A silicon powder processing system and a silicon powder processing method

Abstract

The technical problem to be solved by the present invention is to provide a silicon powder processing system and a silicon powder processing method, by controlling the humidity of the circulating gas, avoiding the generation of static electricity in the silicon blocks in the mill, and reducing potential safety hazards. It includes a silicon block bin, a ball mill, a particle separator, a cyclone separator, a bag filter, and a silicon powder bin; the exhaust port of the cyclone separator is sequentially connected to a first fan, a bag filter, and a second fan through a negative pressure pipeline, and the air outlet of the second fan is connected to the feed port of the ball mill through a circulating air supply pipeline; a gas humidity detector for detecting the humidity of the circulating gas is installed at a position close to the outlet of the second fan on the circulating air supply pipeline, and a steam pipe is connected to the side wall of the circulating air supply pipeline.

Description

Technical Field

[0001] The present invention relates to the field of silicon powder preparation in the silicon powder processing unit of silicone monomer production enterprises, and specifically relates to a silicon powder processing system and a silicon powder processing method. Background Art

[0002] In the silicon powder processing unit of silicone production enterprises, silicon blocks with a size of 10 cm are processed into silicon powder with a size of 10 - 100 μm, and then transported to the monomer synthesis unit to react with methyl chloride to produce a mixed monomer of methylchlorosilane.

[0003] At present, the conventional silicon powder processing method is as disclosed in the patent document with the publication number CN1251967C. In this method, silicon blocks crushed to an average particle size of 15 - 50 mm are transported to a vertical mill. After grinding, the silicon powder is lifted by air flow to a bag filter under a negative pressure of -0.003 MPa to -0.008 MPa, and finally, after screening, qualified silicon powder with an average particle size of 50 μm - 110 μm is sent to the finished product bin, and the coarse powder is returned to the vertical mill. During the silicon powder processing, nitrogen protection is adopted to control the nitrogen content in the main mill at 85 - 95%. However, the defect of this mill system is that the oxygen content is relatively high, and static electricity is easily generated when the silicon blocks in the mill are ground, thus posing a safety hazard to the operation of the system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a silicon powder processing system and a silicon powder processing method, which can avoid the generation of static electricity of silicon blocks in the mill by controlling the humidity of the circulating gas, and reduce potential safety hazards.

[0005] The present invention is realized by the following technical solutions:

[0006] A silicon powder processing system includes a silicon block bin, a ball mill, a particle separator, a cyclone separator, a bag filter, and a silicon powder bin;

[0007] The discharge port of the silicon block bin is connected to the feed port of the ball mill, the feed port of the ball mill is connected to the feed port of the particle separator through a negative pressure pipeline, the coarse material outlet of the particle separator is connected to the feed port of the ball mill, and the fine material outlet is connected to the feed port of the cyclone separator through a negative pressure pipeline;

[0008] The exhaust port of the cyclone separator is successively connected to a first fan, a bag filter, and a second fan through a negative pressure pipeline, and the air outlet of the second fan is connected to the feed port of the ball mill through a circulating air supply pipeline;

[0009] The discharge port of the cyclone separator and the discharge port of the bag filter are both connected to the silicon powder bin;

[0010] The circulating air supply pipeline is installed with a gas humidity detector for detecting the humidity of the circulating gas near the outlet of the second fan, and a steam pipe is connected to the side wall of the circulating air supply pipeline.

[0011] Furthermore, an oxygen content analyzer is installed on the side wall of the circulating air supply pipeline, and a nitrogen gas pipe is connected to the side wall of the circulating air supply pipeline.

[0012] Furthermore, the outlet of the first fan is connected to the discharge port of the ball mill through a branch.

[0013] Furthermore, the silicon block bin is located above the ball mill.

[0014] A method for processing silicon powder, which uses the silicon powder processing system of the present invention to process silicon powder, includes the following steps:

[0015] S1. Add raw silicon into the silicon block bin. The silicon block bin is protected by positive nitrogen pressure. At the same time, the first fan and the second fan are turned on to form a circulating air flow in the pipeline of the silicon powder processing system;

[0016] S2. Continuously and steadily convey silicon blocks from the silicon block bin to the ball mill through a conveyor;

[0017] S3. The silicon blocks are ground into silicon powder in the ball mill. The silicon powder enters the particle separator under the action of the circulating air flow. Among them, the silicon powder with a diameter greater than 80um is collected by the particle separator and returned to the feed inlet of the ball mill; the silicon powder with a diameter less than 80um is collected by the particle separator into the cyclone separator and collected into the silicon powder bin through the cyclone separator;

[0018] S4. The air flow with silicon powder generated by the cyclone separator enters the bag filter through the first fan for filtering and dust removal. The bag filter collects the filtered silicon powder into the silicon powder bin;

[0019] S5. The air flow generated by the bag filter enters the inlet of the ball mill through the second fan;

[0020] S6. Real-time detect the humidity of the circulating gas at the outlet of the second fan through the gas humidity detector, and control the steam supplement amount of the steam pipe to the circulating air supply pipeline to keep the humidity of the circulating gas at 30% - 70%.

