CN101695643A - Coating equipment for spherical particles and coating process thereof - Google Patents

Abstract

The invention discloses a dressing device for spherical particles and a dressing process thereof, which belong to the field of coating technology and equipment in the material modification technology. The dressing equipment is mainly composed of a dressing pot, an alcohol conveying system, a powder feeding system, an exhaust hood and a hot air hood, all of which are installed in a box with an operation window. The window is equipped with a door, and all materials during the dressing process It can move in a sealed state; the powder is transported from the center channel of the rear shaft of the dressing pot to the dressing pot; the body of the dressing pot is evenly distributed with mesh holes. When dressing, put the coated particles into the dressing pot first, and the dressing pot rotates along the axis to drive the movement of the coated particles in the pot, and at the same time spray alcohol and matrix powder on the coated particles, and the coated particles continue to grow Get round. The invention overcomes the disadvantages of the existing equipment such as unstable process, easy sticking to the pot, difficult cleaning of the pot body, etc., is easy to realize automatic operation, and can improve the working environment.

Description

Dressing equipment and dressing process for spherical particles

technical field

The invention belongs to the field of coating technology and equipment in material modification technology, and in particular relates to a dressing equipment for spherical particles and a dressing process thereof in the dressing process of coated particles in the manufacture of high-temperature gas-cooled reactor fuel elements .

Background technique

The diameter of the ceramic fuel element used in the pebble bed high temperature gas-cooled reactor in my country is 60mm, and the structure is that spherical coated particles (TRISO) are dispersed in the graphite matrix of the fuel area, and the quasi-isostatic pressing manufacturing process is adopted. Due to the high pressure during the pressing process, direct contact between the coated particles will easily cause the particles to break, so before pressing, it is necessary to wrap a layer of graphite matrix powder with a thickness of about 0.25mm (commonly known as "dressing layer") around the coated particles. As a buffer between balls and balls during pressing to protect the coating, this process is commonly known as "dressing" (Atomic Energy Science and Technology, Volume 37, Supplement, 41-44).

At present, the main body of dressing equipment manufactured in Germany is a dressing pot driven by a motor and shaped like an inverted truncated cone, and also includes a set of screw powder feeding device, a set of alcohol delivery system and a set of hot air system. The screw powder feeding device is above the dressing pot, and the matrix graphite powder is sent into the dressing pot through the pipeline, and sprinkled on the surface of the coated particles; the alcohol delivery system is to deliver the alcohol to the atomizing nozzle above the coated particles through air pressure, The alcohol is sprayed onto the surface of the coated particles in the form of mist; the hot air system is used to dry the dressing particles after dressing, and the system introduces the hot air into the dressing pot through the pipeline. When dressing, the dressing pot rotates along the axis at a certain inclination angle, and the coated particles form a vortex motion under the friction of the inner wall of the dressing pot. The device feeds the matrix graphite powder into the vortex, and the coated particles are continuously wrapped with the graphite matrix powder and grow up during the movement until the coated particles reach a suitable size. This equipment controls the quality of dressing by adjusting parameters such as the angle and rotation speed of the dressing pot, the speed of adding matrix powder, the speed of spraying alcohol, and the atomization area. The equipment has the following disadvantages: 1. The operating parameters are difficult to control, the stability is poor, and the qualified rate is low. During the dressing process, the particles gradually grow up and the flow state of the particles changes constantly. Therefore, it needs to be adjusted by experience judgment during the operation process. The inclination angle and rotation speed of the dressing pan, so for different operators or different feeding quantities, the yield varies greatly, and the pass rate is as low as 60% to 85%. 2. The base graphite powder and coated particles are seriously adhered to the bottom of the pot. When the base graphite powder is sprinkled on the surface of the moving particles, the powder will move down through the gaps between the particles. During this process, most of the base powder will stick Attached to the surface of the particles to form a dressing layer, a small part will deposit on the bottom of the pot, because the particles are in the state of alcohol wetting, and the matrix graphite powder contains alcohol-soluble resin, as the dressing process proceeds, the matrix graphite powder and particles will gradually Adhere to the bottom of the pan and build up thick. The sticky pot not only affects the yield, but also brings inconvenience to the cleaning of the dressing pot, and also consumes a lot of alcohol. 3. The operation window, powder feeding inlet, alcohol inlet, and hot air pipeline inlet are all located on the front panel of the dressing pot. The material is open, and matrix powder and alcohol escape during dressing, causing deterioration of the working environment.

With the popularization and application of high-temperature gas-cooled reactors, the large-scale production of its fuel elements puts forward higher requirements for the process stability, yield and operating environment of the equipment. The aspects mentioned need to be improved.

