)

65.2% moisture 

* Stack parameters are taken from the APT 7/29/2009 stack test for Hg. 

** Maximum flow expected to be 2,500 dscfm. 

Note 1: Specify "uncontrolled" if no pollution control device is installed. 

Note 2: Manufacturer's guarantee of control efficiency must be attached to this form. 
Appendix 1, Page 6 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66A - TU4.013 

Section 5 - Identify and Describe Work Practice Standards, Etc. (attach additional pages if necessary) 

(Eg., 1. Baghouse housing and bags will be inspected weekly for holes/leaks.) 

Work Practices: 

Autoclave #1: 

(a) The carbonate/sulfide ratio of the ore slurry feed will be maintained below 3. 

Venturi Scrubber: 

(a) The pressure drop across the venturi scrubber will be maintained at or below 70 inches of water. 

(b) The water flow rate to the venturi scrubber will be maintained at or above 50 gallons per minute. 

Section 6 - Identify and Describe Compliance Monitoring Devices or Activities (attach additional 

pages if necessary) 

(Eg., Emissions from this unit will be monitored by CEMS for mercury.) 

Monitoring and Recordkeeping: 

(a) The carbonate/sulfide ratio of the ore feed to Autoclave #1 (TU4.013) will be monitored and recorded once, 

during each shift that TU4.013 is in operation. 

(b) The pressure drop across the venturi scrubber will be monitored and recorded once, during each day of 

operation. 

(c) The water flow rate to the venturi scrubber will be monitored and recorded once, during each day of 

operation. 

Testing Requirements: 

Annual Testing

Before the conclusion of the calendar year, Permittee shall conduct and record a Method 29 (or alternative test method 

approved by the Director) compliance test for mercury on the exhaust stack of TU4.013. 

Annual Reporting

The Permittee shall: 

1. Report the mercury co-product on an annual basis. 

2. Report the mercury emissions on an annual basis which must be based on mercury emissions test data.
Appendix 1, Page 7 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66A - TU4.013 

Section 7 - Proposed Emission Rates

Pollutant Potential to 

Emit 

(pounds/hour*)

Potential to Emit 

(tons/year) 

Calculation (including reference or emissions 

tests) on Which Emissions Information is Based 

(attach supporting information including dates of 

tests/methods, if necessary) 

Total Mercury (all 

forms) 0.0214 0.094 Based on proposed concentration standard, maximum flow, and annual operating limit. 

Total Mercury 

(alternative emissions 

limitations) 

4 x 10-4 gr/dscf Proposed interim NvMACT emission limit. See 

page 3 of Appendix 2. 

 

 

 

 

 

*Note: In addition to lb/hr, alternative emissions limitations (e.g., lb/MMBtu, ppm, grains/dscf) may be requested by the applicant. If alternative 

emissions limitations are requested, please clearly describe the units in column 2 above. Use additional lines, as needed. 
Appendix 1, Page 8 

System 66B, TU4.014-TU4.015, Autoclave Circuit 2, Autoclaves #2 & #3

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

MERCURY OPERATING PERMIT TO CONSTRUCT 

Check here if this is an 

alternative operating scenario

Section 1 - Equipment Description

a. Type of equipment System 66B, TU4.014-TU4.015, Autoclave Circuit, Autoclaves #2 & #3

b. Standard Industrial Classification (SIC) Code 1041 

c. Manufacturer of equipment Eaton 

d. Model number not specified Serial number not specified *Equip. number not specified

e. Date equipment manufactured: 1991

f. UTM Coordinates 4,536,082 meters N; 554,709 meters E; Zone 11 

(Please specify NAD 27 or NAD 83 ; Method used to obtain coordinates: AutoCAD file overlay onto USGS map)

g. Basic equipment dimensions (feet): L N/A W N/A H N/A 

*The equipment number is the facility's own numbering system for this piece of equipment. 

Section 2 - Design Rate/Operating Parameters 

a. Maximum design capacity (tons per hour) 200, each 

b. Requested operating rate (tons per hour)* 

c. Requested operating time: (time of day)* to 

 

 Hours per day 0-24 Days per year 365, 8,760 hr/yr, each

d. Batch load or charge weight (tons) (if applicable) N/A 

e. Total hours required to process batch or charge (if applicable) N/A 

f. Maximum operating rate (tons per year) not specified 

g. Requested operating rate (tons per year)* 

f. Type of material processed ore

*Note: Please complete if other than the maximum design capacity (tons per hour and tons per year) and/or the maximum hours of 

operation (24 hours per day, 8,760 hours per year) are being requested. The permit will be limited to these values. 
Appendix 1, Page 9 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66B - TU4.014-TU4.015 

Section 3 - Fuel Usage / Heat Source

Electric Unit 

Type of Fuel Amount Used Per 

Hour 

Heat Content 

(specify in Btus) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

( % by 

weight) 

Trace 

Elements 

(% by 

weight) 

Oil- Specify 

Type(s) 

 none gallons N/A N/A N/A N/A 

 none gallons N/A N/A N/A N/A 

Gasoline none gallons N/A N/A N/A N/A 

Propane none cubic feet N/A N/A N/A N/A 

Natural Gas none cubic feet N/A N/A N/A N/A 

*Waste Oil none gallons N/A N/A N/A N/A 

Other none N/A N/A N/A N/A 

Type of 

Coal 

Fuel 

Amount 

Used 

Per 

Hour 

(tons) 

Heat 

Content 

(specify 

in 

BTUs) 

Ash 

Content 

(% by 

weight) 

Sulfur 

Content 

(% by 

weight) 

Trace 

Elements 

(% by 

weight) 

Percent 

moisture 

Percent 

volatile 

matter 

Percent 

fixed 

carbon 

Coal - 

Specify 

Type(s) 

 

none N/A N/A N/A N/A N/A N/A N/A N/A 

 

If more than one type of fuel is combusted, under this operating scenario please specify primary fuel and percentage on a 

maximum hourly and annual basis (if fuel blending is the primary fuel, identify percentages of each fuel blended). Attach 

additional information to this form if necessary. 

*Firing of waste oil will require multi metals test to insure fuel is non-hazardous. 
Appendix 1, Page 10 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66B - TU4.014-TU4.015 

Section 4 - Pollution Control Equipment/Exhaust Stack Parameters (this section must be 

completed)

-Complete for emissions exhausting through a stack, chimney or vent: (baghouse, wet scrubber, cyclone, 

sulfur impregnated carbon filter, uncontrolled stack, etc.) 

 Control #1* Control #2 

Type of Control 

(See Note 1) venturi wet dust scrubber 

Pollutant(s) Controlled particulates and mercury 

Manufacturer Hosokawa 

Manufacturer's 

Guarantee (see Note 2) N/A 

Stack height (feet from 

ground level) 100 

Stack inside diameter 

(feet) 6.00 

Temperature (°F) at 

design capacity 197 

Stack exit velocity (feet 

per second) 14.80 

Gas volume flow rate: 

Actual cubic feet per minute 25,106 

Gas volume flow rate: 

Dry standard cubic feet per 

minute

3,927** 

Unusual stack characteristics (e.g. raincap, 

horizontal discharge)

76.1% moisture 

* Stack parameters are taken from the APT 7/28 & 7/30/2009 stack test for Hg. 

** Maximum flow expected to be 5,000 dscfm. 

Note 1: Specify "uncontrolled" if no pollution control device is installed. 

Note 2: Manufacturer's guarantee of control efficiency must be attached to this form. 
Appendix 1, Page 11 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66B - TU4.014-TU4.015 

Section 5 - Identify and Describe Work Practice Standards, Etc. (attach additional pages if necessary) 

(Eg., 1. Baghouse housing and bags will be inspected weekly for holes/leaks.) 

Work Practices: 

Autoclaves #2 & #3: 

(a) The carbonate/sulfide ratio of the ore slurry feed will be maintained below 3. 

Venturi Scrubber: 

(a) The pressure drop across each venturi scrubber will be maintained at or below 70 inches of water. 

(b) The water flow rate to each venturi scrubber will be maintained at or above 50 gallons per minute. 

Section 6 - Identify and Describe Compliance Monitoring Devices or Activities (attach additional 

pages if necessary) 

(Eg., Emissions from this unit will be monitored by CEMS for mercury.) 

Monitoring and Recordkeeping: 

(a) The carbonate/sulfide ratio of the ore feed to Autoclaves #2 and #3 (TU4.014 & TU4.015) will be monitored 

and recorded once, during each shift that TU4.014 and TU4.015, each is in operation. 

(b) The pressure drop across each venturi scrubber will be monitored and recorded once, during each day of 

operation. 

(c) The water flow rate to each venturi scrubber will be monitored and recorded once, during each day of 

operation. 

Testing Requirements: 

Annual Testing

Before the conclusion of the calendar year, Permittee shall conduct and record a Method 29 (or alternative test method 

approved by the Director) compliance test for mercury on the exhaust stack of TU4.014 and TU4.015. 

Annual Reporting

The Permittee shall: 

1. Report the mercury co-product on an annual basis. 

2. Report the mercury emissions on an annual basis which must be based on mercury emissions test data.
Appendix 1, Page 12 

THERMAL MERCURY EMITTING UNIT 

APPLICATION FORM 

(CONTINUED) 

For Unit: System 66B - TU4.014-TU4.015 

Section 7 - Proposed Emission Rates

Pollutant Potential to 

Emit 

(pounds/hour*)

Potential to Emit 

(tons/year) 

Calculation (including reference or emissions 

tests) on Which Emissions Information is Based 

(attach supporting information including dates of 

tests/methods, if necessary) 

Total Mercury (all 

forms) 0.0429 0.188 Based on proposed concentration standard, maximum flow, and annual operating limit. 

Total Mercury 

(alternative emissions 

limitations) 

4 x 10-4 gr/dscf Proposed interim NvMACT emission limit. See 

page 3 of Appendix 2. 

 

*Note: In addition to lb/hr, alternative emissions limitations (e.g., lb/MMBtu, ppm, grains/dscf) may be requested by the applicant. If alternative 

emissions limitations are requested, please clearly describe the units in column 2 above. Use additional lines, as needed. 
Appendix 2, Page 1 

Appendix 2 

Monitoring Plan 

For Each: 

(Check Appropriate Box) 

 Phase 1, Tier 1; 

 Phase 1, Tier 2; 

 Phase 2; or 

 New or Modified 

Thermal Mercury Emitting Unit 
Appendix 2, Page 2 

PHASE 2 MONITORING PLAN 

Air Pollution Equipment: 

(a) Exhaust gases from TU4.013 (System 66A, Autoclave # 1) shall be ducted to a control system consisting of: 

a. Venturi wet dust scrubber on the exhaust stream of TU4.013 

(b) Exhaust gases from TU4.014 and TU4.015 (System 66B, Autoclaves #2 and #3) shall be ducted to a control system 

consisting of: 

a. Venturi wet dust scrubber on the exhaust stream of TU4.014 

b. Venturi wet dust scrubber on the exhaust stream of TU4.015 

(c) Stack Parameters for TU4.013 

a. Height: 100 ft 

b. Diameter: 3.67 ft 

c. Stack Temperature: Approximately 223°F 

d. Flow: Maximum volume flow rate of approximately 2,500 dry standard cubic feet per 

minute (dscfm) 

(d) Stack Parameters for TU4.014 and TU4.015 

a. Height: 100 ft 

b. Diameter: 6.0 ft 

c. Stack Temperature: Approximately 197°F 

d. Flow: Maximum volume flow rate of approximately 5,000 dry standard cubic feet per 

minute (dscfm) 

Operating Requirements: 

(a) Limitations of operation 

a. The maximum allowable throughput rate for TU4.013 shall not exceed 130 tons per any one-hour period. 

b. The maximum allowable throughput rate for TU4.014 and TU4.015, each, shall not exceed 200 tons per any 

one-hour period. 

c. The interim mercury emission limit during the demonstration period for establishment of the final mercury 

emission limit for TU4.013 through TU4.015, each, shall be 4x10-4 gr/dscf mercury. 

d. Hours 

i. TU4.013 through TU4.015, each, may operate 24 hours per day 

ii. TU4.013 through TU4.015, each, may operate 8,760 hours per calendar year. 

Work Practices: 

Autoclaves #1 through #3: 

(a) The carbonate/sulfide ratio of the ore slurry feed to each autoclave will be maintained below 3. 

Venturi Scrubbers: 

(b) The pressure drop across each venturi scrubber will be maintained at or below 70 inches of water. 

(c) The water flow rate to each venturi scrubber will be maintained at or above 50 gallons per minute. 

Monitoring and Recordkeeping: 

(a) The carbonate/sulfide ratio of the ore feed to each autoclave will be monitored and recorded once, during each shift 

that each autoclave is in operation. 

(b) The pressure drop across each venturi scrubber will be monitored and recorded once during each day of operation. 

(c) The water flow rate to each venturi scrubber will be monitored and recorded once during each day of operation. 

Testing Requirements: 

Annual Testing

Before the conclusion of the calendar year, Permittee shall conduct and record a Method 29 (or alternative test method approved

by the Director) compliance test for mercury on the exhaust stacks of TU4.013 and TU4.014/TU4.015, each. 

