CN117623756A - Preparation method of high-purity low-calcium silicate - Google Patents
Preparation method of high-purity low-calcium silicate Download PDFInfo
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- CN117623756A CN117623756A CN202311504473.0A CN202311504473A CN117623756A CN 117623756 A CN117623756 A CN 117623756A CN 202311504473 A CN202311504473 A CN 202311504473A CN 117623756 A CN117623756 A CN 117623756A
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- 239000000378 calcium silicate Substances 0.000 title claims abstract description 96
- 229910052918 calcium silicate Inorganic materials 0.000 title claims abstract description 96
- 238000002360 preparation method Methods 0.000 title claims abstract description 40
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 110
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 55
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 54
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 53
- 239000000920 calcium hydroxide Substances 0.000 claims abstract description 53
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims abstract description 53
- 238000000034 method Methods 0.000 claims abstract description 53
- 239000000843 powder Substances 0.000 claims abstract description 51
- 238000002156 mixing Methods 0.000 claims abstract description 48
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 45
- 230000008569 process Effects 0.000 claims abstract description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 30
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000001354 calcination Methods 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 12
- 238000009740 moulding (composite fabrication) Methods 0.000 claims abstract description 12
- 238000000227 grinding Methods 0.000 claims abstract description 11
- 239000013067 intermediate product Substances 0.000 claims abstract description 10
- 238000003825 pressing Methods 0.000 claims abstract description 8
- 210000004127 vitreous body Anatomy 0.000 claims abstract description 7
- 239000011575 calcium Substances 0.000 claims description 13
- 229910052791 calcium Inorganic materials 0.000 claims description 13
- 238000000748 compression moulding Methods 0.000 claims description 13
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 12
- 238000004321 preservation Methods 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 10
- 239000010703 silicon Substances 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims 2
- 238000003763 carbonization Methods 0.000 abstract description 13
- 238000005245 sintering Methods 0.000 abstract description 9
- 238000000465 moulding Methods 0.000 abstract description 8
- 238000004153 renaturation Methods 0.000 abstract 1
- 235000012241 calcium silicate Nutrition 0.000 description 28
- 239000000463 material Substances 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 23
- 238000010304 firing Methods 0.000 description 22
- 229910052799 carbon Inorganic materials 0.000 description 11
- 239000007787 solid Substances 0.000 description 11
- OSMSIOKMMFKNIL-UHFFFAOYSA-N calcium;silicon Chemical compound [Ca]=[Si] OSMSIOKMMFKNIL-UHFFFAOYSA-N 0.000 description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000012071 phase Substances 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
- 239000003153 chemical reaction reagent Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000004062 sedimentation Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- 238000003991 Rietveld refinement Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000009702 powder compression Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000013558 reference substance Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Abstract
The invention discloses a preparation method of high-purity low-calcium silicate, which comprises the following steps: adding water into calcium hydroxide and silicon dioxide, and uniformly mixing to obtain a mixture; drying the mixture, adding ethanol, uniformly mixing, pressing and forming to prepare a first blank, performing first calcination treatment on the first blank, and cooling to obtain an intermediate product; removing vitreous body from intermediate product, crushing, grinding into powder, adding ethanol into the powder, mixing, press molding to obtain second blank, calcining, and cooling to obtain high purity low calcium silicate. The invention improves the existing calcium silicate sintering process, is highly compatible with the existing preparation process, and can be used for heavyHigh renaturation. The purity of the low-calcium silicate prepared by the method is obviously improved, the interference to the carbonization of the low-calcium silicate in the carbonization process is obviously reduced, and the low-calcium silicate is C 3 S 2 And the carbonization performance study of α -CS provides the basis.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to a preparation method of high-purity low-calcium silicate.
Background
The main carbon emission sources in the cement industry include fuel combustion, limestone decomposition, grinding power consumption and the like. In order to realize carbon dioxide emission reduction in the cement industry, solid carbon gelling materials are produced. The solid carbon gel material can be mixed with CO at normal temperature and pressure 2 The gas reacts spontaneously and rapidly, and can bond other materials into a whole and has a low-carbon gel material with high mechanical strength. The solid carbon gel material mainly comprises gamma-C 2 S、C 3 S 2 And clinker with alpha-CS and other low-calcium non-hydraulic calcium silicate mineral phases as main components and industrial solid waste rich in the calcium silicate mineral phases. Wherein C is 3 S 2 And alpha-CS is becoming more and more interesting as a typical low-calcium silicate, which has the advantages of higher carbonization reactivity and higher carbon fixing capability.
