Lessons
Learned
NaturalGasf
EPA POLLUTION PREVENTER
as
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Most natural gas producers use triethylene glycol (TEG) gas dehydrators to
remove water from the natural gas stream to meet pipeline quality stan-
dards. TEG is circulated through the dehydration system using pumps pow-
ered either by an electric motor or by a gas expansion piston or turbine driv-
er. The latter is called a "gas-assisted" or "energy-exchange" pump. In some
operations, a combination gas-assist/electric pump system may be used.
The gas dehydration process includes the following elements:
* Wet natural gas is fed into a glycol contactor, where it bubbles up count-
er-current through "lean TEG" (triethylene glycol without absorbed water)
in the contactor tower trays.
* Lean TEG absorbs water and under pressure, some methane from the
natural gas stream-becoming "rich TEG."
* Dry gas goes to the sales pipeline.
* A reboiler operating at atmospheric pressure regenerates the rich TEG
by heating the glycol to drive off water, absorbed methane and other
contaminants, which are vented to the atmosphere.
* The regenerated (lean) TEG is pumped back up to contactor pressure
and injected at the top of the contactor tower.
Exhibit 1 is a diagram of a typical glycol dehydrator system. The atmospher-
ic vent stack on the glycol reboiler/regenerator is the main source of
methane emissions. Reduction of methane emissions is achieved by reduc-
ing the amount of wet gas bypassed to supplement the rich TEG that is
regenerated in the reboiler. There are three ways to reduce the methane
content of the rich TEG stream:
* Reducing the TEG circulation rate.
* Installing a flash tank separator in the dehydration loop.
* Replacing gas-assisted pumps with electric pumps.
Replacing gas-assisted pumps with electric pumps is the subject of this
Lessons Learned paper. The other methane emission reduction options are
discussed in EPA's Lessons Learned: Optimize Glycol Circulation and Install
Flash Tank Separators in Glycol Dehydrators.
Gas-Assisted Pumps
The most common circulation pump used in dehydrator systems is the
gas-assisted glycol pump. An example of a popular piston type is shown in
Exhibit 2. These mechanical pumps are specially designed to use rich TEG
and natural gas at high pressure for power. By design, gas-assisted glycol
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Exhibit 1: Dehydrator Schematic
To Atmosphere
(Methane/other
vapors andwater)
Fuel Gas
Energy
Exchange
Pump
Lean TEG
Source: Exxon U.S.A.
pumps increase emissions from dehydrator systems by passing the
pneumatic driver gas entrained with rich TEG to the reboiler. A basic
overview of the pump's operation is described below:
* The high-pressure natural gas entrained in rich TEG from the contactor
(plus additional wet, high pressure gas) expands from contactor pres-
sure (200 to 800 psig) down to reboiler pressure (zero psig), pushing
against the driver side of the main cylinder piston.
* The other side of that piston pushes a cylinder full of low-pressure lean
TEG out to the contactor at high-pressure.
* The driving piston is connected to a mirror-image piston, which simulta-
neously expels low-pressure rich TEG to the regenerator, while sucking
in low-pressure lean TEG from the regenerator.
* At the end of the stroke, slide valves switch the position of the pilot pis-
ton, redirecting high-pressure rich TEG to the opposite drive cylinder.
Check valves on the suction and discharge from the lean TEG cylinders
prevent back-flow.
* The pistons are then driven back in the other direction, one expanding
gas in the rich TEG while pressuring lean TEG to the contactor, the other
expelling the now low-pressure rich TEG to the regenerator while filling
the other side with low-pressure lean TEG from the regenerator.
* The driver-side rich TEG mixture with low-pressure natural gas passes to
the reboiler where the entrained gas separates and water is boiled out of
solution with the TEG.
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* The water vapor and separated gas mixture of methane and other
hydrocarbon gas contaminants (VOCs and HAPs) are vented to the
atmosphere.
