Method for purifying and manufacturing high-purity calcium carbonate by recovering green liquor from pulping alkali

Abstract

The invention provides a method for purifying a pulping alkali-recovered green liquor to prepare high-purity calcium carbonate. The method comprises the following steps of sequentially adding quicklime, talcum powder, an iron shielding agent and an organic polymer flocculant into a turbid green liquor, stirring the mixture uniformly, then conducting standing for a short time, and taking a clear green liquid at the upper layer to obtain a clean green liquor; adding quicklime into the clean green liquor, stirring the mixture for slaking, removing slag to obtain a refined slaking liquid, and further adding hydrogen peroxide for causticization and bleaching to obtain an alkali-recovered white mud suspension; carrying out solid-liquid separation on the alkali-recovered white mud suspension to obtain a white liquid and white mud; making the white mud subjected to washing, acidifying, carbonizing, grinding or sieving and drying to obtain high-purity calcium carbonate with uniform particle size; feeding the white liquid for steaming and boiling. According to the method, rapid flocculation and sedimentation of a green-liquor suspended matter system are achieved by the talcum powder, a high-clarity clear filtrate can be obtained through simple sedimentation, high-purity calcium carbonate can be obtained through causticization, and the method has a significant driving meaning on promotionof the popularization of a white mud solid waste resource utilization technology.

Description

technical field [0001] The invention relates to the technical field of post-treatment of waste generated in the alkali recovery process of the papermaking industry, in particular to a method for purifying and manufacturing high-purity calcium carbonate from green liquor recovered from pulping alkali. Background technique [0002] Green liquor refers to the medicinal solution formed by dissolving the melt recovered in the alkali recovery system in water. The main chemical components are sodium carbonate and sodium sulfide, and contain a small amount of sodium hydroxide and sodium sulfate. The suspended solids in the green liquid are generally called green mud, which is a mixture of aluminum, iron, magnesium, silicon compounds and carbon powder. Because it contains a small amount of ferric hydroxide and ferrous sulfate, it is green, so it is called green liquid. . [0003] If the green liquor is not treated by sedimentation, the green mud will directly enter the turbid liquo...

AI Technical Summary

Problems solved by technology

[0009] Wei Xiang (CN101391794) discloses the method that utilizes papermaking industry alkali to reclaim solid white mud to prepare light mulberry calcium carbonate, the clear green liquor after the steps such as flocculation purification mechanical filtration, can obtain high whiteness through subsequent optimized causticizing process. For the light calcium carbonate of 88 degrees, the mechanical filtration equipment of this method is a filter press or a bag filter, the equipment cost is very high, and it is difficult to adopt in general industry;

[0010] The above-mentioned green liquor purification methods all adopt flocculation filtration as the main method, which has the disadvantages of long settling time and high-cost filtering equipment to achieve the purpose of green liquor purification; in addition, quicklime is used to make milk of lime for causticization reaction technology, the concentration of white liquor produced will be greatly reduced, and it is not suitable for cooking and recycling. These problems make it difficult to apply these technologies in actual production