Gas dehydration is an important process in gas processing. The produced gas is saturated with water, which must be removed. If not removed it can create problems like corrosion, water condensation and plugs created by ice or gas hydrates. In addition other contaminants like H2S, CO2 and mercaptans must also be removed. Gas treatment systems like dehydration and gas sweetening removes these impurities and makes the gas suitable for transportation and further use.
In natural gas streams, water vapour needs to be removed to reduce pipeline corrosion and eliminate line blockages due to hydrate formation. In case of acidic gases are removed by amine treatment, the gas will be water saturated and will need to be dehydrated before it goes for further processing.
Glycol dehydration systems
Water vapour must be removed from natural gas to prevent pipeline corrosion and mechanical damage to downstream equipment. The most commonly used method for this procedure involves use of Triethylene Glycol (TEG) in a continuous process in which the water vapour is absorbed from the gas under conditions of high pressure and moderate temperatures.
How Does It Work?
Wet gas enters the tower at the bottom and flows upwards. Dry glycol flows down the tower from the top through the packing material to remove up to 10 ppm of moisture in dry gas. Finepac structured packings are used for efficient moisture removal. The dehydrated gas leaves the tower at the top and goes to other processing units. The water rich glycol leaves the tower at the bottom and goes to a reconcentration system consisting of a stripper and a regenerator. In this system Finepac random packings are used. Water escapes as steam and purified glycol returns to tower where it contacts wet gas again.
Natural gas streams may contain corrosive gases like hydrogen sulphide and carbon dioxide which require to be removed before the gas goes for further processing. Amine contactors remove these gases from the natural gas streams and make it suitable for downstream processing.
Amine treatment plants
The process used most often for removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) from natural gas also referred to as acid gas removal or gas sweetening is the amine process. This is a continuous process where acid gas compounds are selectively absorbed from the gas stream under conditions of high pressure and moderate temperature.
How Does It Work?
Sour gas enters the contactor tower and rises through the descending amine solution, purified gas flows from the top of the tower. The amine solution, carrying absorbed acid gases, leaves the tower for the heat exchanger. Rich amine is heated by hot regenerated lean amine in the heat exchanger. The rich amine is further heated in the regeneration still column, by heat supplied from the reboiler, the steam rising through the still liberates H2O and CO2 regenerating the amine.
Steam and acid gases separated from the rich amine are condensed and cooled, respectively in the reflux condenser. Condensed steam is separated in the reflux accumulator and returned to the still. Acid gases may be vented or directed to a sulphur recovery system and the hot regenerated lean amine is cooled in a solvent aerial cooler and circulated to the contactor tower thus completing the complete cycle.