What is papermaking black liquor? The black liquor component of papermaking black liquor

The wastewater produced by the alkali (caustic soda and sulfate process) pulping process in the paper industry contains a large amount of lignin and is black-brown, so it is called black liquor. Black liquor contains a large number of suspended solids, organic pollutants and toxic substances, and direct discharge into the water body will cause serious pollution.

1. Papermaking black liquor production and utilization].

1. In the pulping process, the raw pulp is squeezed, and the black liquor contains a large amount of lignin. Through the preparation of lignosulfonate products from papermaking black liquor, it can be comprehensively utilized.

2. The comprehensive utilization of papermaking black liquor resources, which is based on black liquor as raw material, through concentration, sulfonation, powder spraying and drying, to produce lignosulfonate products. It is widely used in concrete superplasticizer, coal-water slurry dispersant, asphalt emulsifier, ceramics, oil well mining auxiliary, etc.

Black liquor contains a large number of suspended solids, organic pollutants and toxic substances, and direct discharge into the water body will cause serious pollution. The main hazards are: papermaking wastewater containing a large amount of fiber, pigment and inorganic salts will make the water body black, and have a special foul odor; The biochemical oxygen consumption (BOD) of papermaking black liquor containing high concentration of organic pollutants can be as high as 5000 40000g L, which will consume a large amount of dissolved oxygen in the water and affect the water quality; The large amount of alkaline substances in black liquor will cause the pH value of the water body to rise sharply and destroy the balance of the water environment.

Papermaking black liquor to make lignin] Papermaking black liquor is made into lignin products, which are comprehensively utilized to eliminate the damage to the ecological environment and create an environmentally friendly and natural harmonious development path.

Causes of papermaking black liquor].

The paper mill discharges three streams of water according to the process, one is the pulp cooking waste liquid, commonly known as papermaking black liquor; the second is the washing, sorting and bleaching of pulp after separating black liquor, also known as middle water; The third is the white water on the papermaking machine, which can be reused after treatment. The middle section of water is the part left over from the incomplete extraction of black liquor, which should account for less than 10% of the total amount. The pollutants contained in the black liquor account for more than 90% of the total pollution discharge of the whole plant.

As a result, black liquor emissions are a major source of pollution in paper mills.

Raw materials such as wood chips and straw are boiled and crushed and bleached to become pulp, and the wastewater generated in this process is called papermaking black liquor.

Black liquor contains lignin, hemicellulose, xylose, potassium, nitrogen, phosphorus and other substances, which have high utilization value in industrial and agricultural production.

The characteristics are that it contains various substances, and there is a strong acid or strong alkali in the wastewater (called white water) in the process of papermaking (non-pulping).

Isn't black liquor polluting?

In fact, the waste liquid of pulp should include the black liquor of papermaking, and the so-called "waste" is the unusable product produced in the process of producing the main product. With the continuous improvement of environmental protection requirements, many waste liquids are slowly trying to be used or further processed and filled.

Pulp waste liquid can refer to the liquid produced by the pulp process in the whole process of pulp and papermaking, such as grass washing water, middle water, black liquor, red liquor, papermaking white water, alkali green liquor and so on. Papermaking black liquor is only the waste liquid produced after the reaction in the pulping process. So these two liquids cannot simply be equated.

Different pulp waste liquids have different treatment methods. It needs to be concrete.

The main treatment method of papermaking black liquor is the alkali ** method, in addition, small-scale ones are also used as adhesives and so on.

There is a difference, mainly the pH, alkaline is not easy to use.

Wastewater at different stages of the papermaking process.

Straw and other raw materials used in papermaking raw materials contain cellulose, lignin and hemicellulose (glycans), and papermaking only uses cellulose (about 40%), and about 25% of lignin and about 28% of hemicellulose and xylose, potassium, nitrogen, phosphorus and other substances are discarded with black liquor. The lignin and hemicellulose contained in black liquor, as well as xylose, potassium, nitrogen, phosphorus and other substances, have high utilization value in industrial and agricultural production.