CN219424369U

CN219424369U - Fluidized bed

Info

Publication number: CN219424369U
Application number: CN202222733961.6U
Authority: CN
Inventors: 邓光付; 常露露; 王永亮; 黄金发; 邱香龙; 吴用
Original assignee: Leshan Gcl New Energy Technology Co ltd; Jiangsu Zhongneng Polysilicon Technology Development Co ltd
Current assignee: Leshan Gcl New Energy Technology Co ltd; Jiangsu Zhongneng Polysilicon Technology Development Co ltd
Priority date: 2022-08-03
Filing date: 2022-10-16
Publication date: 2023-07-28
Anticipated expiration: 2032-10-16
Also published as: WO2024027341A1; CN116969466A; CN117548414A; WO2024027340A1

Abstract

The utility model relates to a fluidized bed, comprising a bed body forming a certain space, a product outlet arranged below the bed body, a seed crystal inlet arranged above the bed body, and a tail gas outlet arranged above the bed body, wherein the bed body comprises: the heating zone is provided with a heating device which is used for providing internal energy for the bed body; the reaction zone is positioned above the heating zone, and is provided with a purging pipe which is used for providing purging gas and/or etching gas for the interior of the bed body; the comprehensive air inlet is arranged below the bed body and is connected with an air inlet switching valve which is used for switching the gas source. The fluidized bed provided by the utility model can be used for efficiently cleaning the silicon on the inner wall of the fluidized bed, and can be used for effectively reducing the silicon on the inner wall of the fluidized bed in the production process of polysilicon.

Description

Fluidized bed

Technical Field

The utility model relates to a polysilicon preparation device and method, in particular to a device and method for preparing granular silicon by a fluidized bed device, and particularly relates to a device and method for removing silicon deposited on the inner wall of a fluidized bed in the polysilicon production process.

Background

As a base material in the fields of semiconductors and solar cells, polycrystalline silicon is widely used for producing precision systems of minute size but complicated functions including various electronic logic devices, memory devices, discrete devices, etc., and is a direct raw material of PN junctions for photoelectric conversion in solar panels. It can be said that the human civilization today is largely built on silicon atoms. With the further development of human civilization, the demand for high-precision electronic systems and the demand for clean energy sources such as solar energy are more vigorous, resulting in a further increase in the demand for polysilicon. Therefore, there is a need to provide a polysilicon production apparatus and process that is low in cost, high in yield, and environmentally safe.

The existing process for producing polysilicon mainly comprises a modified Siemens method and a fluidized bed method. At this stage, the modified siemens process is the most commonly used process, and the polysilicon yield thereof occupies the vast majority of the global polysilicon yield, in contrast to the fluidized bed process, which is a process method gradually popularized in recent years, and the polysilicon yield ratio thereof is rising year by year.

The siemens process (including the modified siemens process) can also be referred to as a hydrogen reduction process, and adopts a bell jar reactor as main equipment, and trichlorosilane and hydrogen are used as main raw materials. As a typical Siemens method for preparing polysilicon, a polysilicon rod with the diameter of about 20mm is heated in a bell jar reactor, so that polysilicon reduced by hydrogen is deposited on the surface of the polysilicon rod, and the polysilicon rod is grown, and when the volume of the polysilicon rod reaches a certain degree, the polysilicon rod is taken out, thus obtaining a polysilicon product.

Typical chemical reactions of the siemens process are:

SiHCl ₃ +H ₂ →Si+3HCl

the Siemens method has wide application and mature technology, and the purity of the polysilicon product can be very high, so the Siemens method is generally used for producing the polysilicon product for semiconductors with higher purity requirements. In the Siemens method, in order to avoid deposition of simple substance silicon on the inner wall of a bell jar reactor, a silicon rod is directly heated, and a cooling device is usually arranged on the outer wall of the bell jar, so that the temperature of the bell jar wall is far lower than that of the silicon rod, and deposition of simple substance silicon on a bell jar reaction gas shell is reduced.

However, the siemens process has problems in that the continuous production is impossible due to the need to stop the machine to remove the grown silicon rod, and the polysilicon product is subjected to an additional pulverizing step when it is applied downstream.

Fluidized bed processes (including silane fluidized bed processes), which may also be referred to as "silane gas pyrolysis processes", employ a primary apparatusCommonly referred to as a "fluidized bed", the feed gas employed comprises monosilane (SiH ₄ ) Silicon tetrachloride (SiCl) ₄ ) Trichlorosilane (SiHCl) ₃ ) Dichlorosilane (SiH) ₂ Cl ₂ ) The silicon-containing gas is thermally decomposed or reduced in the fluidized bed, and the produced polycrystalline silicon is deposited and grown on the surfaces of fine silicon particles (also referred to as "seed crystals") in the fluidized bed, thereby producing a granular polycrystalline silicon product.

Typical reaction equations for a silane fluidized bed process are:

SiH ₄ →Si+2H ₂

since polysilicon is directly deposited on the surface of seed crystals, and the effective deposition area of seed crystals in a fluidized (also called "boiling") state inside the fluidized bed is far greater than that of the surface of silicon rods used in the siemens process, the production efficiency of the fluidized bed process is far greater than that of the siemens process. Meanwhile, since the temperature of thermal decomposition of the silicon-containing raw material gas is low, for example, at 300 to 400 ℃, the silicon-containing raw material gas has already started to decompose. In practice, the heating temperature of the silicon-containing raw material gas of the existing fluidized bed production process is generally 500-700 ℃, and the energy consumption is relatively low. Therefore, the fluidized bed method for preparing granular silicon has been widely used in recent years.

However, the existing fluidized bed process equipment still has certain problems: because of the need to integrally heat the silicon-containing raw material gas in the fluidized bed, various heating modes such as resistance heating, induction heating, convection heating and the like inevitably heat the inner wall of the fluidized bed, and under certain specific heating modes (such as external resistance heating), the temperature of the inner wall of the fluidized bed is highest, in this case, the silicon-containing raw material gas including monosilane is easy to decompose on the inner wall of the fluidized bed, and the simple substance silicon obtained by decomposition is deposited on the inner wall of the fluidized bed. Deposition of elemental silicon on the inner walls of a fluidized bed can present at least three types of problems:

First, as the thickness of silicon deposited on the inner wall of the fluidized bed becomes thicker, and since the resistance and thermal conductivity of polysilicon are large, the heating efficiency in most heating modes will be greatly affected, and in order to maintain the thermal decomposition temperature of the silicon-containing raw material gas, the power of the heating equipment has to be increased, thereby increasing the energy consumption.

