Method for removing flotation reagent on surface of quartz sand for monocrystalline silicon quartz crucible

Abstract

The invention discloses a method for removing a flotation reagent on the surface of quartz sand for a monocrystalline silicon quartz crucible, which comprises the following steps of: pouring the quartz sand into a convection disc cleaning machine, adding an oil removal reagent and RO (Reverse Osmosis) water, heating to be more than 60 DEG C, starting disc washing, and discharging cleaning liquid after the disc washing is finished; rO water is added, when the temperature is increased to be higher than 60 DEG C, disc washing is started, and cleaning liquid is discharged completely after the disc washing is finished; adding deionized water, raising the temperature to be higher than 60 DEG C, starting disk washing, and discharging the cleaning liquid after the disk washing is finished; and the deionized water disc washing step is repeated to complete cleaning. The convection disc washing machine is adopted, the quartz sand is sequentially subjected to disc washing through the oil removing agent, the RO water and the deionized water, the convection disc washing machine conducts strong mutual collision friction washing on the quartz sand, and the oily agent is effectively stripped from the surface and cracks of the quartz sand; the secondary pollution caused by flotation reagent residues on the surface of the high-purity quartz sand to the high-purity quartz sand is solved, the purity of the quartz sand is improved, and the application performance and crystal pulling quality of a downstream quartz crucible are improved.

Description

Technical Field

[0001] The invention relates to the technical field of removing flotation reagents from the surface of quartz sand, and in particular to a method for removing flotation reagents from the surface of quartz sand used for a single crystal silicon quartz crucible. Background Art

[0002] Quartz crucibles are containers made of high-purity quartz sand. They are characterized by high purity, high temperature resistance, and long service life. They are currently widely used in the production process of single-crystal silicon rods in the semiconductor and photovoltaic fields. They are important consumables for silicon melting and crystal growth in the production of semiconductor silicon wafers and photovoltaic silicon wafers. In the crystal growth furnace, quartz crucibles are used as heating containers to directly hold polysilicon materials. After heating and melting, they are processed into silicon rods / wafers, which are further used in the production and processing of downstream semiconductor chips, photovoltaic panels and other products.

[0003] High impurity content in high-purity quartz sand raw materials can cause the crucible to break and affect the growth of single crystals. The impurity elements in high-purity quartz sand have a great influence on the quality of high-purity quartz crucibles. The content of alkali metals, transition metals, Al and P are key indicators of high-purity quartz raw materials. Alkali metal elements such as Li, K and Na will reduce the use temperature and mechanical strength of quartz crucibles, and catalyze the crystallization of quartz glass at high temperatures, resulting in devitrification and high-temperature deformation of quartz crucibles.

[0004] The most difficult minerals to separate in the purification of high-purity quartz sand are aluminum silicate minerals with similar properties to quartz. Flotation is currently the best process for removing aluminum silicate minerals mixed in quartz sand. Commonly used agents for flotation of quartz sand include aliphatic collectors, hydroxylated collectors, amine collectors, organic foaming agents, alkaline regulators, acid regulators, oxidants, reducing agents and other agents. These agents belong to organic substances such as amines, salts, and oils. After the flotation of high-purity quartz sand, these organic substances will remain on the surface of the quartz sand and in the cracks. If they are not cleaned properly, secondary pollution will occur, reducing the purity of high-purity quartz sand and directly affecting the performance of the quartz crucible. The problems of quartz crucibles with many bubbles, high hydroxyl content, and low softening point will greatly affect the performance of quartz products and reduce the service life and crystal pulling quality. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for removing flotation agents on the surface of quartz sand for single crystal silicon quartz crucibles. The method adopts a convection disc washer to sequentially wash the quartz sand with a degreasing agent, RO water and deionized water. The convection disc washer performs strong mutual collision and friction washing on the quartz sand inside the equipment, and the oily agents are stripped off from the surface and cracks of the quartz sand, thereby effectively removing the flotation agents remaining on the surface and in the cracks of the quartz sand, thereby solving the problem of the influence of the agents remaining on the surface of the high-purity quartz sand after flotation on the performance, service life and crystal pulling quality of the downstream quartz crucible.

[0006] In order to solve the above technical problems, the present invention provides a method for removing flotation reagents on the surface of quartz sand for single crystal silicon quartz crucibles, comprising the following steps:

[0007] S1. Pour the quartz sand after flotation into the convection disc cleaning machine, add degreasing agent and RO water, and continue to pass steam into the RO water to increase the temperature. When the temperature is greater than 60°C, start the disc cleaning. After the disc cleaning is completed, turn off the steam and drain the cleaning liquid after sedimentation.

