CN115432676A - System and method for preparing high-quality silicon nitride powder by using multistage fluidized bed - Google Patents
System and method for preparing high-quality silicon nitride powder by using multistage fluidized bed Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 138
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000006298 dechlorination reaction Methods 0.000 claims abstract description 86
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 65
- 239000002243 precursor Substances 0.000 claims abstract description 63
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 62
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 41
- 239000010703 silicon Substances 0.000 claims abstract description 41
- 238000002425 crystallisation Methods 0.000 claims abstract description 36
- 230000008025 crystallization Effects 0.000 claims abstract description 36
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 36
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 239000007789 gas Substances 0.000 claims description 317
- 239000000463 material Substances 0.000 claims description 96
- 238000000926 separation method Methods 0.000 claims description 67
- 229910052757 nitrogen Inorganic materials 0.000 claims description 42
- 238000011084 recovery Methods 0.000 claims description 39
- 238000007906 compression Methods 0.000 claims description 34
- 230000006835 compression Effects 0.000 claims description 34
- 238000010438 heat treatment Methods 0.000 claims description 24
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 20
- 230000008020 evaporation Effects 0.000 claims description 18
- 238000001704 evaporation Methods 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 12
- 230000014759 maintenance of location Effects 0.000 claims description 11
- 235000019270 ammonium chloride Nutrition 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 4
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 229910052582 BN Inorganic materials 0.000 claims description 2
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims 2
- 239000012071 phase Substances 0.000 abstract description 61
- 238000006243 chemical reaction Methods 0.000 abstract description 13
- 239000012535 impurity Substances 0.000 abstract description 10
- -1 silicon amine Chemical class 0.000 abstract description 8
- 238000002360 preparation method Methods 0.000 abstract description 7
- 239000007791 liquid phase Substances 0.000 abstract description 6
- 238000001308 synthesis method Methods 0.000 abstract description 5
- 239000002904 solvent Substances 0.000 abstract description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 abstract description 2
- 238000010521 absorption reaction Methods 0.000 abstract description 2
- 238000009826 distribution Methods 0.000 abstract description 2
- 239000010419 fine particle Substances 0.000 abstract description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract 1
- 229910052801 chlorine Inorganic materials 0.000 abstract 1
- 239000000460 chlorine Substances 0.000 abstract 1
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 229910021417 amorphous silicon Inorganic materials 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 4
- 230000000382 dechlorinating effect Effects 0.000 description 4
- 230000002194 synthesizing effect Effects 0.000 description 4
- 229910003691 SiBr Inorganic materials 0.000 description 3
- 229910003902 SiCl 4 Inorganic materials 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 3
- 239000011863 silicon-based powder Substances 0.000 description 3
- 238000010923 batch production Methods 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000012620 biological material Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 238000000713 high-energy ball milling Methods 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
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- 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
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- 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
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- 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
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
Abstract
The invention discloses a system and a method for preparing high-quality silicon nitride powder by using a multistage fluidized bed. After the gas-phase silicon source reacts with ammonia gas in the fluidized bed, high-quality silicon nitride powder with low impurity content, high alpha phase content, fine particle size and narrow distribution can be prepared by the steps of dechlorination, deep dechlorination, decomposition, crystallization and the like in sequence. The method solves the problem that the gas phase synthesis route in the traditional silicon amine precursor conversion method is difficult to obtain the silicon nitride powder with low chlorine content, and simultaneously compared with the traditional solvent hydrothermal liquid phase synthesis method and the silicon amine precursor liquid phase synthesis method, the method can solve the problem that the moisture absorption and protection of the precursor are difficult, can realize the continuous batch preparation of the high-quality silicon nitride powder, has higher production efficiency, greatly reduces the cost of the high-quality silicon nitride powder, and expands the application range of the powder.
Description
Technical Field
The invention belongs to the field of chemical industry and materials, relates to a preparation method of powder, and particularly relates to high-quality silicon nitride (Si) 3 N 4 ) A preparation process of powder.
Background
Si 3 N 4 The ceramic quilt is known as "all-round ceramic" for machining, aerospace and electronic informationAnd has wide application in the fields of biological materials and the like. High quality Si 3 N 4 The powder is used for preparing high-performance Si 3 N 4 The powder occupies 1/3-2/3 of the cost of the ceramic. The high quality powder needs to have a particle size of about 0.4-1.5 μm and an alpha phase content>95% and O content<0.9wt.%, C content<0.2wt.%, cl content<100ppm, metal impurities<500ppm. Through decades of continuous research and development, si is prepared at present 3 N 4 The powder mainly comprises the following methods:
(1)SiO 2 carbothermal nitridation method of (3 SiO) 2 (s)+2N 2 (g)+6C(s)＝Si 3 N 4 (s) +6CO (g)). The reaction is typically a solid phase nitridation reaction, and mass transfer by diffusion is the limiting step of the overall reaction. This results in a very high oxygen content of the powder, typically greater than 5.0wt.%, and impure product phases, usually containing SiC, siO y N z And residual SiO 2 And free C. Although repeated crushing and nitridation can reduce the O impurities of the powder to some extent, the powder still contains SiC and C and other heterogeneous phases (j.am.center.soc., 1996,82, 1635). In addition, due to Si 3 N 4 The hardness is high, impurities are introduced in the crushing process, and the particle size of the powder is difficult to be reduced to less than 1.0 μm.
(2) Direct nitridation method of Si powder (3 Si(s) +2N 2 (g)＝Si 3 N 4 (s)). The reaction is a strong exothermic reaction, and the Si is synthesized by adopting a self-propagating combustion technology in industry 3 N 4 And (3) powder. However, since the reaction still has a mass transfer barrier and the temperature gradient is large, free Si-containing Si is obtained 3 N 4 Bulk and the alpha content in the product is typically less than 70%. Although raising N in the vessel 2 The pressure of (about 10 MPa) or high energy ball milling can enhance mass transfer and reduce the content of free Si, but free Si cannot be avoided. In addition, a great deal of research adopts the addition of a diluent to regulate and control the synthesis temperature, but the alpha phase content is difficult to be more than 95 percent and does not meet the requirement of high-quality powder.
