CN112209385A - Purification process of fused quartz for polycrystalline silicon crucible - Google Patents

Abstract

The invention belongs to the field of fused quartz production, and particularly discloses a purification process of fused quartz for a polycrystalline silicon crucible, which comprises the steps of (1) crushing, (2) cold quenching, (3) rolling, (4) magnetic separation and impurity removal, (5) flotation, (6) ultrasonic impurity removal, (7) high-temperature vacuum treatment, (8) smelting, (9) grinding and (10) subpackaging.

Description

Purification process of fused quartz for polycrystalline silicon crucible

Technical Field

The invention belongs to the field of fused quartz production, and particularly discloses a purification process of fused quartz for a polycrystalline silicon crucible.

Background

The crucible is a necessary device for producing polycrystalline silicon ingots in the photovoltaic industry, and silicon liquid is subjected to high-temperature heat treatment in the crucible to obtain the silicon ingots. The crucible for the polysilicon ingot casting in China is made of fused quartz ceramic materials, and is prepared by adopting a slip casting or slip casting process. Since silicon ingots require extremely high purity, the purity requirement for fused silica is also extremely high. High-purity fused quartz can be easily obtained in a laboratory, but at present, a common fused quartz production enterprise produces fused quartz powder, and the main process flow from raw materials to finished products is approximately as follows: quartz stone mineral aggregate is processed into smaller stone through a stone knocking machine, the stone is rolled into sand grains through stone, water is continuously added during rolling, the water brings the sand grains to flow into a sedimentation tank, the sand grains in the sedimentation tank are conveyed into a baking room to be baked into dry sand grains, then the dry sand grains are screened through a vibrating screen, a magnet rod and a magnet discharging rod are utilized to remove iron in the screening process, the melted quartz is smelted into fused quartz after being dried, then the fused quartz powder is obtained after the crushing, and then the fused quartz powder is subpackaged and stored. However, the fused silica powder thus obtained still contains many impurities and cannot be fully satisfactory for the production of high-quality crucibles.

At present, in the production of polycrystalline silicon ingots, crucibles are often disposable and are scrapped after being used up, so that huge waste is caused. If a method for recycling and purifying the fused silica in the scrapped crucible can be found, the method has great practical significance for environmental protection and reduction of production cost.

Disclosure of Invention

In view of the above disadvantages, the present invention discloses a purification process for fused silica used in a polysilicon crucible.

The technical scheme of the invention is as follows:

a process for purifying fused silica for use in a polysilicon crucible, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 6-10cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace with the temperature of 1000-;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator under the field intensity of 2000-4000 gausses to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for carrying out ultrasonic cleaning on the quartz sand, wherein the ultrasonic frequency is 110-1000W/m and the ultrasonic power is adjusted to 500-1000W/m according to the amount of the quartz sand³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at the temperature of 1900-2000 ℃ for 2-4h, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 10-20min, and the rotating speed of a ball mill is 90-110 r/min, so as to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.

Further, in the purification process of the fused silica for the polycrystalline silicon crucible, the mass ratio of the volume of the liquid carbon dioxide to the quartz grains is 0.1-0.5 ml/g.

Further, in the purification process of the fused silica for the polycrystalline silicon crucible, in the step 5 flotation, the flotation agent comprises the following components: polymethyl siloxane, oleic acid, palmitic acid, ethylenediamine monooleic acid amide and isooctyl alcohol.

Further, in the purification process of the fused silica for the polycrystalline silicon crucible, the flotation agent comprises the following components in percentage by mass: 70% of polymethylsiloxane, 12% of oleic acid, 10% of palmitic acid, 6% of ethylenediamine monooleic acid amide and 2% of isooctyl alcohol.

Further, in the purification process of the fused quartz for the polycrystalline silicon crucible, the mass ratio of the flotation agent to the quartz sand is 1:1000-1: 5000.

Further, in the purification process of the fused quartz for the polycrystalline silicon crucible, in the step 7, the high-temperature vacuum treatment condition is 800 ℃ and is less than 0.001 Mpa.

Further, the purification process of the fused silica for the polycrystalline silicon crucible comprises the following steps:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 8cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace at 1100 ℃, roasting for 6.5 hours, taking out, immediately spraying liquid carbon dioxide for cold quenching, and cracking large-grain quartz grains into finer quartz grains;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator at a field intensity of 3000 gauss to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for ultrasonic cleaning of the quartz sand, wherein the ultrasonic frequency is 130Hz, and the ultrasonic power is adjusted to 750W/m according to the quartz sand amount³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at 1950 ℃ for 3 hours, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 15min, and the rotating speed of a ball mill is 100r/min to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.

