Reseach And Analysis On The Reduction Process Of Gas-base Direct Reduction Shaft Furnace

At present,the shortage of scrap resources in China,and the iron and steel industry is increasingly serious pollution for environmental,which does not meet China’s sustainable development strategy.Direct reduction of iron technology will emission less harmful gas and has higher energy efficiency,which will promote the development of China’s iron and steel industry.In this background,the change of pellets materials and the influence of the temperature field and pressure field in the different shaft furnace are studied through numerical simulation.The paper calculates the amount of reducing gas under the two aspects of chemical reaction balance and heat balance when the reducing gas is hydrogen and carbon monoxide.The reduction degree of pellets material with time is obtained at different temperatures when the reducing gas is hydrogen and carbon monoxide.The A and E are calculated at different stages of chemical reaction.The 2D model of the gas-based direct reduction shaft furnace is established by Fluent software.The pellets were as porous media and movement of pellets used sliding mesh method.When the temperature T>570℃,the reduction process of pellets is Fe2O3 →Fe3O4 → FeO → Fe.Through the numerical simulation,the change process of pellets under different reducing atmosphere conditions and the influence on the reduction process under different temperature and different particle diameters were obtained.The results show that the reaction rate of hydrogen is higher than carbon monoxide in the same conditions.With the increase of temperature,the chemical reaction rate is faster;The smaller of pellets diameter and the faster of chemical reaction rate and the higher the of metallization rate.The design of reasonable shaft furnace is an important factor to improve the production efficiency.When the reducing gas is hydrogen,the distribution of sponge iron and temperature field and pressure field are studied by designing different shaft-furnace model with different aspect ratio.The results show that the reduction rate of the pellets at the center of the shaft is lower than that at the edge of the shaft furnace.With the increaseof the shaft furnace diameter,the reduction rate of the center of the shaft is reduced at the same height;With the decrease of the shaft furnace diameter,the gradient of the reduction rate is smaller and the reduction effect is better.In the different shaft furnace,there is a little distinction follow the height of shaft furnace for the temperature;The temperature of the shaft furnace is gradually reduced and the temperature gradient is increase from edge of the shaft furnace to center;The temperature gradient will be smaller and the temperature will be better with the decrease of shaft furnace diameter;With the increase of the shaft furnace diameter,there will be more much gas throughput,therefore,the furnace is not conducive to the movement of pellets.