Secondly, the thickness of the deposited silicon on the inner wall of the fluidized bed tends to be uneven, and the uneven heating uniformity of the raw gas containing silicon is affected, so that the diameter of the granular silicon product is uneven.

Thirdly, when the deposited silicon on the inner wall of the fluidized bed reaches a certain thickness, part of simple substance silicon blocks can fall off from the inner wall of the fluidized bed, and the fluidized bed structure is crushed or broken, so that great potential safety hazards are caused, and the falling large silicon blocks easily block the feeding pipe.

The existing fluidized bed process and equipment often cannot avoid the problem of silicon deposition on the inner wall of the fluidized bed, so that after the fluidized bed operates for a certain period, the fluidized bed needs to be stopped to remove the silicon deposition on the inner wall of the fluidized bed. The prior art proposes some schemes for solving the problem of silicon deposition on the inner wall of a fluidized bed:

chinese patent publication No. CN101318654B discloses a granular silicon production apparatus, which comprises a heating device and a reaction device that are physically separated, seed crystals are heated in the heating device and then transferred to the reaction device, a silicon-containing raw material gas is introduced into the reaction device, and the raw material gas is decomposed and deposited on the surface of the seed crystals with higher temperature. This patent reduces the temperature in the reaction zone by separating the heating zone from the reaction zone, thereby reducing the deposition of the silicon-containing feed gas on the inner wall of the reaction zone. However, the system has a complex structure, and in principle, the problem that raw material gas enters the heating zone and is deposited on the high-temperature inner wall of the heating zone, and silicon is deposited on the inner wall still exists.

Chinese patent publication No. CN101928001a discloses a fluidized bed apparatus, which reduces the temperature of the outer wall of the fluidized bed and reduces the deposition of elemental silicon on the inner wall of the fluidized bed by providing a cooling jacket on the outer wall of the fluidized bed and adopting an internal heating means for heating. However, this solution cannot avoid deposition of elemental silicon on the internal heating device, and, due to the addition of the cooling jacket, the temperature of the whole fluidized bed is not uniform, reducing the uniformity of the particle size of the granular silicon product.

Chinese patent publication No. CN101400835B discloses a method for etching deposited silicon on the inner wall of a fluidized bed by using chlorine-containing etching gas, which uses an etching gas pipe penetrating into a reaction zone to supply etching gas, thereby etching deposited silicon on the inner wall of the reaction zone. However, this solution does not empty the granular silicon product prior to etching, which necessarily results in depletion of the granular silicon product, and only etches the deposited silicon on the inner wall of the reaction zone, ignoring the deposited silicon on the inner wall of the heating zone, and does not solve the problem of non-uniformity of the deposited silicon.

Chinese patent publication No. CN103213989B discloses a fluidized bed structure which is inclined and rotated to physically reduce silicon deposition on the inner wall of the fluidized bed, but this structure will cause a problem of poor sealing of the fluidized bed, which cannot be put into practice.

In one aspect, there is a need to provide an apparatus and/or method for solving the problem of silica formation on the inner wall of a fluidized bed to uniformly remove silica formation on the inner wall of the fluidized bed, and at the same time, the method needs to quickly remove silica formation on the inner wall of the fluidized bed, reduce the shutdown loss caused by shutdown, and have lower raw material and equipment costs.

On the other hand, if the inner wall of the fluidized bed is etched too thoroughly, the metal inner wall of the fluidized bed will be exposed to the reaction gas, so that the metal impurities brought by the inner wall material of the fluidized bed are introduced into the granular silicon product, and the quality of the granular silicon product is greatly reduced, therefore, it is necessary to provide a method capable of effectively evaluating the etching progress, uniformly and accurately retaining silicon attached to the inner wall of the fluidized bed with a proper thickness, and avoiding the direct contact of the raw material gas with the inner wall of the fluidized bed.

Meanwhile, it is desirable to provide a fluidized bed structure that reduces the deposition of elemental silicon on the inner walls of the fluidized bed during the production of granular silicon.

The present utility model has been made to solve the above problems.

Disclosure of Invention

In one embodiment, the present utility model relates to a fluidized bed comprising a bed body defining a space, a product outlet disposed below the bed body, a seed crystal inlet disposed above the bed body, and a tail gas outlet disposed above the bed body, the bed body comprising: the heating zone is provided with a heating device which is used for providing internal energy for the bed body; the reaction zone is positioned above the heating zone, and is provided with a purging pipe which is used for providing purging gas and/or etching gas for the interior of the bed body; the comprehensive air inlet is arranged below the bed body and is connected with an air inlet switching valve which is used for switching the gas source.

Further, the axis of the purge tube is tangential to the shell of the reaction zone.

Further, the axis of the purging pipe has a purging included angle with the horizontal plane, and the included angle ranges from 10 degrees to 45 degrees.

Further, the purge angle is in the range of 20 to 35 °.

Further, more than two purge pipes are arranged in the reaction zone, and the more than two purge pipes are centrosymmetric along the axis of the reaction zone.

Further, the purge pipe is provided with a purge switching valve for switching the gas source.

Further, the inner wall of the reaction zone is provided with threads, and the inclination angle of the threads is consistent with the sweeping included angle of the sweeping pipe.

Further, the cross section of the thread is triangular.

Further, the cross section of the thread is trapezoidal.

Further, the fluidized bed further comprises: the gas distributor is arranged below the bed body and is connected with the comprehensive gas inlet; the gas distributor comprises a first gas passage and a second gas passage, and the first gas passage is arranged far away from the inner wall of the bed body compared with the second gas passage; the gas distributor further comprises: and the passage switching valve is respectively connected with the comprehensive air inlet, the first gas passage and the second gas passage, and can be switched between the first gas passage and the second gas passage.

Drawings

Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements. It should be noted that references to "an" or "an" embodiment in this disclosure are not necessarily to the same embodiment.

FIG. 1 illustrates one embodiment of a silicon particle production apparatus;

FIG. 2 illustrates one embodiment of a fluidized bed gas distribution apparatus;

FIG. 3 shows another embodiment of a fluidized bed for producing silicon particles;

FIG. 4 is a schematic top view of the purge tube of the fluidized bed of FIG. 2;

FIG. 5 illustrates another embodiment of a fluidized bed purge tube configuration;

FIG. 6 shows a schematic view of the internal structure of the fluidized bed of FIG. 2 after the top portion has been removed;

fig. 7 shows another embodiment of the internal structure of the fluidized bed after the top portion is removed.

