AU2020100042A4 - Purification process of polycrystalline silicon raw material - Google Patents
Purification process of polycrystalline silicon raw material Download PDFInfo
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Abstract
Abstract Disclosed is a purification process of a polycrystalline silicon raw material, which comprises the 5 following steps: pressurizing back-blown hydrogen of an adsorption tower in a vent gas recovery procedure in the polycrystalline silicon production, and entering a quench tower of a cold hydrogenation procedure with a cold hydrogenation reaction vent gas, wherein the quench tower adopts a self-circulation; fully contacting, within the quench tower, a phosphorus-containing compound in the back-blown hydrogen with the cold hydrogenation reaction vent gas, a 10 boron-containing compound and metal impurities in a kettle liquid for complexing; and carrying out preliminary condensation on a gas phase discharged from a top of the quench tower, and carrying out rectification for purification on a condensate; wherein the kettle liquid is a cold hydrogenation product. According to the purification process of the polycrystalline silicon raw material of the present invention, the contents of impurities B and P in a liquid phase raw material 15 for polycrystalline silicon production are reduced in a complexing form, so that in a later rectification process, the number of stages of a rectification tower can be reduced, thereby reducing the energy consumption and adsorbent consumption; and the purification process is realized on the basis of existing equipment, with simple operation, low investment, and low cost. Drawings Uncooled Hydrogen Recycle Condenser I Refln Tank of Quench Tower Chloro sIaneRecticatin CVD Vent Gas Back-blown Hydrogen Cold Hydrogenation Reaction Vent Gas Towe Figure 1
Description
Description
Purification Process of Polycrystalline Silicon Raw Material
Technical Field
The invention belongs to the technical field of polycrystalline silicon, and particularly relates to a purification process of a polycrystalline silicon raw material.
Background Art
There are two main technologies for polycrystalline silicon production in the world, i.e. improved Siemens process and silane process. From the perspective of capacity comparison, the improved Siemens process accounts for more than 90% of the total capacity, and the silane method is less than 10%.
In the production of polycrystalline silicon, the contents of impurities B and P are the main index for determining the quality of polycrystalline silicon. The existing improved Siemens process mainly achieves the purpose of improving the quality of polycrystalline silicon by removing B, P and other impurities in high-purity trichlorosilane (TCS) in the production of polycrystalline silicon. The removal of impurities in the high-purity TCS mainly includes rectification, adsorption and other methods. With the maturity of polycrystalline silicon production process and the expansion of capacity, downstream enterprises of polycrystalline silicon have higher and higher requirements for polycrystalline silicon product quality. In order to ensure the quality of polycrystalline silicon products, the manufacturers improve the quality of high-purity TCS and stabilize the polycrystalline silicon product, e.g. by increasing the number of rectification stages, increasing the reflux ratio, increasing the number of theoretical plates and adopting a large number of adsorption procedures.
However, these methods have certain disadvantages: (1) the rectification mode with large reflux ratio leads to a higher energy consumption; (2) the increases in the number of rectification stages and theoretical plates lead to more investment; and (3) the adsorbent used for the adsorption process needs to be replaced after being saturated, and the environmental protection treatment requirement of the adsorbent is high.
Therefore, the invention provides a novel purification process of the polycrystalline silicon.
Summary of the Invention
The invention aims to provide a purification process of a polycrystalline silicon raw material, which can greatly reduce the impurity content of a polycrystalline silicon product by reducing the contents of impurities of B, P and the like in a liquid phase raw material for the polycrystalline silicon production in a complexing form.
In order to achieve the above purpose, the technical scheme adopted is as follows:
A purification process of a polycrystalline silicon raw material comprises the following steps: pressurizing back-blown hydrogen of an adsorption tower in a vent gas recovery procedure in the polycrystalline silicon production, and entering a quench tower of a cold hydrogenation procedure with a cold hydrogenation reaction vent gas, wherein the quench tower adopts a self-circulation; fully contacting, within the quench tower, a phosphorus-containing compound in the back-blown hydrogen with the cold hydrogenation reaction vent gas, a boron-containing compound and metal impurities in a kettle liquid for complexing; and carrying out preliminary condensation on a gas phase discharged from a top of the quench tower, and carrying out rectification for purification on a condensate;
wherein the kettle liquid is a cold hydrogenation product.
Further, the back-blown hydrogen gas is pressurized to 2.4-2.5 MPaG.
Further, the kettle liquid enters from a middle part of the quench tower.
Further, in the preliminary condensation procedure, a non-condensed gas phase is returned to the cold hydrogenation procedure.