Annual Reporting

The Permittee shall: 

1. Report the mercury co-product on an annual basis. 

2. Report the mercury emissions on an annual basis which must be based on mercury emissions test data. 
PROJECT TITLE: BY:

Air Sciences Inc. Barrick Goldstrike E. Steen

PROJECT NO: PAGE: OF: SHEET:

59-43-80 1 1 1

ENGINEERING CALCULATIONS SUBJECT: DATE:

Autoclave Hg Standard August 9, 2010

Autoclave stack test data

Emissions

Unit Control lb/hr gr/dscf Test Info

Autoclave 1 Venturi Scrubber 6.63E-03 3.05E-04 8/28/1990

Autoclave 1 Venturi Scrubber 2.30E-03 1.40E-04 07/10/1991

Autoclave 2 & 3 Venturi Scrubber 1.23E-03 2.01E-05 09/17/1992

Autoclave 4 Venturi Scrubber 1.13E-03 1.37E-04 05/02/2006

Autoclave 4 Venturi Scrubber 2.87E-03 2.63E-04 05/03/2006

Autoclave 4 Venturi Scrubber 1.07E-03 6.20E-05 07/23/2009

Autoclave 5 & 6 Venturi Scrubber 1.17E-03 3.65E-05 07/24/2009

Autoclave 2 & 3 Venturi Scrubber 8.63E-04 2.55E-05 07/28/2009

Autoclave 1 Venturi Scrubber 7.13E-04 5.92E-05 07/29/2009

Autoclave 2 & 3 Venturi Scrubber 9.00E-04 3.53E-05 04/28/2010

Autoclave 5 & 6 Venturi Scrubber 3.30E-03 9.49E-05 06/08/2010

Average Hg Concentration 1.1E-04 gr/dscf

Standard Deviation 9.7E-05 gr/dscf

Three standard deviations 2.9E-04 gr/dscf

99.7% confidence interval 4.0E-04 gr/dscf

NvMACT Standard 4.0E-04 gr/dscf

Appendix 2, Page 3

0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

3.00E-04

3.50E-04

Hg Concentration (gr/dscf)

Autoclaves Hg Concentration from Stack Testing

Appendix 2, Page 3
Appendix 3, Page 1 

Appendix 3 

Nevada MACT Analysis 

For Each: 

(Check Appropriate Box) 

 Phase 2; 

 New or Modified; or 

 Not Applicable 

Thermal Mercury Emitting Unit 
Appendix 3, Page 2 

CONTENTS Page

BARRICK GOLDSTRIKE MINES INC. (GOLDSTRIKE) NVMACT ANALYSIS FOR AUTOCLAVES 1 THROUGH 3 ..................... 4

Introduction ................................................................................................................................................................................... 4

Source Description ....................................................................................................................................................................... 4

NvMACT Analysis ......................................................................................................................................................................... 7

Part I – Existing Similar Thermal Units ..................................................................................................................................... 7

Mercury Controls ............................................................................................................................................... 7

Wet Scrubbers ................................................................................................................................................ 7

Work Practices ................................................................................................................................................... 9

Mercury Emissions ............................................................................................................................................ 9

Mercury Control Costs .................................................................................................................................... 11

Non-Air Quality Health and Environmental Impacts and Energy Requirements ............................................ 12

Part II – Other Controls and/or Work Practices ...................................................................................................................... 13

Other Mercury Control Options ....................................................................................................................... 13

Boliden Norzinc ........................................................................................................................................... 13

Selenium Scrubbers ..................................................................................................................................... 14

Wet Electrostatic Precipitators ..................................................................................................................... 14

Activated Carbon Filters .............................................................................................................................. 14

Activated Carbon Injection .......................................................................................................................... 25

Selenium Filters ........................................................................................................................................... 25

Condensers ................................................................................................................................................... 26

Other Work Practices ....................................................................................................................................... 26

Part III - Proposed NvMACT .................................................................................................................................................. 28

Analysis of NvMACT Criteria ........................................................................................................................ 29

445B.3677.3(b)(1)(I) – The Cost of Achieving Mercury Emissions Reduction .......................................... 29

445B.3677.3(b)(1)(II) – Non-air Quality Health and Environmental Impacts and Energy Requirements .. 32

445B.3677.3(b)(2) – Process Changes or Substitution of Materials to Reduce Mercury Emissions ........... 33

445B.3677.3(b)(3) – Enclosure of Systems or Processes to Eliminate Mercury Emissions ........................ 33

445B.3677.3(b)(4) – Collection, Capture or Treatment of Mercury Emissions .......................................... 33

445B.3677.3(b)(5) – Design, Equipment, Work Practice, or Operational Standards of the Thermal Unit .. 33

445B.3677.3(b)(6) – Differences in Age, Remaining Operating Life, Configurations, Ore Mercury 

Concentration, Size, and Any Other Relevant Factors of the Similar Thermal Units .................................. 33

Proposed NvMACT ......................................................................................................................................... 34

Proposed Mercury Emission Limit .................................................................................................................. 35

ENDNOTES .................................................................................................................................................................................... 36

Appendix A - General Arrangement ........................................................................................................................................... 38 

Appendix B - Piping and Instrumentation Diagrams ................................................................................................................... 48

Appendix C - Process Flow Diagrams ........................................................................................................................................ 65

Appendix D - Process Design Criteria ........................................................................................................................................ 69
Appendix 3, Page 3 

Tables 

Table 3.1: Autoclave Stack Testing Mercury Emissions Summary .............................................................................................. 10 

Table 3.2: Autoclave Stack Test Mercury Speciation .................................................................................................................. 11 

Table 3.3: Capital and Annual Operating Costs of Option 1 ........................................................................................................ 16 

Table 3.4: Capital and Annual Operating Costs of Option 2 ........................................................................................................ 18 

Table 3.5: Capital and Annual Operating Costs of Option 3 ........................................................................................................ 19 

Table 3.6: Capital and Annual Operating Costs of the Alkaline Control System ......................................................................... 22 

Table 3.7: Installation and Operating Costs of the Acidic Control System ................................................................................... 24 

Table 3.8: Acidic Autoclaving Mercury Volatilization .................................................................................................................... 27 

Table 3.9: Annual Mercury Emissions from Acidic Operation of Autoclaves 1 through 3 ............................................................ 29 

Table 3.10: Installation and Operating Costs of the Acidic Control System ................................................................................. 30 

Table 3.11: Annualized Installation and Operating Costs of the Acidic Control System .............................................................. 31 

Table 3.12: Cost Effectiveness of the Acidic Control System ...................................................................................................... 32 

Figures 

Figure 3.1: Autoclave Circuit Process Flow Diagram ..................................................................................................................... 5 

Figure 3.2: Autoclave Circuit Emission Controls ............................................................................................................................ 6 

Figure 3.3: Rectangular Throat Venturi Scrubber .......................................................................................................................... 8 

Figure 3.4: Carbon Adsorption Option 1 ...................................................................................................................................... 16 

Figure 3.5: Carbon Adsorption Option 2 ...................................................................................................................................... 17 

Figure 3.6: Carbon Adsorption Option 3 ...................................................................................................................................... 19 

Figure 3.7: Alkaline Control System ............................................................................................................................................. 21 

Figure 3.8: Acidic Control System ................................................................................................................................................ 23 

Figure 3.9: Mercury Saturation Pressure Curve .......................................................................................................................... 26 
Appendix 3, Page 4 

BARRICK GOLDSTRIKE MINES INC. (GOLDSTRIKE) NVMACT 

ANALYSIS FOR AUTOCLAVES 1 THROUGH 3 

Introduction 

Barrick Goldstrike Mines Inc (Goldstrike) operates six autoclaves that vent to four stacks. The autoclaves 

are used to oxidize sulfide ore with pressure, steam, and oxygen. Historically, Goldstrike has used acidic 

autoclaving to process the sulfide ore; however, due to the changing ore characteristics, Goldstrike plans 

to operate three autoclaves (Autoclaves 4 through 6) in an alkaline mode of operation in the future. In 

June 2010, Goldstrike submitted a Phase-2 Application to modify Autoclaves 4 through 6 for alkaline 

operation. The remaining three autoclaves (Autoclaves 1 through 3) will continue to operate in the acidic 

mode of operation. 

Per NAC 445B.3675.1, a Nevada Maximum Achievable Control Technology (NvMACT) analysis is 

required to be conducted for existing thermal units that emit mercury as a part of the Phase-2 

Application. The NvMACT analysis for Autoclaves 1 through 3 provided herein addresses all the 

requirements of NAC 445B.3675.1. 

Source Description 

In the autoclave circuit, sulfide ore is oxidized (see Figure 3.1). In acidic autoclaving, sulfide ore slurry 

from the wet grinding mills is first thickened in thickener tanks. The slurry is then acidulated with 

sulfuric acid in acidulation tanks. Sulfide ore slurry from the acidulation tanks is pre-heated and then 

oxidized in the autoclaves with pressure, steam, and oxygen. The off-gas from each autoclave passes 

through a dedicated venturi scrubber before being released to the atmosphere (the exhaust from 

Autoclaves 2 and 3 and Autoclaves 5 and 6 are ducted together downstream of the venturi scrubbers for a 

total of four stacks) (see Figure 3.2). When the gas exits the venturi scrubber it is saturated with water. 
Appendix 3, Page 5 

Figure 3.1: Autoclave Circuit Process Flow Diagram 

STEAM

GENERATION

PLANT

TO ATMOSPHERE

SLURRY

COOLER

SURGE

TANKS

FLASH

TANKS

SLURRY

COOLERS

STEAM

AUTOCLAVES

AIR LIQUIDE

OXYGEN PLANT

O2

S2.015 - S2.020

SPLASH

CONDENSERS

COOLING

TOWERS

WATER

ORE

FROM WET GRINDING PROCESS

TO CIL TANKS

SLAKED LIME

LIME

SLAKERS

HEAT

PRE

OXIDATION

THICKENERS

TO

ATMOSPHERE

WET

SCRUBBERS

TO RECLAIM WATER TANK

SULFURIC

ACID

TANKS

ACIDULATION

TANKS

NEUTRALIZATION

TANKS

FLOW OF GOLD

LEGEND:

MINOR FLOW

WATER
Appendix 3, Page 6 

Figure 3.2: Autoclave Circuit Emission Controls 

Autoclave #1

S2.015

Autoclave #1

Venturi

Scrubber

Autoclave #3

S2.017

Autoclave #2

S2.016

Autoclave #2

Venturi

Scrubber

Autoclave #3

Venturi

Scrubber

To Atmosphere

(Stack #2)

To Atmosphere

(Stack #1)

Autoclave #4

S2.018

Autoclave #4

Venturi

Scrubber

Autoclave #6

S2.020

Autoclave #5

S2.019

Autoclave #5

Venturi

Scrubber

Autoclave #6

Venturi

Scrubber

To Atmosphere

(Stack #4)

To Atmosphere

(Stack #3)
Appendix 3, Page 7 

NvMACT Analysis 

Part I – Existing Similar Thermal Units 

Part I of this NvMACT analysis provides a list of the similar existing thermal units used for precious 

metal mining and describes the controls and work practices used to reduce mercury emissions. All 

information required by NAC 445B.3675, as described below, is provided herein: 

NAC 445B.3675 Existing thermal unit that emits mercury: Contents of phase-2 application. 

 1.(b) Sets forth a list of similar thermal units that emit mercury which are used for precious metal mining that 

includes, without limitation: 

 (1) Any methods or technologies to control mercury emissions which are associated with the thermal units that 

emit mercury; 

 (2) The level of mercury emissions associated with each method or technology to control mercury emissions 

from the thermal units that emit mercury; 

 (3) The design for each method or technology to control mercury emissions from the thermal units that emit 

mercury; 

 (4) Costs associated with reductions of mercury emissions as a result of each method or technology to control 

mercury emissions from the thermal units that emit mercury; 

 (5) Costs associated with energy for each method or technology to control mercury emissions from the thermal 

that emit mercury; and 

 (6) Consistent with section 112(d)(2) of the Act, any nonair quality health and environmental impacts and 

energy requirements for each method or technology to control mercury emissions from the thermal units that 

emit mercury. 

Mercury Controls 

An examination of the Nevada Mercury Control Program (NMCP) Phase-2 Applications1 showed that 

there is only one other precious metal mining facility in Nevada with an existing autoclave circuit. At 

both Goldstrike and Newmont Twin Creeks, the existing control for these thermal units is venturi wet 

scrubbers. 

Wet Scrubbers 

All of the existing autoclaves employ a venturi scrubber as an off-gas control. The venturi scrubbers are 

installed primarily to control particulate emissions. Wet scrubbers may control oxidized mercury,2 as this 

form of mercury is soluble in the scrubber water, and elemental mercury, if the scrubber exhaust 

temperature is decreased to below the mercury saturation temperature. 

Venturi wet scrubbers control particulates, including particulate mercury, through impaction, diffusion, 

interception, and/or adsorption of the pollutant onto droplets of liquid.3 Venturi scrubbers use a 

converging then diverging flow channel such that the area of the channel decreases then increases along 
Appendix 3, Page 8 

the length of the channel. The narrowest area is called the throat. As the exhaust gas enters the venturi 

scrubber, the decrease in area causes the gas velocity and turbulence to increase. The scrubbing water is 

injected either slightly upstream of or directly into the throat section. As the scrubbing solution is 

injected, the turbulence in the throat causes it to atomize, which improves gas-liquid contact.3 After 

passing through the throat, the gas-liquid mixture decelerates and causes additional particle-droplet 

impacts and agglomeration of the droplets. Before the gas exits the scrubber, the liquid droplets are 

separated from the gas in an entrainment section.3 

As the gas passes through the venturi scrubber, there is a drop in pressure. For venturi scrubbers in 

general, the greater the pressure drop, the higher the particulate control efficiency. However, for 

autoclaves, the temperature and pressure of the autoclave itself is maintained by limiting the release of 

steam and off-gas. Therefore, when the gas flow passing through the scrubber is low, there is low 

pressure drop across the scrubber. 

The liquid to gas ratio also affects venturi scrubber efficiency. There must be sufficient liquid injected 

into the scrubber to allow for coverage over the throat area and to create sufficient collection targets. 

After an optimal point, adding excess liquid to a scrubber does not increase the particulate control 

efficiency. The liquid to gas ratio for wet scrubbers typically ranges from 4 to 20 gallons per 1,000 actual 

cubic feet (gal/kacf).4 A diagram of a typical venturi scrubber is provided as Figure 3.3. 

Figure 3.3: Rectangular Throat Venturi Scrubber5
Appendix 3, Page 9 

Work Practices 

Work practices associated with autoclaves and venturi scrubbers include monitoring the autoclave 

throughput and monitoring the venturi scrubber flow rate and pressure drop. Autoclaves operate under 

pressure and are ducted such that all the exhaust is vented through the venturi scrubber. Total exhaust 

flow and emissions are limited by limiting the release of steam and off-gas to the venturi scrubber as 

previously discussed. 

Mercury Emissions 

The actual mercury emissions from the autoclaves at precious metal mining facilities in Nevada were 

obtained from stack tests.6 Table 3.1 provides the pound-per-hour (lb/hr) emission rate as well as the 

mercury concentration data for autoclaves. 
Table 3.1: Autoclave Stack Testing Mercury Emissions Summary

Emissions Hg Conc.

