Glycol dehydration removes excess water from natural gas for transportation and consumer use. Raw gas is carried through liquid glycol molecules to remove water vapor, which is recycled. Triethylene glycol is the most common glycol used due to its high boiling point.
Glycol dehydration is a process used in the purification of natural gas. It is designed to help remove excess water from raw natural gas to make it suitable for transportation in pipelines and for consumer use. In general, one of three types of glycol can be used, all of which have similar properties and typically function in similar systems.
When natural gas is piped from underground wells, it often contains many substances in addition to the methane that is typically associated with commercial grade natural gas. Such substances, often called contaminants, can include things like ethane, propane, nitrogen and water. Most contaminants generally need to be removed before natural gas can be transported away from the original wells and sold to consumers.
There are several methods of removing contaminants, including several methods for removing water and water vapor. One of the most common methods of removing water vapor is glycol dehydration. The first stage of this process typically takes place in a shrink tower. Here, raw natural gas is typically carried upward through liquid glycol molecules, which attach to water vapor molecules and then sink to the bottom of the apparatus. The waterless natural gas generally then continues to rise through the contractor’s tower and on to the subsequent decontamination process.
In general, the water-laden glycol molecules that sink to the bottom of the glycol dehydration shrink tower are not simply discarded. Instead, they are usually removed from the tower and recycled. To recycle the water-laden glycol, the solution is typically heated above 212 degrees Fahrenheit (100 degrees Celsius) to boil the water, leaving only the glycol, which doesn’t boil to a much higher temperature, behind. This purified glycol is then often reused in the same contractor tower process described above.
Different types of glycol can be used in the glycol dehydration process. One of the most common forms is triethylene glycol, which has one of the highest boiling points, generally making it easier to remove the water vapor and reuse. Other forms that can be used in glycol dehydration include diethylene glycol and tetraethylene glycol. Diethylene glycol is generally cheaper than triethylene glycol, but is typically used less often because more is lost in the dehydration process. In contrast, the loss of tetraethylene glycol is typically lower than that of triethylene glycol or diethylene glycol, but its higher initial cost generally makes it a less commonly used option.
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