Powder fluidized bed treatment furnace

Abstract

The invention discloses a powder fluidized bed treatment furnace and relates to the field of powder materials. The device comprises a heating furnace, a fluidized bed, a gas circulating device, a gas preheater and a tail gas cooling device, a gas distributor is arranged at the bottom of the fluidized bed; the treated powder filled in the fluidized bed is blown up by the auxiliary gas distributor to establish a fluidized state, and then the fluidized state of the treated powder is maintained by the main gas distributor blown by the gas circulating device; in the powder fluidized bed treatment furnace, high-temperature working gas is refluxed and circulated by the gas circulating device so as to maintain the fluid state of ceramic powder in the fluidized bed, and the high-temperature working gas circulation can greatly reduce the consumption of the working gas and heating energy sources and improve the uniformity of the temperature in the fluidized bed at the same time. The multiple gas distributors are arranged at the bottom of the fluidized bed, each gas distributor supplies gas independently, accurate control over the fluidization state can be achieved, multiple gases can be introduced at the same time, and the process applicability is good. The tail gas cooling device is used for cooling and emptying high-temperature gas exhausted from the interior of the heating furnace.

Description

Technical Field

[0001] The invention relates to the field of powder materials, in particular to a powder fluidized bed processing furnace. Background Art

[0002] Ceramic powders have a wide range of applications in the processing and preparation of ceramic materials. High-performance ceramic powders are a prerequisite for the preparation of high-performance ceramic components. During the heat treatment of ceramic powder sintering preparation, surface coating modification, etc., ceramic powders can be divided into static accumulation and dynamic flow according to their fixed state. In static accumulation, due to the long-term contact between ceramic powders, sintering and bonding at high temperature cannot be avoided. The ceramic powders will agglomerate due to bonding, which will eventually lead to a decrease in powder performance. In order to avoid sintering and bonding of ceramic powders, during the heat treatment process, dynamic flow methods such as fluidization, stirring, vibration or rotary kiln can be used to make the powder move and avoid sintering and bonding caused by long-term contact between ceramic powder particles [Wang Yong et al., Preparation of Nano-Silicon Nitride Powder by Fluidized Bed CVD [J]. Journal of Inorganic Materials, 2006, 21 (1): 41-44]. Among the above-mentioned dynamic flow methods, the most commonly used is to use a fluidized bed to heat treat ceramic powder in a fluidized state. The fluidization process can use a single fluidized bed or a series of fluidized beds to achieve batch processing and continuous processing. When processing ceramic powders in a fluidized bed, a large carrier gas flow rate is usually required to keep the ceramic powder in a fluidized state. The working gas is discharged immediately after entering the fluidized bed, and the working gas consumption is extremely high. Especially at higher temperatures, preheating of the large flow rate of working gas will consume more energy, which limits the further application of fluidized beds in the field of ceramic powder heat treatment. Summary of the invention

[0003] The purpose of the present invention is to provide a powder fluidized bed processing furnace in response to the above-mentioned problems. A high-temperature gas circulation device is integrated inside the fluidized bed processing furnace to realize partial reflux circulation of the working carrier gas at high temperature, thereby saving the working gas and the energy consumption of heating the working gas while meeting the working requirements of the fluidized bed, thereby realizing low-cost, batch preparation of high-performance powders.

[0004] A powder fluidized bed processing furnace, comprising a heating furnace, a fluidized bed, a gas circulation device, a gas preheater and an exhaust gas cooling device;

[0005] The heating furnace is used for heating and controlling the temperature; the fluidized bed and gas circulation device are arranged in the heating furnace, and are heated and maintained at a temperature by the heating furnace; the gas preheater and tail gas cooling device are arranged outside the heating furnace;

[0006] The fluidized bed is a vertically placed straight cylinder, with a gas distributor at the bottom of the fluidized bed. The gas blows the powder up through the gas distributor and keeps it in a fluidized state. The different fluidized states of the powder can be adjusted by controlling the gas flow rate. A conical cylinder with a larger diameter from bottom to top is provided on the top of the fluidized bed. The powder that leaves the straight cylinder and enters the cone settles back to the straight cylinder due to the reduced gas flow rate.

