中文摘要：

电站锅炉一般设计排烟温度在120-140℃,其损失的热量可达电站全部输入燃料热量的3%-8%,因此进行锅炉尾部烟气余热回收与利用,可以显著提高锅炉效率、降低电厂煤耗,经济效益显著。运用最广泛的电站锅炉烟气余热利用方式是在空气预热器出口的尾部烟道内加装换热器（通常称为＂低温省煤器＂）,利用电站锅炉的低温烟气加热汽轮机凝结水,节省部分汽轮机抽汽,增加机组出力。该文在常规锅炉余热利用系统的基础上,提出一种新型电站锅炉余热利用综合优化系统：在常规回转式空气预热器后加装一个前置式的低温空气预热器,实现烟气分两级加热空气,从而大幅度降低空气预热过程的换热温差;而在两级空气预热器之间布置低温省煤器,可以实现较高温度的烟气加热凝结水,节省较高级的汽轮机抽汽,从而实现更高的节能效果。论文结合某典型1000MW机组的电站锅炉,分析了新型余热利用优化系统的传热特性和节能效果。结果表明案例电厂在常规余热利用系统下,供电煤耗降低约1.6g/（kW h）,而新型余热利用优化系统供电煤耗降低约达3.6g/（kW h）,按机组年运行5500h计算,新系统每年可减少燃料消耗约2.1万吨标煤、节约燃料费约2100余万元（按标煤1 000元/吨）,经济效益显著。

英文摘要：

Generally, the exhaust gas temperature of boilers in coal-fired power plants is 120-140 ℃ and the thermal loss is up to 3%-8% of total energy input. Therefore, there exists a great potential to improve the whole thermal efficiency and reduce coal consumption through waste heat recovery from exhaust flue gas. In common, t.he waste heat of flue gas is recovered and utilized to heat the low temperature feedwater by installing a low temperature economizer （LTE）, which can reduce the need for steam extracted from steam turbines and increase unit output. Based on the common waste heat recovery system for flue gas, this paper proposed a comprehensive optimization scheme for the tail heating surfaces of utility boilers, along with a new type of waste heat recovery system. A low temperature air preheater was installed downstream of the rotary air preheater to reduce the temperature difference of gas-air heat exchange through two-stage air heating. Further, a LTE was installed between the two stages of air preheaters to save the amount of steam extracted from cylinders of higher pressure. Referring to the data from a typical 1000 MW generating unit, this paper analyzed the heat exchange performance and energy efficiency of the optimized system. The results indicate that the net coal consumption of the optimized system can be about 3.6 g/（kW.h）, compared to the 1.6 g/（kW.h） of a common system. Base on unit service hours of 5 500 per year, the annual fuel expense can be cut by about 21 million RMB（coal price as 1000 RMB/ton）.