RU2304647C2 - Cellulose manufacturing process - Google Patents

Abstract

FIELD: pulp-and-paper industry.

SUBSTANCE: invention relates to manufacture of cellulose from vegetable cellulose-containing raw material and can be used to manufacture cellulose from linen material, designed for chemical processing as well as for manufacturing cotton wool and paper. Cellulose-containing material is simultaneously loosened and cleaned and then subjected to grinding, soaking in NaOH solution, cleaning, and pulping. The latter operation is effected in surfactant-containing alkali solution for 1.5-3 h at water duty 1:(5-20). Material is then washed and bleached in H₂O₂ solution, rewashed, squeezed, and dried. According to this invention, before the washing step, material is acidified with nitric acid solution and, before drying, ground. According to another embodiment of invention, material is simultaneously loosened, cleaned, pulped, and then washed. Then follow: bleaching in H₂O₂ solution for 1-2 h at water duty 1:(5-20), rewashing, squeezing, and drying. After bleaching material is acidified and, before drying, ground.

EFFECT: simplified process and improved environmental safety.

6 cl, 2 tbl, 10 ex

Description

The invention relates to the pulp industry, in particular to the production of cellulose from vegetable cellulose-containing material, and can be used for the production of cellulose from flaxseed raw materials intended for chemical processing, production of cotton wool, in the paper industry, etc.

A known method of producing cellulose from cereal plants, which consists in the fact that plant cellulose-containing raw materials are cut into pieces 3-4 cm long. The cross-section is uniformly sprayed with a 15-40% NaOH or KOH solution with a 2: 5 hydromodule and mixed thoroughly. The mass is loaded into a closed container and treated with compressed air. Washed with water, dried. The cellulose yield is 46.2% (JP No. 52-6362, CL 39 A 4, 1977).

However, in a known manner it is impossible to obtain high-quality cellulose from flaxseed raw materials with a high yield of the target product.

There is also known a method of producing cellulose by loosening plant materials, alkaline cooking using NaOH, surfactant, T = 120-130 ° C for 1 hour, washing with 1-5 times the amount of clarified water, hydrocyclone treatment with clarified water, grinding, fine hydrocyclone treatment with clarified water, 2-fold NaOCl bleaching at pH 9-11.5, Т = 90 ° С for 1 hour, washing with 2-fold softened water, acidification with H ₂ SO ₄ solution at 15-40 ° С within 1 hour, rinsing with softened water, spin, air drying (Permanent technolo Regulation No. 4-2 “Production of cellulose ethers and esters”, approved on January 18, 1995 by the general director of Engelsky AOOT Khimvolokno).

The disadvantages of this method are: the alkaline cooking process in harsh conditions - at a temperature of T = 120-130 ° C, a pressure of 2-3.5 atm, the use of sodium carcinogen for bleaching and scarcity of cotton raw materials.

The closest analogue is the method of producing cellulose, including the mechanical processing of cellulose-containing material by simultaneously loosening and cleaning it, cooking in an alkaline solution at a temperature of 130-140 ° C under a pressure of 3-4 atm. for 180-210 min, washing, bleaching in an acidic solution with sodium hypochlorite, pressing, loosening and drying (RU 2078163, CL D04H 1/02, publ. 1997).

The basis of the present invention is the task of creating an effective economical method of producing cellulose suitable for chemical processing, through the use of autoclave-free low-temperature alkaline cooking and reducing environmental damage due to the rejection of chlorine-containing bleaching reagents.

The technical result is to simplify the process and increase its environmental safety.

This technical result is achieved by the fact that in the method of producing cellulose by simultaneously loosening and cleaning the cellulose-containing material, cooking in an alkaline solution, washing, bleaching, washing, drying, according to the invention, after simultaneous loosening and cleaning, grinding, hardening in a NaOH solution and cleaning are carried out, cooking is carried out in an alkali solution for 1.5-3 hours with a hydromodule 1: (5-20), containing an additional surfactant, bleaching is carried out in a solution of H ₂ O ₂ , and extraction is performed before drying. After bleaching, acidification is carried out in an acid solution. Before drying, grinding is carried out.

This technical result is also achieved by the fact that in the method of producing cellulose by simultaneously loosening and cleaning the cellulose-containing material, cooking in an alkaline solution, washing, bleaching, washing and drying, according to the invention, the cooking is carried out in an alkaline solution additionally containing surfactant for 1, 5-3 hours with a hydraulic module 1: (5-20), bleaching is carried out in a solution of H ₂ O ₂ for 1-2 hours with a hydraulic module 1: (5-20), and before drying, spin. After bleaching, an acid solution is carried out. Before drying, the material is crushed.

