【作者】 张利琴；

【导师】 宋蔷；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2008， 硕士

【摘要】 烟气再循环技术,被视为是未来减排电站锅炉CO2排放的一种有效方法。研究其污染物的排放特性,对于发展对应的污染物控制技术、完善烟气再循环燃烧系统有重要意义。本论文基于15 KW一维下行燃烧炉,开展了烟气再循环和空气燃烧两种工况实验,对比研究了两种工况下以颗粒物为主的污染物排放特性。研究发现,在保证炉温相近的条件下,由于烟气再循环燃烧一次风全部为循环烟气这种特定的一二次风配比的燃烧组织方式,导致了煤粉燃尽率下降4.6%,烟气中CO的浓度也有一定的增加。由于烟气再循环的累积效应以及烟气流量减小,烟气中NOX和SO2的浓度大幅增加,燃料氮和硫的转化率下降,这主要是由于烟气再循环过程中NOX与炉膛内煤粉的反应引起的。烟气再循环工况烟气中高浓度H2O和SO2有利于高钙飞灰的自体固硫。采用ELPI对颗粒物的排放浓度和粒径分布进行了测量,烟气再循环条件下PM10占总灰百分比高于空气工况。两种工况下排放PM10的粒径分布均呈双峰分布。烟气再循环条件下的亚微米区间峰值出现位置略向大粒径方向移动。这主要由于烟气再循环供风氧浓度高、烟气中CO2浓度以及CO浓度高所致。SEM结合EDX的观测发现烟气再循环PM10含有更多的焦炭和碳烟颗粒。采用ICP分析了颗粒物中的元素分布,发现两种工况下颗粒物中的次量元素和大部分痕量元素分布基本一致,但烟气再循环工况PM10中Se的含量要明显高于空气工况,这可能是由于再循环工况下烟气中水蒸汽含量较高,促进了SeO2与灰中CaO的反应。同样,水蒸汽浓度促进了布袋上积灰与SO2的反应。通过对烟气再循环燃烧污染物、尤其是颗粒物排放特性的研究,发现烟气再循环工况下颗粒物的控制技术可采用常规空气燃烧时的控制技术,但SO2的控制技术需要特别考虑。再循环烟气中的高SO2气氛会引起严重的腐蚀问题,对高硫煤必须采用高温脱硫技术。本课题的研究结果和运行经验可为后续研究和烟气再循环燃烧技术的完善提供重要支持。更多还原

【Abstract】 Flue gas recycled (FGR) combustion technology is seen as an effective way to reduce CO2 emission of boiler in power plant. Study on the characteristics of pollutants emission is significant for developing the corresponding pollution control technology and improving flue gas recycled combustion system. In this work, based on 15 KW one-dimensional download furnace, experiments of flue gas recycled and air combustion were developed and pollutants emission under these two conditions were compared.It was found that, because the primary air was completely recycled flue gas, burnout rate of coal particle in FGR condition decreased 4.6% and CO concentration in flue gas increased a little. Because of the accumulation effect and less flue gas flux in FGR combustion, NOX and SO2 concentration in flue gas significantly increased. The conversion rate of fuel-N decreased, due to that NOX reacts with coal during FGR process. The conversion rate of fuel-S also decreased because some fuel-S retents in the deposited ash along the combustion system.ELPI was used to measure emission concentration and size distribution of the particulate matter PM10. The results showed that amount of PM10 in FGR condition was more than that in air conditon and there were two peaks in size distributions of PM10 mass concentration of both combustion conditions. Peak in submicron zone in FGR combustion moved to larger particle size because of high O2, CO2 and CO concentration.Observations of SEM and EDX showed that PM10 in both experiments had the same morphology and components. There were much more soot in PM10 from FGR condition for its lower burnout rate and coal particle burning temperature.ICP was used to analyze element distribution in the particles. It was found that most minor elements and trace elements distribution in PM10 from both combustion conditions changed a lillte except Se. Se content in PM10 from FGR condition was significantly higher than that in air combustion. This may because that the reaction between CaO and SeO2 was promoted by high H2O vapor concentration in FGR combustion. So is the reaction between SO2 and ash sticked on the bag.The study on pollutant, especially particulate matter emission from FGR combustion showed that the PM control technology for FGR combustion can be similar as regular air combustion, but different SO2 control technology must be considered. High SO2 concentration in recycled flue gas will cause severe erosion. High temperature FGD technology should be taken for high sulfur coal. Research in this work will give important support for further research and improvement of FGR combustion technology.更多还原