Treatment method of papermaking black liquor

Abstract

The invention relates to a treatment method which is suitable for papermaking black liquor (in particular to alkaline pulping papermaking black liquor which takes wheat straw hood as raw material). The treatment method comprises the following steps of: firstly performing standing treatment on the fresh black liquor, adding a high-efficient alkaline separation agent into the black liquor after treatment, separating out lignin, and further performing biological strengthening technical treatment on filtrate. According to the process disclosed by the invention, after the combined treatment of thestanding treatment, an alkaline separation method and a biological strengthening system is performed on the black liquor with initial COD (chemical oxygen demand) of 83,000mg / l, pH of 13.1 and chromaticity of 225,000CU, the COD and chromaticity of outlet water are respectively reduced to below 15% and 7% of the original black liquor (namely the COD total removal rate and chromaticity total removal rate of the whole system are about 85% and 93% respectively), the outlet water can be mixed with a quite large quantity of middle-stage wastewater in a papermaking factory, and the treatment can be performed according to the existing comparatively mature middle-stage wastewater treatment method. The process has the characteristics of low investment and operation cost and capability of recycling the lignin, and is suitable for wheat straw pulp papermaking factories above 5000 tons.

Description

technical field [0001] The invention relates to a treatment method suitable for papermaking black liquor (especially alkaline pulping and papermaking black liquor with wheat straw as raw material). Background technique [0002] Paper industry wastewater accounts for about 10% of the total industrial wastewater in the country, and the pollution to my country's water resources and environment is becoming more and more serious. The papermaking black liquor produced in the pulping process is an important source of pollution in the papermaking industry. At present, there is no good treatment process for the black liquor of alkaline pulping and papermaking. Alkali recovery method is the most mature treatment method for papermaking black liquor at this stage, but it is more suitable for wood pulp and papermaking, not suitable for the treatment of wheat straw pulp black liquor The reasons are: 1. Due to the high viscosity and short fibers, it is difficult to extract the black liquo...

AI Technical Summary

Problems solved by technology

At present, there is no good treatment process for the black liquor of alkaline pulping and papermaking. Alkali recovery method is the most mature treatment method for papermaking black liquor at this stage, but it is more suitable for wood pulp and papermaking, not suitable for the treatment of wheat straw pulp black liquor The reasons are: 1. Due to the high viscosity and short fibers, it is difficult to extract the black liquor, resulting in low black liquor recovery rate and high alkali recovery cost. 2. Due to the high viscosity, it is difficult to spray the black liquor in the furnace, and the black liquor The dispersion of the liquid is poor, and the lignin content in the solid matter of the black liquor is low, which brings difficulties to the combustion of the black liquor

Therefore, most papermaking enterprises discharge the cooking black liquor without treatment or incomplete treatment, resulting in serious environmental pollution and becoming a major problem restricting the development of the papermaking industry.

[0003] Traditional papermaking black liquor treatment technologies mainly include chemical methods, physical chemical methods and biological methods, or a combination of these methods. Chemical methods and physical chemical methods will cause secondary pollution due to improper treatment, and cannot achieve pollution control. The ultimate purpose limits its application in papermaking black liquor treatment

In recent years, a lot of research has been carried out on the biological treatment technology of straw pulp black liquor in China, and some achievements have been made. Some technologies have passed the pilot test, but the traditional biological treatment technology generally has the following defects when applied to black liquor treatment: 1. The pH of the black liquor is high, and the pH needs to be adjusted before entering the biological treatment unit; 2. Some high-concentration salt ions in the black liquor are toxic to bacteria, such as Na + ;3. Black liquor contains tannin and other substances that are toxic to microorganisms. Traditional biological methods can only deal with diluted or detoxified black liquor; 4. The lignin dissolved by alkaline cooking is difficult to biodegrade, and most microorganisms cannot degrade and use lignin

Conventional biotechnology treatment methods are not good for black liquor treatment

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