Download or read book Synthesis and Development of Processes for the Recovery of Sulfur from Acid Gases. Part 1, Development of a High-temperature Process for Removal of H2S from Coal Gas Using Limestone -- Thermodynamic and Kinetic Considerations ; Part 2, Development of a Zero-emissions Process for Recovery of Sulfur from Acid Gas Streams written by and published by . This book was released on 1993 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Limestone can be used more effectively as a sorbent for H2S in high-temperature gas-cleaning applications if it is prevented from undergoing calcination. Sorption of H2S by limestone is impeded by sintering of the product CaS layer. Sintering of CaS is catalyzed by CO2, but is not affected by N2 or H2. The kinetics of CaS sintering was determined for the temperature range 750--900°C. When hydrogen sulfide is heated above 600°C in the presence of carbon dioxide elemental sulfur is formed. The rate-limiting step of elemental sulfur formation is thermal decomposition of H2S. Part of the hydrogen thereby produced reacts with CO2, forming CO via the water-gas-shift reaction. The equilibrium of H2S decomposition is therefore shifted to favor the formation of elemental sulfur. The main byproduct is COS, formed by a reaction between CO2 and H2S that is analogous to the water-gas-shift reaction. Smaller amounts of SO2 and CS2 also form. Molybdenum disulfide is a strong catalyst for H2S decomposition in the presence of CO2. A process for recovery of sulfur from H2S using this chemistry is as follows: Hydrogen sulfide is heated in a high-temperature reactor in the presence of CO2 and a suitable catalyst. The primary products of the overall reaction are S2, CO, H2 and H2O. Rapid quenching of the reaction mixture to roughly 600°C prevents loss Of S2 during cooling. Carbonyl sulfide is removed from the product gas by hydrolysis back to CO2 and H2S. Unreacted CO2 and H2S are removed from the product gas and recycled to the reactor, leaving a gas consisting chiefly of H2 and CO, which recovers the hydrogen value from the H2S. This process is economically favorable compared to the existing sulfur-recovery technology and allows emissions of sulfur-containing gases to be controlled to very low levels.