Patent Application
20140112832
The present disclosure relates a nozzle assembly for use with a fluid bed reactor, such as a fluid bed reactor for pyrolytic decomposition of a silicon-bearing gas to produce silicon-coated particles.
Pyrolytic decomposition of silicon-bearing gas in fluidized beds is an attractive process for producing polysilicon for the photovoltaic and semiconductor industries due to excellent mass and heat transfer, increased surface for deposition, and continuous production. Compared with a Siemens-type reactor, the fluidized bed reactor offers considerably higher production rates at a fraction of the energy consumption. The fluidized bed reactor can be continuous and highly automated to significantly decrease labor costs.
Gases, including a silicon-bearing gas, flow into the fluidized bed reactor through nozzles. Silicon is deposited on particles in the reactor by decomposition of the silicon-bearing gas. Control over the gas flow (e.g., volume, velocity) is important to maintain desired conditions within the fluidized bed reactor. Gas flow can affect, for example, the extent of fluidization, rate of silicon deposition, particle size and/or uniformity, temperature in a given area of the reactor, fouling of components, and combinations thereof.
A common problem in fluidized bed reactors is fouling of interior components and surrounding reactor walls as silicon deposits form on surfaces during pyrolysis. Another common problem is clogging of nozzles that can occur when gas flow decreases or ceases, and seed and/or product particles fall into upwardly oriented nozzles. To avoid or minimize these problems with conventional nozzles, a gas (e.g., a non-silicon-containing gas) may be flowed through the nozzle(s) at a sufficient velocity to prevent particles from falling into the nozzle(s). However, when nozzles become fouled or occluded, they may need to be removed and replaced.
Embodiments of a nozzle assembly and a closable valve assembly for use in a fluid bed reactor system are disclosed. Embodiments of the nozzle assembly include a first member configured to extend upwardly from a bottom wall of a fluid bed reaction chamber, and a second member. The first member includes an inlet at a first end positioned at or below the bottom wall of the fluid bed reaction chamber and an upwardly facing outlet at a distal end that is positioned above the inlet when the nozzle is installed in a fluid bed reactor. The first member defines a passageway in fluid communication with the inlet and the outlet. In some embodiments, the inlet also is in fluid communication with a gas source, such as a silicon-bearing gas. The first member further includes threads adjacent to the outlet. The second member includes an inlet at a first end and an upwardly facing orifice at a second end. The second member defines a passageway in fluid communication with the inlet and the outlet. The second member inlet is in fluid communication with the first member outlet. The second member further includes threads adjacent to the inlet. The second member threads are positioned and cooperatively dimensioned to engage with the first member threads on such that the first member and the second member are detachably fitted together. In some embodiments, the first member and/or the second member is rectilinear.
The nozzle assembly may further include an orifice plate positioned within at least one of the passageways to restrict a flow of gas through the passageways, the orifice plate being removable when the first member and the second member are not fitted together.
In one arrangement, the first member threads are on an outer wall surface adjacent to the first member outlet, and the second member threads are on an inner wall surface adjacent to the second member inlet. In another arrangement, the first member threads are on an inner wall surface adjacent to the first member outlet, and the second member threads are on an outer wall surface adjacent to the second member inlet.
In some embodiments, an insulating member is positioned around the first member, the second member, or both the first member and the second member.
In some embodiments, the nozzle assembly further includes a tubular outer member positioned around the first member, the second member, or both. The outer member has a wall spaced apart from an outer surface of the first member, the second member, or both the first member and the second member, thereby defining an annular space between the outer member wall and the outer surface. The annular space may be in fluid communication with a gas source. In certain embodiments, an insulating member is positioned around the outer member. Thus, the nozzle assembly may include an outer member positioned concentrically around the first member and/or second member, and an insulating member positioned concentrically around the outer member.
Embodiments of a closable nozzle assembly for a heated silicon deposition reactor include a nozzle configured to extend upwardly into a reaction chamber of a heated silicon deposition reactor system, and a valve assembly connected to the nozzle. The nozzle has an inlet in fluid communication with a gas source and an upwardly facing orifice in fluid communication with the inlet and positioned to inject a gas upwardly into the reaction chamber. The valve assembly includes a valve body and a gate pivotally connected to the valve body, wherein the gate is movable between a first position wherein the orifice is at least partially covered in the absence of gas flow, and a second position wherein the orifice is not covered when gas flows through the orifice. An insulating member may be positioned around the nozzle.
