Study On Flow Field Simulation And Structure Optimization Of VOCs Adsorption Tank

In the context of carbon neutralization,further increasing the emission reduction of VOCs is the focus of air pollution prevention and control in China.Adsorption method is widely used in the purification of VOCs because of its advantages of simple,efficient and low cost.With the continuous improvement of emission standards,the requirements of VOCs adsorption box are becoming higher and higher.In the actual working conditions,the limitations of the structure design of the adsorption box itself,coupled with the limitations of the actual space and other transformation conditions,resulting in the uneven distribution of the flow field inside the adsorption box,the pressure loss is too large,resulting in the uneven use of the adsorption material inside the box,thus affecting the service life and work efficiency of the adsorption material.Therefore,it is necessary to study the flow field uniformity and pressure drop in the adsorption chamber.In this paper,the horizontal radial flow adsorption chamber of a printing plant is taken as the research object,and the uniformity of flow field inside the adsorption chamber is simulated numerically by using CFD computational fluid dynamics simulation software AnsysFluent19.2.First of all,a simulation model is established and the accuracy of the model is verified.The spatial distribution of the flow field inside the box is studied,and the factors causing the larger root mean square value(unevenness)of the flow field velocity inside the box are identified,and the influence rules are analyzed.Secondly,three kinds of box structure situations are designed:(1)change the box height-diameter ratio,air inlet and other parameters to study the uniformity of air flow inside the box;(2)Change the uniform porous plate aperture,opening rate,plate thickness and other structural parameters;(3)Design the structure of ordinary non-uniform porous plate and variable aperture porous plate.Finally,the DesignExpert experimental design software is used to simulate and analyze three kinds of box structure,explore the influence relationship between factors and the pros and cons of the ranking.The results show that:In single factor analysis,increasing the height to diameter ratio and the length of the gradually expanding layer appropriately improves the uniformity of the internal flow field in the adsorption box.The optimal structure of the box is 1.12 height to diameter ratio,400mm diameter of air inlet and 746.195mm length of gradually expanded layer,and the uneven degree of adsorption section is reduced by 42.1%.For the inhomogeneity,the interaction between the length of the expanding layer and the diameter of the inlet is significant.For pressure drop,factor height-diameter ratio and inlet diameter interact significantly.Aperture 35mm,opening rate 0.35,orifice thickness 6mm and orifice position 712.437mm are the optimal structure of uniform porous plate,and the adsorption cross-section is reduced by 68.4%.The interaction between the factor opening rate and orifice position is significant on the inhomogeneity and pressure drop.Smaller inner aperture and larger outer aperture can significantly improve the uniformity of flow field.The distribution diameter of the inner aperture is 538mm,the inner aperture is 46.8mm and the outer aperture is 48.8mm,which are the optimal design of the non-uniform porous plate,and the adsorption cross-section is reduced by 72.2%.For the inhomogeneity and pressure drop,only the interaction between the inner and outer apertures of the factors was significant.Combined with the advantages of uniform and non-uniform porous plate,the variable aperture porous plate is designed with the inner diameter of 35mm and the outer area aperture gradually enlarging.The adsorption cross-section is reduced by 77.1%,and the air distribution effect is the best,which is the optimal orifice structure design.The simulation results show that the optimized adsorption chamber has a higher breakthrough time and a lower saturation time.These results can be interpreted as the better improvement of the chamber and the design of the variable aperture porous plate during the adsorption process,so that the bed adsorbs more C7H8.Finally,according to the actual working conditions of the printing plant design a honeycomb activated carbon adsorption plate quick replacement device,in addition,based on Siemens programming software,increase the automatic control system for horizontal radial flow adsorption box,and design the PLC automation program.