Further, in the purification process, the temperature of the quench tower is 30-230°C.
Further, after the preliminary condensation on the gas phase discharged from a top of the quench tower, part of the condensate enters the quench tower as a reflux liquid.
Still further, the reflux liquid enters from an upper part of the quench tower.
Compared with the prior art, the invention has the following beneficial effects:
1, according to the purification process of the polycrystalline silicon raw material of the present invention, the contents of impurities B and P in the liquid phase raw material for the polycrystalline silicon production are reduced in a complexing form.
2, according to the purification process of the polycrystalline silicon raw material, the impurity content in the cold hydrogenation product can be greatly reduced before the rectification procedure, thus reducing the difficulty and cost of the procedure in the later rectification procedure, reducing the number of rectification tower stages, reducing the energy consumption, and reducing the adsorbent consumption.
3, according to the purification process of the polycrystalline silicon raw material of the present invention, the impurity content of a polycrystalline silicon product can be greatly reduced.
4, According to the purification process of the polycrystalline silicon raw material of the present invention, system products produced by polycrystalline silicon can be fully utilized, and the
2020100042 09 Jan 2020 purification process is realized on the basis of existing equipment with simple operation, low investment, and low cost.
Brief Description of the Drawings
Figure 1 is a process flow diagram of the present invention.
Detailed Description of the Invention
In order to further illustrate the purification process of the polycrystalline silicon raw material provided by the present invention and achieve the intended purpose of the invention, a purification 10 process of the polycrystalline silicon raw material, the specific embodiments, the structures, the characteristics and the effects thereof will be described in detail with reference to the preferred embodiments. In the following description, different “one embodiment” or “an embodiment” means not necessarily a same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable form.
Before explaining the purification process of the polycrystalline silicon raw material of the present invention in detail, it is necessary to further explain the raw materials, methods and the like mentioned in the present invention so as to achieve better effects.
The kettle liquid is a cold hydrogenation product, the main component is chlorosilane, and the rest are impurities, including impurities such as boron-containing compounds, metal impurities and the 20 like.
The principle of the invention lies in that: impurities such as compounds of P and B are difficult to remove because the boiling point thereof are very close to that of the product chlorosilane, and according to the present invention, compounds of P and B, metal impurities and the like are converted into complexes with high boiling points, so that impurities of P, B, metal and the like 25 can be effectively removed by utilizing the characteristic of large boiling point difference.
The back-blown hydrogen gas contains phosphorus-containing compounds; the cold hydrogenation reaction vent gas contains boron-containing compounds, metal impurities, silicon powder, dust and the like; and the kettle liquid contains boron-containing compounds, metal impurities and the like. The back-blown hydrogen is fully contacted with the cold hydrogenation 30 reaction vent gas and kettle liquid in the quench tower. Namely, the liquid phase and the gas phase are fully contacted in the quench tower, the gas phase and the gas phase are fully contacted in the quench tower, and thus the P and B compounds are fully reacted and complexed to form a complex with a higher boiling point. The complex is subjected to a liquid phase circulation through the quench tower, then complexed with the cold hydrogenation reaction vent gas and 35 metal impurities in the cold hydrogenation product to form a complex with a higher boiling point,
2020100042 09 Jan 2020 and the metal impurities in the product are removed.
Since the high boiling point, the complex is not easy to form a gaseous state together with chlorosilane, and the contents of impurities such as boron, phosphorus, metal and the like in the gaseous chlorosilane discharged from the top of the quench tower can be effectively reduced. The 5 complex with higher boiling point in the kettle liquid can be removed at the later stage by utilizing the characteristic of large difference in boiling points.
The vent gas recovery adsorption tower blows hydrogen back into the cold hydrogenation quench tower to complex a reduction product in the back-blown hydrogen with the cold hydrogenation product. The raw materials are system products for the polycrystalline silicon production, with low 10 cost.
MPaG is a unit of pressure and represents a gauge pressure.
“G” in MPaG represents the gauge pressure, i.e. the pressure indicated by the pressure gauge, not the absolute pressure, but a relative pressure.
ChB: PH3 means CI3B and PH3 are complexed.
CI4B2: P2H4 means CI4B2: P2H4 are complexed.
After understanding the above raw materials, methods and the like, a purification process of a polycrystalline silicon raw material according to the present invention will be described in further detail with reference to a specific embodiment and FIG. 1.