Detailed Description

In this section, we will explain several embodiments of the utility model with reference to the figures. Whenever the shape, relative position and other aspects of the components described in the embodiments are not explicitly defined, the scope of the present utility model is not limited to only the illustrated components, which are shown for illustrative purposes only. In addition, while numerous details are set forth, it should be understood that some embodiments of the utility model may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. Spatially relative terms, such as "under … …," "under … …," "lower," "above … …," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or elements or feature or features as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below … …" may encompass both an orientation of above … … and below … …. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.

The terms "or" and/or "as used herein should be interpreted as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any one of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; a and B; a and C; b and C; A. b and C. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

The term "connection" as used herein includes various connection modes including direct connection and indirect connection, and does not require physical contact between the connected parts, including various specific connection modes including snap connection, screw connection, connection without fixing device, welding, riveting, and integral molding. In the case of component mating, the mating clearance includes a clearance fit, a transition fit, an interference fit, or a variable clearance fit.

The term "consistent" or "constant" as used herein with respect to various chemical parameters such as flow, pressure, temperature, purity, etc. does not require that the two parameters being compared be identical in value, and should also be considered "consistent" or "constant" if the two parameters being compared fluctuate up and down around an approximate value and within a certain range.

A production apparatus for producing granular polycrystalline silicon according to the present utility model is shown in fig. 1. The production facility includes a fluidized bed 100, a filtering device 200, and a gas-liquid separation recovery device 300, and in addition, the production facility includes a gas supply device (not shown in the drawing).

Fluidized bed

The fluidized bed 100 is the core device of the whole granular silicon production apparatus. The fluidized bed 100 comprises a bed body 101, wherein the bed body 101 is made of a material which is hard in texture and convenient to process, and comprises carbon steel, stainless steel, ceramic and the like. The bed 101 forms a space for accommodating reaction raw materials and providing a space for accommodating reaction products. The silicon-containing feed gas is heated after entering the space to undergo thermal decomposition or reduction reactions and produce granular polysilicon in the space, and when the polysilicon product reaches a certain amount, the polysilicon product will be discharged from the fluidized bed through the product discharge conduit 104. The bed 101 has a height and a generally circular cross-section that allows for more uniform heating of the silicon-containing feed gas and easier shaping during manufacture.

The bed body 101 is provided with a plurality of gas inlets and outlets, wherein the integrated gas inlet 102 is located at the bottom of the bed body 101, and the other end thereof is connected to a gas supply device, which can supply various types of gas integrated gas inlets 102 including raw material gas and etching gas, and is connected with an integrated gas inlet valve (not shown in the figure), which serves to close and/or switch the gas passage of the integrated gas inlet 102. Wherein the feed gas comprises monosilane (SiH) ₄ ) Silicon tetrachloride (SiCl) ₄ ) Trichlorosilane (SiHCl) ₃ ) Dichlorosilane (SiH) ₂ Cl ₂ ) And the like, monosilane (SiH is used in this example ₄ ) As feed gas. Monosilane can be prepared by various production processes including a metal hydride method, a silicon-magnesium alloy method and a trichlorosilane disproportionation method.

The reaction temperature in the fluidized bed may vary depending on the particular feed gas, for monosilaneThe fluidized bed may be heated at 600-800 deg.c, and in one alternative embodiment 650-700 deg.c. While trichlorosilane (SiHCl) ₃ ) The fluidized bed may be heated to a temperature of 900 c to 1200 c, alternatively 1000 c to 1050 c.

The intake amounts of the silicon-containing raw material gas and the fluidizing gas are maintained at a gas flow rate of 1.1 to 4.0Umf, but are not limited thereto, and may be, for example, 1.0 to 8.0Umf, or 2.0 to 5.0Umf, or 1.2 to 2.0Umf. Accordingly, the residence time of the silicon-containing feed gas is typically less than 12 seconds, and may be less than 9 seconds, and more preferably less than 4 seconds. The proportion of the silicon-containing raw material gas is not limited at all, and, alternatively, for example, 20mol% to 80mol% of the silicon-containing raw material gas may be used, with the remainder being fluidizing gas.

A seed feed port 105 is provided at the top of the bed 101 for feeding seed crystals as a deposited silicon core to the interior of the bed. In the fluidized bed reactor, the particle size of the particulate silicon seed crystals is typically 50 to 1000 μm, and as an alternative embodiment, the particle size of the particulate silicon seed crystals is 100 to 500 μm; and the granular polycrystalline silicon product produced is typically 500 to 3000 μm in size, and as an alternative embodiment, the granular silicon product has a particle size of 800 to 2000 μm. The above numerical ranges are for example only and should not be construed as limiting the embodiments of the present patent.

The etching gas comprises silicon tetrachloride (SiCl ₄ ) Hydrogen chloride (HCl) and chlorine (Cl) ₂ ) And a series of chlorine-containing substances. The use of these chlorine-containing substances as etching gas can avoid the introduction of impurities other than chlorine into the gas passage of the entire fluidized bed production apparatus.

In the production process of the granular silicon product, the integrated gas inlet 102 is located in a region with higher temperature inside the bed body, and the concentration of the raw material gas is also larger, so that simple substance silicon is more easily deposited at the outlet of the integrated gas inlet 102, and the air inlet of the integrated gas inlet 102 is easy to be blocked or blocked. In this embodiment, the feed gas and the etching gas share one integrated gas inlet management, so that not only can etching gas be provided to the inside of the bed body to etch the elemental silicon deposited on the inner wall of the bed body, but also the elemental silicon deposited at the outlet position of the integrated gas inlet 102 can be sufficiently etched in the etching process, thereby avoiding the blockage of the integrated gas inlet.

The top of the bed body 101 is provided with the tail gas outlet 103, and as the raw material gas or etching gas in the bed body 101 flows upwards after being heated, the top of the bed body 101 is provided with the tail gas outlet, so that the reaction tail gas or etching tail gas in the bed body can be completely discharged, and further treatment is performed. In the production process of polysilicon, since the raw material gas has undergone a sufficient reaction in the bed body 101, the concentration of the raw material gas discharged to the off-gas outlet 103 is low, the temperature thereof is also relatively low, and the gas flow rate is relatively fast, so that the amount of elemental silicon deposited at the off-gas outlet 102 is small. In current processes and equipment, the etching gas during etching is already capable of etching small amounts of elemental silicon deposited at the exhaust vent 102.

