Combustion Reactivity of Biochar and Char Generated from Co-Pyrolysis of Coal and Four Additives: Application in Blast Furnace

A fixed bed pyrolysis reactor is used to prepare biochars and co-pyrolysis chars at different temperatures (723 and 823K). The effect of final pyrolysis temperature and additives on the combustion property of chars is investigated. In order to simulate the injection of chars into the blast furnace through tuyeres, a drop tube test was carried out. Combustion experiments indicate that pyrolysis process and additives elevated the burnout index of pyrolysis chars; in particular, the burnout index of the chars obtained by adding iron oxide red in the co-pyrolysis process was dramatically increased to 98% at final temperature of 823 K. Scanning electron microscope (SEM) results revealed that iron oxide red catalyzes coal pyrolysis and enhances the quantity of the pores and cracks on the surface of co-pyrolysis chars. X-ray diffraction (XRD) analysis demonstrated that iron oxide red significantly increases amorphous carbon structures in chars by inhibiting the trend of graphitization of coal during the pyrolysis process. Consequently, the pyrolysis process and additives improve the combustion reactivity of pyrolysis chars. (C) 2016 American Society of Civil Engineers.