CN114620751A - Spheroidal large primary crystal alpha-Al2O3Method for preparing powder - Google Patents
Spheroidal large primary crystal alpha-Al2O3Method for preparing powder Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 83
- 239000013078 crystal Substances 0.000 title claims abstract description 41
- 238000001354 calcination Methods 0.000 claims abstract description 40
- 239000002245 particle Substances 0.000 claims abstract description 22
- 238000002360 preparation method Methods 0.000 claims abstract description 22
- 239000002131 composite material Substances 0.000 claims abstract description 21
- 238000000498 ball milling Methods 0.000 claims abstract description 20
- 239000002994 raw material Substances 0.000 claims abstract description 19
- 239000011812 mixed powder Substances 0.000 claims abstract description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 12
- 238000003837 high-temperature calcination Methods 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 12
- 229910052594 sapphire Inorganic materials 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 54
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 34
- 235000019270 ammonium chloride Nutrition 0.000 claims description 17
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 13
- 239000004327 boric acid Substances 0.000 claims description 13
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 claims description 9
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- YWYZEGXAUVWDED-UHFFFAOYSA-N triammonium citrate Chemical compound [NH4+].[NH4+].[NH4+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O YWYZEGXAUVWDED-UHFFFAOYSA-N 0.000 claims description 8
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 claims description 4
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 4
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- 238000010298 pulverizing process Methods 0.000 claims description 2
- MXRIRQGCELJRSN-UHFFFAOYSA-N O.O.O.[Al] Chemical compound O.O.O.[Al] MXRIRQGCELJRSN-UHFFFAOYSA-N 0.000 claims 1
- 238000009826 distribution Methods 0.000 abstract description 8
- 238000000227 grinding Methods 0.000 abstract description 6
- 230000008569 process Effects 0.000 abstract description 4
- 238000010923 batch production Methods 0.000 abstract description 2
- 239000012071 phase Substances 0.000 description 27
- 238000004321 preservation Methods 0.000 description 12
- 239000011734 sodium Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 10
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 9
- 229910052708 sodium Inorganic materials 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 6
- 229910052863 mullite Inorganic materials 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- 238000001816 cooling Methods 0.000 description 5
- 230000001976 improved effect Effects 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 4
- 229910052593 corundum Inorganic materials 0.000 description 4
- 239000012528 membrane Substances 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 229910001845 yogo sapphire Inorganic materials 0.000 description 4
- 229910052878 cordierite Inorganic materials 0.000 description 3
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 3
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 230000002035 prolonged effect Effects 0.000 description 3
- 239000011819 refractory material Substances 0.000 description 3
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 229910001948 sodium oxide Inorganic materials 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000010436 fluorite Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/021—After-treatment of oxides or hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
- C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
- C01F7/442—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination in presence of a calcination additive
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a sphere-like large primary crystal alpha-Al2O3The preparation method of the powder has the process of twice calcining, and the first low-temperature calcining comprises the following steps: adding a first mineralizer into an aluminum-containing raw material, calcining for 2-8 hours at 900-1200 ℃, crushing by a ball mill to obtain powder M1, and uniformly mixing M1 with a composite second mineralizer to obtain mixed powder M2; the second high-temperature calcination comprises the following steps: calcining M2 powder at 1350-1600 deg.C for 2-20 hr, crushing, grinding and classifying to obtain high-conversion-rate large primary crystal alpha-Al2O3And (3) powder. The alpha-Al2O3The powder has uniform particle size distribution and spherical-like appearance, and the primary crystal of the powder is controllable at 2-15 μm through a two-step calcination system and the dosage of a mineralizer. The invention can effectively solve the problems of difficult dry ball milling of the aluminum-containing raw material, uneven mineralizer, various shapes, wide original crystal size distribution and the like, and has the advantages of simple process method, small consumption of the mineralizer, calcinationThe time is short, industrial equipment can be adopted, and batch production is easy to realize.
