Novel silicon slurry cold hydrogenation reaction system and method thereof

Abstract

The invention discloses a novel silicon slurry cold hydrogenation reaction system and method, and belongs to the field of chemical engineering. The system comprises a hydrogenation reactor, wherein the output end of a mixed discharge chute is connected with the top of the hydrogenation reactor through a raw material preheating system; the output end of the lower part of the hydrogenation reactor is sequentially connected with a raw material preheating system and a hydrogen preheater. A heat exchange network is optimized, raw materials are preheated through reaction product gas, and system energy is effectively utilized.

Description

Technical Field

[0001] The invention patent belongs to the field of polysilicon production and relates to a new silicon slurry cold hydrogenation reaction system and method Background Art

[0002] Currently, polysilicon production primarily relies on the modified Siemens process. This process consumes 19 to 24 tons of trichlorosilane (TCS) per ton of polysilicon, while also producing 15 to 20 tons of silicon tetrachloride (STC) as a byproduct. These byproducts react with air to form silicic acid and hydrogen chloride, severely polluting the environment and harming human health. The most effective method for recovering silicon tetrachloride is cold chlorination, which converts it into trichlorosilane. This allows for a closed-loop material cycle within the plant, optimizes the process, and achieves zero pollutant emissions.

[0003] Cold hydrogenation technology mainly uses a catalyst to generate trichlorosilane by mixing silicon powder, hydrogen and silicon tetrachloride in a fluidized bed reactor at a temperature of 400℃ to 800℃ and a pressure of 2MPaG to 4MPaG. The main reaction equation is as follows: Si + 2SiCl4 + H2 + HCl = 3SiHCl3

[0004] However, the existing cold hydrogenation system uses solid-state silicon powder feed, which may cause the following problems:

[0005] 1. During the silicon powder transportation process, silicon powder particles will cause a certain degree of wear on the pipeline and equipment, affecting the durability of the equipment and the stability of the system;

[0006] 2. Silica fume has the characteristic of easily clogging pipes. When configuring pipes, it is necessary to use elbows with larger radius and slope design;

[0007] 3. Silicon powder needs to undergo strict drying treatment before use. This process will consume a large amount of hydrogen resources and energy, which will have a direct impact on production costs and resource utilization efficiency.

[0008] 4. Silicon powder has a certain explosion hazard, so its airtightness and explosion-proof measures must be fully considered during the transportation process to ensure production safety.

[0009] Therefore, in order to solve the above problems, it is necessary to develop a new silicon slurry cold hydrogenation reaction system. Summary of the Invention

[0010] The purpose of this patent is to provide a new silicon slurry cold hydrogenation reaction system and its preparation method, which solves the difficulties in silicon powder transportation in the trichlorosilane synthesis process and the problems of local overheating and frequent failure of traditional electric heaters causing device shutdown.

[0011] The purpose of the present invention can be achieved through the following technical solutions:

[0012] A novel silicon slurry cold hydrogenation reaction system includes a hydrogenation reactor, wherein the output end of a mixing discharge trough is connected to the top of the hydrogenation reactor through a raw material preheating system; the output end of the lower part of the hydrogenation reactor is connected to the raw material preheating system and a hydrogen preheater in sequence.

[0013] In the above system, the hydrogen output pipeline is connected to the top and the middle of the hydrogenation reactor respectively through the hydrogen preheater.

[0014] In the above system, an electric heating device is provided on the outer wall of the upper reaction zone of the cold hydrogenation reactor.

[0015] In the above system, an ash baffle is provided at the lower portion of the cold hydrogenation reactor.

[0016] In the above system, the output pipeline of hydrogen chloride is connected to the top of the cold hydrogenation reactor.

[0017] A method for realizing a novel silicon slurry cold hydrogenation reaction using the above-mentioned system comprises the following steps:

[0018] (1) mixing the silicon powder containing the catalyst and the liquid silicon tetrachloride into a slurry in a mixing and discharging tank, and maintaining the slurry in a uniform suspension state;

[0019] (2) The mixed slurry enters the raw material preheating system through the feed pump and undergoes multi-stage heat exchange with the high-temperature product gas produced by the cold hydrogenation reactor; at the same time, the hydrogen from the compressor exchanges heat with the product gas and is mixed with hydrogen chloride to obtain a mixed gas 1; the preheated slurry enters from the nozzle at the top of the reactor, and the mixed gas 1 after heat exchange enters the reactor uniformly at an angle of 20 to 40 degrees, vaporizes and reacts in the reaction zone 1-I, and then hydrogen is introduced into the middle of the reactor for the second time to promote the reaction to move in its positive direction, accelerate the reaction rate and improve the reactant conversion rate;

[0020] (3) The product gas leaves the reactor from the top of the separation zone 1-Ⅱ of the reactor, exchanges heat with the slurry and hydrogen, and then enters the downstream distillation section for purification and reduction to produce polysilicon.

