Study On The Deposition Characteristics Of Active Coke Particles To Mercury Removal In The Bag Filter

Mercury pollutant has the physiological toxicity, can accumulate in the organisms and the food chain, so people pay more attention to the pollution control of mercury. However, due to the elemental mercury unique physical and chemical properties, it becomes the key point and difficulty to Hg0 removal in the control of mercury emissions from coal-fired power plants. In foreign countries, devote to coal-fired boiler flue gas mercury emission control mainly concentrated in the United States and Canada, based on dust removal device of activated carbon injection adsorption method(ACI) become very mature. However, the uniformity of air flow distribution in bag filter and the distribution of activated coke cake on bag not only directly affect the efficiency of dust removal from flue gas and affect the energy consumption of dust collector system, but also affect the efficient of mercury removal from flue gas. Use the model of dispersed phase to analysis the gas solid two phase flow field characteristics in bag filter for mercury removal with injection adsorption method.by analysis of the gas solid two-phase uniformity under the different conditions, and the flow field of bag filter were optimized. And has carried on the analysis and compute the dust filter pressure drop, aiming to improve the filter bag removal efficiency of mercury and provide technical support to reduce the dust filter resistance, it has a certain engineering significance.First, this paper verified the feasibility of discrete phase model(DPM) method by comparing numerical simulation and experiment. We build the physical model was consistent with the experimental model of literature, used the discrete phase model(DPM) method to numerical simulation, and found the conclusions were good agreement with experimental results of literature, so verified the feasibility of discrete phase model(DPM) method.Then numerical simulation about use velocity field、pressure field of gas solid two phase flow and particle trajectory of active coke in bag filter will be done assisted by the model of DPM in Fluent.And designed a lot of conditions from different perspectives, such as different air velocity, different active coke particles particle sizes and different permeability of bag. Through the analysis of the active coke particle trajectory and particle deposition rate on the bag surface to get all kinds of parameters that influence the adsorbent distributed on the bag surface. Through Simulation, The results show that the distribution of activated coke adsorption particles in the bag filter is not ideal, near the wall of the bag filter particle deposition distributed densely and far away from the wall of the bag filter particle deposition distributed sparsely. As to the particles impingement and reflection on the wall, so formed the phenomenon that the activated coke adsorption particles capture by the bag which around the wall. Simulation results also show that on the premise of not affect the efficiency of dust collection for bag filter, increase the inlet air velocity, decreases the adsorbent particle size, increase bag permeability can make the adsorbent in the bag filter distribution more uniform.Based on the analysis of the filter velocity field, pressure field and active coke particle trajectory for original bag filter. We discovered that gas particle two-phase field distribution non-uniform, through a lot of tested and proposed adding composite guide plate to original bag filter flow to improve the problem of non-uniform distribution. By analysis the pressure field, velocity field and particle trajectories of the new and the original bag filter, it comes to the conclusion that the new hybrid type guide plate on the flow field of bag precipitator has better effect of uniform distribution.At the end of this paper, in view of the bag surface active coke adsorption cake for the characteristics of non-uniform distribution along the vertical direction of the filter bag, in summary on the basis of previous one-dimensional pressure drop models, analyze and summarize the filter pressure drop with the adsorption cake thickness variation along the vertical direction of two-dimensional pressure drop model. Also the influence factors of filtering pressure drop were studied by design the orthogonal experimental under no interaction, analyzes and computes the filtration velocity, filter bag permeability, adsorption particle size on the filter pressure drop effects.