Refractory Iron Microwave Magnetic Roasting Drop Phosphorus Synchronization Process Research

With the rapid development of China's iron and steel industry, domestic iron ore resource are in short supply, and the dependence on the outside of iron ore is high. But china's iron resource has not been fully utilized because of difficult beneficiation. The increase of the dependence on iron ore import has already become a major hidden peril of China's iron and steel industry's economic security. So it is urgent to rely on technological advance to maximize the use of existing domestic iron ore resources, raise the self-sufficiency rate of iron ore, and ease the pressure on iron ore import, to ensure the sustained and steady development of the iron and steel industry.In this thesis, based on microwave magnetic roasting combining with magnetic separation process, we look for the technological means to develop and utilize the low grade high phosphorus iron ore. Through the analysis of the property of the Huimin iron ore in Yunnan, the trial process of microwave magnetic roasting-magnetic separation was indentified. The heating up characteristic of material in microwave field was studied,and got the result that heating rate from small to big was raw ore,mixed material and blind coal.The material heats up faster at 300～600℃, combined with the weight loss of material in microwave field, so analysis thatthere are two stages in the microwave magnetic roasting of Huimin iron ore,which are the limonite dehydration stage below 300℃and the iron ore reduction stage above 600℃In the experiment of microwave magnetic roasting-magnetic separation, the effects of roasting temperature, roasting time, the power of microwave,carbon addition, grinding fineness, magnetic field intensity and so on were studied. The optimal experimental conditions are:roast temperature 800℃, reduction time 12min, microwave power 800W, carbon addition 12%, grinding size at-200 meshes over 85%, magnetic filed intensity of magnetic separation 119.37 KA·cm-1. Under this condition, perfect result is obtained, which is iron grade 59.31% in iron concentrate, iron recovery rate 81.92%.The conventional roasting test in resistence furnace was did at the same time,under the conditions:carbon addition 12%, reduction time 1h, roast temperature 1000℃,and the result were:iron grade 67.63% in iron concentrate, iron recovery rate 68.82%.Compared with resistence furnace roasting, microwave roasting shortened the roast time and lowed the roast temperature.After optimal technological parameters had been obtained according to the single factor experiments, we selected roasting temperature, carbon additon, roasting time as three main influencing factors. Using response surface method test design optimization and using the Design-Expert software to anyalysis impact factor and the interaction between various influencing factors of regression model, the influence of best optimizing parameters are analyzed. They are:roast temperature 800℃, roast time 10.50min, carbon additon 12%. Under this condition, perfect result is obtained, which is iron grade 61.34%, iron recovery rate 80.03%.The microwave magnetic roasting dephosphorization test was taken, which confirmed that both the iron minerals and gangue contained phosphorus through spectrum respective analysis of iron minerals and gangue, and disseminated grain sizes between the ore minerals and gangue centralized at 20～30μm. Then,the test of type and dosage of dephosphorization agent was taken,in which the type contained:CaO,Nacl,Na2CO3,NaOH,CaCl2 and MgCl2,and confirmed that Na2CO3 and NaOH can dephosphorize. Iron concentrate phosphoric at 0.172% can be obtained form raw ore phosphoric at 1.05% when the dosage of NaOH is 25%.The warming characteristics in the microwave field of iron ore was studied in the thesis, the technological conditions of microwave magnetized roasting were explored and optimized.Through the experimental exploration,we have found the effective dephosphorization agent and obtained iron concentrate of high grade and low phosphorus, both of which have provided a new way of seperation of the refractory iron ore.