Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Mechanical defibration in the presence of heated gas or gas...
Patent
1978-10-25
1980-06-10
Smith, William F.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Mechanical defibration in the presence of heated gas or gas...
162 26, 162 29, 162 45, 162 46, 162 47, 162 55, 162 71, 162 78, 162 82, 162 87, D21B 116
Patent
active
042071402
ABSTRACT:
A process is provided for preparing groundwood pulp from debarked pulpwood logs, which comprises grinding the logs under a superatmospheric pressure of a gas selected from the group consisting of steam, air, and steam and air, while continuously supplying thereto water comprising spent bleaching liquor at a temperature of at least 70.degree. C. and forming a pulp suspension in the resulting aqueous liquor; centrifugally separating steam from the pulp suspension and using the separated hot steam to heat spent bleaching liquor supplied for the grinding; thickening the pulp suspension to a concentration within the range from about 5 to about 40% and supplying water separated therefrom to the grinding; diluting the pulp suspension to a concentration within the range from about 0.5 to about 4.0%; screening the pulp suspension; thickening the pulp suspension to a concentration within the range from about 10 to about 50% and supplying water separated therefrom to the screening; adding bleaching chemicals to the pulp and bleaching the pulp; diluting the bleached pulp with spent bleaching liquor to a concentration within the range from about 1 to about 6%; thickening the bleached pulp suspension to a concentration within the range from about 10 to about 50%; and separating, heating and recycling to the grinding spent bleaching liquor containing residual bleaching chemicals.
REFERENCES:
patent: 3808090 (1974-04-01), Logan et al.
patent: 4029543 (1977-06-01), Lindahl
patent: 4082233 (1978-04-01), Reinhall
Mo och Domsjo Aktiebolag
Smith William F.
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