Processing method of paper-making pulping black liquor

Abstract

The invention discloses a processing method of paper-making pulping black liquor, and the method comprises polycondensation, acid precipitation, aging, precipitation, solid-liquid separation and drying of the pulping paper-making black liquor, and in the black liquor, the solid phase which mainly comprises lignin and the liquid phase which mainly comprises sodium salt solution are separated; and the Baume degree of the black liquor is larger than or equal to 15 Be degrees. The method has simple process, low cost and wide application range. The obtained lignin can be used as multiple industrial and agricultural raw materials; the chroma, CODcr and BOD5 of the obtained liquid phase are greatly reduced.

Description

Technical field [0001] The invention relates to the field of chemical engineering, in particular to a method for treating black liquor in papermaking and pulping. Background technique [0002] The plant raw materials used for papermaking are mainly composed of cellulose, lignin and polysaccharides. Among them, cellulose is the effective component of papermaking, accounting for about 40% of the plant raw materials; lignin and polysaccharides accounting for about 60% of the plant raw materials %, it is separated into waste liquid in the papermaking pulping process. The papermaking waste liquid formed by alkaline pulping is black liquor, which includes separated lignin, polysaccharides, and residual alkali and water. The black liquor from different plant sources has a CODcr concentration between 15,000 and 500,000 mg / L, and lignin and its degradation products account for about 50% of the total CODcr. If the black liquor is directly discharged without effective treatment, it will n...

AI Technical Summary

Problems solved by technology

However, the alkali recovery method for processing black liquor has huge investment, high maintenance and operation costs, and the combustion process causes the emission of greenhouse gas carbon dioxide and produces a large amount of secondary pollutants—white mud; the purity of lignin separated by acid analysis is low, and waste Acid is easy to cause secondary pollution. When the precipitated lignin particles are small, especially when there is interference from silica gel in straw pulp, reed pulp, and bagasse pulp, it is difficult to wash, filter, and separate lignin; Lignin has the disadvantages of introducing impurities (flocculant), large amount of resin, loose lignin precipitation, and difficult separation operation; membrane separation method has the disadvantages of small water flux, low retention rate, small processing capacity, chroma, CODcr, BOD 5 The removal rate still needs to be improved; the biological method is generally only suitable for the treatment of CODcr and BOD 5 Relatively low dilute black liquor, high operating costs, strict operating conditions, and available lignin, polysaccharides and other organic substances are basically biochemically decomposed, and resources cannot be effectively utilized