However, at present for C 3 S 2 And research and use of α -CS presents several problems. For example, due to C 3 S 2 With alpha-CS, C 2 S has relatively close calcium-silicon ratio and sintering temperature, and is used for preparing C 3 S 2 Is very easy to generate gamma-C 2 S、β-C 2 S, alpha-CS and other impurities; at the same time, due to the generation of gamma-C with higher calcium-silicon ratio 2 S and beta-C 2 S, a certain amount of silica is also formed. The presence of these calcium silicates affects C 3 S 2 Calcium ion elution and carbonization processes of (2) lead to difficulty in studying C 3 S 2 Carbonization activity and products of (a). The same problems exist for the investigation of alpha-CS carbonization activity and carbonization products. These problems lead to C in the carbonization process of the solid carbon gel materials at present 3 S 2 And the role played by α -CS is unclear, and lack of theoretical guidance in adjusting the composition and properties of the solid carbon gelling material limits the application of the solid carbon gelling material. Although gamma-C is currently available 2 Literature relating to the firing and preparation process of S, but gamma-C 2 S has low requirements on firing temperature and calcium-silicon ratio compared with C 3 S 2 The burning difficulty of alpha-CS is obviously lower, and the raw materials are preparedHigh purity C by ratio, molding mode and firing schedule 3 S 2 And the firing of α -CS does not have a guiding effect.
Disclosure of Invention
The invention aims to overcome the technical defects, and provides a preparation method of high-purity low-calcium silicate, which solves the problems of high purity C in the prior art 3 S 2 And the technical problem of difficult preparation of alpha-CS.
The invention provides a preparation method of high-purity low-calcium silicate, which comprises the following steps:
adding water into calcium hydroxide and silicon dioxide according to a certain proportion, and uniformly mixing to obtain a mixture;
drying the mixture, adding ethanol, uniformly mixing, pressing and forming to prepare a first blank, performing first calcination treatment on the first blank, and cooling to obtain an intermediate product;
removing vitreous body from the intermediate product, crushing, grinding into powder, adding ethanol into the powder, mixing uniformly, pressing and forming to obtain a second blank, performing second calcination treatment on the second blank, and cooling to obtain high-purity low-calcium silicate; wherein,
the high-purity low-calcium silicate is C 3 S 2 The molar ratio of calcium and silicon in the calcium hydroxide and the silicon dioxide is (1.45-1.55): 1, a step of; or alternatively, the first and second heat exchangers may be,
the high-purity low-calcium silicate is alpha-CS, and the molar ratio of calcium to silicon in the calcium hydroxide to the silicon dioxide is (0.95-1.05): 1.
compared with the prior art, the invention has the beneficial effects that:
according to the invention, calcium hydroxide and silicon dioxide are added with water and then are wet mixed so as to ensure that the powder is fully and uniformly mixed; the distance between particles is reduced by a powder compression molding and re-firing method, so that the full performance of solid phase reaction is ensured; the fluctuation of the calcium-silicon ratio of the partial area of the blank body is reduced by a method of crushing and uniformly mixing the blocks after firing and repeatedly firing; the optimal sintering temperature and the heat preservation time are obtained through experiments, and the generation of amorphous calcium silicate is reduced. The preparation method of the high-purity low-calcium silicate provided by the invention is specific to the existing calcium silicateThe sintering process is improved, and the preparation method is highly compatible with the existing preparation process and has high repeatability. The purity of the low-calcium silicate prepared by the method is obviously improved (more than 90 percent), the content of amorphous calcium silicate is obviously reduced, and the content of gamma-C is obviously reduced 2 S and beta-C 2 S content is also obviously reduced, and the interference to low-calcium silicate carbonization in the carbonization process is obviously reduced, and the content is C 3 S 2 And the carbonization performance study of α -CS provides the basis.
