NHD - Polyethylene Glycol Dimethyl Ether — Frequently Asked Questions

A chemical solvent such as an amine reacts with carbon dioxide to form a compound, which must then be broken apart with heat to release the gas and regenerate the solvent, consuming large amounts of steam. A physical solvent simply dissolves the gas in proportion to its partial pressure, so the gas is released by dropping the pressure rather than by boiling the solvent.

At high pressure and high acid gas concentration. Because absorption follows Henry's law, a physical solvent picks up much more gas as partial pressure rises, and regeneration by pressure letdown costs far less energy than thermal stripping. At low partial pressure, as in atmospheric flue gas, a physical solvent absorbs too little and an amine is required instead.

Yes. It absorbs hydrogen sulphide considerably more strongly than carbon dioxide, which allows the two to be separated in staged flash vessels rather than removed together. That selectivity is commercially valuable where the hydrogen sulphide must be routed to a sulphur recovery unit while the carbon dioxide is vented or used.

It is non-corrosive, so carbon steel can be used where an amine plant needs upgraded metallurgy; it does not foam readily; it is thermally and chemically stable so degradation and reclaiming are minimal; and it has very low vapour pressure so solvent losses are small. Together those reduce both capital and maintenance cost.