CN115432676B - System and method for preparing high-quality silicon nitride powder by multistage fluidized bed - Google Patents
System and method for preparing high-quality silicon nitride powder by multistage fluidized bed Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 139
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 61
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 38
- 238000006298 dechlorination reaction Methods 0.000 claims abstract description 86
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 66
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 64
- 239000002243 precursor Substances 0.000 claims abstract description 63
- 238000002425 crystallisation Methods 0.000 claims abstract description 39
- 230000008025 crystallization Effects 0.000 claims abstract description 39
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 32
- 239000010703 silicon Substances 0.000 claims abstract description 32
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 11
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 252
- 239000000463 material Substances 0.000 claims description 85
- 238000000926 separation method Methods 0.000 claims description 68
- 238000011084 recovery Methods 0.000 claims description 33
- 238000007906 compression Methods 0.000 claims description 31
- 230000006835 compression Effects 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 23
- 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
- 239000002253 acid Substances 0.000 claims description 13
- 239000002245 particle Substances 0.000 claims description 12
- 235000019270 ammonium chloride Nutrition 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 230000009471 action Effects 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 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
- 238000004064 recycling Methods 0.000 claims description 4
- 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
- 238000004140 cleaning Methods 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 239000000203 mixture 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
- 239000003054 catalyst Substances 0.000 claims description 2
- 239000012071 phase Substances 0.000 abstract description 62
- 239000012535 impurity Substances 0.000 abstract description 10
- 238000002360 preparation method Methods 0.000 abstract description 10
- 239000007791 liquid phase Substances 0.000 abstract description 6
- 238000001308 synthesis method Methods 0.000 abstract description 4
- -1 silicon amine Chemical class 0.000 abstract description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 abstract description 2
- 229910052801 chlorine Inorganic materials 0.000 abstract description 2
- 238000009826 distribution Methods 0.000 abstract description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract 1
- 239000000460 chlorine Substances 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 13
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 229910021417 amorphous silicon Inorganic materials 0.000 description 4
- 239000000919 ceramic Substances 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
- 230000008569 process Effects 0.000 description 4
- 229910003691 SiBr Inorganic materials 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 239000011863 silicon-based powder Substances 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 229910003902 SiCl 4 Inorganic materials 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 238000005121 nitriding Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000010923 batch production Methods 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
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 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
- 239000007790 solid phase Substances 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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- 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
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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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- C—CHEMISTRY; METALLURGY
- 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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- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- 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 a multistage fluidized bed. After the gas phase silicon source reacts with ammonia gas in a fluidized bed, high-quality silicon nitride powder with low impurity content, high alpha phase content, fine grain size and narrow distribution can be prepared through the steps of dechlorination, deep dechlorination, decomposition, crystallization and the like in sequence. The method solves the problem that the silicon nitride powder with low chlorine content is difficult to obtain by a gas phase synthesis route in the traditional method for converting the silicon amine precursor, and simultaneously can solve the problem that the precursor is difficult to absorb moisture and protect compared with the traditional solvothermal liquid phase synthesis method and the silicon amine precursor liquid phase synthesis method, and simultaneously can realize continuous batch preparation of 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, in particular to high-quality silicon nitride (Si) 3 N 4 ) The preparation process of the powder.
Background
Si 3 N 4 Ceramics are known as 'all-round ceramics', and have wide application in the fields of machining, aerospace, electronic information, biological materials and the like. High quality Si 3 N 4 The powder is used for preparing high-performance Si 3 N 4 The ceramic is based, and the powder occupies 1/3 to 2/3 of the cost of the ceramic. The high-quality powder needs to have the grain diameter of about 0.4-1.5 mu m and alpha phase content>95%, O content<0.9wt.%, C content<0.2wt.% Cl content<100ppm of metallic impurities<500ppm. After 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 (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 diffusion mass transfer is the limiting step of the overall reaction. This results in a very high powder oxygen content, typically greater than 5.0wt.%, and an impure product phase, typically containing SiC, siO y N z And residual SiO 2 And free C. Although repeated crushing and repeated nitriding can reduce O impurities of the powder to some extent, the powder still contains a hetero-phase such as SiC and C (j.am.ceram.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 below 1.0 mu m.