Mine Unit Control lb/hr gr/dscf Test Infoa

Twin Creeks Mine Phase I & II Autoclave Venturi Scrubber 1.16E-01 1.12E-03 10/21/1997

Autoclave Venturi Scrubber 5.77E-02 1.29E-03 06/22/1998

Autoclave Venturi Scrubber 1.53E-02 6.57E-04 01/27/2001

Phase I Autoclave Venturi Scrubber 8.25E-02 1.27E-03 10/04/2005

Phase I Autoclave Venturi Scrubber 3.87E-02 5.81E-04 10/04/2005

Phase I Autoclave Venturi Scrubber 5.26E-02 9.68E-04 06/13/2007

Phase I Autoclave Venturi Scrubber 4.34E-02 8.37E-04 06/13/2007

Phase I Autoclave Venturi Scrubber 6.55E-02 1.02E-03 06/15/2007

Phase I Autoclave Venturi Scrubber 6.62E-02 1.15E-03 06/15/2007

Phase II Autoclave Venturi Scrubber 3.30E-02 6.06E-04 06/16/2007

Phase II Autoclave Venturi Scrubber 2.54E-02 4.23E-04 06/16/2007

Phase I Autoclave Venturi Scrubber 8.47E-02 1.72E-03 08/18/2008

Phase II Autoclave Venturi Scrubber 3.30E-02 6.73E-04 08/21/2008

Barrick Goldstrike Mine Autoclave 1 Venturi Scrubber 6.63E-03 3.05E-04 08/28/1990

Autoclave 1 Venturi Scrubber 2.30E-03 1.40E-04 07/10/1991

Autoclave 2 & 3 Venturi Scrubber 1.23E-03 2.01E-05 09/17/1992

Autoclave 4 Venturi Scrubber 1.13E-03 1.37E-04 05/02/2006

Autoclave 4 Venturi Scrubber 2.87E-03 2.63E-04 05/03/2006

Autoclave 4 Venturi Scrubber 1.07E-03 6.20E-05 07/23/2009

Autoclave 5 & 6 Venturi Scrubber 1.17E-03 3.65E-05 07/24/2009

Autoclave 2 & 3 Venturi Scrubber 8.63E-04 2.55E-05 07/28/2009

Autoclave 1 Venturi Scrubber 7.13E-04 5.92E-05 07/29/2009

Autoclave 2 & 3 Venturi Scrubber 9.00E-04 3.53E-05 04/28/2010b

Autoclave 5 & 6 Venturi Scrubber 3.30E-03 9.49E-05 06/08/2010b

a

 Obtained from the Nevada Mercury Control Program (NMCP) Mercury Emission Management System (MEMS) database.

b

 Source Emissions Test Report for Barrick Goldstrike Mines, Inc. Mercury Testing - EPA Method 29. MOPTC No. AP1041-2221. APT Project

 BAR0064. August 6, 2010. 

Appendix 3, Page 10
Appendix 3, Page 11 

Ontario Hydro Method (OHM) stack test reports provided mercury speciation data for the autoclaves at 

Goldstrike. Flue-gas Absorbent Mercury Speciation (FAMS) test data was available for Newmont Twin 

Creeks. For all these autoclaves, the test data is representative of an autoclave controlled by a venturi wet 

scrubber. The mercury speciation data is provided in Table 3.2. 

Table 3.2: Autoclave Stack Test Mercury Speciation7,8,9

Mine Source Controls 

Elemental

Mercury 

Oxidized 

Mercury 

Particulate

Mercury 

Goldstrike Autoclave 1 Venturi Scrubber 92.8% 5.1% 2.2% 

 Autoclaves 2 & 3 Venturi Scrubber 69.8% 23.3% 6.9% 

 Autoclave 4 Venturi Scrubber 78.1% 8.3% 13.6% 

 Autoclaves 5 & 6 Venturi Scrubber 66.4% 26.8% 6.7% 

Twin Creeks Phase I Autoclave Venturi Scrubber 97.9% 1.6% 0.5% 

Average 81.0% 13.0% 6.0% 

As shown by Table 3.2, a majority of the emissions from the existing autoclaves is in the form of 

elemental mercury (81 percent on average). A smaller percentage of the emissions is oxidized mercury 

(13 percent on average), and the remaining smallest percentage of emissions is particulate mercury (6 

percent on average). 

Mercury Control Costs 

The Phase-2 Applications submitted by precious metal mining facilities in Nevada provided estimated 

total installed costs for the existing mercury controls for autoclaves. According to Newmont Twin 

Creek’s Phase-2 Application, the total installed costs of their venturi scrubbers for Autoclaves 1 and 2 

were $347,000 and $364,000 in 2007 dollars, respectively. The annual operating and maintenance costs 

were not provided. 

Annual utility costs represent the cost of the energy required for each of the control technologies. Venturi 

scrubbers require energy for the pumps that circulate scrubber solution through the system. Due to the 

fact that autoclaves are pressurized, the venturi scrubbers do not require a fan to push the exhaust 

through the scrubbers. According to the EPA Control Cost Manual, for a typical venturi scrubber with a 

liquid flow rate of 10 gallons per minute (gpm), a pressure of 20 pounds per square inch gauge (psig), 

and a pressure drop of 15 inches of water gauge (in. H2O g), the water pump energy requirement is 

estimated to be 0.233 horsepower per thousand cubic feet per minute (hp/1,000 cfm).3 Assuming 24 

hours per day and 7 days per week operation and an electricity cost of 9 cents per kilowatt-hour (kW-hr), 

the annual utility cost of a venturi scrubber with a gas flow rate of 30,000 actual cubic feet per minute 

(acfm) is approximately $4,000. 
Appendix 3, Page 12 

Non-Air Quality Health and Environmental Impacts and Energy Requirements 

For autoclaves, the typical venturi scrubber installation uses process water as the scrubbing solution. 

This results in non-air quality health and environmental impacts from the discharge of the scrubbing 

solution. Venturi scrubbers also cause non-air quality health and environmental impacts from the 

increased energy consumption due to the scrubber water pump. For a typical venturi scrubber with a gas 

flow rate of 30,000 acfm, the energy requirement is estimated at 46,000 kW-hr/yr. 
Appendix 3, Page 13 

Part II – Other Controls and/or Work Practices 

This part of the NvMACT analysis examines other control options and/or work practices that are not 

currently employed on existing autoclaves. (See Part I.) 

Other Mercury Control Options 

In addition to the mercury technologies employed at existing autoclaves at precious metal mining 

facilities in Nevada, other mercury control options for autoclaves have been examined. These control 

technologies include: 

 Boliden Norzinc, 

 selenium scrubbers, 

 wet electrostatic precipitators (ESPs), 

 activated carbon filters, 

 activated carbon injection, 

 selenium filters, and 

 condensers. 

Boliden Norzinc 

In the Boliden Norzinc process, a mercuric chloride solution reacts with the elemental mercury in the offgas to form a mercurous chloride precipitate, known as calomel, which is settled and recovered. This 

reaction occurs in a packed column. Once the solid is removed, the wash solution can be recirculated. A 

portion of the precipitate can be used to regenerate the mercuric chloride solution using chlorine gas.10 

The rest of the calomel is sent off-site for reclamation. The Boliden Norzinc process uses the following 

reaction: 

 HgCl2(sol’n) + Hg(gas) → 2HgCl(solid)

The Boliden Norzinc process is installed at Goldstrike’s roasters, which have a gas stream with high 

mercury content. The Boliden Norzinc process can achieve outlet concentrations of 0.03 to 0.05 mg/Nm3. 

Because these outlet concentrations are similar to the outlet mercury concentrations from the autoclaves, 

the Boliden Norzinc process would not be expected to provide significant additional mercury control. 

The ideal operating temperature for the Boliden Norzinc process is 104 ̊F. The average outlet 

temperature for autoclaves is approximately 190 ̊F, and would therefore require gas stream cooling 

before control by the Boliden Norzinc process. The cooling of the saturated gas stream would require 

significant energy input, as energy is required to both condense the water and cool the gas stream. At the 

Goldstrike autoclaves, over 100 million British thermal units per hour (MMBtu/hr) would be required to 

cool the combined gas stream to 100 ̊F. 
Appendix 3, Page 14 

The Boliden Norzinc process has not been applied to an existing autoclave at precious metal mining 

facilities in Nevada. Thus, there is no basis for assessing its performance in such an application given the 

dissimilarities between the autoclaving process (and its characteristic emission stream) and those 

units/emission streams where Boliden Norzinc has been applied. In addition, this technology requires a 

significant capital investment and results in increased wastewater (process water containing chloride 

ions) and solid waste (calomel). 

Selenium Scrubbers 

Selenium scrubbers use selenium or a selenium compound within a scrubber to react with the elemental 

mercury in the off-gas to form mercuric selenide (HgSe). Mercuric selenide has a lower vapor pressure 

than other common mercury compounds, which allows for mercury capture. The mercuric selenide is 

removed in a sludge separation circuit, which requires a thickener and HgSe reclamation. Sulfuric acid, 

at concentrations between 10 and 60 percent, is used as the wash solution for the process. 

Selenium scrubbers are appropriate for gas streams with high mercury loading. The outlet 

concentrations from this process are typically higher than the concentrations achieved from the Boliden 

Norzinc process discussed above. Selenium scrubbers are not widely used due to the low removal 

efficiencies as well as the expensive reagent and reclamation requirements. 

Wet Electrostatic Precipitators 

Wet electrostatic precipitators (ESPs) use electrostatic charges to move particulates from a gas stream 

onto a collection surface. The electric field is created through electrodes that are maintained at a high 

voltage. Wash water is used to clean the particulates from the collection plates.10 Wet ESPs are designed 

for saturated gas streams and have a maximum operating temperature of 170 to 190 ̊F. Wet ESPs will 

collect dust, fumes, aerosol mist, and liquid droplets from a gas stream; however, they do not provide 

any effective control of oxidized or elemental mercury.10 Therefore, gaseous elemental and oxidized 

mercury, which is a majority of autoclave mercury emissions, will not be controlled. The particulate 

mercury is already controlled by the existing venturi scrubber. 

Activated Carbon Filters 

Carbon adsorption filters use activated carbon particles to adsorb mercury from the gas stream. 

Adsorption occurs when gas molecules are passed through a bed of solid particles, and the gas molecules 

migrate from the gas stream to the surface of the solids, where they are held by physical attraction.11 

Carbon impregnated with elemental sulfur increases the adsorption efficiency of the beds due to the 

mercury reacting with the sulfur to form mercury sulfide (HgS). Mercury sulfide has a lower vapor 

pressure than elemental mercury and is more readily removed.10 

Activated carbon beds control all types of mercury: particulate-bound, oxidized, and elemental. The 

mercury in the gas stream is adsorbed to the carbon and collected as carbon loaded with mercury. Once 

the carbon reaches adsorptive capacity, it is replaced, and the spent carbon is reclaimed. Monitoring of 

the carbon bed mercury content is performed to ensure that the mercury loading does not exceed the 
Appendix 3, Page 15 

value recommended by the manufacturer. For activated carbon beds, the typical carbon loading capacity 

is approximately 20 percent (or more) mercury by weight.12,13 Carbon mercury loading can be monitored 

directly, or the mercury concentration in the exhaust at the outlet of the carbon bed can be monitored to 

ensure the effectiveness of the carbon adsorber. 

Some factors that can affect carbon bed adsorption efficiency include residence time of the gas in the 

carbon bed, carbon particle size, and exhaust stream moisture content. Longer residence times (a lower 

flow rate and larger carbon bed with more carbon mass increases the residence time) and smaller carbon 

particle sizes increase the mercury removal efficiency of the carbon bed.10 Excessive water collection in a 

carbon filter will reduce control efficiency. Water can enter the pore structure of the carbon and block 

active adsorption sites, reducing the surface area available for mercury collection. 

Original Carbon Filter Control Design 

In February 2008, the possibility of controlling all six autoclaves at Goldstrike with carbon adsorption 

technology was investigated. To accommodate the specific conditions at Goldstrike, three different 

options were considered based on the best information available at that time. As discussed below, since 

this initial investigation, further engineering of the add-on carbon adsorption filter control system has 

resulted in a more final design, which supersedes these original three control options. The three original 

control options are summarized below. In each option, the size of the carbon bed was primarily 

determined by the exhaust flow rate entering the bed (i.e., large flow rates require large beds to allow 

sufficient residence time). 

Option 1 included installing an individual carbon filter at each of the stacks, modifying the existing 

venturi scrubbers to convert the mist eliminator portion into cooling towers, installing plate and frame 

heat exchangers at each scrubber, and installing one mechanical draft cooling tower. Autoclave gas 

would be cooled at each scrubber tower and passed directly to a carbon filter. The cooled gas would 

have a lower flow rate and, although still saturated, would contain less water, reducing the amount of 

water vapor entering the carbon filter. The carbon filter on Autoclave 1 would hold 7,140 pounds of 

carbon, the filter on Autoclaves 2 and 3 would hold 18,000 pounds of carbon, the filter on Autoclave 4 

would hold 10,680 pounds of carbon, and the filter on Autoclaves 5 and 6 would hold 18,100 pounds of 

carbon. This option would require significant structural modifications to install a carbon filter and heat 

exchanger at each scrubber tower; however, ductwork would be minimized. Monitoring and 

maintenance would be difficult at the elevation of the towers. The operating complexity of running four 

heat exchangers and four carbon filters would also be much greater than a single condenser and carbon 

filter design. A flow diagram of Option 1 is shown as Figure 3.4, and the capital and annual operating 

costs are shown in Table 3.3. 
Appendix 3, Page 16 

Figure 3.4: Carbon Adsorption Option 1 

Table 3.3: Capital and Annual Operating Costs of Option 1 

Item Description 

Year of 

Quote Cost 

Capital Cost of the Carbon Adsorption Option 1 2007 $ 6,664,000 

Operating Labor ($12.00/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr, 15% for supervision)11 2007 $ 4,968 

Maintenance Labor ($13.20/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr)11 2007 $ 4,752 

Maintenance Materials (100% of maintenance labor)11 2007 $ 4,752 

Utilities (at $0.09/kW-hr) 2007 $ 670,487 

Indirect Annual Cost (including overhead, administration, taxes, 

and insurance)11 2007 $ 275,243 

Annual Operating and Maintenance Cost for Option 1 $ 960,202 

Due to the saturated moisture content in the gas stream, it was uncertain if this option was viable. Three 

vendors were approached to provide a carbon adsorption filter estimate for the analysis. None had 

experience in treating saturated gas streams, especially with such high moisture levels. All were 

concerned that moisture condensing in the filter would negatively affect performance. Removal 

AUTOCLAVE 1

VENTURI SCRUBBER

COOLING

TOWER

CARBON

ADSORBER

AUTOCLAVE 1

EXHAUST

TO

ATMOSPHERE

HEAT

EXCHANGER

AUTOCLAVE 2/3

VENTURI SCRUBBER

CARBON

ADSORBER

AUTOCLAVE 2/3

EXHAUST

TO

ATMOSHPERE

HEAT

EXCHANGER

AUTOCLAVE 5/6

VENTURI SCRUBBER

CARBON

ADSORBER

AUTOCLAVE 5/6

EXHAUST

TO

ATMOSPHERE

HEAT

EXCHANGER

AUTOCLAVE 4

VENTURI SCRUBBER

CARBON

ADSORBER

AUTOCLAVE 4

EXHAUST

TO

ATMOSPHERE

HEAT

EXCHANGER
Appendix 3, Page 17 

efficiency, carbon life expectancy, and optimal filter design were all contingent on determining the effect 

of a high-moisture gas stream. Significant research and testing was still needed to assess the viability of 

this option. 

Option 1 required energy for the four heat exchanger recirculation pumps, two cooling tower 

recirculation pumps, and one cooling tower induced draft fan. Assuming 24 hours per day and 7 days 

per week operation, this equipment required approximately 7,450,000 kilowatt-hours per year (kWhr/yr) of energy. 

