Study On Gas-solid Simultaneous Gasification Of Biomass For High Efficient Hydrogen Production

The integrated process for hydrogen production, which included pyrolysis, gas-solid simultaneous gasification and catalytic steam reforming, improved the utilization rate of raw material greatly. The interaction and conversion of pyrolysis gas and char in the gas-solid simultaneous gasification process played an important role in the whole hydrogen-production process. In this paper, three main parts were investigated:the simultaneous gasification of pyrolysis gases and char in an entrained flow bed reactor, the catalytic behavior of char on aromatic hydrocarbons and process simulation of biomass gas-solid simultaneous gasification.Utilizing this integrated process for hydrogen-rich production, the roles of gas-solid simultaneous gasification were evaluated. Due to the interaction of pyrolysis products (gases and char) in the entrained flow bed reactor, the distributions of products have changed significantly. Pyrolysis char and tar are utilized simultaneously and more efficiently. The char yield decreases from 20.47% to 8.95% and the carbon conversion is greatly increased by 13.2%. The compositions and yields of tar components are changed. Particularly, since the polycyclic aromatic compounds are converted, the burden on the following catalytic steam reforming process is alleviated and the deposition over catalyst is decreased by 4 times approximately. The hydrogen yield of 78.19g/Kg-biomass was obtained.The catalytic steam reforming of aromatic hydrocarbons by char was investigated in a fixed bed reactor. Benzene was selected as the model compound of monocyclic aromatics while naphthalene was considered as that of polycyclic aromatic hydrocarbons (PAHs). The catalytic steam reforming of benzene and naphthalene over char could convert them into lower boiling point and smaller molecules, played an important role in opening loop of PAHs, so that more gases were produced and the conversions of benzene and naphthalene were up to 92wt.% and 90.3wt.%, respectively.Based on Aspen Plus, process simulation of gas-solid simultaneous gasification of biomass was carried out. And the effects of gasification temperature and steam to biomass mass ratio (S/B) on the gas composition were investigated by Sensitivity Analysis block. Then, the model could reflect well the results of experiments. The presence of high temperature and steam was favored for the hydrogen yield. And the optimum gasification temperature was 800℃-850℃ while the optimum S/B was 2.5 approximately.