WO2022073351A1

WO2022073351A1 - Aluminum nitride nanopowder synthesis production line

Info

Publication number: WO2022073351A1
Application number: PCT/CN2021/096745
Authority: WO
Inventors: 韩召; 陆献平; 王澎; 任小平
Original assignee: 浙江宇耀新材料有限公司
Priority date: 2020-10-10
Filing date: 2021-05-28
Publication date: 2022-04-14
Also published as: CN112299385A; CN112299385B

Abstract

An aluminum nitride nanopowder synthesis production line is provided. The production line comprises an aluminum nitride nanopowder synthesis apparatus (1), a material collection system, a nitrogen supply system, a refrigeration system (2), and an argon supply system (3). The aluminum nitride nanopowder synthesis apparatus comprises: an outer casing (100), a spray unit, a gasification unit, a reaction unit, and a cooling unit. The material collection system is connected to an outlet of the cooling unit and is used for gas-powder separation, recovery, and packaging of a material. The nitrogen supply system is used to supply nitrogen gas for the spray unit, the reaction unit, and the cooling unit. The refrigeration system is used for supplying, in a circulatory manner, a coolant medium for the spray unit, the gasification unit, the reaction unit, and the cooling unit. The argon supply system is in communication with spray unit and the outer casing, and is used for supplying argon gas. The present production line allows for the complete reaction of a raw material, an aluminum nitride powder obtained has high purity, is uniform in particle size, is nanoscale in size, and is not prone to agglomeration, said production line can implement continuous production, has high yield and rapid output, little ancillary equipment is necessary, and is low cost.

Description

A kind of nano aluminum nitride powder synthesis production line

technical field

The invention relates to the field of aluminum nitride synthesis, in particular to a nanometer aluminum nitride powder synthesis production line.

Background technique

Human beings have entered the 21st century. Materials, information and energy are known as the three pillars of science. Materials are the material basis of human production and life, and the symbol of human progress and human civilization. With the emergence and development of new technologies such as space technology, infrared technology, sensing technology, and energy technology, materials are required to have superior properties such as high temperature resistance, corrosion resistance, and high insulation before they can be used in harsh environments. Aluminum nitride materials stand out from new materials due to their unique and excellent characteristics, and are increasingly valued by scientists from all over the world. Aluminum nitride does not exist in nature and is artificially synthesized. It is an industrial special ceramic material. Aluminum nitride has excellent thermal, electrical and mechanical properties, high temperature resistance, good thermal conductivity (second only to aluminum), high insulation, high hardness, resistance to Grinding, low expansion, corrosion resistance, it is an ideal material for large-scale integrated circuit heat dissipation substrates, melting crucibles, casting molds, heat conduction and other materials. At present, the purity of aluminum nitride powder produced by most enterprises is within 95%, and the particle size is above 0.5 microns. The current preparation methods mainly include the following categories:

(1) Direct nitriding method: The direct nitriding method of aluminum powder is under the condition of continuous flowing N ₂ (or NH ₃ ) atmosphere (or in a closed nitrogen atmosphere container), and the aluminum powder and N ₂ (or NH ₃ ) are relatively The method for preparing AlN powder by direct chemical reaction at high temperature, the reaction equation is:

2Al+N ₂ →2AlN

The disadvantage of this method is that the melting point of aluminum is 660°C, and the nitriding temperature is 1000-1600°C. During nitriding, an aluminum nitride layer will be formed on the surface of the aluminum water (liquid), which will prevent _N2 from further migrating to the aluminum water (liquid). Internal infiltration, the heat released during nitridation results in a bulky product with low purity.

(2) Thermal reduction method: AlN powder is prepared by nitrogen reduction reaction of Al ₂ O ₃ powder and excess C (activated carbon) powder under flowing N ₂ atmosphere at a certain temperature (1200-1800°C). The reaction equation is:

Al ₂ 0 ₃ +3C+N ₂ →AlN+3CO↑

The disadvantages of this method are: long synthesis time, high temperature, separation of excess C and CO after synthesis and high cost.

(3) Arc plasma torch gasification method: Put aluminum in a crucible in a closed container and melt it into aluminum water (liquid), and the flame of the plasma torch is sprayed against the aluminum water (liquid), so that the aluminum vaporizes and sublimates into the reaction chamber , while introducing nitrogen to cool the reaction synthesis.

The disadvantages of this method are: the thermal conversion rate of the plasma torch is lower than 20%, high energy consumption, and large equipment investment; the electrodes for generating the arc are copper and tungsten alloys, which are quickly ablated and gasified when the temperature exceeds 5,000 degrees, and the gasified tungsten The mixing of copper and aluminum gas affects the purity; the tungsten-copper electrode is replaced in about 100 hours, and the cost of consumables is high; the torch electrode is cooled by water, and the copper electrode is ablated and perforated at ultra-high temperature. Once the cooling water is sprayed into the crucible, the instantaneous water vapor expands and explodes; Due to the high production cost, industrial production has not yet been formed.

(4) Arc atomization method: two aluminum wires that can move evenly in the same direction are used as electrodes. When the two ends of the aluminum wires are close to each other, an arc (high temperature) is generated, and the ends of the aluminum wires are instantly atomized, and nitrogen is sprayed into the middle of the arc to spray the aluminum mist. , aluminum mist and nitrogen are synthesized in the reaction kettle.

The disadvantage of this method is that due to the size and temperature of the aluminum mist particles, the surface of some particles is nitrided, the middle is not nitrided, and the purity is not high.

To sum up, the technical difficulties of several methods in the prior art mainly lie in:

(1) The raw materials cannot be completely reacted, or contain impurities and have low purity.

(2) The direct nitriding method and thermal reduction method are mostly used in China. The products are agglomerated and lumpy. Pulverization and grinding are the biggest problems. The cost is high, the thickness is uneven, the abrasive loss enters the powder, and the particles after grinding are difficult to reach the fineness. greatly affected.

(3) Most of the current production processes cannot achieve high-purity nano-powders.

(4) Intermittent production: feeding→preheating→heating→reaction→heat preservation→cooling→discharging→crushing→separation→grinding→separation→drying→classification→packaging, one furnace for one furnace, the equipment utilization rate is low.

(5) Difficulty in production management: there are many equipment, large workshops, many links, many processes, large investment, and many personnel.