Option 2 included installing one large carbon filter for all four autoclaves, one condenser, and one 

mechanical draft cooling tower. The autoclave gas from all four scrubbers would be ducted together to a 

condenser to cool the gas stream. The gas would then be reheated to raise the exhaust temperature above 

the dew point, reducing the risk of water condensing in the carbon filter. The exhaust would then pass 

through one 41,600 pound carbon filter. This option would require significant ductwork; however, the 

equipment would be accessible at ground level. This option tied the four autoclave gas streams together, 

which could cause flow complications. A flow diagram of Option 2 is provided as Figure 3.5, and the 

capital and annual operating costs are shown in Table 3.4. 

Figure 3.5: Carbon Adsorption Option 2 

AUTOCLAVE 1

VENTURI SCRUBBER

COOLING

TOWER

AUTOCLAVE 1

EXHAUST

AUTOCLAVE 2/3

VENTURI SCRUBBER

CARBON

ADSORBER

AUTOCLAVE 2/3

EXHAUST

TO

ATMOSPHERE

AUTOCLAVE 5/6

VENTURI SCRUBBER

AUTOCLAVE 5/6

EXHAUST

AUTOCLAVE 4

VENTURI SCRUBBER

AUTOCLAVE 4

EXHAUST

TO

PROCESS

TO

PROCESS

TO

PROCESS

TO

PROCESS

CONDENSATE TO

PROCESS

SEAL

TANK

ELECTRIC HEATER
Appendix 3, Page 18 

Table 3.4: Capital and Annual Operating Costs of Option 2 

Item Description 

Year of 

Quote Cost 

Capital Cost of the Carbon Adsorption Option 2 2007 $ 10,133,000 

Operating Labor ($12.00/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr, 15% for supervision)11 2007 $ 4,968 

Maintenance Labor ($13.20/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr)11 2007 $ 4,752 

Maintenance Materials (100% of maintenance labor)11 2007 $ 4,752 

Utilities (at $0.09/kW-hr) 2007 $ 620,142 

Indirect Annual Cost (including overhead, administration, taxes, 

and insurance)11 2007 $ 414,003 

Annual Operating and Maintenance Cost for Option 2 $ 1,048,617 

Option 2 required energy for the condensate pump, electric heater, two cooling tower recirculation 

pumps, and one cooling tower induced draft fan. Assuming 24 hours per day and 7 days per week 

operation, this equipment requires approximately 6,890,000 kW-hr/yr of energy. 

Option 3 included installing one large carbon filter for all four autoclaves. The autoclave gas from all 

four scrubbers would be ducted together and passed directly through the 164,000-pound carbon filter. 

The gas would not be cooled. The gas stream entering the carbon filter in this option would have the 

most water vapor of any of the options. Option 3 would require significant ductwork; however, the 

equipment would be accessible at ground level. This option tied the four autoclave gas streams together, 

which could cause flow complications. A flow diagram of Option 3 is provided as Figure 3.6, and the 

capital and annual operating costs are shown in Table 3.5. 
Appendix 3, Page 19 

Figure 3.6: Carbon Adsorption Option 3 

Table 3.5: Capital and Annual Operating Costs of Option 3 

Item Description 

Year of 

Quote Cost 

Capital Cost of the Carbon Adsorption Option 3 2007 $ 6,505,000 

Operating Labor ($12.00/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr, 15% for supervision)11 2007 $ 4,968 

Maintenance Labor ($13.20/hr, 0.5 hr/shift, 2 shifts/day, 360 

days/yr)11 2007 $ 4,752 

Maintenance Materials (100% of maintenance labor)11 2007 $ 4,752 

Indirect Annual Cost (including overhead, administration, taxes, 

and insurance)11 2007 $ 268,883 

Annual Operating and Maintenance Cost for Option 3 $ 283,355 

Option 3 did not require any energy in addition to the current energy requirements. However, as with 

Option 1, it was uncertain if this option was viable due to the very high moisture content in the gas 

stream. Significant research and testing was still needed to assess the viability of this option. 

For all of the options, it was assumed that the autoclaves would provide sufficient pressure so that fans 

would not be required to push or pull the exhaust through the carbon filter(s). 

AUTOCLAVE 1

VENTURI SCRUBBER

COOLING

TOWER

AUTOCLAVE 1

EXHAUST

AUTOCLAVE 2/3

VENTURI SCRUBBER

CARBON

ADSORBER

AUTOCLAVE 2/3

EXHAUST

TO

ATMOSPHERE

AUTOCLAVE 5/6

VENTURI SCRUBBER

AUTOCLAVE 5/6

EXHAUST

AUTOCLAVE 4

VENTURI SCRUBBER

AUTOCLAVE 4

EXHAUST

TO

PROCESS

TO

PROCESS

TO

PROCESS

TO

PROCESS

CONDENSATE TO

PROCESS

SEAL

TANK

ELECTRIC HEATER
Appendix 3, Page 20 

Alkaline Autoclaving Control Design Update 

Since February 2008, Goldstrike has continued to develop the engineering of an add-on carbon 

adsorption filter control option. The latest engineering analysis was conducted for the alkaline mode of 

operation for Autoclaves 4 through 6 (see June 2010 Phase-2 Application). In March 2010, mercury stack 

test data indicated that the mercury emissions from processing ore under alkaline conditions are higher 

than the emissions from acidic autoclaving. (Testing was authorized by NDEP pursuant to NAC 

445B.232.) The additional controls for Autoclaves 4 through 6 were engineered based on this higher 

mercury emission data. 

The engineering analysis for Autoclaves 4 through 6 determined that gas conditioning, to prevent 

condensation in the filter, would be necessary upstream of any carbon filter. This updated design 

analysis of an add-on carbon adsorption filter control eliminated the original Options 1 and 3 as viable 

control options due to the unavoidable water condensation problem inherent to these options. The 

updated design also resolved the combined exhaust flow problem inherent to the original Option 2, but it 

determined that the gas conditioning equipment in Option 2 was grossly under-sized, under-engineered, 

and under-budgeted. 

The June 2010 Phase-2 Application for the alkaline mode of operation for Autoclaves 4 through 6 

proposed an add-on carbon adsorption filter control with upstream gas conditioning (alkaline control 

system). This control system is designed to remove water (and Hg) from the gas stream prior to the 

carbon adsorption filter. The equipment upstream of the carbon filter consists of a secondary venturi 

scrubber, a scrubber mist eliminator, a gas cooling tower, a condenser, a refrigeration unit for the 

condenser, a wet gas separator, a humidity control heater, and a water cooling tower. The water cooling 

tower provides cooling water for the scrubber mist eliminator, gas cooling tower, and refrigeration unit. 

The heater is located downstream of the wet gas separator and raises the exhaust temperature above the 

dew point prior to entering the carbon bed. Figure 3.7 provides a flow diagram of the alkaline control 

system (without the water cooling tower, refrigeration unit, and heater shown). 
Appendix 3, Page 21 

Figure 3.7: Alkaline Control System 

Although the engineering for the alkaline control system has not been finalized, preliminary design 

specifications and cost data were obtained from Aker Solutions. Based on this preliminary data, the 

carbon adsorption filter will contain 12,000 pounds of carbon in the primary bed and 28,800 pounds of 

carbon in the secondary bed, for a total of 40,800 pounds of activated sulfur-impregnated carbon. The 

controls are designed so that the exhaust flow rate through the carbon filter is expected to be 

approximately 15,500 acfm. Based on this flow rate, the residence time would be approximately 1.2 

seconds in the primary bed and 2.8 seconds in the secondary bed, for a total residence time of 4 seconds. 

Appendices A through D provide the general arrangement, piping and instrumentation diagrams, 

process flow diagrams, and process design criteria for the alkaline control system. Estimated capital and 

annual operating costs for the alkaline control system are provided in Table 3.6. 
Appendix 3, Page 22 

Table 3.6: Capital and Annual Operating Costs of the Alkaline Control System 

Item Description Cost Basis 

Capital Costs 

Engineering Costs $ 3,506,350 2010 estimate 

Material Costs $ 13,219,950 2010 estimate

Labor Costs $ 11,583,070 2010 estimate 

Barrick Project Support $ 977,500 2010 estimate 

Total Capital Costs $ 29,286,870 2010 estimate 

Annual Operating Costs 

Operating Labor (4 operators at $90,000/yr) $ 360,000 Per year 

Maintenance Labor (1 maintenance at $90,000/yr) $ 90,000 Per year 

Maintenance Supplies $ 533,774 Per year 

Utilities ($0.08/kW-hr) $ 911,129 Per year 

Consumables (replacement carbon, reagents and 

flocculants, cooling tower treatment chemical) $ 251,550 Per year 

Total Annual Operating Costs $ 2,146,453 Per year 

The alkaline control system requires energy for the venturi scrubber variable throat, venturi 

scrubber/scrubber mist eliminator pump, gas cooling tower pump, condensate pump, effluent pump, 

refrigeration unit, booster fan, cooling tower fans, cooling tower pumps, and humidity control heater. 

The maximum annual estimate of total energy required for these units, assuming 24 hours per day and 7 

days per week operation is 11,389,107 kW-hr/yr. As shown in Table 3.6, assuming an electricity cost of 8 

cents per kW-hr, the total energy cost is $911,129 per year. 

Before the sulfur-impregnated carbon in the carbon filter reaches the maximum carbon loading capacity, 

it will need to be replaced. The new carbon and each carbon replacement will cost approximately 

$82,800. In addition, disposal costs of spent carbon are approximately $2.50 per pound of carbon14 or 

$100,000 per replacement. 

Non-air quality health, environmental, and energy impacts are associated with the alkaline control 

system. The control system will increase energy use due to the additional fans and pumps, as well as the 

energy required to cool the exhaust stream and run the refrigeration unit. The total heat duty of the 

alkaline control system includes the latent heat of condensing the water vapor and the specific heat of 

cooling the exhaust stream. The alkaline control system has a total heat duty of 190 MMBtu/hr. 

The alkaline control system also causes non-air quality health and environmental impacts due to the 

increased water use by the additional controls and the recirculation of water by the cooling tower. The 

water condensed from the exhaust stream must be treated and reused to offset the additional water input. 

The water that is not recirculated in the controls must be sent to water treatment. 
Appendix 3, Page 23 

Furthermore, the shipping and reclamation of the spent carbon and elemental mercury has non-air 

quality health, environmental, and energy impacts. 

Acidic Autoclaving Control Design Update 

Based on the engineering design of the alkaline control system for Autoclaves 4 through 6, Goldstrike has 

investigated the possibility of using a similar control system for the acidic mode of operations at 

Autoclaves 1 through 3. Because of the high moisture content in the exhaust streams from Autoclaves 1 

through 3, gas conditioning (similar to the alkaline control system) would be necessary upstream of any 

carbon filter. Unlike the alkaline operation of Autoclaves 4 through 6, the mercury concentration in the 

exhaust from Autoclaves 1 through 3 is so low that mercury condensation upstream of the carbon bed is 

not practical (see Condenser discussion below). 

The add-on carbon adsorption filter control option for Autoclaves 1 through 3 includes one carbon filter 

(two beds) for all three autoclaves with upstream gas conditioning for water removal (acidic control 

system). The equipment upstream of the carbon filter consists of a secondary venturi scrubber, a 

scrubber mist eliminator, a gas cooling tower, a wet gas separator, a humidity control heater, and a water 

cooling tower. The water cooling tower provides cooling water for the scrubber mist eliminator and gas 

cooling tower. The heater is located downstream of the wet gas separator and raises the exhaust 

temperature above the dew point prior to entering the carbon bed. Figure 3.8 provides a flow diagram of 

the acidic control system (without the water cooling tower shown). 

Figure 3.8: Acidic Control System 

Autoclave #1

S2.015

Secondary

Venturi

Scrubber

Scrubber

Mist

Eliminator

Gas Cooling

Tower

Wet Gas

Separator

Carbon

Filter

Booster

Fan

Autoclave #1

Primary

Venturi

Scrubber

Autoclave #3

S2.017

Autoclave #2

S2.016

Autoclave #2

Primary

Venturi

Scrubber

Autoclave #3

Primary

Venturi

Scrubber

To Atmosphere Humidity Control

Heater

Purge Air
Appendix 3, Page 24 

Due to the low mercury concentration in the exhaust stream, a wet gas condenser and a refrigeration unit 

are not included in the acidic control system. In addition, the exhaust flow rate from the acidic operation 

of the autoclaves is lower than from the alkaline operation; therefore, the exhaust flow rate to the carbon 

bed in the acidic control system would be approximately 54% lower than the exhaust flow rate in the 

alkaline control system. 

Although the engineering for the acidic control system has not been finalized, preliminary design 

specifications and cost data were obtained from Aker Solutions. Based on this preliminary data, the 

carbon adsorption filter will contain 6,600 pounds of carbon in the primary bed and 15,800 pounds of 

carbon in the secondary bed, for a total of 22,400 pounds of activated sulfur-impregnated carbon. The 

exhaust flow rate through the carbon filter is expected to be approximately 8,500 acfm. Based on this 

flow rate, the residence time would be approximately 1.2 seconds in the primary bed and 2.8 seconds in 

the secondary bed, for a total residence time of 4 seconds. 

The general arrangement, piping and instrumentation diagrams, and process flow diagrams for the 

alkaline control system provided in Appendices A through C are also generally applicable to the acidic 

control system. However, there are some differences in the acidic control system, such as lower mercury 

concentration in the exhaust and no condenser and associated refrigeration unit. 

Estimated installation and operating costs for the acidic control system are provided in Table 3.7. 

Operating costs, except carbon replacement and reclamation costs, were estimated from the alkaline 

control system costs (shown in Table 3.6) using the ratio of the total installed cost for the alkaline control 

system to the total installed cost for the acidic control system (i.e., $18,600,000/$29,290,000 = 63.5%). 

Carbon replacement and reclamation costs are based on 22,400 pounds of carbon. 

Table 3.7: Installation and Operating Costs of the Acidic Control System 

Item Description Cost Basis 

Installation Costs $18,600,000 2010 Estimate 

Operating Costs 

Operating Labor and Overhead $229,000 Per year 

Maintenance Labor and Overhead $57,000 Per year 

Maintenance Supplies $339,000 Per year 

Utilities ($0.08/kW-hr) $579,000 Per year 

Carbon Replacement/Reclamation $100,800 Per replacement 

Consumables (reagents and flocculants, cooling tower 

treatment chemical) $107,000 Per year 

The acidic control system requires energy for the venturi scrubber variable throat, venturi 

scrubber/scrubber mist eliminator pump, gas cooling tower pump, effluent pump, booster fan, cooling 

tower fans, cooling tower pumps, and humidity control heater. The maximum annual estimate of total 

energy required for these units, assuming 24 hours per day and 7 days per week operation is 
Appendix 3, Page 25 

approximately 7,233,000 kW-hr/yr. As shown in Table 3.7, assuming an electricity cost of 8 cents per kWhr, the total energy cost is $579,000 per year. 

Before the sulfur-impregnated carbon in the carbon filter reaches the maximum carbon loading capacity, 

it will need to be replaced. The new carbon and each carbon replacement will cost approximately 

$44,800. In addition, disposal costs of spent carbon are approximately $2.50 per pound of carbon14 or 

$56,000 per replacement. 

