Method of wood pulp production

FIELD: textile, paper.

SUBSTANCE: method is referred to bleached wood pulp production from hardwood chips for their further use in different compositions for paper and cardboard production. Chipped wood is impregnated with alkali solution of sodium sulfite. Spent impregnating solution is then removed. Chipped wood is milled in two stages. In between components are treated by alkali solution of hydrogen peroxide at weight concentration 14-18% and final pH=9.5-10.0. Following the second stage of milling, pulp is dissolved to concentration 3.0-5.0% and cured during 30-60 minutes to pH=7.5-8.0. Pulp is chemically treated by alkali solution of hydrogen peroxide between milling stages at 75-85°C during 15-20 minutes.

EFFECT: decrease of chemicals consumption for impregnation and improvement of mechanical and optical properties of target product.

2 cl, 1 tbl, 4 ex

 

The invention relates to the field of pulp and paper industry and can find application in the manufacture of bleached wood pulp from hardwood chip for subsequent use in various compositions for the manufacture of paper and cardboard products.

When obtaining wood pulp from hardwoods important technique is the processing of wood chips with an alkaline reagent, in particular sodium hydroxide, sodium carbonate, etc. because by its morphological structure of hardwoods is significantly different from the wood of coniferous species, for which the effect of alkaline reagents is not required.

A method of obtaining wood pulp from hardwood, when the alkaline reagent is used alkaline solution of hydrogen peroxide. The solution for the processing of wood fibre in its composition contains sodium hydroxide, hydrogen peroxide, sodium silicate, alkaline solution of complexing agents and magnesium sulfate. The varied use of this alkaline solution upon exposure to hardwood reflected in the known method [1].

The essence of the method is that alkaline hydrogen peroxide solution is used for processing:

- chips before the first stage of grinding;

- chips in the zones of the first stage of grinding;

weight before the second step of grinding;

- mass in the zone of the second stage grinding;

weight after the second stage of grinding;

- or combination of treatments chips before the first stage of grinding and mass before the second stage of grinding.

Stages of treatment of wood chips with an alkaline solution of hydrogen peroxide before grinding, or in the process of grinding in the first stage is directed essentially to the plasticization of the wood components to more easily separate the chips into individual fibers. The use of alkaline hydrogen peroxide solution as the plasticizing reagent is effective, but sufficiently expensive technique, because the consumption of sodium hydroxide is from 32 to 91 kg/t, and the consumption peroxide hydrogen ranges from 41 to 58 kg/so

In addition, when handling chips or fibrous mass of an alkaline solution of hydrogen peroxide a prerequisite for the implementation of this method is the exposure of wood fibers in a special container some time about 60 min before performing further operations.

A method of obtaining wood pulp, when wood chips are subjected to washing, heat treatment at 105-120°, razvlecheniy on the primary refiner grinding with simultaneous supply to the zone refining of a solution containing hydrogen peroxide, hydroxide NAT the Oia, sodium silicate and complexing agents [2]. The consumption of alkaline reagents sodium hydroxide, sodium silicate and a solution of complexing agents in the area of the first grinding step is carried out in full, and the consumption of hydrogen peroxide 20-40% of its total amount.

Then from the spongy mass is separated pairs and sent to the mixer, where add the remaining part (60-80%) of hydrogen peroxide, after which the fiber is directed into the reactor, where it is left it at 90°C for 40 minutes. After this time the mass is diluted with water to a concentration of 3% and transfer the slurry to dewatering press, where thicken it up to a concentration of 25% and grind on the second refiner stage, then the mass is sorted and cleaned.

The use of technology of reception of grinding chips in the presence of an alkaline hydrogen peroxide solution aims to reduce the degree of acid hydrolysis and degradation of wood fibers at the first stage of grinding and thereby increase the mechanical strength of the target product.

The main disadvantage of this method is the complexity and the significant duration of the implementation process in achieving its stated goals.

Closest to the present invention is a method of obtaining wood pulp, comprising the impregnation of the wood chips alkaline what astora sodium sulfite, the Department spent impregnating solution, the grinding chips in two stages and chemical treatment of the pulp between refining stages [3].

The essence of the described method is that the wood chips from aspen standard dimensions washed with water and separation from her sawdust and mineral inclusions and served in impregnating the boiler, where the temperature is not below 80°C for 20 min chips treated with an alkaline solution of sodium sulfite. Consumption of these reagents on the plasticization and the dissolution of the wood components is about 20 kg/t of each of them.

This processing chips aimed at the partial removal of chips easy-hydrolyzed components such as low molecular weight lignin, water-soluble substances, tar substances and carbohydrates.

Then the chips with the spent impregnation solution served in a screw press, where the separation impregnating solution from the chip, which is sent on the primary refiner, refining, where it turns into a coarse fibrous mass.

