RU2768635C1 - Method for obtaining flaxseed pulp - Google Patents

Abstract

FIELD: flaxseed pulp production.

SUBSTANCE: present invention relates to a method for producing flaxseed pulp. This method includes mechanical processing of raw materials. After mechanical processing of raw materials, deep mechanical processing is carried out in a cleaner by cleaning it from dust and fire, partial shortening and loosening. Next, two-stage delignification is carried out at a temperature of 100°C by sequential processing of raw materials in an alkaline solution with a concentration of 0.15-0.17 wt.% for 30 min at the first stage and in an alkaline solution with a concentration of 0.25-0.35 wt.% for 30 min in the second stage. Next, oxidative cooking is carried out in two stages, the first stage at a temperature of 100°C for 60 minutes and the second stage at a temperature of 100°C for 120 minutes. At the first stage, the solution for oxidative pulping contains components (wt.%): Trilon B - 0.10-0.20, sodium hydroxide - 0.10-0.20, sodium metasilicate - 0.30-0.45, magnesium sulfate - 0.01-0.05, surfactant OP-10 - 0.40-0.50 and hydrogen peroxide - 1.5-1.9. At the second stage, the solution for oxidative digestion contains components (wt.%): Trilon B - 0.15-0.20, sodium hydroxide - 0.25-0.35, sodium metasilicate - 0.60-0.85, magnesium sulfate - 0.01-0.05, surfactant OP-10 - 0.40-0.50 and hydrogen peroxide - 2.5-3.0. After oxidative cooking, treatment is carried out with a solution of sulfuric acid with a concentration of 0.10-0.20 wt. % at a temperature of 20-25°C for 30 minutes. Washing with water is carried out after each stage of delignification, oxidative digestion and treatment with a sulfuric acid solution. After the first stage of delignification, first washed with water at a temperature of 80°C, then with water at a temperature of 60°C. After the second stage of delignification and the first stage of oxidative cooking, first washed with water at a temperature of 80°C, then with water at a temperature of 40°C. After the second stage of oxidative digestion, it is first washed three times with water at a temperature of 80°C, then with water at a temperature of 60°C, then twice with water at a temperature of 40°C and water at a temperature of not more than 20°C. After treatment with a solution of sulfuric acid, it is washed twice with water at a temperature of 20-25°C, and after pressing and drying, fine loosening is carried out.

EFFECT: development of an effective method for producing flax pulp, which has a lower dynamic viscosity, fiber moisture content and mass fraction of fibrous dust and is suitable in its characteristics for its further use in the manufacture of lacquer colloxylins and gunpowders for civil purposes.

1 cl, 2 tbl, 1 ex

Description

The invention relates to the field of the chemical industry, and in particular to methods for producing flax pulp for the manufacture of varnish colloxylins and gunpowders for civilian use.

A known method for the production of purified cellulose from flax fiber (patent RU No. 2637015, IPC C 08 B 1/08, D 01B 1/10, D 01B 1/14, publ. 29.11.2017, bull. No. 34), including mechanical processing, liquid processing for destroying related impurities, washing with warm water, oxidizing treatment with an alkaline hydrogen peroxide solution containing a stabilizer, first washing with hot water, oxidizing cooking, second washing with hot and warm water, centrifuge pressing, while the liquid treatment for destroying related impurities is performed with hot water at a constant water temperature of 98-100°C for 30 minutes, oxidative treatment and cooking is carried out at a constant value of the silicate modulus and a constant value of the solution temperature of 98-100°C.

The disadvantages of the known method are:

- mechanical cleaning of flax straw, consisting of drying flax straw, a flax-scutching unit (MTA) and a short flax fiber apparatus (AKLV), makes it possible to obtain short flax fiber No. 2 and 3, which contains up to 29% fire and weed impurities, which in turn does not allow to obtain cellulose with an alpha-cellulose index of 98.2% and a wettability of 150 with the described actions;

- the data given in table 1 according to GOST 595 regarding the amount of lignin-containing impurities and the degree of polymerization of cellulose are not reliable, since it is impossible to obtain cellulose with the stated characteristics;

- physical and chemical indicators of cellulose, such as dynamic viscosity, mass fraction of ash, mass fraction of dust, humidity, etc., are not indicated, which does not allow one to fully judge the quality of the product.