In this embodiment, two exhaust outlets are disposed at the top of the bed body, the exhaust outlet a is used for discharging exhaust generated in the process of etching the inner wall of the fluidized bed, and the exhaust outlet B is used for discharging exhaust generated in the process of preparing granular silicon.

The space formed by the bed 101 is divided into a heating zone 1011 and a reaction zone 1012 in the vertical direction, the reaction zone being located above the heating zone. In the production of polysilicon or the cleaning process of the inner wall of the fluidized bed, from the view of the movement path of the gas, the raw material gas or etching gas enters the space inside the bed through the comprehensive gas inlet 102 arranged at the bottom of the bed, and moves upwards to the reaction area 1012 after being heated by the heating device in the heating area 1011, and the raw material gas is fully subjected to thermal decomposition or reduction reaction in the reaction area to generate polysilicon products, or the etching gas is fully subjected to etching in the whole inner wall of the bed, so that the inner wall of the fluidized bed is cleaned.

As shown in fig. 1 and 2, as an embodiment, a gas distributor 106 is disposed at the bottom of the heating zone of the bed 101, the shape of the gas distributor 106 is the same as the cross-sectional shape of the bottom of the bed 101, and in this embodiment, the cross-section of the bottom of the heating zone of the bed 101 is circular, and the shape of the gas distributor 106 is also circular. The gas distributor 106 is connected to the integrated gas inlet 102 and forms a gas passage, and a plurality of gas outlet holes are provided in the gas distributor 106, and the raw gas and/or etching gas enters the gas distributor 106 through the integrated gas inlet 102 and is then ejected from the gas outlet holes of the gas distributor 106. The gas distributor is adopted to redistribute the raw material gas entering the bed body, so that the raw material gas is distributed more uniformly in the bed body, the diameter of the granular silicon product is more uniform, and the utilization ratio of the raw material gas is higher. On the other hand, the raw material gas can be directly used as the fluidization gas by adopting the arrangement of the gas distributor, so that the fluidization gas acts to pass through solid particles in the bed body from bottom to top, so that the solid particles generate upward acting force under the action of the tensile force of the fluid, and under the condition that the upward acting force of the solid particles is greater than or equal to the gravity of the solid particles, the solid particle silicon in the bed body can be in a suspended or boiling state, and the fluidized state in the fluidized bed is named. The material of the gas distributor 106 comprises quartz, silicon carbide, silicon nitride or simple substance silicon, and by adopting the nonmetallic material, the introduction of metal element impurities into the granular silicon product can be avoided, and the quality of the granular silicon product can be improved.

As shown in fig. 2, as an embodiment, the gas distributor is provided with a plurality of openings, wherein the openings 1061 located in the gas distributor are used for the passage of the raw material gas and/or the fluidizing gas, and the openings of the part are far away from the inner wall of the fluidized bed body, so that the contact between the raw material gas and the inner wall of the fluidized bed can be reduced, and the deposition of the simple substance silicon on the inner wall of the fluidized bed can be reduced. The openings 1062 at the edge of the gas distributor are used for the passage of etching gas, the openings 1062 are closer to the inner wall of the fluidized bed, and the etching gas can fully contact with the inner wall of the fluidized bed after entering the bed body through the openings 1062, so that the etching effect is improved. The central opening of the gas distributor is used to connect the product discharge conduit 104.

As an alternative embodiment, the bottom of the bed body also comprises a fluidization gas inlet (not shown in the figure) independent of the comprehensive gas inlet, and the fluidization gas can be selected from a plurality of gases including nitrogen, argon and helium, and the principle of the type of fluidization gas is that the fluidization gas does not react with the raw material gas in the fluidized bed or the material composition of the bed body. As an alternative embodiment, the fluidizing gas may be directly selected from a raw gas (including silane, chlorosilane, hydrogen chloride, etc.) or a reducing gas (such as hydrogen), and although these gases participate in the reaction, the reaction products of these gases do not introduce other impurity elements.

As an embodiment, the heating area adopts an induction heating mode, and in the case of adopting induction heating, a heating device 107 is arranged at a position of the bed body corresponding to the heating area, as an alternative embodiment, the heater 107 sequentially comprises a coil and a metal magnetic flux structure from outside to inside, when in heating, alternating current is provided for the coil so as to generate an alternating magnetic field, eddy current is induced in the metal magnetic flux structure by the alternating magnetic field, and the metal magnetic flux structure is heated under the action of the eddy current, so that heat is conducted into the bed body. As an alternative embodiment, no metal magnetic flux structure is provided, and induced eddy current is directly generated in the shell of the bed body to generate heat. In addition, since silicon itself has a certain conductivity, it is also possible to heat the silicon particles itself by inducing an electric current inside the silicon particles in a fluidized state in the fluidized bed. The induction heating has the characteristics of simple structure, high heat efficiency and capability of heating silicon particles.

As an alternative embodiment, the silicon seed and/or silicon-containing feed gas and/or fluidizing gas is preheated to 300-500 ℃, or 350-450 ℃, or to 400 ℃ before entering the fluidized bed reactor. The preheating mode can be a mode of heat exchange with reaction tail gas or a mode of conventional electric heater, microwave heating and the like. By preheating the feed gas and/or the fluidizing gas and the silicon seed, it is advantageous to reduce the load on the induction heating apparatus. Under the occasion of adopting induction heating, the conductivity of the seed crystal can be improved by preheating the seed crystal, so that induction vortex can be directly generated in the seed crystal, and the heating efficiency is greatly improved.

As an alternative embodiment, the heater 107 may also adopt various heating modes such as thermal resistance heating, microwave heating, and radiation heating.

As an alternative embodiment, the bottom of the bed 101 is of an inclined design, by which the granular silicon product can be more completely discharged from the product discharge conduit 104.

Protective gas purge

Fig. 3 shows another fluidized bed structure, the fluidized bed 200 in this embodiment comprises a bed 201, the bed 201 comprising a heating zone 2011 and a reaction zone 2012. At the bottom of the bed 201 there are provided a comprehensive gas inlet 202, a product discharge 204, a fluidising gas inlet 208. A seed crystal inlet 205 and a tail gas outlet 203 are provided at the top of the bed 201, wherein the tail gas outlet 203 can be used for discharging the tail gas generated in the normal production process and the etching cleaning process of the inner wall of the fluidized bed.