[0007] The gas circulation device is arranged in the heating furnace, and the gas circulation device can operate at the working temperature of the heating furnace to maintain gas circulation; the high-temperature circulating working gas is mixed with the newly entered gas and then enters the fluidized bed to blow up the powder; the gas distributor is provided with at least two, and each gas distributor supplies gas independently; the gas distributor connected to the gas circulation device is the main distributor, and the one directly connected to the outside to provide working gas is the auxiliary distributor. The main distributor provides the main working gas for fluidizing the ceramic powder in the fluidized bed, and the auxiliary distributor provides gas with the same or different components as the main distributor according to the working conditions, and is used to adjust the total gas flow of the main gas distributor and the auxiliary gas distributor to maintain a stable fluidized state of the ceramic powder in the fluidized bed. In the initial stage, the ceramic powder loaded in the fluidized bed is blown up by the auxiliary gas distributor to establish a fluidized state, and then the main gas distributor maintains its fluidized state;

[0008] The air inlet of the main gas distributor and the auxiliary gas distributor are both provided with a gas preheater. The preheated main gas is mixed with the gas in the heating furnace in the gas circulation device through the preheating of the gas preheater, and the preheated auxiliary gas enters the fluidized bed; the auxiliary gas is preheated by the gas to avoid the interference of the low inlet temperature on the temperature uniformity of the fluidized bed;

[0009] The tail gas cooling device is installed outside the heating furnace, and is used to cool and discharge the high-temperature gas exhausted from the interior of the heating furnace.

[0010] The number of the gas distributors can be 2 to 4, and each gas distributor has an independent gas supply.

[0011] The gas circulation device may be a jet pump, a centrifugal circulation fan or a piston fan.

[0012] The inlet of the main gas distributor and the auxiliary gas distributor are both equipped with a gas preheater. Through the preheating of the gas preheater, the preheated main gas is mixed with the gas in the heating furnace in the gas circulation device, and the preheated auxiliary gas enters the fluidized bed. Gas preheating can avoid the interference of low inlet temperature on the temperature uniformity of the fluidized bed.

[0013] The tail gas cooling device is installed outside the heating furnace, and the tail gas cooling device can be water-cooled, air-cooled, etc.

[0014] The benefits of the present invention are:

[0015] 1. The ceramic powder is fluidized at high temperature by adopting the method of high-temperature gas internal circulation. Compared with the traditional working gas fluidization treatment, it can greatly reduce the consumption of working gas and heating energy.

[0016] 2. The internal circulation of high-temperature gas improves the temperature uniformity and stability inside the fluidized bed.

[0017] 3. By setting different gas distributors, accurate control of the fluidization state and simultaneous introduction of multiple gases can be achieved, with good process applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the functional structure of a powder fluidized bed processing furnace.

[0019] Figure 2 It is a structural schematic diagram of a powder fluidized bed processing furnace.

[0020] The marks in the figure are: fluidized bed 1, powder feed port 101, powder discharge port 102, jet pump 2, main gas distributor 3, vent 301 on the main gas distributor, auxiliary gas distributor 4, vent 401 on the auxiliary gas distributor, working gas preheater 5, auxiliary gas preheater 6, exhaust gas cooler 7, heating furnace 8. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the following embodiments will be further described in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Matters not covered in the present invention are known technologies.

[0022] Example 1

[0023] In this embodiment, the fluidized bed treatment furnace is used to pyrolyze high molecular weight polycarbosilane (HMPCS) powder in ammonia at high temperature to form silicon nitride powder.

