Removal of acid gases from natural gas, fuel gas and syngas by physical absorption in NMP (N-methyl-pyrrolidone). Typical cases: 1. High CO2 contents to low residual level, 2. Bulk acid gas removal to moderate purity by simple flash regeneration, 3. Selective H2S removal. Ideally suited for (3) in an IGCC based on POX of coal or oil, as NMP, is the most selective solvent on the market. 4. Selective removal of mercaptans from gas streams, e.g., from spent regeneration gas coming from a molecular sieve mercaptan removal unit from natural gas. It is a cheap, stable, noncorrosive and easily available solvent with a broad range of further industrial applications.
Raw gas from a POX of heavy residue is cooled; HCN and organic sulfur compounds are removed in prewash (1). H2S is removed in main absorber (1) by hot-regenerated, lean solvent cooled slightly below ambient temperature. NMP traces are backwashed on top of (1) with H2O. Laden solvent from (1) is flashed at medium pressure in a reabsorber (2). H2S traces in the flash gas are reabsorbed by a small quantity of lean NMP. The sulfur-free gas from (2) is compressed back to the produced fuel gas (1). Flashed solvent from (2) is heated by hot lean solvent and flashed again (3). Hot-flashed gas is cooled and sent back to reabsorber (2). Solvent from (3) is finally hot-regenerated in (4). The resulting, cooled acid gas, very rich in H2S, is processed in an OxyClaus unit, the tail-gas is hydrogenated, formation water is removed by quenching, recompressed to reabsorber (2) for desulfurization and finally ending up in fuel gas. This closed cycle is offgas free and leads to increasing overall efficiency of the IGCC plant.
Licensor: Lurgi Oel-Gas-Chemie GmbH