Polycrystalline silicon cold hydrogenation reaction system and reaction method

Abstract

The invention provides a polycrystalline silicon cold hydrogenation reaction system and a polycrystalline silicon cold hydrogenation reaction method. The polycrystalline silicon cold hydrogenation reaction system comprises a coarse separation tower, a cold hydrogenation reactor, a first preheater, a second preheater, an air cooler, a first cooler, a second cooler, a first heat exchanger and a third cooler. According to the reaction system, the consumption of a cooling medium can be reduced, the energy consumption of the reaction system is reduced, the production cost is saved, the contents of high-boiling residues and metal chlorides in silicon tetrachloride laterally collected by the coarse separation tower can be reduced, the corrosion to equipment and pipelines of a cold hydrogenation reaction system is reduced, and the long-period operation of the cold hydrogenation reaction system is ensured.

Description

Technical Field

[0001] The invention relates to a polysilicon cold hydrogenation reaction system and a reaction method, belonging to the technical field of chemical separation. Background Art

[0002] The modified Siemens process is one of the methods for preparing high-purity polysilicon. It converts silicon tetrachloride into trichlorosilane through cold hydrogenation to achieve the comprehensive utilization of silicon tetrachloride. It is one of the important signs of the transition from the traditional Siemens process to the modified Siemens process.

[0003] At present, cold hydrogenation technology mainly uses a catalyst to react silicon powder, hydrogen and silicon tetrachloride in a cold hydrogenation reactor to generate trichlorosilane at a temperature of 400°C to 800°C and a pressure of 2MPa to 4MPa. The reaction tail gas (including unreacted silicon tetrachloride, unreacted hydrogen, unreacted silicon powder and trichlorosilane generated by the reaction) is output from the top of the cold hydrogenation reactor for dust removal and is cooled in one step using a cooling medium to obtain circulating hydrogen and chlorosilane solution in the reaction tail gas. The obtained chlorosilane solution enters a coarse separation tower for separation, and trichlorosilane is extracted from the top of the coarse separation tower, and silicon tetrachloride is extracted from the middle section of the coarse separation tower to continue to participate in the cold hydrogenation reaction.

[0004] However, the use of one-step cooling in the prior art easily increases the consumption of cooling medium and the energy consumption of the reaction system, and the side-sampled silicon tetrachloride contains more high-boiling substances and metal chlorides, which is not conducive to the long-term operation of the cold hydrogenation reaction system. Summary of the invention

[0005] The invention provides a polysilicon cold hydrogenation reaction system, which can reduce the consumption of cooling medium, reduce the energy consumption of the reaction system, save production costs, and can reduce the content of high boiling points and metal chlorides in silicon tetrachloride sampled from the coarse fractionation tower side, reduce the corrosion of equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system.

[0006] The polysilicon cold hydrogenation reaction method of the present invention is carried out using the above-mentioned reaction system. The reaction method can not only reduce the consumption of cooling medium, reduce the energy consumption of the reaction system, and save production costs, but also reduce the content of high boiling substances and metal chlorides in silicon tetrachloride sampled from the coarse fractionation tower side, reduce the corrosion of equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system.

[0007] The present invention provides a polysilicon cold hydrogenation reaction system, which includes a coarse fractionation tower, a cold hydrogenation reactor, an air cooler, a first preheater, a second preheater, a first cooler, a second cooler, a first heat exchanger and a third cooler;

[0008] The outlet of the cold hydrogenation reactor is communicated with the inlet of the reboiler of the coarse fraction tower, the outlet of the reboiler is communicated with the heat source inlet of the first preheater, the heat source outlet of the first preheater is communicated with the heat source inlet of the second preheater, the silicon tetrachloride outlet of the coarse fraction tower is communicated with the cold source inlet of the second preheater, and the heat source outlet of the second preheater is communicated with the inlet of the air cooler;

[0009] The outlet of the air cooler is communicated with the inlet of the first cooler, the gas phase outlet of the first cooler is communicated with the inlet of the second cooler, the gas phase outlet of the second cooler is communicated with the heat source inlet of the first heat exchanger, the heat source outlet of the first heat exchanger is communicated with the inlet of the third cooler, the gas phase outlet of the third cooler is communicated with the heat exchange medium inlet of the first heat exchanger, and the heat exchange medium outlet of the first heat exchanger is communicated with the cold source inlet of the first preheater;

[0010] The liquid phase outlet of the first preheater, the liquid phase outlet of the second preheater, the liquid phase outlet of the first cooler, the liquid phase outlet of the second cooler, the liquid phase outlet of the first heat exchanger, and the liquid phase outlet of the third cooler are respectively connected to the feed port of the coarse fractionation tower;

[0011] The silicon tetrachloride outlet is located at the 26th to 46th tower plate below the feed port;

[0012] The cooling medium in the first cooler is circulating water, the cooling medium in the second cooler is at least one of chilled water, ethylene glycol, and -25°C Freon, and the cooling medium in the third cooler is -45°C Freon.

[0013] The reaction system as described above, wherein it further comprises a silicon tetrachloride buffer tank, and the silicon tetrachloride outlet is connected to the silicon tetrachloride buffer tank;

[0014] The minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank is 8-30m.

[0015] The reaction system as described above, wherein further comprises a second heat exchanger;

[0016] The chlorosilane solution enters the second heat exchanger through the cold source inlet of the second heat exchanger, the silicon tetrachloride outlet is connected to the heat source inlet of the second heat exchanger, the cold source outlet of the second heat exchanger is connected to the feed port, and the heat source outlet of the heat exchanger is connected to the silicon tetrachloride buffer tank.