[0024] like Figure 1 and 2 As shown, the powder fluidized bed treatment furnace described in this embodiment is provided with a heating furnace 8, a fluidized bed 1, a jet pump 2, a working gas preheater 5, an auxiliary gas preheater 6, a gas auxiliary distributor 4 and an exhaust gas cooling device 7;

[0025] The heating furnace 8 is used to provide the necessary high temperature environment for the internal system, so that the HMPCS powder is pyrolyzed and nitrided into silicon nitride powder; the heating furnace 8 is heated and the temperature is controlled by an electric heating rod; the heating furnace 8 is equipped with a fluidized bed 1 and a jet pump 2 as a gas circulation device. The main body of the fluidized bed 1 is a vertically installed straight cylinder, and the fluidized bed 1 is filled with heat-treated HMPCS powder; the bottom of the fluidized bed 1 is equipped with a gas main distributor 3 and an auxiliary distributor 4. The gas is evenly distributed in the fluidized bed through the gas main distributor 3 and the gas auxiliary distributor 4, so that the powder is in a fluidized state. A conical cylinder with a larger diameter from bottom to top is installed on the upper part of the fluidized bed 1. The powder leaving the straight cylinder and entering the conical cylinder settles back to the straight cylinder due to the reduced gas flow rate. The main working gas ammonia is sprayed into the jet pump 2 after being preheated by the working gas preheater 5. The jet pump 2, as a gas circulation device, will simultaneously absorb the main working gas ammonia that has passed through the preheater 5 and the high-temperature ammonia-nitrogen mixed gas circulating inside the heating furnace 8. The two parts of gas are mixed in the jet pump 2 and then discharged into the main gas distributor 3, and then evenly enter the fluidized bed 1 through the vents 301 on the main gas distributor 3.

[0026] The gas auxiliary distributor 4 is used to evenly distribute the auxiliary gas (nitrogen) into the fluidized bed 1 to help maintain the fluidized state of the fluidized bed;

[0027] The working gas preheater 5 is used to preheat the main working gas (ammonia) to a suitable temperature so as to be mixed with the high-temperature gas in the jet pump 2;

[0028] The auxiliary gas preheater 6 is used to preheat the auxiliary working gas (nitrogen) to make its temperature close to the temperature in the heating furnace 8 to maintain the temperature stability and uniformity in the fluidized bed; the auxiliary gas nitrogen enters the gas auxiliary distributor 4 after passing through the auxiliary gas preheater 6, and then enters the fluidized bed 1 evenly through the vent 401 on the gas auxiliary distributor 4. The HMPCS powder in the fluidized bed 1 is blown up by the working gas and auxiliary gas entering the fluidized bed and maintained in a fluidized state.

[0029] The tail gas cooling device 7 is installed on the exhaust port of the heating furnace 8. The tail gas cooling device 7 adopts a water cooling method, and can cool the tail gas discharged from the heating furnace 8 to below 200° C. and discharge it.

[0030] In the initial stage, the HMPCS powder to be treated loaded in the fluidized bed 1 can be blown up by the auxiliary gas distributor 4 to establish a fluidized state, and then switched to the main gas distributor 3 to maintain its fluidized state.

[0031] The HMPCS powder in the fluidized bed 1 is heated by the heating furnace and gradually increases in temperature to be nitrided into silicon nitride powder; the main working gas ammonia is preheated in the main gas distributor 5 and then mixed with the high-temperature gas in the heating furnace in the jet pump 2; the auxiliary working gas nitrogen is also preheated in the auxiliary gas preheater 6. The temperature of all gases is close to the temperature in the heating furnace 8 to improve the stability and uniformity of the gas flow temperature in the fluidized bed and avoid the temperature interference of the HMPCS powder in the fluidized bed 1 caused by the low inlet temperature.

