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
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 ...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 （aK） 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 aK, 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 aK 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
The effect of composite agglomeration process(CAP) on fluoric iron concentrates sintering was investigated.The yield and quality of the sinter are greatly improved when using CAP assisted with heat airflow and enhanci...The effect of composite agglomeration process(CAP) on fluoric iron concentrates sintering was investigated.The yield and quality of the sinter are greatly improved when using CAP assisted with heat airflow and enhancing magnesium oxide(MgO) contents.For conventional sintering of fluoric iron concentrate,due to lower viscosity of binding phase and higher fluidity of liquid phase,the sinter is formed with large thin-walled holes and the strength of the sinter is deteriorated consequently.The novel process forms composite agglomerate in which acid pellets are embedded in basic sinter.The pellets are solid with interconnecting crystals of hematite(Fe2O3) and magnetic(Fe3O4).For basic sintering,after adding MgO,the viscosity of the melting phase increases and the fluidity decreases;and calcium and aluminum silico-ferrites and magnesium ferrite are formed with perfect crystals and good sintering microstructure.展开更多
城市间的高度融合,使城市群成为全球经济发展的重要载体之一.然而,城市群快速的经济发展和产业结构演变所推动的新技术、新材料和新产品的应用,以及高强度的人类活动,导致新污染物环境排放和累积的问题日益严重.新污染物(contaminants o...城市间的高度融合,使城市群成为全球经济发展的重要载体之一.然而,城市群快速的经济发展和产业结构演变所推动的新技术、新材料和新产品的应用,以及高强度的人类活动,导致新污染物环境排放和累积的问题日益严重.新污染物(contaminants of emerging concern,CECs)的复杂性、多样性及其在表层环境中的迁移、转化、累积与生态风险,使得其成为当前表层环境过程研究中的核心科学问题.本文系统阐述了城市群CECs多介质时空分异特征与迁移机制,归纳总结了城市群CECs源排放与贡献的国内外研究进展,综述了城市群CECs多介质归趋模型及生态健康风险评估方法,探讨了当前城市群CECs污染研究中存在的不足,并展望了今后研究中需要重点解决的科学问题.展开更多
Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions ...Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions (AE) from a bubbling fluidized bed.By comparison between acoustic and pressure signals,we found that acoustic signals are very sensitive to large particles such as agglomeration and particle sintering occurred in the bed and so on.Analysis of AE mechanism shows that AE measurement mainly stems from particle-chamber collisions and friction.AE measurements are completely non-intrusive and are not subject to erosion, corrosion, or plugging.Therefore, study and measurement of AE in different fluidization conditions will provide many new methods and trains of thought for detecting early deterioration of the fluidization quality.展开更多
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 （aK） 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 aK, 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 aK 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Project(50725416) supported by the National Science Fund for Distinguished Young Scholars
文摘The effect of composite agglomeration process(CAP) on fluoric iron concentrates sintering was investigated.The yield and quality of the sinter are greatly improved when using CAP assisted with heat airflow and enhancing magnesium oxide(MgO) contents.For conventional sintering of fluoric iron concentrate,due to lower viscosity of binding phase and higher fluidity of liquid phase,the sinter is formed with large thin-walled holes and the strength of the sinter is deteriorated consequently.The novel process forms composite agglomerate in which acid pellets are embedded in basic sinter.The pellets are solid with interconnecting crystals of hematite(Fe2O3) and magnetic(Fe3O4).For basic sintering,after adding MgO,the viscosity of the melting phase increases and the fluidity decreases;and calcium and aluminum silico-ferrites and magnesium ferrite are formed with perfect crystals and good sintering microstructure.
文摘城市间的高度融合,使城市群成为全球经济发展的重要载体之一.然而,城市群快速的经济发展和产业结构演变所推动的新技术、新材料和新产品的应用,以及高强度的人类活动,导致新污染物环境排放和累积的问题日益严重.新污染物(contaminants of emerging concern,CECs)的复杂性、多样性及其在表层环境中的迁移、转化、累积与生态风险,使得其成为当前表层环境过程研究中的核心科学问题.本文系统阐述了城市群CECs多介质时空分异特征与迁移机制,归纳总结了城市群CECs源排放与贡献的国内外研究进展,综述了城市群CECs多介质归趋模型及生态健康风险评估方法,探讨了当前城市群CECs污染研究中存在的不足,并展望了今后研究中需要重点解决的科学问题.
文摘Diagnosis of malfunction in fluidized beds is always a very difficult problem for a long time in academic circles and industrial circles. In this paper,we use acoustic sensor to measure the passive acoustic emissions (AE) from a bubbling fluidized bed.By comparison between acoustic and pressure signals,we found that acoustic signals are very sensitive to large particles such as agglomeration and particle sintering occurred in the bed and so on.Analysis of AE mechanism shows that AE measurement mainly stems from particle-chamber collisions and friction.AE measurements are completely non-intrusive and are not subject to erosion, corrosion, or plugging.Therefore, study and measurement of AE in different fluidization conditions will provide many new methods and trains of thought for detecting early deterioration of the fluidization quality.
