Adsorbent thermal activation apparatus and method

Abstract

The application discloses an adsorbent heat activation device and method, relates to the technical field of polysilicon production, and aims to improve controllability of exothermic reaction in an adsorbent activation process of an adsorption tower. The main technical scheme of the application is as follows: the adsorbent heat activation device comprises a vaporization heat exchanger, a top-sampling silicon tetrachloride pipe, a top-sampling trichlorosilane pipe and a flow guide pipe; the inlet of the vaporization heat exchanger is connected to a first nitrogen pipe; the top-sampling silicon tetrachloride pipe is connected to the inlet of the vaporization heat exchanger, and the top-sampling silicon tetrachloride pipe is provided with a first regulating valve; the top-sampling trichlorosilane pipe is connected to the inlet of the vaporization heat exchanger, and the top-sampling trichlorosilane pipe is provided with a second regulating valve; one end of the flow guide pipe is connected to the outlet of the vaporization heat exchanger, and the other end of the flow guide pipe is connected to the inlet of the adsorption tower; the flow guide pipe is provided with a control valve; the wall of the flow guide pipe between the control valve and the adsorption tower is connected to a second nitrogen pipe; and the outlet of the adsorption tower is connected to a geosyncline.

Description

Technical Field

[0001] This invention relates to the field of polycrystalline silicon production technology, and in particular to an adsorbent thermal activation device and method. Background Technology

[0002] With the development of the photovoltaic industry, the requirements for the quality of polysilicon are constantly increasing. The quality of trichlorosilane, a key raw material, directly affects the quality and yield of polysilicon products. Trichlorosilane purification technologies mainly include distillation and distillation-adsorption. Adsorption-distillation, a combination of adsorption and distillation, is the most widely used purification technology in China. There are generally two ways to use trichlorosilane adsorbents. One method involves directly filling the adsorbent into the adsorption column through the manhole, purging it with nitrogen, and then slowly introducing silicon tetrachloride. However, the exothermic reaction between silicon tetrachloride and residual moisture in the adsorbent cannot be carried away in time, leading to localized overheating, pulverization, loss of active groups, and deactivation of the adsorbent, potentially even causing safety accidents. The other method involves injecting a certain amount of silicon tetrachloride into the adsorption column and slowly pressing the adsorbent into the column using other drying equipment. This method requires long-distance transport and high pressure, resulting in high flow velocity of the adsorbent in the pipeline, significant wear, and a high risk of pipeline blockage.

[0003] During routine activation operations, various factors such as adsorbent packing density, adsorbent quantity, and nitrogen pressure can lead to unsatisfactory activation results, resulting in substandard sampling data and posing certain safety risks. For example, if a small amount of moisture remains in the adsorbent and is not dried and removed, it can cause a very violent reaction when the adsorbent is put into use, which may result in equipment damage or personal injury in severe cases. Summary of the Invention

[0004] In view of this, the present invention provides an adsorbent thermal activation device and method, the main purpose of which is to improve the controllability of the exothermic reaction during the adsorbent activation process in the adsorption tower.

[0005] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0006] On one hand, the present invention provides an adsorbent thermal activation device, which includes: a vaporization heat exchanger, a top-extraction silicon tetrachloride tube, a top-extraction trichlorosilane tube, and a drainage tube;

[0007] The inlet of the vaporization heat exchanger is connected to the first nitrogen pipe;

[0008] The top-extraction silicon tetrachloride tube is connected to the inlet of the vaporization heat exchanger, and the top-extraction silicon tetrachloride tube is equipped with a first regulating valve;

[0009] The top-extraction trichlorosilane tube is connected to the inlet of the vaporization heat exchanger, and a second regulating valve is installed on the top-extraction trichlorosilane tube;

[0010] One end of the diversion pipe is connected to the outlet of the vaporization heat exchanger, and the other end is connected to the inlet of the adsorption tower. The diversion pipe is equipped with a control valve. The wall of the diversion pipe between the control valve and the adsorption tower is connected to a second nitrogen pipe. The outlet of the adsorption tower is connected to a ground tank.