Exhaust impregnating solution comprises unreacted chemicals - sodium hydroxide and sodium sulfite, and part of the dissolved organic matter. The solution accumulate in a separate tank and then mixed with the fibrous mass before the second stage of grinding. Additional impact otrabotannogo solution for fiber wood pulp provides more complete consumption of chemicals and improves boyhoodparadise properties of the target product.

When carrying out the known method is mandatory increased consumption of chemicals for the impregnation of chips, because under certain temperature and time parameters conditions impregnation (only steep) consumption of chemicals can ensure their availability in sufficient quantities of waste treatment solution.

Increased consumption of chemicals for treatment leads to significant dissolution of the wood components, and thus increased their content in spent impregnating solution. When interacting spent impregnating solution with the fiber obtained after the first stage of grinding, there is a further dissolution of the wood from exposure to residual quantities of sodium hydroxide and sodium sulfite, which ultimately leads to the decrease of the pH of the mass. With the decrease in the alkalinity of the pulp from the spent treating solution of the dissolved part of the organic matter adsorbed on the fiber, thereby increasing the number of substances extractable with spiritosanto. During the processing of the target product in paper or cardboard occurs technological need to increase the alkalinity of the stream, or organic matter, free from fiber, create problems of pitch problems.

New technical result of the proposed technical solution is the reduction R is vanishing chemical impregnation and the enhancement of the mechanical and optical properties of the target product.

Achieved technical result of the fact that in a method of producing wood pulp, comprising the impregnation of wood chips with an alkaline solution of sodium sulfite, the Department spent an impregnating solution, the grinding chips in two stages and chemical treatment of the pulp between refining stages, according to the invention a chemical treatment of the pulp between refining stages carried out with an alkaline solution of hydrogen peroxide at a concentration of mass 14-18% and the final pH of 9.5 to 10.0, and after the second stage of grinding the mass is diluted to a concentration of 3.0 to 5.0% and incubated for 30-60 min until a pH of 7.5 to 8.0.

Chemical treatment of the pulp with an alkaline solution of hydrogen peroxide between refining stages is carried out at 75-85°C for 15-20 minutes

Having specific anatomical structure, hardwoods are not sufficiently suitable for the production of wood pulp thermo-mechanical method compared to coniferous species. Therefore, to obtain wood pulp from wood chips hardwood, particularly aspen, provided for processing its alkali chemicals - sodium hydroxide, sodium carbonate, etc. To stabilize the whiteness of weight and for the development of mechanical properties it is used sodium sulfite.

The combination of sodium hydroxide and sodium sulfite is a main pair of chemicals in obtaining wood pulp from the leaves of the different species. The mechanism of action of their timber the following: sodium hydroxide causes swelling of the wood fibers and partial hydrolysis of its components, sodium sulfite, penetrating deep into the swollen chips, blocks the chromophore group of the lignin, preventing the loss of white, and a simultaneous sulfonation of lignin to improve the mechanical properties of wood pulp. Subsequent passage of the chips through Empresarial plasticized chips easier deformed, compressed and partially destroyed, and exhaust impregnating solution containing sodium hydroxide, sodium sulfite and dissolved organic matter separated out and sent for regeneration.

Partially destroyed chips ground on the primary refiner on individual fibers and fiber bundles. During the subsequent further processing of the pulp with an alkaline solution of hydrogen peroxide is a more in-depth reaction of sodium hydroxide and hydrogen peroxide with wood components of the complex. The presence of fibrous mass traces of sodium sulfite provides a synergistic effect of the interaction of hydrogen peroxide and sodium sulfite. Grind the mixture in the second stage residual hydrogen peroxide enters the pool, where it is diluted with water and at elevated temperature is maintained a certain time.

redlagaemyi way pulping is as follows: chips from aspen wood washed with water to separate from her sawdust and mineral inclusions, dehydrate and served in the apparatus of continuous operation, where the processing of wood chips with an alkaline solution of sodium sulfite. Treatment of wood chips with chemicals should be performed within 25-50 minutes at 50-90°C. After the processing chips are sent to impressiveness, where it is separated from the chip exhaust impregnating solution, and grind on the primary refiner with obtaining fibrous mass concentration of 20-30%. The fiber is mixed with an alkaline solution of hydrogen peroxide, which also includes sodium silicate. Consumption of these following reagents: sodium hydroxide 10-15 kg/t, hydrogen peroxide 15-25 kg/t sodium silicate 15-20 kg/tons Processed at a concentration of 14-18%, at a temperature of 75-85°C for 15-20 min mass grind on the second stage at pH of 9.5 to 10.0. After grinding the fibrous mass is diluted with water to a concentration of 3.0 to 5.0% and incubated for 30-60 min to a final pH of 7.5 to 8.0. Then the mass colout, sorted, concentrated and sent for recycling in paper or cardboard production.

The invention is illustrated by the following examples of its implementation.

