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Experimental verification of mathematical model for multiphase flow in air-agitated seed precipitation tank 被引量:3
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作者 陈乔平 闫红杰 +1 位作者 葛世恒 周孑民 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第7期1680-1684,共5页
In order to check the validity of the mathematical model for analyzing the flow field in the air-agitated seed precipitation tank,a scaled down experimental apparatus was designed and the colored tracer and KCl tracer... In order to check the validity of the mathematical model for analyzing the flow field in the air-agitated seed precipitation tank,a scaled down experimental apparatus was designed and the colored tracer and KCl tracer were added in the apparatus to follow the real flow line.Virtue tracers were considered in the mathematical model and the algorithm of tracers was built.The comparison of the results between the experiment and numerical calculation shows that the time of the tracer flows out of stirring tube are 40 s in the experiment and 42 s in numerical calculated result.The transient diffusion process and the solution residence time of the numerical calculation are in good agreement with the experimental results,which indicates that the mathematical model is reliable and can be used to predict the flow field of the air-agitated seed precipitation tank. 展开更多
关键词 model experiment numerical simulation multiphase flow seed precipitation
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Periodical attenuation of Al(OH)_3 particles from seed precipitation in seeded sodium aluminate solution 被引量:5
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作者 吴玉胜 张迪 +2 位作者 李明春 毕诗文 杨毅宏 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第3期528-532,共5页
Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investig... Periodical attenuation of particles,which interferes seriously the normal alumina production,exists in Bayer process.In order to solve this problem,the rule of periodical attenuation of Al(OH) 3 particles was investigated by laboratory experiments under simulated industrial conditions.The results show that at higher temperature the variation period of particle size is shortened,while prolongs with more solid content.Particle size fluctuation amplitude reduces with the temperature rising but increases with the solid content increasing.Particle size distribution becomes more uniform by replenishing fine seeds,enabling the periodical fluctuation of Al(OH)3 particle size to be attenuated.Combining properly the additives with controlling the seed size is able to reduce the amplitude of periodical fluctuation and shorten the attenuation time.With unbalance of particle size distribution,the particles gradually become bigger,even inducing the decrease of the specific surface area of seeds,which is the major reason causing explosive attenuation of Al(OH)3 particles in seed precipitation process. 展开更多
关键词 Bayer process sodium aluminate solution periodical attenuation ADDITIVE seed precipitation
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Effect of lithium ion on seed precipitation from sodium aluminate solution 被引量:3
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作者 Wen-qiang HUANG Gui-hua LIU +4 位作者 Jin-bin JU Xiao-bin LI Qiu-sheng ZHOU Tian-gui QI Zhi-hong PENG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2019年第6期1323-1331,共9页
Effect of lithium ion in sodium aluminate solution on precipitation rate,lithium content,morphology,and crystallization of alumina trihydrate(ATH) was investigated. Results showed that increasing lithium ion concentra... Effect of lithium ion in sodium aluminate solution on precipitation rate,lithium content,morphology,and crystallization of alumina trihydrate(ATH) was investigated. Results showed that increasing lithium ion concentration in solution improved the precipitation rate and lithium content in ATH,whereas reduced the mass fraction of lithium precipitation from solution. Lithium ion in solution generated the fine ATH, and thereafter significantly increased the total particle number due to the preferential nucleation.Elevating temperature or reducing lithium ion concentration decreased lithium content in ATH and reduced the fine particle amount.Moreover, lithium ion in the solution changed the morphology of ATH by improving the growth of the(110) and(200) planes of gibbsite.A large amount of fine bar-or flake-shaped ATH attached on the coarse particles also benefited the secondary nucleation and led to the poor strength of alumina.All results will further contribute to improving the quality of alumina. 展开更多
关键词 LITHIUM sodium aluminate solution seed precipitation alumina trihydrate
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Numerical simulation of flow field and optimization of structure parameters of seed precipitation tank for production of alumina 被引量:1
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作者 闫红杰 周孑民 +1 位作者 吕子剑 周怀敏 《Journal of Central South University of Technology》 2005年第2期229-232,共4页