[0011] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0012] Optionally, the walls of the adsorption tower are connected to a temperature sensor and a pressure sensor.

[0013] Optionally, the outlet of the adsorption tower is also connected in sequence to a first-stage distillation tower, a second-stage distillation tower, and a third-stage distillation tower.

[0014] Optionally, it also includes a coarse fractionation column, a primary coarse distillation column, a secondary coarse distillation column, and a liquid phase extraction pipe, wherein the coarse fractionation column, the primary coarse distillation column, the secondary coarse distillation column, and the top extraction trichlorosilane pipe are connected in sequence, and one end of the liquid phase extraction pipe is connected to the secondary coarse distillation column and the other end is connected to the primary rectification column.

[0015] Optionally, the inlet of the adsorption tower is located at the lower end of the adsorption tower, the outlet of the adsorption tower is located at the upper end of the adsorption tower, and the outlet pipe of the adsorption tower is also connected to a nitrogen-containing pressure relief pipe.

[0016] On the other hand, the present invention provides a method for thermal activation of an adsorbent, comprising the following steps:

[0017] (1) When the adsorbent in the adsorption tower fails, the liquid phase sampling pipe is used to replace the online operation of the adsorption tower. After the adsorbent in the adsorption tower is replaced, the tube side of the vaporization heat exchanger is cleaned with silicon tetrachloride and then steam is introduced into the shell side of the vaporization heat exchanger. The first regulating valve is opened to allow silicon tetrachloride to enter the tube side of the vaporization heat exchanger. Then the first regulating valve is closed, and then the silicon tetrachloride is purged into the adsorption tower with nitrogen from the first nitrogen pipe.

[0018] (2) In the adsorption tower, silicon tetrachloride reacts with the bound water in the adsorbent and releases heat, and hydrogen chloride gas is generated in the adsorption column. The generated hydrogen chloride gas is discharged to the ground tank. If the temperature in the adsorption tower is greater than 140°C, the control valve is closed and the flow rate of nitrogen purging in the second nitrogen pipe is increased so that the temperature of the adsorption tower is less than 160°C.

[0019] (3) After the temperature of the adsorption tower is below 135℃ for 1 hour, open the control valve to half opening degree and repeat step (1);

[0020] (4) Repeat steps (1), (2) and (3). When the temperature of the adsorption tower is maintained at 135°C, the adsorbent in the adsorption tower is activated and the first regulating valve is closed.

[0021] (5) When the temperature of the adsorption tower drops to 100°C, open the second regulating valve to one-tenth of its opening and introduce trichlorosilane into the adsorption tower. If the temperature inside the adsorption tower is greater than 140°C, close the second regulating valve in time and introduce nitrogen into the adsorption tower through the second nitrogen pipe to cool it down.

[0022] (6) After the temperature of the adsorption tower drops to 135°C, reopen the second regulating valve to one-tenth of its opening and continue to clean the adsorbent in the adsorption tower for more than 24 hours. When the temperature in the adsorption tower no longer rises and the sample taken from the outlet of the adsorption tower does not contain silicon tetrachloride, the adsorption tower replacement is complete.

[0023] (7) After the replacement is completed, the top-collected trichlorosilane pipe is gradually replaced with the liquid phase collection pipe. The trichlorosilane gas phase is fed into the adsorption tower at a flow rate of 2T / H. At the same time, the trichlorosilane collected from the top of the three-stage distillation tower is fed into the experimental furnace for testing. When the quality test result of the polysilicon product is better than the previous batch, the flow rate of trichlorosilane is increased to 4T / H again. The quality test result of the polysilicon product is tested again in the experimental furnace. If there is no abnormality in the test result, the flow rate of trichlorosilane can be increased to 8T / H. This operation is repeated, and the flow rate is increased to 16T / H and 24T / H in turn. The flow rate of the liquid phase collection pipe is gradually reduced to 0T / H.