(3) Chemical vapor deposition. SiCl in general 4 -N 2 -H 2 /NH 3 And SiHCl 3 N 2 -H 2 /NH 3 The system needs high-energy plasma to assist in synthesizing the powder (US 4416863). However, the synthesized powder is not an α -phase powder but a β -phase powder. . To solve this problem, germany Basff corporation developed amorphous seed powder (BET)>50m 2 /g) fluidized gas phase synthesis method for assisting fluidization and strengthening deposition (US 4859443), and amorphous Si with a coating structure is prepared at 500-1500 DEG C 3 N 4 Powder and mixed Si of alpha phase and beta phase 3 N 4 And (3) powder. However, the content of the alpha phase in the powder is small, and wherein the Cl impurity content is higher (>1.0 wt%), which does not meet the requirements of high quality powder. In comparison, siH 4 And NH 3 The reaction is easier to synthesize the powder (3 SiH) 4 (g)+4NH 3 (g)＝Si 3 N 4 (s)+12H 2 (g) ). However, the synthesized amorphous powder is crystallized to Si 3 N 4 Powder, rather than alpha phase powder (US 4122155, US4929432, proceedings for inorganic materials 2006, 21, 41; proceedings of the university of chem, zhejiang, 2007, 24, 36). Meanwhile, the powder contains a large amount of free Si, so that the requirement of high-quality powder is not met. In addition, siH 4 Is a toxic and hazardous gas, is flammable and explosive, and about 45 percent of accidents occur in the process stage, and 21 percent of accidents occur when bottles are replaced. Thus, chemical vapor deposition produces high quality Si 3 N 4 Powders also face significant challenges.
(4) Silicon amine precursor conversion process, i.e. SiCl 4 And NH 3 Firstly, synthesizing a silicon amine precursor Si (NH) at low temperature 2 ) 4 Or Si (NH) 2 Then separating out by-product, finally crystallizing and synthesizing Si 3 N 4 And (3) powder. Alpha-phase was obtained by a low-temperature liquid-phase synthesis process developed by Japan department of Japan (US 4405589, 5585084, 5595718), toyo Cauda Co., ltd., japan (US 4387079), and the United states air force (US 3959446)>95% and a BET of about 6m 2 Per g, and Cl<100ppm of high purity ultra-fine Si 3 N 4 Powder (A)>99.95%). However, the reaction conditions of the process are very harsh, continuous batch production is difficult to carry out, and batch production is necessary, so that the yield of powder is low, and the efficiency is low.
In summary, siO 2 The carbothermal nitridation method, the direct nitridation method of Si powder, and the chemical vapor deposition method are all difficult to prepare high quality Si 3 N 4 And (3) powder. The solvent hydrothermal liquid phase synthesis method and the silicon amine precursor conversion method can prepare high-quality Si 3 N 4 However, the yield of the synthesized powder is small, the efficiency is low, the cost is high, and the application range of the high-quality silicon nitride powder is limited. The moisture absorption protection problem in intermittent production can be effectively solved by continuous production, so that the cost is reduced. Therefore, there is a need in the art to develop a method for continuously producing high quality Si in batches at low cost and high efficiency 3 N 4 A method for preparing powder.
Disclosure of Invention
Aiming at the problems, the invention provides a system and a method for preparing high-quality silicon nitride powder by a multistage fluidized bed, which can realize continuous large-scale production of high-quality Si by synthesizing a precursor in the fluidized bed, dechlorinating in a grading way, decomposing and crystallizing 3 N 4 Powder, high efficiency and output and low cost.
In order to achieve the purposes, the invention adopts the following technical scheme:
the invention provides a system for preparing high-quality silicon nitride powder by a multistage fluidized bed, which comprises: the device comprises a powder feeding device 1, a precursor gas-phase synthesis fluidized bed 2, a first gas purifier 3-1, a second gas purifier 3-2, a third gas purifier 3-3, a silicon source evaporation device 4, a first cyclone separation device 5, a tail gas recovery and compression device 6, a dechlorination fluidized bed 7, a first energy supply device 8, a second cyclone separation device 9, a heating device 10, an ammonium chloride collecting device 11, a deep dechlorination fluidized bed 12, a third cyclone separation device 13, an acid gas processor 14, a decomposition fluidized bed 15, a fourth cyclone separation device 16, a crystallization device 17, a silicon nitride powder collecting device 18 and a second energy supply device 19;
the discharge hole of the powder feeding device 1 is connected with the feed inlet at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a material valve; ar or N 2 Is connected with the air inlet of the first gas purifier 3-1 through a pipeline; the first isThe gas outlet of the gas purifier 3-1 is connected with the gas inlet of the silicon source evaporation device 4 through a pipeline and a gas valve; the gas outlet of the silicon source evaporation device 4 is connected with the gas inlet at the lower part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a gas valve; the gas outlet of the first gas purifier 3-1 is connected with the gas inlet at the bottom of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a gas valve; NH (NH) 3 Is connected with the gas inlet of the second gas purifier 3-2 through a pipeline; the gas outlet of the second gas purifier 3-2 is connected with the gas inlet at the bottom of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a gas valve; h 2 Is connected with the gas inlet of the third gas purifier 3-3 through a pipeline;
an air outlet at the upper part of the precursor gas-phase synthesis fluidized bed 2 is connected with an air inlet of the first cyclone separation device 5 through a pipeline; a discharge hole at the bottom of the first cyclone separation device 5 is connected with a feed hole at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline; an air outlet at the top of the first cyclone separation device 5 is connected with an air inlet of the tail gas recovery and compression device 6 through a pipeline;
a discharge port at the lower part of the precursor gas-phase synthesis fluidized bed 2 is connected with a feed port of the dechlorination fluidized bed 7 through a pipeline and a material valve; the dechlorination fluidized bed 7 is provided with the first energy supply device 8; the gas inlet at the bottom of the dechlorination fluidized bed 7 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve; the air outlet at the top of the dechlorination fluidized bed 7 is connected with the air inlet of the second cyclone separation device 9 through a pipeline provided with the heating device 10; the air outlet of the second cyclone separation device 9 is connected with the air inlet of the tail gas recovery and compression device 6 through a pipeline; the discharge hole of the second cyclone separation device 9 is connected with the feed inlet of the ammonium chloride collection device 11 through a pipeline and a material valve;
