Effects of Temperature, Pressure, and Carrier Gas on the Cracking of Coal Tar over a Char−Dolomite Mixture and Calcined Dolomite in a Fixed-Bed Reactor

Abstract

A distillation fraction of a coal-derived liquid (tar) was cracked over a char−dolomite mixture, calcined dolomite, and silicon carbide in a fixed-bed reactor. The char−dolomite mixture (FWC) was produced from Pittsburgh No. 8 coal and dolomite in a Foster Wheeler carbonizer. The experiments were conducted under nitrogen and simulated coal gas (SCG), which was a mixture of CO, CO2, H2S, CH4, N2, and steam, at 1 and 17 atm. The conversion over these materials under nitrogen was much higher at 17 atm than at 1 atm. At higher pressures, tar molecules were trapped in the pores of the bed material and underwent secondary reactions, resulting in the formation of excess char. However, when nitrogen was replaced by SCG, the reactions that induce char formation were suppressed, thus increasing the yield of gaseous products. The analysis of the gaseous products and the spent bed materials for organic and inorganic carbons suggested that the product distribution can be altered by changing the carrier gas, temperature, and pressure.