Drawings
FIG. 1 is a C prepared in example 1 of the present invention 3 S 2 An XRD pattern of (b);
FIG. 2 is an XRD pattern of α -CS prepared in example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The applicant has found after repeated experiments that the following problems exist in the existing preparation process of low-calcium silicate, which results in the prepared C 3 S 2 And the alpha-CS purity is lower. Firstly, silicon dioxide and calcium hydroxide are difficult to mix uniformly in the mixing process, so that the ratio of calcium to silicon in partial areas of a blank is too high, the ratio of calcium to silicon in partial areas of the blank is too low, and finally, other calcium silicate is generated; next, C 3 S 2 And alpha-CS has no liquid phase in the firing process, and the silicon dioxide and calcium hydroxide particles in the green body have larger intervals and are difficult to fully contact, so that the silicon dioxide and the calcium hydroxide are difficult to fully react; in addition, due to C 3 S 2 And alpha-CS and C 2 The calcium-silicon ratio of S is relatively close, and small fluctuation of the calcium-silicon ratio of local areas can lead to the generation of different calcium silicate. Finally, due to alpha-CS and C 3 S 2 The firing temperature range is narrow, and the generation of amorphous calcium silicate is easy to occur when the temperature is high. These amorphous calcium silicates, as a non-reactive glass phase, can become inert fillers, reducing the purity of the calcium silicate and affecting the mechanical properties of the sample after carbonization.
The invention skillfully solves the problems by using the method of adding water for wet mixing, pressing and forming a blank body, repeatedly firing and determining the optimal firing temperature in the mixing process. Specifically, in the mixing stage of the silicon dioxide and the calcium hydroxide, the powder is fully moved in the liquid and is mutually mixed by adding water and stirring, and the full mixing of the silicon dioxide and the calcium hydroxide is ensured by prolonging the mixing time, so that the condition that the calcium hydroxide and the silicon dioxide are difficult to mix uniformly when being mixed is avoided. In the green body forming stage, the compact combination of the silicon dioxide and the calcium hydroxide is ensured by compression forming, and the forming pressure is increased to further reduce the gap between the middle powder of the green body. In the firing process, fluctuation of the calcium-silicon ratio of a local area of the green body is reduced by a method of regrinding, uniformly mixing, press forming and re-firing the fired clinker; and reducing the generation of amorphous calcium silicate in the sintering process by determining the optimal sintering temperature.
Based on this, the present invention has been proposed.
The invention provides a preparation method of high-purity low-calcium silicate, which comprises the following steps:
s1, adding water into calcium hydroxide and silicon dioxide according to a certain proportion, and uniformly mixing to obtain a mixture;
s2, drying the mixture, adding ethanol, uniformly mixing, pressing and forming to prepare a first blank, performing first calcination treatment on the first blank, and cooling to obtain an intermediate product;
s3, removing the glass body of the intermediate product, crushing and grinding the intermediate product into powder, adding ethanol into the powder, uniformly mixing, pressing and forming to prepare a second blank, and performing second calcination treatment on the second blank, and cooling to obtain the high-purity low-calcium silicate.
In some embodiments of the invention, the purity of both calcium hydroxide and silica is greater than or equal to 95%.
In some embodiments of the invention, the particle size of both calcium hydroxide and silica is less than or equal to 100 μm, and even more preferably less than or equal to 75 μm.
In this embodiment, the high-purity low-calcium silicate is C 3 S 2 The molar ratio of calcium and silicon in the calcium hydroxide and the silicon dioxide is (1.45-1.55): 1, preferably 3:2.
in this embodiment, the high-purity low-calcium silicate is α -CS, and the molar ratio of calcium to silicon in calcium hydroxide to silica is (0.95 to 1.05): 1, preferably 1:1.
in this embodiment, the amount of water added is 1 to 3 times, and more preferably 1 to 2 times the total mass of calcium hydroxide and silica. If too little water is added, the powder cannot be completely wetted by the water, the powder is not uniformly mixed, and finally the purity of the low-calcium silicate is reduced; excessive water addition can cause powder sedimentation, uneven powder mixing and finally lower purity of low-calcium silicate.
In some embodiments of the invention, the mixing time is 0.3-3 h, and further 0.5-1 h in the process of adding water to the calcium hydroxide and the silicon dioxide according to a certain proportion and uniformly mixing. If the mixing time is too short, the powder cannot be uniformly mixed, and the purity of the prepared calcium silicate is low; too long mixing time can cause powder to be stuck on the wall of the container, the mixing is uneven, and the purity of the prepared calcium silicate is lower.
