| With the increasing severity of the greenhouse effect,all parts of the manufacturing industry are facing tremendous pressure to reduce emissions,including the steel industry.The traditional ironmaking process cannot get rid of its dependence on metallurgical coke due to its inherent characteristics,and the carbon emission problem cannot be solved well although its process technology is relatively mature.This makes the hydrogen direct reduction shaft furnace elying on "green power" stand out.The current traditional shaft furnace usually uses a mixture of H2 and CO as the reductant.In order to further reduce carbon emissions on this basis,the reducing gas can be converted into pure hydrogen.However,the full hydrogen operation will inevitably aggravate the endothermic effect of the reduction reaction,thus increasing the heat demand of the shaft furnace.Therefore,the hydrogen shaft furnace has to increase the gas feed rate,which,however,will inevitably exacerbate the problem of low utilization of chemical energy.Due to the lack of relevant research,this study carries out numerical simulations regarding the process characteristics of hydrogen shaft furnace,aiming to systematize and complete the relevant theories of hydrogen shaft furnace,and to provide a certain theoretical support for the early completion of the "short route" for hydrogen metallurgy.In the present study,a static model and a dynamic model of the hydrogen shaft furnace are established successively based on the conservation of mass and the conservation of energy.First,the static model is used to quantitatively investigate the three processes of hydrogen reduction,nitrogen blending,and microwave heating,and analyze the changes in gas feed rate and chemical energy utilization with various operating parameters.In order to further analyze the process characteristics of the hydrogen shaft furnace,the kinetic model is used to assess the effects of gas feed temperature,length of the reduction section and solid feed rate on the gas feed rate,chemical energy utilization,heat utilization as well as total energy consumption.Finally,optimal process parameters are determined.The main conclusions obtained in this study are as follows:(1)Increasing the gas feed temperature,nitrogen blending amount and microwave heating energy within a certain range can reduce the amount of hydrogen and increase its chemical energy utilization.During full hydrogen reduction,the hydrogen demand at feed temperatures of 800～950℃ is 2519.1～2178.6 Nm3/t-DRI,the corresponding chemical energy utilization rate is 21.3%～24.6%;When the gas feed temperature is 900℃ and the volume fraction of nitrogen blending is 10%～50%,the amount of hydrogen is reduced by 248.5～723.6 Nm3/t-DRI,and the chemical energy utilization rate is increased by 3%～25%;When the feed temperature is 900℃ and the microwave heating energy increases from 0.54 GJ/t-DRI to 0.90 GJ/t-DRI,the amount of hydrogen is reduced from 1561.6 Nm3/t-DRI to 1127.5 Nm3/t-DRI,and the chemical energy utilization rate increases by 14%～25%.(2)Extending the length of the reduction zone within a certain range can reduce the feed rate of hydrogen and improve its chemical energy utilization and heat utilization.When the reduction zone length is extended from 3.5 to 6.5m,the feed rate of hydrogen is gradually reduced,but the total energy consumption reaches the lowest at 5.5m.(3)The top gas temperature of the hydrogen shaft furnace is lower than that of the traditional shaft furnace.When the gas feed temperature is 800～950℃,the top gas temperature of the hydrogen shaft furnace is 350～370℃. |
