Acid Gas Treating

In addition to heavy hydrocarbons and water vapor, natural gas often contains other contaminants that may have to be removed. Carbon dioxide (CO2), hydrogen sulfide (H2S), and other sulfur compounds such as mercaptans are compounds that may require complete or partial removal for acceptance by a gas purchaser. These compounds are known as acid gases. H2S combined with water forms a weak form of sulfuric acid, while CO2 and water forms carbonic acid, thus the term acid gas.  

Natural gas with H2S or other sulfur compounds present is called sour gas, while gas with only CO2 is called sweet. Both H2S and CO2 are undesirable, as they cause corrosion and reduce the heating value and thus the sales value of the gas. In addition, H2S may be lethal in very small quantities. Table 7-1 shows physiological effects of H2S concentrations in air. 

13 ppm by volume, H2S can be sensed by smell. At 4.6 ppm the smell is quite noticeable. As the concentration increases beyond 200 ppm, the sense of smell fatigues, and the gas can no longer be detected by odor. Thus, H2S cannot always be detected by smell. Even if H2S cannot be smelled, it is possible that there is sufficient H2S present to be life threat- 

0(3013 0,13 0.008 0.18 Obvious and unpleasant odor generally perceptible at 0.13 ppm and quite noticeable at 4. 6 nmn As tbe concentration e sense of smell fatigm h can no longer be deteeieu oy ouoi 

001 10 0.63 14.41 Acceptable ceiling concentration permitted by federal OSH A. standards. 

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Propylene carbonate has the following characteristics, which make k suitable as a solvent for acid gas treating ... 

Bosch, H., Solvents and reactors for acid gas treating. Ph.D. thesis in Chemical Engineering, University of Twente, Enschede, The Netherlands, 1989. 

Composition of Acid gas Treated gas after implementation of the above change ... 

Lee, J. I., Otto, F. D., and Mather, A. E., I973C, Design Data for Diethanolamine Acid Gas Treating Systems, Gas Processing Canada, March-April, pp. 26-34. 

Sivalls, C. R., 1982, Slurrisweet Acid Gas Treating Process Proc. Gas Conditioning Conference, University of Oklahoma, Norman, OK. 

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