(6) There are many supporting facilities: auxiliary facilities such as dust removal, anti-static, vibration isolation, and noise reduction.

To this end, it is necessary to develop a new technology for aluminum nitride powder production to solve the above-mentioned technical problems.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a production line for synthesizing nano-aluminum nitride powder. Through the production line of the present invention, the synthesis of aluminum nitride powder is carried out, the raw materials are fully reacted, and the synthesized aluminum nitride powder has high purity (up to 99.99 % or more), the particle size of the powder is uniform in nano-scale and not easy to agglomerate, which can realize continuous production, high output, fast output, less supporting equipment and low cost.

The specific technical scheme of the present invention is:

A nano-aluminum nitride powder synthesis production line comprises: a nano-aluminum nitride powder synthesis device, a material collection system, a nitrogen supply system, a refrigeration system and an argon supply system.

The nano-aluminum nitride powder synthesis device includes: a casing, a spray unit arranged in the casing, a gasification unit arranged in the casing and connected below the spray unit, and a reaction unit arranged in the casing and connected below the gasification unit unit and a cooling unit connected below the gasification unit.

The invention prepares the synthesis of aluminum nitride based on the aluminum gasification reaction, and the reaction equation is: 2Al+N ₂ →2AlN+heat. The synthesis process can be summarized as:

In the spraying unit, solid aluminum particles (preferably deoxidized, high-purity, aluminum pellets of the same size) are heated and melted (above 1500° C.), and nitrogen gas transports the aluminum liquid to the gasification unit in the form of aluminum mist.

In the gasification unit, the aluminum mist and nitrogen gas are heated in the gasification chamber (about 2500° C.) to form aluminum gas (monatomic), and the aluminum gas and nitrogen gas continue to lead to the reaction unit.

In the reaction unit, nitrogen is introduced to cool down to 1300-1500°C, and aluminum gas (monatomic) reacts with nitrogen to synthesize aluminum nitride.

In the cooling unit, the synthesized aluminum nitride is further cooled and discharged.

The device of the invention is used to synthesize aluminum nitride powder, the raw materials are completely reacted, the purity of the synthesized aluminum nitride powder is high (up to 99.99% or more), the particle size of the powder is uniform in nano-scale and not easy to agglomerate, and continuous production can be realized. , high output, fast output, less supporting equipment and low cost.

The material collection system is connected with the outlet of the cooling unit for gas-powder separation, recovery and packaging of materials.

The nitrogen supply system is used for nitrogen supply of spray unit, reaction unit and cooling unit.

The refrigeration system is used for the circulating supply of the cooling medium of the spraying unit, the gasification unit and the cooling unit.

The argon supply system is communicated with the spray unit (the top of the aluminum liquid silo) and the outer shell for argon gas supply.

Preferably, the material collection system includes a gas powder separation device, a packaging device and a recovered gas storage tank; the gas powder separation device is connected to the outlet of the cooling unit, and the packaging device and the recovered gas storage tank are respectively connected with the gas powder separation device The powder outlet and the gas outlet are connected; the recovered gas storage tank also provides power gas for the packaging device and the spray unit (aluminum feeding mechanism).

Preferably, the nitrogen supply system includes a nitrogen generator, a nitrogen tank, a nitrogen freezer and a liquid ammonia tank; the nitrogen generator is connected to the nitrogen tank, the nitrogen tank is respectively connected to the spray unit, the reaction unit and the cooling unit, and the nitrogen The nitrogen refrigerator is provided on the pipeline connecting the tank with the reaction unit and the cooling unit; the liquid ammonia tank is connected with the reaction unit.

The present invention simultaneously adopts nitrogen gas and liquid ammonia to transport nitrogen source to the reaction unit, and its advantages are: (1) a trace amount of liquid ammonia is added to the nitrogen gas outside the device to be input into the reaction unit, and the liquid ammonia is decomposed into hydrogen atoms and nitrogen atoms after the temperature of the reaction unit is heated up. The aluminum material and nitrogen contain trace oxygen atoms, and the hydrogen atoms combine with the oxygen atoms in the gas going down the gasification unit to form water, which plays a role in deoxidation; ② the nitrogen input to the reaction unit is mixed with the gas going down the gasification unit and then cooled to 1300-1500° Then nitrogen reacts with aluminum gas to synthesize aluminum nitride, and nitrogen is the raw material for the reaction; ③In the reaction unit, nitrogen reacts with aluminum gas to synthesize aluminum nitride powder. The gas becomes solid, and the temperature is lowered by 800-1000°, and the pressure drops rapidly. Air pressure maintained.

In the present invention, the argon gas of the argon supply system is passed into the aluminum liquid silo of the spray unit, and is pressurized synchronously with the nitrogen conveying pipe in the aluminum liquid silo, so that the aluminum liquid is ejected through the nozzle;

The distribution trend of the refrigerant medium in the refrigeration system of the present invention: (1) one channel leads to the top cover of the spray unit; (2) two channels lead to the connecting pipe of the gasification unit and the pressure measuring port of the reaction unit for cooling; (3) one channel leads to the induction coil for cooling; (4) The two paths lead to the upper and lower sections of the cooling unit.

In the present invention, the nitrogen in the nitrogen tank is divided into five distribution directions: 1) pass into the aluminum feeding mechanism, which is used as protective gas; 2) pass into the nitrogen nozzle of the spray unit for air-borne spray; 3) pass into the reaction unit to cool down and react , pressurization; ④ Pass into the cooling unit, play the role of cooling and pressurization; The liquid ammonia in the present invention is passed into the reaction unit.

In the present invention, after the gas powder from the outlet of the cooling unit is separated by the gas powder, the gas is recovered by the booster pump, and the gas powder is 25-30°C.

The use and distribution trends of the recovered gas in the present invention are: ① power gas for packaging equipment; ② power gas for aluminum feeding mechanism; ③ power gas for blanking valve of aluminum feeding mechanism.

