Patent GB-576056-A (GB)
Title: Improvements relating to the drying of materials
IPC: F26B17/10
Filed: 1943-08-07
Abstract: 576,056. Drying systems. MANNING, A. H., and HELLE R, O. Aug. 7, 1943, No. 12785. [Class 34 (ii)] [Also in Group VI] Material to be dried, e.g., organic material for food or industrial use, is propelled upwardly with an upward stream of hot gases surrounded by a rising helical current of warm gases in a chamber, and is dried successively in the hot and warm gases, the lighter dried elements being separated in the helical flow from abnormally wet or dense elements which are recirculated into the hot gas flow. As they rise the central currents of material and hot gases lose their initial momentum and disperse radially into the helical flow. The drier, lighter elements continue to rise in the helical flow, and the heavier, wetter ones tend to fall either until they have been sufficiently dried to rise again or until they drop out of the helical flow. Material fed from a hopper 60 by a screw conveyer 59 to a rotary cutter or disintegrator 64 is projected by a rotary thrower 65 in a vertical stream through a duct 68 into a chamber 1. Hot gases such as combustion products from a furnace enter the chamber 1 through a passage 6 and a nozzle 5 surrounding the duct 68. Warm gases enter the chamber 1 tangentially through a duct 2. The mixture of warm gases and dried material is drawn off at the top of the chamber 1 through a pipe and fan 10, and delivered through a pipe 18 to a cyclone separator 20, which has an outlet 22 for warm gases, controlled by a damper 25. Some of the warm gases are returned through the pipe 24 to the drying chamber, part passing to the duct 2, part if necessary being admitted to the passage 6 to cool the furnace gases, and part being supplied through the pipe 28 to an annular jacket surrounding the hot gas nozzle 5, so that any partly dried material falling to the bottom of the chamber 1 is not overheated by that nozzle. A controlled amount of hot gases may be added through the pipe 33 to the warm gases passing to the duct 2. The hot gases supplied to the nozzle 5 may be diluted with air instead of warm gases from the separator. Material falling to the bottom of the chamber 1 drops on to pairs of inclined ledges outside the annular jacket, and slides down these ledges into ducts 43 through which it is returned, with gases drawn from the bottom of the chamber 1 by the suction effect of the rotary thrower 65 which operates like a centrifugal fan, to the cutter or disintegrator 64 for recirculation with fresh material. One or more helical ledges may replace the pairs of ledges, and a stream of hot or warm gases directed tangentially down them may assist the movement of material along them. The interior surface of the walls of the chamber 1 is provided with one or more helical vanes, which may be continuous or broken, and may be downwardly inclined from the wall. A conical baffle 16 may be adjusted vertically to vary the annular gap between it and the tapering wall of the chamber 1, and so control the flow of gases and material out of the drying chamber. Alternatively, gases and material may be discharged tangentially from the top of the chamber 1, which is then provided with a cylindrical obturator.