Contents of the invention

The purpose of the present invention is to provide a kind of dressing equipment for spherical particles and its wearing equipment which can effectively overcome the problems of unstable process, low product qualification rate, complicated operation and cleaning, and poor working environment in the production of existing equipment. Clothing process; the dressing equipment is mainly composed of a dressing pot, an alcohol delivery system, a powder feeding system, an exhaust hood and a hot air hood.

The body of the dressing pot is evenly distributed with mesh holes, the front has an operation window, and the back is the rear shaft connected to the transmission motor. The rear shaft of the dressing pot is connected to the transmission motor through a transmission chain or gear, and the speed of the dressing pot is adjusted The transmission motor speed is controlled. During work, the transmission motor drives the dressing pan to rotate along the axis of the rear axle.

The alcohol delivery system includes an alcohol tank, a flow control valve, a nozzle and a pipeline, the nozzle is fixed in the dressing pot through a positioning rod installed on the door, and the hose for transporting alcohol is perforated from the door and enters the dressing pot to connect with the nozzle; When working, the alcohol in the alcohol tank is transported to the nozzle through the flow control valve by the air pressure or peristaltic pump for atomization; the alcohol is used to wet the surface of the particles to make the matrix powder adhere to the particles.

The powder feeding system includes a hopper for storing matrix graphite powder, a powder feeding motor, and a screw feeder; the pipeline of the screw feeder passes through the rear shaft axis of the dressing pot and enters the dressing pot, and one end is connected to the powder feeding motor , the other end is preferably a vertical elbow, and the hopper communicates with the pipeline at one end of the powder feeding motor. When working, the powder feeding motor drives the screw feeder to push the matrix powder in the hopper to the dressing pot until it falls into the dressing pot at the bend. Pot; the elbow can reduce the dusting of the base powder in the dressing pan.

The exhaust hood is buckled on the lower left side of the outer wall of the dressing pot, which is the concentrated part of the particle movement during work. The exhaust hood is connected to the exhaust and dust removal system of the workshop through pipelines. When dressing, the exhaust system is turned on to prevent dust from being generated in the pot. .

The hot air cover is buckled on the upper right side of the outer wall of the dressing pot, and the position is opposite to the exhaust cover. The hot air cover can be connected with the workshop hot air system through pipelines. The hot air is used to dry the particles after dressing, and works together with the exhaust system to ensure that the hot air passes through the particles and fully transfers heat.

The above-mentioned dressing machine, the dressing pot, the exhaust hood, and the hot air hood are all installed in a sealed box with a door. The operating window of the dressing pot is used as the feeding and discharging port. All materials move in a sealed state during the process.

The dressing pot is cylindrical or biconical, preferably biconical.

The inner wall of the dressing pot is equipped with "herringbone"-shaped obliquely staggered deflectors. When the coated particles rotate with the dressing pot, the deflectors pick up the coated particles at the bottom of the pot and scatter them on the surface of the material. , at the same time, the coating particles will also move back and forth with the staggered deflectors. These two forms of movement of the coated particles ensure that the coated particles receive evenly the alcohol and the matrix powder.

The mesh of the dressing pot is circular, square or rectangular, preferably rectangular. The size of the mesh is preferably to ensure that the coated particles do not leak out and the matrix powder can leak out. The diameter of the round hole and the side length of the square hole The length of the short side of the rectangular mesh is 0.3-0.65mm, and the length of the long side is 1-10mm.

The mesh of the dressing pan mainly has three functions in the dressing process: (1) powder falling channel. When the above-mentioned German equipment is used for dressing, the sticky pan is mainly caused by the accumulation of part of the matrix powder passing through the coated particles at the bottom of the pan. The mesh on the wall of the dressing pot sieves out and falls into the powder receiving tray directly below the dressing pot, which avoids the accumulation of matrix powder at the bottom of the pot, and can avoid sticking to the pot through process control. (2) Exhaust channel. The exhaust hood tightly fastened outside the dressing pot is connected to the exhaust and dust removal system through pipes, which allows the base powder blown by the alcohol atomized gas to pass through the coated particles with the airflow, and most of the dust will be wetted and coated The particles adhere, and the unadhered matrix powder passes through the mesh of the dressing pan and is taken away by the exhaust and dust removal system. (3) hot air channel. After the dressing is completed, hot air needs to be passed into the dressing pot to dry the particles. The hot air is blown in through the pipe from the wind hood that is fastened outside the dressing pot, and works together with the exhaust and dust removal system to allow the hot air to pass through. Clothes granules, in this way, the hot air can fully exchange heat with the granules, which improves the drying efficiency.