Preferably, the spraying unit includes: an aluminum feeding mechanism, a thermal insulation shell, a heating cover, an aluminum liquid silo, a nitrogen nozzle and an insulating cover seat. The heating cover is arranged in the heat preservation shell, and the inner wall of the heating cover is provided with electric heating wires; the middle and lower sections of the aluminum liquid silo are arranged in the heating cover and have a gap with the inner wall of the heating cover, and the bottom of the aluminum liquid silo extends out The bottom of the heating mantle is provided with a downward atomizing nozzle; the nitrogen nozzle is passed into the center of the aluminum liquid silo and its air outlet faces the atomizing nozzle; the aluminum feeding mechanism is arranged on the top of the aluminum liquid silo; The insulating cover seat is arranged below the heat preservation shell and the heating cover, and a gap is provided between the inner ring of the insulating cover seat and the bottom outer wall of the aluminum liquid silo.

The working principle of the spraying unit of the present invention is as follows: the aluminum liquid silo is pressurized with argon gas to 0.5-0.55MPa (5-5.5 kg), the heating cover is heated in parts, the temperature is controlled in parts, and solid aluminum particles are placed on the upper part of the aluminum liquid silo. Heating to 700-800 ℃, heating the aluminum liquid to 1600-1700 ℃ with different electric power in the middle and lower part; feeding nitrogen into the nitrogen nozzle to pressurize 0.55-0.6MPa (5.5-6 kg) as a spraying gas, through the atomizing nozzle The aluminum mist is sprayed into the gasification unit.

Preferably, the spray unit is fixed in the housing through a bracket. Specifically, the bracket may be formed by connecting four metal bars perpendicular to each other with the middle ring (ceramic material), and the bracket metal bars are placed on the stopper on the inner wall of the housing to make the bracket hang. The heating cover is hung on the bracket, and the bottom is embedded with an insulating cover. The aluminum liquid silo is inserted into the heating hood from the flange port on the top of the housing, and there is a gap between the heating wire of the heating hood and the upper flange of the spray unit is fixed on the flange on the top of the housing.

Preferably, the gap between the inner ring of the insulating cover seat and the bottom outer wall of the aluminum liquid silo is 1-2 mm.

The bottom of the spray unit is separated from the inner ring of the insulating cover seat embedded in the vaporizing unit, and the insulating cover seat is arranged above the vaporizing unit. It should be noted that there is a gap of 1-2mm between the inner ring of the annular insulating cover base and the bottom outer wall of the aluminum liquid silo. The gap can ensure that the aluminum liquid silo has enough space for expansion and contraction after heating and expansion. The function of the insulating cover is: the gasification unit adopts intermediate frequency induction heating, the heating inner layer is provided with a heating inner layer, which will generate induced electricity, the aluminum liquid silo is made of tungsten alloy, and the insulating cover can isolate the heating inner layer and aluminum liquid. After the thermal expansion of the warehouse, etc., the contact is conductive.

Preferably, the shell is provided with an argon gas inlet, and the top of the aluminum liquid silo is provided with an argon gas inlet.

The effects of the present invention on the argon flow inside the casing are: 1. Since the heating filler, the heat insulating layer and the heat insulating plate in the device of the present invention are preferably made of graphite and graphite hard felt, carbon particles are easily emitted at high temperatures. For this reason, the present invention provides a protective effect by directing argon gas into the shell, so that the carbon particles do not emit and maintain durability; and the carbon particles are prevented from infiltrating into the gasification unit and the reaction unit, so that the purity of the aluminum nitride is reduced. ②Because there is a gap between the insulating cover and the aluminum liquid silo, the air pressure generated by the expansion of aluminum in the gasification unit will overflow into the gap, and the pressure of the argon gas to be controlled ≥ the pressure of the gasification chamber can make The indoor and outdoor air pressure remained relatively stable.

Preferably, an argon gas inlet is provided at the top of the aluminum liquid silo. The effect of the present invention on the top of the liquid aluminum silo vented with argon is as follows: (1) Since the diameter of the spray nozzle is less than 0.5mm, the liquid aluminum has poor fluidity and large resistance, and when the nitrogen nozzle is sprayed against the spray nozzle, nitrogen gas is emitted from the aluminum liquid. In the upper space of the upper aluminum liquid silo, one is that the sprayed aluminum liquid cannot be atomized, and the upper temperature is too high, and the other is that the upper aluminum liquid surface and nitrogen are nitrided to form a layer of aluminum nitride film, so that the aluminum liquefaction and atomization are terminated. ②Introduce argon gas into the upper part and pressurize the nitrogen nozzle at the same time. The nitrogen gas is sprayed from the nozzle with the aluminum liquid to form a mist. The argon gas is an inert gas and does not react with the aluminum liquid.

Preferably, the pipeline between the aluminum feeding mechanism and the aluminum liquid silo is provided with two valves which are connected in series and are switched on and off in a staggered manner.

In the prior art, there is usually only one valve in the pipeline between the aluminum feeding mechanism and the heating and melting mechanism, or even if there are multiple valves, it is only used as a backup, and no targeted linkage is performed. In the present invention, two valves which are connected in series and staggered are provided on the pipeline between the aluminum feeding mechanism and the aluminum liquid silo. The two valves are separated by aluminum pellets. When the lower valve is opened, the aluminum pellets will automatically fall off into the spray unit; when the upper valve is opened, the aluminum pellets will fall into the pipe from the silo, for example, every 2-3 seconds as required. The upper and lower valves are switched on and off once, and the material is fed once. The small and frequent special feeding method can effectively reduce the pressure pulse fluctuation in the spray unit and make the spray uniform.

Preferably, the aluminum feeding mechanism is provided with a nitrogen inlet.

The production line is carried out in a fully enclosed device. The inventor found in practice that the solid aluminum feeding device in the prior art is prone to static electricity and aluminum oxidation due to friction between the materials due to air being carried during feeding. . Therefore, in the present invention, nitrogen is passed through the silo and the conveying pipeline of the aluminum feeding mechanism to discharge the air, and works under the protection of nitrogen, which can avoid static electricity generated by friction and aluminum oxidation.

Preferably, the shape of the material sprayed from the atomizing nozzle is conical, with an inner angle of 90-120°, a side length of 30-40 mm, and a mist particle size of 3-5 microns. The sprayed aluminum mist weighs 1.5-2 grams per second, and the spray conveys nitrogen gas at 0.8-1 cubic decimeter per second.