[0017] The reaction system as described above, wherein the separation system further comprises a gas phase balance pipe;

[0018] The coarse fraction tower further comprises a gas phase equilibrium port, the gas phase equilibrium port is located at the 26th to 46th tower plate below the feed port, and the number of tower plates between the gas phase equilibrium port and the silicon tetrachloride outlet differs by 0-2;

[0019] The gas phase balance port is communicated with the silicon tetrachloride buffer tank through the gas phase balance pipe.

[0020] The reaction system as described above, wherein the pressure of the silicon tetrachloride buffer tank is 0.1-0.6 MPaG; and / or,

[0021] The top operating pressure of the crude fraction tower is 0.15-0.65 MPaG; and / or,

[0022] The top temperature of the crude fraction tower is 55-95°C.

[0023] The reaction system as described above, wherein in the chlorosilane solution, the mass percentage of silicon tetrachloride is 60.5-79.45%, the mass percentage of trichlorosilane is 20-35%, the mass percentage of dichlorosilane is 0.05-3%, the mass percentage of high boiling substances and metal chlorides is 0.5-1.5%, the mass percentage of hydrogen is 0.01-0.015%, and the mass percentage of hydrogen chloride is 0.004-0.009%.

[0024] The reaction system as described above, wherein, further comprises a washing and cooling unit, wherein the outlet of the cold hydrogenation reactor is connected to the inlet of the washing and cooling unit, and the outlet of the washing and cooling unit is connected to the inlet of the reboiler of the coarse fraction tower.

[0025] The reaction system as described above, wherein it also includes a heating vaporization unit, the cold source outlet of the first preheater is connected to the inlet of the heating vaporization unit, the cold source outlet of the second preheater is connected to the inlet of the heating vaporization unit, and the outlet of the heating vaporization unit is connected to the cold hydrogenation reactor.

[0026] The reaction system as described above, wherein it further comprises a detection unit and a pressure swing adsorption unit;

[0027] The heat exchange medium outlet of the first heat exchanger is connected to the detection unit, the outlet of the detection unit is connected to the inlet of the pressure swing adsorption unit, and the outlet of the pressure swing adsorption unit is connected to the cold source inlet of the first preheater; or,

[0028] The heat exchange medium outlet of the first heat exchanger is communicated with the detection unit, and the outlet of the detection unit is communicated with the cold source inlet of the first preheater.

[0029] The present invention provides a method for cold hydrogenation of polysilicon, wherein the method is carried out using the reaction system as described above.

[0030] The polysilicon cold hydrogenation reaction system of the present invention can reduce the consumption of cooling medium, reduce the energy consumption of the reaction system, save production costs, and reduce the content of high boiling substances and metal chlorides in silicon tetrachloride sampled from the side of the coarse separation tower, reduce the corrosion of equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system through the organic connection of the coarse separation tower, the cold hydrogenation reactor, the air cooler, the first cooler, the second cooler, the first heat exchanger, the third cooler, the first preheater and the second preheater.

[0031] The polysilicon cold hydrogenation reaction method of the present invention is carried out using the above-mentioned reaction system. The reaction method can not only reduce the consumption of cooling medium, reduce the energy consumption of the reaction system, and save production costs, but also reduce the content of high boiling substances and metal chlorides in silicon tetrachloride sampled from the coarse fractionation tower side, reduce the corrosion of equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 Schematic diagram of a polysilicon cold hydrogenation reaction system in some embodiments of the present invention;

[0034] Figure 2 FIG. 1 is a partial schematic diagram of a polysilicon cold hydrogenation reaction system in some embodiments of the present invention.

[0035] Description of reference numerals:

[0036] 1: Heating and vaporizing unit; 2: Cold hydrogenation reactor; 3: Washing and cooling unit; 4: Coarse fractionation tower; 5: Reboiler; 6: First preheater; 7: Second preheater; 8: Air cooler; 9: First cooler; 10: Second cooler; 11: First heat exchanger; 12: Third cooler; 13: Detection unit; 14: Pressure swing adsorption unit;

[0037] 21: Silicon tetrachloride buffer tank; 22: Second heat exchanger; 23: Gas phase balance pipe. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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.

[0039] Figure 1 Schematic diagram of a polysilicon cold hydrogenation reaction system in some embodiments of the present invention; Figure 2 FIG. 1 is a partial schematic diagram of a polysilicon cold hydrogenation reaction system in some embodiments of the present invention. Figure 1 and Figure 2 As shown, the first aspect of the present invention provides a polysilicon cold hydrogenation reaction system, which includes a coarse fractionation tower 4, a cold hydrogenation reactor 2, a first preheater 6, a second preheater 7, an air cooler 8, a first cooler 9, a second cooler 10, a first heat exchanger 11, and a third cooler 12;

[0040] The outlet of the cold hydrogenation reactor 2 is communicated with the inlet of the reboiler 5 of the coarse fraction tower 4, the outlet of the reboiler 5 is communicated with the heat source inlet of the first preheater 6, the heat source outlet of the first preheater 6 is communicated with the heat source inlet of the second preheater 7, the silicon tetrachloride outlet of the coarse fraction tower 4 is communicated with the cold source inlet of the second preheater 7, and the heat source outlet of the second preheater 7 is communicated with the inlet of the air cooler 8;

[0041] The outlet of the air cooler 8 is communicated with the inlet of the first cooler 9, the gas phase outlet of the first cooler 9 is communicated with the inlet of the second cooler 10, the gas phase outlet of the second cooler 10 is communicated with the heat source inlet of the first heat exchanger 11, the heat source outlet of the first heat exchanger 11 is communicated with the inlet of the third cooler 12, the gas phase outlet of the third cooler 12 is communicated with the heat exchange medium inlet of the first heat exchanger 11, and the heat exchange medium outlet of the first heat exchanger 11 is communicated with the cold source inlet of the first preheater 6;

[0042] The liquid phase outlet of the first preheater 6, the liquid phase outlet of the second preheater 7, the liquid phase outlet of the first cooler 9, the liquid phase outlet of the second cooler 10, the liquid phase outlet of the first heat exchanger 11, and the liquid phase outlet of the third cooler 12 are respectively connected to the feed port of the coarse fractionation tower 4;

[0043] The silicon tetrachloride outlet is located at the 26th to 46th tray below the feed port;

[0044] The cooling medium in the first cooler 9 is circulating water, the cooling medium in the second cooler 10 is at least one of chilled water, ethylene glycol, and -25°C Freon, and the cooling medium in the third cooler 12 is -45°C Freon.

