CN110156026A - A kind of purification process of polysilicon raw material - Google Patents

Abstract

The invention relates to a process for purifying polysilicon raw materials. A process for purifying polysilicon raw materials, comprising the following steps: pressurizing the backflush hydrogen in the adsorption tower in the tail gas recovery process of polysilicon production, and then entering the quench tower in the cold hydrogenation process with the tail gas of the cold hydrogenation reaction, and the quench tower adopts self-circulation; The phosphorus-containing compound in the backflushing hydrogen mentioned above, and the cold hydrogenation reaction tail gas, the boron-containing compound and metal impurities in the tower still liquid, are fully contacted in the quenching tower to carry out complexation; the gas phase coming out of the top of the quenching tower is initially condensed , the condensate is purified by rectification; wherein, the bottom liquid of the tower is a cold hydrogenation product. The purification process of a polysilicon raw material according to the present invention reduces the B and P impurity content in the liquid phase raw material for polysilicon production through complexation, so that in the later rectification process, the number of rectification tower stages can be reduced and energy consumption can be reduced , Reduce the amount of adsorbent, and realize on the basis of existing equipment, simple operation, low investment and low cost.

Description

A kind of purification process of polysilicon raw material

technical field

The invention belongs to the technical field of polysilicon, and in particular relates to a process for purifying polysilicon raw materials.

Background technique

There are two main processes for global polysilicon production, namely the improved Siemens process and the silane process. From the perspective of production capacity comparison, the improved Siemens process accounts for more than 90% of the total production capacity, and the silane process accounts for less than 10%.

In polysilicon production, the B and P impurity content is the main index to determine the quality of polysilicon. The existing improved Siemens method production process mainly produces B, P and other impurities in high-purity silicon tetrachloride (TCS) by removing polysilicon. To achieve the purpose of improving the quality of polysilicon products. The removal of high-purity TCS impurities mainly includes rectification, adsorption and other methods. With the maturity of polysilicon production process and the expansion of production capacity, polysilicon downstream enterprises have higher and higher requirements for the quality of polysilicon products. In order to ensure the quality of polysilicon products, polysilicon manufacturers improve the quality of high-purity TCS by increasing the number of rectification stages, increasing the reflux ratio, increasing the number of theoretical plates, etc., and adopting a large number of adsorption processes, so as to achieve stable polysilicon product quality .

But there are certain shortcomings in these methods: (1) the energy consumption of the rectification mode adopting large reflux ratio is higher. (2) Increase the number of rectification stages and increase the number of theoretical plates in the rectification column. (3) The adsorbent in the adsorption process needs to be replaced after saturation, and the environmental protection treatment requirements of the adsorbent are relatively high.

In view of this, the present invention proposes a new polysilicon purification process.

Contents of the invention

The object of the present invention is to provide a polysilicon raw material purification process, which can reduce the impurity content of polysilicon production liquid phase raw materials such as B and P in the form of complexation, and can greatly reduce the impurity content of polysilicon products.

In order to achieve the above purpose, the adopted technical scheme is:

A purification process for polysilicon raw materials, comprising the following steps:

After pressurizing the blowback hydrogen in the adsorption tower in the tail gas recovery process in polysilicon production, it enters the quench tower in the cold hydrogenation process with the tail gas of the cold hydrogenation reaction, and the quench tower adopts self-circulation; the phosphorus-containing compound in the backflush hydrogen, and The tail gas of the cold hydrogenation reaction, boron-containing compounds and metal impurities in the tower kettle liquid are fully contacted in the quenching tower for complexation;

After the gas phase from the top of the quenching tower is condensed initially, the condensate is purified by rectification;

Wherein, the tower bottom liquid is a cold hydrogenation product.

Further, the backflushing hydrogen is pressurized to 2.4-2.5MPaG.

Further, the liquid in the bottom of the tower enters from the middle of the quenching tower.

Further, during the preliminary condensation process, the uncondensed gas phase is returned to the cold hydrogenation process.

Further, in the purification process, the temperature of the quench tower is 30-230°C.