[0021] In the above preparation method, the catalyst in step (1) is copper chloride, and the content of the catalyst in the silicon powder is 0.1 to 1 wt%.

[0022] In the above preparation method, in step (2), the flow ratio of hydrogen in the mixed gas 1 to the second hydrogen introduced is 3 to 5:1.

[0023] In the above preparation method, in step (2), the molar ratio of silicon powder, liquid silicon tetrachloride, hydrogen, and hydrogen chloride is 1:1-3:0.5-1.5:0.5-1.5.

[0024] In the above preparation method, the reaction temperature in step (2) is 500-550° C. and the pressure is 2-3 MPaG.

[0025] In the above preparation method, the mixed gas 1 enters the reactor 1 uniformly at an angle of 20 to 40 degrees for the following reasons: 1. to guide the flow of materials; 2. to prevent solid materials in the reactor from entering the pipeline and causing accumulation of materials.

[0026] Beneficial effects of the present invention:

[0027] The process technology of the synthetic trichlorosilane hydrogenation system, by changing the way silicon tetrachloride and silicon powder enter the reactor, optimizes the process to achieve the following beneficial effects:

[0028] (1) Trichlorosilane hydrogenation technology can be applied to various specifications of raw silicon, without the need for pre-drying, thus reducing resource and energy consumption;

[0029] (2) Silicon powder made into slurry effectively solves the problem of wear and blockage of pipes and equipment by silicon powder particles, improves the durability of equipment and pipes, and reduces production costs;

[0030] (3) In the system, silicon powder and liquid silicon tetrachloride are mixed into a slurry, which avoids problems such as airtightness and explosion-proof measures during silicon powder transportation and improves production safety;

[0031] (4) The cold hydrogenation reactor is equipped with an electric heating device, thereby eliminating the traditional raw material electric heater, avoiding local overheating and frequent failures that lead to device shutdown, and reducing equipment investment;

[0032] (5) Liquid silicon tetrachloride is mixed with raw silicon and then enters the reactor together with hydrogen. The reactants are evenly distributed and no distributor is required.

[0033] (6) After optimizing the heat exchange network, the reaction product gas is used to preheat the raw materials, making effective use of the system energy;

[0034] (7) A baffle is set in the separation zone below the reactor to reduce the content of unreacted silicon powder in the product gas;

[0035] (8) The mixed slurry can be pumped into the reactor, which is safe and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the patent structure of the present invention.

[0037] Among them, 1. Hydrogenation reactor (Ⅰ is the reaction zone, Ⅱ is the separation zone); 2. Raw material preheating system; 3. Mixing and discharging trough (including agitator); 4. Heating device; 5. Ash baffle; 6. Nozzle; 7. Hydrogen preheater; 8. Feed pump;

[0038] Logistics: 9. Slurry; 10. Waste residue; 11. Silicon powder; 12. Silicon tetrachloride; 13. Hydrogen chloride; 14. Hydrogen; 15. Product gas; 16. Primary hydrogen; 17. Secondary hydrogen. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the embodiments, but the protection scope of the present invention is not limited thereto:

[0040] like Figure 1 A novel silicon slurry cold hydrogenation reaction system includes a hydrogenation reactor 1, wherein the output end of the mixing discharge trough is connected to the top of the hydrogenation reactor 1 through a raw material preheating system 2; the output end of the lower part of the hydrogenation reactor 1 is connected to the raw material preheating system 2 and the hydrogen preheater 7 in sequence. The hydrogen output pipeline is connected to the top and the middle of the hydrogenation reactor 1 respectively through the hydrogen preheater 7. An electric heating device (4) is provided on the outer wall of the upper reaction zone of the cold hydrogenation reactor 1. An ash baffle 5 is provided at the lower part of the cold hydrogenation reactor 1. The output pipeline of hydrogen chloride is connected to the top of the cold hydrogenation reactor 1.

