Method for refining high-purity calcium carbonate from green liquor by causticization

Abstract

The invention provides a method for refining high-purity calcium carbonate from green liquor by causticization. The method mainly comprises the following steps: adding aluminum sulfate to the green liquor, and obtaining concentrated green liquor for later use after flocculation, purification and concentration; digesting selected high-calcium quicklime with hot weak white liquor to generate lime milk, and performing slag removal and purification on the obtained lime milk to obtain high-quality lime milk for later use; adding the obtained high-quality lime milk to the obtained concentrated greenliquor under stirring for causticization reaction; performing solid-liquid separation on causticized slurry to obtain white liquor and white mud, recovering the white liquor as caustic soda liquid, adding sodium carbonate to the white mud washed by hot water for causticization, and performing further oxidizing whitening, acidifying and grinding to obtain high-purity calcium carbonate. High-puritycalcium carbonate prepared with the method does not contain silicon and can be used as papermaking filler, process steps are simple, and the cost is low, so that calcium carbonate has remarkable economic benefits and environmental benefits.

Description

technical field [0001] The invention relates to the field of calcium carbonate produced and recovered by causticizing green liquor in the pulp and paper industry, in particular to a method for refining high-purity calcium carbonate by causticizing green liquor. Background technique [0002] At present, the scale of my country's paper industry is growing rapidly, but "resources" and "environmental protection" have become two important factors restricting the rapid development of the paper industry. Papermaking white mud refers to the precipitated calcium carbonate formed after the causticizing reaction of green liquor and slaked lime in the alkali recovery process. It is called white mud because it contains a certain amount of water. In order to make full use of resources, the recovery process of papermaking soda is equipped with the recycling technology of lime mud, that is, the lime mud is calcined in the converter to obtain quicklime, and then the quicklime is reused in th...

AI Technical Summary

Problems solved by technology

Silicon-containing crude calcium carbonate is difficult to be effectively reused

In the general treatment method, the white mud is transported and buried, resulting in a waste of calcium carbonate resources, and it requires a lot of processing costs and even has the problem of secondary pollution.

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