[0045] In the present invention, silicon powder, catalyst, hydrogen and silicon tetrachloride undergo cold hydrogenation reaction in a cold hydrogenation reactor 2 to obtain polysilicon cold hydrogenation reaction tail gas including trichlorosilane, silicon tetrachloride and hydrogen, and the reaction tail gas is output through the outlet of the cold hydrogenation reactor 2 and enters the reboiler 5 of the coarse fractionation tower 4, and is used as a heat source for the reboiler 5 to provide heat for the reboiler 5. After utilizing part of the heat in the reaction tail gas, the reaction tail gas enters the first preheater 6 through the heat source inlet of the first preheater 6, and is cooled in the first preheater 6 to obtain a first intermediate reaction tail gas and liquid chlorosilane; the first intermediate The intermediate reaction tail gas is output through the heat source outlet of the first preheater 6, and enters the second preheater 7 through the heat source inlet of the second preheater 7. The circulating silicon tetrachloride is output through the silicon tetrachloride outlet of the coarse fraction tower 4, and enters the second preheater 7 through the cold source inlet of the second preheater 7. In the second preheater 7, the first intermediate reaction tail gas preheats the circulating silicon tetrachloride to increase the temperature of the circulating silicon tetrachloride to obtain preheated silicon tetrachloride, cooled reaction tail gas and liquid chlorosilane. The cooled reaction tail gas is output through the heat source outlet of the second preheater 7, and enters the air cooler 8 through the inlet of the air cooler 8.

[0046] The reaction tail gas is subjected to air cooling treatment in the air cooler 8. After the temperature of the reaction tail gas is preliminarily reduced, the reaction tail gas is output from the outlet of the air cooler 8 and enters the first cooler 9 through the inlet of the first cooler 9. In the first cooler 9, the circulating water performs a first cooling treatment on the reaction tail gas to further reduce the temperature of the reaction tail gas and convert part of the chlorosilane in the reaction tail gas into a chlorosilane solution; the reaction tail gas after the temperature is reduced is output through the gas phase outlet of the first cooler 9 and enters the second cooler 10 through the inlet of the second cooler 10. In the second cooler 10, at least one of chilled water, ethylene glycol, and -25°C Freon is used to perform a second cooling treatment on the reaction tail gas to further reduce the temperature of the reaction tail gas and convert part of the chlorosilane in the reaction tail gas into a chlorosilane solution; the reaction tail gas after the temperature is further reduced is output through the gas phase outlet of the second cooler 10 and enters the first heat exchanger 11 through the heat source inlet of the first heat exchanger 11. Heat exchange treatment is performed in the first heat exchanger 11 to further reduce the temperature of the reaction tail gas, and The chlorosilane in the reaction tail gas is further converted into a chlorosilane solution; the reaction tail gas after cooling is output through the heat source outlet of the first heat exchanger 11, and enters the third cooler 12 through the inlet of the third cooler 12, and the reaction tail gas is subjected to a third cooling treatment by Freon at -45°C in the third cooler 12 to further reduce the temperature of the reaction tail gas, convert part of the chlorosilane into a chlorosilane solution, and obtain circulating hydrogen. The obtained circulating hydrogen is output through the gas phase outlet of the third cooler 12, and enters the first heat exchanger 11 through the heat exchange medium inlet of the first heat exchanger 11, and is used as a heat exchange medium in the first heat exchanger 11 to reduce the temperature of the reaction tail gas. At the same time, the reaction tail gas will heat the circulating hydrogen to obtain the first intermediate circulating hydrogen. The first intermediate circulating hydrogen is output through the heat exchange medium outlet of the first heat exchanger 11, and enters the first preheater 6 through the cold source inlet of the first preheater 6. The reaction tail gas is cooled in the first preheater 6, and at the same time, the reaction tail gas will heat the first intermediate circulating hydrogen to obtain preheated circulating hydrogen;

[0047] The chlorosilane solution produced in the first preheater 6 can be output through the liquid phase outlet of the first preheater 6, and enter the coarse separation tower 4 through the feed port of the coarse separation tower 4 for coarse treatment; the chlorosilane solution produced in the second preheater 7 can be output through the liquid phase outlet of the second preheater 7, and enter the coarse separation tower 4 through the feed port of the coarse separation tower 4 for coarse treatment; the chlorosilane solution produced in the first cooler 9 can be output through the liquid phase outlet of the first cooler 9, and enter the coarse separation tower 4 through the feed port of the coarse separation tower 4 for coarse treatment; the chlorosilane solution produced in the second cooler 10 can be output through the outlet of the second cooler 10, and enter the coarse separation tower 4 through the feed port of the coarse separation tower 4 for coarse treatment; the chlorosilane solution produced in the third cooler 12 can be output through the outlet of the third cooler 12, and enter the coarse separation tower 4 through the feed port of the coarse separation tower 4 for coarse treatment;

[0048] The silicon tetrachloride obtained after the coarse treatment of the chlorosilane solution is taken out through the silicon tetrachloride outlet of the coarse separation tower 4, and the silicon tetrachloride outlet is located at the 26th to 46th tower plates below the feed inlet.