Description
Technical Field
The invention relates to high temperature alpha-Al2O3A preparation process of powder, in particular to large primary crystal alpha-Al used in the fields of refractory (casting material), environmental protection (ceramic filter membrane), electronics (heat-conducting filler) and the like2O3A preparation process of powder.
Background
High temperature alpha-Al2O3The powder has the characteristics of high melting point, good high-temperature stability, high heat conductivity coefficient and the like, and is especially spherical or quasi-spherical high-temperature alpha-Al2O3And (3) pulverizing. The method can be applied to the field of refractory materials, improves the flowability and the filling property of powder, reduces the forming water content and stress strain, and improves the density and the high-temperature service performance of the refractory materials; high temperature alpha-Al of spheroidic large primary crystal2O3The powder can be used as a support raw material of a ceramic filter membrane in the field of environmental protection, and uniform pores are formed by particle accumulation; high-temperature alpha-Al of spherical-like large primary crystal2O3The high heat conductivity of the powder can be applied to inorganic heat-conducting fillers in the electronic field. The applications all require the conversion rate, the primary crystal size and the crystal grain morphology of the alumina powder, in particular to the alumina powder with the primary crystal size of more than 2 mu m and the high alpha-phase conversion rate of a similar sphere.
Chinese patent (application No. 201510996824.3) discloses a preparation method and application of near-spherical alpha-alumina micropowder, wherein the preparation method comprises the steps of selecting industrial alumina, industrial aluminum hydroxide or mixed powder of two raw materials, adding 3 per mill to 5 percent of boric acid and magnesium oxide composite mineralizer, ball-milling and mixing for 3 to 4 hours, calcining for 12 to 22 hours at 1450 to 1600 ℃, and ball-milling for 10 to 20 hours to obtain the near-spherical micron-grade alumina micropowder with wide particle size distribution, D50 about 3 microns and the maximum grain size about 10 microns. The preparation method has the advantages of long calcination time and high energy consumption, and simultaneously, the purity of the alumina is greatly reduced due to the high addition amount of the composite mineralizer, the particle size distribution is wide and uneven, and the grading difficulty is high.
Chinese patent application No. 200810029087.X discloses a preparation process of alpha-alumina powder for ceramic membrane support, which comprises the steps of selecting industrial alumina as a raw material, adding a composite mineralizer (boric acid, ammonium chloride, calcium fluoride or fluorite, aluminum fluoride) to prepare an alumina mixture, wherein the weight of the composite mineralizer accounts for 9-21.5 wt%, calcining at 1500-1700 ℃ for 2-15 hours, grinding, washing, grading and drying to prepare alumina powder for ceramic membrane support, which has wide particle distribution, large primary crystal (the maximum crystal grain size is more than or equal to 15 mu m) and high alpha-phase conversion rate and is approximately spherical. The composite mineralizer added in the preparation process has high content, great corrosion to the refractory material of the kiln for calcination, greatly reduced service cycle and greatly increased production cost; meanwhile, the mineralizer is large in dosage and cannot be completely and effectively volatilized, so that a part of the mineralizer is solidified in crystal lattices or forms solid solution and glass which are equal, the activity of the powder is improved, and the purity of the alumina is greatly reduced; meanwhile, the volatile mineralizer has serious pollution to the environment, the environmental protection treatment pressure is increased, and the large amount of the fluorine-containing mineralizer has serious damage to the human body.
Chinese patent (application No. 202110398630.9) discloses a preparation method of large primary crystal alpha-alumina, which selects gamma-Al 2O3 powder as a raw material, adds 2 per mill-3% of boric acid and calcium carbonate composite mineralizer as the raw material, calcines the mixture for 2-8 hours at 1300-1500 ℃, and grinds the mixture for 1-3 hours to obtain large primary crystal alpha-Al 2O3 powder with D50 being 2-6 mu m. However, the raw material is gamma-Al 2O3 powder, the specific surface area is large, the loose packing density is small, the kiln loading density is low, nitrogen and air are used for alternate blowing in the temperature rising process, the process control difficulty is large, cold gas is blown in, the heat loss is large, the production cost is greatly increased, the crystal grain appearance is not controlled, and the embodiment shows that the boric acid has large using amount, and the boric acid can remain and enter alumina crystal lattices to influence the performance of the powder.
