CN1641100A - Method for recovering superfine calcium carbonate by clean causticization of green liquor - Google Patents
Method for recovering superfine calcium carbonate by clean causticization of green liquor Download PDFInfo
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- CN1641100A CN1641100A CN 200410053077 CN200410053077A CN1641100A CN 1641100 A CN1641100 A CN 1641100A CN 200410053077 CN200410053077 CN 200410053077 CN 200410053077 A CN200410053077 A CN 200410053077A CN 1641100 A CN1641100 A CN 1641100A
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- calcium carbonate
- green liquor
- recovering
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- causticization
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 title claims abstract description 137
- 229910000019 calcium carbonate Inorganic materials 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 38
- 239000007788 liquid Substances 0.000 claims abstract description 33
- 238000006243 chemical reaction Methods 0.000 claims abstract description 29
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 26
- 239000000920 calcium hydroxide Substances 0.000 claims abstract description 26
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000013078 crystal Substances 0.000 claims abstract description 14
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 13
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000000292 calcium oxide Substances 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 6
- 239000013049 sediment Substances 0.000 claims abstract description 6
- 239000002002 slurry Substances 0.000 claims description 51
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 39
- 239000011248 coating agent Substances 0.000 claims description 16
- 239000012065 filter cake Substances 0.000 claims description 14
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 13
- 238000009993 causticizing Methods 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 238000004537 pulping Methods 0.000 claims description 11
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 10
- 239000000725 suspension Substances 0.000 claims description 10
- 238000003763 carbonization Methods 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 235000021355 Stearic acid Nutrition 0.000 claims description 6
- 235000012255 calcium oxide Nutrition 0.000 claims description 6
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical group CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 6
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 claims description 6
- 238000000926 separation method Methods 0.000 claims description 6
- 239000008117 stearic acid Substances 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 5
- 239000006087 Silane Coupling Agent Substances 0.000 claims description 4
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 4
- 229930006000 Sucrose Natural products 0.000 claims description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 229910021538 borax Inorganic materials 0.000 claims description 4
- 239000007822 coupling agent Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- 239000000706 filtrate Substances 0.000 claims description 4
- 235000010339 sodium tetraborate Nutrition 0.000 claims description 4
- 239000005720 sucrose Substances 0.000 claims description 4
- 239000012756 surface treatment agent Substances 0.000 claims description 4
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 3
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical group [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 claims description 3
- 230000007935 neutral effect Effects 0.000 claims description 3
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 3
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 3
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 3
- 235000011151 potassium sulphates Nutrition 0.000 claims description 3
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical group [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 3
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 3
- 235000011152 sodium sulphate Nutrition 0.000 claims description 3
- 239000004328 sodium tetraborate Substances 0.000 claims description 3
- 229920002472 Starch Polymers 0.000 claims description 2
- 239000008107 starch Substances 0.000 claims description 2
- 235000019698 starch Nutrition 0.000 claims description 2
- 238000004381 surface treatment Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 abstract description 7
- 239000006188 syrup Substances 0.000 abstract 6
- 235000020357 syrup Nutrition 0.000 abstract 6
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 abstract 1
- 239000008394 flocculating agent Substances 0.000 abstract 1
- 229920002521 macromolecule Polymers 0.000 abstract 1
- 239000003643 water by type Substances 0.000 abstract 1
- 235000010216 calcium carbonate Nutrition 0.000 description 47
- 239000003513 alkali Substances 0.000 description 19
- 239000000047 product Substances 0.000 description 18
- 239000002245 particle Substances 0.000 description 15
- 239000000945 filler Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 5
- 235000011941 Tilia x europaea Nutrition 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000004571 lime Substances 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 238000004062 sedimentation Methods 0.000 description 4
- 235000017550 sodium carbonate Nutrition 0.000 description 4
- 239000006228 supernatant Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000006911 nucleation Effects 0.000 description 3
- 238000010899 nucleation Methods 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000004568 cement Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012767 functional filler Substances 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000011882 ultra-fine particle Substances 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000002050 diffraction method Methods 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000001804 emulsifying effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 235000013336 milk Nutrition 0.000 description 1
- 239000008267 milk Substances 0.000 description 1
- 210000004080 milk Anatomy 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000001509 sodium citrate Substances 0.000 description 1
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000010902 straw Substances 0.000 description 1
- BSVBQGMMJUBVOD-UHFFFAOYSA-N trisodium borate Chemical compound [Na+].[Na+].[Na+].[O-]B([O-])[O-] BSVBQGMMJUBVOD-UHFFFAOYSA-N 0.000 description 1
- -1 which is not reacted Substances 0.000 description 1
Landscapes
- Paper (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
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
The technical field is as follows:
the invention relates to the technical field of liquid alkali recovery and environmental protection of black liquor generated in papermaking, in particular to a method for recovering superfine calcium carbonate by cleaning and causticizing green liquor.
