### MONTANA SULPHUR & 

### CHEMICAL COMPANY

627 ExxonMobil Road· P.O. Box 31118 BILLINGS, MONTANA 59107-1118 OFFICE: 406-252-9324 • FAX: 406-252-8250



### March20, 2009

U.S, Environmental ProtectionAgencyRegion 8 1595 Wynkoop Street Denver, Colorado 80202-1129

Attention: Laurel Dygowski, 8P-AR

DearLaurel:



### RE: ResponsetoInformationRequestLetterof1/29/09Pursuantto Section 114(a) CleanAirAct

OnFebruary5,2009,Montana Sulphur & 

### Chemical Co (MSCC) received aletterfrom your officerequesting informationregardingourfacility as itrelatesto EPA'splansto address 'reasonableprogress andlong-term strategies' for meetingrequirementsunderthe Regional HazeRule (40 CFR 51.308). Therequest wasmade, accordingtotheletter, underauthority ofSection 114(a) ofthe CleanAirAct [42 USC 7414(a)].

Accordingto theletter, MSCChas 30 businessdays to respondto therequest. We calculate that to beno laterthanMarch20. (Thatdate was calculatedusingfive businessdaysper weekwithone four-day weekaccountingfor the President's DayHoliday.) OnMarch6, 2009, we sent aletterto you requesting anextensionofthis deadline date for certainpartsof the requested information. Since wehavenotreceived areplyfrom youregardingthat request, we are herewithproviding as muchinformationas we havebeenableto gather and verifyto date.

A responsefrom yourofficewith additional definitions for thetermsthatwelistedinour March6requestfor an extensionwould greatlyhelpus answermorequicklyandaccurately the remainingquestions. Youmayrecallthat theterms for whichwe sought clarification are:

• DesignEfficiency

• ExpectedRemainingEquipmentLife

• Control Measures (forthe flare system)

• FlareGasRecovery SystemAnticipatedbyEPA

• AirPollutionControlEquipmentIntendedbyEPA

Notwithstandingthedefinitionsrequested above and in accordancewithourMarch6 letterwe areprovidingas complete aresponse as is reasonablypossiblewiththis letter. Theinfonnation availableatthistimeis includedas AttachmentA. 

### Ifyouhave any questions regardingAttachmentA, please contactus andwewillprovideclarification

as best wecan.Ms. LaurelDygowski March20, 2009 Pagetwo



### Also in accordancewith ourMarch 6letter, we expectto provide aresponseto the remainderofyourJanuary29,2009,letter (receivedbyMontana Sulphur & 

### Chemical Companyon February5, 2009) no laterthanMay22,2009. Again, ifyou have any questions in this regard, pleasecontactus so wemayrespond accordingly.

I certifyunderpenaltyoflawthatIhavepersonallyexamined and amfamiliarwith the infonnation submittedinthis document and all attachments and that, based onmy inquiryofthoseindividualsimmediatelyresponsiblefor obtaininginfonnation, I believethattheinfonnationis true, accurate, and complete [insofar as is possible at this date]. I am aware that there are significantpenalties for submittingfalse infonnation, includingthepossibilityoffine orimprisonment.

Date: March 20, 2009

## AttachmentA MontanaSulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29, 2009

1. ContactInformation

a. Name: MargaretHofackerand LarryZink b. Title: RegulatoryManager and President, respectively

c. TelephoneNumber: 406.252.9324 d. FaxNumber: 406.252.8250

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

2. Clausprocess
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 sulfurperday. Pleaseconfirmthe maximumdailyproductionrate. 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 ofshort tons (2000 Ibs). This value is equivalent to 252 long tons (2240 Ibs), which is the traditional measurement ofsulfur in the industry.

The document titled Developmentofa SulfurDioxide Emissions InventoryforBillings 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 ofsulfur per day.

Evidence ofearlier estimates ofthis 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 perday by adding 

### a parallelreaction 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 ofthe 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

## AttachmentA MontanaSulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29, 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 oreven 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 maychange with time. A review ofavailable data records for the period between January 1, 2000, and December31, 2008, found a maximum calendardaily production rate (input ofsulfur) 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. Whatis the average dailyproductionrate? 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 otherfactors.

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 custodytransfer data.



