进风加热方式对空气预热器热力性能的影响

为比较分析不同进风加热方式下,采用烟气脱硝技术的火电机组回转式空气预热器出口烟风温度、蓄热元件金属壁温,以及酸腐蚀区域和硫酸氢铵沉积区域的影响趋势和变化规律,基于热力计算模型,结合某电厂600 MW机组空气预热器实例,分别在热风再循环和暖风器进风加热方式下,对其热力性能进行了计算。结果表明,热风再循环方式下,随着热风再循环比率的增大,冷段蓄热元件出口平均壁温升高,热段蓄热元件出口平均壁温降低,冷端酸腐蚀区域缩小的同时,硫酸氢铵沉积区域上移,将加剧空气预热器的积灰堵塞;暖风器加热方式下,热段、冷段蓄热元件出口平均壁温同时升高,酸腐蚀区域和硫酸氢铵沉积区域同时下移;对于燃用高硫煤并采用烟气脱硝技术的火电机组空气预热器,应进行冬季调峰运行工况下的热力校核计算,推荐优先选用暖风器作为其进风加热方式。

Impact of Inlet Air Heating Mode on Thermal Performance of Rotary Air Preheaters

Under the circumstances of different inlet air heating modes for thermal units with rotary air preheaters using flue gas denitrification, in order to perform the comparison and analysis on the outlet gas and air temperatures, the wall temperature of the heat storage element, and the influencing trend and variation patterns of the acid corrosion area and ammonium bisulfate deposition area , the thermodynamic properties of the air preheater are calculated. Based on the thermodynamic model, the calculation are done on the air preheaters of a 600-MW power plant, with hot air recirculation mode and inlet air heating mode respectively. The results show that in the hot air recirculation mode, with the hot air recirculation ratio increasing, the average outlet wall temperature of the cold-section thermal storage element goes up, while that of the hot-section thermal storage element goes down. Meanwhile, with the acid corrosion area in the cold section shrinking, the ammonium bisulfate deposition area ascends, which intensifies ash clogging in the air preheater. In the steam air heater mode, the average outlet wall temperatures of the heat storage elements at both the hot and cold sections increase, and the acid corrosion and ammonium bisulfate buildup areas descend simultaneously. Thus, for the air heater of thermal power units using flue gas denitrification technology and high-sulphur coal, the calculations for thermal check should be conducted for winter peak load scenarios, and the inlet air heating by steam air heater is more preferable to be applied in practice.