CN115872408B - Quartz sand purification method based on thermal plasma jet - Google Patents
Quartz sand purification method based on thermal plasma jet Download PDFInfo
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Abstract
The invention discloses a quartz sand purification method based on thermal plasma jet flow, and belongs to the technical field of material purification. The purification method comprises the following steps: heating quartz sand particles by adopting thermal plasma jet, crushing quartz sand to remove impurities in the quartz sand, collecting the quartz sand by deionized water, and cleaning the quartz sand to obtain purified quartz sand; the working power of the plasma torch for generating the thermal plasma jet is 6-12 kW, and the flow rate of the quartz sand particles is 0.008-0.02 kg/s. The working power of the plasma torch and the particle inlet flow are controlled to ensure that the temperature of quartz particles is always lower than the melting point of the quartz particles, so that the quartz particles are broken but not melted. The quartz sand particles are heated by adopting the thermal plasma jet flow, and thermal stress and compressive stress are generated in the particles, so that the particles are broken, and gas-liquid impurities and low-boiling-point metal impurities in the particles are volatilized to achieve the effect of removing the impurities in the particles.
Description
Technical Field
The invention belongs to the technical field of material purification, and particularly relates to a quartz sand purification method based on thermal plasma jet.
Background
The high-purity quartz is a main raw material for producing quartz glass, optical fibers, solar cells and integrated circuit board substrates, and is an important strategic resource. Although quartz mineral reserves are abundant, high-grade quartz concentrate resources are increasingly scarce. The existing quartz purification process generally comprises a plurality of steps of calcining, water quenching, crushing, magnetic separation, flotation, acid leaching, washing, dehydration, drying and the like, the process is complex, the purity of the produced quartz product is low, and the requirement of the fields of photovoltaic power generation and the like on high-purity quartz is difficult to meet. Therefore, there is an urgent need to develop a simpler and more efficient method for purifying quartz to obtain high purity quartz.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a quartz sand purifying method based on thermal plasma jet flow, which adopts a method of heating quartz sand particles by the thermal plasma jet flow to purify quartz sand so as to solve the problems of complex process and low product purity in the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the invention provides a quartz sand purification method based on thermal plasma jet flow, which comprises the following steps: heating quartz sand particles by adopting thermal plasma jet flow, crushing quartz sand to remove impurities in the quartz sand, collecting the quartz sand by deionized water, and then performing ultrasonic cleaning to obtain purified quartz sand;
the working power of the plasma torch for generating the thermal plasma jet is 6-12 kW, and the flow rate of the quartz sand particles is 0.008-0.02 kg/s.
Further, when the thermal plasma jet heating is adopted, the plasma generating device is a radio frequency plasma torch or an arc plasma torch;
the frequency of the radio frequency plasma torch is 3MHz.
Further, the particle size of the quartz sand particles is 0.1-0.4mm.
Further, the generating gas of the thermal plasma includes argon.
Further, boundary protection gas is also introduced into the plasma torch; the boundary shielding gas comprises a mixture of argon and hydrogen.
Further, in the mixed gas of argon and hydrogen, the volume fraction of the hydrogen is 2-7%.
Further, the quartz sand particles are blown in by carrier gas, and the flow rate of the carrier gas is 100-360 slpm.
The thermal plasma jet can be generated by an arc plasma torch and a radio frequency plasma torch, the temperature of a discharge area can reach ten thousands of K, and the jet temperature can reach thousands of K, and the two plasma torches are smaller in size, so that a very high temperature gradient and a very large energy density can be generated, a sample can be rapidly heated, and the thermal plasma jet is suitable for material purification.
When the quartz sand is purified by the method of the invention, the principle of particle breakage can be specifically described as follows: the particles themselves expand by heat to generate thermal stress; generally, cavities which encapsulate gas-liquid impurities exist in naturally formed quartz particles, and the gas-liquid impurities in the cavities expand by heating so as to generate compressive stress in the particles. Under the combined action of thermal stress and compressive stress, the total stress in the interior of the particles exceeds the stress fracture limit (50 MPa) of the particles, cracks are generated in the interior of the particles, and the cracks gradually expand to cause the particles to fracture.
