REACTOR SYSTEMS HAVING MULTIPLE PRESSURE BALANCERS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62/266,375, filed 11 December 2015, which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The field of the disclosure relates to reactor systems having a multiple pressure balancer devices to counter-balance the hydrostatic end force of one or more system chambers .

BACKGROUND

[0003] Polycrystalline silicon may be produced economically and at relatively large scale by pyrolysis of thermally decomposable silicon-containing compounds (e.g., silane, trichlorosilane , dichlorosilane or

monochlorosilane) in a fluidized bed reactor. Such polycrystalline silicon may be used for production of solar cells or may be further processed according to the so- called Czochralski method to produce electronic grade single crystal silicon.

[0004] Recent advances in production of polycrystalline silicon involve use of relatively high reactor pressures (e.g., 3 bar or more) . Such pressures create a large hydrostatic force within the reactor and increase the closing force required to seal the reactor. The closing force reacts out the hydraulic end force and should provide adequate clamping force for the reactor internals. Due to the large hydrostatic end force of high pressure reactors, accurate control of the clamping force on internal components is difficult.

[0005] A continuing need exists for reactor systems that react out the hydrostatic end force of the reactor without changes to the force applied to internal components of the reactor. A need also exists for reactor systems that include an annular chamber external to the reaction chamber in which variation in the core to annulus pressure does not require adjustment of the clamping force on the internal components of the reactor.

[0006] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

SUMMARY

[0007] One aspect of the present disclosure is directed to a reactor system for producing a reaction product. The reactor system includes a reactor liner defining a reaction chamber therein for receiving reaction components. An outer shell is around the reactor liner. An annular chamber is formed between the reactor liner and the outer shell. The system includes a seal plate for sealing the annular chamber and the reaction chamber. A reaction chamber pressure balancer is fluidly connected to the reaction chamber and an annular chamber pressure balancer is fluidly connected to the annular chamber.

[0008] Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may also be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present

disclosure may be incorporated into any of the above- described aspects of the present disclosure, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a perspective view of a reactor system having six pressure balancer expansion joints ;

[0010] Figure 2 is a perspective cross-section view of the reactor system;

[0011] Figure 3 is a perspective cross-section view of a pressure balancer of the reactor system of Figure 1 ; and

[0012] Figure 4 is a perspective cross-section view of another embodiment of the pressure balancer of the reactor system of Figure 1.

[0013] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION

[0014] An embodiment of a reactor system for producing a reaction product is generally referred to as "5" in Figure 1. The reactor system 5 includes a reactor liner 17 (Fig. 2) that defines a reaction chamber 15 therein for receiving reaction components. The liner 17 may include a number of separate sections joined by gaskets to seal the various sections. An outer shell 20 surrounds the reaction liner 17 and an annular chamber 12 is formed between the reaction liner 17 and the outer shell 20. A seal plate 7 or reactor "head" seals the reaction chamber 15 and the annular chamber 12 to separate the fluids in each chamber. The seal plate 7 includes an opening 9 through which a piping conduit (not shown) may extend to introduce or withdraw reactants to the reaction chamber 15.

[0015] A clamping assembly 29 (Fig. 1) secures the seal plate 7 by applying a clamping force between the seal plate 7 and the liner 17 and outer shell 20. The clamping assembly 29 generally resists the hydraulic end force from the reaction chamber 15 or annular chamber 12. The clamping assembly 29 adds additional force to the liner 17 to create a seal between the seal plate 11 and the liner 17. The hydraulic end force is balanced by one or more expansion joints discussed below. In the illustrated embodiment, the clamping assembly 29 is a number of powered cylinders (e.g., hydraulic or pneumatic cylinders) . The cylinders 29 are attached to the seal plate 7 and the outer shell 20 (e.g., a clamping ring (not shown) attached to the outer shell 20) . In other embodiments, the clamping assembly 29 includes a number of springs, weights, screw jacks or counterbalances to seal the annular chamber and the reaction chamber. [0016] The reactor system 5 includes reactor chamber pressure balancers 10a, 10b, 10c (collectively "10") and annular chamber pressure balancers 11a, lib, 11c (collectively "11") . The reactor chamber pressure

balancers counteract changes in the reaction chamber 15 pressure and the annular chamber pressure balancers 11 counteract changes in the annular chamber 12 pressure.

