Amisol process

Some acid-gas removal systems include mixed solvents - usually an amine in a physical solvent. This approach modifies the relative characteristics of the physical solvent by the amine and provides many of the advantages of each. Generally, only a moderate degree of selectivity can be achieved, but the total system appears to be improved. Typical in this area are the Sulfinol and Amisol processes. 

The use of solvent mixtures helps to combine the chemical and physical effects of absorption. This mainly involves the following systems methanol and ethanolamines (Lurgi Amisol processes), sulfolane and diisopropyiamine (Shdl Sulfmol process). 

More selective versions were developed for the Amisol process, too. One of them uses diethylamine (DETA) as a chemical component. This alkylamine component is characterized by such a high COS absorptivity that no water needs to be added to the solvent to accelerate COS hydrolysis. Unlike MEA and MDEA, its stronger physical effect when dissolved in methanol makes it more selective for COS over CO2. Table 2.4 illustrates the high natural selectivity of this mixed solvent. DETA differs from a wash liquor made up of DEA and methanol also insofar that it removes any mercaptanes that may be contained in the raw gas at least partially. 

Sulfinol Process, 1225 Amisol Process, 1231 Selefining Process, 1232... 

The flow diagram for one of the cases (selective desulfurization of gas from an air-blown VEW entrained bed gasifier) is shown in Figure 14-23. This plant uses the newer version of the Amisol process that employs DETA as the chemical solvent. 

Bratzler, K and Doerges, A., 1974, Amisol Process Purifies Gas, Hydro. Process., April, pp. 78-80. 

Kriebel, M., 1985, Improved Amisol Process for Gas Purification, in Acid and Sour Gas Treating Processes, S. A. Newman, editor. Gulf Publishing Co., Houston, TX, pp. 112-130. (See also Energy Prog., Vol. 4, No. 3, September, pp. 143-146). 

The Rectisol and Amisol processes, which were developed in Germany by Liirgi, are physical and physical-chemical absorption processes using organic solvents to remove acid gas and sulfur, respectively, from various gas streams. Both processes use methanol as the physical absorption solvent the Amisol process also uses monoethanolamine (MEA) as the chemical absorber to improve the overaU purification efficiency. The MEA used in the Amisol process is not pertinent to our topic. Only methanol used in the Retisol process is discussed here, and the discussion is also applicable to the physical absorption by methanol used in the Amisol process. 

AMISOL A process for removing sulfur compounds and carbon dioxide from refinery streams by absorption in methanol containing mono- or di-ethanolamine and a proprietary additive. Developed by Lurgi, Germany, in the 1960s and first commercialized in the early 1970s. 

Bgure 2.15 shows the process flow diagram for a single-stage Amisol unit. Having been cleaned in the absorber at something like 40 bar, the gas has to be fed to a water scrubber to avoid major solvent losses which would otherwise be... 

Fig. 2.15. Amisol gas purification process, (a) AbsOTber, (b) regaierator, (c) methanol/ water distillation... 

---