Different from other material purification methods, the use of a thermal plasma jet to purify quartz to obtain optical grade high purity quartz needs to ensure that the quartz particles do not melt, as melting damages the crystal structure of quartz, reducing the optical properties of quartz, which can ensure that the temperature of the quartz particles is always below its melting point (1850K) by adjusting the working power of the plasma torch and the particle inlet flow rate (the working power determines the temperature of the plasma jet, the particle inlet flow rate determines the speed of the particles entering the device and thus the residence time of the particles in the high temperature zone).
The invention adopts argon as the generating gas of the plasma, and the argon is inert gas, and is one of the inert gas which has lower price and easier ionization, and can not pollute the processed sample.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the quartz sand particles are heated by adopting the thermal plasma jet, and a higher temperature and a larger temperature gradient are formed in the quartz sand particles in the rapid heating process, so that higher thermal stress and compressive stress are generated in the particles; when the total value of the hot pressing stress is higher than the damage limit of the quartz particles, the quartz particles are broken, so that gas-liquid impurities and low-boiling-point metal impurities in the particles are volatilized, and the effect of removing the impurities in the particles is achieved.
According to the invention, the temperature of quartz sand particles is always lower than the melting point (1850K) of the quartz sand particles by controlling the working power of the plasma torch and the feeding amount of the quartz particles, so that the quartz sand particles can be broken but not melted in the heating process of the plasma jet, the crystal structure of quartz is not damaged, and the optical performance of quartz is not reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic structural diagram of a RF plasma torch used in example 1;
FIG. 2 is a dimensional diagram of the RF plasma jet purification apparatus used in example 1;
FIG. 3 is a schematic diagram of thermal plasma jet purification of quartz in example 1;
FIG. 4 is a graph of microscopic surface topography of the high purity quartz prepared in example 1;
in fig. 5, (a), (b) and (c) are photomicrographs at different magnifications of quartz sand after plasma purification.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The invention provides a quartz sand purification method based on thermal plasma jet flow, which comprises the following steps: heating quartz sand particles by adopting thermal plasma jet flow, crushing quartz sand to remove impurities in the quartz sand, collecting the quartz sand by deionized water, and then performing ultrasonic cleaning to obtain purified quartz sand;
the working power of the plasma torch for generating the thermal plasma jet is 6-12 kW, and the flow rate of the quartz sand particles is 0.008-0.02 kg/s.
In some preferred implementations, the operating power of the plasma torch that generates the thermal plasma jet is 7kW and the flow rate of the quartz sand particles is 0.014kg/s.
In some preferred implementations, when heated with a thermal plasma jet, the plasma generating device is a radio frequency plasma torch or an arc plasma torch;
the frequency of the radio frequency plasma torch is 3MHz.
In some preferred implementations, the silica sand particles have a particle size of 0.1 to 0.4mm.
In some preferred implementations, the hot plasma generating gas is argon.
In some preferred implementations, a boundary shielding gas is also introduced into the radio frequency plasma torch; the boundary shielding gas is a mixed gas of argon and hydrogen, and the volume fraction of the hydrogen in the mixed gas is 5%.
In some preferred implementations, the flow rates of the plasma generating gas and the boundary shielding gas are 8slpm and 90slpm, respectively.
In some preferred implementations, the quartz sand particles are blown in by a carrier gas at a flow rate of 80 to 120slpm.
In some preferred implementations, the carrier gas flow is 100slpm.
