The control techniques for indirect heating digestion in Bayer process of alumina production were researched and developed. They include controlling chemical composition of slurry to be digested and controlling diges...The control techniques for indirect heating digestion in Bayer process of alumina production were researched and developed. They include controlling chemical composition of slurry to be digested and controlling digestion status and energy consumption. Very good performances and technical and technical and economical figures for digestion process have been obtained by carefully applying these comprehensive control techniques in Pingguo alumina refinery.展开更多
A quantitative Fourier transform infrared (FTIR) technique mas established by comparison with chemical analysis and quantitative X-ray diffraction (XRD) analysis. By the quantitative FTIR analysis of bauxite during di...A quantitative Fourier transform infrared (FTIR) technique mas established by comparison with chemical analysis and quantitative X-ray diffraction (XRD) analysis. By the quantitative FTIR analysis of bauxite during dissolution , the process of dissolution and precipitation of silica was found to occur in three stages. In the first stage, there was no precipitation of desilication product (DSP). All the silica dissolved from kaolinite went into the solution. In the second stage, the silica concentration in solution attained a maximum and then dropped very quickly. The precipitation of DSP was the main cause of the reduction of the silica concentration in solution. In the third stage, the concentration of DSP reached a constant level. The dissolution and precipitation process gradually attained an equilibrium. The mechanism of silica dissolution and DSP precipitation was discussed on the basis of the FTIR quantitative analysis of kaolinite and DSP in bauxite.展开更多
Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce effici...Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce efficiently serious scaling problem of bauxite slurry on indirect heating surface, which certainly happens in the single stream process and brings about great troubles to the indirect heating. As a result of a great number of experiments and the theoretical analysis, a new lime adding technology for the two-stream digestion process is developed in this paper that lime is added into spent liquor stream instead of bauxite slurry, which is more suitable to the two-stream process of diasporic bauxite. The influences of the new lime addition technology on preheating and digestion process were discussed. It was deduced that the new technology can be used efficiently in the two-stream process of non-diasporic bauxite.展开更多
A new technology was developed to recover V2O5 from Bayer spent liquor by ion exchange.The experimental results show that in the conditions of 105℃ and 0.20-0.25 mass ratios between CaO in lime and Al2O3 in spent liq...A new technology was developed to recover V2O5 from Bayer spent liquor by ion exchange.The experimental results show that in the conditions of 105℃ and 0.20-0.25 mass ratios between CaO in lime and Al2O3 in spent liquor, the precipitation rate of vanadium in Bayer liquor is more than 85%.The vanadium-bearing precipitation is leached by NaHCO3 solution.The leaching rate of vanadium can reach 85% in the conditions of 95℃, 40 g·L-1 of NaHCO3 concentration, and ventilating of CO2.The 201 × 7 type of resin has good adsorption effect on vanadium in the leaching solution.The adsorption rate is more than 94% with the flow rate of 0.09 mL·min-1·g-1 of leaching solution and the temperature of 40-50℃.By using 3 mol·L-1 of NaOH to desorb the saturated resin after adsorption at 40-50℃, a solution with more than 5 g·L-1 of V2O5 can be obtained.After roasting ammonium metavanadate that precipitates from the desorption solution when NH4Cl is added at the temperature of 500-550℃ for 2 h, V2O5 with more than 99% of purity is obtained.展开更多
By means of Malvern laser particle size analyzer and scanning electron microscopy, the influences of seed size and number on agglomeration in Bayer process were investigated. Agglomeration is almost finished in 8h, ...By means of Malvern laser particle size analyzer and scanning electron microscopy, the influences of seed size and number on agglomeration in Bayer process were investigated. Agglomeration is almost finished in 8h, seeds, below 5μm, especially below 2μm, gather together rapidly and almost disappear in 8h. In the same supersaturation of aluminate solution and seed size, the smaller the number of seed is, the bigger the degree of agglomeration is. With the same primary number of seed, the agglomeration of larger seed is superior to that of small seed, and the agglomeration does not happen among the coarse seeds. The agglomeration mainly happens among fine particles, and the combinations among the fine particles are unconsolidated.展开更多
Fine Al(OH)3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and in...Fine Al(OH)3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and initial molar ratio of Na2O to Al2O3 (αK) on agglomeration of fine seed in Bayer process were investigated. The results show that agglomeration is almost finished in 8 h, and seeds with size less than 2 μm are easily aggregated together, and almost disappear in 8 h under the optimal process conditions. In the aluminate solution with the same moderate initial αK, when the reaction temperature reaches 75 ℃, the secondary nucleation does not occur, and the effect of agglomeration is better. And at the same reaction temperature, when the initial αK is 1.62, the initial supersaturation of aluminate solution is moderate, the binders on the surfaces of the seed are enough to maintain the agglomeration process, and the agglomeration degree is better. From SEM images, agglomeration mainly occurs in the fine particles, the combinations among the fine particles are loose and the new formed coarse crystal shapes are irregular.展开更多
In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2...In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.展开更多
文摘The control techniques for indirect heating digestion in Bayer process of alumina production were researched and developed. They include controlling chemical composition of slurry to be digested and controlling digestion status and energy consumption. Very good performances and technical and technical and economical figures for digestion process have been obtained by carefully applying these comprehensive control techniques in Pingguo alumina refinery.
