HYDROGEN REDUCTION OF LIQUID-IRON OXIDE FINES IN GAS-CONVEYED SYSTEMS

A laboratory scale fine particles-gas conveyed system was utilized to measure the reduction rates of liquid wustite with hydrogen at high te mperatures. N2-H-2 mixtures having various flow rates and compositions were flowed downward through a cylindrical reactor maintained at a co nstant temperature of 1 723 to 1 823 K. A batch of pure spherical wust ite particles (mean dia.; 58 mum) was concurrently fed into the reacto r at a small constant rate and reduced in a hot zone. The reduction pr ocess was found to proceed in such a manner that metallic iron particl es were enclosed inside a wustite droplet. Rate analysis was made of o ne dimensional mass balance equations for particles and gas in a stead y moving bed under an isothermal condition using the reaction rate for a single-particle taking the shrinkage into consideration. Under rela tively small reducing potentials, it was concluded that the major frac tion of overall reaction resistance is attributable to chemical reacti on. However, under higher reducing potentials, the reduction process w as estimated to include an appreciable diffusion resistance within the liquid phase. From the temperature dependence of forward chemical rea ction rate constants, the activation energy was evaluated to be 110 kJ /mol.