Solid material comminution or disintegration – Apparatus – Cooperating comminuting surfaces
Patent
1997-02-11
1997-11-04
Husar, John M.
Solid material comminution or disintegration
Apparatus
Cooperating comminuting surfaces
2412613, 241296, 241297, B02C 712
Patent
active
056830483
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the disintegration and refining of lignocellulosic material, such as mechanical pulp (TMP, CTMP), reject pulp, recycled fiber pulp and the like in a disk refiner. More precisely, the present invention relates to refining elements for use in a refiner of this type.
BACKGROUND OF THE INVENTION
Known disk refiners comprise two opposed refining disks which rotate relative to each other, one or both of which are thus rotary. A plurality of refining elements are arranged on the refining disks, and include a pattern of bars and intermediate grooves. The refining disks are positioned so that the refining elements form a refining gap therebetween, through which the fiber material is intended to pass outwardly from within, whereby disintegration is carried out by the bars of the refining elements. These bars can be of various designs and, thus, may be continuous or discontinuous, and of uniform of varying height. In certain cases serrated bars can be used.
The fiber material is first defibered in the refining gap between the refining surface, i.e., the fibers are freed, which takes place in the interior portion of the refining gap where the distance between the refining surfaces is the greatest. The refining gap narrows thereafter outwardly so that the desired working of the fiber material is obtained. Large amounts of energy are thus required to bring about this working The material concentration can be between about 3% and 50%, which implies that simultaneously large amounts of steam are generated from the water associated therewith.
The refining surfaces are formed in different ways, depending on the desired degree of working, and thus on the desired pulp quality. The pulp quality is also affected by other factors, for example the size of the refining gap, the liquid content in the fiber material, feed, temperature, etc.
The appearance of the refining surfaces is of great importance, especially with regard to the fiber length of the material so worked. With a substantially radial orientation of the bars on the refining surfaces, a large proportion of long and well fibrillated fibers is obtained in the pulp. This can be explained by the fact that the fiber material orients itself in the refining gap with the fiber in a direction substantially parallel to the far edges. In this manner, defibering and working take place by virtue of the fact that the fiber material substantially rolls between the bars on opposed refining surfaces whereby the fibers are freed and fibrillated along their entire length. This type of pulp obtains high strength, and is therefore particularly valuable for many applications such as for newsprint. The energy consumption during the manufacture of this type of pulp is relatively high.
At an oblique orientation of the bars in relation to the radius, the proportion of long fibers in the pulp decreases, because in this case the bar edges exert a cutting effect on the fiber material. At the same time that the cutting effect increases, the fibrillation effect decreases. The strength properties of this pulp type are certainly lower, but the pulp is particularly suitable for use in the manufacture of fine paper qualities where forming, printability and opacity are appreciated.
The bar angle is also of importance for feeding the material through the refining gap. When the bars are angled obliquely outward rearward with respect to the direction of rotation, an outward pumping action is obtained, while angling in the opposite direction yields a braking effect. The stay time of the material in the refining gap is thus affected by the angle of the bars.
Known refining elements are specifically designed so as to produce desired properties in the pulp. This implies in many cases that compromises must be made with regard to the design of the refining surfaces in order to bring about a suitable balance between fibrillation and cutting of the fibers and, on the other hand, between feeding and braking.
SUMMARY OF THE INVENTION
In accordance with th
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Husar John M.
Sunds Defibrator Industries AB
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