Water-gas Shift Reaction in an Olivine Pellet Layer in the Upper Part of Blast Furnace Shaft

摘要

In order to reduce CO_2 emissions in the iron and steel industry, the utilization of H_2 gas as a reducing agent is a feasible option. The use of hydrogen bearing injectants in the lower blast furnace (BF) area increases H_2O concentration in the upper part of the BF shaft and the charging of moist burden has a similar effect as well. For efficient BF operation, it is important to investigate the effect of high H_2 and therefore high H_2O concentrations in the reducing gas. This study focuses on the upper BF shaft area where hematite to magnetite reduction takes place and temperature is in the range of the forward water-gas shift reaction (WGSR). The effect of the WGSR on the composition of the reducing gas was estimated by experimental methods. A layer furnace (LF) was used to determine the temperature for the occurrence of the WGSR under simulated BF shaft conditions. The feed gas conversion was investigated in an olivine pellet layer. The WGSR was observed in an empty LF with CO-H_2O-N_2 gas at 500℃. With CO-CO_2-H_2O-N_2 gas the WGSR was observed in an olivine pellet layer at 400-450℃ and in a pre-reduced magnetite pellet layer at 300-400℃ indicating the catalyzing effect of magnetite on the WGSR. The results offer additional information about the effect of high H_2O concentration on the composition of the reducing gas througlfthe WGSR. The occurrence of the WGSR in the actual BF and its effects were discussed.