Coal Pyrolysis in a Fluidized Bed for Adapting to a Two-Stage Gasification Process

Coal pyrolysis is generally performed in atmospheres without oxygen and at temperatures below 650 °C for producing pyrolysis liquid and gas. To support the development of a new two-stage gasification process integrating a fluidized-bed pyrolyzer and a downdraft fixed-bed gasifier, this paper investigated the coal pyrolysis in atmospheres containing oxygen and steam and at temperatures up to 900 °C to understand the viable pyrolysis conditions in view of process adaptation. The examined pyrolysis characteristics include the product distribution, char gasification reactivity, and tar composition. The pyrolysis gas yield, especially the yields of H2 and CO, increased with elevating the temperature and mass ratio of steam/coal (S/C). Adding O2 to the reaction atmosphere promoted the formation of CO and CO2 but decreased that of H2. The inclusion of O2 and steam in the atmosphere resulted in chars with a larger surface area and more micropores. At 900 °C in N2 atmosphere or at 850 °C with oxygen in the atmosph...