Research On Operation Characteristics And Optimization Of Circulating Cooling Water System Coupled With Turbines

The circulating cooling water system is widely used in industrial production.The energy consumption of this system is characterized by large total amount,many influencing factors,and variable characteristics,and its energy saving optimization potential is huge.on the one hand,Under the influence of external uncertainties,such as ambient temperature and process load,The operating condition of the system is changeable and deviates from the design expectation most of the time.on the other hand,In the system with high-level heat exchanger,the pressure of cooling water flowing from the high heat exchanger to the tower pipe of the cooling tower is still large,resulting in excess residual pressure and energy waste.This study proposes a new method to recover the residual pressure energy of the circulating cooling water system by using the upper tower pipeline bypass tubular turbine and investigates the operation characteristics and optimization of the circulating cooling water system around the goal of low-carbon and stable operation of the existing system.The main work of this study are as follows:(1)A synchronous regulation strategy of the characteristic curve of pipe network and pump station is proposed by combining the advantages of two traditional hydraulic regulation strategies for the circulating cooling water system.On this basis,an optimization method of overall operation of the system under the condition of variable ambient temperature and process load is proposed.Using the mathematical programming method,The overall operation optimization model of the circulating cooling water system based on the superstructure is established by using the mathematical programming method,taking the minimum of the total energy consumption of the system as the objective function,and considering the environmental temperature,production load,equipment height,equipment speed regulation,bypass filter,and other energy consumption factors,expanding the application scope of the model.The accuracy of the overall operation optimization model of the circulating cooling water system is verified through case experiments,and the influence of environmental temperature and process load on the system energy consumption and the optimal water supply temperature is clarified.(2)This study analyzes the basic conditions for the existence of the residual pressure energy in the circulating cooling water system,proposes a calculation model of the system’s available residual pressure energy,and clarifies the factors affecting the system’s available residual pressure energy.A new method of recovering the residual pressure energy of the system by using the tubular turbine with the upper tower pipe bypass is proposed on the basis of the characteristics of the residual pressure energy of the circulating cooling water system.By analyzing the structural and hydraulic characteristics of the coupling between the hydraulic turbine and the circulating cooling water system,this method optimizes the hydraulic coupling relationship between the hydraulic turbine and the system,and makes up for the shortcomings of the low energy recovery efficiency and the decline of the cooling tower’s heat dissipation capacity in the traditional residual pressure energy recovery methods.In addition,considering the operating characteristics of the circulating cooling water system under multiple operating conditions,the calculation model of annual power generation of hydraulic turbine is established,and the optimal hydraulic turbine structure applicable to the system is determined from the perspective of economy and safety.(3)A coupling algorithm for 1D circulating cooling water system and 3D tubular turbine transient process is established by combining 1D characteristic method and 3D computational fluid dynamics method.A numerical calculation method of turbine runaway is established,and 1D and 3D multiscale simulations of turbine runaway and runaway shutdown processes under small flow,optimal flow,and large flow conditions are conducted.The hydraulic characteristics of turbine and circulating cooling water system in transient process are analyzed in depth.The change characteristics of system pressure and flow after turbine runaway are evaluated.The evolution law for the pressure pulsation of various parts of runaway turbine and the force on runner is determined.In addition,the opening and closing law of the control valve of the hydraulic turbine is optimized,the runaway shutdown water hammer is effectively suppressed,and the system operation stability of the coupled hydraulic turbine is improved.(4)Aiming at the energy consumption characteristics of the circulating cooling water system of the coupled hydraulic turbine,an optimization method for the synchronous operation of the hydraulic turbine and the system is proposed,and the optimization model for the synchronous operation of the hydraulic turbine and the circulating cooling water system is established by combining it with the overall operation optimization model of the conventional circulating cooling water system and the calculation model of the power generation of the hydraulic turbine,so as to further reduce the energy consumption of the system on the basis of the step-by-step operation optimization of the hydraulic turbine and the system.Through case simulation,the characteristics of the influence of hydraulic turbine on system energy consumption,water supply temperature,flow and water supply pressure are clarified,the influence law of environmental temperature and process load on the energy consumption of circulating cooling water system of coupled hydraulic turbine is clarified,and the advantages of synchronous operation optimization model are verified.