* At the end of each stroke, the flow paths are switched, and high-pres-
sure rich TEG pushes the pistons back.
This type pump has an inherent design requirement that extra high-pressure
gas be added to supplement the gas absorbed in the rich TEG from the
contactor (about two volumes for one) to provide mechanical advantage on
the driver side. This means that a gas-assisted pump passes about three
times as much gas to the regenerator as an electric motor driven pump
would. Furthermore, gas-assisted pumps place high-pressure wet TEG
opposite low-pressure dry TEG in four locations with rings on the two pis-
tons and "O-rings" on the central piston connecting rod separating them.
As the piston rings becomes worn, grooved, or the O-rings wear, rich TEG
leaks past, contaminating the lean TEG. This contamination decreases the
dehydrator's capacity to absorb water and reduces system efficiency.
Eventually, the contamination becomes sufficient to prevent the gas from
meeting pipeline specifications (commonly 4 to 7 Ib of water per MMcf).
As little as 0.5 percent contamination of the lean TEG stream can double the
circulation rate required to maintain the same effective water removal. In
some cases, operators can over circulate the TEG as the dehydrator loses
efficiency, which in turn, can lead to even greater emissions.
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Electric Pumps
In contrast to gas-assisted pumps, electric motor driven pumps have less
design-inherent emissions and no pathway for contamination of lean TEG by
the rich stream. Electric pumps only move the lean TEG stream; the rich TEG
flows by pressure drop directly to the regenerator, and contains only dis-
solved methane and hydrocarbons. Exhibit 2 shows an example of an elec-
tric glycol pump assembly.
Electric Motor
Exhibit 2: Electric Drive Gear Pump
Specialized Electric Drive GEAR PUMPS
For Glycol (TEG) Natural Gas Dehydrators
Oil Fill/Drain Plugs
Drive Shaft
Pump Seal
_^^^^ ^^^^^ Pump Gear
Shaft Seals for Motor
Coupling j I -^^/ 'Pump Module
"Lube Oil" Reservoir Ball Thrust Bearing
Source: Kimray, Inc.
Using electric pumps as alternatives to gas-assisted pumps can yield signifi-
cant economic and environmental benefits, including:
* Financial return on investment through reduced gas losses. Using
gas-assisted glycol pumps reduces methane emissions by a third or
more. All of the wet production gas remains in the system to be dehy-
drated and sold as product. In many cases, the cost of implementation
can be recovered in less than 1 year.
* Increased operational efficiency. Worn O-rings in gas-assisted glycol
pumps can cause contamination of the lean TEG stream in the dehydra-
tor, reducing system efficiency and requiring an increase in glycol circula-
tion rate, compounding the methane emissions. The design of electric
pumps eliminates the potential for this contamination to occur and there-
by increases the operational efficiency of the system.
* Reduced maintenance costs. Replacing gas-assisted glycol pumps
often results in lower annual maintenance costs. The floating piston
O-rings in gas-assisted pumps must be replaced when they begin to
leak, typically every 3 to 6 months. The need for this replacement is elimi-
nated when electric pumps are employed.
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* Reduced regulatory compliance costs. The cost of complying with
federal regulations of hazardous air pollutants (HAPs) can be reduced
through the use of electric pumps. Dehydrator HAP emissions, including
volatile organic compounds such as benzene, toluene, ethyl benzene,
and xylene (BTEX), are significantly lower in units powered by electric
pumps.
A five-step process can be used to evaluate replacement of gas-assisted
glycol pumps with electric pumps. Each step requires field data to accurate-
ly reflect conditions at the site being evaluated.
