基于实验室中速磨模型机的褐煤破碎特性研究

发布时间：2018-05-25 19:32

本文选题：褐煤 + VTI可磨性指数　；参考：《中国矿业大学》2015年硕士论文

【摘要】：我国煤炭大部分被用于直接燃烧,其中发电用煤占有量最大,增长也最快,近几年被认为是劣质煤种的褐煤越来越受到重视,越来越多的火力发电厂已经燃用或准备燃用褐煤。目前我国90%以上的燃煤电厂采用煤粉燃烧方式,磨煤是制粉系统的必备环节,磨煤能耗和磨后产品的粒度分布是整个制粉系统中最为关注的问题,电厂希望以最低的磨煤能耗获得最佳的煤粉细度。因此研究褐煤的可磨性指数变化情况及其磨碎过程,对于降低磨矿能耗、提高破碎效率和控制煤粉的粒度分布有着重要的意义。论文首先对来自内蒙古地区的褐煤的矿物学特性做了详细的研究。煤样的灰分为23.69%,属于中等灰分的煤,发热量Qnet.ar为20.05MJ·kg-1,属于中等发热量的煤,煤样的矿物质主要为石英(Si O2)、黄铁矿(Fe S2)和高岭石(Al2Si2O5(OH)4),矿物质的嵌布以分散状分布为主,煤和矿物质紧密连生,矿物质嵌布粒度细。论文研究了褐煤的密度和粒度对褐煤VTI可磨性指数的影响。结果表明,同一粒度级下褐煤的VTI可磨性指数随着密度增大而增大;同一密度级下褐煤的VTI可磨性指数随着初始粒度的增大有增大的趋势。研究中,运用实验室中速磨模型机对褐煤的破碎过程进行了探究。褐煤在中速磨模型机中的研磨属于一级破碎动力学过程,煤样的破碎速率随着初始粒级的增大而增大;随着初始粒度的增大,-0.09mm粒级的生成速率随研磨时间的延伸由逐渐减小向先增大而后减小的趋势变化;磨机功率随着研磨的进行逐渐减小,最终达到相对稳定的状态;随着研磨时间的增加和初始粒级的减小,磨矿产品的细度逐渐减小,在各个研磨时间段的粒度呈近似正态分布;罗逊—拉姆勒粒度特性方程能较好的反映中速磨模型机磨矿产物的粒度特性,给料粒度为11.2~8.0mm、磨矿时间为1min的磨矿产物的罗逊—拉姆勒粒度特性方程为: = 100-0.58321.183论文初步分析了添加助磨剂炭黑对褐煤破碎特性的影响。-0.09mm粒级产率的增大量随着炭黑用量的增大,先快速增大后缓慢减小,在炭黑用量为煤样质量的1%左右时达到最大值;添加助磨剂后,各个密度级煤样的VTI可磨性指数均有所增大,并且其增大量随密度的增大而增大;另外,褐煤在中速磨模型机研磨过程中-0.09mm粒级生成速率与未添加助磨剂时具有相同的变化规律,但数值均有所增大;助磨剂的效果会随着研磨时间的增大而变好;在磨机功耗大致相同的情况下,添加炭黑作为助磨剂可以降低磨矿产品的细度,从而起到降低磨矿功耗的作用。
[Abstract]:Most of the coal in our country is used for direct combustion, among which the coal for power generation is the largest and the growth is fastest. In recent years, lignite, which is regarded as inferior coal, has been paid more and more attention, and more thermal power plants have burned or prepared to burn lignite. At present, more than 90% of coal-fired power plants in China adopt pulverized coal combustion mode. Grinding coal is an essential part of pulverizing system. The energy consumption of grinding coal and the particle size distribution of products after grinding are the most concerned problems in the whole pulverized coal making system. The power plant hopes to obtain the best pulverized coal fineness with the lowest energy consumption. Therefore, it is of great significance to study the change of grindability index and grinding process of lignite for reducing grinding energy consumption, improving crushing efficiency and controlling particle size distribution of pulverized coal. Firstly, the mineralogical characteristics of lignite from Inner Mongolia are studied in detail. The ash of coal samples is divided into two parts: coal of medium ash, calorific Qnet.ar of 20.05MJ kg-1 and coal of medium calorific value. The minerals of coal samples are mainly quartz siloxane, pyrite and pyrite, and kaolinite Al2Si2O5OH4, and the distribution of minerals is mainly dispersed. Coal and minerals are closely linked, mineral distribution fine grain size. The influence of density and particle size of lignite on VTI grindability index of lignite was studied in this paper. The results show that the VTI grindability index of lignite increases with the increase of density, and the VTI grindability index of lignite increases with the increase of initial particle size. In the study, the crushing process of lignite was studied by using the model machine of medium-speed mill in laboratory. The grinding of lignite in medium speed mill belongs to the first order crushing dynamic process, and the crushing rate of coal sample increases with the increase of initial particle size. With the increase of the initial particle size, the rate of particle size formation changes from decreasing gradually to increasing first and then decreasing with the extension of grinding time, and the mill power decreases gradually with the grinding, and finally reaches a relatively stable state. With the increase of grinding time and the decrease of initial particle size, the fineness of grinding products decreases gradually, and the granularity of grinding products is approximately normal distribution in each grinding period. Rosson-Ramler particle size characteristic equation can well reflect the particle size characteristics of grinding products of medium speed grinding model machine. The particle size of the grinding product with grinding time of 1min is: = 100-0.58321.183. The effect of the addition of grinding aid carbon black on the crushing characteristics of lignite is analyzed preliminarily. The increase of particle yield of .-0.09mm is with the increase of the amount of carbon black, and the grain size is 11.2mm and 8.0mm respectively, and the grinding time is 1min, and the particle size characteristic equation of grinding product is: = 100-0.58321.183. The content of carbon black was about 1% of the coal sample mass, and the VTI grindability index of each density grade coal sample increased after adding grinding aids, and the increase increased with the increase of coal density, the content of carbon black reached the maximum when the content of carbon black was about 1% of the coal sample mass, and the grindability index of each density grade coal sample increased with the addition of grinding aids. In addition, the formation rate of -0.09mm grain size of lignite in the grinding process of medium speed mill model machine has the same change law as that without adding grinding aid, but the value of lignite increases, and the effect of grinding aid will be improved with the increase of grinding time. When the mill power consumption is about the same, adding carbon black as grinding aid can reduce the fineness of grinding products and thus play the role of reducing grinding power consumption.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD849.2

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