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PERMIT MEMORANDUM 2007-193-TVR DRAFT
OKLAHOMA DEPARTMENT OF ENVIRONMENTAL QUALITY
AIR QUALITY DIVISION
MEMORANDUM February 28, 2008
TO: Phillip Fielder, P.E., Engineer Manager, Air Quality Division
THROUGH: Kendall Stegmann, Environmental Programs Manager, Enforcement
THROUGH: Phil Martin, P.E., Engineering Section
THROUGH: Grover Campbell, P.E., Existing Source Permit Section
THROUGH: Peer Review
FROM: Donna Lautzenhiser, E.I., New Source Permit Section
SUBJECT: Evaluation of Permit Application Number 2007-193-TVR
Enogex Inc.
Thomas Tie Compressor Station
SE/4 Sec.33-T15N-R15W, Custer County
Latitude: 35.740°, Longitude: -98.795°
Driving Directions: From Thomas, OK, travel two (2) miles west on SH-33, then travel north a half (1/2) mile and west a half (1/2) mile into the facility.
SECTION I. INTRODUCTION
Enogex has requested a Title V operating permit renewal for their Thomas Tie Compressor Station (SIC Code 4922). Enogex acquired this facility from Transok, L.L.C. in July 1999. Enogex submitted a Title V operating permit renewal application on September 21, 2007. The facility is a transmission line compressor station and currently operating under Permit No. 97-119-TV, which was issued on April 4, 2003. Major process equipment include four (4) compressor engines, one (1) glycol dehydration unit, and six (6) 400-bbl condensate storage tanks at the site. The first three compressor engines are lean burn engines and the fourth compressor engine is a rich burn engine without a catalytic converter. Minor equipment includes various smaller storages tanks and associated piping.
By taking a runtime limit of 2,190 hours per year, the uncontrolled emissions of total volatile organic compounds (VOC) and total hazardous air pollutants (HAP) from the 0.5-MMBTUH glycol dehydration unit have been estimated at 55.72 TPY and 14.00 TPY, respectively. A condenser (BTEX eliminator), with a 95% control efficiency, and limited operating hours, reduces the total VOC and total HAP emissions to 14.53 TPY and 1.19 TPY, respectively, from the glycol dehydration unit. Establishing a federally enforceable condition requiring emissions from the dehydration unit to be controlled by the BTEX eliminator exempts the facility from all requirements except the recordkeeping requirements of NESHAP, Subpart HH. This facility emits more than 100 TPY of regulated pollutants (NOx, CO and VOC) and is subject to Title V permitting requirements. Supplemental information submitted on May 4, 2006 revised emission limitations for the six condensate storage tanks to include flash emissions along with revising emissions associated with the glycol dehydrator, piping fugitives, and condensate truck loading. Currently, the modified permit has not been issued, therefore, the changes will be incorporated in this permit renewal.
SECTION II. FACILITY DESCRIPTION
The facility is a natural gas transmission line compressor station. Natural gas is transported to the facility via a pipeline gathering system. The gas stream enters the facility through five inlet separators, where free liquids (water and condensate) are removed from the inlet stream and collected in six 400-barrel condensate tanks (E-TANK-1 to E-TANK-6). The natural gas stream then enters three compressors (E-401, E-402, and E-412), which boost the gas pressure from 450~500 psig to 700~750 psig. Under normal conditions, the compressed gas is returned to the discharge pipeline and exits the facility.
