Research On The Direct Reduction Technology Of Magnetite Concentrate

More and more attentions are paid to the environmental protection problem in China,so short process of electric arc furnace steelmaking has got great development.The scrap is main raw materials for electric arc furnace steelmaking,but our country is lack of the scrap resources,so the direct reduced iron which is the substitute of scrap began to catch the attention of people.Direct reduced iron is not only a substitute for scrap,but also an indispensable raw material to produce high quality special steel materials because of its chemical stability and less harmful impurities.The direct reduced iron production technology in China is backward.It is necessary to develop some new processes which are efficient and friendly to the environment to solve the current problem.Some theoretical guidance for the direct reduced iron production are provided through the research on the subject about direct reduction technology of magnetite concentrate.This research uses magnetite concentrate and anthracite as raw material,and in a certain proportion of additive,to study the solid-state direct reduction technology of magnetite,finally through the grinding and magnetic separation technology to obtain high quality direct reduced iron powder.The characteristics are the using of coal mixed pellets,high quality direct reduced iron in shorter time and lower temperature.The magnetic separation technology improves the quality of the direct reduced iron.Because of low energy consumption,high production efficiency,no pollution,low cost,this technology will have a great development prospect.The main results are as follows:(1)The calculation of thermodynamics and kinetics show the reduction process of iron oxide and matrix phase reactions can occur,and more appropriate temperature is in the range of 1000-1200?.Finally,the empirical formula of rate contants,reaction kinetics mechanism functions,activation energy and frequency factors can be obtain.(2)The effects of reducing agent adding quantity,different amount of additive,reduction temperature and reduction time on metallization rate of DRI were studied.The optimum condition:reduction temperature was 1150 ?,reduction time was 60 min,the addition of anthracite and CaO was 16wt%and 0.9wt%respectively,the metallization rate of the DRI can be more than 96%and the iron grade can be 89%or more.(3)The effects of different additives on the iron particles size,phase composition and distribution of elements were studied,and finally got a larger size of iron particles,and carry out the phase separation of the iron particles and matrix under the condition.(4)The effects of the magnetic field strength and grind size on the separation of iron particles and matrix were studied,and the condition for grinding and magnetic separation was determined.In the condition of 60mT magnetic field strength and 48-75?m of grind size,the recovery rate of iron was more than 95%and the iron grade of direct reduced iron powder was more than 95%.