The technical scheme of the invention is as follows:
back-blown hydrogen of an adsorption tower in a vent gas recovery procedure in the polycrystalline silicon production is pressurized, and enters a quench tower of a cold hydrogenation procedure with a cold hydrogenation reaction vent gas, wherein the quench tower adopts a self-circulation. And the kettle liquid is a cold hydrogenation product.
Within the quench tower, the back-blown hydrogen (containing a phosphorus-containing 25 compound) is fully contacted with the cold hydrogenation reaction vent gas (containing boron-containing compounds, metal impurities, silicon powder, dust and the like) and the kettle liquid (containing boron-containing compounds and metal impurities); the liquid phase and gas phase are fully contacted in the quench tower, and the gas phase and gas phase are fully contacted in the quench tower, so that P and B compounds are fully reacted and complexed to form 30 complexes (CI3B: PH3 and CI4B2: P2H4 and the like) with higher boiling points. The complexes are subjected to a liquid phase circulation through the quench tower, and subjected to complex adsorption with the cold hydrogenation reaction vent gas and metal impurities in the cold hydrogenation products to form complexes (CI3B: PH3 and CI4B2: P2H4 and the like adsorbed with metal impurities) with higher boiling points, so that the metal impurities in the product can be 35 removed.
And the cold hydrogenation reaction vent gas is contacted with the kettle liquid, so that impurities such as dust, silicon powder and the like can be washed.
After the gas phase discharged from the top of the quench tower is preliminarily condensed, the condensate is fed to a rectification procedure to be purified.
Preferably, the back-blown hydrogen is pressurized to 2.4-2.5 MPaG. And the back-blown hydrogen needs to be pressurized to a same pressure as the cold hydrogenation reaction vent gas to enter the quench tower.
Preferably, the kettle liquid enters from a middle of the quench tower, discharges from a bottom of the quench tower and then is conveyed to the middle of the quench tower through a pump, so that the kettle liquid can be contacted with the back-blown hydrogen to the maximum extent.
Also, the quench tower needs to maintain flow equilibrium. When the kettle liquid in the quench tower is reduced, the kettle liquid needs to be replenished.
Preferably, during the preliminary condensation procedure, the non-condensed gas phase is returned to the cold hydrogenation procedure, improving the utilization rate, and realizing the economic maximization.
Preferably, in the purification process, the temperature of the quench tower is 30-230°C.
Preferably, after the preliminary condense of the gas phase discharged from the top of the quench tower, part of the condensate enters the quench tower as a reflux liquid. This step maintains the natural flow of the quench tower and maintains flow equilibrium. Moreover, the existing equipment is adopted, with low cost.
Still further preferably, the reflux liquid enters from an upper part of the quench tower. The flux liquid enters from the upper part of the quench tower, namely the liquid moves from top to bottom, so that better mass transfer and gas phase contact can be realized, reducing the temperature of the quench tower, improving the safety, and washing impurities such as dust, silicon powder and the like.
Example 1.
Referring to FIG. 1, the specific operation steps are as follows:
back-blown hydrogen of an adsorption tower in a vent gas recovery procedure in the polycrystalline silicon production was pressurized to 2.5 MPaG, and entered a quench tower of a cold hydrogenation procedure with a cold hydrogenation reaction vent gas.
The quench tower adopted a self-circulation. The temperature of the quench tower was 230°C. The kettle liquid (a cold hydrogenation product, wherein the main component is chlorosilane, namely silicon tetrachloride) entered from the middle of the quench tower, and discharged from the bottom of the quench tower, and was conveyed to the middle of the quench tower through a pump.
And the quench tower needed to maintain flow equilibrium.
The phosphorus-containing compounds in the back-blown hydrogen were fully contacted with the cold hydrogenation reaction vent gas, the boron-containing compounds and the metal impurities in the kettle liquid within the quench tower for complexing to form complexes with higher boiling points. And the gas phase was fully contacted with the liquid phase, so that impurities such as dust, silicon powder and the like can be washed.
The gas phase discharged from the top of the quench tower was sent to a condenser. After the preliminary condensation, the non-condensed gas phase was returned to the cold hydrogenation procedure. The condensate was collected in the reflux tower of the quench tower. Part of the condensate was used as the reflux liquid and enters the quench tower from the upper part of the quench tower through a pump. And the remaining condensate was purified by rectification. Example 2.
The procedures of Example 2 were the same as those of Example 1, except that the temperature of the quench tower was 30 °C.
Example 3.
The procedures of Example 3 were the same as those of Example 1, except that the back-blown hydrogen was pressurized to 2.4 MPaG and the temperature of the quench tower was 150 °C. Example 4.
