MONTANA SULPHUR & CHEMICAL COMPANY 

627 ExxonMobil Road • P.O. Box 31118
 

BILLINGS, MONTANA 59107-1118
 

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

June 4,2009 

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) ofthe Clean Air Act [42 USC 

7414(a)]. 

According to the letter, MSCC has 30 business days to respond to the request. On March 6, 2009, we sent 

a letter to you requesting an extension ofthis deadline date for certain parts ofthe requested lllformation. 

Since we had not received a reply from you regarding that request, we provided as much information as 

we were able to gather and verify as ofMarch 20, 2009. 

Subsequently, we received a response to our request for additional definitions for the terms that we listed 

in our March 6 request for an extension. With that additional insight into the desired data and additional 

time to examine our records, we are herewith providing additional response to your request for 

information. 

Our supplement information is provided in Attachment A Addendum. If you have any questions 

regarding Attachment A Addendum, please contact us and we will provide clarification as best we can. 

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

submitted in this document and all artachnlents and that, based on my inquiry ofthose individuals 

immediately responsible for obtaining information, I believe that the iriformation is true, accurate, and 

complete [insofar as is possible at this date]. I am aware that there are significant penalties for submitting 

false information, including the possibility offine or inlprisonment. 

Date: June 4, 2009 
Addendunl to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

1. Contact Information 

a. Narne: 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@n10ntanasulphur.comandlarry@montanasulphur.com 

2. Claus Process 

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

ANSWER: 

Thank you for the clarification of your definition of "design efficiency." MSCC takes 

this opportunity to provide additional response to this question. 

You have stated: 

We're looking for a value to compare to the NSPS efficiency 

level, which is 99.7%. (That is: at the NSPS level, less 

than 0.3% of the sulfur entering the unit would be 

emitted.) The efficiency is not explicitly defined in the 

NSPS rule, since the rule is expressed as ppm in the 

exhaust gas (250 ppmv is [sic] the gas is 

[sic] incinerated) . 

MSCC does not have readily available any measures directly comparable to the 

NSPS rule, which itself is not applicable to MSCC. The NSPS (40 CFR 60 Subpart J) 

does not address or represent efficiency of a Claus process per se, but rather 

addresses the emissions from downstream treatment unit(s) operating on Claus tail 

gas. 

As to Claus processes generally, AP-42 provides estimates for typical process 

production efficiencies, as previously indicated in our response(s). 

We do measure, record and report to the Montana Department of Environmental 

Quality (MDEQ) the hourly average concentration of sulfur dioxide at the CEMS in 

our main SRU stack. These data, which are not directly comparable to NSPS 

concentrations, are available to EPA and to the public. That being said, we note that 

the CEMS measurements on the main SRU stack are made on wet stack gas; no 

diluent gas measurements are made by the CEMS. The main stack is also a merged 

stack, thus there is generally a flow contribution to the measured stream from the 

Claus process, the SuperClaus 1M processes and the tail gas incinerator process, as 

well as from other gas-fired boilers at times. There are also uncertainties in the 

CEMS measurements, which are determined at the time of our annual RATA 

(Relative Accuracy Test Audit). A review of our RATA results show that our CEMS 

concentration measurements have ranged between +2.55 and +12.3 percent of the 

reference method (EPA Method 6/6C). Thus, the reported data are conservative and 

may overestimate the actual S02 emissions. 

In addition, for the same stack, MSCC documented an Alternative Monitoring Plan 

(AMP) for MDEQ as part of the 1998 Stipulation requirements. This plan provides 

1
 
Addendum to Attachment A
 

Montana Sulphtlf & Chemical Company
 

Request fOf Information PtlfSuant to Section 114 ofthe CAA
 

January 29, 2009
 

methods for estimating emissions based on the calculation of a daily process 

efficiency value using CEMS S02 mass emission data and separate daily 

measurements of plant raw material feed gas inputs. This AMP methodology does 

not address the Claus process separately from the other SRU processes (Le., 

SuperClaus TM/lncinerator) except to the extent that such other processes happen to 

be offline for a particular calculation. 

There are also uncertainties in developing the AMP production process efficiency 

estimations. The amount of incoming sulfur is calculated using orifice plate metering 

and routine daily laboratory testing of several input streams for H2S content. This 

information is determined on a daily basis and is adequate for commercial custody 

transfer purposes. This AMP calculation does not require information on stack gas 

water or oxygen content and is essentially insensitive to whether other boilers are 

contributing to the stack emission stream. The AMP method is directly affected by 

the above-mentioned uncertainties in CEMS measurement of S02 concentration in 

the stack gas and by plant input measurement (metering and laboratory) 

uncertainties. Accuracy is sensitive to process upsets related to the composition of 

the feed gases that may change throughout the day but are characterized by one 

daily grab sampling and analysis for H2S content. 

