Cold hydrogenation fluidized bed reaction system and regulation and control method

Abstract

The invention discloses a cold hydrogenation fluidized bed reaction system and a regulation and control method, and the system comprises a fluidized bed reactor which comprises a fluidized bed reactor body, and a silicon powder inlet, a mixed gas inlet, a synthesis gas outlet and a pipeline through hole which are formed in the fluidized bed reactor body; the built-in cyclone separator is arranged in the fluidized bed, and a gas outlet of the built-in cyclone separator is connected with the synthesis gas outlet; the air inlet element is connected with the built-in cyclone separator; the air inlet pipeline penetrates through the pipeline through hole and is connected with the air inlet element; the controller is used for controlling the opening and closing of the gas inlet element and adjusting the gas flow, and controlling and adjusting the gas flow in a preset flow range, so that the particle size of the silicon powder in the fluidized bed reactor is in a preset particle size range, and the concentration of the silicon powder is in a preset concentration range. The method realizes stable and reliable discharge of invalid silicon powder in the fluidized bed reactor, ensures system stability, improves the reaction conversion rate, and can realize effective discrimination and regulation of cyclone efficiency in the fluidized bed.

Description

Technical Field

[0001] The invention belongs to the technical field of polysilicon production, and in particular relates to a cold hydrogenation fluidized bed reaction system and a control method. Background Art

[0002] At present, the fluidized bed reactor is the most important reaction equipment in the cold hydrogenation process. The fluidized bed reactor is equipped with a built-in cyclone separator, referred to as the inner cyclone, to separate the silicon powder particles entrained by the fluidized bed mixed gas from the mixed gas. The efficiency of the inner cyclone determines the loss of silicon powder at the outlet of the fluidized bed. When the efficiency of the inner cyclone is low, a large amount of silicon powder is discharged, resulting in raw material loss, and causing certain wear and tear on the outer cyclone, heat exchanger and other equipment, and a large amount of slurry processing in subsequent processes. When the efficiency of the inner cyclone is too high, a large amount of failed silicon powder entrained by the mixer on the upper part of the fluidized bed will fall back into the fluidized bed, forming an invalid bed layer, which will cause a decrease in the conversion rate of the fluidized bed.

[0003] At present, the existing technology mainly solves the problem of decreased trichlorosilane conversion rate caused by accumulation of failed silicon powder in the fluidized bed by adjusting the efficiency of the internal cyclone. Patent CN

[0004] 118577214A, a fluidized bed reactor and its cold hydrogenation system are proposed, the fluidized bed reactor includes: a cyclone separator, which is built into the fluidized bed reactor; an ash hopper, which is used to collect and store silicon powder, and the ash hopper is connected to the lower end of the cyclone separator; a material leg, which is used to discharge silicon powder, and the material leg is connected to the lower end of the ash hopper; a regulating system, including an ash discharge subsystem, which can pass purge gas into the ash hopper to adjust the pressure drop of the cyclone separator, so that the fluidized bed reactor is in normal working condition or slag discharge condition. Under normal working condition, the pressure drop of the cyclone separator is high to reduce the amount of silicon powder taken out of the cyclone separator and reduce silicon powder consumption; under slag discharge condition, the pressure drop of the cyclone separator is reduced to allow most of the silicon powder, deactivated materials and impurities to be taken out of the cyclone separator. In this way, the deactivated materials and impurities in the fluidized bed reactor can be discharged on the basis of keeping the fluidized bed reactor running, so as to increase the proportion of effective reaction materials in the fluidized bed reactor and reduce the attenuation of trichlorosilane conversion rate. The method proposed in this patent for determining the accumulation of failed silicon powder in a fluidized bed is mainly based on the trichlorosilane content in the synthesis gas. When the trichlorosilane content is continuously lower than the preset target, it is determined that the conversion rate of the fluidized bed reactor has decreased, and the ash removal subsystem is then adjusted to operate in a slag removal condition.

[0005] However, the reduction in trichlorosilane efficiency is not only determined by the activity of silicon powder. The catalyst content, gas flow and ratio, bed height, reaction temperature and pressure, etc. will affect the conversion efficiency of trichlorosilane. Therefore, it is impossible to determine the failure of silicon powder by trichlorosilane content. This method will cause feedback errors in the inner cyclone operation, which will cause a large amount of effective silicon powder to be discharged, resulting in waste of raw materials or untimely ash discharge of the inner cyclone. The cycle of adjusting the inner cyclone to discharge silicon powder based on the conversion rate is long. During the ash discharge, a large amount of silicon powder will be lost, which will cause instantaneous wear on the heat exchanger. The elution operation and subsequent slurry treatment operation will cause large fluctuations and unsafe risks, and the overall system will fluctuate greatly. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a cold hydrogenation fluidized bed reaction system and a control method in view of the above-mentioned deficiencies in the prior art, so as to realize the stable and reliable discharge of failed silicon powder in the fluidized bed reactor, ensure the stability of the system and improve the reaction conversion rate, and realize the effective judgment and control of the cyclone efficiency in the fluidized bed.

