ECF bleaching method for reducing AOX formation amount

A bleaching tower and weight technology, applied in pulp bleaching, textiles and papermaking, papermaking, etc., can solve the problems of unsatisfactory effect, increase of additional investment, consumption of chemicals, etc., to reduce content, reduce pollution, and save usage Effect

Inactive Publication Date: 2015-03-04
GUANGXI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, there are many ways to reduce the formation of AOX in the pulp ECF bleaching process, mainly adding chemicals in the bleaching process, including adding hydrogen peroxide, sodium chlorite, sulfamic acid and dimethyl sulfoxide (DMSO), etc., these Although the method can effectively reduce the AOX content in the bleaching wastewater and ensure the quality of the

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0015] ECF bleaching methods to reduce AOX formation:

[0016] 1. Pretreatment of unbleached pulp with hemicellulase:

[0017] The washed and screened unbleached bagasse pulp is sent to the pretreatment bleaching tower for enzyme pretreatment. The process conditions are: the temperature is 40°C, and the enzyme dosage is 100IU / g 浆 , the reaction pH value is 9, and the reaction time is 90 minutes to obtain bagasse slurry after hemicellulase pretreatment.

[0018] 2. ECF bleaching of bagasse pulp in the presence of chlorine dioxide, sodium hydroxide, hydrogen peroxide and potassium sulfide:

[0019] In the traditional ECF bleaching process D 0 E. p D. 1 Add potassium sulfide in the alkali extraction section of the step 1, and send the bagasse slurry after the hemicellulase pretreatment in step 1 to the chlorine dioxide bleaching tower for delignification after washing. 0 The amount of chlorine dioxide is 1% of the weight of the bagasse slurry after hemicellulase pretreatment...

Embodiment 2

[0021] ECF bleaching methods to reduce AOX formation:

[0022] 1. Pretreatment of unbleached pulp with hemicellulase:

[0023] The washed and screened unbleached bagasse pulp is sent to the pretreatment bleaching tower for enzyme pretreatment. The process conditions are: the temperature is 50°C, and the enzyme dosage is 150IU / g 浆 , the reaction pH value is 10, the reaction time is 100min, and the bagasse slurry after hemicellulase pretreatment is obtained.

[0024] 2. ECF bleaching of bagasse pulp in the presence of chlorine dioxide, sodium hydroxide, hydrogen peroxide and potassium sulfide:

[0025] In the traditional ECF bleaching process D 0 E. p D. 1 Add potassium sulfide in the alkali extraction section of the step 1, and send the bagasse slurry after the hemicellulase pretreatment in step 1 to the chlorine dioxide bleaching tower for delignification after washing. 0 , the amount of chlorine dioxide is 3% of the bagasse slurry weight after hemicellulase pretreatment;...

Embodiment 3

[0027] ECF bleaching methods to reduce AOX formation:

[0028] 1. Pretreatment of unbleached pulp with hemicellulase:

[0029] Send the washed and screened unbleached bagasse pulp to the pretreatment bleaching tower for enzyme pretreatment. The process conditions are: temperature is 60°C, enzyme dosage is 200IU / g 浆 , the reaction pH value is 11, and the reaction time is 120 minutes to obtain bagasse slurry after hemicellulase pretreatment.

[0030] 2. ECF bleaching of bagasse pulp in the presence of chlorine dioxide, sodium hydroxide, hydrogen peroxide and potassium sulfide:

[0031] In the traditional ECF bleaching process D 0 E. p D. 1 Add potassium sulfide in the alkali extraction section of the step 1, and send the bagasse slurry after the hemicellulase pretreatment in step 1 to the chlorine dioxide bleaching tower for delignification after washing. 0 , chlorine dioxide consumption is 5% of the bagasse slurry weight after hemicellulase pretreatment; p , wherein the a...

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PUM

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Abstract

The present invention relates to an ECF bleaching method for reducing the AOX formation amount. The method is mainly characterized by comprising: (1) carrying out hemicellulase pretreatment on an unbleached pulp, and (2) in the presence of chlorine dioxide, sodium hydroxide, hydrogen peroxide and potassium sulfide, carrying out ECF bleaching on the bagasse pulp. According to the present invention, the hemicellulase pretreatment is performed on the unbleached bagasse pulp so as to remove hexenuronic acid capable of reacting with chlorine dioxide and concurrently remove hemicelluloses, such that the more residual lignin can be exposed; with the addition of potassium sulfide, the sulfur ions can be provided for the alkali extraction stage, the alkali extraction stage can be strengthened, the dissolution of the lignin is easily achieved, it can be ensured that the chlorine dioxide bleaching stage uses the less chlorine dioxide, and the AOX generated during the bleaching process can be reduced; and compared with the traditional ECF bleaching, the bleaching method of the bagasse pulp in the present invention has the following characteristics that: the chlorine dioxide consumption can be saved by 15-20%, and the AOX formation amount can be reduced by 20-30%.

Description

technical field [0001] The invention relates to a pulp bleaching clean production method for pulp and papermaking enterprises, in particular to an ECF bleaching method for reducing AOX formation. Background technique [0002] Pulp and paper companies can achieve the unity of environmental, economic and social benefits by using chlorine dioxide-based elemental chlorine-free (ECF) technology to bleach pulp. North America has fully completed the process of converting from conventional chlorine bleaching to ECF bleaching, and other regions are also converting from elemental chlorine bleaching to ECF bleaching. However, the ECF bleaching process still generates a small amount of adsorbable organic halides (AOX). AOX is the main persistent organic pollutant (POPs) in the ECF bleaching process, which is toxic, bioaccumulative and semi-volatile, and is difficult to degrade. Long-distance migration can occur. With the improvement of society's environmental requirements, the polluti...

Claims

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Application Information

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IPC IPC(8): D21C9/10D21C9/14
CPCD21C9/144D21C9/1026D21C9/1036
Inventor 聂双喜王双飞姚双全宋雪萍覃程容
Owner GUANGXI UNIV
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