Improved preparation technology of white mud calcium carbonate for papermaking filler

Abstract

The invention relates to an improved preparation technology of white mud calcium carbonate for a papermaking filler. The improved preparation technology comprises the following steps of: firstly, pretreating a turbid green liquor from a combustion section by using fine milk of lime, and then adding causticized milk of lime for causticization to obtain an alkali recovery white mud suspension liquid; introducing the white mud suspension liquid into a white mud pre-coating machine or a vacuum pulp washer for separating white mud and white liquor, washing the white mud, and then sieving to remove large granular coarse residues; introducing industrial liquid CO2 into the washed and coarsely sieved white mud suspension liquid for carrying out deflocculation and secondary carbonization; and finally adding a decolorizer for reaction, and sieving to obtain the white mud calcium carbonate. The improved preparation technology has the advantages that the fine milk of lime is used for pretreating the green liquor and enabling solid matters in the green liquor to be cooperatively precipitated in a precipitation generation process, so that the impact of the solid matters on the whiteness of the white mud is eliminated; and colored matters formed by non-ferrous metal ions introduced by the causticized milk of lime are reserved in the causticized white mud, and the causticized white mud is bleached to remove the color after secondary carbonization, so that the whiteness of the white mud is increased, and the refining of the white mud calcium carbonate for the papermaking filler is realized.

Description

technical field [0001] The invention relates to high-value utilization of white mud recovered from wheat straw pulping alkali, in particular to an improved preparation process of white mud calcium carbonate for papermaking filler. Background technique [0002] 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. Because it contains a certain amount of water, it is called white mud. The annual production of white mud in my country's paper industry exceeds 4 million Ton. As a residue from the alkali recovery process, lime mud contains a large amount of CaCO 3 , also contains a small amount of alkaline substances and other ingredients. Since the silicon content of grass raw materials is much higher than that of wood raw materials, the silicon content of alkali recovery lime mud from grass materials is high, and the quicklime after calcination is easy to harden, ...

AI Technical Summary

Problems solved by technology

However, in this way, the S in the causticizing reaction system is firstly consumed 2- , so that there is no Na in the generated white liquor 2 S, affects the secondary pulping effect of white liquor; at the same time, this method will produce sulfur in the green liquor, so that the green liquor will become a white emulsion, which is not conducive to the washing of white mud after causticizing, and the production Difficult to operate