Aiming at the process, the following problems exist, which cause that the alpha-alumina with uniform granularity, similar spherical large primary crystal and high purity is difficult to be industrially produced in batch:
1) the raw materials are harsh, such as gamma-alumina powder, the content of a gamma phase is limited, and the specific surface area is large, so that moisture is easy to absorb, and the ball milling and thinning are difficult to realize;
2) the mineralizer has high dosage, namely the mineralizer has the functions of removing sodium, reducing phase transformation temperature, promoting crystal growth and inducing crystal grain appearance; however, most of the mineralizers can be decomposed or can form high-temperature volatile sodium salt with sodium oxide, so that the mineralizers have great influence on kiln equipment and environmental pollution, and the dosage needs to be controlled, wherein the smaller the dosage is, the better the dosage is;
3) powder purity: the mineralizer is added in a large amount and can enter crystal lattices to be remained, so that the purity of the alumina powder is greatly reduced, and meanwhile, the introduction of calcium and magnesium can form a liquid phase or a solid solution, so that the purity of the powder is reduced;
4) calcining temperature and heat preservation time: the preparation of large primary crystal alumina powder has the disadvantages of high calcination temperature (some of which are even 1600-1700 ℃), heat preservation time as high as more than 20 hours, low unit productivity, high energy consumption and large kiln damage.
Disclosure of Invention
The invention aims to solve the technical problems that the raw materials are easy to be ball-milled, refined and uniformly mixed; the mineralizer content is low, the calcination temperature is low, and the heat preservation time is short; a preparation method of high-purity spheroidal large primary crystal alpha-alumina powder.
In order to solve the technical problems, the technical scheme of the invention is a twice calcining method:
the first calcination is low-temperature calcination: the method comprises the steps of mixing an aluminum-containing raw material and a trace amount of first mineralizer uniformly according to a proportion by a mixing device, calcining at 900-1200 ℃, and keeping the temperature for 2-8 hours. Introducing a micro first mineralizer, wherein the aim is to obtain loose, porous and easily-ground non-gamma-phase transition alumina, and a gamma-phase alumina framework is not collapsed or slightly collapsed, so that the attached alkali is fully exposed on the surface of an alumina powder framework, and the high-temperature reaction of a second mineralizer is facilitated to volatilize and remove sodium; the first low-temperature calcination temperature is preferably 950-1150 ℃, more preferably 1000-1150 ℃, and the heat preservation time is 2-6 hours.
Crushing and ball-milling the powder calcined at the low temperature to obtain alumina powder M1 with the powder size less than or equal to 1 mu M, introducing a composite second mineralizer, and continuing ball-milling and homogenizing to obtain uniformly mixed powder M2;
the second calcination is high-temperature calcination: calcining the mixed powder at 1350-1600 ℃ for 2-20 hours, introducing a small amount of composite second mineralizer, wherein the aim is to volatilize sodium by high-temperature reaction, induce the growth and growth of crystal grains in a similar spherical shape by gas-solid and liquid-solid mass transfer, and obtain the sodium-free sodium-solid mixed powder through crushing, ball milling and grading; preferably, the high-temperature calcination temperature is 1400-1550 ℃, and the heat preservation time is 6-16 hours;
the invention is further explained and illustrated below:
in the preparation method, the aluminum-containing raw material (aluminum source for short) is one or a mixture of two of industrial aluminum hydroxide and industrial aluminum oxide; preferably, the source of aluminium is technical alumina, in particular, Na2O% is less than or equal to 500ppm, D50 is less than or equal to 30 μm, and the main crystal phase is gamma phase.
