煤循环流化床富氧燃烧NO转换机理实验研究

发布时间：2018-05-21 20:16

本文选题：循环流化床 + 富氧燃烧　；参考：《中国科学院工程热物理研究所》2017年博士论文

【摘要】：煤炭作为我国一次能源主体,其利用过程中所带来的二氧化碳问题正日益得到关注。为应对全新气候变化形势,发展适应于燃煤电厂的二氧化碳捕集封存技术刻不容缓。富氧燃烧凭借其投资少,成本低等优点,成为目前最有可能大规模商业应用的二氧化碳捕集封存技术之一。循环流化床富氧燃烧技术因其燃料适应性广、燃烧强度大、气体污染物排放浓度低等优点,现已成为各国学者的研究热点。此外,大型循环流化床锅炉均配备有外置换热器,能够有效缓解富氧燃烧过程中炉膛热流密度集中的问题,使安全的提高富氧燃烧氧气浓度,发展第二代富氧燃烧技术成为可能。在富氧燃烧过程中,由于烟气再循环的作用,使得进入二氧化碳压缩纯化系统的烟气中NO浓度较高,这会直接影响CO2的压缩、运输以及储存过程,是一个不可忽视的问题。目前,针对于循环流化床富氧燃烧过程中NO的研究仍然处于探索阶段,研究不具有系统性,仍有许多问题尚待解决。本文主要针对循环流化床富氧燃烧过程中NO的生成及转化规律进行相关的研究工作。通过实验分别系统性的研究了煤快速热解过程中燃料氮的迁移转化特性、煤循环流化床02/CO2气氛时NO生成及排放特性、再循环NO-煤焦还原分解特性,并基于兆瓦级循环流化床富氧燃烧中试实验平台,探索了中试规模条件下操作条件变化对富氧燃烧烟气中NO排放的影响。主要研究内容如下:1、在固定床反应器上,探究了煤在CO2及N2气氛下快速热解时燃料氮的迁移转化过程,并获得了 CO2对燃料氮向挥发分氮以及焦炭氮转化的影响规律。研究结果表明,CO2对燃料氮向挥发分氮转化的影响与温度密切相关,低温下CO2会抑制燃料氮向挥发分氮转化,高温下CO2会促进燃料氮的转化。此外,CO2还会促进煤中N-Q向NH3的转化。2、在50 1kW循环流化床富氧燃烧实验台上,通过沿炉膛轴向测量烟气中NO浓度,获得了 NO在炉膛内部的变化规律。研究结果表明,密相区NO浓度最高,沿炉膛轴向存在强烈的NO还原分解行为。提高二次风高度、增加二次风比例、降低一次风氧气浓度均会强化密相区还原性,抑制密相区NO的生成。3、在小型鼓泡流化床反应器上,系统性的探究了再循环NO在炉膛内部的还原分解行为以及不同操作条件对再循环NO-煤焦还原分解反应的影响规律。研究结果表明,煤焦燃烧会降低再循环NO-煤焦还原反应的活化能,促进再循环NO与煤焦的还原反应。再循环NO以及低浓度再循环CO均对再循环NO在炉膛内部的还原几乎没有影响,而再循环SO2会促进再循环NO的分解。提高燃烧反应温度以及整体氧气浓度,同样能够促进再循环NO在煤焦表面的还原分解,提高再循环NO的还原率。4、在兆瓦级循环流化床富氧燃烧中试实验平台上开展了高氧气浓度循环流化床富氧燃烧实验,并探究了不同操作条件变化对富氧燃烧烟气中NO排放浓度的影响规律。研究结果表明,煤在O2/RFG燃烧时NO的排放浓度远低于空气气氛下燃烧时NO的排放浓度(以mg/MJ计)。提高燃烧温度以及整体氧气浓度均会促进燃料氮向NO的转化。由于石灰石的催化作用,添加脱硫剂会造成NO的排放浓度略有增加。此外,实验还证明了氧气分级是一种有效的适应于高氧气浓度富氧燃烧的低NO控制方法。
[Abstract]:As one of the main energy sources in China, coal has been paid more and more attention to the problem of carbon dioxide in the process of utilization. In order to cope with the new climate change situation, the development of carbon dioxide capture and storage technology adapted to coal-fired power plants is of great urgency. With the advantages of low investment and low cost, the oxygen rich combustion has become the most likely large scale at present. As one of the technology of carbon dioxide capture and storage in commercial application, the circulating fluidized bed oxygen rich combustion technology has become a hot topic for scholars in various countries because of its wide adaptability, high combustion strength and low emission concentration of gas pollutants. In addition, large circulating fluidized bed boilers are equipped with external heat exchangers, which can effectively relieve oxygen rich combustion. In the process of heat flux concentration in the furnace, it is possible to improve the oxygen concentration of oxygen enriched and develop the second generation oxygen rich combustion technology. In the process of oxygen rich combustion, the concentration of NO in the flue gas which enters the carbon dioxide compression purification system is higher because of the effect of the gas recycling, which will directly affect the compression of the CO2. At present, the research on NO in the process of oxygen rich combustion in circulating fluidized bed is still at the stage of exploration. The research is not systematic, and there are still many problems to be solved. This paper focuses on the related research work on the generation and transformation of NO during the process of oxygen rich combustion in circulating fluidized bed. The transfer and transformation characteristics of fuel nitrogen in the rapid pyrolysis of coal were systematically studied. The NO generation and emission characteristics of coal circulating fluidized bed 02/CO2 atmosphere, the reduction and decomposition characteristics of NO- coal char were recirculated, and based on the pilot test platform of MW grade circulating fluidized bed oxygen rich combustion, the operation conditions were explored under the pilot scale condition. The main contents of the study are as follows: 1. 