Flax raw materials are used as cellulose-containing material: flax flax according to GOST 10330-76, or short flax fiber according to GOST 9394-76.

The process according to claim 1 of the claims is carried out using the apparatuses and chemicals described below as follows.

Loosening and cleaning of flaxseed raw materials is carried out simultaneously using balers of types SRTSK, GRP to remove mechanical impurities, weeds, coarsened stems, flowers, seeds and aero cyclone to remove dust.

Coarse grinding is carried out using a multi-disc mill type MMDR-379 to a fiber size of 5-9 mm.

Lock the crushed raw materials in a solution containing NaOH with a concentration of 0.3-1.0 g / l in circulating water for 0.25-2.0 hours at a temperature of 20-80 ° C. The hydraulic module is 1: (5 ÷ 20).

Thin hydrocyclone purification of a 0.5-2.0% suspension of raw materials in a NaOH solution with a concentration of 0.3-1.0 g / l and using recycled water is carried out on hydrocyclones of the type GTs-70 and GTs-100. The pressure of the suspension at the entrance to the hydrocyclones 4.0 ± 0.2 kg / cm ² . This cleaning helps to separate the bonfire from the mass of fiber.

Cooking in an alkaline solution is carried out by maintaining the purified and ground raw materials in a solution containing 10-30 g / l NaOH and 0.5-2.0 g / l surfactant at a temperature of 95-105 ° C for 1.5-3, 0 hours The hydraulic module in this operation 1: (5 ÷ 20).

As surfactants use syntanol - ALM-10 - monoalkyl ether of polyethylene glycol based on higher synthetic fatty alcohols according to TU 6-14-864-88.

The spent alkaline solution, together with the non-cellulose components of flaxseed raw materials dissolved in it, is separated from flaxseed by decantation for possible reuse.

The pulp is washed in softened water to remove alkali residues from the pulp. The operation is carried out in 2 stages by aging in containers with water at a temperature of 80-90 ° C for 0.3-0.5 hours in the first stage and 40-50 ° C for 0.3-0.5 hours in the second stage . The hydraulic module during flushing is 1: (5 ÷ 20) at each stage.

Flax bleaching is carried out in a solution of hydrogen peroxide with a concentration of 2-10 g / l at a temperature of 75-95 ° C for 1-2 hours. Hydraulic module - 1: (5 ÷ 20).

Rinsing from the bleaching solution is carried out with softened water in the same way as when washing after an alkaline cooking operation.

The spin operation is carried out on centrifuges such as AG or AOG.

The drying of cellulose is carried out by feeding flax pulp with a moisture content of 60-80% together with a drying agent in a two- or three-armed airborne dryer.

The dried cellulose is fed into a cyclone to separate it from the air and then onto the packaging.

According to claim 1 after bleaching the pulp, if necessary, to reduce the mass fraction of ash, an acid operation is carried out in an acid solution with a concentration of 1-7 g / l at a temperature of 75-95 ° C for 1-2 hours and fed to washing with softened water in 2 stages, as described above. Sulfuric or nitric acids are used as the acid.

According to claim 2 washed wet cellulose, if necessary, is additionally crushed in a multi-disc mill to the required fiber size and fed to an air dryer.

The process according to claim 4 of the claims is carried out using the apparatuses and chemicals described below as follows.

Loosening and cleaning of crushed flaxseed with a fiber length of 2-4 mm is carried out simultaneously with the help of bale feeders of types SRTSK, GRP to remove mechanical impurities and aero cyclone to remove dust.

Cooking in an alkaline solution is carried out by keeping the purified and ground raw materials in a solution containing 10-20 g / l NaOH and 0.5-2.0 g / l surfactant, at a temperature of 95-105 ° C for 1.5-3, 0 hours The hydraulic module in this operation is 1: (5 ÷ 20).

The spent alkaline solution, together with the non-cellulose components of flaxseed raw materials dissolved in it, is separated from flaxseed by decantation for possible reuse.

The pulp is washed in softened water to remove alkali residues from the pulp. The operation is carried out in 2 stages by aging in containers with water at a temperature of 80-90 ° C for 0.3-0.5 hours in the first stage and 40-50 ° C for 0.3-0.5 hours in the second stage . The hydraulic module during flushing is 1: (5 ÷ 20) at each stage.

