CN113697815A - Method for removing boron in metallurgical-grade silicon by using composite boron-philic additive - Google Patents

Method for removing boron in metallurgical-grade silicon by using composite boron-philic additive Download PDF

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CN113697815A
CN113697815A CN202111082145.7A CN202111082145A CN113697815A CN 113697815 A CN113697815 A CN 113697815A CN 202111082145 A CN202111082145 A CN 202111082145A CN 113697815 A CN113697815 A CN 113697815A
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boron
silicon
metallurgical
composite
philic
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任永生
曾毅
马文会
雷云
魏奎先
伍继君
吕国强
谢克强
颜恒维
刘战伟
李绍元
于洁
万小涵
陈正杰
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Kunming University of Science and Technology
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    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/02Silicon
    • C01B33/037Purification

Abstract

The invention relates to a method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive, belonging to the technical field of silicon purification. Heating and melting metallurgical-grade silicon to obtain a B-containing Si melt, and adding a composite boron-philic additive into the B-containing Si melt to obtain a mixed melt; introducing argon into the mixed melt, refining at 1414-1600 ℃ for 1-3 h, and cooling to room temperature along with the furnace to obtain refined silicon; and grinding the refined silicon into silicon powder with 150-200 meshes, and sequentially cleaning the silicon powder for 0.5-6 h by using aqua regia and HF-HCl mixed acid to obtain the high-purity silicon. The composite boron-philic additive provided by the invention is used for synergistically strengthening the removal of boron in metallurgical-grade silicon in a refining process, the removal rate of boron is close to 100%, and secondary pollution to Si is avoided.

