In order to find out the optimal applicable flue gas waste heat utilization scheme for utility boilers, based on the principle of energy cascade utilization, the waste heat recovery system has been idealized as a heat exchanger network composed of many temperature matching heaters according to the temperature distribution of hot and cold fluids. The optimization variables and constraints have been identified according to the system structure, the conservations of energy and mass. The mathematical optimization mode, that the maximum increase of power generation is the optimization target, has been built. Moreover, the optimization results have been calculated by using the fmincon function. The ideal waste heat recovery scheme for an ultra supercritical 1000 MW unit has been achieved through the optimization model. The maximum increase of power generation of the ideal scheme is 22.34 MW. By reducing the system complexity according to the project engineering needs, the project scheme has been obtained from the ideal scheme. Compared with the pre-existing waste heat recovery schemes, the project scheme is much simpler and more energy efficient, and its net coal consumption dropped by 5.05 g/(kW·h).%为了确定电站锅炉烟气余热利用最佳方案,基于能量梯级利用的原则,先根据冷热流体的温度分布情况,将余热利用系统理想化为多个温度匹配的换热器组成的换热网络,再根据系统结构和能量与质量守恒确定优化变量和约束条件,最后以发电功率增加最大为优化目标建立数学优化模型,运用fmincon函数计算出优化结果.以某超超临界1000 MW机组为例,优化后得出采用多个换热器的理想余热回收方案,其发电功率的增加达到22.34 MW.再根据工程需要简化为工程可用方案.与已有的余热利用方案相比,本文通过优化提出的简化工程方案系统简单,节能效果更好,供电煤耗率下降了5.05 g/(kW·h).
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