a discharge hole at the lower part of the dechlorination fluidized bed 7 is connected with a feed hole at the upper part of the deep dechlorination fluidized bed 12 through a pipeline and a material valve; the deep dechlorination fluidized bed 12 is provided with the second energy supply device 19; an air outlet at the top of the deep dechlorination fluidized bed 12 is connected with an air inlet of the third cyclone separation device 13 through a pipeline; a discharge hole at the bottom of the third cyclone separation device 13 is connected with a feed inlet at the upper part of the deep dechlorination fluidized bed 12 through a pipeline; an air outlet at the top of the third cyclone separation device 13 is connected with an air inlet of the acid gas processor 14 through a pipeline; the acid gas processor 14 is connected with the gas inlet of the tail gas recovery and compression device 6 through a pipeline and a gas valve; the gas inlet at the bottom of the deep dechlorination fluidized bed 12 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve;
a discharge hole at the lower part of the deep dechlorination fluidized bed 12 is connected with a feed inlet of the decomposition fluidized bed 15 through a pipeline and a material valve; an air outlet at the upper part of the decomposition fluidized bed 15 is connected with an air inlet of the fourth cyclone separation device 16 through a pipeline; the air outlet at the top of the fourth cyclone separation device 16 is connected with the air inlet of the tail gas recovery and compression device 6 through a pipeline and an air valve; a discharge hole at the bottom of the fourth cyclone separation device 16 is connected with a feed inlet at the upper part of the decomposition fluidized bed 15 through a pipeline; the gas inlet at the bottom of the decomposition fluidized bed 15 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve;
a discharge port at the lower part of the decomposition fluidized bed 15 is connected with the crystallization device 17 through a pipeline and a material valve; an air outlet at the upper part of the crystallization device 17 is connected with an air inlet of the tail gas recovery and compression device 6 through a pipeline and an air valve; the gas inlet at the bottom of the crystallization device 17 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve; and a discharge port at the lower part of the crystallization device 17 is connected with a feed port of the silicon nitride powder collecting device 18 through a pipeline and a material valve.
The first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 are respectively communicated with the gas outlets of corresponding gas sources.
The method for preparing high-quality silicon nitride powder based on the system comprises the following steps:
the material in the powder feeding device 1 passes through Ar or N 2 After cleaning, ar or N enters the cleaning tank through a pipeline and a material valve 2 The washed precursor gas phase synthesis fluidized bed 2 is kept fluidized; ar or N 2 Carrying the silicon source in the silicon source evaporation device 4 into the precursor gas-phase synthesis fluidized bed 2, and simultaneously NH 3 With Ar or N 2 Enters the precursor gas-phase synthesis fluidized bed 2 through a pipeline to generate a precursor synthesis reaction; the fine powder in the precursor gas-phase synthesis fluidized bed 2 is separated by the first cyclone separation device 5 and then enters the precursor gas-phase synthesis fluidized bed 2 again; tail gas separated by the first cyclone separation device 5 enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
the material in the precursor gas phase synthesis fluidized bed 2 enters the dechlorination fluidized bed 7 through a pipeline and a material valve, and simultaneously, a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the dechlorination fluidized bed 7 and ensures that the material therein is in a fluidized state; under the action of the first energy supply device 8, NH in the material in the dechlorination fluidized bed 7 4 Decomposition of Cl into NH 3 And HCl and with the off-gas via a pipe provided with said heating means 10 into said second cyclone 9, NH 3 And HCl is condensed and crystallized to form NH 4 Cl solid particles enter the ammonium chloride collecting device 11, and tail gas enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
NH is removed in the dechlorination fluidized bed 7 4 Cl material enters the deep dechlorination fluidized bed 12 through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the deep dechlorination fluidized bed 12 and ensures that the materials in the deep dechlorination fluidized bed are in a fluidized state; under the action of the second energy supply device 19, the material in the deep dechlorination fluidized bed 12 is deeply dechlorinated, and fine powder in the tail gas is separated by the third cyclone separation device 13 and then enters the deep dechlorination fluidized bedEntering the deep dechlorination fluidized bed 12; the tail gas separated by the third cyclone separation device 13 passes through the acid gas processor 14 and then enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
the material in the deep dechlorination fluidized bed 12 enters the decomposition fluidized bed 15 through a pipeline and a material valve, and a certain amount of NH is added 3 Or H 2 With Ar or N 2 The gas enters the decomposition fluidized bed 15, and the material is converted into amorphous powder under a certain temperature condition; fine powder in the tail gas is separated by the fourth cyclone separation device 16 and then enters the decomposition fluidized bed 15; tail gas separated by the fourth cyclone separation device 16 enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
the material in the decomposing fluidized bed 15 enters the crystallizing device 17 through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the crystallization device 17, under a certain temperature condition, amorphous powder is converted into crystalline powder and enters the silicon nitride powder collecting device 18 through a pipeline and a material valve; and tail gas in the crystallization device 17 enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused.
Preferably, the material in the powder feeding device 1 is amorphous or crystalline silicon nitride powder or the combination of the amorphous or crystalline silicon nitride powder in any proportion, the purity is more than 99.9 percent, and the particle size is more than 0.5 mu m.
Preferably, ar, N 2 、NH 3 、H 2 The purity is more than 99.9 percent, and the oxygen content and the water vapor content are all less than 500ppm after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3.
