燃气锅炉烟气冷凝余热回收与净化模拟研究

发布时间：2018-08-12 19:33

【摘要】：随着城市的发展,能源消耗及污染物排放量急剧加大,节能减排成为当今城市能源发展的主题。天然气作为一种高热值且清洁的能源被普遍应用,天然气的燃烧产物中含有大量的水蒸气及冷凝潜热,过高的排烟温度必然造成能源的浪费,天然气过高的燃烧温度加大了氮氧化物的排放量,如何高效地回收烟气余热及降低氮氧化物的排放量已经迫在眉睫。首先,本文通过分析现有燃气锅炉烟气冷凝余热回收技术及氮氧化物减排技术的优点和不足,提出了提高烟气冷凝余热回收量的方法及降低氮氧化物的相关建议,并建议应把烟气余热回收与氮氧化物减排技术相结合。其次,通过燃气的燃烧特性分析了排烟温度对烟气中水蒸气冷凝率的影响及燃气锅炉供热效率的影响,研究了空气含湿量对烟气露点温度的影响及负荷比?对燃气锅炉供热性能的影响,研究结果表明,排烟温度越高烟气中水蒸气的冷凝率及燃气锅炉供热效率越低,空气含湿量越高烟气露点温度越高,负荷比?越低燃气锅炉供回水温度及排烟温度越低。最后,本文基于2蒸吨的燃气锅炉对常规冷凝式烟气余热回收技术、基于吸收式热泵的直接接触式烟气冷凝余热回收技术及基于空气加湿的直接+间接式烟气冷凝余热回收技术进行了全工况模拟,分析了三种烟气冷凝余热回收技术在节能性、经济性及环保性方面的差异。研究表明,三种烟气余热回收技术分别使锅炉供热效率提高3.46%、9.66%及9.53%,分别节省燃料费2.59万元、6.80万元及6.72万元,投资回收期分别是2.32年、3.23年及1.26年。因节省燃料而减排的氮氧化物分别是11.01kg、28.89kg、28.53kg,第三种余热回收技术因空气含湿量的增加降低了炉膛内的燃烧温度,从而降低了氮氧化物生成量,故第三种烟气余热回收技术氮氧化物减排量远超过28.53kg,但具体数值还应通过试验测得。
[Abstract]:With the development of the city, energy consumption and pollutant emissions increase rapidly, energy conservation and emission reduction become the theme of the city energy development. Natural gas is widely used as a high calorific value and clean energy. Natural gas combustion products contain a large number of steam and condensation latent heat. Excessive exhaust temperature will inevitably lead to energy waste. The excessive combustion temperature of natural gas increases the emission of nitrogen oxides. How to recover the waste heat of flue gas efficiently and reduce the emission of nitrogen oxides is imminent. Firstly, this paper analyzes the advantages and disadvantages of the existing waste heat recovery technology of flue gas condensation and nitrogen oxides emission reduction technology of gas boilers, and puts forward to improve the residual heat of flue gas condensation. The method of heat recovery and the suggestion of reducing nitrogen oxides are put forward. It is suggested that the waste heat recovery of flue gas should be combined with the technology of reducing nitrogen oxides emission. The results show that the higher the exhaust gas temperature is, the lower the condensation rate of water vapor in the flue gas and the heating efficiency of the gas-fired boiler are, the higher the air moisture content is, the higher the dew point temperature of the flue gas is, and the lower the load ratio is, the lower the supply and return water temperature and the exhaust gas temperature of the gas-fired boiler are. Full-scale simulation of conventional condensing flue gas waste heat recovery technology, direct contact flue gas condensation waste heat recovery technology based on absorption heat pump and direct and indirect flue gas condensation waste heat recovery technology based on air humidification was carried out. Energy-saving, economic and other three kinds of flue gas condensation waste heat recovery technologies were analyzed. The results show that the three waste heat recovery technologies can increase the boiler heating efficiency by 3.46%, 9.66% and 9.53%, save fuel cost by 25.9 million yuan, 68.8 million yuan and 67.2 million yuan respectively, and the investment payback period is 2.32 years, 3.23 years and 1.26 years respectively. The third kind of waste heat recovery technology reduces the combustion temperature in the furnace because of the increase of air humidity, which reduces the production of nitrogen oxides. Therefore, the emission reduction of nitrogen oxides by the third kind of waste heat recovery technology is far more than 28.53 kg, but the specific value should be measured by experiment.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701;TK229.8;TK115

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