[0024] Optionally, in step (1), the amount of silicon tetrachloride introduced into the tube side of the gasification heat exchanger is 5 kg.

[0025] Optionally, in step (5), the flow rate of trichlorosilane introduced into the adsorption tower is 10 Nm³. 3 / h.

[0026] By employing the above technical solution, the present invention has at least the following advantages:

[0027] Using this device to thermally activate the adsorbent allows for better control of the temperature and pressure of the adsorption tower, preventing damage to the adsorbent and adsorption tower caused by violent reactions between chlorosilane and water during the subsequent disproportionation reaction due to incomplete drying of the adsorbent. It also avoids personnel casualties and ensures the quality of polysilicon products from the production system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an adsorbent thermal activation device provided in an embodiment of the present invention.

[0029] The reference numerals in the accompanying drawings include: vaporization heat exchanger 1, top-extracting silicon tetrachloride pipe 2, first regulating valve 4, top-extracting trichlorosilane pipe 5, second regulating valve 6, drain pipe 7, control valve 8, adsorption tower 9, first nitrogen pipe 10, second nitrogen pipe 11, ground tank 12, silicon tetrachloride purification tower 13, temperature sensor 14, pressure sensor 15, primary distillation tower 16, secondary distillation tower 17, tertiary distillation tower 18, crude distillation tower 19, primary crude distillation tower 20, secondary crude distillation tower 21, liquid phase outlet pipe 22, and nitrogen-containing pressure relief pipe 23. Detailed Implementation

[0030] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0032] like Figure 1 As shown, an embodiment of the present invention provides an adsorbent thermal activation device, which includes: a vaporization heat exchanger 1, a top-extraction silicon tetrachloride tube 2, a top-extraction trichlorosilane tube 5, and a drainage tube 7;

[0033] The inlet of the vaporization heat exchanger 1 is connected to the first nitrogen pipe 10;

[0034] The top-extraction silicon tetrachloride tube 2 is connected to the inlet of the vaporization heat exchanger 1, and the top-extraction silicon tetrachloride tube 2 is equipped with a first regulating valve 4;

[0035] The top-extraction trichlorosilane tube 5 is connected to the inlet of the vaporization heat exchanger 1, and the top-extraction trichlorosilane tube 5 is equipped with a second regulating valve 6.

[0036] One end of the diversion pipe 7 is connected to the outlet of the vaporization heat exchanger 1, and the other end is connected to the inlet of the adsorption tower 9. The diversion pipe 7 is equipped with a control valve 8. The pipe wall of the diversion pipe 7 between the control valve 8 and the adsorption tower 9 is connected to the second nitrogen pipe 11. The outlet of the adsorption tower 9 is connected to the ground tank 12.

[0037] Specifically, one end of the top-extraction silicon tetrachloride tube 2 is connected to the silicon tetrachloride purification tower 13, and the other end is connected to the inlet of the vaporization heat exchanger 1.

[0038] In a specific embodiment, the wall of the adsorption tower 9 is connected to the temperature sensor 14 and the pressure sensor 15.

[0039] In this embodiment, the temperature sensor 14 and the pressure sensor 15 are integrated into the DCS control system, which facilitates remote monitoring of the temperature and pressure of the adsorption tower 9 by the operator.

[0040] In a specific embodiment, the outlet of the adsorption tower 9 is also connected in sequence to the first-stage distillation tower 16, the second-stage distillation tower 17, and the third-stage distillation tower 18.

[0041] In this embodiment, the trichlorosilane treated by the adsorption tower 9 is then purified by sequentially passing through the first-stage distillation tower 16, the second-stage distillation tower 17, and the third-stage distillation tower 18. The adsorption process and the distillation process are carried out in sequence to improve the quality of the finished polycrystalline silicon rod.

