Cold And Hot Model Study On Chemical Heat Recovery Two-stage Gasification

The flow field distribution, residence time distribution, bed pressure drop of fixed bed and drag coefficient were studied by the two-stage cold model equipment. We got conclusion as follows:Attenuated fitting formula of one-dimensional axial velocity distribution is ; In the radial velocity distribution, when z/D>2, the radial velocity distribution meets the request that the flow should be well distributed in the second stage. There is a critical value of the bed height (Hc) which affects with the residence time. When the bed height is higher than Hc, the residence time is shortened by the addition of bed height; when bed height is lower than Hc, the residence time is extended by the addition of bed height.In this paper, different kinds of coal and char were investigated to research the effect on the second stage gasification of a two-stage gasification process on a laboratory-scale hot model equipment. Coal char was optimized as the medium of the second gasification, which profited for improving the gasification efficiency of second stage and avoiding the influence of the pyrolysis gas to the quality of the first syngas. Influence of particle diameter on the heat recovery efficiency of the second stage, content of effective components and heat value of syngas, influence to the efficiency of carbon conversion, and the distribution of residue carbon content in slag layer were studied in detail. The results showed that for the second stage gasification the optimized coal particle diameter is 10-15mm, comparing with CO2 content from the first stage gasification, CO2 content in the second stage gasification section can be reduced from 34.9% to 28.6%, the outlet gas heat value increases 719kJ/Nm3, increasing about 9.3% compare to the first stage, and the distribution of residue carbon content in slag layer is well distributed. The results provide essential parameter to the design and development of new technology.