Generally the balancers 10, 11 are external to the reactor components (e.g., external to the reaction chamber and/or the shell) .

[0017] Each reaction chamber pressure balancer 10 (Fig. 3) and each annular chamber pressure balancer 11 includes a bottom plate 77 that contacts or is otherwise connected to the seal plate 7 (Fig. 1) . A shaft 46 is connected to a top plate 79 of the pressure balancer 10/11 and to the outer shell 20 (Fig. 1) . Each balancer 10, 11 includes an inner expansion joint 40 defining an inner chamber 43 therein. The shaft 46 extends through the inner chamber 43 and is connected to the outer shell 20 (Fig. 1) . An outer expansion joint 48 surrounds the inner expansion joint 40. The inner expansion joint 40 and outer expansion joint 48 define an annular inner chamber 52 between the inner expansion joint 40 and the outer expansion joint 48. In another embodiment shown in Figure 4, each pressure balancer 10, 11 includes an expansion joint 48 and shafts 46 external to the joint 48 that are connected to the top plate 79 and the outer shell 20 (Fig. 1) .

[0018] The reaction chamber pressure balancers 10 and annular chamber pressure balancers 11 are generally arranged about the circumference of the seal plate 7. The balancers 10, 11 are positioned on the seal plate 7 radially outward to the points at which the outer shell 10 (or corresponding gasket) contacts the seal plate 7. This arrangement allows the shaft 46 of each balancer 10, 11 to be external to annular chamber 12 and reaction chamber 15 to maintain the pressure integrity of the chambers 12, 15.

[0019] The expansion joints 40, 48 have a flexible construction to allow for their expansion and contraction. As shown, expansion joints 40, 48 (and outer shell expansion joint 81 described below) are bellows.

Suitable bellows include formed bellows and edge welded bellows. The expansion joints may alternatively be composed of a material that stretches such as rubber.

[0020] In the illustrated embodiment, the bottom plate 77 directly contacts the seal plate 7. In other embodiments, the bottom plate of the balancers 10, 11 is eliminated and the expansion joints 40, 48 are attached directly to the seal plate 7. Alternatively, the bottom plate 77 and seal plate 7 may be connected through supports (not shown) that extend between the bottom plate 77 and seal plate 7.

[0021] The inner chambers 52 (Fig. 3) of each annular chamber pressure balancer 11a, lib, 11c is fluidly connected to the annular chamber 12 (Fig. 2) by piping conduits 13a, 13b, 13c (Fig. 1) . The inner chambers 52 (Fig. 3) of each inner chamber reactor chamber pressure balancer 10a, 10b, 10c is fluidly connected to the reaction chamber 15 (Fig. 2) through piping conduits 14a, 14b, 14c (Fig. 1) . In the illustrated embodiment, the piping conduits 13, 14 extend through the top plate 79 (Fig. 3) of the balancers 10, 11 and loop downward and extend through the seal plate 7. In other embodiments, the piping conduits 13, 14 extend through the bottom plate (Fig. 3) and seal plate 7 to directly fluidly connect to the annular chamber 12 or reaction chamber 15.

[0022] The shafts 46 may be fixed in length or may be adjustable. As an alternative to shafts 46, the balancer top plates 79 may be fixed relative to the shell 20 by fixing both the shell 20 and the top plates 79 to external structures such as the building structure in which the reactor is located.

