Effects of impregnated iron and chrome on gas evolution of Lingshi coking coal during pyrolysis

Abstract：The effects of impregnated Fe3＋ and Cr3＋ on gas evolution of Lingshi coking coal dur- ing pyrolysis were investigated using GC-FPD and TPD-MS. The results indicate that for the coal impregnated with Fe3＋ and Cr3＋ , the volatile matter increases and the fixed carbon decrea- ses compared with those of the raw coal. This is resulted from that Fe3＋ and Cr3＋ break hydro-gen bond of coal and form active complex with functional groups of coal. Fe3＋ and Cr3＋ pro-mote the removal of organic sulfur and enhance the evolution of H2S and SO2 during pyrolysis below 300℃. The evolution of H2S significantly decreases at 300-700℃, because H2S in the gas phase is captured by Fe3＋ and Cr3＋. The evolution of H2 S significantly increases above 700℃ after the pyrolysis atmosphere was changed from N2 to the mixture of N2 and H2. This is at- tributed to the hydride sulfurization of the stable organic sulfur in coal and the sulfur captured by iron and chrome. The amount of CO2, CO, H20, and CH4 increases during pyrolysis of the impregnated coal because Fe3＋ and Cr3＋ promote pyrolysis of coal and the cracking of primary tar. The amount of H＋ also increases due to the promotion of the repolymerization of aromatic structure in coal by Fe3＋ and Cr3＋. The effect of Cr3＋ on gas evolution from coal is stronger than that of Fe3＋.