JP2006097199A - Method for producing kraft pulp and apparatus for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing kraft pulp, by which the pulp can be obtained in a high yield and in a high pulp strength (especially a tensile index), and to provide an apparatus for producing the same. <P>SOLUTION: In this method for producing the kraft pulp, the cooking degree of a pulp raw material is lowered to enhance a kappa number. The pulp raw material is mechanically beat and perfectly pulped with a refiner at the exit of a continuous digester and before or in a refining process to produce the kraft pulp in a high yield. The pulp raw material is mechanically beat with the refiner in a pulp concentration of 10 to 20% to accelerate the fibrillation of the pulp fibers, thereby enabling the production of the pulp having a high strength and containing few knotted fibers. Thus, the employments of steam / a cooking agent liquid in the cooking process can be reduced by lowering a cooking degree in the cooking process. The kraft pulp having a high pulp strength (especially a tensile index) can be produced by beating the pulp raw material with the refiner in a high pulp concentration. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing kraft pulp and an apparatus for producing the same.

  Kraft pulp (hardwood kraft pulp) that produces pulp through the process of cooking pulp raw materials (hardwood chips and softwood chips) made of lignocellulosic material with cooking chemicals and then separating pulp components and knots and other contaminants in the selection process Alternatively, in the production process of coniferous kraft pulp, kraft pulp is pulped in the cooking process and knots (and other contaminants) that could not be cooked in the selective process are removed. And the knot produced | generated at a cooking process is supposed to be removed with the knot processing equipment called a knotter or a knot separator etc. in the conventional common kraft pulp manufacturing equipment. In order not to generate knots in a process that does not have a refiner, it is necessary to operate with a lower kappa number, which is a factor in yield reduction. The amount of knots increases and decreases with the degree of cooking. In that case, the degree of chip cooking is represented by the kappa number, and the higher the kappa number (higher kappa number), the higher the yield but the more knots. Moreover, there exists a general tendency that pulp strength (especially specific tear degree) is so high that a copper number is high.

  In addition, regarding the knot removal performed in the kraft pulp manufacturing process, there is a general description in Non-Patent Document 1 below.

Paper Pulp Technology Association, Paper Pulp Manufacturing Technology Series (3) “Pulp washing, selection and bleaching”, pages 31-32 “2.2 Nota”.

  The inventor of the present application is a craft that has a high pulp strength (particularly, specific tear) and can obtain pulp with a high yield by lowering the degree of cooking in the cooking process of kraft pulp (especially softwood kraft pulp). The object of the present invention is to develop a pulp manufacturing method and manufacturing apparatus, and the present invention has been achieved.

  That is, in the kraft pulp manufacturing method and the manufacturing apparatus of the present invention, in the kraft pulp manufacturing process, the pulp beating process normally performed in the stock preparation process (the pre-process of the paper making process) is performed after the pulp cooking process. The basic feature is that it is performed before or during the selection process.

  The pulp raw material targeted by the kraft pulp manufacturing method and manufacturing apparatus of the present invention may be hardwood or softwood, but the present invention is particularly advantageous when applied to softwood kraft pulp.

  In carrying out the invention of the present application, the pulp value of the pulp raw material is lowered to increase the kappa number, and the pulp is completely pulped by a continuous digester outlet and mechanically beaten with a refiner before or during the selection process. , Producing high yield kraft pulp. By mechanically beating with a refiner at a pulp concentration of 10% to 20%, fibrillation of the pulp fibers can be promoted, and a pulp having high strength and few binding fibers can be produced. In addition, by reducing the degree of cooking in the cooking process in this way, the amount of steam and cooking chemical used in the cooking process can be reduced, and the pulp strength (particularly the ratio) can be reduced by high concentration beating with a refiner. Kraft pulp having a high degree of tearing can be produced. Thus, if the amount of the cooking chemical solution (caustic soda, sodium sulfide, etc.) is decreased, it is possible to reduce the damage of the pulp fibers and increase the pulp strength (particularly, the specific tear rate).

  In carrying out the present invention, the kappa number indicating the degree of cooking in the cooking process is preferably 30 or more. When the copper number is below 30, knots are almost eliminated and it is not necessary to beat with a refiner.

  If the degree of cooking in the cooking process is suppressed, a relatively large amount of knots is generated compared to the conventional method. In the present invention, the knots are deliberately beaten mechanically with a refiner, thereby producing a yield. High kraft pulp (especially softwood kraft pulp) is obtained.

  From the above viewpoint, in carrying out the present invention, a knot processing facility called a knotter or a knot separator may not be installed during the entire pulp manufacturing process. The pulp produced by the method of the present invention is not particularly limited, but is suitable as a raw material pulp for liners and a raw material pulp for grain bags such as rice wheat.