Background art:
at present, in a paper mill, a large amount of black liquor is generated during the production of alkaline pulping, and the environment is seriously polluted. In order to eliminate the pollution of black liquor to the environment, all large-scale pulping and papermaking enterprises have black liquor alkali recovery, the pollution of the black liquor is eliminated, and the recovered liquid alkali is continuously used for pulping by an alkali method. The traditional process for recovering alkali from black liquor in paper making only obtains one product, namely caustic soda (white liquor), and simultaneously produces a large amount of waste residues, namely white mud. In these white muds, there are contained both calcium carbonate, which is causticized, and excess lime, which is not reacted, and various impurities, which are entrained in the raw materials (green liquor and lime) to the reaction system. The white mud has complex components, is alkaline waste residue which seriously pollutes the environment, and has extremely large quantity. With the development of the paper industry, especially the enlargement of the production scale of alkaline pulping, the pollution is very serious, and the sustainable development of national economy is seriously restricted.
The domestic research on the treatment of white mud generated by alkali pulping and alkali recovery for many years mainly comprises three treatment methods: (1) the white mud is burnt into lime for recycling. As the white mud generated when the straw pulp black liquor recovers the alkali has high silicon content, the silicon is accumulated when the white mud is calcined into lime for recycling, and vicious circle of silicon interference is formed to influence the normal operation of alkali recovery. (2) The white mud is treated by washing, grinding and other processes, and the calcium carbonate recovered by the method has high impurity content and whiteness of only about 80, and can only be used as low-grade papermaking filler. Meanwhile, the calcium carbonate filler has large abrasion to a paper machine, is not approved by a paper mill and is difficult to popularize and apply. (3) The white mud waste residue is transported to a cement plant to replace part of limestone as a raw material for producing cement, and the waste material resource is recycled. The method has low economic benefit and cannot be popularized and applied.
So far, the existing large-scale alkali method pulp mill in China only can discharge the white mud generated after alkali liquor is recovered into rivers or landfills because no good treatment method exists. In fact, the method only transfers the pollution of the white mud, which is the current expediency and causes secondary pollution. The chemical and chemical system of the national Henan university deeply researches the recovery of the papermaking black liquor alkali and applies for the invention patent of an improved new process for recovering the papermaking black liquor alkali (publication No. CN 14368944). The size of the particle size of the recovered calcium carbonate product is effectively controlled in the causticizing process. The calcium carbonate product used as a paper making filler and a coating not only has the requirement on the particle size, but also has the more important requirement on the appearance; secondly, the process reduces the alkalinity of the calcium carbonate by secondary causticization. In fact, since the causticizing reaction is a reversible reaction, it is impossible to completely reduce the basicity of the product by increasing the causticizing reaction time and finally using the washing method according to the thermodynamic principle of the chemical reaction, so that the alkali content of the recovered calcium carbonate product is high.
With the development of paper industry, different particle size and morphology requirements are imposed on calcium carbonate for fillers and surface coatings. The method has the advantages that more researches are made on how to control the particle size and the shape of the product by introducing kiln gas into the lime milk for carbonization to generate calcium carbonate, and no research is made on the aspects of particle size control and particle size shape control for causticizing and recovering liquid caustic soda and calcium carbonate from green liquor; meanwhile, when calcium carbonate is recycled, the alkalinity of the recycled product cannot be effectively controlled.