Further, the gas phase coming out of the top of the quench tower is preliminarily condensed, and part of the condensed liquid enters the quench tower as reflux liquid.

Still further, the reflux liquid enters from the upper part of the quenching tower.

Compared with prior art, the beneficial effect of the present invention is:

1. The purification process of a polysilicon raw material according to the present invention reduces the B and P impurity content in the liquid phase raw material for polysilicon production through complexation.

2. The purification process of a polysilicon raw material according to the present invention greatly reduces the impurity content in the cold hydrogenation product before the rectification process, so that in the later rectification process, the difficulty and cost of the rectification process can be reduced, and the The number of rectification towers reduces energy consumption and the amount of adsorbent.

3. The polysilicon raw material purification process described in the present invention can greatly reduce the impurity content of polysilicon products.

4. A polysilicon raw material purification process according to the present invention makes full use of the system products produced by polysilicon, and is realized on the basis of existing equipment, with simple operation, low investment and low cost.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

In order to further elaborate the purification process of a kind of polysilicon raw material of the present invention, achieve the expected purpose of the invention, below in conjunction with preferred embodiment, to the purification process of a kind of polysilicon raw material proposed according to the present invention, its specific implementation, structure, feature and effect , as detailed below. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures or characteristics of one or more embodiments may be combined in any suitable manner.

Before elaborating the purification process of a polysilicon raw material of the present invention in detail, it is necessary to further explain the raw materials and methods mentioned in the present invention in order to achieve better results.

The tower bottom liquid described in this application is a product of cold hydrogenation, the main component is chlorosilane, and the rest are impurities, including boron-containing compounds and metal impurities.

The principle of the present invention is that impurities such as compounds of P and B are very close to the boiling point of the product chlorosilane, so they are difficult to remove. The invention converts P and B compounds, metal impurities, etc. into complexes with high boiling points, and effectively removes P, B, metals, and other impurities by utilizing the characteristics of large differences in boiling points.

Phosphorus-containing compounds are contained in the backflush hydrogen, boron-containing compounds, metal impurities, silicon powder and dust are contained in the tail gas of the cold hydrogenation reaction, and boron-containing compounds and metal impurities are contained in the tower bottom liquid. Backflushing hydrogen, cold hydrogenation reaction tail gas and tower bottom liquid are fully contacted in the quenching tower. That is, the liquid phase and the gas phase are fully contacted in the quenching tower, and the gas phase and the gas phase are fully contacted in the quenching tower, and the compounds of P and B are fully reacted and complexed to form a complex with a higher boiling point. The complex is circulated in the liquid phase through the quenching tower, and then complexed with the cold hydrogenation reaction tail gas and the metal impurities in the cold hydrogenation product to form a complex with a higher boiling point and remove the metal impurities in the product.

Due to the high boiling point of the complex, it is not easy to form a gaseous state together with chlorosilane, which can effectively reduce the content of boron, phosphorus, metal and other impurities in the gaseous chlorosilane coming out of the top of the quenching tower. The complex with a higher boiling point can be removed in the tower bottom liquid by utilizing the characteristics of a large difference in boiling point at a later stage.

In the present invention, the tail gas recovery adsorption tower blows back the hydrogen into the cold hydrogenation quenching tower, so that the reduction product in the backflush hydrogen is complexed with the cold hydrogenation product. These raw materials are the products of the system for producing polysilicon, and the cost is low.

MPaG is a unit of pressure and means gauge pressure.

The "G" in MPaG stands for gauge pressure, which is the pressure indicated by the pressure gauge. Not absolute pressure, but relative pressure.

Cl ₃ B: PH ₃ means that Cl ₃ B and PH ₃ are complexed.

Cl ₄ B ₂ : P ₂ H ₄ means that Cl ₄ B ₂ : P ₂ H ₄ is complexed.

After having understood above-mentioned raw material and method etc., the purification process of a kind of polysilicon raw material of the present invention will be described in further detail below in conjunction with specific embodiment and Fig. 1:

Technical scheme of the present invention is:

After pressurizing the blowback hydrogen of the adsorption tower in the tail gas recovery process of polysilicon production, it enters the quenching tower of the cold hydrogenation process with the tail gas of the cold hydrogenation reaction, and the quenching tower adopts self-circulation. The bottom liquid of the tower is a product of cold hydrogenation.

