The method of obtaining wood pulp

 

(57) Abstract:

Use: in the manufacture of bleached wood pulp from deciduous or coniferous wood chips for subsequent use in various compositions for the manufacture of paper and cardboard products. The inventive wood chips coniferous or deciduous species are razvlecheniy in the presence of an alkaline solution containing hydrogen peroxide, sodium hydroxide, sodium silicate and complexing agents, hydrogen peroxide take colcheste 20 - 40% of its total consumption. After razvlechenija in the resulting mass is injected hydrogen peroxide in the amount of 60 - 80% of its total consumption, and stand her in the reactor at a temperature of 70 - 90oC for 30 - 60 minutes Then the mass is washed, concentrated to the desired concentration and subjected to resolu. table 1.

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

A method of obtaining wood pulp, when the chips during grinding is subjected to steamboat sodium hydroxide, sodium silicate and complexing agents. The flow of each of these components in percentage terms is: hydrogen peroxide from 0.2 to 5%, sodium hydroxide, from 1 to 2% of sodium silicate from 1 to 8% and complexing agents from 0.05 to 1% (all by weight of the absolutely dry fiber). Immediately after grinding fibrous mass is diluted with water to a concentration of 2 - 4% and passes through the stages of sorting, cleaning and thickening. Processing wood flails in the zone refining alkaline solution of hydrogen peroxide can improve boyhoodparadise the properties of the finished weight as white, and mechanical strength [1].

However, this method is not without disadvantages. Since the reaction of the bleaching zone refining passes in seconds, that a minor breach of the ratio of consumption of bleaching reagents leads to a negative effect on the whiteness of the finished mass. In addition, for a short period of time exposure of alkaline reagents in a single phase on the wood components, albeit at a high temperature in the zone refining, fiber fibrillose insufficient, and therefore the mechanical strength of the mass increases insignificant.

Closest to the proposed ways is the containing hydrogen peroxide, sodium hydroxide, sodium silicate and complexing agents, exposure of the mass in the reactor, flushing mass, thickening and subsequent grinding [2].

The essence of this method lies in the fact that wood chips are served at the primary refiner refining, where it is separated into individual fibers and fiber bundles (stage razvlechenija). The obtained fibrous mass is mixed with an alkaline peroxide solution containing: hydrogen peroxide, sodium hydroxide, sodium silicate, and complexing agents. The mass concentration of 15 - 25% is sent to the reactor, where it is left for 0.5 to 2 hours at a temperature of 32 - 96oC. after this time the mass is diluted with water to a concentration of 3 to 4% and serves on the stage of condensation in a dewatering press, where it is thickened to a concentration of about 20% and served on the stage of grinding in the second stage refiner. Milled mass is sorted and sent for the production of paper products.

Processing wood fiber between levels of razvlechenija and grinding using for this purpose alkaline hydrogen peroxide solution has a positive impact on the development boomgaarden properties of the target product. This is manifested in the fact that content is reduced in weight bonfires and took the rather large cost for processing fibers bleaching chemicals, and including hydrogen peroxide and sodium hydroxide, the increase in mechanical strength at rupture length are not strong enough, and the increase of the degree of whiteness is practically absent.

New technical result of the proposed technical solution is to increase the mechanical strength and the degree of whiteness of the target product.

Achieved technical result of the fact that in a method of producing wood pulp, comprising razvlechenie wood chips, processing of fibers with an alkaline solution containing hydrogen peroxide, sodium hydroxide, sodium silicate t complexing agents, exposure of the mass in the reactor, flushing mass, thickening and subsequent grinding, according to the invention, the processing of the specified alkaline solution, put the wood chips in the process of razvlechenija, at this stage razvlechenija hydrogen peroxide charge in the amount of 20 - 40% of total consumption, while the remainder of the hydrogen peroxide in the amount of 60 - 80% injected into the spongy handled a lot before you extract it into the reactor.

Razvlechenie wood refiner is a complex and multifactorial process. To obtain a large number of solid, but enough of fibrillarin is and by steaming the wood chips with live steam the wood components are softened, fibers become more elastic and subsequent separation from each other is less susceptible to cutting and breaking. However, in the process of steaming from the wood components are separated and acetyl metaxylene groups that cause low pH. Add in the area of razvlechenija alkaline reagent designed to remove the acid hydrolysis of wood, caused by the process of steaming. In addition, in an alkaline environment is the gap ether bonds in lignin, which results in a greater degree of elasticity of the fibers, and hence the more their not in damaged condition. The feasibility of using sodium hydroxide under razvlechenija chips is due to the fact that the process of plasticization of wood was due to the swelling of the fibers, and not due to the dissolution of the components of wood. For a short time finding wood in the area razvlechenija, but at a sufficiently high temperature and vigorous stirring, prevails swelling process before the process of dissolution. However, the alkaline environment causes the development of condensation processes in lignin and related loss of whiteness of the target product. Adding a small amount of peroxide water which result in unreasonably increased its consumption. Since a high concentration of hydrogen peroxide and high temperature in the zone of razvlechenija largely contribute to the decomposition of hydrogen peroxide, not allowing the bleaching in the optimal mode, the addition of a significant part of hydrogen peroxide in mass after razvlechenija chips and the subsequent exposure of the mass at moderate temperatures contributes to the course of the bleaching process in the optimal direction.

