Sealing device for inlet and/or outlet of tunnel dryer - consists of three chambers, first operating under vacuum, second under dryer process gas atmosphere and third under clean inert gas atmosphere

摘要

A tunnel dryer is used for drying goods which consist of a substrate material to which a liquid dispersion containing volatile solvents has been applied. The dryer uses process gas at a pressure p0 slightly above atmospheric pressure. A new sealing system for the dryer inlet and/or outlet consists of: (a) a first chamber (2) fitted to the dryer (1) and containing a pressure p1 below atmospheric pressure. At the inlet and outlet of this chamber the uncoated underside of the goods passes over guide rollers (5,6), above which sealing elements (8,9) are located close to the upper coated side of the goods, (b) a second chamber (3) fitted to the first and supplied with cleaned dryer process gas at a pressure p2, (c) a third chamber (4) fitted to the second and supplied with clean inert gas. At the inlet and outlet of this chamber the uncoated underside of the goods passes over guide rollers (10,11) above which sealing members (12,13) are located close to the upper coated side of the goods. The pressure p0 is greater than p1 and p1 is less than p2 which is in turn less than p3. Also claimed is appts. in which the final or third chamber is omitted. Pref. the process gas recovered from the first chamber (2) is taken with the dryer exhaust process gas to a solvent recovery unit. USE/ADVANTAGE - For preventing the escape of process gas and solvents from tunnel dryers. No solvent can escape from the dryer, and process gas taken from the dryer inlet and/or outlet zone is recycled to the drying process. Atmospheric oxygen is also prevented from entering the dryer.