[0008] S2, adding RO water to the convection cleaning plate in step S1, and continuously passing steam into the RO water to increase the temperature. When the temperature is greater than 60°C, start the plate washing. After the plate washing is completed, turn off the steam, and drain the cleaning liquid after settling;

[0009] S3, adding deionized water to the convection cleaning plate in step S2, and continuously passing steam into the deionized water to increase the temperature, when the temperature is greater than 60°C, starting the plate washing, turning off the steam after the plate washing is completed, and draining the cleaning liquid after precipitation;

[0010] S4. Repeat step S3 1-5 times. When the conductivity of the cleaning solution is less than 5 μS / cm, the cleaning is completed.

[0011] The present invention adopts a convection dish washer, and cooperates with a degreasing agent, RO water, and deionized water to dish wash quartz sand in sequence, and heats the dish washing liquid by steam. The heating efficiency is high and the temperature field of the dish washing liquid is uniform, which makes it easier to improve the cleaning effect.

[0012] Furthermore, the convection cleaning disc includes a shell, and a main shaft arranged in the shell, an upper turntable and a lower turntable are fixedly installed at the lower part of the main shaft, the upper turntable and the lower turntable are arranged opposite to each other and a plurality of blades are installed on the opposite surfaces, the plurality of blades are arranged in a semi-spiral shape and the spiral directions of the upper turntable and the lower turntable blades are opposite, and a driving mechanism is installed on the top of the main shaft. When the disc washing is started, the main shaft is driven to rotate by the driving mechanism, thereby driving the upper turntable and the lower turntable to rotate. Since the semi-spiral directions of the upper turntable and the lower turntable blades are opposite, huge convection collisions can be generated when rotating at high speed, accelerating the surface friction of the quartz sand, and stripping off the residual flotation reagents on the surface and gaps of the quartz sand.

[0013] Furthermore, the shell is made of 316 stainless steel.

[0014] Furthermore, an opening is provided at the top of the shell, and cleaning agents and cleaning liquids are introduced through the opening, and a cover is installed at the opening.

[0015] Furthermore, a drain port is provided at the bottom of the shell, and the cleaning liquid is discharged through the drain port.

[0016] Furthermore, a plurality of circular holes are arranged on the upper turntable and the lower turntable, and the diameter of the circular holes is 45-55 mm. When the upper turntable and the lower turntable rotate at high speed driven by the main shaft, the quartz sand is adsorbed through the circular holes and enters and exits between the two turntables for back and forth washing, thereby improving the cleaning effect.

[0017] Furthermore, the driving mechanism includes a motor and a conveyor belt, and the two ends of the conveyor belt are respectively sleeved on the output end of the motor and the main shaft. The conveyor belt is driven to rotate by the motor, thereby driving the main shaft to rotate at a high speed.

[0018] Furthermore, the degreasing agent is fatty acid methyl ester ethoxylate (FMCC), or a mixture of fatty acid methyl ester ethoxylate and one or more of alcohol amine, sodium hydroxide, potassium hydroxide, ammonia water, and sodium carbonate. Among them, fatty acid methyl ester ethoxylate has extremely high degreasing and dispersing properties, which is convenient for stripping the residual flotation agent on the surface and gaps of quartz sand, and the cleaning effect is better.

[0019] Furthermore, in S1, the mass ratio of the degreasing agent to the quartz sand is (2.5-3.5):1.

[0020] Furthermore, in S1 and S2, the volume ratio of the RO water to the quartz sand is independently (2.5-2.5):1, and the conductivity of the RO water is less than 0.5 μS / cm.

[0021] Furthermore, in S1 and S2, the dish washing time is independently selected from 35-40 minutes; in S3, the dish washing time is 10-15 minutes.

[0022] Furthermore, in S3, the volume ratio of the deionized water to the quartz sand is (2.5-3.5):1, and the resistivity of the deionized water is greater than 15 MΩ·cm.

[0023] Furthermore, the sodium content in the quartz sand after flotation in S1 is greater than 3 ppm, and the sodium content in the quartz sand after washing in S4 is less than 1 ppm.

[0024] Beneficial effects of the present invention:

[0025] The present invention adopts a convection disk washer to wash quartz sand in sequence by using a degreasing agent, RO water and deionized water. The convection disk washer performs strong mutual collision and friction washing on the quartz sand inside the equipment, and the oily agent is stripped from the surface and cracks of the quartz sand, and the flotation agent remaining on the surface and in the cracks of the quartz sand is effectively removed, thereby solving the problem of secondary pollution of the high-purity quartz sand caused by the flotation agent remaining on the surface of the high-purity quartz sand, and improving the purity of the high-purity quartz sand, as well as the application performance of the downstream quartz crucible and the quality of crystal pulling; meanwhile, the method is simple to operate, efficient in cleaning, and easy to popularize and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the convection dish washer of the present invention;

