Enabling Sulfur-rich Coal Sources for Gasification without Emissions

Nowadays H2S and CO2 are strongly undesired coal gasification by-products. Nonetheless, despite his bad reputation, H2S is quite an interesting chemical since it contains a highly noble species, the hydrogen. Basing on recent advances, it is possible to convert H2S and CO2 into valuable products and specifically into syngas according to the oxi-reduction reaction: 2H2S + CO2 → H2 + CO + S2 + H2O, whenever it takes place into a regenerative thermal reactor and at specific operating conditions. Such a technology allows to enable some energy sources currently still unexploited due to their relevant content in sulfur, such as some crude oils, natural gases, and coal sources. For example, the Sulcis coal in Italy has the 5 to 9%w/w, the Hungarian coal has the 3 to 5%w/w, and the Inner Mongolia-Chinese coal has up to 18% of sulfur content. In the coal gasification process, the sulfur is converted into H2S and COS according to the operating conditions. Looking forward to the use of these sulfur-rich sources of energy, it is of key importance to consider the possible formation of organosulfur compounds such as COS and CS2: H2S + CO2 → COS + H2O, H2S + COS → CS2 + H2O, as they could reduce the effectiveness of the technology and could cause environmental problems. The paper is aimed at studying the coal gasification process including the oxi-reduction reaction and the hydrolysis system in a catalytic reactor of the organosulfur compounds. The target is to demonstrate that higher content in sulfur means lower emissions of CO2 without any additional environmental impact due to organosulfur species. Detailed kinetic and reactor models for coal gasification will be integrated in process simulation packages. Prior studies on the hydrolysis of organosulfur compounds will be also integrated in the simulation.