Subject to the comments above regarding uncertainties and a reiteration that the 

AMP calculated production process efficiency is not a measure of "design efficiency," 

a review of calendar year 2008 AMP calculated efficiencies was conducted. Our 

records indicate that production process efficiency levels (daily) averaged 

approximately 98.3 percent and varied in the range of 95.8 to 99.4 percent during 

days of SuperClausTM operation. (The standard deviation over the particular year 

was less than 0.2 percent.) This may represent a level of 'actual' efficiency during 

SuperClausTM operation for that year; please note, however, that uncertainties of 

measurement of both input and output sulfur can affect calculated efficiency 

substantially at these high levels of recovery. Actual efficiencies will also be affected 

by process upsets as well as the catalyst ages and types, feed material quality, and 

conditions of related equipment. The year 2008 involved operation with both the 

1998 unit and the 2008 unit for parts of the year. 

Also subject to the comments above, a review of older AMP calculated efficiencies 

was conducted to identify (daily) periods during which neither of the SuperClausTM 

units was in operation for comparison. Over the past five years, several such periods 

were identified. The longest of these identified periods was seventeen days between 

July 30 and August 17, 2002. However, after the initial SuperClausTM was first put 

into service, the only identified periods when the SuperClausTM was not in operation 

were non-typical periods of turnaround or malfunction. For that reason, data prior to 

the startup of the first SuperGlausTM on December 8, 1998, were examined. GEMS 

recordkeeping was initiated on January 1, 1998, and our records for calendar year 

1998 indicate that prior to the SuperClaus TM startup, the calculated process 

efficiencies averaged 95.5 percent and varied in the range between 91.0 and 96.6 

percent. (Standard deviation of these values was 0.27 percent.) By comparison, with 

new SuperGlausTM catalyst and equipment after the initial startup, the calculated 

2
 
Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

(average) process efficiency for December 9 through December 31, 1998, was seen 

to increase to 98.1 percent. These values may represent a level of 'actual' Claus 

process production efficiency, but, again, they are not suitable to be compared with 

the non-applicable NSPS requirements. Please also note again that uncertainties of 

measurement of both input sulfur to the Claus and final output sulfur at the stack can 

affect calculated production efficiency very substantially at these high levels of 

recovery. 

Not surprisingly, the AMP information can be seen to confirm that operations with the 

SuperClausTM processing online result in substantially lower emissions and higher 

efficiencies in sulfur recovery based on the CEMS measurements. 

After reviewing our data in light of the additional information that you provided, we 

respectfully decline to provide a design efficiency or a surrogate for "design" 

efficiency for the Claus Process. We find that term is not defined in applicable law or 

regulations. As we stated in our earlier response to this question, "design efficiency" 

is not a concept used in designing or running the subject processes at MSCC or at 

comparable sources. We note that NSPS itself does not use the term, but instead 

uses a specific "adjusted" ppmv measurement, corrected for water vapor and oxygen 

content, and which we presume is based on thermal incineration rather than catalytic 

incineration. The non-comparable regulatory measure for MSCC would be S02 mass 

emissions, which is measured and used for regulatory purposes other than for 

comparison with NSPS. These values should not be directly compared with the nonapplicable NSPS measurements. 

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

ANSWER: 

Thank you also for the clarification of your definition of "expected remaining 

equipment life." MSCC takes this opportunity to provide additional comment on this 

question. 

In your clarification you have stated: 

Does the company expect to take the emission source out of 

service within the 15-20 [year] time period over which the 

cost of pollution controls would be amortized. If so, for 

how many more years will the source be generating 

emissions[?] 

We have again reviewed our available information and find that MSCC has 

insufficient information to know or estimate when the emission source(s) will be 

taken out of service. That said, MSCC has no current plans or expectation to take 

the emission source(s) permanently out of service. See prior response. Thus 

"expected" remaining useful life remains indeterminate. 

3
 
Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

3.	 SuperClaus process 

d.	 What is the design efficiency? 