Flax bleaching is carried out in a solution of hydrogen peroxide with a concentration of 2-10 g / l at a temperature of 75-95 ° C for 1-2 hours. Hydraulic module - 1: (5 ÷ 20).

Rinsing from the bleaching solution is carried out with softened water in the same way as when washing after an alkaline cooking operation.

The spin operation is carried out on centrifuges such as AG or AOG.

The drying of cellulose is carried out by feeding flax pulp with a moisture content of 60-80% together with a drying agent in a two- or three-armed airborne dryer.

The dried cellulose is fed into a cyclone to separate it from the air and then onto the packaging.

According to claim 5, after bleaching the cellulose, if it is necessary to reduce the mass fraction of ash, an acid operation is carried out in an acid solution with a concentration of 1-7 g / l at a temperature of 75-95 ° C for 1-2 hours and fed to washing with softened water in 2 steps, as described above. Sulfuric or nitric acid is used as the acid.

According to claim 6, the washed wet cellulose, if necessary, is additionally crushed in a multi-disc mill to the required fiber size and fed to an aerial dryer.

To prove the conformity of the claimed method to the criterion of "industrial applicability" we give specific examples of the method.

Example 1

500 kg of unpacked flax raw materials with a degree of taperedness of up to 30% in layers are fed to a 22 kW drum type cultivating machine with a capacity of 800 kg / h, where they are shredded and removed by random mechanical impurities, litter, seeds, earth, and dust is removed using an aero cyclone.

Purified flax raw materials are fed to a multi-disk mill MMDR-379 (power 10 kW, capacity 25 tons / day) for fiber grinding to 5-9 mm.

Then the crushed flaxseed is soaked in a vertical cylindrical container with a volume of 10 m ³ in a NaOH solution with a concentration of 0.5 g / l in recycled water at a temperature of 20-30 ° C for 1 hour. The hydraulic module is 1:10.

Next, the mass is fed into a mixing tank with a volume of 10 m ³ to create a suspension with a concentration of 4-6 g / l by dilution with circulating water.

A suspension of crushed raw materials by a mass pump (productivity - 470 m ³ / h) is fed to a thin hydrocyclone treatment carried out according to a three-stage scheme. At the first stage, the cleaning is carried out in a hydrocyclone GTs-70 (productivity - 140 l / min). The pressure of the suspension at the inlet to the hydrocyclone is 4 ± 0.2 kgf / cm ² .

The concentration of the suspension of raw materials at the outlet of the hydrocyclone HZ-70 is 4-6 g / l, the concentration of the suspension of waste 15-20 g / l. A suspension of purified raw material after the first stage of purification is fed into a mixing tank, and then at a concentration of 4-6 g / l - by a mass pump into a hydrocyclone of the second stage of purification of the GC-100 (capacity - 100 l / min). The pressure is 1.2-1.8 kgf / cm ² . The concentration of the suspension at the outlet of the second-stage hydrocyclone is 4-6 g / l, the concentration of the suspension of the waste is 20 ± 5 g / l.

The purified suspension of raw materials from the second stage of purification is returned to the mixing tank and then, at a concentration of 4-6 g / l, the mass pump is fed into the hydrocyclone of the third stage GC-100. The pressure of the suspension at the inlet to the hydrocyclone of the third stage of purification is 1.7 ± 0.2 kgf / cm ² . The concentration of the suspension at the outlet of the 3rd stage of purification is 2.5-3.5 g / l.

The cleaned flaxseed by the mass pump is fed into a 10 m ³ cooking tank and subjected to alkaline cooking in a solution containing 15 g / l NaOH and 1 g / l syntanol ALM-10 at a temperature of 100 ° C for 2 hours. The hydraulic module of the cooking process is 1:20.

At the end of alkaline cooking and separation of the spent solution, flaxseed pulp is washed twice in a container of 10 m ³ with softened water for 30 minutes at a temperature of 85 ± 5 ° C and for 30 minutes at a temperature of 35 ± 5 ° C. The hydraulic module is 1:20.

Next, washed flaxseed pulp is placed in a container of 10 m ³ with a solution of hydrogen peroxide concentration of 5 g / l for bleaching at a temperature of 90 ° C for 1.5 hours. The hydraulic module during bleaching is 1:20.

Bleached cellulose is washed with softened water in a container of 10 m ³ volume, first for 30 minutes at a temperature of 85 ± 5 ° C, then for 30 minutes at a temperature of 35 ± 5 ° C. The hydraulic module at both stages of this flushing operation is 1:20.