The closest is a method for obtaining a cellulose product with maximum alpha-cellulose and an industrial process for its production from short flax fiber (patent RU No. 2703250, IPC C 08 B 1/08, D 21 C 1/06, D 21 C 1/08, D 21 С 9/16, publ. 15.10.2019, bull. No. 29), which includes obtaining a cellulose product from the cotton-like mass of flax by mechanical processing, washing, boiling, delignification, which is carried out by sequential processing of the cotton-like mass of flax in an alkaline solution at a temperature of 50 °C, delignification, which is carried out in an aqueous solution containing sodium hydroxide 5-10 g/l and a surfactant 2.7-2.9 g/l, for 30 minutes at a temperature of 95-100°C, oxidative cooking for 60 minutes at a temperature of 100°C, washing: first with hot water at a temperature of 80°C, then with warm water at a temperature of 40°C, then squeezing, drying, to obtain a linen cellulose product with a mass fraction of alpha-cellulose 98.5 %, mass 0.1% lignin, degree of polymerization above 1100 and dynamic viscosity 228 mPa s.

The disadvantages are:

- insufficient washing of the fiber, which negatively affects the products made on its basis, therefore, the required quality of the resulting product is not achieved;

- grinding of non-oriented fiber after drying does not provide the required fiber length and leads to an increase in the dusty fraction and a decrease in the yield of cellulose;

- it is impossible by this method to obtain in the industry a cellulose product with the claimed characteristics presented in the description.

The technical task is to create an effective method for producing flax pulp by improving the quality of the resulting product through deep processing of raw materials, more complete and high-quality purification from lignin and removal of impurities.

The technical problem is solved by a method for producing flax pulp, including mechanical processing of raw materials, two-stage delignification in an alkaline solution, oxidative pulping, washing, further pressing and drying.

What is new is that after mechanical processing of raw materials, deep mechanical processing is carried out in a cleaner by cleaning it from dust and fire, partial shortening and loosening, two-stage delignification is carried out at a temperature of 100 ° C by sequential processing of raw materials in an alkaline solution with a concentration of 0.15-0.17 wt. % for 30 min at the first stage and in an alkaline solution with a concentration of 0.25-0.35 wt. % for 30 minutes in the second stage, oxidative cooking is carried out in two stages, the first stage at a temperature of 100°C for 60 minutes and the second stage at a temperature of 100°C for 120 minutes, while the solution for oxidative cooking contains components in the following ratio, wt. %:

- at the first stage

Trilon B 0.10-0.20 sodium hydroxide 0.10-0.20 sodium metasilicate 0.30-0.45 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 1.5-1.9

- at the second stage

Trilon B 0.15-0.20 sodium hydroxide 0.25-0.35 sodium metasilicate 0.60-0.85 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 2.5-3.0,

after oxidative cooking, treatment is carried out with a solution of sulfuric acid with a concentration of 0.10-0.20 wt. % at a temperature of 20-25°C for 30 minutes, while washing with water is carried out after each stage of delignification, oxidative digestion and treatment with a solution of sulfuric acid, and after the first stage of delignification, it is first washed with water at a temperature of 80°C, then with water at a temperature of 60 °C, after the second stage of delignification and the first stage of oxidative cooking, first washed with water at a temperature of 80 °C, then with water at a temperature of 40 °C, after the second stage of oxidative pulping, first washed three times with water at a temperature of 80 °C, then with water at a temperature of 60 °C C, then twice with water at a temperature of 40 ° C and water at a temperature of not more than 20 ° C, after treatment with a solution of sulfuric acid, washed twice with water at a temperature of 20-25 ° C, and after pressing and drying, fine loosening is carried out.

