Sheet material and method and apparatus for drying therefor
AssigneeTokushu Paper Mfg. Co., Ltd.
InventorMorimasa Hanaya
Life of this patent
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Abstract
A sheet material, a production method therefor and a drying apparatus is provided wherein a heating gas comprising mainly superheated steam is blown directly to reach the sheet internal water content via a permeable belt for restricting free shrinkage of the sheet, to give instantaneous evaporation (pressure flow) and form a porous sheet. A wet sheet 35 is clamped between an externally heated rotor 1 having heated gas blowing ports 19 for blowing heated gas from an outer peripheral direction, and a permeable endless fabric belt 36 which moves in synchronous with the rotor under a tension capable of restraining dry shrinkage of the sheet material, to thereby give rapid direct moisture evaporation and form a porous sheet.
Claims8
A method of producing a sheet material by drying a wet sheet material web in a selected drying zone, which is enclosed by a sealed hood and which comprises a plurality of cylindrical rotors externally heated by super-heated steam used as heated gas, and a heat-resistant endless fabric belt, comprising the steps of:
- supporting an inner surface of the sheet material in a wet condition by an externally heated cylindrical rotor having a rotatable arc-shaped smooth surface mounted in the sealed hood, inside of which is maintained at a predetermined pressure and temperature;
- and
- clamping the outer surface of said sheet material by the endless heat-resistant fabric belt movable in synchrony with the rotation of said rotor and having a gas permeability of at least 7,500 cm3/cm2/min., while said fabric belt applies a tension so as to be capable of restraining dry shrinkage of the sheet material by pressing the sheet material on said rotor by the fabric belt;
- and
- blowing super-heated steam of at least 150° C. as the heated gas to the outer surface of said rotor through the fabric belt in a selected drying zone according to the paper grade to thereby dry said sheet material mainly by external heating;
- wherein super-heated steam of at least 150° C. obtained by circulating and reheating super-heated steam from said sealed hood interior is used as heated gas for blowing to the outer surface of the rotor, and super-heated steam of at least 130° C. substantially corresponding to the steam content carried into said hood by the sheet material in a wet condition is discharged outside of said hood.
A method of producing sheet material according to claim t wherein said heated gas to be blown to the rotor is obtained by mixing high temperature and high humidity air discharged from the sealed hood having a dry-bulb temperature of at least 130° C. containing steam substantially corresponding to the sum of a weight of steam evaporated from said sheet material and steam carried in from other channels, with newly adding low humidity air substantially equivalent weight obtained by weight conversion of the discharged humid air, and by rehearing the mixed gas to a dry-bulb temperature of at least 150° C. and a dew-point temperature of at least 65° C.
A method of producing sheet material according to claim wherein an excess gas of at least 130° C., containing steam evaporated from said sheet material is recycled as a heat source for another apparatus.
Dependencies are inferred from the claim text.