Coal Gasification For Syngas In An External Circulating Radial Moving Bed Reactor

Coal steam gasification was conducted in an external circulating radial moving bed reactor system at varied gasification temperature, steam to carbon ratio (S/C)and heat carrier circulating rate to feeding rate ratio (C/F) with sea sand, calcined olivine, NiO/olivine and Fe2O3/olivine catalyst as circulating bed material, respectively. The gasification process is decoupled into pyrolysis, tar-steam reforming and char combustion process, and then optimized and recombined. The system is composed of three main reactors, a downward moving bed pyrolyzer, a gas-solid radial cross flow moving bed gasifier and a riser combustor. The results indicate that the external circulating radial moving bed reactor system is a promising technology for syngas production, characterized by free of nitrogen and low tar content. The increase of gasification temperature and S/C are preferable for gas yield improvement and tar abatement. C/F has a little influence on gasification process with sea sand as inventory. With olivine as inventory, low C/F is beneficial for catalyst reduction and tar steam reforming. Nickel based catalyst shows high activity for tar elimination, however, it also consumes the product gas during catalyst reduction. The qualitative and quantitative analysis of tar obtained from gasification was performed using GC/MS method, the results indicate that the compounds substituted by side chains and aliphatic hydrocarbons are easily removed, phenol, biphenyl, naphthalene and polycyclic aromatic hydrocarbons, such as anthracene, phenanthrene,fluorene compounds, are difficult to completely eliminate even though using catalysts.