The first mineralizer added in the first low-temperature calcination is one or more of ammonium chloride, ammonium fluoride and ammonium citrate, and the addition amount is 0.1-0.5 wt% of the weight of the aluminum source; one of ammonium chloride and ammonium citrate which is nontoxic, harmless and easy to be processed in an environment-friendly way is preferably selected, and the adding amount of the ammonium chloride and the ammonium citrate is 0.1 to 0.3 weight percent of the weight of the aluminum source; a more preferred first mineralizer is ammonium citrate.
The industrial kiln selected for the first low-temperature calcination in the preparation method is a shuttle kiln, a tunnel kiln or a roller kiln; because the temperature of the first low-temperature calcination is far lower than 1300 ℃, the roller kiln is preferably selected as the calcination kiln to ensure that the material is heated uniformly, the phase change is stable and controllable, and the continuous batch production is realized.
Crushing and ball-milling the alumina powder subjected to the first low-temperature calcination to obtain transition-phase alumina powder M1 with the D50 being less than or equal to 1.0 mu M; adding a composite second mineralizer into the M1, and continuing to perform ball milling and mixing for 2-4 hours to obtain uniform mixed powder M2.
In the invention, the second high-temperature calcination is to calcine the mixed powder M2 in an industrial kiln at 1350-1600 ℃ and keep the temperature for 2-20 hours; preferably, the calcining temperature is 1450-1550 ℃, and the holding time is 4-16 hours; the large primary crystal type spherical alpha-alumina powder with narrow particle size distribution is obtained through crushing, grinding and grading, the grain size can be controlled to be 2 microns, 5 microns, 10 microns and more than 10 microns under D50, and the particle size of the powder can be regulated and controlled by a mineralizer, a calcination temperature and a heat preservation time according to the index requirements of products.
The composite second mineralizer is one or more of boric acid, aluminum fluoride, calcium fluoride, ammonium chloride, ammonium fluoride and ammonium citrate, and the addition amount of the composite second mineralizer is 0.5-1.0 wt% of the weight of M1; preferably, the composite mineralizer consists of boric acid, aluminum fluoride and ammonium chloride, and the addition amount of the composite mineralizer is 0.6 to 0.9 weight percent of the weight of M1.
The industrial kilns used for the second high-temperature calcination are a shuttle kiln, a high-temperature tunnel kiln and a high-temperature pusher kiln; the high-temperature tunnel kiln which can be produced continuously and in batch is preferred.
The powder obtained after the second high-temperature calcination is crushed, ground and classified by a classifier, so that large-grain spheroidal alpha-alumina powder with the grain size D50 of 2 mu m, 5 mu m, 10 mu m and more than 10 mu m can be obtained.
The core technology of the invention is a twice calcination method for preparing the large-primary-crystal spherical high-purity alpha-alumina powder, and the beneficial effects of the process control method are mainly embodied in the following aspects:
(1) the purpose of the first low-temperature calcination is to obtain framework and non-gamma transition phase alumina in a gamma phase, wherein the transition phase alumina is mixed phase alumina, and the crystal phase composition is q/u-Al2O3, k-Al2O3 and not more than 50% of alpha-Al 2O 3. The mineralizer selected in the stage is a low-temperature decomposable and volatile mineralizer, and has the main functions of three: firstly, decomposing, volatilizing and forming a pore to form a heat transfer channel; secondly, the sodium ions are combined and volatilized, so that the low-temperature sodium removal effect is achieved; thirdly, the gas phase mass transfer mode induces the crystal form transformation of the alumina to promote the crystal growth.
(2) The mixed phase alumina after the first low-temperature calcination is loose and porous, has extremely low apparent density, but is easy to be ball milled, crushed and refined, and the alumina micro powder with the D50 being less than or equal to 1 mu m can be obtained by ball milling in a shorter time, the apparent density is increased, the fine crystal micro powder can be fully homogenized with a composite mineralizer, the uniform growth of crystals is promoted, and the size difference is small.
