MONTANA SULPHUR & CHEMICAL COMPANY 

627 ExxonMobil Road· P.O. Box 31118
 

BILLINGS, MONTANA 59107-1118
 

OFFICE: 406-252-9324 • FAX: 406-252-8250
 

March 20, 2009 

U.S, Environmental Protection Agency Region 8 

1595 Wynkoop Street 

Denver, Colorado 80202-1129 

Attention: Laurel Dygowski, 8P-AR 

Dear Laurel: 

RE: Response to Information Request Letter of 1/29/09 Pursuant to Section 114(a) 

Clean Air Act 

On February 5,2009, Montana Sulphur & Chemical Co (MSCC) received a letter from your 

office requesting information regarding our facility as it relates to EPA's plans to address 

'reasonable progress and long-term strategies' for meeting requirements under the Regional 

Haze Rule (40 CFR 51.308). The request was made, according to the letter, under authority 

of Section 114(a) of the Clean Air Act [42 USC 7414(a)]. 

According to the letter, MSCC has 30 business days to respond to the request. We calculate 

that to be no later than March 20. (That date was calculated using five business days per 

week with one four-day week accounting for the President's Day Holiday.) On March 6, 

2009, we sent a letter to you requesting an extension of this deadline date for certain parts of 

the requested information. Since we have not received a reply from you regarding that 

request, we are herewith providing as much information as we have been able to gather and 

verify to date. 

A response from your office with additional definitions for the terms that we listed in our 

March 6 request for an extension would greatly help us answer more quickly and accurately 

the remaining questions. You may recall that the terms for which we sought clarification are: 

• Design Efficiency 

• Expected Remaining Equipment Life 

• Control Measures (for the flare system) 

• Flare Gas Recovery System Anticipated by EPA 

• Air Pollution Control Equipment Intended by EPA 

Notwithstanding the definitions requested above and in accordance with our March 6 

letter we are providing as complete a response as is reasonably possible with this letter. 

The infonnation available at this time is included as Attachment A. If you have any 

questions regarding Attachment A, please contact us and we will provide clarification 

as best we can. 
Ms. Laurel Dygowski 

March 20, 2009 

Page two 

Also in accordance with our March 6 letter, we expect to provide a response to the 

remainder of your January 29,2009, letter (received by Montana Sulphur & Chemical 

Company on February 5, 2009) no later than May 22,2009. Again, if you have any 

questions in this regard, please contact us so we may respond accordingly. 

I certify under penalty of law that I have personally examined and am familiar with the 

infonnation submitted in this document and all attachments and that, based on my 

inquiry of those individuals immediately responsible for obtaining infonnation, I 

believe that the infonnation is true, accurate, and complete [insofar as is possible at this 

date]. I am aware that there are significant penalties for submitting false infonnation, 

including the possibility of fine or imprisonment. 

Date: March 20, 2009 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

1.	 Contact Information 

a.	 Name: Margaret Hofacker and Larry Zink 

b.	 Title: Regulatory Manager and President, respectively 

c.	 Telephone Number: 406.252.9324 

d.	 Fax Number: 406.252.8250 

e.	 e-Mail: margaret@montanasulphuLcom and larry(almontanasulphuLcom 

2. Claus process 

a.	 The Montana Department of Environmental Quality (DEQ) "Operating Permit Technical 

Review Document" for Montana Sulphur lists that plant's rated capacity at 282 tons of 

elemental sulfur per day. Please confirm the maximum daily production rate. 

ANSWER: 

Yes, the Operating Permit Technical Review Document lists the facility capacity at 

282 tons per day. Please note that this is expressed in units of short tons (2000 Ibs). 

This value is equivalent to 252 long tons (2240 Ibs), which is the traditional 

measurement of sulfur in the industry. 

The document titled Development of a Sulfur Dioxide Emissions Inventory for Billings 

and Laurel, Montana, Volume 6, Montana Sulphur & Chemical Company Sulfur 

Recovery Plant (February 1991) prepared for EPA Region VIII by EPA's contractor 

E. H. Pechan & Associates, Inc. ("Pechan Report") provides independent 

calculations of the "potential-to-emit" S02 emissions from the SRU stack. The 

Pechan Report states that the emission rates are based on the NEDS "hourly 

maximum design rates" for the two Claus trains (the "old" plant and the "new" plant) 

at MSCC. (Our search of available documents reveals that "NEDS" refers to EPA's 

National Emission Data System, which has been replaced by EPA's AIRS/AFS 

databases that compile emissions sources information.) The Pechan Report further 

states that output rates and gas input streams were back-calculated from these 

levels. Pechan's calculations resulted in a total Claus production rate of 11.75 tons of 

100 percent sulfur per hour, or 282 short tons of sulfur per day. 

