| The installation of exhaust gas scrubbing device（EGCS）is the most effective way to solve Sox emission from ships,make the ship emission standard meet the International Maritime Organization（IMO）Tier III regulations,and realize the coordinated removal of particulate matter.For this technology,foreign countries have carried out more comprehensive and extensive work,but domestic research on this technology is relatively weak.In this paper,through the combination of theory and experiment,and with the method of numerical simulation,taking WD10C190-15 four stroke diesel engine as the target object,the design and Simulation of U-type exhaust gas desulfurization and washing system are carried out.The main work and conclusions of this paper are as follows:（1）Based on the gas-liquid mass transfer and chemical reaction of SO2 absorption by Na OH solution,the physical absorption model and chemical absorption model were established respectively,and the factors influencing the absorption rate of SO2 were analyzed.At the same time,aiming at the target diesel engine and desulfurization demand,the U-shaped marine exhaust gas desulfurization and washing system experimental platform was built,and the desulfurization and washing experimental scheme was designed,and the experiment was carried out according to the operation characteristics of the diesel engine.The experimental results show that:1)The increase of engine load will reduce the desulfurization efficiency of the whole U-shaped flue gas desulfurization tower,and the sharp decline of the venturi section desulfurization efficiency plays a major role;2)the p H value of spray washing solution is the key factor affecting the desulfurization efficiency,and properly increasing the p H value of washing solution is conducive to improving the desulfurization efficiency.3)When the spray rate of cooling spray layer is kept at 0.5m3/h,the spray rate of main spray layer and Venturi spray layer are positively correlated with the desulfurization efficiency and pressure drop of the whole U-shaped flue gas desulfurization tower.Through the analysis of the interaction between the two,it can be seen that the spray amount of Venturi spray layer plays a major role in the influence of desulfurization efficiency and pressure drop,he desulfurization efficiency increased by 39.83%and the pressure drop increased by 0.151kpa for every 1m3/h increase in the main spray layer.When the spray rate of Venturi spray layer increased by 1m3/h,the desulfurization efficiency increased by 54.22%,and the pressure drop increased by 1.22k Pa.Finally,through data analysis,the best parameters of all test operation parameters are venturi spray layer spray rate of 0.8m3/h,main spray layer spray rate of0.2m3/h,at this time,desulfurization efficiency is 99.685%,pressure drop is 2.156k Pa.（2）Based on the basic equations of computational fluid dynamics,a simulation model of U-shaped scrubber was built to simulate the gas-liquid two-phase flow in the whole scrubber.At the same time,for the problem of gas-solid two-phase flow in venturi,the mathematical model of velocity inlet form,particle drag force and Magnus lift force is optimized,and the optimization program is compiled by C language,and then linked to the shared library of FLUENT software to realize the simulation and optimization of gas-solid two-phase flow in venturi.The simulation results show that:1)the increase of Venturi throat diameter will reduce the gas-phase flow rate,make the particles carried by waste gas movement speed decrease and residence time increase,so it is easier to capture and remove.2)The increase of particle size will reduce the relative velocity of gas-solid phase and increase its residence time,thus improving the removal efficiency.3)Small spray droplets are more likely to be disturbed by the exhaust gas and gather near the spray layer,and the larger spray droplets will quickly penetrate the exhaust gas and reduce the reaction time.4)Increasing the flow rate of waste gas properly can improve the uniformity of liquid phase in the U-shaped desulfurization tower,thus improving the desulfurization efficiency.5)Reducing the spray cone angle properly can increase the penetration distance of the spray liquid,thus increasing the probability of gas-liquid reaction and improving the desulfurization efficiency.6)The best position of the venturi spray layer is the gradually shrinking section of the venturi tube,where spraying can avoid the spray liquid gathering in the throat and increase the spray liquid coverage rate.7)The cooling spray layer should be properly away from the exhaust gas inlet of the main scrubber to avoid the spray liquid being disturbed by the rapid exhaust gas.The main spray layer should be properly away from the outlet of the desulfurization tower to prevent the spray liquid from overflowing from the outlet and causing pollution.At the same time,a proper distance should be kept between the two spray layers to ensure the full utilization of the spray liquid.In this paper,through the experimental study on the desulfurization efficiency and pressure drop influencing factors of marine U-shaped desulfurization tower,at the same time,the numerical simulation study on the gas-solid and gas-liquid two-phase flow law in the marine diesel U-shaped desulfurization tower is carried out.The conclusion can play a supporting role in the optimization design of the U-shaped exhaust gas desulfurization and washing system of marine diesel engine. |