The invention content is as follows:
the invention aims to provide an improved method for recovering superfine calcium carbonate by cleaning and causticizing green liquor, which changes waste white mud into an industrial product with higher added value by controlling the particle size, morphology and alkalinity of a recovered calcium carbonate product.
In order to achieve the purpose, the technical scheme of the invention is as follows: a method for recovering superfine calcium carbonate by cleaning and causticizing green liquor is characterized by comprising the following steps: the method for recovering the liquid caustic soda and the superfine calcium carbonate by cleaning and causticizing the green liquor comprises the following steps: a. adding 0.01-0.1 wt% of polymeric flocculant into the green liquor, stirring, naturally settling, removing the lower layer sediment, and collecting the upper layer clear liquor as refined green liquor; b. adding 10-25 wt% of quicklime into hot water of 40-60 ℃ to prepare calcium hydroxide slurry, and separating and removing impurities from the slurry by using a screen or a rotary liquid; c. mixing the refined green liquor and calcium hydroxide slurry according to the theoretical reaction amount of 1: 1-1.05, carrying out causticization reaction at 30-100 ℃, and adding a crystal form regulator accounting for 0.2-1.5% of calcium carbonate in weight percentage in the reaction; d. carrying out solid-liquid separation on the causticized slurry, washing a filter cake by hot water at 50-70 ℃, and recovering the filtrate as liquid caustic soda; e. pulping the filter cake, adding water to prepare suspension slurry with the solid content of 15-20%, and introducing carbon dioxide for further carbonization until the slurry is neutral to obtain the superfine calcium carbonate slurry.
The technology adopted by the invention is to control the nucleation of the crystal and the growth rate of each crystal face by adding the crystal form regulator in the causticization reaction of the calcium hydroxide slurry and the refined green liquor according to the basic principle of crystallography so as to achieve controllable grain size and morphology. The colloidal substances are removed to the maximum extent in the refining process of the green liquor, the viscosity of the system is reduced, and the sedimentation rate of particles is accelerated; in the causticizing process, the nucleation period and the growth period of the calcium carbonate are controlled to be separated by the stirring speed and the mixing mode of the materials, so that the particle size is uniform, the sedimentation rate is prevented from being influenced by the existence of ultrafine particles, and the solid-liquid separation effect is improved. The recycled superfine calcium carbonate slurry is subjected to secondary carbonization after being filtered, washed and recycled to obtain liquid alkali, so that the alkalinity of the product is effectively reduced, and the product quality is improved. The superfine calcium carbonate with different morphologies recovered by the technology is suitable for different purposes, such as the application of the calcium carbonate which is micro-aggregated into flower shapes to paper making filler, the application of the calcium carbonate which is rice-shaped to paper making coating, and the application of the calcium carbonate which is superfine and is treated by stearic acid to high-grade rubber and plastic filler. Has good social benefit and considerable economic benefit.
The specific implementation mode is as follows:
the present invention will be further described with reference to the following examples.
