Study On The Removal Of Arsenic During The Process Of Iron Extraction From Waste Copper Slag

With the rise of researching on copper slag,a large number of researchers have made a deep research on the extraction of iron from copper slag,but the high arsenic content not only affect metal quality but also contribute to enterprise benefit because the discount of iron sale is very high by the arsenic content.Therefore,it is essential to choose appropriate process to removing arsenic from the slag.The main experimental results are as follows:1.The content of arsenic in copper slag is 0.30%,which is far greater than the requirements of arsenic content of general low carbon steel.The chemical phase composition of arsenic revealed that arsenic sulfide is the major constituent accounting for 55.17 mass% in the slag,and the amount of arsenate and arsenic oxide is 22.99 mass% and 2.53 mass%,respectively.The SEM images shows that no separate phases of arsenic were found in the slag,but they were randomly combined with sulfides and glassy phase.2.From the perspective of thermodynamic equilibrium,the equilibrium composition of different arsenic phases under different conditions was analyzed.The results shows that arsenates,arsenic sulfides and arsenic oxides do not decompose at temperatures below 1000? in an insert atmosphere.When the temperature is between 500 ? ~700 ?,As2S3,As4S4 and As4O6 are first gasified.When the temperature exceeds 1000 ?,arsenic sulfide begins to decompose and the products are S2(g),S3(g),As2(g),As4(g)and As S(g).As2O5 is decomposed into gaseous As4O6 and O2.From the analysis of thermodynamic,it is feasible to decompose arsenic sulfide and arsenic oxide in an inert atmosphere.In the oxidizing atmosphere,arsenic sulfide can be oxidized and the oxidation products produced by oxidation at different temperatures are different.In the reducing atmosphere,the reaction temperature of magnesium arsenate,calcium arsenate and iron arsenate is800-100?,the temperature of copper arsenate is 500-600?.During the indirect reduction process,the reaction temperature of the iron and copper arsenate is 200 to 400?,and the calcium arsenate does not react.3.The study on pre-removal of copper slag under inert atmosphere and N2-CO atmosphere was carried out.The results showed that the removal rate of arsenic was 65.0% and the residual amount of arsenic was 0.15% at 1100?,60 min.In the N2-CO atmosphere,the results show that the removal rate of arsenic is 70.71% under the condition of reducing temperature 1100?,CO concentration 2.5% and constant temperature 60 min.In addition,during the process of arsenic reduction,zinc and lead are simultaneously reduced.The volatilization rate of Pb,Zn was maintained at 26.85%,6.32% respectively.4.The results of coal-based reduction process show that the content of As,Cu and S in slag changed little,while the removal rate of Pb and Zn is above 97%.Under the optimum conditions(T=1300?,C/O=1.2,R=1.0,t=30min),the metallization rate of the pellets was 87.81%,the grade of Zn is 0.0039%,the grade of Pb is 0.0031%,the grade of As and Cu are 0.073% and 0.29%respectively.The removal rate of arsenic was greatly influenced by the addition of Ca O and Ca F2.The results show that the separation efficiency of slag is the best,and the content of As in grain iron is 0.082%,the content of Cu is 0.75%,the content of S,P is,respectively,0.0081% and0.089%,when the melting temperature is 1480?,the addition amount of Ca O is 4%,the addition amount of Ca F2 is 1% and the holding time is 30 min.The quality of grain meets the industry standard for DRI.5.Since the content of arsenic in the pre-arsenic flue gas is less,mainly in the form of trace elements,it is difficult to study on the removal of arsenic in flue gas by experimental means.In this paper,the CASTEP module in the Materials Studio simulation software was used to simulate the behavior of arsenic atoms adsorbed on the Ca O surface.And the charge distribution,state density,surface relaxation of the system under different adsorption sites and different coverage were analyzed in the simulation process.The simulation results show that the arsenic atoms tend to adsorb to the O top,then the hollow site and the bridge site,finally the Ca top.With the increase of coverage(0.25ML~1.0ML),the adsorption energy can be reduced;The surface relaxation phenomenon of the adsorbed system indicates that the position of atoms in the first layer is displaced along the OZ direction and also causes the reconstruction of the Ca atom in the the adsorbed surface;The Ca atoms in the surface of the model provide electrons to the O atoms and the As atoms at the same time.As the coverage increases,the charge of the arsenic atoms decreases,the number of bonds between the O atoms decreases,and the As-O covalent bond and Ca-As ionic bond formed at the same time.