TEG Gas Dehydration Unit: A Video Overview

A TEG Gas Dehydration Unit is used to dehydrate natural gas into a state where it can be sold downstream.

What is Gas Dehydration? 

When you hear dehydration, you may think of physical dehydration, where your body has a shortage of water. Or maybe you think of meat or fruit that has had the water taken out of it

In natural gas dehydration, it's the same ideaproducers dehydrate gas by removing the water from it.

Uses of Natural Gas

Societies use natural gas is for heat, cooking, manufacturing, transportation, and to generate electricity. However, none of these things would be possible if the water content of the gas were too high. 

Why is Gas Dehydrated?

Producers dehydrate gas for two primary reasons:  

  1. To remove water vapor from natural gas to a level mandated by the purchaser  
  2. To prevent damage to gas pipelines that results when water accumulates in the system 

Where IS Gas Dehydrated?

Gas dehydration takes place anywhere that hydrates can fall out and cause the quality of the gas to be below contractual agreements or safety standards. All three sectors of the oil & gas industry use dehydration, including: 

  • Upstream at individual well locations
  • Midstream at gathering stations and delivery points
  • Downstream at processing plants. 

What is a TEG Gas Dehydration Unit?

To take the water out of natural gas, producers use a liquid called triethylene glycol, also known as TEG.  

When gas comes into contact with triethylene glycol, the water vapors entrained in the gas are absorbed in the TEGIn effect, the glycol "soaks up" the water. The glycol is then removed from the gas stream for processing so that it can be purified and reused. 

How a TEG Gas Dehydration Unit Processes Gas

The dehydration process involves several different pieces of equipment. Natural gas only travels through the inlet scrubber and the contactor tower. On some sites, these two vessels are combined into one unit. All the other equipment is used to regenerate the glycol.   

As the glycol moves through the contactor tower, it absorbs the moisture from the natural gas. At this point, it is either "rich" or "wet" glycol, depending on your region. Now it must be distilled in order to be reused.  

Ithen flows into a three-phase flash separator which separates the rich glycol from contaminants, lubrication oil, free water, and condensate. The contaminated liquids exit and are moved to storage tanks, while the glycol then goes to the reboiler. The reboiler removes the water contained in the "wet" glycol. 

Distilling the triethylene glycol in the reboiler is easily accomplished because of the extreme differences in the boiling points of water and glycol. Water boils at 212° F while glycol boils at 550° F.   

However, TEG begins to degrade at 404° F, which is its critical temperature. 

For this reason, producers heat the wet glycol between 212° F and 400° F. This allows the water to be boiled off and glycol to be distilled to an appropriate level of purity so it can be reused. 

The water flashes off as steam, but the glycol drops into the reboiler. Glycol in this stage is "lean" or "dry" glycol.  

With the right equipment, the system will regenerate the wet glycol to 98% purity. With good filtration, this allows producers to reuse it repeatedly, around 18-24 months before it needs to be changed. 

TEG Gas Dehydration Unit Sizes

Dehydration units vary in size depending on gas flow. In a unit this size, the flow rate can be a few million cubic feet per day 

A large dehydration system located at a central gathering station can dehydrate millions of cubic feet of gas every day (MMCFD). 

To speak with an expert about how to optimize the production of your TEG Gas Dehydration Unit, contact your local Kimray store or authorized distributor.