Treatment of the filtrate after bleaching the pulp with hydrogen peroxide

 

Processing relates to a method of bleaching cellulose and can be used in the pulp and paper industry. Cellulose is subjected to stage bleaching with hydrogen peroxide, after which it is washed and the wash liquid after washing is separated from the pulp in the form of a filtrate. Then the filtrate is treated with a compound of aluminum to precipitate interfering substances. The precipitated material is removed from the filtrate. The content of aluminum in the filtrate after precipitation of interfering substances establish the largest 20 parts per thousand, and the filtrate is then sent for recycling on stage peroxide bleaching. The technical result is to reduce the consumption of hydrogen peroxide on stage peroxide bleaching. 9 C.p. f-crystals, 3 tables.

Description text in facsimile form (see graphic part).

Claims

1. The method of bleaching cellulose in which the cellulose is subjected to a stage of bleaching peroxide, after which the pulp is washed and the washed liquid after washing is separated from the pulp in the form of a filtrate, wherein the filtrate is treated with a compound of aluminum to precipitate interfering substances, saidabout most 20 ppm, and the filtrate is then sent for recycling on stage peroxide bleaching.

2. The method according to p. 1, characterized in that the filtrate, recirculating stage peroxide bleaching, includes connection, which together with aluminum contains alkaline earth metal.

3. The method according to p. 2, characterized in that the alkaline earth metal is magnesium.

4. The method according to p. 3, characterized in that the molar ratio of SB:A1 is 3:1 to 6:1.

5. The method according to p. 3 or 4, characterized in that the compound containing aluminum, is hydrotalcite General formula

[Mg1-xAlx(OH)2]x+[(CO3)x/2ĚnH2O]x-,

where to 0.10<x<0.34, n=1-3x/2.

6. The method according to any one of paragraphs.1-5, characterized in that the filtrate is treated with a compound of aluminum selected from the group consisting of aluminum chloride, aluminum nitrate, aluminum sulfate, chloride of polyalanine, nitrate of polyalanine and sulphate of polyalanine.

7. The method according to any one of paragraphs.1-6, characterized in that the filtrate is treated with a compound of aluminum, which is added to the filtrate in a quantity at least sufficient to basically precipitate interfering substances.

8. The method according to p. 7, characterized in that the compound of aluminium is added to the filtrate in the amount of 1 - 600 mg A1/l filter the application of aluminum is carried out at pH 4 - 11.

10. The method according to any one of the preceding paragraphs, characterized in that the processing of the filtrate connection of aluminum is carried out at a temperature in the range 60 - 100C.

 

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1 tbl, 9 ex

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1 tbl, 17 ex

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2 cl, 1 tbl

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2 tbl, 11 ex

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2 cl, 1 tbl, 4 ex

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2 cl, 17 ex, 16 tbl

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1 tbl, 7 ex

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1 tbl, 3 ex

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