RU2687982C1 - Processing method of cellulose-containing wastes - Google Patents

Abstract

FIELD: pulp industry.SUBSTANCE: invention relates to preparation of pulp from cellulose-containing wastes, in particular from waste paper for production of paper and cardboard. At insignificant humidification of cellulose materials there is reduction of cutting effect at dry grinding, due to which number of fractions of fine fibers is reduced, which increases mechanical strength of produced cellulose material. Besides, mechanical properties of cardboard are increased due to separation of flow into long-fiber fraction and fraction of fine fibers. This provides the possibility of using the proposed method for production of large-capacity high-strength multilayer types of cardboard, including a multilayer test liner or white liner. Set task is achieved due to that in the method of processing cellulose-containing, comprising grinding in air with further removal of ground wastes through the chamber with vacuum, dispersing the ground wastes in an aqueous medium, adding auxiliary components, by grinding, characterized in that milling cellulose-containing wastes in air is carried out at moisture content of 10 to 20 % in two steps, namely, coarse grinding of cellulose-containing wastes and fine dispersion into fibers, after which dry fibers are separated into short and long-fiber fractions, wherein dispersion and grinding in water medium of long-fiber fraction is carried out directly at stages of wet preparation of mass, which is supplied to molding of lower layer of cardboard, and fraction of fine fibers is dispersed at stages of wet preparation, and then supplied to molding of upper layer of cardboard.EFFECT: increased mechanical properties of cardboard (resistance to expansion, breaking length, breaking strength, modulus of elasticity) due to grinding of cellulose-containing wastes in air medium at low humidity (from 10 % to 20 %).1 cl, 1 dwg, 1 tbl

Description

The invention relates to the preparation of pulp from cellulosic waste, in particular from waste paper for the production of paper and cardboard.

A known method of preparation of waste mass for the production of paper and cardboard (see Application: 2004106002/12, IPC D21C 5/02, published 08/20/2000), which includes the stages of dissolving waste paper in water, coarse cleaning of waste paper from contaminating inclusions, pre-release, final pre-release of waste paper into fibers, fine sorting and cleaning of waste paper from contaminating inclusions, grinding a semi-finished fibrous material and water-repellent sizing of paper and cardboard in paper pulp using polyoxychloride flocculant-coagulant Yumin. Technical result: obtaining high-quality test liner. The high cost of water and energy, as well as a large load on water treatment plants are disadvantages of the method of preparation of waste paper. Waste pulp prepared by this method contains about 4% fiber and 96% water. The transportation and cleaning of 4% waste mass requires a large expenditure of energy.

Known dry method of preparation of waste paper, which involves minimal use of water (Osipov PS and others. Modeling the process of obtaining a fibrous semi-finished product from cellulosic waste in the air / Cellulose. Paper. Cardboard. "- 2012. - №4. P. 50 -53). Dry dispersion of waste paper production is carried out in a hammer mill. In the working area of the crusher, waste is crushed under the impact of hammers. The air dispersion of particles formed in the working area of the crusher after separation through a sieve is sent to the cyclone for cleaning, then through the storage hopper enters the packing unit. Excess air cleaned on the filter is released into the atmosphere. The waste mass in this way is obtained with minimal water use, while reducing energy costs associated with transportation and reduces the load on water treatment plants. The disadvantage of the dry method is the low strength of the resulting paper or cardboard product. According to the description of the dry method of paper and cardboard production, the strength of the final product can be reduced by more than 5 times in terms of resistance to bursting, breaking length, tensile strength and modulus of elasticity. For this reason, the dry method of producing paper and cardboard has not found application in the practice of producing durable pulp and paper materials, including cardboard test liner.

To increase the strength of the paper or cardboard product while reducing water and energy costs and reducing the load on water treatment plants, a combined method of mass preparation is used [US Pat. Ru 2583362, D21B 1/32, publ. 10.05.16.]. According to this method, the cellulosic material is ground in air in a hammer mill, equipped with hammers with a double-sided working surface, removing the crushed material from it through a chamber with an air depression of 140 mm of water. at the same time, waste from the production of tea filter bags is used as cellulosic waste, their grinding is carried out at a rotor speed of 3500 rpm and the speed of movement of the material flow in the crusher 30 m / s, the crushed material is dispersed in water, auxiliary components, the mixture is subjected to additional grinding, get the paper pulp and molded from her paper web. Additional grinding is carried out to the degree of grinding of 19-65 ° SHR, auxiliary components are taken from a series that includes wood pulp, bleached softwood and hardwood pulp, synthetic fibers, and chemicals from the next row - powdered mineral filler, synthetic thermosetting resin, a binder based on ethers pulp.

The known method does not provide high quality fiber semi-finished product, namely, sufficient paper forming the properties of waste paper after grinding in a hammer mill. The semi-finished product obtained by the claimed method cannot be used in the production of liner cardboard, which requires high mechanical properties.

The technical result of the claimed solution is to increase the mechanical performance of cardboard (resistance to bursting, breaking length, tensile strength, modulus of elasticity) due to the grinding of cellulosic waste in air at low humidity (from 10% to 20%). With an insignificant moistening of cellulosic materials, a decrease in the chopping effect is observed during dry grinding, thereby reducing the fraction of fine fibers, which increases the mechanical strength of the resulting cellulosic material. In addition, the mechanical performance of cardboard increases due to the separation of the stream into a long-fiber fraction and a fraction of small fibers. This provides the possibility of applying the proposed method for the production of large-capacity high-strength multi-layered types of cardboard, including a multi-layer test liner or a white liner.