(2) Si powder direct nitriding method (3 Si(s) +2N) 2 (g)＝Si 3 N 4 (s)). The reaction is a strong exothermic reaction, and the industrial synthesis of Si is commonly carried out by adopting a self-propagating combustion technology 3 N 4 And (3) powder. However, since the reaction still has mass transfer barrier and a large temperature gradient, si containing free Si is obtained 3 N 4 The blocks and the alpha content of the product is generally less than 70%. Although lifting N in the reaction vessel 2 The pressure (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 requires high energy plasma assistance to synthesize the powder (US 4416863). However, the synthesized powder is not an alpha-phase powder, but a beta-phase powder. . To solve this problem, the German Basv company developed amorphous seed powder (BET>50m 2 (g) fluidized gas phase synthesis (US 4859443) with assisted fluidization and enhanced deposition, amorphous Si of the 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 alpha phase content in the powder is less, and the Cl impurity content is higher>1.0 wt%) of a high quality powderRequirements. Comparatively, siH comparatively 4 And NH 3 The reaction is easier to synthesize powder (3 SiH) 4 (g)+4NH 3 (g)＝Si 3 N 4 (s)+12H 2 (g) A kind of electronic device. However, the synthesized amorphous powder is crystallized to Si 3 N 4 Powders other than alpha-phase powders (US 4122155, US4929432, inorganic materials journal, 2006, 21, 41; university of zhejiang university journal, 2007, 24, 36). Meanwhile, the powder contains a large amount of free Si, which does not meet the requirement of high-quality powder. Furthermore, siH 4 Is a toxic and hazardous gas, is inflammable and explosive, and about 45% of accidents occur in the process stage, and 21% of accidents occur when bottle changing occurs. Thus, chemical vapor deposition produces high quality Si 3 N 4 Powder also faces a major challenge.
(4) Conversion of silamine precursors, i.e. SiCl 4 And NH 3 Firstly, synthesizing a silamine precursor Si (NH) at low temperature 2 ) 4 Or Si (NH) 2 Then separating out by-products, and finally crystallizing to synthesize Si 3 N 4 And (3) powder. The alpha phase is obtained by a low temperature liquid phase synthesis process developed by the United states air force (US 3959446) of the United states department of Japan (US 4405589, 5585084, 5595718), toyota manufacturing Co., ltd., japan (US 4387079)>95%, BET of about 6m 2 /g, and Cl<100ppm of high-purity superfine Si 3 N 4 Powder [ ]>99.95%). However, the process has very harsh reaction conditions, is difficult to continuously carry out in batch, and needs to carry out batch production, so that the powder yield is low and the efficiency is low.
To sum up, siO 2 Is difficult to prepare high-quality Si by carbothermal nitridation method, si powder direct nitridation method and chemical vapor deposition method 3 N 4 And (3) powder. Although the solvent-thermal liquid phase synthesis method and the conversion method of the silamine precursor can prepare Si with higher quality 3 N 4 The powder, however, the synthetic powder has small yield, low efficiency and high cost, and limits the application range of the high-quality silicon nitride powder. The continuous production can effectively solve the problem of moisture absorption and protection in intermittent production, thereby reducing the cost. Therefore, there is a need in the art to develop a low cost, high efficiency, continuous mass production of high quality Si 3 N 4 Powder preparation method.