Example 1. The method of obtaining wood pulp is as follows. Aspen chips in standard sizes washed with water, dewatered and sent to the office of continuous action, where it is treated with sodium hydroxide when R is the gathering of 15 kg/t and sodium sulfite at the rate of 10 kg/t for 30 min at a temperature of 80° C. Chips after processing in an impregnating apparatus is sent to impressiveness, in which the chip is separated exhaust impregnating solution, and served on the first stage of grinding, the grinding is carried out at a concentration of 30 mass% and the temperature of the mass 95°C. In the fiber introducing an aqueous solution containing hydrogen peroxide in the amount of 15 kg/t sodium hydroxide - 10 kg/t sodium silicate - 15 kg/t, which provides the mass concentration of 18% and a temperature of 85°C. After mixing the pulp with an alkaline solution of hydrogen peroxide it can withstand within 15 minutes after the specified time of mass at pH 9.5 to grind on the second stage of grinding. Milled mass is diluted with water to a concentration of 3.0% and incubated for 30 minutes to pH 7.5, then it colout, sorted, concentrated and examined for the degree of grinding, the content of crude fiber, dirtiness. From mass produce castings weighing 75 g/m2determine physical and mechanical properties. The results of the experiment are given in the table.

Example 2. Method of pulping carried out analogously to example 1. The differences are that in the fiber after the first stage of grinding injected aqueous solution containing hydrogen peroxide in an amount of 20 kg/t sodium hydroxide - 12 kg/t sodium silicate - 17 kg/t, which provides the mass concentration of 16% and a temperature of 80°and vyd ribaut with 17 minutes After this time the mass at a pH of 9.7 grind on the second stage of grinding. Then it is diluted to a concentration of 4.0% and incubated for 40 minutes to a pH of 7.7, then the mass colout, sorted, concentrated and analyzed. The results of the experiment are given in the table.

Example 3. Method of pulping carried out analogously to example 1. The differences are that in the fiber after the first stage of grinding injected aqueous solution containing hydrogen peroxide in a quantity of 25 kg/t sodium hydroxide - 15 kg/t sodium silicate - 20 kg/t, which is the concentration of mass 14%, temperature 75°S, and incubated for 20 minutes. After a specified time of mass at pH of 10.0 grind on the second stage of grinding. After which it is diluted to a concentration of 5.0% and incubated for 60 minutes up to pH 8.0. Then the mass colout, sorted, concentrated and analyzed. The results of the experiment are given in the table.

Example 4 (prototype). Method of pulping carried out analogously to example 1. The differences are that in the fiber after the first stage of grinding injected exhaust impregnating solution in an amount to provide a concentration of 18% and a temperature of 90°C. At this temperature, incubated 10 minutes at the initial processing, the pH of the mass of 10.4, and finish at pH 7.4. Mass passed processing, RA is maliwat at the second stage, dilute with water, sorted, concentrated and analyzed. The results of the experiment are given in the table.

The analysis in the table data indicate that the proposed method of producing wood pulp can significantly improve the physico-mechanical properties of the target product.

So breaking length is increased by 20-22%, and the content of the fires at the same degree of grinding of the investigated mass is reduced by 40-50%. Significantly reduced dirtiness 2.5-2.7 times the finished semi-finished product and increases its white. From the table it is seen that the decrease in the content of the target product substances extracted alcohol-benzol mixture aims to reduce pitch problems on the paper machine in the processing of pulp in the paper.

Literature

1. Published application No. 2004/0069427, A1 D21 3/10, 162/78, publ. 17.06.2004.

2. Patent RU No. 2106447, C1 D21 1/16, D21 9/16, publ. 10.03.1998.

3. A.S. NO. 979554, D21 1/16, publ. 07.12.1982.

Conditions for obtaining and quality wood pulp from aspen
№№ p/pConditions for the processing of mass between refining stagesProcessing mass in the poolThe degree of grinding, °SR ContentBreaking length, mWhite, %Resin %
The consumption of chemicals, kg/tTemperature, °Time minConcentration %pHConcentration %Time minPHbonfires, %Sora, picture 1 m2
H2O2NaOHNa2SiO3
11510158515189,53,0307,5481,39303450761,45
2201217801716the 9.74,0407,7501,210503400761,50
325152075201410,05,0608,0491,2 3500771,38
4 prototypeImpregnating solution901018*10,4/7,4---481,827002900574,32
* pH = the beginning and the end processing of the mass of spent treatment solution.

1. The method of obtaining wood pulp, comprising the impregnation of wood chips with an alkaline solution of sodium sulfite, the Department spent an impregnating solution, the grinding chips in two stages and chemical treatment of the pulp between refining stages, characterized in that the chemical treatment of the pulp between refining stages carried out with an alkaline solution of hydrogen peroxide at a concentration of mass 14-18% and the final pH of 9.5 to 10.0, and after the second stage of grinding the mass is diluted to a concentration of 3.0-5.0% and incubated for 30-60 min until a pH of 7.5 to 8.0.

2. The method according to claim 1, characterized in that between refining stages of chemical treatment of the pulp with an alkaline solution of hydrogen peroxide is carried out at 75-85°C for 15-20 minutes



 

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