Organic Rankine Cycle System Design For Heating Boiler Flue Gas Waste Heat Recovery And Power Generation

At present,the energy situation at home and abroad is becoming increasingly severe.China's energy efficiency is low and its structure is irrational,it shows that coal is still the main energy and cannot be completely replaced in a short time and industrial waste heat and pressure are huge but they cannot be used effectively,therefore,it is of great significance for energy conservation,emission reduction,and consumption reduction to carry out research work on low-temperature waste heat utilization technology in the industrial sector.Due to the small size and wide distribution of industrial coal-fired heating boilers,the potential for waste heat recovery is small and economical,therefore,less relevant research.The existing waste heat recovery technology can not use this part of the low temperature waste heat well,resulting in serious energy waste.In recent years,under the guidance of national policies,heating boilers have begun to develop in a centralized and large scale,and the recoverable low-temperature waste heat has increased,the problem of how to effectively recover the waste heat becomes even more urgent.In this study,the low-temperature flue gas waste heat recovery of the 155.44 °C tail temperature of a 90 MW coal-fired industrial boiler in Shenyang was studied,and a scheme of the organic Rankine cycle(ORC)waste heat recovery power generation was proposed.Through in-depth analysis and rational optimization of the entire system including boiler operation system and ORC recovery system,further improve the energy quality level and energy efficiency,and effectively reduce the boiler exhaust temperature,improve the efficiency of the boiler,provide theoretical guidance and calculation reference for practical engineering applications.By establishing an ORC system thermal model,the effect of different working media on the cycle performance of the system is studied,the final working fluid is R245 fa.The optimization of cyclic parameters is discussed and the theoretical ORC system physical model of the 90% optimal load condition is designed by using the optimal parameters.The optimal cycle efficiency of the system is 16.45% and the net output power is 7485.58 k W.In the main equipment,the multistage centrifugal pump is selected for the working fluid pump and the radial turbine expander is selected for the turbine.Analysis of the effect of the boiler on the performance of the ORC system at 75%,65%,55% and 45% load conditions,the average reduction in cycle efficiency is 0.52% and the average drop in net output is 1054.95 k W.In order to improve the system efficiency,an optimization strategy for adding a preheater before the evaporator is proposed,that is,using the hot water produced by the boiler to preheat the organic working fluid.From a macro perspective,it is concluded that the entire system is more economical and environmental benefits after optimization,and promotes the efficient and economical operation of the system.In order to prevent the system from high-pressure operation and accompanied by the phase change of the working medium,and the occurrence of safety issues such as the explosion of the tube,a combination of a flue gas heat recovery heat exchanger and a decompression device is used to realize the function of the evaporator.Through the design calculation and numerical simulation analysis of the waste heat recovery heat exchanger,it is found that the structural optimization measures with the addition of the guide baffle can effectively improve the heat transfer effect and verify the rationality of the design of the heat exchanger.