-------
TECHNICAL REPORT DATA
(Pleea read lasouetions on the reverse before cample.
1. REPORT NO,
EPA-60G/R-96-080o
4. TITLE AND SUBTITLE
Methane Emissions from the Natural Gas Industry,
Volumes 1-15 (Volume 15: Gas-Assisted Glycol
Pumps)
6. REPORT DATE1
June 1996
6. PERFORMING ORGANIZATION CODE
PB97-143069
7. AUTHOB(S)
. Campbell, M, Campbell, M, Cowgill, D. Ep-
person, M. Hall, M. Harrison, K . Hummel, D. Myers,
T, Shires, B. Stapper, C. Stapper, J. Wessels, and *
8. PERFORMING ORGANIZATION REPORT NO.
DCN 96-263-081-17
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian International LLC
P. O. Box 201088
Austin, Texas 78720-1088
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
5091-251-2171 (GRI)
68-D1-0031 (EPA)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Mr Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND
Final; 3/81-4/96
PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
is.SUPPLEMENTARY NOTES EPA project officer is D. A. Kirchgessner, MD-S3,919/541-4021.
Cosponsor GRI project officer is R. A. Lofct, Gas Research Institute, 8600 West Bryn
Mawr Ave.. Chicago. IL 60631. (*)H. Williamson (Block 7).
ABSTRACT-];^ 15~volume report summarizes the results of a comprehensive program
to quantify methane (CH4) emissions from the U,S. natural gas industry for the base
year. The objective was to determine CH4 emissions from the wellhead and ending
downstream at the customer's meter. The accuracy goal was to determine these
emissions within +/-0. 5% of natural gas production for a 80% confidence interval. For
the 1992 base year, total CH4 emissions for the U. S. natural gas industry was 314
+/-- 105 Bscf (6.04 +/- 2.01 Tg). This is equivalent to 1.4 +/- 0.5% of gross natural
gas production, and reflects neither emissions reductions (per the voluntary Ameri-
Gas Association/EPA Star Program) nor incremental increases (due to increased
gas usage) since 1992. Results from this program were used to compare greenhouse
gas emissions from tne fuel cycle for natural gas, oil, and coal using the global war-
ming potentials (GWPs) recently published by the Intergovernmental Panel on Climate
Change (IPCC). The analysis showed that natural gas contributes less to potential
global warming than coal or oil, which supports the fuel switching strategy suggested
by the IPCC and others. In addition, study results are being used by the natural gas
industry to reduce operating costs while reducing emissions.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution
Emission
Greenhouse Effect
Natural Gas
Gas Pipelines
Methane
b.lOENTIFIEBS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Prevention
Stationary Sources
Global Warming
13 B
14G
04A
21D
15E
07C
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport}
Unclassified
21. NO. OF PAGES
30
20. SECURITY CLASS (This page)
Unclassified
EPA Form 2220-1 (9-73)
-------
FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national
environmental lawa, the Agency strives to formulate and implement actions lead-
ing to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research
program is providing data and technical support for solving environmental pro-
blems today and building a science knowledge base necessary to manage our eco-
logical resources wisely, understand how pollutants affect our health, and pre-
vent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks
from threats to human health and the environment. The focus of the Laboratory1 s
research program is on methods for the prevention and control of pollution to air,
land, water, and subsurface resources! protection of water quality in public water
systems; remediation of contaminated sites and groundwater; and prevention and
control of indoor air pollution. The goal of this research effort is to catalyze
development and implementation of innovative, cost- effective environmental
technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and infor-
mation transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Re-
search and Development to assist the user community and to link researchers
with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161.
PROTECTED UNDER INTERNATIONAL COPYRIGHT
ALL RIGHTS RESERVED.
NATIONAL TECHNICAL INFORMATION SERVICE
U.S. DEPARTMENT OF COMMERCE
-------
EPA-600/E-86-080o
June
METHANE EMISSIONS FROM
THE NATURAL GAS INDUSTRY,
15; GLYCOL
Prepared by:
Duane B, Myers
R,
LLC
8501 N.
P.O. Box
Austin, TX 78720-1088
DCN: 95-263-081-11
For
GM Project A. Lett
GAS
No, 5091-251-2171
8600 West Bryn Mawr Ave.
Chicago, IL 60631
and
EPA David A.
