Research On Acid Pretreatment-Flotation Desulfurization Of Iron Concentrate In Liaoyang Wanli Mining

Sulphur is one of the common harmful substances in iron concentrate,the iron concentrate with high sulfur content must be desulfurized to meet the feeding requirements of smelting.Pyrrhotite is a common sulfur mineral in magnetite concentrate and flotation is an effective separation method for iron concentrate desulfurization.However,pyrrhotite can be easily oxidized and has poor floatability after oxidation and brings great difficulty to flotation desulfurization,which makes it difficult to remove sulfur from iron concentrate.In this paper,for the extremely oxidized high sulphur-bearing iron concentrate in Liaoyang Wanli mining,we proposed acid pretreatment-flotation desulfurization technological process,which can significantly reduce the sulfur content of iron concentrate in this area and make it meet the requirements of the industry.Besides,the useful iron mineral in the concentrate is further enriched.It has important theoretical significance and application value to solve high-sulfur iron concentrate.In this paper,the interaction mechanism of acid pretreatment-flotation desulfurization was further studied by flotation tests of single mineral,contact angle measurements,Zeta potential,X-ray photoelectron spectroscopy and infrared spectra analysis.The main research contents and results are as follows:Analysis of iron concentrate properties showed that the TFe grade is 64.74%.It mainly exists in the form of magnetite and sulfide,and a small amount occurs in hematite,siderite and ferric silicate.The main harmful impurity in iron concentrate is S,and the content of S element is 4.57%,which mainly occurs in pyrrhotite.Based on the analysis of the properties of iron concentrate,the conventional flotation desulfurization test and acid pretreatment-flotation desulfurization test were carried out.It was found that the acid pretreatment-flotation desulfurization process was extremely remarkable and the acid pretreatment-flotation desulfurization process was determined as the subsequent desulfurization technological process.The acid pretreatment-flotation desulfurization of iron concentrate results showed that when the open circuit floation of one roughing and two scavenging was adopted in the flotation desulfurization process,and the acid pretreatment conditions:mass concentration of sulfuric acid 3.28%,concentration of pulp 35%,stirring strength 600r/min stirring time 60min;flotation desulfurization conditions:pulp pH value about 5.0,no activator,butyl xanthate as collector,and its roughing dosage 600g/t,first scavenging dosage 400g/t,second scavenging dosage 200g/t.Results showed that the iron concentrate yield is 75.68%,the TFe grade is 66.86%,the TFe recovery is 78.43%and the sulfur content is 0.25%,the desulfurization is extremely remarkable.Besides,the acid pretreatment solution can be recycled,which can effectively reduce the amount of acid consumption and save the cost of reagent.In addition,no activator is needed in the flotation process and the desulfurization cost is further reduced.The effect of acid pretreatment on the floatability of pyrrhotite was studied by single mineral flotation test.The results show that unoxidized hexagonal pyrrhotite and monoclinic pyrrhotite have good floatability.The floatability of oxidized hexagonal pyrrhotite and monoclinic pyrrhotite is poor and the floatability of pyrrhotite with deeper oxidation is worse.Acid pretreatment can improve the floatability of oxidized pyrrhotite and the rate of recovery is greatly increased,which is close to or even higher than that of unoxidized pyrrhotite.The lower pH value and longer time of acid pretreatment improved flotation performance significantly.Under lower pH value of acid pretreatment,the shorter time of acid pretreatment is needed to improve pyrrhotite floatability.The flotation speed of pyrrhotite increases firstly and then decreases with the increase of acid pretreatment mixing intensity.The influence of acid pretreatment on the surface properties of pyrrhotite was analyzed by contact angle measurement,Zeta potential measurement,photoelectron spectroscopy and infrared spectroscopy.After acid pretreatment,the hydrophilic oxidation products on the surface of pyrrhotite are desorbed and the atomic concentration on the surface is close to that of unoxidized pyrrhotite,the fresh surface is exposed.Butyl xanthate adsorbed chemically on the surface of pyrrhotite and formed dixanthate.And acid pretreatment can promote the reaction of butyl xanthate with pyrrhotite.