[0021] Furthermore, in step S6, real-time detect the humidity of the circulating gas at the outlet of the second fan through the gas humidity detector, and control the steam supplement amount of the steam pipe to the circulating air supply pipeline to keep the humidity of the circulating gas at 40%.

[0022] Furthermore, an oxygen content analyzer is installed on the side wall near the outlet of the second fan on the circulating air supply pipeline, and a nitrogen gas pipe is connected to the side wall of the circulating air supply pipeline. According to the oxygen content concentration, adjust the nitrogen supplement amount to make the oxygen content of the circulating gas less than 7%.

[0023] The beneficial effects achieved by the present invention compared with the prior art are as follows:

[0024] 1. A gas humidity detector for detecting the humidity of the circulating gas is installed at a position close to the outlet of the second fan in the circulating air supply pipeline. A steam pipe is connected to the side wall of the circulating air supply pipeline. The humidity of the circulating gas at the outlet of the second fan is detected in real time by the gas humidity detector, and the steam supplement amount of the steam pipe into the circulating air supply pipeline is controlled to keep the humidity of the circulating gas at 30% - 70%, so as to ensure that the air in the ball mill has a certain humidity, avoid generating static electricity when the silicon blocks in the mill are ground, and reduce potential safety hazards in the system operation;

[0025] 2. An oxygen content analyzer is installed on the side wall of the circulating air supply pipeline at a position close to the outlet of the second fan. A nitrogen pipe is connected to the side wall of the circulating air supply pipeline. According to the oxygen content concentration, the nitrogen supplement amount is adjusted to make the oxygen content in the circulating gas lower than 7%. By maintaining a low oxygen content concentration, the explosion of silicon powder is avoided and the safety is improved;

[0026] 3. The silicon block bin is located above the ball mill, which reduces the floor area and at the same time facilitates the continuous entry of silicon blocks into the ball mill, improving the working efficiency;

[0027] 4. The air outlet of the first fan is connected to the discharge port of the ball mill through a branch. By supplementing air flow, the silicon powder can overcome gravity and enter the particle separator, reducing the air intake. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the silicon powder processing system described in the present invention;

[0029] In the figure: 1. Silicon block bin, 2. Ball mill, 3. Particle separator, 4. Cyclone separator, 5. Bag filter, 6. Silicon powder bin, 7. First fan, 8. Second fan, 9. Gas humidity detector, 10. Steam pipe, 11. Oxygen content analyzer, 12. Nitrogen pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0031] In the description of the invention, it should be understood that the orientation or positional relationship indicated by terms such as "front", "rear", "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. The present invention will be further described below in conjunction with the drawings and embodiments.

[0032] This embodiment discloses a silicon powder processing system, which mainly includes a silicon block bin 1, a ball mill 2, a particle separator 3, a cyclone separator 4, a bag filter 5, a silicon powder bin 6, a first fan 7 and a second fan 8. The silicon block bin 1 and the ball mill 2 are installed in a frame, and the silicon block bin 1 is installed above the ball mill 2. Taking the silicon powder processing unit with a production capacity of 20 t / h and an average particle size of 50 μm of the present invention as an example, the frame covers an area of about 30 meters in length, 20 meters in width and 40 meters in height. Compared with the vertical mill production unit, it saves about 400 square meters of factory building area.

[0033] The discharge port of the silicon block bin 1 is connected to the feed port of the ball mill 2, the feed port of the ball mill 2 is connected to the feed port of the particle separator 3 through a negative pressure pipeline, the coarse material outlet of the particle separator 3 is connected to the feed port of the ball mill 2, and the fine material outlet is connected to the feed port of the cyclone separator 4 through a negative pressure pipeline; the exhaust port of the cyclone separator 4 is connected to the first fan 7, the bag filter 5 and the second fan 8 in sequence through a negative pressure pipeline, and the discharge ports of the cyclone separator 4 and the bag filter 5 are both connected to the silicon powder bin 6; the air outlet of the second fan 8 is connected to the feed port of the ball mill 2 through a circulating air supply pipeline.

[0034] In this embodiment, a gas humidity detector 9 for detecting the humidity of the circulating gas is installed at a position close to the outlet of the second fan 8 on the circulating air supply pipeline. A steam pipe 10 is connected to the side wall of the circulating air supply pipeline, and the steam pipe 10 is connected to a steam source (not marked in the figure). An oxygen content analyzer 11 is installed on the side wall of the circulating air supply pipeline, and a nitrogen pipe 12 is connected to the side wall of the circulating air supply pipeline. In order to supplement the air flow to enable the silicon powder to overcome gravity and enter the particle separator and reduce the air intake, the air outlet of the first fan 7 is connected to the discharge port of the ball mill 2 through a branch.