To implement the method use:

Trilon B is a 2-aqueous disodium salt of ethylenediamine-N,N,N',N'-tetraacetic acid, which is a white crystalline powder or white crystals, highly soluble in water, very slightly soluble in alcohol (GOST 10652 "Ch ").

Sodium hydroxide NaOH (caustic soda), intended for the chemical, petrochemical, pulp and paper industry, non-ferrous metallurgy and other sectors of the national economy according to STO 00203312-017-2011.

Sodium metasilicate Na ₂ SiO ₃ is the sodium salt of metasilicic acid and is a hydrated sodium silicate. It is a light fine-crystalline powder, easily soluble in water, absorbs carbon dioxide and water in air. The aqueous solution has an alkaline reaction (TU 2611-011-00207787-2003 "Ch").

Magnesium sulfate - inorganic substance MgSO ₄ , white powder, forms several crystalline hydrates (GOST 4523 "HCh").

Surfactant - surfactant OP-10 is a product of processing a mixture of mono- and dialkylphenols with ethylene oxide and used as a wetting and emulsifying surfactant (GOST 8433).

Hydrogen peroxide H ₂ O ₂ is a colorless liquid with a "metallic" taste, unlimitedly soluble in water, alcohol and ether. Concentrated aqueous solutions are explosive. Hydrogen peroxide is a good solvent (GOST 177 grade A).

For treatment with a solution of sulfuric acid H ₂ SO ₄ , sulfuric acid is used, it is a colorless, transparent, oily liquid, odorless, without sediment, miscible with water (with strong heating) and with alcohol (GOST 4304 Kh.Ch.).

The essence of the invention.

As a feedstock for the production of flax pulp for civil use, flax weed in the form of rolls is used, short flax fiber or cottonine (hereinafter referred to as raw materials) can also be used. : it is installed on a roll unwinder, where a roll of linen trust is unwound, the exfoliated layers are fed to the receiving conveyor of the drying machine and dried to the required moisture content.

Dried flax straw through an inclined conveyor enters the flax feeder, where uniform formation of the layer of flax vine stems takes place and is then fed into the thinning mechanism of the apparatus, after which it passes through the crushing machine, during which the destruction and partial separation of the lignified part of the stem - fires. The partially cleaned fiber is transferred to the scutching and cleaning machine, where the cleaning and reduction of the staple length of the fiber takes place. In this way a short flax fiber is obtained. At the exit from the scutching machine, the fiber enters the receiving funnel of the pneumatic transport system and is carried away by the transport fan. The fiber passes through the metal detector through the pneumatic transport system.

After mechanical processing of raw materials, they are subjected to deep mechanical processing in the cleaner - in the pre-cleaner condenser by cleaning it from dust and fire. From the pre-cleaner, the fiber is sent by pneumatic transport to the cleaner, where the fiber is dedusted, subjected to fine loosening, partial shortening, defibration, cleaning, and loosening. Thus, on the line of deep mechanical processing, cottonine is obtained from short flax fiber with a mass fraction of fires and weed impurities of not more than 1%.

From the cleaner, the cottonine is sent by a transport fan through the transport air ducts through the condenser to the stuffing machine, where the fiber is moistened with water, moistened, given a technological shape and formed into the so-called "cakes".

Formed "cakes" from flax fiber, with the help of an overhead crane, are placed in the basket of the apparatus - the carrier of the fiber, the finished basket with Easter cakes is installed in the cooking apparatus - an apparatus for dyeing under pressure with incomplete filling (AKDN). In the AKDN apparatus, chemical treatment of flax fiber (cotonin) is carried out - delignification and oxidative pulping and treatment with sulfuric acid (acidification). Ready cooking solutions prepared in the cooking solution tank are pumped into the working volume of the AKDN apparatus (solutions are in constant circulation). During the treatments, the fibers change the direction of circulation of the cooking liquor.

