Method for bleaching natural color pulp

Abstract

The invention discloses a method for bleaching natural color pulp. The method adopts the bleaching flows of oxygen delignification (O), alkali extraction (E), ozone bleaching (Z) and hydrogen peroxide bleaching (P), wherein the oxygen delignification can be divided into single section or two sections; the alkali extraction process can adopt the reinforcing treatment of hydrogen peroxide or oxygen and hydrogen peroxide; and the hydrogen peroxide bleaching section comprises normal-pressure hydrogen peroxide bleaching and oxygen reinforced hydrogen peroxide bleaching. The bleaching flow uses the chemicals such as oxygen, hydrogen peroxide, ozone, alkali and the like, and does not use any chlorine-containing bleaching agent. The bleaching flow of the invention is efficient and simple, and is suitable for the natural color pulp of various materials of between 5 and 40 kappa valences. The obtained bleached pulp can be used for making various paper. The waste water produced by the method has no AOX, and can be directly recycled to a washing or digesting section of the natural color pulp. The method improves the product quality and production efficiency, reduces the energy consumption, has strong environment friendliness, obviously reduces the production cost, and has remarkable economic benefit and social benefit.

Description

technical field [0001] The invention relates to a method for bleaching natural color pulp in the field of pulp and papermaking. Background technique [0002] As we all know, pulping and bleaching is the most polluting section in the papermaking industry. Different pulping and bleaching methods are often used, and the degree of pollution varies. At present, cooking and pulping black liquor can achieve better pollution control effect through alkali recovery; however, there is still no good treatment method for bleaching wastewater; especially for bleaching wastewater containing elemental chlorine bleaching method. Because it contains a large amount of organic halides (AOX), especially dioxins, furans and other substances with teratogenic and carcinogenic effects, it is difficult to treat wastewater, the treatment cost is high, and the pollution is serious and long-lasting after direct discharge or simple treatment. . The use of advanced, low-pollution or non-polluting bleach...

AI Technical Summary

Problems solved by technology

Compared with the single-stage hypochlorite bleaching method and the CEH method, this method has higher production efficiency and better pulp quality; since elemental chlorine is not used, the pollution is reduced; Chlorine, the system control is more difficult, prone to explosion, and the production risk is greater; and because chlorine dioxide inevitably contains a certain amount of elemental chlorine (chlorine gas), the AOX in the bleaching wastewater still contains more dioxins and Furans, dioxins, and furans have teratogenic and carcinogenic effects on organisms, and these substances accumulate in organisms and can be transferred; therefore, this method is severely restricted by production costs, investment costs, and environmental protection.