基于持续节能的多周期换热网络优化设计

摘要

In petrochemical industry, operating conditions of heat exchanger networks (HEN) are always changed, which particularly fouling-induced heat resistance keeps increasing over time. To overcome variation of operating conditions, several optimizing methods on design and retrofit of multi-period HENs are available with no consideration of fouling effect on HEN. The inevitable HEN fouling and increase of heat resistance will drive operation deviate from optimum value and make it difficult to sustain energy saving. A synthesis design method of multi-period HENs based on continuous energy saving was proposed which optimal synthesis was achieved by targeting total accumulative cost and considering fouling influence. First, case study to analyze fouling influence on multi-period HENs showed that optimal value of multi-period HEN in each period had been changed due to fouling. Then, a model on optimizing multi-period HEN was established by considering continuous energy saving and objective function of total accumulative cost. Finally, case study indicated effectiveness of the design optimization method.%在石油化工工业中，换热网络的操作条件时常发生改变，尤其是结垢热阻随运行时间不断增大。针对操作条件的改变，有研究者提出多周期换热网络最优综合的设计与改造方法。但是，这些方法不涉及结垢热阻对设计结果的影响。然而，换热器结垢不可避免，传热系数随之改变，将导致操作工况偏离最优值，难以实现持续节能优化。以多周期换热网络优化为基础，提出一种基于持续节能的多周期换热网络综合设计方法，以换热网络累积总费用为目标函数，考虑换热器结垢对多周期换热网络优化结果的影响，进而实现多周期换热网络的最优综合。首先，结合示例分析换热器结垢对多周期换热网络优化结果的影响，得出考虑到结垢热阻的影响多周期换热网络在各个周期内的优化结果将改变；然后，基于持续节能优化，以换热网络累积总费用为目标函数，提出一种多周期换热网络优化方法；最后，结合示例验证了该设计方法的有效性。