Description

Method for removing boron in metallurgical-grade silicon by using composite boron-philic additive
Technical Field
The invention relates to a method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive, belonging to the technical field of silicon purification.
Background
So far, solar grade silicon (SOG-Si) is mainly made of metallurgical grade silicon (MG-Si) by various purification processes. Impurity removal is a purification process required for obtaining solar grade silicon from metallurgical grade silicon and is crucial to the preparation of silicon-based solar cells.
The requirement for removing boron in the production process of the solar cell is higher and higher, and when the concentration of B is higher than 0.3ppmw, the service life of minority carriers is shortened rapidly due to B-O defects, so that the photoelectric conversion efficiency of the cell is seriously influenced.
The production of SOG-Si by a metallurgical method effectively reduces the production cost, reduces the photovoltaic power generation cost, and promotes the high-speed development and the overall improvement of the solar cell industry level. Various metallurgical purification processes in the metallurgical method mainly comprise gas blowing, slag treatment, plasma refining, acid leaching, solvent refining and the like, wherein the gas blowing can effectively remove boron in silicon, but part of silicon can be oxidized into silicon dioxide and silicon monoxide, so that a small amount of silicon is lost. In addition, the saturated vapor pressure of the boride is normally low, which limits the rate of reaction other than B. Slag treatment can reduce the boron content in silicon, but refining silicon requires a large slag-to-silicon ratio (μ), and slag particles are difficult to contact sufficiently with liquid silicon. The plasma refining has good removing effect on aluminum, calcium, iron and boron, but the technology has the defects of expensive production equipment, high energy consumption, intermittent production and the like, and limits the development of industrial application of the technology. Acid-soaking silicon extraction does not purify Si at B concentrations below its solubility limit at the corresponding solidification composition.
Disclosure of Invention
The invention provides a method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive, aiming at the problem that boron in metallurgical-grade silicon is difficult to treat, namely, the composite boron-philic additive is adopted to remove boron in metallurgical-grade silicon in a refining process in a synergistic manner, the removal rate of boron is close to 100%, and secondary pollution to Si is avoided.
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon to obtain a B-containing Si melt, and adding a composite boron-philic additive into the B-containing Si melt to obtain a mixed melt;
(2) introducing argon into the mixed melt, refining at 1414-1600 ℃ for 1-3 h, and cooling to room temperature along with the furnace to obtain refined silicon;
(3) and grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 0.5-6 h by aqua regia and HF-HCl mixed acid in sequence to obtain the high-purity silicon.
The composite boron-philic additive in the step (1) comprises Hf and Zr, and the molar ratio of Hf to Zr is 3: 1-1: 3;
the molar content of the composite boron-philic additive in the mixed melt in the step (1) is 200-10000 ppm;
the volume ratio of HF to HCl in the HF-HCl mixed acid in the step (3) is 1: 5-5: 1.
The principle of the synergistic removal of boron in metallurgical-grade silicon by the composite boron-philic additive is as follows:
when the Zr-Hf composite additive is used for deboronation, the following deboronation reactions are simultaneously carried out:
[Hf]+2[B]=(HfB2)
Figure BDA0003264456790000021
[Zr]+2[B]=(ZrB2)
Figure BDA0003264456790000022
at the same time, the following coupling reactions also occur in the melt:
[Hf]+(ZrB2)=(HfB2)+[Zr] (3)
(ZrB2)+(HfB2)=(ZrB2·HfB2) (4)
two boron removing elements simultaneously participate in boron removal, and products formed by coupling are combined into a complex compound ZrB2·HfB2In relation to the equilibrium concentration of the boron-removing elements, thus enabling a reduction in the activity of the products formed by their respective boron removal, and thus an equilibrium w [ B ]]And decreases. In addition, their deboronated products form complex compounds with low melting points, which in turn make the deboronated products easy to polymerize and discharge. Since Hf has a stronger boron-removing ability than Zr, a strong boron-removing element can also deprive boron from a boron-removed product formed from a weak boron-removing element to decompose it, resulting in reaction (3). With w [ B ] in the melt]Balanced weakly deoxidizing elemental w [ Zr ]]Is higher than w [ B ] than]Balanced strong boron-removing element w [ Hf ]]Much higher. Therefore w [ Zr ]]W [ B ] of reaction (2) can be controlled only]And w [ Hf ]]The boron concentration of the entire melt is controlled and is lower than when Hf alone is deboronated (because of a)(HfB2)Reduced), the weak boron removing agent can improve the boron removing capability of the strong boron removing agent.
The invention has the beneficial effects that:
(1) according to the invention, the composite boron-philic additive Hf and Zr synergistically remove boron in metallurgical-grade silicon, Zr promotes Hf to capture B to form boride, the boride is easier to migrate to a liquid phase to reduce the segregation coefficient of B, the purpose of removing B by strengthening is achieved, and the removal rate of boron in silicon is close to 100%;
(2) the composite boron-philic additives Hf and Zr have small segregation coefficients in Si and silicon alloy melts and are easy to remove in the solidification refining process without causing secondary pollution to Si;
(3) the composite boron-philic additive Hf and Zr can synchronously remove impurities such as Ti, V, Al and the like of metallurgical-grade silicon on the basis of refining and boron removal;
(4) the method can be used for large-scale production of high-purity silicon, low-temperature operation is favorable for reducing cost, and the method is simple to operate and high in practicability.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.
Example 1: the contents of elements in metallurgical grade silicon in this example are shown in table 1,
TABLE 1 elemental content ppmw in metallurgical grade silicon
Figure BDA0003264456790000031
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive (see figure 1) comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon by adopting a vertical resistance furnace to obtain a Si melt containing B, and adding a composite boron-philic additive into the Si melt containing B to obtain a mixed melt; wherein the composite boron-philic additive comprises Hf and Zr, and the molar ratio of the Hf to the Zr is 1: 3; the molar content of the composite boron-philic additive in the mixed melt is 200 ppm;
