Basic Research On Reduction Characteristics Of Hematite Ore Based On Hydrogen Reduction

China is rich in iron ore resources,with proven reserves of more than 84 billion tons,ranking fifth in the world.However,the iron ore is of low grade,fine grain size,and many impurities.97%of the iron ore needs to be beneficiated.In order to make rational use of refractory iron ore resources,only using traditional beneficiation methods cannot effectively solve the problem of separation of refractory iron ore resources,Suspension magnetization roasting technology is one of the most typical and effective methods for processing refractory iron ore resources.Therefore,it is of great significance to carry out relevant basic research on the magnetic roasting technology of complex and difficult-to-dress iron ore.In 2018,China’s carbon emissions were 9.53 billion tons,which is still in the growth stage.In 2019,the global average temperature was 1.1℃ higher than the pre-industrial level.The greenhouse gas CO2 emissions caused by human activities are the main cause of global warming.During the United Nations General Assembly in 2020,China proposed to adopt more powerful policies and measures.We strive to reach a peak in carbon dioxide emissions by 2030 and strive to achieve carbon neutrality by 2060.Forced by the demand for carbon peaks,the development of hydrogen energy to replace other energy sources can realize the innovation of steel process flow and the optimization of energy structure,and provide a new way for low-carbon steel production.This paper mainly conducts basic research on two types of hematite suspension magnetization roasting based on hydrogen reduction.Using Qidashan hematite and Hainan Shilu hematite as raw materials,the suspension magnetization roasting process under two different reducing atmospheres(H2-N2,CO-N2)was used to study the effect of reduction time and roasting temperature on the magnetization roasting process.The change rule of FeO/TFe value of two hematite roasted products is obtained.The reduction effect of hydrogen and CO is compared,and the difference of the reduction effect of the two hematites is compared by testing the indicators of the roasted product.The thermodynamic changes in the hydrogen reduction process are calculated,and the microscopic morphology and structure changes of the two hematites during the roasting process are analyzed through scanning electron microscope and pore structure.The kinetic reaction parameters during the roasting process are determined through kinetic studies.The TFe grade of the test sample of the Qidashan hematite ore is 65.18%,and the iron in the ore is 92.79%in the hematite.The TFe grade of the experimental ore sample of Shilu hematite in Hainan is 65.41%,and the iron distribution in hematite is 78.39%.The Qidashan hematite deposit is a marine volcanic-sedimentary metamorphic iron deposit,mainly iron-bearing quartzite.Hainan Shilu hematite is a volcanic sedimentary-metamorphic iron deposit,dominated by hematite.During the magnetic roasting process of the two test samples,under the conditions of optimum roasting temperature and reduction time,the magnetic ratio of the roasted product after hydrogen reduction is higher than that after CO reduction,indicating that the hydrogen reduction effect is better than the CO reduction effect.The thermodynamic calculation shows that the conversion of hematite to magnetite can occur at a very low hydrogen concentration(about 0.2%)within the range of the experimental roasting temperature of 450℃ to 600℃.Compared with the reduction rate of CO,the reducing gas hydrogen,under the hydrogen reducing atmosphere,hematite can be converted into magnetite more quickly,and the reduction effect is better.Continue to maintain the hydrogen reduction atmosphere,and other equilibrium components of iron oxides(FeO,Fe)will be formed.During the roasting process,the process of transforming hematite into magnetite diffuses from the edge of the ore particles to the inside,the hematite core gradually decreases,cracks and pores gradually increase with the extension of the reduction time,and the content of magnetite increases.The reduction rate is gradually accelerating.When a large amount of hematite is converted into magnetite,the gas-solid reaction interface decreases and the reduction rate gradually slows down.The surface of Hainan Shilu hematite particles is denser,and the rate of hydrogen molecules entering the hematite particles is slower.Under the same reducing conditions,the reduction effect of Qidashan hematite is better than that of Hainan Shilu hematite.The reaction kinetics of Qidashan hematite accords with the random nucleation model A4 model,the correlation coefficient R2=0.97723,the apparent activation energy Ea=66.18kJ/mol,and the pre-exponential factor A=1073.69min-1.The reaction kinetics of the experimental ore samples of Shilu hematite in Hainan conforms to the power function rule model P3 model,the correlation coefficient R2=0.9794,the apparent activation energy Ea=91.87kJ/mol,and the pre-factor A=15071.64min-1.Since the purity of the Qidashan hematite test ore sample is higher than that of Hainan Shilu hematite,and the hardness and compactness of the Qidashan hematite test ore sample are lower than that of Hainan Shilu hematite,hydrogen molecules are more likely to enter the ore with cracks Internally,it undergoes a reduction reaction with Fe2O3.Therefore,the precursor factor and apparent activation energy(the minimum energy required for the reaction to occur)for the reduction reaction of the Qidashan hematite test sample is lower than that of the Shilu hematite in Hainan,The reaction is easier to proceed.In this paper,by studying the influence of hydrogen reduction on the suspension magnetization roasting of different types of hematite,it provides theoretical support for the basic research of the magnetization roasting process of hematite under hydrogen reduction conditions,and provides a clean and efficient resource for my country’s hard-to-select hematite ore.Use to provide technical reference.