U.S.
No. 6S-D1-OG31
National Research Laboratory
Triangle Park:, NC 27711
-------
DISCLAIMER
LEGAL NOTICE; This report was prepared by Radian International IXC as an account
of work by Gas (GRI) the U.S. Environmental Protection
Agency (EPA). EPA, GB1, of GH, nor any on of
either:
a. Makes any warranty or representation, express or implied, with respect to fee
accuracy, completeness, or usefulness of the information contained in this
report, or that the use of any apparatus, method, or process disclosed in this
report not privately owned rights; or
b. any liability with to the use of, or for resulting
from the use of, any information, method, or disclosed in
this report.
NOTE: EPA's Office of Research and Development quality assurance/quality control
(QA/QC) requirements are to of the count by this project
and are or and are not
to EPA/ORD's QA/QC policies. In all and were reviewed by the
panel of experts listed in Appendix D of Volume 2.
-------
Title
Contractor
Principal
Investigators
Report Period
Objective
Technical
Perspective
Results
Methane Emissions from the Natural Gas Industry,
Volume 15; Gas-Assisted Glyeol Pumps
Report
LLC
GRI Contract 5091-251-2171
EPA Contract Number 68-D1-0031
Duane B. Myers
Matthew R, Harrison
1991 - June 1996
Final Report
This report describes a study to quantify the
from gas-assisted glycol pumps, which are significant sources of methane
emissions within the gas industry.
The increased use of natural gas has been suggested as a strategy for
reducing the potential for global warming. During combustion, natural
gas less carbon dioxide (CO2) per unit of energy produced than
or oil. On the of the of CO2 the
for global warming could be reduced by gas
for or oil. However, gas is a
gas, of natural gas during production, processing,
and distribution reduce the of its
lower CO2
To investigate this, Gas Research Institute (GRI) and the U.S.
Environmental Protection Agency's Office of Research and Development
(EPA/ORD) cofunded a major study to quantify from
U.S. gas for the 1992 year. The of this
study can be used to construct and to
the on of gas oil.
The for glycol pumps are production,
11.0 ± 110% Bscf and gas 0.1? ±
Based on data from the entire program, methane emissions from natural
gas operations are estimated to be 314 ± 105 Bscf for the 1992 base
year. This is about 1.4 ± 0,5% of gross natural gas production. The
HI
-------
overall the of for an
in gis be lower
the
The program reached its accuracy goal and provides an accurate estimate
of methane emissions that can be used to construct U.S. methane
inventories and analyze feel switching strategies.
Technical Olyeol are to gas
Approach A (low glycol is the
gas and the glyeol most of the water. At locations
without electricity, pumps that circulate the glycol may recover energy
from the high-pressure gas/glycoi mixture to provide motive force for the
lean glycol. Additional gas is with the glycol to supply the
The gas is from the
glycol in a or in the reboiler the glycol is
Gas removed in the is typically as fuel, but gas
removed in me regenerator is often emitted to the atmosphere,
The techniques used to determine methane emissions were developed to
be of from the gas industry,
However, it is to every for a
year. Therefore, for glycol pumps
by for in
industry segmeiJ and these on activity
factors to develop a national estimate, where the national emission rate is
the product of the emission factor and activity factor.
by of gas
from site and
to develop the of glycol
dehydratero. An emission factor was developed for gas-assisted glycol
pumps that reported the amount of methane emitted per unit of natural
gas throughput.
The of activity for industry are
in a report. In general, the gas throughput for
the
entire Industry, No active pumps were found during the site
visits to transmission and storage stations, so the activity factors for these
industry segments are zero.
Project For the 1992 year the for the
U.S. gas Is 314 Bsef ± 105 Bscf (± 33%). This is
to 1.4% ± 0,5% of gas production.
IV
-------
this program were used to compare greenhouse gas emissions from the
cycle fat oil, coal the
(GWPs) by the on
Climate (IPCC), The gas
contributes less to potential global warming than or oil, which
supports the fuel switching strategy suggested by IPCC and others.
