Study Of Key Process Parameters Of Gas-Based Shaft Furnace Direct Reduction Based On Hydrogen Metallurgy

In order to cope with climate change,China has put forward the goal of carbon peaking and carbon neutrality,among which the steel industry is one of the most carbon emitting industries in China.Hydrogen energy is regarded as the most promising clean energy in the 21 st century,and the hydrogen metallurgy process for steel manufacturing is a transformative technology,which is one of the effective ways to improve the energy structure,process flow and industrial structure of the steel industry and to achieve low carbon and green sustainable development.As a result,the idea of hydrogen metallurgy was born,and the gas-based shaft furnace,which has many advantages,became our main research object.In this paper,based on the direct reduction process in a hydrogen metallurgical gas-based shaft furnace,the reduction gas utilization rate and the thermal effect of the reduction gas under thermodynamic conditions are first calculated and studied.Then,using a steel enterprise’s homemade oxide pellets as raw materials,the reduction behavior of the pellet reduction degree,metallization rate,as well as reduction expansion,reduction bonding and post-reduction strength changes were studied under different reduction atmospheres,temperatures and time conditions in the laboratory,and the suitable process parameters for the preparation of DRI with different metallization rates and the optimization scheme of metallurgical properties of hydrogen metallurgical gas-based shaft furnace charge were proposed in this way.The following conclusions are drawn:(1)Thermodynamic analysis shows that the reaction equilibrium in the third stage of reduction is the key to determine the reduction gas demand and thermodynamic utilization,and the increase of H2/CO ratio and temperature in the reduction gas is beneficial to improve the gas utilization,while the H2 ratio in the gas should also be increased to improve the production efficiency and reduce energy consumption.In the process of hydrogen metallurgical gas-based reduction,both increasing the H2 ratio and increasing the temperature can accelerate the reduction reaction rate,speed up the reaction and increase the reduction degree.(2)Suitable process parameters for the preparation of 92%metallization rate DRI are:H2=100%,reduction temperature 1050℃,when under hydrogen-rich atmosphere,H2/CO=2.6,1050℃ is recommended;suitable process parameters for the preparation of 50%metallization rate pellets are:H2=100%,reduction temperature 950℃,H2/CO=2.6,1000℃ is recommended when under hydrogen-rich atmosphere.(3)With the increase of reduction temperature,the reduction behavior of the pellets will be greatly affected and thus become worse,while with the increase of the ratio of H2 in the reduction gas,the reduction behavior of the pellets will be improved.in the experimental process,the maximum RSI and the minimum CS of the pellets obtained are 16.3%and 207.2 N respectively,the indexes are in line with the standard,and the process parameters need to be adjusted appropriately to make the SI reach reasonable standards.(4)The suitable pellet reduction process parameters are:under the pure hydrogen atmosphere,the reduction temperature is selected to be 1050℃,and the maximum RSI,final SI,and minimum CS of the resulting pellets are 15.83%,30.27%,and 337.1 N,and the H2/CO=2.6,950℃ is selected under the hydrogen-rich atmosphere,and the indexes are 13.58%,36.67%,and 640.2 N.