Preferably, the temperature of the precursor gas phase synthesis fluidized bed 2 is in the range of-10 to 200 ℃, and the fluidizing gas is Ar and N 2 And H 2 Any one or any ratio of the above, and bed NH 3 The molar ratio of the silicon source to the gas-phase silicon source is more than or equal to 6, and the synthesis time is more than 1min and less than or equal to 600min.
Preferably, the silicon source in the silicon source evaporation device 4 is pureGreater than 99.9% SiCl 4 、SiHCl 3 、SiH 2 Cl 2 、SiBr 4 、SiF 4 And any one or any combination of the common silicon halides in any proportion, and the temperature of the silicon source evaporation device 4 is-10 to 100 ℃.
Preferably, the temperature range of the materials in the dechlorination fluidized bed 7 is 300-800 ℃, and the fluidizing gas is Ar and N 2 、NH 3 And H 2 Any one or any proportion of the above, and the material retention time is more than or equal to 3min and less than or equal to 600min.
Preferably, the first energy supply device 8 and the second energy supply device 19 are any one or a combination of two heating methods of conventional resistance heating or microwave heating.
Preferably, the heating device 10 maintains a temperature of 400 to 600 ℃.
Preferably, the temperature in the deep dechlorination fluidized bed 12 is 600-1000 ℃, and the fluidizing gas is Ar and N 2 、NH 3 And H 2 Any one or any proportion of the above, the material retention time is more than or equal to 10min and less than or equal to 600min.
Preferably, the temperature of the decomposition fluidized bed 15 is 800-1200 ℃, and the fluidizing gas is Ar, N 2 、NH 3 And H 2 The gas is mixed in any proportion, and the material retention time is more than or equal to 5min and less than or equal to 600min.
Preferably, the inner wall of the crystallization device 17 is made of high-melting-point inert materials such as high-purity graphite, silicon nitride, silicon carbide or boron nitride and the like, the crystallization temperature is 1350-1600 ℃, and the bulk density of the materials in a bed layer is more than or equal to 0.2g/cm 3 The residence time of the materials is more than or equal to 10min and less than or equal to 180min, and the gas in the crystallization device 17 is Ar and N 2 、NH 3 And H 2 Any one or any combination of the proportions of the gases.
After the gas-phase silicon source reacts with ammonia gas in the fluidized bed, high-quality silicon nitride powder with low impurity content, high alpha phase content, fine particle size and narrow distribution can be prepared by the steps of dechlorination, deep dechlorination, decomposition, crystallization and the like in sequence.
Compared with the prior art, the invention has the following advantages:
with conventional SiO 2 Compared with the direct nitridation method of Si powder, the silicon nitride powder prepared by the method has higher purity and alpha phase content and finer particle size; compared with the traditional chemical vapor deposition method, the silicon nitride powder prepared by the method has higher efficiency and alpha phase content; compared with the gas phase synthesis route in the silicon amine precursor conversion method, the method solves the problem that the silicon nitride powder with low Cl impurity content is difficult to synthesize, and compared with the traditional solvent hydrothermal liquid phase synthesis method and the liquid phase synthesis route in the silicon amine precursor conversion method, the method can realize continuous mass preparation of high-quality silicon nitride powder, has higher production efficiency, can greatly reduce the price of the high-quality silicon nitride powder, and expands the application range of the powder.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a schematic configuration diagram of a system for preparing high-quality silicon nitride powder according to the present invention;
FIG. 2 is an XRD pattern of silicon nitride powder prepared by example 3;
FIG. 3 is an SEM photograph of a silicon nitride powder prepared in example 4;
FIG. 4 is an XRD pattern of silicon nitride powder prepared in example 5;
reference numerals:
1. a powder feeding device; 2. a precursor gas-phase synthesis fluidized bed; 3-1, a first gas purifier; 3-2, a second gas purifier; 3-3, a third gas purifier; 4. a silicon source evaporation device; 5. a first cyclonic separating apparatus; 6. a tail gas recovery and compression device; 7. a dechlorination fluidized bed; 8. a first energy supply device; 9. a second cyclonic separating apparatus; 10. a heating device; 11. an ammonium chloride collecting device; 12. a deep dechlorination fluidized bed; 13. a third cyclonic separating apparatus; 14. an acid gas processor; 15. decomposing the fluidized bed; 16. a fourth cyclone separating device; 17. a crystallization device; 18. a silicon nitride powder collecting device; 19. a second energy supply device.
Detailed Description
Any feature disclosed in this specification may be replaced by alternative features serving an equivalent or similar purpose, unless expressly stated otherwise. Unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. The description is only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.
The invention is described in further detail below with reference to the figures and the detailed description.