[0049] In the reaction system of the present invention, the reaction tail gas is processed in sequence by a coarse fractionation tower 4, a first preheater 6, a second preheater 7, an air cooler 8, a first cooler 9, a second cooler 10, a first heat exchanger 11 and a third cooler 12 to obtain a chlorosilane solution and circulating hydrogen, and then the circulating hydrogen is used again as a cold source to cool the reaction tail gas, so that the heat of the reaction tail gas can be fully utilized, the consumption of the cooling medium can be reduced, the energy consumption of the reaction system can be reduced, the production cost can be saved, and the competitiveness of the enterprise can be improved; the present invention also uses a coarse fractionation tower 4 with a specific structure to separate and process the chlorosilane solution to obtain circulating silicon tetrachloride and trichlorosilane, the coarse fractionation tower 4 has a high separation efficiency, can reduce the content of high boiling substances and metal chlorides in silicon tetrachloride, reduce the corrosion of the equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system.

[0050] In some embodiments of the present invention, a silicon tetrachloride buffer tank 21 is further included, and the silicon tetrachloride outlet is connected to the silicon tetrachloride buffer tank 21;

[0051] The minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 is 8-30 m.

[0052] Specifically, the silicon tetrachloride extracted through the silicon tetrachloride outlet enters the silicon tetrachloride buffer tank 21 for storage and standby.

[0053] The minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 of the present invention is 8-30m, which means that the vertical distance between the central axis of the silicon tetrachloride outlet and the plane where the top of the silicon tetrachloride buffer tank 21 is located is 8-30cm.

[0054] When the minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 is 8-30m, not only can the pipeline cost be reduced, but also silicon tetrachloride can flow to the silicon tetrachloride buffer tank 21 under the action of gravity, thereby reducing the transportation cost of silicon tetrachloride.

[0055] In some embodiments of the present invention, a second heat exchanger 22 is further included;

[0056] The chlorosilane solution enters the second heat exchanger 22 through the cold source inlet of the second heat exchanger 22, the silicon tetrachloride outlet is connected to the heat source inlet of the second heat exchanger 22, the cold source outlet of the second heat exchanger 22 is connected to the feed port, and the heat source outlet of the heat exchanger is connected to the silicon tetrachloride buffer tank 21.

[0057] Specifically, the chlorosilane solution enters the second heat exchanger 22 through the cold source inlet of the second heat exchanger 22, the circulating silicon tetrachloride is extracted through the silicon tetrachloride outlet, and enters the second heat exchanger 22 through the heat source inlet of the second heat exchanger 22. In the second heat exchanger 22, the circulating silicon tetrachloride will preheat the chlorosilane solution, and the chlorosilane will reduce the temperature of the circulating silicon tetrachloride. The preheated chlorosilane solution is output through the cold source outlet of the second heat exchanger 22 and enters the coarse fractionation tower 4 through the feed port, while the cooled circulating silicon tetrachloride is output through the heat source outlet of the second heat exchanger 22 and enters the silicon tetrachloride buffer tank 21.

[0058] The present invention utilizes the side-collected circulating silicon tetrachloride to preheat the chlorosilane solution and reduces the temperature of the circulating silicon tetrachloride, which can not only reduce the steam consumption of the coarse fractionation tower 4, reduce the energy consumption of the coarse fractionation tower 4, and improve the separation efficiency of the coarse fractionation tower 4, but also reduce the amount of cooling circulating water for the circulating silicon tetrachloride, thereby achieving further energy saving.

[0059] In some embodiments of the present invention, the separation system further comprises a gas phase balance pipe 23;

[0060] The coarse fraction tower 4 further comprises a gas phase equilibrium port, which is located at the 26th to 46th tower plates below the feed port, and the number of tower plates between the gas phase equilibrium port and the silicon tetrachloride outlet differs by 0 to 2;

[0061] The gas phase balance port is connected to the silicon tetrachloride buffer tank 21 through a gas phase balance pipe 23 .

[0062] It can be understood that when the gas phase equilibrium port is located at the 26th tower plate below the feed port, the silicon tetrachloride outlet can be located at the 26th to 28th tower plate below the feed port. When the number of tower plates between the gas phase equilibrium port and the silicon tetrachloride outlet differs by 0 to 2, the pressure of the gas phase equilibrium port can be kept as consistent as possible with the pressure of the silicon tetrachloride outlet.

[0063] Specifically, one end of the gas phase balance pipe 23 is connected to the gas phase balance port, and the other end of the gas phase balance pipe 23 is connected to the silicon tetrachloride buffer tank 21. Compared with the prior art in which the silicon tetrachloride buffer tank 21 is stabilized by using supplementary hydrogen, the present invention connects the silicon tetrachloride buffer tank 21 with the gas phase balance port through the gas phase balance pipe 23 to achieve pressure balance between the silicon tetrachloride buffer tank 21 and the silicon tetrachloride outlet of the coarse fractionation tower 4, which can reduce the discharge of waste gas when the silicon tetrachloride buffer tank 21 is fed with liquid.

[0064] Furthermore, when the difference in the number of tower plates between the gas phase equilibrium port and the silicon tetrachloride outlet is 0, that is, the gas phase equilibrium port and the silicon tetrachloride outlet are located at the same tower plate, the pressures of the gas phase equilibrium port and the silicon tetrachloride outlet can be more consistent, thereby achieving pressure balance between the silicon tetrachloride buffer tank 21 and the silicon tetrachloride outlet of the coarse fractionation tower 4, and reducing the discharge of waste gas when the silicon tetrachloride buffer tank 21 is filled with liquid.