According to the technical scheme, the invention has the following beneficial effects: the invention provides a method for purifying, impurity-removing and recycling crucible waste for polysilicon production, which can obtain high-purity fused quartz meeting the requirement of the crucible for polysilicon production, thereby remarkably relieving excessive dependence on quartz ore, realizing cyclic utilization of quartz, greatly reducing the manufacturing cost of the crucible for polysilicon production, solving the problems of pollution and recovery of solid waste of production enterprises, and being green and more environment-friendly.

Detailed Description

Example 1

1. A process for purifying fused silica used in a polysilicon crucible, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 6cm by using a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace at 1000 ℃, roasting for 5 hours, taking out, immediately spraying liquid carbon dioxide for cold quenching, and cracking large-grain quartz grains into finer quartz grains;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator at a field intensity of 2000 gauss to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for ultrasonic cleaning of the quartz sand, wherein the ultrasonic frequency is 110Hz, and the ultrasonic power is adjusted to be 500W/m according to the amount of the quartz sand³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at 1900 ℃ for 2 hours, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 10min, and the rotating speed of a ball mill is 90r/min, so as to obtain high-purity fused quartz powder;

(10) subpackaging: vacuum subpackaging and warehousing the high-purity fused quartz powder obtained in the step 9; in the step 2, in the cold quenching, the mass ratio of the volume of the liquid carbon dioxide to the quartz grains is 0.1 ml/g;

in the step 5, the flotation agent comprises the following components in percentage by mass: 70% of polymethylsiloxane, 12% of oleic acid, 10% of palmitic acid, 6% of ethylenediamine monooleic acid amide and 2% of isooctyl alcohol; the mass ratio of the flotation agent to the quartz sand is 1: 1000;

in the step 7, the high-temperature vacuum treatment condition is 800 ℃, and the temperature is less than 0.001Mpa in the embodiment 2

A process for purifying fused silica for use in a polysilicon crucible, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 8cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace at 1100 ℃, roasting for 6.5 hours, taking out, immediately spraying liquid carbon dioxide for cold quenching, and cracking large-grain quartz grains into finer quartz grains;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator at a field intensity of 3000 gauss to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator to perform ultrasonic cleaning on the quartz sand, wherein the ultrasonic frequency is 130Hz, and the ultrasonic power is adjusted to 750W/m3 according to the amount of the quartz sand;

(7) high-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at 1950 ℃ for 3 hours, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 15min, and the rotating speed of a ball mill is 100r/min to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.

In the step 2, in the cold quenching, the mass ratio of the volume of the liquid carbon dioxide to the quartz grains is 0.25 ml/g;

in the step 5, the flotation agent comprises the following components in percentage by mass: 70% of polymethylsiloxane, 12% of oleic acid, 10% of palmitic acid, 6% of ethylenediamine monooleic acid amide and 2% of isooctyl alcohol; the mass ratio of the flotation agent to the quartz sand is 1: 2500;

in the step 7, the high-temperature vacuum treatment condition is 800 ℃ and less than 0.001 Mpa.

Example 3

A process for purifying fused silica for use in a polysilicon crucible, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 10cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace at 1200 ℃, roasting for 8 hours, taking out, immediately spraying liquid carbon dioxide for cold quenching, and cracking large-grain quartz grains into finer quartz grains;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator under the field intensity of 4000 gausses to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for ultrasonic cleaning of the quartz sand, wherein the ultrasonic frequency is 150Hz, and the ultrasonic power is adjusted to 1000W/m according to the quartz sand amount³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at 2000 ℃ for 4 hours, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 20min, and the rotating speed of a ball mill is 110r/min, so as to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.

In the step 2, in the cold quenching, the mass ratio of the volume of the liquid carbon dioxide to the quartz grains is 0.5 ml/g;

in the step 5, the flotation agent comprises the following components in percentage by mass: 70% of polymethylsiloxane, 12% of oleic acid, 10% of palmitic acid, 6% of ethylenediamine monooleic acid amide and 2% of isooctyl alcohol; the mass ratio of the flotation agent to the quartz sand is 1: 5000;

in the step 7, the high-temperature vacuum treatment condition is 800 ℃ and less than 0.001 Mpa.

Test example

The high purity fused silica powders obtained in the above examples 1 to 3 were subjected to the composition test and compared with the silica powder obtained after the crucible pulverization before the purification as a control, and the specific results are shown in Table 1.

Table 1 ingredient testing.

