Study On Mn-Based Desulfurizer Prepared By Super(Sub) Critical Water Impreganation For Removal Of H2S From Coal Gas At Mid-Temperature

Poly-generation technology based on coal gasification is the inevitable trend of technology development to efficiently and cleanly use coal. In the coal gasification process, the sulfur in coal can be released and mainly present in the form of hydrogen sulfide in coal gas. The content of H2S in coal gas must be limited in order to obviate its poisoning catalyst and corrosive facilities in the subsequent use. The desulfurization purification of coal gas is one of the key technologies of the large-scale application of coal gasification.Desulfurization from hot coal gas is mainly performed with the help of the renewable single or composite metal oxides reacting with H2S to generate metal sulfides, and then the metal sulfides in the regeneration process being eventually converted to elemental sulfur. The preparation method has the direct effect on the morphology and structure of desulfurizer, which further affects their desulfurization efficiency. By adjusting the desulfurizer preparation method, the mechanical strength, sulfur capacity, physical and chemical properties (including the chemical stability and et al.) of desulfurizer can be improved to meet the needs of different working conditions, which has been the focus of many scholars.The manganese based desulfurizers were prepared by the super (sub) critical water impregnation method for removing H2S from hot coal-based gas at medium temperature in this paper. Desulfurization efficiency of desulfurizers prepared with different precursor solution of manganese was explored, and the properties of desulfurizers were tested by atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM), nitrogen physical adsorption instrument, X-ray photoelectron spectrometer (XPS) techniques. Study of desulfurization performance of desulfurizers prepared with multi-component composite metal oxide was performed, and the preparation temperature, preparation time and other operation conditions of Mn-Cu desulfurizer were optimized. The desulfurizers were evaluated in the simulated coal-based gas containing CO2and H2O and their regeneration performances were also studied. The main results are shown as follows.(1) The Mn-based desulfurizer prepared with acetate solution as precursor has the best desulfurization activity, in which the penetrating time reaches400min and the sulfur capacity is about2.07g sulfur/100g sorbent. In comparison, other desulfurizers prepared from the nitrate, sulfate and chloride solution used as precursors perform rather poor desulfurization activity. Their penetrating time is below100min and the sulfur capacity is only about25%of acetate precursor desulfurizer. The results from AAS, SEM, BET, XPS characterization show that the active metal oxide of desulfurizer prepared with manganese acetate solution as precursor presents the properties of small particle size, uniform dispersion and high uploading rate (the maximum of91.8%).(2) The Mn-based desulfurizer modified by copper has the best desulfurization efficiency and mechanical strength. The optimal preparing conditions of Mn-Cu bi-metal oxides desulfurizer are350℃,30min and Mn:Cu mole ratio of7:3. The preparing temperature of above410℃or time of above45min can make the mechanical strength of desulfurizer greatly decrease. The desulfurization efficiency and sulfur capacity of Mn-Cu-Fe desulfurizer is improved comparing with Mn-Cu based desulfurizer.(3) The atmosphere effect of desulfurizer is obvious. CO2and H2O in inlet gas causes the decrease of desulfurization activity of desulfurizer, its penetration time is reduced by nearly250min.(4) The desulfurizer prepared by the super (sub) critical water impregnation method has the good regeneration performance, which still keeps good desulfurizing properties after three times of continuous sulfidation and regeneration cycle experiments. The surface properties of alumina earrier after impregnated by super (sub) critical water are obviously changed and the new compound may be formed by A1and OH-1. The mechanical strengths of desulfurizer after sulfidation are higher than the fresh and regenerated desulfurizers.(5) Alumina carrier can be improved by impregnating liquid paraffin and then the active components are well dispersed on the surface of carrier, which increases the effective contact between H2S and carrier.