The reason why the present invention specifically limits the conditions for the spraying of aluminum mist to the above-mentioned conditions is that: (1) when the spray angle is less than 90°, the volume of the mist cone decreases, the distribution density of the mist particles increases, the particles increase, and it is not easy to gasify; (2) when the spray angle is smaller than 90° When the angle is less than 90°, the volume of the fog cone decreases, the height of the fog cone increases, the aluminum fog is close to the waist shrinking structure, and the temperature of the waist shrinking port is relatively low. (chamber) pressure difference, the non-atomized aluminum mist flows directly into the reaction plug (chamber), so that the reaction is not complete.

Preferably, the diameter of the upper section of the heating mantle and the liquid aluminum silo is larger than the diameter of the lower section.

Preferably, an upper refrigerant jacket is provided on the top wall of the aluminum liquid silo.

The aluminum liquid silo, the atomizing nozzle and the nitrogen nozzle are made of tungsten alloy material; the heating cover and the insulating cover seat are made of ceramic material.

Preferably, the gasification unit includes: a gasification chamber and an induction coil sequentially formed by an upper heat-insulating and insulating outer layer, a heat-insulating middle layer and a heating inner layer. The center of the top of the gasification chamber is provided with an opening for placing the insulating cover; the center of the bottom of the gasification chamber is provided with an opening to communicate with the reaction unit; the induction coil is wrapped on the outer side of the upper thermal insulation outer layer; the heating body is The bottom of the layer is a cone with a decreasing diameter, and the space between the cone and the heat insulating middle layer is filled with a heating filler and a heat insulating plate; the heat insulating plate is located at the bottom of the gasification chamber.

The working principle of the gasification unit of the present invention is as follows: the intermediate frequency induction coil is used to inductively heat the inner layer of the heating body to about 2500°C, so that the space temperature in the gasification chamber exceeds 2327°C (aluminum gasification temperature is 2327°C), and the aluminum gas in the gasification chamber, After the nitrogen gas is heated, the volume expands, the aluminum mist is continuously sprayed, and a certain air pressure is generated in the gasification chamber, and the air flow downwards into the reaction unit.

An hourglass-shaped waisted structure is designed between the bottom of the gasification unit and the reaction unit. The function of this structure is: ①It plays a role of heat preservation. After shrinking the waist, the flow rate of the upper and lower gas slows down, so that the residence time of the aluminum mist in the gasification chamber is increased, and the aluminum mist is completely gasified; ②The temperature of the gasification chamber is required to be 2500℃, and the temperature of the reaction chamber is 2500℃. It is required to be 1300-1500 ℃ and the temperature difference is 1000-1200 ℃. It is separated by a waist shrinking structure, and the temperature of the upper and lower chambers can be controlled.

Since the inner layer of the heating body at the waist-shrinking structure is far away from the induction coil, the induction heating effect is poor. For this reason, the present invention fills the heat-generating filler inside the structure, and the heat-generating filler transfers heat to the waist shrinking portion. During induction heating, the heat-generating filler is first heated, and then the heat-generating filler transfers heat to the inner layer of the heat-generating body to ensure the bottom of the gasification chamber. temperature.

The temperature difference between the gasification chamber and the reaction chamber reaches 900-1000°C. In order to maintain the corresponding temperature in the respective areas, the bottom of the waist-reduced structure of the present invention is provided with a heat insulation board to prevent heat transfer from top to bottom.

Preferably, the reaction unit includes: a reaction chamber composed of a lower thermal insulation outer layer and a heat-resistant inner layer, and a vortex nozzle. The bottom of the heat-resistant inner layer is in the shape of a cone with a decreasing diameter, and a discharge pipe is connected in the center of the cone bottom. The end is provided with a vortex nozzle, the vortex nozzle is located just below the bottom opening of the gasification chamber and the air jet direction is upward.

The working principle of the reaction unit of the present invention is as follows: when the aluminum gas and nitrogen gas flow into the reaction chamber, the temperature is greater than 2327° C. At this time, the aluminum gas and nitrogen gas (partially dissociated single atoms) are very active, and the optimum reaction temperature is 1300-1500° C. , In order to achieve rapid cooling, the present invention adopts the method of passing nitrogen to cool down to the reaction temperature, and the reaction raw materials are rapidly reacted to synthesize aluminum nitride.

However, the inventor discovered a new technical problem during the test: the synthesis reaction is a process of gas becoming solid, the gas volume shrinks rapidly, and the pressure shrinks rapidly, resulting in a pressure difference between the gasification chamber and the reaction chamber, and the up and down flow rate will be too fast . To this end, the present invention blows the external nitrogen gas downward in a spiral form through the vortex nozzle, and the oppositely blown gas spreads spirally around, so that the gas distribution is uniform, the temperature is uniform, the reaction is uniform, and the reaction is complete. The incoming nitrogen is excess nitrogen, and the excess nitrogen drives the flow of the powder. In this way, after the external nitrogen is input, the upper and lower pressures of the gasification chamber and the reaction chamber can be kept balanced, and the material flow rate can be slowed down.

Preferably, the air flow ejected from the swirl nozzle is a fan-shaped spiral with an internal angle of 50-70°.

The reason why the present invention specifically limits the airflow to the above-mentioned angle is: 1. when the inner angle is less than 50°, the fan arc is short, and the jetting force of the airflow is large, and it is easy to spray the descending aluminum gas to the top of the reaction chamber, the top temperature is too high, and the rebounded airflow Rapidly flowing into the cooling unit, resulting in uneven cooling and incomplete reaction; ②When the inner angle is greater than 70°, the fan arc is long, the gas density is small, and the spray force is small, and it is not easy to blow the descending aluminum gas, and the aluminum gas is wrapped in the vortex nozzle. Around, the cooling is uneven and the reaction is not complete.

Preferably, the upper thermal insulation outer layer and the lower thermal insulation outer layer are integrally formed; the heating inner layer and the heat-resistant inner layer are separately formed and connected by insertion.

Preferably, the upper and lower heat-insulating outer layers are made of heat-insulating cotton; the heat-insulating middle layer and the heat-insulating plate are made of graphite hard felt; and the heat-generating filler is made of graphite. The heating inner layer and the heat-resistant inner layer are made of tungsten alloy material.

