Preparation and combustion behavior of carbon-based synfuel from biomass/coal/CaO by co-carbonization process

An environmentally friendly and low-cost co-carbonization technology has been reported as an effective route for the preparation of carbon-based synfuel for sintering processes employed in the steel industry, in which loaded CaO catalysts promote the synergistic role between sawdust (SD) and bituminous coal (BC). In this work, a series of experiments were conducted to research the effects of the co-carbonization temperature, co-carbonization holding time and addition amount of CaO on synfuel. Finally, a co-carbonization temperature of 550 °C, a co-carbonization holding time of 30 min, and the added amount of CaO at 4 wt% were reasonable preparation conditions based on the biomass/coal of 4/6. According to the above experimental parameters, the solids yield, bulk density and heat value of SD/BC synfuel were 61.07%, 403 kg m⁻³ and 27.82 MJ kg⁻¹, respectively. These results showed that adding CaO increases the order and density of synfuel microcrystals. For the surface structure, the addition of CaO could improve the content of aromatic CC and C–O, whereas the content of carbonyl CO decreased in the carbonization process, which demonstrated that the addition of CaO could improve transformation of the graphite-like structure. Additionally, SD/BC synfuel loaded with CaO exhibited a rougher surface and larger pores compared to that without CaO loading, and the number of pores decreased because the formation of CaCO₃ coated the synfuel surface. The above indicators of carbon-based synfuel obtained from this study agree with the practical requirements of sintering operations. This work reveals the mechanism of biomass/coal and CaO interaction on the preparation of carbon-based synfuel.