First, a two-stage delignification (alkaline cooking) is carried out by sequential processing of raw materials in an alkaline solution of sodium hydroxide - NaOH with increasing concentration. The first stage of delignification is carried out at a temperature of 100°C in an alkaline solution of sodium hydroxide NaOH with a concentration of 0.15-0.17 wt. % within 30 min. After the first stage of delignification, washings are carried out with water, first with a temperature of 80 °C for 15 minutes, then with water with a temperature of 60 °C for 15 minutes. The second stage of delignification is carried out in an alkaline solution of sodium hydroxide NaOH at a temperature of 100°C with a concentration of 0.25-0.35 wt. % within 30 min. After the second stage of delignification, washing with water at a temperature of 80 °C for 15 minutes and washing with water at a temperature of 40 °C for 15 minutes are carried out. Carrying out two-stage delignification, increasing the concentration of sodium hydroxide NaOH in the second stage of delignification allows for a deeper and better purification from lignin.

After two-stage delignification, oxidative cooking is carried out in two stages. During the second stage of oxidative digestion, the concentration of reagents (components) of the solution for oxidative digestion increases. Each stage of the oxidative digestion is carried out at a temperature of 100°C, with the first stage for 60 minutes and the second stage for 120 minutes. The solution for oxidative cooking contains components in the following ratio, wt. %:

- at the first stage

Trilon B 0.10-0.20 sodium hydroxide 0.10-0.20 sodium metasilicate 0.30-0.45 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 1.5-1.9

- at the second stage

Trilon B 0.15-0.20 sodium hydroxide 0.25-0.35 sodium metasilicate 0.60-0.85 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 2.5-3.0.

After the first stage of oxidative digestion, rinsing with water at a temperature of 80 °C for 15 minutes and water at a temperature of 40 °C for 15 minutes is carried out. After the second stage of oxidative digestion, washing with water is carried out: first, they are washed three times with water at a temperature of 80 ° C for 15 minutes each, then with water at a temperature of 60 ° C for 15 minutes, then twice with water at a temperature of 40 ° C for 15 minutes each washing and cold water with a temperature not exceeding 20 ° C for 15 minutes.

Carrying out oxidative pulping in two stages with an increase in the concentration of reagents in solutions for oxidative pulping allows for a deeper processing of the fiber, increasing the quality of bleaching while maintaining the dynamic viscosity of the pulp. In this case, a more complete removal of non-cellulose impurities occurs with the prevention of their re-settlement on the fiber.

After the first and second stages of oxidative digestion and washings, treatment is carried out with a solution of sulfuric acid with a concentration of 0.10-0.20 wt. % at a temperature of 20-25°C for 30 minutes. Treatment with a weak solution of sulfuric acid H ₂ SO ₄ is necessary to neutralize the remaining alkali, as well as to dissolve transition and alkaline earth metal ions insoluble in an alkaline and neutral medium. Carrying out this stage makes it possible to obtain cellulose oriented for processing into civilian gunpowder and varnish colloxylins. Further, after treatment with a solution of sulfuric acid, they are washed twice with water at a temperature of 20-25 ° C for 15 minutes each wash.

Fiber processing modes - two-stage delignification, oxidative pulping and sulfuric acid treatment are presented in table 1.