The cross-sectional area of the reaction zone 2012 is larger than the area of the heating zone 2011, and by adopting such a design, the gas flow rate in the reaction zone 2012 can be reduced, so that the raw material gas and/or etching gas can react in the reaction zone more fully. The content of fine silicon powder in the tail gas can be reduced even when the flow rate is reduced.

In this embodiment, a purge tube 209 is disposed at a position of the bed body corresponding to the reaction zone 2012. The purge tube 209 is connected at one end to an opening in the bed reaction zone and at the other end to a purge and/or etching gas supply (not shown). The purge tube may supply a purge gas to the inner wall of the bed body or an etching gas to the inner wall of the bed body.

The purge tube is provided with a purge valve that functions to close and/or switch the gas passage of the purge tube 209.

In the case of providing the purge gas, the purge gas includes various gases including nitrogen, argon and helium, and the principle of the purge gas is that the purge gas does not react with the raw material gas in the fluidized bed or the material component of the bed body. As an alternative implementation mode, the purge gas can directly select hydrogen chloride or hydrogen, and although the gases participate in the reaction process with the elemental silicon, the reaction products of the gases can not introduce other impurity elements, and the deposition of the elemental silicon on the inner wall of the fluidized bed can be avoided. Alternatively, the purge gas and the fluidizing gas may be of the same composition.

The purge gas moves along the inner wall of the bed body and can isolate the silicon-containing reaction gas from the inner wall of the bed body, thereby reducing the deposition of elemental silicon on the inner wall of the fluidized bed.

The etching gas comprises silicon tetrachloride (SiCl ₄ ) Hydrogen chloride (HCl) and chlorine (Cl) ₂ ) And a series of chlorine-containing substances. The use of these chlorine-containing substances as etching gas can avoid the introduction of impurities other than chlorine into the gas passage of the entire fluidized bed production apparatus. The etching gas moves along the inner wall of the bed body and reacts with the simple substance silicon on the inner wall of the bed body to play a role in etching.

As shown in fig. 3 and 4, the outlet direction of the purge pipe 209 is tangential to the housing of the reaction zone, and the purge pipe 209 is inclined upward at an inclination angle of 10 to 45 ° with respect to the horizontal direction, preferably 20 to 35 °. Through tangential arrangement, the gas sprayed out of the purging pipe 105 can be tightly attached to the inner wall of the bed body, and the contact between the purging gas and/or etching gas and the inner wall of the bed body is increased, so that the isolation effect of the purging gas and/or the etching effect of the etching gas are better; through the setting of slope, can make the sweep and/or etching gas after getting into the bed body through the sweep pipe, can follow the spiral of the internal wall of bed and rise, fully contact with the internal wall of bed for the sweep gas can fully carry out motion and/or etching in the reaction section and mention and can carry out abundant etching to the inner wall silicon of reaction section.

As an alternative embodiment, as shown in fig. 5, the axis of the air inlet direction of the purge pipe and the tangent line of the air inlet have a certain included angle θ, and the value of θ ranges from 5 ° to 45 °. By properly inclining the purge pipe relative to the tangential direction, the difficulty in manufacturing the purge pipe can be reduced. Meanwhile, because the angle between the purging pipe and the tangential direction is set, the gas entering the fluidized bed body through the purging pipe can still generate larger tangential separation on the inner wall of the bed body, and the purging gas is driven to move along the inner wall of the bed body.

As an alternative embodiment, as shown in fig. 3 to 4, more than two purge pipes are arranged in the reaction zone, and the purge pipes are distributed in a central symmetry manner along the axis of the reaction zone, and each purge pipe is simultaneously introduced with purge gas and/or etching gas in the process of cleaning the silicon on the inner wall of the isolated reaction gas and/or fluidized bed. With such an arrangement, the purge gas and/or the etching gas can be sufficiently distributed over the entire inner wall of the fluidized bed, and the effect of isolating the reaction gas and/or the effect of etching the inner wall of the fluidized bed can be improved.

In another embodiment, as shown in fig. 6, threads 4013 are provided on the inner wall of the bed corresponding to the reaction zone, and the angle of threads 4013 is consistent with the inclination angle of the purge tube. The threads form a gas path between them, and after the purge gas and/or etching gas is blown into the bed through the purge tube, the gas will move along the path formed between the threads. By arranging the screw thread passage, the movement path of the purge gas and/or the etching gas can be effectively limited, so that the effect of isolating the reaction gas of the purge gas and/or the effect of etching the inner wall of the fluidized bed are better.

As shown in fig. 7, as an alternative embodiment, regarding the shape of the cross section of the thread 4013, the width of the cross section of the thread becomes gradually smaller from the inner wall of the bed body to the top of the thread, and the cross section of the thread 4013 is triangular or trapezoid with a smaller top and a larger bottom. By adopting the cross-sectional shape of the thread, the deposition of simple substance silicon on the top end of the thread can be reduced, and the isolation effect of the purge gas and/or the etching effect of the etching gas can be improved.

Fluidized bed inner wall etching process

The build-up of silicon on the inner wall of the fluidized bed is a gradual and cumulative process, and the deposited silicon on the inner wall of the fluidized bed is only required to be cleaned under the condition that the build-up of silicon on the inner wall of the fluidized bed reaches a certain severity and can influence the heat transfer efficiency or the physical structure of the fluidized bed.

In the general production of granular silicon, the fluidized bed generally maintains its maximum throughput in the event that the supply of feedstock is relatively stable and the demand for the granular silicon product is relatively vigorous. For a fluidized bed with an annual production of 3000 tons, in general, the inner wall of the fluidized bed should be etched once when the fluidized bed is operated at full load for 3 to 6 months. Since the reaction temperature, the concentration of the raw materials, etc. of the other fluidized beds having larger or smaller production amounts are kept uniform, the silicon forming speed of the inner wall thereof is also substantially uniform, and thus the timing of the shutdown etching of this type is also kept uniform with the above 3000 ton fluidized bed for 3 to 6 months.

When the silicon removal operation is performed on the inner wall of the fluidized bed, the fluidized bed is firstly stopped and all the granular silicon in the bed body is emptied. The granular silicon in the bed body is completely emptied, so that the excessive etching of the granular silicon product by etching gas can be avoided, and the waste of the product is avoided. Meanwhile, the inner wall of the fluidized bed can be completely exposed after the granular silicon is emptied, so that the deposited silicon on the inner wall of the fluidized bed is more completely etched.

