Revised Best Available Retrofit Technology ( BART ) Analysis for SO 2 at ASARCO Hayden

–

Converters 1, 3, 4, and 5 (Revised June 2014)

I. Source Description

Owner/Operator: ASARCO Incorporated (formerly American Smelting And Refining

Company), a wholly owned subsidiary of Grupo Mexico S.A. de C. V.

Source Type : Batch

– process copper smelting and converting (SIC 3331)

BART Units : Converter #1 (SCC 3

- 03

- 005

- 04 )

Converter #3 (SCC 3

- 03

- 005

- 04) Converter #4 (SCC 3

- 03

- 005

- 04) Converter #5 (SCC 3

- 03

- 005

- 04)

The Envir onmental Protection Agency ( EPA or we) has updated the BART analysis for
converters #1 and #3

- 5 at the ASARCO Hayden Smelter based on additional information received by EPA following publication of our proposed BART determination on February 18,
2014

. 1 For a description of the facility and BART Units please see the Technical Support Document that accompanied that proposed rulemaking.

II. Baseline Emissions

O ur assessment of baseline SO 2 emissions from the converters remains unchanged from the proposal

.

Ta ble I : BART Baseline SO 2 Emissions in TPY

Converters Acid Plant Secondary Capture Uncaptured
SO 2 1,034 20,341 1,209

III. SO 2 BART Evaluation for the Converters

Step 1: Identify all Available Technologies

EPA initially identified two possible control technologies for controlling SO 2 emissions from the converters: a double contact acid plant and a wet alkali scrubber. Commenters on EPA’s proposal, including National Parks Conservation Association and ASARCO identified a third possibility: a mine scrubbi ng (e.g. Cansolv)

Because SO 2 emissions captured by the primary capture system are already controlled by a double contact acid plant, we evaluated potential upgrades to the existing plant, as well as the

1 79 FR 9318

.possibility of adding a tailstack scrubber to the ex isting acid plant . For emissions from the

secondary capture system, we evaluated the use of a double co ntact acid plant, traditional scrubbing, and amine scrubbing.

Double Contact Acid Plant

A double contact acid plant uses a solid state catalyst to convert SO 2 to SO 3 , which reacts with water to form sulfuric acid. Sulfuric acid plants typically are designed to control feed streams containing several percent SO 2 so the exothermic catalytic reaction can operate autothermally. However, acid plants can be designed to process feed streams that contain only a fraction of a percent of SO 2 , although it may be necessary to heat the inlet gas stream or the catalyst. In 1984, EPA reported that SO 2 conversion rates of 99.8 percent and above can be achieved by do uble contact acid plants operating in steady state. 2

There are two types of catalysts used in double contact acid plants. The traditional catalyst uses a potassium/vanadium salt mixture on a silica substrate. The other is a cesium promoted catalyst,
where some of the potassium in a traditional catalyst is replaced with an equal molar quantity of
cesium. According to Monsanto, t he cesium promoted catalyst is more stable , less prone to deactivation, and active at lower temperatures. Traditional and cesium pro moted catalysts can be used in combination, typically in the first and fourth passes of a double contact acid plant. 3

As noted above, ASARCO Hayden currently uses a double contact acid plant to control SO 2 emissions captured by primary capture system. ASARCO reports that approximately 30 percent of the catalyst used in the first and fourth passes is cesium promoted. 4

Wet Alkali Scrubbing

Wet alkali scrubbing involves the reaction of SO 2 with liquid phase absorbents to yield sulfur compounds that can be sold, reprocessed, or discarded. The absorbent can be based on lime (calcium oxide, CaO) or caustic (sodium hydroxide, NaOH). Wet alkali scrubbing is commonly used in many industries for control of SO 2 . Alkali scrubbing produces sulfite (SO 3 2

- ) or bisulfi te (HSO 3 - ) salts as a waste product.

Amine Scrubbing

An amine scrubbing system, such as the Cansolv ® system, uses an aqueous amine solution to
absorb SO 2 from gas streams. The process is regenerable, as the amine absorbent is not consumed in the process. SO 2 absorbed by the process is stripped and introduced to the acid plant.