Table 1. Processing modes

No. The name of the operation,
Components Concentration,
% mass Temperature, ^o C Duration, min Pressure, atm one. The first stage of delignification
NaOH 0.15 - 0.17 one hundred thirty no more than 3.6 2. The second stage of delignification
NaOH 0.25 - 0.35 one hundred thirty no more than 3.6 3. First stage of oxidative digestion
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
PAVOP-10
H ₂ O ₂ 0.10 - 0.20
0.10 - 0.20
0.30 - 0.45
0.01 - 0.05
0.40 - 0.50
1.5 - 1.9 one hundred 60 no more than 3.6 4. The second stage of oxidative cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
PAVOP-104
H ₂ O ₂ 0.15 - 0.20
0.25 - 0.35
0.60 - 0.85
0.01 - 0.05
0.40 - 0.50
2.50 - 0.30 one hundred 120 4.0 - 4.2 five. Sulfuric acid treatment
H ₂ SO ₄ 0.10 - 0.2 20-25 thirty -

Multiple washings with water after each stage of delignification, oxidative pulping, as well as treatment with a sulfuric acid solution make it possible to qualitatively rinse the fiber and remove impurities released into the pulping solution, as well as prepare the fiber for the next processing. After the end of the treatments and washings with water, the spent cooking solutions and water from the washings are poured into a storage tank, where neutralization is carried out.

The temperature conditions of fiber processing at the indicated excess pressure, the concentration ranges of the reagents used in the solutions are optimal for removing impurities, refining the fiber, and also preserving the fiber from destruction.

The flax fiber (flax pulp) treated in this way is removed from the AKDN machine using an overhead crane and loaded into a centrifuge to remove water and squeeze.

The squeezed flax pulp is removed from the centrifuge using a cantilever crane and placed on the table of the fiber drying machine, where the cake is loosened and the pulp is dried.

At the exit from the dryer, flax pulp through the belt conveyor enters the mixing conveyor, where fine loosening is carried out.

The pulp is removed from the mixing conveyor by a transport fan and enters the large-capacity mixing station through a metal detector. Further, the pulp is transported by a transport fan to the shaft of a thin ripper, where the pulp is finished to the required length. Then the transport fan, through the condenser is fed to the trolley located on the scales. From the trolley, the pulp is loaded into the horizontal press chamber, where bales are formed. Finished bales of flax pulp are packed and transported to the finished product warehouse.

As the determining parameters in assessing the quality of the resulting product, we used dynamic viscosity h (from 35 and higher), fiber moisture - no more than 10%, and the mass fraction of fibrous dust (no more than 0.6%).

Dynamic viscosity h is an important parameter in obtaining products based on cellulose and derivatives with desired properties, including strength properties, while taking into account the economic aspect in the manufacture of cellulose nitrates. Fiber moisture determines the readiness of pulp for further processing, which in turn affects the economy. The mass fraction of fibrous dust determines the amount of cellulose dust in cellulose, a high dust content negatively affects the processing of cellulose into cellulose nitrates and reduces the product yield. Large dust formation entails additional requirements for fire safety.

The results of the experiments carried out on the proposed method and the closest analogue are shown in Table 2. Multi-stage washing with water was carried out for 15 minutes each: after the first stage of delignification, it was first washed with water at a temperature of 80 °C, then at a temperature of 60 °C; after the second stage of delignification and the first stage of oxidative pulping, they were first washed with water at a temperature of 80 °C, then with a temperature of 40 °C; after the second stage of oxidative digestion, it was first washed three times with water at a temperature of 80 ° C, then with water at a temperature of 60 ° C, twice with water at a temperature of 40 ° C and water at a temperature of not more than 20 ° C (in 1 example - 15 ° C, in 2 example - 18°C, in example 3 - 20°C, in example 4 - 16°C), after treatment with a solution of sulfuric acid, washed twice with water at a temperature of 20-25 °C (in example 1 - 20°C, in example 2 - 25°C, in example 3 - 23°C, in example 4 - 25°C).

As can be seen from table 2, (in terms of dynamic viscosity, fiber moisture, mass fraction of fibrous dust) dynamic viscosity, fiber moisture and mass fraction of fibrous dust of flax pulp by the proposed method is much lower than that of cellulose according to the closest analogue, which indicates the best strength properties and quality indicators of flax pulp according to the proposed method.