In the embodiment, the temperature is 100-150 ℃ and the humidity is less than or equal to 60% in the drying process. If the humidity is too high, water loss is too slow, powder material is settled, so that the distribution is uneven, and the purity of the final clinker is reduced.
In this embodiment, the mass of ethanol is 0.1 to 0.5 times, and more preferably 0.1 to 0.3 times the mass of the mixture in the process of adding ethanol after drying the mixture.
In the embodiment, in the process of compression molding, the peak value of the pressure is more than or equal to 5MPa, and the dwell time is 10-60 s, and further 20-40 s. Too low pressure can cause too large distance between the powder bodies, and insufficient reaction can be caused in the sintering process, so that the purity of the low-calcium silicate is reduced; the too high pressure has little influence on purity, but causes energy waste and prolongs the preparation time, so that the pressure is preferably 5-10 MPa.
In the embodiment, the thickness of the first blank body and the second blank body is not more than 1.2cm; further, the thickness is not more than 1cm. If the thickness of the green body is too large, the green body is heated unevenly in the sintering process, the internal temperature and the external temperature of the green body are inconsistent, and the purity of the finally prepared calcium silicate is reduced.
In this embodiment, the particle size of the powder obtained in the process of grinding into powder is less than 500. Mu.m, and more preferably less than 300. Mu.m. If the particle size of the ground material is too large, calcium silicate in the material cannot be uniformly mixed, and the purity of the calcium silicate is reduced.
In this embodiment, the mass of ethanol is 0.1 to 0.5 times, and more preferably 0.1 to 0.3 times the mass of the powder in the process of adding ethanol to the powder and uniformly mixing the powder.
In this embodiment, the calcination temperature is 1300 to 1450 ℃ during the first calcination treatment and the second calcination treatment.
In this embodiment, the high-purity low-calcium silicate is C 3 S 2 In the processes of the first calcination treatment and the second calcination treatment, the heat preservation time is 1.5-2.5 h, and further 2h.
In the embodiment, the high-purity low-calcium silicate is alpha-CS, and the heat preservation time is 0.5-1.5 h, and further 1h in the first calcination treatment process; in the second calcination treatment process, the heat preservation time is 1.5-2.5 h, and further 2h.
In the present invention, the preparation materials are commercially available products well known to those skilled in the art unless otherwise specified.
The invention has no special limitation on the mixing mode and the stirring speed, and the liquid can drive all the powder to move and realize full and even mixing in the stirring process.
The present invention is not particularly limited to the drying apparatus and the drying time, and may be carried out according to a well-known process using a device well known in the art.
The present invention is not particularly limited to a tablet press and a die used in compression molding, and may be a device well known in the art.
The heating apparatus used in the process of firing clinker is not particularly limited, and any apparatus known in the art may be used.
The method of removing the vitreous body is not particularly limited, and any method known in the art may be used. For example, since the vitreous tends to adhere to the surface or edge portion of the clinker, which is significantly different in color from the clinker, the vitreous can be removed by direct manual breaking.
In the following examples and comparative examples, the purity of calcium hydroxide and silica used was 95% and the particle size was 75 μm or less, for avoiding redundancy.
Example 1
(1) The calcium hydroxide reagent and the silicon dioxide reagent are mixed according to a calcium-silicon ratio of 3:2 adding water, uniformly mixing, wherein the amount of the added water is 1 time of the mass of the solid, and the mixing time is 1h;
(2) Putting the uniformly mixed materials into a 105 ℃ oven for drying, wherein the humidity in the oven is 50%; adding ethanol into the dried powder, uniformly mixing, and performing compression molding to obtain a blank, wherein the mass of the ethanol is 0.3 times of that of the powder, the peak value of the pressure is 6MPa, the pressure maintaining time is 30s, and the thickness of the blank is 0.5cm; heating the blank to 1420 ℃, preserving heat for 2 hours, and cooling along with a furnace;
(3) Removing vitreous body from the heated block, crushing, grinding, and grinding to obtain particle size<300 μm; adding ethanol into the powder, and uniformly mixing, wherein the mass of the ethanol is 0.2 times of that of the powder; then the blank is manufactured by compression molding, the peak value of the pressure is the same as that of the first compression molding, and the thickness of the blank is 0.5cm; heating the blank to 1420 deg.c, maintaining the temperature for 2 hr, and cooling in furnace to obtain high purity C 3 S 2 。
Example 2
(1) The calcium hydroxide reagent and the silicon dioxide reagent are mixed according to a calcium-silicon ratio of 1:1 adding water, uniformly mixing, wherein the amount of the added water is 1 time of the mass of the solid, and the mixing time is 1h;
(2) Putting the uniformly mixed materials into a 105 ℃ oven for drying, wherein the humidity in the oven is 50%; adding ethanol into the dried powder, uniformly mixing, and performing compression molding to obtain a blank, wherein the mass of the ethanol is 0.3 times of that of the powder, the peak value of the pressure is 6MPa, the pressure maintaining time is 30s, and the thickness of the blank is 0.5cm; heating the blank to 1420 ℃, preserving heat for 1h, and cooling along with a furnace;
(3) Removing the glass body from the heated block, crushing and grinding, wherein the particle size of the ground block is less than 300 mu m; adding ethanol into the powder, and uniformly mixing, wherein the mass of the ethanol is 0.2 times of that of the powder; then the blank is manufactured by compression molding, the peak value of the pressure is the same as that of the first compression molding, and the thickness of the blank is 0.5cm; heating the blank to 1420 ℃, preserving heat for 2 hours, and cooling along with a furnace to obtain the high-purity alpha-CS.