2 “Review of New Source Performance Standards for Primary Copper Smelters,” US EPA, Office of Air Quality Planning and Standards, March 1984, EPA 450 /3

- 83

- 018a

. 3 Letter from Jack Garrity, ASARCO to Thomas Webb, EPA, Item #8 (January 25, 2013)

. 4 Letter from Jack Garrity, ASARCO to Thomas Webb, EPA, Item #7 (January 25, 2013)

.Step 2: Eliminate Technically Infeasible Options

According to information provided by ASARCO, double contact acid pla nts, wet alkali scrubbing , and amine scrubbing are all technica lly feasible for the secondary capture system

. 5 A double contact acid plant is already in use on the primary capture system.

Step 3: Evaluate the Control Effectiveness of Each Remaining Technology

In its July 11, 2013 response to EPA’s June 27, 2013 information request, ASARCO indicated
that its double contact acid plant, which controls emissions from the primary capture system, was capable of recovering 99.81 percent of the SO 2 vented to it. 6 The expected control effectiveness
of wet alkali scrubbing and amine scrubbing as well as a double contact acid plant on the secondary capture system was provided by ASARCO in the February, 2014 letter from GCT

. These values are as follows:

Control Technology SO 2
- Redu ction Effectiveness Double Contact Acid Plant 98.81% on primary, 96% on secondary
Wet Alkali Scrubber 90

– 95 % Amine Scrubber “close to 99 % ”

Step 4: Evaluate Impacts

Factor 1: Cost of Compliance

We calculated the cost to control SO 2 collected by the secondary capture sy stem with an acid plant, a wet alkali scrubber , and an amine scrubber . We also calculated the addition of a tailstack scrubber to the existing acid plant that controls SO 2 collected by the primary capture system.

Doubl e Contact Acid Plant t o C ontrol Secondary Capture System

EPA had previously calculated the cost of construction for an acid plant for the secondary capture system using an equation published in the1984 review of the NSPS for primary copper
smelters , page 8

- 13

. 7 In the February, 2014 letter from GCT to ASARCO, some refinements to the cost estimate were provided.

We applied a control efficiency of 96 percent , which GCT indicated as possible to ASARCO

. T he emission reduction was applied to the secondary capture system baseline emissions.

Control Effectiveness Tons SO 2

Reduced Capital Cost Annualized Capital Cost Annual

Variable Cost Total Annual

Cost $/ton SO 2

Removed
96 % 19,527 $ 163,242

, 594 $ 15

, 408

, 946 $18

, 1 6 9

, 779 $33

, 578

, 725 $ 1,720

5 Letter from GCT to Jack Garrity, ASARCO (February 12, 2014)

. 6 Letter from Jack Garrity, ASARCO

, to Thomas Webb, EPA (July 11, 2013).

7 Review of the New Source Performance Standards for Primary Copper Smelters. U.S. EPA, Office of Air Quality, Planning, and Standards. March, 1984. EPA 450/3

- 83

- 018aWet Alkali Scrubber t o C ontrol Secondary Capture System

EPA calculated costs of constructing and operating a wet scrubber to control SO 2 from the secondary capture system based on information from ASARCO

. 8

Control Effectiveness Tons SO 2

Reduced Capital Cost Annuali zed Capital Cost Annual

Variable Cost Total Annual

Cost $/ton SO 2

Removed
90 % 18,307 $ 2 8 ,000,000 $2 ,64 3

, 002 $14,000 ,000 $16

, 643

, 002 $ 909

According to ASARCO, these costs do not include the cost of treating or landfilling sludge that
is classified as hazardous waste , which it considers likely

. If the sludge is hazardous waste, this will increase the annual cost by at least $7,000,000.

Amine Scrubber t o C ontrol Secondary Capture System

Based on estimates of capital and operating costs for an amine scrubber provided by ASARCO, 9
EPA calculated the $/ton of SO 2 removed from the secondary capture system . We app l ied a control efficiency of 98.5% for an amine scrubber, which we consider to be reasonable and conservative, given that Cansolv has i ndicated that such a scrubber could achieve “ close to 99% ” removal efficiency for this application. 10

Control Effectiveness Tons SO 2

Reduced Capital Cost Annualized Capital Cost Annual

Variable Cost Total Annual

Cost $/ton SO 2

Removed 98.5% 20,036 $85,000,000 $8,023,399 $9,3 00 ,000 $17

, 323

, 399 $ 865

EPA’s complete cost calculations are available in the docket. 11

Wet Scrubber t o C ontrol Acid Plant Tailstack

EPA calculated costs of constructing and operating a wet scrubber to control SO 2 from the existing acid plant tailstack based on information provided by ASARCO. 12 In this case we used
the low

- end estimate of operating costs. We also included a sludge hauling fee of $60 per ton and

assumed one ton of SO 2 controlled would result in five tons of sludge.

