使用净现值法优化余热回收换热器

Applying Net Present Value Method to Optimize the Heat Recovery Exchanger

引入最优化方法,提出以净现值(NPV)为优化目标,以余热回收换热器换热面积为设计变量的优化设计模型。引入传热单元数(NTU)作为换热面积的度量,分析NTU变化对NPV的影响,从而确定优化方案,并且获得最优化条件下空气预热出口温度(t_2)。通过对燃烧二甲醚年产4万t玻璃炉窑烟气余热回收换热器的分析,结果显示在NTU=1.51时,换热器得到最大净现值NPV=7.53万元,空气预热出口温度t_2=100℃。同时,每年可节约燃料194.1 t和减少CO_2的排放量33.82。因此,采用余热回收换热器优化设计模型,通过对投资后整个运行期内的经济效果分析,可以对回收方案的合理性进行更为全面的评价。

An optimization model has been proposed, which is used net present value （NPV） as optimization object and heat transfer area of waste heat recovery exchanger as design variation. The number of heat transfer unit （NTU） has been employed as measurement to analyze its influence on NPV. In addition, the outlet air preheating temperature （t2） can be obtained with optimal conditions. Based on analyzing the exchanger used on the recovery of waste heat from flue gas from glass furnace, with the production of 40 thousand t/year and dimethyl ether as fuel, the result shows that NPV=75.3 thousand Yuan and air preheating temperature t2=100℃can be gained with NTU=I.51. Furthermore, 194.1 t/year of fuel and 33.82 t/year of CO2 emission are saved. Therefore, applying the design model of waste heat recovery exchanger, the overall assessment of recovery program in rational could be obtained by analyzing the economic effects in whole operation period after investment and optimizing the model with the waste heat recovery exchanger.