Simultaneous Optimization Of Cooler Network And Pump Network Of Cooling Water System

Cooling water systems are widely used in industry to remove the waste heat that cannot be recovered.Cooling water system is a large energy-consuming section in the industry.It consists of two subsystems: the cooler network and the pump network.The cooling water system requires a large amount of energy to deliver cooling water.Therefore,reducing the energy consumption of the pump network is of great significance for the reduction of the overall energy consumption of the cooling water system.On the other hand,the circulating cooling water system needs to constantly replenish fresh water to maintain the normal operation of the entire system.In the refinery,the system takes up about 70% of the water consumption of the entire site.Therefore,it is also necessary to propose an optimization model to reduce the water consumption of the circulating water system.In this Paper,Chapter 2 presents a model that can optimize the pump network and cooler network simultaneously.The interactions between the pump network and the cooler network were explained.Typically,the two subsystems are optimized separately.Due to the inherent relationship between pump,cooler and the flowrate of cooling water,the cooler network and pump network should be optimized simultaneously.The cooler network is based on a series-Parallel configuration to ensure that cooling water can be reused between the coolers.The pump network is based on the main-auxiliary pump network to reduce the overall pumping energy of the pump network.The third chapter proposes a pump network coupled with the hydroturbine network to further reduce the energy consumption of the cooling water system.The hydroturbine can be placed in each branch or main pipe of the system.Main-auxiliary pump network is employed to reduce energy consumption at first stage.Then,the extra pressure energy of the system is further recovered to achieve overall consumption reduction.Chapter 4 presents anair-cooled and water-cooled coupled cooling system.The proposed model allows the system to automatically select the cooling method.After introducing air coolers to the cooling water system,the total annual cost of the cooling system is significantly reduced,due to the proper distribution of the heat load.The model optimized the system based on the price of electricity and fresh water.The optimal heat load distribution is obtained with the proposed model.Chapter 5 presents a model for simultaneously optimizing cooling water and refrigeration systems.Given the high energy consumption of the compressor if the refrigeration system,it is necessary to optimize the two system simultaneously and obtain the optimal heat distribution between two systems.For the model formulation,the MINLP(mixed integer nonlinear programming)is employed.The objective function is minimizing the annual cost TAC(Total Annual Cost)of the systems.