Method for cleaning junction silicon of heat exchanger

Abstract

The invention provides a cleaning method for heat exchanger junction silicon, and relates to the technical field of polycrystalline silicon production, and the method comprises the following steps: step 1, introducing HCl gas in the process that mixed gas of TCS, STC and H2 and silicon powder flow into a heat exchanger group tube pass from a hydrogenation reactor; 2, promoting STC, H2 and silicon powder to react again by HCl gas; and 3, etching the HCl gas and caked silicon powder in the tube pass of the heat exchanger unit. According to the method, the phenomenon of silicon junction in the tube pass of the heat exchanger group can be reduced, the heat exchange efficiency and the operation duration of the heat exchanger group are greatly enhanced, the maintenance frequency of the hydrogenation reactor is reduced, and the conversion rate of the hydrogenation reactor is improved. Meanwhile, the heat exchange efficiency of the heat exchanger set is enhanced, the power of the electric heater can be effectively reduced, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of polysilicon production, and in particular to a cleaning method for heat exchanger junction silicon. Background Art

[0002] In the cold hydrogenation process of polysilicon production, the STC (SiCl4) and H2 mixed gas entering the hydrogenation reactor needs to be heated as a whole to react with the silicon powder in the hydrogenation reactor to generate TCS (SiHCl3). During the reaction, due to various restrictions, a complete reaction cannot be achieved. A trace amount of silicon powder will enter the heat exchanger tube at the outlet of the hydrogenation reactor with the TCS, STC, and H2 mixed gas, and exchange heat with the STC and H2 mixed gas in the heat exchanger shell, eventually causing silicon deposition in the heat exchanger. This will affect the heat exchange efficiency of the heat exchanger, causing the power of the electric heater at the inlet of the hydrogenation reactor to increase, increasing energy consumption, and thus affecting the conversion rate of the hydrogenation reactor. Summary of the invention

[0003] The purpose of the present invention is to provide a method for cleaning silicon deposits on heat exchangers to alleviate the technical problems existing in the prior art that silicon deposits on heat exchangers affect heat exchange efficiency, increase energy consumption of electric heaters, and affect conversion rate of hydrogenation reactors in the cold hydrogenation process.

[0004] The present invention provides a method for cleaning silicon in a heat exchanger, comprising the following steps: Step 1: When the TCS, STC, H2 mixed gas and silicon powder flow from the hydrogenation reactor into the tube side of the heat exchanger group, HCl gas is introduced; Step 2: HCl gas promotes the reaction of STC, H2 and silicon powder again; Step 3: HCl gas etches the silicon powder agglomerated inside the tube of the heat exchanger group.

[0005] Further, in step 1, HCl gas is introduced into the connecting pipe between the hydrogenation reactor and the heat exchanger group through a compressor.

[0006] Furthermore, the Cl2 and H2 obtained during the chlor-alkali process are used to synthesize the required HCl gas.

[0007] Furthermore, in the chlor-alkali process, the NaCl concentrated solution obtained during the waste treatment is treated to remove impurities and electrolyzed to obtain Cl2, H2 and NaOH solutions.

[0008] Furthermore, the heat exchanger group includes a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger which are connected in sequence; the introduced HCl gas enters the tubes of the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger in sequence, and the three are cleaned in sequence.

[0009] Furthermore, the reaction in step 2 occurs in the connecting pipe between the hydrogenation reactor and the heat exchanger group, and in the tube side of the heat exchanger group.

[0010] Furthermore, before step 1, the method further includes the following steps: before the mixed gas of TCS, STC, H2 and silicon powder flows out of the hydrogenation reactor, a cyclone separation process is performed to filter the silicon powder.

[0011] The present invention provides a method for cleaning silicon deposits in a heat exchanger. During operation, when the STC and H2 mixed gas passes through the shell side of the heat exchanger group, it exchanges heat with the TCS, STC, and H2 mixed gas that enters the tube side of the heat exchanger group after the reaction in the hydrogenation reactor, and then enters the hydrogenation reactor after being heated by an electric heater to react with the silicon powder in the hydrogenation reactor. The reacted TCS, STC, and H2 mixed gas and the silicon powder that has not reacted completely flow into the tube side of the heat exchanger group again. During this process, HCl gas is introduced, and the HCl gas promotes the STC, H2 and silicon powder to react again to generate TCS, and consumes the mixed silicon powder. When the HCl gas contacts the silicon powder agglomerated inside the tube side of the heat exchanger group, the silicon powder is etched to generate TCS, thereby reducing silicon deposits inside the tube side of the heat exchanger group.