[0027] Figure 2 In the figure, a and b are schematic diagrams of the upper turntable and the lower turntable of the present invention respectively;

[0028] Explanation of the numbers in the figure: 1. Shell, 2. Spindle, 3. Upper turntable, 4. Lower turntable, 5. Blades, 6. Motor, 7. Conveyor belt, 8. Cover, 9. Drain port, 10. Round hole. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0030] This embodiment provides a method for removing flotation reagents on the surface of quartz sand for single crystal silicon quartz crucibles, comprising the following steps:

[0031] S1. Pour the quartz sand after flotation into the convection disc cleaning machine, add degreasing agent and RO water, and continue to pass steam into the RO water. When the temperature is greater than 60°C, start the disc cleaning. After 35 minutes of disc cleaning, turn off the steam and drain the cleaning liquid after sedimentation.

[0032] S2, adding RO water to the convection cleaning plate in step S1, and continuously passing steam into the RO water, when the temperature is greater than 60°C, start the plate washing, turn off the steam after the plate washing for 35 minutes, and drain the cleaning liquid after settling;

[0033] S3, adding deionized water to the convection cleaning plate in step S2, and continuously passing steam into the deionized water, when the temperature is greater than 60°C, starting the plate washing, turning off the steam after the plate washing for 10 minutes, and draining the cleaning liquid after settling;

[0034] S4, repeat step S3 twice to complete the cleaning. During the dish washing process, the conductivity of the dish washing liquid is shown in Table 1.

[0035] Table 1

[0036] step Conductivity S1 degreasing agent + RO water tray cleaning liquid 800μS / cm S2 RO water tray cleaning liquid 200μS / cm S3 Deionized Water Disk Wash Solution 50μS / cm S4 First Repeat Deionized Water Disk Wash 10μS / cm S4 Second repeat of deionized water dish wash 4μS / cm standard <5μS / cm

[0037] This embodiment uses a convection dish washer, and washes the quartz sand in turn with a degreasing agent, RO water, and deionized water. The dish washing liquid is heated by steam, and the heating efficiency is high and the temperature field of the dish washing liquid is uniform, which is easier to improve the cleaning effect. As shown in Table 1, after the dish washing liquid is washed with a degreasing agent, RO water, and deionized water three times, the conductivity of the dish washing liquid is reduced to 4μS / cm. In addition, the quartz sand before and after washing is detected by an inductively coupled plasma emission spectrometer ICP-OES, and it can be seen that the content of the alkali metal element Na is reduced from 3ppm before washing to 1ppm, and the cleaning effect is obvious.

[0038] Specifically, refer to Figure 1 As shown, the convection cleaning disc includes a shell 1 and a main shaft 2 arranged in the shell 1. The lower part of the main shaft 2 is fixedly installed with an upper turntable 3 and a lower turntable 4. The upper turntable 3 and the lower turntable 4 are arranged opposite to each other and three blades 5 are installed on the opposite surfaces. The three blades 5 are arranged in a semi-helical shape and the spiral directions of the blades 5 of the upper turntable 3 and the lower turntable 4 are opposite. Figure 2 As shown, a driving mechanism is installed on the top of the main shaft 2, and the driving mechanism includes a motor 6 and a conveyor belt 7. The two ends of the conveyor belt 7 are respectively sleeved on the output end of the motor 6 and the main shaft 2. The conveyor belt 7 is driven by the motor 6 to rotate, thereby driving the main shaft 2 to rotate at a high speed. When the disk washing is started, the main shaft 2 is driven to rotate by the driving mechanism, thereby driving the upper turntable 3 and the lower turntable 4 to rotate. Because the semi-spiral directions of the blades 5 of the upper turntable 3 and the lower turntable 4 are opposite, huge convection collisions can be generated during high-speed rotation, accelerating the surface friction of the quartz sand, and stripping off the residual flotation reagents on the surface and gaps of the quartz sand. Preferably, the material of the shell 1 is 316 stainless steel.

[0039] Specifically, the top of the housing 1 is provided with an opening, and a cover 8 is installed at the opening, through which cleaning agents and cleaning liquids are put in, and the cover 8 is closed during dishwashing to prevent splashing. A drain port 9 is provided at the bottom of the housing 1, and the cleaning liquid is discharged through the drain port 9 after cleaning is completed.

[0040] Preferably, in this embodiment, the bottom of the shell 1 is set as a conical structure, and at the same time, the lower turntable 4 is set at the bottom of the main shaft 2 and is located in the conical structure part, and the upper turntable 3 is set above the lower turntable 4 and is located below the middle of the main shaft 2.

