Pipeline operations generate hydrocarbon vent gas (e.g., natural gas and petroleum product vapors) when pipeline sections are depressured. The depressuring can result from planned and emergency venting operations. This blog discusses options to reduce air emissions from planned depressuring pipelines associated with pigging operations and pipeline maintenance and inspections.

Air Quality Rules

Air quality permits/authorizations for pigging and pipeline depressuring emissions vary across States and local regulatory agencies. Some State and local environmental agencies require an air permit or other environmental regulatory authorization for venting or flaring for planned pipeline depressuring operations. One-time permit and/or State-wide permits for these operations are also issued. Emission controls (e.g., flaring, ECD) may be required by the State regulatory agency, depending on the product (e.g., natural gas, gasoline) in the pipeline and the amount of gas/vapors to be released.

Consult your State or local air quality rules for specific permitting, reporting and emission controls requirements for pigging and pipeline venting operations.

Pigging Operations

Pigging is the practice of using mechanical devices known as ‘pigs’ to perform various pipeline maintenance, cleaning and inspection operations.

This is accomplished by inserting a pig into a “pig launcher” or “pig trap.” The pig launcher is closed, and the pressure driven flow of the product in the pipeline is used to push the pig along the pipe until it reaches the receiving trap also called the “pig catcher” or “receiving station”. As the pig moves through the pipeline, it sweeps the inside walls and scrape the sides, pushing removed buildup in front of the pig.

Utility pigs are used to clean debris from the pipeline. “Smart pigs” have sensors used to detect and measure corrosion, deformations, and metal loss from the pipeline walls. These smart pigs can be simple to complex devices that have various sensors used to gather needed data. Specialty pigs, such as sealing pigs/plugs, are used to isolate a section of the pipeline for maintenance work.

Pipeline pigs are used in natural gas, oil, midstream products (e.g., volatile organic products such as ethane, propane, butane, pentane, NGL, natural gasoline) and refinery product pipelines, as well as food and pharmaceutical industries.

Pigging Venting Emissions

A part of the pigging operation involves the depressuring of the pig launcher (during launching) and pig catcher (during retrieval). Depressuring results in air emissions if the product gas/vapors are vented to the atmosphere or combusted in a flare or enclosed combustion device (ECD).

For natural gas pipelines, the pigged liquids (captured ahead of the pig) are separated from the natural gas prior to entering the processing plant compressors. This recovered liquid would be sent to a storage tank. At the storage tank, the liquids, recovered at pipeline pressure, will flash and liberate light hydrocarbon gases.

The venting emissions from pigging can include:

• Methane and VOC emissions from venting of gas from natural gas, crude oil and condensate pipelines.
• VOC and hazardous air pollutants (HAPs) from venting of vapors from refined products pipelines transporting gasoline, jet fuel, and diesel. The HAPs include benzene, toluene, ethylbenzene, xylenes, and naphthalene.
• Methane, VOCs, and/or HAPs from flash gas liberated by pigging liquids sent to storage tanks.

Criteria pollutants (NOx, CO, VOC, particulate matter, SO2) and smaller amounts of HAPs result from combustion of pigging vent gas/vapors.

Options for Pigging Emissions Reduction

• Use an inert gas (e.g., nitrogen) to purge the pig launcher section prior to pig insertion and use an inert gas to purge the pig catcher prior to pig retrieval. With this method only inert gas would be vented to the atmosphere.
• Combust vapors from pigging in a flare or ECD. For pigging at locations not equipped with a flare or ECD, use a portable flare/ECD unit.
• Recover the pigging vapors with a portable vapor recovery unit (VRU) compressor and send the gas/vapors to the pipeline system.
• Use a VRU to recover vent gas/vapors from storage tanks that receive pigging liquids.
• Use a flare or ECD to combust vent gas from storage tanks that receive pigging liquids.

Pipeline Maintenance Operations

There are thousands of miles of pipelines transporting valuable and needed petroleum fuels (natural gas, crude oil) petrochemical feedstock (ethane, propane, butane, pentane) and refined products (gasoline, diesel) to U.S. markets. Pipeline operators work diligently to minimize product loss and air pollution emissions from their operations. Some product loss and air emissions are unavoidable in pipeline operations.