  The kraft pulp manufacturing method and manufacturing apparatus of the present invention promotes fibrillation of pulp fibers by beating the pulp components after the cooking process in the kraft pulp manufacturing process and before the screening process or in the middle of the screening process, There is an effect that a pulp having high strength and few binding fibers can be produced. In addition, according to the present invention, the degree of cooking in the cooking process is reduced by taking the means of beating the pulp components after the cooking process and before or during the refinement process. As a result, the amount of steam and cooking chemical used in the cooking process is reduced, and it is possible to produce kraft pulp with high pulp strength (particularly, specific tear) and high yield. (Especially advantageous for softwood kraft pulp). Moreover, in the implementation of the present invention, if knot processing equipment such as a knotter or a knot separator is omitted, an effect can be obtained for reduction of equipment cost.

  Next, a specific example for carrying out the present invention will be described with reference to FIG. 1. In FIG. 1, reference numeral 1 is a continuous digester, and in the continuous digester 1, raw material chips (in this embodiment, softwood chips) by cooking chemicals. ) And the black liquor-mixed (unwashed) pulp slurry P <b> 1 is taken out from the bottom of the continuous digester 1. In this embodiment, the pulp slurry P1 has a copper number (cooking degree) of 30 or more.

  In the embodiment of FIG. 1, this pulp slurry P1 is fed to a primary refiner 2 provided at the outlet of the continuous digester 1 and is first beaten.

  The pulp slurry P1 that has been primarily beaten as described above is stored in the blow pulp tank 3, and then fed to the washing machine (drum washer) 4 and washed with washing water, and then (washed) pulp slurry P2. Are fed to the secondary refiner 5 provided at the entrance of the selection process and secondarily beaten.

  The refiner mechanically beats the pulp components, so the pulp concentration is supplied at 10% to 20%, and the degree of beating is controlled by the load of the electric motor that changes depending on the interval between the segments (fixed blade / rotating blade). By treating this, it is possible to produce a pulp that promotes fibrillation of the pulp fiber and has high strength and few binding fibers.

  The pulp slurry P3 that has been secondarily beaten is then fed to the selection screen 6 and the selection cleaner 7, and is part of the impurities (undigested wood pieces such as bark and knots) from the pulp slurry (N1, N2). Is separated and discharged out of the system.

  The pulp slurry P4 that has undergone the selection process is subsequently washed by a washing machine (drum washer) 8, and then sent to the finished parfstock tank 9 for storage.

  In the embodiment shown in the figure, in order to reduce the degree of cooking in the cooking process, the use of cooking chemicals is reduced, the maximum temperature of the digester is lowered, and the temperature distribution is maintained gently so that cooking at a high concentration / high temperature is achieved. Prevents decomposition and disappearance of carbohydrates including cellulose due to chemicals, and increases pulp yield. Thus, if the degree of cooking is lowered in the cooking step, the amount of steam and cooking chemical used for controlling the temperature of the cooking chemical can be reduced.

  In the illustrated embodiment, the pulp component is beaten with a refiner at a high concentration to lower the degree of cooking in the cooking process and increase the kappa number to improve the pulp yield by 5% (46% → 51%). Conifer kraft pulp having high pulp strength (specific tear degree 190 → 240 (JIS)) could be produced.

  In the illustrated embodiment, a knot processing facility called a knotter or a knot separator is not provided during the entire process (between the continuous digester 1 and the finished parfstock tank 8). , Further improving the yield of pulp).

It is a principal part conceptual diagram of the manufacturing method and manufacturing apparatus concerning the Example of this invention.

Explanation of symbols

  1 is a continuous digester, 2 is a primary refiner, 4 is a washing machine, 5 is a secondary refiner, 6 is a screening screen, 7 is a screening cleaner, and 8 is a cleaning machine.

Claims (5)

  A method for producing kraft pulp, comprising a cooking step for cooking a pulp raw material comprising a lignocellulosic material, and a selection step for selecting a pulp component produced in the cooking step, after the cooking step and before or after the selection step. A method for producing kraft pulp, wherein the pulp component is beaten in the middle of the process.   The method for producing kraft pulp according to claim 1, wherein the pulp raw material is a softwood material.   The method for producing kraft pulp according to claim 1 or 2, wherein the cooking degree in the cooking step is set to a kappa value of 30 or more.   An apparatus for producing kraft pulp, comprising an outlet of a continuous digester for performing a cooking process and a refiner facility for beating the pulp components before or during the selection process. The kraft pulp manufacturing apparatus according to claim 4, wherein a knot processing facility such as a knotter or a knot separator is not provided during the entire pulp manufacturing process.

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