生物质与低挥发分煤粉混合燃烧特性研究

发布时间：2018-04-14 04:36

本文选题：生物质 + 低挥发分煤　；参考：《山东建筑大学》2014年硕士论文

【摘要】：能源危机已成为全球面临的重大问题之一,我国的发电厂主要以火力发电为主,需要燃烧大量的煤炭资源,在我国低挥发分煤的量较大但是其挥发分含量低不易点燃。生物质是一种挥发分含量高的可再生能源,生物质与低挥发分煤粉混合燃烧方式既可以对生物质能进行规模化利用又能改善低挥发分煤粉的着火特性,对生物质和低挥发分煤粉燃烧特性的研究具有重要意义。同时,在电厂中锅炉点火与低负荷稳燃需要大量的煤粉及燃料油,微油点火技术是解决这一问题的有效途径,对微油点燃生物质和低挥发分煤粉混合物的研究具有现实意义。本文研究内容主要分为三大块进行,以玉米秸秆、棉花秸秆、苹果木三种生物质和某低挥发分煤为研究对象,包括生物质与低挥发分煤的燃烧特性热重试验研究、生物质与低挥发分煤粉的污染物排放特性试验研究及微油点火数值模拟。由热重试验可以得到燃料燃烧的TG和DTG曲线,发现生物质和煤粉燃烧过程经历水分蒸发阶段、挥发分析出燃烧阶段和焦炭燃烧阶段三个阶段,生物质燃烧主要是挥发分析出燃烧阶段,煤粉主要的失重在焦炭的燃烧阶段。随着升温速率增大,燃烧曲线有向高温侧移动的现象。生物质掺混比例越大,着火温度降低着火会越提前,燃尽性能也越好,掺混生物质有利于改善低挥发分煤粉的燃烧特性,使其燃烧更稳定。在污染物排放特性的研究中发现低挥发分煤粉NO的排放量上远大于生物质的,三种生物质的加入都降低了NO和SO2的排放量,随着生物质掺混比例的增大,煤粉混合物的污染物排放量逐渐减小,生物质对NO和SO2排放量的减小效果非常明显,生物质的掺混燃烧可以降低对环境造成的污染。通过数值模拟方式对煤粉在燃烧器内的点火过程进行了模拟,对燃烧器内部的点火过程有了更深刻的认识；改变生物质的掺混比例煤粉混合物的着火总体特征没有明显的变化,但是生物质掺混比例越大煤粉混合物着火越提前,考虑到掺混比例过大会影响燃料的热值及产生过多焦油掺混比例不能过大；一次风速度越低,着火点越靠前对煤粉点火越有利,但一次风风速降低造成空气量不足问题和加大燃料结焦的可能性,一次风风速增大时混合燃料在燃烧器内停留的时间会减小,燃料气流和油火焰的热交换的时间变短,燃料的点燃会延后,增大燃料点燃的难度,燃烧器中心线的温度最大值越接近燃烧器的出口；颗粒尺寸越小对燃烧对点火越有利,颗粒直径小燃料相对受热面积大,挥发分析出会越迅速,燃料的着火燃烧性能越好,但考虑到现实煤粉混合物的粒径越小对制粉系统的要求会越高、能耗越高,结合模拟结果本文认为煤粉混合物燃料的尺寸在0.120mm(120目)左右较理想。
[Abstract]:The energy crisis has become one of the major problems facing the whole world. The power plants in our country mainly focus on thermal power generation and need to burn a lot of coal resources. In our country, the quantity of low volatile coal is large, but the low volatile content is not easy to ignite.Biomass is a kind of renewable energy with high volatile content. The mixed combustion of biomass and low volatile pulverized coal can not only make use of biomass energy on a large scale but also improve the ignition characteristics of low volatile pulverized coal.It is of great significance to study the combustion characteristics of biomass and low volatile pulverized coal.At the same time, a large amount of pulverized coal and fuel oil are needed for boiler ignition and low load stable combustion in power plant. The micro-oil ignition technology is an effective way to solve this problem, and it is of practical significance to study the mixture of biomass and low volatile coal powder ignited by micro-oil.The research contents of this paper are divided into three parts: corn straw, cotton stalk, apple wood biomass and some low volatile coal, including the combustion characteristics of biomass and low volatile coal.Experimental study on pollutant emission characteristics of biomass and low volatile coal powder and numerical simulation of micro-oil ignition.TG and DTG curves of fuel combustion can be obtained by thermogravimetric test. It is found that the combustion process of biomass and pulverized coal goes through the water evaporation stage, and the three stages of combustion and coke combustion are analyzed by volatilization.Biomass combustion is mainly analyzed by volatilization, and the main weight loss of pulverized coal is in the combustion stage of coke.With the increase of heating rate, the combustion curve moves to the high temperature side.The higher the proportion of biomass is, the earlier the ignition temperature will be and the better the burnout performance will be. The blending of biomass can improve the combustion characteristics of low volatile coal powder and make its combustion more stable.In the study of emission characteristics of pollutants, it was found that the emission of no from low volatile pulverized coal was much larger than that from biomass. The addition of three kinds of biomass reduced the emission of no and SO2, and with the increase of biomass mixing ratio,The pollutant emission of pulverized coal mixture decreases gradually, and the effect of biomass on no and SO2 emissions is very obvious. The mixed combustion of biomass can reduce the pollution to the environment.The ignition process of pulverized coal in the burner is simulated by numerical simulation, and the ignition process inside the burner is understood more deeply, and the overall ignition characteristics of the pulverized coal mixture with different blending ratio of biomass are not changed obviously.However, the higher the ratio of biomass to coal, the earlier the ignition of pulverized coal mixture. Considering that the ratio of blending too much to the calorific value of fuel and the proportion of producing too much tar can not be too large, the lower the primary air velocity is,The closer the ignition point is, the more favorable it is to ignite the pulverized coal, but the lower the primary wind speed, the lower the air volume and the greater the possibility of coking the fuel. The residence time of the mixed fuel in the burner decreases when the primary wind speed increases.The time of heat exchange between fuel flow and oil flame becomes shorter, the ignition of fuel will be delayed, the difficulty of fuel ignition will be increased, the maximum temperature of the central line of the burner is closer to the outlet of the burner, and the smaller the particle size is, the more favorable the ignition is to the ignition.The smaller the particle diameter fuel is relative to the larger the heating area, the faster the volatilization analysis will be, and the better the ignition and combustion performance of the fuel is, but considering that the smaller the particle size of the real pulverized coal mixture is, the higher the requirement for the pulverizing system is and the higher the energy consumption is.Based on the simulation results, it is considered that the fuel size of pulverized coal mixture is about 0.120mm(120.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM621.2

【参考文献】