Analysis And Optimization Of Low Temperature Economizer Erosion Process Based On CFD-DPM-EPM Simulation

With the full implementation of "ultra-low emission" of flue gas from coal-fired power plants,the low-temperature electrostatic precipitation technology shows obvious advantages among many new electrostatic precipitation technologies.By installing low-temperature economizer(LTE)on the flue,the technology cannot only achieve high-efficiency dust removal and stable emission,but also achieve many energy-saving and emission reduction effects,such as reducing smoke loss and desulfurization water consumption.However,as the most important equipment in the technology,LTE are prone to heat exchange tube wear leakage problems in high dust areas all year round.This directly affects the safe and stable operation of electrical dust removal equipment,and even more will lead to the shutdown of the unit,which will cause greater economic losses.Either in physical experiments or practical engineering,it is difficult to monitor the flow of flue gas and equipment wear process ’ on line’.As a result,wear conditions can only be post-investigated after the equipment is shut down,resulting in the lack of solutions of engineering problems which cannot meet the actual needs.Especially,the research on the wear situation caused by the impact of solid particles in the flue flow field is still in its infancy,so that great difficulties exist in the flue design,transformation and operation parameter optimization.In this thesis,the coupled Computational Fluid Dynamics-Discrete Phase Model-Erosion Prediction Model(CFD-DPM-EPM)is used to deeply study the erosion process of LTE caused by particle impacts,and the process operation and structure design optimization of anti-wear equipment are proposed,which can provide theoretical basis for the wear analysis and optimization of boiler flue equipments.The coupled CFD-DPM-EPM model is developed to understand the particle-to-wall wear in the flow field,and the capability of different EPM is compared in the respect of applicability and accuracy with the best one determined.Numerical simulations on the experimental process are carried out and the accurate solution of the two-phase flow movement is obtained.The numerically predicted results have quite good agreement with experimental and the ability of CFD-DPM-EPM model is thus validated.The influence of process parameters on particle erosion of LTE is discussed,and the erosion process due to particle impact is revealed.Not only the erosion distribution characteristics of the three regions of the tube array are found,but also the important influence of the flue gas corridor on the wear resistance of the equipment is captured.The influence of equipment parameters on particle erosion of LTE is also discussed.Through a large number of modeling and simulation,from the internal structure of the equipment,upstream and downstream flue structure and reflow device and other aspects of the actual equipment layout,the recommendations to guide the structural design are proposed.The phenomenon of serious erosion of flue gas on the middle of the inlet plate of LTE after SCR denitrification is observed,and the optimization idea of adjusting the velocity field(size,angle)and particle concentration field is put forward.By changing the shell and arranging different types of deflectors,the correctness of the optimization idea is verified.For avoiding serious erosion,it is more practical to optimize the particle distribution rather than fluid flow field,which enriches the experience of process operation and structural design optimization of the anti-wear LTE.The wear analysis of large and complex SCR denitration reactor flue is carried out.Aiming at solving the erosion problem of key parts,combined with the theoretical basis of the above research and the treatment experience of anti-wear equipment,the optimization schemes are proposed.Practical simulation suggestions are put forward to better solve the wear problem in large and complex flow field.