Step 1: Determine whether an electricity source is available. Electricity
to power an electric pump can be purchased from a local grid or generated
onsite using lease or casing head gas that might otherwise be flared. If a
source of electricity is available or can be obtained cost-effectively, the oper-
ator should proceed to Step 2. When no electricity source is available, a
gas-assisted glycol pump might be the only option. Combination hydraulic-
electric pumps should also be considered for field situations where only sin-
gle-phase power is available, purchased power costs are high, or there is
insufficient electrical service for a large electric motor. A combination pump
uses high-pressure, wet glycol to drive a hydraulic rotary gear motor/pump;
a small single-phase electric motor is added for mechanical advantage, in
place of the bypassed wet gas in the gas-assisted pump. In either case,
using a properly sized, well-maintained, efficient pump maintained at the cor-
rect circulation rate can minimize gas loss.
Step 2: Determine the appropriate size of the electric pump. A variety of
electric pumps are available to meet site-specific operational requirements.
Electric TEG pumps can be pow-
ered by AC or DC, single phase or
3-phase, 60 Hz or 50 Hz. They
are available with a choice of vari-
able or constant operating
speeds. Pump capacities range
from 10 to 10,000 gallons per
hour (GPH).
Five Steps to Evaluate the Use of
Electric Pumps
1.
Determine whether an electricity
source is available.
2. Determine the appropriate size of the
electric pump.
3. Estimate the capital, operation, and
maintenance costs.
4. Estimate the quantity and value of
gas savings.
5. Calculate the net economic benefit of
replacement.
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The correct pump size for a dehydrator system should be calculated based
on the circulation rate and the operating pressure of the system. Exhibit 3
illustrates how to calculate the horsepower needed (in Brake Horsepower or
BMP) for an electric pump using typical system information.
Exhibit 3: Sizing the Pump
Given:
Q = Circulation rate (in gallons per minute) = 5 gal/min
P = Pressure (in psig) = 800 psig
E = Efficiency = 0.85
Calculate:
= (QxP/1,714)x(1/E)
= (5 x 800/1,714) x (1/0.85)
BMP = 2.75
In the example shown in Exhibit 3, an operator would need at least a 2.75
horsepower pump, and would therefore round up to the next available size
(i.e., a 3.0 BMP pump).
Operators might wish to obtain a pump one size larger than called for by the
formula above. A larger pump provides additional capability to increase the
glycol circulation rate, if needed, to accommodate input gas with higher wa-
ter content, or to meet more stringent output specifications. Variable speed
electric pumps are also available. Although larger pumps or variable speed
pumps can cost slightly more to operate, a larger size provides an additional
measure of safety and flexibility to cover contingencies.
Step 3: Estimate the capital, operation, and maintenance costs. Costs
associated with electric pumps include capital to purchase the equipment,
installation, and ongoing operation and maintenance.
(a) Capital and installation costs
Electric pumps can cost from $1,100 to nearly $10,000, depending on the
horsepower of the unit. Exhibit 4 presents a range of sample capital costs
for electric pumps of different sizes typically used for glycol dehydrators.
Operators should also consider installation costs when evaluating the overall
economics of electric pumps. Estimate 10 percent of capital costs for instal-
lation. Coordinating replacements with planned maintenance shutdowns can
minimize installation costs.
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Exhibit 4: Capital Cost of Electric Pumps
Pump Motor
Size (BHP)
Pump and
Motor Cost ($)
.25
1,100
.50
1,150
.75
1,200
1.0
1,260
1.5
1,300
2.0
1,370
3.0
1,425
5.0
2,930
7.5
3,085
10
3,250
Source: Kimray, Inc.
(b) Operation and maintenance costs
The primary operational cost of an electric pump is the electricity needed to
power the unit. In general, the kilowatt (kW) requirement to run a pump is
nearly the same as BHP. For example, a 3.0 BHP pump would require ap-
proximately 3.0 kW to operate.
In 2003, the average cost of purchased electricity in the commercial and in-
dustrial sectors ranged from $0.046 to $0.075 per kilowatt-hour (kWh) na-
tionally; site-generated electricity cost approximately $0.02 per kWh. If elec-
tricity costs are assumed to be approximately $0.06 per kWh, the estimated
cost for purchased power for the 3.0 BHP pump identified above would be
$1,600 per year (3.0 kW x 8,760 hrs/yr x $0.06/kWh). The cost for site-gen-
erated electricity would be about $525 per year (3.0 kW x 8,760 hrs/yr x
$0.02/kWh).