In the embodiment, the etching gas is high-purity hydrogen chloride gas, the purity (w/w) of the etching gas is more than or equal to 99.5 percent and 99.95 percent, and the preparation method of the high-purity hydrogen chloride gas comprises the following steps: mixing 31% concentrated hydrochloric acid with concentrated calcium chloride solution, then entering a resolving tower, continuously heating the solution through a resolving reboiler, stripping hydrogen chloride gas from the mixed solution of the concentrated hydrochloric acid and the calcium chloride and discharging the hydrogen chloride gas from the top of the tower, then enabling the stripped HCl gas to enter a sulfuric acid drying process through a demister, and then dehydrating the HCl gas to finally obtain high-purity hydrogen chloride gas. Compared with the method for preparing the hydrogen chloride gas by electrolyzing the sodium chloride solution, the method is safer and more economical, and particularly, the process and the equipment for preparing the hydrogen chloride gas by the process are widely applied in the Siemens method, so that the existing equipment is only needed to prepare the hydrogen chloride gas to etch the deposited silicon on the inner wall of the fluidized bed, and the additional equipment and the cost are not needed to be increased.

In the etching process of cleaning the inner wall of the fluidized bed, high-purity hydrogen chloride gas is introduced by using a comprehensive gas inlet pipe 102 arranged at the bottom of the fluidized bed 101, and the flow rate of the hydrogen chloride gas is regulated by a pipeline regulating valve. The flow rate (Kg/h) of the hydrogen chloride gas and the surface area (M) of the inner wall of the fluidized bed ² ) The numerical proportional relation range of (2) is: 0.5 to 3, and as an alternative embodiment, the ratio ranges from 1 to 1.5. The surface area of the inner wall here is in particular the surface area of the inner wall of the fluidized bed, from which the floor of the fluidized bed is removed, which, for a profiled fluidized bed,the lateral surface area of the cylindrical structure corresponding to the largest diameter in the horizontal cross section of the entire fluidized bed may be substituted. For the 3000 ton yield fluidized bed used in this example, the flow rate of the hydrogen chloride gas was 33 to 200Kg/h, and as an alternative embodiment, the flow rate of the hydrogen chloride gas was 60 to 100Kg/h. The purpose of controlling the flow of hydrogen chloride above the lower limit value is to ensure the concentration of etching gas in the bed body, thereby ensuring the speed of etching reaction and completing the etching process as soon as possible. Meanwhile, an upper limit is set for the hydrogen chloride flow, and if the upper limit is exceeded, the hydrogen chloride gas cannot fully react with the deposited silicon on the inner wall of the fluidized bed, so that more hydrogen chloride gas is wasted. As an alternative implementation manner, the flow of the hydrogen chloride is kept constant in the whole etching process, as the etching object of the hydrogen chloride is the deposited silicon on the inner wall of the fluidized bed, the area of the deposited silicon on the inner wall of the fluidized bed does not change greatly along with the progress of etching, which means that the amount of the reactant corresponding to the etching gas is kept constant basically at all time points of etching, so that the flow of the hydrogen chloride gas in the whole etching process is kept constant, the control mode is relatively simple, and the whole etching process is not influenced.

The heating power of the fluidized bed is regulated by a power regulating cabinet of the fluidized bed heater, so that the temperature in the bed body is maintained at 400-1000 ℃, and the temperature in the bed body is 600-800 ℃ in an alternative implementation mode. The lower limit of the temperature is set for the purpose of securing the reaction rate, thereby avoiding yield loss due to long-time stop of production. The purposes of setting the upper temperature limit include: on the one hand, since the heating device adopted in the etching process uses the original heating equipment of the fluidized bed, and the temperature adopted in the process of producing polysilicon by the fluidized bed is lower than the temperature adopted in the Siemens method, if the original heating equipment of the fluidized bed is utilized to provide the temperature far exceeding the temperature adopted in the preparation of the fluidized bed, the power burden of the heating equipment can be greatly increased, and the service life of the heating equipment is reduced. In addition, since the relationship between the temperature and the reaction rate of the etching gas is not a simple linear relationship, in other words, the marginal rate of the reaction of the etching gas with the deposition silicon on the inner wall of the fluidized bed is decreased during the temperature increase, and in the case that the temperature is higher than 1000 ℃, the cost required to increase the etching rate by further increasing the temperature is drastically increased. In addition, too high a temperature can have an unpredictable effect on the thermal reliability and chemical stability of the fluidized bed housing, and thus may present a potential safety hazard.

The pressure in the bed body is maintained at 0.1Mpa to 0.2Mpa by controlling a regulating valve connected to the exhaust outlet. The pressure value higher than 0.1Mpa can ensure the concentration of etching gas in the bed body and ensure the rapid and efficient etching process. The upper limit of the set pressure value is mainly from the safety of the fluidized bed, so that the explosion hidden trouble caused by the excessive pressure is prevented.

The high-purity hydrogen chloride enters the fluidized bed through a comprehensive air inlet pipe at the bottom of the fluidized bed and reacts with simple substance silicon deposited on the inner wall of the fluidized bed to generate silane and hydrogen, and the main reaction formula is as follows:

HCl+Si→SiH _x CL _y +H ₂

wherein the chlorosilane generated in the etching process mainly comprises silicon tetrachloride (SiCl ₄ ) Trichlorosilane (SiHCl) ₃ ) Dichlorosilane (SiH) ₂ Cl ₂ ) And chlorosilane is the main component of etching tail gas, besides, the etching tail gas also comprises hydrogen and fine silicon powder which moves along with the ascending airflow.

As shown in FIG. 3, in the etching process of the present embodiment, hydrogen chloride gas is introduced into the integrated gas inlet pipe 202 and the purge pipe 209 simultaneously, and the total flow rate (Kg/h) of the hydrogen chloride gas and the surface area (M) of the inner wall of the fluidized bed ² ) The numerical proportional relation range of (2) is: 0.5 to 3, and as an alternative embodiment, the ratio ranges from 1 to 1.5. The surface area of the inner wall here is in particular the surface area of the inner wall of the fluidized bed, from which the floor of the fluidized bed is removed, and for a profiled fluidized bed it is possible to replace it with the surface area of the side of the cylindrical structure corresponding to the largest diameter in the horizontal cross section of the entire fluidized bed. The flow rate of the hydrogen chloride gas introduced through the comprehensive air inlet pipe 202 is greater than or equal to the flow rate of the hydrogen chloride gas introduced through the purge pipe 209, and the ratio ranges from 4:1 to 1:1. Warp yarn The hydrogen chloride gas introduced into the fluidized bed through the comprehensive air inlet pipe 202 enters from the bottom of the fluidized bed, firstly passes through the heating zone of the fluidized bed, and fully reacts with the deposited silicon on the inner wall 2011 of the heating zone after being heated in the heating zone 2011, thereby playing a role in etching. Because the deposited silicon on the inner wall of the whole fluidized bed is uneven, i.e. the deposited silicon on the inner wall of the reaction zone 2012 is excessive, the hydrogen chloride gas introduced from the bottom of the fluidized bed always has undergone sufficient reaction when reaching the reaction zone, so that the concentration of the hydrogen chloride is reduced, and the deposited silicon on the inner wall of the reaction zone 2012 cannot be sufficiently etched, so that the deposited silicon on the inner wall of the whole fluidized bed cannot be sufficiently etched. At this time, the hydrogen chloride gas is replenished through the purge pipe 209 provided in the reaction zone to maintain the concentration of hydrogen chloride in the reaction zone, thereby performing more sufficient etching of the inner wall of the reaction zone 2012. With this arrangement, the deposited silicon at each position on the inner wall of the fluidized bed can be sufficiently and uniformly etched.

