Partner Reported Opportunities (PROs) 

### PRO Fact Sheet No. 201 for Reducing Methane Emissions



# Reroute Glycol Skimmer Gas

Technology/Practice Overview

Description In the glycol dehydration process, rich glycol is circulated through a regenerator where the dissolved water, methane, volatile organic compounds (VOCs), and Hazardous Air Pollutants (HAPs) are vaporized and vented to the atmosphere. Some glycol dehydrators have glycol vent condensers and condensate separators to recover natural gas liquids and reduce VOC and HAP emissions. The non-condensable gas from the condensate separator, which contains mostly methane, is vented to the atmosphere.
A Partner reported rerouting the condensate separator gas, called skimmer gas, to the reboiler firebox or other low pressure fu el gas systems for fuel use. In addition to reducing methane emissions, this practice further reduces VOC and HAP emissions, and increases product revenue.

Operating Requirements The condensate separator must operate at a higher pressure than the destination to which the skimmer gas is routed.

Applicability This practice can be employed on all dehydrators with vent condensers but is based on the assumption that fuel gas consumption levels can accommodate the volume of re-routed skimmer gas.



### Methane Emissions
The methane emissions savings are based on the dehydrator having a gas entrainment rate of 3 scf per gallon of TEG, and vent gas containing 95 percent methane.

Estimated Gas Price Annual Methane Savings Value of Annual Gas Savings* Estimated Implementation Cost Incremental Operating Cost Payback (months)

$7.00/Mcf 790 Mcf $5,900 $2,000 $100—$1,000 4 - 7

$5.00/Mcf 790 Mcf $4,200 $2,000 $100—$1,000 6 - 9

$3.00/Mcf 790 Mcf $2,520 $2,000 $100—$1,000 10 - 15 

### Economic and Environmental Benefits

Economic Evaluation

Additional Benefits
 Fuel gas savings Estimated annual methane emission reductions 790 Mcf per dehydrator unit Methane Savings

* Whole gas savings are calculated using a conversion factor of 94% methane in pipeline quality natural gas. Compressors/Engines
Dehydrators
Directed Inspection & Maintenance
Pipelines

Pneumatics/Controls

Tanks

Valves

Wells

Other

Applicable Sector(s)

Production
Processing

Transmission

Distribution

Other Related Documents:

Pipe Glycol Dehydrator to Vapor Recovery Unit, PRO No. 203PRO Fact Sheet No. 201 Continued 

# Reroute Glycol Skimmer Gas (Cont’d)

Methane emissions reductions of 7,600 Mcf per year can be achieved for a 20 MMcf per day dehydrator having a vent condenser, without a flash tank separator, circulating 300 gallons of glyc ol per hour with an energy exchange pump. The absence of a flash tank separator (as is common with some International Natural Gas STAR Partners) would result in greater emissions and, by extension, a greater am ount of gas possibly being recovered through this practice. One Partner reported methane savings of 24 Mcf per day per unit (8,760 Mcf per year per unit). Methane savings may be limited by the amount of low-pressure fuel gas consumption at the site.



### Economic Analysis

Basis for Costs and Savings Methane emissions reductions of 790 Mcf per year apply to a 20 MMcf per day dehydrator with a vent condenser and a flash tank separator, circulating 300 gallons of glycol per hour with an energy exchange pump.
The cost of this project would include planning, design, and implementation by an engineer and installation of additional rudimentary installation estimated to piping. Using expert judgment estimates of equipment capital

costs, the implementation costs be approximately $2,000. and and

are

Discussion This technology pays back quickly. Using glycol skimmer gas as a fuel directly offsets use of saleable natural gas, increasing product revenues. The significant gas savings from rerouting glycol skimmer gas to a fuel gas system will offset the low capital, operating, and maintenance costs. This practice is more cost effective for dehydrators without flash tank separators. The average methane content of na tural gas varies by natural gas industry sector. The Natural Gas STAR Program assumes the following methane content of natural gas when estimating methane savings for Partner Reported Opportunities.

Production 79 %

Processing 87 %

Transmission and Distribution 94 % 

### Methane Content of Natural Gas

EPA provides the suggested methane emi ssions estimating methods contained in this document as a tool to develop basic methane emissions estimates only. As regulatory reporting demands a higher-level of accuracy, the methane emis

sion estimating methods and terminology contained in this document may not conform to the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W methods or those in other EPA regulations.

2 2011