Method for producing purified precipitated calcium carbonate from lime sludge

A technology for precipitating calcium carbonate and limestone, applied in chemical instruments and methods, calcium carbonate/strontium/barium, lime production, etc., can solve the problems of increasing the specific surface area of ​​lime mud particles and being unsuitable

Pending Publication Date: 2022-06-07
SPECIALITY MINERALS (MICHIGAN) INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Lime marls produced from pulping non-wood species such as reed and straw often contain higher levels of high surface area siliceous minerals, which increase the specific surface area of ​​the lime marl particles and make them unsuitable for use as fillers in conventional papermaking

Method used

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  • Method for producing purified precipitated calcium carbonate from lime sludge
  • Method for producing purified precipitated calcium carbonate from lime sludge
  • Method for producing purified precipitated calcium carbonate from lime sludge

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0084] Example 1: Heat aging (HA) in sodium carbonate

[0085] The lime mud is treated to provide a precipitated calcium carbonate material with reduced specific surface area and reduced impurity content compared to the starting material. The lime mud cake is obtained as a waste product from the pulp mill. The lime mud cake is slurried in a 25%-30% sodium carbonate solution with a calcium carbonate solid content of 10%-20%. In particular, in 1 kg of slurry, 200 g of CaCO 3 (20%CaCO 3 ), 240gNa 2 CO 3 , 560g H 2 O(30%Na 2 CO 3 ).

[0086] The slurry was then heat aged at 100°C for 8 hours to form a mixed salt, calcium hydroxide (Na 2 Ca(CO 3 ) 2 ·5H 2 O). Methods without the heat aging step were compared and the results are presented in the table below.

[0087] The slurry was then filtered or separated into solid and liquid phases by vacuum filtration using a Buchner funnel and filter paper. The filter cake was washed in a Buchner funnel with three portions of w...

Embodiment 2

[0093] Example 2: Removal of impurities using phase separation

[0094] The lime mud cake obtained as waste from the pulp mill was slurried at 20% solids in water. The pulp is processed using a filter press with a wash cycle to remove excess white liquor from the pulp mill. A filter press was used to first form a filter cake from the 20% solids slurry and then force water through the filter cake. The wash cycle was performed with an amount of water four times the mass of dry solids.

[0095] The washed filter cake was dispersed in water at 20% solids using sodium poly(acrylate) as the chemical dispersant. The resulting dispersed slurry had a viscosity of about 10 cps at 100 rpm.

[0096] The dispersed slurry was then aerated with flue gas having a carbon dioxide content of about 15% to lower the pH to a pH of about 10.5.

[0097] The pH adjusted slurry is then ground to the desired particle size suitable for use as a paper filler or coating pigment. In this example, the p...

Embodiment 3

[0101] Example 3: Removal of impurities using phase separation of lime mud prior to grinding

[0102]The lime mud cake obtained as waste from the pulp mill was slurried at 20% solids in water. The slurry was processed using a horizontal filter press with a wash cycle to remove excess white liquor in the liquid phase. A filter press was used to first form a filter cake from a 20% solids slurry, resulting in a 65% solids filter cake, and then water was forced through the filter cake. The wash cycle was performed with an amount of water four times the mass of dry solids.

[0103] The resulting washed filter cake was slurried in water at 23% solids and then treated by aeration with carbon dioxide-containing flue gas to lower the pH to 10.9.

[0104] The pH adjusted slurry was then continuously centrifuged at 1300 rpm to obtain a g-force of 615, with residence times varying as indicated in the table. The centrifuge filtrate containing fine particulate impurities was removed and ...

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Abstract

A method of making purified precipitated calcium carbonate from lime mud can include mixing a lime mud cake with water and sodium carbonate to form a first slurry; heating the first slurry under conditions to age the slurry and form one or more of calcium hydroxide, sodium calcium carbonate, and monoclinic natrolite; separating a solid fraction from the aged slurry; washing the solids fraction under conditions sufficient to decompose one or more of the calcareite, the sodium calcium carbonate, and the monoclinic natrolite into a CaCO3 solid fraction and a Na2CO3 solid fraction and remove the sodium salt; and mixing the CaCO3 solid fraction with water and a dispersant to disperse the CaCO3 solid fraction in water and form a dispersed slurry having a Brookfield viscosity of less than about 1000 cps at 100 rpm, thereby producing a dispersed slurry containing the purified precipitated calcium carbonate.

Description

technical field [0001] The present disclosure relates generally to methods of processing lime mud cakes produced as waste products to produce precipitated calcium carbonate, and in particular to methods for processing lime mud cakes produced as waste products to produce fillers and / or pigments suitable for use as paper and paperboard Method for precipitating calcium carbonate. Background technique [0002] The main components in paper and board are cellulose pulp fibers produced from wood or other vegetable sources by various mechanical and / or chemical pulping processes. The main chemical pulping process used in the paper industry is the alkaline "kraft" process, which uses sodium hydroxide (caustic soda) and sodium sulfide in a cooking process step to extract and separate non-cellulosic materials from cellulosic pulp fibers . In particular, another common variation in pulping is the absence of sodium sulfide, and this is known as caustic pulping. [0003] To maximize the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F11/18
CPCC01F11/183C01P2006/12C01P2006/80C01F11/185C01P2006/22C01P2004/61C01P2004/62Y02P40/40
Inventor 谢尔曼·科思马克·戴格尔蒂莫西·萨马尔科
Owner SPECIALITY MINERALS (MICHIGAN) INC
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