In this are by the gas
to while
are in the Natural Gas-Star a
voluntary by EPA's Office of Air In
cooperation with the American Gas Association to implement cost-
effective emission reductions and to report reductions to the EPA. Since
this program was begun after the 1992 baseline year, any reductions in
this are not reflected in this study's
total
Robert A. Lott
Senior Project Manager, Environment and Safety
-------
OF
1.0 , , , , , , 1
2.0 INTRODUCTION , 2
3,0 .... 3
4.0 6
5.0 ACTIVITY FACTOR , 7
6.0 10
6.1 Emission-Affecting 10
6.2 Factor Calculations , 10
7.0 ANNUAL METHANE EMISSIONS 14
8.0 .......... 15
A - . A-l
VI
-------
LIST OF FIGURES
Page
3-1 Isometric Flow Diagram of a Glyeol Dehydrator Unit ., ..,,,,,,,,... 4
3-2 Block Process Flow Diagram of Glycol Pumping System . , , 5
LIST OF TABLES
Page
5-1 U.S. Gas Industry'Characteristics for of Activity for
Gas-Assisted Glycol Pumps 8
5-2 U.S. Gas Industry Characteristics for Calculation of Emission Factors for
Gas-Assisted Glycol Pumps ..,,....,..,... 9
VII
-------
1.0
This report is one of several volumes that provide background information
supporting the Gas Research Institute and U.S. Environmental Protection Agency Office of
and (GRI-EPA/ORD) project. The objective of
this comprehensive program is to quantify the methane emissions from the gas industry for
the 1992 base year to within ± 0,5% of natural gas production starting at the wellhead and
of the
This report documents the basis for calculating the emissions from gas-
glyeol in the gas industry. glycol are one
of the types of Gas the
High-pressure glycol and gas are let down across the driver side of the pump, and the
energy recovered is used to recirculate the glycol. Most of these pumps emit the spent gas
to the through the glycol to pumps are a
but of
The for glycol are production, 10.96 ±
1 IG% and gas 0,1? ±
-------
2,0 INTRODUCTION
This report their
and provides U.S. for the 1992 year,
Background information on gas-assisted pumps is given in Section 3, and sources of data
are listed in Section 4. Activity factors, which are the yolume of gas processed in each
by with are to 5.
are the per of gas are
in 6, for fa are
given in Section 7.
For on and for
on to dehydretors, to Volume 14 on glycol
dehydrators.1
-------
3.0 GAS-ASSISTED PUMP APPLICATIONS
Al! components: a driver and a
side. The driver provides the for pumping, and the motive the
to the fluid being moved. In a typical centrifugal pump, the driver is an electric motor and
the motive side is an impeller within a pump casing. This report discusses positive-
displacement, glycol pumps (also called gas-driven pumps)
Other gas are in a
report, Volume 13 on injection pumps,2
In many glycol dehydrators in the gas industry, small gas-assisted pumps are
to the glycol. These recover the high-pressure rich
the and use to the
glycol into the absorber. Figure 3-1 shows an isometric flow diagram of a typical
field glyeol dehydrator unit with a gas-assisted glycol pump.
Normal electrical pump configurations would have level controllers in the
to gas from the the rich glycol. The
pumps in glycol circulation have a design and construction.
The gas-assisted glycol pump configuration, by design, has no level control; natural gas is
intentionally entrained with the rich glycol feeding the pump. The natural gas mixed with
the rich glycol is a source of pressure energy. The gas is not burned, as in an
driver, but is from the at a The gas is not
directly from the pump, but is exhausted into the pumped glycol stream that flows to the
regenerator.
If the glycol unit a flash tank, most of the pump exhaust gas can be
recovered ss fuel or If the gas is as stripping or if
there is no flash tank, all of the pump exhaust gas will be vented through
the regenerator's atmospheric vent stack. Figure 3-2 shows a block flow diagram of the
configuration. The of the is complex. For a detailed
to the
-------
Fyel-Qas
Preheat Coil
Water Vapor
Out
Gas Relief
Valve
Reflux
Condenser. Jl
Pressure Gauge
Thermometer
OH-Water-Qas
Separator
-Glycol Relief Valve
- Dry-Giyeol Strainer
- Glycol Pump
Mainline Bypass
-Dry Gas Out
1 Water to Pit
"Oil to Stock
Glycol Reboiter
Fuel
Plot Gas
Temperature Control
Wet-Gas inlet
3-1. Glycol
-------
Dry Gas to
Pipeline
(High Pressure)
(Optional)
at Intermediate
Pressure
Water Vapor and
Light Hydrocarbons,
Including CH4
(to Atmosphere or
to Control System)
Combnsttott
Gases
GSycol
Sefeoiler/
Firebox <3 Fuel
(Atmospheric
Pressure)
Figure 3-2, Process of Glyeol
-------
4.0 DATA
The manufacturer's data for a pump operating at typical design conditions
were used to calculate emissions. No direct measurements of pump gas usage were used in
the calculations.