Etching tail gas recovery

Referring to fig. 1, the primary exhaust gas generated by etching is discharged from the fluidized bed through the exhaust gas discharge port 103, and enters the filtering device 200 connected to the exhaust gas discharge port 103, and the components of the primary exhaust gas include chlorosilane, hydrogen gas, and fine silicon particles. In this embodiment, the filtering device 200 includes at least one set of filter screens for filtering the primary exhaust gas with fine silicon particles discharged from the exhaust gas outlet, and leaving the fine silicon particles in the filtering device. Alternatively, the filtering area of the filtering device 200 is 20-50 m ³ The filtering precision is 0.4-0.8 mu m. As an alternative embodiment, the filter device may also be a cyclone separator. The fine silicon particles obtained by filtration through the filter device 200 can be recovered and used as seed crystals for producing granular silicon. In the etching process of etching the silicon on the inner wall of the fluidized bed by HCl, the middle exhaust gas component after passing through the filtering device 200 is mainly chlorosilane (mainly silicon tetrachloride and trichlorosilane) and hydrogen. The silicon dust filtered by the filtering device 200 can be re-input into the production of fluidized bed granular silicon as seed crystal raw material of the fluidized bed.

The gas-liquid separation and recovery device 300 is connected to the filtering device 200. As an alternative embodiment, the gas-liquid separation device may be a rectifying tower, where the rectifying tower uses the characteristic that boiling points of different components in the mixture are different, or vapor pressures of the components are different at the same temperature to transfer light components in the liquid phase to the gas phase, and transfer high components in the gas phase to the liquid phase, so as to achieve the purpose of gas-liquid separation.

In the present embodiment, the gas-liquid separation recovery apparatus 300 includes a heat exchanger 301 and a gas-liquid separation tank 302. The heat exchanger 301 is used for cooling the filtered intermediate exhaust gas. The middle exhaust gas comprises chlorosilane and hydrogen, wherein the chlorosilane comprises silicon tetrachloride (SiCl ₄ ) Trichlorosilane (SiHCl) ₃ ) Dichlorosilane (SiH) ₂ Cl ₂ ) Such gases containing chlorine and silicon are collectively referred to herein. Since the boiling point of chlorosilane is low, for example, the boiling point of silicon tetrachloride as a main component is 57.6 ℃, the boiling point of trichlorosilane is 31.8 ℃, the heat exchanger 301 reduces the temperature of etching tail gas to below 30 ℃, at the temperature, the main chlorosilane components including silicon tetrachloride and trichlorosilane all become liquid, the rest gas is tail gas of which the main component is hydrogen, and the tail gas of the tail gas can be directly discharged into the atmosphere after reaching the environmental standard because the hydrogen is pollution-free and can also be recycled. As an alternative embodiment, the heat exchanger 301 reduces the temperature of the etching tail gas to below 8 ℃, at which temperature the dichlorosilane will also become liquid (the boiling point of dichlorosilane is 8.2 ℃), which can further increase the purity of the hydrogen in the tail gas.

The gas-liquid mixture cooled by the heat exchanger enters the gas-liquid separation tank 302, the gas-liquid separation tank generally comprises an inlet, a gas outlet and a liquid outlet, the gas-liquid mixture enters the gas-liquid separation tank through the inlet and then is separated from the liquid in the separation tank, the tail gas obtained by separation is discharged from the gas outlet, and the liquid obtained by separation is discharged from the liquid outlet. As an alternative embodiment, the gas-liquid separation device inside the gas-liquid separation tank 302 may include various types of gas-liquid separation devices such as a distributor, a liquid separation plate, a filter, a cyclone, and the like.

The heat exchanger is adopted as a gas-liquid separation and recovery device, hydrogen and chlorosilane can be completely separated, and although the accuracy of separating etching tail gas through the heat exchanger and a gas-liquid separation tank is lower than that of adopting a rectifying tower, the separated chlorosilane (comprising a mixture of silicon tetrachloride and trichlorosilane) can be directly used as a raw material for preparing polysilicon by a Siemens method without further separating each component in a liquid mixture. Therefore, the heat exchanger can greatly reduce the cost of etching tail gas treatment, simultaneously reduce the complexity of the whole system and ensure the stable operation of the system.

In addition, since chlorosilanes are easily reacted with water at high temperatures, the following two reactions are performed:

SiHCl ₃ +2H ₂ O＝SiO ₂ +3HCl+H ₂

SiCl ₄ +4H ₂ O＝H ₄ SiO ₄ ↓+4HCl↑

that is, if more water is present in the system, the chlorosilane generated during the etching process will undergo hydrolysis reaction to generate silica and orthosilicic acid as impurities, thereby reducing the availability of etching tail gas. The high-purity hydrogen chloride gas is adopted as the etching gas in the etching process, so that the introduction of moisture in the whole etching process can be avoided, the purity of etching tail gas is ensured, and the recycling property of the etching tail gas is improved.

As an alternative embodiment, the existing dry tail gas recovery equipment and process in the improved siemens method can be used for recovery, including various tail gas recovery technologies such as pressure condensation, gas-liquid separation, absorption, adsorption and the like. As an alternative embodiment, the existing fluidized bed tail gas recovery device is directly adopted for recovery, and a separate etching tail gas recovery device is not required.