[0035] The silicon powder processing system provided by the present invention adopts a series of measures such as a nitrogen slightly positive pressure protection system for the silo, installing an on-line oxygen content analyzer on the mill circulating air pipeline and adding nitrogen in time according to the analysis results, connecting the steam pipe 10 line to control the humidity of the system to prevent static electricity generated by internal friction in the ball mill 2, etc., to eliminate operation hazards and improve the intrinsic safety of the process system. A corresponding silicon powder processing method is provided through the silicon powder processing system of the present invention, which includes the following steps:

[0036] S1. Add raw silicon into the silicon block silo 1. The silicon block silo 1 is protected by positive nitrogen pressure, and the nitrogen pressure is 5 kPa. At the same time, the first fan 7 and the second fan 8 are turned on to form a circulating air flow in the pipeline of the silicon powder processing system;

[0037] S2. Continuously and steadily convey the silicon blocks from the silicon block silo 1 to the ball mill 2 through the conveyor;

[0038] S3. The silicon blocks are ground into silicon powder in the ball mill 2. The silicon powder enters the particle separator 3 under the action of the circulating air flow. Among them, the silicon powder with a diameter greater than 80 μm is collected by the particle separator 3 and returned to the feed inlet of the ball mill 2; the silicon powder with a diameter less than 80 μm is collected by the particle separator 3 into the cyclone separator 4 and collected into the silicon powder silo through the cyclone separator 4;

[0039] S4. The air flow with silicon powder generated by the cyclone separator 4 enters the bag filter 5 through the first fan 7 for filtration and dust removal. The bag filter 5 collects the filtered silicon powder into the silicon powder silo 6;

[0040] S5. The air flow generated by the bag filter 5 enters the inlet of the ball mill 2 through the second fan 8;

[0041] S6. The humidity of the circulating gas at the outlet of the second fan 8 is detected in real time by the gas humidity detector 9. When the detector shows that the humidity is lower than 40%, the interlock is triggered to increase the opening of the steam make-up valve; when the detector shows that the humidity is higher than 40%, the interlock is triggered to decrease the opening of the steam make-up valve; to keep the humidity of the circulating gas in the system at about 40%, and the humidity range is within 37% - 43%. The oxygen content of the circulating gas is detected by the oxygen content analyzer 11, and the nitrogen supplement amount is adjusted according to the oxygen content concentration to make the oxygen content of the circulating gas lower than 7%. It should be noted that maintaining the humidity of the circulating gas at 40% will not wet the silicon powder, because 40% humidity conforms to the air humidity in summer, which can reduce the generation of static electricity in the silicon powder and will not cause the silicon powder to agglomerate. The oxygen content is controlled below 7% because we found that the lower limit of the oxygen content for silicon powder explosion is 9.7%.

Claims

1. A method for processing silicon powder, characterized in that, Silicon powder is processed using a silicon powder processing system. The silicon powder processing system includes a silicon block silo, a ball mill, a particle separator, a cyclone separator, a bag filter, and a silicon powder silo. The discharge port of the silicon block silo is connected to the feed port of the ball mill. The feed port of the ball mill is connected to the feed port of the particle separator through a negative pressure pipeline. The coarse material outlet of the particle separator is connected to the feed port of the ball mill, and the fine material outlet is connected to the feed port of the cyclone separator through a negative pressure pipeline. The exhaust port of the cyclone separator is sequentially connected to a first fan, a bag filter, and a second fan through a negative pressure pipeline. The outlet of the first fan is connected to the discharge port of the ball mill through a branch. The outlet of the second fan is connected to the feed port of the ball mill through a circulating air supply pipeline. The discharge port of the cyclone separator and the discharge port of the bag filter are both connected to the silicon powder silo. A gas humidity detector for detecting the humidity of the circulating gas is installed at a position close to the outlet of the second fan on the circulating air supply pipeline. A steam pipe is connected to the side wall of the circulating air supply pipeline. The silicon powder processing method includes the following steps: S1. Raw silicon is added into the silicon block silo. The silicon block silo is protected by positive nitrogen pressure. At the same time, the first fan and the second fan are turned on to form a circulating air flow in the pipeline of the silicon powder processing system. S2. The silicon blocks are continuously and steadily conveyed from the silicon block silo to the ball mill through a conveyor. S3. The silicon blocks are ground into silicon powder in the ball mill. The silicon powder enters the particle separator under the action of the circulating air flow. Among them, the silicon powder with a diameter greater than 80 μm is collected by the particle separator and returned to the feed port of the ball mill; the silicon powder with a diameter less than 80 μm is collected by the particle separator into the cyclone separator and collected into the silicon powder bin by the cyclone separator. S4. The air flow with silicon powder generated by the cyclone separator enters the bag filter through the first fan for filtration and dust removal. The bag filter collects the filtered silicon powder into the silicon powder silo. S5. The air flow generated by the bag filter enters the inlet of the ball mill through the second fan. S6. The humidity of the circulating gas at the outlet of the second fan is detected in real time by the gas humidity detector, and the steam addition amount of the steam pipe to the circulating air supply pipeline is controlled to keep the humidity of the circulating gas at 40%. An oxygen content analyzer is installed on the side wall of the circulating air supply pipeline at a position close to the outlet of the second fan. A nitrogen pipe is connected to the side wall of the circulating air supply pipeline. According to the oxygen content concentration, the nitrogen supplement amount is adjusted to make the oxygen content in the circulating gas lower than 7%.

2. The method for processing silicon powder according to claim 1, characterized in that, The silicon block silo is located above the ball mill.

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