Example 1
With reference to fig. 1, the high-quality silicon nitride powder preparation system of this embodiment includes a powder feeding device 1, a precursor gas-phase synthesis fluidized bed 2, a first gas purifier 3-1, a second gas purifier 3-2, a third gas purifier 3-3, a silicon source evaporation device 4, a first cyclone separation device 5, a tail gas recovery and compression device 6, a dechlorination fluidized bed 7, a first energy supply device 8, a second cyclone separation device 9, a heating device 10, an ammonium chloride collecting device 11, a deep dechlorination fluidized bed 12, a third cyclone separation device 13, an acidic gas processor 14, a decomposition fluidized bed 15, a fourth cyclone separation device 16, a crystallization device 17, a silicon nitride powder collecting device 18, and a second energy supply device 19;
the discharge hole of the powder feeding device 1 is connected with the feed inlet at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a material valve; ar or N 2 Is connected with the air inlet of the first gas purifier 3-1 through a pipeline; the gas outlet of the first gas purifier 3-1 is connected with the gas inlet of the silicon source evaporation device 4 through a pipeline and a gas valve; the gas outlet of the silicon source evaporation device 4 is connected with the gas inlet at the lower part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a gas valve; the gas outlet of the first gas purifier 3-1 is connected with the gas inlet at the bottom of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a gas valve; NH (NH) 3 Is connected with the gas inlet of the second gas purifier 3-2 through a pipeline; the gas outlet of the second gas purifier 3-2 and the bottom of the precursor gas-phase synthesis fluidized bed 2The air inlet of the part is connected with the air valve through a pipeline;
an air outlet at the upper part of the precursor gas-phase synthesis fluidized bed 2 is connected with an air inlet of the first cyclone separation device 5 through a pipeline; a discharge hole at the bottom of the first cyclone separation device 5 is connected with a feed inlet at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline; an air outlet at the top of the first cyclone separation device 5 is connected with an air inlet of the tail gas recovery and compression device 6 through a pipeline;
a discharge hole at the lower part of the precursor gas-phase synthesis fluidized bed 2 is connected with a feed inlet of the dechlorination fluidized bed 7 through a pipeline and a material valve; the dechlorination fluidized bed 7 is provided with the first energy supply device 8; the gas inlet at the bottom of the dechlorination fluidized bed 7 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve; the air outlet at the top of the dechlorination fluidized bed 7 is connected with the air inlet of the second cyclone separation device 9 through a pipeline provided with the heating device 10; the gas outlet of the second cyclone separation device 9 is connected with the gas inlet of the tail gas recovery and compression device 6 through a pipeline; the discharge hole of the second cyclone separation device 9 is connected with the feed inlet of the ammonium chloride collecting device 11 through a pipeline and a material valve;
a discharge hole at the lower part of the dechlorination fluidized bed 7 is connected with a feed hole at the upper part of the deep dechlorination fluidized bed 12 through a pipeline and a material valve; the deep dechlorination fluidized bed 12 is provided with the second energy supply device 19; the air outlet at the top of the deep dechlorination fluidized bed 12 is connected with the air inlet of the third cyclone separation device 13 through a pipeline; a discharge hole at the bottom of the third cyclone separation device 13 is connected with a feed inlet at the upper part of the deep dechlorination fluidized bed 12 through a pipeline; an air outlet at the top of the third cyclone separation device 13 is connected with an air inlet of the acid gas processor 14 through a pipeline; the acid gas processor 14 is connected with the gas inlet of the tail gas recovery and compression device 6 through a pipeline and a gas valve; the gas inlet at the bottom of the deep dechlorination fluidized bed 12 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve;
a discharge hole at the lower part of the deep dechlorination fluidized bed 12 is connected with a feed inlet of the decomposition fluidized bed 15 through a pipeline and a material valve; an air outlet at the upper part of the decomposition fluidized bed 15 is connected with an air inlet of the fourth cyclone separation device 16 through a pipeline; an air outlet at the top of the fourth cyclone separation device 16 is connected with an air inlet of the tail gas recovery and compression device 6 through a pipeline and an air valve; a discharge hole at the bottom of the fourth cyclone separation device 16 is connected with a feed inlet at the upper part of the decomposition fluidized bed 15 through a pipeline; the gas inlet at the bottom of the decomposition fluidized bed 15 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve;
a discharge port at the lower part of the decomposition fluidized bed 15 is connected with the crystallization device 17 through a pipeline and a material valve; an air outlet at the upper part of the crystallization device 17 is connected with an air inlet of the tail gas recovery and compression device 6 through a pipeline and an air valve; the gas inlet at the bottom of the crystallization device 17 is connected with the gas outlets of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 through a pipeline and a gas valve; and a discharge port at the lower part of the crystallization device 17 is connected with a feed port of the silicon nitride powder collecting device 18 through a pipeline and a material valve.
Example 2
The method for preparing high-quality silicon nitride powder by using the system in the embodiment 1 specifically comprises the following steps:
the material in the powder feeding device 1 passes through Ar or N 2 After cleaning, ar or N enters the cleaning tank through a pipeline and a material valve 2 The washed precursor gas phase synthesis fluidized bed 2 is kept fluidized; ar or N 2 The silicon source in the silicon source evaporation device 4 enters the precursor gas phase synthesis fluidized bed 2, and NH is carried at the same time 3 With Ar or N 2 Enters the precursor gas-phase synthesis fluidized bed 2 through a pipeline to generate a precursor synthesis reaction; the fine powder in the precursor gas-phase synthesis fluidized bed 2 is separated by the first cyclone separation device 5 and then enters the first cyclone separation device againIn the precursor gas-phase synthesis fluidized bed 2; tail gas separated by the first cyclone separation device 5 enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
the material in the precursor gas phase synthesis fluidized bed 2 enters the dechlorination fluidized bed 7 through a pipeline and a material valve, and simultaneously, a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the dechlorination fluidized bed 7 and ensures that the material therein is in a fluidized state; under the action of the first energy supply device 8, NH in the material in the dechlorination fluidized bed 7 4 Decomposition of Cl into NH 3 And HCl and with the off-gas via a pipe provided with said heating means 10 into said second cyclone 9, NH 3 And HCl is condensed and crystallized to form NH 4 The Cl solid particles enter the ammonium chloride collecting device 11, and the tail gas enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
NH is removed in the dechlorination fluidized bed 7 4 Cl material enters the deep dechlorination fluidized bed 12 through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the deep dechlorination fluidized bed 12 and ensures that the materials are in a fluidized state; under the action of the second energy supply device 19, the material in the deep dechlorination fluidized bed 12 is subjected to deep dechlorination, and fine powder in the tail gas enters the deep dechlorination fluidized bed 12 after being separated by the third cyclone separation device 13; the tail gas separated by the third cyclone separation device 13 passes through the acid gas processor 14 and then enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused;
the material in the deep dechlorination fluidized bed 12 enters the decomposition fluidized bed 15 through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the decomposition fluidized bed 15, and the material is converted into amorphous powder under a certain temperature condition; fine powder in the tail gas is separated by the fourth cyclone separation device 16 and then enters the decomposition fluidized bed 15; the tail gas separated by the fourth cyclone separation device 16 enters the tail gas recovery and compression device 6 to realize the recovery and reutilization of the tail gasThe preparation method comprises the following steps of (1) using;
the material in the decomposing fluidized bed 15 enters the crystallizing device 17 through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the crystallization device 17, under a certain temperature condition, amorphous powder is converted into crystalline powder and enters the silicon nitride powder collecting device 18 through a pipeline and a material valve; and tail gas in the crystallization device 17 enters the tail gas recovery and compression device 6, so that the tail gas is recovered and reused.