1, on a fixed bed reactor, the migration and transformation of fuel nitrogen in fast pyrolysis of coal under the atmosphere of CO2 and N2 was explored, and the influence of CO2 on the fuel nitrogen to the volatile nitrogen and the conversion of coke nitrogen was obtained. The results showed that CO2 was volatile to the fuel nitrogen. The effect of nitrogen conversion is closely related to the temperature. At low temperature, CO2 will inhibit the conversion of fuel nitrogen to volatile nitrogen, and CO2 will promote the conversion of fuel nitrogen at high temperature. In addition, CO2 will also promote the transformation of N-Q into NH3 in coal. On the 50 1kW circulating fluidized bed oxygen rich combustion experimental platform, the concentration of NO in the flue gas is measured along the furnace axis, and NO in the furnace is obtained. The results show that the density of NO is the highest in the dense phase area, and there is a strong NO reduction and decomposition behavior along the axial direction of the furnace. It will increase the two air height, increase the proportion of two times, and reduce the oxygen concentration of the primary air, which will strengthen the reducibility of the dense phase area and inhibit the formation of NO in the dense phase area, and the systematic exploration on the small bubbling fluidized bed reactor. The reduction and decomposition behavior of recirculating NO in the furnace and the effect of different operating conditions on the reduction and decomposition reaction of recirculating NO- char are investigated. The results show that the coal char combustion will reduce the activation energy of the recirculating NO- coal char reduction reaction and promote the reduction of the recirculating NO and the coal char. The recirculating NO and the low concentration recirculating CO are both. The recirculating NO has little effect on the reduction of the furnace inside the furnace, and the recycling of SO2 will promote the decomposition of the recirculating NO. Increasing the combustion temperature and the overall oxygen concentration can also promote the reduction and decomposition of the recirculating NO on the coal char surface, and improve the reduction rate of the recirculating NO,.4, in a megawatt grade circulating fluidized bed oxygen rich combustion test. On the platform, a high oxygen concentration circulating fluidized bed oxygen rich combustion experiment was carried out, and the influence of different operating conditions on the NO emission concentration in the oxygen rich combustion flue gas was explored. The results showed that the emission concentration of NO in the combustion of coal at O2/RFG was much lower than that of the emission concentration of NO in the air combustion (mg/MJ). The combustion temperature was improved and the combustion temperature was improved. The overall oxygen concentration can promote the conversion of fuel nitrogen to NO. As a result of the catalytic action of limestone, the addition of desulfurizer will cause a slight increase in the emission concentration of NO. In addition, the experiment also proves that the oxygen classification is an effective low NO control method adapted to high oxygen concentration oxygen enriched combustion.
【学位授予单位】：中国科学院工程热物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TK16

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