The flax pulp suspension is fed by a mass pump to a horizontal centrifuge (capacity 900 kg / h). Cellulose is squeezed to a moisture content of not more than 80%.

The drying of cellulose is carried out by feeding flax pulp together with a drying agent in a two- or three-apron air dryer. The temperature of the drying agent supplied to the dryer is 250-400 ° C. The two-room aeropontane dryer operates under a vacuum of 300-400 mm of water. Art. The diameter of each glass is 3000 mm, the height is 4700 mm, the temperature in the first glass is not higher than 160 ° C, in the second - not higher than 140 ° C. The dried cellulose is fed into a cyclone to separate it from the air and then onto the packaging. Cellulose is obtained in a yield of 66%, with an ash content of 1.2%.

Example 2

The conditions are the same as in example 1. The difference is that in order to reduce the mass fraction of ash in the pulp, acidification is introduced after the bleaching operation. The acidification operation is carried out in a container with a volume of 10 m ³ in a solution of nitric acid with a concentration of 5 g / l at a temperature of 90 ° C for 1.5 hours. The hydraulic module is 1:20. After washing with softened water in two stages according to the conditions of Example 1, cellulose is obtained with a yield of 62% and an ash content of 0.1%.

Example 3

The conditions are the same as in example 2, but alkaline cooking is carried out with a NaOH content of 30 g / l. In this case, cellulose is obtained in a yield of 62%, with a mass fraction of α-cellulose of 96.2%, and a dynamic viscosity of 17.47 mPa · s.

Example 4

The conditions are the same as in example 2, but alkaline cooking is carried out for 4 hours. In this case, cellulose is obtained with a yield of 61%, with a mass fraction of α-cellulose - 95.8%.

Example 5

Acidification is carried out under the same conditions as in example 2, only sulfuric acid is used instead of nitric acid. Replacing acid with sulfuric acid makes it possible to obtain cellulose with a yield of 64%.

Example 6

The conditions are the same as in example 1. The difference is that to reduce the flow of water and chemicals, the hydraulic module in all operations is 1:10. In this case, cellulose is obtained with a yield of 67%, mass fraction of α-cellulose - 96%, dynamic viscosity of 200 MPa · s.

Example 7

The conditions are the same as in examples 1-6. The difference is that before drying, the resulting cellulose is additionally crushed in a multi-disc mill MMDR-379 (power 10 kW, capacity 25 tons / day). Cellulose is obtained with a yield of 61-63%, fiber length up to 5 mm.

The technological parameters of obtaining flax pulp and indicators of its quality are given in tables 1 and 2.

Table 1 Technological parameters of the method Units Examples and parameter values one 2 3 four 5 6 1. Alkaline cooking using: - caustic soda g / l fifteen fifteen thirty fifteen fifteen fifteen - syntanol ALM-10 g / l one one one one one one Temperature ° C one hundred one hundred one hundred one hundred one hundred one hundred Duration h 2 2 2 four 2 2 Hydraulic module 1:20 1:20 1:20 1:20 1:20 1:10 2. Bleaching in a solution of hydrogen peroxide g / l 5 5 5 5 5 5 Temperature ° C 90 90 90 90 90 90 Duration h 1.5 1.5 1,5 1,5 1,5 1,5 Hydraulic module 1:20 1:20 1:20 1:20 1:20 1:10 3. Acidification using: - nitric acid g / l - 5 5 5 - - - sulfuric acid g / l - - - - 5 - Temperature ° C - 90 90 90 90 - Duration h - 1,5 1,5 1,5 1,5 - Hydraulic module - 1:20 1:20 1:20 1:20 - Exit % 66 62 62 61 64 67

table 2 Name of quality indicator of flax pulp Units Examples and parameter values one 2 3 four 5 6 1. Mass fraction of α-cellulose % 96.5 97 96.2 95.8 95.5 96 2. Dynamic viscosity MPa · s 270 23.83 17.47 16 106 200 3. Mass fraction of ash % 1,2 0.1 0.3 0.2 0.1 0.1 4. White % 75 72 72 72 73 70

Example 8

200 kg of unpacked flax raw materials with a fiber length of 2-4 mm are fed to a drum-type cultivating machine with a capacity of 22 kW and a capacity of 800 kg / h, where they are subjected to shredding and removal of random mechanical impurities, litter, seeds, earth and dust.

The purified flax raw materials are fed into a mixing tank with a volume of 10 m ³ to create a suspension with a concentration of 4-6 g / l by dilution with circulating water.

