Patent Publication Number: US-2022226795-A1

Title: Reactor

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of priority under 35 U.S.C 119(e) to U.S. Provisional Application No. 63/138,022, filed Jan. 15, 2021, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosure relates to a reactor, in particular to a reactor for methanol synthesis. 
     BACKGROUND 
     Global climate change has been deemed to be the “most pressing environmental challenge of our time.” The National Aeronautics and Space Administration (NASA) cites that “scientific evidence for warming of the climate system is unequivocal.” Climate change results from the warming effects of greenhouse gases such as water vapor, nitrous oxide, methane, and carbon dioxide. Of these, carbon dioxide emissions are a key culprit, as global atmospheric concentration of CO 2  has increased by a third since the Industrial Revolution began. CO 2  emissions largely stem from human activities, such as the consumption of fossil fuels, the byproducts of which are emitted into the atmosphere. 
     Chemical energy storage has been explored as a solution to the problem of renewable energy sources such as wind and solar power being inherently intermittent and unpredictable. Because of the intermittency of wind and solar power, power grids and utilities must meet baseline power demands through fossil fuel-based sources, with suddenly available wind and solar power being difficult to incorporate into the grid due to the difficulty of quickly scaling down and scaling up such fossil fuel-based sources, like coal-fired power plants. Because many renewable energy sources are difficult to scale up as a replacement for traditional fossil fuel-based power sources, high-density energy storage of renewable energy, such that the renewable energy can be stored and used when the grid is able to accommodate the energy, is critical for combating climate change. 
     Existing energy storage modalities, including thermal energy storage, compressed air energy storage, hydrogen storage, pumped hydroelectric storage, and large-scale batteries have so far proven to be prohibitively expensive and/or difficult to scale up. Chemical storage of renewable energy in the form of electrolyzing water to produce hydrogen, such as for combustion, fuel cell consumption, or chemical synthesis such as methanol synthesis, is a promising approach to providing sufficiently dense and stable storage of renewable energy that may be used when needed, allowing renewable energy to supply energy needs consistently rather than intermittently. 
     Reactors used in methanol synthesis from syngas are typically limited to boiling water reactors (BWRs) due to the high heat profile of typical reaction suites, which include substantial amounts of CO. BWRs are complex and expensive equipment, but are typically necessary in order to mitigate the heat generated from the exothermic production of methanol from syngas in order to protect the reaction product, the reactor, and the catalyst. 
     Shell-and-tube reactors for catalytic and/or exothermic reactions, such as synthesizing methanol from CO 2  and H 2  using a suitable catalyst such as a copper and zinc oxide (Cu/ZnO)-based catalyst or other suitable catalyst, must receive regular maintenance, such as loading and/or removing and recharging catalyst, de-fouling the reactor shell, performing repairs of various components, or otherwise. The ability to access the interior of the reactor for loading catalyst, performing maintenance, and other purposes must be balanced against the need to retain the tubes in a bundle. 
     Existing designs of shell-and-tube reactors are difficult to scale up or scale down based on the needs of a particular facility, such as a desired throughput. The throughput of the facility may change with time due to debottlenecking efforts, which may increase the throughput requirements of the reactor. Scaling up a reactor for debottlenecking a facility can be a difficult, expensive, and time-consuming endeavor, with the entire reactor, including the internals, needing to be revamped or redesigned in many instances. 
     This can require significant design and engineering effort, as an engineer must essentially “reinvent the wheel” when scaling up the design, with consideration given to the arrangement and cross-sectional area of the tubes, the size and configuration of the shell, the volume and cross-sectional surface area of the catalyst bed, among other things. Existing shell-and-tube reactor designs and providers are poorly suited to adapting reactor designs to changing requirements in an efficient manner. If the reactor is not properly designed, uneven distribution of catalyst, reactants, and heat may result, which can damage the catalyst and/or components of the reactor and reduce the efficiency of the reaction. In some cases, a runaway exothermic reaction can result in catastrophic failure of the reactor. 
     Additionally, it is difficult to scale and properly fabricate feed tubes in and/or for a reactor. Improperly designed, arranged, and/or fabricated feed tubes often lead to the creation of blockages, eddies, and uneven areas of reactants within reactors, which disadvantageously reduces the efficiency and throughput of a reactor and can result in hot spots. Hot spots in exothermic reactions are particularly dangerous and damaging to the reactor and catalyst. 
     Another problem in reactor design is the difficulty of measuring internal reactor temperature at one or more desired locations. It is difficult to properly control a process including a reactor, particularly in high-risk applications such as exothermic reactions, without an understanding of the temperature profile of the reactor internals, particularly at different locations along the reactor body corresponding to different stages of the reaction and/or different reactor conditions. 
     However, thermocouple joints including a gasket seat may sustain damage over time, leading to thermocouple joint leakage. While such leakages may be repaired, doing so requires deactivating the catalyst and replacing the gasket seat. This involves costly, potentially dangerous, and time-consuming shut-downs, deactivation of catalyst, and start-ups, each of which entails high costs, including substantial opportunity costs. Given that the expected lifetime of catalysts tends to be between three and five years, such repairs constitute highly expensive disruptions to the operation of a facility. Further, in high pressure and/or temperature reactions involving hydrogen, the risk of leakage from flanged joints is particularly high, both of hydrogen or other reactants/products outwardly and of oxygen, a catalyst poison, inwardly. 