[0023] The reactor system 5 may include at least 2, 3, 4, 5 or more reaction chamber pressure

balancers 10 and/or at least 2, 3, 4, 5 or more annular chamber pressure balancers 11. The reaction chamber pressure balancers 10 and annular chamber pressure

balancers 11 are generally arranged about the circumference of the seal plate 7 to provide for a symmetric clamping force (i.e., at least three of each type are used with about equal spacing along the circumference) .

[0024] Each reaction chamber pressure balancer 10 and each annular chamber pressure balancer 11 has a total effective area (i.e., the effective area of the expansion joint 48) . The reaction chamber pressure balancers 10 are sized such that the sum of the effective areas of the reaction chamber pressure balancers 10 is substantially the same as the effective area exerting force on the seal plate 7 from the reaction chamber 15 (Fig. 2) . The annular chamber pressure balancers 11 are sized such that the sum of the effective areas of the annular chamber pressure balancers 11 is substantially the same as the effective area exerting force on the seal plate 7 from the annular chamber 12 (Fig. 2) . [0025] The reactor system 5 may be operated by reacting reactor fluids in the reaction chamber 15. A second fluid may be present in the annular chamber 12 to prevent the reaction chamber from being contaminated. The reaction fluid in the annular chamber 12 is generally inert to the reaction components within the reaction chamber 15. In some embodiments, the fluids in the reaction chamber 15 and annular chamber 12 are both gases . The annular chamber 12 may be operated at a pressure greater than the reaction chamber 15 such as at least about 0.01 bar greater or at least about 0.05 bar, at least about 0.1 bar, at least about 0.5 bar, at least about 1 bar or at least about 2 bar greater (e.g., from about 0.1 bar to about 5 bar, from about 0.1 bar to about 2 bar or from about 0.1 bar to about 0.9 bar greater) . In other embodiments, the pressure in the annular chamber 12 is less than the pressure in the reaction chamber 15 such as at least about 0.01 bar less or at least about 0.05 bar, at least about 0.1 bar, at least about 0.5 bar, at least about 1 bar or at least about 2 bar less (e.g., from about 0.1 bar to about 5 bar, from about 0.1 bar to about 2 bar or from about 0.1 bar to about 0.9 bar less) . The annular chamber 12 may include a heater (not shown) therein to heat the reactor components in the reaction chamber 15.

[0026] In some embodiments, the reactor system 5 is used to produce polycrystalline silicon. A silicon feed gas comprising a silicon-containing compound is introduced into the reaction chamber 15. The silicon feed gas may be introduced with a carrier gas such as hydrogen, argon, helium, silicon tetrachloride or combinations thereof. Silicon particles (e.g., seed particles) are fluidized in the reaction chamber 15 by the incoming gases. Silicon deposits on the particles by the thermal

decomposition of the silicon-containing compound. When the particulate has grown to sufficient size, particulate is withdrawn from the reaction chamber 15 through a product withdrawal tube (not shown) . Exhaust gases are withdrawn from a gas withdrawal tube that extends through opening 9 in the seal plate 7. The reaction chamber 15 may be maintained at a pressure of at least about -0.5 barg, at least about 0 barg, at least about 0.5 barg, at least about 1 barg, at least about 3 barg, at least about 5 barg or at least about 10 barg (e.g., from about -0.5 barg to about 25 barg, from about 3 barg to about 25 barg or from about 3 barg to about 10 barg) .