Determination of etching progress

After being discharged through the exhaust gas discharge pipe 103, the etching exhaust gas is filtered by the filtering device 200 to remove fine silicon powder in the exhaust gas, and enters a gas analysis device (not shown) arranged at the rear end of the filtering device 200 at the C end. The gas analysis device analyzes the content of the silicon-containing gas in the etching tail gas, so as to judge the silicon etching condition of the inner wall of the fluidized bed. Because the gas inlet of the gas analysis device is thinner, the filtering of the fine silica powder before the detection of the tail gas components can avoid the inlet blockage of the gas analysis device and prolong the service life of the gas analysis device. As an alternative embodiment, the etching gas can also be introduced directly into the gas analysis device.

In a first example, the fluidized bed was a 3000 ton fluidized bed, the flow rate of high purity hydrogen chloride gas was 100Kg/h, the reaction temperature was 1000℃and the reaction pressure was 0.2MPa. In the etching start stage, each silicon-containing gas component in the etching off-gas is analyzed by a gas analysis device, and the data are: 113800ppmv of trichlorosilane and 277240ppmv of silicon tetrachloride. In the later stage of etching, each silicon-containing gas component in the etching tail gas is analyzed by a gas analysis device, and the data are as follows: 1120ppmv of trichlorosilane and 9260ppmv of silicon tetrachloride. In this case, the content of trichlorosilane is already lower than one percent of the data of starting etching, namely, the etching process is considered to be completed, and at the moment, a simple substance silicon protective layer is still remained on the inner wall of the fluidized bed, and the protective layer can avoid introducing metal or other types of impurity elements from the inner wall of the fluidized bed of metal or ceramic in the production process of the granular silicon, so that the quality of the granular silicon product is improved.

In another embodiment, the fluidized bed is a 3000 ton fluidized bed, the flow rate of high-purity hydrogen chloride gas is 50Kg/h, the reaction temperature is 400 ℃, and the reaction pressure is 0.1Mpa. In the etching start stage, each silicon-containing gas component in the etching off-gas is analyzed by a gas analysis device, and the data are: 41250ppmv of trichlorosilane and 115420ppmv of silicon tetrachloride. In the later stage of etching, each silicon-containing gas component in the etching tail gas is analyzed by a gas analysis device, and the data are as follows: 910ppmv of trichlorosilane and 2340ppmv of silicon tetrachloride. In this case the silicon tetrachloride content was already below one fiftieth of the data for the start of the etching, i.e. the etching process was considered to have been completed, at which time a protective layer of elemental silicon remained on the inner wall of the fluidized bed.

As an alternative embodiment, a cooling device is arranged between the filtering device and the gas analysis device, and is used for cooling the high-temperature tail gas, so that the high-temperature tail gas is prevented from damaging the gas analysis device or influencing the measurement accuracy of the gas analysis device. The cooling device reduces the temperature of the etching tail gas to below 300 ℃ and above 100 ℃, and the main components of the etching tail gas still keep the gas state in the temperature range. As an alternative implementation mode, the cooling device reduces the temperature of etching tail gas to the range of 80-150 ℃, and then the gas analysis device samples and detects the etching tail gas.

As an alternative embodiment, each silicon-containing gas component in the etching tail gas is detected three or more times during the whole etching process, and the time interval between each detection is gradually shortened. Since the whole etching process usually takes 10-30 days, the silicon on the inner wall of the fluidized bed is thicker at the initial stage of etching, the effective reaction area of the silicon on the inner wall of the fluidized bed is not changed greatly in the etching process, and the silicon-containing gas component in the detection result is not changed greatly under the condition that the purity, flow, temperature, pressure and other conditions of the hydrogen chloride gas are kept unchanged, the main purpose of the detection is to judge whether the etching process is normally performed or not, so that the detection can be performed one day at this stage, but the detection is not limited to the time.

In the latter stage of etching, since it is necessary to judge whether or not it is necessary to terminate the etching process by the degree of etching, it is necessary to detect the silicon-containing gas component in the etching off-gas relatively frequently. The time between the detection at the later stage of etching is shorter than the time between the detection at the initial stage of etching, for example, one hour may be detected at a stage near the end of etching, but the time is not limited to this detection. By setting such a detection time interval, the accuracy of determining the etching degree can be ensured while the service life of the gas analysis device can be prolonged.

The utility model is not limited to the specific device structures, arrangements and methods shown in the claims or the description, but rather should be understood to fall within the scope of the utility model as long as structures, steps or methods similar to those of the utility model are adopted and similar effects can be achieved.

Claims

1. The utility model provides a fluidized bed, includes the bed body that forms certain space, sets up the product export of the below of bed body, sets up seed crystal entry of the top of bed body, and set up the tail gas export of the top of bed body, its characterized in that:

the bed body includes:

the heating zone is provided with a heating device which is used for providing internal energy for the bed body;

the reaction zone is positioned above the heating zone and is provided with a purging pipe which is used for providing purging gas and/or etching gas for the inside of the bed body;

the comprehensive air inlet is arranged below the bed body and is connected with an air inlet switching valve which is used for switching a gas source.

2. The fluidized bed of claim 1, wherein:

the axis of the purge tube is tangential to the shell of the reaction zone.

3. The fluidized bed of claim 2, wherein:

the axis of the purging pipe and the horizontal plane form a purging included angle, and the range of the purging included angle is 10-45 degrees.

4. A fluidized bed according to claim 3, characterized in that:

the purge angle is in the range of 20 to 35 °.

5. The fluidized bed of claim 2, wherein:

the reaction zone is provided with more than two purging pipes which are centrosymmetric along the axis of the reaction zone.

6. The fluidized bed according to any one of claims 1 to 4, characterized in that:

the purge pipe is provided with a purge switching valve for switching the gas source.

7. The fluidized bed of claim 1, wherein:

the inner wall of the reaction zone is provided with threads, and the inclination angle of the threads is consistent with the sweeping included angle of the sweeping pipe.

8. The fluidized bed of claim 7, wherein:

the cross section of the thread is triangular.

9. The fluidized bed of claim 7, wherein:

the cross section of the thread is trapezoid.

10. The fluidized bed of claim 1, wherein:

The fluidized bed further comprises:

the gas distributor is arranged below the bed body and is connected with the comprehensive gas inlet;

the gas distributor comprises a first gas passage and a second gas passage, wherein the first gas passage is arranged far away from the inner wall of the bed body compared with the second gas passage;

the gas distributor further comprises:

and the passage switching valve is respectively connected with the comprehensive air inlet, the first gas passage and the second gas passage and can be switched between the first gas passage and the second gas passage.