[0065] Furthermore, the inventors have also found that when the pressure of the silicon tetrachloride buffer tank 21 is 0.1-0.6 MPaG, the pressure of the booster pump can be reduced to save energy.

[0066] The present invention can also select the operating pressure and temperature of the crude fractionation tower 4, in order to further improve the separation efficiency of the crude fractionation tower 4 and to extract silicon tetrachloride with higher purity. For example, in some embodiments of the present invention, the top operating pressure of the crude fractionation tower 4 is 0.15-0.65 MPaG; and / or,

[0067] The top temperature of the crude fraction tower 4 is 55-95°C.

[0068] In some embodiments of the present invention, in the chlorosilane solution, the mass percentage of silicon tetrachloride is 60.5-79.45%, the mass percentage of trichlorosilane is 20-35%, the mass percentage of dichlorosilane is 0.05-3%, the mass percentage of high boiling substances and metal chlorides is 0.5-1.5%, the mass percentage of hydrogen is 0.01-0.015%, and the mass percentage of hydrogen chloride is 0.004-0.009%.

[0069] In some embodiments of the present invention, the reaction system further comprises a washing and cooling unit 3, the outlet of the cold hydrogenation reactor 2 is connected to the inlet of the washing and cooling unit 3, and the outlet of the washing and cooling unit 3 is connected to the inlet of the reboiler 5 of the coarse fraction tower 4.

[0070] Specifically, the reaction tail gas is output through the outlet of the cold hydrogenation reactor 2, enters the washing and cooling unit 3 through the inlet of the washing and cooling unit 3, undergoes preliminary washing and cooling in the washing and cooling unit 3, and then is output through the outlet of the washing and cooling unit 3, enters the reboiler 5 of the coarse fractionation tower 4 through the inlet of the reboiler 5 of the coarse fractionation tower 4 for heat utilization.

[0071] In the present invention, by making the reaction system further include a washing and cooling unit 3, the reaction tail gas can be initially washed and cooled, thereby reducing the processing load of subsequent processes and extending the service life of the reaction system.

[0072] In some embodiments of the present invention, the reaction system also includes a heating vaporization unit 1, the cold source outlet of the first preheater 6 is connected to the inlet of the heating vaporization unit 1, the cold source outlet of the second preheater 7 is connected to the inlet of the heating vaporization unit 1, and the outlet of the heating vaporization unit 1 is connected to the cold hydrogenation reactor 2.

[0073] Specifically, the preheated circulating hydrogen is output through the cold source outlet of the first preheater 6, and enters the heating vaporization unit 1 through the inlet of the heating vaporization unit 1. The preheated silicon tetrachloride is output through the cold source outlet of the second preheater 7, and enters the heating vaporization unit 1 through the inlet of the heating vaporization unit 1. After the preheated circulating hydrogen and the preheated silicon tetrachloride are heated and vaporized in the heating vaporization unit 1, they are output through the outlet of the heating vaporization unit 1, enter the cold hydrogenation reactor 2 through the inlet of the cold hydrogenation reactor 2, and continue to participate in the cold hydrogenation reaction.

[0074] The present invention can realize resource recycling and save production costs by mixing preheated circulating hydrogen with preheated silicon tetrachloride to participate in cold hydrogenation reaction.

[0075] In some embodiments, the cold hydrogenation reaction system further includes a detection unit 13 and a pressure swing adsorption unit 14;

[0076] Among them, the cold source outlet of the first heat exchanger 11 is connected to the inlet of the detection unit 13, and the outlet of the detection unit 13 is respectively connected to the inlet of the pressure swing adsorption unit 14 and the cold source inlet of the first preheater 6; the outlet of the pressure swing adsorption unit 14 is connected to the cold source inlet of the first preheater 6, and the outlet of the heating vaporization unit 1 is connected to the inlet of the cold hydrogenation reactor 2.

[0077] The second aspect of the present invention provides a polysilicon cold hydrogenation reaction method, which is performed using the polysilicon cold hydrogenation reaction system of the first aspect.

[0078] The reaction method can make full use of the heat of the reaction tail gas, reduce the consumption of cooling medium, reduce the energy consumption of the reaction system, save production costs, and help improve the competitiveness of the enterprise; it can also improve the separation efficiency of the coarse fractionation tower 4, reduce the content of high boiling substances and metal chlorides in silicon tetrachloride, reduce the corrosion of equipment and pipelines of the cold hydrogenation reaction system, and ensure the long-term operation of the cold hydrogenation reaction system.

[0079] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0080] Example 1

[0081] The polysilicon cold hydrogenation reaction system of this embodiment includes: an air cooler 8, a first cooler 9, a second cooler 10, a first heat exchanger 11, a third cooler 12, a coarse fractionation tower 4, a reboiler 5, a first preheater 6, a second preheater 7, a detection unit 13, a pressure swing adsorption unit 14, a heating vaporization unit 1, a cold hydrogenation reactor 2, a washing and cooling unit 3, a silicon tetrachloride buffer tank 21, a second heat exchanger 22, and a gas phase balance pipe 23;

[0082] The outlet of the cold hydrogenation reactor 2 is communicated with the inlet of the washing and cooling unit 3, the gas phase outlet of the washing and cooling unit 3 is communicated with the reboiler 5 of the coarse fraction tower 4, the reboiler 5 is communicated with the heat source inlet of the first preheater 6, the liquid phase outlet of the first preheater 6 is communicated with the cold source inlet of the second heat exchanger 22, the cold source outlet of the first preheater 6 is communicated with the inlet of the heating vaporization unit 1; the heat source outlet of the first preheater 6 is communicated with the heat source inlet of the second preheater 7, the liquid phase outlet of the second preheater 7 is communicated with the cold source inlet of the second heat exchanger 22, the cold source outlet of the second preheater 7 is communicated with the inlet of the heating vaporization unit 1;