The procedures of Example 4 were the same as those of Example 1, except that the back-blown hydrogen was pressurized to 2.4 MPaG and the temperature of the quench tower was 120°C. Example 5.
The procedures of Example 5 were the same as those of Example 1, except that the back-blown hydrogen was pressurized to 2.4 MPaG and the temperature of the quench tower was 100°C.
The chlorosilane after rectification was analyzed. The gas phases discharged from the top of the quench tower when the back-blown hydrogen was not added were collected in the examples 1 -5 for detecting the total impurity content of P, B and metal. And the gas phases discharged from the top of the quench tower when the back-blown hydrogen was added were collected in the examples 1-5 for detecting the total impurity content of P, B and metal. The results are shown in Table 1.
Table 1
| EXAMPLES | No Back-blown Hydrogen Added | Back-blown Hydrogen Added |
| 1 | 3000 ppbw | 1700 ppbw |
| 2 | 1000 ppbw | 500 ppbw |
| 3 | 2100 ppbw | 1040 ppbw |
| 4 | 1860 ppbw | 890 ppbw |
| 5 | 2430 ppbw | 11320 ppbw |
As can be seen from Table 1, with the present invention, the contents of B, P and metal impurities were greatly reduced in the gas phase discharged from the top of the quench tower.
The complex method is a common method for chemical production, and is widely applied to chemical unit operations such as complex catalysis, complex reaction, sewage treatment and the like. However, according to the invention, the complex method is used in the chemical operation unit for purifying the polycrystalline silicon raw material for the first time, and reduces the contents of impurities such as B, P and the like in the polycrystalline silicon production liquid phase raw material.
According to the purification process of the polycrystalline silicon raw material of the present invention, the contents of impurities B and P in the liquid phase raw material for polycrystalline silicon production are reduced in a complexing form, and the impurities content of a polycrystalline silicon product can be greatly reduced. Therefore, in the later rectification process, the number of stages of the rectification tower can be reduced, the energy consumption is reduced, the adsorbent consumption is reduced, facilitating the later rectification purification treatment, and reducing the rectification cost. Furthermore, the invention can be realized on the basis of the existing equipment, with simple operation, low investment and low cost.
While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that any simple modifications, equivalent changes made to the above embodiments according to the technical essence of the embodiments of the present invention still fall within the scope of the present invention.
Claims (7)
- Claims1. A purification process of a polycrystalline silicon raw material, characterized by comprising the following steps:pressurizing back-blown hydrogen of an adsorption tower in a vent gas recovery procedure in polycrystalline silicon production, and entering a quench tower of a cold hydrogenation procedure with a cold hydrogenation reaction vent gas, wherein the quench tower adopts a self-circulation; fully contacting, within the quench tower, a phosphorus-containing compound in the back-blown hydrogen with the cold hydrogenation reaction vent gas, a boron-containing compound and metal impurities in a kettle liquid for complexing; and carrying out preliminary condensation on a gas phase discharged from a top of the quench tower, and carrying out rectification for purification on a condensate;wherein the kettle liquid is a cold hydrogenation product.
- 2. The purification process of claim 1, characterized in that, the back-blown hydrogen is pressurized to 2.4-2.5 MPaG.
- 3. The purification process of claim 1, characterized in that, the kettle liquid enters from a middle part of the quench tower.
- 4. The purification process of claim 1, characterized in that, in the preliminary condensation procedure, a non-condensed gas phase is returned to the cold hydrogenation procedure.
- 5. The purification process of claim 1, characterized in that, in the purification process, the temperature of the quench tower is 30-230°C.
- 6. The purification process of claim 1, characterized in that, after the preliminary condensation on the gas phase discharged from a top of the quench tower, part of the condensate enters the quench tower as a reflux liquid.
- 7. The purification process of claim 6, characterized in that, the reflux liquid enters from an upper part of the quench tower.
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| CN101486465B (en) * | 2009-01-09 | 2011-06-01 | 北京先锋创新科技发展有限公司 | Production method of refined trichlorosilane |
| US8404205B2 (en) * | 2011-01-07 | 2013-03-26 | Mitsubishi Polycrystalline Silicon America Corporation (MIPSA) | Apparatus and method for producing polycrystalline silicon having a reduced amount of boron compounds by forming phosphorus-boron compounds |
| CN102328906B (en) * | 2011-07-18 | 2014-02-12 | 中国科学院大连化学物理研究所 | Recycling hydrogen purification processing method for producing polysilicon by reducing trichlorosilane |
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