Patent ID: 6694639
Filing Date: 2004-02-24
Classification: D21F,F26B

Abstract:
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 150Â° 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 150Â° 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 130Â° 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.