Typical maintenance costs for gas-assisted glycol pumps range from $200
to $400 annually. Maintenance cost is primarily associated with internal CD-
ring replacements and related labor costs. Normally, these replacements are
necessary once every three to six months.
Electric pumps are usually gear-driven. They have no reciprocating pump
parts and do not depend on elastomeric parts, slides, pistons, check valves,
or internal O-rings, which are all subject to wear, deterioration, and replace-
ment. As a result, maintenance costs for electric pumps are generally less
than maintenance costs for gas-assisted glycol pumps. Annual costs for
electric pumps can be expected to be about $200 per year for labor, con-
sumables (lubrication and seals), and inspection.
Step 4: Estimate the quantity and value of gas savings. Because electric
pumps emit no methane, emissions savings from an electric pump installa-
tion are equal to the emissions from the gas-assisted pump being replaced.
The quantity of avoided emissions can then be multiplied by the market
price of gas to determine the total value of gas savings. Note: if the glycol
dehydration unit has a flash tank separator, and a beneficial use for all gas
recovered, then the gas savings might not, by itself, provide enough justifica-
tion for installing an electric pump.
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(a) Estimate methane emissions from the gas-assisted pump
Estimating emissions is a two-step process, which consists of calculating an
emissions factor for the unit's operational characteristics (pressure, tempera-
ture, moisture specs) and then multiplying the unit emissions factor by an
activity factor (amount of gas processed annually). Exhibit 5 presents formu-
las for estimating the potential methane emissions from a gas-assisted
pump and, consequently, the potential methane savings from replacing the
gas-assisted pump with an electric pump.
Exhibit 5: Estimate Methane Emissions from Glycol Dehydrators1
Step 1: Calculate Emissions Factor
Given:
EF = Emission Factor (scf natural gas emitted/MMcf gas processed)
PGU = Pump Gas Usage (scf natural gas emitted/gallon of TEG)2
G = Glycol-to-Water Ratio (gallons of TEG/lb water removed)5
WR = Water Removed Rate (Ib water removed/MMcf gas processed)
OC = Over Circulation Ratio
Calculate:
EF =PGUxGxWRxOC
Step 2: Calculate Total Emissions
Given:
TE = Total Emissions
AF = Activity Factor (MMcf gas processed annually)
Calculate:
TE =EFxAF
1 Calculation methods and standard values are presented in EPA's Lessons Learned:
Optimize Glycol Circulation and Install Flash Tank Separators in Glycol Dehydrators.
2 Industry Rule-of-Thumb: 3 cubic-ft/gal for gas-assisted pump, 1 cubic-ft/gal for electric
pump; the difference being 2 cubic-ft/gal.
3 Industry accepted Rule-of-Thumb: 3 gal TEG/lb water.
Field operators often know or can calculate the pump gas usage and the
glycol-to-water ratio. To determine the quantity of water that needs to be
removed (WR), refer to Appendix A, which presents a set of empirically
derived curves. Using the gas inlet temperature and system pressure, the
saturated water content can be determined by reading the corresponding
value where the psig curve intersects the temperature. Subtract 4 Ib/MMcf
to 7 Ib/MMcf of water from the water content value to determine WR. The 4
Ib/MMcf to 7 Ib/MMcf water content limitation is based on typical pipeline
specifications for water content in the gas stream.
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To estimate the over circulation ratio, use a 1:1 ratio (OC = 1) if there is no
over circulation and a 2.1:1 ratio (OC = 2.1) if over circulation is an issue.
These ratios are based on the average of measured ratios from 10 field units
reported by the Gas Research Institute.