When the incoming gas stream is wet and the molecular sieve columns in the adjacent Thomas Processing Plant fail, then, the natural gas from the Thomas Plant will be directed to the dehydration unit for water removal. The water removal is to prevent formation of hydrate and corrosion in the pipeline. A lean glycol stream contacts the wet gas where water is absorbed from the wet gas. The rich glycol stream, which contains the absorbed moisture and hydrocarbons, is flashed then transferred to the glycol regenerator (reboiler). The glycol stream is stripped of water and recycled to the contactor/absorber for reuse. Vapors from the glycol dehydrator still vent are routed through the JATCO BTEX Eliminator condenser. The condenser controls the HAP and VOC emissions and is designed to operate as a “closed system.” The non-condensable vapors are routed to the reboiler for combustion as fuel. The condenser is operated in such a way that if the reboiler discontinues operation, the non-condensable vapors are vented to a “glow plug” which acts as an incineration device. The overall minimum control efficiency for VOCs and HAPs is 95%. Liquids collected from the condenser are sent to the existing condensate storage tanks. The dehydration unit is equipped with a 0.50 MMBTUH gas-fired burner to provide heat to distill water and volatile organic compounds out of rich glycol stream. The natural gas is processed through the dehydration unit at maximum 160 MMSCFD. After water-removal, the dried and compressed natural gas is returned to the discharge pipeline.
The fourth compressor unit, a White-Superior engine (E-416), is used only for VOC recovery during pipeline pigging operations. The pigging operation involves a mechanical cleaning process where the pig is pressured through the gas line. The pig is a piece of equipment, made of hard rubber or elastic thermoplastics, that is inserted into a pipeline and is propelled along by the flow of the gas; used to clean or monitor the internal condition of the pipeline or to mark an interface between two different products. On the receiving end, the pipeline diameter widens allowing for easy removal of the pig from the line. Block-off valves seal behind and in front of the pig. Vapor recovery through a closed vent system begins, using the White-Superior 8G825 (E-416) compressor. Condensate is sent to a sump and then pumped to a condensate tank. The vapor and useable product is sent back to the inlet. The pigging system allows the recovery of "lost" product, pipeline cleaning and inspection. The E-416 compressor is operated with 5~10 psig at the suction side and 650~750 psig at the discharge side. Some fugitives are emitted from this process as well as from other components throughout the plant.
SECTION III. EQUIPMENT
Emission units (EUs) have been arranged into Emission Unit Groups (EUGs) in the following outline.
EUG 1. Natural Gas-Fired Internal Combustion Engines
EU ID # / Point # / Make/Model / HP / Serial # / Date InstalledE-401 / P-401 / MEP/6GT Engine / 1,500 / 80299 / 1981
E-402 / P-402 / MEP/6GT Engine / 1,500 / 952535 / 1981
E-412 / P-412 / MEP/8GT Engine / 2,000 / 81327 / 1990
E-416 / P-416 / White Superior 8G825 / 800 / 282989 / 1993