Disclosure of Invention
In view of the above problems, the present invention provides a system and a method for preparing high quality silicon nitride powder by using a multistage fluidized bed, which can realize continuous large-scale production of high quality Si by synthesizing a precursor in the fluidized bed, and performing fractional dechlorination, decomposition and crystallization 3 N 4 The powder improves the efficiency and the yield and reduces the 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 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 collection 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 collection device 18 and a second energy supply device 19;
the discharge port of the powder feeding device 1 is connected with the feed port at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a feed valve; ar or N 2 The air inlet of the first gas purifier 3-1 is connected with the air inlet of the first gas purifier through a pipeline; the air outlet of the first gas purifier 3-1 is connected with the air inlet of the silicon source evaporation device 4 through a pipeline and a gas valve; the air outlet of the silicon source evaporation device 4 is connected with the air inlet at the lower part of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve; the air outlet of the first gas purifier 3-1 is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve; NH (NH) 3 The air inlet of the second gas purifier 3-2 is connected with the air inlet of the second gas purifier through a pipeline; the air outlet of the second gas purifier 3-2 is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve; h 2 The air inlet of the third air purifier 3-3 is connected with the air inlet of the third air purifier through a pipeline;
the gas outlet at the upper part of the precursor gas phase synthesis fluidized bed 2 is connected with the gas 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; the air outlet at the top of the first cyclone separation device 5 is connected with the air inlet of the tail gas recovery compression device 6 through a pipeline;
the discharge port at the lower part of the precursor gas-phase synthesis fluidized bed 2 is connected with the feed port of the dechlorination fluidized bed 7 through a pipeline and a feed valve; the dechlorination fluidized bed 7 is provided with the first energy supply device 8; the air inlet at the bottom of the dechlorination fluidized bed 7 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves; 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 compression device 6 through a pipeline; the discharge port of the second cyclone separation device 9 is connected with the feed port 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 feed valve; said deep dechlorination fluidized bed 12 is provided with said second energy supply means 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 hole at the upper part of the deep dechlorination fluidized bed 12 through a pipeline; the air outlet at the top of the third cyclone separation device 13 is connected with the 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 compression device 6 through a pipeline and a gas valve; the air inlet at the bottom of the deep dechlorination fluidized bed 12 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves;
the discharge port at the lower part of the deep dechlorination fluidized bed 12 is connected with the feed port of the decomposing fluidized bed 15 through a pipeline and a feed valve; the air outlet at the upper part of the decomposing fluidized bed 15 is connected with the 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 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 an upper feed hole of the decomposing fluidized bed 15 through a pipeline; the air inlet at the bottom of the decomposing fluidized bed 15 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves;
a discharge hole at the lower part of the decomposing fluidized bed 15 is connected with the crystallization device 17 through a pipeline and a material valve; the air outlet at the upper part of the crystallization device 17 is connected with the air inlet of the tail gas recovery compression device 6 through a pipeline and an air valve; the air inlet at the bottom of the crystallization device 17 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves; the discharge hole at the lower part of the crystallization device 17 is connected with the feed hole 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 the corresponding gas sources.
The method for preparing high-quality silicon nitride powder based on the system comprises the following steps:
ar or N is passed through the materials in the powder feeding device 1 2 After cleaning, the mixture enters into a pipeline and a material valve to be subjected to Ar or N 2 The cleaned 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 precursor synthesis reactionThe method comprises the steps of carrying out a first treatment on the surface of 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; the tail gas separated by the first cyclone separation device 5 enters the tail gas recovery 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 meanwhile, a certain amount of NH is formed 3 Or H 2 With Ar or N 2 Gas enters the dechlorination fluidized bed 7 and ensures that the materials therein are 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 enter the second cyclone device 9 along with tail gas through a pipeline provided with the heating device 10, NH 3 And HCl are 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 recycling and compressing device 6, so that the tail gas is recycled;
NH is removed from the dechlorination fluidized bed 7 4 The Cl material enters the deep dechlorination fluidized bed 12 through a pipeline and a material valve, and a certain amount of NH is simultaneously added 3 Or H 2 With Ar or N 2 Gas enters the deep dechlorination fluidized bed 12 and ensures that the material therein is in a fluidised state; under the action of the second energy supply device 19, the materials in the deep dechlorination fluidized bed 12 are deeply dechlorinated, and fine powder in 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 enters the tail gas recovery compression device 6 after passing through the acid gas processor 14, so that the tail gas is recovered and reused;
the material in the deep dechlorination fluidized bed 12 enters the decomposing fluidized bed 15 through a pipeline and a material valve, and a certain amount of NH is simultaneously supplied 3 Or H 2 With Ar or N 2 The gas enters the decomposing fluidized bed 15, and under the condition of a certain temperature, the material is converted into amorphous powder; fine powder in the tail gas is separated by the fourth cyclone separation device 16 and then enters the decomposing fluidized bed 15;the tail gas separated by the fourth cyclone separation device 16 enters the tail gas recovery compression device 6, so that the tail gas is recovered and reused;
the material in the decomposing fluidized bed 15 enters the crystallization device 17 through a pipeline and a material valve, and a certain amount of NH is simultaneously provided 3 Or H 2 With Ar or N 2 The gas enters the crystallization device 17, and 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; the tail gas in the crystallization device 17 enters the tail gas recovery compression device 6, so that the tail gas is recovered and reused.
