Performance of commercial-size plasmapolymerized PDMS-coated hollow fiber modules in removing VOCs from N₂/air

Selective removal of volatile organic compounds (VOCs) from a N₂ stream via vapor permeation using microporous polypropylene hollow fibers having an ultrathin plasmapolymerized silicone skin on the outside surface, has been a subject of both pilot-plant and laboratory studies. The hollow fiber-based vapor permeation process employs a lumen-side feed flow essentially at atmospheric pressure and vacuum on the shell side. The excellent separation performance obtained with small membrane modules has inspired the exploration of the performances of larger commercial-size hollow fiber cartridges and multiple cartridge-containing modules for treating real-life VOC-containing gas streams. Results from two pilot-scale studies where the VOC-containing feed was the emission from a batch reactor in a pharmaceutical plant or the air emissions from a paint booth are reported here. The VOC concentration in the gas stream was as high as 14% of methanol in the batch reactor study; other VOCs emitted from the reactor were toluene (2.5%) and ethyl acetate (4%). The gas flow rates encountered varied between 10-80l/min. Very low levels of VOC in the range of 5-100ppmv were involved in the paint booth emission study. More than 95% of the VOC present in the feed was successfully removed in each study.