ANSWER: 

In our initial response dated March 20, 2009, MSCC reserved the right to supplement 

these responses at a later date if additional information were obtained. Review of the 

process engineering design package for the SuperClausTM indicates that the licensor 

offered an initial performance guarantee of 98.5 percent recovery of sulfur with a 

three-stage Claus process followed by a SuperClausTM process with all new catalyst 

and condenser equipment and very specific process and feed conditions. Please 

note that this number is not a design efficiency value, but is an initial process 

production "performance" value taken in conjunction with the Claus process. No 

other additional design efficiency information has been identified. Please see the 

response to item 2.d above, which provides some insight into 'actual' process 

production efficiencies of the combined SuperClausTM and Claus processes, subject 

to the uncertainties of measurement and variations of day-to-day operation 

discussed there. 

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

ANSWER: 

MSCC reserved the right to supplement this response at a later date if additional 

information or definition were obtained. Please see the response to item 2.e above. 

The expected life of thise equipment remains indeterminate. 

i.	 Expected remaining life of the older SuperClaus process? 

ANSWER: 

In our March 20, 2009, submittal, MSCC reserved the right to supplement this 

response at a later date if additional information or definition were obtained. Please 

see the response to item 2.e above. The expected life of the equipment remains 

indeterminate. 

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

after the SuperClaus effluent units? 

ANSWER: 

In the March 20, 2009, submittal, MSCC reserved the right to supplement this 

response at a later date if additional information or definition were obtained. No 

additional clarification was provided. 

Making room for additional significant tail gas treatment units after the SuperClausTM 

units is not viewed as practical; and no discernible or significant improvement in 

regional haze could result. Please note that MSCC's processing equipment, 

including the two SuperClausTM units, and incineration equipment, now occupy a 

space originally designed, in 1954, to accommodate one Claus train. Please note 

also that MSCC is sited on a narrow parcel of land with roadways and railroad on 

either side making expansion onto adjacent land (owned by others) infeasible. 

4
 
Addendtlffi to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29,2009
 

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

ANSWER: 

MSCC has developed a spreadsheet to respond more fully to this question. The 

spreadsheet is based on information and estimates provided by the designer of the 

first SuperClausTM unit, which in turn were based on various assumptions. (The 

second unit, added in 2008, is substantially identical; each unit is designed to be 

capable of handing Claus tail gases for up to 170 LT per day of upstream Claus feed 

rate, at specific identified conditions. The two SuperClausTM units together are 

believed to be at least adequate for the entire output stream from the upstream 

Claus process and are licensed to process up to 250 LTSE/d). This spreadsheet 

estimates the following values: 

i.	 Maximum volumetric flow rate (acfm): The expected flow rate at the design rate 

(170 LT/day) is 17,650 acfm for either one of the two units. For both of the 

units together, operating at maximum licensed Claus unit sulfur input (250 

LT/day), this spreadsheet indicates a maximum combined expected flow of 

25,958 acfm at the effluent of the SuperClausTM process equipment. Actual 

maximum expected rates would be different under different assumptions. 

ii.	 Average volumetric flow rate (acfm): The estimated flow rate at the average 

2008 process rate of 106 LTSE/d plant input rates was approximately 62 

percent of the design rate for one SuperClausTM unit at approximately 11,006 

acfm. Of course, actual rates will vary substantially with feed gas 

hydrocarbon composition. 

iii.	 Temperature (OF): The temperature of the process gas from the SuperClaus TM 

condenser was modeled by the designer to be approximately 260°F and 

typical actual is more like 290°F. The higher temperature was subsequently 

suggested by the designers to help address corrosion issues found with the 

original design and the feed that is specific to this plant. For 12 'randomly' 

selected days (one day each month) in calendar year 2008, the 

SuperClausTM condenser gas outlet temperature measurement averaged 

283°F. 

iv.	 Moisture (percent): The process gas 'from the SuperClaus TM condenser was 

modeled to contain approximately 23 weight percent water. This also can 

vary substantially, depending on feed composition and other factors. 

v.	 Hours of operation: The sulfur recovery process at MSCC is a continuous 

operation. While operation of the SuperClausTM process is voluntary, one or 

both of the two SuperClausTM units typically operates 24 hours a day, seven 

days a week. This provides a substantial margin of safety for MSCC in 

meeting main stack emission limitations. The primary exceptions to this 

schedule are short (typical durations areef minutes to hours) emergency 

bypass events to protect the expensive and delicate SuperClaus TM catalyst 

from excessively high temperatures and reducing conditions such as may be 

caused by utility interruptions, training events, and startup/shutdown events. 