[0007] The technical solution adopted to solve the technical problem of the present invention is to provide a cold hydrogenation fluidized bed reaction system, comprising:

[0008] The fluidized bed reactor comprises a fluidized bed reactor body, a silicon powder inlet, a mixed gas inlet, a synthesis gas outlet, and a pipeline through hole arranged on the fluidized bed reactor body, wherein the silicon powder inlet is used to introduce silicon powder, the mixed gas inlet is used to introduce reaction gas, and the synthesis gas outlet is used to discharge synthesis gas from the cold hydrogenation reaction;

[0009] A built-in cyclone separator is arranged in the fluidized bed, and a gas outlet of the built-in cyclone separator is connected to a synthesis gas outlet;

[0010] An air intake element connected to a built-in cyclone separator;

[0011] An air intake duct, which passes through the duct through-hole and is connected to the air intake element, and through which the regulated air is introduced into the built-in cyclone separator;

[0012] The controller controls the opening and closing of the air inlet element and adjusts the air flow rate, and controls the air flow rate to be within a preset flow rate range, so that the particle size of the silicon powder in the fluidized bed reactor is within the preset particle size range, and the concentration of the silicon powder is within the preset concentration range.

[0013] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0014] The mixed gas electric heater is connected to the mixed gas inlet and is used to heat the reaction gas introduced into the fluidized bed reactor.

[0015] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0016] The heat exchanger has a tube side connected to the synthesis gas outlet, and a shell side connected to the mixed gas inlet, and is used to use the high-temperature mixed gas at the synthesis gas outlet to heat the mixed gas fed into the fluidized bed reactor.

[0017] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0018] An online particle size detector is arranged on a pipeline connected to the syngas outlet, and the online particle size detector sends the detected silicon powder particle size to the controller;

[0019] An online dust concentration detector is arranged on a pipeline connected to the syngas outlet, and the online dust concentration detector sends the detected silicon powder concentration to the controller;

[0020] When the silicon powder particle size is smaller than the preset particle size range or the silicon powder concentration is smaller than the preset concentration, the controller controls the air intake element to adjust the air flow rate to increase;

[0021] When the particle size of the silicon powder is greater than a preset particle size or the concentration of the silicon powder is greater than a preset concentration, the controller controls the air intake element to adjust the air flow rate to decrease.

[0022] Preferably, the online dust concentration detector is installed in a plug-in manner.

[0023] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0024] The sealed protection box is arranged outside the online dust concentration detector.

[0025] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0026] The pressure detector is arranged outside the sealed protection box and is used to detect the pressure inside the sealed protection box.

[0027] Preferably, the cold hydrogenation fluidized bed reaction system further comprises: an alarm, wherein the pressure detector sends the detected pressure value to the controller, and when the pressure value is greater than a preset pressure value, the controller controls the alarm to sound an alarm.

[0028] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0029] The external dust removal device is connected to the synthesis gas outlet and is used for dust removal. Preferably, the external dust removal device is any one of a cyclone separator, a filter dust collector, a Venturi dust collector, and a wet scrubbing dust collector.

[0030] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0031] The external dust removal silicon powder receiving tank is connected to the external dust removal device, and the external dust removal silicon powder receiving tank is used to receive dust.

[0032] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0033] The material level meter is installed in the external dust removal silicon powder receiving tank. The material level meter is used to detect the height of the solid material in the external dust removal silicon powder receiving tank and send it to the controller.

[0034] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0035] The ash hopper is connected to the lower cone of the built-in cyclone separator. The lower cone of the built-in cyclone separator and the ash hopper are both sandwich structures. The sandwich structure is connected to the cavity for cyclone separation of the built-in cyclone separator. Adjusted air is introduced into the sandwich structure through an air intake pipe and then enters the cavity for cyclone separation of the built-in cyclone separator through an air intake element.

[0036] Preferably, the air intake direction of the air intake element is opposite to the swirl direction of the built-in cyclone in the built-in cyclone separator and is inclined upward, with an upward vertical inclination angle of 0° to 75°, and a horizontal direction opposite to the tangent line of the inner wall of the built-in cyclone separator of 15° to 90°.

[0037] The present invention also provides a control method using the cold hydrogenation fluidized bed reaction system, comprising the following steps:

[0038] The air flow rate at the air intake component is adjusted by the controller. The air flow rate of each air intake component is Q, where 100Nm 3 / h<Q<2000Nm 3 / h, so that the particle size D50 of the silicon powder in the fluidized bed reactor is within the preset particle size range, where 30μm<D50<70μm, and the concentration C of the silicon powder is within the preset concentration range, where 0.5g / Nm 3 <C<1.4g / Nm 3 .

[0039] Preferably, using the cold hydrogenation fluidized bed reaction system, the control method further comprises the following steps:

[0040] When the silica powder particle size D50 is less than 30 microns or the silica powder concentration is less than 0.5g / Nm 3 When the controller controls the air intake element to adjust the air flow rate to increase;

[0041] When the silica powder particle size D50 is greater than 70 microns or the silica powder concentration is greater than 1.4g / Nm 3 When the air flow is reduced, the controller controls the air intake element to adjust the air flow rate.

[0042] Preferably, using the cold hydrogenation fluidized bed reaction system, the control method further comprises the following steps:

[0043] The controller calculates the silicon powder concentration Csi based on the material level detected by the material level meter in the external dust removal silicon powder receiving tank.

[0044] Among them, the mixed gas flow rate is Q VN , the unit is standard cubic meter per hour Nm 3 / h, the material level of the external dust removal silicon powder receiving tank in a dust removal cycle passes through time X, the unit is hour h, the material level rises Δh, the unit is meter m, and the corresponding material level volume change is Δ

[0045] V, its unit is cubic meter m 3 , calculated silica powder concentration Csi, its unit is grams per standard cubic meter g / Nm 3 , Csi is:

[0046]

[0047] The bulk density of silicon powder in the tank is 1200kg / m 3 , converted to 1200000g / m 3 .

