本文選題：循環(huán)流化床 + 富氧燃燒��； 參考：《中國科學院工程熱物理研究所》2017年博士論文

【摘要】：煤炭作為我國一次能源主體,其利用過程中所帶來的二氧化碳問題正日益得到關注。為應對全新氣候變化形勢,發(fā)展適應于燃煤電廠的二氧化碳捕集封存技術刻不容緩。富氧燃燒憑借其投資少,成本低等優(yōu)點,成為目前最有可能大規(guī)模商業(yè)應用的二氧化碳捕集封存技術之一。循環(huán)流化床富氧燃燒技術因其燃料適應性廣、燃燒強度大、氣體污染物排放濃度低等優(yōu)點,現(xiàn)已成為各國學者的研究熱點。此外,大型循環(huán)流化床鍋爐均配備有外置換熱器,能夠有效緩解富氧燃燒過程中爐膛熱流密度集中的問題,使安全的提高富氧燃燒氧氣濃度,發(fā)展第二代富氧燃燒技術成為可能。在富氧燃燒過程中,由于煙氣再循環(huán)的作用,使得進入二氧化碳壓縮純化系統(tǒng)的煙氣中NO濃度較高,這會直接影響CO2的壓縮、運輸以及儲存過程,是一個不可忽視的問題。目前,針對于循環(huán)流化床富氧燃燒過程中NO的研究仍然處于探索階段,研究不具有系統(tǒng)性,仍有許多問題尚待解決。本文主要針對循環(huán)流化床富氧燃燒過程中NO的生成及轉化規(guī)律進行相關的研究工作。通過實驗分別系統(tǒng)性的研究了煤快速熱解過程中燃料氮的遷移轉化特性、煤循環(huán)流化床02/CO2氣氛時NO生成及排放特性、再循環(huán)NO-煤焦還原分解特性,并基于兆瓦級循環(huán)流化床富氧燃燒中試實驗平臺,探索了中試規(guī)模條件下操作條件變化對富氧燃燒煙氣中NO排放的影響。主要研究內(nèi)容如下:1、在固定床反應器上,探究了煤在CO2及N2氣氛下快速熱解時燃料氮的遷移轉化過程,并獲得了 CO2對燃料氮向揮發(fā)分氮以及焦炭氮轉化的影響規(guī)律。研究結果表明,CO2對燃料氮向揮發(fā)分氮轉化的影響與溫度密切相關,低溫下CO2會抑制燃料氮向揮發(fā)分氮轉化,高溫下CO2會促進燃料氮的轉化。此外,CO2還會促進煤中N-Q向NH3的轉化。2、在50 1kW循環(huán)流化床富氧燃燒實驗臺上,通過沿爐膛軸向測量煙氣中NO濃度,獲得了 NO在爐膛內(nèi)部的變化規(guī)律。研究結果表明,密相區(qū)NO濃度最高,沿爐膛軸向存在強烈的NO還原分解行為。提高二次風高度、增加二次風比例、降低一次風氧氣濃度均會強化密相區(qū)還原性,抑制密相區(qū)NO的生成。3、在小型鼓泡流化床反應器上,系統(tǒng)性的探究了再循環(huán)NO在爐膛內(nèi)部的還原分解行為以及不同操作條件對再循環(huán)NO-煤焦還原分解反應的影響規(guī)律。研究結果表明,煤焦燃燒會降低再循環(huán)NO-煤焦還原反應的活化能,促進再循環(huán)NO與煤焦的還原反應。再循環(huán)NO以及低濃度再循環(huán)CO均對再循環(huán)NO在爐膛內(nèi)部的還原幾乎沒有影響,而再循環(huán)SO2會促進再循環(huán)NO的分解。提高燃燒反應溫度以及整體氧氣濃度,同樣能夠促進再循環(huán)NO在煤焦表面的還原分解,提高再循環(huán)NO的還原率。4、在兆瓦級循環(huán)流化床富氧燃燒中試實驗平臺上開展了高氧氣濃度循環(huán)流化床富氧燃燒實驗,并探究了不同操作條件變化對富氧燃燒煙氣中NO排放濃度的影響規(guī)律。研究結果表明,煤在O2/RFG燃燒時NO的排放濃度遠低于空氣氣氛下燃燒時NO的排放濃度(以mg/MJ計)。提高燃燒溫度以及整體氧氣濃度均會促進燃料氮向NO的轉化。由于石灰石的催化作用,添加脫硫劑會造成NO的排放濃度略有增加。此外,實驗還證明了氧氣分級是一種有效的適應于高氧氣濃度富氧燃燒的低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.
【學位授予單位】：中國科學院工程熱物理研究所
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TK16

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