Utilize the dressing process of described dressing equipment, its step is as follows:

a. Load coated particles into the dressing pan;

b. Turn on the transmission motor and exhaust system of the dressing pot, and the rotating speed of the dressing pot is 8-18rpm, preferably 12-15rpm;

c. Turn on the powder feeding system and alcohol delivery system, the powder feeding speed is 60-120g/min, and the alcohol flow rate is 15-60ml/min;

d. The coated particles to be dressed are 1.2-1.6mm long, and the alcohol delivery system and the powder feeding system are turned off;

e. Turn on the hot air to dry, the temperature is 40-80°C, and the time is 5-30min;

f. Turn off the hot air, exhaust, and stop the transmission motor of the dressing pan.

The beneficial effect of the present invention is that it can effectively solve the problems existing in the production of existing equipment, and has the following advantages: 1. The setting of process parameters is simple, and no manual adjustment is required during operation, so the product is stable and the qualified rate is high, generally reaching 90%. above. 2. The parameters are easy to control and can realize automatic operation. 3. The equipment and process are matched to ensure that the particles do not stick to the pan. At the same time, the powder leaked from the dressing pan can be recycled. 4. When cleaning the dressing pot, spray alcohol through the nozzle to clean the pot body. The cleaning liquid flows out from the upper hole of the dressing pot and is collected at the bottom of the pot. Compared with the German dressing machine, it is easy to clean and can save more than 50% of alcohol. 5. The whole dressing process is carried out in a closed box, which can ensure a clean and environmentally friendly operating environment.

Description of drawings

Fig. 1 is a schematic front view of the dressing machine. FIG. 2 is a cross-sectional view of FIG. 1 .

Fig. 3 is a working diagram of the dressing machine.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Example 1:

The invention provides a dressing device for spherical particles and a dressing process thereof, which can effectively overcome the problems of unstable process, low product qualification rate, complicated operation and cleaning, poor working environment and the like existing in the production of the existing equipment. In the structural diagrams of the dressing equipment shown in FIGS. 1 and 2 , the dressing machine includes a perforated frustum-shaped dressing pot 1 , an alcohol delivery system, a powder feeding system, an exhaust hood 16 and a hot air hood 4 . Dressing pot 1 front has operating window, door 13 is set on the operating window, dressing pot 1 back links to each other with rear axle 3, and transmission motor 8 is connected with rear axle 3 by chain, to drive dressing pot 1 to rotate. The mesh 10 distributed on the body of the dressing pot 1 is rectangular, the length of the short side is 0.55mm, and the length of the long side is 5mm; The powder feeding system includes a hopper 5, a powder feeding motor 6, and a screw feeder 7. The screw feeding tube of the screw feeder 7 passes through the axis of the rear shaft 3 and enters the dressing pot 1, and one end is connected to the powder feeding motor 6. The other end is a vertical elbow 11, and the hopper 5 communicates with the screw feeding pipe at one end of the powder feeding motor 6. During work, the powder feeding motor 6 rotates to drive the screw feeder 7 to rotate, and the matrix powder in the hopper 5 is sent to the dressing pan. 1, the base powder is pushed to the elbow 11 and falls into the dressing pot 1; the alcohol delivery system includes an alcohol tank, a peristaltic pump, a flow control valve, a nozzle 15 and a pipeline, and the pipeline for delivering alcohol enters through a hole in the door 13 The dressing pot 1 is connected with the nozzle 15, and the nozzle 15 is fixed in the dressing pot 1 through the positioning rod 14 installed on the door 13. Under the action of the peristaltic pump, the alcohol is output from the alcohol tank through the pipeline and the flow control valve to the nozzle 15. Dressing pot 1 just below is placed with powder receiving tray 9.

The exhaust cover 16 is buckled on the lower left side of the outer wall of the dressing pot 1, and the exhaust cover 16 is connected with the exhaust and dust removal system of the workshop through pipelines. The hot air cover 4 is buckled on the upper right side of the outer wall of the dressing pot, and the position is opposite to the exhaust cover. Hot blast cover 4 links to each other with workshop hot blast system by hot blast pipeline.

Above-mentioned dressing pan 1, powder receiving tray 9, exhaust cover 16, hot blast cover 4 are all installed in the sealed casing 12. The operating window of dressing pot is equipped with door 13, and door 13 seals the operating window. When working, all materials are in a sealed state.

During work (seeing Fig. 2 and Fig. 3), dressing pot 1 is driven to rotate by the transmission motor 8 that is connected with rear axle 3, and the coating particle 17 in dressing pot 1 relies on the friction of dressing pot wall and along wherein The flow guide direction of the deflector 2 moves. The base powder in the hopper 5 is sent into the dressing pan 1 by the screw feeder 7, and the powder feeding speed is controlled by the powder feeding motor 6 rotating speeds. Alcohol flow can be controlled by adjusting the opening of the flow control valve of the alcohol delivery system. Alcohol of a certain flow is sprayed in mist form from the nozzle 15, and is sprinkled on the surface of the coated particles, so that the surface of the coated particles is wetted. With the rotation of the dressing pot 1, the wet coated particles will move downward along the inclined surface of the material in the pot, and when they pass through the outlet of the elbow 11, they will contact the falling matrix powder and adhere the matrix powder. This cycle goes on and on, and the coated particles gradually grow up and round, and finally become the dressing particles of the required size. When the coated particles rotate with the dressing pot, the deflector 2 picks up the coated particles at the bottom of the pot and scatter them on the surface of the material. The two types of movement of the coated particles ensure that the coated particles receive the alcohol and matrix powder evenly.