Kimray, the leading manufacturer of gas-assiated glyeo! pumps, provided
technical The of is the gas per
unit of glycol pumped, usually as actual cubic feet* (acf) per gallon cf glycol.
Therefore, the usage rate and inherent emissions per pump depend oti the size of the unit.
Kimray reports that gas usage ranges from 0.081 acf/gallon for high-pressure pumps (>40G
psig) to 0.130 acf/gallon for low-pressure pumps (<400 psig).J These data underwent QA
by other and reviewers and by Kimray as a
of analysis. As a result, the manufacturer's are believed to be and
representative.
To estimate the glycol circulation rate for a typical dehydrator, and
consequently, the amount of gas used to drive the pump, it was necessary to choose values
for wet gas water content and giyeol circulated per pound of water. It that a
typical high-pressure would remove 53 of per MMscf of gas and a
typical low-pressure dehydrator would remove 127 of water per MMscf of
The glyeol-to-gas ratio is using 3 gallons of glycol per pound of water
removed.
3Actual cubic feet of gas are in the calculations because the pump cylinders fill with
the same ratio of gas and glycol regardless of the pressure.3
-------
5.0 ACTIVITY FACTOR
The activity for glycol circulation pumps is
in detail in Volume 5 on activity 1 ar.ton 5 The activity factor for gas-driven
glycol circulation is on the as the dehydrator vented emissions
in Volume 14 (i.e., Tscf/year gas throughput for each industry segments).1 The total gas
throughputs listed in Table 5-1 were multiplied by the fraction of dehydrators using gas-
driven to the gas-driven activity factor. This value is on the
average from Radian site of the number of per dehydrator. The gas
throughputs for glycol dehydrators using gas-assisted ^umps are as follows:
« 11,1 Tscf/year ± 62.0%;
» Processing: 0.96 ±
» Transmission; 0 Tscf/year; and
• Storage: 0 Tscf/year.
These are on dehydrator gas for and the
estimates of gas-assisted pump usage on site visit data. No active gas-assisted pumps
were found at transmission or storage facilities during the site visits, so no throughput is
for two Although may be a of
in or service, the will be
in to the and
Table 5-1 lists the characteristics of glycol dehydrators used to develop the
activity factors for PumPs- Table 5-2 of glycol
dehydrators that affect from gas-assisted but are not used in the activity
factor calculations. These are for in the factor
described in Section 5. These characteristics were developed from the site visit data
discussed in the Activity Factor Report.1
-------
TABLE 54. UJS. GAS FOR OF
'^.^^i^^^MM
Production
Gas Processing Plants
Transmission
Storage
Gas
J '"iflii-lMalSififeiiiiif; ;•..•:;•••: **:- •; :;-•"• ••••-;.,•.::...: v: ••:- - -,--
yy'^i;^J^^W^!^^-M?S'^
12.4Tscf/yr ± 61.9%
S-eSTscf/yi ±22.4%
l,09Tscf/yr± 144%
2.00Tscf/yr ±25%
24.1 Tscf/yr ±
ii:i:;:i::::;®Mi(6i;:ii':isWiif8m:nj::v-;
: '-• ' :-':•• :' : : .••'"'.•'-''.•'-'•.'"•'.''••'•.:< •: ••• •-.:•::' •:*:.' ;.:::: -;. *':*. ' "::
L:: :- '- ..^Oi^iSMjyfcGasiKiiiifeiMJ!.:-:!
0.891 ± 2,79%
0.111 ± 186%
0
0
;•' ' : : ': •;'||i);ilp|nil:^i ISjsftliliyt^S; : :
: v i ••.•: 'i.i^^j^is^^isii^^ii^s •; ' . .