[0042] In a specific embodiment, it also includes a crude fractionation column 19, a primary crude distillation column 20, a secondary crude distillation column 21, and a liquid phase extraction pipe 22. The crude fractionation column 19, the primary crude distillation column 20, the secondary crude distillation column 21, and the top extraction trichlorosilane pipe 5 are connected in sequence. One end of the liquid phase extraction pipe 22 is connected to the secondary crude distillation column 21, and the other end is connected to the primary rectification column 16.

[0043] In this embodiment, specifically, during normal production, the light components of the coarse fractionation tower 19 enter the primary coarse distillation tower 20, the light components of the primary coarse distillation tower 20 enter the secondary coarse distillation tower 21, and the light components of the secondary coarse distillation tower 21 enter the adsorption tower 9 through the top-feed trichlorosilane pipe 5. When the adsorbent in the adsorption tower 9 loses its activity, the liquid phase outlet pipe 22 replaces the adsorption tower 9. The liquid phase outlet pipe 22 operates online, which facilitates the operator to replace the adsorbent in the adsorption tower 9 and reactivate the adsorbent.

[0044] In a specific embodiment, the inlet of the adsorption tower 9 is located at the lower end of the adsorption tower 9, the outlet of the adsorption tower 9 is located at the upper end of the adsorption tower 9, and the outlet pipe of the adsorption tower 9 is also connected to the nitrogen-containing pressure relief pipe 23.

[0045] In this embodiment, specifically, when the pressure inside the adsorption tower 9 rises too quickly and simply venting the pressure to the ground tank 12 is insufficient to meet the pressure relief requirements, the valve of the nitrogen-containing pressure relief pipe 23 is opened to release pressure to the recovery pipeline network, thereby reducing the equipment pressure and increasing the equipment throughput.

[0046] On the other hand, another embodiment of the present invention provides a method for thermal activation of an adsorbent, comprising the following steps:

[0047] (1) When the adsorbent in the adsorption tower 9 fails, the liquid phase sampling pipe 22 is used to replace the adsorption tower 9 for online operation. After the adsorbent in the adsorption tower 9 is replaced, the tube side of the vaporization heat exchanger 1 is cleaned with silicon tetrachloride and then steam is introduced into the shell side of the vaporization heat exchanger 1. The first regulating valve 4 is opened to allow 5 kg of silicon tetrachloride to be introduced into the tube side of the vaporization heat exchanger 1. Then the first regulating valve 4 is closed, and then the silicon tetrachloride is purged into the adsorption tower 9 with nitrogen from the first nitrogen pipe 10.

[0048] (2) In the adsorption tower 9, silicon tetrachloride reacts with the bound water in the adsorbent and releases heat, and hydrogen chloride gas is generated in the adsorption column. The generated hydrogen chloride gas is discharged to the ground tank 12. If the temperature in the adsorption tower 9 is greater than 140°C, the control valve 8 is closed and the flow rate of nitrogen purging in the second nitrogen pipe 11 is increased so that the temperature of the adsorption tower 9 is less than 160°C.

[0049] (3) After the temperature of the adsorption tower 9 is below 135℃ for 1 hour, open the control valve 8 to half opening and repeat step (1);

[0050] (4) Repeat steps (1), (2) and (3). When the temperature of the adsorption tower 9 is maintained at 135°C, the adsorbent in the adsorption tower 9 is activated and the first regulating valve 4 is closed.

[0051] (5) When the temperature of the adsorption tower 9 drops to 100°C, open the second regulating valve 6 to one-tenth of its opening and introduce 10 Nm of trichlorosilane into the adsorption tower 9. 3 If the temperature inside the adsorption tower 9 is greater than 140°C, close the second regulating valve 6 in time and introduce nitrogen into the adsorption tower 9 through the second nitrogen pipe 11 to cool it down.