### 2

## AttachmentA Montana Sulphur& Chemical Company Requestfor InformationPursuantto Section 114 ofthe CAA January29, 2009

c. TheDEQpermitreviewdocumentindicates that the sulfurrecoveryunit(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 descriptioncorrect? 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 ofthe H2 S in air in a reactor furnace to form sulfur dioxide according to the following reaction: 2H2 S + 302

### -7 2S02+ 2 H2 0 + 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 ofthe) 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: 2H2 S + S02 

### (--7 3S + 2 H2 0 + 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 halfto two-thirds ofthe 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 H2 S and contaminations in the feed stream, the stoichiometric balance ofgaseous components ofthe 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 ofthe feed stream,
we find that configurations involving either two or three catalytic stages in series are



### 3

## AttachmentA Montana Sulphur& 

## Chemical Company Requestfor Information Pursuantto Section 114ofthe CAA January29,2009

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. Whatis the design efficiency oftheClausprocess? 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 H2 S 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 ofthe number ofcatalytic stages employed. Two stages can recover 92 to 95 percent ofthe 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 athree-stage Claus efficiency (as they have defined it) of95 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 S02from 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. Whatis the expectedremainingequipmentlife oftheClausprocess? 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 ofthe sulfur business generally and ofthis location specifically; remaining life of the feed stock supply; remaining viable life ofoil production in the region; competition in the oil and sulfur industry; geographical changes; demand for sulfur and phosphate



### 4

## AttachmentA Montana Sulphur & 

## Chemical Company Requestfor InformationPursuant to Section 114ofthe CAA January29,2009

fertilizers; war; terrorism; accident, fire, explosion, etc. The remainIng life of contract(s) or any extensions, renewals or replacements thereof, is also afactor, 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. SuperClausprocess
a. The operatingpermit and a letter from Bison Engineering datedFebruary26, 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 informationcorrect? 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 unitswould not, however, operate in serieswith each other.

5

## AttachmentA Montana Sulphur& 

## Chemical Company Requestfor InformationPursuantto Section 114 ofthe CAA January29, 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. Whatis the design capacityofthe original SuperClausunit (giveunits)? ANSWER: The 1998 unitwas designed or specified to handle 170 long tons ofsulfur 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 agreementfor the process also allows "for the practice ofthe licensed process by the addition of a SuperClaus stage adequate for 170 LTPD capacity."

c. Whatis the design capacityofthe second SuperClausunit (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 of252 LTSE discussed above.

d. Whatis the design efficiency? i. Ofthe SuperClausprocess? ANSWE"'R: We are presuming that by design efficiencyyou referto 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 ofthe process generally or typically converts up to about 90 percent of input H2 S 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 varywith 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 agreementfor the first SuperClaus process states thatthe "PLANT" shall be capable of converting 90 percent or more ofthe incoming H2 S 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 Requestfor InformationPursuantto Section 114 ofthe CAA January29,2009

ii. OftheSuperClausprocessand theClausprocesscombined: ANSWER: A search ofthe available information has not located such design efficiencyfactor as having been specified. However, the license agreementfor 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 H2 S 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 S02for 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. Installedcostofthemostrecentlyinstalled SuperClausprocess? 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. Annualoperatingcostofthemostrecentlyinstalled 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. Yearinstal1ed? 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 May5. 2008.

h. Expectedremaininglife ofthemostrecentSuperClausprocess? ANSWER:



### 7

## AttachmentA Montana Sulphur& 

## Chemical Company Requestfor InformationPursuantto Section 114 ofthe CAA January29, 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 ofthe catalyst is 7to 

### 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. Expectedremaininglife oftheolderSuperClausprocess? 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, ifadditional information
or definition is obtained.

j. Is there sufficient physical space in the facility to add an additional tail gas treatment unit afterthe SuperClauseffluentunits? 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 ofthe 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 agreat deal ofadditional nearby space. Neither is it clear what sort oftechnology would be used afterthe SuperClaus units perse. The effluent gas is lean in H2 S 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. ConditionsoftheSuperClausexhaustgas (combined streamfrom both units)'?
Response to be provided.

4. Tailgas incinerator

a. Whatis the expectedremainingequipmentlife ofthe tail gasincinerator'? ANSWER: It remains unclearwhat is meant by "expected remaining life." We anticipate that this unit will continue to operate indefinitely, with normal and customary maintenance,



### 8

## AttachmentA Montana Sulphur & 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29, 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 thereenough physical spaceto add a scrubber after the tailgas incinerator? ANSWER: More information is needed about the operation, requirements, size, footprint and height ofthe "scrubber" technology being contemplated by the EPA. A photograph of the area in question is shown on the final page ofthis attachment.

Msee may supplement this response as additional information and clarification are obtained.

c. Incineratoroperatingcharacteristics: i. Maximumheatinput? 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. underthe discussion ofOP2611-02.

Msee may supplement this response as additional information and clarification are obtained.

ii. Averageheatinput?
Response to be provided.

d. Fuelused, and sulfurcontent(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 perthe 1977 Stipulation between MSCC and the State of Montana, paragraph 18 ofthe Stipulation decidedbefore the BoardofHealth andEnvironmental Sciences ofthe State ofMontana in the Matterofthe ProposedRevising ofthe State Implementation Plan forthe BillingsAir QualityMaintenance Area.