EUG 2. Glycol Dehydration Unit Reboiler/Still Vent
EU ID # / Point # / Make/Model / MMBTUH / Date InstalledE-DEHY
/ P-VENT / Dehydrator Still Vent / ----- / 1996E-RBLR / P-RBLR / Dehydrator Reboiler / 0.5 MMBTUH / 1996
EUG 3A. Condensate Storage Tanks
EU ID # / Point # / Capacity (barrel/gallon) / Material Stored /Date Constructed
/ EU ID #E-TANK-1 / P-TANK-1 / 400/16,800 / Condensate / 1981 / E-TANK-1
E-TANK-2 / P-TANK-2 / 400/16,800 / Condensate / 1981 / E-TANK-2
E-TANK-3 / P-TANK-3 / 400/16,800 / Condensate / 1981 / E-TANK-3
E-TANK-4 / P-TANK-4 / 400/16,800 / Condensate / 1993 / E-TANK-4
E-TANK-5 / P-TANK-5 / 400/16,800 / Condensate / 1993 / E-TANK-5
E-TANK-6 / P-TANK-6 / 400/16,800 / Condensate / 1993 / E-TANK-6
EUG 3B. Insignificant Storage Tanks
EU ID # / Point # / Capacity (barrel/gallon) / Material Stored /Date
Constructed
E-TANK-7 / P-TANK-7 / 14.3/600 / Lube Oil / 1981E-TANK-8 / P-TANK-8 / 14.3/600 / Lube Oil / 1981
E-TANK-9 / P-TANK-9 / 14.3/600 / Lube Oil / 1981
E-TANK-12 / P-TANK-12 / 14.3/600 / Lube Oil / 1981
E-TANK-13 / P-TANK-13 / 14.3/600 / TEG / 1996
E-TANK-15 / P-TANK-15 / 50/2,100 / Used Oil / 1993
E-TANK-16 / P-TANK-16 / 210/8,820 / Methanol / 1999
E-TANK-17 / P-TANK-17 / 9.5/400 / Methanol / Unknown
E-TANK-18 / P-TANK-18 / 14.3/600 / Methanol / Unknown
E-TANK-19 / P-TANK-19 / 14.3/600 / Lube Oil / Unknown
E-TANK-20 / P-TANK-20 / 11.9/500 / Ambitrol / Unknown
E-TANK-21 / P-TANK-21 / 14.3/600 / Ambitrol / Unknown
E-TANK-22 / P-TANK-22 / 120/5,040 / Wastewater / Unknown
EUG 4. Fugitive VOC Emission Sources
EU ID # / Type of Equipment / Number*Gas / Liquid
E-FUG / Valves / 100 / 20
Flanges / 220 / 22
Compressor Seals / 80 / 0
Pump Seals / 0 / 12
Relief Valves / 50 / 10
* Estimate only, not a permit limit
SECTION IV. AIR EMISSIONS
The emission factors for compressor engines are presented in Table 1. Table 2 lists the engine specifications. Table 3 presents the criteria pollutant emissions from the compressor engines based on 8,760 hours per year operation except for E-416, which will be limited to 6,200 hours per year. Table 5 lists the fugitive VOC emissions from the facility. Fugitive emissions are based on Table 2-4 of “1995 Protocol for Equipment Leak Emission Estimates” (EPA 453/R-95-017), Oil and Gas Production Operations Average Emission Factors. Working and breathing losses from storage tanks were determined using TANKS 4.0. Flash emissions were estimated using the WinSim, Inc. Design II process simulation program.
Table 1 Emissions Factors for Compressor Engines
Source / Qty / NOx(g/hp-hr) / CO
(g/hp-hr) / VOC
(g/hp-hr) / HCOH
E-401, E-402, E-412, MEP
Engines without C/C / 3 / 4.0 / 2.0 / 1.0 / 0.14(g/hp-hr)*
E-416, 800-hp White Superior
8G825 Engine without C/C / 1 / 10.0 / 10.0 / 0.4 / 0.0205(lb/MMBtu)**
*HCOH emission factor is based on stack tests performed by CETCON on August 7, 2003.
** HCOH emission factor based on AP-42 (7/00) Sec. 3.2
Table 2 Engine Specifications
Parameter / E-401 & E-402 / E-412 / E-416Manufacturer / MEP / MEP / White Superior
Model / 6GT / 8GT / 8G825
Control / None / None / None
Input Parameter
Horsepower (max) / 1,500 / 2,000 / 800
Fuel Consumption (BTU/hp-hr) / 7,100 / 7,400 / 8,000
