烟气余热回收利用系统节能效果试验研究

Experimental Study on the Energy-saving of Flue Gas Waste Heat Utilization Systems

以某660 MW机组低温省煤器为研究对象,以试验数据为基础,运用等效热降基本原理,科学划分烟气余热回收利用能级,将低温省煤器系统排挤做功划为三部分:第一部分为排挤8、7、6段抽汽做功;第二部分为排挤6段抽汽做功;第三部分为低温省煤器出水温度与5号低加进水温度偏差,排挤5段抽汽做功,综合三部分计算低温省煤器系统节能效果。试验结果表明:低温省煤器吸热量35.2 MW,8号低加进水至6号低加出水排挤做功2.3 MW,7号低加出水至6号低加出水段吸热排挤做功2.8 MW,5号低加抽汽量增加,机组出力降低0.7 MW,总排挤做功4.4 MW,装置循环效率提高0.66%,热耗降低51.9 kJ/(kW·h),折合发电煤耗为1.91 g/(kW·h)。与低温省煤器系统停、投运汽轮机整机热力试验结果相比,热耗相差1.7 kJ/(kW·h),发电煤耗相差0.07 g/(kW·h)。由此可知,这种与试验方法相结合,基于烟气余热梯级利用的能效评估方法,在低温度省煤器系统能效评估中是可行的。与常规烟气余热回收系统停、投汽轮机热耗试验法相比,基于烟气余热梯级利用的能效评估方法,具有概念清晰、科学合理、简单易操作的特点。

Low temperature economizer technology is one of the effective measures for recovering the flue gas waste heat in coal-fired power plant. In this paper,the low temperature economizer of a 660 MW coal-fired unit is studied. Based on the test data and the basic principle of equivalent enthalpy drop method,the utilization level of flue gas waste heat is classified and the power required and yielded by the low temperature economizer system is divided into three parts based on the work flow,then the overall energy saving via the low temperature economizer can be computed by integrating the total power over these three parts. The power calculation and comparison for each part are presented in detail in this paper. And the results indicate that this presented energy efficiency evaluation method,based on the cascade use of flue gas waste heat and combined with the test method,is feasible for the low temperature economizer system efficiency assessment. Compared to the conventional experimental method,the proposed method has a clear concept,and is simple and easy to implement.