Non-air quality health, environmental, and energy impacts are associated with the acidic control system. 

The control system will increase energy use due to the additional fans and pumps, as well as the energy 

required to cool the exhaust stream. The total heat duty of the acidic control system includes the latent 

heat of condensing the water vapor and the specific heat of cooling the exhaust stream. The acidic control 

system has a total heat duty of 101 MMBtu/hr. 

The acidic control system also causes non-air quality health and environmental impacts due to the 

increased water use by the additional controls and the recirculation of water by the cooling tower. The 

acidic control system will require 240 gallons per minute (gpm) of additional fresh water. The control 

system will also require shipping and reclamation of the spent carbon, which has non-air quality health 

and environmental impacts. 

Activated Carbon Injection 

Activated carbon injection is similar to activated carbon filters in that activated carbon particles are used 

to adsorb mercury from the gas stream. With carbon injection, the carbon particles are injected directly 

into the gas stream where they adsorb mercury and are then collected in downstream particulate controls 

such as baghouses, wet scrubbers, or wet ESPs. As with activated carbon filters, the control effectiveness 

of activated carbon injection will be limited if water enters the activated adsorption sites. There is no 

precedent for using the carbon injection technology on gas streams with high moisture content as in the 

case of the Goldstrike autoclaves. In addition, the control efficiency for carbon injection is typically lower 

than for carbon beds. Therefore, the appropriate application of the activated carbon technology for 

autoclaves is a carbon adsorption filter. 

Selenium Filters 

Selenium filters are similar to selenium scrubbers in that they use selenium to react with the elemental 

mercury in the gas stream to form mercuric selenide. Selenium filters use a selenium-impregnated 

porous carrier structure which is housed in a cylindrical tower. The selenium filter’s maximum operating 

temperature is approximately 250 ̊F. The filters require a dry gas stream because water will degrade the 

filter media. This provides a significant limitation to its application for the Goldstrike autoclaves. The 

typical filter carrying capacity is between 10 and 15 percent mercury by weight. 

There are only a few installations of selenium filters in the world, primarily in Sweden, and there is no 

operating data from these applications. Selenium filters are expensive to produce and to regenerate. 
Appendix 3, Page 26 

There is no basis to believe that selenium filters would provide a better alternative than activated carbon. 

In addition, there is some concern that the filters cause selenium air emissions. 

Condensers 

Condensers control mercury by cooling a gas stream and causing the elemental mercury to condense. In 

order for condensation to occur with a drop in temperature, the gas stream must be saturated with 

mercury vapor. Mercury saturation is determined by the mercury saturation pressure curve as shown 

below. 

Figure 3.9: Mercury Saturation Pressure Curve15

As shown by Table 3.1, the concentration of mercury in the exhaust from the autoclaves at Goldstrike 

(operating in acidic mode) ranges from 2.01x10-5 to 3.05x10-4 gr/dscf. This concentration is below the 

mercury saturation concentration even if the gas stream is cooled to 32 ̊F. (The saturated mercury 

concentration at 32 ̊F is approximately 9.7x10-4 gr/dscf.15) Therefore, mercury condensation is not an 

effective control technology for the autoclaves at Goldstrike. 

Other Work Practices 

As discussed above, mercury stack testing conducted in March 2010 indicated that the mercury emissions 

from acidic autoclaving are significantly less than the emissions from alkaline autoclaving. (Testing was 

authorized by NDEP pursuant to NAC 445B.232.) By allowing only acidic autoclaving ore to be 

processed by Autoclaves 1 through 3, the mercury emissions from these autoclaves can be minimized. 

0.000

0.005

0.010

0.015

0.020

0.025

0.030

30 50 70 90 110 130 150 170 190

Temperature (F)

Vapor Pressure (kPa)
Appendix 3, Page 27 

All of the autoclaves treat single refractory ores by oxidizing sulfides to sulfates. Sulfides that are present 

in the slurry can encapsulate the gold in sulfide matrices, making it unavailable to cyanide leaching. In 

acidic autoclaving, carbonates in the ore slurry react with sulfuric acid in the acidulation tanks and 

release carbon dioxide. If the ore slurry has too high of a percentage of carbonates, then acidulation with 

sulfuric acid is not viable, and the ore is processed with alkaline autoclaving. To ensure the processing of 

only acidic autoclaving ore, the carbonate/sulfide ratio of the ore slurry can be monitored. 

In addition, using autoclaves in an acidic mode of operation to oxidize ore is an inherently lower mercury 

emitting process. Based on 2007 mercury testing of the post-venturi scrubber emissions at Goldstrike, 

mercury volatilization by the autoclaves operating in an acidic mode is extremely low. As shown in 

Table 3.8, the average mercury volatilization is approximately 0.02 percent. 

Table 3.8: Acidic Autoclaving Mercury Volatilization 

Source 

Hg 

Throughput 

lb/hr 

Hg 

Emissions 

lb/hr 

Hg 

Volatilization 

percentage 

Autoclave 1 4.17 0.00112 0.027 

Autoclave 1 3.58 0.00308 0.086 

Autoclaves 2 and 3 10.06 0.00074 0.007 

Autoclaves 2 and 3 8.62 0.00086 0.010 

Autoclave 4 4.76 0.00018 0.004 

Autoclaves 5 and 6 8.56 0.00137 0.016 

Autoclaves 5 and 6 10.05 0.00069 0.007 

Average 0.022 
Appendix 3, Page 28 

Part III - Proposed NvMACT 

Per NAC 445B.3675.1.(a), the applicant must propose “standards, methods of control or other limitations to be 

applied to the thermal unit for the reduction of mercury emissions that the applicant deems sufficient for the 

Director to determine to be NvMACT for the thermal unit that emits mercury.” Therefore, the NvMACT 

proposed in this part follows the criteria that are required by the Director pursuant to NAC 

445B.3677.3(b). All items considered in this NvMACT analysis are checked in the criteria list provided 

below: 

NAC 445B.3677 Review of and action on application for tier-1 or tier-2 thermal unit that emits mercury. 

3.(b) Make a determination of NvMACT for the thermal unit that emits mercury in which the Director shall consider the 

following for each thermal unit that emits mercury: 

 (1) The maximum degree of reduction of mercury emissions that is achievable for the thermal unit after 

considering: 

(I) The cost of achieving such a reduction; and 

(II) Consistent with section 112(d)(2) of the Act, any nonair quality health and environmental impacts and 

energy requirements for each method or technology to control mercury emissions from the thermal unit 

that emits mercury to implement the NvMACT. 

 (2) The measures that reduce the volume or eliminate mercury emissions through process changes, substitution 

of materials or any other modifications. 

 (3) The enclosure of systems or processes to eliminate mercury emissions. 

 (4) The collection, capture or treatment of mercury emissions. 

 (5) The design, equipment, work practice or operational standards of the thermal unit that emits mercury, 

including, without limitation, the requirements for training and certification of operators of the thermal unit 

that emits mercury. 

 (6) The differences in the age, remaining operating life and configurations of similar thermal units that emit 

mercury. The Director may also consider the differences in the concentration of mercury in the ore, size and 

any other relevant factors of the similar thermal units that emit mercury. 

As discussed in Part I, the control technology currently installed on autoclaves at precious metal mining 

facilities in Nevada is a venturi scrubber. Of the other possible control options, discussed in Part II, the 

carbon adsorption filter is the most potentially viable option. The carbon adsorption filter control option 

is sized at 22,400 pounds and would require upstream gas conditioning to remove the water from the 

exhaust stream. The gas conditioning equipment includes: a secondary venturi scrubber, a scrubber mist 

eliminator, a gas cooling tower, a wet gas separator, a humidity control heater, and a water cooling tower. 

The estimated control efficiency of the carbon filter in the acidic control system (after gas conditioning to 

remove water) is 95 percent or greater for elemental mercury, 50 percent for oxidized mercury, and 25 

percent for particulate mercury. Therefore, it is expected that over 91 percent of the total mercury 

entering the carbon filter will be removed. The acidic control system is not expected to get any control 
Appendix 3, Page 29 

efficiency from mercury condensation in the gas conditioning equipment, as the mercury concentration is 

below the saturated vapor pressure, even at 32F. However, due to the moisture in the exhaust, the gas 

conditioning equipment is necessary for proper operation of the downstream carbon adsorption filter. 

The total amount of mercury emissions available for removal from Autoclaves 1 through 3 is shown in 

Table 3.9. 

Table 3.9: Annual Mercury Emissions from Acidic Operation of Autoclaves 1 through 3 

Autoclave 2007 2008 2009 

Autoclave 1 8.9 8.0 3.9 

Autoclaves 2 and 3 6.3 13.0 6.2 

Total 15.2 21.0 10.1 

Emissions based on stack testing during acidic operation and total annual hours of operation. 

As shown by Table 3.9, the amount of mercury emissions available for control ranges from 10.1 to 21.0 

pounds per year. Therefore, the achievable reduction in mercury emissions by the acidic control system 

is less than 10.1 to 21.0 pounds per year. 

Analysis of NvMACT Criteria 

445B.3677.3(b)(1)(I) – The Cost of Achieving Mercury Emissions Reduction 

The cost of achieving mercury reduction is typically viewed on a cost-benefit basis described as the cost 

effectiveness of the controls. In this case, the cost is the annualized cost of installing and operating the 

control system and the benefit is the annual reduction of mercury emissions (i.e., the lower the cost and 

the higher the mercury emission reduction, the greater the cost effectiveness). The cost to install and 

operate the acidic control system is provided in Table 3.10. 

Operating costs, except carbon replacement and reclamation costs, were estimated from the alkaline 

control system costs (shown in Table 3.6) using the ratio of the total installed cost for the alkaline control 

system to the total installed cost for the acidic control system (i.e. $18,600,000/$29,290,000 = 63.5%). 

Carbon replacement and reclamation costs are based on 22,400 pounds of carbon. 
Appendix 3, Page 30 

Table 3.10: Installation and Operating Costs of the Acidic Control System 

Item Description Cost Basis 

Installation Costs $18,600,000 2010 Estimate 

Operating Costs 

Operating Labor and Overhead $229,000 Per year 

Maintenance Labor and Overhead $57,000 Per year 

Maintenance Supplies $339,000 Per year 

Utilities ($0.08/kW-hr) $579,000 Per year 

Carbon Replacement/Reclamation $100,800 Per replacement 

Consumables (reagents and flocculants, cooling tower 

treatment chemical) $107,000 Per year 

Annualized Cost 

To annualize the costs presented in Table 3.10, one must account for the costs and benefits of the 

investment over a period of time rather than at the moment of purchase. Consequently, several 

assumptions must be made. These assumptions include the useful life of the equipment and the interest 

rate to estimate the time value of money. 

Useful Life:

The useful life of both the autoclaves and the acidic control system are an important aspect of the 

annualized cost. The autoclaves at Goldstrike have a limited supply of ore that can be processed under 

acidic conditions. Goldstrike has proposed to operate Autoclaves 4 through 6 under alkaline conditions 

to extend the life of these autoclaves. However, Autoclaves 1 through 3 are expected to run out of ore 

that can be processed under acid conditions in the near future. 

The exact date that Autoclaves 1 through 3 will run out of feed stock cannot be determined at this time. 

However, Autoclave 1 has already been shut down for all of 2010 due to the limited feed stock. The 

current assessment of ore reserves estimates that the autoclaves have a 6- to 12-month supply of ore that 

can be processed under acidic conditions. This time frame could be extended to 2 years if Autoclaves 4 

through 6 are allowed to process ore under alkaline conditions (i.e., all ore that can be processed under 

acidic conditions would then be reserved for Autoclaves 1 through 3). However, these time frames are 

wholly dependent on known ore reserves. Exploration and ore characteristic analyses continue, which 

could reveal additional ore reserves then are currently known. Thus, the annualized cost provided herein 

is based on an autoclave life range of 2 or more years. 

Because of the limited feed stock, the useful life of the acidic control system is expected to exceed that of 

the autoclaves. In addition, the carbon beds are expected to last the life of the autoclaves. The beds have 

been sized to handle the large exhaust flow rate of the autoclaves in order to provide adequate residence 

time of the exhaust stream; approximately 1.2 seconds on the primary bed and 2.8 seconds on the 
Appendix 3, Page 31 

secondary bed. At the low mercury loading rates, these beds are not expected to reach their mercury 

loading capacity during the life of the autoclaves. (i.e., The mercury emissions from Autoclaves 1 

through 3 have averaged approximately 15 pounds per year during acidic operations. At 22,400 pounds 

of carbon, with a loading capacity of at least 15 percent, the theoretical life of the carbon is over one 

hundred years.) 

As discussed above, the useful life of the acidic control system is expected to be limited by the life of 

Autoclaves 1 through 3. Therefore, the annualized cost analysis is based on a minimum life of 2 years 

and a maximum life of more than 2 years. Because the maximum number of years Autoclaves 1 through 

3 will operate cannot be determined at this time, the longest period provided in Table A.2, Capital 

Recovery Factors for Equal Payments on a Dollar over a Number of Years, of the EPA Control Cost Manual16 of 

25 years is used to provide a conservatively low estimate of the annualized cost. 

Interest Rate:

The annualized cost requires an assumed interest rate to estimate the time value of money. According to 

the EPA Control Cost Manual, types of rates include: the rate of return a firm can obtain by investing, the 

rate at which it can borrow money, the real interest rate, and the social interest rate. In order to define the 

possible of range of annualized costs, the range of interest rates provided in Table A.2, Capital Recovery 

Factors for Equal Payments on a Dollar over a Number of Years, of the EPA Control Cost Manual of 5.5 percent 

to 15 percent is used. Because the rate of return a firm can obtain by investing can be greater than 15 

percent, this range of rates provides a conservatively low estimate of the annualized cost. 

Annualized Cost:

The annualization of the costs presented in Table 3.10 for the ranges of the useful life and the interest rate 

are provided in Table 3.11. As shown in this table, the annualized cost of the acidic control system ranges 

from $2,702,000 per year (at 25 years and 5.5 percent) to $12,786,000 per year (at 2 years and 15 percent). 

Table 3.11: Annualized Installation and Operating Costs of the Acidic Control System 

 Annualized Costs ($/Year) 

Item Description At 25 years; 5.5% At 2 years; 15% 

Installation Costs 

Capitol Recovery $ 1,387,000 $ 11,441,000 

Operating Costs

Operating Labor and Overhead $ 229,000 $ 229,000 

Maintenance Labor and Overhead $ 57,000 $ 57,000 

Maintenance Supplies $ 339,000 $ 339,000 

Utilities ($0.08/kW-hr) $ 579,000 $ 579,000 

Carbon Reclamation $ 4,000 $ 34,000 

Consumables (reagents and flocculants, cooling tower 

treatment chemical) 

 $ 107,000 $ 107,000 

Total Annualized Costs $ 2,702,000 $ 12,786,000 
Appendix 3, Page 32 

Mercury Emission Reduction 

As shown in Table 3.9 above, actual emissions from Autoclaves 1 through 3 have ranged from 10.1 to 21.0 

pounds per year for the last three years. Therefore, the achievable reduction in mercury emissions by the 

acidic control system is less than 10.1 to 21.0 pounds per year. However, for the purposes of determining 

an absolute low cost effectiveness value, the theoretical maximum achievable reduction in mercury 

emissions may be calculated by assuming all three autoclaves operating at the maximum emission rate 

for 8,760 hours per year. 