In some embodiments, the nozzle is a threaded nozzle assembly as disclosed herein. In such embodiments, the valve assembly may be connected to the second member. In one embodiment, the closable nozzle assembly further includes an insulating member positioned around the first member, the second member, or both the first member and the second member. In another embodiment, the closable nozzle assembly further includes a tubular outer member positioned around the first member, the second member, or both the first member and the second member, wherein the outer member comprises a wall spaced apart from an outer surface of the first member, the second member, or both the first member and the second member, thereby defining an annular space between the outer member wall and the outer surface, wherein the annular space is in fluid communication with a gas source. An insulating member may be positioned around the outer member.
In some embodiments, the valve assembly is removably connected to the nozzle. In one embodiment, the nozzle includes threads on an inner wall surface adjacent to the orifice and the valve assembly includes threads on an outer wall surface of a lower portion of the valve body. In another embodiment, the nozzle includes threads on an outer wall surface adjacent to the orifice and the valve assembly includes threads on an inner wall surface of a lower portion of the valve body. The valve assembly threads are positioned and cooperatively dimensioned to engage with the nozzle threads such that the valve assembly and the nozzle are detachably fitted together.
Embodiments of a fluid bed reactor may include an outer wall surrounding a reaction chamber, a nozzle assembly as disclosed herein, and a gas source in fluid communication with the first member inlet. The fluid bed reactor further may include an embodiment of a closable valve assembly as disclosed herein.
Embodiments of the disclosed nozzle assembly facilitate maintenance of a fluid bed reactor. With the reactor in a non-fluidized state, the second member of the nozzle is detached from the first member by disengaging the second member threads from the first member threads, and removed from the reaction chamber. A replacement second member is then inserted into the reaction chamber. The replacement second member includes an inlet at a first end in fluid communication with an upwardly facing orifice at a second end, and threads adjacent to the inlet that are positioned and cooperatively dimensioned to engage with the threads on the first member. The replacement second member threads are engaged with the first member threads to provide a nozzle assembly. The replacement second member may have a different length, a different diameter or configuration (e.g., an outward flare or inward taper at its upper end), and/or be constructed of different material(s) than the original second member.
The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
Disclosed herein are embodiments of a threaded nozzle assembly and a closable valve assembly for use in a fluid bed reactor system, such as a fluid bed reactor system for the formation of polysilicon by pyrolytic decomposition of a silicon-bearing gas and deposition of silicon onto fluidized silicon particles or other seed particles (e.g., silica, graphite, or quartz particles).
The manufacture of particulate polycrystalline silicon by a chemical vapor deposition method involving pyrolysis of a silicon-containing substance such as for example silane, disilane or halosilanes such as trichlorosilane or tetrachlorosilane in a fluidized bed reactor is well known to a person skilled in the art and exemplified by many publications including the following patents and publications: U.S. Pat. No. 8,075,692, U.S. Pat. No. 7,029,632, U.S. Pat. No. 5,810,934, U.S. Pat. No. 5,798,137, U.S. Pat. No. 5,139,762, U.S. Pat. No. 5,077,028, U.S. Pat. No. 4,883,687, U.S. Pat. No. 4,868,013, U.S. Pat. No. 4,820,587, U.S. Pat. No. 4,416,913, U.S. Pat. No. 4,314,525, U.S. Pat. No. 3,012,862, U.S. Pat. No. 3,012,861, US2010/0215562, US2010/0068116, US2010/0047136, US2010/0044342, US2009/0324479, US2008/0299291, US2009/0004090, US2008/0241046, US2008/0056979, US2008/0220166, US 2008/0159942, US2002/0102850, US2002/0086530, and US2002/0081250.
Silicon is deposited on particles in a reactor by decomposition of a silicon-bearing gas selected from the group consisting of silane (SiH4), disilane (Si2H6), higher order silanes (SinH2n+2), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), silicon tetrachloride (SiCl4), dibromosilane (SiH2Br2), tribromosilane (SiHBr3), silicon tetrabromide (SiBr4), diiodosilane (SiH2I2), triiodosilane (SiHI3), silicon tetraiodide (SiI4), and mixtures thereof. The silicon-bearing gas may be mixed with one or more halogen-containing gases, defined as any of the group consisting of chlorine (Cl2), hydrogen chloride (HCl), bromine (Br2), hydrogen bromide (HBr), iodine (I2), hydrogen iodide (HI), and mixtures thereof. The silicon-bearing gas may also be mixed with one or more other gases, including hydrogen (H2) or one or more inert gases selected from nitrogen (N2), helium (He), argon (Ar), and neon (Ne). In particular embodiments, the silicon-bearing gas is silane, and the silane is mixed with hydrogen.
