RU2321696C1 - Cellulose manufacturing process - Google Patents

Abstract

FIELD: paper-and-pulp industry.

SUBSTANCE: invention is directed to manufacture fibrous intermediate products from agricultural wastes originating from groats and grain crop (straw and fruit coats) processing. Cellulose manufacturing process is conducted in two steps. In the first step, preliminarily milled annual plants are treated with NaOH solution having concentration 20-60 g/L at temperature not lower than 70°C during at least 20 min. Cellulose-containing raw material is then separated from alkali solution. In the second step, pulping is conducted with mixture of peracetic acid, acetic acid, and hydrogen peroxide at weight ratio (1.25-1.75):1.0:(0.25-0.75), respectively, used in amount 0.3-1.0 g per 1 g bone-dry raw material in presence of stabilizer selected from organic phosphonate series, namely organophosphonate mixture containing sodium nitrilotrimethylenephosphonate and sodium methyliminodimethylenephosphonate salts as major components. Stabilizer is added in amount 0.005-0.02% based on the weight of bone-dry raw material.

EFFECT: extended resource of raw materials, improved quality of desired product, and thereby enabled manufacture of high-quality cellulose products and reduced expenses on industrial-scale cellulose manufacture.

6 cl, 4 tbl

Description

The invention relates to the field of pulp and paper production, can be used to obtain fibrous semi-finished products from agricultural waste processing cereals and cereals (straw, fruit shells).

A widely known method of producing cellulose from annual plants by alkaline cooking in an aqueous solution of caustic soda and sodium sulfide at a temperature of 150 ... 160 ° C under pressure in one stage [Yu.N. Nepenin Cellulose Technology, vol. 2, M.: Forestry, 1990]. However, this method does not allow the processing of cellulose-containing raw materials with a high content of mineral components (SiO ₂ ). This is due to the fact that during cooking SiO ₂ passes into the solution in the form of poorly soluble silicates by reaction (1), which leads to a significant decrease in the quality of the product, as well as to the appearance of silicate deposits on the surfaces of technological equipment by reaction (2).

Closest to the proposed is a two-stage method for producing cellulosic material, according to which the cooking process is carried out by alkaline treatment of crushed plant material at an elevated temperature in two stages at different pH. [Pazukhina G.A. Stepwise pulp production methods. M .: Forest industry, 1990, 216 p.]. It should be noted that even with this method of producing cellulose, the issue of mineral components contained in the initial plant material is not resolved, since in an alkaline environment, SiO ₂ passes into solution in the form of sparingly soluble silicates by reaction (1), and in acidic silicic acid is formed it does not dissolve in the cooking solution, but remains in the cellulosic material, thus increasing the ash content, worsening delignification and, as a result, leading to a deterioration in consumer properties.

The objective of the invention is to improve the quality of the resulting cellulosic material (increasing whiteness) while increasing the yield of the target product, expanding the raw material base and reducing the consumption of chemicals for production.

The problem is achieved in that in the method of producing cellulose from pre-crushed vegetable raw materials, carried out by cooking the raw materials in two stages: the first stage of cooking is carried out in an alkaline medium, followed by separation of the cellulose-containing raw materials from the alkaline solution, the second stage of cooking of cellulose-containing raw materials is carried out in an acidic environment, According to the invention, annual plants are used as plant materials, and the second cooking stage is carried out with a mixture of peracetic acid, acetic acid and hydrogen peroxide. and a mass ratio of 1.25 ... 1.75: 1: 0.25 ... 0.75, respectively, in the presence of a stabilizer, a stabilizer is a mixture of organophosphonates containing the sodium salt of nitrile trimethylene phosphonic acid (3) and the sodium salt of methyl iminodimethylene phosphonic acid ( four). A mixture of peracetic acid, acetic acid and hydrogen peroxide is introduced in an amount of 0.3-1.0 g / g of absolutely dry raw materials. At the first stage, cooking is carried out in a NaOH solution with a concentration of 20 ... 60 g / l at a temperature of at least 70 ° C and a duration of at least 20 minutes. The stabilizer is introduced in an amount of 0.005 ... 0.02% by weight of absolutely dry raw materials. As a mixture of organophosphonates, an inhibitor of mineral salt deposits (IOMS) is used. As annual plants, waste from the processing of cereals and cereals in the form of straw and fruit shells is used.

The used mixture of organophosphonates is known as an inhibitor of the deposition of mineral salts (IOMS) and is commercially available according to TU-2434-369-05763441-2003.

The inventive method allows to increase the yield of the target product, reduce the consumption of chemicals, improve the quality of the final product due to the preliminary removal of silicon-containing compounds and stabilization of peroxide compounds IOMS during cooking of plant materials.

The claimed method is illustrated by the following examples.

Processing the feedstock with an alkaline solution

During treatment with an alkaline solution, the structure of the natural polymer swells and loosens, which ensures a deeper interaction with the components of the cooking solution in the subsequent stages while removing silicon-containing compounds.

As the cellulose-containing raw materials, rice straw (SiO ₂ content _of 11.5%), oat straw (SiO ₂ content _of 4.5%) and fruit shells of rice grains (SiO ₂ content _of 15.0%) were used. Cellulose-containing raw materials were treated with alkali (10-60 g / l) at 50-100 ° C for 20-120 minutes.