Evidence of earlier estimates of this capacity value was found in annual reports. The 

MSCC Annual Report dated March 31, 1964, on page 2 states: "Our former 

maximum sulfur production capacity of 55 long tons per day was inadequate [for 

anticipated future uses}. Consequently, the basic capacity of the sulfur plant [the 

"old" plant] was doubled to 110 long tons per day by adding a parallel reaction train 

and its associated machinery." Later, the Annual Report to MSCC stockholders 

dated March 31, 1970, discussed the 1969 addition of the "Manderson" equipment 

[the "new" plant] and, on page 2, stated that the capacity of that plant addition was 

an additional 120 long tons per day. The "Manderson" equipment is a two-stage 

sulfur train originally built in 1953, which the company purchased and integrated into 

the Billings facility in 1969-1970. Following the addition of the "Manderson" 

equipment, the total capacity of the MSCC plant was 110+120=230 long tons (257.6 

short tons) per day as rated by the company in its annual reports at the time. We 

have not determined from this documentation if these reported capacities were 

intended as maximum or limiting ratings or as an example conservative rating or an 

expected minimum capacity rating. The wording suggests the emphasis was on 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

"production" which normally refers to recovered product rather than defining input 

sulfur maxima, which would be slightly higher (by 5% to 15% -- see below). 

It should be understood that the potential maximum daily production or daily input 

rate in sulfur (one of which we assume is what you mean by "rated capacity") is 

influenced by the quality of the acid gases received and which of the available 

configurations of the plant is selected by the operator. Higher concentrations of H2S 

and lower concentrations of competing materials (C02, hydrocarbons, water vapor, 

etc.) in the feed gas tends toward higher production or input expectations when 

expressed as sulfur. The equipment may be configured in multiple different 

configurations depending on load (feed gas flow rates), maintenance requirements, 

and other user objectives. These configurations include, without limitation, operation 

with between one and four sulfur recovery boilers, operation as two separate 

catalytic trains, and operation as a combined catalytic train which may involve two, 

three, four or even five Claus reactors. Configurations involving two or three catalytic 

stages in series are the most common in recent years due to loads, production, and 

maintenance objectives. 

If the information requested instead is referring to an actually 'demonstrated' 

maximum daily production rate, a different value is appropriate, and may change with 

time. A review of available data records for the period between January 1, 2000, and 

December 31, 2008, found a maximum calendar daily production rate (input of sulfur) 

of 146.6 long tons of sulfur equivalent (or 164.1 short tons), which occurred on 

September 13, 2005. On this day, operations included four sulfur boilers and the 

1998 SuperClaus unit followed by tail gas incineration. It is believed that the 

operating configuration on that date involved three catalytic stages in series. It is 

recollected by management that similarly high rates were observed occasionally in 

the further past, when the Claus process also served the nearby ConocoPhillips 

refinery. By such recollection also, intra-day rates observed have been in the mid150 long-ton-per-day range. 

b. What is the average daily production rate? 

ANSWER: 

The average daily production input rate of sulfur in the feed stock at end of fiscal 

year 2008 was 112.0 long tons (125.4 short tons) of sulfur equivalent on March 31, 

2008. 

For the calendar year 2008, the average daily production input rate of sulfur in the 

feed stock was 104.2 long tons (116.7 short tons). Note that feed and production 

rates during this 12-month period were affected by a refinery fire and explosion that 

occurred in October 2007 and other factors. 

The average daily production input rate of sulfur in the feed stock for the period 

between January 1, 2000, and December 31, 2008, was 99.1 long tons of sulfur 

equivalent (LTSE)1. 

I These production rates are based on custody transfer data. 

2 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

c.	 The DEQ permit review document indicates that the sulfur recovery unit (SRU) includes 

5 Claus reactor stages, which can be operated in a single train or a dual parallel train. 

The Technical Review Document also states that the Claus process is generally 

configured in a 3-stage operation. [Footnote TRD2611-03 final permit.) Is this 

description correct? 

ANSWER: 

There are five Claus reactors at this facility. These reactors can be operated in a 

single train or in dual parallel trains, although operating in a parallel train (with all 

reactors in service at one time) is a rare occurrence. The unit is most typically 

operated in a 3-stage operation. A 2-stage operation does, however, occur. The 2­

stage scenario is generally, although not exclusively, used during periods of 

maintenance on other reactors or equipment at the facility, and also works well with 

the SuperClaus process online. 

As discussed in AP-42 Fifth Edition, the Claus sulfur recovery process is a multistage 

catalytic oxidation of hydrogen sulfide. Each catalytic stage consists of a catalyst 

chamber and a condenser; a stage may include operation with a gas re-heater. The 

typical Claus process involves burning approximately one-third of the H2S in air in a 

reactor furnace to form sulfur dioxide according to the following reaction: 

2H2S + 302-7 2S02+ 2 H20 + heat 

Hot gas from the combustion chamber is quenched in a waste heat boiler that 

generates high to medium pressure steam, and may produce sulfur condensation. 

(Downstream sulfur condensers associated with the catalytic stages also generate 

low pressure steam.) About 80 percent of the heat released can be recovered as 

useful energy, according to AP-42. Liquid sulfur from the waste heat boiler(s) and 

condenser(s) runs through seal legs into a covered pit from which it is pumped to 

trucks or railcars for shipment to end users or to further product storage or 

manufacturing equipment as at MSCC. Approximately 65 to 70 percent of the sulfur 

is recovered in the waste heat boiler, according to AP-42. The cooled gases exiting 

the waste heat boiler(s) or condenser(s) are then sent to the catalyst beds. The 

remaining un-combusted (-two-thirds of the) hydrogen sulfide undergoes the Claus 

reaction (Le., it reacts with the S02 typically formed from the above reaction) to form 

elemental sulfur in a reversible reaction generally described as follows: 

2H2S + S02 (--7 3S + 2 H20 + heat 

Because this reaction represents an equilibrium chemical reaction, it is not possible 

for a Claus plant to convert all the incoming sulfur compounds to elemental sulfur. 