Example 3
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, the calcination temperature in the preparation method is 1300 ℃, and the other steps are the same as in example 1.
Example 4
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, the calcination temperature in the preparation method is 1450 ℃, and the other steps are the same as in example 1.
Example 5
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, the amount of water added in the preparation method is 2 times of the mass of solids, and the other steps are the same as in example 1.
Example 6
The ratio of calcium hydroxide to silicon dioxide was the same as in example 1, and the powder was mixed with water for 0.5h in the preparation method, otherwise the same as in example 1.
Example 7
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, and the peak value of pressure is 5MPa when the mixture is pressed and molded in the preparation method, and the other materials are the same as in example 1.
Example 8
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, and the peak value of pressure is 10MPa when the mixture is pressed and molded in the preparation method, and the other materials are the same as in example 1.
Example 9
The ratio of calcium hydroxide to silicon dioxide is the same as that of example 1, and the thickness of the blank body is 1cm after the first and second compression molding in the preparation method, otherwise the blank body is the same as that of example 1.
Comparative example 1
The proportion of calcium hydroxide to silicon dioxide is the same as that in example 1, and the temperature of an oven is 40 ℃ in the drying process of materials in the preparation method, and the other materials are the same as that in example 1.
Comparative example 2
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, and the amount of water added in the preparation method is 0.5 times of the mass of solids, otherwise the same as in example 1.
Comparative example 3
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, the amount of water added in the preparation method is 5 times of the mass of solids, and the other steps are the same as in example 1.
Comparative example 4
The ratio of calcium hydroxide to silicon dioxide was the same as in example 1, and the powder was mixed with water for 10 minutes in the preparation method, otherwise the same as in example 1.
Comparative example 5
The ratio of calcium hydroxide to silicon dioxide was the same as in example 1, and the powder was mixed with water for 5 hours in the preparation method, otherwise the same as in example 1.
Comparative example 6
The proportion of calcium hydroxide to silicon dioxide is the same as that of example 1, and the mass of ethanol added before the first compression molding in the preparation method is 0.8 times of that of powder, and the other materials are the same as that of example 1.
Comparative example 7
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, and the peak value of pressure is 2MPa when the preparation method is compression molding, otherwise the preparation method is the same as in example 1.
Comparative example 8
The ratio of calcium hydroxide to silicon dioxide is the same as in example 1, and the thickness of the blank body is 3cm after the first and second compression molding in the preparation method, otherwise the blank body is the same as in example 1.
Comparative example 9
The proportion of calcium hydroxide to silicon dioxide is the same as that of example 1, clinker is only burned for 1 time in the preparation method, the heat preservation time is 2 hours, and the other materials are the same as that of example 1.
Comparative example 10
The proportion of calcium hydroxide and silicon dioxide is the same as that of example 2, clinker is only burned for 1 time in the preparation method, the heat preservation time is 2 hours, and the other materials are the same as that of example 2.
Comparative example 11
The proportion of calcium hydroxide to silicon dioxide is the same as that of example 2, clinker is fired 4 times in the preparation method, the heat preservation time is 2 hours during each firing, and the other materials are the same as that of example 2.