Pipeline operations that result in venting emissions include the venting of natural gas and petroleum product vapors can include the following:

• Pipeline pressure reduction
• Pipeline blowdowns prior to maintenance
• Section replacement
• Hot tap repairs
• Line abandonment
• Line replacement

Depressuring Emissions

Depressuring of pipelines can generate substantial volumes of natural gas or hydrocarbon product vapors that must be handled properly. This can result in venting of the gas or vapors to the atmosphere.

The venting emissions can include:

• Methane and VOC emissions from venting of gas from natural gas, crude oil and condensate pipelines and natural gas products (propane, butane, pentane, natural gasoline, etc.).
• VOC and hazardous air pollutants (HAPs) from venting of vapors from refined products pipelines transporting gasoline, jet fuel, and diesel. The HAPs include benzene, toluene, ethylbenzene, xylenes, and naphthalene.

Criteria pollutants (NOx, CO, VOC, particulate matter, SO2) and smaller amounts of HAPs result from combustion of vent gas/vapors.

Options to Reduce Pipeline Depressuring Emissions

• Composite Wraps. Use composite wraps to repair pipeline defects and eliminate the need for depressuring.
• Use isolation valves to block the shortest linear section of pipeline and depressure the section to the atmosphere or combust in a flare or ECD. This method will shut down the flow in the pipeline.
• Hot Tapping
  • Use hot tapping to make new connections into the pipeline.
  • Use hot tapping and a bypass line (which allows the pipeline to flow while maintenance if performed) to block the shortest linear section of pipeline and depressure that section to the atmosphere or combust in a flare or ECD. Use a portable flare or ECD if needed.
• Pipeline Pump-Down Techniques
  • For pipelines sections located between two compressor stations, depressure the pipeline section to the lowest pressure possible. Use a portable compressor to further reduce pressure of the pipeline section.
  • If portable compressor not available, send remaining lower pressure pipeline gas/vapors a flare or ECD.

Conclusions

Air quality regulations that apply to pigging and pipeline depressuring operations vary across the different State and local environmental regulatory agencies.

Pigging operations release natural gas or volatile organic product vapors during the pig launching and pig retrieval operations. Controlling these emissions can include using inert purge gases for the pigging operation and use of flares and ECDs to combust gas/vapors.

Depressuring pipelines also release natural gas or volatile organic product vapors during depressuring operations. Controlling these emissions can include using composite wraps and pipeline pump-down techniques and using flares and ECDs to combust gas/vapors.

For more information on methods and technologies to reduce pigging and pipeline depressuring emissions check out the following:

• EPA Gas STAR
• OneFuture
• The Environmental Partnership

Cimarron Solutions

Cimarron solutions to assist with compliance with the new flaring and venting rules include:

• Measurement of vent gas from storage tanks using our IQR Teams.
• Fugitive leak detection and repair monitoring
• Installation of vent and flare gas meters
• Vapor recovery units (VRU)
• Vapor recovery towers (VRT)
• Flares and enclosed combustors
• Retrofit flares and enclosed combustors with automatic igniters, pilot systems and alarm systems for flare pilot/ignitor malfunction.
• Automated alarm system technology (SyteLink360TM)

Cimarron – Who We Are

Cimarron’s vision is to work with our clients to create a cleaner environment.

The company engineers and manufactures environmental, production and process equipment for the upstream, midstream and downstream energy industries, as well as environmental control solutions for biogas at wastewater facilities, digester tanks and landfills.

Cimarron offers our customers the know-how and environmental expertise to meet the environmental standards of today and tomorrow. Cimarron is committed to bring value to the Energy industry and their shareholders based on our financial strength, experienced personnel, and engineering capabilities.

As a company, we thrive every day to make a difference through innovation (e.g. ESG), customer focus, and operational efficiency. In addition to being present in all major regions in the US, Cimarron serves more than 45 countries around the world, ranging from offshore to desert. From key operational centers in the United States, Italy and the United Arab Emirates, Cimarron offers ongoing service and support through its own field service personnel and strategic third-party partners, creating a cleaner environment for our customers and their shareholders.

Since its founding in the mid-1970’s in Oklahoma, the company’s product offering has expanded from production equipment to include the largest line of environmental solutions that capture or incinerate fugitive vapors. With the acquisitions of HY-BON/EDI in 2019 and AEREON (including Jordan Technologies) in 2020, Cimarron has added strong brands, products, and services to its portfolio.

Please contact us to learn more about our products and services and about all our ESG solutions at sales@cimarron.com or visit our website www.cimarron.com.