The Simulation Of Fluid Dynamics And Mass Transfer In An Ammonia-based Cascade-ring Foam Tower

:The enhancement factor during dynamic mass transfer and partial pressure of S02and NH3at equilibrium status were under investigated by a MATLAB program. Application condition and model accuracy of empirical model were studied by comparing with experiment data. With the understanding of NH3-SO2-H2O solution system, the two-phase fluid dynamic and the ammonia-based mass-transfer model were built up by the Fluent software. By analyzing the relationship between the independent variables, such as liquid-gas ratio, SO2concentration at inlet area and temperature of absorption solution and the dependent variable, such as desulfurization efficiency, pressure drop and ammonia escape rate, the simulation obtains the following conclusion:(1) with the application of the MATLAB program in the condition of low SO2concentration, the enhancement factor of NH3is unity and that of SO2is in the range of7to18.(2) the empirical model is less accurate than the equilibrium model especially at a low solution concentration. The empirical model, since it is ready-to-use, was applied in the mass-transfer model, and the equilibrium model was applied to calculate the enhancement factor.(3) the capture of droplets by the wall of equipment begins at the height of0.95m and vanish below the height of0.8m. The movement region and residual time of droplets in the equipment is quiet limited. While most region of the wall is covered by liquid film, hence, the mass transfer of liquid film cannot be neglected.(4) the breakdown occurs during the movement of liquid film. Part of absorption solution move towards the top of the equipment. The discrete model is incapable to represent these phenomenon.(5) though the inaccuracy of simulation of discrete model in the calculation of the movement of absorption solution, the relative error between the result of experiments and simulation based on discrete model is within10%. Hence, the application of discrete model in the set up of mass-transfer model is reasonable.The influence of operation conditions, such as liquid-gas ratio, SO2 concentration at inlet area and temperature of absorption solution, on desulfurization efficiency, pressure drop, ammonia escape rate and distribution of SO2were analyzed. The results are listed below:(1) With the increase of temperature of absorption solution, the escape rate of ammonia is enhanced and the desulfurization efficiency is declined. Ammonia concentration is above the national regulation when the temperature is above40℃. At around50℃, the desulfurization efficiency decrease swiftly because of the decomposing of byproducts.(2) With the increase of SO2concentration, the total mass of SO2absorption is increasing and desulfurization efficiency decrease. The lower the SO2concentration at the inlet region the more uniform the distribution of SO2.(3) Liquid-gas ratio has great impact on the pressure drop of the equipment. The pressure drop with liquid-gas ratio at2.5L·m-3is two times the amount of the pressure drop without spray. The relationship of liquid-gas ratio and desulfurization efficiency is linear.