Preferably, the materials in the powder feeding device 1 are amorphous or crystalline silicon nitride powder or any combination of the amorphous or crystalline silicon nitride powder in any proportion, the purity is more than 99.9%, 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%, and the oxygen and water vapor content after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 is less than 500ppm.
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 combination of the proportions and NH in the bed 3 The molar ratio of the catalyst to the gas phase silicon source is more than or equal to 6, 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 SiCl with purity of more than 99.9% 4 、SiHCl 3 、SiH 2 Cl 2 、SiBr 4 、SiF 4 Any one or any combination of the common silicon halides, and the temperature of the silicon source evaporation device 4 is-10-100 ℃.
Preferably, the temperature 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 combination of the above materials in any proportion, wherein the material residence 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 modes of conventional resistance heating or microwave heating.
Preferably, the heating device 10 maintains a temperature of 400-600 ℃.
Preferably, 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 Any one or any combination of the above materials in any proportion, wherein the material residence time is more than or equal to 10min and less than or equal to 600min.
Preferably, the decomposing fluidized bed 15 has a temperature of 800 to 1200 ℃, and the fluidizing gas is Ar, N 2 、NH 3 And H 2 The material residence time of any one or any combination of the gases 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, 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 material residence time is more than or equal to 10min and less than or equal to 180min, and the gases in the crystallization device 17 are Ar and N 2 、NH 3 And H 2 Any one or any combination of the gases in any proportion.
After the gas phase silicon source reacts with ammonia gas in a fluidized bed, high-quality silicon nitride powder with low impurity content, high alpha phase content, fine grain size and narrow distribution can be prepared through the steps of dechlorination, deep dechlorination, decomposition, crystallization and the like in sequence.
Compared with the prior art, the invention has the following advantages:
compared with the traditional SiO 2 Compared with a carbothermal nitridation method and a Si powder direct nitridation method, the silicon nitride powder prepared by the method has higher purity and alpha phase content and finer grain 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 a gas phase synthesis route in a silamine precursor conversion method, the method solves the problem that silicon nitride powder with low Cl impurity content is difficult to synthesize, and is similar to a liquid phase synthesis route in a traditional solvothermal liquid phase synthesis method and a silamine precursor conversion methodCompared with the method, the method can realize continuous batch preparation of the 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 are included to provide a further illustration of the invention and are a part of the specification, and together with the description serve to explain the invention, and do not limit the invention.
FIG. 1 is a schematic diagram of a preparation system for preparing high-quality silicon nitride powder according to the present invention;
FIG. 2 is an XRD pattern for the preparation of silicon nitride powder according to example 3;
FIG. 3 is an SEM image of the preparation of silicon nitride powder according to example 4;
FIG. 4 is an XRD pattern for the preparation of silicon nitride powder according to 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 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 collection device; 12. deep dechlorination fluidized bed; 13. a third cyclonic separating apparatus; 14. an acid gas processor; 15. decomposing the fluidized bed; 16. a fourth cyclonic separating apparatus; 17. a crystallization device; 18. a silicon nitride powder collection device; 19. and a second energy supply device.
Detailed Description
Any feature disclosed in this specification may be replaced by alternative features serving the same or equivalent purpose, unless expressly stated otherwise. Each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise. The description is only intended to aid in the understanding of the invention and should not be taken as limiting the invention in any way.
The invention is described in further detail below with reference to the drawings and the detailed description.