Two examples of determining water removal (WR), emission factor (EF), and
total emissions (TE) are provided on the pages that follow. Each example
shows a range of savings based upon the two different inlet assumptions. Ex-
ample 1 presents a high-pressure gas stream, and Example 2 presents a low-
pressure stream.
Example 1: High-Pressure Gas Stream:
This example dehydration system has an inlet pressure of 800 psig, a tem-
perature of 94° F, and a glycol-to-water ratio of 3.0 gallons of TEG per Ib
water recovered. Using Appendix A, the saturated water content for the gas
stream is estimated by reading the corresponding value where the 800-psig
curve intersects the 95° F line. In this example, the water content is about 60
Ib per MMcf. Subtracting the pipeline requirement of 7 Ib/MMcf, results in 53
Ib of water, which must be removed from the gas stream and absorbed by the
TEG. The pump gas usage is 2 scf of natural gas per gallon of TEG.
Applying these data to the emissions factor formula results in a range of 318
to 668 scf gas emitted for every MMcf gas processed. Assuming the dehydra-
tor processes 10 MMcf of wet gas daily, the additional volume of the gas re-
covered would be 1,160 to 2,440 Mcf per year. Exhibit 6 summarizes this
example.
10
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Exhibit 6. Example 1: Estimated Methane Emissions from a Glycol
Dehydrator with High Pressure (800 psig) Inlet Gas
Where:
EF = Emission Factor (scf natural gas emitted/MMcf gas processed)
PGU = Pump Gas Usage (scf natural gas emitted/gallon of TEG)
G = Glycol-to-Water Ratio (gallons of TEG/lb of water removed)
WR = Water Removed Rate (Ib of water removed/MMcf gas processed)
OC = Over circulation Ratio
TE = Total Emissions
AF = Activity Factor (MMcfd gas processed)
Given:
PGU = 2 scf natural gas emitted/gallon TEG
G = 3.0 gallons of TEG/lb of water removed
WR = 53 Ib of water removed/MMcf gas processed
OC =1:1 to 2.1:1
AF = 10 MMcfd gas processed
Calculate:
EF = PGUxGxWRxOC
= 2x3.0x53x(Range: 1 to 2.1)
= 318to668scf/MMcf
TE = EFxAF
= (318 to 668) x 10
= (3,180 to 6,680) scfd x 365 days/year -=-1,000 scf/Mcf
= 1,160to2,440Mcf/year
Example 2: Low-Pressure Gas Stream:
The system uses an inlet pressure of 300 psig and a temperature of 94° F,
and a glycol-to-water ratio of 3.0 gallons of TEG per Ib water recovered.
Again referring to the Smith Industries' curves (Appendix A), the water con-
tent is about 130 Ib per MMcf. Therefore, 123 Ib of water must be removed
from the natural gas stream and absorbed by the TEG to meet the pipeline
stan-dards. In this example, the pump size is 3.0 BMP, and the pump gas
usage is 2.8 scf of natural gas emitted per gallon of TEG. Using the formula,
an Emissions Factor (EF) of 1.03 to 2.17 Mcf/MMcf is estimated. Assuming
the dehydrator processes 10 MMcf of wet gas daily, the additional volume of
the gas recovered would be 3,760 to 7,921 Mcf per year. Exhibit 7 summa-
rizes this example.
