MEMBRANE-BASED ABSORPTION OF VOCS FROM A GAS-STREAM

A regenerative absorption-based process was developed for removing VOC s from N-2 in an inert, nonvolatile, organic liquid flowing in compact hollow-fiber devices. The process eliminates flooding, loading, and e ntrainment, and can replace activated carbon adsorption. Two types of hollow-fiber membranes were studied: one with a microporous wall and t he other with a highly VOC-permeable nonporous coating on the outer su rface of a microporous hollow fiber. Criteria for nondispersive operat ion were developed for each case. Experiments were conducted for the a bsorption of acetone, methylene chloride, toluene, and methanol from t he respective VOC-N-2 gas mixture using two absorbents: silicone oil a nd mineral oil. The highest mass-transfer coefficient was obtained for toluene followed by methylene chloride, acetone, and methanol. Differ ent resistances making up the overall resistance in VOC absorption wer e characterized comprehensively to develop a predictive capability and compare the absorption performances of two types of fibers and the tw o absorbents. The absorbent-filled porous membrane contributed signifi cantly to the total mass-transfer resistance. Numerical simulations of governing equations based on a cell model agree well with experimenta l results.