Preferably, the reaction unit is erected on the bottom of the shell through a bottom bracket; the bottom bracket is made of metal,

Preferably, the spraying unit, the gasification unit and the reaction unit are installed in the same stainless steel shell, and are installed in layers in a structured way. During installation, the heat-resistant inner layer is placed on the ceramic base bracket, and the heat-resistant inner layer is stacked on the inner layer. The heating plate, the heat-generating filler is placed on the heat-insulating plate, the heating inner layer of the gasification unit is placed on the heating-filling body, the heat insulating plate is placed on the heating body layer, and the insulating cover is placed on the heat insulating plate at the same time. The unit is installed with thermal insulation materials, an induction coil is installed around the outer wall of the gasification unit, a bracket is installed on the upper part of the casing, the heating cover is inserted from the inner ring of the bracket ring and placed on the ring, and the upper cover of the outer casing is covered. The flange port on the top of the upper cover is inserted into the inner ring of the insulating cover seat through the inner ring of the heating cover. The flange of the aluminum liquid tank is fixed with the flange of the upper cover. The assembled installation does not require welding. It needs to be replaced, repaired and cleaned during use. Great convenience.

Preferably, the cooling unit includes: a cooling chamber casing, a spiral nozzle and a lower refrigerant jacket; an opening is provided in the center of the top of the cooling chamber casing, and the spiral nozzle is arranged at the opening and is connected to the reaction unit through the connecting flange. The discharge pipe is connected, and the direction of the spiral nozzle is downward; the cooling chamber shell is provided with a nitrogen inlet, the bottom of the cooling chamber shell is in the shape of a cone with decreasing diameter, and the center of the cone bottom is the gas powder outlet; the lower refrigerant jacket is provided with on the outside of the cooling chamber housing.

The cooling unit of the present invention adopts two methods of combined cooling: refrigerant jacket (preferably water cooling) and nitrogen cooling. The advantages of this combined cooling are: 1. The temperature of the gas powder flowing into the cooling unit from the reaction chamber needs to be reduced from about 1450°C to about 50°C , the temperature difference reaches 1400 °C, and it cannot be quickly cooled in a short period of time. Compared with nitrogen cooling, water cooling has lower cost, but the time is long, the cooling is uneven, the cooling rate is slow, and the particles are easy to agglomerate and bond; and the combination of nitrogen cooling can not only reduce the cooling time, but also And can effectively disperse agglomerated particles. ②After the gas powder is rapidly cooled in the cooling unit, the pressure decreases rapidly, resulting in an increase in the pressure difference between the reaction chamber and the cooling chamber, which makes the gas powder flow too fast. The flow rate of the gas powder from the reaction chamber to the cooling chamber slows down, and the gas powder slows down and also buys more time for its cooling.

As an option, the cooling unit adopts the upper and lower two-section split flange connection. The advantages are: when the lower section is removed, it is extremely convenient to install, replace, repair and clean the spiral nozzle and spiral nozzle from the open port.

The cooling unit of the present invention is provided with a spiral nozzle that opens toward the bottom of the reaction chamber, and its functions are: (1) The gas powder passes through the helical bar in the spiral nozzle to reduce the sinking speed of the gas powder direct injection, thereby effectively reducing the impact of the powder on the inner wall. ②When the synthetic powder in the reaction chamber passes through the discharge port, the particles are extruded, and the density increases easily to agglomerate, which can be broken up after being hit by the spiral strip of the spiral nozzle. ③The spiral gas powder sprayed by the spiral nozzle is evenly distributed in the cooling chamber, and the cooling is fast and uniform.

The spiral nozzle of the cooling unit of the present invention is tightly connected with the discharge pipe at the bottom of the reaction chamber through the connecting flange, which can play the role of controlling the flow of gas and powder (selecting different inner diameters of the connecting pipe).

Preferably, the air powder is ejected from the spiral strip gap of the spiral nozzle to form a fan-shaped spiral rotating airflow with an inner angle of 90-120°.

The reason why the present invention specifically limits the spiral rotating airflow to the above-mentioned angle is: 1. the particles are easy to agglomerate when passing through the nozzle pipe, and when the inner angle is greater than 120°, the jet force of the air powder on the nozzle spiral is reduced, and it is difficult to disperse the agglomerated particles; 2. the inner angle is less than At 90°, the ejection force is large, the flow rate is too fast, the cooling is uneven, and the particles will agglomerate.

Preferably, the discharge pipe and the connecting flange are made of tungsten alloy material; the spiral nozzle is made of ceramic material.

Preferably, a temperature measuring port and a pressure measuring port are provided at different positions of the casing, the spraying unit, the gasification unit, the reaction unit and the cooling unit.

To sum up, in the implementation process of the device of the present invention, the following points need to be done: 1. Control the pressure and temperature of the aluminum water in the spray unit, the air pressure and air flow in the nitrogen nozzle, and ensure that the particle size of the aluminum mist is 3-5 between microns. ②The temperature of the gasification chamber is more than 2327℃, and the reaction chamber is 1300-1500℃. ③In order to promote the reaction and keep the flow rate of gas and gas powder stable, it is necessary to adopt the partial pressure to exist pressure difference. ④ In order to achieve an ideal reaction, it is necessary to cool down to 1300-1500 °C; and the reaction synthesis is an exothermic reaction, and it is easy to produce large agglomerated particles when falling; in addition, the reaction of aluminum gas and nitrogen to synthesize aluminum nitride powder is a reaction after cooling, and the gas changes. solid, the pressure in the reaction chamber decreases. Therefore, it is necessary to control the method and process of introducing nitrogen into the reaction chamber to achieve cooling, air supply, uniform temperature, pressurization, and prevention of particle agglomeration.

In the present invention, a vortex nozzle whose outlet is a vortex nozzle is introduced into the discharge pipe of the reaction chamber. The nozzle is centered upward and blows against the downward gas in the gasification chamber. Mix evenly, cool down to 1300-1500 ℃ to produce reaction, after cooling, reduce the air pressure, aluminum gas reacts with nitrogen to synthesize aluminum nitride particles, the proportion of excess nitrogen and particles increases, and nitrogen and particles sink slowly, while reacting Drop into the cooling unit. The reaction chamber is funnel-shaped. When the gas powder enters the cooling unit and passes through the reducing pipe, the temperature is 1300-1500 ℃, and the density of the gas powder increases, resulting in collision and agglomeration. Therefore, the discharge pipe at the lower end of the reaction chamber extends to the cooling unit, and the gas powder is broken up after being hit by the spiral strips of the spiral nozzle and is ejected through the gap between the spiral strips to form a fan-shaped rotating airflow. Agglomerate large particles. There is no need for subsequent crushing and grinding, which ensures the direct formation of high-purity, high-fineness, nano-scale powder, which is easy to further process and has good sintering activity.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The production line of the present invention is used for the synthesis of aluminum nitride through the synergistic cooperation and optimal design of the various systems and units in the synthesis device. Not only the raw materials are reacted completely, but the purity of the synthesized aluminum nitride is high (up to 99.99% or more) , the powder particle size is uniform in nano-scale and not easy to agglomerate.