[0032] A powder feed port 101 is provided at the top of the heating furnace, and HMPCS powder is fed into the fluidized bed 1 through the powder feed port 101. Through the powder feed port 101, raw materials can be easily replenished for continuous or batch processing. A powder discharge port 102 is provided at the bottom of the fluidized bed 1, and the powder discharge port 102 is used to discharge the silicon nitride powder generated by the reaction. In this embodiment, the gas-assisted distributor 4 and the plug of the powder discharge port 102 are the same component. When installed on the powder discharge port 102, the gas-assisted distributor 4 plays a role to ensure uniform distribution of gas; when the component is removed, the powder discharge port 102 is opened, and the silicon nitride powder generated by the reaction can be discharged from the fluidized bed 1. This design not only simplifies the equipment structure, but also improves the flexibility and efficiency of operation, making the entire fluidized bed treatment furnace system more practical and efficient.

[0033] Example 2

[0034] In this embodiment, the fluidized bed treatment furnace is used to heat silicon powder in nitrogen gas to 1300° C. for high-temperature reaction to prepare silicon nitride powder.

[0035] This embodiment is provided with a heating furnace 8, a fluidized bed 1, a gas circulation device (centrifugal fan) 2, gas distributors 3, 4, and an exhaust gas cooling device 7;

[0036] The heating furnace is heated by electrified carbon rods and is equipped with a temperature control system to ensure that the heating temperature is precisely controlled. The internal space of the heating furnace is used to accommodate the fluidized bed and gas circulation device.

[0037] The fluidized bed 1 is a vertically placed straight cylinder with gas distributors 3 and 4 at the bottom. A cone with a larger diameter from bottom to top is provided at the top of the fluidized bed 1 to ensure that the powder can smoothly settle back to the straight cylinder when the gas flow rate decreases. The fluidized bed is made of graphite.

[0038] The gas circulation device uses a centrifugal circulation fan, which can maintain nitrogen circulation at the working temperature of the heating furnace. The high-temperature circulation and the newly entered nitrogen are mixed and then enter the fluidized bed to ensure that the silicon powder in the fluidized bed can be heated evenly.

[0039] There are three gas distributors, namely one main distributor and two auxiliary distributors. Each gas distributor supplies gas independently. The main distributor provides the main working gas for the fluidization of silicon powder in the fluidized bed. The auxiliary distributor provides the same nitrogen as the main distributor or argon, hydrogen and other gases used to dilute the nitrogen concentration according to the working conditions, and is used to adjust the total gas flow of the main gas distributor and the auxiliary gas distributor to maintain the fluidization state of the stable silicon powder and the formed silicon nitride in the fluidized bed. Among them, the main distributor has a gas component of nitrogen; the first auxiliary distributor has a gas component of nitrogen, and the second auxiliary distributor has a gas component of argon and hydrogen.

[0040] The main gas distributor and the auxiliary gas distributor are each equipped with a gas preheater at the air inlet. Through the preheating of the gas preheater, the preheated main gas is mixed with the gas in the heating furnace in the gas circulation device, and the preheated auxiliary gas enters the fluidized bed. Gas preheating can avoid the interference of low inlet temperature on the temperature uniformity of silicon powder and silicon nitride powder in the fluidized bed. The preheating temperature is 1100~1300℃.

[0041] The tail gas cooling device is installed outside the heating furnace. It is used to cool the high-temperature gas discharged from the heating furnace and then discharge it to ensure that the temperature of the exhaust gas will not affect the environment. The tail gas cooling device adopts water cooling, and the temperature of the cooled tail gas is 60~200℃.

[0042] The working process is as follows:

[0043] 1) Startup phase: Turn on the electric heating rod and set the heating temperature to 1100°C. Start the gas circulation device to ensure that the gas circulation is normal and the air volume is set to 1500m 3 / h.

[0044] 2) Powder loading: 200 kg of ceramic powder is loaded into the fluidized bed.

[0045] 3) Initial fluidization: The ceramic powder is blown up by the auxiliary gas distributor to establish a fluidized state. The gas flow rate is set to 500m 3 / h.

[0046] 4) Maintain fluidized state: The main gas distributor starts to supply gas, and the gas flow rate is set to 1000m 3 / h, maintain the fluidized state of ceramic powder. Adjust the gas flow rate of the auxiliary gas distributor as needed and set it to 500m 3 / h, ensuring the stability of temperature and gas flow in the fluidized bed.

