Natural Gas Dehydration Unit With TEG
Process modeling and simulation with ProSimPlus
Natural Gas TEG dehydration process [click to expand]

Background information

Most natural gas producers use Triethylene glycol (TEG) to remove water from the natural gas stream in order to meet the pipeline quality standards. This process is required to prevent hydrates formation at low temperatures or corrosion problems due to the presence of carbon dioxide or hydrogen sulfide (regularly found in natural gas).
Dehydration, or water vapor removal, is accomplished by reducing the inlet water dew point (temperature at which vapor begins to condense into a liquid) to the outlet dew point temperature which will contain a specified amount of water.
Absorption of water vapor in the TEG is the common method. The wet gas is brought into contact with dry glycol in an absorber. Water vapor is absorbed in the glycol and consequently, its dew point reduces. The wet rich glycol then flows from the absorber to a regeneration system in which the entrained gas is separated and fractionated in a column and reboiler. The heating allows boiling off the absorbed water vapor and the water dry lean glycol is cooled (via heat exchange) and pumped back to the absorber.
Natural Gas TEG dehydration process scheme [click to expand]
Modeling the process

Rigorous process simulation is today widely used to design and optimize TEG dehydration processes. An example of natural gas dehydration, using TEG, was built with ProSimPlus.
The interesting points of this example lie in the use of the “absorption” module for the contactor model and in the representation of two columns connected in series (the TEG regenerator and the TEG stripper) by a single ProSimPlus “stripper” module. Additionally, the Windows Script module is used in different parts of the flowsheet to perform specific calculations (gas water dew point, TEG losses for make-up calculation).

This example is meant to provide a starting point for advanced simulation of such process by presenting a set of components with their physical properties, and the relevant unit operation modules with their specific interconnections.

This example can be used to analyze and understand the main areas of the process and shows one way to model these particular areas and their interconnections. Additional investigations can also be the testing of new equipment configuration to enhance production yield and analysis of energy efficiency.

Generally speaking, advanced simulation software like ProSimPlus enable pre-size equipment, run troubleshooting and debottlenecking analysis. Their ability to run in-depth analysis and what-if scenarios allows solving many problems within a reduced time and a minimum investment.
It is to be noted that this particular model is not intended to be used in equipment detailed design, manufacturing or even producing engineering documents without further review by a process engineer.

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