The content of SiO ₂ in the feed after the treatment was determined by the standard method gravimetrically [GOST 9428-73. Reagents: Silicon (IV) oxide]. The results are presented in table 1.

To determine the optimal conditions (corresponding to the removal of more than 90% SiO ₂ ) pulping was carried out. Silicon dioxide was removed at a concentration of 40 g / l, a temperature of 90 ° C and a duration of 60 minutes (examples 19, 31, 37).

Cooking raw materials treated with an alkaline solution

Optimization of the composition of the cooking solution

The process of cooking raw materials (straw of rice, oats, fruit shells of rice) after alkaline treatment is carried out with a mixture at the following weight ratios of PUK (0.5 ÷ 2), acetic acid (0.5 ÷ 1.5), hydrogen peroxide (0.5 ÷ 1.5). The consumption of PUK for absolutely dry raw materials amounted to 0.7 g per 1 g of absolutely dry raw materials.

In a thermostatically controlled round-bottom flask equipped with a reflux condenser and a stirrer, 10 g (in terms of absolutely dry state) of the plant raw material treated (in accordance with examples 19, 31, 37) of the plant material are placed, and poured with a cooking solution. Cooking is carried out at a temperature of 90 ° C, for 90 minutes Then the cellulose is filtered off and washed.

The evaluation criteria for the resulting product are the yield in percentage of the feedstock, the lignin content (GOST 10070), whiteness (GOST 7690).

The cooking results are presented in table.2.

Table 2. The influence of the ratio of the components of the cooking composition on the quality of the resulting pulp Example No. The ratio of the components of the cooking composition PUK: CH ₃ COOH: H ₂ About ₂ Exit, % White,% Residual lignin,% Rice straw (treatment with alkaline solution in accordance with example 19) 40. 1.75: 1: 0.25 74.8 89.7 3.2 41. 0.5: 1.5: 1 86.5 66.0 6.2 42. 1: 1: 1 81.6 79.0 6.0 43. 1.5: 1: 0.5 76,2 90.0 3.4 44. 1.25: 1: 0.75 78,2 92.3 3,5 45. 2: 0.5: 0.5 73.6 91.5 3.0 Straw oats (siliconized in accordance with example 31) 46. 1.75: 1: 0.25 66.7 84.0 2.0 47. 0.5: 1.5: 1 75,4 65.0 5,0 48. 1: 1: 1 70.5 80.5 4.9 49. 1.5: 1: 0.5 68.1 85.0 2.2 fifty. 1.25: 1: 0.75 69.2 87.2 2,4 51. 2: 0.5: 0.5 64.6 89.5 1.9 Rice fruit shells (siliconized according to Example 37) 52. 1.75: 1: 0.25 65.5 76.0 3.0 53. 0.5: 1.5: 1 68.6 70.5 8.5 54. 1: 1: 1 68.0 80.5 7.9 55. 1.5: 1: 0.5 67.5 76.5 3.2 56. 1.25: 1: 0.75 68.1 79.5 3.3 57. 2: 0.5: 0.5 64,2 80.5 2.9

From the data presented in table 2, it is seen that the desired result is achieved with a mass ratio of components of 1.25 ... 1.75: 1: 0.25 ... 0.75 (examples 40, 43, 44, 46, 49 , 50, 52, 55, 56). Changing the ratio between the components of the reaction mixture either worsens the performance of the cellulosic material (examples 41, 42, 47, 48, 53, 54), or does not lead to improvement (examples 45, 51, 57).

PUK consumption optimization

The process of cooking raw materials (straw of rice, oats, fruit shells of rice) after treatment with alkali is carried out with a mixture of PUA, acetic acid, hydrogen peroxide with an optimal mass ratio of 1.5: 1: 0.5. The consumption of the composition (in terms of PUK to absolutely dry raw materials) ranged from 0.2 ... 1.5 g per 1 g of absolutely dry raw materials, the cooking temperature was 90 ° C, and the duration was 90 minutes. In a thermostatic round-bottom flask equipped with a reflux condenser and a stirrer, place 10 g (in terms of absolutely dry state) of the vegetable raw material treated with an alkaline solution, pour in a cooking solution, based on the consumption of PUK 0.2 ... 1.5 g per 1 g absolutely dry raw materials. Cooking is carried out at a temperature of 90 ° C for 90 minutes Then the cellulose is filtered off and washed. The results are presented in table.3.