[0047] 5) Cooling and emptying: After the treatment is completed, turn off the electric heating rod and stop the gas circulation. The high-temperature gas is cooled to 100°C through the exhaust gas cooling device and then emptied.

[0048] Example 3

[0049] Similar to Example 2, the gas circulation device in this embodiment adopts a piston fan, and there are two gas distributors, namely a main distributor and an auxiliary distributor. The exhaust gas cooling device adopts a combination of water cooling and air cooling.

[0050] The invention is applicable to the heat treatment process of materials such as ceramic powders and has broad application prospects.

[0051] The above embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A powder fluidized bed treatment furnace, Features It is equipped with a heating furnace, a fluidized bed, a gas circulation device, a gas preheater and an exhaust gas cooling device; The heating furnace is provided with a temperature control heating device for heating the fluidized bed, the gas circulation device and the processed powder inside the heating furnace; The fluidized bed is a vertically placed straight cylinder, with a gas distributor at the bottom of the fluidized bed. The gas blows the powder up through the gas distributor and keeps it in a fluidized state. The different fluidized states of the powder are adjusted by controlling the gas flow rate. A conical cylinder with a larger diameter from bottom to top is provided on the top of the fluidized bed. The powder that leaves the straight cylinder and enters the conical cylinder settles back to the straight cylinder due to the reduced gas flow rate. The fluidized bed and the gas circulation device are arranged in the heating furnace, and are heated and kept warm by the heating furnace; the gas circulation device operates at the working temperature of the heating furnace to maintain gas circulation; the high-temperature working gas is circulated back by the gas circulation device, mixed with the newly entered gas, and then enters the fluidized bed to maintain the fluid state of the ceramic powder in the fluidized bed; The gas distributor is provided with at least two, each of which supplies gas independently; the gas distributor connected to the gas circulation device is the main distributor, and the one directly connected to the outside to provide working gas is the auxiliary distributor; the main distributor provides the main working gas for fluidizing the ceramic powder in the fluidized bed, and the auxiliary distributor provides gas with the same or different components as the main distributor according to the working conditions, and is used to adjust the total gas flow of the main gas distributor and the auxiliary gas distributor to maintain the fluidized state of the ceramic powder in the fluidized bed; in the initial stage, the ceramic powder loaded in the fluidized bed is blown up by the auxiliary gas distributor to establish the fluidized state, and then blown up by the main gas distributor to maintain its fluidized state; The gas preheater and the tail gas cooling device are arranged outside the heating furnace; the tail gas cooling device is used to cool and then discharge the high-temperature gas discharged from the heating furnace.

2. A powder fluidized bed treatment furnace as claimed in claim 1, Features The air inlet parts of the main gas distributor and the auxiliary gas distributor are both provided with gas preheaters. Through the preheating of the gas preheater, the preheated main gas is mixed with the gas in the heating furnace in the gas circulation device, and the preheated auxiliary gas enters the fluidized bed; the auxiliary gas is preheated to avoid the interference of low inlet temperature on the temperature uniformity of the fluidized bed.

3. A powder fluidized bed treatment furnace as claimed in claim 1, Features The gas distributors are provided with 2 to 4 gas distributors, each of which has an independent gas supply, and one of the gas distributors is connected to the gas circulation device.

4. A powder fluidized bed treatment furnace as claimed in claim 1, Features The gas circulation device adopts a gas circulation device such as a jet pump, a centrifugal circulation fan or a piston fan which can work at the working temperature.

5. A powder fluidized bed treatment furnace as claimed in claim 1, Features The gas inlet of the gas distributor is provided with a gas preheater. Through the preheating of the gas preheater, the preheated main gas is mixed with the gas in the heating furnace in the gas circulation device, and the preheated auxiliary gas enters the fluidized bed.

6. A powder fluidized bed treatment furnace as claimed in claim 1, Features The tail gas cooling device adopts water cooling or air cooling.

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