11.1 Tscf/yr ± 62.0%
0.958 fscf/yr ± 192%
12.1 ±
00
-------
TABLE 5-2. U.S. GAS FOR CALCULATION
OF
Segment . •
Production
Gas Processing
Transmission
Storage
Fraction rf Behydratprs '
. with. Fiasli Drums
±
±10.1%
±
0.520 ± 33.6%
Fraction . of Debydrators
with Vapor Recovery that
' - Consumes Methane
0,0118 ±73.1%
0.100 ±
±
0.160 ± 80.0%
-------
6.0 EMISSION FACTOR
In the for a was to be a
of the gas and the vent on the dehydtator. Tbe use of a
tank virtually eliminates methane emissions associated with pump gas because the flash gas is
typically burned as fuel,
6.1
The characteristics that affect methane emissions from the gas-assisted pumps
in glycol circulation service are:
8 Frequency of operation (pumping rate);
* Size of the unit (volume displacement of the motive chamber);
* Supply gas pressure;
» Met composition; and
* Use of a
— of a
Disposition of the flash gas,
It has that the of the has no on
to the vest from the If the
reaches the regenerator/reboiler, all of the from the is assumed to
vent to the atmosphere.
6.2
The following equation was used to determine the emission factor for the
average pump in each industry segment;
10
-------
x CR x WR x OC x PMD x FKVC (1)
where:
PGU = pump gas usage (scf CH4)/(galIon glycol)
CR = circulatioii ratio (gallons glycol)/(pound water removed from gas)
WR = removed from gas (pounds H2O/MMscf gas)
OC = oveictrculation
FND = fraction of
PIWC — fraction of the without combustion vent
CR, WR, PHD, and FNVC were discussed in Sections 4 and 5. The
overcirculation factor (OC) was determined from data collected from ten glycol dehydrators.6
The PGU rate on the glycol circulation rate, the absorber and
and the model. PGU from values reported by the
High use on 0.081 acf gas per of glycol,
to 4,49 for gas at 800 Low pomps use on
average 0.130 acf gas per gallon of glycol, which is equivalent to 2.78 scf/gallon for 300
psig gas. Multiplying by 83 mole% methane in the pump gas results in a methane usage of
3,73 scf/gallon for high pressure and 2.31 scf/gallon for low pressure. The estimated split
for high low in production is 80% and 20% low pressure.7 AH
to be pressure.
The (EFpmi>) for from an
glycol pump was determined for the production and processing industry using
Equation 1. The transmission and storage segments do not use gas-assisted pumps. The
results are as follows:
11
-------
Production - High Pressure:
PGU = 3.73 scf/gallon ± 30%
CR = 3.0 H20 ± 33,3%
WR = 53 Ib gas ± 20%
OC = 2.1 4 71.4%
FND = 0.735 ± 2.99%
FOTC = 0.988 ±
EFW = (3-73) x (3.0) x (53) x (2.1) x (0,735) x
= ±
Production - Low Pressure:
PGU - 2.31 ± 30%
CR = 3,0 H20 ± 33.3%
WR = 127 Ib H20/MMscf gas ±20%
OC = 2,1 ± 71,4%
F» = 0.735 ±
pmc = 0.988 ±
EFp™p = (2-31) x (3.0) x (127) x (2.1) X (0.735) X
= 1342.2 scf/MMscf ± 95.0%
- Combined:
Fraction High pressure = 0.80 ± 12.5%
Fraction Low Pressure = 0.20 ± 50%
IP = ±
EF (Low = 1342.18 +
EFW = (O.SO) + (1342.18)
= 992.00 scf/MMscf ± 77.29%
12
-------
Processing:
PGU = 3.73 scf/gallon ± 30%
CR = 3.0 gallons glycol/lb H20 + 33.3%
WR = 53 Ib H2O/MMscf gas ± 20%
OC = 1.0 ± 0%
FND = 0.333 ± 20.1%
PNVC = 0-900 ±10%
EFpump = (3.73) x (3.0) X (53) X (1.0) x (0.333) x (0.900)
- 177.8 scf/MMscf ± 56.85%
13
-------
7.0 ANNUAL METHANE EMISSIONS
Annual methane emissions from gas-assisted glycol pumps were calculated to
be 11.1 Bscf. This was calculated by multiplying the activity factor (number of pumps) by
the emission factor (scf/MMscf) for each industry segment and then summing the values,
The results are as follows:
8 Production:
(992.0 scf/MMscf) x 11.05 Tscf= 10.96 Bscf
» Gas Processing:
(177.745 scf/MMscf) X 0.9579 Tscf = 0.170 Bscf
e Transmission: no emissions
» Storage: no emissions
14
-------
8.0 REFERENCES
1, Myers, D.B. Methane Emissions from the Natural Gas Industry, Volume 14:
Glycol Dehydr:,'ors. Final Report, GRI-94/0257.31 and EPA-60Q/R-96-080n.