(2) introducing argon into the mixed melt, refining at 1420 ℃ for 1h, closing the argon, and cooling to room temperature along with the furnace to obtain refined silicon; wherein the flow rate of the introduced argon is 10L/min;
(3) grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 0.5h by aqua regia and HF-HCl mixed acid in sequence to obtain high-purity silicon, wherein the volume ratio of HF to HCl in the HF-HCl mixed acid is 1: 5;
the contents of elements in the high-purity silicon were measured by ICP-AES and ICP-MS (see Table 2),
TABLE 2 elemental content ppmw in high purity silicon
Figure BDA0003264456790000032
In this example, the removal rate of boron in silicon reaches 98.82% by using the composite boron-philic additive.
Example 2: the elemental content of metallurgical grade silicon in this example is shown in table 3,
TABLE 3 elemental content ppmw in metallurgical grade silicon
Figure BDA0003264456790000033
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive (see figure 1) comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon by adopting a vertical resistance furnace to obtain a Si melt containing B, and adding a composite boron-philic additive into the Si melt containing B to obtain a mixed melt; wherein the composite boron-philic additive comprises Hf and Zr, and the molar ratio of the Hf to the Zr is 1: 2; the molar content of the composite boron-philic additive in the mixed melt is 1000 ppm;
(2) introducing argon into the mixed melt, refining at 1500 ℃ for 2h, closing the argon, and cooling to room temperature along with the furnace to obtain refined silicon; wherein the flow rate of the introduced argon is 15L/min;
(3) grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 3.0h by aqua regia and HF-HCl mixed acid in sequence to obtain high-purity silicon, wherein the volume ratio of HF to HCl in the HF-HCl mixed acid is 1: 3;
the contents of elements in the high purity silicon were measured by ICP-AES and ICP-MS (see Table 4),
TABLE 4 elemental content in high purity silicon
Figure BDA0003264456790000041
In this embodiment, the removal rate of boron in silicon reaches 98.96% by using the composite boron-philic additive.
Example 3: the elemental content of metallurgical grade silicon in this example is shown in table 5,
TABLE 5 elemental content in metallurgical grade silicon
Figure BDA0003264456790000042
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive (see figure 1) comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon by adopting a vertical resistance furnace to obtain a Si melt containing B, and adding a composite boron-philic additive into the Si melt containing B to obtain a mixed melt; wherein the composite boron-philic additive comprises Hf and Zr, and the molar ratio of the Hf to the Zr is 1: 1; the molar content of the composite boron-philic additive in the mixed melt is 4000 ppm;
(2) introducing argon into the mixed melt, refining for 3 hours at the temperature of 1600 ℃, closing the argon, and cooling to room temperature along with the furnace to obtain refined silicon; wherein the flow rate of the introduced argon is 20L/min;
(3) grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 6.0 hours by aqua regia and HF-HCl mixed acid in sequence to obtain high-purity silicon, wherein the volume ratio of HF to HCl in the HF-HCl mixed acid is 1: 1;
the contents of elements in the high purity silicon were measured by ICP-AES and ICP-MS (see Table 6),
TABLE 6 elemental content in high purity silicon
Figure BDA0003264456790000043
In this embodiment, the boron removal rate of silicon reaches 99.25% by using the composite boron-philic additive.
Example 4: the elemental content of metallurgical grade silicon in this example is shown in table 7,
TABLE 7 elemental content in metallurgical grade silicon
Figure BDA0003264456790000044
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive (see figure 1) comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon by adopting a vertical resistance furnace to obtain a Si melt containing B, and adding a composite boron-philic additive into the Si melt containing B to obtain a mixed melt; wherein the composite boron-philic additive comprises Hf and Zr, and the molar ratio of the Hf to the Zr is 2: 1; the molar content of the composite boron-philic additive in the mixed melt is 8000 ppm;
(2) introducing argon into the mixed melt, refining at 1500 ℃ for 2h, closing the argon, and cooling to room temperature along with the furnace to obtain refined silicon; wherein the flow rate of the introduced argon is 15L/min;
(3) grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 3.0h by aqua regia and HF-HCl mixed acid in sequence to obtain high-purity silicon, wherein the volume ratio of HF to HCl in the HF-HCl mixed acid is 3: 1;
the contents of elements in the high purity silicon were measured by ICP-AES and ICP-MS (see Table 8),
TABLE 8 elemental content in high purity silicon
Figure BDA0003264456790000051
In this embodiment, the boron removal rate of silicon reaches 99.64% by using the composite boron-philic additive.
Example 5: the elemental contents of metallurgical grade silicon in this example are shown in table 9,
TABLE 9 elemental content in metallurgical grade silicon
Figure BDA0003264456790000052
A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive (see figure 1) comprises the following specific steps:
(1) heating and melting metallurgical-grade silicon by adopting a vertical resistance furnace to obtain a Si melt containing B, and adding a composite boron-philic additive into the Si melt containing B to obtain a mixed melt; wherein the composite boron-philic additive comprises Hf and Zr, and the molar ratio of the Hf to the Zr is 3: 1; the molar content of the composite boron-philic additive in the mixed melt is 10000 ppm;
(2) introducing argon into the mixed melt, refining at 1500 ℃ for 2h, closing the argon, and cooling to room temperature along with the furnace to obtain refined silicon; wherein the flow rate of the introduced argon is 15L/min;
(3) grinding the refined silicon into silicon powder of 150-200 meshes, and cleaning the silicon powder for 3.0h by aqua regia and HF-HCl mixed acid in sequence to obtain high-purity silicon, wherein the volume ratio of HF to HCl in the HF-HCl mixed acid is 5: 1;
the contents of elements in the high purity silicon were measured by ICP-AES and ICP-MS (see Table 10),
TABLE 10 elemental content in high purity silicon
Figure BDA0003264456790000053
In this embodiment, the removal rate of boron in silicon reaches 99.75% by using the composite boron-philic additive.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.

