Cellulose bleaching process

FIELD: pulp-and-paper industry.

SUBSTANCE: unbleached sulfate cellulose obtained from hardwood is subjected oxygen-alkali delignification, after which treated with chlorine dioxide in presence of oxyethylidenediphosphonic acid and then consecutively hydrogen peroxide and chlorine dioxide solutions. Process may be used in production of bleached fibrous intermediates.

EFFECT: increased whiteness and strength characteristics of cellulose and improved environmental safety of bleaching process.

2 cl, 1 tbl

 

The invention relates to a method of bleaching cellulose and can be used in the pulp and paper industry in the production of bleached fibrous semi-finished products.

There is a method of bleaching pulp, comprising the stage of oxygen-alkali delignification (CSD), processing pulp Trilon B or other complexing agents, treatment of pulp with hydrogen peroxide and chlorine dioxide (möller L. the Possibility of reducing the content AOH in the effluent. Bleaching pulp without elementary chlorine free and totally chlorine-free bleaching. PAPFOR - 93. Plenary reports of the International scientific-technical conference, St. Petersburg, October 4-6, 1993, s-208.)

However, the known method has a number of disadvantages. For processing pulp Trilon B or other complexing agents requires additional equipment (tower, wash the filter, pumps, mixers). In addition, to achieve the required level of white pulp (88-90%) required an increased consumption of chemicals (chlorine dioxide or hydrogen peroxide).

The closest to the technical nature of the present method is a method of bleaching pulp, comprising a stage CSD, combined treatment of pulp with chlorine dioxide and complexing agents (Trilon B), the processing solutions of hydrogen peroxide and chlorine dioxide (EN 2123552, class D 21 C 9/10,op.)

However, this method has significant drawbacks. Upon receipt of cellulose with a high level of whiteness (88-90%) reduced strength properties of pulp (breaking length) and requires increased consumption of hydrogen peroxide or chlorine dioxide.

The technical result is to increase the whiteness and strength properties of cellulose ecologically safe technology of bleaching without the use of molecular chlorine.

This technical result is achieved by a method for bleaching pulp, comprising an oxygen-alkali delignification, combined treatment of pulp with chlorine dioxide and complexing agents, the treatment of pulp with a solution of hydrogen peroxide and chlorine dioxide, according to the invention, after the oxygen-alkali delignification spend processing pulp with chlorine dioxide in the presence of 1-oksietilidendifosfonovaya acid (APC). This acid is added in amounts of 1 to 7 kg/t of pulp.

Example 1

Unbleached sulphate pulp from hardwood after oxygen-alkali delignification (CSD) is treated sequentially with chlorine dioxide in the presence of complexing agents-trylon B, an alkaline solution of hydrogen peroxide and oxygen. The bleaching conditions and indicators of pulp are presented in table 1 (experiment 1).

Example 2

Unbleached sulphate is ellulose of hardwood after CSD treated sequentially with chlorine dioxide in the presence of complexing agents APC with a flow rate of 0.5 to 9.0 kg/t pulp, an alkaline solution of hydrogen peroxide and oxygen. The machining conditions and quality of pulp are presented in table 1 (experiments 2-7).

Comparison of the results of laboratory experiments (table 1) shows that the pulp obtained after bleaching of the proposed method in comparison with the prototype at the same flow rate of complexing agents (2.0 kg/t of pulp), has a higher brightness level (respectively: 87,4 and 88,8%) and rupture length (respectively: 8.4 and 8.8 km). In addition, to maintain pH (2.8 to 3.0) application of DCS in comparison with the prototype allows to reduce the consumption of sulfuric acid at 2.0 kg/t pulp (40%).

The results presented in table 1 show that adding the APC at the stage of processing pulp chlorine dioxide in the range of 1,0-7,0 kg/t of pulp increased white indices and breaking length bleached fibrous semi-finished product. When the consumption of ODS less than 1.0 kg/t of pulp and more than 7.0 kg/t is not marked improvements in data quality indicators pulp.

Thus, the proposed method allows to obtain a pulp with a high (compared to the prototype) brightness level and breaking length.

8,4
Table 1

Improvement in pulp quality when using complexing agents (UEC) is tupeni
pulp bleaching with chlorine dioxide. Indicators of unbleached hardwood pulp: the degree of delignification - 16,3% Kappa; breaking length is 10.1 km
Stage bleaching indicesThe number of experience
1234567
12345678
Step CSD

Temperature is 95°C; the concentration of mass to 8.0%; 90 minutes;
The NaOH consumption, kg/t18,018,018,018,018,018,018,0
The oxygen partial pressure, MPa

at the beginning of the reaction
0,80,80,80,80,80,80,8
at the end of the reaction0,40,40,40,40,40,40,4
The degree of delignification, % Kappa8,48,48,48,48,48,4
Breaking length, km9,59,59,59,59,59,59,5
Level D/Q
Temperature 90°C; the concentration of mass 10%; time 120 minutes
The flow ClO2kg/t (in units of the act. chlorine)26,326,326,326,326,326,326,3
The consumption of H2SO4kg/t5,03,03,03,03,03,03,0
The ODS consumption, kg/t00,51,02,05,07,09,0
Consumption trylon B, kg/t2,00,00,00,00,00,00,0
the pH at the end of the bleaching3,03,03,03,02,82,82,7
Mod. the chlorine content, g/DM3no nononononono
The degree of delignification, % Kappa3,22,72,72,82,72,93,0
White, %to 75.275,075,676,375,575,675,3