[0052] (6) After the temperature of the adsorption tower 9 drops to 135°C, the second regulating valve 6 is reopened to one-tenth of its opening. The adsorbent in the adsorption tower 9 is continuously cleaned for more than 24 hours. When the temperature in the adsorption tower 9 no longer rises and the sample taken from the outlet of the adsorption tower 9 does not contain silicon tetrachloride, the replacement of the adsorption tower 9 is complete.

[0053] (7) After the replacement is completed, the top-collected trichlorosilane pipe 5 gradually replaces the liquid phase collection pipe 22. The trichlorosilane gas phase is fed into the adsorption tower 9 at a flow rate of 2T / H. At the same time, the trichlorosilane collected from the top of the distillation three-stage tower 18 is fed into the experimental furnace for testing. When the quality test result of the polysilicon finished product is better than the result of the previous batch, the flow rate of trichlorosilane is increased to 4T / H again. The quality test result of the polysilicon finished product is tested again in the experimental furnace. If there is no abnormality in the test result, the flow rate of trichlorosilane can be increased to 8T / H. This operation is repeated, and the flow rate is increased to 16T / H and 24T / H in turn. The flow rate of the liquid phase collection pipe 22 is gradually reduced to 0T / H.

[0054] Specifically, the experimental furnace is a small polycrystalline silicon reduction furnace, and the finished product quality test results include silicon core diameter, product grade, physicochemical index grade, resistivity, minority carrier lifetime, PN type, and the contents of boron, phosphorus, carbon, oxygen, aluminum, gallium, arsenic, and antimony.

[0055] In this embodiment, the adsorbent is activated using high-purity silicon tetrachloride, a byproduct of reduction. The reaction heat between silicon tetrachloride and water in the adsorbent is relatively small, making it highly controllable and safe. During normal production, after adsorption tower 9, there are distillation tower 16, distillation tower 17, and distillation tower 18 for sequential purification. If TET (silicon tetrachloride) is not cleaned properly, trace amounts of silicon tetrachloride in adsorption tower 9 will be discharged from the reactor of distillation tower 16 during the replacement process. Initially, the discharge of residue from distillation tower 16 will be increased to replace silicon tetrachloride out of the system as quickly as possible.

