Selexol process

The Rectisol process is more readily appHcable for acid gas removal from synthesis gas made by partial oxidation of heavy feedstocks. The solvents used in Purisol, Fluor Solvent, and Selexol processes have low vapor pressures and hence solution losses are minimal. Absorption systems are generally corrosion-free. 

The solvent can be tailored to provide selective acid gas removal based on the Hquid—gas solubiHties. For example, the Selexol process, Hcensed by Union Carbide Corporation, uses the dimethyl ether of polyethylene glycol (DMPEG) to provide high hydrogen sulfide selectivity. The solubiHty of hydrogen sulfide in DMPEG is 8—10 times that of carbon dioxide. 

Important processes commercially used are the Selexol, the Sulfinol, and the Rectisol processes. In these processes, no chemical reaction occurs between the acid gas and the solvent. The solvent, or absorbent, is a liquid that selectively absorbs the acid gases and leaves out the hydrocarbons. In the Selexol process for example, the solvent is dimethyl ether of polyethylene glycol. Raw natural gas passes countercurrently to the descending solvent. When the solvent becomes saturated with the acid gases, the pressure is reduced, and hydrogen sulfide and carbon dioxide are desorbed. The solvent is then recycled to the absorption tower. Figure 1-1 shows the Selexol process. ... 

Figure 1-1. The Selexol process for acid gas removal (1) absorber, (2) flash drum, (3) compressor, (4) low-pressure drum, (5) stripper, (6) cooler.

Breckenridge, W. et al., Use of SELEXOL Process in Coke Gasification to Ammonia Project, Proceedings ofLaurance Reid Gas Conditioning Conference, http //www.uop.com/objects/92Selex CokeGasifAmm.pdf, March 2000. 

Sepasolv MPE [Methyl isopropyl ester] A variation on the Selexol process, using the methyl isopropyl ethers of polyethylene glycol as the solvent. Developed by BASF. Four commercial plants were operating in 1985, removing hydrogen sulfide from natural gas. Wolfer, W., Hydrocarbon Process., 1982,61(11), 193. 

SOLINOX SO,. Linde NO,] A process for removing both NOx and SOx from fluegases. The SOx is removed by scrubbing with tetra-ethylene glycol dimethyl ether, circulated in a packed tower (the Selexol process). The NOx is destroyed by Selective Catalytic Reduction ( SCR). The sorbent is regenerated with steam the SOx is recovered for conversion to sulfuric acid. Developed by Linde in 1985 and used in a lead smelter in Austria and several power stations in Germany. In 1990 it was announced that it would be used at the titanium pigment plant in The Netherlands operated by Sachtleben. 

Selexol Process Dimethyl Ethers of Polyethylene Glycol... 

The DMPEG is chemically inert and is not subject to degradation. Due to its non-aqueous nature and inert chemical characteristics, the most of the Selexol process equipment can be made of carbon steel. Acid gas partial pressure is the key driving force for the Selexol process. Typical feed conditions range between 300 and 2000 psia with acid gas composition (CO2 + H2S) from 5% to more than 60% by volume. The product specifications depend on the application and can range from ppmv up to percent levels of acid gas198. 

Figure 5.39. Selexol Process for removal of acid gases. (Reproduced by permission of UOP)...

The Selexol process removes acid gases from hydrocarbon gas streams by selective absorption in polyethylene glycol dimethyl ether (DMPEG). It absorbs H2S, C02, COS, and mercaptans. The process has been used to remove carbon dioxide from syngas, natural gas, and coal gas. The process was developed by Allied Chemical in the 1960s and is now... 

The applicability of the Selexol process for partial oxidation gases [568] was already mentioned. With high H2S concentrations in the raw synthesis gas a H2S rich fraction can be separated and fed to a Claus plant for production of elemental sulfur. At lower H2S concentrations a liquid-phase oxidation has to be applied. As shown in the example of Figure 73, two H2S-containing C02 streams are treated in separate... 

At high syngas pressure, physical solvent-based processes become increasingly attractive, for example, the Rectisol and Selexol processes. There are more than 55 Selexol plants worldwide, treating natural and syngas.51 The Selexol process solvent is a mixture of dimethyl ethers of polyethylene glycol, and has the formulation... 

Figure 5.24. Flow diagram of typical Selexol processing scheme.189...

Figure 5.25. Flow diagram of a two-stage Selexol process for acid gas removal from coal-derived...

Physical solvent processes give some, but not all, ofthe above qualities. The Selexol process has several industrial applications, most of them for synthesis gas deacidification and some for natural gas treatment [6-8]. A methanol-based refrigerated solvent process such as the Ifpex-2 process from the Ifpexol technology matrix ofIFP is also a good contender [9]. However, physical solvents have a high affinity for hydrocarbons and the separated acid gas stream contains large quantities of valuable hydrocarbon products. 

Shah, V.A. and Huurdeman, T.L. (1990) Syndiesis gas treating with physical solvent process using Selexol process technology. Ammonia Plant Safety, AIChE, 86. 279. 

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