【作者】 李化建；

【导师】 黄佳木； 盖国胜；

【作者基本信息】 重庆大学 ， 材料学， 2002， 硕士

【摘要】 本文主要针对目前磨料微粉分级存在的困难，自行研制了垂直式多级水力分级装置来实现磨料微粉的窄粒级分级。实验表明：分散是分级的前提；设计强有力的稳定力场是分级的关键；分级产品及时排除是分级的保障。基于此，本课题研究内容分为两部分。一、解决超微颗粒的分散问题。针对两大类磨料微粉——普通磨料和超硬材料，选择碳化硅和金刚石为例进行分散实验。分散实验研究了金刚石和碳化硅在水介质中的分散行为规律，分析了pH值、分散剂以及表面活性剂对颗粒分散性的影响，用颗粒间相互作用DLVO和EDLVO理论进行分析分散行为的机理。研究表明：pH对颗粒分散的影响主要体现在对颗粒间双电层静电排斥力的改变；添加合适分散剂可以改变颗粒在水中的分散性；无机电解质的分散机制主要是增加颗粒表面的双电层静电排斥作用能，而高分子分散剂的分散机制主要是增加颗粒的水化膜排斥能和位阻排斥能；复合分散剂的分散效果要优于单一分散剂；提出了用经时损失性来评价分散稳定性。二、超微颗粒的分级研究。针对磨料硬度大对分级设备磨损严重、磨料微粉属于窄粒级分级产品而设计出一种新型垂直式多级水力分级系统，该系统主要特点：1、垂直式多级分级。2、连续进料连续出料。3、动态分散装置。4、上升水的均化装置。5、短程射流分级。通过实验来分析颗粒粒度分布、颗粒的形状、给料速度、料浆浓度以及温度对分级精度和分级效率的影响。针对颗粒粒度分布对分级效果的影响提出了预分级和二次分级的思想，极大程度地减少了尾流和漂流的影响，同时提高了分级精度。颗粒形状对分级的影响可以通过测量颗粒的长径比来确定形状系数。给料速度和料浆浓度共同决定了分级体系浓度，两者要满足斯托克斯公式的使用条件——保证颗粒在流体介质中自由沉降。温度对分级的影响体现在影响体系的粘度和表面张力上，可以使用数显温控仪来实现体系的恒温。研究表明：分级系统可以实现对5微米的颗粒进行分级，分级产品可以满足国家标准和苏联标准的W7（5/7）产品要求。为减少分级过程中的人为因素影响，提出了自动控制思想。针对多级分级设备的特点建立了多级分级效率模型，为评价多级分级设备提供依据。更多还原

【Abstract】 Aiming at the problems exiting in grain classification at present, a vertical multistage waterpower device was developed to realize abrasive narrow-grade-classification. The experiments shows: (1) dispersing is a prerequisite to classification; (2) designing a powerful and steady force field is the key to classification, and (3) the guarantee to classification is to let the product be in time gotten rid of. This paper consists of two parts. The first part is about dispersing of super-fine powder. For the two kinds of abrasive grain—ordinary abrasive and ultra hard material, carborundum and diamond were chosen as samples for dispersing experiment. The law of dispersion behavior of diamond and carborundum in medium of water was studied. The influence of the pH, dispersants and surface-active agent on the dispersion behavior of particles was researched. By calculation of potential energy the essence of dispersion behavior of particles in water was analyzed. The interactions between particles were discussed based on DLVO and EDLVO theories. Experiment results show the effect of the pH on the dispersion is due to the repulsion interactions of electrical double layer; and addition suitable inorganic dispersant or organic macromolecule dispersant results in improvement the stabilization of the dispersion. The main action of the inorganic dispersants is to increase the repulsion interactions of electrical double layer and the main action of organic macromolecule dispersant is to increase hydration shell and steric hindrance. The compound dispersant is superior to the single dispersant. The dispersion action of the surface-active agent mainly embodies in particle surface wettability adjustment. The loss with time was put forward to value dispersion. The second part is about classifying the super-fine powder. Due to the abrasive grain being hard, seriously wearing the equipment and requiring the narrow-grade, a new-type of vertical multistage waterpower system was developed. The main characters of this system are (1) a vertical multistage classifier, (2) continuous feeding and putting out, (3) dynamical dispersion, (4) system of pacifying rising water and (5) the short distance efflux. The effect of the shape of particles, the density and velocity of feeding, grain size distribution and temperature to the efficiency and precision of classification were studied. According to the effect of size distribution to classification, the idea of pre-classification and two times classification was proposed, which, to great degree, reduces the effect of tail flowing and drift flowing and improves the precision of classification. Shape-coefficient can be determined by the ratio of the particle length<WP=6>and diameter. System concentration is decided by the density and velocity of feeding which must satisfy with the condition of Stokes’ formulae, that is, to guarantee the freedom subsiding of particle among the fluid medium. Under different temperature the system has different viscidity and surface tension, and a digital temperature-controller can keep the constant temperature of the system. Experiments show this system can classify 5μm super-fine powder, and the product can accord with the China national standard and Soviet Union standard of W7. An auto-controlled idea was put forward to reduce the influence of human factors, and a mathematics model of multistage classification efficiency was designed for the reference to value the efficiency of multistage classifier.更多还原