In order to overcome the defects of air-agitated seed precipitation, such as scaring, liquid short-(circuiting,) the three-dimension flow fields with different structure are numerically simulated by computational flui... In order to overcome the defects of air-agitated seed precipitation, such as scaring, liquid short-(circuiting,) the three-dimension flow fields with different structure are numerically simulated by computational fluid dynamics software. Euler/Euler approach was used to study the effects of structure on the flow field in the tank. Multi-fluid model, body-fitted coordinates and multi-block gird were adopted in the simulation. The simulating results are well consonant with the practical situations. The flow field is improved obviously when the flow velocity increases from (0.089m/s) to 0.1920.300m/s at the bottom of the optimized tank and therefore the scaring is reduced greatly in the industrial production. With a gathering sill, the problem of short-circuiting, which always appeares in the upper of the tank, can be solved very well. 展开更多
关键词 multi-phase flow air-agitated numerical simulation seed precipitation tank
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Continuous changes in electrical conductivity of sodium aluminate solution in seeded precipitation 被引量:3
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作者 刘桂华 李铮 +3 位作者 齐天贵 周秋生 彭志宏 李小斌 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第12期4160-4166,共7页
The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pai... The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pair. The results show that the electrical conductivity of sodium aluminate slurry linearly decreases with increasing aluminum hydroxide addition. Moreover, both the electrical conductivity of slurry and the difference in electrical conductivity between sodium aluminate solution and slurry remarkably decline in the first 60 min before gradually increasing in the preliminary 10 h and finally reaching almost the same level after 10 h. In low Na2 O concentration solution the activities of Na OH and Na Al(OH)4 in seeded precipitation are high, which can enlarge the difference in conductivity between slurry and solution. Additionally, more ion pairs exist in solution in preliminary seeded precipitation, and the adsorption of Na+Al(OH)4- on seed surface is likely to break the equilibrium of ion pair formation and to decrease the difference in conductivity in preliminary seeded precipitation. 展开更多
关键词 sodium aluminate solution seeded precipitation electrical conductivity activity coefficient ion pair
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Variation of soda content in fine alumina trihydrate by seeded precipitation 被引量:2
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作者 刘桂华 王鹏 +4 位作者 齐天贵 李小斌 田侣 周秋生 彭志宏 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第1期243-249,共7页
High soda content in fine alumina trihydrate(ATH) limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of elect... High soda content in fine alumina trihydrate(ATH) limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of electric conductivity of solution, soda content in ATH, measurement of particle size distribution and microscopic analysis. The results show that high concentration of sodium aluminate solution, ground circulative seed, low temperature or fast initial precipitation rate increases the soda content in ATH. Soda mainly exists in lattice soda and less soda in desilication product (DSP) exists in the fine ATH precipitated from sodium aluminate solution with concentration of Al2O3 (ρAl2O3) more than 160 g/L and mass ratio of alumina to silica (μSiO2) of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that -+ 4)Na Al(OH ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation. 展开更多
关键词 alumina trihydrate seeded precipitation soda content lattice soda sodium aluminate solution
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Model of apparent crystal growth rate and kinetics of seeded precipitation from sodium aluminate solution 被引量:3
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作者 李小斌 刘志坚 +3 位作者 徐晓辉 周秋生 彭志宏 刘桂华 《Journal of Central South University of Technology》 EI 2005年第6期662-666,共5页
Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was de... Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve- loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size. 展开更多
关键词 sodium aluminate solutions seeded precipitations aluminum hydroxides apparent crystal growth rates KINETICS
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Effects of Na_4EDTA and EDTA on seeded precipitation of sodium aluminate solution 被引量:1
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作者 吕保林 陈启元 +1 位作者 尹周澜 胡慧萍 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第S1期37-41,共5页