[0041] Example 1

[0042] Silicon powder containing 0.5 wt% catalytic copper chloride and liquid silicon tetrachloride are mixed into a slurry 9 in a mixing and discharging tank, maintaining a uniform suspension. The mixed slurry enters a feed preheating system 2 via a feed pump 8, undergoing multi-stage heat exchange with the high-temperature product gas 15 produced by a cold hydrogenation reactor 1. Simultaneously, hydrogen 14 from a compressor exchanges heat with the product gas and then mixes with hydrogen chloride to produce a mixed gas 1. The preheated slurry enters the reactor through a nozzle 6 at the top. The heat-exchanged mixed gas 1 enters the reactor 1 uniformly at an angle of 20 to 40 degrees, vaporizing and reacting within reaction zone 1-I. Hydrogen is then introduced a second time into the middle of the reactor to promote the reaction in its positive direction, accelerating the reaction rate and improving the reactant conversion rate. The flow ratio of hydrogen in the mixed gas 1 to the second introduced hydrogen is 4:1. The molar ratio of silicon powder, liquid silicon tetrachloride, hydrogen, and hydrogen chloride is 1:2:1:1. The reaction temperature in step (2) is 500-550° C., and the pressure is 2.5-2.8 MPaG.

[0043] The product gas leaves the reactor from the top of the separation zone 1-Ⅱ of the reactor, exchanges heat with the slurry and hydrogen, and then enters the downstream distillation section for purification and reduction to produce polysilicon.

[0044] Product gas specification parameter list

[0045] product Content wt% Remark Trichlorosilane 70％～80％ Main products Silicon tetrachloride 10％～15％ Incompletely reacted raw materials Hydrogen chloride 5％～10％ by-products hydrogen 1％～5％ Recyclable through recycling system Other chlorosilanes ≤1％ By-products such as dichlorosilane Metal impurities (total) <1ppm Such as Fe, Al, Cr, etc.

[0046] By adopting the new silicon slurry cold hydrogenation reaction system in this patent, the selectivity of trichlorosilane is improved, the concentration of by-products is reduced, the quality of the product gas is further improved, and the energy consumption of subsequent separation is reduced.

Claims

1. A novel silicon slurry cold hydrogenation reaction system, characterized in that: The system comprises a hydrogenation reactor (1), wherein the output end of a mixing discharge trough is connected to the top of the hydrogenation reactor (1) via a raw material preheating system (2); and the output end of the lower part of the hydrogenation reactor (1) is sequentially connected to the raw material preheating system (2) and a hydrogen preheater (7).

2. The novel silicon slurry cold hydrogenation reaction system according to claim 1, characterized in that: The hydrogen output pipeline is connected to the top and the middle of the hydrogenation reactor (1) through the hydrogen preheater (7).

3. The novel silicon slurry cold hydrogenation reaction system according to claim 1 is characterized in that: An electric heating device (4) is provided on the outer wall of the upper reaction zone of the cold hydrogenation reactor (1).

4. The novel silicon slurry cold hydrogenation reaction system according to claim 1, characterized in that: An ash baffle (5) is provided at the lower part of the cold hydrogenation reactor (1).

5. The novel silicon slurry cold hydrogenation reaction system according to claim 1, characterized in that: The output pipe of hydrogen chloride is connected to the top of the cold hydrogenation reactor (1).

6. A method for realizing a novel silicon slurry cold hydrogenation reaction using the system according to claim 1, characterized in that: The method comprises the following steps: (1) mixing silicon powder containing a catalyst and liquid silicon tetrachloride into a slurry in a mixing and discharging tank (9), and maintaining the slurry in a uniform suspension state; (2) The mixed slurry enters the raw material preheating system (2) through the feed pump (8) and undergoes multi-stage heat exchange with the high-temperature product gas (15) produced by the cold hydrogenation reactor (1); at the same time, the hydrogen (14) from the compressor exchanges heat with the product gas and is mixed with hydrogen chloride to obtain a mixed gas 1; the preheated slurry enters from the nozzle (6) at the top of the reactor, and the mixed gas 1 after heat exchange enters the reactor (1) uniformly at an angle of 20 to 40 degrees, vaporizes and reacts in the reaction zone 1-I, and then hydrogen is introduced into the middle of the reactor for the second time to promote the reaction to move in its positive direction, accelerate the reaction rate and improve the reactant conversion rate; (3) The product gas leaves the reactor from the top of the separation zone 1-Ⅱ of the reactor, exchanges heat with the slurry and hydrogen, and then enters the downstream distillation section for purification and reduction to produce polysilicon.

7. The method according to claim 6, characterized in that The catalyst described in step (1) is copper chloride, and the content of the catalyst in the silicon powder is 0.1-1 wt%.

8. The method according to claim 6, characterized in that In step (2), the flow ratio of hydrogen in the mixed gas 1 to the second hydrogen introduced is 3 to 5:

1.

9. The method according to claim 6, characterized in that In step (2), the molar ratio of silicon powder, liquid silicon tetrachloride, hydrogen and hydrogen chloride is 1:1-3:0.5-1.5:0.5-1.

5.

10. The method according to claim 6, characterized in that The reaction temperature in step (2) is 500-550° C. and the pressure is 2-3 MPaG.

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