Example 3
In this embodiment, based on the above embodiment 2, the material in the powder feeding device 1 is α -phase silicon nitride powder with an average particle size of about 0.5 μm, and after granulation, the material is in the form of 30 μm porous particles with a purity of 99.95%; the silicon source in the silicon source evaporation device 4 is SiCl with the purity of 99.99 percent 4 At-5 deg.C; ar, N 2 ，NH 3 ，H 2 The purity is 99.99%, and the oxygen content and the water vapor content are all 60ppm after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3; the temperature of the precursor gas-phase synthesis fluidized bed 2 is 0 ℃, and the fluidizing gas is N 2 Purity of 99.99%, NH entering the gas phase synthesis fluidized bed 2 of the precursor per unit time 3 And SiCl 4 The molar ratio of (A) is equal to 8, and the synthesis time is 600min; dechlorinating the material in the dechlorinating fluidized bed 7 for 600min at the temperature of 400 ℃ and the fluidizing gas Ar; the first energy supply device 8 and the second energy supply device 19 are conventional resistance heating; the heating device 10 is maintained at 450 ℃; the temperature in the deep dechlorination fluidized bed 12 is 800 ℃, and the fluidizing gas is N 2 And H 2 The molar ratio of the mixed gas is 100/1, and the material retention time is 100min; the temperature of the decomposition fluidized bed 15 is 1000 ℃, and the fluidizing gas is Ar and NH 3 The molar ratio of the mixed gas is 100/1, and the material retention time is equal to 5min; the inner wall of the crystallization device 17 is made of high-purity graphite, the crystallization temperature is 1350 ℃, and the gas is N 2 Crystallizing for 180min to obtain silicon nitride powder. FIG. 2 is an XRD pattern for preparing a silicon nitride powder, from which it can be seen that only alpha-phase nitridation was detectedDiffraction peaks of silicon, indicating 100% synthesis of alpha-Si 3 N 4 Powder, etc. In addition, the powder is in a random shape, the average particle size of the powder is about 0.48 mu m, and the Cl impurity of the powder is about 80ppm.
Example 4
In this embodiment, on the basis of the above embodiment 2, the material in the powder feeding device 1 is amorphous silicon nitride powder with a primary particle size of about 0.2 μm, and the granulated powder is porous particles with a size of about 10 μm, and the powder purity is 99.99%; the silicon source in the silicon source evaporation device 4 is SiHCl with the purity of 99.95 percent 3 At a temperature of 50 ℃; ar, N 2 ，NH 3 ，H 2 The purity is 99.999%, and the oxygen and water vapor contents are all 30ppm after being treated by the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3; the temperature of the precursor gas-phase synthesis fluidized bed 2 is 25 ℃, the fluidizing gas is Ar, the purity is 99.99 percent, and NH enters the precursor gas-phase synthesis fluidized bed 2 in unit time 3 With SiHCl 3 The molar ratio of (a) is equal to 6, and the synthesis time is 5min; the temperature range of the materials in the dechlorination fluidized bed 7 is 750 ℃, and the fluidizing gas is N 2 Containing 20% by volume of NH 3 Dechlorination for 3min; the first energy supply device 8 and the second energy supply device 19 are used for microwave heating; the heating device 10 is maintained at 550 ℃; the temperature in the deep dechlorination fluidized bed 12 is 650 ℃, and the fluidizing gas is N 2 And H 2 The molar ratio of the mixed gas is 100/1, and the material stays for 600min or more; the temperature of the decomposing fluidized bed 15 is 800 ℃, and the fluidizing gas is N 2 And H 2 The molar ratio of the mixed gas is 100/1, and the material retention time is equal to 600min; the inner wall of the crystallization device 17 is made of silicon nitride, the crystallization temperature is 1550 ℃, and the gas is N 2 Crystallizing for 10min to obtain silicon nitride powder. FIG. 3 is an SEM image of the preparation of silicon nitride powder, from which it can be seen that the powder exhibits equiaxed hexagonal morphology, the average particle size of the powder is about 0.96 μm, the Cl impurity in the powder is about 60ppm, and the alpha phase content in the powder is greater than 95%.
Example 5
The present embodiment is described in the above embodimentOn the basis of the embodiment 2, the material in the powder feeding device 1 is silicon nitride powder with the average particle size of 800 microns, and the purity of the powder is 99.99 percent; the silicon source in the silicon source evaporation device 4 is SiBr with the silicon source of 99.99 percent 4 The temperature is 80 ℃; ar, N 2 ，NH 3 ，H 2 The purity is 99.999%, and the oxygen and water vapor contents are all less than 10ppm after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3; the temperature of the precursor gas-phase synthesis fluidized bed 2 is 150 ℃, and the fluidizing gas is N 2 NH with a purity of 99.999% entering the precursor gas phase synthesis fluidized bed 2 per unit time 3 With SiBr 4 The molar ratio of (a) is equal to 10, and the synthesis time is 100min; the material temperature range in the dechlorination fluidized bed 7 is 650 ℃, and the fluidizing gas is N 2 Containing 10% by volume of H 2 Dechlorinating for 60min; the first energy supply device 8 and the second energy supply device 19 are conventional resistance heating; the heating device 10 is maintained at a temperature of 400 ℃; the temperature in the deep dechlorination fluidized bed 12 is 950 ℃, and the fluidizing gas is N 2 And NH 3 The molar ratio of the mixed gas is 100/1, and the material stays for 10min or more; the temperature of the decomposing fluidized bed 15 is 1150 ℃ and the fluidizing gas is N 2 Gas, the retention time of the material is equal to 400min; the temperature of the crystallization device 17 is 1450 ℃, wherein the gas is N 2 Crystallizing for 90min to obtain silicon nitride powder. FIG. 4 is an XRD pattern for preparing silicon nitride powder, from which it can be seen that only the diffraction peak of alpha-phase silicon nitride is detected, i.e., it is shown that 100% of alpha-Si is synthesized 3 N 4 And (3) powder. The powder was equiaxed, and had an average particle diameter of about 0.58 μm and a powder Br impurity of about 90ppm.
