Recycling solvent vapour
7 Aug 2002
A research team at the University of Bath has won a prestigious UK award, after they developed a way to recover and recycle solvent vapour safely, cheaply and using just a fraction of the resources previously used.
The team from the Department of Chemical Engineering, led by Professor Barry Crittenden and Dr Semali Perera, developed the technology jointly with MAST Carbon Ltd, a Guildford-based company under a research project funded by the UK DTI LINK scheme and EPSRC. The result is a machine that allows harmful solvent vapours to be collected from small sites where traditional methods would be too expensive and bulky.
The company estimates the market for the new technology at around £400m, and its impact on safety earned it the IChemE Vision 2002 - Severn Trent Water Safety Award at the recent Institution of Chemical Engineers' ceremony in London.
The process the team developed is based on monolithic activated carbon that can be fitted easily into existing air management systems. When electricity is passed through the carbon it heats up and removes the solvent which was adsorbed.
The solvent can then be recovered and recycled. Previously any industrial process that dealt with the same type and volume of solvents would need several tonnes of adsorbing material to cope. Regenerating the adsorbent used to require large amounts of steam and created solvent solutions that could not be re-used directly.
Regeneration by electric heating can take a mere 30 minutes, rather than the 6 - 10 hours needed by beds of granular adsorbent. The upshot is that you need much less adsorbent - 500 kg rather than several tonnes for dealing with 10,000 m3/hour containing 1000 ppm vapour.
Another benefit of the system is the low pressure drop of monolithic adsorbents, allowing the system to be integrated directly into effluent air ducts without the need for recompression. This saves on capital outlay. And solvent can be recovered essentially water-free, compared with the dilute aqueous phase generated using steam; direct re-use improves the economics considerably.
The Bath-designed system fits in a space about the size of two filing cabinets. Operating costs are realistically estimated at less than a third of conventional systems.
