TransTex keeps many sizes of Triethylene Glycol (TEG) dehydration units in our fleet to remove entrained water from the gas stream.
When natural gas is produced from the reservoir, it is typically saturated with water vapor. In order to meet the pipeline specification, that water vapor needs to be removed. For sales of gas in warmer climates, as in the southern areas of the U.S., water content for pipeline quality specifications should not exceed 7 pounds per million standard cubic feet. At a minimum, glycol dehydration units must typically meet this specification. Further removal may be required if additional hydrate formation temperature depression is required, such as upstream of a cryogenic process or gas plant.
BENEFITS OF DEHYDRATION UNITS
- Reduces the possibility of water freezing in piping
- Reduces the probability of hydrate formation and helps prevent plugging of equipment and piping
- Helps reduce corrosion in the piping
- TEG can be reused, providing for efficient use of chemical and costs
HOW DOES IT WORK?
- A glycol dehydration unit is typically a simple unit – an absorber tower and a reboiler
- The inlet, water-saturated gas enters the system at the base of the absorber
- The gas flows upward through the down-flowing TEG making contact on random packing or through bubble cap trays
- The TEG removes the water from the gas, allowing for the now-dry gas to exit through the top of the absorber
- The water saturated TEG flows into the reboiler where the mixture is separated by boiling the water off
- The TEG is then pumped back to the absorber to start the process over again.
GLYCOL DEHYDRATION UNITS ALSO REMOVE BTEX
BTEX, otherwise known as benzene, toluene, ethylbenzene, and xylenes, are compounds that occur naturally in crude oil. BTEX compounds have emissions maximums that are monitored by the EPA. These compounds are liquid at atmospheric temperature and pressure, however it is possible for them to be vapors in natural gas streams. BTEX is typically accompanied by other volatile organic compounds, or VOCs.
BTEX and VOCs in natural gas is absorbed by TEG in the dehy tower and driven off by the dehy reboiler. The vapors from the reboiler are sent to a piece of equipment called a BTEX eliminator. This is a simple system that is typically an atmospheric cooled heat exchanger and a two-phase separator. The condensed BTEX liquids are sent to storage while VOCs are burned as fuel for the dehy reboiler.
RIGHT-SIZED READILY AVAILABLE EQUIPMENT
By providing us with your gas specifications, our process engineers can simulate and determine what size system is appropriate for your applications specific needs. Send TransTex your gas analysis today by clicking here.