Fuel Usage (SCFH) / 10,650 / 14,800 / 6,400
Stack Diameter (Inches) / 10 / 24 / 12
Height above Grade (Feet) / 14 / 39 / 15
Exhaust Flow (ACFM) / 11,500 / 13,300 / 4,140
Exhaust Temperature (oF) / 700 / 625 / 1,300
Table 3 Emissions From Compressor Engines
ID # / Source / NOx / CO / VOC / HCOClb/hr / TPY / lb/hr / TPY / lb/hr / TPY / lb/hr / TPY
E-401 / 1,500-hp
MEP/6GT Engine / 13.23 / 57.94 / 6.61 / 28.97 / 3.31 / 14.48 / 0.46 / 2.01
E-402 / 1,500-hp
MEP/6GT Engine / 13.23 / 57.94 / 6.61 / 28.97 / 3.31 / 14.48 / 0.46 / 2.01
E-412 / 2,000-hp
MEP/8GT Engine / 17.64 / 77.25 / 8.82 / 38.62 / 4.41 / 19.31 / 0.62 / 2.71
E-416 / 800-hp
White Superior 8G825 / 17.64 / 54.67 / 17.64 / 54.67 / 0.71 / 2.19 / 0.13 / 0.57
Total Emissions / 61.74 / 247.80 / 41.68 / 151.23 / 11.74 / 50.46 / 1.67 / 7.30
Table 4 Tanks
EU ID # / Point # / Capacity (barrel/gallon) / Annual VOCEmissions
E-TANK-1 / P-TANK-1 / 400/16,800 / 166.02
E-TANK-2 / P-TANK-2 / 400/16,800
E-TANK-3 / P-TANK-3 / 400/16,800
E-TANK-4 / P-TANK-4 / 400/16,800
E-TANK-5 / P-TANK-5 / 400/16,800
E-TANK-6 / P-TANK-6 / 400/16,800
Table 5 Fugitive VOC Emissions
Component / Type of Service / Number / Emission Factor(lb/hr-source) / VOC Emissions
lb/hr / TPY
Valves
/ GV / 100 / 0.00992 / 0.11 / 0.50Flanges / GV / 220 / 0.00086 / 0.02 / 0.10
Compressor Seals / GV / 80 / 0.0194 / 0.18 / 0.78
Relief Valves / GV / 50 / 0.0194 / 0.11 / 0.49
Valves
/ LL / 20 / 0.0055 / 0.11 / 0.48Flanges / LL / 22 / 0.0002 / 0.01 / 0.02
Pump Seals / LL / 12 / 0.0287 / 0.34 / 1.51
Relief Valves / LL / 10 / 0.0165 / 0.17 / 0.72
Subtotal
/ 534 / 1.05 / 4.60The dehydration unit is equipped with a 0.50 MMBTUH gas-fired burner to provide heat to distill water and volatile organic compounds out of rich glycol stream. The natural gas is processed through the dehydration unit at maximum 160 MMSCFD. Emission estimates for this facility were supplied by Enogex. The 0.50 MMBTUH glycol reboiler unit emission estimates are based on 2,190 hr/yr operation, 1,020 BTU/SCF average heating value, and on the emission factors in AP-42 (7/98), Tables 1.4-1, 1.4-2, and 1.4-3, Section 1.4, “Natural Gas Combustion”. Table 6 shows the parameters for the glycol dehydration unit. The following table lists the inputs used in GRI-GLYCalc 4.0 to calculate emissions from the glycol dehydration unit.
Table 6 Parameters for the Glycol Dehydration Unit (GRI-GLYCalc 4.0)
Parameter /Value
/Unit
I. D. / E-DEHY / ------Throughput / 160.0 / MMSCFD
Operating Hours / 2,190 / hr/yr
Temperature / 65 / °F
Pressure / 700 / Psig
Lean Glycol Flow Rate / 7.5 / gpm
Flash Tank / Yes / ------
Flash Tank Temperature / 90 / °F
Flash Tank Pressure / 44 / Psig
Add-on Controls-Reboiler
Still Vent/Flash Tank / Still Vent – BTEX Eliminator/
Flash Tank – Routed to Fuel / ------
Control Efficiency used in GRI-GLYCalc / Still Vent - 95%
Flash Tank - 50% / ------
Dehydration units using glycol desiccants emit benzene, toluene, ethyl benzene, xylene (BTEX), and n-hexane. The applicant has estimated the air toxics emissions using the “Atmospheric Rich/Lean” (ARL) method per GRI-GLYCalc 4.0 Manual, The VOC and HAP emissions are estimated and presented below.
Table 7 VOC and HAP: Uncontrolled and Controlled Emissions (GRI-GLYCalc 4.0)