Example 1
Purifying quartz by using a radio frequency thermal plasma jet excited by a 3MHz radio frequency plasma torch, wherein the structural schematic diagram of the adopted radio frequency plasma torch is shown in figure 1, and 1-carrier gas and quartz particles are introduced into a channel; 2-a plasma generating gas inlet channel; 3-introducing a boundary shielding gas into the channel;
the radio frequency plasma jet purifying device for purifying quartz sand by using the method consists of a plasma torch, a reaction chamber, a powder supply system and the like, and the size diagram of the device is shown in figure 2. Quartz particles are introduced into the reaction chamber through a powder supply gun, the introduction position of the quartz particles is positioned at the downstream of the plasma jet flow, the action of the particles and the high-temperature plasma jet flow is rapidly heated, when the temperature and the temperature gradient of the particles reach a certain limit, the sum of the compressive stress and the thermal stress in the particles exceeds the stress damage limit of quartz, the particles can be broken to become particles with smaller particle size, the impurities in the particles are exposed in the plasma jet flow, and the gas-liquid and low-boiling-point metal impurities can be directly volatilized after the impurities are heated, so that the impurities are separated. The crushed quartz particles are collected in deionized water at the bottom of the reaction chamber, and then are further cleaned by ultrasonic waves to obtain the high-purity quartz particles.
The operation steps are as follows:
(1) Introducing plasma generating gas Ar and boundary shielding gas Ar-H into the radio frequency plasma torch from the No. 2 channel and the No. 3 channel respectively 2 The flow rates of the mixed gas of (2) are respectively Q 2 ＝8slpm，Q 3 ＝90slpm(Q 2 And Q 3 Representing the gas flow rate introduced into the No. 2 channel and the No. 3 channel respectively) Ar-H 2 H in the mixed gas 2 Is 5% by volume. Ar-H 2 The mixed gas has the function of isolating the high temperature area from the wall surface, thereby protecting the discharge tube.
(2) And switching on a radio frequency power supply to supply power to the radio frequency plasma torch, wherein the power of the radio frequency power supply is set to 7kW, and the frequency is set to 3MHz.
(3) Introducing carrier gas argon and quartz particles from a No. 1 pipeline, wherein the carrier gas flow is Q 1 The included angle between the inlet direction and the axial direction of the torch is 30 degrees, the inlet flow rate of quartz particles is 0.014kg/s, and the particle size of the quartz particles is 0.1-0.4mm. Wherein the carrier gas acts to blow the quartz powder into the reaction chamber.
(4) The quartz particles are collected in deionized water at the bottom of the reaction chamber, and then are subjected to ultrasonic cleaning, deionized water washing and drying to obtain the high-purity quartz.
The quartz powder is rapidly heated in the reaction chamber by interaction with the plasma jet, thermal stress is generated inside the heated quartz particles, and compressive stress is generated by heating gas-liquid inclusion impurities inside the quartz particles. Under the combined action of thermal stress and compressive stress, quartz particles are broken, and gas-liquid inclusion is exposed in plasma jet. Next, the lower boiling impurities volatilize, and other impurities are melted, but under appropriate conditions the quartz particles themselves are not melted.
In this example, a schematic diagram of the thermal plasma jet purification of quartz is shown in FIG. 3.
The impurity content (ppm) of the quartz particle raw material used and the high purity quartz obtained in this example was measured using a mass spectrometer and compared with the content specified in GB/T32649-2016, and the results are shown in Table 1:
TABLE 1
As can be seen from Table 1, the impurity content in the quartz granule raw material can be reduced to the range specified by the national standard, namely, the standard of high purity quartz (Highpurity quartz, HPQ) is reached by adopting the method of the invention.
FIG. 4 is a microscopic surface topography of the high purity quartz prepared in this example, wherein 1, 2, and 3 are deposited impurities, and it can be seen from FIG. 3 that impurity particles having a diameter of about 0.1 μm are deposited on the surface of the processed quartz particles.
In FIG. 5, (a), (b) and (c) are photomicrographs at different magnifications of quartz sand after plasma purification, wherein 1-cracks, 2-traces after impurity release, 3-traces of gas-liquid inclusions and 4-plasma etched pits. Fig. 5 demonstrates that the breaking process does occur for the processed quartz particles.
In the present invention, when quartz sand is purified by heating quartz sand particles with a thermal plasma jet, an arc plasma torch (similar to the treatment described in patent application CN110015721 a) may also be used for the thermal plasma generating device, and the principle of purifying quartz sand is the same as that of example 1, and will not be described in detail here.
In the foregoing, the protection scope of the present invention is not limited to the preferred embodiments, and any person skilled in the art, within the scope of the present invention, should be covered by the protection scope of the present invention by equally replacing or changing the technical scheme and the inventive concept thereof.