[0027] Incoming gases (silicon feed gas and carrier gases) may be pre-heated to a temperature of at least about 200°C (e.g., from about 200°C to about 500°C of from about 200 °C to about 350 °C) . The reactor chamber 15 may be maintained at a temperature of at least about 600°C (e.g., 600°C to about 900°C or from about 600°C to about 750 °C) by use of external heating means such as induction heating or use of resistive heating elements positioned in the annular chamber 12. The gas velocity through the fluidized bed reactor 30 may be generally maintained at a velocity of from about 1 to about 8 times the minimum fluidization velocity necessary to fluidize the particles within the fluidized bed. The mean diameter of the particulate polycrystalline silicon that is withdrawn from the reactor 30 may be at least about 600 μπι (e.g., from about 600 μπι to about 1500 μπι or from about 800 μιη to about 1200 μτ ) . The mean diameter of the silicon seed particles introduced into the reactor may be less than about 600 μιη (e.g., from about 100 μιη to about 600 μιη) . Quench gases may be introduced into the reactor 30 (e.g., at a freeboard region of the reactor) to reduce the temperature of the effluent gas 39 before being discharged from the reactor to suppress formation of silicon dust.

[0028] Inert gas may be introduced into the annular chamber 15 and maintained at a pressure below or above the pressure of the process gases of the reaction chamber 15 as noted above to chemically isolate the reaction chamber. The thermally decomposable gases may be directed to the core region of the reactor and carrier gas (e.g., hydrogen) may be directed to the peripheral portion of the reactor near the reactor walls to reduce the deposition of silicon on the walls of the reactor as disclosed in U.S. Pat. No. 8,906,313 and U.S. Pat. Pub. No. 2011/0158888, both of which are incorporated herein by reference for all relevant and consistent purposes.

[0029] In embodiments in which silane is used as the thermally decomposable compound, the reactor may be operated in accordance with the reaction conditions disclosed in U.S. Patent Publication No. 2013/0084233, which is incorporated herein by reference for all relevant and consistent purposes. In embodiments in which

dichlorosilane is used as the thermally decomposable compound, the reactor may be operated in accordance with the reaction conditions disclosed in U.S. Patent

Publication No. 2012/0164323, which is incorporated herein by reference for all relevant and consistent purposes. In embodiments in which trichlorosilane is used as the thermally decomposable compound, the reactor may be operated in accordance with the reaction conditions disclosed in U.S. Patent Publication No. 2012/0100059, which is incorporated herein by reference for all relevant and consistent purposes.

[0030] During operation of the reactor system 5, the reaction chamber pressure balancers 10 respond to changes in the pressure of the reaction chamber 15 (Fig. 2) . As the pressure increases, the pressure in the inner chamber 52 (Fig. 3) formed between the outer expansion joint 48 and inner expansion joint 40 increases causing the expansion joints 48, 40 to exert a higher pressure and increase the clamping force applied to by the seal plate 7 to the liner 17 and outer shell 20. The annular chamber pressure balancers 11 respond to changes in the pressure of the annular chamber 12 (Fig. 2) . An increase in pressure in the annular chamber 12 causes the pressure in the inner chamber 52 to increase causing the expansion joints 48, 40 to expand and increase the clamping force applied to by the seal plate 7 to the liner 17 and outer shell 20.

[0031] Compared to conventional reactor systems, embodiments of the reactor system described above have several advantages. The reaction chamber and annular chamber pressure balancers may vary the clamping force of the seal plate based on changes in the pressure in the reaction chamber and/or annular chamber. This allows the clamping assembly to be simplified (e.g., a passive system may be used) as the clamping force of the apparatus is a function of gasket pressure and expansion joint

expansion/contraction. Further, the pressure balancers operate in the event the reactor rupture disk (not shown) ruptures allowing the system to remain pressure balanced (i.e., a sudden decrease in reaction chamber and/or annular chamber pressure is counteracted by a sudden decrease in force applied by the pressure balancers. The pressure balancers are relatively compact and allow access to the center of the seal plate 7.

[0032] As used herein, the terms "about," "substantially, " "essentially" and "approximately" when used in conjunction with ranges of dimensions,

concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.

[0033] When introducing elements of the present disclosure or the embodiment (s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," "containing" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., "top", "bottom", "side", etc.) is for convenience of description and does not require any particular orientation of the item described .

[0034] As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawing [s] shall be interpreted as

illustrative and not in a limiting sense.