Control Effectiveness Tons SO 2

Reduced Capital Cost Annualized Capital Cost Annual

Variable Cost Total Annual

Cost $/ton SO 2

Removed 85% 879 $28,000,000 $2,643,002 $9,274,521 $11,917,523 $13,564

8 Letter from Jac k Garrity, ASARCO, to Thomas Webb, EPA (July 11, 2013); Email from Jack Garrity, ASARCO to Geoffrey Glass, EPA (May 19, 2014)

. 9 Id.

10 Letter from GCT to Jack Garrity, ASARCO (February 12, 2014).

11 BART Analysis of Control Options for ASARCO Hayden

– June 2014.xls x
12 Letter from Jack Garrity to Thomas Webb (July 11, 2013).Again, these costs do not include the cost of a booster fan or a modified stack that may be

needed. Although the calculation includes the cost hauling sludge off site, it does not include the cost of treating or landfilling the sludge, which may be classified as hazardous waste depending
on the me tals content. In addition, we note that some of the SO 2 that passes through the acid plant was emitted by the flash furnace which is not BART eligible.

Factor 2: Energy Impacts

Operation of a sulfuric acid plant at the ASARCO Hayden smelter would require energy to heat inlet air from approximately 177° F to 735° F. EPA estimated that t his would require a heat input of approximately 114 MMBtu/hr and could require 1,200 MMscf of natural g as per year, result ing in up to 30 tpy NOx emissions. 13 GCT estimated emissions of NO x closer to 40 tons per

year. 14 Th is assumes 100 percent of the needed heat resulted from natural gas combustion.

Operation of an amine scrubber would require the installation of a boiler capable of producing 30

tons

- per

- hour of lo w quality steam to strip SO 2 from the absorbent solution. ASARCO estimated
this would result in NO x emissions of about 12.5 tons per year. 15

Factor 3: Non

- air Quality Environmental Impacts

Non

- air quality environmental impacts from a second acid plant are not expected to be signifi cant given that ASARCO already has the capacity to handle and store the much larger quantities of sulfuric acid produced by the primary acid plant.

Addition of a scrubber would result in sludge which would have to be shipped off site to be treated or landfilled. Because of metals in the sludge, it may need to be treated as hazardous

waste.

ASARCO did not identify any significant non

- air environmental impacts resulting from construction or operation of an amine scrubber

.

Factor 4: Remaining Useful Life

The BART

- eligible converters have each been in place for approximately 40 years or longer. Although ASARCO has identified replacement of the existing converters as part of their plan to bring the Hayden Area into attainment with t he one

- hour SO 2 NAAQS, ASARCO has not
committed to removal of these units. Therefore, we have assumed that these units have a remaining useful life of at least twenty years.

13 Based on the AP 42 factor for low NOx burners

14 Letter from GCT to Jack Garrity, ASARCO (February 12, 2014)

15 Email from Jack Garrity, ASARCO to Geoffrey Glass, EPA (May 19, 2014)Step 5: Visibility Impacts

We previously calculated visibility improvements for a 99.81 percent reduction is SO 2 emissions from the secondary capture system as part of the proposed rulemaking (79 FR 9318, February 18, 2014). 16 The 98.5 percent control efficiency achievable by the amine scrubber is lower than the 99.81 percent assumed i n our proposal, and yields visibility benefits that are 1.5%
lower. 17 The visibility benefits are so large that this changes makes a negligible difference, and
does not affect our BART determination.

98 th Percentile Visibility (DV) (2001

- 2003) Days Modeled > 0.5 DV (2001

- 2003)
Base Amine Scrubber Base Amine Scrubber Chiricahua NM 1.02 0.14 117 0 Chiricahua WA 1.04 0.15 112 0 Galiura WA 1.76 0.28 239 2 Gila WA 0.69 0.09 52 0 Mazatzal WA 0.88 0.13 73 0 Mount Baldy WA 0.66 0.09 40 0

Petrified Forest
NP 0.68 0.10 43 0

Pine Mountain WA 0.67 0.10 42 0

Saguaro NP 1.28 0.18 108 0 San Pedro Parks
NP 0.44 0.06 13 0

Sierra Ancha WA 1.09 0.15 83 0

Superstition WA 1.74 0.27 197 2 Sycamore Canyon WA 0.51 0.07 23 0

Conclusion

We identified three possible control strategies to reduce SO 2 emissions from the converters :

1. Control of the secondary capture system by a double contact acid plant.
2. Control of the secondary capture system by a wet alkali scrubber.
3. Control of the secondary capture system by an amine s crubber
4. Control of acid tailstack emissions by a wet scrubber.

