Analysis of Gas Thermodynamic Utilization and Reaction Kinetic Mechanism in Shaft Furnace

The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways, i. e. thermodynamics and kinetics, the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment. The results showed that the gas utilization increased with the rise of temperature when xH2/xco≥1 and with the increase of xco/(xH2 + xco) when temperature is less than 1073 K. The water-gas shift reaction restrains efficient utilization of gas, particularly in high temperature and hydrogen-rich gas. The gas utilization dropped with increase of carburization quantity of direct reduction iron (DRI) and oxygen potential of atmosphere. With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased. At 100% H2 atmosphere, the interfacial chemical reaction is the dominant reaction restricted step. For the H2-CO mixture atmosphere, the reduction process is controlled by both interfacial chemical reaction and internal diffusion.