[0048] The cold hydrogenation fluidized bed reaction system and control method of the present invention have the following advantages:

[0049] Beneficial effects:

[0050] 1. This solution can effectively identify failed silicon powder: This patent has obtained the relationship between silicon powder activity and particle size through experimental verification, and based on this, a cold hydrogenation fluidized bed control system is designed to achieve accurate discharge of failed silicon powder. The particle size and concentration of the discharged silicon powder are monitored in real time using an online particle size detector and an online dust concentration detector, and the failure of the silicon powder is automatically and accurately determined based on the logic judgment program in the upper computer.

[0051] 2. Reduce the risk of equipment leakage and improve system stability: The online dust concentration detector provided by this system adopts plug-in installation and welds a sealed protective box on the outside, which effectively reduces the risk of equipment leakage. By monitoring the particle size and concentration of silicon powder, the system can detect and adjust abnormal conditions in time, thereby improving the stability of the entire fluidized bed reaction system. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a schematic structural diagram of a cold hydrogenation fluidized bed reaction system in Example 2 of the present invention;

[0053] Figure 2 It is a pipeline installation diagram of the online dust concentration detector in Example 2 of the present invention;

[0054] Figure 3 is a graph showing the change in the proportion of total impurities in silicon powder as a function of particle size in Example 2 of the present invention;

[0055] Figure 4 This is a diagram for adjusting the hydrogen gas flow in Example 2 of the present invention;

[0056] Figure 5 It is a top view of the ash hopper in Example 2 of the present invention.

[0057] In the figure: 1 fluidized bed reactor, 1-1 silicon powder inlet, 1-2 mixed gas inlet, 1-3 synthesis gas outlet, 2 built-in cyclone separator, 2-1 ash hopper, 2-2 built-in cyclone separator lower cone, 3 air intake element, 4 controller, 5 heat exchanger, 6 mixed gas electric heater, 7 online particle size detector, 8 online dust concentration detector, 8-1 sealed protection box, 9 external dust removal device, 10 external dust removal silicon powder receiving tank. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0059] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0060] In the description of this patent, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this patent and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0061] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0062] Example 1

[0063] This embodiment provides a cold hydrogenation fluidized bed reaction system, comprising:

[0064] The fluidized bed reactor comprises a fluidized bed reactor body, a silicon powder inlet, a mixed gas inlet, a synthesis gas outlet, and a pipeline through hole arranged on the fluidized bed reactor body, wherein the silicon powder inlet is used to introduce silicon powder, the mixed gas inlet is used to introduce reaction gas, and the synthesis gas outlet is used to discharge synthesis gas from the cold hydrogenation reaction;

[0065] A built-in cyclone separator is arranged in the fluidized bed, and a gas outlet of the built-in cyclone separator is connected to a synthesis gas outlet;

[0066] An air intake element connected to a built-in cyclone separator;

[0067] An air intake duct, which passes through the duct through-hole and is connected to the air intake element, and through which the regulated air is introduced into the built-in cyclone separator;

[0068] The controller controls the opening and closing of the air inlet element and adjusts the air flow rate, and controls the air flow rate to be within a preset flow rate range, so that the particle size of the silicon powder in the fluidized bed reactor is within the preset particle size range, and the concentration of the silicon powder is within the preset concentration range.

[0069] This embodiment also provides a control method using the cold hydrogenation fluidized bed reaction system, comprising the following steps:

[0070] The air flow rate at the air intake component is adjusted by the controller. The air flow rate of each air intake component is Q, where 100Nm 3 / h<Q<2000Nm 3 / h, so that the particle size D50 of the silicon powder in the fluidized bed reactor is within the preset particle size range, where 30μm<D50<70μm, and the concentration C of the silicon powder is within the preset concentration range, where 0.5g / Nm 3 <C<1.4g / Nm 3 .

[0071] This embodiment timely regulates and controls the internal cyclone of the fluidized bed so that the internal cyclone can maintain a reasonable efficiency and work stably, thereby achieving timely discharge of failed silicon powder and maintaining stable system operation.

[0072] Example 2

[0073] like Figures 1 to 5 As shown, this embodiment provides a cold hydrogenation fluidized bed reaction system, comprising:

[0074] The fluidized bed reactor 1 comprises a fluidized bed reactor body, a silicon powder inlet 1-1, a mixed gas inlet 1-2, a synthesis gas outlet 1-3, and a pipeline through hole arranged on the fluidized bed reactor body, wherein the silicon powder inlet 1-1 is used to introduce silicon powder, the mixed gas inlet 1-2 is used to introduce reaction gas, and the synthesis gas outlet 1-3 is used to discharge synthesis gas from the cold hydrogenation reaction;

[0075] A built-in cyclone separator 2 is arranged in the fluidized bed, and a gas outlet of the built-in cyclone separator 2 is connected to the synthesis gas outlet 1-3;

[0076] An air intake element 3 connected to the built-in cyclone separator 2;

[0077] An air intake pipe, which passes through the pipe through-hole and is connected to the air intake element 3, and the regulated air is introduced into the built-in cyclone separator 2 through the air intake pipe;

[0078] The controller 4 controls the opening and closing of the air inlet element 3 and adjusts the air flow rate to control the air flow rate within a preset flow rate range, so that the particle size of the silicon powder in the fluidized bed reactor 1 is within the preset particle size range, and the concentration of the silicon powder is within the preset concentration range.

