EFFECT OF VERTICAL BAFFLES ON PARTICLE MIXING AND DRYING IN FLUIDIZED BEDS OF GROUP D PARTICLES

This study reports the effect of vertical baffles on the group D powder mixing and drying characteristics in a batch fluidized bed dryer. Results obtained in this study showed that operating the fluidized bed dryer with vertical baffles gave better particle mixing. This is due to the fact that the vertical baffles acted to limit the growth of small bubbles into large bubbles and the small bubbles caused more vigorous mixing in the bed of particles before finally erupting at the bed surface. Thus, insertion of vertical baffles is a useful way to process group D particles in a fluidized bed, especially when the fluidized bed is large.     

EFFECTS OF GAS TYPE AND TEMPERATURE ON FINE PARTICLE FLUIDIZATION

The influence of gas type (helium and argon) and bed temperature (77-473 K) on the fluidization behaviour of Geldart groups C and A particles was investigated. For both types of particles tested, i.e., Al2O3 (4.8 μm) and glass beads (39 μm), the fluidization quality in different gases shows the following priority sequence: Ar＞He. In the same gaseous atmosphere, the particles when fluidized at an elevated temperature usually show larger bed voidages, higher bed pressure drops, and a lower umf for the group A powder, all indicating an enhancement in fluidization quality. Possible mechanisms governing the operations of gas type and temperature in influencing the fluidization behaviours of fine particles have been discussed with respect to the changes in both gas properties and interparticle forces (on the basis of the London-van der Waals theory). Gas viscosity (varying significantly with gas-type and temperature) proves to be the key parameter that influences the bed pressure drops and umf in fluidization of fine particles, while the interparticle forces (also varying with gas-type and temperature) may play an important role in fine-particle fluidization by affecting the expansion behaviour of the particle-bed.     

超声波辅助萃取－高效液相色谱法测定食品中碱性玫瑰精

建立超声波辅助萃取—高效液相色谱法测定含辣椒食品中非法添加剂碱性玫瑰精的方法.样品经均质,辣椒面样品、辣椒油样品、红油豆瓣酱样品分别用乙腈:水=7:3(V/V)溶液、正己烷:50％乙醇=1:2(V/V)溶液、无水乙醇经超声波辅助萃取后,用高效液相色谱仪测定碱性玫瑰精.线性范围0.026～26 μg/mL,相关系数0.9...     

搅拌磨超细粉磨金精矿工艺的优化

研究了搅拌磨超细粉磨金精矿的工艺,考察了主要参数对粉磨效果的影响.结果表明,通过优化磨矿过程中各种影响因素,可以获得细度-20μm＞99%的金精矿产品.     

Dissolution behavior and dissolution mechanism of palygorskite in HCl solution

The 1 mol/L, 3 mol/L and 5 mol/L HCl solutions were employed to leach two palygorskites with different trioctahedral contents in their crystal structure for different period of time. The results of the dissolution experiments show that the dissolution process could be divided into three steps, and that this dissolution behavior can be attributed to its higher Mg2+ content, and is restricted by the extraction behavior of Si4+. The preferential extraction for Mg2+ promotes the extraction behavior of Si4+ from Si-O framework. Because the Si4+ in the form of amorphous SiO2 is adsorbed onto the surface of palygorskite fibre, the reaction between palygorskite and acid is obstructed. With the elapsing of time, or the increasing of the acid concentration, the amorphous SiO2 flocculates, and then the channels of chemical reaction are reopened. The ratio value of Mg2+/(Fe3++Al3+) in leaching solution tends to a fixed value, showing that the acid attacks not only the surface but also the structural channels. There are no obvious three steps observed during the acid attack on the palygorskite with a lower trioctahedral content. The differential behavior for two palygorskites is discussed.     

SO_2法浸出锰矿石中的有价元素

在小型浮选槽和3连圆底烧瓶浸出实验的基础上,在实验型空气搅拌浸出槽中进行了用SO_2浸出东湘桥地区氧化锰矿石2kg的实验。取得了良好的、与小型实验相符的实验结果。Mn、Co、Ni的平均浸出率分别为94.80％、89.70％和81.50％。尾气中SO_2浓度可以降低到0.01％以下,符合排放标准。     

冶金级硅酸洗提纯研究

冶金工艺被认为是非常有前途的一种有别于传统的西门子工艺而且能够满足市场对太阳能级硅需求的工艺.冶金级硅的预处理是冶金提纯工艺路径中非常重要的一个环节,因为酸洗可以有效地去除硅中的金属杂质例如铝、铁和钙等.通过系统性的对比试验对酸洗工艺去除硅中杂质的效果进行了详细的研究,分别探讨了酸的种类、酸的浓度、酸洗时间、酸洗温度以及硅粉颗粒粒径对杂质去除效率的影响.研究结果表明最佳的酸洗工艺参数为15%的盐酸,80℃,10h和100μm.在最佳酸洗工艺参数条件下金属杂质铝、铁和钙的去除率分别为70.90%、94.82%和82.69%.