The method for recovering the liquid caustic soda and the superfine calcium carbonate by cleaning and causticizing the green liquor comprises the following steps: a. adding 0.01-0.1 wt% of polymeric flocculant into the green liquor, stirring, naturally settling, removing lower-layer sediment, reducing system viscosity, accelerating particle settling rate, and collecting upper-layer clarified liquor as refined green liquor; b. adding 10-25 wt% of quicklime into hot water at 40-60 ℃ to prepare calcium hydroxide slurry, separating and removing impurities from the slurry by using a screen or hydrocyclone, and performing hydrocyclone separation and impurity removal refining treatment on the calcium hydroxide slurry after slaking the quicklime so as to prevent harmful components from entering a causticization system; c. mixing calcium hydroxide and sodium carbonate in green liquor according to the theoretical quantity ratio of reaction of 1.05, carrying out causticization reaction at 30-100 ℃, controlling the nucleation period and the growth period of calcium carbonate to be separated by stirring speed and a material mixing mode in the causticization process, so as to achieve uniform particle size, avoid influence on sedimentation rate due to existence of ultrafine particles, improve solid-liquid separation effect, adding a crystal form regulator with calcium carbonate weight percentage of 0.2-1.5% in the reaction, controlling the mixing mode and the stirring speed of green liquor and calcium hydroxide suspension, regulating the growth rate of each crystal face, and controlling the particle size and the appearance of the calcium carbonate; d. carrying out solid-liquid separation on the causticized slurry, washing a filter cake by hot water at 50-70 ℃, and recovering the filtrate as liquid caustic soda; e. pulping the filter cake, adding water to prepare suspension slurry with the solid content of 15-20%, and introducing carbon dioxide for further carbonization until the slurry is neutral, so that the alkali content in the product is effectively reduced, the product quality is improved, and the superfine calcium carbonate slurry is obtained. The green liquor is obtained by calcining black liquor to obtain alkaline ash and then leaching with water, which is the prior art and is not described herein again.
In the reaction of the refined calcium hydroxide slurry and the refined green liquor, the solid content of the calcium hydroxide slurry is 25-40%; adding a crystal form regulator in the first 0-40 minutes of the causticization reaction, wherein the crystal form regulator is disodium hydrogen phosphate, sodium sulfate, potassium sulfate, borax and sucrose; adding carbon dioxide into the suspension slurry from kiln gas or paper mill at 20-35% concentration and 10-40 deg.C; carrying out surface treatment on the superfine calcium carbonate by using a surface treatment agent accounting for 1.0-3.5 wt% of the superfine calcium carbonate to prepare superfine active calcium carbonate, wherein the surface treatment agent is stearic acid, a water-soluble titanate coupling agent AT-15 and a water-soluble KH-550 silane coupling agent, and the treatment temperature is 45-90 ℃; the final drying temperature of the superfine active calcium carbonate is 85-110 ℃.
In the implementation, a polymeric flocculant sodium polyacrylate or water-soluble starch is added into the green liquor, the addition amount is 0.01-0.1% of the liquid amount, the mixture is stirred uniformly and then naturally settled, the sediment at the lower layer is removed, and the supernatant at the upper layer is refined green liquor for later use; adding quicklime into hot water of 40-60 ℃, standing for 15-20 minutes, stirring for 15 minutes, and further separating residues of the crude calcium hydroxide slurry by a secondary hydrocyclone to obtain refined calcium hydroxide slurry. Naturally settling the calcium hydroxide slurry, using the supernatant for secondary digestion, and using the sediment at the lower layer as the calcium hydroxide slurry with high solid content for later use; mixing and stirring the calcium hydroxide slurry and the refined green liquor, heating to 50-100 ℃ for reaction, adding crystal form regulators such as disodium hydrogen phosphate, sodium sulfate, potassium sulfate, borax and sucrose when the conversion rate of causticization reaction is 0-30%, wherein the adding amount is 0.2-1.5% of the amount of calcium carbonate, and adjusting the particle size and morphology of calcium carbonate.
The reaction formula is as follows:
then the causticized slurry is naturally settled and then centrifugally dewatered, and filter cakes are washed by hot water. Supernatant and filtrate are recovered liquid caustic soda, and can be used in paper industry. The washing liquid is used for leaching the soda ash to prepare green liquor; adding water into the filter cake to prepare suspension slurry with the solid content of 15-20%, introducing kiln gas under stirring for further carbonization to the end point (pH is 7), and directly conveying the superfine calcium carbonate slurry to a paper mill to be used as a paper making filler or preparing the superfine calcium carbonate paper coating after dehydration; heating the superfine calcium carbonate slurry to 45-95 ℃, and adding 0.5-3.5% of coating agent by weight of calcium carbonate for coating treatment, wherein the coating treatment time is 0.5-3.5 hours. The coating agent is one or two of stearic acid, a water-soluble titanate coupling agent AT-15, a water-soluble KH-550 silane coupling agent and the like, and the preparation method comprises the steps of preparing the coating agent into an aqueous solution with the concentration of 5-20%, adjusting the pH value of the aqueous solution to 8-13 within the temperature range of 50-80 ℃, and dissolving and emulsifying the aqueous solution in water for later use. The superfine active calcium carbonate treated by the method can be used as a functional filler for high-grade rubber, plastics and automobile primers.
