Abstract: In order to achieve sustainable energy saving of heat exchanger network in the life cycle,bypasses were set in the network to increase its control degree of freedom,while a certain margin was designed to provide operating space of optimal control.To better use bypass adjustment and margin of operating space,an optimal control approach method based on dynamic model of heat exchanger network was presented and combined with existing conventional control loop,not only expanding the feasible region of optimal control,but also meeting the accuracy requirements of the original conventional control loop.The cumulative cost minimization of heat exchanger network within a certain period was considered as the objective function,while considering the impact of disturbances on heat exchanger network.To meet the process conditions,the best bypass opening in the life cycle was solved in order to achieve sustained energy saving of heat exchanger network.Closed-loop correction,iterative and rolling implementation were adopted,and optimization was based on actual conditions.A global sub-optimal solution could only be arrived at every turn.However,the actual control result could achieve the optimum.Finally,a refinery's crude oil heat exchanger network was treated as the specific study object,illustrating the effectiveness and application prospect of the presented method.

Key words: heat exchanger network, optimization control, energy saving, life cycle, bypass

摘要： 为了实现换热网络的全周期持续节能,在网络上设置旁路从而增加其控制自由度,同时设计一定的裕量来提供优化控制的操作空间。为了较好地利用旁路调节和裕量空间,提出一种基于换热网络动态模型的在线优化控制方法,巧妙地结合原有常规控制回路,不但扩大了优化控制的可行域,并且满足原常规控制回路的精度要求。该方法以换热网络一定周期内的累积费用最小为目标函数,同时考虑扰动对换热网络的影响,在满足工艺条件的基础上,求解最佳旁路开度,以实现换热网络的持续节能。由于采用闭环校正、迭代计算和滚动优化的实施方法,始终把优化建立在实际的基础上,尽管它每次不一定能得到全局最优解,然而使得实际控制结果达到最优。最后,以某炼油厂的常减压脱盐前换热网络为具体的研究对象,说明所提方法的有效性和使用前景。

关键词: 换热网络, 优化控制, 节能, 全周期, 旁路