Study On Optimal Operation Of Cooling Tower And System In Industrial Circulating Cooling Water System

With the rapid economic development,the energy shortage problem has become increasingly prominent.Efficient use of energy is particularly important.Industrial circulating cooling water system is a kind of common and important public energy-consuming system.Due to the unreasonable selection of cooling towers and pumps,extensive management and unreasonable operation modes,energy consumption is ultimately severe.The current energy saving potential of circulating cooling water system is huge.In this paper,the circulating cooling water system of aniline production was taken as an example to study the energy-saving.According to the cooling load and heat transfer performance of each layer in the heat transfer side of the system,the minimum required water flow rate for the system operating in a balanced manner at different wet bulb temperatures all year round was determined.The operation schemes of cooling water flow rate in the cooling tower were optimized.With variable fan angle only and variable frequency along with variable fan angle control technology respectively.It ensured that the cooling tower fan can operate energy consumption,adjustment and equipment the lowest cost.Considering the cooling tower and water pump,the height of the cooling tower and the low two positions,the cooling water pump number,the variable valve and the frequency control operation scheme were optimized.The optimization scheme enabled the cooling tower fan to operate at the optimal blade installation angle,and the cooling water system had the lowest energy consumption in the whole year.According to different rotating speed of fan,the optimal operation scheme of water pump was solved.The optimal operation scheme of the water pump and fan with the lowest energy consumption in the system was determined.Research had achieved the following innovative results:(1)Based on the theory of Michael’s enthalpy difference,a fast approach for controlling the inlet and outlet water temperatures of cooling tower to solve the gas-water ratio was proposed,which greatly simplified the determination process of the air-water ratio iterative calculation and saved the computational time.(2)To study operation optimizing of the semi-regulating fan throughout the year,which belonged to forced ventilation counter flow cooling tower with wet-type and based on constant water flux,different optimization schemes were determined by optimized operation using variable fan angle only and variable frequency along with variable fan angle control technology respectively,it ensured that the lowest total cost of cooling tower fan including operation energy consumption,adjustable angle and frequency transformer investment.The results showed that for variable fan angle regulation,the system with blade installation angles of 9.6°,7.0°,and 2.0°,reached the optimal condition when changing the operating angle 4 times annually.And for the variable fan frequency and angle regulation,the system with the operating fan angle of 10.1°reached its optimal condition when adjusting the frequency every hour every day annually.Compared with the original conditions,the total cost when employing the variable angle optimization was reduced by 48.77%,while the total cost of variable fan frequency and angle optimization was saved by 74.39%.(3)Re-initializing several feasible fans,the precise quantitative optimization selections of efficiency characteristics and regulation manners of the cooling tower fan were realized by comparing the energy-saving,adjustment and equipment costs for the semi-regulating fans with different efficiency characteristics.The optimization schemes employed the year-round variable angle only,variable frequency only,and variable angle frequency conversion respectively.(4)For the optimal operation of the circulating cooling water system,with the fan operating under fixed condition,optimization of the original low position cooling tower using variable pump number,valve and frequency strategy was optimal.After optimization,the energy consumption was saved by 50.16%.While the variable pump quantities and frequency strategy was best for the high position cooling tower,with 62.76%energy saved after optimization.(5)For the high and low towers,the optimal operation scheme of the pump with different speeds of the fan using variable frequency technique under different wet-bulb temperatures was calculated,to reach the lowest total energy consumption.Then the optimal frequency conversion ratio and the optimal operation scheme for the whole system were determined.Compared with the constant operating condition,the whole system optimal operation scheme saved total energy consumption by 50.38%for low towers,and 68.05%for high towers.