GB1018492A - Improvements in or relating to the spray drying of solutions, slurries or pastes - Google Patents

Abstract

1,018,492. Drying solutions, slurries and pastes in spray evaporators. R. O. H. BULL. Oct. 31, 1962 [July 31, 1961], No. 17145/61. Headings BIB and B2F. Solution slurries and pastes are dried by subjecting thin films of the material, in a drying chamber 13, to vibrations in the frequencyrange of 5 kilocycles to 50 megacycles per second by means of a transducer 12, and contacting the fine droplets of material so formed with a countercurrent stream of hot air, introduced into chamber 13 through a duct 18 from a heater 17. The finely-divided solid product collects in the base of chamber 13 where it is withdrawn by a pneumatic or worm conveyer, while the moisture-laden air passes out of the top of the chamber. In the spraying device shown in Fig. 2, the liquid is fed from the base of compartment 22 over the wall 23 of a hollow cone 24 which is vibrated vertically by a transducer 25 motivated by oscillator amplifier 14. The thickness of the liquid film on wall 23 can be controlled by regulating the distance between the outlet end of compartment 22 and the wall 23. In a modification, particularly suitable for slurries and pastes, the hollow cone is replaced by a perforated plate suspended from the base of compartment 22 by rubber bellows. In another spraying device, the liquid is supplied to two curved elements on each of which a magnetostrictive transducer is mounted. The liquidto-be-sprayed may alternatively be led into a cylindrical transducer which is joined to a tapered discharge-tube. The transducer may also be of the piezo-electric crystal type or of the moving coil type. The spray drying of milk and of antibiotics is referred to.