Study On The Influence Of Gas-solid Two-phase Flow On The Dust Distribution On The Bag Of Filter

The electrolytic aluminum industry is one of the heavy polluting industries.The electrolytic production process produces a large amount of flue gas.Its composition is mainly composed of hydrogen fluoride（HF）,carbon dioxide（CO₂）and other gases,alumina（A1₂O₃）,electrolyte dust and other pollutants,which are harmful to humans.health.Most of the flue gas purification in the aluminum electrolysis production process uses alumina dry purification.The fresh alumina particles are used for adsorption reaction with the flue gas to remove HF and other dust pollutants in the flue gas.The reacted alumina particles are recovered by the bag filter.The bag filter for electrolytic aluminum is an important part of the aluminum electrolytic flue gas dry purification system.The gas-solid two-phase flow inside the filter is evenly distributed so that the alumina and the flue gas are fully and uniformly mixed,which provides favorable conditions for the alumina to adsorb the hydrogen fluoride in the flue gas.The distribution of alumina particles and airflow directly affects the uniform distribution of the dust layer on the surface of the filter bag.If the gas-solid two-phaseflow is unevenly distributed,the dust layer on the surface of the filter bag is unevenlydistributed,the hydrogen fluoride adsorption effect is poor,the purification efficiency is low,and the filter bag may even be damaged,causing dusty gas to be discharged into the atmosphere.Therefore,it is of great significance to carry out research on the gas-solid two-phase flow distribution inside the dust collector,and to adjust the gas-solid two-phase flow distribution reasonably to achieve uniform distribution,improve purification efficiency,extend the service life of filter bags,and reduce pollutant emissions.This paper uses numerical simulation and experimental testing methods to carry out the following research:（1）The physical and chemical properties of alumina,filter bags and filter materials from different aluminum plants are evaluated to obtain the particle size distribution of different alumina and the air permeability and thickness of the filter bags.A three-dimensional physical model is established based on the actual bag filter to obtain a tetrahedral mesh that meets the requirements under the condition of ensuring the calculation speed and accuracy.Based on the above conditions,the general fluency model is selected for simulation calculation,the accuracy of the boundary conditions of the selected model is evaluated,and then the velocity cloud graph,pressure cloud graph,and particle trajectory graph are used for analysis.It is found that the back of the filter bag is seriously scoured,the bottom pressure is too large,and the utilization rate of the front filter bag is less.（2）Optimization measures are proposed in response to the uneven distribution of the gas-solid two-phase distribution:deflectors are installed at the inlet,the rear wall,and the ash hopper,and the influence of the setting angle,position,and number of the deflector on the distribution of two-phase flow is studied.The results show that the180°deflector is conducive to the distribution of the flow field,too many deflectors hinder the uniform distribution of particles,and deflectors placed too high hinder the particles from rising.After comprehensive settings,the airflow and particles are evenly distributed.The analysis of the corresponding particle trajectory diagram provides a reference for the structure optimization of the filter.（3）The test platform of pilot plant test is numerically simulated,fully in line with the dimensions of real objects,and without reducing the filter bag quantity.The settings of the deflector are adjusted according to the results of the numerical simulation,and an optimized deflector is installed at the bottom of the ash hopper.It is found that the air flow rate and particle distribution of the filter bags beside the intake channel are increased,the impact of the filter bags on the rear wall surface is relieved,and the gas-solid two phase flow is equally distributed.An optimized deflector is installed on the test platform to run for 2000 hours;after that,its local air flow velocity and inlet and outlet dust are tested.It is found that that the airflow is evenly distributed,and the efficiency of filtering smoke in the flue gas purification reaches 99.99%.