Study On Catalytic Gasification Reactivity Of Coal Char Supported With K₂CO₃

Coal gasification has an important function on high efficient and clean utilization of coal resource. Compared with traditional coal gasification technologies, catalytic coal gasification technology has lots of advantages, such as lower gasification reaction temperature, higher reaction speed, more simple technology and regulable components of gaseous production. Many research work for catalytic coal gasification is limited to laboratory scale, while industrial application has not been realized so far. In this study, the catalytic gasification behavior, which can provide basic data for design of catalytic gasification process and semi-industrial R&D pilot plant, was investigated by high-pressure fixed-bed.Shenmu and Wangjiata raw coal were used in this study, and water was selected as gasification agent. Catalytic coal char gasification was studied by high-pressure fixed-bed and gas chromatograph. The major work and research results are shown as follows:(1) Catalyst preparation method. In this paper, K₂CO₃ was selected as gasification catalyst, which was regarded as the best catalyst for coal gasification. The results showed that the incipient wetness method was better than the physical mixing method, and the process which K₂CO₃ catalyst applied before coal pyrolysis was better than the process which K₂CO₃ catalyst applied after coal pyrolysis.(2) Catalytic behavior of K₂CO₃ catalyst. H2 and CO were passed over K₂CO₃ and coal char supported K₂CO₃ catalyst respectively at 700℃, 3.5 MPa. It was found that the rate of methanation reaction was accelerated significantly by the latter, and the methanation reaction approaches thermodynamic equilibrium at 700℃. K₂CO₃ alone shows no catalytic activity.(3) The main technological parameters. In this paper, the effects of main technological parameters, gasification time, temperature, pressure, catalysts loading, and initial water/carbon mole ratio, on gasification rate and product gas component are determined.(4) Intrinsic kinetics. Influences of steam partial pressure and gasification temperature on the rate of catalytic gasification were investigated by an nth order and Langmuir-Hinshelwood expression. The results indicated that the gasification activities significantly increased with increasing of reaction temperature and steam partial pressure. In the nth order expression, the order n was 0.732 and the activation energy was 102.63 kJ·mol-1; In the L-H expression, the activation energy was 109.23 kJ·mol-1. L-H expression was more accurate than the nth order expression in describing the effect of steam partial pressure on the gasification reaction.