Numerical Simulation On Erosion Of Ventilation And Dust Removal Pipeline

In recent years,environmental pollution was caused by the rapid development of China's heavy industry(electricity,chemicals,cement and steel),especially,the pollution caused by the dust particles from the factory emission was very serious.In order to control the discharge of solid particles,various of dust removal equipments were used to reduce the factory emissions of dust particles to a large extent,but the erosion of the ventilation pipeline caused by the dust will reduce the closure of the pipeline,and lead to the leakage of the pipeline system,affect the dust source control effect,destroy the function of the dust removal system,seriously decrease dust removal effect of the ventilation and dust removal system,which caused the highest proportion of failure.Therefore,in order to prolong the service life of ventilation and dust removal system and improve its effectiveness,it is great practical significance to study the erosion law of ventilation and dust removal pipeline.Based on the CFD-DPM(Discrete Phase Model)method,the erosions in the pipe of 90° elbow,straight pipe and tee of the ventilation and dust removal pipeline were numerically simulated,and the influences of the bend diameter ratio(k=R/D),inlet gas velocity,particle concentration,particle size and the materials properties of the duct wall on the erosion were also studied.Then,based on the CFD-DEM(Discrete Element Method,DEM)coupling simulation method,the collision of the particle group in the 90° elbow of the ventilation and dust removal pipeline and the force law of the pipeline wall are simulated.Finally,the CFD-DPM method was used to study the effect of the bend diameter ratio k and the Reynolds number Re on the erosion using RSM(Response Surface Methodology),and the structural and operating parameters were optimized.The results show:(1)The results of CFD-DPM simulation show that,in the 90° elbow of the ventilation and dust removal,the maximum erosion rate of the dust particle on the pipeline decreases first and then increases with the bend diameter ratio,and the location of the maximum erosion rate is gradually close to the pipeline entrance.When k is 3 ? 4,the erosion rate is relatively small.In addition,the relationship between the average erosion rate and the inlet gas velocity is basically quadratic,and the relationship between the average erosion rate with the dust particle size is basically cubed.At the same time,the simulation results also show that the erosion law of monodisperse particles and polydisperse particles is the same.(2)For the ventilation dust pipe in the straight pipe section,the simulation resultsshow that it is found that the maximum erosion rate of the dust particles increases first and then decreases with the inlet gas velocity,the average erosion rate decreases with the inlet gas velocity,and the average erosion is roughly linear with the inlet concentration of the dust.In addition,the relationship between the average erosion with the dust particle size is basically cubed.For tee pipeline,the maximum erosion rate of the vertical tee under the same conditions is less than that of the Y-shaped tee,and the maximum erosion rate of the Y-type tee is less than the maximum erosion rate of the oblique tee,and the maximum erosion rates of the Y-type and oblique tees increase with the angle Y-type tee and the inclination of the oblique tee,and then ultimately stabilize.When the inclination of the oblique tee and the angle of the Y-type tee are near 30°,the maximum erosion rates at this time are minimal.(3)The results of CFD-DEM coupling show that the number of particles in the ventilation and dust removal pipeline increases with the bend diameter ratio in the case of the same conditions.The larger the inlet gas velocity,the faster the number of particles striking the wall,but the smaller the total number of particles on the wall of the pipeline.The increase in inlet particle concentration leads to directly increase the number of particles entering the pipeline per unit time,so the greater the inlet particle concentration,the number of impact on the wall increases.For the particle size,it has little effect on the number collision.The position of the maximum erosion rate of the elbow and the maximum force point are basically the same,and the law of the maximum erosion rate is consistent with the law of the maximum impact force.By comparing with the maximum erosion point position and the erosion law OF CFD-DPM,the prediction of pipeline erosion based on CFD-DEM is verified.(4)The pipeline erosion predictions and the law based on CFD-DPM and CFD-DEM are basically the same.However,the accuracy of CFD-DEM simulation results is lower than CFD-DPM as a whole,and the fitting effect is not ideal.At the same time,CFD-DEM method can only judge the erosion of the pipeline indirectly by the force.The CFD-DPM method can directly simulate the erosion rate of the pipeline.In addition,there is a long running time based on the CFD-DEM method.Therefore,CFD-DPM is more suitable from the perspective of the law of erosion.(5)The quadratic polynomial prediction model of 90° elbow erosion is obtained by using the response surface methodology.Through the analysis of variance,we can see that the erosion of the dust particles has a certain influence on the bend diameterratio and the Reynolds number of the pipeline when the diameter of the pipeline and the particle size are constant.The effect degree on erosion is k>Re.In the scope of this work,the ventilation and dust removal pipeline has optimal structural parameters and operating parameters to minimize the erosion of the pipeline.When the particle size is5 ?m and the diameter is 500 mm,the optimal parameter is k=4.2 and Re=2.4830×106,respectively.When the particle size is 10?m and the diameter is 500 mm,the optimal parameter is k=3.7 and Re =2.4830×106,respectively.The optimal bend diameter ratio decreases with the particle size.