Absorption removal of sulfur dioxide by falling water droplets in the presence of inert solid particles

Abstract

An experimental analysis of the absorption removal of sulfur dioxide by the free falling water droplets containing the inert solid particles is presented. The wheat flour powder is introduced as the inert solid particles. Tests with and without the flour powder in the water droplets are examined. The mass fluxes and mass transfer coefficients of SO 2 for the cases with and without the flour powder are compared to elucidate the effects of the inert solid particles contained in the water droplets on the gas absorption. The results indicate aignificant difference between the two cases for the concentrations of the flour powder in the absorbent droplets ( C s) within the ranges of the experimental conditions, namely 0.1 to 10 wt% flour powder in the absorbent droplets. In general, the inert solid particles of the flour powder as the impurities in the water droplets tend to decrease the SO 2 absorption rate for the experimental absorption system under investigation. Various values of C s cause various levels of the interfacial resistance and affect the gas absorption rate. The interfacial resistance is recognized by introducing an interfacial mass transfer coefficient k s with its reciprocal being proportional to the magnitude of the interfacial resistance. The values of 1/ k s may be computed by the use of the equation 1/ k s=(1/ K OLs−1/ K OL), where K OLs and K OL are the overall liquid-phase mass transfer coefficients with and without the inert solid particles, respectively. The values of k s with C s of 0.1 to 10 wt% are about 0.295−0.032 cms −1 for absorbing 1000–3000 ppmv SO 2 with the water droplets. This kind of information is useful for the SO 2 removal and the information of acid rain that the impurities of the inert solid particles contaminate the water droplets.