Font Size: a A A

Numerical Simulation And Optimal Design For Heat Pipe Demister

Posted on:2018-10-07Degree:MasterType:Thesis
Country:ChinaCandidate:Y X ZhangFull Text:PDF
GTID:2322330536978159Subject:Engineering
Abstract/Summary:PDF Full Text Request
Wet flue gas desulfurization(WFGD)is the most widely adopted technology among numerous desulfurization processes.However,in this technology,some droplets with smaller diameter are still carried out by flue gas after passing through the demister,causing the corrosion and scaling phenomenon in the downstream equipments and parts,and may produce gypsum rain,which pollutes the environment.Therefore,it’s theoritically and practically significant to design efficient and reasonable demisters.Based on the existing demisters,a gravity heat pipe demist device based on steam condensation phase change defogging was proposed in this paper.The bottom of the gravity heat pipe in this device was located in the desulfurization tower roof.The gravity heat pipe used natural wind for air cooling and relied on gravity to complete working medium circulating,thus causing droplets condensation and agglomeration in the desulfurization tower.Also,the effect of partical turbulence and coalescence was strengthened because of adding gravity heat pipes to the desulfurization tower top.Under the synthetic action of what mentioned above,the average diameter of particles increased,the amount of particles decreased,so fine particles could be effectively removed.To analyze the performance of gravity heat pipe demister,the process of particle coalescence was theoretical analyzed,a simplified model was built for the system using related drawing softwares and a non heat pipe model was also built for controls.Then the grid division of the model with heat pipes and without heat pipes were generated,the changing process of particals was analyzed using population balance model(PBM),the growth rate of particals was described by writing user-defined functions and the analogue simulation for the system under different conditions was conducted using Computational Fluid Dynamics software.The simulation results show that the gas phase in the gravity heat pipe demist is at a low velocity when it’s away from breeching exit below the tower top or around the heat pipe or entering the breeching exit,and the demist efficiency of the system increases after using the heat pipe demister.Different arrangement patterns and various environmental temperatures have little influence on the demist efficiency of the system.The demist efficiency is significantly impacted by the inlet velocity,the tube pitch,the inlet particle size distribution and the inlet droplet volume fraction.Increasing the inlet velocity decreases the demist efficiency of the system but rises the pressure drop markedly.Besides,when the amount of pipes is certain,the demist efficiency will be raised at first and decreased then by increasing the tube pitch.In addition,increasing the average inlet particle size decreases the demist efficiency of the system but rises the pressure drop slightly.Meanwhile,The defogging efficiency and pressure drop increase with the increasing of inlet droplet volume fraction.Besides,by making an analysis of the flow field,the demist efficiency and so on,some design suggestions were proposed in this paper,such as adding deflectors and using L-type tubes,which is of certain guiding significance to the optimization of the gravity heat pipe system.
Keywords/Search Tags:gravity heat pipe, demister, steam condensation, population balance model, numerical simulation
PDF Full Text Request
Related items