	Example 1	Example 2	Example 3	Comparative example
					SiO2/％	99.98％	99.99％	99.97％	97.5％
Fe/ppm	0.6	0.5	0.7	24
					AL/ppm	12	9	11	250
K/ppm	0.9	0.7	1.1	18

According to the test data, the purification method disclosed by the invention is simple in process and remarkable in purification effect, and the obtained high-purity fused quartz can be used for a crucible for producing polycrystalline silicon.

The above are only preferred embodiments of the present invention, and the scope of the present invention should not be limited thereby, and all the equivalent changes and modifications made by the claims and the summary of the invention should be covered by the protection scope of the present patent application.

Claims (7)

1. A process for purifying fused silica used in a polysilicon crucible, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 6-10cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace with the temperature of 1000-;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator under the field intensity of 2000-4000 gausses to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for carrying out ultrasonic cleaning on the quartz sand, wherein the ultrasonic frequency is 110-1000W/m and the ultrasonic power is adjusted to 500-1000W/m according to the amount of the quartz sand³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at the temperature of 1900-2000 ℃ for 2-4h, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 10-20min, and the rotating speed of a ball mill is 90-110 r/min, so as to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.

2. The process of claim 1, wherein in the step 2 of quenching, the mass ratio of the volume of the liquid carbon dioxide to the quartz grains is 0.1-0.5 ml/g.

3. The process of claim 1, wherein in the step 5 flotation, the flotation agent comprises the following components: polymethyl siloxane, oleic acid, palmitic acid, ethylenediamine monooleic acid amide and isooctyl alcohol.

4. The process for purifying fused silica used in a polysilicon crucible as recited in claim 3, wherein the flotation agent comprises the following components in percentage by mass: 70% of polymethylsiloxane, 12% of oleic acid, 10% of palmitic acid, 6% of ethylenediamine monooleic acid amide and 2% of isooctyl alcohol.

5. The purification process of fused silica for a polysilicon crucible as recited in claim 4, wherein the mass ratio of the flotation agent to the quartz sand is 1:1000 to 1: 5000.

6. The process of claim 4, wherein the high temperature vacuum treatment in step 7 is performed at 800 ℃ and less than 0.001 MPa.

7. The process of purifying molten quartz for a polysilicon crucible as recited in claim 1, comprising the steps of:

(1) crushing: the method comprises the following steps of (1) crushing waste crucibles for producing polycrystalline silicon into quartz grains with the grain size of 8cm by a stone knocking machine;

(2) and (3) cold quenching: putting the quartz grains into a resistance furnace at 1100 ℃, roasting for 6.5 hours, taking out, immediately spraying liquid carbon dioxide for cold quenching, and cracking large-grain quartz grains into finer quartz grains;

(3) rolling: rolling the quartz grains obtained in the step 2 into quartz sand by using a rolling machine, wherein the average grain diameter is less than 1 cm;

(4) magnetic separation and impurity removal: magnetically separating the quartz sand obtained in the last step by using a magnetic separator at a field intensity of 3000 gauss to remove magnetic impurities;

(5) flotation: putting the quartz sand obtained in the step 4 into a flotation machine, adding a flotation agent for flotation, and floating out non-quartz particles and other impurities by utilizing the density difference of various minerals and the surface wettability difference of the minerals;

(6) ultrasonic impurity removal: putting the quartz sand obtained in the step 5 into a cleaning tank with an ultrasonic generator for ultrasonic cleaning of the quartz sand, wherein the ultrasonic frequency is 130Hz, and the ultrasonic power is adjusted to 750W/m according to the quartz sand amount³；

(7) High-temperature vacuum treatment: performing high-temperature vacuum treatment on the quartz sand obtained in the step 6 to remove surface and gaseous impurities;

(8) smelting: putting the quartz sand obtained in the step 7 into an electric furnace for high-temperature smelting at 1950 ℃ for 3 hours, taking out after smelting, and cooling to room temperature to form fused quartz stone;

(9) grinding, namely crushing the fused quartz stone obtained in the step 8 into small blocks, and then carrying out dry grinding by using a ball mill, wherein the lining and the grinding ball of the ball mill tank are made of manganese oxide, and the ball material ratio is 3: 1, carrying out weight grading on 4 grinding balls with the diameters of 10 mm, 15 mm, 25 mm and 35mm, wherein the ball milling time is 15min, and the rotating speed of a ball mill is 100r/min to obtain high-purity fused quartz powder;

(10) subpackaging: and (4) carrying out vacuum sub-packaging on the high-purity fused quartz powder obtained in the step (9) and warehousing.