11
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Exhibit 7: Example 2: Estimated Methane Emissions from a Glycol
Dehydrator with Low Pressure (300 psig) Inlet Gas
Where:
EF =
PGU =
G =
WR =
OC =
TE =
AF =
Given:
PGU =
G =
WR =
OC =
AF =
Calculate:
EF =
TE =
Emission Factor (scf natural gas emitted/MMcf gas processed)
Pump Gas Usage (scf) natural gas emitted/gallon of TEG)
Glycol-to-water Ratio (gallons of TEG/lb of water removed)
Water Removed Rate (Ib of water removed/MMcf gas processed)
Over circulation Ratio
Total Emissions
Activity Factor (MMcfd gas processed)
2.8 scf natural gas emitted/gallon TEG
3.0 gallons of TEG/lb of water removed
123 Ib of water removed/MMcf gas processed
1:1 to 2.1:1
10 MMcfd gas processed
PGU x G x WR x OC= 2.8 x 3.0 x 123 x (Range: 1 to 2.1)= 1,030 to 2,170
scf/MMcf
EF x AF= (1030 to 2170) x 10= 10,300 to 21,700 scfd x 365 days/year -=-
1000 scf/Mcf= 3,760 to 7,921 Mcf/year
(b) Calculate the value of the methane savings
To determine the total value of the methane savings, simply multiply the total
emissions reduction by the price of gas. Assuming a value of $3.00 per Mcf,
both the high- and low-pressure examples presented above yield significant
annual savings. Increased gas sales from the high-pressure system will
range from $3,480 to $7,320 per year, while the low-pressure system will
yield savings from $11,280 to $23,760 per year.
Step 5: Calculate the net economic benefit of replacement. To estimate
the net economic benefit of replacing a gas-assisted glycol pump with an
electric pump, compare the value of the gas saved to the initial cost of the
electric pump, plus the electricity and the operation and maintenance costs.
As a general rule, if the cost of electricity exceeds the value of recovered
methane and avoided operation and maintenance costs, replacing the gas-
assisted glycol pump cannot be justified on a cost-only basis. Even in such
cases, however, other factors, such as lower cross contamination rates and
environmental benefits (e.g., reduced VOC and HAP emissions) might still
make the electric pumps an attractive option at certain sites.
12
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The following exhibit uses the low-pressure example from Step 4 to demon-
strate the possible savings available to operators who purchase electricity.
Exhibit 8: Economic Benefit of Replacing Gas-Assisted Glycol Pump with an
Electric Pump— Low Pressure Inlet Gas Example
Gas Volume
Saved per
Year (Mcf)
3,760 -
7,921
Value of Gas
Saved per
Year1
$11,280-
$23,763
3.0 BMP
Electric-
Pump Cost2
$1,853
Electricity
Cost per
Year
$1,576
Electric
Pump
Maintenance
($/Year)
200
Gas-Assisted
Pump
Maintenance
($/Year)
400
Payback in
months
2-4
1 Gas valued at $3.00 per Mcf.
2 Including capital cost and installation cost, which is assumed to be 30 percent of the capital cost for this
example.
It is important to note that larger pump sizes require a larger up-front invest-
ment, and higher electricity costs might result in longer payback periods. It is
therefore important to correctly calculate the pump size required and to cir-
culate the TEG at the optimal rate.
In addition, as part of looking at the overall replacement economics, opera-
tors should consider the timing of any replacements. Older gas-assisted
glycol pumps, at the end of their useful lives, are typically good candidates
for replacement with an electric pump. Gas-assisted pumps that might not
be at the end of their useful life, but that have started to need more frequent
maintenance as a result of increased contamination, might also be good
candidates for replacement.
Partner Reported Savings
One Natural Gas STAR Partner reported
recovering an average of 15,000 Mcf/year
of methane by replacing four gas-assisted
glycol pumps with electric pumps. At $3.00
per Mcf, this amounted to an average of
$45,000 in additional product sales.
13
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Installing electric pumps to replace gas-assisted glycol pumps can offer
significant operational, environmental, and economic advantages. Natural
Gas STAR partners offer the following lessons learned:
* Gas-assisted glycol pumps can often be cost-effectively replaced with
electric pumps if there is a readily available source of electricity.
* Electric pumps are available with varying capabilities and efficiencies.
Operators are encouraged to work with various pump manufacturers to
find the most appropriate type.
* In sizing an electric pump, operators might wish to obtain a pump that is
one size larger than normal. This will allow for additional circulation
capacity that can prove useful if the water content increases as the field
matures or "waters out."