The maximum emission rate is calculated by multiplying the maximum mercury emission concentration, 

prior to the acidic control system, by the maximum combined exhaust flow rate for Autoclaves 1 through 

3. The maximum emission concentration is estimated at 4.0x10-4 grain per dry standard cubic foot 

(gr/dscf). See the section titled, Proposed Mercury Emission Limit, at the end of this Part. The maximum 

combined exhaust flow rate is 7,500 dry standard cubic feet per minute (dscfm). See Appendix 1. 

Multiplying these values together and by 8,760 hours per year yields 225.3 pounds of mercury per year. 

Cost Effectiveness 

Table 3.12 provides the range of cost effectiveness of the acidic control system for Autoclaves 1 through 3. 

Note that because this analysis requires several assumptions as discussed above, a range is presented so 

that the upper and lower limits of the assumptions are accurately defined. 

Table 3.12: Cost Effectiveness of the Acidic Control System 

 Cost Effectiveness ($/lb) 

Item Description At 25 years; 5.5% At 2 years; 15% 

Actual Mercury Reduction of 21.0 lb/yr $ 129,000 $ 609,000 

Theoretical Maximum Mercury Reduction of 225.3 lb/yr $ 12,000 $ 57,000 

445B.3677.3(b)(1)(II) – Non-air Quality Health and Environmental Impacts and Energy Requirements 

The acidic control system, consisting of the carbon adsorption filter and upstream gas conditioning 

equipment, would cause increased energy requirements. The control system would increase energy use 

due to the additional venturi scrubber variable throat, venturi scrubber/scrubber mist eliminator pump, 

gas cooling tower pump, effluent pump, booster fan, cooling tower fans, cooling tower pumps, and 

humidity control heater. The maximum annual estimate of total energy required for these units, 

assuming 24 hours per day and 7 days per week operation is 7,233,000 kW-hr/yr. Part of the energy 

required by the acidic control system is the energy to cool the exhaust stream. The total heat duty of the 

acidic control system includes the latent heat of condensing the water vapor and the specific heat of 

cooling the exhaust stream. The acidic control system has a total heat duty of 101 MMBtu/hr. 

The acidic control system also causes non-air quality health and environmental impacts due to the 

increased water use by the additional controls and the recirculation of water by the cooling tower. The 

acidic control system will require 240 gallons per minute (gpm) of additional fresh water. The control 
Appendix 3, Page 33 

system will also require shipping and reclamation of the spent carbon, which has non-air quality health 

and environmental impacts. 

445B.3677.3(b)(2) – Process Changes or Substitution of Materials to Reduce Mercury Emissions 

Autoclaves 1 through 3 only operate under an acidic mode of operations and only process acidic 

autoclaving ore. As indicated by the March 2010 stack testing at Goldstrike, mercury emissions from 

acidic autoclaving are significantly lower than alkaline autoclaving. Therefore, processing only acidic 

autoclaving ore minimizes mercury emissions. In addition, acidic autoclaving is an inherently low 

mercury emitting process, as only 0.02 percent of the mercury entering the autoclaves in volatilized. (See 

Table 3.8). 

445B.3677.3(b)(3) – Enclosure of Systems or Processes to Eliminate Mercury Emissions 

The existing venturi scrubber controls are designed so that all emissions from Autoclaves 1 through 3 are 

captured and ducted to the venturi scrubbers. There are no additional enclosures that could be added to 

eliminate mercury emissions. 

445B.3677.3(b)(4) – Collection, Capture or Treatment of Mercury Emissions 

Mercury collection through condensation is not an effective method to reduce mercury emissions from 

autoclaves operating in acidic mode. The mercury concentration in the exhaust stream is below the 

mercury saturation concentration even if the gas stream is cooled to 32 ̊F. As shown by the stack tests in 

Table 3.1, the maximum concentration of mercury in the exhaust from the autoclaves at Goldstrike 

(operating in acidic mode) is 3.05x10-4 gr/dscf. 

The carbon adsorption filter would capture mercury as carbon loaded with mercury. Once the sulfurimpregnated carbon in the carbon filter reaches the maximum carbon loading capacity, it would be 

replaced by new carbon. The carbon loaded with mercury that is removed from the filter would need to 

be sent off-site for reclamation. 

445B.3677.3(b)(5) – Design, Equipment, Work Practice, or Operational Standards of the Thermal Unit 

As discussed above, by allowing only acidic autoclaving ore to be processed by Autoclaves 1 through 3, 

the mercury emissions from these autoclaves can be minimized. If the ore slurry has too high of a 

percentage of carbonates, then acidulation with sulfuric acid is not viable, and the ore is processed with 

alkaline autoclaving. To ensure the processing of only acidic autoclaving ore, the carbonate/sulfide ratio 

of the ore slurry can be monitored. 

445B.3677.3(b)(6) – Differences in Age, Remaining Operating Life, Configurations, Ore Mercury Concentration, 

Size, and Any Other Relevant Factors of the Similar Thermal Units 

The autoclaves at Goldstrike have a limited supply of ore that can be autoclaved. The ore that is 

currently being processed is increasingly carbonaceous. Due to this increase of carbonates in the ore, the 

amount of ore that can be processed with acidic autoclaving is limited. If Goldstrike is not able to permit 

Autoclaves 4 through 6 for alkaline autoclaving, it is estimated that the remaining acidic ore will run out 

in six to twelve months (with all autoclaves processing the acidic ore). If Autoclaves 4 through 6 are 
Appendix 3, Page 34 

converted to an alkaline mode of operations, the remaining acidic ore is expected to run out in 

approximately two years (with Autoclaves 1 through 3 primarily processing the acidic ore). Unless 

additional processing techniques or ore reserves are discovered, by the end of 2012, Autoclaves 1 through 

3 are expected to be shut down. 

Proposed NvMACT 

After considering the inherently low mercury emissions of the acidic autoclaving process; the cost and 

energy, water, and disposal requirements of the carbon filter and upstream gas conditioning equipment; 

the reduction of mercury emissions through only processing acidic autoclaving ore; and the remaining 

operating life of Autoclaves 1 through 3, Goldstrike has concluded that the add-on carbon adsorption 

filter control with upstream gas conditioning (acidic control system) does not meet NvMACT. Therefore, 

based on the existing control technologies and work practices described in Part I and the additional 

control technology options described in Part II, Goldstrike proposes that the venturi scrubbers currently 

installed on Autoclaves 1 through 3 and the following work practices are NvMACT: 

 maintaining the pressure drop for each venturi scrubber at or below 70 inches of water, 

 maintaining the water flow rate for each venturi scrubber at or above 50 gallons per minute, 

and 

 maintaining the carbonate/sulfide ratio of the ore slurry below 3. 

At Goldstrike, there is a dedicated venturi scrubber for each autoclave. Autoclave 1 exhausts to its own 

stack, and Autoclaves 2 and 3 exhaust to a shared stack. 

For each venturi scrubber, the pressure drop across the scrubber is monitored daily. The pressure drop 

for each scrubber is maintained at or below 70 inches of water; however, due to the design of the 

scrubbers, the pressure drop is typically much lower. At Goldstrike, in order to prevent steam loss for 

the autoclave vessel and the high pressure splash vessel, the release valves on these vessels are kept 

closed as much as possible. By limiting the release of steam from the autoclave and high pressure splash 

vessels, the autoclave system can operate more efficiently by requiring less heat input. Due to the small 

amount of off-gas passing through the scrubber, the pressure before the scrubber is typically low, 

resulting in a small drop in pressure across the scrubber. For these venturi scrubbers, a low pressure 

drop is an indication of low emissions because it occurs when there is little or no exhaust from the 

autoclave and high pressure splash vessels. The system is designed so that all the emissions from the 

autoclaves are captured and ducted through the venturi scrubbers. 

Water flow rate is also monitored daily and is kept at or above 50 gallons per minute. For the scrubbers 

at Goldstrike, a flow rate of at least 50 gallons per minute allows for sufficient coverage of the scrubber 

throat and creates sufficient collection targets. The scrubber water is pumped to each venturi scrubber by 

the water feed pump. Each scrubber has an isolation valve to stop scrubber water flow if an autoclave is 

not operating. The scrubber water is pumped from each venturi scrubber by scrubber underflow pumps. 

Each scrubber has one underflow pump. 
Appendix 3, Page 35 

The venturi scrubbers require energy for the water feed pump and each scrubber underflow pump. The 

maximum annual estimate of total energy required for these units, assuming 24 hours per day and 7 days 

per week operation is approximately 474,000 kilowatt-hours per year (kW-hr/yr).17,18 

The carbonate/sulfide ratio of the ore slurry feed to Autoclaves 1 through 3 will be monitored each shift 

and kept below 3. By maintaining the carbonate/sulfide ratio below 3, Autoclaves 1 through 3 will only 

be able to process acidic autoclaving ore, which will minimize mercury emissions from these autoclaves. 

Proposed Mercury Emission Limit 

Goldstrike proposes to establish a final NvMACT emission limit for Autoclaves 1 through 3 based on the 

Nevada Mercury Control Program's (NMCP) True-Up/True-Down (TUTD) methodology. The final 

NvMACT limit would be established based on six Method 29 stack tests during a three-year 

demonstration period. The proposed "interim NvMACT" emission limit for Autoclaves 1 through 3, each, 

is 4.0x10-4 gr/dscf. This interim limit was determined from the average of all the Goldstrike source tests 

provided in Table 3.1 (all tests are for Autoclaves 1 through 6 while operating in acidic mode) plus three 

standard deviations. This calculation method (shown on page 3 of Appendix 2) accounts for limited test 

data as well as stack testing and operational variability. 
Appendix 3, Page 36 

ENDNOTES 

1 Nevada Division of Environmental Protection, Bureau of Air Quality Planning. Nevada Mercury 

Control Program (NMCP) – NvMACT Clearinghouse. Phase-2 Applications. 2008. 

http://ndep.nv.gov/BAQP/hg/clearinghouse.html 

2 Rong Yan et al. “Bench-scale experimental evaluation of carbon performance on mercury 

vapour adsorption.” Fuel. Vol. 83, No. 17-18, 2004, p. 2402. 

3 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Control Cost 

Manual, 6th ed. U.S. EPA Office of Air Quality Planning and Standards. Research Triangle Park, North 

Carolina. 2002. Section 6, Chapter 2 – Wet Scrubbers for Particulate Matter. 

4 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Training Institute 

(APTI) SI:412C Scrubber Systems Operation Review. Lesson 2, 1998. 

5 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Training Institute 

(APTI)SI:412C Scrubber Systems Operation Review. 1998. Lesson 3. 

6 Nevada Division of Environmental Protection, Bureau of Air Quality Planning. Nevada Mercury 

Control Program (NMCP) – NvMACT Clearinghouse. Mercury Emissions Management System (MEMS). 2010. 

http://www.ndep.nv.gov/baqp/search 

7 Nevada Division of Environmental Protection, Bureau of Air Pollution Control. Precious Metals 

Mining Mercury Air Emissions Questionnaires. 2006. 

8 2006 OHM Test Data for Tier-1 Units. Nevada Mercury Control Program (NMCP) Data Site. 

http://ndep.nv.gov/bapc/mercury/. 

9 TRC Environmental Corp. Final Report - Emissions Compliance Demonstration for Systems 18, 19, 

61, and 66 (Class I Operating Permit No. AP1041-0739.01) - September 2007. September 2, 2007. 

10 Booz Allen & Hamilton Inc. Report prepared for U.S. EPA Region 9. Mercury Mass Balance and 

Emission Factor Estimates for Gold Ore Processing Facilities (Draft), U.S. EPA Region 9. January 14, 2001. 

11 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Control Cost 

Manual, 6th ed. U.S. EPA Office of Air Quality Planning and Standards. Research Triangle Park, North 

Carolina. 2002. Section 3.1, Chapter 1 – Carbon Adsorbers. 

12 Scotia International of Nevada, Inc. Product Bulletin COL-IS 60 Coal Based Activated Carbon 

Impregnated with Sulfur. 
Appendix 3, Page 37 

 

13 Michael G. Klett, Russell C. Maxwell, and Michael D. Rutkowski. Parsons Infrastructure and 

Technology Group Inc. Report prepared for the United States Department of Energy National Energy 

Technology Laboratory. The Cost of Mercury Removal in an IGCC Plant Final Report. September 2002. 

14 Cole, Andy. Environmental Manger, Barrick Goldstrike Mines, Inc. [Communication with K. 

Lewis, Air Sciences Inc.]. January 23, 2008. 

15 Taylor and Francis Group. CRC Handbook of Chemistry and Physics, 86th Ed. New York. 2005, p. 

6-126. 

16 United States Environmental Protection Agency (U.S. EPA). EPA Air Pollution Control Cost 

Manual, 6th ed. U.S. EPA Office of Air Quality Planning and Standards. Research Triangle Park, North 

Carolina. 2002. Section 1, Chapter 2 – Cost Estimation: Concepts and Methodology. 

17 Tsu, Wilson. Barrick Goldstrike Mines, Inc. [Communication with E. Steen, Air Sciences Inc. 

(pump horsepower)]. November 2, 2007. 

18 Valdez, Ron. Barrick Goldstrike Mines, Inc. [Communication with E. Steen, Air Sciences Inc. 

(pump horsepower)]. November 5, 2007. 
Appendix 3, Page 38 

Appendix A

GENERAL ARRANGEMENT









Appendix 3, Page 48 

Appendix B

PIPING AND INSTRUMENTATION

DIAGRAMS
















Appendix 3, Page 65 

  

Appendix C

PROCESS FLOW DIAGRAMS



Appendix 3, Page 69 

Appendix D

PROCESS DESIGN CRITERIA
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 1 of 16 

Rev: Date: Status: Prepared By: Checked By: Approved By: 

B 1-Jun-10 Issued for Permit Y. Weng A. McIntosh J. Wright 

A 1-Jun-10 Issued for Permit Y. Weng A. McIntosh J. Wright 

 

1. Purpose 

The purpose of this document is to record the process requirements for the project and 

present a summary of the process design criteria used for the alkaline autoclave mercury 

controls. 

2. POX Offgas Treatment Plant 

2.1. System Overview 

Known principles of gas cleaning and mercury removal have been used in the system design. 

