REMOVAL OF VOCS FROM AIR BY MEMBRANE-BASED ABSORPTION AND STRIPPING

Atmospheric emission of volatile organic compounds (VOCs) such as tolu ene, xylene, acetone etc. from industrial facilities causes serious en vironmental problems and financial losses. Existing technologies for V OC emission abatement have many strengths as well as considerable limi tations. A regenerative absorption-based process for removal of VOCs f rom N-2 in an inert, nonvolatile, organic liquid flowing in compact ho llow fiber devices has been studied here. These devices eliminate floo ding, loading and entrainment encountered in conventional absorption u nits. Detailed experimental results and theoretical analyses for absor ption studies were communicated elsewhere. The overall performance of the combined absorption-stripping process is described here; it appear s to be controlled by stripping due to the low temperature and the low er membrane surface area in the stripper. The difference between only absorption and combined absorption-stripping results was more pronounc ed for VOC-absorbent systems having higher Henry's law constant and di ffusivity. A theoretical model has been developed from first principle s to simulate the behavior of the membrane stripper; this has been com bined with the model for the membrane absorber to determine the overal l process performance. Simulated results obtained from the mathematica l models agree well with the experimental results for combined absorpt ion-stripping. Simulation results suggest that higher stripping temper ature and larger stripper area enhance the performance considerably.