Gas Research Institute and U.S. Environmental Protection Agency, June 1996.
2. Shires, T.M. Methane Emissions from the Natural Gas Industry, Volume 13:
Chemical Injection Pumps. Final Report, GRI-94/0257.30 and EPA-600/R-96-
080m. Gas Research Institute and U.S. Environmental Protection Agency,
June 1996.
3. Kiniray, Inc. Glycol Pumps and Accessories, Tulsa, OK, undated.
4. Sivalls, Inc. Glycol Dehydration Design Manual. Odessa, TX, 1982.
5. Stapper, B.E. Methane Emissions from the Natural Gas Industry, Volume 5:
Activity Factors. Final Report, GRI-94/0257.22 and EPA-600/R-96-080e.
Gas Research Institute and U.S. Environmental Protection Agency, June 1996.
6. Rueter, C.O., et al. Glycol Dehydrator Emissions: Sampling and Analytical
Methods and Estimation Techniques. GRI-94/0324. Gas Research Institute,
Chicago, IL. . March 1995.
7. Memorandum from Richard Garrett (Roger-Tech, Inc., Houston, TX) to
Rhone Resch (U.S. EPA OAR), March 4, 1996.
8, Texas Mid-Continent Oi) and Gas Association Glycol Dehydrator Survey.
Personal communication with L. Litzen (Sliell Oil Western Exploration and
Production) and C.O. Rueter (Radian Coiporation). June 17, 1991.
15
-------
A
Source Sheets
A-l
-------
P-7
PRODUCTION SOURCE SHEET
SOURCES: Dehydrators
COMPONENTS: Gas Driven Kimray Pumps
OPERATING MODE: Normal Operation
EMISSION TYPE: Unsteady, Vented
ANNUAL EMISSIONS: 10.96 Bscf + 110.0%
BACKGROUND:
Gas driven Kimray glycoi circulation pumps use a mixed phase of wet glycol liquid and absorber gas to drive
pistons that pump dry (lean) glycol circulation. Uniike chemical injection pumps which vent the driving gas
directly to the atmosphere, Kimray pumps pass the driving gas along with the wet glycol to the reboiler. in
the reboiler the methane is driven off into the vent line. Depending on dehydrator vent gas dispositions, the
methane may be vented to the atmosphere or controlled and burned.
EMISSION FACTOR: (992.0 scf CH4/MMscf gas processed)
The average glycol pump gas emission factor was determined by an equation describing the gas generation
and disposition of gas from the pump. The disposition of gas generated by the pump depends upon the
existence of a flash tank and vent controls. Measured and estimated parameters were input into the equation.
In general, the emission factor for a gas-assisted pump was determined by the following equation:
Efpumf = PGU x CR x WR x OC x FOT x Fwc
EF DATA SOURCES:
3. Equation 1, i.e. the effects of operating variables on emissions, was defined by the report on Methane
Emissions from the Natural Gas Industry, Volume 15, Gas-Assisted Glycol Pumps (1).
2. CR = glycol circulation ratio = 3.0 gal glycol/Ib water + 33.3%.
3. WR = water removed from gas
= 53 Ib/MMscf ± 20% for high pressure
= 127 Ib/MMscf ± 20% for low pressure
4. OC = factor to account for overcirculation of glycol = 2.1 ± 71.4%.
5. FOT = fraction of dehydrators without flash tanks = 0.735 ± 2.99%.
6- FNVC = fraction of the dehydrators without combustion vent controls = 0.9882 + 0.87%.