The proposed method of producing wood pulp is as follows: chips from hardwood washed with water to separate from her sawdust and mineral inclusions and served in a steaming chamber, where it is subjected chips heat treatment with saturated steam at a temperature of 105 - 120oC for 2 - 5 minutes stage heat treatment is preferred, but optional. After heat treatment, the chips are sent to stage razvlechenija in the primary refiner refining, at the same time this serves alkaline solution containing hydrogen peroxide, sodium hydroxide, sodium silicate and complexing agents. The consumption of chemicals is: sodium hydroxide 10 - 30 kg/t of dry fiber.with.in.), sodium silicate 15 - 20 kg/t.with.in., kompleksoobrazovatel total consumption. After razvlechenija the resulting mass is mixed with the rest of the hydrogen peroxide in the amount of 24 - 32 kg/t.with.in., what is 60 - 80% of its total consumption. The resulting mixture is sent to the reactor, where it is maintained at a temperature of 70 - 90oC for 30 - 60 minutes after a specified time the mass is diluted with water to a concentration of 3 to 4% and is pumped to dewatering press, where it is thickened to a concentration of 20 to 25%, and the mass enters the second stage refiner refining. After grinding the mass is sorted, cleaned, analyzed and sent for recycling in paper production.

The invention is illustrated by the following examples:

Example 1. The method of obtaining wood pulp is as follows. Birch chips in standard sizes washed with water and loaded into the steaming chamber, where it is subjected to processing saturated steam at a temperature of 110oC for 3 minutes Steamed chips are served on the stage of razvlechenija in the primary refiner refining, working under pressure. Simultaneously with the chips in the zone refining injected aqueous solution containing sodium hydroxide, sodium silicate, Trilon B and hydrogen peroxide, with the consumption of each of them respectively: 10, 15, is Assu is sent to the cyclone, where it separates pairs and then into the mixer where it is mixed with the rest of the hydrogen peroxide in the amount of 32 kg/t.with.in., that is 80% of its total consumption. The mixture of pulp and alkaline hydrogen peroxide solution fed into the reactor and maintain it at a temperature of 90oC for 40 minutes after the specified time the mass is diluted with water to a concentration of 3% and is pumped to dewatering press, where it is thickened to a concentration of 25%, and fed into the refiner second stage of grinding. The last step of grinding the mass is sorted, cleaned and analysed.

The results of the experiment are shown in table.

Example 2. Method of pulping carried out analogously to example 1. The differences are that under razvlechenija in the zone refining of the primary refiner injected sodium hydroxide in the amount of 20 kg/t.with.S., and of hydrogen peroxide in the amount of 12 kg/t.with.in that 30% of its total consumption. The remaining 70% of hydrogen peroxide, which corresponds to the flow rate of 28 kg/t. S. C., is mixed with an alkaline weight, formed after the stage of razvlechenija.

The results of the experiment are shown in table.

Example 3. The method of obtaining the tree is and the primary refiner injected sodium hydroxide in the amount of 30 kg/t.with.in., that is 40% of its total consumption. The remaining 60% of the hydrogen peroxide in the amount of 24 kg/t.with.in. mixed with alkaline mass, formed after the first stage of grinding.

The results of the experiment are shown in table.

Example 4. (similar). Method of pulping carried out analogously to example 1. The differences are that in the zone refining of the primary refiner enter all the chemicals in full, with the consumption of each of them: sodium hydroxide - 30 kg/t.with.in., sodium silicate - 15 kg/t.with.in., Trilon B - 2 kg/t.with.in., hydrogen peroxide - 40 kg/t.with.in.

The results of the experiment are shown in table.

Example 5 (prototype). The method of obtaining wood pulp is as follows. Birch chips in standard sizes washed with water and loaded into the steaming chamber, where it is subjected to processing saturated steam at a temperature of 110oC for 3 minutes Steamed chips are served on the stage of razvlechenija in the primary refiner refining, working under pressure. The resulting fibrous mass is directed into the cyclone where it is separated pairs, and then into the mixer, where in addition impose a solution containing sodium hydroxide, sodium silicate, Trilon B and per the s and alkaline hydrogen peroxide solution fed into the reactor and maintain it at a temperature of 90oC for 40 minutes after the specified time the mass is diluted with water to a concentration of 3% and is pumped to dewatering press, where it is thickened to a concentration of 25% and serves on the mill in the second stage refiner. Past the grinding mass is sorted, cleaned and analysed.

The results of the experiment are shown in table.

Analysis of the table shows that the proposed method of producing wood pulp can significantly increase the mechanical strength of the target product, breaking length is increased by 15 - 40%, and the content of the fires is reduced more than 3 times. The high content in the mass of fibers of the first fraction of good causes dehydration paper at low tide. Fractional introduction of hydrogen peroxide in the weight helps increase the whiteness of the finished product.

The method of obtaining wood pulp, comprising razvlechenie wood chips, processing spongy mass of an alkaline solution containing hydrogen peroxide, sodium hydroxide, sodium silicate and complexing agents, exposure of the mass and its leaching, thickening and subsequent grinding, characterized in that the processing specified by the alkaline solution is subjected to wood school the total consumption and the rest of the hydrogen peroxide in the amount of 60 - 80% is introduced into spongy processed mass before exposure.

 

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