Recovery can be enhanced by removing one of the reaction products (sulfur) by 

condensation. Therefore, two or more stages are used in series to produce and 

recover the sulfur. Each catalytic stage can recover approximately half to two-thirds 

of the incoming sulfur, according to AP-42. The percent overall recovery in the Claus 

process depends on the type of re-heating method used, and the stability of 

concentrations of H2S and contaminations in the feed stream, the stoichiometric 

balance of gaseous components of the inlet, oxygen content in the process "air", the 

effectiveness of inter-stage sulfur removal, operating temperature and catalyst 

conditions. 

At MSCC, given the re-heat method and the quantity and quality of the feed stream, 

we find that configurations involving either two or three catalytic stages in series are 

3
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29,2009
 

most practical and efficient and allow maintenance, economic, and reliability 

objectives to be met while continuing to process the typical feed stream. Further, we 

find that additional post-Claus processing in the SuperClaus process at MSCC 

increases overall recovery and reduces overall emissions, whether two or three 

stages are used. 

d. What is the design efficiency of the Claus process? 

ANSWER: 

At the time these units were designed, "design efficiency" was not a particularly 

meaningful term. It is also not clear how EPA defines the term in this question. We 

presently interpret it to mean the ratio of sulfur recovered to H2S sulfur input content 

on a mole basis determined at the time of equipment design and manufacture. We 

have not located any documents from the design period specific to the plant that 

state a "design efficiency" for the Claus process at MSCC. However, MSCC 

contractual documents from the period 1955-1969 suggest that MSCC "guaranteed" 

and expected a recovery (on good quality gases) of 85 percent or more on an 

average basis. 

Sulfur recovery via the modified Claus process first appears as a chapter in AP-42 in 

the Second Edition (April 1973), which states: "The degree of reaction completion is 

a function of the number of catalytic stages employed. Two stages can recover 92 to 

95 percent of the potential sulfur; three stages, 95 to 96 percent; and four stages, 96 

to 97 percent." We surmise that AP-42 may have equated "reaction completion" with 

"recovery". This is not clear; however, recovery cannot exceed reaction completion. 

The aforementioned Pechan Report assumed a three-stage Claus efficiency (as they 

have defined it) of 95 percent and a two-stage efficiency of 92 percent. Pechan and 

Associates, as EPA's contractor, further assumed that the MSCC facility was 

operated at that time as a three-stage plant 90 percent of the year and as a twostage plant 10 percent of the year, and without any SuperClaus equipment. We 

believe that the Pechan Report conclusions were based on AP-42 statements and on 

comparisons made with input sulfur streams and stack S02 from on-site stack testing 

done prior to the Pechan Report. It is recalled that EPA also performed some stack 

testing at the site. 

MSCC may supplement this response at a later date, if additional information or 

definition is obtained. 

e. What is the expected remaining equipment life of the Claus process? 

ANSWER: 

It is not clear what EPA means by this phrase. MSCC does not have a specific date 

for the Claus equipment to be removed from service. With the continuation of 

reasonable and customary repair and maintenance practices no particular 'remaining 

equipment life' date can be applied, as we might understand that phrase. Actual 

remaining life is dependent on many factors including, without limitation: economics 

of the sulfur business generally and of this location specifically; remaining life of the 

feed stock supply; remaining viable life of oil production in the region; competition in 

the oil and sulfur industry; geographical changes; demand for sulfur and phosphate 

4
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29,2009
 

fertilizers; war; terrorism; accident, fire, explosion, etc. The remainIng life of 

contract(s) or any extensions, renewals or replacements thereof, is also a factor, and 

is confidential business information. 

We do not know what the typical expected life of similar plant equipment, if any, is. 

Claus equipment in some form is commonly used in petroleum refineries and natural 

gas plants. The last refinery built in the United States was constructed over 30 years 

ago, and many older refineries are still running. Sulfur recovery equipment in 

refineries is typically of long life and, we believe, more likely to be phased out in 

specific cases when it lacks adequate capacity for increased sulfur loads, rather than 

due to age. Our plant has adequate capacity for all presently foreseen growth in oil 

refining at the client refinery. Natural gas plants typically have shorter expected lives, 

but we have reason to believe this is primarily due to the short life of typical gas 

fields rather than any intrinsic lifespan for such equipment. 

3.	 SuperClaus process 

a.	 The operating permit and a letter from Bison Engineering dated February 26, 2007, indicate 

that effluent from the Claus process is routed to two SuperClaus processes, which are 

installed in a parallel configuration. The February 26, 2007, letter indicates that these 

SuperClaus processes are optional, in that they are not required by the permit. Is this 

information correct? 