A primary purpose of the second SuperClaus TM is to ensure that one unit is 

available for the sulfur recovery process at MSCC, while the other is shut 

down for maintenance. Of course, unusual conditions, such as force majeure 

events, could result in both units being down at the same time. 

5
 
Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

vi.	 S02 concentration (ppm): The S02 concentration in the process gas from the 

SuperClausTM condenser was estimated to be approximately 4600 ppm by 

weight. 

vii. H2S concentration (ppm): The H2S concentration in the process gas from the 

SuperClausTM condenser was estimated to be approximately 385 ppm by 

weight. Other reduced sulfur species, including elemental sulfur, are 

estimated to total about 1250 ppm by weight; these species and H2S typically 

oxidize to S02 in the downstream incinerator which is used for control of odor 

and opacity. 

Please note that all detailed process information, other than direct emission 

rates and temperatures at the main stack, relating to the SuperClaus TM 

process as modeled or operated is Confidential Business Information. 

4.	 Tail gas incinerator 

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

ANSWER: 

In our submittal of March 20, 2009, MSCC reserved the right to supplement this 

response at a later date if additional information or definition were obtained. Please 

see the response to item 2.e above. The expected life of the equipment remains 

indeterminate. 

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 EPA. The area is 

occupied by existing equipment, such as the existing Claus and SuperClaus TM 

equipment. See response above. A photograph of the area in question is shown on 

the final page of this attachment. 

MSCC may supplement this response as additional information and clarification are 

obtained. 

c.	 Incinerator operating characteristics: 

ANSWER: 

i.	 Maximum heat input? 

MSCC reserved the right tQfAaY supplement this response as additional information 

and clarification weare obtained. MSCC has no information to expand on the design 

information provided earlier of 35 MMBtu/hr. This value is documented in MSCC's Air 

Quality Permit AQP2611-03 and also is applicable for the new redundant incinerator 

operating in non-catalytic mode of operation. A review of the 2008 data suggests that 

the actual maximum heat (daily) input during the calendar year was approximately 8 

million Btu/hr for the existing incinerator, which runs essentially all of the time. Heat 

input varies with production rates, weather conditions, and operating temperatures. 

Fuel use, operating temperature, flow, inerts and CO2 errtissions are expected to be 

substantially higher when the less energy efficient non-catalytic option is used. 

6
 
Addendum to Attachmel1t A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 of the CAA
 

January 29, 2009
 

ii. Average heat input? 

The review of calendar 2008 data suggests that the average heat input to the 

existing incinerator was 4 to 5 million Btu/hr. Average heat input will vary with 

average plant throughput and mode of operation. The unit operated in the more 

energy efficient catalytic mode during the year 2008. 

e. Conditions of the incinerator exhaust gas: 

ANSWER: 

MSCC does not directly measure conditions at the outlet of the tail gas incinerator 

other than temperature at this time. The conditions in the main SRU stack are the 

most characteristic data available for the variety of information requested, as much of 

the gas at that stack arises from the incinerator outlet flows. As stated above, the 

main SRU stack is a merged stack, with contributions to the measured stream from 

the Claus process and the SuperClausTM process feeding the incinerator, along with 

intermittent contributions from other gas-fired boilers, etc. CEMS and operating data 

for 2008 were reviewed to identify periods when the Claus and one or more 

SuperClausTM processes were operating, but other gas-fired boilers were not 

operating and thus not expected to be contributing significant flow to the merged 

stack stream. The responses below generally provide main-stack CEMS values 

characteristic of such periods. Main stack moisture percentage is measured only 

during the annual RATA. These values are the most representative actual 

measurement data for the tail gas incinerator output stream for the calendar year 

2008. 

i.	 Maximum volumetric flow rate (acfm): The CEMS measures the flow rate 

continuously and records the information in units of wet standard cubic feet per 

hour. The CEMS also measures stack temperature and stack pressure 

continuously and records these data on an hourly basis. Using that information, 

the maximum hourly average volumetric flow rate when no gas-fired boilers were 

operating, but the Claus and SuperClausTM processes were operating in 

calendar year 2008 was determined to be 29,057 ac'fm. No specific design 

information was identified as to potential "maximum volumetric 'flow." 

ii.	 Average volumetric flow rate (acfm): Using the same methodology as discussed 

in i. above, the hourly average volumetric flow rate for calendar year 2008 when 

no gas-fired boilers were operating, but the Claus and SuperClausTM processes 

were operating was determined to be 24,704 ac'fm. 