[0079] Specifically, the air intake element 3 is regulated by the controller 4, including opening and closing the air intake element 3 and adjusting the air velocity and air volume. The air intake element 3 is provided by a gas source with a pressure not lower than 0.3Mpa of the fluidized bed, preferably hydrogen, and the temperature is greater than 150°C.

[0080] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0081] The mixed gas electric heater 6 is connected to the mixed gas inlet 1 - 2 , and is used to heat the reaction gas introduced into the fluidized bed reactor 1 .

[0082] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0083] The heat exchanger 5, the tube side of the heat exchanger 5 is connected to the synthesis gas outlet 1-3, and the shell side of the heat exchanger 5 is connected to the mixer inlet 1-2, which is used to use the high-temperature mixed gas from the synthesis gas outlet 1-3 to heat the mixed gas sent to the fluidized bed reactor 1.

[0084] In this embodiment, the heat exchanger 5 is a multi-stage heat exchanger, and the multi-stage heat exchanger is a three-stage heat exchanger.

[0085] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0086] The online particle size detector 7 is arranged on the pipeline connected to the synthesis gas outlet 1-3, and the online particle size detector 7 sends the detected silicon powder particle size to the controller 4;

[0087] An online dust concentration detector 8 is provided on a pipeline connected to the synthesis gas outlet 1-3, and the online dust concentration detector 8 sends the detected silicon powder concentration to the controller 4;

[0088] When the silicon powder particle size is smaller than the preset particle size range or the silicon powder concentration is smaller than the preset concentration, the controller 4 controls the air intake element 3 to adjust the air flow rate to increase;

[0089] When the particle size of the silicon powder is greater than the preset particle size or the concentration of the silicon powder is greater than the preset concentration, the controller 4 controls the air intake element 3 to adjust the air flow rate to decrease.

[0090] Specifically, the online particle size detector 7 in this embodiment is an online laser particle size analyzer.

[0091] The online laser particle size analyzer and the online dust concentration detector 8 can be installed before the multi-stage heat exchanger 5 and after the fluidized bed outlet, or can be installed after the multi-stage heat exchanger 5 and before the inlet of the external dust removal device 9, or can be installed between the multi-stage heat exchangers 5; there is no position requirement between the online laser particle size analyzer and the online dust concentration detector 8, and the installation pipeline can be either a horizontal pipeline or a vertical pipeline, but both cannot be installed near the pipeline elbow.

[0092] Preferably, the online dust concentration detector 8 is installed in a plug-in manner.

[0093] like Figure 2 As shown, preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0094] The sealed protection box 8 - 1 is arranged outside the online dust concentration detector 8 .

[0095] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0096] The pressure detector is arranged outside the sealed protection box 8-1, and is used to detect the pressure inside the sealed protection box 8-1.

[0097] Specifically, the pressure detector in this embodiment is a pressure gauge.

[0098] Preferably, the cold hydrogenation fluidized bed reaction system further comprises: an alarm, a pressure detector connected to the controller 4, the pressure detector sends the detected pressure value to the controller 4, and when the pressure value is greater than a preset pressure value, the controller 4 controls the alarm to sound an alarm.

[0099] The type of online dust concentration detector 8 is plug-in type. When installing, remove the base interface of the transmitter and weld it vertically on the top of the horizontal pipeline with a long straight pipe section. The base should be that the top of the insulating sleeve of the sensor probe is flush with the inner wall of the pipeline or protrudes from the inner wall of the pipeline. To prevent material leakage due to poor sealing effect. The sealed protection box 8-1 is welded on the outside of the online dust concentration detector 8. The sealed protection box 8-1 allows the transmission wire to be transmitted. The pressure gauge is installed on the sealed protection box 8-1 to monitor the leakage of the dust meter. When a pipeline leak occurs, the pressure indicator changes. Prompt the operator to perform maintenance and necessary protective measures.

[0100] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0101] The external dust removal device 9 is connected to the synthesis gas outlet 1-3, and the external dust removal device 9 is used for dust removal.

[0102] Preferably, the external dust removal device 9 is any one of a cyclone separator, a filter dust collector, a Venturi dust collector, and a wet scrubbing dust collector.

[0103] Specifically, in this embodiment, the external dust removal device 9 is an external cyclone separator.

[0104] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0105] The external dust-removing silicon powder receiving tank 10 is connected to the external dust-removing device 9, and the external dust-removing silicon powder receiving tank 10 is used to receive dust.

[0106] The outlet of the cyclone in the fluidized bed is connected to a heat exchanger 5 to exchange heat between the outlet synthesis gas and the inlet raw gas. An external dust removal device 9 is installed after the heat exchanger 5. An online particle size detector 7 and an online dust concentration detector 8 are installed in the pipeline between the fluidized bed and the external dust removal device 9.

[0107] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0108] The material level meter is arranged in the external dust removal silicon powder receiving tank 10 , and is used to detect the height of the solid material in the external dust removal silicon powder receiving tank 10 and send it to the controller 4 .

[0109] Before the silicon-containing synthesis gas enters the external dust removal device 9, it passes through a pipeline equipped with an online laser particle size analyzer and an online dust concentration detector 8. The online laser particle size analyzer obtains the particle size information of the discharged silicon powder, and the online dust concentration detector 8 obtains the concentration information of the discharged silicon powder. The silicon powder particle size information obtained by the online laser particle size analyzer is the particle size distribution of the silicon powder carried by the mixed gas. By averaging, D50 can be obtained as the average value of the silicon powder particle size; the silicon powder particle size D50 is called the median diameter or median particle size, which indicates the particle size corresponding to the cumulative particle size distribution percentage in the sample reaching 50%; the silicon powder concentration information obtained by the online dust concentration detector 8 is the mass of silicon powder particles in the unit volume of the mixed gas.