ANSWER: 

Yes, this information is correct. The SuperClaus processes are installed and can 

operate in parallel. The effluent from the Claus process is routed to one or two 

SuperClaus processes2

, depending on how many are in operation and when all or 

part of the SuperClaus process is not bypassed for one reason or another (such as 

maintenance or malfunction). The second unit operating the SuperClaus process 

was successfully brought online in the spring of 2008. MSCC presently has two 

adjacent and parallel SuperClaus process units, which are generally used to reduce 

emissions and to increase recovery from the Claus system(s). Generally, either one 

or both of these systems are running, in part to provide a comfortable margin of 

safety below the existing, applicable emissions limitations on the main stack. It is true 

that the company is not obligated to operate either unit, but does so voluntarily. 

There are also periods of time when emissions from the Claus process (alone) are 

low enough to comply with applicable main stack emissions limitations, for example, 

during periods of low input flows. The design of the units necessarily and prudently 

incorporates the ability to bypass the licensed SuperClaus process during periods of 

maintenance and severe process upset(s), which could destroy the selective 

catalyst. The design also generally allows maintenance work to go on without need 

to disrupt the critical upstream Claus operations, which prevent the vast majority of 

sulfur dioxide emissions. 

While MSCC typically operates today with SuperClaus processing, there are times 

when this is infeasible and/or unnecessary. The facility is under contract to be in 

essentially continuous operation. The necessity to conduct maintenance and repairs 

2 The two SuperClaus units would not, however, operate in series with each other. 

5 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

on the SuperClaus system (should both units be inoperable) and to address cases of 

process upset unsuitable as SuperClaus feed cannot be ignored. 

b. What is the design capacity of the original SuperClaus unit (give units)? 

ANSWER: 

The 1998 unit was designed or specified to handle 170 long tons of sulfur equivalent 

(LTSE) per day of input, assuming a typical acid gas mixture in the feed stock. This 

makes it a good fit for typical operations and still allows adequate turndown during 

periods of low flow. The 1998 license agreement for the process also allows "for the 

practice of the licensed process by the addition of a SuperClaus stage adequate for 

170 LTPD capacity." 

c. What is the design capacity of the second SuperClaus unit (give units)? 

ANSWER: 

The 2008 module was built to be functionally identical to the 1998 module, and is 

therefore designed to handle 170 LTSE/day of input, assuming a typical acid gas 

feed stock. Since the rated and actual capacity of the upstream Claus unit is 

reasonably believed to be less than the capacity of the two SuperClaus units 

together, our license for the SuperClaus process, which now includes the two 

modules together, presently limits and allows "that the total throughput to both 

SuperClaus Units shall not exceed 250 LTPD." This authority essentially matches the 

long-recognized Claus capacity of 252 LTSE discussed above. 

d. What is the design efficiency? 

i. Of the SuperClaus process? 

ANSWE"'R: 

We are presuming that by design efficiency you refer to recovery rate. This term may 

also mean conversion rate, which is different. We have not located a specific design 

efficiency of the SuperClaus process per se as installed at this facility. Review of 

general information on the process suggests that the catalytic portion of the process 

generally or typically converts up to about 90 percent of input H2S received at the 

SuperClaus reactor to sulfur. The process does not appreciably convert S02 to 

SUlfur, nor appreciably convert other sulfur compounds according to the process 

description of the designers. The sulfur recovery percentage will generally be less 

than the conversion rate and will vary with the concentration of inlet sulfur vapor and 

of outlet sulfur vapor and other compounds in the outlet gas. In other words, the 

more efficiently the upstream equipment operates at "recovery," the less "efficient" 

the SuperClaus recovery will be as a percentage, even though overall emissions 

trend lower in such cases and overall recovery is higher. 

The license agreement for the first SuperClaus process states that the "PLANT" shall 

be capable of converting 90 percent or more of the incoming H2S in the feed stock to 

the "PLANT" to sulfur, where the "PLANT" begins at the inlet to the SuperClaus unit. 

The license for the second SuperClaus process sets this design conversion rate at 

85 percent. These licenses address "conversion," and no specific "design efficiency" 

is noted. 

6
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29,2009
 

ii. Of the SuperClaus process and the Claus process combined: 

ANSWER: 

A search of the available information has not located such design efficiency factor as 

having been specified. However, the license agreement for the 1998 SuperClaus unit 

also includes a Guaranteed Performance schedule. With 'new' catalyst and other 

conditions constrained to particular assumed levels (including the conversion of H2S 

in the feed stock to sulfur after the third Claus stage being at a minimum of 96.5 

percent), the guaranteed performance of the Claus and SuperClaus processes 

combined was stated by its designers to be 98.5 percent of the sulfur in the feed 

stock to the combined plant. 

Other contractual constraints at the time required a performance test demonstrating 

that (with new catalyst) the combined process would consistently produce less than a 

specified emission rate of S02 for a specified feed rate and gas chemistries over a 

multi-day period. The unit passed this test regime readily in 1999 at various 

complying rates, as indicated by the CEMS. In addition, actual determined recovery 

of the overall plant during another three-day testing period (October 26-28, 1999) 

appears to be about 98.9 percent, based on the assumption that measured plant 

inputs and CEMS measured outputs are correct. (It should be noted that a small 

error in input measurements or output measurements can result in relatively large 

variation in calculated recovery.) 

