Method for recovering superfine calcium carbonate by clean causticization of green liquor

A technology of ultra-fine calcium carbonate and activated calcium carbonate, which is applied in the regeneration of lye, can solve the problems of affecting the normal progress of alkali recovery, high content of calcium carbonate impurities, unsatisfactory recovery products, etc., to improve the effect of solid-liquid separation, The effect of uniform particle size and good social benefits

Active Publication Date: 2005-07-20
SHANGHAI DONGSHENG NEW MATERIALS +1
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  • Summary
  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

Due to the high silicon content of the white mud produced when straw pulp black liquor is recovered from alkali, it will accumulate silicon when it is calcined into lime for recycling, forming a vicious cycle of silicon interference, which affects the normal progress of alkali recovery
(2) The white mud is processed by washing, grinding and other processes. The calcium carbonate recovered by this method has a lot of impurities and a whiteness of only about 80, so it can only be used as a low-grade paper-making filler.
There have been many studies on how to control the particle size and shape of the product when passing through kiln gas into lime milk for carbonization to produce calcium carbonate. However, no one has ever studied the size and shape of the product for causticizing green liquor to recover liquid alkali and calcium carbonate. However, there are no satisfactory results on how to effectively control the alkalinity of recovered products when recovering calcium carbonate.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] Add an aqueous solution with a solid content of 3.0% sodium polyacrylate flocculant to a certain amount of green liquor, the amount added is 0.01% of the green liquor, stir and mix, then stand still for 30 minutes and filter, and the clear liquor is used for causticizing reaction.

[0017] Add quicklime into hot water at 50°C, stand still for 15 minutes, and stir for another 15 minutes to obtain calcium hydroxide coarse slurry. The coarse slurry passes through a 200-mesh sieve to remove residue. After the slurry naturally settles, extract the supernatant , to obtain the calcium hydroxide slurry with high solid content in the lower layer. According to the ratio of the theoretical amount of calcium hydroxide to the reaction of sodium carbonate in the green liquor is 1.05, mix them in the causticization reactor, heat up to 90°C under stirring, and add 0.5% crystal form of the theoretical amount of calcium carbonate after 10 minutes of reaction Regulator sodium citrate aque...

Embodiment 2

[0019]After refining the green liquid and calcium hydroxide slurry, mix the two liquids and raise the temperature to 70°C, react at a constant temperature for 15 minutes, then add 1.0% of the theoretical amount of calcium carbonate in an aqueous solution of sodium borate, and continue the reaction for 1 hour, the same as the implementation Example 1 Filtrate and recycle the lye, add the filter cake to clean water and then make a slurry to form a slurry with a solid content of 18%, then pass through the kiln gas at room temperature for secondary carbonization, when the pH value of the suspension drops to about 7 is the end point of the reaction. The product is in the form of flakes, with an average particle size of 0.50 microns and a whiteness greater than 92. The slurry is filtered to obtain a filter cake with a high solid content, which is suitable for making papermaking coatings after dispersion treatment.

Embodiment 3

[0021] After refining the green liquid and the calcium hydroxide slurry, mix the two liquids, add 1.0% sucrose aqueous solution of the theoretical amount of calcium carbonate, raise the temperature to 50-70°C, and react at constant temperature for 1 hour. Same as embodiment 1, filter and reclaim alkali lye, add the filter cake to clear water and make an oar, be made into a slurry with a solid content of 14%, and then pass into the kiln gas at normal temperature to carry out secondary carbonization, when the pH value of the suspension drops to 7 or so is the end point of the reaction. Dissolve the 2.5% stearic acid coating agent of calcium carbonate in hot water at 90°C, add alkali to adjust the pH value of the solution to about 13, and emulsify the coating agent. Then add the coating agent to the calcium carbonate slurry that has been heated to 80°C, and react at a constant temperature of 80°C for 1 hour, filter and dry the slurry while it is hot, and the final drying temperat...

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Abstract

The invention relates to the method to recover super thin calcium carbonate, mainly including the following step: a, join the high macromolecule flocculating agent in green liquid, mix blend even then do away with to descend the sediments, stay the upper level clearness liquid to provide as refined green liquid; b, make the calcium oxide join in the water into the calcium hydroxide syrup, separate the syrup with impurity using the griddle net; c, mix the refined green liquid and the calcium hydroxide syrup, carry on the reaction, add crystal regulator; D: After the syrup responded, carry on the solid- liquid separate, rinse the sieve cake by hot water, take back the sieved liquid; E: prepare sieve cake and waters into suspended liquid syrup, put into the carbon dioxide, get the very thin calcium carbonate syrup.

Description

Technical field: [0001] The invention relates to the technical field of recovering liquid caustic soda from black liquor produced in papermaking and environmental protection, in particular to a method for cleaning and causticizing green liquor and recovering superfine calcium carbonate. Background technique: [0002] At present, in paper mills, a large amount of black liquor is produced during the production of alkaline pulp, which seriously pollutes the environment. In order to eliminate the pollution of black liquor to the environment, all large-scale pulp and paper manufacturing enterprises have black liquor alkali recovery, which eliminates the pollution of black liquor, and the recovered liquid alkali continues to be used for alkaline pulp making. The traditional papermaking black liquor alkali recovery process only obtains one product - caustic soda (white liquor), and produces a large amount of waste residue - white mud. These lime muds contain not only causticizing ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): D21C11/04
Inventor 顾达刘泽华施晓旦
Owner SHANGHAI DONGSHENG NEW MATERIALS
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