(3) The purpose of the second high-temperature calcination is to promote the crystal growth and smooth particle appearance through the gas phase mass transfer and the solid phase mass transfer of the composite mineralizer at high temperature, and simultaneously the composite mineralizer reacts with sodium oxide to generate volatile sodium salt, so that the sodium is effectively removed, the crystal grain growth is further promoted, the large spheroidic or hexagonal columnar primary crystal is formed, the sodium is effectively removed, and the purity of the alumina powder is improved.
alpha-Al prepared according to the method of the invention2O3The alpha conversion rate of the powder is more than 98 percent, the particle size range is 2-15 mu m, the particle size D50 of the powder is 2 mu m, 5 mu m, 10 mu m and more than 10 mu m after classification, and the crystal grain appearance is similar to a sphere.
Drawings
FIG. 1 is an XRD spectrum of the powder after the first low-temperature calcination in example 1;
FIG. 2 is the XRD spectrum of the powder after the second high temperature calcination in example 1;
FIG. 3 is a Scanning Electron Microscope (SEM) image of the final powder of example 1;
FIG. 4 is a Scanning Electron Microscope (SEM) image of the final powder of example 2;
FIG. 5 is a Scanning Electron Microscope (SEM) image of the final powder of example 3.
Detailed Description
The invention is further illustrated by the following examples:
example 1:
in this example, low sodium industrial alumina was used as a raw material (Na)2O% is less than or equal to 600ppm, D50 is less than or equal to 30 mu m), ammonium chloride is used as a mineralizer, the addition amount is 0.2 percent of the mass of the industrial alumina, and the materials are mixed for 4 hours by a ball mill or a mixer for standby.
And (3) putting the mixed powder into a square cordierite/mullite sagger, calcining in a roller kiln, cooling by a kiln tail to obtain blocky loose and porous transition phase alumina powder M1, wherein the temperature of a heat preservation section is 1100 ℃, the operation time of the heat preservation section is 4 hours.
Putting the blocky powder into a ball mill, adding a composite mineralizer prepared from boric acid, aluminum fluoride and ammonium chloride according to the mass ratio of 3:0.5:0.5, and carrying out ball milling together, wherein the total amount is 0.4% of the mass of M1. The ball milling time is 4-8 hours, the particle size D50 of the powder is less than or equal to 1.0 mu M, the ball milling time can be properly prolonged or shortened according to the final powder particle size, and the mixed powder M2 is obtained, and the loose framework is opened, so that the loose packing density is greatly improved.
Putting M2 powder into square sagger of corundum-mullite, compacting, placing on shuttle kiln or tunnel kiln car, and keeping the temperature at 1400 deg.C for 4 ℃Cooling to obtain block alumina material with certain strength, crushing in jaw crusher, crushing in double roll crusher and grinding in ball mill to obtain single spherical alpha-Al material with homogeneous grain size distribution2O3The particle size of the micro powder of the powder is about 2 mu m, and the alpha phase is more than 96 percent.
The XRD spectrum of the first low-temperature calcined powder is shown in FIG. 1, and the composition of the crystalline phase is q/u-Al2O3、k-Al2O3And less than 50% of alpha-Al2O3And no gamma phase with large specific surface area and easy moisture absorption.
The XRD spectrum of the second high-temperature calcined powder is shown in figure 2, and the crystal phase composition is single alpha-Al 2O 3.
The Scanning Electron Microscope (SEM) image of the crushed, ground and classified alumina micro powder is shown in figure 3, and the single spherical-like alumina micro powder is obtained.
Example 2:
in this example, low sodium industrial alumina was used as a raw material (Na)2O% is less than or equal to 600ppm, D50 is less than or equal to 30 mu m), ammonium chloride is used as a mineralizer, the addition amount is 0.2 percent of the mass of the industrial alumina, and the materials are mixed for 4 hours for standby application by a ball mill or a mixer.