(2) The nano aluminum nitride powder synthesis device of the present invention continuously feeds from the aluminum feeding mechanism of the spray unit, and continuously discharges from the bottom of the cooling unit to form continuous flow production, which can realize continuous production with high output and fast output.

(3) The production line of the present invention requires less supporting equipment and low cost.

Description of drawings

Fig. 1 is a kind of connection schematic diagram of the production line of the present invention;

2 is a cross-sectional view of an internal structure of the nano-aluminum nitride powder synthesis device of the present invention;

Fig. 3 is a kind of top view of the bracket used for suspending the spray unit in the nano-aluminum nitride powder synthesis device of the present invention;

Fig. 4 is a kind of structural schematic diagram of the aluminum liquid silo and nitrogen nozzle in the spray unit of the nano-aluminum nitride powder synthesis device of the present invention;

5 is a schematic structural diagram of a heating cover in the spray unit of the nano-aluminum nitride powder synthesis device of the present invention;

6 is a schematic structural diagram of the gap between the aluminum liquid silo and the insulating cover seat in the spray unit of the nano-aluminum nitride powder synthesis device of the present invention;

7 is a schematic structural diagram of the gasification unit of the nano-aluminum nitride powder synthesis device of the present invention;

8 is a schematic structural diagram of the reaction unit of the nano-aluminum nitride powder synthesis device of the present invention;

9 is a schematic structural diagram of the cooling unit of the nano-aluminum nitride powder synthesis device of the present invention;

Fig. 10 is a schematic diagram of a disassembly of the discharge pipe of the reaction unit, the connecting flange and the spiral nozzle of the cooling unit in the nano-aluminum nitride powder synthesis device of the present invention.

The reference numbers are:

Nano aluminum nitride powder synthesis device 1, refrigeration system 2, argon supply system 3, gas powder separation device 4, packaging device 5, recovery gas storage tank 6, nitrogen generator 7, nitrogen tank 8, nitrogen refrigerator 9, liquid Ammonia tank 10;

housing 100, argon gas inlet 101, bracket 102, bottom bracket 103, temperature measuring port 104, pressure measuring port 105;

Aluminum feeding mechanism 201, thermal insulation shell 202, heating cover 203, aluminum liquid silo 204, nitrogen nozzle 205, insulating cover seat 206, electric heating wire 207, argon gas inlet 208, atomizing nozzle 209, valve 210, nitrogen gas inlet 211, Upper refrigerant jacket 212;

The upper thermal insulation outer layer 301, the thermal insulation middle layer 302, the heating inner layer 303, the induction coil 304, the heating filler 305, and the thermal insulation board 306;

Lower thermal insulation outer layer 401, heat-resistant inner layer 402, vortex nozzle 403, discharge pipe 404, vortex nozzle 405;

Cooling chamber shell 501 , spiral nozzle 502 , lower refrigerant jacket 503 , connecting flange 504 , nitrogen inlet 505 , gas powder outlet 506 .

Detailed ways

The present invention will be further described below in conjunction with the examples.

Example 1

As shown in FIG. 1 , a nano-aluminum nitride powder synthesis production line includes: a nano-aluminum nitride powder synthesis device 1 , a material collection system, a nitrogen supply system, a refrigeration system 2 and an argon supply system 3 .

specifically:

As shown in FIG. 2 , the nano-aluminum nitride powder synthesis device includes: a casing 100 , a spray unit disposed in the casing, a vaporization unit disposed in the casing and connected below the spray unit, disposed in the casing and connected The reaction unit below the gasification unit and the cooling unit connected below the gasification unit.

As shown in Figure 1, the material collection system is connected to the outlet of the cooling unit for the separation, recovery and packaging of the material. The material collection system includes a gas-powder separation device 4 , a packaging device 5 and a recovered gas storage tank 6 . The gas-powder separation device is connected with the outlet of the cooling unit, and the packaging device and the recovered gas storage tank are respectively connected with the powder outlet and the gas outlet of the gas-powder separation device (between the recovered gas storage tank and the gas-powder separation device). There is a booster pump on the pipeline); the recovered gas storage tank is also connected with the packaging device and the spray unit (aluminum feeding mechanism) to supply nitrogen for power. As shown in FIG. 1 , the nitrogen supply system includes a nitrogen generator 7 , a nitrogen tank 8 , a nitrogen refrigerator 9 and a liquid ammonia tank 10 . The nitrogen generator is connected with the nitrogen tank, the nitrogen tank is respectively connected with the spray unit, the reaction unit and the cooling unit, and a nitrogen refrigerator is provided on the pipeline connecting the nitrogen tank with the reaction unit and the cooling unit; the liquid ammonia tank is connected with the reaction unit and the cooling unit. unit connection.

As shown in FIG. 1 , the refrigeration system is used for circulating supply of the cooling medium of the spray unit, the gasification unit and the cooling unit, and a delivery pump is arranged in the pipeline.

As shown in FIG. 1 , the argon supply system is communicated with the spray unit (the top of the aluminum liquid silo) and the outer shell for argon supply.

More specifically, in the nano-aluminum nitride powder synthesis device:

As shown in FIG. 2 , an argon gas inlet 101 is provided on the upper part of the side wall of the casing.

