Electric Glycol Circulation Pumps
Summary
Glycol dehydrators are used in the oil and gas industry to remove water from the natural gas stream. Most glycol dehydrators use triethylene glycol (TEG) as the dewatering agent. During the dehydration process, as TEG is regenerated through heating in a reboiler, absorbed methane, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs) are vented to the atmosphere with the water vapor. Additionally, the TEG is often circulated with a gas-assist glycol circulation pump wherein the assist gas is combined with the rich glycol stream prior to regeneration and is emitted as well. Replacing a gas-assist glycol circulation pump with an electric glycol circulation pump avoids the additional emissions from the assist gas.
Description
Glycol dehydrators can be equipped with electric motor-driven glycol circulation pumps, if electricity is available, to reduce emissions. If the glycol dehydration unit uses a gas-assist pump to circulate regenerated (lean) glycol back to the contactor, the assist gas is exhausted from the pump into the rich glycol stream prior to the regenerator. For a glycol dehydrator with a gas-assist glycol circulation pump, most of the methane emissions are from the assist gas. Figure 1 shows a typical glycol dehydrator system using a gas-assist glycol circulation pump. Replacing the gas-assist glycol circulation pump with an electric motor-driven glycol circulation pump eliminates the assist gas stream. Figure 2 shows a glycol dehydrator with an electric glycol circulation pump. When electric glycol circulation pumps are used, only the methane, VOCs, and HAPs dissolved in the rich glycol are boiled off with water in the regenerator and vented to the atmosphere.
Applicability
Retrofitting a gas-assist pump with an electric motor-driven glycol circulation pump is most applicable at sites that have reliable electric power available and which would have limited beneficial use for gas captured at low pressure with a flash tank separator.
Methane Emissions Reductions
Methane emission reductions can be determined by taking the difference in emissions from the source before and after the specific mitigation action was applied. Glycol dehydrators are an integrated system with multiple components and methods to operate and reduce emissions. As a result, replacing a gas-assist glycol circulation pump with an electric glycol circulation pump will impact emissions throughout the entire system. Because there are multiple glycol dehydrator configurations and unique parameters to consider, such as the volume of natural gas and water content, a default emission factor is not available to adequately estimate emissions. Alternate methodologies for estimating emissions from glycol dehydrators include the use of simulation software, which can model emissions from the glycol dehydrator for the existing configuration and after implementation of the mitigation option. Further information on calculating glycol dehydrator emissions using simulation software is available in subpart W of EPA’s Greenhouse Gas Reporting Program at 40 CFR 98.233(e).
The calculation methodology in this emissions reduction section is based upon current information and regulations (as of August 1, 2023). EPA will periodically review and update the methodology as needed.
Other Benefits
In addition to reducing emissions of methane, installing an electric glycol circulation pump may:
- Reduce air pollution: Reduces emissions of volatile organic compounds and hazardous air pollutants.
- Reduce operational costs for maintaining the pump: Reduces need for maintenance given that electric pumps have fewer parts than gas-assist pumps (e.g., O-rings).
- Reduce product loss: Reduces the loss of produced gas that would be used to power the assist gas pump.
Lessons Learned
References
Mokhatab, S., Poe, W. A., & Speight, J. G. (2006). Handbook of natural gas transmission and processing. Gulf Professional Publishing. https://doi.org/10.1016/B978-0-7506-7776-9.X5000-3
Please Note: This platform reflects experiences and lessons learned from voluntary program partners. Some of these emission sources and technologies are now regulated at the federal, state, and/or local level in the United States and in other countries. The end user is solely responsible for complying with any and all applicable federal, state, and local requirements. For information on U.S. regulations for the oil and gas industry, refer to eCFR. EPA makes no expressed or implied warranties as to the performance of any technology and does not certify that a technology will always operate as advertised. Mention of names of specific companies or commercial products and services does not imply endorsement.