背压机组与抽凝机组经济性计算方法改进研究

Study on Improvement of Economic Calculation Method of Back Pressure Units and Condensate Pumping Units

传统的火电厂技术经济指标计算方法着眼于系统用能的数量平衡,反映的只是能量的外部损失,无法揭示系统内部存在的能量质量损失,在计算背压机组的技术经济指标方面存在缺陷,无法真实体现采用背压机组热电联产项目的能量利用水平。对三类计算热电联产机组技术经济指标的分析方法进行简要分析,并基于热力学第二定律,提出兼顾能量的数量特性与质量特性分析热电联产项目能量利用水平的改进方法,结合具体算例,计算并对比背压机组和抽凝机组的技术经济指标。结果表明:随着供热量的增加,热电联产的供热煤耗率将下降;当抽凝机组的热电比高于某个临界值时,抽凝机组的能源转换效率将高于背压机组,证明“背压机组是效率最高的热电联产方式”的观点是值得商榷的。

The traditional calculation method of technical and economic indicators of thermal power plants focuses on the quantity balance of energy used by the system,which reflects only the external energy loss,and cannot reveal the energy quality loss inside the system.There are defects in the calculation of technical and economic indicators of back pressure units,which cannot truly reflect the energy utilization level of cogeneration projects using back pressure units.Three types of analysis methods for calculating technical and economic indicators of cogeneration units were briefly analyzed,and based on the second law of thermodynamics,a new method for analyzing the energy utilization level of cogeneration projects by considering the quantity and quality characteristics of energy was proposed.Combined with specific examples,the technical and economic indicators of back pressure units and condensate pumping units were calculated and compared.The results show that with the increase of heat supply,the heating coal consumption rate of cogeneration will decrease.The energy conversion efficiency of the condensate pumping units will be higher than that of the back pressure units when the thermoelectric ratio of the condensing unit is higher than a certain critical value.The view that the back pressure unit is the most efficient cogeneration mode is worth discussing.