As shown in FIG. 2 and FIGS. 4-5 , the spraying unit includes: an aluminum feeding mechanism 201 , a thermal insulation shell 202 , a heating cover 203 , an aluminum liquid silo 204 , a nitrogen nozzle 205 and an insulating cover seat 206 . The aluminum feeding mechanism is arranged on the top of the aluminum liquid silo, and two valves 210 which are connected in series and staggered are provided on the pipeline between the aluminum feeding mechanism and the aluminum liquid silo. A nitrogen gas inlet 211 is provided on the aluminum feeding mechanism. The heating cover is arranged in the heat preservation shell, and the inner wall of the heating cover is provided with electric heating wires 207; the middle and lower sections of the aluminum liquid silo are arranged in the heating cover and there is a gap between the heating cover and the aluminum liquid silo. The diameter of the upper section is larger than the diameter of the lower section. The top of the aluminum liquid silo is provided with an argon gas inlet 208, the top wall of the aluminum liquid silo is provided with an upper refrigerant jacket 212, and the bottom of the aluminum liquid silo extends out of the bottom of the heating cover and is provided with a downward atomizing nozzle 209; the The nitrogen nozzle is passed into the center of the aluminum liquid silo and its air outlet faces the atomizing nozzle; the insulating cover seat is arranged below the heat preservation shell and the heating cover, as shown in Figure 5, the inner ring of the insulating cover seat is connected to the There is a gap (preferably 1-2mm) between the bottom outer walls of the aluminum liquid silo. Among them, the shape of the material sprayed by the atomizing nozzle is conical, the inner angle is 90-120°, the side length is 30-40mm, and the mist particle size is 3-5 microns.

The spray unit is fixed in the casing through a bracket 102 made of metal. As shown in Figure 3, the bracket is made of four metal strips that are perpendicular to each other and connected to the middle ring of ceramic material. The metal strips of the bracket are placed on the block on the inner wall of the shell, so that the bracket is suspended, and the upper part of the heating cover is hung. On the ring, the ring is cushioned with heat insulating material, and the bottom of the heating cover is embedded with an insulating cover seat that is placed on the gasification unit and plays a positioning role. In the spray unit, the aluminum liquid silo, the atomizing nozzle, the nitrogen nozzle, and the heating wire are made of tungsten alloy material; the heating cover and the insulating cover seat are made of ceramic material.

As shown in FIG. 2 and FIG. 7 , the gasification unit includes: a gasification chamber and an induction coil 304 sequentially formed by an upper thermal insulation outer layer 301 , a thermal insulation middle layer 302 and a heating inner layer 303 . The top center of the gasification chamber is provided with an opening for arranging the insulating cover; the bottom center of the gasification chamber is provided with an opening for communicating with the reaction unit; the induction coil is wrapped on the outer side of the upper thermal insulation outer layer; The bottom is in the shape of a cone with decreasing diameter, and the space between the cone and the heat insulating middle layer is filled with a heating filler 305 and a heat insulating plate 306; the heat insulating plate is located at the bottom of the gasification chamber.

As shown in FIG. 2 and FIG. 8 , the reaction unit is erected on the bottom of the casing through a base bracket 103 made of ceramic material. The reaction unit includes: a reaction chamber composed of a lower heat-insulating and insulating outer layer 401 and a heat-resistant inner layer 402 , and a vortex nozzle 403 . The bottom of the heat-resistant inner layer is in the shape of a cone with a decreasing diameter, and a discharge pipe 404 is connected to the center of the conical bottom. The gas outlet end is provided with a vortex nozzle 405, and the vortex nozzle is located just below the opening at the bottom of the gasification chamber and the air blowing direction is upward. The airflow ejected from the vortex nozzle is a fan-shaped 50-70° internal angle spiral.

The upper thermal insulation outer layer and the lower thermal insulation outer layer are integrally formed; the heating inner layer and the heat-resistant inner layer are in a split-type insertion connection. The upper and lower thermal insulation outer layers are made of thermal insulation cotton; the thermal insulation middle layer and the thermal insulation board are made of graphite hard felt; the heating filler is made of graphite. The heating inner layer and the heat-resistant inner layer are made of tungsten alloy material.

As shown in FIGS. 2 and 9 , the cooling unit includes a cooling chamber casing 501 , a spiral nozzle 502 and a lower refrigerant jacket 503 . The top center of the cooling chamber housing is provided with an opening. As shown in FIG. 10 , the spiral nozzle is located at the opening and is connected to the discharge pipe of the reaction unit through the connecting flange 504. The spiral nozzle is directed downward, and the gas powder is ejected from the gap between the spiral strips of the spiral nozzle to form Fan-shaped (preferably 60-90°) helical swirling airflow. The cooling chamber shell is provided with a nitrogen inlet 505, the bottom of the cooling chamber shell is a cone with decreasing diameter, and the center of the cone bottom is a gas powder outlet 506; the lower refrigerant jacket is sleeved on the outer side of the cooling chamber shell. Among them, the discharge pipe and the connecting flange are made of tungsten alloy material; the spiral nozzle is made of ceramic material.

In addition, a temperature measuring port 104 and a pressure measuring port 105 are provided at different positions of the casing, the spray unit, the gasification unit, the reaction unit and the cooling unit.

In the production line of the invention, the air pressure in the nano aluminum nitride powder synthesis device is controlled to be 1.2-1.5 kg, the air pressure of the gasification chamber to be 1-1.3 kg, the air pressure of the reaction chamber to be 0.9-1.2 kg, and the air pressure in the cooling unit to be 0.7-1 kg. Control the aluminum liquid silo of the spray unit at 700-800°C, nitrogen nozzle at 1600-1700°C, gasification chamber at 2400-2500°C, reaction chamber at 1300-1500°C, and cooling unit temperature at 40-60°C.

The production line of the present invention is compared with peers (equivalent equipment investment), and the data are as follows:

The raw materials and equipment used in the present invention, unless otherwise specified, are the common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are the conventional methods in the art.

The above are only preferred embodiments of the present invention and do not limit the present invention. Any simple modifications, changes and equivalent transformations made to the above embodiments according to the technical essence of the present invention still belong to the technical solutions of the present invention. scope of protection.

