Evaluation of Carbonisation Gas from Coal and Woody Biomass and Reduction Rate of Carbon Composite Pellets

Carbon composite iron oxide pellets using semichar or semicharcoal were proposed from the measured results of the carbonisation gas release behaviour. The carbonisation was done under a rising temperature condition until arriving at a maximum carbonisation temperature T_c,max to release some volatile matter (VM). The starting point of reduction of carbon composite pellets using semicharcoal produced at T_c,max = 823 K under the rising temperature condition was observed at the reduction temperature T_R = 833 K, only a little higher than T_c,max, which was the aimed phenomenon for semicharcoal composite pellets. As T_c,max increases, the emitted carbonisation gas volume increases, the residual VM decreases, and, as a whole, the total heat value of the carbonisation gas tends to increase monotonically. The effect of the particle size of the semicharcoal on the reduction rate was studied. When T_R is higher than T_c,max, the reduction rate increases, as the particle size decreases. When T_R is equal to T_c,max, there is no effect. With decreasing T_c,max, the activation energy E_a of semicharcoal decreases. The maximum carbonisation temperature T_c,max may be optimised for reactivity (1/E_a) of semicharcoal and the total carbonisation gas volume or the heat value.