Example 1
Adding an aqueous solution of sodium polyacrylate flocculant with the solid content of 3.0% into a certain amount of green liquor, wherein the addition amount is 0.01% of the amount of the green liquor, stirring and mixing, standing for 30 minutes, and filtering, wherein clear liquid is used for causticization reaction.
Adding quicklime into hot water of 50 ℃, standing for 15 minutes, stirring for 15 minutes to obtain calcium hydroxide crude slurry, sieving the crude slurry with a 200-mesh sieve, removing residues, naturally settling the slurry, and then extracting supernatant to obtain lower-layer high-solid-content calcium hydroxide slurry. Mixing the calcium hydroxide and sodium carbonate in the green liquor according to the theoretical amount ratio of the calcium hydroxide to the sodium carbonate in the green liquor of 1.05, heating the mixture to 90 ℃ under stirring, reacting the mixture for 10 minutes, adding a crystal form regulator sodium citrate aqueous solution with the theoretical amount of the calcium carbonate of 0.5 percent, and continuously reacting the mixture for 1 hour at constant temperature. After the reaction is finished, filtering the causticized liquid, washing a filter cake by hot water and recovering liquid caustic soda. Adding clear water into the filter cake, pulping to prepare slurry with the solid content of 15%, and introducing kiln gas to perform secondary carbonization at normal temperature, wherein the reaction end point is obtained when the pH value of the suspension is reduced to about 7. The product is a fusiform micro-aggregate, has whiteness of more than 92, pH value of 8.2 and sedimentation volume of 3.1, and is suitable for being used as a papermaking filler.
Example 2
Refining the green liquor and the calcium hydroxide slurry, mixing the two liquors, heating to 70 ℃, reacting at a constant temperature for 15 minutes, adding an aqueous solution of sodium borate with the theoretical amount of calcium carbonate being 1.0%, continuing to react for 1 hour, filtering and recovering alkali liquor in the same way as in example 1, adding clear water into a filter cake, pulping to prepare slurry with the solid content of 18%, introducing kiln gas at normal temperature for secondary carbonization, and obtaining a reaction end point when the pH value of the suspension is reduced to about 7. The product is in the form of tablet, the average particle size is 0.50 micron, and the whiteness is more than 92. The slurry is filtered to obtain a filter cake with high solid content, and the filter cake is suitable for being used as a papermaking coating after dispersion treatment.
Example 3
And refining the green liquor and the calcium hydroxide slurry, mixing the two liquors, adding a sucrose aqueous solution with the calcium carbonate accounting for 1.0% of the theoretical amount, heating to 50-70 ℃, and reacting at constant temperature for 1 hour. Filtering and recovering alkali liquor in the same way as in the example 1, adding clear water into a filter cake, pulping, preparing slurry with the solid content of 14%, introducing kiln gas at normal temperature for secondary carbonization, and obtaining the reaction end point when the pH value of the suspension is reduced to about 7. Stearic acid coating agent, 2.5% of calcium carbonate, is dissolved in hot water at 90 ℃, alkali is added to adjust the pH value of the solution to about 13, and the coating agent is emulsified. And then adding a coating agent into the calcium carbonate slurry heated to 80 ℃, carrying out constant-temperature coating reaction for 1 hour at 80 ℃, filtering and drying the slurry while the slurry is hot, and finally obtaining the superfine activated calcium carbonate product at the drying temperature of not more than 100 ℃, wherein the average particle size of the product is 0.15 micron, the whiteness is more than 92, the activation degree is more than 99%, the oil absorption value is 28-35 g/100g of CaCO3, and the product does not have the agglomeration phenomenon. Can be used as functional filler for high-grade rubber and plastics.