These include: 

 Intimate contact between liquid / gas streams at a controlled pressure drop 

 Multiple contact points through stages of liquid spray 

 Several steps of impurity removal and gas conditioning in series 

 Process gas residence time to promote condensation and particle / droplet growth 

 Cooling of process gas to known levels where elemental mercury will condense 

 Application of proven carbon bed adsorption technology for mercury removal to meet 

required emission limits 

The system can be broken into wet and dry areas. In the wet area the process gas is 

conditioned to remove water vapour and further cooled to promote elemental mercury 

condensation. Removal of mercury particulate and fume will be achieved using the 

mechanisms of gas / liquid contact and residence time. Conditioning of the process gas is 

required for the downstream carbon bed. A key intent of the system design is to shift 

mercury capture away from the carbon bed system by removing the maximum amount of 

mercury from the gas stream before the carbon bed. The carbon bed has the ability to 

handle excursions in mercury inlet loading but at the expense of reduced life and more 

frequent change-outs. 

Of particular importance to the system design is the mercury speciation that is projected for 

the system. A very high proportion (94%) of the mercury as elemental was determined 

during the trial1

. The wet gas condenser and carbon bed are critical to the system 

operation. Special care has been taken with the carbon bed design to ensure effective gas 

distribution and mercury removal. 

2.2. Background of Aker Chemetics / Application of Experience 

Aker Chemetics is a technology based engineering design company. The technologies are 

offered on a worldwide basis to customers in the form of engineered systems, proprietary 

and non-proprietary equipment, as well as fully erected systems and plants. 

Aker Chemetics technical expertise is divided into two areas. The Acid Technology Group 

offers technology for the cooling, recovery, re-concentration and production of sulphuric 

 

1

 An alkaline plant trial was completed in March 2010, per approval from NDEP under NAC 445B.232. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 2 of 16 

acid to the chemicals, fertiliser and non-ferrous smelting industries. The Chemical 

Technology Group offers technology for the production of sodium chlorate, chlorine and 

caustic soda, chlorine dioxide, hydrochloric acid, and calcium hypochlorite to the chemical 

and pulp industries. 

In a non-ferrous (Copper, Lead, Zinc, etc.) smelting system a roaster, converter, or furnace 

is typically used to process concentrate to a metal product. These pyro-metallurgical 

processes produce a gaseous vent stream at elevated temperatures and containing high 

levels of impurities in the form of dust (e.g.- metal oxides /sulphides), fumes (e.g.- Lead, 

Arsenic), and acid mist. The gas must be conditioned and impurities removed to low levels 

in a gas cleaning section to prevent contamination of the product acid or damage to 

downstream equipment. 

These plants range in capacity from 80,000 to 180,000 SCFM (wet basis). A typical 

specification inlet to the Gas Cleaning section is provided in the attached table. 

Item Inlet to Gas Cleaning System 

Flow Rate, wet basis (ACFM) 120,000 to 400,000 

Flow Rate, dry basis (DSCFM) 44,000 to 152,000 

Temperature (F) 640 

Pressure (psig) -0.05 

Composition (volume %) 

 SO2 11.73 

 SO3 0.04 

 O2 10.61 

 N2 61.30 

 CO2 1.06 

 H2O 15.26 

Impurities 

 Total Particulate (grains / DSCF) 0.06 

 Arsenic Fume (grains / DSCF) 0.24 

 Lead Fume (grains / DSCF) 0.19 

The above conditions are both larger in volumetric capacity and magnitudes higher in 

impurity loading than that under consideration for the POX Offgas Treatment Plant. 

Aker Chemetics has taken experience gained in past projects and equipment supply within 

metallurgical gas cleaning systems and applied it to the POX Offgas Treatment Plant. The 

Scrubber Venturi, Separator Vessel, Gas Cooling Tower, and Wet Gas Condenser have all 

been proven in operation for many years at other locations. Process Criteria used in their 

design have been applied to the POX Offgas Treatment Plant with adjustments made 

where appropriate. 

2.3. Process Description 

The POX Offgas Treatment Plant (the Plant) treats the vent gas from the pressureoxidation autoclave circuits to reduce mercury emissions to the atmosphere. The Plant 

consists of the following major treatment stages: 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 3 of 16 

1) Scrubber Venturi/Separator System – quenches the process gas from 203°F to 120°F 

and removes the bulk of the particulate mercury and part of the oxidized mercury 

contaminants from the gas stream. 

2) Gas Cooling Tower System – quenches the process gas, to provide further cooling and 

removes a portion of particulate and oxidized mercury contaminants. 

3) Wet Gas Condenser System – further cools the process gas using an ammonia 

refrigerant and separates condensed elemental mercury from the gas stream. 

4) Carbon Bed System – removes elemental and oxidized mercury via chemio-adsorption 

onto sulphur-impregnated activated carbon. 

The vent gases requiring treatment are drawn to the Plant under the suction of a Booster 

Fan. 

The autoclave vent gases, saturated with water at 203o

F, enter the variable throat Scrubber 

Venturi, and are adiabatically quenched by the circulating cold condensate. The venturi 

effect removes not only the condensed water, but also a portion of the particulate and 

oxidized mercury contaminates from the process gas. From the Scrubber Venturi, the 

process gas proceeds to the Separator Vessel, which also draws in ambient vent gas from 

the Slurry Cooler Surge Tanks. The Separator Vessel is equipped with staged liquid sprays 

to further quench the gas and provides residence time for growth of droplets. The vessel 

diameter has been sized for a slow gas velocity that will allow separation of the majority of 

liquid droplets. The Separator Vessel is equipped with a chevron mist eliminator on the top 

to minimize carryover of liquid droplets. 

The condensate liquid from the Separator Vessel bottom is circulated by the Scrubber 

pump and cooled in the plate and frame Scrubber Cooler. The cooled condensate is 

delivered to the Venturi Scrubber and the Separator Vessel sprays to cool the incoming gas 

stream. Excess liquid from the circuit is purged on level control to the Water Treatment 

System. 

From the Separator Vessel, the process gas flows to the Gas Cooling Tower, where it is 

further quenched via counter-current contact with circulating cold condensate. The tower 

packing provides additional contact to remove particulate and oxidized mercury 

contaminants from the gas stream. 

The condensate liquid exiting the Gas Cooling Tower bottom is cooled in the plate and 

frame Gas Cooling Tower Cooler and circulated to the tower trough distributor via the Gas 

Cooling Tower Pump. Excess liquid from the circuit is purged on level control to the Water 

Treatment System. The tower is equipped with a chevron mist eliminator on the top to 

minimize liquid carryover. The target gas stream temperature exiting the Gas Cooling 

Tower System is 77°F. 

In the duct exiting the Gas Cooling Tower, an in-line Gas Cooling Tower Separator is 

provided to remove any condensed elemental mercury. Mercury condensation may begin at 

this stage during cold weather, when the condensate loop is running colder than the design 

temperature. The Separator consists of a dual-layer mist eliminator, a coalescing mesh pad 

followed by a chevron. 

From the in-line Gas Cooling Tower Separator, the gas enters the Wet Gas Condenser, a 

counter-current shell-and-tube exchanger. The tube-side process gas is cooled by the 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 4 of 16 

vaporization of liquid ammonia, supplied at 32°F to the shell. The target gas stream 

temperature exiting the Wet Gas Condenser is expected to be as low as 39°F. At this 

temperature, elemental mercury is expected to be condensed out from the gas stream. 

Cold condensate is continuously sprayed onto the tubes to capture the condensed mercury 

and flows to the Condensate Tank. The Condensate pump circulates the spray liquor and 

purges the excess condensate from the circuit to the Water Treatment System. 

From the Wet Gas Condenser, the process gas flows to the in-line Wet Gas Coalescer, a 

dual-layer mist eliminator. This separator offers additional agglomeration and separation of 

the condensed elemental mercury. The process gas then proceeds to the Wet Gas 

Separator Vessel, which provides several mechanisms to minimize carryover of water and 

condensed mercury droplets to the Carbon Bed System. The tangential inlet on the Wet 

Gas Separator Vessel creates a swirling effect on the gas. Two horizontal perforated 

baffles provide additional tortuous path and impingement as the gas flows upward through 

the vessel. Fine mist carryover is minimized via a mesh pad in the vessel top section. 

Excess condensate from the Wet Gas Separator Vessel, as well as the inline separators, is 

collected in the Condensate Tank. 

Prior to entering the Carbon Filter, the process gas is conditioned to 70% relative humidity 

to prevent moisture condensation in the Filter. Condensation, which creates a liquid barrier 

on the activated carbon, hinders the adsorption kinetics and therefore the performance of 

the Filter. Humidity control is achieved by introducing heated ambient air to the saturated 

process gas exiting the Wet Gas Separator. Direct heating of the process gas is not 

recommended as the process gas is rich in oxygen. 

The conditioned process gas enters the Carbon Filter horizontally and passes through two 

trains of carbon absorbers. Each train consists of a primary followed by a secondary bed. 

Mercury contaminants in the gas stream are captured by the sulphur on the activated 

carbon to form mercury sulphide. The configuration of 2-bed in series minimize spent 

carbon. A mercury breakthrough in the primary bed would trigger its replacement and 

extend the life of the secondary bed. 

The treated gas exiting the Carbon Bed System is drawn by the Booster Fan to the Plant 

Stack. 

Cooling water to the Plant is supplied in an evaporative cooling tower circuit. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 5 of 16 

2.4. Plant Capacity 

The Plant is designed to receive the following vent gas streams 

Item Vent from Scrubber 

#252-424-610 

Autoclave 4 Circuit 

Vent from Scrubber 

#252-424-620 

Autoclaves 5 & 6 

Circuit 

Combined Vent from 

Slurry Cooler Surge 

Tanks 

#252-482-230A & 611 

Flow Rate, wet basis (ACFM) 33,364 66,729 766 

Flow Rate, dry basis (DSCFM) 2,448 4,895 556 

Temperature (F) 203 203 77 

Pressure (psig) 0 0 0 

Composition (volume %) 

 O2 10.0 10.0 20.2 

 N2 0.0 0.0 76.8 

 CO2 2.0 2.0 - 

 H2O 88.0 88.0 3.0 

 

Mercury Total (grains/DSCF) 6.8 (10-3) 6.8 (10-3) 0 

 Particulate (wt %) 1 1 - 

 Oxidized (wt %) 5 5 - 

 Elemental (wt %) 94 94 - 

 

Tie-Point Existing Stack Existing Stack Tank Vent 

Autoclave vent gas flows and compositions are derived from testing conducted in an 

alkaline feed trial. These are then adjusted for projected peak ore feed rates and autoclave 

operating conditions. 

The Slurry Cooler Surge Tank vents are open to atmosphere and will be collected under 

vacuum at the inlet of the Separator Vessel. Vent flows have been estimated based on 

maximum inflow and outflow conditions to the tanks. Mercury content and speciation has 

not been tested but is expected to be negligible in comparison to the autoclave conditions. 

A gooseneck at the tank vent allows ambient air to be drawn to the POX Offgas Treatment 

System thereby preventing excess vacuum at the tanks. The vent flow for design purposes 

has been assumed to be air as this adds the maximum quantity of inert gas to the plant. 

Turndown Capability

The Plant is designed to handle turndown operation where only 1 Autoclave circuit is 

running. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 6 of 16 

2.5. Design Basis 

Stack Gas Characteristics 

 

 Flow 13,500 ACFM 

 9,850 DSCFM 

 Temperature 89 o

F 

 Pressure Ambient psig 

 Composition 

 O2 66.7 vol % 

 N2 19.9 vol % 

 CO2 12.2 vol % 

 H2O 1.2 vol % 

 Mercury 7.8 (10-5) grain/dscf 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 7 of 16 

2.6. Equipment Design Criteria 

2.6.1. Scrubber Venturi / Separator Vessel System

Equipment Function 

Scrubber Venturi

- Quench feed gas via direct contact with circulating cold condensate 

- Separate particulates and fumes from gas stream through venturi effect 

- Variable throat to maintain pressure drop and particle removal efficiency at turndown 

Separator Vessel

- Quench process gas via direct contact with 3 stages of cold condensate spray 

- Promote separation of condensate via design residence time / limit to gas superficial 

velocity 

- Minimize droplet carryover via chevron mist eliminator 

Scrubber Cooler

- Cool circulating condensate prior to Scrubber Venturi and Separator Vessel sprays. 

Scrubber Pump

- Provide cold condensate to the Scrubber Venturi and Separator Vessel to maintain 

minimum liquid to gas ratios 

- Provide sufficient head to ensure spray performance. 

- Transfer excess condensate to water treatment system 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Scrubber Venturi

Minimum Liquid to Gas 

Ratio 

usgpm /1000 

acfm ( gas inlet) 

7.5 Liquid Flow (FI-652506) 

Pressure Drop in wc 20 Throat Pressure Drop (PDI-652001) 

Separator Vessel

Residence Time Sec >5 Based on gas inlet conditions, inherent 

to separator vessel design 

Gas Superficial 

Velocity 

ft/sec <7.5 Based on gas inlet conditions, inherent 

to separator vessel design 

Minimum Liquid to 

Gas Ratio 

usgpm / 1000 

acfm (gas inlet) 

29 Liquid Flow (FI-652506) 

Exit Gas 

Temperature 

o

F 120 Gas Temperature (TI-652102) 

Scrubber Cooler 

Condensate Exit 

Temperature 

o

F 77 Liquid Temperature 

(TI-652502, TI-652505) 

 

Basis of Design Parameters 

 Scrubber Venturi Minimum Liquid to Gas Ratio. The ratio selected is based on past 

experience and industry norms. Higher ratios lead to greater opening of variable 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 8 of 16 

throat to maintain system pressure drop and can also lead to material erosion over 

time. 

 Scrubber Venturi Pressure drop. Value selected is a balance between required fan 

capacity and desired impurity removal efficiency. For pressure drop shown the Aker 

Chemetics predictive models show removal efficiencies of greater than 99% for 

particles of 1 micron and 97% for particles of 0.5 micron. There are diminishing 

returns for any higher pressure drop selection and with given mercury speciation. 

 Separator Vessel Residence Time. Value selected is based on past experience and 

industry norms for condensation of arsenic fume from a process stream where a 

retention time of 3 seconds has been used. The retention time for the POX Offgas 

Treatment System has been increased to reflect requirement for gas cooling in 

addition to growth of particles / droplets. Retention time is based on separator inlet 

volumes which will reduce as process gas passes through the vessel. True retention 

time is higher than value shown. 

 Separator Vessel Gas Superficial Velocity. Value selected is based on published 

information for liquid / gas separators. Value used in design is less than maximum 

allowable of 10ft/sec by calculation. 

 Separator Vessel Minimum Liquid to Gas Ratio. The ratio selected is based on three 

equilibrium approaches from multi-stage contact of the process gas with liquid 

sprays. Resultant temperatures of liquid and gas are an outcome of this energy 

balance. 

 Separator Vessel Exit Gas Temperature. The temperature selected is based on 

optimizing the split of expected elemental mercury free condensate. 

