Coordination Between Control And Economic Optimization For Heat Exchanger Network

During the life cycle of the heat exchanger network,the heat transfer performance keeps decreasing because of fouling and equipment aging,so the working point will gradually deviate from the design point.The utility can satisfy the control requirement but it increases the operating cost.Bypass control which meets requirements quickly is adopted widely.However,to ensure the feasibility of the bypass control sufficient margins must be designed.The margins of heat transfer area will influence process control performance.The control strategy may be invalidated since the insufficient margins.Large margin may bring more flexibility in operation and control,but requires larger equipment investment and operating costs.In the operation process,the optimal control realized better control performance without considering the margin.Therefore,the control strategy and economic efficiency should be considered simultaneously to optimize the economies and the control performance.In this paper,based on the strategies of two-stage coordination and one-step coordination between bypass control and economic optimization,the coordination design method between bypass control and economic optimization is put forward.Firstly,the relationship between the bypass control,margin and the economic efficiency is analyzed.The strategies of two-stage coordination and one-step coordination between bypass control and economic optimization are proposed.Then,the split ratio is pointed out as an economic optimization variable,and the method of matching the split ratio and bypass is assembled.The coordination design method based on split ratio adjustment is performed and applied in a heat exchanger network with splits.Finally,in the heat exchange network with multi-bypasses,the bypasses are classified as the control bypass used to control and the optimization bypass used to economic optimization.Similarly,the matching method of bypasses is proposed.The coordination design framework for effective control and economic optimization is constructed.The coordination design method based on bypass regulating is put forward.The practical heat exchange network experiment shows that coordinate design can achieve the continuous control and optimization of economic benefits.