Process for removing silicon in green liquor of papermaking alkali recovery section by seeding

Abstract

The invention provides a process for removing silicon in green liquor of a papermaking alkali recovery section by seeding. The technical scheme of the process is as follows: adding silica crystal micro-particles to the green liqor of the papermaking alkali recovery section, or regulating the pH value of the green liquor to 9-14 by utilizing acid or a carbon dioxidegas, and adding the silica crystal micro-particles to the green liquor; or adding acid to the green liquor in which the silica crystal micro-particles are added, wherein the reaction temperature is 20-100 DEG C, the reaction time is 5-120 minutes, and the pH value of the green liquor at an end point is controlled 7.5-11.5; and after finishing the reaction, and then removing separated silicic acid. In the process, the silica crystal micro-particles are added to the green liquor of the papermaking alkali recovery section, and then the acid or the carbon dioxide gas is added to the green liquor so as to gradually reduce the pH value of the green liquor, thus the silicon separated out from the green liquor grows on silica crystals to produce the particles with larger partical size; and the particles are deposited in and separated out from the green liquor as well as are removed by centrifugal separation or mechanical filter or sedimentation and other modes, thus the rate of silicon removal reaches over 90%.

Description

technical field [0001] The invention belongs to the fields of chemical industry and papermaking industry, and in particular relates to a process for removing silicon by a green liquor seeding method in a papermaking alkali recovery section. Background technique [0002] Due to the shortage of wood resources, my country's papermaking uses a large number of grass materials such as wheat straw, reed, asparagus, and bamboo. However, grass raw materials contain a large amount of elemental silicon, and most of these silicon elements enter into the black liquor during the pulping process. The mud (mainly composed of calcium carbonate) contains a large amount of silicon, which makes the white mud impossible to recycle. Although, some researchers in our country have carried out research on the utilization of lime mud, such as two-step causticization method for silicon removal, causticization white mud calcium carbonate crystal form control, etc., some paper mills have also launched ...

AI Technical Summary

Problems solved by technology

However, grass raw materials contain a large amount of elemental silicon, and most of these silicon elements enter into the black liquor during the pulping process. The mud (the main component is calcium carbonate) contains a lot of silicon, which makes the white mud impossible to recycle.

Although, some researchers in our country have carried out research on the utilization of lime mud, such as two-step causticization method for silicon removal, causticization white mud calcium carbonate crystal form control, etc., some paper mills have also launched green liquor two-step causticization method for silicon removal system and follow-up lime mud recycling devices, but according to the on-site inspection, none of them are really running well, and the lime mud has not been effectively reused. Most enterprises still choose places to bury or pile up the lime mud, which not only wastes resources, but also causes environmental pollution