Wheat straw pulp elemental-chlorine-free bleaching wastewater recycling method

Abstract

The invention discloses a wheat straw pulp elemental-chlorine-free bleaching wastewater recycling method which is characterized in that a paper pulp bleaching mode is DQP three-section bleaching, and the whole washing wastewater of pulp from hydrogen peroxide (P) section bleaching is reused, without being processed, in washing pulp from chlorine dioxide (D) section bleaching. The specific method is as follows: after the washing wastewater of pulp from the P section bleaching is reused in the D section bleaching, the pulp is diluted to the washing pulp concentration of 0.5-2%; the pulp is fully mixed and washed and then is concentrated to 15-18%; and the concentrated pulp is diluted with clear water and then is processed in a Q section. The amount of residual bleached chemicals in washing water from the P section is no less than 40%. By the method of directly recycling P-section bleaching wastewater in washing pulp from D-section bleaching without being processed, water consumption during the wheat straw pulp bleaching process and yield of bleaching wastewater can be reduced effectively. In addition, dosage of a bleaching agent can be decreased remarkably, pollution load can be reduced, and performance of the bleached pulp is basically not influenced. Heat energy of wastewater from the P section also can be utilized, and energy consumption of the bleaching section can be reduced effectively.

Description

technical field [0001] The invention relates to a method for recycling waste water from elemental chlorine-free bleaching of wheat straw pulp, in particular to a method in which the washing waste water of wheat straw pulp DQP bleached P-stage bleached pulp is fully reused for washing the D-stage bleached pulp without treatment. Background technique [0002] Wheat straw pulp has always been an important part of raw materials in my country's pulp and paper industry, but the scale of my country's wheat straw pulp production enterprises is generally small, the level of technical equipment and technology is generally low, the level of clean technology is relatively backward, and the pollution load per unit product is relatively high. At present, chlorine-containing bleaching agents are mostly used for bleaching wheat straw pulp, which not only produces high loads of COD Cr 、BOD 5 , and produce carcinogenic and mutagenic adsorbable organic chloride AOX; at the same time, the conc...

AI Technical Summary

Problems solved by technology

At present, there is no relevant process or technology that directly reuses the wastewater from the elemental chlorine-free bleaching of wheat straw pulp to the washing process water in the previous bleaching section without treatment.

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