7. PGU = pump gas usage (assume 83% methane)
= 3.73 scf CH4/ga! glycol ± 30% for high pressure
A-2
-------
- 2.31 scf CH/gal glyeol ± 30% for low pressure
CALCULATION
It is estimated that 80% of the production dehydrators would be high pressure (R. Garrett memo) (4). The
overall production emission factor is then calculated as a weighted average of the high and low pressure
emission factors.
EF (high = (3.73 x (3.0 H2O) x (53 Ib HjO/MMsef)
x (2.1) x (0.735) x
= 904.45 ±
EF (tow - (2.31 x (3.0 HjG) * (12? II)
x (2.1) x (0.135) x
= 1342.18 ±
EF (Production) = (0.80 ± 12.5%) (904.45 scf/MMscf ± 95.04%) +
(0.20 ± 50%) (1342.18 scf?MMscf ± 95.04%)
992.00 scf CH4/MMscf ± 77.29%
EF ACCURACY: (±
Basis;
1. Assumption: The manufacturer's date and are relatively (±30%).
2. Dehydrator characteristics based on site visit observations TMOGA survey.
ACTIVITY FACTOE; (11.05 Tsc&year in the production segment with gas-assisted pumps)
The volume of gas processed through dehydrators using gas-assisted pumps was calculated from the total
throughput for production dehydrators and the fraction of dehydrators using gas-assisted pumps determined
from site visits. The activity factor is then:
AF = (fcBvtion of dehydrators with gts-assisied pumps) x (throughput for production dehydrators)
= (0.8913 ± 2.79%) x (12,4 Tsef/year ±
= 11.05 Tseffyear ±
AF DATA
1. See Methane Emissions front she Natural Gas Industry, Volume 14: Glycol Dehydrators (2) for
an explanation of production dehydrator throughpnt. See the Melhane Emissions from the
Natural Gas Industry, Volume S: Activity Factors (3) for more details.
2. Fraction of dehydrators using gas-assisted pumps came from data from site visits.
AF ACCURACY: (± 61.96%)
Basis:
Calculated from confidence limits of gis throughput and fraction of dehydrators by error
propagation analysis.
A-3
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ANNUAL METHANE EMISSIONS: (10.962 Bscf ± 110.03%)
The annual methane emissions were determined by multiplying an emission factor (scf CH^/MMscf) by the
total throughput for production dehydrators using gas-assisted pumps.
(992.00 scfMMscf) x (11.05 Tscf) = 10.962 Bscf (± 110.03%)
REFERENCES
1. Myers, D.B. and M.R. Harrison. Methane Emissions from the Natural Gas Industry, Volume 15: Gas-
Assisted Gfycol Pumps. Final Report, GRI-94/0257.33 and EPA-600/R-96-0800, Gas Research
Institute and U.S. Environmental Protection Agency, June 1996,
2. Myers, D.B. Methane Emissions from the Natural Gas Industry, Volume 14: Gfycol Dehydrators.
Final Report, GRI-94/0257.31 and EPA-600/R-96-080n. Gas Research Institute and U.S.
Environmental Protection Agency, June 1996.
3. Stepper, B.E. Methane Emissions pom the Natural Gas Industry, Volume 5: Activity Factors. Final
Report, GRI-94/0257.22 and EPA-600/R-96-080e. Gas Research Institute and U.S. Environmental
Protection Agency, June 1996.
4. Memorandum from Richard Garrett (Roger-Tech, Inc., Houston, TX) to Rhone Resch (U.S. EPA OAR),
March 4, 1996.
A-4
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GP-5
PROCESSING SOURCE SHEET
SOURCES: Giycol Dehydrators
COMPONENTS: Gas Assisted Kimray Pumps
OPERATING MOPE: Normal Operation
EMISSION TYPE: Unsteady, Vented
ANNUAL EMISSIONS: 0.170 scf ± 228%
BACKGROUND:
Most glycol circulation pumps in gas plants are electric. However, some gas driven pumps do exist. Gas-
assisted Kimray glycol circulation pumps use a mixed phase of wet glycol liquid and absorber gas to drive
pistons that pump dry (lean) glycol circulation. Unlike chemical injection pumps which vent the driving gas
directly to the atmosphere, Kimray pumps pass the driving gas along with the wet glycol to the reboiler. In
the reboiler the methane is driven off into the vent line. Depending on dehydrator vent gas dispositions, the
methane may be vented to the atmosphere or controlled and burned.