[0110] The above-mentioned outward silicon powder particle size information and concentration information are preferably obtained through an online laser particle size analyzer and an online dust concentration detector 8, and the outward silicon powder concentration information can also be calculated by the material level meter in the external dust removal silicon powder receiving tank 10, and the silicon powder particle size information can be measured offline by sampling silicon powder in the external dust removal silicon powder receiving tank 10. Compared with online detection, the acquisition frequency of the offline material level back-calculation silicon powder concentration information and the offline measurement of silicon powder particle size information is low, the feedback timeliness is poor, and the outward silicon powder control stability is relatively poor.

[0111] Among them, the mixed gas flow rate is Q VN , whose unit is standard cubic meter per hour. The material level of the external dust removal silicon powder receiving tank 10 passes through a dust discharge cycle for a period of time X, whose unit is hour. The material level rises by Δh, whose unit is meter. The corresponding material level volume change is ΔV, whose unit is cubic meter. The calculated silicon powder concentration Csi, whose unit is gram per standard cubic meter g / Nm 3 , Csi is:

[0112]

[0113] Preferably, the cold hydrogenation fluidized bed reaction system further comprises:

[0114] The ash hopper 2-1 is connected to the ash discharge port of the built-in cyclone separator 2. The ash hopper 2-1 is connected to the lower cone of the built-in cyclone separator 2. The lower cone of the built-in cyclone separator 2 and the ash hopper 2-1 are both sandwich structures. The sandwich structure is connected to the cavity for cyclone separation of the built-in cyclone separator 2. Adjusted air is introduced into the sandwich structure through an air intake pipe and then enters the cavity for cyclone separation of the built-in cyclone separator 2 through an air intake element 3.

[0115] The built-in cyclone separator 2 includes a cavity for cyclone separation and a lower cone, and the cavity for cyclone separation is connected to the lower cone. The lower cone of the built-in cyclone separator 2 is connected to the ash hopper 2-1. The ash hopper 2-1 and the lower cone of the built-in cyclone separator 2 are both double-layer structures, and the interlayer is a hydrogen gas chamber, and the hydrogen is regulated to flow into the hydrogen gas chamber through a pipeline.

[0116] The air inlet element 3 is installed in the ash hopper 2-1 or the opening of the inner wall of the sandwich air chamber at the lower cone of the built-in cyclone separator 2, preferably installed in the ash hopper 2-1.

[0117] like Figure 4 , 5 As shown, preferably, the air intake direction of the air intake element 3 is opposite to the swirl direction of the built-in cyclone in the built-in cyclone separator 2 and is inclined upward, with an upward vertical inclination angle of 0° to 75°, and a horizontal direction opposite to the tangent line of the inner wall of the built-in cyclone separator 2 is 15° to 90°.

[0118] Specifically, a host computer is provided in the controller 4 in this embodiment.

[0119] This embodiment also provides a control method using the cold hydrogenation fluidized bed reaction system, comprising the following steps:

[0120] The controller 4 adjusts the air flow rate at the air inlet element 3. The air flow rate of each air inlet element 3 is Q, where 100 Nm 3 / h<Q<2000Nm 3 / h, so that the particle size D50 of the silicon powder in the fluidized bed reactor 1 is within the preset particle size range, where 30μm<D50<70μm, and the concentration C of the silicon powder is within the preset concentration range, where 0.5g / Nm 3 <C<1.4g / Nm 3 .

[0121] Preferably, using the cold hydrogenation fluidized bed reaction system, the control method further comprises the following steps:

[0122] When the silica powder particle size D50 is less than 30 microns or the silica powder concentration is less than 0.5g / Nm 3 When the controller 4 controls the air intake element 3 to adjust the air flow rate to increase;

[0123] When the silica powder particle size D50 is greater than 70 microns or the silica powder concentration is greater than 1.4g / Nm 3 When the air flow rate is reduced, the controller 4 controls the air intake element 3 to adjust the air flow rate.

[0124] Specifically, in this embodiment, when the silicon powder particle size D50 is less than 30 microns or the silicon powder concentration is less than 0.5 g / Nm 3 When the preset first time is reached, the controller 4 controls the air intake element 3 to adjust the air flow rate to increase;

[0125] When the silica powder particle size D50 is greater than 70 microns or the silica powder concentration is greater than 1.4g / Nm 3 When the preset second time is reached, the controller 4 controls the air intake element 3 to adjust the air flow rate to decrease.

[0126] Preferably, using the cold hydrogenation fluidized bed reaction system, the control method further comprises the following steps:

[0127] The controller 4 calculates the silicon powder concentration Csi according to the material level height detected by the material level meter in the external dust removal silicon powder receiving tank 10.

[0128] Among them, the mixed gas flow rate is Q VN , the unit is standard cubic meter per hour Nm 3 / h, the material level of the external dust removal silicon powder receiving tank 10 passes through a dust discharge cycle for a period of time X, the unit of which is hours h, the material level rises Δh, the unit of which is meters m, and the corresponding material level volume change is ΔV, the unit of which is cubic meters m 3 , calculated silica powder concentration Csi, its unit is grams per standard cubic meter g / Nm 3 , Csi is:

[0129]

[0130] The bulk density of silicon powder in the tank is 1200kg / m 3 , converted to 1200000g / m 3 .