Continuation of table 1
12345678
Step soda treatment wash
Temperature 90°; time 120 min, Cm=8%
The NaOH consumption, kg/tto 12.0to 12.0to 12.0to 12.0to 12.0to 12.0to 12.0
The consumption of H2About2kg/t20,020,020,020,020,020,020,0
The oxygen partial pressure, MPa0,20,20,2 0,20,20,20,2
The PH at the end of the bleaching11,9the 11.611,311,7the 11.611,211,2
Mod. The content of NaOH, g/DM30,430,500,540,560,460,490,47
Indicators of cellulose:
White, %87,787,7of 89.1and 88.888,788,988,7
Breaking length, km8,48,48,78,88,89,08,8

1. Method of bleaching pulp, comprising an oxygen-alkali delignification, combined treatment of pulp with chlorine dioxide and complexing agents, processing of cellulose solutions of hydrogen peroxide and chlorine dioxide, characterized in that after the oxygen-alkali delignification spend processing pulp with chlorine dioxide in the presence of 1-oksietilidendifosfonovaya acid.

2. The method according to claim 1, characterized in that 1-oksietilidendifosfonovaya acid is added in amounts of 1 to 7 kg/t of pulp.



 

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FIELD: pulp-and-paper industry, in particular method for pulp whitening.

SUBSTANCE: pulp mass with concentration of 5-10 % after oxygen-alkaline treatment in step I is treated with sulfuric acid in consumption of 5 % based on dry cellulose mass and pH 2.6-3.0. In step II peroxide treatment is carried out in alkali consumption of 1.0-1.3 % based on dry cellulose mass, and in step III pulp is treated with chlorine dioxide in consumption of 1.0-1.6 % based on dry cellulose mass at 70°C.

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1 tbl, 17 ex

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SUBSTANCE: craft pulp mass with concentration of 2.5-5.0 % after oxygen-alkaline treatment is treated with potassium permanganate in consumption of 0.01-0.1 % based on dry cellulose at 40-80°C and pH 1.6-3.0 or with sulfuric acid solution in consumption of 1.0-1.5 % at 90°C for 30 min. In steps II and IV cellulose with concentration of 10 % is treated with hydrogen peroxide in consumption of 2 % based on mass of dry cellulose for 120 min at 80-90°C and pH 9.5-10.5 wherein consumption of sodium alkali and sodium silicate is 1.3 % and 2.5 %, respectively. In step III cellulose is treated with potassium permanganate in consumption of 0.01-0.4 % under step I conditions.

EFFECT: reduced consumption of whitening agents.

1 tbl, 9 ex

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FIELD: pulp-and-paper industry, in particular method for pulp whitening.

SUBSTANCE: pulp mass with concentration of 5-10 % after oxygen-alkaline treatment in step I is treated with sulfuric acid in consumption of 5 % based on dry cellulose mass and pH 2.6-3.0. In step II peroxide treatment is carried out in alkali consumption of 1.0-1.3 % based on dry cellulose mass, and in step III pulp is treated with chlorine dioxide in consumption of 1.0-1.6 % based on dry cellulose mass at 70°C.

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1 tbl, 17 ex

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SUBSTANCE: craft pulp mass with concentration of 2.5-5.0 % after oxygen-alkaline treatment is treated with potassium permanganate in consumption of 0.01-0.1 % based on dry cellulose at 40-80°C and pH 1.6-3.0 or with sulfuric acid solution in consumption of 1.0-1.5 % at 90°C for 30 min. In steps II and IV cellulose with concentration of 10 % is treated with hydrogen peroxide in consumption of 2 % based on mass of dry cellulose for 120 min at 80-90°C and pH 9.5-10.5 wherein consumption of sodium alkali and sodium silicate is 1.3 % and 2.5 %, respectively. In step III cellulose is treated with potassium permanganate in consumption of 0.01-0.4 % under step I conditions.

EFFECT: reduced consumption of whitening agents.

1 tbl, 9 ex

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SUBSTANCE: pulp mass with concentration of 5-10 % after oxygen-alkaline treatment in step I is treated with sulfuric acid in consumption of 5 % based on dry cellulose mass and pH 2.6-3.0. In step II peroxide treatment is carried out in alkali consumption of 1.0-1.3 % based on dry cellulose mass, and in step III pulp is treated with chlorine dioxide in consumption of 1.0-1.6 % based on dry cellulose mass at 70°C.

EFFECT: pulp with increased whiteness.

1 tbl, 17 ex

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