The task is achieved by the fact that in the method of processing cellulose-containing, including grinding in air with further withdrawal of crushed waste through the chamber with air discharge, dispersion of crushed waste in the aquatic environment, with the addition of auxiliary components, grinding, characterized in that the grinding of cellulose-containing waste in air the medium is carried out at a humidity of from 10 to 20% in two stages, namely, the rough grinding of cellulosic waste and fine dispersion into fibers, according to Only dry fibers are divided into short and long fiber fractions, while dispersion and grinding in the aqueous medium of the long fiber fraction is carried out directly at the wet preparation stages of the mass, which is fed to the molding of the lower layer of cardboard, and the fraction of small fibers is dispersed at the wet preparation stages, and then fed to the molding of the top layer of cardboard.

The mechanical characteristics of products obtained on the basis of recycled cellulosic waste, increase by grinding the material, in particular waste paper, at a moisture content of from 10 to 20%. It is known that with the wetting of the cellulosic material, the negative effect of cutting the fiber in the dispersants is reduced, and therefore the proportion of long and strong fibers increases, increasing the mechanical parameters of the cardboard. A small amount of moisture (up to 20%) is removed from the material during its transportation in air after grinding without additional heat supply. Crushing in two stages also contributes to an increase in the mechanical properties of the paperboard due to a reduction in the chopping effect on the fibrous material.

For a better understanding of the proposed method, a scheme for preparing waste paper for the production of a two-layer test liner in FIG. one.

Waste paper containing mostly corrugated cardboard (MS-5B waste paper) is fed to the stage of dissolution into the hydraulic pulper 8 of the traditional scheme for preparing waste paper mass, then fed to the backspace and grinding of non-dispersed fiber bundles, and then sent to the mixing in a massive pool. From a massive pool with a concentration of about 4%, the waste mass is pumped by pump 11 to the primary cleaning stage in hydrocyclones 12. After hydrocyclones, solid inclusions (sand, metal particles) are removed to the dump, and the cleaned mass is sent for sorting to the turbo separator 13. From the turbo separator unspent fiber bundles sent to the vibration sorting 14, from which the mass is fed back to the pool 10. Then the waste mass is pumped to the fractionation stage 15. In the fractionator, the mass is divided into long-fiber and into fraction m lkih fibers. The long fiber fraction is fed to the metal pool 16, where dry fibers are also mixed. Preparation of dry fibers begins with the conveyor 1 feeding to the first coarse grinding stage 2. Then the crushed dry cellulose-containing waste (waste paper) is fed to the second stage of fine dispersion onto the fibers 3. The air flow carries the fibers with the help of fan 4 through pipelines 5. Then the mixture of fibers and air is fed to the purification in aero cyclone 6, where it is divided into a fraction of small fibers and into a long-fiber fraction. The long fiber fraction of the fibers is fed to the metal basin 16 and in the composition no more than 30% is mixed with the waste paper for the bottom layer of cardboard. The fraction of small fibers from the air filter 7 is fed to the line for the second layer, mixed with the waste mass into the metal basin 16. The long fiber fraction of the fibers obtained by the combined method (dry and traditional) is milled in an aqueous medium in mills 17, where they are grinded to enhance the paper-forming properties of the mass. After that, the fibers are fed to the mixture with the reagents in the composite pool 18, after which the multi-composition mass is fed to the mixing pump 19 and then to the engine pool 20. The overflow tank 21 stores a certain predetermined mass level. Then the mass is fed to the fine cleaning in hydrocyclones 12, and then fed to the stage of injecting the waste mass into the headbox 23. From the headbox, the mass is fed to the molding of the lower layer of cardboard, to the lower forming mesh 24. The upper layer, mainly consisting of a fraction of small fibers metal basin 16 is served in the overflow tank 21 of the parallel line of preparation. Then the mass is cleaned in hydrocyclones 12 and in the catcher 22. A fraction of small fibers is fed through the headbox to the grid 24 to form the top layer of cardboard. The connection of two layers occurs in the contact area of two grids. After molding, the two-layer cardboard goes to the pressing stage and through the further stages of the cardboard machine.

Indicators of consumer properties of the resulting multilayer cardboard test liner (breaking length, resistance to bursting, whiteness of castings) are measured according to standard methods. Determination of breaking length was carried out according to the method presented in GOST 1924-96, pushing resistance - according to GOST 13525.8-86, whiteness - GOST 30113-94, thickness of castings - GOST 27015-86, mass of a square meter of casting was determined according to GOST 131999-88. Wet molding of castings was carried out according to the international standard ISO 529-2 (2004).

The table presents the data on the mechanical parameters of the cardboard liner containing in the composition of fibers prepared by the dry method. Dry fibers were added to the composition up to 50% by weight of a multilayer test liner, the weight of a square meter of which is 150 grams.

As can be seen from the table, the mechanical parameters of samples containing up to 30% dry fibers in a multilayer test liner composition differ slightly from those prepared in the traditional way without the addition of dry fibers.

If we take into account the use of hardening chemicals that increase the strength by an average of 20%, then when the content of 30% dry fiber cardboard corresponds to the brand K-2, K-3 according to GOST 7420-99.

Thus from the data table on the parameter of resistance to bursting, it follows that the technical problem of the invention is implemented in full.

Claims (1)

A method of processing cellulose-containing waste, including grinding in air with further withdrawal of crushed waste through a chamber with air dilution, dispersing crushed waste in an aqueous medium, with the addition of auxiliary components, grinding, characterized in that grinding of cellulosic waste in air is carried out at humidity from 10 up to 20% in two stages, namely coarse grinding of cellulosic waste and fine dispersion into fibers, after which I separate the dry fibers the short and long fiber fraction, while dispersion and grinding in the aqueous medium of the long fiber fraction is carried out directly at the stages of wet preparation of the mass, which is fed to the molding of the lower layer of cardboard, and the fraction of small fibers is dispersed at the stages of wet preparation, and then served to the molding of the upper layer of cardboard .

Images