Comparative example 12
The proportion of calcium hydroxide to silicon dioxide is the same as that of example 1, the particle size of the powder after grinding in the preparation method is more than 1mm, and the other materials are the same as that of example 1.
Comparative example 13
The ratio of calcium hydroxide to silica was the same as in example 2, and the heated block in the preparation method did not remove the vitreous body, otherwise the same as in example 2.
Comparative example 14
The preparation method is the same as that of example 1 by adopting a calcium carbonate reagent and a silicon dioxide reagent as raw materials and mixing the raw materials according to the same proportion as that of example 1.
Performance testing
(1) The low-calcium silicate prepared in the above examples 1 and 2 was ground and then subjected to an X-ray diffraction test, and the results are shown in fig. 1 and 2;
(2) The low-calcium silicate prepared in examples 1 to 9 and comparative examples 1 to 14 were ground and mixed with 10wt.% of alpha-Al 2 O 3 And (3) taking the sample as an internal standard reference substance, then carrying out X-ray diffraction test, wherein the test parameters are a scanning angle of 5-70 degrees, a step length of 0.02 degrees, a scanning speed of 2 degrees/min, and refining by a Rietveld method to obtain the content ratio of each crystalline phase. The test results are shown in Table 1.
Table 1 phase ratios of high purity low calcium silicate prepared in examples 1 to 9 and comparative examples 1 to 14
As is clear from examples 1 to 9 in Table 1, the low-calcium silicate prepared by the present invention has high purity, low amorphous phase content, and gamma-C 2 S and beta-C 2 The S content is low.
As can be seen from the comparison of the data of the low-calcium silicate prepared in examples 1 to 9 and the low-calcium silicate prepared in comparative example 1 in table 1, the temperature during the drying process of the material has an important effect on the purity of the low-calcium silicate, and too low temperature can result in too long drying time, uneven distribution of calcium hydroxide and silicon dioxide caused by powder sedimentation in the material, and finally the purity of the low-calcium silicate is reduced.
As can be seen from the comparison of the data of the low-calcium silicate prepared in examples 1 to 9 and the low-calcium silicate prepared in comparative examples 2 to 5 in table 1, the amount of water added and the mixing time when calcium hydroxide is mixed with silica have an important effect on the preparation of the low-calcium silicate, too little water added results in that the powder cannot be completely wetted by water, the powder is not uniformly mixed, and finally the purity of the low-calcium silicate is reduced; excessive water addition can cause powder sedimentation, uneven powder mixing and finally lower purity of low-calcium silicate; too short mixing time can also lead to non-uniform mixing of the powder, and the purity of the prepared calcium silicate is low; too long mixing time can cause powder to be stuck on the wall of the container, the mixing is uneven, and the purity of the prepared calcium silicate is lower.
As can be seen from the comparison of the data of the low-calcium silicate prepared in examples 1 to 9 and the low-calcium silicate prepared in comparative example 6 in Table 1, the quality of ethanol added to the green body before press molding has a significant effect on the purity of the low-calcium silicate, and excessive addition of ethanol causes excessive spacing of powder after press molding and difficulty in sufficient reaction during firing, resulting in a decrease in the purity of the calcium silicate.
As can be seen from the comparison of the data of the low-calcium silicate prepared in examples 1 to 9 and the low-calcium silicate prepared in comparative examples 7 to 8 in table 1, the molding pressure of the green body during press molding and the thickness of the green body have an important influence on the purity of the low-calcium silicate, and too low molding pressure can cause too large a distance between powders, and insufficient reaction during firing can result in a decrease in the purity of the low-calcium silicate; the excessive thickness of the green body can cause uneven heating in the sintering process, the internal and external temperatures of the green body are inconsistent, and the purity of the finally prepared calcium silicate is reduced.
From comparison of the data of the low-calcium silicate prepared in examples 1 to 9 in Table 1 with the low-calcium silicate prepared in comparative examples 9 to 13, it is understood that the repeated firing process has an important effect on the purity of calcium silicate. If the repeated firing process is not carried out, the fluctuation of the calcium-silicon ratio exists in the blank body, so that the purity of the calcium silicate is lower; if the repeated firing times are too large, the content of amorphous phase is increased, so that the purity of the calcium silicate is reduced; if the particle size of the ground material is larger in the repeated firing process, calcium silicate in the material cannot be uniformly mixed, and the purity of the calcium silicate is reduced; if the vitreous body in the material is not removed in the repeated firing process, amorphous calcium silicate is mixed into clinker, so that the purity of low-calcium silicate is reduced.