And (3) putting the mixed powder into a square cordierite/mullite sagger, calcining in a roller kiln, cooling by a kiln tail to obtain blocky loose and porous transition phase alumina powder M1, wherein the temperature of a heat preservation section is 1100 ℃, the operation time of the heat preservation section is 4 hours.
Putting the blocky powder M1 into a ball mill, adding a composite mineralizer prepared from boric acid, aluminum fluoride and ammonium chloride according to the mass ratio of 4:1:0.5, and carrying out ball milling together, wherein the ball-to-material ratio is 3:1, and the total mass is 0.55% of the mass of M1. The ball milling time is 4-8 hours, the particle size D50 of the powder is less than or equal to 1.0 mu M, the ball milling time can be properly prolonged or shortened according to the final powder particle size, and the mixed powder M2 is obtained, and the loose framework is opened, so that the loose packing density is greatly improved.
Loading M2 powder into square sagger of corundum-mullite, compacting, placing on shuttle kiln or tunnel kiln, holding at 1450 deg.C for 8 hr, cooling to obtain block alumina material with certain strength, crushing with jaw crusher, crushing with double-roller mill, and grinding with ball mill to obtain particle sizeUniformly distributed alpha-Al2O3The particle size of the micro powder of the powder is about 5 mu m, the appearance is a single sphere-like shape, and as shown in figure 4, the alpha phase is more than 98 percent.
Example 3:
in this example, low sodium industrial alumina was used as a raw material (Na)2O% is less than or equal to 600ppm, D50 is less than or equal to 30 mu m), ammonium chloride is used as a mineralizer, the addition amount is 0.2 percent of the mass of the industrial alumina, and the materials are mixed for 4 hours for standby application by a ball mill or a mixer.
And (3) putting the mixed powder into a square cordierite/mullite sagger, calcining in a roller kiln, cooling by a kiln tail to obtain blocky loose and porous transition phase alumina powder M1, wherein the temperature of a heat preservation section is 1100 ℃, the operation time of the heat preservation section is 4 hours.
Putting the blocky powder into a ball mill, adding a composite mineralizer prepared from boric acid, aluminum fluoride and ammonium chloride according to the mass ratio of 6:1:1, and carrying out ball milling together, wherein the total amount is 0.8% of the mass of M1. The ball milling time is 4-8 hours, the particle size D50 of the powder is less than or equal to 1.0 mu M, the ball milling time can be properly prolonged or shortened according to the final powder particle size, and the mixed powder M2 is obtained, and the loose framework is opened, so that the loose packing density is greatly improved.
Loading M2 powder into square sagger of corundum-mullite, compacting, placing on shuttle kiln or tunnel kiln, holding at 1520 deg.C for 12 hr, cooling to obtain block alumina material with certain strength, and jaw crusherCrushingCrushing by a double-roller mill and grinding by a ball mill to obtain alpha-Al with uniform particle size distribution2O3The particle size of the micro powder of the powder is about 8 mu m, the appearance is a single sphere-like shape, and as shown in figure 5, the alpha phase is more than 98 percent.
Claims (10)
1. Spheroidal large primary crystal alpha-Al2O3The preparation method of the powder is characterized by adopting a twice calcining method and comprising the following steps:
1) low-temperature calcination: uniformly mixing an aluminum-containing raw material and a first mineralizer by a mixer, and calcining for 2-8 hours in a first kiln at 900-1200 ℃;
2) and (3) low-temperature calcination powder treatment: crushing and ball-milling the powder after low-temperature calcination to obtain aluminum oxide powder M1 with the particle size of less than 1.0 mu M; uniformly mixing the alumina powder M1 and the second mineralizer by a mixer to obtain mixed powder M2;
3) high-temperature calcination: calcining the mixed powder M2 in a second kiln at 1350-1600 ℃ for 2-20 hours;
4) high-temperature calcination powder treatment: the powder after high-temperature calcination is crushed, ball-milled and graded to obtain 2-15 mu m spheroidal alpha-Al crystal grains2O3And (3) pulverizing.
