Removal Of Phosphorus From Magnetite Concentrate By Reverse Flotation-acid Leaching-alkline Washing Technique

High-pure pig iron is the necessary raw material for high-quality cast iron producing.With the rapid development of economy, science and technology, the demand for high-qualitycast iron is becoming bigger and bigger, so that the demand for high-pure pig iron isincreasing rapidly. However, due to the lag in technology and the shortage in high-quality ironore resources, the production of high-pure pig iron is far from self-sufficiency, most of thedemand still relies on imports. Phosphorus is one of the major harmful elements in high-purepig iron. At present, the removal of phosphorus from high-pure pig iron mainly relies onoxidation process, that is, removing phosphrus by adding dephosphorization agent into the hotmetal during the ironmaking process to oxidize the phosphorus. Due to its disadvantages ofstrict process conditions, complex operation, high chemical medicine comsumption, highproduction costs and environmental pollution during the actual producing, more and morecompanies of high-pure pig iron producing are urgently finding more efficient, environmentalfriendly and low energy consumption dephosphorization process.This article studied the deep dephosphorization process for the magnetite concentrateduring the benefication period. The magnetite concentrate, which is one of the raw material ofhigh-pure pig iron producing, was taken form one iron and steel company in Chengde, Hebei,China. This article is trying to realize the magnetite concentrate’s deep dephosphorizationduring the benefication period, that is, to reduce the phosphrus grade to be below0.005%according to the company’s request. According to the composition of the ore and orecharacteristics, this article used the reverse flotation, acid leaching and alkline washing tocarry out a series of tests of deep dephosphorization and determined feasibledephosphorization process.The reverse flotation dephosphorization tests showed that: reverse flotation was effectivefor the phosphorus removal, the phosphorus grade in the flotation concentrate could reach thedesired result, but the recoveries of iron was a little low. Under the optimal conditions ofgrinding fineness-0.074mm100%, pulp density30%, collector amount1.0kg/t and flotationtime15min, the reverse flotation concentrate yeild was61.3%, iron grade was62.37%,phosphorus grade was0.004%, and the reverse flotation tailing yeild was38.7%, iron gradewas60.18%, phosphorus grade was0.190%.The acid leaching dephosphorization tests indicated that: for the green ore, when theoptimal conditions of grinding fineness, hydrochloric acid amount, liquid-solid ratio, mixingspeed, leaching time and leching temperature were fixed in-0.074mm100%,15%,0.8:1, 60r/min,4h and20℃, respectively, the leaching tailing’s phosphorus grade dropped to bearound0.003%, iron grade was up to be around62.3%and the iron loss was less than0.5%.The recycling of acid leaching liquor was infeasible, because the dephosphorization effectobviously get worse. For the reverse flotation tailing, acid leaching dephosphorizaiton usingcannot reach the desired result by one step.The acid leaching-alkline washing dephosphorization tests showed that: it was surelythat the adsorption of magnetite ore to phosphorus existed, and it desorbed under alklineconditions. For the green ore, under the optimal acid leaching conditions of grinding fineness-0.074mm75%, hydrochloric acid amount8%, liquid-solid ratio0.8:1, mixing speed60r/min,leaching time4h, leaching temperature20℃, and alkline washing conditions of washingliquor pH value9.0, mixing speed60r/min, washing time1h, washing temperature20℃, theultimate washing tailing’s phosphorus grade dropped to0.003%, iron grade was up to62.2%,iron loss is less than0.6%. For the reverse flotation tailing, when the hrdrochloric acidamount was9%and the other conditions were the same, the ultimate washhing tailing’sphosphorus grade could be dropped to0.004%, iron grade was up to60.8%from60.18%.Defined the feasible dephosphorization process of acid leaching-alkline washing andreverse flotation and acid leaching-alkline washing according to the tests results and processcontrast.