Backflush hydrogen (containing phosphorus-containing compounds) and cold hydrogenation reaction tail gas (containing boron-containing compounds, metal impurities, silicon powder and dust, etc.), tower bottom liquid (containing boron-containing compounds and metal impurities, etc.) are fully contacted in the quench tower, The liquid phase and the gas phase are fully contacted in the quenching tower, and the gas phase and the gas phase are fully contacted in the quenching tower, and the compounds of P and B are fully reacted and complexed to form a complex with a higher boiling point (Cl ₃ B : PH ₃ and Cl ₄ B ₂ : P ₂ H ₄ etc.). The complex is circulated in the liquid phase through the quenching tower, and is complexed and adsorbed with the cold hydrogenation reaction tail gas and metal impurities in the cold hydrogenation product to form a complex with a higher boiling point (Cl ₃ B: PH ₃ and Cl ₄ B ₂ : P ₂ H ₄ and other adsorption metal impurities), remove the metal impurities in the product.

And the tail gas of the cold hydrogenation reaction is in contact with the tower kettle liquid, which can wash impurities such as dust and silicon powder.

After the gas phase from the top of the quench tower is condensed initially, the condensate is sent to the rectification process for purification.

Preferably, the backflushing hydrogen is pressurized to 2.4-2.5MPaG. The backflush hydrogen needs to be pressurized to the same pressure as the cold hydrogenation reaction tail gas and enters the quench tower.

Preferably, the liquid in the tower bottom enters from the middle of the quenching tower, comes out from the bottom of the tower, and is transported to the middle of the tower through a pump, so that the liquid in the bottom of the tower can be contacted with backflushing hydrogen to the greatest extent.

Also, the quench tower needs to maintain flow balance. When the tower bottom liquid in the quenching tower decreases, the tower bottom liquid needs to be replenished.

Preferably, during the preliminary condensation process, the uncondensed gas phase is returned to the cold hydrogenation process, which can improve the utilization rate and realize economical maximization.

Preferably, in the purification process, the temperature of the quench tower is 30-230°C.

Preferably, the gas phase coming out of the top of the quenching tower is initially condensed, and part of the condensed liquid enters the quenching tower as reflux liquid. This step can maintain the inherent flow of the quench tower and maintain flow balance. And the existing equipment is adopted, and the cost is low.

Still further preferably, the reflux liquid enters from the upper part of the quenching tower. The reflux liquid enters from the upper part of the quench tower, that is, the liquid goes from top to bottom, which can better mass transfer and contact with the gas phase, which can reduce the temperature of the quench tower, improve safety, and wash away impurities such as dust and silicon powder.

Example 1.

Combined with Figure 1, the specific operation steps are as follows:

After pressurizing the blowback hydrogen of the adsorption tower in the tail gas recovery process of polysilicon production to 2.5MPaG, it enters the quenching tower of the cold hydrogenation process with the tail gas of the cold hydrogenation reaction.

The quench tower adopts its own circulation. The temperature of the quenching tower is 230°C. The liquid in the tower kettle (the product of cold hydrogenation, the main component is chlorosilane, i.e. silicon tetrachloride) enters from the middle of the quenching tower, comes out from the bottom of the tower, and is transported to the middle of the tower by a pump, and the quenching tower needs Keep traffic balanced.

Phosphorus-containing compounds in the backflush hydrogen, and cold hydrogenation reaction tail gas, boron-containing compounds and metal impurities in the tower still liquid, fully contact in the quenching tower to form complexes with higher boiling points. And the full contact between the gas phase and the liquid phase can wash away impurities such as dust and silicon powder.

The gas phase from the top of the quenching tower is sent to the condenser for preliminary condensation, and the uncondensed gas phase is returned to the cold hydrogenation process, and the condensate is collected in the reflux tank of the quenching tower, and part of the condensate is used as reflux liquid, which enters from the upper part of the quenching tower through a pump Quenching tower, the rest of the condensate goes to rectification and purification.