Ill.	 Temperature (OF): The CEMS measures the stack temperature continuously 

and records these data on an hourly basis. The average stack temperature for 

calendar year 2008 when no gas-fired boilers were operating, but the Claus and 

SuperClausTM processes were operating was determined to be 548°F. Over 

these selected periods in calendar year 2008, the stack temperature ranged from 

497°F to 612°F at the CEMS. The temperature at the incinerator outlet is 

somewhat higher than the temperature observed at the stack. A random 

sampling of incinerator outlet temperature process data for calendar year 2008 

showed an average of 608°F and a range of 550°F to 648°F (standard deviation 

of 2.9°F). The maximum expected temperature at the main stack is -1200°F, 

which might be seen in the event of non-catalytic operation of the incinerator. 

7
 
Addendllm to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

iv.	 Moisture (percent): The moisture in the SRU stack is measured only during the 

a.nnual RATA. Over the past three years, only the RATA conducted in 2006 

occurred on a day when there were no additional contributions from gas-fired 

boilers. The moisture ranged from 17.85 to 18.64 during the RATA on November 

21,2006. 

v.	 Hours of operation: The sulfur recovery process at MSCC is a continuous 

operation. Thus, the incinerator normally operates 24 hours a day, seven days a 

week. The prima.ry exceptions to this schedule would be for repairs to the 

incinerator itself, training events, malfunctions, utility interruptions, or other force 

majeure events. 

vi.	 S02 concentration (ppm): During such hours of non-operation of other boiler 

contributors to the stack in calendar year 2008, the average 1-hour S02 

concentration was determined to be 2,629 parts per million by volume (ppmv). 

The CEMS value ranged from 6,191 ppmv to 1,442 ppmv. The higher value 

occurred during an hour that a Claus recovery boiler was re-started after being 

off-line for approximately two weeks because of very low input gas feed flows. 

Concentrations of S02 at the main SRU stack are generally lower during periods 

of fuel gas boiler operation with this merged stack, since these fuel gas-fired 

boilers contribute only trivial amounts of sulfur dioxide. 

vii.	 H2S concentration (ppm): The purpose of the tail gas oxidizer (TGO) is to 

oxidize substantially all of the H2S and other reduced sulfur in the incoming 

stream to the TGO to S02. H2S is not monitored in the stack gas, nor is it 

expected to be present in significant amounts or concentrations due to the 

operation of the incinerator itself. 

5.	 Flares 

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

ANSWER: 

See the March 20, 2009, response. MSCC may supplement this response as 

additional information and clarification are obtained. MSCC is considering the 

possibilities of re-routing certain low volumetric (currently defined as de minimis) 

flows of potentially waste gases that are currently potentially sent to the flare system 

to more beneficial destinations in the facility. Details are not available at this time. No 

significant impact on flare or plant S02 emissions is expected from this possible 

work. 

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

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

ANSWER: 

Thank you for the clarification of your thinking concerning a flare gas recovery 

system. MSCC takes this opportunity to provide additional response to this question. 

Please also see our response in the March 20, 2009, submittal. 

You have stated: 

Flare gas recovery system 

8
 
Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

We were thinking of a system referred to in a STAPPA/ALAPCO 

menu of controls, which states: "Refineries can also install flare 

gas recovery systems to collect and treat refinery gases, reducing 

the need for flaring while at the same time recovering the gas for 

use in refinery furnaces and boilers. Several such installations 

already exist in New Jersey ... " This and other examples of 

potential flare controls are discussed by the California Bay Area 

APCD at http://www.baagmd.gov/enf/flares.htm. 

MSCC is considering how such a system might be constructed and operated and the 

implications associated with re-routing some low volumetric flows of gases otherwise 

destined for combustion at the flare. Safety concerns preclude "holding" flare gases 

that might arise in large volumes from emergency, malfunction, or startup/shutdown 

activities at MSCC. Please note that MSCC is not a refinery. 

Review of the documentation referred to in EPA's response did not fiRidentifya a 

system in use that claims to Ihold' gases of high H2S concentration per se for future 

treatment or use. Our review found refinery flare gas recovery systems that appear 

to treat gases (up to some flow, pressure, concentration or temperature limit) as they 

arrive, by limited redirection to a refinery fuel gas recovery system. As previously 

indicated, operations at MSCC already assist in the successful operation of such a 

limited system at a nearby refinery. However, these methods by their nature presuppose and require the operation of the fuel gas treatment system (e.g., amine unit) 

and downstream sulfur recovery plant operations, and are therefore impractical or 

limited during periods of malfunction, startup or shutdown affecting either of those 

critical systems. They also require an appropriate and large enough user to be 

operating at the facility to consume the fuel as it is recovered. Since most significant 

flaring that occurs at MSCC currently arises from startup/shutdown and malfunction 

events affecting precisely these two types of systems (sulfur recovery and fuel gas 

treatment), we must conclude that such a system would not be practical here for 

mitigating such events. 

