An experimental investigation on gasification-pyrolysis coupling characteristics of pulverized coal in circulating fluidized bed

In this study, a reaction device coupling with gasification and pyrolysis was designed for multi-stage utilization of pulverized coal. The gasification-pyrolysis coupling characteristics and staged conversion of pulverized coal were investigated. The results showed that the temperature of gasification-pyrolysis region have a significant influence in gasification-pyrolysis products. With the increase of temperature in the gasification-pyrolysis region, the calorific value of syngas increased, whereas the yield of tar decreased. When gasification temperature was above 850 degrees C, the alkene converted into polycyclic aromatic hydrocarbons in gasification-pyrolysis tar during the gasification-pyrolysis process. Meanwhile, the reactivity of gasification-pyrolysis char was improved. The polycondensation reaction of polycyclic aromatic hydrocarbons and carbon skeleton cracking existed at the gasification-pyrolysis process simultaneously, corresponding to the gasification temperature above 700 degrees C and pyrolysis temperature above 550 degrees C. In addition, the combustion efficiency of gasification-pyrolysis products can reach above 99 %. The multi-staged utilization of pulverized coal was achieved by the gasification-pyrolysis coupling mode.