GB475635A - Spray drying and solvent recovery system - Google Patents

Abstract

<PICT:0475635/III/1> The volatile solvents are recovered from solutions of thermoplastic heat-sensitive materials, such as vinyl and styrol resins, by heating and spray-drying the solution in a chamber 21 in the pre <PICT:0475635/III/2> sence of a hot inert gas admitted by the pipe 41 to precipitate the resins at a temperature below their softening point, recovering the solvent, and recycling the inert gas. The gas may be nitrogen, hydrogen, methane, hydrogen-methane mixtures, flue gases, vinyl chloride, acetone vapour, air, and mixtures of these. The solution is fed from tanks 11, 13 by a pump 55 and pipe 34 to a centrifugal sprayer comprising an inner cone 33, an intermediate slotted chamber 35, and an outer slotted distributor 36, all rotating together, which throws the solution in atomized condition into the hot gas in the chamber 21 provided with conical guide surfaces 23, 25. The hot gas is drawn from a heater 123 by a compressor 131 and forced into the chamber 21 through pipe 41 p and conduit 27. The gas is maintained in a whirling condition by drawing it off through a pipe 47 by means of a compressor 51 and forcing it back into 21 by a pipe 45. The mixture of separated solids, vapours and gases is drawn off by a fan 63 and forced into a separator 59, from which the solids pass to a receiver 65, while the vapours and gas pass by a pipe 71 to a bag filter 69 where residual solids are separated and fall into a chamber 73. The gas and vapours are forced by a fan 83 through pipes 79, 80 into a heat-exchanger 77, from which the condensed solvent passes to a receiver 89, while the gas passes, by pipe 87 to a brine condenser 85. The gas and residual condensed solvent pass from 85 to a separator 99, from which the solvent flows to 89 while the cooled gas passes by pipe 183 to act as the cooling agent in the heat-exchanger 77. From 77 the gas passes by pipe 121 to the heater 123 to be recycled. In a modification, the heat-exchanger 77 and condenser 85 are replaced by a single heat-exchanger, which may be water-cooled.