From the comparison of the data of the low-calcium silicate prepared in examples 1 to 9 in Table 1 with the low-calcium silicate prepared in comparative example 14, it is understood that the raw materials have an important influence on the purity of calcium silicate. If calcium carbonate is used as a calcium source, the calcium carbonate is easy to settle in the water adding mixing process, so that the mixing is uneven, and the purity of the low-calcium silicate is reduced.
The above-described embodiments of the present invention do not limit the scope of the present invention. Any of various other corresponding changes and modifications made according to the technical idea of the present invention should be included in the scope of the claims of the present invention.
Claims (10)
1. The preparation method of the high-purity low-calcium silicate is characterized by comprising the following steps of:
adding water into calcium hydroxide and silicon dioxide according to a certain proportion, and uniformly mixing to obtain a mixture;
drying the mixture, adding ethanol, uniformly mixing, pressing and forming to prepare a first blank, performing first calcination treatment on the first blank, and cooling to obtain an intermediate product;
removing vitreous body from the intermediate product, crushing and grinding the intermediate product into powder, adding ethanol into the powder, uniformly mixing, pressing and forming to prepare a second blank, performing second calcination treatment on the second blank, and cooling to obtain high-purity low-calcium silicate; wherein,
the high-purity low-calcium silicate is C 3 S 2 The molar ratio of calcium and silicon in the calcium hydroxide to the silicon dioxide is (1.45-1.55): 1, a step of; or alternatively, the first and second heat exchangers may be,
the high-purity low-calcium silicate is alpha-CS, and the molar ratio of calcium to silicon in the calcium hydroxide to silicon dioxide is (0.95-1.05): 1.
2. the method for preparing high-purity low-calcium silicate according to claim 1, wherein the purity of the calcium hydroxide and the silica is not less than 95%, and the particle size of the calcium hydroxide and the silica is not more than 100 μm.
3. The method for producing high-purity low-calcium silicate according to claim 1, wherein the high-purity low-calcium silicate is C 3 S 2 The molar ratio of calcium and silicon in the calcium hydroxide to the silicon dioxide is 3:2; or, the high-purity low-calcium silicate is alpha-CS, and the molar ratio of calcium to silicon in the calcium hydroxide to silicon dioxide is 1:1.
4. the method for preparing high-purity low-calcium silicate according to claim 1, wherein in the process of adding water into calcium hydroxide and silicon dioxide according to a certain proportion and uniformly mixing, the adding amount of water is 1-3 times of the total mass of the calcium hydroxide and the silicon dioxide, and the mixing time is 0.3-3 hours.
5. The method for preparing high-purity low-calcium silicate according to claim 1, wherein the temperature is 100-150 ℃ and the humidity is less than or equal to 60% in the drying process.
6. The method for preparing high-purity low-calcium silicate according to claim 1, wherein the mass of ethanol is 0.1 to 0.5 times the mass of the mixture in the process of adding ethanol after drying the mixture; in the process of adding ethanol into the powder, the mass of the ethanol is 0.1 to 0.5 times of the mass of the powder.
7. The method for preparing high-purity low-calcium silicate according to claim 1, wherein the peak pressure is not less than 5MPa and the dwell time is 10-60 s in the compression molding process.
8. The method of producing high purity low calcium silicate according to claim 1, wherein the thickness of both the first green body and the second green body is not more than 1.2cm.
9. The method for preparing high-purity low-calcium silicate according to claim 1, wherein the particle size of the powder obtained in the process of grinding into powder is less than 500 μm.
10. The method for producing high-purity low-calcium silicate according to claim 1, wherein the calcination temperature is 1300 to 1450 ℃ during the first calcination treatment and the second calcination treatment;
the high-purity low-calcium silicate is C 3 S 2 The heat preservation time is 1.5-2.5 h in the processes of the first calcination treatment and the second calcination treatment; or alternatively, the first and second heat exchangers may be,
the high-purity low-calcium silicate is alpha-CS, the heat preservation time is 0.5-1.5 h in the first calcination treatment process, and the heat preservation time is 1.5-2.5 h in the second calcination treatment process.
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