Example 2:

Adopt the dressing machine of embodiment 1, used dressing process steps are as follows:

1. Put 5000g of coated particles into the dressing pan 1;

2. Turn on the transmission motor 8 and the exhaust system of the dressing pot, and the rotating speed of the dressing pot is 12rpm;

3. Turn on the powder feeding system and alcohol delivery system, the powder feeding speed is 90g/min, and the alcohol flow rate is 28ml/min;

4. After dressing for 60 minutes, turn off the alcohol delivery system and the powder feeding system, blow hot air at 50°C into the dressing pot 1 to dry the coated particles for 20 minutes;

5. Turn off the hot air, exhaust air, and stop the rotation of the dressing pan.

Adopt the equipment of embodiment 1 and the technique of embodiment 2 to produce three batches of dressing particles after sieving each size range dressing particle weight percent result is as follows table (unit: %):

Particle size of 1.2-1.6mm is qualified. It can be seen that the yield rate is above 90%, which is high and stable.

Claims (5)

1. equipment of wearing the clothes that is used for spheric granules, described wear the clothes equipment mainly by coating pot, alcohol induction system, constitute for powder system, exhaust hood and air bells cap, it is characterized in that,

Be evenly distributed with mesh on the described coating pot pot body, the front is an action pane, and the back is for connecting the rear axle of driving motor, and during work, coating pot is rotated along the rear axle axial line by driving motor;

Described alcohol induction system comprises alcohol container, flow control valve, nozzle and pipeline, nozzle is fixed in the coating pot by the backstay that is contained on the door, the flexible pipe of conveying alcohol enters coating pot from the door perforation and is connected with nozzle, during work, alcohol in the alcohol container is delivered to nozzle atomization by air pressure or peristaltic pump through flow control valve;

Describedly comprise the hopper that is used to store the matrix graphite powder, give powder motor, screw feeder to powder system; The pipeline of screw feeder passes from coating pot rear axle axle center and enters coating pot, during work, the matrix powder in the hopper is advanced in the coating pot for powder driven by motor screw feeder;

Described exhaust hood is buckled in coating pot outer wall lower left, the concentrated position of movement of particles when promptly working, and exhaust hood links to each other with the exhausting-dusting system by pipeline;

Described air bells cap is buckled in coating pot outer wall upper right side, and the position is relative with exhaust hood.Air bells cap can link to each other with hot-air system by pipeline;

The above-mentioned machine of wearing the clothes, coating pot, exhaust hood, air bells cap all are installed in the seal case of a band door, and the coating pot action pane is as throwing discharge port, and the door on the casing can seal action pane, and all materials move in sealing state in the process of wearing the clothes.

2. according to the described equipment of wearing the clothes that is used for spheric granules of claim 1, it is characterized in that described coating pot is two taper types or cylindrical.

3. according to the described equipment of wearing the clothes that is used for spheric granules of claim 1; it is characterized in that; the inwall of described coating pot is equipped with the oblique staggered deflector of " people " font; when coated particle rotatablely moves with coating pot; deflector scatters on the material surface after the pot bottom coated particle is taken up; simultaneously, coated particle also can produce with staggered deflector and seesaw, and guarantees the even material feeding of coated particle to alcohol and matrix powder.

4. according to the described equipment of wearing the clothes that is used for spheric granules of claim 1, it is characterized in that, mesh on the described coating pot body is circular, square or rectangle, the size of mesh does not get stuck and the matrix powder can spill and is advisable to guarantee that coated particle does not spill, wherein rectangle mesh minor face is long is 0.3-0.65mm, and long limit is 1-10mm.

5. the described technology of wearing the clothes that is used for the equipment of wearing the clothes of spheric granules of claim 1 is characterized in that, the wear the clothes technology of wearing the clothes of equipment of described utilization, and its step is as follows:

A. the coated particle of in coating pot, packing into;

B. open coating pot driving motor and exhaust system, the coating pot rotating speed is 8-18rpm,

C. open and give powder system and alcohol induction system, powder-supplying speed is 60-120g/min, and the alcohol flow is 15-60ml/min;

D. the long 1.2-1.6mm of coated particle to be worn the clothes closes the alcohol induction system, gives powder system;

E. open heated-air drying, temperature 40-80 ℃, time 5-60min;

F. close hot blast, air draft, stop the coating pot driving motor.

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