 Scrubber Cooler Condensate Exit Temperature. The temperature selected is based 

on highest expected cooling water supply conditions of 68o

F and an approach of 9oF 

at the heat exchanger. A tighter approach makes cooler selection uneconomic. 

Estimated Mercury Removal 

The estimated mercury removal efficiency is based on correlation between venturi throat 

pressure drop and removal efficiency of particles of various sizes. Particle size distribution 

was not measured during the alkaline trials. A reduction in efficiency from the predictive 

model was used as shown below due to uncertainty with size distribution and lower inlet 

loads than past experience. Exit gas temperature exceeds level where condensation of 

elemental mercury is expected to occur. 

 

Mercury Species % Removal efficiency 

 Particulate 90 

 Oxidized 80 

 Elemental 0 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 9 of 16 

2.6.2. Gas Cooling Tower System

Equipment Function 

Gas Cooling Tower

- Cool process gas via direct contact in a packed section with circulating cold condensate 

- Capture particulates and fumes from gas stream in packed section by liquid / gas contact 

- Provide constant heat load to downstream wet gas condenser / refrigeration skid 

- Condense elemental mercury when ambient conditions allow operation of circulated liquid 

at lower temperatures 

Gas Cooling Tower Cooler

- Cool circulating condensate prior to Gas cooling Tower. 

Gas Cooling Tower Pump

- Provide cold condensate and maintain minimum liquid to gas ratios 

- Provide sufficient head to ensure distributor performance. 

- Transfer excess condensate to water treatment system 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Gas Cooling Tower

Minimum Liquid to Gas 

Ratio 

lb liquid / lb 

process gas 

outlet 

>5 Liquid Flow (FI-654006) 

Packed Height ft 16 Inherent to tower design 

Packing Loading % of load 75 Inherent to Gas Cooling Tower design 

and packing selection 

Exit Gas 

Temperature 

o

F 77 Gas Temperature (TI-653003) 

Gas Cooling Tower Cooler

Condensate Exit 

Temperature 

o

F 77 Liquid Temperature 

(TI-654003) 

 

Basis of Design Parameters 

 Gas Cooling Tower Venturi Minimum Liquid to Gas Ratio. The ratio selected is 

based on past experience and industry norms for packed tower applications. 

 Gas Cooling Tower Packed Height. Value selected is based on past experience and 

industry norms for metallurgical applications. Measured plant data at metallurgical 

sites has shown that this is sufficient packing for cooling to a tight temperature 

approach. 

 Gas Cooling Tower % of loading. Value selected is based on past experience and 

industry norms. Loading is within recommended range provided by packing 

vendors. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 10 of 16 

 Gas Cooling Tower Exit Gas Temperature. The temperature selected is the lowest 

that can be considered based on ambient conditions. 

 Gas Cooling Tower Cooler Condensate Exit Temperature. The temperature 

selected is based on highest expected cooling water supply conditions of 68o

F and 

an approach of 9o

F at the heat exchanger. A tighter approach makes cooler 

selection uneconomic. 

Estimated Mercury Removal 

A packed column is effective for impurity removal in the 1 to 2 micron range. It is expected 

that the retention time, gas / liquid contact, and cooling of the process gas will promote 

growth of condensed fume and particulate. Without definition of inlet particle distribution 

and actual system measurements an accurate calculation of estimated removal is not 

possible. A value of 50% removal for particulate and fume was therefore assumed. Exit gas 

temperature at design exceeds level where condensation of elemental mercury is expected 

to occur. Inlet to the gas cooling tower elemental mercury comprises approximately 99% of 

total remaining and assumptions made in terms of particulate and fume removal efficiency 

have a limited impact to overall system performance. 

 

Mercury Species % Removal efficiency 

 Particulate 50 

 Oxidized 50 

 Elemental 0 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 11 of 16 

2.6.3. Wet Gas Condenser System

Equipment Function 

Gas Cooling Tower Separator

- Coalesce and remove condensed elemental mercury (potentially in cold weather 

condition) in the gas exiting the Gas Cooling Tower via inertial impaction. 

Wet Gas Condenser

- Cool the process gas indirectly via liquid ammonia to condense elemental mercury vapour 

- Capture the condensed mercury via circulating liquid spray 

Wet Gas Coalescer and the Wet Gas Separator Vessel

- Coalesce and remove fine mercury droplets via inertial impaction. 

- Minimize water droplet carryover, via inertial impaction, to the Carbon Bed System 

Condensate Tank

- Collect drains from in-line Separators, Wet Gas Separator Vessel, and Wet Gas 

Condenser 

- Allow settling of condensed mercury 

- Provide hold-up volume for the overall Wet Gas Condenser System 

Condensate Pump

- Deliver cold condensate to the Wet Gas Condenser spray 

- Transfer excessive condensate to water treatment 

- Deliver washing fluid to mist eliminators intermittently 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Wet Gas Condenser

Process Gas Outlet 

Temperature 

F As low as 39 Gas Temperature T-655002 

Liquid Spray Flow usgpm 44 Liquid Flow F-655204 

Gas Cooling Tower Separator and Wet Gas Coalescer 

Mist Eliminator Type Mesh pad + 

Chevron 

Wet Gas Separator Vessel 

Superficial Gas 

Velocity 

ft/s 8.5 Based on gas inlet conditions, 

inherent to vessel design 

Inlet Gas Velocity ft/s 175 Based on gas inlet conditions, 

inherent to vessel design 

Basis of Design Parameters 

 Wet Gas Condenser Gas Outlet temperature. temperature selected prevents 

freezing on the heat exchanger tubes 

 Liquid Spray Flow to Wet Gas Condenser. value selected is based on tube wetting 

rates from past experience and industry norm for wet gas condenser applications. 

The liquid spray serves to capture the condensed mercury. Due to its high surface 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 12 of 16 

tension, condensed mercury tends not to precipitate out of the gas stream on its 

own. 

 Mist Eliminator Selection for Gas Cooling Tower Separator and Wet Gas Coalescer.

selected dual layer (mesh pad followed by chevron vane) takes advantage of the 

high removal efficiency of mesh pad and the high gas velocity of chevron vane. High 

gas velocity through the mesh pad improves its capture of fine mist droplets. Most of 

the liquid captured in the mesh is re-entrained as larger droplets, which are then 

removed by the second layer of chevron vane. 

 Wet Gas Separator Superficial Gas Velocity. velocity is calculated based on 

published information for liquid / gas separators and represents the terminal velocity 

of the entrained liquid particle. This velocity is the basis for sizing the diameter of 

the Separator Vessel. 

 Wet Gas Separator Inlet Gas Velocity- value is within typical cyclone separator 

design range. 

Expected Mercury Removal 

The Wet Gas Condenser System removes elemental mercury by cooling the gas below its 

mercury saturation temperature. The expected elemental mercury content in the gas exiting 

this system is determined based on mercury vapour pressure curve as shown. 

Figure 1: Saturated Mercury Vapor over Pure Mercury 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

30 40 50 60 70 80 90

Temperature (F)

Hg Vapor Pressure 

(ppmv, based on 1 atm barometric)

 (source: NIST Chemistry Web Book and Perry’s Chemical Engineering Handbook)

As the proposed process is over an aqueous medium, the elemental mercury in the gas 

exiting the Wet Gas Condenser is expected to be lower than the saturation concentration 

derived from the curve over pure mercury. A conservative assumption to use the saturation 

concentration over pure mercury was taken to calculate the removal efficiency of this stage 

and to design the downstream Carbon Filter. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 13 of 16 

The expected elemental mercury removal efficiency is the difference between the mercury 

content at 39F and that in the feed gas to the Plant. 

The various separation mechanisms in the Wet Condenser System are expected to remove 

a portion of the particulate and oxidized mercury. The removal efficiency is assumed to be 

50% for each form and has minimal impact on the overall system performance given the 

dominant content of the elemental form. 

Mercury Species % Removal efficiency 

 Particulate 50 

 Oxidized 50 

 Elemental Up to 80 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 14 of 16 

2.6.4. Carbon Bed System

Equipment Function 

Humidity Control Package (Inlet Screen, Heater, Mixer) 

- Condition process gas to 70% relative humidity prior to Carbon Filter by introducing warm 

ambient air to the oxygen rich process gas. 

- Prevent water vapour condensation which hinders mercury adsorption kinetics. 

Carbon Filter

- Adsorb mercury from the gas via chemical reaction with the sulphur-impregnated 

activated carbon. 

- Reduce overall spent carbon through a staged bed configuration. The primary bed is to be 

replaced at a higher frequency to extend the life of the secondary bed. 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Carbon Bed

Inlet Gas Humidity % RH 70 Humidity Analyzer (A-662001) 

Inlet Mercury Load grain/dscf 1.3 - 6.0 (10-3) Manual Sampling & Testing 

Primary Bed 

 Residence Time sec 1.2 Based on gas inlet condition, 

inherent to bed design 

 Fresh Carbon lb 12,000 

 Hg Adsorption Capacity % min. 15 Manual Sampling & Testing 

Expected Replacement Years >1 

Secondary Bed 

 Residence Time sec 2.9 Based on gas inlet condition, 

inherent to bed design 

 Fresh Carbon lb 28,800 

 Hg Adsorption Capacity % min 15 Manual Sampling & Testing 

Expected Replacement Years >5 

Outlet Mercury Load grain/dscf 7.8 (10-5) Stack Testing 

Basis of Design Parameters 

 Inlet Gas Humidity. value stated is specified by the carbon supplier 

 Inlet Mercury Load. value selected is based on the expected mercury removal 

efficiencies in the upstream equipment 

 Outlet Mercury Load. value selected is the allowable emission 

 Bed Residence Time . value stated is specified by the carbon supplier to meet the 

outlet mercury load. The primary bed residence time is sufficient to concentrate 

mercury loading within the primary bed, thus allowing the secondary bed to function 

largely as a guard bed. 

 Hg Adsorption Capacity. value stated is inherent to the property of the activated 

carbon and is provided by the carbon supplier 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 15 of 16 

 Fresh Carbon and Expected Replacement. values states are based on the design 

residence time and the properties of the activated carbon. 

Expected Mercury Removal 

The sulphur impregnated carbon has high affinity for elemental mercury and some affinity 

for the oxidized form. The bed packing is expected to remove a portion of the particulate 

mercury as well. The mercury removal efficiency is provided by the carbon filter supplier. 

Mercury Species % Removal efficiency 

 Particulate 50 

 Oxidized 25 

 Elemental ≥ 95 

2.6.5. Booster Fan & Stack

Equipment Function 

The Booster Fan moves the process gas through the Plant and releases it to atmosphere. 

The Stack allows for safe discharge to the atmosphere. 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Booster Fan

Pressure Drop in WC 77 Pressure (P-662041 & P-663070) 

Stack 

Stack Height ft 100 

Tip Velocity ft/s ≥ 60 Based on inlet gas condition, 

inherent to design 

Basis of Design Parameters 

 Booster Fan Pressure Drop. Value selected is based on plant pressure profile, 

accounting for the design pressure drop of equipment and ducting. An allowance for 

system pressure drop increase over time has been made in the fan selection. 

 Stack Height - value selected matches the elevation of the existing autoclave 

scrubber stack tip. The release point is above other structures and equipment in the 

vicinity. 

 Stack Tip Velocity – value selected provides adequate gas dispersion, typical of 

stack design. 
Barrick Gold Corporation 

POX Offgas Treatment 

Goldstrike, Nevada Aker Chemetics 

A division of Aker Solutions Canada Inc.

Client Document Number 

Procedure 

Process Design Criteria 

10L18680-1-PRC-0001-RB

© Aker Chemetics, a division of Aker Solutions Canada Inc. Unpublished. Unauthorised use or reproduction prohibited. Page 16 of 16 

2.6.6. Cooling Tower

Equipment Function 

Water is circulated from a dedicated evaporative cooling tower to the Scrubber Cooler, Gas 

Cooling Tower Cooler, and refrigeration skid. At design conditions the energy transferred 

into the water system is estimated at 195 MMBtu/h. 

Design Parameters 

PARAMETER UNIT DESIGN PROCESS PARAMETERS 

Cooling Tower

Maximum Wet bulb 

Temperature 

o

F 59 Inherent to site ambient conditions 

Cooling Water 

Supply Temperature 

o

F 68 Liquid Temperature 

(TI-918305) 

 

Basis of Design Parameters 

 Maximum wet bulb temperature. value selected is based on evaluation of 

psychometric data on an hourly basis at the site for the calendar years 2007, 2008, 

and 2009. This value is consistent with existing evaporative cooling towers at site 

and previous studies. 

 Cooling Water Supply temperature. value selected is based on past experience and 

industry norms. The value has been confirmed though cooling tower vendor 

quotations. 

2.7. Control Philosophy 

The Plant will be controlled via existing Autoclave DCS system and operations staff. 

Alarms, Interlocks, data acquisition, trending, and control will be incorporated into the plant 

design. 

Full installed spares will be provided for equipment critical to plant operation. 

Emergency Power is to be provided to the Booster Fan. 
Appendix 4, Page 1 

Appendix 4 

Request for de minimis 

Emissions Determination 

Thermal Mercury Emitting Unit 

 
Appendix 5, Page 1 

Appendix 5 

APPLICATION 

CERTIFICATION 

The responsible official must sign and date the application certification found in Appendix 5. If the 

application is signed by a person other than the responsible official, as defined in NAC 445B.156, the 

application will be returned as incomplete. 

Note: According to NAC 445B.156, Responsible Official means: 

1. For a corporation: 

 (a) A president; 

 (b) A vice president in charge of a principal business function; 

 (c) A secretary; 

 (d) A treasurer; or 

 (e) An authorized representative of such a person who is responsible for the overall operation of 

the facility and who is designated in writing by the officer of the corporation and approved in 

advance by the director. 

2. For a partnership or sole proprietorship: a general partner or the proprietor, respectively. 

3. For a municipality or a state, federal or other public agency: a ranking elected official or a principal 

executive officer, including, for a federal agency, a chief executive officer who has 

responsibility for the overall operations of a principal geographic unit of the agency. 

4. For an affected source: the designated representative or his alternate, as defined in 42 U.S. C. § 

7651 a (26). 
Appendix 5, Page 2 

PLEASE NOTE THE FOLLOWING REQUIREMENTS WHICH APPLY TO PERMIT 

APPLICANTS DURING THE APPLICATION PROCESS: 

A. A permit applicant must submit supplementary facts or corrected information upon 

discovery [NAC 445B.297.1(b)]. 

B. A permit applicant is required to provide any additional information which the Director 

requests in writing within the time specified in the Director's request [NAC 

445B.297.1(c)]. 

C. Submission of fraudulent data or other information may result in prosecution for an 

alleged criminal offense (NRS 445B.470). 

CERTIFICATION: I certify that, based on information and belief formed after reasonable 

inquiry, the statements contained in this application are true, accurate and complete. 

 

Signature of Responsible Official 

Joseph Giraudo Environmental Manager 

Print or Type Name and Title 

 

Date