GB746244A - Method of drying or similarly treating web-like material - Google Patents

Abstract

746,244. Drying weblike material. AKTIEBOLAGET SVENSKA FLAKTFABRIKEN. June 29, 1954 [June 30, 1953], No. 19029/54. Class 34(1). In a method of drying web-like material 1 which is carried on one or more heated cylinders 3 and at the same time exposed to a gaseous medium the drying is divided into at least one step before the fibre saturation stage C and one step after, the treating medium being recirculated and some being discharged to the open air during the first step while a corresponding quantity from the steps after the fibre saturation stage is used to replace that discharged in the first step and the medium used in the later steps is made up by a quantity supplied from outside, the fibre saturation stage being the point at which there ceases to be free water in the material and evaporation thence takes place with decreasing intensity. The cylinder 3 is partly surrounded by boxes 6 supplying the medium through slots 4, the used medium being exhausted through the space 5 between the boxes, collected in the space 8 between the boxes 6 and outer casing 9a and discharged through duct 34, some being discharged to atmosphere by fan 10 and some being recirculated via fan 12 the amount being controlled by damper 11. Medium from the second step exhausted via duct 35 mixes with the recirculated medium and the mixture is returned to the first step via heat exchanger 18, damper 19 and duct 20. In the second step medium is supplied via boxes 29 having openings 30 used medium being exhausted to duct 35 via spaces 31 and 28. Some medium is recirculated via damper 21 duct 23 and fan 24 for repeated use, fresh medium being supplied via damper 22 either as unconditioned medium or as medium heated by heat exchangers 13, 14 through which the medium exhausted by fan 10 passes and the mixture in duct 23 being heated by heat exchanger 25 and returned to boxes 29.