Removing solvent vapour from off-gases contg. oil, grease etc. - by passing the gas through a wide-pore adsorption filter and then through a fine-pore adsorbent

摘要

Eliminating solvent vapour (I) from off-gas streams (II) in the presence of oil and fat vapours and other high-boiling substances comprises passing (II) (previously purified to remove droplets and solid particles) first through an adsorption filter with wide-pore adsorbents (III), and then through a filter with small-pore adsorbents (IV). Specifically (III) is large-pore active carbon as used for water purification, or an oleophilic, porous polymer, pref. styrene/divinylbenzene copolymer, pref. with mean micro/meso-pore dia. = 20-100A; (IV) is fine-pore active carbon (gas carbon), styrene/DVB copolymer or a zeolite, pref. with mean micro-pore dia. = 4-5 to 10-12 A; (III) and (IV) are in the form of spherical particles, or are bonded to an open-pore support, pref. open-pore, reticulated PU foam with 10-30 PPI, and have particle size 0.1-2 (pref. 0.2-1) mm; pref. the adhesive is crosslinked after loading the support, passing through a pronounced viscosity minimum; desorption is carried out with a countercurrent of hot air, nitrogen or argon, and the oil is desorbed from time to time by flushing out the adsorbents, pref. with perchloroethylene; the adsorbents are arranged as segments of a wheel which pass alternately through the adsorption and desorption zones, each segment contg. at least one layer of (III) and one layer of (IV), arranged so that the adsorption flow passes through (III) first and the desorption flow passes through (IV) first. USE/ADVANTAGE - Useful, e.g. in the metal-working industry, for removing perchloroethylene etc. from the waste gas after metal degreasing operations. The above sequence of filters prevents poisoning of the solvent adsorber (IV) by residual oil vapours etc.. (Dwg.0/0)