[0083] The cold source outlet of the second heat exchanger 22 is connected to the feed inlet of the coarse fraction tower 4, the silicon tetrachloride outlet of the coarse fraction tower 4 is connected to the heat source inlet of the second heat exchanger 22, the heat source outlet of the second heat exchanger 22 is connected to the silicon tetrachloride buffer tank 21, and the minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 is 16m; the silicon tetrachloride outlet is located at the 28th tower plate below the feed inlet, and the silicon tetrachloride outlet is located at the 28th tower plate below the feed inlet;

[0084] The outlet of the silicon tetrachloride buffer tank 21 is communicated with the cold source inlet of the second preheater 7, the heat source outlet of the second preheater 7 is communicated with the inlet of the air cooler 8, the outlet of the air cooler 8 is communicated with the inlet of the first cooler 9, the liquid phase outlet of the first cooler 9 is communicated with the chlorosilane inlet of the tetrachloride crude fractionation tower 4; the gas phase outlet of the first cooler 9 is communicated with the inlet of the second cooler 10, the liquid phase outlet of the second cooler 10 is communicated with the chlorosilane inlet of the crude fractionation tower 4; the gas phase outlet of the second cooler 10 is communicated with the heat source inlet of the first heat exchanger 11, and the heat source inlet of the first heat exchanger 11 is communicated with the heat source inlet of the first heat exchanger 11. The source outlet is communicated with the inlet of the third cooler 12, the liquid phase outlet of the third cooler 12 is communicated with the chlorosilane inlet of the coarse fractionation tower 4, the gas phase outlet of the third cooler 12 is communicated with the cold source inlet of the heat exchanger 11, the cold source outlet of the first heat exchanger 11 is communicated with the inlet of the detection unit 13, the outlet of the detection unit 13 is respectively communicated with the inlet of the pressure swing adsorption unit 14 and the cold source inlet of the first preheater 6; the outlet of the pressure swing adsorption unit 14 is communicated with the cold source inlet of the first preheater 6, and the outlet of the heating vaporization unit 1 is communicated with the inlet of the cold hydrogenation reactor 2;

[0085] The cooling medium in the first cooler is circulating water, the cooling medium in the second cooler is ethylene glycol, and the cooling medium in the third cooler is -45℃ Freon;

[0086] In the chlorosilane solution, the mass percentage of silicon tetrachloride is 73.15%, the mass percentage of trichlorosilane is 26.16%, the mass percentage of dichlorodihydrosilane is 0.6%, the mass percentage of high boiling substances and metal chlorides is 0.071%, the mass percentage of hydrogen is 0.015%, and the mass percentage of hydrogen chloride is 0.004%;

[0087] The pressure of silicon tetrachloride buffer tank 21 is 0.12MPaG;

[0088] The top operating pressure of the crude fraction tower 4 is 0.15 MPaG;

[0089] The top temperature of the crude fraction tower 4 was 60°C.

[0090] Example 2

[0091] The polysilicon cold hydrogenation reaction method of this embodiment is carried out through the reaction system of embodiment 1, comprising:

[0092] Silicon powder, silicon tetrachloride, hydrogen and catalyst are subjected to cold hydrogenation reaction in cold hydrogenation reactor 2 to obtain polysilicon cold hydrogenation reaction tail gas including trichlorosilane, silicon tetrachloride and hydrogen, and the reaction tail gas is output through the outlet of cold hydrogenation reactor 2 to enter washing and cooling unit 3 for washing and cooling treatment, and then enters reboiler 5 of coarse fractionation tower 4 to provide heat for coarse fractionation treatment, and then enters first preheater 6 through heat source inlet of first preheater 6 for first preheating treatment, and obtains preheated circulating hydrogen. The inlet of the heat vaporization unit 1 enters the heating vaporization unit 1, and the obtained chlorosilane solution is output through the cold source outlet of the first preheater 6, and enters the second heat exchanger 22 through the cold source inlet of the second heat exchanger 22; the obtained first intermediate reaction tail gas enters the second preheater 7 through the heat source inlet of the second preheater 7, and the first intermediate reaction tail gas utilizes heat in the second preheater 7 to obtain the chlorosilane solution, which is output through the cold source outlet of the second preheater 7 and enters the second heat exchanger 22 through the cold source inlet of the second heat exchanger 22;

[0093] After being heated in the second heat exchanger 22, the chlorosilane solution is outputted through the cold source outlet of the second heat exchanger 22, and enters the coarse fractionation tower 4 through the feed port of the coarse fractionation tower 4. In the coarse fractionation tower 4, the chlorosilane solution is separated to obtain circulating silicon tetrachloride and trichlorosilane. The circulating silicon tetrachloride is outputted through the silicon tetrachloride outlet of the coarse fractionation tower 4, and enters the second heat exchanger 22 through the heat source inlet of the second heat exchanger 22. In the second heat exchanger 22, heat is exchanged with the chlorosilane solution to preliminarily reduce the temperature of the circulating silicon tetrachloride. The cooled silicon tetrachloride is outputted through the heat source outlet of the second heat exchanger 22, and enters the silicon tetrachloride buffer tank 21 through the inlet of the silicon tetrachloride buffer tank 21 for storage. The minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 is 16 m. The silicon tetrachloride outlet is located at the 28th tower plate below the feed port. The silicon tetrachloride outlet is located at the 28th tower plate below the feed port.

