Solid material comminution or disintegration – Apparatus – With separation or classification of material
Reexamination Certificate
1999-07-15
2001-04-03
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Apparatus
With separation or classification of material
C241S028000, C241S135000, C241S143000
Reexamination Certificate
active
06209812
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of and an apparatus for treating wood chips and in particular for improving the wood chips properties particularly in pulping processes of the pulp and paper industry. In said method the chips are divided into various fractions on the basis of a fragment size before any other treatment phases of the chips.
In pulping processes wood chips treating methods, in which over-thick (e.g. above 8 mm) chip fragments are separated from the wood chips by a screen and directed to be treated by a chip compressor, have been used for years. Known chip compressor structures are described, for example, in U.S. pat. Nos. 4,953,795 and 5,385,309, Finnish patent application (No.) 911 972 and Finnish utility model (No.) 2412. The chip compressor basically comprises two adjacent conveniently profiled rolls arranged to rotate in relation to parallel rotation axes. The chips to be treated are fed between the rolls.
Advantages gained by treating over-thick chips with compressors are thoroughly described, for example, in U.S. pat. No. 4,953,795. In brief, using compressor treatment the cooking properties of over-thick chips are improved to the level of accept-size chips.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is to further develop the method in question and the apparatus implementing the method so that the cooking properties of the treated chips can further be improved. This object is achieved with the method and apparatus characterized by what is disclosed in the independent claims. The preferred embodiments of the invention are the subject of the dependent claims.
The basic idea of the invention is that accept-size chips, too, are treated by a compressor similar to the one previously employed only for treating over-thick chips. According to studies the cooking properties of accept chips, too, can further be significantly improved by compressor treatment.
An efficient but gentle compressor treatment of chip fragments of various sizes requires a nip, or the distance between press rolls, of various sizes and in some cases also a different profiling of roll surfaces, rotation speed and compressive force of the rolls. On this account a chip stream is divided into several fractions by a screen on the basis of the fragment size, whereupon each of the different fractions are directed to a specific chip compressor, whose nip, profiling, speed and compressive force are selected to suit this particular chip fraction.
Employing the method and apparatus according to the invention a more even cooking is achieved in the cooking process of the pulp, a higher total yield and a lower rejection level when cooking to the same kappa level compared with untreated chips or with chips from which only the over-thick fraction is treated.
REFERENCES:
patent: 3622089 (1971-11-01), Quinn
patent: 4050980 (1977-09-01), Schmidt et al.
patent: 4332353 (1982-06-01), Lario et al.
patent: 4953795 (1990-09-01), Bielgaus
patent: 5385309 (1995-01-01), Bielagus
patent: 208/63 (1968-09-01), None
patent: 47390 (1973-11-01), None
patent: 77699 (1989-04-01), None
patent: 1542981 (1990-02-01), None
BMH Wood Technology Oy
Fish & Neave
Rosenbaum Mark
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