Mechanism And Optimization Study Of Desulfurization In The Spray Dispersion Tower

The systematic approach of physical and chemical mechanisms and mathematical models of gas-liquid flow,heat transfer,mass transfer,and the calcium desulfurization in the tower were implemented by analyzing the technical process of the spray dispersion tower and bubble dispersion tower.In the spray zone,the Euler-Lagrangian framework was used to calculate the gas-liquid flow,while the Euler-Euler framework was applied in predicting the multiphase flow in the bubble zone(reactor).The calculation models were then validated by the real test results.Since the bubble dispersion tower has similar desulfurization characteristics with the bubble section,the model construction and numerical simulation of the bubble dispersion tower were first carried out to provide a reference for desulfurization mechanism analysis of the spray dispersion tower.In the bubble dispersion tower,the large decrease gradient of the SO₂ mass fraction was observed in the area close to the dispersion plates.Also,the average SO₂ mass fraction decrease as the height increase.Furthermore,in the spray dispersion tower,the liquid spray could have a rectification and cooling effect on the down-flow flue gas,leading to high desulfurization efficiency.While in the bubble zone,the temperature of the up-flow flue gas could decrease as the bubble height increase.The back-mixing of the slurry could be caused by the high-intensity gas-liquid interaction,which creates larger number of small bubbles and causes the SO₂ concentration to decrease as the height increase.Due to the spray section play a major role in flue gas desulfurization,and the bubble section can deeply absorb most of the remaining SO₂,the high desulfurization efficiency of the spray dispersion tower is guaranteed.The influence of the different operating conditions on the bubble dispersion tower and spray dispersion tower was then studied.In the bubble dispersion tower,the desulfurization efficiency increases as the tube immersion depth,PH,and Ca CO₃ mass fraction increase.Also,the SO₂ absorption efficiency could decrease as the gas volume flow rate,inlet SO₂concentration,inlet gas temperature increase.Considering that it is difficult to maintain the desulfurization efficiency at a high level under different working conditions,its load adaptability needs to be improved.While in the spray dispersion tower,it shows that the desulfurization efficiencies decrease as the liquid-to-gas ratios and tubes'immersion depth rise.The most influenced factors of the desulfurizations in the spray zone and bubble zone are liquid-to-gas ratios and tubes'immersion depth respectively.Also,the SO₂ removal efficiency could slightly decrease as the gas volume flow rate increases.Considering that the desulfurization efficiency could be kept at a high level under various operation conditions,so it has fine load adaptability.The CFD tools were also used to simulate the multiphase flow and desulfurization efficiency of two optimization designs-the dual entrance spray section and the bubble section with the circular dispersion plates.After compared with the original design,the distribution of the flue gas streamlines path is more homogeneous with more vortexes inside and the SO₂removal efficiency is 3%higher in the dual entrance spray section.While in the optimal bubble section,there is a stronger interaction of gas-liquid,and the slurry back mixing phenomenon is more violent with a larger number of small bubbles.Then,a steeper decrease of SO₂ mass fraction along the gas flow direction can be seen from the optimized structure than the original one.More importantly,the desulfurization of the optimal bubble section is 8%higher than the original one.Thus,the optimized structures have better desulfurization efficiencies and more glorious future application potentials.Lastly,to find out the operating condition optimization,the complex coupling effects of various parameters inside the spray dispersion tower were considered by machine learning models.The XGBoost and other approaches were introduced for the importance rank of critical parameters.The strongest predictive performance of the XGBoost was shown after verified by the true values.Based on the prediction,the most contributing indexes which contribute to the running results like the desulfurization efficiency,oxidation fan current,and gas outlet temperature are the tube's immersion depth,oxidation fan pressure,and gas inlet temperature in the spray dispersion tower.The largest contribution attributes of the spray dispersion tower are different from the spray tower,which means these indicators should be considered in the design,build,and modification of the spray dispersion tower.Furthermore,the load adaptability of the spray dispersion tower can be deduced by analyzing the relationship between the important index distribution of desulfurization efficiency and the working load.The accurate prediction of the influence index distribution that affect the operating parameters can provide reference for the optimization of the adjustment space of the operating parameters of the spray dispersion tower,and streamline the operating process.