Example 1
Referring to fig. 1, the preparation system of high quality silicon nitride powder of this embodiment 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 collection 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 collection device 18, and a second energy supply device 19;
the discharge port of the powder feeding device 1 is connected with the feed port at the upper part of the precursor gas-phase synthesis fluidized bed 2 through a pipeline and a feed valve; ar or N 2 The air inlet of the first gas purifier 3-1 is connected with the air inlet of the first gas purifier through a pipeline; the air outlet of the first gas purifier 3-1 is connected with the air inlet of the silicon source evaporation device 4 through a pipeline and a gas valve; the air outlet of the silicon source evaporation device 4 is connected with the air inlet at the lower part of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve; the air outlet of the first gas purifier 3-1 is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve; NH (NH) 3 The air inlet of the second gas purifier 3-2 is connected with the air inlet of the second gas purifier through a pipeline; the air outlet of the second gas purifier 3-2 is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed 2 through a pipeline and an air valve;
the gas outlet at the upper part of the precursor gas phase synthesis fluidized bed 2 is connected with the gas 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; the air outlet at the top of the first cyclone separation device 5 is connected with the air inlet of the tail gas recovery compression device 6 through a pipeline;
the discharge port at the lower part of the precursor gas-phase synthesis fluidized bed 2 is connected with the feed port of the dechlorination fluidized bed 7 through a pipeline and a feed valve; the dechlorination fluidized bed 7 is provided with the first energy supply device 8; the air inlet at the bottom of the dechlorination fluidized bed 7 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves; 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 compression device 6 through a pipeline; the discharge port of the second cyclone separation device 9 is connected with the feed port 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 feed valve; said deep dechlorination fluidized bed 12 is provided with said second energy supply means 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 hole at the upper part of the deep dechlorination fluidized bed 12 through a pipeline; the air outlet at the top of the third cyclone separation device 13 is connected with the 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 compression device 6 through a pipeline and a gas valve; the air inlet at the bottom of the deep dechlorination fluidized bed 12 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves;
the discharge port at the lower part of the deep dechlorination fluidized bed 12 is connected with the feed port of the decomposing fluidized bed 15 through a pipeline and a feed valve; the air outlet at the upper part of the decomposing fluidized bed 15 is connected with the 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 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 an upper feed hole of the decomposing fluidized bed 15 through a pipeline; the air inlet at the bottom of the decomposing fluidized bed 15 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves;
a discharge hole at the lower part of the decomposing fluidized bed 15 is connected with the crystallization device 17 through a pipeline and a material valve; the air outlet at the upper part of the crystallization device 17 is connected with the air inlet of the tail gas recovery compression device 6 through a pipeline and an air valve; the air inlet at the bottom of the crystallization device 17 is connected with the air outlets of the first air purifier 3-1, the second air purifier 3-2 and the third air purifier 3-3 through pipelines and air valves; the discharge hole at the lower part of the crystallization device 17 is connected with the feed hole 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:
ar or N is passed through the materials in the powder feeding device 1 2 After cleaning, the mixture enters into a pipeline and a material valve to be subjected to Ar or N 2 The cleaned 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 Entering the precursor gas phase synthesis fluidized bed 2 through a pipeline to perform 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; the tail gas separated by the first cyclone separation device 5 enters the tail gas recovery 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 meanwhile, a certain amount of NH is formed 3 Or H 2 With Ar or N 2 Gas enters the dechlorination fluidized bed 7 and ensures that the materials therein are 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 withThe tail gas enters the second cyclone separation device 9 through a pipeline provided with the heating device 10, and NH 3 And HCl are 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 recycling and compressing device 6, so that the tail gas is recycled;
NH is removed from the dechlorination fluidized bed 7 4 The Cl material enters the deep dechlorination fluidized bed 12 through a pipeline and a material valve, and a certain amount of NH is simultaneously added 3 Or H 2 With Ar or N 2 Gas enters the deep dechlorination fluidized bed 12 and ensures that the material therein is in a fluidised state; under the action of the second energy supply device 19, the materials in the deep dechlorination fluidized bed 12 are deeply dechlorinated, and fine powder in 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 enters the tail gas recovery compression device 6 after passing through the acid gas processor 14, so that the tail gas is recovered and reused;
the material in the deep dechlorination fluidized bed 12 enters the decomposing fluidized bed 15 through a pipeline and a material valve, and a certain amount of NH is simultaneously supplied 3 Or H 2 With Ar or N 2 The gas enters the decomposing fluidized bed 15, and under the condition of a certain temperature, the material is converted into amorphous powder; fine powder in the tail gas is separated by the fourth cyclone separation device 16 and then enters the decomposing fluidized bed 15; the tail gas separated by the fourth cyclone separation device 16 enters the tail gas recovery compression device 6, so that the tail gas is recovered and reused;
the material in the decomposing fluidized bed 15 enters the crystallization device 17 through a pipeline and a material valve, and a certain amount of NH is simultaneously provided 3 Or H 2 With Ar or N 2 The gas enters the crystallization device 17, and 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; the tail gas in the crystallization device 17 enters the tail gas recovery compression device 6, so that the tail gas is recovered and reused.