* Glycol pumps, whether gas-assisted or electric, represent only one ele-
ment of a dehydration system. Operators should consider the dehydra-
tion process as a whole, including glycol composition, circulation rates,
contactor temperature and pressure, inlet gas composition, dew point
requirements, and reboiler temperatures.
* Partners considering replacing gas-assisted pumps with electric pumps
should review the other opportunities for reducing methane emissions
from dehydration systems. See EPA's Lessons Learned: Optimize Glycol
Circulation And Install Flash Tank Separators In Glycol Dehydrators.
* Glycol dehydrators with flash tank separators might not be good can-
didates for replacing the gas-assisted pump, because most of the ex-
cess gas is recovered and put to beneficial use or recycled.
* Include reduction in methane emissions from replacing gas-assisted gly-
col pumps with electric pumps in annual reports submitted as part of the
Natural Gas STAR Program.
14
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American Petroleum Institute. Specifications for Glycol-Type Dehydration
Units (Spec 12 GDU). July 1993.
American Petroleum Institute. Glycol Dehydration. PROFIT Training Series,
1979.
Ballard, Don. How to Improve Glycol Dehydration. Coastal Chemical Com-
pany.
Collie, J., M. Hlavinka, and A. Ashworth. An Analysis of BTEX Emissions from
Amine Sweetening and Glycol Dehydration Facilities. 1998 Laurance Reid
Gas Conditioning Conference Proceedings, Norman, OK.
Garrett, Richard. Making Choices—A Look at Traditional and Alternative Gly-
col Pump Technology.
Gas Research Institute. Technical Reference Manual for GRI-GLYCalc TM
Version 3.0 (GRI-96/0091).
Gas Research Institute and U.S. Environmental Protection Agency. Methane
Emissions from Gas-Assisted Glycol Pumps. January 1996.
The Hanover Compressor Company. Personal Contact.
Kim ray, Inc. Personal Contact.
Radian International LLC, "Methane Emissions from the Natural Gas Industry.
Volume 15: Gas-Assisted Glycol Pumps" Draft Final report, Gas Research In-
stitute and U.S. Environmental Protection Agency, April 1996
Rotor-Tech, Inc. Personal Contact.
Tannehill, C.C., L. Echterhoff, and D. Leppin. "Production Variables Dictate
Glycol Dehydration Costs." American Oil and Gas Reporter, March 1994.
Tingley, Kevin. U.S. EPA Natural Gas STAR Program. Personal Contact.
U.S. Environmental Protection Agency. National Emission Standards for Haz-
ardous Air Pollutants for Source Categories: Oil and Natural Gas Production
and Natural Gas Transmission and Storage-Background Information for Pro-
posed Standards (EPA-453/R-94-079a, April 1997).
U.S. Environmental Protection Agency. Lessons Learned: Reducing the
Glycol Circulation Rates in Dehydrators (EPA430-B-97-014, May 1997).
U.S. Environmental Protection Agency. Lessons Learned: Installation of Flash
Tank Separators (EPA430-B-97-008, October 1997).
U.S. Environmental Protection Agency. "Methods for Estimating Methane
Emissions from National Gas and Oil Systems". Emissions Inventory Im-
provement Program, Vol. Ill, Chapter 3, October 1999
15
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Water Vapor Content of Natural Gas at Saturation
1000
100'
03
a.
O
-n
W
m
O
O
DC
LU
I
WATER VAPOR CONTENT OF NATURAL GAS AT SATURATION
SMITH INDUSTRIES. INC
OIL $ GAS DIVISION
HOUSTON, TEXAS
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130
TEMPERATURE, °F
Source: Kimray, Inc.
16
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&EPA
United States
Environmental Protection Agency
Air and Radiation (6202J)
1200 Pennsylvania Ave., NW
Washington, DC 20460
PA430-B-03-014
anuary 2004
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