The silicon-bearing gas, along with any accompanying hydrogen, halogen-containing gases and/or inert gases, is introduced via one or more nozzles into a fluidized bed reactor and thermally decomposed within the reactor to produce silicon which deposits upon seed particles inside the reactor. Nozzle fouling may occur as silicon deposits form on exterior and interior surfaces of the nozzles. Interior fouling may occur when a portion of the silicon-bearing gas decomposes and deposits silicon on an interior surface of the nozzle.
Interior nozzle fouling and/or clogging also may occur if seed and/or product particles fall into the nozzle. Occlusion is a particular problem when the fluid bed reactor is initially being charged with seed particles prior to reactor operation. Occlusion also can occur if gas flow to one or more nozzle(s) ceases while an upper boundary of the fluidized (or non-fluidized) bed is above the nozzle opening(s).
Fouling and/or clogging produce a variable inner diameter within the nozzle and/or affect gas flow velocity through the nozzle. When a nozzle become sufficiently fouled or clogged, fluid bed reactor operation is halted for maintenance. In some instances, it may be possible to drill through the debris clogging the nozzle and re-establish sufficient gas flow. However, some variability in nozzle diameter and flow characteristics may remain, thereby affecting flow velocity and/or gas plume geometry.
When the nozzle performance is sufficiently comprised, the nozzle is removed and replaced. Because injection and fluidization nozzles typically extend through a fluid bed reactor's lower wall, or bottom head, nozzle replacement is not a trivial matter. Reactor operation must be halted, and typically the reactor must be substantially emptied of seed and/or product particles. Fittings and/or seals may become worn or damaged as nozzles are removed and replaced, leading to reactive gas leaks and potential fires.
The illustrated second member 30 includes a substantially tubular section comprising a first end 31 comprising an inlet 32 and a second end 33 comprising an orifice, or outlet, 34. The illustrated second member is a pipe defining a passageway for delivering gas into reaction chamber 7. In the illustrated embodiment of
In some embodiments, first member 20 further includes an orifice plate 50 positioned within the passageway defined by the pipe.
In some embodiments, first member 20 includes external threads 26 on an outer wall adjacent to outlet 24 (
In another arrangement (not shown), an orifice plate 50 could rest on and be supported by the upper end 23 of the first member 20. When the first and second members are engaged, an upper edge of threads 36 may exert a downward pressure on orifice plate 50, thereby firmly seating the orifice plate. Alternatively, the second member may include an inwardly facing support having a downwardly facing surface adjacent an upper edge of threads 36, which may exert downward pressure on the orifice plate when the first and second members are coupled.
In another arrangement (
Components of the disclosed nozzle assemblies, including first member 20, second member 30, and orifice plate 50 are constructed using any material that is acceptable within the expected pressure, temperature and stress requirements within the fluidized bed reactor. Suitable materials for use in a heated silicon deposition reactor include high-temperature metal alloys such as, but not limited to, INCOLOY® and HASTALLOY™ alloys. First member 20, second member 30, and orifice plate 50 may be constructed of the same materials, or different materials. In some embodiments, first member 20 and second member 30 are constructed of different materials to reduce galling. Surfaces exposed to seed particles, product particles, and/or reaction gases may be coated, e.g., with silicon carbide, for product quality.
Embodiments of the disclosed threaded nozzle assemblies provide advantages over conventional nozzles. For example, second member 30 may be uncoupled from first member 20, allowing replacement of second member 30. Replacement of the entire nozzle assembly 10 is avoided. Additionally, second member 30 can be removed from inside the reaction chamber 7, and can be replaced without cutting, welding, or risk of reactive gas leaks. Embodiments of the disclosed threaded nozzle assemblies and are suitable for use with a welded gas ring header, thereby reducing fire risk when reactive gases are utilized within the reactor. If the upper surface of the particle bed in the reactor is below threaded portion 60 when the reactor is at rest (i.e., in a non-fluidized state), second member 30 can be replaced without emptying the reactor of seed and/or product particles. Orifice plate 50 also may be removed and replaced when second member 30 is uncoupled from first member 20. Threaded nozzle assembly 10 also provides versatility. As desired, second member 30 can be replaced with a subsequent second member that has a different length, a different diameter or configuration (e.g., an outward flare or inward taper at its upper end), and/or is constructed of different material(s).
As desired, second member 130 can be uncoupled from first member 120 and replaced without having to remove or replace outer member 170, and without having to remove nozzle assembly 110 from the reactor. Outer member 170 can be removed by disrupting the gas-tight seal formed by lower wall portion 172a, and then removing outer member 170. As desired, a replacement outer member can be fitted over the nozzle and sealed at a lower edge by any suitable means.
