关键词: 热力计算, 回转式空气预热器, 热风再循环, 暖风器, 烟气脱硝

Abstract: 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.

Key words: thermodynamic calculation, rotary air preheater, hot air recirculation, steam air heater, flue gas denitrification