Gasification Characteristics of Coal-Residual Oil Slurry in the Pressurized Fluidized Bed Gasifier

Abstract

In order to improve the "Hybrid Gasification Process" for the effective conversion of coal and residual oil slurry to clean fuel gas, experimental tests have been conducted in a benchscale pressurized fluidized bed gasifier with external electric heaters. In the thermal cracking zone, yields of gaseous hydrocarbons and carbon oxides increased with temperature and pressure, while that of by-product tar decreased with pressure. Gas compositions in the char partial oxidation zone were nearly equal to those in an equilibrium of the shift reaction.
On the basis of the experimental data, heat- and material-balances in the internally fired gasification have been investigated. Overall heat of reaction (endothermic) in the thermal cracking zone increased with temperature and decreased with pressure, showing that endothermic reactions such as thermal cracking and steam cracking were dominant at higher temperatures and exothermic hydrogasification took place at higher pressures. Product gas yields in the purely internally fired conditions were calculated under the simplified gasification model in which the heat required in the slurry thermal cracking zone could be supplied by the fluidized char and the partial oxidation gas from the char partial oxidation zone. Thermal efficiency (product gas heating value/raw materials heating value) was optimum at about 750-800°C in the thermal cracking zone, and increased as the pressure rose from 5 to 30 kg/cm²·G. Experimental results in the internally fired fluidized bed gasifier agreed with the calculated values.