[0056] Taking a polysilicon plant with an annual production capacity of 45,000 tons as an example, two 11.5m... 3 The adsorption tower 9 has a volume of 7.2 m³ of adsorbent. 3 When the adsorption effect of one of the adsorption towers 9 decreases, it is removed from the system and refilled. This method is used to activate the adsorption column in the gas phase separately without affecting the existing operating equipment. The activation time is reduced to 12 hours. During the activation process, the parameters of adsorption tower 9 are effectively monitored to avoid the rapid exothermic reaction between chlorosilane and the bound water in the adsorbent and the exothermic reaction of physical adsorption, thus ensuring the safety of personnel and equipment, as well as the product quality of the production system.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for thermally activating an adsorbent, characterized in that, The adsorbent activation device used includes: A vaporization heat exchanger, the inlet of which is connected to a first nitrogen pipe; A top-harvested silicon tetrachloride tube is connected to the inlet of the vaporization heat exchanger, and a first regulating valve is installed on the top-harvested silicon tetrachloride tube. A top-extraction trichlorosilane tube is connected to the inlet of the vaporization heat exchanger, and a second regulating valve is installed on the top-extraction trichlorosilane tube; A diversion pipe is provided, with one end connected to the outlet of the vaporization heat exchanger and the other end connected to the inlet of the adsorption tower. A control valve is installed on the diversion pipe, and the wall of the diversion pipe between the control valve and the adsorption tower is connected to a second nitrogen pipe. The outlet of the adsorption tower is connected to a ground tank. The wall of the adsorption tower is connected to a temperature sensor and a pressure sensor; The outlet of the adsorption tower is also connected in sequence to a first-stage distillation tower, a second-stage distillation tower, and a third-stage distillation tower; It also includes a crude fractionation column, a primary crude distillation column, a secondary crude distillation column, and a liquid phase extraction pipe. The crude fractionation column, the primary crude distillation column, the secondary crude distillation column, and the top extraction trichlorosilane pipe are connected in sequence. One end of the liquid phase extraction pipe is connected to the secondary crude distillation column, and the other end is connected to the primary rectification column. The method includes the following steps: (1) When the adsorbent in the adsorption tower fails, the liquid phase sampling pipe is used to replace the online operation of the adsorption tower. After the adsorbent in the adsorption tower is replaced, the tube side of the vaporization heat exchanger is cleaned with silicon tetrachloride and then steam is introduced into the shell side of the vaporization heat exchanger. The first regulating valve is opened to allow silicon tetrachloride to enter the tube side of the vaporization heat exchanger. Then the first regulating valve is closed, and then the silicon tetrachloride is purged into the adsorption tower with nitrogen from the first nitrogen pipe. (2) In the adsorption tower, silicon tetrachloride reacts with the bound water in the adsorbent and releases heat, and hydrogen chloride gas is generated in the adsorption column. The generated hydrogen chloride gas is discharged to the ground tank. If the temperature in the adsorption tower is greater than 140°C, the control valve is closed and the flow rate of nitrogen purging in the second nitrogen pipe is increased so that the temperature of the adsorption tower is less than 160°C. (3) After the temperature of the adsorption tower is below 135℃ for 1 hour, open the control valve to half opening and repeat step (1). (4) Repeat steps (1), (2) and (3). When the temperature of the adsorption tower is maintained at 135°C, the adsorbent in the adsorption tower is activated and the first regulating valve is closed. (5) When the temperature of the adsorption tower drops to 100°C, open the second regulating valve to one-tenth of its opening and introduce trichlorosilane into the adsorption tower. If the temperature inside the adsorption tower is greater than 140°C, close the second regulating valve in time and introduce nitrogen into the adsorption tower through the second nitrogen pipe to cool it down. (6) After the temperature of the adsorption tower drops to 135°C, reopen the second regulating valve to one-tenth of its opening and continue to clean the adsorbent in the adsorption tower for more than 24 hours. When the temperature in the adsorption tower no longer rises and the sample taken from the outlet of the adsorption tower does not contain silicon tetrachloride, the adsorption tower replacement is complete. (7) After the replacement is completed, the top-collected trichlorosilane pipe is gradually replaced with the liquid phase collection pipe. The trichlorosilane gas phase is fed into the adsorption tower at a flow rate of 2T / H. At the same time, the trichlorosilane collected from the top of the three-stage distillation tower is fed into the experimental furnace for testing. When the quality test result of the polysilicon finished product is better than the previous batch, the flow rate of trichlorosilane is increased to 4T / H again. The quality test result of the polysilicon finished product is tested again in the experimental furnace. If there is no abnormality in the test result, the flow rate of trichlorosilane can be increased to 8T / H. This operation is repeated, and the flow rate is increased to 16T / H and 24T / H in turn. The flow rate of the liquid phase collection pipe is gradually reduced to 0T / H.

2. The method for thermal activation of the adsorbent according to claim 1, characterized in that, The inlet of the adsorption tower is located at the lower end of the adsorption tower, and the outlet of the adsorption tower is located at the upper end of the adsorption tower. The outlet pipe of the adsorption tower is also connected to a nitrogen-containing pressure relief pipe.

3. The method for thermal activation of the adsorbent according to claim 1, characterized in that, In step (1), the amount of silicon tetrachloride introduced into the tube side of the vaporization heat exchanger is 5 kg.

4. The method for thermal activation of the adsorbent according to claim 1, characterized in that, In step (5), the flow rate of trichlorosilane introduced into the adsorption tower is 10 Nm3 / h.

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