GB816794A - Improvements in or relating to apparatus for drying culture media and the like - Google Patents

Abstract

<PICT:0816794/III/1> In apparatus, for dyring culture media and heat-sensitive food products, wherein the material is spread as a film of a moving endless belt 10 and the film is heated by elements 22 which emit radiant energy, adjustable shutters 30 are mounted between the radiators and the belt to regulate the amount of radiant energy reaching the belt. The shutters 30 comprise metal slats mounted on oscillatable rods 31. In the inclined position these slats reflect radiant energy away from the faces of the belt to a degree dependent upon their inclination from the vertical. The belt, which may be made of stainless steel, is mounted on pulleys 11, 12; and pulley 11 is rotated in the direction shown by a source of power (not shown). The belt is enclosed in a housing 35 which is evacuated through a pipe 36 connected to a vacuum pump. The material to be dried is supplied to the belt from receptacle 17 by roll 20. The radiant elements comprise chambers 23 through which a heat-transfer liquid of the chlorinated bi-phenyl type is circulated by pipes 24, 27. Pulley 12 has a hollow shaft which is connected by pipes 15, 16 to a peripheral compartment 13 through which cold water is circulated, whereby the dried product is cooled. The cooled product is scraped off the belt blade 38, and collected in one or other of the two containers 43. Piping 44, controlled by valves 45, is adapted to supply an inert gas, such as nitrogen, to fittings 42 whereby the vacuum below valves 41 can be broken after a container has been filled. The slats 30 may be individually adjustable, but they are preferably interconnected in sets of two or more. In order to achieve any desired differences of radiation intensity at various points on the belt, the effect of the shutters may be supplemented by contructing or arranging the radiators in a stepped configuration, or inclined to the belt, so that the spacing of the radiators from the belt differs as between the various points where such different radiation intensities are required. Likewise, the radiators may be divided into sections each fed by heating-liquid at different temperature, or fed in cascade to provide a temperature-gradient over the extent of the radiators. The water-vapour resulting from the drying may be removed from the housing by the employment of steam-jets, by absorption by silica gel, by freezing on refrigerated surfaces, or by condensation by sprays of refrigerated lithium chloride solution.