Processing technique for residual papermaking black liquor

Abstract

The invention provides a processing technique for residual papermaking black liquor, relating to the processing technique for industrial sewage. The provided processing technique clears the black liquor by leading lignin and glycan in the papermaking black liquor to become inorganic so as to solidify and discharge harmful substances in the black liquor. As to the papermaking black liquor containing the lignin and the glycan, the processing technique in the invention includes the following steps: 1) oxidizing reaction; 2) neutralization and coagulation. Certain quantity of sulfuric acid, ferrous sulfate and hydrogen peroxide is added to the black liquor, and the pH value is adjusted, so as to carry out the oxidizing reaction; then, most of the lignin and the glycan become inorganic, the COD of supernate which is precipitated for 12 to 16 hours is reduced to about 600mg / L, the color of waste water becomes light yellow from dark black, and the chroma is about 80 times. Certain quantity of sodium hydroxide and aluminum sulfate is added to the light yellow supernate so as to carry out the reaction of neutralization and coagulation, the COD of the precipitated water is reduced to lower than 350mg / L, the chroma is lowered to about 16 times, and the water quality is stable and reaches the standard.

Description

technical field [0001] The invention relates to a process for treating industrial sewage, in particular to a process for treating papermaking black liquor with a COD of about 3000-30000 mg / L. Background technique [0002] The COD of the leftover papermaking black liquor is about 3000-30000mg / L, and its main components are lignin and polysaccharides. Lignin is a complex bond type polymer organic matter, the basic structure is phenylpropane, containing phenolic hydroxyl groups, methoxyl groups, etc., which are linked by ether bonds and carbon-carbon bonds. [0003] With the in-depth development of environmental protection work, many small and medium-sized paper mills have been shut down, shut down, merged, and transferred. The papermaking black liquor produced during the normal operation of these paper mills has been stored in natural or artificially excavated low-lying ponds for a long time. Hundreds of thousands of cubic meters, as many as more than one million cubic meters...

AI Technical Summary

Problems solved by technology

[0003] With the in-depth development of environmental protection work, many small and medium-sized paper mills have been shut down, shut down, merged, and transferred. The papermaking black liquor produced during the normal operation of these paper mills has been stored in natural or artificially excavated low-lying ponds for a long time. Hundreds of thousands of cubic meters, as many as more than one million cubic meters, have not been effectively treated, forming a series of hidden dangers of environmental pollution, especially in rainy seasons: continuous rainfall may cause black liquor in the pond to overflow, pollute the surrounding environment, and destroy Nearby water bodies, farmland, fish ponds, etc.

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