GB402707A - Improvements relating to pneumatic drying devices - Google Patents

Abstract

402,707. Pneumatic driers. ROSIN, P., 86, Bautznerstrasse, Dresden, Germany. July 26, 1933, No. 21082. Convention date, Aug. 27, 1932. [Class 34 (ii).] A pneumatic drier comprises a system of drying conduits in series or parallel, and a grading device, such as an air sifter, connected with each conduit, and arranged so that the larger particles are passed to the following conduit while the smaller particles are conveyed to a separator, each of said grading devices separating out larger particles than the preceding one. Heating gases are passed through the conduits, only one fan being required. The gases in the several drying branches may be at different and variable temperatures, obtained, for example, by the addition of cold air or waste gases in the parallel branches, or, in the series-connected branches, by adding fresh heating gases in each branch. The distribution of material to the various branches may be varied by means of control members in the air sifters. In one form, material is fed in by the device 17, and the fan 6 draws hot gases from the channel 7 through branches 1<1> and 1<11>, 21 and 2<11>, and 3. The lightest particles are separated from the remainder in sifter 8 and pass to the cyclone or other separator 5 through pipe 1<11>, the heavier material through feeding device 10 to the branch 2. A further sifting occurs in the device 11, the heaviest particles being passed to the last branch 3. The feeding devices 10 and 13 may be replaced by crushing devices, and the gas temperature may be varied by adjusting inlets 14 for cold air or the waste gases from the separator. In other forms, the branches 1, 2 and 3 may be straight; a cyclone separator may be provided for each drying stage ; and the conduits sifters and separators may be so arranged that the gases pass in series through all of the drying stages. The conduits may have one common insulation, and the sifters may be arranged in a single casing. The pipes 1, 2 and 3 may have different diameters to correspond with the distribution of the material, and the gas velocity may be controlled by throttle valves 15.