Unsteady analyses of the top gas recycling oxygen blast furnace

Abstract

An unsteady model of the top gas recycling oxygen blast furnace (TGR-OBF) process was established according to material and thermal balance principles. The restrictive kinetic step of the reaction in the bosh of oxygen blast furnace was considered, as well as the key nodes' gas recycling processes and combustion equilibrium of the shaft injection gas. Typical unsteady analyses of the TGR-OBF processes are demonstrated by the unsteady model. It is concluded that the whole TGR-OBF processes could reach equilibrium in case of reasonable operation. Based on the default conditions in this paper, it takes about 6 times for the main gas elements travelling from tuyere zone to the furnace top, until the unsteady process turns to be a stable one. The fuel rate decreases from 496 kg/t to 426 kg/t and 403 kg/t when the blast oxygen content is increased from 21.5% to 50% and 98%, and instantaneously, the top gas volume drops from 1 582 Nm3 to 1 462 Nm3 and 1 031 Nm3. Because most carbonaceous gases are deprived in the VPSA (Vacuum Pressure Swing Absorption) segment and also recycled inside of the blast furnace, the CO2 emissions in the TGR-OBF cases are 206.06 Nm3 and 99.56 Nm3/t compared to the CO2 emission of 664.58 Nm3/t in the conventional blast furnace.