Modeling SO2 absorption into water accompanied with reversible reaction in a hollow fiber membrane contactor

Abstract

The authors developed an efficient flue gas desulfurization (FGD) process employing a hydrophobic polypropylene hollow fiber membrane contactor (HFMC) using deionized water as scrubbing liquid. A novel mathematical reactor model for gas absorption accompanied by a reversible reaction in an HFMC was developed for the first time. This new model employed the resistance-in-series theory, along with partial pore wetting, and a chemical enhancement factor for an instantaneous reversible reaction. This model was validated agreeably with experimental data. The validated reactor model was then employed to investigate the resistance distribution along the main axis and the effects of temperature on SO2 removal efficiency. It was shown that the reactor model with the assumption of non-wetted pores overestimated the absorption efficiency, and a wetted pore length between 6.25–9.75% would yield a very good agreement with the experimental data. The deviations between the predicted and experimental values were less than ±3.0% with an exception of 3.4% at the highest gas rate for gas flow rates ranging from 1.38×10−4 to 3.01×10−4m3s−1, liquid flow rates between 3.00×10−6−8.00×10−6m3s−1, and the inlet SO2 concentration of 2000 ppmv. Furthermore, the reactor model described the impact of inlet SO2 concentration on the SO2 removal efficiency within ±0.5% of measured values for liquid rates between 4.35×10−6 and 5.50×10−6m3s−1 under a gas flow rate of 1.90×10−4m3s−1. The resistances of shell side, fiber side and membrane are all important due to high solubility of SO2 and partial pore wetting. The SO2 removal efficiency decreased gradually as the temperature increased from 283 to 333K based on model predictions.