[0012] As can be seen from the above, the above method can reduce the occurrence of silicon deposition inside the tube of the heat exchanger group, greatly enhance the heat exchange efficiency and operation time of the heat exchanger group, reduce the inspection and maintenance frequency of the hydrogenation reactor, and improve the conversion rate of the hydrogenation reactor. At the same time, the heat exchange efficiency of the heat exchanger group is enhanced, which can effectively reduce the power of the electric heater, thereby reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 A flowchart of a method for cleaning silicon junctions of a heat exchanger provided by an embodiment of the present invention; Figure 2 A schematic structural diagram of a cold hydrogenation process apparatus provided in an embodiment of the present invention.

[0015] Icons: 1-hydrogenation reactor; 2-heat exchanger group; 3-electric heater; 4-compressor; 5-cyclone separator; 6-silicon powder feed port; 7-air inlet; 8-air outlet; 201-primary heat exchanger; 202-secondary heat exchanger; 203-tertiary heat exchanger. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] like Figure 1 and Figure 2 As shown, a method for cleaning silicon agglomerates in a heat exchanger provided by an embodiment of the present invention comprises the following steps: Step 1: In the process of TCS, STC, H2 mixed gas and silicon powder flowing from the hydrogenation reactor 1 into the tube side of the heat exchanger group 2, HCl gas is introduced; Step 2: HCl gas promotes the reaction of STC, H2 and silicon powder again; Step 3: HCl gas etches the silicon powder agglomerated inside the tube side of the heat exchanger group 2.

[0018] Specifically, the TCS gas is SiHCl3, and the STC gas is SiCl4.

[0019] The chemical reaction equation involved in step 2 is: 2SiCl4+Si+H2+HCl=3SiHCl3 The chemical reaction equation involved in step 3 is: 3HCl+Si=SiHCl3+H2 Furthermore, the reaction in step 2 occurs in the connecting pipe between the hydrogenation reactor 1 and the heat exchanger group 2, and in the tube side of the heat exchanger group 2.

[0020] Specifically, during the reaction process of step 3, step 2 can continue to react, that is, when the HCl gas performs an etching reaction in the tube side of the heat exchanger group 2, it also simultaneously promotes the reaction of STC, H2 and silicon powder again.

[0021] Specifically, silicon powder is fed into the lower part of the cylinder of the hydrogenation reactor 1. A silicon powder feed port 6 is provided at the lower part of the cylinder of the hydrogenation reactor 1. An inlet 7 for a mixed gas of STC and H2 is also provided at the lower part. An outlet 8 for a mixed gas of TCS, STC and H2 is provided at the upper part of the cylinder of the hydrogenation reactor 1.

[0022] Furthermore, a jacket may be provided outside the hydrogenation reactor 1, an annular cavity is formed between the jacket and the shell of the hydrogenation reactor 1, and a pressure measuring port and a temperature measuring port are provided at the lower part of the jacket.

[0023] The embodiment of the present invention provides a method for cleaning silicon deposits in a heat exchanger. During operation, when the STC and H2 mixed gas passes through the shell side of the heat exchanger group 2, it exchanges heat with the TCS, STC, and H2 mixed gas that enters the tube side of the heat exchanger group 2 after the reaction of the hydrogenation reactor 1, and then enters the hydrogenation reactor 1 after being heated by the electric heater 3 to react with the silicon powder in the hydrogenation reactor 1. The reacted TCS, STC, and H2 mixed gas and the incompletely reacted silicon powder flow into the tube side of the heat exchanger group 2 again. During this process, HCl gas is introduced, and the HCl gas promotes the reaction of STC, H2 and silicon powder to generate TCS again, and consumes the mixed silicon powder. When the HCl gas contacts the silicon powder agglomerated inside the tube side of the heat exchanger group 2, the silicon powder is etched to generate TCS, thereby reducing the silicon deposits inside the tube side of the heat exchanger group 2.

[0024] As can be seen from the above, the above method can reduce the occurrence of silicon deposition inside the tube of the heat exchanger group 2, greatly enhance the heat exchange efficiency and operation time of the heat exchanger group 2, reduce the inspection and maintenance frequency of the hydrogenation reactor 1, and improve the conversion rate of the hydrogenation reactor 1. At the same time, the heat exchange efficiency of the heat exchanger group 2 is enhanced, which can effectively reduce the power of the electric heater 3, thereby reducing energy consumption.

[0025] On the basis of the above embodiment, further, in step 1, HCl gas is introduced into the connecting pipe between the hydrogenation reactor 1 and the heat exchanger group 2 through the compressor 4.

[0026] Specifically, when introducing HCl gas, the gas flow rate is set to: 600-1000m 3 , the temperature is room temperature, the pressure is 2.9-3.3MPa, and the purity of the HCl gas introduced is 50-100%.