Claims

A nano-aluminum nitride powder synthesis production line, characterized by comprising: a nano-aluminum nitride powder synthesis device (1), a material collection system, a nitrogen supply system, a refrigeration system (2) and an argon supply system (3);

The nano-aluminum nitride powder synthesis device comprises: a casing (100), a spray unit disposed in the casing, a gasification unit disposed in the casing and connected to the lower part of the spray unit, disposed in the casing and connected to the gasification unit The lower reaction unit and the cooling unit connected to the lower part of the gasification unit;

The material collection system is connected with the outlet of the cooling unit for gas-powder separation, recovery and packaging of materials;

The nitrogen supply system is used for the nitrogen supply of the spraying unit, the reaction unit and the cooling unit;

The refrigeration system is used for the circulating supply of the cooling medium of the reaction unit and the cooling unit;

The argon supply system is communicated with the spray unit and the housing for argon supply.
The production line according to claim 1, characterized in that: the material collection system comprises a gas-powder separation device (4), a packaging device (5) and a recovered gas storage tank (6); the gas-powder separation device and a cooling unit The packaging device and the recovered gas storage tank are respectively connected with the powder outlet and the gas outlet of the gas-powder separation device; the recovered gas storage tank is also connected with the packaging device and the spray unit to supply power gas.
The production line according to claim 1, characterized in that: the nitrogen supply system comprises a nitrogen generator (7), a nitrogen tank (8), a nitrogen freezer (9) and a liquid ammonia tank (10); the nitrogen generator The device is connected with a nitrogen tank, the nitrogen tank is respectively connected with the spray unit, the reaction unit and the cooling unit, and the nitrogen refrigerator is provided on the pipeline connecting the nitrogen tank with the reaction unit and the cooling unit; the liquid ammonia tank is connected with the reaction unit .
The production line according to claim 1, characterized in that: an argon gas inlet (101) is arranged on the outer shell, and an argon gas inlet (208) is arranged on the top of the aluminum liquid silo.
The production line according to claim 1, characterized in that: the spraying unit comprises: an aluminum feeding mechanism (201), a thermal insulation shell (202), a heating mantle (203), an aluminum liquid silo (204), a nitrogen nozzle ( 205) and an insulating cover seat (206); the heating cover is arranged in the thermal insulation shell, and the inner wall of the heating cover is provided with electric heating wires (207); There is a gap between them, an argon gas inlet (208) is arranged on the top of the aluminum liquid silo, and the bottom of the aluminum liquid silo extends out of the bottom of the heating mantle and is provided with a downward atomizing nozzle (209); The center of the aluminum liquid silo and its air outlet faces the atomizing nozzle; the aluminum feeding mechanism is arranged on the top of the aluminum liquid silo; the insulating cover seat is arranged under the heat preservation shell and the heating cover, There is a gap between the ring and the bottom outer wall of the aluminum liquid silo;

The gasification unit includes: a gasification chamber and an induction coil (304) sequentially formed by an upper heat-insulating and insulating outer layer (301), an insulating middle layer (302) and a heating inner layer (303); the top of the gasification chamber The center is provided with an opening for placing the insulating cover; the center of the bottom of the gasification chamber is provided with an opening to communicate with the reaction unit; the induction coil is wrapped on the outer side of the upper thermal insulation outer layer; A cone, the space between the cone and the heat insulating middle layer is filled with a heating filler (305) and a heat insulating plate (306); the heat insulating plate is located at the bottom of the gasification chamber;

The reaction unit comprises: a reaction chamber composed of a lower thermal insulation outer layer (401) and a heat-resistant inner layer (402), and a vortex nozzle (403); the bottom of the heat-resistant inner layer is in the shape of a cone with decreasing diameter , the center of the conical bottom is connected with a discharge pipe (404), the vortex nozzle extends from the reaction chamber into the reaction chamber through the discharge pipe, and the gas outlet end of the vortex nozzle is provided with a vortex nozzle (405), so The swirl nozzle is located just below the bottom opening of the gasification chamber and the air blowing direction is upward.
The production line of claim 5, wherein:

The gap between the inner ring of the insulating cover base and the bottom outer wall of the aluminum liquid silo is 1-2mm; and/or

Two valves (210) connected in series and staggered are provided on the pipeline between the aluminum feeding mechanism and the aluminum liquid silo; and/or

The shape of the material sprayed by the atomizing nozzle is conical, with an inner angle of 90-120°, a side length of 30-40mm, and a mist particle size of 3-5 microns; and/or

A nitrogen gas inlet (211) is provided on the aluminum feeding mechanism; and/or

The diameter of the upper section of the heating mantle and the liquid aluminum silo is larger than that of the lower section; and/or

An upper refrigerant jacket (212) is provided on the top wall of the aluminum liquid silo; and/or

The electric heating wire, the aluminum liquid silo, the atomizing nozzle and the nitrogen nozzle are made of tungsten alloy material; the heating cover and the insulating cover seat are made of ceramic material.
The production line of claim 5, wherein:

The airflow ejected from the vortex nozzle is a fan-shaped 50-70° internal angle spiral; and/or

The upper thermal insulation outer layer and the lower thermal insulation outer layer are integrally formed; the heating inner layer and the heat-resistant inner layer are connected separately; and/or

The upper and lower heat-insulating and insulating outer layers are made of heat-insulating cotton; the heat-insulating middle layer and the heat-insulating plate are made of graphite hard felt; the heating filler is made of graphite; the heating inner layer and the heat-resistant inner layer are tungsten alloy material; and/or

The spraying unit is fixed on the inner and upper part of the casing through a bracket (102); the reaction unit is erected on the bottom of the casing through a base bracket (103); the bracket and the base bracket are made of ceramic materials.
The production line according to claim 5, characterized in that: the cooling unit comprises: a cooling chamber shell (501), a spiral nozzle (502) and a lower refrigerant jacket (503);

The top center of the cooling chamber shell is provided with an opening, and the spiral nozzle is arranged at the opening and is connected with the discharge pipe of the reaction unit through a connecting flange (504), and the spiral nozzle is directed downward; the cooling chamber shell is provided with nitrogen gas In the inlet (505), the bottom of the cooling chamber shell is in the shape of a cone with decreasing diameter, and the center of the cone bottom is the gas powder outlet (506); the lower refrigerant jacket is sleeved on the outer side of the cooling chamber shell.
The production line of claim 8, wherein:

Air powder is ejected from the spiral strip gap of the spiral nozzle to form a 60-90° fan-shaped spiral rotating airflow; and/or

The discharge pipe and the connecting flange are made of tungsten alloy material; the spiral nozzle is made of ceramic material.
The production line according to claim 1, characterized in that: a temperature measuring port (104) and a pressure measuring port (105) are provided at different positions of the casing, the spray unit, the gasification unit, the reaction unit and the cooling unit.