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## AttachmentA Montana Sulphur& 

## Chemical Company Request for InformationPursuantto Section 114 oftheCAA January29,2009

header and source calculations. In any event, the sUlfur content ofthe low-sulfur fuel gas is an insignificant portion ofthe incinerator plant S02 emissions, which primarily arise from processing the Claus process tail gases.

c. Conditions oftheincineratorexhaustgas: Response to be provided.

5. Flares

a. Areanycontrolmeasurescurrentlyin useorplannedforflares atMS&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) ofthe 1998 ExhibitA-1 ofthe STIP states that "Montana Sulphurshall 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 of271 tons per year ofS02 on the flares.

Air Quality Permit 2611-03 (final January 4, 2002) added coverage ofthe 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 ofcontrolling flare emissions.

Two SuperClaus emissions limiting equipment (ELE) units are now part ofthe 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 ofthe 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



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## AttachmentA Montana Sulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29, 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 aflare gas recovery system of some sort. This may include measures that might intercept and scrub H2 S or treat or incinerate H2 S 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. Pleaseprovideestimatedemissions ofS02and NO.for the mostrecentyear. ANSWER: The annual emission inventoryfor 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. NOxemissions of23.7 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 ofthe 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 of29 events comprising a total of 8.4 hours ofstartup/shutdown/malfunction.

c. Is there any impediment to installing a nare gas recovery system, which would hold narc gasesuntil they can be treated to remove sulfur orreturned to the refineryfuel 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 thatflaring during malfunctions/startups/shutdowns may also involve light hydrocarbon contamination.



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## AttachmentA MontanaSulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29,2009

Other policy considerations, including national goals to minimize inventories ofhighly 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 submitthat 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 dayduring that period for flaring was June 20, 2001, when malfunction flaring constituted 83% ofthe 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 directlyfacilitates 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 ofgas would have to be held by a flare gasrecovery system in order to reduce flare emissionsofS02 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 ofthe factor of compression applied, or, if liquefaction occurs, ofthe density ofthe resulting liquid. Applying some ofthese principles, it can be seen thatthe volume ofgas can be quite large. Gases flared at MSCC during majorflaring



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## AttachmentA MontanaSulphur& 

## Chemical Company Requestfor InformationPursuantto Section 114 ofthe CAA January29,2009

events range from a few percent H2 S to nearly 100 percent on a dry basis. The more dilute the gas, the more volume it will occupyfor a given S02 equivalence.

A review of records indicates that the second largest release ofS02 at the flare since January 1, 1998, was quantified at 29,504 pounds ofS02. 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 necessaryto 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 H2 S), the volume ofgas 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 ofthe emergency backup generator at MSCC. With similar assumptions as above, containing 90 percent of the gas that was flared for this eventwould likely have required nearly400,000 standard cubic feet.

MSCC may supplement this response as additional information and clarification are obtained.

6. Otherpollution controlequipment(ifapplicable)

a. Please describe any additional airpollutioncontrolequipmentfor the Clausprocess. 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 ofthe 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.



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## AttachmentA MontanaSulphur& 

## Chemical Company Requestfor InformationPursuantto Section 114 oftheCAA January29, 2009

b. How does this equipmentinterface with the Claus process, the SuperClaus process, and the taiJ gasincinerator? 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 ofthe 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. Whatis theexpectedremainingequipmentlife ofthecontrolequipment'? 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. Conditionsofthe device exhaustgas: ANSWER: Response to be provided.

7. Finalcontrolled emissions:

a. What were the total controlled S02 emissions from the process, after all control devices, in the mostrecentyearfor whichdata areavaiJable? 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 ofthis
answerto be uncontrolled emissions.

MSCC may supplement this response as additional information and clarification are obtained.



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## AttachmentA Montana Sulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29, 2009

i. Annual (tons/year)? ANSWER: 1430.33 tons per year. (2008)

ii. Averagehourly (lb/hr)? ANSWER: 325.67 pounds per hour. (2008)

b. Indicatetheyearforwhich emissions are provided. ANSWE'R: Calendar year2008.

c. Were the SuperClausunitsbypassed atanytime duringthecourseoftheyear? ANSWER: Yes. Operational requirements and occasional process upsets required bypass or partial bypass ofthe 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 ofthe 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 approximatelyfour hours.

MSCC may supplement this response as additional information and clarification are obtained.

i. Howmany 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. Forhow manyhours? 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 ofthe year, one orthe other ofthe 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.



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## AttachmentA Montana'Sulphur& 

## Chemical Company Request for InformationPursuantto Section 114 ofthe CAA January29,2009

MSCC may supplement this response as additional information and clarification are obtained.

d. What would emissions have been in that year with no bypassing ofthe 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, withoutfeed.

MSCC may supplement this response as additional information and clarification are obtained.



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## AttachmentA Montana Sulphur& 

## Chemical Company Request for Information Pursuantto Section 114 ofthe CAA January29, 2009

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