Example 3
This embodiment is based on embodiment 2 described aboveThe material in the powder feeding device 1 is alpha-phase silicon nitride powder with the average particle diameter of about 0.5 mu m, and the alpha-phase silicon nitride powder is granulated to form 30 mu m porous particles with the purity of 99.95 percent; the silicon source in the silicon source evaporation device 4 is SiCl with the purity of 99.99 percent 4 The temperature is-5 ℃; ar, N 2 ，NH 3 ，H 2 The purity is 99.99 percent, and the oxygen and water vapor content after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 is 60ppm; 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 precursor gas phase synthesis fluidized bed 2 per unit time 3 With SiCl 4 The molar ratio of (2) is equal to 8, and the synthesis time is 600min; the temperature range of the materials in the dechlorination fluidized bed 7 is 400 ℃, the fluidizing gas is Ar, and dechlorination is carried out for 600min; the first energy supply device 8 and the second energy supply device 19 are conventional resistance heating; the temperature of 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 mol ratio of the mixed gas is 100/1, and the material residence time is 100min; the decomposing fluidized bed 15 has a temperature of 1000 ℃ and a fluidizing gas of Ar and NH 3 The mol ratio of the mixed gas is 100/1, and the material residence time is equal to 5min; the inner wall of the crystallization device 17 is 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 of a silicon nitride powder, from which it can be seen that only diffraction peaks of alpha-phase silicon nitride are detected, indicating that 100% of alpha-Si is synthesized 3 N 4 Powder. In addition, the powder has random morphology, the average particle size of the powder is about 0.48 μm, and the Cl impurity of the powder is about 80ppm.
Example 4
In this embodiment, based on 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 after granulation, the powder is formed into porous particles with a particle size of about 10 μm, and the purity of the powder is 99.99%; the silicon source in the silicon source evaporation device 4 is SiHCl with the purity of 99.95 percent 3 The temperature is 50 ℃; ar, N 2 ，NH 3 ，H 2 The purity is 99.999 percent, and the oxygen and water vapor contents after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 are 30ppm; the temperature of the precursor gas phase synthesis fluidized bed 2 is 25 ℃, the fluidizing gas is Ar, the purity is 99.99%, and NH which enters the precursor gas phase synthesis fluidized bed 2 in unit time 3 With SiHCl 3 The molar ratio of (2) 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 Which contains NH in an amount of 20% by volume 3 Dechlorination for 3min; the first energy supply device 8 and the second energy supply device 19 are heated by microwaves; the temperature of 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 retention is equal to 600min; the decomposing fluidized bed 15 has a temperature of 800 ℃ and a fluidizing gas of N 2 And H is 2 The mol ratio of the mixed gas is 100/1, and the material residence time is equal to 600min; the inner wall of the crystallization device 17 is 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 prepared silicon nitride powder, from which it can be seen that the powder exhibits an equiaxed hexagonal morphology, the average particle size of the powder is about 0.96 μm, the Cl impurity of the powder is about 60ppm, and the α -phase content in the powder is greater than 95%.