[0041] Preferably, a plurality of circular holes 10 are provided on the upper turntable 3 and the lower turntable 4, and the diameter of the circular holes 10 is 50 mm. When the upper turntable 3 and the lower turntable 4 rotate at high speed driven by the main shaft 2, the quartz sand is adsorbed through the circular holes 10 and enters and exits between the two turntables for back-and-forth washing, thereby improving the cleaning effect.

[0042] In this embodiment, the degreasing agent is fatty acid methyl ester ethoxylate (FMCC), and the mass ratio of FMCC to quartz sand is 3: 1. Fatty acid methyl ester ethoxylate has extremely high degreasing and dispersing properties, which facilitates the stripping of residual flotation agents on the surface and in the gaps of quartz sand.

[0043] Specifically, in S1 and S2, the volume ratio of the RO water to the quartz sand is 3:1, and the conductivity of the RO water is less than 0.5 μS / cm; in S3, the volume ratio of the deionized water to the quartz sand is (2.5-3.5):1, and the resistivity of the deionized water is greater than 15 MΩ·cm.

[0044] In summary, the present invention adopts a convection disc washing machine to wash quartz sand in sequence by using a degreasing agent, RO water and deionized water. The convection disc washing machine performs strong mutual collision and friction washing on the quartz sand inside the equipment, and the oily agent is stripped from the surface and cracks of the quartz sand, and the flotation agent remaining on the surface and in the cracks of the quartz sand is effectively removed, thereby solving the secondary pollution of the high-purity quartz sand caused by the flotation agent residue on the surface of the high-purity quartz sand, improving the purity of the high-purity quartz sand, as well as the application performance and crystal pulling quality of the downstream quartz crucible; at the same time, the method is simple to operate, efficient in cleaning, and easy to promote and apply.

[0045] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for removing flotation reagents from the surface of quartz sand for single crystal silicon quartz crucibles, characterized in that: The steps include: S1. Pour the quartz sand after flotation into the convection disc cleaning machine, add degreasing agent and RO water, and continue to pass steam into the RO water to increase the temperature. When the temperature is greater than 60°C, start the disc cleaning. After the disc cleaning is completed, turn off the steam and drain the cleaning liquid after sedimentation. S2, adding RO water to the convection cleaning plate in step S1, and continuously passing steam into the RO water to increase the temperature. When the temperature is greater than 60°C, start the plate washing. After the plate washing is completed, turn off the steam, and drain the cleaning liquid after settling; S3, adding deionized water to the convection cleaning plate in step S2, and continuously passing steam into the deionized water to increase the temperature, when the temperature is greater than 60°C, starting the plate washing, turning off the steam after the plate washing is completed, and draining the cleaning liquid after precipitation; S4. Repeat step S3 1-5 times. When the conductivity of the cleaning solution is less than 5 μS / cm, the cleaning is completed.

2. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: The convection cleaning disk includes a shell and a main shaft arranged in the shell, an upper turntable and a lower turntable are fixedly installed on the lower part of the main shaft, the upper turntable and the lower turntable are arranged opposite to each other and a plurality of blades are installed on the opposite surfaces, the plurality of blades are arranged in a semi-helical shape and the spiral directions of the blades of the upper turntable and the lower turntable are opposite, and a driving mechanism is installed on the top of the main shaft.

3. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 2, characterized in that: A plurality of circular holes are arranged on the upper turntable and the lower turntable, and the diameter of the circular holes is 45-55 mm.

4. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 2, characterized in that: The driving mechanism comprises a motor and a conveyor belt, and two ends of the conveyor belt are respectively sleeved on the output end of the motor and the main shaft.

5. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: The degreasing agent is fatty acid methyl ester ethoxylate, or a mixture of fatty acid methyl ester ethoxylate and one or more of alcohol amine, sodium hydroxide, potassium hydroxide, ammonia water, and sodium carbonate.

6. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: In S1, the mass ratio of the degreasing agent to the quartz sand is (2.5-3.5):

1.

7. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: In S1 and S2, the volume ratio of the RO water to the quartz sand is independently (2.5-2.5):1, and the conductivity of the RO water is less than 0.5 μS / cm.

8. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: In S1 and S2, the dish washing time is independently selected from 35-40 minutes; in S3, the dish washing time is 10-15 minutes.

9. The method for removing the flotation agent on the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: In S3, the volume ratio of the deionized water to the quartz sand is (2.5-3.5):1, and the resistivity of the deionized water is greater than 15 MΩ·cm.

10. The method for removing flotation reagents from the surface of quartz sand for single crystal silicon quartz crucible according to claim 1, characterized in that: The sodium content in the quartz sand after flotation in S1 is greater than 3 ppm, and the sodium content in the quartz sand after washing in S4 is less than 1 ppm.

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