[0094] The circulating silicon tetrachloride is outputted from the outlet of the silicon tetrachloride buffer tank 21, and enters the second preheater 7 through the cold source inlet of the second preheater 7. In the second preheater 7, the first intermediate reaction tail gas performs a second preheating treatment on the circulating silicon tetrachloride to obtain preheated silicon tetrachloride, which is outputted from the outlet of the second preheater 7, and enters the heating vaporization unit 1 through the inlet of the heating vaporization unit 1. In the heating vaporization unit 1, the preheated silicon tetrachloride and the circulating hydrogen are heated and vaporized, and then outputted from the outlet of the heating vaporization unit 1. , enters the cold hydrogenation reactor 2 through the inlet of the cold hydrogenation reactor 2 to participate in the cold hydrogenation reaction, and the obtained chlorosilane solution is output through the liquid phase outlet of the second preheater 7, and enters the coarse fraction tower 4 through the chlorosilane inlet of the coarse fraction tower 4; the minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank 21 is 16m; the coarse fraction tower 4 also includes a gas phase balance port, which is located at the 29th tower plate below the feed port, and the gas phase balance port is connected to the silicon tetrachloride buffer tank 21 through a gas phase balance pipe 23;

[0095] The first intermediate reaction tail gas obtained in the second preheating treatment is output through the heat source outlet of the second preheater 7, enters the air cooler 8 through the inlet of the air cooler 8 for air cooling treatment, the reaction tail gas after the air cooling treatment is output through the outlet of the air cooler 8, enters the first cooler 9 through the inlet of the first cooler 9 for the first cooling treatment, the obtained chlorosilane solution is output through the liquid phase outlet of the first cooler 9, enters the coarse fractionation tower 4 through the inlet of the coarse fractionation tower 4, the obtained reaction tail gas is output through the gas phase outlet of the first cooler 9, enters the second cooler 10 through the inlet of the second cooler 10 for the second cooling treatment, the obtained chlorosilane solution is output through the liquid phase outlet of the second cooler 10, enters the coarse fractionation tower 4 through the inlet of the coarse fractionation tower 4, the obtained reaction tail gas is output through the gas phase outlet of the second cooler 10, and passes through the first heat exchanger 11 in sequence. The heat source inlet enters the first heat exchanger 11 for heat exchange treatment and enters the third cooler 12 through the inlet of the third cooler 12 for third cooling treatment, wherein the reaction tail gas output through the heat source outlet of the first heat exchanger 11 enters the third cooler 12 through the inlet of the third cooler 12 for third cooling treatment, the obtained chlorosilane solution is output from the liquid phase outlet of the third cooler 12, enters the coarse fractionation tower 4 through the inlet of the coarse fractionation tower 4, the obtained circulating hydrogen is output from the gas phase outlet of the third cooler 12 and enters the first heat exchanger 11 through the heat exchange medium inlet of the first heat exchanger 11 for heat exchange treatment, the obtained chlorosilane solution is output from the liquid phase outlet of the first heat exchanger 11, enters the coarse fractionation tower 4 through the inlet of the coarse fractionation tower 4, and the obtained first intermediate circulating hydrogen is output from the cold source outlet of the first heat exchanger 11;

[0096] The first intermediate cycle hydrogen obtained in the heat exchange process is output from the cold source outlet of the first heat exchanger 11 and enters the detection unit 13 through the inlet of the detection unit 13 for nitrogen content detection processing;

[0097] After the nitrogen content detection process is performed, if the nitrogen content in the first intermediate circulating hydrogen is ≥3%, the first intermediate circulating hydrogen is output from the outlet of the detection unit 13 and enters the pressure swing adsorption unit 14 through the inlet of the pressure swing adsorption unit 14 for pressure swing adsorption process, and the obtained pure hydrogen is output from the outlet of the pressure swing adsorption unit 14 and enters the first preheater 6 through the cold source inlet of the first preheater 6 for first preheating process;

[0098] If the nitrogen content in the first intermediate circulating hydrogen is less than 3%, the first intermediate circulating hydrogen is output from the outlet of the detection unit 13 and directly enters the first preheater 6 through the cold source inlet of the first preheater 6 for the first preheating treatment;

[0099] When the pressure of the recovered hydrogen outlet is greater than 0.6MPaG, the recovered hydrogen outlet is connected to the inlet of the hydrogen supplement compressor air inlet buffer tank; when the pressure of the recovered hydrogen outlet is less than or equal to 0.6MPaG, the recovered hydrogen outlet is connected to the hydrogen-containing tail gas recovery system;

[0100] Wherein, in the cold hydrogenation reactor 2, the temperature is 550°C and the pressure is 3.0MPa;

[0101] In the chlorosilane solution, the mass percentage of silicon tetrachloride is 73.15%, the mass percentage of trichlorosilane is 26.16%, the mass percentage of dichlorodihydrosilane is 0.6%, the mass percentage of high boiling substances and metal chlorides is 0.071%, the mass percentage of hydrogen is 0.015%, and the mass percentage of hydrogen chloride is 0.004%;

[0102] The pressure of silicon tetrachloride buffer tank 21 is 0.12MPaG;

[0103] The top operating pressure of the crude fraction tower 4 is 0.15 MPaG;

[0104] The top temperature of the crude fraction tower 4 is 60°C;

[0105] After washing and cooling treatment, the temperature of the reaction tail gas is 150°C. After providing heat for coarse separation, the temperature of the reaction tail gas is 120°C. The temperature of the first intermediate reaction tail gas is 115°C. After the second preheating treatment, the temperature of the first intermediate reaction tail gas is 105°C. After air cooling treatment, the temperature of the reaction tail gas is 60°C. After the first cooling treatment, the temperature of the reaction tail gas is 40°C. After the second cooling treatment, the temperature of the reaction tail gas is -15°C. After the third cooling treatment, the temperature of the reaction tail gas is -40°C. The temperature of the first intermediate circulating hydrogen is 10°C.

