Natural gas contains water vapor that cannot be removed by conventional filters or separators. This water vapor can condense and form hydrates, a crystallized gas/water compound. These hydrates can create havoc in downstream processes, as well as promote corrosion in equipment and piping.
MEI Maverick Engineering has designed numerous projects to dehydrate natural gas to meet pipeline specifications. Depending on the application, MEI’s process design is based on ProMax or HYSYS software, will limit plot and height of the dehydration unit, and limit the volume of gaseous (VOCs) emissions.
Most dehydration projects involve either absorption or adsorption technology.
Adsorption
Adsorption utilizes a solid desiccant dehydrating media, usually silica gel, calcium chloride, activated alumina, or molecular sieve. A minimum of two adsorption towers are filled with the solid desiccant. The wet gas passes downward over the media and the water is retained on the surface of the solid desiccant. The dry gas exits the bottom of the tower and goes to continued processing or pipelining. These adsorption units are adequate for small flowrates of natural gas.
Absorption
Absorption utilizes a regenerable, liquid hydroscopic solvent, such as triethylene glycol (TEG), to remove water vapor from the natural gas stream in a contactor tower. Absorption units are more appropriate for moderate to higher flowrates of natural gas.
The contactors usually contain a structured packing or bubble cap trays to promote the interface of the TEG with the water vapor in the natural gas, thereby increasing removal efficiency.
A regenerator is required to drive off the water vapor from the spent TEG so it can be recycled to the contactor tower for further gas dehydration. TEG also can absorb volatile hydrocarbons from the natural gas. The regeneration process releases these VOCs, and a BTEX (Benzene, Toluene, Ethyl Benzene, and Xylene) control system is used to condense and recover these VOCs for safe disposal.
A MEI designed dehydration unit, as a part of your gas processing project, will insure safe and reliable operation, while providing the most cost effective solution available.