Claims (8)
1. A method for recovering superfine calcium carbonate by cleaning and causticizing green liquor is characterized by comprising the following steps: the method for recovering the liquid caustic soda and the superfine calcium carbonate by cleaning and causticizing the green liquor comprises the following steps: a. adding 0.01-0.1 wt% of polymeric flocculant into the green liquor, stirring, naturally settling, removing the lower layer sediment, and collecting the upper layer clear liquor as refined green liquor; b. adding 10-25 wt% of quicklime into hot water of 40-60 ℃ to prepare calcium hydroxide slurry, and separating and removing impurities from the slurry by using a screen or a rotary liquid; c. mixing calcium hydroxide and sodium carbonate in green liquor according to the theoretical amount ratio of reaction of 1.05, carrying out causticization reaction at 30-100 ℃, and adding a crystal form regulator with calcium carbonate weight percent of 0.2-1.5% in the reaction; d. carrying out solid-liquid separation on the causticized slurry, washing a filter cake by hot water at 50-70 ℃, and recovering the filtrate as liquid caustic soda; e. pulping the filter cake, adding water to prepare suspension slurry with the solid content of 15-20%, and introducing carbon dioxide for further carbonization until the slurry is neutral to obtain the superfine calcium carbonate slurry.
2. The method for recovering the ultrafine calcium carbonate by clean causticization of the green liquor as claimed in claim 1, which is characterized in that: and adding a coating agent accounting for 0.5-3.5 wt% of the superfine calcium carbonate into the superfine calcium carbonate slurry in the coating process, wherein the coating treatment time is 0.5-3.5 hours, and the coating agent is stearic acid, a water-soluble titanate coupling agent AT-15 and a water-soluble KH-550 silane coupling agent to prepare the superfine active calcium carbonate.
3. The method for recovering the ultrafine calcium carbonate by clean causticization of thegreen liquor as claimed in claim 1, which is characterized in that: in the reaction of the refined calcium hydroxide slurry and the refined green liquor, the solid content of the calcium hydroxide slurry is 25-40%.
4. The method for recovering the ultrafine calcium carbonate by clean causticization of the green liquor as claimed in claim 1, which is characterized in that: adding a crystal form regulator in the first 0-40 minutes of the causticization reaction, wherein the crystal form regulator is disodium hydrogen phosphate, sodium sulfate, potassium sulfate, borax and sucrose.
5. The method for recovering the ultrafine calcium carbonate by clean causticization of the green liquor as claimed in claim 1, which is characterized in that: the carbon dioxide added to the suspension slurry comes from kiln gas or paper mill, its concentration is 20-35%, and its temperature is 10-40 deg.C.
6. The method for recovering the liquid caustic soda and the ultrafine calcium carbonate by the clean causticization of the green liquor as claimed in claim 1, wherein the method comprises the following steps: the superfine calcium carbonate is subjected to surface treatment by using a surface treatment agent accounting for 1.0-3.5 wt% of the superfine calcium carbonate to prepare the superfine active calcium carbonate, wherein the surface treatment agent is stearic acid, a water-soluble titanate coupling agent AT-15 and a water-soluble KH-550 silane coupling agent, and the treatment temperature is 45-90 ℃.
7. The method for recovering the liquid caustic soda and the ultrafine calcium carbonate by the clean causticization of the green liquor as claimed in claim 1, wherein the method comprises the following steps:the polymeric flocculant is sodium polyacrylate or water-soluble starch.
8. The method for recovering the liquid caustic soda and the ultrafine calcium carbonate by the clean causticization of the green liquor as claimed in claim 6, wherein the method comprises the following steps: the final drying temperature of the superfine active calcium carbonate is 85-110 ℃.
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| CNB2004100530771A CN1321243C (en) | 2004-07-20 | 2004-07-20 | Method for recovering superfine calcium carbonate by clean causticization of green liquor |
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