Example 5
In this embodiment, based on the above embodiment 2, the material in the powder feeding device 1 is silicon nitride powder with an average size of 800 μm, and the purity of the powder is 99.99%; the silicon source in the silicon source evaporation device 4 is 99.99 percent SiBr 4 The temperature is 80 ℃; ar, N 2 ，NH 3 ，H 2 The purity is 99.999 percent, and the oxygen and water vapor content after the treatment of the first gas purifier 3-1, the second gas purifier 3-2 and the third gas purifier 3-3 is less than 10ppm; the temperature of the precursor gas phase synthesis fluidized bed 2 is 150 ℃, and the fluidizing gas is N 2 Purity of 99.999% and enter the precursor gas phase synthesis fluidized bed 2 per unit timeNH 3 With SiBr 4 The molar ratio of (2) is equal to 10, and the synthesis time is 100min; the temperature range of the materials in the dechlorination fluidized bed 7 is 650 ℃, and the fluidizing gas is N 2 Which contains H in an amount of 10% by volume 2 Dechlorination for 60min; the first energy supply device 8 and the second energy supply device 19 are conventional resistance heating; the temperature of the heating device 10 is maintained at 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; the decomposing fluidized bed 15 has a temperature of 1150 ℃ and a fluidizing gas of N 2 The gas and material residence time is equal to 400min; the crystallization device 17 has a temperature of 1450 ℃, wherein the gas is N 2 Crystallizing for 90min to obtain silicon nitride powder. FIG. 4 is an XRD pattern of a silicon nitride powder, from which it can be seen that only diffraction peaks of alpha-phase silicon nitride are detected, indicating that 100% of alpha-Si is synthesized 3 N 4 And (3) powder. In addition, the powder had an equiaxed shape, the average particle size of the powder was about 0.58 μm, and the Br impurity of the powder was about 90ppm.
The invention is not described in detail in part as being well known in the art.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and are not limiting. 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 modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the appended claims.
Claims (10)
1. A system for preparing high quality silicon nitride powder in a multistage fluidized bed, the system 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 collection 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 collection device (18) and a second energy supply device (19);
the discharge port of the powder feeding device (1) is connected with the feed port at the upper part of the precursor gas-phase synthesis fluidized bed (2) through a pipeline and a feed valve; ar or N 2 Is connected with an air inlet of the first air purifier (3-1) through a pipeline; the air outlet of the first gas purifier (3-1) is connected with the air inlet of the silicon source evaporation device (4) through a pipeline and an air 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 air outlet of the first gas purifier (3-1) is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed (2) through a pipeline and an air valve; NH (NH) 3 The air source is connected with an air inlet of the second air purifier (3-2) through a pipeline; the air outlet of the second gas purifier (3-2) is connected with the air inlet at the bottom of the precursor gas phase synthesis fluidized bed (2) through a pipeline and an air valve;
the gas outlet at the upper part of the precursor gas phase synthesis fluidized bed (2) is connected with the gas 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 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 hole of the dechlorination fluidized bed (7) through a pipeline and a feed valve; the dechlorination fluidized bed (7) is provided with the first energy supply device (8); an air inlet at the bottom of the dechlorination fluidized bed (7) is connected with air outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through pipelines and air valves; an air outlet at the top of the dechlorination fluidized bed (7) is connected with an 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 compression device (6) through a pipeline; the discharge port of the second cyclone separation device (9) is connected with the feed port of the ammonium chloride collection device (11) through a pipeline and a feed 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 feed 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 hole 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 air inlet of the tail gas recovery compression device (6) through a pipeline and an air valve; an air inlet at the bottom of the deep dechlorination fluidized bed (12) is connected with air outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through pipelines and air valves;
the discharge port at the lower part of the deep dechlorination fluidized bed (12) is connected with the feed port of the decomposition fluidized bed (15) through a pipeline and a feed valve; an air outlet at the upper part of the decomposing 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 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 hole at the upper part of the decomposing fluidized bed (15) through a pipeline; an air inlet at the bottom of the decomposing fluidized bed (15) is connected with air outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through pipelines and air valves;
a discharge hole at the lower part of the decomposing 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 compression device (6) through a pipeline and an air valve; an air inlet at the bottom of the crystallization device (17) is connected with air outlets of the first gas purifier (3-1), the second gas purifier (3-2) and the third gas purifier (3-3) through pipelines and air valves; the discharge hole at the lower part of the crystallization device (17) is connected with the feed inlet of the silicon nitride powder collecting device (18) through a pipeline and a material valve.
