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Gas Processing
- Glycol Dehydration
- Dew Point Control Units
- Industrial Gas
Natural gas is produced from wells with a range of impurities and contaminants that need to be removed for the gas to meet typical specifications for use as commercial fuel or feedstock for LNG plants, gas turbines, industrial, domestic use, etc. These impurities include moisture (water), H2S, CO2, BTEX, and hydrocarbon liquids.
A number of different technologies are required to separate and remove contaminants, including the following processes:
- Glycol Dehydration and Regeneration (TEG, MEG & DEG)
- Molecular Sieve Dehydration
- Gas Sweetening (CO2 and/or H2O removal via Amines)
- Hydrocarbon Dew Point Control
- Fuel Gas Conditioning
Depending on the process conditions required and the specific gas processing requirements, Process Group can establish a process design to meet your targets. Some solutions are relatively straightforward and routine, while other applications require novel and innovative designs to provide a suitable solution. Either way, we have the expertise and experience and creative thinking to create a customized solution just for you.
Glycol Dehydration
The use of Glycol to dehydrate gas streams is an established method that has proven its functionality and versatility time and again. Process Group has decades of experience in designing and supplying Gas Dehydration, including numerous successful installations.
There are three common types of Glycol used for gas dehydration:
- Mono-Ethylene Glycol (MEG)
- Di-Ethylene Glycol (DEG)
- Tri-Ethylene Glycol (TEG)
The type of Glycol used and the package design depends on several factors, as well as the end-user's specific requirements and objectives for processing the gas stream. To ensure that the best overall design is produced, Process Group designs each package in close consultation with our client.
Design Basis
The design of TEG and MEG Dehydration Systems is unique for every requirement. The overall package design will vary to meet the specified moisture content of the gas at the process conditions. Each system is typically designed and built as a complete turn-key package with particular emphasis on the following issues:
Process Description
In a typical TEG package, water saturated gas enters near the bottom of the Contactor Tower and flows upward through the internal trays/packing (1). Lean Glycol enters the Contactor Tower near the top and cascades down through the Contactor internals (9), making contact with the up-flowing gas stream. The counter-current flow path of the Glycol, and the high contact surface area, adsorbs water into the Glycol from the gas stream. Dehydrated gas flows out of the top of the Contactor, while the Rich Glycol flows out of the bottom of the Contactor and to the Glycol Regeneration Package.
The TEG Regeneration process typically involves passing the Rich Glycol through the still column to gain some heat (2) before entering the Flash Drum (3). The Glycol is then passed through particle filters to remove particulates and then Activated Carbon Filters to remove any dissolved hydrocarbon and/or chemical compounds (4). The Rich Glycol is heated in a cross exchanger to preheat the feed (5) to the Still Column where the Glycol present in the water vapour leaving the Reboiler is recovered (6).Depending on the application, it may be necessary to increase the Lean Glycol concentration by using stripping gas (7), or running the Reboiler/Still Column under a slight vacuum. Lean TEG (typically >99wt%) is then cooled and pumped back to the top of the Contactor Tower (8) to repeat the process.
Dew Point Control Units
Hydrocarbon Dew Point Control Units (DPCUs) are designed to inhibit the formation of solid hydrates in gas streams; by default they perform dehydration to a certain extent. This is achieved through the injection of a liquid agent directly into the gas stream. The liquid agent is selected based on low viscosity and low freezing temperature, rather than its dehydration ability.
There are two common types of liquid agents used for Dew Point Depression:
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Mono-Ethylene Glycol (MEG)
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Methanol (MeOH)
The type of liquid agent used and the package design depends on several factors, as well as the end-user's specific requirements and objectives for the gas stream being processed. Process Group works closely with its clients to ensure the best overall design is achieved.
Design Basis
The design of a DPCU follows a basic structure. However, there are a number of approaches to achieve the end result; Dew Point Depression. Each system is typically designed and built as a complete turn-key package, with particular emphasis given to the following issues:
- Discharge gas hydrocarbon dew point
- Discharge gas moisture content
- Minimum glycol losses
- Minimum power consumption
- Optimum plant efficiency and design integrity
- Compliance with HSE requirements
- Environmentally conscientious design
The resulting design will be influenced by all of the above factors in addition to the emphasis and importance given to each particular issue.
MEG DPCU (155TJ/day) package for Minerva project, Victoria, Australia.
Process Description
In a typical MEG Injection Dew Point Control Unit (DPCU), the gas is first passed through an Inlet Separator (1) where any free liquids are removed.
Just prior to entering the gas/gas exchanger pressurised Lean MEG is injected into the gas stream (2). Additional MEG is injected and the MEG-gas mixture is then further cooled through either Expansion (Joule-Thompson Valve/Orifice) or Refrigeration (3).
Further cooling condenses any residual water and/or hydrocarbons. A Low Temperature Separator (LTS) (4) is located downstream to remove any free liquids now including the condensed water, condensed hydrocarbons and injected MEG. The cooled gas with a depressed dew point is circulated back into the gas/gas exchanger for pre-cooling of the inlet gas (2).
There are two possible process trains available to the free liquids removed in the Inlet Separator and LTS. If significant condensate is present it may be necessary to install a Condensate Stabilisation Unit (5). Otherwise, the liquid's typically containing MEG, water and condensate will be processed in a MEG Regeneration Package (6) to remove sufficient amounts of water and condensate to produce a Lean MEG product. This Lean MEG is then recycled back into the system and injected back into the DPCU.
Project References and Case Studies
Process Group has successfully completed a wide variety or projects all over the world working with governments and name companies. Read the case studies below to learn more about some of our gas processing projects and the technical solutions and value we delivered.
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