[0027] In this embodiment, the staff pressurizes the HCl gas through the compressor 4 and passes it into the connecting pipe between the hydrogenation reactor 1 and the heat exchanger group 2, so that the HCl gas can be quickly mixed into the mixed gas to improve the reaction efficiency.

[0028] On the basis of the above embodiment, the Cl2 and H2 obtained in the chlor-alkali process are further used to synthesize the required HCl gas.

[0029] In this embodiment, the gas obtained in the chlor-alkali process is used to react with the required HCl gas, which can save production raw materials and is more environmentally friendly.

[0030] On the basis of the above embodiment, further, in the chlor-alkali process, the NaCl concentrated solution obtained during the waste treatment is treated to remove impurities and electrolyzed to obtain Cl2, H2 and NaOH solutions.

[0031] In this embodiment, the NaCl concentrate obtained from waste treatment is electrolyzed to obtain Cl2 and H2, thereby synthesizing HCl gas, which solves the problem of comprehensive utilization of by-products and reduces the amount of production waste discharged.

[0032] On the basis of the above embodiment, further, the heat exchanger group 2 includes a primary heat exchanger 201, a secondary heat exchanger 202 and a tertiary heat exchanger 203 which are connected in sequence; the introduced HCl gas enters the tubes of the primary heat exchanger 201, the secondary heat exchanger 202 and the tertiary heat exchanger 203 in sequence, and the three are cleaned in sequence.

[0033] Specifically, the STC and H2 mixed gas enters the shell side of the tertiary heat exchanger 203, the secondary heat exchanger 202 and the primary heat exchanger 201 in sequence, and the TCS, STC, and H2 mixed gas flowing out from the outlet of the hydrogenation reactor 1 enters the tube side of the primary heat exchanger 201, the secondary heat exchanger 202 and the tertiary heat exchanger 203 in sequence, and the two mixed gases undergo heat exchange.

[0034] In this embodiment, the series connection of multiple heat exchangers can improve the heat exchange efficiency, reduce the power of the electric heater 3, thereby reducing energy consumption and being more environmentally friendly.

[0035] On the basis of the above embodiment, further, before step 1, the following steps are included: before the TCS, STC, H2 mixed gas and silicon powder flow out of the hydrogenation reactor 1, a cyclone separation process is performed to filter the silicon powder.

[0036] Specifically, a cyclone separator 5 is provided inside the hydrogenation reactor 1 to perform a cyclone separation process. The cyclone separator 5 separates the unreacted silicon powder and the mixed gas of TCS, STC and H2 by centrifugal action.

[0037] In this embodiment, the cyclone separation process can filter out some micro-reacted silicon powder in advance, reducing the pressure of subsequent cleaning of silicon.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for cleaning silicon in a heat exchanger, characterized in that: The following steps are involved: Step 1: When the TCS, STC, H2 mixed gas and silicon powder flow from the hydrogenation reactor into the tube side of the heat exchanger group, HCl gas is introduced; Step 2: HCl gas promotes the reaction of STC, H2 and silicon powder again; Step 3: The HCl gas etches the silicon powder agglomerated inside the tube of the heat exchanger group.

2. The cleaning method for heat exchanger junction silicon according to claim 1, characterized in that: In step 1, HCl gas is introduced into the connecting pipe between the hydrogenation reactor and the heat exchanger group through a compressor.

3. The cleaning method for heat exchanger junction silicon according to claim 1 or 2, characterized in that: The Cl2 obtained during the chlor-alkali process is used to synthesize the required HCl gas with H2.

4. The cleaning method for heat exchanger junction silicon according to claim 3, characterized in that: In the chlor-alkali process, the NaCl concentrated solution obtained during waste treatment is treated to remove impurities and electrolyzed to obtain Cl2, H2 and NaOH solutions.

5. The cleaning method for heat exchanger junction silicon according to claim 1, characterized in that: The heat exchanger group includes a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger which are connected in sequence; the introduced HCl gas enters the tubes of the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger in sequence, and the three are cleaned in sequence.

6. The cleaning method for heat exchanger junction silicon according to claim 1, characterized in that: The reaction in step 2 occurs in the connecting pipe between the hydrogenation reactor and the heat exchanger group, and in the tube side of the heat exchanger group.

7. The cleaning method for heat exchanger junction silicon according to claim 1, characterized in that: Before step 1, the following steps are also included: Before the mixed gas of TCS, STC, H2 and silicon powder flows out of the hydrogenation reactor, a cyclone separation process is performed to filter the silicon powder.

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