The invention has not been described in detail and is within the skill of the art.
Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or substituted with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.
Claims (10)
1. A system for preparing high-quality silicon nitride powder by a multistage fluidized bed is characterized by comprising: the device comprises a powder feeding device (1), a precursor gas-phase synthesis fluidized bed (2), a first gas purifier (3-1), a second gas purifier (3-2), a third gas purifier (3-3), a silicon source evaporation device (4), a first cyclone separation device (5), a tail gas recovery compression device (6), a dechlorination fluidized bed (7), a first energy supply device (8), a second cyclone separation device (9), a heating device (10), an ammonium chloride collecting device (11), a deep dechlorination fluidized bed (12), a third cyclone separation device (13), an acid gas processor (14), a decomposition fluidized bed (15), a fourth cyclone separation device (16), a crystallization device (17), a silicon nitride powder collecting device (18) and a second energy supply device (19);
a discharge hole of the powder feeding device (1) is connected with a feed inlet at the upper part of the precursor gas-phase synthesis fluidized bed (2) through a pipeline and a material valve; ar or N 2 The air source of the first air purifier (3-1) is connected with the air inlet of the first air purifier through a pipeline; the gas outlet of the first gas purifier (3-1) is connected with the gas inlet of the silicon source evaporation device (4) through a pipeline and a gas valve; the gas outlet of the silicon source evaporation device (4) is connected with the gas inlet at the lower part of the precursor gas-phase synthesis fluidized bed (2) through a pipeline and a gas valve; the gas outlet of the first gas purifier (3-1) is connected with the gas inlet at the bottom of the precursor gas-phase synthesis fluidized bed (2) through a pipeline and a gas valve; NH (NH) 3 The gas source is connected with the gas inlet of the second gas purifier (3-2) through a pipeline; the gas outlet of the second gas purifier (3-2) is connected with the gas inlet at the bottom of the precursor gas-phase synthesis fluidized bed (2) through a pipeline and a gas valve;
an air outlet at the upper part of the precursor gas-phase synthesis fluidized bed (2) is connected with an air inlet of the first cyclone separation device (5) through a pipeline; a discharge hole at the bottom of the first cyclone separation device (5) is connected with a feed inlet at the upper part of the precursor gas-phase synthesis fluidized bed (2) through a pipeline; an air outlet at the top of the first cyclone separation device (5) is connected with an air inlet of the tail gas recovery and compression device (6) through a pipeline;
a discharge port at the lower part of the precursor gas-phase synthesis fluidized bed (2) is connected with a feed port of the dechlorination fluidized bed (7) through a pipeline and a material valve; the dechlorination fluidized bed (7) is provided with the first energy supply device (8); the gas inlet at the bottom of the dechlorination fluidized bed (7) is connected with the gas outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through a pipeline and a gas valve; the air outlet at the top of the dechlorination fluidized bed (7) is connected with the air inlet of the second cyclone separation device (9) through a pipeline provided with the heating device (10); the gas outlet of the second cyclone separation device (9) is connected with the gas inlet of the tail gas recovery and compression device (6) through a pipeline; the discharge hole of the second cyclone separation device (9) is connected with the feed inlet of the ammonium chloride collection device (11) through a pipeline and a material valve;
a discharge hole at the lower part of the dechlorination fluidized bed (7) is connected with a feed hole at the upper part of the deep dechlorination fluidized bed (12) through a pipeline and a material valve; the deep dechlorination fluidized bed (12) is provided with the second energy supply device (19); an air outlet at the top of the deep dechlorination fluidized bed (12) is connected with an air inlet of the third cyclone separation device (13) through a pipeline; a discharge hole at the bottom of the third cyclone separation device (13) is connected with a feed inlet at the upper part of the deep dechlorination fluidized bed (12) through a pipeline; an air outlet at the top of the third cyclone separation device (13) is connected with an air inlet of the acid gas processor (14) through a pipeline; the acid gas processor (14) is connected with the gas inlet of the tail gas recovery and compression device (6) through a pipeline and a gas valve; the gas inlet at the bottom of the deep dechlorination fluidized bed (12) is connected with the gas outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through a pipeline and a gas valve;
a discharge hole at the lower part of the deep dechlorination fluidized bed (12) is connected with a feed inlet of the decomposition fluidized bed (15) through a pipeline and a material valve; an air outlet at the upper part of the decomposition fluidized bed (15) is connected with an air inlet of the fourth cyclone separation device (16) through a pipeline; an air outlet at the top of the fourth cyclone separation device (16) is connected with an air inlet of the tail gas recovery and compression device (6) through a pipeline and an air valve; a discharge hole at the bottom of the fourth cyclone separation device (16) is connected with a feed inlet at the upper part of the decomposition fluidized bed (15) through a pipeline; a gas inlet at the bottom of the decomposition fluidized bed (15) is connected with gas outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through a pipeline and a gas valve;
a discharge port at the lower part of the decomposition fluidized bed (15) is connected with the crystallization device (17) through a pipeline and a material valve; an air outlet at the upper part of the crystallization device (17) is connected with an air inlet of the tail gas recovery and compression device (6) through a pipeline and an air valve; the gas inlet at the bottom of the crystallization device (17) is connected with the gas outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through a pipeline and a gas valve; and a discharge hole at the lower part of the crystallization device (17) is connected with a feed inlet of the silicon nitride powder collecting device (18) through a pipeline and a material valve.
