Acid gas removal using an organic solvent at low temperatures. In general, methanol is used for H2S, COS and bulk CO2 removal, whereby organic and inorganic impurities are also removed. It is possible to produce a clean gas with less than 0.1 ppm sulfur and a CO2 content down to the ppm range. The main advantage over other processes is the use of a cheap, stable and easily available solvent, a very flexible process and low utilities.
Rectisol unit for the selective desulfurization and CO2 removal in the production of methanol synthesis gas. Raw gas (from SGP-POX) is cooled and trace components are removed in the prewash (1) with cold methanol. Prewashed gas is desulfurized (1) by using CO2-laden solvent down to 0.1 ppm. H2S-laden solvent is regenerated first by flashing to medium pressure (4) to recover H2 and CO, and second, by heating to boiling temperature and stripping with methanol vapors (3). The stripped H2Senriched gases are sent to a Claus unit. The portion of the desulfurized gas which has been shifted in the CO-shift conversion unit (6) has a typical CO2 content of 33%. Shifted gas re-enters the Rectisol unit, is cooled and the CO2 is removed in a two-stage absorber (2). In the lower section, the gas CO2 content is reduced to about 5% using flash-regenerated methanol (5). Remaining CO2 is removed using hot regenerated (3), cold methanol in the upper section; thus, about 3% CO2 is contained in the synthesis gas. The flashed CO2 is free of sulfur and can be discharged to atmosphere or used further. The refrigeration balance of the system is maintained by a conventional refrigeration unit. Methanol is injected in the raw gas cooling to prevent icing. The condensed methanol/water mixture is separated in a methanol/water column (not shown).
Licensor: Lurgi Oel-Gas-Chemie GmbH and Linde AG