Method for producing fertilizer from paper-making black liquor

Abstract

The invention discloses a method for producing a fertilizer from paper-making black liquor. The method comprises the following steps of: adjusting strongly alkaline black liquor into weakly alkaline or neutral black liquor with the pH value of between 7 and 9; evaporating and concentrating the black liquor; concentrating the black liquor until the solid content is between 20 percent and 90 percent; and charging the concentrated black liquor into a pelletizer for guniting and pelletizing to produce fertilizer particles. By adopting the method, the black liquor can be treated and purified to produce pure water steam, and organic matters and the like, which are good for crops, in the black liquor can be prepared into the fertilizer, so that the value of the black liquor is brought into full play. Moreover, the process of the method is easy, purification treatment is performed completely, and environmental pollution is avoided. The invention has the characteristics that: 1, investment is small, and the black liquid produced by pulping of wheat straw hood and straw in a small plant is up to standard; 2, purification treatment is performed completely, and environmental pollution is avoided; 3, straw returning is realized, and an ecological economic chain is formed; 4, deforestation caused by paper making is reduced; and 5, a process is simple, and running cost is low.

Description

technical field [0001] The invention relates to a wastewater treatment method, in particular to a method for making fertilizer by using papermaking black liquor. Background technique [0002] In agriculture, wheat straw is mostly treated by returning it to the field. Since the surface of the straw has a smooth waxy layer and a cuticle, it needs to be treated with caustic soda and heating. The treatment cost is relatively high. In the actual operation process, incineration is often used for treatment. Wheat straw, the ash produced by incineration is easy to float into the air, causing pollution to the environment. The development of papermaking technology provides a more economical and effective method for the treatment of wheat straw. High-quality paper can be produced by using wood fibers in wheat straw, but the black liquor produced during the production process has a high pH value of about 12-13, a COD value of 60,000-100,000, and an organic matter content of 10%-30%; I...

AI Technical Summary

Problems solved by technology

High-quality paper can be produced by using wood fibers in wheat straw, but the black liquor produced during the production process has a high pH value of about 12-13, a COD value of 60,000-100,000, and an organic matter content of 10%-30%; If the black liquor is discharged directly, it will cause serious pollution to the environment, so the black liquor needs to be purified before being discharged.

The current purification method mostly adopts the alkali recovery method, which is concentrated first, and then sent to the combustion chamber for fuel injection and combustion, and then limestone is added to react to generate caustic soda. Pulp recovery is better, straw pulp is not effective, and it is still impossible to use a large amount of straw; moreover, burning produces greenhouse gases, and calcium carbonate is produced during caustic soda recovery, causing secondary pollution.

In the traditional method, first do preliminary treatment by means of sedimentation, isolation, etc., and then add microorganisms to the black liquor to generate biogas under the action of microorganisms. During this process, the activity of microorganisms will be affected by environmental temperature changes. Treatment The cycle is long and the purification treatment is not complete

Therefore, most of the papermaking black liquor is discharged directly, causing great damage to the environment

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