Straw pulp bleaching technique

Abstract

The invention discloses a bleaching process with low pollution used for straw pulp by virtue of elemental chlorine-free bleaching agents such as oxygen, chlorine dioxide, hydrogen peroxide and the like. The invention is characterized in that the process comprises the steps as follows: (1) on oxygen delignification section, sealing, sifting and washing are carried out; (2) on chlorine dioxide delignification section, washing is carried out; (3) on alkaline extraction section, washing is carried out; (4) on chlorine dioxide whitening section, washing and papermaking are carried out. The process of the invention is simple and feasible, applicable for reed pulps and the mixed pulp thereof and anaphalis yedoensis, the final brightness of the pulp of the reed pulps (ISO) reaches 78-85%, the brightness stability and the strength are good, and tear index is more than or equal to 8.0mN.m<2> / g; as no elemental chlorine joins the bleaching process, the generation amount of organic chloride during the bleaching process is greatly lowered and the pollution to ecological environment is reduced, thus having obvious social and economic benefits.

Description

Technical field: [0001] The invention relates to a bleaching process for removing lignin from straw pulp, in particular to a straw pulp bleaching process using element-free chlorine bleaching agent. Background technique: [0002] my country is a big producer of straw pulp, and the output of straw pulp accounts for more than half of the world's output. In our country, the bleaching of straw pulp has always been using hypochlorite (H) single-stage bleaching or hypochlorite (HH) two-stage bleaching or chlorine-alkali treatment-hypochlorite (CEH) and other chlorine-containing bleaching. craft. When this process is used for bleaching, the bleaching loss of the slurry is large, the whiteness stability is poor, and it is easy to return to yellow, especially in the bleaching process. Phenols, some are extremely toxic, and even contain very toxic dioxins. These toxic substances are extremely harmful to humans and the ecological environment. Therefore, many countries have imposed str...

AI Technical Summary

Problems solved by technology

Compared with the traditional multi-stage bleaching process, these two bleaching processes have reduced the amount of AOX produced in the bleaching process due to the cancellation of the chlorination stage, but because they both retain the hypochlorite bleaching stage, there is still A considerable amount of elemental chlorine participates in the bleaching reaction, and also produces chloroform, which is carcinogenic. The wastewater discharged by these two bleaching processes still contains certain toxic substances, which are still harmful to the ecological environment.