FI69326C - FOER FARING MILLING WITH CELLULOSAHALTIGA ELLER ANDRA HYDROFILA FIBER - Google Patents

Description

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Ή & Γα [β] <11) UTLÄGGNI NGSSKRIFT

C / 45) Patent granted

Patent rae.ltlelat 10 01 1986 (51) Kv.lk. * / Lnt.CI.4 D 21 B 1/34, D 21 0 1/20 SUOMI FINLAND (21) Patent application - Patentansökning 792176 (22) Application date - Ansökningsdag 11.07 .79 (F ') (23) Starting date - Giltighetsdag 11.07.79 (41) Became iuli - Blivit offentlig 12.01 .81

National Board of Patents and Registration Date of display and hearing publication—

Patent-och registerstyrelsen '' Ansökan utlagd och utl.skriften publlcerad 30.09.85 (32) (33) (31) Privilege requested - Begärd priority (71) Oy Tampella Ab, PO Box 256, 33101 Tampere, Finland-Fin 1 and (FI ) (72) Kari Ebeling, Espoo, Finland-Finland (FI) (7 * 0 Oy Koi ster Ab (54) Method for grinding cellulosic or other hydrophilic fibers - Förfarande för malning av cel 1u1osaha11iga eller andra hydofila fibrer or for grinding other hydrophilic fibers, the method comprising directing the fibers into a grinding zone between two opposing and spaced apart grinding surfaces and subjecting them to grinding in the grinding zone by means of grinding surfaces having blades and slots therebetween.

Pulp fibers are currently ground in the manufacture of paper and board mainly at a consistency of about 3-4%. At this consistency, the pulp fibers are flocculated, i.e. attached to each other, and the individual fibers cannot move freely. When such a fiber stream is introduced into the grinding zone between the refining surfaces of currently used refiners, much of the energy fed to the refiner is converted to heat and does not provide the actual purpose of refining, i.e. increasing the external and internal surface area of the fibers by refining.

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It has previously been known to perform the disintegration of fiber stock flocs before introducing the fibers into the grinding zone, and it has also been known to use very narrow blade slots in low consistency grinders for chemical pulps. In fact, the low-consistency grinder only grinds when the gap between the ridges of the rotor and stator blades of the grinder is in the range of 0.05 to 0.5 mm. In order for the low-consistency grinder to simultaneously handle large amounts of chemical pulp to be ground, it has been necessary to place a sufficient number of grooves sufficiently deep and wide between the blade brushes. In plate grinders, it has been possible to use narrower and lower grooves with a certain flow rate due to a higher circumferential speed and a higher centrifugal force (pumping effect). However, in practice, the groove depth of the disc refiner has not been allowed to wear below 2 mm, because the capacity of the refiner (the permeability of the fiber stock) is then substantially reduced.

Em. the fall in the capacity of the low-consistency grinder at low blade grooves is due to the fact that chemical pulps - especially long-fiber softwood pulps - already form flocs at low consistencies, ie fiber piles, which clog the grinder unless the stator and rotor blades of the grinder have sufficient cross-sections. Thus, it has been shown that the permeability of a disc refiner is zero unless there are sufficiently large pits on the smooth surfaces of the refiner, which are further located so that the pits form a solids from the feed circumference of the refiner to the outer circumference of the refiner. It has been considered important that the pits "break" the outer circumference of the grinding blades, i.e. the outer circumference must not have a complete dam to block the flow of the fibrous stock.

The object of the present invention is to provide a method which enables a better grinding capacity, and this object is achieved by the method according to the invention, characterized in that - the fibers are subjected to a flock disintegration treatment just before the fibers are fed as a thin flat fiber layer about 1-5 fibers. , and - the fibers to be ground are treated as a substantially flock-free thin web with a distance between the grinding surfaces in the range of 0.03-0.25 mm known per se (corresponding to 1-5 fiber thickness) and a depth of the soles of 0.06-0.25 mm known per se (corresponding to 2-5 fiber thicknesses).

By connecting the floc dispersing unit in front of the refiner and shaping the refining zone by means of narrow and low blade grooves so that the flock-free fibers do not re-flocculate in the grinding zone, a refining device is obtained. paper technology properties that are not achieved with current low-consistency refiners. Both of these factors, i.e. the cost-effectiveness of energy consumption and the new paper properties, are based on the fact that all fibers passed through the refiner are treated individually in the coarse zone and not occasionally as flocs as in current low-consistency refiners. In this case, a large part of the passed fibers slips in flocs along the blade grooves of the refiner through the refiner without obtaining any grinding hands at all.

In addition, the flocculant dispersant in front of the grinding zone makes it possible to achieve a high grinding capacity (flow rate) with low-blade blades, since the flow resistance of the floc-free fibrous stock of individual fibers .

When the fibrous slurry is obtained from the flocs as a thin and smooth fibrous web between the blades of the refiner, and when the blades are shaped in such a way that the the fiber path does not escape between the blades into the blade grooves, the refiner's blade zone is used much more efficiently than in normal refiners.

The disperser can be used to construct a more efficient grinding zone, i.e. to use high blade loads. A prerequisite for achieving high blade loads is that there is a flat thin fiber path between the blades of the refiner, which receives the grinding effect over the entire area of the grinding zone. The groove depth of the rotor and stator blades of the refiner is therefore chosen close to the thickness dimensions of the fiber, so that the fibrous material does not escape between the blades into the blade grooves, at the same time reducing the blade load and the risk of catching the blades.

The invention will be explained in more detail below with reference to the accompanying drawing, which schematically shows a schematic diagram for carrying out the grinding method according to the invention.

In the drawing, reference numeral 1 shows a type from which a fiber flow is fed by a high-pressure (high-density) pump 2 to a deflocculation device 3, in which the fiber flow is spread and the flocs are disintegrated to obtain a thin, uniform fiber path. It is known in papermaking technology to use, for example, various deflocculation devices in a headbox, and such devices known per se are also suitable for use in connection with the present invention. Reference numeral h denotes a refiner known per se, e.g. a disc or car refiner, the refiner slot and refiner members of which are dimensioned according to the above-mentioned thin, flock-free fiber web. The ground fiber web is removed from the refiner via line 6. If necessary, the water released in connection with a possible thickening can be transferred via lines 5 for diluting the ground fiber web.

Claims (1)

Il 69326 In order for the refiner to be fed without any return flow caused by the refiner surfaces, the feed pressure of the refiner and the network strength of the fibers must be high enough. The high feed pressure can also be used to thicken the pulp if necessary. The drawing and the related explanation are only intended to illustrate the idea of the invention. The details of the method according to the invention may vary within the scope of the claim. Claim: A method for grinding cellulosic or other hydrophilic fibers, the method comprising introducing the fibers into a grinding zone (h) between two opposing and spaced-apart grinding surfaces and subjecting them to grinding in the grinding zone. characterized in that - the fibers are subjected to a flock disintegration treatment (3) known per se just before the fibers are passed as a thin flat fiber web with a thickness of about 1-5 layers to the grinding zone, and - the fibers to be ground are treated substantially as In the range of 0.03-0.25 mm (corresponding to 1-5 fiber thickness) and the depth of the soles being in the range of 0.06-0.25 mm known per se (corresponding to 2-5 fiber thickness). il