The proposed method for producing flax pulp is an effective method that allows obtaining high-quality flax pulp by deep processing of raw materials, more complete and high-quality purification from lignin and removal of impurities, and corresponding in its characteristics for its further use in the manufacture of varnish colloxylins and gunpowders for civil purposes.

Table 2. Experimental results.

No.
example The name of the operation,
Components Concentration,
% wt. Dynam. viscosity,
mPa s fiber moisture,
% Mass fraction of an ox. dust,
% one. First st. delignif. NaOH 0.15 125 6.8 0.2 Second Art. delignif. NaOH 0.25 First st. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.10
0.10
0.30
0.01
0.40
1.5 Second Art. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.15
0.25
0.60
0.01
0.40
2.50 Processing H ₂ SO _{4 ,} 20°C 0.10 2 First st. delignif. NaOH 0.17 64 6.6 0.3 Second Art. delignif. NaOH 0.30 First st. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.18
0.18
0.40
0.03
0.45
1.7 Second Art. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.19
0.30
0.70
0.04
0.47
2.70 Processing H ₂ SO _{4 ,} 25°C 0.15 3 First st. delignif. NaOH 0.16 89 7.0 0.5 Second Art. delignif. NaOH 0.35 First st. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.20
0.20
0.45
0.05
0.50
1.9 Second Art. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.20
0.35
0.85
0.05
0.50
3.00 Processing H ₂ SO _{4 ,} 23°C 0.20 4 First st. delignif. NaOH 0.15 35 7.5 0.6 Second Art. delignif. NaOH 0.30 First st. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.16
0.20
0.40
0.01
0.45
1.9 Second Art. oxide cooking
Trilon B
NaOH
Na ₂ SiO _3
MgSO4
Surfactant OP-10
H ₂ O ₂ 0.20
0.35
0.85
0.05
0.50
3.00 Processing H ₂ SO _{4 ,} 25°C 0.20 five Method according to the closest analogue 228 10 2

Claims (6)

A method for producing flax pulp, including mechanical processing of raw materials, two-stage delignification in an alkaline solution, oxidative pulping, washing, further pressing and drying, characterized in that after mechanical processing of raw materials, deep mechanical processing is carried out in a cleaner by cleaning it from dust and fire, partial shortening and loosening, two-stage delignification is carried out at a temperature of 100°C by sequential processing of raw materials in an alkaline solution with a concentration of 0.15-0.17 wt. % for 30 min at the first stage and in an alkaline solution with a concentration of 0.25-0.35 wt. % for 30 minutes in the second stage, oxidative cooking is carried out in two stages, the first stage at a temperature of 100°C for 60 minutes and the second stage at a temperature of 100°C for 120 minutes, while the solution for oxidative cooking contains components in the following ratio, wt. %: - at the first stage Trilon B 0.10-0.20 sodium hydroxide 0.10-0.20 sodium metasilicate 0.30-0.45 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 1.5-1.9 - at the second stage Trilon B 0.15-0.20 sodium hydroxide 0.25-0.35 sodium metasilicate 0.60-0.85 magnesium sulfate 0.01-0.05 surfactant OP-10 0.40-0.50 hydrogen peroxide 2.5-3.0, after oxidative cooking, treatment is carried out with a solution of sulfuric acid with a concentration of 0.10-0.20 wt. % at a temperature of 20-25°C for 30 minutes, while washing with water is carried out after each stage of delignification, oxidative digestion and treatment with a solution of sulfuric acid, and after the first stage of delignification, it is first washed with water at a temperature of 80°C, then with water at a temperature of 60 °C, after the second stage of delignification and the first stage of oxidative digestion, first washed with water at a temperature of 80°C, then with water at a temperature of 40°C, after the second stage of oxidative digestion, first washed three times with water at a temperature of 80°C, then with water at a temperature of 60°C C, then twice with water at a temperature of 40°C and water at a temperature of not more than 20°C, after treatment with a solution of sulfuric acid, washed twice with water at a temperature of 20-25°C, and after pressing and drying, fine loosening is carried out.