Hydrogen sulfide from coal carbonization

Carbon monoxide, trace metals, and sulfur compounds, such as HjS, COS, mercaptans, and thiophenes, exist in hydrogen produced from coal gasification and used in molten carbonate Hj/Oj fuel cells. In addition, nitrogen compounds from coal, such as HCN and HCNS can be present or they might oxidize to corrosive NO. While carbon monoxide is reactive in these cells, the rest impurities can either poison the Ni anode or they can attack chemically cell and electrodes 249), for example, HjS sulfidizes nickel and stainless steel. HjS could also undergo oxidation to deposit sulfur 250) ... 

This process, which was described by Hise et al. in 1982, has apparently not been applied commercially. It is mentioned here because of the unusual concepts incorporated into the flow scheme. These include the use of crystallization of one component (carbon dioxide) as a means of stripping another component (hydrogen sulfide) from solution, and the use of a slurry of carbon dioxide crystals in an organic solvent to condense and absorb additional carbon dioxide. The process was a joint development of CNG Research Corporation, the U.S. Elepartment of Energy, and Helipump Corporation. It was proposed for use in the removal of acid gas from coal-derived gas streams at pressures above 300 psig. 

Chemo-Trenn A process for absorbing ammonia, carbon dioxide, hydrogen sulfide, and other undesirable gases from coal gas by absorption in a warm solution of a salt of a weak organic acid such as sodium cresylate. Invented by H. Bahr at I.G. Farbenindustrie, Germany, in 1938. 

Hydrogen sulfide in manufactured gases may range from approximately 2.30 g/m (100 gr/100 ft ) in blue and carbureted water gas to sever hundred grains in coal- and coke-oven gases. Another important sulfur impurity is carbon disulfide, which may be present in amounts varying from 0.007 to 0.07 percent by volume. Smaller amounts of carbon oj sulfide, mercaptans, and thiophene may be found. However, most of the impurities are removed during the purification process and either do not exist in the finished product or are present in only trace amounts. 

The barium salt is easier to obtain in solid form than is the corresponding potassium salt. Dissolve 15 g. of crystallized barium hydroxide in 50 cc. of warm water and divide the solution into two equal parts. Completely saturate the one portion (in a stoppered flask) with hydrogen sulfide and then add the other portion, thus forming a solution of barium sulfide. Add about 1 cc. of carbon disulfide and shake from time to time. It is better to add the carbon disulfide by conducting a current of coal gas (from the laboratory gas supply) through a little carbon disulfide in a wash flask and thence into the solution of barium sulfide. The barium salt precipitates as a yellow crystalline powder. The filtered precipitate should be washed first with water, then with half alcohol, finally with pure alcohol and dried on a hot plate. A second crop of crystals may be obtained by allowing the wash alcohol to drain into the mother liquor. 

In the chelates of glycine, aspartic acid, and glutamic acid all the carbon and nitrogen atoms form part of the ring structure. This probably is the reason why these three acids appear to outlast all others in high rank coal. It should be pointed out that in the presence of hydrogen sulfide, copper is precipitated as the sulfide from copper-amino acid chelates. Thus, copper and perhaps other elements could be transported as amino acid chelates until sufficient hydrogen sulfide was encountered to cause precipitation. 

Existing AGR processes envisioned for use in the production of synthetic fuels from coal face unique challenges because these AGR processes were developed primarily in response to the needs of the petroleum and natural gas industries where crude gas mixtures are relatively well-defined. In contrast to crude gas mixtures in the petroleum and natural gas industries, crude coal gasifier gas generally contains much more carbon dioxide, a much higher ratio of carbon dioxide to hydrogen sulfide, and many trace contaminants. The AGR step in synthetic fuels production from coal must be capable of performing two tasks (1) separation... 

Figure 11.24 Facilitated transport of hydrogen sulfide through an immobilized carbon-ate/bicarbonate solution [26]. Reprinted with permission from S.L. Matson, C.S. Herrick and W.J. Ward III, Progress on the Selective Removal of H2S from Gasified Coal Using an Immobilized Liquid Membrane, Ind. Eng. Chem., Prod. Res. Dev. 16, 370. Copyright 1977, American Chemical Society and American Pharmaceutical Association...

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