Claims (7)
1. The quartz sand purifying method based on the thermal plasma jet is characterized by comprising the following steps of: heating quartz sand particles by adopting thermal plasma jet flow, crushing quartz sand to remove impurities in the quartz sand, collecting the quartz sand by deionized water, and then performing ultrasonic cleaning to obtain purified quartz sand;
the working power of the plasma torch for generating the thermal plasma jet is 6-12 kW, and the flow rate of the quartz sand particles is 0.008-0.02 kg/s.
2. The quartz sand purification method based on thermal plasma jet according to claim 1, wherein the plasma generating device is a radio frequency plasma torch or an arc plasma torch when the thermal plasma jet is used for heating;
the frequency of the radio frequency plasma torch is 3MHz.
3. The method for purifying quartz sand based on thermal plasma jet according to claim 1, wherein the particle size of the quartz sand particles is 0.1-0.4mm.
4. The method for purifying quartz sand based on thermal plasma jet according to claim 1, wherein the gas generating thermal plasma is argon.
5. The quartz sand purification method based on thermal plasma jet according to claim 4, wherein a boundary protection gas is also introduced into the plasma torch; the boundary shielding gas comprises a mixture of argon and hydrogen.
6. The method for purifying quartz sand based on thermal plasma jet according to claim 5, wherein the volume fraction of hydrogen in the mixture of argon and hydrogen is 2-7%.
7. The method for purifying quartz sand based on thermal plasma jet according to claim 1, wherein the quartz sand particles are blown by carrier gas, and the flow rate of the carrier gas is 100-360 slpm.
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| US5182091A (en) * | 1990-05-30 | 1993-01-26 | Kawasaki Steel Corporation | Method and apparatus for purifying silicon |
| JPH06115922A (en) * | 1992-10-07 | 1994-04-26 | Kawasaki Steel Corp | Method for purifying silicon |
| JPH11199220A (en) * | 1998-01-08 | 1999-07-27 | Kawasaki Steel Corp | Production of fine particle silicon oxide |
| CN102452651A (en) * | 2010-10-28 | 2012-05-16 | 内蒙古神舟硅业有限责任公司 | Process for removing boron impurity out of silicon by utilizing wet argon plasma |
| CN102459077A (en) * | 2009-04-17 | 2012-05-16 | 西利梅尔特公司 | Method and apparatus for purifying a silicon feedstock |
| CN105253891A (en) * | 2015-11-05 | 2016-01-20 | 湖南工业大学 | Method for removing gas-liquid inclusion in quartz sand by using microwave bursting method |
| CN112062131A (en) * | 2020-09-07 | 2020-12-11 | 齐鲁工业大学 | Production system and production process of high-purity quartz raw material |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102381711A (en) * | 2011-07-05 | 2012-03-21 | 兰州大学 | Method for purifying metallurgical-grade polycrystalline silicon by using microwave plasmas |
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- 2022-10-19 CN CN202211278010.2A patent/CN115872408B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5182091A (en) * | 1990-05-30 | 1993-01-26 | Kawasaki Steel Corporation | Method and apparatus for purifying silicon |
| JPH06115922A (en) * | 1992-10-07 | 1994-04-26 | Kawasaki Steel Corp | Method for purifying silicon |
| JPH11199220A (en) * | 1998-01-08 | 1999-07-27 | Kawasaki Steel Corp | Production of fine particle silicon oxide |
| CN102459077A (en) * | 2009-04-17 | 2012-05-16 | 西利梅尔特公司 | Method and apparatus for purifying a silicon feedstock |
| CN102452651A (en) * | 2010-10-28 | 2012-05-16 | 内蒙古神舟硅业有限责任公司 | Process for removing boron impurity out of silicon by utilizing wet argon plasma |
| CN105253891A (en) * | 2015-11-05 | 2016-01-20 | 湖南工业大学 | Method for removing gas-liquid inclusion in quartz sand by using microwave bursting method |
| CN112062131A (en) * | 2020-09-07 | 2020-12-11 | 齐鲁工业大学 | Production system and production process of high-purity quartz raw material |
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