Example 2.

The operation steps of embodiment 2 are the same as embodiment 1. The difference is that the temperature of the quench tower is 30°C.

Example 3.

The operation steps of embodiment 3 are the same as embodiment 1. The difference is that the backflush hydrogen is pressurized to 2.4MPaG, and the temperature of the quench tower is 150°C.

Example 4.

The operation steps of embodiment 4 are the same as embodiment 1. The difference is that the backflush hydrogen is pressurized to 2.4MPaG, and the temperature of the quench tower is 120°C.

Example 5.

The operation steps of embodiment 5 are the same as embodiment 1. The difference is that the backflush hydrogen is pressurized to 2.4MPaG, and the temperature of the quenching tower is 100°C.

Analysis was performed on de-rectified chlorosilanes. Collect the gaseous phase coming out from the top of the quenching tower when no backflushing hydrogen is added in Example 1-5, and carry out the detection of the total impurity content of P, B, and metals. Collect the gaseous phase coming out from the top of the quenching tower after adding backflushing hydrogen in Example 1-5, and carry out the detection of the total impurity content of P, B, and metals. The results are shown in Table 1.

Table 1

Example Without backflushing hydrogen Add backflush hydrogen 1 3000ppbw 1700ppbw 2 1000ppbw 500ppbw 3 2100ppbw 1040ppbw 4 1860ppbw 890ppbw 5 2430ppbw 11320ppbw

As can be seen from Table 1, after adopting the present invention, in the gas phase coming out from the top of the quenching tower, the B, P and metal impurity contents are greatly reduced.

The complexation method is a common method in chemical production, and is widely used in chemical unit operations such as complexation catalysis, complexation reaction, and sewage treatment. However, the present invention is the first time that the complexation method is used in a chemical operation unit for the purification of polysilicon raw materials to reduce the content of impurities such as B and P in the liquid phase raw materials for polysilicon production.

The polysilicon raw material purification process described in the present invention can reduce the B and P impurity content in the polysilicon production liquid phase raw material in the form of complexation, and can greatly reduce the polysilicon product impurity content. In this way, in the rectification process in the later stage, the number of stages of rectification towers, energy consumption and the amount of adsorbent can be reduced, which facilitates rectification and purification treatment in the later stage and reduces the cost of rectification. In addition, the present invention can be realized on the basis of existing equipment, and has simple operation, low investment and low cost.

The above is only a preferred embodiment of the embodiment of the present invention, and does not limit the embodiment of the present invention in any form. Any simple modification, equivalent change and Modifications still fall within the scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. a kind of purifying technique of polycrystalline silicon raw material, which comprises the following steps:

In tail gas recycle process after the blowback pressurized with hydrogen of adsorption tower, it will enter with cold hydrogenation tail gas cold in production of polysilicon The chilling tower of hydrogenation process, chilling tower use repeats itself；Phosphorus-containing compound in the blowback hydrogen, with cold hydrogenation Boron-containing compound, metal impurities in tail gas, tower bottoms, come into full contact in chilling tower, are complexed；

For the gas phase that chilling top of tower comes out after tentatively condensing, condensate liquid goes rectification and purification；

Wherein, the tower bottoms is cold hydrogenation product.

2. purifying technique according to claim 1, which is characterized in that the blowback pressurized with hydrogen to 2.4-2.5MPaG.

3. purifying technique according to claim 1, which is characterized in that the tower bottoms in the middle part of chilling tower by entering.

4. purifying technique according to claim 1, which is characterized in that in the preliminary condensation process, uncooled gas Mutually return to cold hydrogenation process.

5. purifying technique according to claim 1, which is characterized in that in the purifying technique, the temperature of chilling tower is 30-230℃。

6. purifying technique according to claim 1, which is characterized in that the gas phase that the chilling top of tower comes out is by just Step condensation, partial condensation liquid enter chilling tower as phegma.

7. purifying technique according to claim 6, which is characterized in that the phegma enters from chilling tower top.