[0131] Failed silicon powder or deactivated materials are mainly fine powders below 40 microns, especially fine powders below 20 microns. It is generally believed that the smaller the particle size of silicon powder, the higher the impurity content and the lower the activity. By introducing adjustment gas into the built-in cyclone separator 2, the separation efficiency of the built-in cyclone separator 2 of the fluidized bed can be adjusted, and then the failed silicon powder can be discharged from the fluidized bed reactor. At the same time, a large amount of fine powder discharged during the slag discharge operation will cause the fine powder to deposit on the heat exchange tube bundle at the outlet of the fluidized bed reactor, affecting the heat exchange efficiency of the heat exchange gas; a large amount of silicon powder above 100 microns discharged during the slag discharge operation will cause the tube bundle to wear, and in severe cases, the tube bundle will be worn through and even the mixed gas pipeline will be worn through, causing safety risks such as failure of the heat exchanger 5 series gas and pipeline leakage; the silicon powder concentration in the tail gas of the fluidized bed reactor during the slag discharge operation will increase significantly, resulting in an increase in the external dust removal load and a decrease in efficiency. In the subsequent mixed gas elution process, a large amount of dust enters the elution tower, causing the elution tower to be blocked, the slurry load to increase dramatically, and a series of problems affecting production stability such as pipeline blockage will occur easily. Therefore, by controlling the silicon powder particle size and particle concentration information at the outlet of the fluidized bed reactor, the working efficiency of the built-in cyclone in the fluidized bed reactor can be controlled in real time, so that the silicon powder particle size and concentration at the outlet of the fluidized bed reactor can be stably maintained within a reasonable range, which can not only ensure that the failed silicon powder is discharged in time, but also ensure that it does not cause wear, heat exchange efficiency reduction and production fluctuations in subsequent heat exchange and elution processes.

[0132] This embodiment timely regulates and controls the internal cyclone of the fluidized bed so that the internal cyclone can maintain a reasonable efficiency and work stably, thereby achieving timely discharge of failed silicon powder and maintaining stable system operation.

[0133] Specifically, the control method based on online detection in this embodiment specifically includes:

[0134] Silicon powder, catalyst, hydrogen and silicon tetrachloride enter the fluidized bed reactor 1, react under a certain pressure and temperature, and undergo a cold hydrogenation reaction to generate trichlorosilane.

[0135] The synthesis gas and some silicon powder particles enter the inner cyclone inlet of the built-in cyclone separator 2 at the top of the fluidized bed for gas-solid separation. Most of the silicon powder falls back into the fluidized bed reactor 1 after cyclone separation to continue the reaction. A small amount of silicon powder escapes and runs away with the synthesis gas through the synthesis gas outlet 1-3 of the fluidized bed reactor 1, and enters the subsequent heat exchanger 5 and the external dust removal device 9.

[0136] The silicon powder discharged from the external dust removal device 9 is collected, sieved according to the particle size, and its impurity content is tested. The result of the impurity content corresponding to the silicon powder particle size is obtained. The test results show that when the silicon powder particle size is greater than 400 microns or less than 100 microns, the impurity content is high, that is, it is invalid silicon powder. Silicon powder particles larger than 400 microns are difficult to be entrained from the bed layer of the fluidized bed reactor 1 to the inner cyclone inlet of the built-in cyclone separator 2. The silicon powder particles larger than 400 microns detected are mainly "silicon skin" or particles agglomerated from the inner cyclone and subsequent pipelines and heat exchangers 5. Particles larger than 400 microns are not the focus of internal cyclone regulation, and subsequent regulation is mainly aimed at silicon powder particles smaller than 100 microns.

[0137] Based on the above statements, the control target of this method is that the silicon powder particle size D50 is greater than 30 microns and less than 70 microns, and the silicon powder concentration is greater than 0.5g / Nm 3 And less than 1.4g / Nm 3 The control method is to adjust the hydrogen flow rate at the intake element 3. The hydrogen flow rate adjustment range of each intake element 3 is greater than 100Nm 3 / h and less than 2000Nm 3 / h. When the silicon powder particle size D50 is less than 30 microns or the silicon powder concentration is less than 0.5g / Nm 3 When the silicon powder particle size D50 is greater than 70 microns or the silicon powder concentration is greater than 1.4g / Nm 3 When the hydrogen flow rate is controlled to decrease, the hydrogen flow rate is controlled to remain unchanged in other cases.

[0138] Based on the above results, a judgment program is constructed in the host computer to determine whether the silicon powder particle size is failed.

[0139] The program includes data input, judgment statements, loop statements, and result output. First, the obtained silicon powder particle size and concentration are input into the judgment statement. When the silicon powder particle size is less than 30 microns, or the silicon powder concentration is less than 0.5g / Nm 3When the silicon powder particle size is greater than 70 microns, or the silicon powder concentration is greater than 1.4g / Nm 3 When the silicon powder particle size is greater than 30 microns and less than 70 microns, and the silicon powder concentration is greater than 0.5g / Nm 3 Less than 1.4g / Nm 3 , the system outputs number 3, which means "control the hydrogen flow rate unchanged". The system enters a cycle to obtain the particle size concentration data again and make a judgment. When number 1 and number 2 appear continuously, the system will perform superimposed statistics. The data collection is 1min / time. When number 1 or number 2 is output continuously for more than 30 times, the system will output "the hydrogen flow rate needs to be controlled to increase, please adjust" or "the hydrogen flow rate needs to be controlled to decrease, please adjust". The silicon powder particle size and concentration are uploaded to the host computer system and automatically brought into the judgment program. According to the output judgment result, the host computer sends the corresponding signal to the controller 4. Controller 4 adjusts the hydrogen flow rate and delivers it to the air inlet element 3 to timely regulate the fluidized bed.

