GB223298A - Improvements in or relating to heating or drying apparatus employing a gaseous heating medium - Google Patents

Abstract

223,298. Sterling, Sir J. W. July 17, 1923. Screw conveyers; air and gases, controlling direction of flow of.-In heating or drying apparatus of the type in which the material to be treated, e.g. wet organic or mineral matter, is propelied by a screw through a conduit into which a gaseous heating or drying medium is admitted, the hot air or super-heatsd steam employed is injected under pressure through the conveyer conduit wall 5, Fig. 1, into direct contact with the material under treatment, and means such as non-return valves, are provided at the inlet 24 and outlet 14<1> for the material to prevent leakage of the gaseous medium at these points. The steam or hot air is led through a pipe 17 extending parallel to the conduit 5 and discharged through separate valve controlled branch pipes 18, Fig. 3, from which the steam or hot air issues in two diverging jets 21, 22, the former imping- ing directly upon the area where the material 20 tends to accumulate. The steam or hot air is discharged from the conduit through an outlet 23 at the same end as the inlet 24 for the material, so that to a limited extent the process is carried out on the counter-current principle. Leakage of the gaseous medium at the inlet 24 is prevented either by the bulk of the material itself or by a hinged flap-valve, while a rotary discharge valve 14 for the material located in the outlet 14<1> and geared to the shaft 9 prevents leakage of the gaseous medium at the outlet 14<1>. The blades 13 tor propelling the material through the conduit are formed with stems adapted to engage apertures in the shaft 9 and to be secured by nuts so that, by turning the stem, the rake or pitch of the blade may be varied, while one or more of the blades as shown at 25 may be reversed so as to increase the time during which the material is subjected to the heating medium. In order to facilitate access to the shaft and blades, the conduit is split longitudinally at 26, both the upper and lower halves being built up of detachable sections.