[Post author: Scott Butner]
this is a mixing station at one of the factories we visited here in Busan — this is where polyurethane is mixed with solvent and dyes to the customer’s specifications, then mixed before being sent to the knife coater.
The factory recently installed fume hoods over each mixing station, to reduce vapor concentrations (the solvent mix is a blend of toluene, MEK and DMF — DMF is relatively non volatile (bp around 153 C) but the other two are of course fairly volatile.
Some of the material is sprayed onto the floor and fume hood walls, as it wicks up the impeller shaft and is then scattered about. This creates a clean-up problem as well as some loss of working material.
Perhaps a bigger concern is that the facility emits about 30 tons/mo of solvent vapors which is not recovered. The b.p. range and water miscibility of DMF make this a problematic recovery, but I’d be interested in hearing if anyone’s aware of case studies…..