Modeling and experimental studies on chemical absorption of sulphur dioxide with ethylenediamine-phosphoric acid solution in a θ-ring packed tower for purification of flue gas

Abstract

In this paper, the main results of an experimental study on SO2 absorption in a bench-scale θ-ring packed tower using 0.3 mol·L−1 ethylenediamine-phosphoric acid solution was reported, and the effects of main technological parameters on the desulfurization efficiency were investigated. To uncover the mechanism behind the experimental observation, a one-dimensional model incorporated with equations of vapor-liquid equilibrium, heat, and mass transfer for simulating chemical absorption of SO2 with packed tower was also presented. Furthermore, the parameter distributions associated with heat and mass transfer characteristics along the absorber were also investigated. The results indicated that the relative errors of desulfurization efficiency between predicted and experimental values are less than 18.5% under different conditions and the model had depicted the tendency quite well. In addition, the desulfurization efficiency has positive correlation with increasing liquid-gas ratio, packing height, and ethylenediamine concentration, and declines with the increasing of inlet SO2 concentration, S(IV) concentration of lean amine, and operating temperature, respectively. Insights are given on the contribution of liquid chemistry reaction and interphase mass transfer on effective utilization of packing layer. Especially, enhancement factor and mass-transfer driving force along the absorber impact directly the SO2 absorption efficiency. Furthermore, the temperature rise has multiple effects on SO2 flux distribution, as mainly reflected in gradual accumulation of SO2(free) and decreasing of SO2 solubility in amine solution. This model can provide engineering guidance to design a packed tower as well as desulfurization process optimization.