Paper making and fiber liberation – Apparatus – Automatic control
Patent
1981-01-12
1984-07-03
Chin, Peter
Paper making and fiber liberation
Apparatus
Automatic control
162261, 241245, 241247, D21D 130
Patent
active
044578040
ABSTRACT:
Apparatus for producing thermo-mechanical pulp from wood chips and the like in which the chips are first heated in a steaming chamber or preheater to a fiber temperature below the softening point of the lignin of middle lamella section of the wood fibers. The thus heated chips are conveyed in a sealed system to the inlet of a defibrating zone enclosed within a housing in a gaseous atmosphere of superatmospheric pressure, where it is compressed by a screw conveyor into a plug which seals the defibrator housing against blow-back of the pressurized gaseous medium. The defibrating space is defined between a pair of grinding discs which rotate relatively to one another in the housing and comprises a first substantially central zone into which the compressed plug is advanced by the compressor screw and broken up and the fibers subjected to an initial defibration step at a fiber temperature below the softening point of the lignin, to cause the fibers to unravel and to expose the different fiber layers without any substantial separation thereof. As the fiber bundles progress radially outwards under the centrifugal force of the rotating discs into a second zone radially surrounding the first zone, the temperature increases by the heat of the grinding friction which converts water accompanying the chips into high temperature, high pressure steam, in which environment the lignin is softened so that the wood structure is broken in the lignin-rich middle lamella section of the fibers to permit the fibers to become completely separated and fibrillated in undamaged condition. The resultant pulp is discharged from the pressurized housing through a blow valve which is adjustable to control the pressure and temperature within the defibrator housing.
REFERENCES:
patent: 2396587 (1946-03-01), Lowgren et al.
patent: 3215355 (1965-11-01), Shouvin et al.
patent: 3910505 (1975-10-01), Reinhall
Defibrator News, 1:1974, pp. 1-12.
Chin Peter
Munson Eric Y.
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