Influence of Preformation Process on Combustibility of Biochar and its Application in Iron Ore Sintering

A study was carried out into the use of preformation process to prepare biochar for replacing coke breeze in iron ore sintering. Two types of preformation process, thermo-compression process (TCP) and normal temperature process (NTP), were adopted. Results show that preformation contributed to improving the density of both raw biomass and biochar. Recommended preformation parameters for TCP were 200°C, 1 min and 120 MPa respectively, while the recommended preformation pressure for NTP was 180 MPa. Compared with non-preformed biochar, the specific surface area and porosity of preformed biochar were considerably reduced. The inner structure of biochar was therefore compacted to close to that of coke breeze. These changes bridged the differences in terms of combustion properties between biochar and coke breeze. Laboratory-scale sintering tests showed that the proper replacement percentage of biochar to coke breeze was increased from 20% to 40% after preformation process, and the emission reduction of SOx and NOx were correspondingly increased from 18.37% and 15.88% to about 38.00% and 27.00% respectively.