2. The preparation method according to claim 1, wherein the low-temperature calcination is performed at 950 ℃ to 1150 ℃ for 3 to 6 hours.
3. The preparation method of claim 1, wherein the high-temperature calcination is carried out at 1400 ℃ to 1550 ℃ for 6 to 16 hours.
4. The preparation method according to claim 1, wherein the aluminum-containing raw material is one or a mixture of industrial aluminum hydroxide powder and industrial aluminum oxide powder.
5. The preparation method according to claim 1, wherein the first mineralizer is one or more of ammonium chloride, ammonium fluoride and ammonium citrate, and is added in an amount of 0.1-1.0 wt% of the aluminum-containing raw material; one of ammonium chloride and ammonium citrate is preferably selected, and the addition amount is 0.2 to 0.5 weight percent of the weight of the aluminum-containing raw material.
6. The preparation method according to claim 1, wherein the second mineralizer is one or more of boric acid, aluminum fluoride, calcium fluoride, ammonium chloride, ammonium fluoride and ammonium citrate, and is added in an amount of 0.5 wt% to 1.0 wt% based on the weight of M1.
7. The preparation method according to claim 6, wherein the second mineralizer is a composite mineralizer of boric acid, aluminum fluoride and ammonium chloride, and is added in an amount of 0.6 wt% to 0.9 wt% based on the weight of M1.
8. The method of manufacturing according to claim 1, wherein the first kiln is a shuttle kiln, a tunnel kiln or a roller kiln, preferably a roller kiln with a more uniform temperature field.
9. Preparation method according to claim 1, wherein the second kiln is a shuttle kiln, a tunnel kiln, a pushed slab kiln, preferably a tunnel kiln.
10. The preparation method according to claim 1, wherein the second mineralizer is prepared from boric acid, aluminum fluoride and ammonium chloride according to a mass ratio of 3-7: 0.5-1.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4379134A (en) * | 1981-02-13 | 1983-04-05 | Union Carbide Corporation | Process of preparing high purity alumina bodies |
| JPH06329412A (en) * | 1993-05-20 | 1994-11-29 | Sumitomo Chem Co Ltd | Production of alpha-alumina |
| CN104556167A (en) * | 2014-12-19 | 2015-04-29 | 贵州天合国润高新材料科技有限公司 | Method for preparing flaky alumina powder |
| CN105565785A (en) * | 2015-12-25 | 2016-05-11 | 山东硅元新型材料有限责任公司 | Preparation method of ceramic membrane support body |
| CN111498883A (en) * | 2020-03-13 | 2020-08-07 | 苏州盛曼特新材料有限公司 | Preparation method of large-primary-crystal high-purity calcined α -alumina micropowder |
-
2022
- 2022-04-28 CN CN202210461818.8A patent/CN114620751A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4379134A (en) * | 1981-02-13 | 1983-04-05 | Union Carbide Corporation | Process of preparing high purity alumina bodies |
| JPH06329412A (en) * | 1993-05-20 | 1994-11-29 | Sumitomo Chem Co Ltd | Production of alpha-alumina |
| CN104556167A (en) * | 2014-12-19 | 2015-04-29 | 贵州天合国润高新材料科技有限公司 | Method for preparing flaky alumina powder |
| CN105565785A (en) * | 2015-12-25 | 2016-05-11 | 山东硅元新型材料有限责任公司 | Preparation method of ceramic membrane support body |
| CN111498883A (en) * | 2020-03-13 | 2020-08-07 | 苏州盛曼特新材料有限公司 | Preparation method of large-primary-crystal high-purity calcined α -alumina micropowder |
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