[0140] Specifically, in this embodiment, the raw silicon powder and raw gas enter from the silicon powder inlet 1-1 on the side of the fluidized bed reactor 1 and the mixed gas inlet 1-2 at the bottom of the fluidized bed reactor 1 respectively. The synthesis gas outlet 1-3 is located at the top of the fluidized bed reactor 1, and the other end is connected to the tube side inlet of the heat exchanger 5 through a pipeline. After being heated, pressurized and mixed, the raw silicon tetrachloride and hydrogen enter from the shell side of the heat exchanger 5 and exchange heat with the synthesis gas at the outlet of the fluidized bed. After heat exchange, the gas enters the mixed gas electric heater 6 and enters the fluidized bed reactor 1 after being overheated.

[0141] The air supply of the air intake element 3 is controlled by the controller 4. The air intake element 3 is installed at the lower cone of the built-in cyclone separator 2, or in the ash hopper 2-1, and ventilates the built-in cyclone separator 2 to control the amount of silicon powder discharged from the built-in cyclone separator 2.

[0142] The built-in cyclone separator 2 is installed in the fluidized bed reactor 1 for gas-solid separation, separating most of the silicon powder and returning it to the fluidized bed reactor 1 for further reaction. The separated syngas carrying a certain amount of silicon powder is discharged from the syngas outlet 1-3 and enters the heat exchanger 5 for heat exchange, and then enters the external dust removal device 9 for secondary gas-solid separation. The online particle size detector 7 and the online dust concentration detector 8 are installed on the pipeline after the outlet of the fluidized bed reactor 1 and before the inlet of the external dust removal device 9.

[0143] like Figure 2 As shown, since the joint of the online dust concentration detector 8 contains insulating components, the joint is prone to leakage risk after installation. A protective box 8-1 is installed outside the online dust concentration detector 8, the box is evacuated, and a pressure gauge is installed outside. When the pressure indication number changes, it means that there is a leakage inside.

[0144] After the particle size and concentration of silicon powder in the synthesis gas are detected, the particle size data and concentration data are transmitted to the host computer identification system, and the judgment is made according to the built-in logic and data limit of the identification system.

[0145] The particle size data of the built-in discrimination system is obtained only through experimental testing. Figure 3 As shown, the relationship between the particle size and impurity content of the external dust removal silicon powder receiving tank 10 is tested. The boron, phosphorus, iron, aluminum, calcium, magnesium, chromium, nickel, copper, zinc, lead and titanium content of silicon powder with a particle size range of 750-375μm, 375-187.5μm, 187.5-125μm, 125-95μm, 95-46μm and less than 46 microns are tested respectively. The total impurity content is calculated to obtain its relationship with the particle size. The results show that when the silicon powder particle size is greater than 400 microns or less than 100 microns, the impurity content is high, which is defined as failed silicon powder.

[0146] According to the basic logic judgment procedure, it is preferred to make certain improvements on this basis. The core is to judge the relevant results based on the particle size and concentration of silicon powder.

[0147] After the host computer obtains the data and makes judgments, it will output two results, one is to control the hydrogen flow rate to increase, and the other is to control the hydrogen flow rate to decrease.

[0148] The preferred air intake velocity and air volume are adjusted according to the exhaust spent silicon powder concentration.

[0149] The cold hydrogenation fluidized bed reaction system and control method in this embodiment have the following characteristics:

[0150] Beneficial effects:

[0151] 1. This solution can effectively identify failed silicon powder: This patent has obtained the relationship between silicon powder activity and particle size through experimental verification, and based on this, a cold hydrogenation fluidized bed control system is designed to achieve accurate discharge of failed silicon powder. The particle size and concentration of the discharged silicon powder are monitored in real time by using the online particle size detector 7 and the online dust concentration detector 8, and the silicon powder is automatically and accurately judged whether it is failed according to the logic judgment program in the upper computer.

[0152] 2. Reduce the risk of equipment leakage and improve system stability: The online dust concentration detector 8 provided by this system is installed in an inserted manner, and a sealed protection box 8-1 is welded on the outside, which effectively reduces the risk of equipment leakage. By monitoring the particle size and concentration of silicon powder, the system can detect and adjust abnormal conditions in time, thereby improving the stability of the entire fluidized bed reaction system.

[0153] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A cold hydrogenation fluidized bed reaction system, characterized in that: include: The fluidized bed reactor comprises a fluidized bed reactor body, a silicon powder inlet, a mixed gas inlet, a synthesis gas outlet, and a pipeline through hole arranged on the fluidized bed reactor body, wherein the silicon powder inlet is used to introduce silicon powder, the mixed gas inlet is used to introduce reaction gas, and the synthesis gas outlet is used to discharge synthesis gas from the cold hydrogenation reaction; A built-in cyclone separator is arranged in the fluidized bed, and a gas outlet of the built-in cyclone separator is connected to a synthesis gas outlet; An air intake element connected to a built-in cyclone separator; An air intake duct, which passes through the duct through-hole and is connected to the air intake element, and through which the regulated air is introduced into the built-in cyclone separator; The controller controls the opening and closing of the air inlet element and adjusts the air flow rate, and controls the air flow rate to be within a preset flow rate range, so that the particle size of the silicon powder in the fluidized bed reactor is within the preset particle size range, and the concentration of the silicon powder is within the preset concentration range.

2. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: Also includes: The mixed gas electric heater is connected to the mixed gas inlet and is used to heat the reaction gas introduced into the fluidized bed reactor.

3. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: Also includes: The heat exchanger has a tube side connected to the synthesis gas outlet and a shell side connected to the mixed gas inlet.

4. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: Also includes: An online particle size detector is arranged on a pipeline connected to the syngas outlet, and the online particle size detector sends the detected silicon powder particle size to the controller; An online dust concentration detector is installed on the pipeline connected to the syngas outlet, and the online dust concentration detector sends the detected silicon powder concentration to the controller; When the silicon powder particle size is smaller than the preset particle size range or the silicon powder concentration is smaller than the preset concentration, the controller controls the air intake element to adjust the air flow rate to increase; When the particle size of the silicon powder is greater than a preset particle size or the concentration of the silicon powder is greater than a preset concentration, the controller controls the air intake element to adjust the air flow rate to decrease.

5. The cold hydrogenation fluidized bed reaction system according to claim 4, characterized in that: The online dust concentration detector is installed in a plug-in manner.

6. The cold hydrogenation fluidized bed reaction system according to claim 4, characterized in that: Also includes: The sealed protection box is arranged outside the online dust concentration detector.

7. The cold hydrogenation fluidized bed reaction system according to claim 6, characterized in that: Also includes: The pressure detector is arranged outside the sealed protection box and is used to detect the pressure inside the sealed protection box.

8. The cold hydrogenation fluidized bed reaction system according to claim 7, characterized in that: Also includes: Alarm, the pressure detector sends the detected pressure value to the controller. When the pressure value is greater than the preset pressure value, the controller controls the alarm to sound an alarm.

9. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: Also includes: An external dust removal device is connected to the synthesis gas outlet, and the external dust removal device is used for dust removal.

10. The cold hydrogenation fluidized bed reaction system according to claim 9, characterized in that: The external dust removal device is any one of a cyclone separator, a filter dust collector, a Venturi dust collector, and a wet scrubbing dust collector.

11. The cold hydrogenation fluidized bed reaction system according to claim 9, characterized in that: Also includes: The external dust removal silicon powder receiving tank is connected to the external dust removal device, and the external dust removal silicon powder receiving tank is used to receive dust.

12. The cold hydrogenation fluidized bed reaction system according to claim 11, characterized in that: Also includes: The material level meter is installed in the external dust removal silicon powder receiving tank. The material level meter is used to detect the height of the solid material in the external dust removal silicon powder receiving tank and send it to the controller.

13. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: Also includes: The ash hopper is connected to the lower cone of the built-in cyclone separator. The lower cone of the built-in cyclone separator and the ash hopper are both sandwich structures. The sandwich structure is connected to the cavity for cyclone separation of the built-in cyclone separator. Adjusted air is introduced into the sandwich structure through an air inlet pipe and then enters the cavity for cyclone separation of the built-in cyclone separator.

14. The cold hydrogenation fluidized bed reaction system according to claim 1, characterized in that: The air intake direction of the air intake element is opposite to the swirl direction of the built-in cyclone in the built-in cyclone separator and is tilted upward. The upward vertical tilt angle is 0° to 75°, and the horizontal direction is opposite to the tangent line of the inner wall of the built-in cyclone separator and is 15° to 90°.

15. A control method using the cold hydrogenation fluidized bed reaction system according to any one of claims 1 to 14, characterized in that: The following steps are involved: The air flow rate at the intake element is adjusted by the controller. The adjusted mixed air flow rate of each intake element is Q, where 100Nm 3 / h<Q<2000Nm 3 / h, so that the particle size D50 of the silicon powder in the fluidized bed reactor is within the preset particle size range, where 30μm<D50<70μm, and the concentration C of the silicon powder is within the preset concentration range, where 0.5g / Nm 3 <C<1.4g / Nm 3 .

16. The control method according to claim 15, characterized in that: Using the cold hydrogenation fluidized bed reaction system described in claim 4, the control method further comprises the following steps: When the silica powder particle size D50 is less than 30 microns or the silica powder concentration is less than 0.5g / Nm 3 When the controller controls the air intake element to adjust the air flow rate to increase; When the silica powder particle size D50 is greater than 70 microns or the silica powder concentration is greater than 1.4g / Nm 3 When the air flow is reduced, the controller controls the air intake element to adjust the air flow rate.

17. The control method according to claim 15, characterized in that: Using the cold hydrogenation fluidized bed reaction system described in claim 12, the control method further comprises the following steps: The controller calculates the silicon powder concentration Csi based on the material level detected by the material level meter in the external dust removal silicon powder receiving tank. Among them, the mixed gas flow rate is Q VN , whose unit is standard cubic meter per hour. The material level of the external dust removal silicon powder receiving tank passes through a dust discharge cycle for a period of time X, whose unit is hour. The material level rises by Δh, whose unit is meter. The corresponding material level volume change is ΔV, whose unit is cubic meter. The calculated silicon powder concentration Csi, whose unit is grams per standard cubic meter g / Nm 3 , Csi is:

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