Then, the suspension of the purified flaxseed raw material by the mass pump is fed into a 10 m ³ cooking container and subjected to alkaline cooking in a solution containing 15 g / L NaOH and 1 g / L syntanol ALM-10, at a temperature of 100 ° C for 2 hours. Hydro-module of the cooking process 1:10.

At the end of alkaline cooking and separation of the spent solution, flaxseed pulp is washed twice in a container of 10 m ³ with softened water for 30 minutes at a temperature of 85 ± 5 ° C and for 30 minutes at a temperature of 35 ± 5 ° C. The hydraulic module is 1:10.

Next, washed flaxseed pulp is placed in a container of 10 m ³ with a solution of hydrogen peroxide concentration of 5 g / l for bleaching at a temperature of 90 ° C for 1.5 hours. The hydraulic module during bleaching is 1:10.

Bleached pulp is washed with softened water in a container of 10 m ³ volume, first for 30 minutes at a temperature of 85 ± 5 ° C, then for 30 minutes at a temperature of 35 ± 5 ° C. The hydraulic module in both stages of this flushing operation is 1:10.

A suspension of flax pulp by a mass pump is fed to a horizontal centrifuge (capacity 800 kg / h). Cellulose is squeezed to a moisture content of not more than 80%.

Cellulose is dried by feeding flaxseed pulp together with a drying agent into a double-blown aerial fountain dryer. The temperature of the drying agent supplied to the dryer, 250-400 ° C. The two-room aeropontane dryer operates under a vacuum of 300-400 mm of water. Art. The diameter of each glass is 3000 mm, the height is 4700 mm, the temperature in the first glass is not higher than 160 ° C, in the second - not higher than 140 ° C. The dried cellulose is fed into a cyclone to separate it from the air and then onto the packaging.

The result is cellulose with a yield of 78% and the following physicochemical parameters: mass fraction of α-cellulose - 97%, dynamic viscosity - 100 MPa · s, mass fraction of ash - 0.3%.

Example 9

The conditions are the same as in example 1. The difference is that to reduce the content of the mass fraction of ash in the pulp, acidification is introduced after the bleaching operation. The acidification operation is carried out in a container with a volume of 10 m ³ in a solution of nitric acid with a concentration of 5 g / l at a temperature of 90 ° C for 1.5 hours. The hydraulic module is 1:10. After washing with softened water in two stages according to the conditions of example 1, cellulose is obtained with a yield of 76% and a mass fraction of ash of 0.1%.

Example 10

The conditions are the same as in examples 1, 2. The difference is that before drying, the resulting cellulose is additionally crushed in a multi-disc mill MMDR-379 (power 10 kW, capacity 25 tons / day.). The result is cellulose with a yield of 75-76%, fiber length up to 5 mm.

Analysis of the data in tables 1 and 2, as well as examples 8-10 shows that the proposed method is efficient, simpler and more economical due to the use of autoclave-free low-temperature alkaline cooking and reduction of environmental damage due to the rejection of chlorine-containing bleaching reagents and allows to obtain cellulose with a sufficiently high the yield of the target product suitable for chemical processing in order to further obtain cellulose ethers, cotton wool, paper, cardboard, and is based on the use of available flaxseed raw materials.

Claims (6)

1. The method of producing cellulose by simultaneously loosening and cleaning the cellulose-containing material, cooking in an alkaline solution, washing, bleaching, washing, drying, characterized in that after simultaneous loosening and cleaning, grinding, hardening in a NaOH solution and cleaning, cooking are carried out in an alkali solution within 1.5-3 hours with a hydraulic module 1: (5-20), containing an additional surfactant, bleaching is carried out in a solution of H ₂ O ₂ , and before drying, spin. 2. The method according to claim 1, characterized in that after bleaching, acidification is carried out in an acid solution. 3. The method according to claim 1 or 2, characterized in that before drying, grinding is carried out. 4. The method of producing cellulose by simultaneously loosening and cleaning the cellulose-containing material, cooking in an alkaline solution, washing, bleaching, washing, drying, characterized in that the cooking is carried out in an alkaline solution, additionally containing surfactant, for 1.5-3 hours with a water module 1: (5-20), bleaching is carried out in a solution of H ₂ O ₂ for 1-2 hours with a hydraulic module of 1: (5-20), and extraction is carried out before drying. 5. The method according to claim 4, characterized in that after bleaching, acidification is carried out with an acid solution. 6. The method according to claim 4 or 5, characterized in that before drying the material is crushed.