MSCC may supplement this response at a later date, if additional information is 

obtained. 

e. Installed cost of the most recently installed SuperClaus process? 

ANSWER: 

Documents prepared recently for other purposes indicate the total capitalized costs 

for the second SuperClaus process are approximately $4,350,500. This value 

excludes the costs of capital and includes certain design efficiencies arising from 

duplication. 

This is Confidential Business Information. 

f. Annual operating cost of the most recently installed process? 

ANSWER:
 

This cost is yet to be determined, as the unit has run for less than one complete year.
 

Actual costs, when developed, are Confidential Business Information.
 

g. Year instal1ed? 

ANSWER: 

The first unit, also known as the "west" or "1998" SuperClaus process, was installed 

in 1998 and began operation in December of 1998. The second (most recent) unit, 

also known as the "east," "new," or "2008" SuperClaus process was installed in 

2007-2008 and became operational on or about May 5. 2008. 

h. Expected remaining life of the most recent SuperClaus process? 

ANSWER: 

7 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

Again, it is unclear what is meant by the term "expected remaining life." MSCC does 

not have a specific date for the Claus equipment to be removed from service. We 

believe that the process will continue at MSCC for the foreseeable future with 

reasonable and customary maintenance. We expect that the life of the catalyst is 7 to 

10 years or longer, based on operating experience here and, as reported to us, 

elsewhere. Replacement of catalyst in no way reflects need for replacement of the 

unit. Tax life is 5 or 7 years per IRS guidelines for income tax purposes. Please note 

that IRS tax life is not necessarily correlated with actual or "expected life" or for 

expected property tax life in Montana. See also item 2.e. 

MSCC may supplement this response at a later date, if additional information or 

definition is obtained. 

i.	 Expected remaining life of the older SuperClaus process? 

ANSWER: 

Again, it is unclear what is meant by the term "expected remaining life." We believe 

the process will continue at MSCC for the foreseeable future with reasonable and 

customary maintenance. The useful life of the 1998 process is currently not 

discernibly different or shorter than that for the new process, assuming that normal 

and customary maintenance and repair occur and the business continues as a viable 

entity. MSCC may supplement this response at a later date, if additional information 

or definition is obtained. 

j.	 Is there sufficient physical space in the facility to add an additional tail gas treatment unit 

after the SuperClaus effluent units? 

ANSWER: 

More information is needed to respond to this question. What "additional tail gas 

treatment" is contemplated by this question, and what is the expected 'footprint.' It 

should be noted that construction of the redundant incinerator is underway and it will 

be added (as it must be) adjacent to the source equipment. With that tail gas 

treatment unit in place, there is not a great deal of additional nearby space. Neither is 

it clear what sort of technology would be used after the SuperClaus units per se. The 

effluent gas is lean in H2S and S02, but still contains minimal amounts of elemental 

sulfur prior to the incinerator. MSCC from time to time investigates new technology 

that appears to provide an economic benefit by recovering additional sulfur from the 

feed stock. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

k. Conditions of the SuperClaus exhaust gas (combined stream from both units)'? 

Response to be provided. 

4.	 Tail gas incinerator 

a.	 What is the expected remaining equipment life of the tail gas incinerator'? 

ANSWER: 

It remains unclear what is meant by "expected remaining life." We anticipate that this 

unit will continue to operate indefinitely, with normal and customary maintenance, 

8
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

assuming continued business viability. The existing incinerator dates from 1967, so it 

is more than 40 years old and is still running well. The second (redundant) 

incinerator is under construction. Upon its installation, there will be two incinerators 

operating as needed or convenient. See also item 2.e. 

Msee may supplement this response as additional information and clarification are 

obtained. 

b. Is there enough physical space to add a scrubber after the tail gas incinerator? 

ANSWER: 

More information is needed about the operation, requirements, size, footprint and 

height of the "scrubber" technology being contemplated by the EPA. A photograph of 

the area in question is shown on the final page of this attachment. 

Msee may supplement this response as additional information and clarification are 

obtained. 

c. Incinerator operating characteristics: 

i. Maximum heat input? 

ANSWER: 

This value depends on the burner that is in use and whether it is in catalytic 

operation or not. The preferred operation for the current incinerator is catalytic mode. 

The redundant incinerator is permitted at a fuel input of as much as 35 MM Btu per 

hour as stated in the MDEQ "Operating Permit Technical Review Document" Section 

I.e. under the discussion of OP2611-02. 

Msee may supplement this response as additional information and clarification are 

obtained. 

ii. Average heat input? 

Response to be provided. 

d. Fuel used, and sulfur content (give units)? 

