| The Bayer process is an operation to extract by dissolution at high temperature and high pressure,the alumina content in the bauxite by a concentrated solution of soda.This process is based on the solubility of alumina in relation to the other constituents of the ore:by placing it under basic conditions,alumina dissolves to give the aluminates ion Al(OH)4-while the other constituents remain insoluble called by red mud or red sludge(0.8-1.5 tons of red mud per ton of alumina).Red sludge is obtained by Settling-in during the separation of the sodium alumina solution and the insoluble particles.The stacking of red mud occupies a substantial amount of land,The alkali in the red mud infiltrates the ground and results in groundwater and soil contaminations,the dust formed by the naked red mud is dispersed in the wind and pollutes the atmosphere,which causes negative impacts on the survival of humans,animals,and plants,polluting the ecological environment.We should note that the main component of red mud is iron oxide,which can act as the oxidant of flux agent,soda and alumina in the red mud can improve the melting properties.In this paper,firstly the physical and chemical properties of red mud will be determined,the process of metallization reduction-separation iron from red mud based on hot briquette is put forward.Utilizing the advantages of hot briquette technique through reduction-separation experiments to study the influence of process parameters such as reduction time,FC/O and reduction temperature,second,using response surface method to optimize the process parameters,establishing optimization model of iron recovery rate and iron grade on reduction process parameters,third,a comprehensive utilization process of red mud is carried out,the process is red mud metallized reduction--magnetic separation-metallic iron powder could be used as iron-bearing materials-slag used for steelmaking flux agent.The following conclusions are obtained:(1)Without adding additive,improving the reduction temperature,increasing reduction time and lessening carbon ratio at a certain value could increase the recovery ratio of iron and promote the iron grade in magnetic product.In the single factor experiment of recovery iron,the suitable process parameters of metallization reduction-magnetic separation process of red mud based on hot briquette as follows:carbon ration of 1.00,reduction temperature of 1350?,reduction time of 100 min,first-stage magnetic field strength of 50 mT,and second-stage intensity of magnetic field of 250 mT.Under this condition,the iron recovery rate is 87.97%,the iron grade in separating product is 80.58%.(2)The central composite design response surface methodology regression model is able to explain the role of the various parameters and their interactions on the response value,which is predictive;various process parameters show different effects on the process of iron recovery and iron grade,while reduction temperature plays the most part,carbon ratio and reduction time flows.(3)The established prediction model for iron recovery ratio with the process of metallization reduction-separation iron from red mud based on hot briquette as follows:Y1=-2680.32735-85.65957 x1+3.97094 x2-0.3056 x3+0.076375 x1x2+0.026562 x1x3+2.1 × 10-4 x2x3-22.5057 x12-1.42622 × 10-3x22+1.2927 × 10-3 x32.The correlation coefficient is 0.9028.The established prediction model for iron grade in separating product with the process of metallization reduction-separation iron from red mud based on hot briquette is as follows:Y2=-21.04435+180.92734 x1-0.065585 x2-0.38597 x3-0.13981 x1x2-9.92188×10-3 x1x3+1.89375×10-4 x2x3-1.47537 x12+1.06395×10-4 x22+1.06891×10-3 x32.The correlation coefficient is 0.8983,two equations could predict the variation of iron recovery ratio and iron grade in separate product with the process parameters.(4)Within the scope of the experiments,the best technological parameters obtained by the response surface methodology are carbon ratio 0.8,reduction temperature of 1400 ?,and reduction time of 100 min.Under theses conditions,the experimental value of iron recovery ratio and iron grade in separation product are 99.10%and 82.52%,respectively.Comparing with the corresponding predictive value in model of 100%and 80.66%,the errors are 0.9%and 2.3%,respectively.(5)In the Research on recovery of iron and preparing flux agent,the optimum process parameters for the reduction and separation of the red mud briquette are as follows:0.8 of FC/O,0.8 of basicity,the reduction temperature 1325?,30 min for the reduction time,the grinding time is 1 min and the two stages magnetic field strength are 50 mT,the iron recovery rate is 93.83%,the iron grade of the separate product is 89.66%,the metalized iron is 86.88%for 96.89%of metallization.The melting temperature of the obtained slag is about 1171?,the slag owns the characteristic of low melting temperature and high liquid ratio,it could be used as fluxing medium,which need further research in the future. |
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