GB1080297A - Improvements in method and apparatus for drying wet pulverulent material - Google Patents

Abstract

1,080,297. Spray drying wet pulverulent material. FLUID ENERGY PROCESSING & EQUIPMENT CO. April 27, 1965, No. 17674/ 65. Headings B1B and B2F. Dry pulverulent material of fine particle size is obtained from wet pulverulent material by atomizing it in a heated atmosphere, centrifugally separating lighter particles from heavier particles after drying, and returning the heavier particles to the heated atmosphere. The wet material is drawn through conduit 44 into the inner chamber 34 of a nozzle assembly (Fig. 3) where the wet material is subjected to vortex action by a high-pressure gas at low temperature, introduced through conduit 38 into annular chamber 36 and issuing into chamber 34 through three passages 40. The dispersion of wet material in gas formed in chamber 34 is discharged through nozzle 46 into flash-drying chamber 14 (Fig. 1) where it is contacted with hot, low-pressure gas introduced through inlets 16, and rapid evaporation of liquid on the particles takes place. Chamber 14 leads into the inlet section 20 of a vortex-type drying mill which is supplied with hot gas through tangential ducts 22. The cross-section of chamber 14 and of section 20 is wider at the top than at the bottom. The dispersion moves as a vortex along section 20, and is then conducted by upstack 24 into classifier section 26, from which the fine dry particles are withdrawn through outlet 28, while the heavier particles are returned through end 30 into the section 20 of the mill. The high-pressure gas supplied to the nozzle assembly through conduit 38 may be air. The gas passes through passages 40 with at least acoustic velocity. Low pressure air is supplied through conduit 54 to the shroud 52, and issues into the flash chamber through nozzle 56 which envelops the main nozzle 46. The hot gas supplied to the flash-drying chamber and the inlet of the mill through inlets 16 and ducts 22 may be air, superheated steam or hot combustion gases. The apparatus may be used to obtain fine particles of calcium carbonate, titanium dioxide, and kaolin. An apparatus comprising two units of the type shown in Fig. 1, but with a common upstack, may be assembled; and it is stated that coating of one material by another may be effected in the upstack.