FI111089B - Procedure for splitting chips into fractions - Google Patents

Description

111089

Method for splitting chips into fractions

Background of the Invention

The invention relates to a method for sorting, storing and feeding chips, wherein the chips are divided by a sieve into two fractions, the first fraction of which is passed to a chipping thickener or a similar device for treating thick material, and the second fraction containing mainly chips. a flat screen, where it is divided into several different fractions.

Traditionally, wood chips used in the production of cellulose have been classified by thickness. The most well-known type of thickness screen is a wafer screen, the structure of which is disclosed in Fl patent application 780685. The excess of the thickness screen, i.e., chips larger than a certain thickness, is treated with a chipper, chipper or similar device designed to reduce the effect of thickness.

Known screening methods are exemplified by Fl patent 82719. A similar solution has been previously disclosed in Akhtaruzzama et al., "Screening of Chips and Its Economic Benefits in Kraft Pulping," TKK Laboratory for Cellulose Technology, Report 6, Series C.

Diffusion in the preparation of cellulose has been described in the so-called. Fick's other 20. In all works in the field, thickness is assumed to be the only decisive factor. The conclusion that other dimensions have no effect is based on 60s research and its referencing without further experimentation.

Later, space-based and aerospace-based computing software has become available, with the aforementioned 25 Fick's second law in three-dimensional form. These softwares can simulate the diffusion of a three-dimensional chip. Based on the simulations, it has been found that not only the thickness but also other dimensions of the chips are important for diffusion.

Thus, the problem with previous practical methods has been a lack of understanding of the key factors influencing the mass production process and how these other factors influence the end result.

Summary of the Invention

It is therefore an object of the invention to develop the method mentioned above in such a way that all the physical properties of the chips that affect diffusion are taken into account when treating the chips. This object is achieved by the process of the invention, characterized in that the first fraction from the chipsetter and at least a part of the fractional fractions from the second fraction through the second screen are each fed to their separate stores, from which they are unloaded and mixed in the desired manner.

The invention is based on the fact that once the chips have been screened, the different size fractions are stored in their own storage, whereby, when using the chips, the fractions in stock are appropriately mixed to produce the exact desired mixture. Techniques based on the prior art produce only one acceptable chip stream which rarely has the properties that are desired.

List of figures

The invention will now be described by way of one preferred exemplary embodiment with reference to the accompanying drawing, which shows a diagrammatic representation of the various steps of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, wood chips 1 used in the process of the invention for the production of cellulose are fed to a thickness screen 2 known per se, from where the overhang, i.e. ha-20 beakers 3 of greater than a certain thickness, is fed to a chip chopper 4 or similar storage facility.

Thickness sieve undercut 6, i.e. chips smaller than a certain thickness, is led to a known flat screen 7, i.e. a multi-level sieve screen, from which the chips are divided into several fractions 8a, 8b, 8c and 8d, the finest fraction 8d being generally incinerated. The other fractions 8a to 8c are led to separate stores 9a, 9b, 9c. By doing this, the chips can also be sorted by their diagonal, which correlates with the width and length of the chips.

From the individual storage chips, the chips are unloaded by the unloading devices 10a, 10b, 10c 30 and 10d either in the desired proportions or from different stores at different times. Thus, it is possible to produce wood chips of a uniform quality in addition to their thickness.

3, 111089

The above description of the invention is intended only to illustrate the basic idea of the invention. However, a person skilled in the art can implement its details in many ways within the scope of the appended claims.

Claims (3)

111089 A method for sorting, storing and feeding chips, the chipping stream being divided into two fractions, the first fraction (3) of which is over-thick, which is fed to a chip chopper (4) 5 or a similar over-thick material handling device, and the second fraction (6), containing mainly chips of acceptable thickness, is introduced into a flat screen (7), where it is divided into several different fractions (8a-8d), characterized in that the first fraction (3) from the chip grinder (4) and at least a portion (8a-8c) of the flat screen (7) the subsequent fractional fractions 10 (8a-8c) of the second fraction (6) divided on the basis of their diagonals are each led to their separate stores (5, 9a-9c), from which they are discharged by a discharge apparatus (10a-10d) and mixed as desired. Process according to Claim 1, characterized in that part of the fractions (8a to 8d) is subjected to several different cooking processes. Method according to Claim 1 or 2, characterized in that at least three separate chips which are fed to the cellulose digestion are separated from the flat screen (7). 111089