ANSWER: 

The fuel used comprises low sulfur refinery fuel gas and natural gas mixture with 

constantly varying relative concentrations. The current MSee operating permit 

(#2611-03) and the Montana Sulfur in Fuel rule [ARM 17.8.322(5)] requires that 

gaseous fuels contain no more than one pound of sulfur per million Btu fired. 3 Note 

that Refinery New Source Performance Standards (NSPS) require that refinery fuel 

gas contain no more than 160 ppm H2S. The gas used at MSee is not subject to 

NSPS Subpart J, although it normally complies with it. The average H2S content of 

the gas fired is typically -0-100 ppm on a daily average basis, outside of plant 

malfunctions, startups, shutdowns, based on measurements taken at the fuel gas 

3 Which is to be calculated on a daily average basis per the 1977 Stipulation between MSCC and the State 

of Montana, paragraph 18 of the Stipulation decided before the Board of Health and Environmental Sciences 

of the State of Montana in the Matter of the Proposed Revising of the State Implementation Plan for the 

Billings Air Quality Maintenance Area. 

9 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29,2009
 

header and source calculations. In any event, the sUlfur content of the low-sulfur fuel 

gas is an insignificant portion of the incinerator plant S02 emissions, which primarily 

arise from processing the Claus process tail gases. 

c. Conditions of the incinerator exhaust gas: 

Response to be provided. 

5. Flares 

a. Are any control measures currently in use or planned for flares at MS&CC? 

ANSWER: 

A definition of "Control Measures" is needed to address this question properly. Even 

so, at the current time, flare emissions are "controlled" under several regulatory 

vehicles including: 

As part of the Billings/Laurel S02 State Implementation Plan development, a 

Stipulation (STIP) between MSCC and the Montana Department of Environmental 

Quality (MDEQ) considers sulfur dioxide emissions from seven specific stacks and 

three flares at the facility. Section 3(A) of the 1998 Exhibit A-1 of the STIP states that 

"Montana Sulphur shall not allow S02 emissions from any flare, unless the emissions 

are a Minor Flaring Event [less than or equal to 150 pounds of S02 per three-hour 

period], or the result of startup, shutdown, or malfunction as defined in 

ARM17.8.110." 

Operating Permit 2611-03 (effective date October 31, 2005) places opacity limits on 

emissions from the flares, reiterates the limitations and exceptions found in the STIP, 

requires that MSCC take immediate action to correct a malfunction, and also places 

an annual emission limitation of 271 tons per year of S02 on the flares. 

Air Quality Permit 2611-03 (final January 4, 2002) added coverage of the addition of 

an emergency/backup electric generator to allow the sulfur plant to operate more 

normally during periods of utility power outage, thus significantly reducing the need 

to flare incoming gases during a prolonged power failure. The emergency generator 

therefore may be viewed as a means of controlling flare emissions. 

Two SuperClaus emissions limiting equipment (ELE) units are now part of the sulfur 

recovery strategy at MSCC. These units were installed in 1998 and 2008 and serve 

to control emissions from the Claus process at the main stack. The SuperClaus units 

also act in some cases to reduce flare emissions by allowing the SRU and 

incinerator(s) to satisfactorily process feed gases somewhat higher in hydrocarbons 

during upsets than was the case prior to their installation. 

The Federal Implementation Plan for the Billings/Laurel, Montana Sulfur Dioxide 

Area (FIP) (effective date May 21,2008) states that, "Total combined emissions of 

S02 from [all of the flares at MSCC] shall not exceed 150 pounds per 3-hour period." 

Emissions in excess of that amount are subject to enforcement actions and civil 

actions and contemplate compliance determination through an approved monitoring 

10
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

plan, presently under development. These limits contemplate a flare monitoring plan 

(FMP) as a "control" strategy. 

Flare management practices have very substantially reduced actual flare emissions 

in the past twenty years. MSCC has no firm plans for additional flare controls at this 

time. 

Even so, MSCC is looking for measures to control or manage flare emissions and is 

presently exploring options and possibilities for a flare gas recovery system of some 

sort. This may include measures that might intercept and scrub H2S or treat or 

incinerate H2S collected from process streams that might alternatively be destined 

for the flare system. There are many considerations to be dealt with including 

development costs, safety, ultimate economic viability, etc. MSCC considers such 

work proprietary and potentially patentable for this use. It is premature to state that 

any such measure is planned or practical. This paragraph is confidential business 

information. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

b. Please provide estimated emissions of S02 and NO. for the most recent year. 

ANSWER: 

The annual emission inventory for calendar year 2008 provides estimated emissions 

from the flare system at MSCC. Emissions of S02 of 39,062 pounds were estimated 

based on process parameters and operating conditions at the time of the flaring 

event. NOx emissions of 23.7 Ibs. were estimated based on an AP-42 emission factor 

for industrial flares of 0.068 pounds of 1\J0x per million Btu in the flared gas (AP-42, 

Chapter 13.5 Industrial Flares, Table 13.5-1). The heat value of the flare gas, which 

is generally acid gas and hydrocarbons, was taken to be 1300 Btu per standard 

cubic foot4

. These 2008 emissions occurred during a total of 29 events comprising a 

total of 8.4 hours of startup/shutdown/malfunction. 

c. Is there any impediment to installing a nare gas recovery system, which would hold narc 

gases until they can be treated to remove sulfur or returned to the refinery fuel gas system? 

ANSWER: 

Even without a definition of such flare gas recovery/holding system as EPA is 

considering, it is possible to say that there are major impediments, which include: 

cost, feasibility, safety, economic disposal of materials, and confidence in the design. 