2. A method of preparing high quality silicon nitride powder based on a multi-stage fluidized bed of the system of claim 1, the method comprising the steps of: the materials in the powder feeding device (1) pass through Ar or N 2 After cleaning, the mixture enters into a pipeline and a material valve to be subjected to Ar or N 2 The cleaned precursor gas phase synthesis fluidized bed (2) is kept fluidized; ar or N 2 Carrying a silicon source in the silicon source evaporation device (4) into the precursor gas-phase synthesis fluidized bed (2) and simultaneously carrying NH 3 With Ar or N 2 Entering the precursor gas phase synthesis fluidized bed (2) through a pipeline to perform precursor synthesis reaction; fine powder in the precursor gas-phase synthesis fluidized bed (2) enters the precursor gas-phase synthesis fluidized bed (2) again after being separated by the first cyclone separation device (5); tail gas separated by the first cyclone separation device (5) enters the tail gas recovery compression device (6) to realize recovery and reutilization of the tail gas;
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 meanwhile, a certain amount of NH is formed 3 Or H 2 With Ar or N 2 Gas enters the dechlorination fluidized bed (7) and ensures that the materials therein are 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 enter the second cyclone separation device (9) along with tail gas through a pipeline provided with the heating device (10), NH 3 And HCl are condensed and crystallized to form NH 4 Cl solid particles enter the ammonium chloride collecting device (11), tail gas enters the tail gas recovery compression deviceA device (6) for recycling tail gas;
NH is removed from the dechlorination fluidized bed (7) 4 The Cl material enters the deep dechlorination fluidized bed (12) through a pipeline and a material valve, and a certain amount of NH is simultaneously carried out 3 Or H 2 With Ar or N 2 Gas enters the deep dechlorination fluidized bed (12) and ensures that the materials therein are in a fluidized state; under the action of the second energy supply device (19), the materials in the deep dechlorination fluidized bed (12) are deeply dechlorinated, and fine powder in 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) enters the tail gas recovery compression device (6) after passing through the acid gas processor (14), 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 simultaneously formed 3 Or H 2 With Ar or N 2 The gas enters the decomposing fluidized bed (15), and under the condition of a certain temperature, the material is converted into amorphous powder; fine powder in the tail gas enters the decomposing 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 compression device (6) to realize recovery and reutilization of the tail gas;
the material in the decomposing fluidized bed (15) enters the crystallization device (17) through a pipeline and a material valve, and a certain amount of NH is simultaneously supplied 3 Or H 2 With Ar or N 2 The gas enters the crystallization device (17), and 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; tail gas in the crystallization device (17) enters the tail gas recycling and compressing device (6) to recycle the tail gas.
3. A method for producing high quality silicon nitride powder according to claim 2, wherein Ar, N 2 、NH 3 And H 2 The purity of the gas is more than 99.9 percent, and the gas passes through the first gas purifier (3-1) and the second gas purifier3-2), and the oxygen and water vapor content after the treatment of the third gas purifier (3-3) is less than 500ppm.
4. A method for preparing high quality silicon nitride powder according to claim 2, characterized in that 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, N 2 Or H 2 Any one or any combination of the proportions and NH in the bed 3 The molar ratio of the catalyst 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. A method for preparing high quality silicon nitride powder according to claim 2, characterized in that the material temperature in the dechlorination fluidized bed (7) is 300-800 ℃, and the fluidizing gas is Ar, N 2 、NH 3 And H 2 Any one or any combination of the gases in any proportion, and the material residence time is more than or equal to 3min and less than or equal to 600min.
6. A method for preparing a high quality silicon nitride powder according to claim 2, characterized in that the energy supply means (8) is any one or a combination of two heating modes of conventional resistance heating or microwave heating.
7. A method of producing high quality silicon nitride powder according to claim 2, characterized in that the heating device (10) is maintained at a temperature of 400-600 ℃.
8. A method for preparing high quality silicon nitride powder according to claim 2, characterized in that the temperature in the deep dechlorination fluidized bed (12) is 600-1000 ℃, and the fluidizing gas is Ar, N 2 、NH 3 And H 2 The material residence time of any one or any combination of the gases is more than or equal to 10min and less than or equal to 600min.
9. A method for preparing a high quality silicon nitride powder according to claim 2, characterized in that the decomposing fluidized bed (15) The temperature of (2) is 800-1200 ℃, and the fluidizing gas is Ar and N 2 、NH 3 And H 2 The material residence time of any one or any combination of the gases 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 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 material residence time 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 gases in any proportion.
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