EMISSION FACTOR: (177.75 scf CH4/MMscf gas processed)
The average glyco! p.< np gas emission factor was determined by an equation describing the gas generation
and disposition of gas from the pump. The disposition of gas generated by the pump depends upon the
existence of a flash tank and vent controls. Measured and estimated parameters were input into the equation.
In general, the emission factor for a gas-assisted pump was determined by the following equation:
EFpump = POU x CR x '7R x OC x FOT x F^
= (3.73 scf/gal) x (3.0 gal/lb H2O) x (53 Ib H,O/MMscf) x (1.0) x (0.333) x (0.900)
= 177.75 scf CH4/MMscf gas ± 56.85%
EF DATA SOURCES:
1. Equation 1, i.e. the effects of operating variables on emissions, was defined in Methane Emissions from
the Natural Gas Industry, Volume 15: Gas-Assisted Glycol Pumps (1).
2. CR = glycol circulation ratio = 3.0 gal giycol/lb water ± 33.3%.
3. WR = water removed from wet gas = 53 Ib water/MMscf gas ± 20%. For inlet gas stream of 95°F and
800 psig dried to 7 Ib water/MMscf gas.
4. OC = factor to account for overcirculation of giycol = 1.0 ± 0%.
5. FOT = fraction of dehydrators without flash tanks = 0.333 ± 20.12%.
6- FNVC = fraction of the dehydrators without combustion vent controls = 0.900 ± 10%.
7. PGU = pump gas usage = 3.73 scf CH4/gal glycol ± 30%. Determined by multiplykg the volume of
gas used by high-pressure pump models by a typical fraction of methane in the natural gas (83 mole%).
A-5
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POU - 4,49 x 83%
= 3.73 ± 30%
EF ACCURACY- (± 56.85%)
Basis:
1. Assumption: The manufacturer's data and ranges are relatively accurate (±30%).
2. Dehydrator characteristics based on site visit observations and TMOGA survey.
ACTIVITY FACTOR: (8.9579 Tscf/year in the processing segment with gas-assisted pumps)
The volume of gas through dehydrators wis calculated the total
throughput for gas processing dehydration fa fraction of dehydrators using gas-assisted pumps
from site visits. The activity factor is then:
AF = (fraction of dehydrators with gas-assisted pumps) x (throughput for gas processing
dehydrators)
= {0.111 ± 186%) x (8,63 Tscf/year ± 22.4%)
= 0.9579 Tscffyear± 191.95%
AF DATA
1. See Methane Emissions from the Natural Gas Industry, Volume 14; Gfycol Bekydrators (2) for
an explanation of processing dehydrator throughput (8,63 Tscf/year). See the Methane Emissions
from the Natural Gas iadvslry, Volvme 5; Activity Factors (3) for more details,
2. Fraction of dehydrators using pumps came from data site visits.
AF ACCURACY: <± 192%)
Basis:
Calculated from confidence limits of gas throughput and fraction of dehydrators by standard error
propagation analysis.
ANNUAL (&1703 Bscf ±
The annual methane emissions were determined by multiplying an emission factor (scf CR,/MMscf) by the
total throughput for processing dehydrators using gas-assisted pumps.
(177.75 scf/MMscfj x (0.9579 Tscf) «• 0.1703 Bscf (± 228.00%)
REFERENCES
1. Myers, D.8. and MR. Harrison. Methane Emissions from the Natural Gas Industry, Volume 15: Gas-
Assisted Glycol Pumps, Final Report, GRI-94/0257.33 and EPA-6Q0/R-96-08Qo, Gas Research
Institute and U.S. Environmental Protection Agency, June 1996.
2. Myers, D.B. Methane Emissions from the Natural Gas Industry, Yobane 14: Glycol Dehydrators.
Final Report, GR1-94/0257.31 and EPA-600/R-96-080n. Gas Research Institute and U.S.
Environmental Protection Agency, June- 1996.
A-6
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3. Stapper, B.E. Methane Emissions from the Natural Gas Industry, Volume 5: Activity Factors. Final
Report, GR1-94/0257.22 and EPA-600/R-96-080e. Gas Institute and U.S. Environmental
Protection Agency, June 1996,
A-?
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