Others involve space considerations, utilities, reagents, and interference with primary 

flare safety purposes and/or with continuous flare availability during construction. 

4 According to Engineering Data Book compiled by the Gas Processors Supplier Association 

(1994) Figure 22-26, the enthalpy of H2S at 200 degrees F is 1375 Btu/lb-mole compared to 

methane, which, at 200 degrees F, has an enthalpy of 1474 Btullb-mol. This suggests that the 

heating value of acid gas (conservatively 80 to 90 percent H2S) is likely slightly smaller than that 

for natural gas, which is approximately 1050 Btu/set. Even so, a slightly larger number was 

estimated for the heating value of acid gas combusted in the flare in order to provide a very 

conservative estimate of NOx emissions from the flare, and to allow for the fact that flaring during 

malfunctions/startups/shutdowns may also involve light hydrocarbon contamination. 

11 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29,2009
 

Other policy considerations, including national goals to minimize inventories of highly 

toxic gases and homeland security concerns are also seen as impediments to such 

systems. At MSCC, the larger flare emissions arise in cases of 

startup/shutdown/malfunction, which makes 100% reliable operation of any flare gas 

recovery system especially problematic and unlikely. We also respectfUlly submit that 

there exists a lack of clear benefit to the Regional Haze Rule reasonable progress 

purposes through installation of a flare gas recovery system at MSCC. EPA 

previously conducted modeling to determine if MSCC was subject to BART. The 

results of that modeling were reported in a letter from Stephen S. Tuber of EPA 

dated June 22, 2007. It states that: 

"For MSCC, the modeling results show a maximum 98th percentile impact 

within a[ny] Class I area of .30 deciviews, which does not exceed the 

threshold of 0.5 deciviews. Since MSCC does not exceed the 0.5 

deciview threshold, EPA Region 8 believes that MSCC is not subject to 

BART." 

The EPA BART modeling assumed 3259 tons per year of S02. BART modeling 

guidelines indicate that emissions used are those for the worst 24-hour period during 

2001, 2002 and 2003. At MSCC the worst day during that period for flaring was June 

20, 2001, when malfunction flaring constituted 83% of the emissions for the day. For 

the year 2001, flaring contributed 2.5% of the emissions. The June 20, 2001, 

malfunction event was due to a prolonged utility power outage. MSCC's voluntary 

installation of the emergency backup generator in 2002 makes such a large flaring 

event in the future considerably less likely. 

Conversely, we respectfully submit that the emergency generator system, the 

installations of SuperClaus processing in the periods since 1998 and other MSCC 

emissions minimization efforts since the passage of the CM amendments of 1990, 

in addition to the SIP stipulations of 1998, are also demonstrative of significant 

reasonable progress toward the goals of the regional haze program. It may be 

notable also that MSCC already directly facilitates flare gas recovery operations that 

help to minimize flaring at the adjacent refinery, through reliable operation of its 

sulfur recovery plant and its sour gas processing operations. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

d.	 What volume of gas would have to be held by a flare gas recovery system in order to reduce 

flare emissions of S02 by 90 %? 

ANSWER: 

The volume of gas that would have to be held by a flare gas recovery system is a 

function of the concentration of hydrogen sulfide in the gas to be held, a function of 

the size of the flare event, and a function of the recovery efficiencies. The space 

occupied is a function of the factor of compression applied, or, if liquefaction occurs, 

of the density of the resulting liquid. Applying some of these principles, it can be seen 

that the volume of gas can be quite large. Gases flared at MSCC during major flaring 

12
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29,2009
 

events range from a few percent H2S to nearly 100 percent on a dry basis. The more 

dilute the gas, the more volume it will occupy for a given S02 equivalence. 

A review of records indicates that the second largest release of S02 at the flare since 

January 1, 1998, was quantified at 29,504 pounds of S02. This event was a planned 

startup/shutdown event, with the refinery operating at minimal rates before shutdown 

and coinciding with other refinery maintenance. It was necessary to bring back online 

some Claus equipment worn and damaged in prior malfunctions. This may be a 

typical scenario for large flare events under the flare controls discussed above. If the 

gas is assumed to be typical acid gas (88 percent H2S), the volume of gas containing 

30,000 pounds equivalent of S02 (when burned) is about 203,000 standard cubic 

feet to be collected and stored (some how) in four hours. If 90 percent of this gas 

were to be held in the hypothetical system, it would be about 182,000 standard cubic 

feet. 

The largest release of S02 at the flare since January 1, 1998, was quantified at 

65,367 pounds of S02 and occurred during a sudden and extended power failure at 

a time when the plant and the refinery were operating at typical levels. This event 

occurred prior to the installation of the emergency backup generator at MSCC. With 

similar assumptions as above, containing 90 percent of the gas that was flared for 

this event would likely have required nearly 400,000 standard cubic feet. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

6. Other pollution control equipment (if applicable) 

a. Please describe any additional air pollution control equipment for the Claus process. 

ANSWER: 

Pollution controlling equipment at MSCC includes the previously discussed 

SuperClaus processes and the tail gas incinerators. The S02 CEMS equipment and 

other plant data systems provide near instantaneous information to assist in 

compliance determinations and in operating the plant more efficiently, thus reducing 

sulfur dioxide emissions. These may be considered to be pollution control practices. 