In some fluid bed reactors, the temperature within one or more nozzles may exceed a desirable operating temperature for the fluidized bed. For example, in a polysilicon fluid bed reactor, the temperature in a fluidization nozzle may reach temperatures greater than 600° C. Accordingly, it may be advantageous to insulate the nozzle to avoid overheating the fluidized bed.
In certain embodiments, nozzle 210 is an embodiment of a threaded nozzle as described herein. Accordingly, nozzle 210 may include a first substantially tubular member 220 and a second substantially tubular member 230. First member 220 and second member 230 are removably coupled via a threaded portion 260. First member 220 is in fluid communication with second member 230 such that a gas 265 (e.g., a fluidization gas) can flow upwardly through first and second members 220, 230. Insulating member 280 may surround first member 220, second member 230, or both as illustrated.
In certain embodiments, nozzle 310 is an embodiment of a threaded nozzle as described herein. Accordingly, nozzle 310 may include a first substantially tubular member 320 and a second substantially tubular member 330. First member 320 and second member 330 are removably coupled via a threaded portion 360. First member 320 is in fluid communication with second member 330 such that a gas 365 (e.g., a fluidization gas) can flow upwardly through first and second members 320, 330.
In some arrangements, outer member 370 comprises an outer wall 372 spaced concentrically apart from an outer wall surface 320a of first member 320, an outer wall surface 330a of second member 330, or both, to form an annular space 374. Outer member 370 further comprises an inlet 376 in fluid communication with annular space 374. A gas 378 (for example, a secondary or fluidizing gas) can flow into annular space 374 through inlet 376, and upwardly through annular space 374.
Embodiments of the disclosed nozzle assemblies enable removal and/or replacement of the second member without removal and/or replacement of the entire nozzle assembly. When the second member is in need of removal and/or replacement, the fluid bed reactor is placed into a resting state, i.e., fluidization and reaction gas flows are reduced or stopped so that fluidization ceases, and the reactor temperature may be reduced. With reference to
Upwardly-facing nozzles within a fluid bed reactor, such as a silicon deposition reactor, can become occluded if seed particles fall into the nozzle when charging the reactor. Upwardly-facing nozzles also can become clogged when there is insufficient gas flow through the nozzle during reactor operation, and seed and/or product particles fall into the nozzle. Disclosed herein are embodiments of a closable valve assembly configured to prevent nozzle clogging from particles falling into the nozzle during low and/or no gas flow situations.
Valve assembly 510 can be secured to nozzle 520 by any suitable means including, but not limited to, welding, spot welding, riveting, or threaded means. In some embodiments, valve 510 may be removably secured to nozzle assembly by threaded means. For example, valve assembly 510 may include external threads on an outer wall surface on a lower portion of valve body 530, and nozzle 520 may include internal threads on an inner wall surface adjacent to orifice 525, wherein the threads are cooperatively dimensioned to removably fit together with the threads on valve body 530. Alternatively, valve assembly 510 may include internal threads on an inner cylindrical surface of lower portion of valve body 530, and nozzle 520 may include external threads on an outer wall surface adjacent to orifice 525, wherein the threads are cooperatively dimensioned to removably fit together with the threads on valve body 530.
In some embodiments, a reclosable valve assembly is secured to a threaded nozzle assembly as disclosed herein. Desirably, the valve assembly is secured to the nozzle assembly in a manner that permits removal and/or replacement of the nozzle's second member. In one embodiment, the valve assembly is secured only to the second member. The valve assembly and second member may be removed together as a single unit, such as when the valve assembly is welded, spot welded, or riveted to the second member. Alternatively, the valve assembly may be removably attached to the second member so that the valve assembly can removed in a first step, and the second member can be removed in a subsequent step. In another embodiment, the valve assembly may be detachably secured to a nozzle assembly, e.g., a nozzle assembly that includes an outer member and/or an insulated jacket, so that the valve assembly can be removed in a first step and the second member can be removed in a subsequent step.
Components of the disclosed closable valve assemblies are constructed using any material that is acceptable within the expected pressure, temperature and stress requirements within the fluidized bed reactor. Suitable materials for use in a heated silicon deposition reactor include high-temperature metal alloys such as, but not limited to, INCOLOY® and HASTALLOY™ alloys. Surfaces exposed to seed particles, product particles, and/or reaction gases may be coated, e.g., with silicon carbide, for product quality.
In view of the many possible embodiments to which the principles of the disclosure may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosure. Rather, the scope of the disclosure is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.
