Simulation Research On Spray Drying Process In A Semi-dry Desulfurization Tower

The semi-dry flue gas desulfurization process has the advantages of low initial investment and easy handling of desulfurization products and is widely used in small and medium-sized enterprises.However,if the desulfurization product is not completely dried,it is easy to block the subsequent filter device,so the boiler exhaust gas temperature is required to be higher,which reduces the boiler thermal efficiency and increases the energy consumption of the enterprise.In order to improve the drying efficiency of the desulfurization product in the semidry desulfurization tower,reduce the inlet flue gas temperature.The paper focuses on an experimental spray drying tower,using numerical simulation methods to discuss the influence of nozzle parameters,drying tower structure,and operating parameters on the spray drying efficiency of the spray drying tower.Based on the law of conservation of energy and mass,the process parameters of spray drying were calculated;by analyzing the movement trajectory of a single drop in the drying tower,the size of the drying tower was calculated,and a semi-dry desulfurization simulation spray drying experiment platform was designed and built.Applying FLUENT software,using Realizable turbulence model and DPM discrete phase model,the spray drying calculation method is constructed,and the spray drying process is numerically simulated,focusing on the analysis of the gas flow in the drying tower,the movement and evaporation characteristics of atomized droplets,and the heat and mass transfer process between two phases.The experimental results are in good agreement with the numerical simulation,which verifies the rationality of the numerical calculation model and the size of the drying tower.Orthogonal analysis shows that the significance of the effect on drying efficiency is as follows: droplet size,nozzle insertion depth,air inlet angle,atomization angle,and droplet outlet velocity.A detailed analysis of the key factors shows that the smaller the droplet size,the higher the drying efficiency,but when the droplet size is less than 40μm,the improvement of the drying efficiency is not obvious,and the economy is unreasonable;increasing the nozzle insertion depth will reduce the droplet residence time;the air inlet angle has a greater influence on the gas flow field in the drying tower,and also affects the drying efficiency;when the droplet size is small,the atomization angle mainly affects the gas-liquid flow in the upper part of the drying tower,which affects the drying efficiency smaller.After comprehensively optimizing the parameters,the flue gas inlet temperature can be reduced to 448K～458K,which is more economical.The influence of structural parameters on the gas-liquid two-phase flow and mass and heat transfer in the drying tower was discussed by changing the height,diameter,and inlet mode of the drying tower.The results show that the height of the drying tower increases,the gas velocity decreases,the droplet residence time increases,and the drying efficiency first increases and then decreases;the diameter of the drying tower increases,the droplet residence time increases,and the central low-speed zone expands,and the drying efficiency first increases and then decreases;the symmetrical tangential inlet or the annular inlet can obviously improve the uneven gas flow in the drying tower,prolong the residence time of the droplets,and further improve the drying efficiency of the drying tower.The results of the thesis guide for carrying out spray drying experimental research and improving the drying efficiency of the desulfurization tower.