文摘A quantitative Fourier transform infrared (FTIR) technique mas established by comparison with chemical analysis and quantitative X-ray diffraction (XRD) analysis. By the quantitative FTIR analysis of bauxite during dissolution , the process of dissolution and precipitation of silica was found to occur in three stages. In the first stage, there was no precipitation of desilication product (DSP). All the silica dissolved from kaolinite went into the solution. In the second stage, the silica concentration in solution attained a maximum and then dropped very quickly. The precipitation of DSP was the main cause of the reduction of the silica concentration in solution. In the third stage, the concentration of DSP reached a constant level. The dissolution and precipitation process gradually attained an equilibrium. The mechanism of silica dissolution and DSP precipitation was discussed on the basis of the FTIR quantitative analysis of kaolinite and DSP in bauxite.
基金the financial supports from the National Key R&D Program of China(No.2022YFC2904401)the National Natural Science Foundation of China(Nos.22078055,52074083,51774079)the Fundamental Research Funds for the Central Universities,China(No.N2225002)。
文摘Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce efficiently serious scaling problem of bauxite slurry on indirect heating surface, which certainly happens in the single stream process and brings about great troubles to the indirect heating. As a result of a great number of experiments and the theoretical analysis, a new lime adding technology for the two-stream digestion process is developed in this paper that lime is added into spent liquor stream instead of bauxite slurry, which is more suitable to the two-stream process of diasporic bauxite. The influences of the new lime addition technology on preheating and digestion process were discussed. It was deduced that the new technology can be used efficiently in the two-stream process of non-diasporic bauxite.
文摘A new technology was developed to recover V2O5 from Bayer spent liquor by ion exchange.The experimental results show that in the conditions of 105℃ and 0.20-0.25 mass ratios between CaO in lime and Al2O3 in spent liquor, the precipitation rate of vanadium in Bayer liquor is more than 85%.The vanadium-bearing precipitation is leached by NaHCO3 solution.The leaching rate of vanadium can reach 85% in the conditions of 95℃, 40 g·L-1 of NaHCO3 concentration, and ventilating of CO2.The 201 × 7 type of resin has good adsorption effect on vanadium in the leaching solution.The adsorption rate is more than 94% with the flow rate of 0.09 mL·min-1·g-1 of leaching solution and the temperature of 40-50℃.By using 3 mol·L-1 of NaOH to desorb the saturated resin after adsorption at 40-50℃, a solution with more than 5 g·L-1 of V2O5 can be obtained.After roasting ammonium metavanadate that precipitates from the desorption solution when NH4Cl is added at the temperature of 500-550℃ for 2 h, V2O5 with more than 99% of purity is obtained.
基金Project(G19990649) supported by the National Key Fundamental Research and Development Programof China project(59874031) supported by the National Natural Science Foundation of China
文摘By means of Malvern laser particle size analyzer and scanning electron microscopy, the influences of seed size and number on agglomeration in Bayer process were investigated. Agglomeration is almost finished in 8h, seeds, below 5μm, especially below 2μm, gather together rapidly and almost disappear in 8h. In the same supersaturation of aluminate solution and seed size, the smaller the number of seed is, the bigger the degree of agglomeration is. With the same primary number of seed, the agglomeration of larger seed is superior to that of small seed, and the agglomeration does not happen among the coarse seeds. The agglomeration mainly happens among fine particles, and the combinations among the fine particles are unconsolidated.
基金Project(2005CB623702)supported by the Major State Basic Research and Development Program of ChinaProject(20476107) supported by the National Natural Science Foundation of China
文摘Fine Al(OH)3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and initial molar ratio of Na2O to Al2O3 (αK) on agglomeration of fine seed in Bayer process were investigated. The results show that agglomeration is almost finished in 8 h, and seeds with size less than 2 μm are easily aggregated together, and almost disappear in 8 h under the optimal process conditions. In the aluminate solution with the same moderate initial αK, when the reaction temperature reaches 75 ℃, the secondary nucleation does not occur, and the effect of agglomeration is better. And at the same reaction temperature, when the initial αK is 1.62, the initial supersaturation of aluminate solution is moderate, the binders on the surfaces of the seed are enough to maintain the agglomeration process, and the agglomeration degree is better. From SEM images, agglomeration mainly occurs in the fine particles, the combinations among the fine particles are loose and the new formed coarse crystal shapes are irregular.
基金financially supported by the National Natural Science foundation of China (Nos. 51234008 and 51174230)the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-11-0515)
文摘In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.
