Glycol/TEG Plants
What Are Glycol / TEG plants
Glycol (TEG) gas dehydration plants are effective in the removal natural gas stream water vapor removal to an outlet water content that is capable of meeting a 7 lb/ MMSCF pipeline specification or less. This is accomplished through a process known as glycol gas dehydration. TEG Dehydration, also referred to as water vapor removal, is achieved through the reduction of the water’s dew point, allowing water vapor to condense into a liquid at a lower temperature.
Dew point depression is based on a variety of factors that include the circulation rate of TEG as well as the amount of equilibrium stages in the absorber, lean TEG concentration, pressure, and contact temperature. Dew point depression is also very responsive to inlet gas temperature as a result of the change that occurs in gas-glycol contact efficiency in relation to temperature. Inlet gas temperature increase will result in a higher dew point depression. Alternately, inlet gas temperature decrease will result in a lower dew point depression. A low inlet gas temperature is more desirable.
The most commonly used method of gas dehydration is the absorption of water vapor within Triethylene Glycol. Wet gas is passed in contact with lean dry glycol within an absorber tray tower where the water vapor is then absorbed into the glycol. This allows the dew point of the water to become depressed. The wet rich glycol can then be reduced by pressure and transported from the absorber to the regeneration system. Heat exchange can then be utilized in order to preheat the wet rich TEG for separating the entrained gas. It is then heated once again and fractioned using a reboiler and still column. The absorbed water vapor is boiled off during this process. The water dry lean glycol can then be cooled through heat exchange and ultimately pumped back into the absorber.
Why Water Vapor Removal from Natural Gas Is Important
Changes that occur in the temperature and pressure of water vapor that is present in a natural gas system can result in the alteration of the vapor state from a gas to a liquid and in some cases, even into a solid. This can result in damage to the system.
By removing water vapor from a natural gas stream, it is possible to prevent:
- System corrosion
- Clogged equipment due to hydrate formation
- Line capacity reduction as a result of free liquid water formation