Claims (4)

1. A method for removing boron in metallurgical-grade silicon by using a composite boron-philic additive is characterized by comprising the following specific steps:
(1) heating and melting metallurgical-grade silicon to obtain a B-containing Si melt, and adding a composite boron-philic additive into the B-containing Si melt to obtain a mixed melt;
(2) introducing argon into the mixed melt, refining at 1414-1600 ℃ for 1-3 h, and cooling to room temperature along with the furnace to obtain refined silicon;
(3) and grinding the refined silicon into silicon powder with 150-200 meshes, and sequentially cleaning the silicon powder for 0.5-6 h by using aqua regia and HF-HCl mixed acid to obtain the high-purity silicon.
2. The method of claim 1 for removing boron from metallurgical grade silicon using a composite boron-philic additive, wherein: the composite boron-philic additive in the step (1) comprises Hf and Zr, and the molar ratio of Hf to Zr is 3: 1-1: 3.
3. The method of claim 1 for removing boron from metallurgical grade silicon using a composite boron-philic additive, wherein: the molar content of the composite boron-philic additive in the mixed melt in the step (1) is 200-10000 ppm.
4. The method of claim 1 for removing boron from metallurgical grade silicon using a composite boron-philic additive, wherein: and (3) the volume ratio of HF to HCl in the HF-HCl mixed acid is 1: 5-5: 1.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115650239A (en) * 2022-09-13 2023-01-31 昆明理工大学 Method for efficiently removing impurities in metallurgical-grade silicon

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007314403A (en) * 2006-05-29 2007-12-06 Sharp Corp Silicon purification method and apparatus
CN106115717A (en) * 2016-08-23 2016-11-16 昆明理工大学 A kind of remove the method for impurity in metallurgical grade silicon

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007314403A (en) * 2006-05-29 2007-12-06 Sharp Corp Silicon purification method and apparatus
CN106115717A (en) * 2016-08-23 2016-11-16 昆明理工大学 A kind of remove the method for impurity in metallurgical grade silicon

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115650239A (en) * 2022-09-13 2023-01-31 昆明理工大学 Method for efficiently removing impurities in metallurgical-grade silicon
CN115650239B (en) * 2022-09-13 2024-04-26 昆明理工大学 Method for efficiently removing impurities in metallurgical-grade silicon

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