Simulation And Analysis Of Cooling Water System With Multi-supply Loops

Cooling water systems are basic elements in petrochemicals and other industry.As the energy consumption of cooling water system is still high,optimization is required.As main power consumption equipment in petrochemical enterprises,energy consumption of pump accounts for a large proportion of overall power consumption.At present,using high efficiency pump or series-parallel structure of cooler network are the main ways for improving energy saving.And the scholars have also done a lot of work on the optimization of the cooling water system.The optimization,in the past,of the cooling water system was limited to a single plant.In fact,the cooling water system usually has multiple plants.A cooling water station normally provide water to several processes,and every process has different pipeline characteristics.The conventional cooling water system use a uniform pumping system to transport cooling water,without considering different pipeline characteristics,leading to higher energy consumption.Therefore,this work propose a multi-supply loops structure to better fit different pipeline characteristics.Meanwhile,by using modeling,applicable conditions of applying multi-supply loops is explored.Different factors affected performance of multi-supply loops are discussed.At the same time,according to the facts mentioned above,this paper presents an optimization model for multi-plants cooling water system with multi-supply loops.Instead of using a set of uniform pumps to transport cooling water,this work proposed a novel multi-loops pump network and an updated main-auxiliary pump network to reduce pumping energy.Connecting patterns of different pump networks are investigated and corresponding piping costs are treated as optimized variables.Cooler and pump networks,cooling tower and pipeline layouts are optimized simultaneously.The model is formulated as a mixed-integer nonlinear programming(MINLP)problem.The objective is to obtain the cooling water system with minimized total annual cost.Two case studies are used to illustrate the effectiveness of the proposed structure.With structural improvement above,the scheme of using hydro turbine to save energy is proposed,and case studies will be used to testify its feasibility.The simulated results show that singular supply loop can be changed to multi-supply loops.Energy saving can be realized through reasonable consideration of using initial pumps,valve opening adjustment and applying new pumps according to practical situation.The simulation results also illustrate that the above two structures are effective,but the application of the two is inconsistent.Cooling water system with multi-supply loops is suitable for the system with complex pipeline layout and large number of coolers,while in the simpler cooling water system,the design of main-auxiliary pump is more appropriate.And hydro turbine would effectively save energy through recycling those energy that would probably be wasted in the cooling water system.