Numerical Simulation Of The Wave-plate Mist Eliminators For Ship Desulphurization

Exhaust gas treatment is the most effective technique to control SOx emissions from ships,including which wet exhaust gas desulfurization technology is the most mature technology.In order to meet the increasingly stringent regulatory requirements,wet exhaust gas desulfurization system is widely used on the ship.Mist eliminator is one of the key equipment of the system,it is installed at the exhaust outlet and to capture droplets carried in waste gas.It can reduce the deposition of pollutants,improve corrosion,and save feed water recharging to the system.Wave-plate demister has the advantage of compact structure,small volume and high separation efficiency,therefore it was widely used in the desulfurization system.On the wave-plate demister properties and particle deposition was studied to design and optimize separation devices to make it more efficient and compact,as well as improve the mist Eliminator wash rule.In this paper,the demister performance and particle fouling of demister were studied by numerical simulation.In this study,the characteristics of droplets,the causes of secondary droplets generation and the process of particle deposition in the SOx scrubber are investigated at the micro level.On the basis of this,the numerical simulation of flow fields,droplets removal and phenomenon of secondary carrying are calculated by using computational fluid dynamic(CFD).The performance of mist eliminator under different wave-plate type,structural parameters and operating parameters are analyzed.In addition,a performance prediction model of mist eliminator is established,and contraposed structural parameters,and optimized multiple target.The main research contents and conclusions are as follows:Numerical analysis was carried out about structural form of a wave-plate mist eliminator in the simulation of a wave-plate mist eliminator's properties,which was based droplet removal efficiency and pressure drop as performance indicators.Compared the performance of four different types of plate,under the same structure parameter,non-hook streamline plate channel pressure loss is the lowest and the separation efficiency is the lowest;hook streamline plate channel separation efficiency is the highest and needing to overcome the greatest pressure loss;the water membrane is concentrated in front of the first and second hydrophobic hooks on hook broken line plate,indicating the separation process is mainly achieved by the first two hydrophobic hooks.;the tear of the liquid membrane of the hydrophobic hook is an important reason for the formation of secondary droplet through the tear of the surface of the tablet and the membrane of the corner judged by Weber number;The performance prediction model is constructed by simulation results,drawing a conclusion that the main factors affecting droplet removal efficiency and pressure drop are the angle of turning and the velocity of the exhaust gas.Combined with droplet removal efficiency and pressure drop,structure parameters of mist eliminator have been optimized through genetic algorithm.Under study of particulate matter scaling in mist eliminator,numerical model of particle deposition process is built and drawing a conclusion that the velocity of exhaust gas,the concentration of grain,the length of hydrophobic hook and the angle of turning are the parameters that have positive correlation with scale thickness,drain hook width and plate spacing are the parameters that have positive correlation with scale thickness.Model and numerical simulation approach used in this paper can provide powerful support for mist eliminator design,selection of optimum operating parameters as well as flushing time.It can achieve the purpose of servicing for engineering.