16 79 FR 9318, February 18, 2014

17 See spreadsheet in docket, ASARCO_scaled_benefit.xlsxOption #4 is ruled out because of cost (> $13,000/ton SO 2 ). Ranking the other three options in

order of effectiveness:

Control Control

Effectiveness Tons SO 2

Reduced Total Annual

Cost $/ton SO 2

Removed Incremental Cost

Effectiveness ($/ton)
Amine Scrubber 98.5% 20,036 $17

, 323

, 399 $ 865
Acid Plant 96% 19,527 $33

, 578

, 725 $ 1,720

- $31,966
Alkali Scrubber 90% 18,307 $16,643,002 $909 $394

Because it would be both more expensive and less effective at removing SO 2 compared to an
amine scrubber

, an acid plant for the secondary capture system is an inferior option . Therefore, we are ruling out construction of a new acid plant as BART for the secondary capture system

.
With regard to the remaining two options, we note that ASARCO has indicated that it believes the secondary gas stream would be “more practically controlled by caustic [alkali] scrubbing”
than an amine scrubber. However, the cost and control effectiveness e stimates provided by ASARCO do not support this contention. In particular, while the total annual cost of an alkali scrubber is higher than that of an amine scrubber, the amine scrubber is more cost effective on $/ton basis due to its higher control effect iveness

. We further note that if alkali scrubber sludge had to be treated as hazardous waste, which ASARCO had indicated was likely, the total
annual ized cost of an alkali wet scrubber would actually be greater than the total annual ized cost
of an amine sc rubber. (According to cost data provided by ASARCO, the annual operating cost of an alkali scrubber would be greater than the annual operating cost of an amine scrubber. See above.)

Furthermore, a n amine scrubber would have greater visibility benefits than an alkali scrubber because it would result in lower emission rates. Although the energy usage of amine scrubber would be greater, we consider the amount of energy required to be reasonable in light of its greater effectiveness. In addition, an amine scrub ber would have fewer non

- air environmental impacts than an alkali scrubber, which would not result in the creation of potentially hazardous sludge

.

B ased on consideration of the five BART fac tors, we have determined that a level of control equi valent to an amine scrubber constitutes BART for the secondary capture system. We express
the limit in terms of a mass

- based control efficiency (i.e. rolling 365

- day percent reduction)
because of the high variability in SO 2 concentration vented to a control device during batch operations. A concentration based limit (e.g. ppm) would allow the owner or operator to demonstrate compliance by including in the averaging calculations many hours with low outlet
concentrations because of low inlet concentrati ons.

With regard to the primary capture system, we are finalizing our proposed determination that use of the existing double contact acid plant constitutes BART. In our proposal

, we noted that ASARCO had indicated that its double contact acid plant is capa ble of recovering 99.8 percent ofthe SO 2 vented to it. 18 In its comments to EPA, ASARCO noted that this figure is an annualized

performance estimate for the acid plant and therefore is not an appropriate basis for setting a 30

- day rolling average control e fficiency

. 19 Therefore, we are revising the proposed limit from a rolling 30

- day limit to a rolling 365

- day limit.

W e are requiring the following as BART for SO 2 for the converters :

1. An SO 2 control efficiency of 99.8 percent, 365

- day rolling average, on all SO 2 captur ed by the primary control system

. 2. An SO 2 contro l efficiency of 98.5 percent, 365

- day rolling average, on all SO 2 captured by the secondary control system.
3. Compliance with each SO 2 BART limit may be verified either through the use of SO 2 CEMS before and after controls in each system or by monitoring acid production and the
use of outlet SO 2 CEMS

. 4. Operation and maintenance of primary and secondary capture systems meeting the requirements of 40 CFR 63, subpart QQQ, as it applies to Peirce Smith converters

.

18 79 FR 9344 (citing Letter from Jack Garrity, ASARCO to Thomas Webb, EPA, July 11, 2013.

19 ASARCO Comment Letter at 13

- 14 (March 31, 2014).