Presses – With additional treatment of material – Separating materials
Patent
1993-11-29
1995-12-05
Gerrity, Stephen F.
Presses
With additional treatment of material
Separating materials
100106, 100121, 100126, 100169, 100173, B30B 902
Patent
active
054719216
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a method and an apparatus for dewatering and loosening raw biopulp using roll dewatering. The invention concerns in particular a method and an apparatus for dewatering and loosening chipped and precrushed raw wood using roll dewatering. The invention is of especial interest in connection with the production of powdered fuel, but also e.g. in connection with the production of fillers for plastics and the production of paper pulp.
DESCRIPTION OF THE PRIOR ART
Plants in general contain 50-90 weight percent water and energy forests (for example sallow or poplar) contain 70 weight percent. Raw wood consists in principle of water filled cells.
A technical field in which dewatering of raw biopulp is practiced on a large scale is pressing of sugar cane. Here the raw biopulp must pass at least twelve pairs of rolls before effective dewatering can be obtained. In such a treatment of sugar cane the intention is to make use of the liquid that is pressed out, while for the dewatering procedure according to the present invention the desired product is the dewatered material itself.
A method of removing water from wood is to use a bark press but the only result is that the water outside the wood is removed.
SUMMARY OF THE INVENTION
The present invention concerns a method for production of dewatered and loosened biopulp, which method is characterized in that precrushed raw biopulp is pressed against a pair of counter-rolling press rolls between which the biopulp is subjected to a pressure between 500 and 1000 bars. Hereby the biopulp is dewatered and then fed into a backpressure vessel which is maintained at an overpressure of at least 1 bar. This causes air to blow out through the nip between the rolls, thus preventing the water pressed out from entering the backpressure vessel and avoiding remoistening of the dewatered biopulp. The dewatered and loosened biopulp is then transferred from the backpressure vessel and subjected to well-known chemical and mechanical treatments, for instance for production of powdered fuel, fillers for plastics or pulp for paper production.
The invention also concerns an apparatus for dewatering and loosening the raw biopulp, which apparatus is characterized by including a system of feeding pistons for pressing the biopulp against two profiled press rolls one of which is made of solid metal and the other, in a width corresponding to that of the solid roll, is composed of a number of elastically mounted plates which can move radially in response to radial loads. On the exit side of the press rolls is a backpressure vessel at overpressure and a compartment feeder for transferring the biopulp from the backpressure vessel,
With the method and apparatus according to the invention the wood, in the form of chips which have been precrushed to a size of approximately 2-5 mm, is subjected to large press or compressive forces, whereby the water pressure in the cells is increased so much that they break, water is pressed out and the water content is reduced from about 70 to 35 weight percent. The water pressed out thus produces a number of canals and cracks in the compressed wood structure and when the roll pressure ends the partially dewatered raw wood is loosened through its elasticity. By use of this treatment exceptionally favorable preconditions for an effective continued process treatment of the dewatered and loosened material are achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
The attached drawings show an apparatus according to the present invention for dewatering and loosening raw biopulp.
FIG. 1 shows a side view of an apparatus in section while
FIG. 2 shows a cross section through the upper and lower rolls of the apparatus.
FIG. 3 is a cross-sectional view of a rectangular piston 2 in a rectangular channel 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 the number 1 designates precrushed wood, approximately 2-5 mm in size while 2 designates a feeder piston which presses the raw wood through a channel 3 equipped with c
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Abom Jan
Klason Carl
Kubat Josef
von Bulsingslowen Frederik
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