生物质颗粒燃料工业锅炉大气污染物排放特征模拟研究

发布时间：2018-09-14 07:51

【摘要】：随着社会经济的快速发展,人类面临能源短缺、污染严重等威胁,研发替代能源、可持续能源是解决该问题的关键,生物质能是一种可再生的清洁能源,具有广阔的应用前景。目前我国生物质能利用技术尚处于起步阶段,存在技术相对落后、缺乏排放标准等问题。本研究旨在通过模拟实验,研究生物质颗粒燃料燃烧特性及燃烧过程中NOX、SO2、颗粒物及HCl等大气污染物排放特征,这对生物质燃料的推广使用及生物质燃烧污染物排放标准的制定具有重要意义。本实验以松木锯末、混合木质刨花、玉米秸秆三种燃料为研究对象,进行生物质颗粒燃料工业锅炉大气污染物排放特征模拟研究。通过热重分析及管式炉实验研究生物质燃烧特性;利用管式炉模拟工业锅炉,研究燃料种类、燃烧温度(700℃、800℃、900℃、1000℃)及进气量(3L/min、4L/min、5L/min)等条件对常规大气污染物和特征污染物排放浓度的影响,进而建立动力学模型,以掌握生物质颗粒燃料燃烧烟气中污染物的释放特征。具体研究内容及结果如下:(1)生物质燃料燃烧特性研究。三种生物质燃料的热解均分为预热干燥、挥发分析出及燃烧、焦炭燃烧三个阶段,且在第二阶段TG曲线有最大变化,DTG曲线相应位置出现峰值,为热解最主要阶段。松木和玉米燃料在燃烧后期,焦炭析出时需要向外界吸收一定热量,而混合木质燃料并不需要。三种燃料因其挥发分含量较高均能呈现出较好的燃烧性能,但松木锯末的燃烧稳定性最好,燃烧速率最大,点火和燃尽温度最低,比其他两种燃料更为优良。燃烧温度、进气量等因素对颗粒燃料的燃烧特性均有影响:同样进气量下,温度越高对应的浓度峰越窄,达到峰值所需时间越短。燃料在不完全燃烧状态下,CO排放浓度会明显增大。(2)生物质颗粒燃料燃烧过程中,常规大气污染物排放特征研究。NOX产生量的多少及排放浓度的变化是燃料种类、进气量、燃烧温度等因素共同作用的结果。NOX和SO2主要产生于挥发分析出燃烧阶段,产生量与燃料本身N、S含量有一定关系。SO2在不完全燃烧或较为温和的温度(800~900℃)条件下会有少量释放。而NOX相对复杂,800℃时,因CO排放量增加而导致NOX浓度有所降低。生物质燃料燃烧后颗粒物产生量远低于煤,排放量大致随着温度和进气量的增加而增加;高温且进气量较大时,挥发分析出迅速,部分来不及燃烧便随烟气排出而被滤膜截留,会导致颗粒物排放量有所增加。(3)生物质颗粒燃料燃烧过程中,特征污染物HCl排放特征研究。比浊法是生物质颗粒燃料燃烧烟气中微量氯测定的有效方法,1g生物质颗粒燃烧后的HCl排放量在0.2~1.2mg左右,其排放量与生物质本身含氯量及燃料的物理特性有关,且与燃烧温度及进气量等也有较大关系。HCl释放量随着进气量及温度的增加而增加,但温度过高也会使K以KCl(g)形式直接进入气态而使得HCl有所减少。(4)生物质颗粒燃料燃烧反应动力学研究。采用Coats-Redfern积分方法进行动力学分析,选取合适的反应机理函数,研究不同温度阶段的反应动力学。每一种生物质燃料的燃烧反应级数不同,且在不同反应阶段,也有所不同。生物质颗粒燃料燃烧反应活化能随着反应的推进呈先降低后增加的趋势,与挥发分、焦炭等主要可燃组分的析出燃烧机理一致。(5)最优燃烧条件。温度控制在800℃左右,进气量控制在4~5L/min范围内可一定程度的降低NOX、SO2、颗粒物及HCl等污染物的排放。此条件下松木锯末、混合木质、玉米秸秆的燃料N转化率最低,分别为13.0%、4.6%、11.8%。
[Abstract]:With the rapid development of society and economy, human beings are facing the threat of energy shortage and serious pollution. Research and development of alternative energy, sustainable energy is the key to solve this problem. Biomass energy is a renewable clean energy, with broad application prospects. The purpose of this study is to study the combustion characteristics of biomass particulate fuels and the emission characteristics of NOX, SO2, particulate matter and HCl during combustion through simulation experiments, which is of great significance to the promotion of biomass fuels and the formulation of emission standards for biomass combustion pollutants. In the end, the air pollutant emission characteristics of biomass pellet fuel industrial boilers were simulated with three kinds of fuels, wood shavings and corn straw. The effects of temperature and air intake (3L/min, 4L/min, 5L/min) on the emission concentration of conventional and characteristic pollutants were studied. A kinetic model was established to understand the emission characteristics of pollutants in flue gas from biomass particulate fuel combustion. The pyrolysis of the material is divided into three stages: preheating drying, volatilization analysis and combustion, and coke combustion. The TG curve of the second stage has the greatest change, and the corresponding position of the DTG curve has the peak value, which is the main stage of pyrolysis. The burning characteristics of the three fuels are better than those of the other two fuels because of their high volatile content, but the burning stability of pine sawdust is the best, the burning rate is the highest, the ignition and burnout temperatures are the lowest, which are better than those of the other two fuels. The higher the temperature, the narrower the concentration peak, the shorter the time needed to reach the peak. Under incomplete combustion condition, the CO emission concentration will increase significantly. (2) Study on the emission characteristics of conventional air pollutants during biomass pellet fuel combustion. NOX and SO2 are mainly produced in the combustion stage of volatile analysis. The amount of NOX and SO2 produced is related to the content of N and S in the fuel itself. Particulate emission from biomass fuel combustion is much lower than that from coal, and increases with the increase of temperature and air intake. When the temperature is high and the air intake is large, volatilization analysis is rapid, and some of them are intercepted by filters before burning, resulting in the increase of particulate emission. The turbidimetric method is an effective method for the determination of Trace Chlorine in the flue gas of biomass pellet fuel combustion. The HCl emission of 1G biomass pellet after combustion is about 0.2~1.2 mg. The HCl emission is related to the chlorine content of biomass and the physical characteristics of fuel, and is also related to combustion temperature and air intake. The amount of Cl released increases with the increase of intake and temperature, but the high temperature will also make K enter the gaseous phase directly in the form of KCl (g) and reduce HCl. (4) Study on the combustion kinetics of biomass pellet fuel. The activation energy of biomass particulate fuel combustion decreases first and then increases with the advance of the reaction, which is consistent with the combustion mechanism of volatile, coke and other major combustible components. (5) Optimal combustion conditions. The nitrogen conversion of pine sawdust, mixed wood and corn straw was the lowest, 13.0%, 4.6% and 11.8% respectively.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701

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