ECF bleaching method for reducing AOX formation amount

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...

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 paper, it consumes chemicals and increases the additional investment of the factory

Some researchers have also adopted the method of adding chlorine dioxide in stages, but the effect is not very satisfactory. Therefore, it is urgent to find an economical and environmentally friendly method to control the formation of AOX under the premise of ensuring paper whiteness and viscosity.