2. A method for preparing high quality silicon nitride powder based on the multi-stage fluidized bed of the system of claim 1, the method comprising the steps of: the material in the powder feeding device (1) passes through Ar or N 2 After cleaning, ar or N enters the cleaning tank through a pipeline and a material valve 2 The washed precursor gas phase synthesis fluidized bed (2) is kept fluidized; ar or N 2 The silicon source in the silicon source evaporation device (4) enters the precursor gas phase synthesis fluidized bed (2) and simultaneously NH 3 With Ar or N 2 Enters the precursor gas-phase synthesis fluidized bed (2) through a pipeline to generate a precursor synthesis reaction; fine powder in the precursor gas-phase synthesis fluidized bed (2) is separated by the first cyclone separation device (5) and then enters the precursor gas-phase synthesis fluidized bed (2) again; tail gas separated by the first cyclone separation device (5) enters the tail gas recovery and compression device (6) to realize the recovery and reutilization of the tail gas;
the material in the precursor gas-phase synthesis fluidized bed (2) passes through a pipelineA feed valve enters the dechlorination fluidized bed (7) and a certain amount of NH is added at the same time 3 Or H 2 With Ar or N 2 The gas enters the dechlorination fluidized bed (7) and ensures that the material therein is in a fluidized state; NH in the material in the dechlorination fluidized bed (7) under the action of the first energy supply device (8) 4 Decomposition of Cl into NH 3 And HCl and, with the off-gas, into the second cyclone (9) via a line equipped with the heating device (10), NH 3 And HCl is condensed and crystallized to form NH 4 Cl solid particles enter the ammonium chloride collecting device (11), tail gas enters the tail gas recovery and compression device (6), and the tail gas is recovered and reused;
NH is removed in the dechlorination fluidized bed (7) 4 The Cl material enters the deep dechlorination fluidized bed (12) through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the deep dechlorination fluidized bed (12) and ensures that the material therein is in a fluidized state; under the action of the second energy supply device (19), the material in the deep dechlorination fluidized bed (12) is subjected to deep dechlorination, and fine powder in the tail gas enters the deep dechlorination fluidized bed (12) after being separated by the third cyclone separation device (13); tail gas separated by the third cyclone separation device (13) passes through the acid gas processor (14) and then enters the tail gas recovery and compression device (6) to realize the recovery and reuse of the tail gas;
the material in the deep dechlorination fluidized bed (12) enters the decomposition fluidized bed (15) through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 The gas enters the decomposition fluidized bed (15), and the material is converted into amorphous powder under a certain temperature condition; fine powder in the tail gas enters the decomposition fluidized bed (15) after being separated by the fourth cyclone separation device (16); tail gas separated by the fourth cyclone separation device (16) enters the tail gas recovery and compression device (6) to realize the recovery and reutilization of the tail gas;
the material in the decomposition fluidized bed (15) enters the crystallization device (17) through a pipeline and a material valve, and simultaneously a certain amount of NH 3 Or H 2 With Ar or N 2 Gas entryThe crystallization device (17) converts amorphous powder into crystalline powder at a certain temperature, and the crystalline powder enters the silicon nitride powder collecting device (18) through a pipeline and a material valve; and tail gas in the crystallization device (17) enters the tail gas recovery and compression device (6) to realize the recovery and reutilization of the tail gas.
3. The method for producing high-quality silicon nitride powder according to claim 2, wherein Ar and N are 2 、NH 3 And H 2 The purity of the nitrogen-containing gas is more than 99.9 percent, and the oxygen content and the water vapor content are less than 500ppm after the nitrogen-containing gas is treated by the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3).
4. The method for preparing high-quality silicon nitride powder according to claim 2, wherein the temperature of the precursor gas-phase synthesis fluidized bed (2) is in the range of-10 to 200 ℃, and the fluidizing gas is Ar or N 2 Or H 2 Any one or any ratio of the above, and NH in the bed 3 The molar ratio of the silicon source to the gas-phase silicon source is more than or equal to 6, and the synthesis time is more than 1min and less than 600min.
5. The method for preparing high-quality silicon nitride powder according to claim 2, wherein the temperature of the material in the dechlorination fluidized bed (7) is 300-800 ℃, and the fluidizing gas is Ar or N 2 、NH 3 And H 2 Any one or any proportion of the gases are combined, and the material retention time is more than or equal to 3min and less than or equal to 600min.
6. The method for producing high-quality silicon nitride powder according to claim 2, wherein the energy supply device (8) is one of or a combination of two heating methods selected from conventional resistance heating and microwave heating.
7. The method for producing high-quality silicon nitride powder according to claim 2, wherein the heating device (10) is maintained at a temperature of 400 to 600 ℃.
8. The method for preparing high-quality silicon nitride powder according to claim 2, wherein the temperature in the deep dechlorination fluidized bed (12) is 600-1000 ℃, and the fluidizing gas is Ar or N 2 、NH 3 And H 2 The gas is combined in any proportion, and the material retention time is more than or equal to 10min and less than or equal to 600min.
9. The method for producing a high-quality silicon nitride powder according to claim 2, wherein the temperature of the decomposition fluidized bed (15) is 800 to 1200 ℃, and the fluidizing gas is Ar or N 2 、NH 3 And H 2 The gas is mixed in any proportion, and the material retention time is more than or equal to 5min and less than or equal to 600min.
10. The method for preparing high-quality silicon nitride powder according to claim 2, wherein the inner wall of the crystallization device (17) is made of high-purity graphite, silicon nitride, silicon carbide or boron nitride, the crystallization temperature is 1350-1600 ℃, and the bulk density of the material in the bed layer is greater than or equal to 0.2g/cm 3 The retention time of the materials is more than or equal to 10min and less than or equal to 180min, and the gas in the crystallization device (17) is Ar and N 2 、NH 3 And H 2 Any one or any combination of the proportions of the gases.
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