CN102303885A - Method for refining white clay calcium carbonate from green solution produced in alkali recovery from grass pulp - Google Patents

Abstract

A method for grass pulping soda to recover green liquor and refine white mud calcium carbonate. Quicklime is added to water to digest the quicklime to make a lime solution; add straw pulp green liquor to the lime solution for causticization reaction or add the lime solution to Make white mud calcium carbonate into the straw pulp green liquor. The present invention improves the existing alkali recovery process conditions by studying the alkali recovery mechanism, separates the digestion reaction and the causticization reaction, and controls the reaction conditions so that the appearance of the white mud calcium carbonate produced by the causticization reaction is needle-shaped, so that Calcium carbonate, a by-product of alkali recovery, has high whiteness and uniform crystal form. It can be used for paper filling with high quality, and can partially or even completely replace commercial calcium carbonate, saving pulping enterprises costs and reducing environmental pollution.

Description

A method for recovering green liquor from grass pulping alkali to refine white mud calcium carbonate

technical field

The invention belongs to the field of papermaking industry, and in particular relates to a method for recovering green liquor from grass pulping soda and refining lime mud calcium carbonate.

Background technique

China lacks forest resources, and most pulp mills still use grass raw materials for pulping. In the pulping process, alkali recovery is an essential process, and the process of alkali recovery will produce a large amount of white mud calcium carbonate. The traditional alkali recovery process is to add quicklime directly to the grass pulp green liquor, that is, the digestion reaction and the causticization reaction are carried out simultaneously. The white mud calcium carbonate produced under this technological condition cannot be used for paper filling due to quality problems. Most enterprises can only choose to stack and landfill it, causing secondary pollution.

Contents of the invention

The purpose of the present invention is to provide a white mud calcium carbonate, a by-product of alkali recovery, with high whiteness and uniform crystal form, which can be used for paper filling with high quality, partly or even completely replace commercial calcium carbonate, and save pulping enterprises. The method of recovering green liquor and refining white mud calcium carbonate by grass pulping soda which reduces environmental pollution.

In order to achieve the above object, the technical scheme adopted in the present invention is:

1) adding quicklime into water to react for 10-120min at a reaction temperature of 5-100°C, so that the quicklime is completely digested and made into a lime solution with a mass concentration of 10%-40%;

2) Add 0.02-0.5ml of straw pulp green liquor per gram of quicklime, add grass pulp green liquor to lime solution for causticization reaction; or add 0.01-0.5g of straw pulp green liquor to lime solution Add it into the grass pulp green liquor, the reaction temperature is 10-100°C, and the stirring speed is 100-5000rpm to make white mud calcium carbonate.

The present invention improves the existing alkali recovery process conditions by studying the alkali recovery mechanism, separates the digestion reaction and the causticization reaction, and controls the reaction conditions so that the appearance of the white mud calcium carbonate produced by the causticization reaction is needle-shaped, so that Calcium carbonate, a by-product of alkali recovery, has high whiteness and uniform crystal form. It can be used for paper filling with high quality, and can partially or even completely replace commercial calcium carbonate, saving pulping enterprises costs and reducing environmental pollution.

Description of drawings

Fig. 1 is the scanning electron micrograph of the needle-shaped white mud calcium carbonate prepared by the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Embodiment 1, quicklime is added in water and quicklime is digested and made mass concentration completely and is 10% lime solution; Add 0.02ml straw pulp green liquor by every gram of quicklime, straw pulp green liquor is added in lime solution and causticizing reaction occurs, reaction The temperature is 10°C, and the stirring speed is 5000rpm to make white mud calcium carbonate.

Embodiment 2, quicklime is added in water and quicklime is digested and made mass concentration completely and is 30% lime solution; Add the straw pulp green liquor of 0.08ml by every gram of quicklime, straw pulp green liquor is added in the lime solution and causticizing reaction occurs, reaction The temperature is 50°C, and the stirring speed is 100rpm to make white mud calcium carbonate.

Embodiment 3, quicklime is added in water and quicklime is digested and made mass concentration completely and is 20% lime solution; Add the straw pulp green liquor of 0.3ml by every gram of quicklime, straw pulp green liquor is added in the lime solution and causticizing reaction occurs, reaction The temperature is 80°C, and the stirring speed is 2000rpm to make white mud calcium carbonate.

Embodiment 4, quicklime is added in water and quicklime is digested and made mass concentration completely and is 40% lime solution; Add the straw pulp green liquor of 0.5ml by every gram of quicklime, straw pulp green liquor is added in the lime solution and causticizing reaction occurs, reaction The temperature is 100°C, and the stirring speed is 3500rpm to make white mud calcium carbonate.

Example 5, adding unslaked lime into water to make the unslaked lime fully digested makes a lime solution with a mass concentration of 25%; add 0.01 g of unslaked lime per ml of straw pulp green liquor and add the lime solution to the straw pulp green liquor at a reaction temperature of 30°C , the stirring speed is 500rpm to make white mud calcium carbonate.

Example 6, adding unslaked lime into water to make the unslaked lime fully digested makes a lime solution with a mass concentration of 15%; add 0.2 g of unslaked lime per ml of straw pulp green liquor and add the lime solution to the grass pulp green liquor at a reaction temperature of 60°C , the stirring speed is 1000rpm to make white mud calcium carbonate.

Example 7, adding unslaked lime into water to make the unslaked lime completely digested to make a lime solution with a mass concentration of 35%; adding 0.5 g of unslaked lime per ml of grass pulp green liquor to add lime solution to the grass pulp green liquor at a reaction temperature of 20°C , the stirring speed is 4200rpm to make white mud calcium carbonate.

As can be seen from Figure 1, the present invention separates the digestion reaction and the causticizing reaction, and controls the reaction conditions so that the appearance of the white mud calcium carbonate generated by the causticizing reaction is needle-shaped.

Claims (1)

1. a grass type slurrying alkali reclaims the method that green liquor is made with extra care white mud calcium carbonate, it is characterized in that:

1) unslaked lime is added to make quicklime slaking process mass concentration fully in the entry be the 10%-40% lime solution;

2) the straw pulp green liquor that adds 0.02-0.5ml by every gram unslaked lime is added to the straw pulp green liquor causticizing reaction takes place in the lime solution, and temperature of reaction 10-100 ℃, stirring velocity is that 100-5000rpm processes white mud calcium carbonate; Or by the amount that every ml straw pulp green liquor adds 0.01-0.5g unslaked lime lime solution is joined in the straw pulp green liquor, temperature of reaction 10-100 ℃, stirring velocity is that 100-5000rpm processes white mud calcium carbonate.

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