The plant has extensive gas pre-treatment to remove liquids and excess water 

vapor. The plant also installed an acid gas "bullet" system or surge tank to provide 

smoothing of erratic acid gas concentrations thus improving control of the processes 

to reduce the need for flaring. This was done following an agreement with MDEQ in 

about 1999, and has acted to reduce flaring needs since then. Availability and use of 

the emergency/backup generator, operator-to-operator communications with 

ExxonMobil, and use of near instantaneous data from process analyzers, when 

available, and placed at strategic locations in the process also serve as pollution 

control practices and/or equipment. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

13 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

b.	 How does this equipment interface with the Claus process, the SuperClaus process, and the 

taiJ gas incinerator? 

ANSWER: 

The S02 CEMS measures the non-flare emissions from the facility in the main stack; 

process analyzers measure process air and other parameters for the incoming feed 

stock, as well as the Claus and SuperClaus processes. The emergency generator 

starts when utility power fails. The availability of backup power allows Claus 

processing to resume quickly and limits flaring emissions, provides power for 

instrumentation, cooling water, etc., all of which are critical to operations. The gas 

pre-treatment and "bullet" systems condition incoming gases to prevent or mitigate 

upsets in downstream equipment caused by upstream problems at the supplier 

facilities. We believe the interface of the SuperClaus process to the Claus plant and 

to the incinerators, and of the incinerators to the Claus plant and the SuperClaus 

process have been addressed above. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

c.	 What is the expected remaining equipment life of the control equipment'? 

ANSWER: 

The "expected" remaining life of the equipment has been discussed above. The 

practices mentioned in 6.a and b are expected to be in use indefinitely or until other 

procedures supersede them. The equipment is repaired, maintained and replaced as 

necessary and as preventive maintenance practices and experience indicate. The 

practices of obtaining and using these data are expected to be used indefinitely or 

until superseded by other methods. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

d.	 Conditions of the device exhaust gas: 

ANSWER: 

Response to be provided. 

7.	 Final controlled emissions: 

a.	 What were the total controlled S02 emissions from the process, after all control devices, in 

the most recent year for which data are avaiJable? 

ANSWER: 

The sulfur recovery and incinerator process normally vents through the main stack. 

Emissions through the main stack are monitored by an S02 CEMS. It is reasonably 

believed that the CEMS data represent the tons of S02 for the SRU, including the 

SuperClaus, with very small de minimis contributions from other units exhausting to 

this emission point, specifically, from fuel burning boilers and incinerator(s). Flare 

emissions are not included at this CEMS, and are presumed for the purposes of this 

answer to be uncontrolled emissions. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

14 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

i. Annual (tons/year)? 

ANSWER: 

1430.33 tons per year. (2008) 

ii. Average hourly (lb/hr)? 

ANSWER: 

325.67 pounds per hour. (2008) 

b. Indicate the year for which emissions are provided. 

ANSWE'R: 

Calendar year 2008. 

c. Were the SuperClaus units bypassed at any time during the course of the year? 

ANSWER: 

Yes. Operational requirements and occasional process upsets required bypass or 

partial bypass of the SuperClaus processes for brief periods during the year. We do 

not directly track most transient bypasses that occur for process upsets; they are 

typically brief, lasting a few minutes. The SuperClaus may also be bypassed during 

periods of startup/shutdown when the Claus process is not operating; these events 

may last a few hours. Note that with two units, one of them may be offline for 

extended periods without bypass of the process itself. This was the case in 2008 and 

2009. 

A check of records shows that a bypass occurred for a short period on November 11, 

2008, during an upset and flare event. It is also known that during the period related 

to the plant shutdown/startup of April 28, 2008, the SuperClaus process was shut 

down and restarted. The recorded bypass in November lasted approximately seven 

minutes. The April startup/shutdown lasted approximately four hours. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

i. How many times? 

ANSWER: 

Two events are recorded or known; other brief bypasses may have likely occurred. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

ii. For how many hours? 

ANSWER: 

Records or operator memory indicate that the entire process; Le., both SuperClaus 

reactors, was bypassed for a total of approximately four hours during 2008. During 

much of the year, one or the other of the units was offline (bypassed) either due to a) 

being under construction, b) being superfluous and/or c) being repaired/inspected. 

During most of such periods, the SuperClaus process continued to operate and to 

process Claus tail gas. 

15 
Attachment A
 

Montana 'Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29,2009
 

MSCC may supplement this response as additional information and clarification are 

obtained. 

d.	 What would emissions have been in that year with no bypassing of the SuperClaus units, if 

different? 

ANSWE'R: 

This amount has not been calculated at this time. However, there would have been 

no discernable significant difference for annual periods of Claus operation, since the 

SuperClaus process (in one or both units) is know to have operated almost the entire 

time that the Claus process operated. The two units comprising the SuperClaus 

process operate in parallel and provide redundancy for each other. The SuperClaus 

process does not operate without the Claus operation in practice, as it would have no 

feed, and could only operate in warm-up or hot-standby mode, without feed. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

16
 
Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA 

January 29, 2009 

17