Na4EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of... Na4EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of sodium aluminate solution, particle size distribution (PSD) and morphology of precipitated gibbsite were investigated using titration method, particle size analyzer and scanning electron microscope (SEM), respectively. The results show that the two additives can accelerate the seeded precipitation rate of sodium aluminate solution. At relatively high concentration, the facilitative effect of EDTA on sodium aluminate solution is more obvious than that of Na4EDTA. EDTA makes gibbsite particles thinner than Na4EDTA. The Na+ and H+ result in the different effects on the seeded precipitation rate of sodium aluminate solution in spite of the same EDTA anion in the two additives. 展开更多
关键词 sodium aluminate solution seeded precipitation rate Na4EDTA EDTA interaction mechanism
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Intensifying gibbsite precipitation from sodium aluminate solution by adding a mixed seed
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作者 LI Xiao-bin YE Pu-hong +4 位作者 ZHOU Qiu-sheng LIU Jing-hui PENG Zhi-hong LIU Gui-hua QI Tian-gui 《Journal of Central South University》 SCIE EI CAS CSCD 2019年第2期312-322,共11页
Gibbsite precipitation from sodium aluminate solution was intensified by adding mixed industrial and self-prepared active seeds,and its mechanism was researched preliminarily.The interfacial properties of seed/alumina... Gibbsite precipitation from sodium aluminate solution was intensified by adding mixed industrial and self-prepared active seeds,and its mechanism was researched preliminarily.The interfacial properties of seed/aluminate solution were determined for separate industrial and active seed.Contact angles of seed/aluminate solution and the specific surface area of seeds were respectively measured by sessile drop and BET method,and the morphology and particle size of precipitates were recorded by SEM and laser diffraction.The results show that,compared with the industrial seed,the active seed has a better wettability,lower interfacial tension,and larger specific surface area,being conducive to enhancing gibbsite precipitation from sodium aluminate solution.SEM analysis of the precipitates indicates that the embedment and accumulation/agglomeration of extremely fine particles on the surface of coarse industrial seed can effectively control the content of fine particles in the precipitation product.With extra 3.1–4.6 g/L active seed,the gibbsite precipitation ratio was increased by 3.23%–3.92%.Moreover,the mass percentage of particles<45μm in precipitation product has even a slight decrease compared with that for the traditional precipitation product or of the industrial seed itself.The result presented is favorable to developing an intensified gibbsite precipitation process for commercial alumina manufacture. 展开更多
关键词 GIBBSITE seeded precipitation sodium aluminate solution active seed INTENSIFICATION
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Influences of seed size and number on agglomeration in synthetic Bayer liquors 被引量:2
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作者 张斌 周科朝 陈启元 《Journal of Central South University of Technology》 EI 2006年第5期511-514,共4页
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, se... 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
关键词 bayer process seeded precipitation screen separation AGGLOMERATION
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Poly(methyl methacrylate)/Poly(N-isopropylacrylamide) Core-Shell Particles Prepared by Seeded Precipitation Polymerization: Unusual Morphology and Thermo-sensitivity of Zeta Potential
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作者 石山 Yang Yu +3 位作者 Tao Wang Qian-man Wang Chun Wang Shin-ichi Kuroda 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2014年第5期524-530,共7页
Poly(methyl methacrylate)/poly(N-isopropylacrylamide) (PMMA/PNIPAM) core-shell particles were synthesized by seeded precipitation polymerization of N-isopropylacrylamide (NIPAM) in the presence of PMMA seed pa... Poly(methyl methacrylate)/poly(N-isopropylacrylamide) (PMMA/PNIPAM) core-shell particles were synthesized by seeded precipitation polymerization of N-isopropylacrylamide (NIPAM) in the presence of PMMA seed particles. The anionic potassium persulfate was used as initiator, and acrylic acid as functional comonomer. It was shown that the weight ratio of the PNIPAM shell to the PMMA core can be greatly increased through continuous addition of NIPAM monomer at a relatively slow rate. PMMA/PNIPAM particles with different shell thickness were obtained by varying the amount of charged NIPAM monomers. These particles exhibited unique nonspherical core-shell morphology. PMMA core was partially coated by dense hair-like or antler-like PNIPAM shell depending on the shell thickness. The measurement of these particles' zeta potential at different temperatures showed that the absolute value of zeta potential unusually decreased as the particle size decreased with temperature. 展开更多
关键词 Core-shell particle THERMO-SENSITIVE seeded precipitation polymerization Synthesis.
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