Study On Technology Of Marine Diesel Engine Exhaust Heat To Desalinate Seawater Coupled With Flue Gas Purification

Under the dual requirements of the strategy of building a strong transportation country and the“carbon peaking and carbon neutrality”goals,it is vital to promote the development of green shipping.At the same time,with the increasingly stringent requirements for Marine pollution prevention under the International Maritime Organization Convention on the Prevention of Pollution from Ships,the enhancement of energy-saving and emission reduction technology for ships has become one of the key research contents of green shipping.In this thesis,Pneumatic emulsification technology combined with high pressure water mist technology,a technology of marine diesel engine exhaust heat seawater desalination coupled with flue gas purification is developed,which is dedicated to using flue gas exhaust heat to realize seawater desalination while making full use of high concentration seawater by-products to achieve flue gas purification,helping to solve the problems of low desulfurization efficiency when ships are sailing in low salinity waters,high demand for flue gas purification desulfurization agents,and large floor space.（1）Construct a flue gas purification system coupled with ship flue gas waste heat seawater desalination.The technology scheme of flue gas waste heat seawater desalination combined with high pressure water mist technology and the technology scheme of flue gas purification combined with aeroemulsification technology are put forward.（2）Design a new efficient heat exchanger.Taking Kincaid B&W 6L90 GBE Marine diesel engine as the research object,the process parameters of evaporation section and condensation section of the heat exchange device were designed and calculated.The heat transfer coefficients of evaporation section and condensation section are 31.03 W/（m²·℃）and 1063.56 W/（m²·℃）respectively,and the heat transfer areas of evaporation section and condensation section are 456.46m² and 15.14 m²,respectively.The structural design of the whole system was completed.（3）The ship flue gas purification system was simulated to analyze the flue gas purification process and the operating state of the system.Based on Ansys Fluent numerical simulation software,the RNG k-εturbulence model and DPM droplet tracking model were invoked,the SO₂mass transfer model was established based on the double film theory,and the SIMPLE algorithm was used to complete the numerical simulation calculation.The results show that there is a biased flow phenomenon in the flue gas intake area,and the flow field and temperature field in the flue gas purification area are distributed“low in the middle and high outside”.The system pressure drop is 10.16 Pa.The overall removal rate of SO₂ is 92.28%.（4）The effects of system structure and operating parameters on flue gas purification effects were simulated.With inlet flue gas velocity of 4 m/s,flue gas temperature of 435 K,flue gas sulfur content of 0.0731%and liquid-gas ratio of 17 L/m³ as the initial parameters,the simulation analysis shows that:comprehensively considering energy consumption of the system and two-phase mixing effect,reducing inlet flue gas velocity and increasing liquid-gas ratio are conducive to improving desulfurization rate.With the increase of inlet flue gas temperature and the setting height of concentrated seawater nozzle,the SO₂ absorption rate distribution is parabolic.Comprehensively considering the mixing condition of two-phase flow,the service life of equipment and the heat transfer condition of coupling system,the optimal inlet flue gas temperature is between 395 K and435 K,and the optimal setting height range of the upper spray point and lower spray point of the pneumatic emulsification desulfurization cylinder and the secondary washing spray point is0.67～0.77 m,1.05～1.15 m,1.50～1.60 m respectively.In order to improve the flue gas purification rate,reduce the system pressure drop and energy consumption,the three-stage concentrated seawater spraying is used.The spraying angle of concentrated seawater is positively correlated with the purification effect of flue gas,and the best spraying angle is between 120°and 150°.When the liquid-gas ratio exceeds 19 L/m³,the SO₂ absorption rate tends to be stable.However,in order to reduce pump power and system resistance,the liquid-gas ratio should be reduced while ensuring the flue gas purification effect.（5）Design the experimental bench for ship flue gas exhaust heat recovery seawater desalination coupled with flue gas purification and complete the selection of related instruments and equipments.The selection of equipment and instruments,external body processing of the system,and overall assembly and construction were completed,laying a solid foundation for the design,manufacture,verification and optimization of the integrated device for flue gas exhaust heat recovery,seawater desalination and flue gas purification of ocean-going ships.