[0106] When the annual processing capacity is 350,000 tons of silicon tetrachloride (STC), in the polysilicon cold hydrogenation reaction method of this embodiment: after the reaction tail gas is used in the roughing tower reboiler, the refrigerant heat load can be saved by about 5300Kw, which is equivalent to about 455t / h of circulating water (10°C temperature difference); the reaction tail gas can also save hydrogen and silicon tetrachloride heating medium through the first preheater and the second preheater. When 10 kg of steam is used as the heating medium, 3-4t / h can be saved; the reaction tail gas can save about 870Kw of -45°C refrigerant cooling capacity and recover 600-1500Nm of hydrogen through heat exchange treatment. 3 / h.

[0107] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A polysilicon cold hydrogenation reaction system, characterized in that: It includes a coarse fraction tower, a cold hydrogenation reactor, an air cooler, a first preheater, a second preheater, a first cooler, a second cooler, a first heat exchanger and a third cooler; The outlet of the cold hydrogenation reactor is communicated with the inlet of the reboiler of the coarse fraction tower, the outlet of the reboiler is communicated with the heat source inlet of the first preheater, the heat source outlet of the first preheater is communicated with the heat source inlet of the second preheater, the silicon tetrachloride outlet of the coarse fraction tower is communicated with the cold source inlet of the second preheater, and the heat source outlet of the second preheater is communicated with the inlet of the air cooler; The outlet of the air cooler is communicated with the inlet of the first cooler, the gas phase outlet of the first cooler is communicated with the inlet of the second cooler, the gas phase outlet of the second cooler is communicated with the heat source inlet of the first heat exchanger, the heat source outlet of the first heat exchanger is communicated with the inlet of the third cooler, the gas phase outlet of the third cooler is communicated with the heat exchange medium inlet of the first heat exchanger, and the heat exchange medium outlet of the first heat exchanger is communicated with the cold source inlet of the first preheater; The liquid phase outlet of the first preheater, the liquid phase outlet of the second preheater, the liquid phase outlet of the first cooler, the liquid phase outlet of the second cooler, the liquid phase outlet of the first heat exchanger, and the liquid phase outlet of the third cooler are respectively connected to the feed port of the coarse fractionation tower; The silicon tetrachloride outlet is located at the 26th to 46th tower plate below the feed port; The cooling medium in the first cooler is circulating water, the cooling medium in the second cooler is at least one of chilled water, ethylene glycol, and -25°C Freon, and the cooling medium in the third cooler is -45°C Freon.

2. The reaction system according to claim 1, characterized in that: It also includes a silicon tetrachloride buffer tank, and the silicon tetrachloride outlet is connected to the silicon tetrachloride buffer tank; The minimum distance between the silicon tetrachloride outlet and the top of the silicon tetrachloride buffer tank is 8-30m.

3. The reaction system according to claim 1 or 2, characterized in that: Also included is a second heat exchanger; The chlorosilane solution enters the second heat exchanger through the cold source inlet of the second heat exchanger, the silicon tetrachloride outlet is connected to the heat source inlet of the second heat exchanger, the cold source outlet of the second heat exchanger is connected to the feed port, and the heat source outlet of the heat exchanger is connected to the silicon tetrachloride buffer tank.

4. The reaction system according to any one of claims 1 to 3, characterized in that: Also includes a gas phase balance tube; The coarse fraction tower further comprises a gas phase equilibrium port, the gas phase equilibrium port is located at the 26th to 46th tower plate below the feed port, and the number of tower plates between the gas phase equilibrium port and the silicon tetrachloride outlet differs by 0-2; The gas phase balance port is communicated with the silicon tetrachloride buffer tank through the gas phase balance pipe.

5. The reaction system according to any one of claims 1 to 4, characterized in that: The pressure of the silicon tetrachloride buffer tank is 0.1-0.6 MPaG; and / or, The top operating pressure of the crude fraction tower is 0.15-0.65 MPaG; and / or, The top temperature of the crude fraction tower is 55-95°C.

6. The reaction system according to claim 3, characterized in that: In the chlorosilane solution, the mass percentage of silicon tetrachloride is 60.5-79.45%, the mass percentage of trichlorosilane is 20-35%, the mass percentage of dichlorosilane is 0.05-3%, the mass percentage of high boiling substances and metal chlorides is 0.5-1.5%, the mass percentage of hydrogen is 0.01-0.015%, and the mass percentage of hydrogen chloride is 0.004-0.009%.

7. The reaction system according to any one of claims 1 to 6, characterized in that: It also includes a washing and cooling unit, the outlet of the cold hydrogenation reactor is connected to the inlet of the washing and cooling unit, and the outlet of the washing and cooling unit is connected to the reboiler inlet of the coarse fraction tower.

8. The reaction system according to any one of claims 1 to 7, characterized in that: It also includes a heating vaporization unit, wherein the cold source outlet of the first preheater is connected to the inlet of the heating vaporization unit, the cold source outlet of the second preheater is connected to the inlet of the heating vaporization unit, and the outlet of the heating vaporization unit is connected to the cold hydrogenation reactor.

9. The reaction system according to any one of claims 1 to 8, characterized in that: It also includes a detection unit and a pressure swing adsorption unit; The heat exchange medium outlet of the first heat exchanger is connected to the detection unit, the outlet of the detection unit is connected to the inlet of the pressure swing adsorption unit, and the outlet of the pressure swing adsorption unit is connected to the cold source inlet of the first preheater; or, The heat exchange medium outlet of the first heat exchanger is communicated with the detection unit, and the outlet of the detection unit is communicated with the cold source inlet of the first preheater.

10. A method for cold hydrogenation of polysilicon, characterized in that: The method is carried out using the reaction system described in any one of claims 1 to 9.

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