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 900

/O? 

ANSWER: 

In the March 20, 2009, submittal, MSCC reserved the right to supplement this 

response as additional information and clarification are obtained. No such additional 

information or clarification was identified. It may be noted that the volume of toxic 

and flammable gases hypothetically "held" identified in the March 20, 2009, response 

could be much larger if the concentration of H2S in flare gases were lower than the 

90 percent H2S assumed in the example. 

6. Other pollution control equipment (if applicable) 

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

ANSWER: 

In our subrrlittal of March 20, 2009, MSCC reserved the right to supplement this 

response at a later date if additional information or definition were obtained. Please 

see the response to item 2.e above. 

9
 
Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

Jal1uary 29,2009
 

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 available? 

ANSWER: 

In the March 20, 2009, submittal, MSCC reserved the right to supplement this 

response as additional information and clarification are obtained. Final or total 

emissions from the main stack (and flares) have already been identified and are 

publicly available. No additional information was identified. 

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

ANSWER: 

In our submittal of March 20, 2009, MSCC reserved the right to supplement this 

response as additional information and clarification are obtained. No such additional 

information was identified; however, we would like to expand on our previous 

response. 

Yes, on information and belief, bypass certainly occurred as needed. Bypass is an 

essential design function of the catalytic selective oxidation process and is necessary 

during startup/shutdown and malfunction to prevent damage to the system and to the 

selective oxidation catalyst in particular. MSCC does not maintain records 

specifically that allow ready identification of all periods of bypass for a particular 

SuperClausTM unit or for the SuperClausTM process as a whole. However, the unit(s) 

and/or process were bypassed from time to time during calendar 2008, as 

appropriate, for periods involving utility interruptions and for startup and shutdown of 

particular units in the process or during startup/shutdown activities related to the 

upstream Claus system. The identified activities for the SuperClausTM units are 

shown in the table below. It shows that the second unit was brought online for the 

first time on May 5, 2008. The first SuperClausTM unit was normally running during 

calendar year 2008 though occasionally it was bypassed for short periods of time 

until it was shut down for repairs on November 11. During the second unit startup, 

testing and conditioning time, the second unit was bypassed numerous times as 

needed. The first unit was taken offline (and fully bypassed) on November 11, 2008, 

and remained shut down until March 12, 2009. During that remaining period in 2008, 

the second SuperClausTM process was normally running, although it may have been 

occasionally bypassed for short periods of time. 

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Addendum to Attachment A
 

Montana Sulphur & Chemical Company
 

Request for Information Pursuant to Section 114 ofthe CAA
 

January 29, 2009
 

Date 

1/1/2008 

5/5/2008 

6/30/2008 

7/3/2008 

7/22/2008 

8/17/2008 

10/24/2008 

10/3112008 

SuperClausTM West 

(first unit) 

Operating normally 

Shut down for maintenance at 

16:40 

Returned to service after 

maintenance 

Hot temperature trip during flare 

event (minutes) 

SuperClausTM East 

(second unit) 

Started up for first time 

Down 1.25 hours due to malfunction 

between 20:30 and 21 :45 

Shut down for a few hours for repairs 

High concentration trip during flare 

event (minutes) 

Bypassed for 199 minutes for 

troubleshooting and maintenance 

Trip (12 minutes) due to electrical 

interruption 

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

different? 

ANSWER: 

MSCC reserved the right to supplement this response as additional information and 

clarification are obtained. No such additional specific information was identified. 

Since, on information and belief, one or both units were running during substantially 

the entire year, we do not believe emissions would have been substantially different 

if there had been uno periods of bypass" of the SuperClausTM process arising from 

malfunction, startup, shutdown, or maintenance/training activities for the year 2008. 

The SuperClausTM process does not process tail gas during periods when there is no 

normal Claus processing upstream; for example, during periods of startup/shutdown 

of the entire upstream Claus process. One such period occurred on a partial day in 

2008 as has been previously reported in our March 20, 2009, submittal. It should be 

noted that Ubypass" during certain adverse input conditions and malfunctions is a 

design necessity for this process to prevent damage to the process itself; operation 

during such conditions could actually lead to increased emissions arising from 

equipment damage and downtime. 

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