Table 3 The influence of cooking conditions on the quality of the pulp Example No. PUK consumption,% Exit, % White,% Residual lignin,% Rice straw 58. 0.8 74,4 95.0 2.0 59. 0.7 76,2 90.0 3.4 60. 0.5 88.7 86.0 3,5 61. 0.3 92.1 86.5 3,7 62. 0.2 96.0 70.0 4.2 Oats straw 63. 0.8 65.1 89.0 1.7 64. 0.7 68.1 85.0 2.2 65. 0.5 69.5 84.5 2,5 66. 0.3 70.6 81.5 3.2 Rice fruit shells (husk, husk) 67. 1,5 56.6 80.5 2,5 68. 1,0 60,2 79.0 2,8 69. 0.9 64.5 78.5 3.0 70. 0.7 67.5 76.5 3.2 71. 0.5 72.3 70.0 4.0

According to the data in Table 3, the optimal flow rate of the composition (in terms of PUK to absolutely dry raw materials) is 0.3-0.7 for rice straw (examples 59-61), 0.5-0.7 for oat straw (examples 64, 65), for the fruit shells of rice 0.7-1.0 g per 1 g of absolutely dry raw materials (examples 68-70). An increase in the consumption of the composition according to PUK does not lead to an improvement in the quality of the fibrous material (examples 58, 63, 67), and a decrease in the flow does not allow to obtain the fibrous material of the desired quality (examples 62, 66, 71).

Organophosphonate flow rate optimization

The process of cooking silica-free raw materials (rice straw, oats, rice fruit shells) is carried out with a mixture of PUA, acetic acid, hydrogen peroxide in a mass ratio of 1.5: 1: 0.5. The consumption of the composition (in terms of PUK to absolutely dry raw materials) for rice straw 0.3-0.7 g (examples 59-61), for straw oats 0.5-0.7 g (examples 64, 65), for fruit rice shells 0.7-1.0 g per 1 g of absolutely dry raw materials (examples 68, 70), cooking temperature 90 ° C, duration 90 minutes

In a thermostatically controlled round-bottom flask equipped with a reflux condenser and a stirrer, 10 g (in terms of absolutely dry state) of the vegetable raw material treated with an alkaline solution are placed, poured with a cooking solution, heated, at the end of cooking, the cellulosic material is filtered off and washed. The results are presented in table 4.

Table 4 The effect of organophosphonate consumption on the quality of cellulose Example No. PUK consumption,% Organophosphonate consumption,% Exit, % White,% Residual lignin,% Rice straw 72. 0.7 0.005 76.3 91.0 3.2 73. 0.01 78,2 94.0 3.0 74. 0.02 78.6 94.5 2.9 75. 0.5 0.01 89.5 90.0 3.2 76. 0.3 0.01 94.1 88.5 3,7 77. 0.2 0.01 93.8 88.2 3.8 Oats straw 78. 0.7 0.005 68.6 87.5 2.2 79. 0.01 69.9 89.0 1.8 80. 0.02 70.0 90.0 1.7 81. 0.5 0.01 70.5 88.5 1.9 82. 0.3 0.01 71.6 86.5 2.0 Rice fruit shells (husk, husk) 83. 1,0 0.005 65.3 79.0 2.9 84. 0.01 67.5 80.5 2,8 85. 0.02 67.8 81.2 2,8 86. 0.7 0.01 69.5 79.5 3.0 87. 0.5 0.01 74.3 77.0 3.2

As can be seen from the table, the use of organophosphonate in an amount of 0.01% to absolutely dry raw materials can significantly increase the delignifying ability of the cooking solution (examples 73, 79, 84). An increase in the consumption of organophosphonate does not lead to an improvement in the results (examples 74, 80, 85), and a decrease in the consumption does not allow to achieve the desired effect (examples 72, 78, 83). It should be noted that the use of organophosphonate allows to reduce the consumption of the composition (in terms of PUK to absolutely dry raw materials) for cooking without compromising the quality of the resulting product (examples 77, 82, 87).

Using the proposed method allows to expand the raw material base of the feedstock used for pulping, improve the quality of the resulting target product and, as a result, provides the opportunity to obtain high-quality pulp and paper products, reduce the cost of producing pulp on an industrial scale.

Claims (6)

1. The method of producing cellulose from pre-crushed plant material by cooking it in two stages, the first stage of cooking is carried out in an alkaline medium, followed by separation of the cellulose-containing raw materials from the alkaline solution, the second stage of cooking of cellulose-containing raw materials is carried out in an acidic environment, characterized in that as a vegetable The raw materials are used in annual plants, and the second stage of cooking is carried out with a mixture of peracetic acid, acetic acid and hydrogen peroxide in a mass ratio of 1.25-1.75: 1: 0.25-0.75, respectively, at utstvii stabilizer, as stabilizer, a mixture of organophosphonate containing nitriltrimetilenfosfonovoy acid sodium salt and sodium salt metiliminodimetilenfosfonovoy acid. 2. The method according to claim 1, characterized in that the mixture of peracetic acid, acetic acid and hydrogen peroxide is introduced in an amount of 0.3-1.0 g / g of absolutely dry raw materials. 3. The method according to claim 1, characterized in that in the first stage, cooking is carried out in a NaOH solution with a concentration of 20-60 g / l at a temperature of at least 70 ° C and a duration of at least 20 minutes 4. The method according to claim 1, characterized in that the stabilizer is introduced in an amount of 0.005-0.02% by weight of absolutely dry raw materials. 5. The method according to claim 1, characterized in that the inhibitor of mineral salts is used as a mixture of organophosphonates. 6. The method according to claim 1, characterized in that as annual plants use waste processing of cereals and cereals in the form of straw and fruit shells.