     Accordingly, existing reactor designs that incorporate multiple thermowells for providing thermocouples at different elevational locations along a reactor body are susceptible to significant operational disruptions due to thermocouple joint leakage, and reactor designs that omit such thermowells to avoid disruptions lack the necessary reactor-conditions data to properly control the reaction. Additionally, existing thermowell configurations in reactors insert the thermocouple transversely to a flow direction, e.g. radially into the reactor body. This disadvantageously results in temperature readings for larger reactors of conditions close to the outer shell, which further renders scaling of a reactor design difficult. Reactor designs are further ill-suited to allowing a thermocouple to be inserted into the reactor body when the catalyst is present without damaging the thermocouple. 
     Existing reactor designs may comprise one or more nozzles for unloading spent catalyst, for example from a bottom portion of the reactor body. The configuration of existing reactors&#39; catalyst-unloading nozzles is poorly adapted to effectively and quickly removing catalyst, such that an operator must scrape catalyst out of the reactor body. 
     Certain shell-and-tube-type reactors and other types of reactors may comprise an inlet nozzle from which reactant gases are routed through a pipe extending through a center of the reactor body. The pipe may be drilled to fit one or more feed tubes, which each may be bent to both connect to the pipe and then feed the reactant upwardly through the reactor body. Such reactor configurations are not adapted to scaling up, for example to several hundred tubes, given the precise and tube-specific adjustments that must be made to connect the pipe to each of the feed tubes. 
     The inlet pipe in certain reactor configurations is further utilized to support the feed tubes at different elevations within the reactor body, with one or more flat bars welded to and extending between the inlet pipe and one or more feed tubes. This configuration is highly time-consuming particularly for manufacturing, assembling, and maintaining a large-scale reactor, which complicates the task of scaling a reactor design depending on the requirements of a facility. Additionally, the inlet pipe disadvantageously occupies significant cross-sectional area that could otherwise be occupied by catalyst. While tie rods have been contemplated for supporting feed tubes in shell-and-tube reactors, such supports take up catalyst space and present obstructions during catalyst loading and unloading. 
     From the foregoing, there is a need for an improved reactor that is configured for maintaining the reactor internals and managing the catalyst, for scaling the reactor throughput up or down based on the throughput needs of a facility, for improved measurement of reactor conditions without compromising reactor integrity and maintainability, for effectively removing spent catalyst, for improved manufacture, and for overcoming the challenges of constructing a shell-and-tube reactor. 
     SUMMARY 
     Reactor embodiments according to the present disclosure advantageously address the drawbacks of existing reactor designs by providing a reactor that is scalable and/or configured for improved access and maintainability of the reactor, particularly of an interior of the reactor. The reactor embodiments may be configured to facilitate access to the reactor internals without sacrificing strength and robustness of the reactor internals, such as a reactor tube bundle comprising one or more tubes and one or more support structures, such that the tube bundle remains intact and undamaged. 
     The reactor embodiments further comprise a tube arrangement that is configured for scaling up or down readily based on the needs of a particular facility. Whereas in existing reactor designs, tubes cannot be easily added to or removed from a tube bundle in accordance with a reactor shell shape when building a reactor without significant redesign work, the embodiments of the present disclosure advantageously allow for circumferential bands or other arrangements of tubes to be modularly arranged based on the required throughput of the reactor and the associated facility. In embodiments the arrangements of tubes may define regular and/or repeating patterns that can be simply added to and/or removed from an existing tube bundle design when designing a reactor. This has the advantage of making debottlenecking operations or other design work much easier and less costly from a manufacturing perspective. 
     The arrangement of the tube bundle further facilitates heat and reactant distribution throughout the reactor interior, in particular through the catalyst bed, without disrupting catalyst loading, which typically occurs as an operator loads or dumps the catalyst particles into the reactor interior from an open top end of the reactor. The arrangement of the reactor and the tube bundle of embodiments advantageously provides both modularity of design for improved constructability while maintaining desired properties regarding heat and reactant distribution while also ensuring that the catalyst particles are evenly distributed within the reactor interior. 
     The tube bundle of reactor embodiments according to the disclosure are further configured to provide improved structural support to one or more tubes for increased robustness of the reactor during construction, transportation, and installation, as well as during operation. In embodiments, one or more structural supports are provided and/or one or more of the tubes is provided with increased thickness for ensuring structural support at desired locations of the tube bundle. 
     In embodiments, the reactor and components thereof are configured to facilitate easy access for maintenance of critical parts. One or more plates configured for supporting the tube bundle may be modular such that an operator may load catalyst, unload catalyst, or access components in the reactor interior with ease compared to existing reactors, where components such as support plates are welded to an interior surface of the reactor shell and prohibit access to the reactor internal components. 
     The reactor embodiments address the problem of existing reactor designs being poorly suited to provide proper flow and reactant distribution, and consequently heat distribution, within the reactor and the catalyst bed, by providing an improved inlet nozzle and distribution mechanism configured to directing reactants into a tube bundle arranged within an interior of the reactor. In embodiments, the inlet nozzle is provided proximate a gas inlet plate and is arranged with a flow direction transverse to a flow direction of the tubes of the tube bundle. A secondary inlet nozzle may be provided at a bottom of the reactor and may be configured with a structure for evenly distributing flow into the tubes of the tube bundle. In embodiments, one or more catalyst unloading nozzles are provided in an improved configuration for removing catalyst, with the unloading nozzles configured at a downward angle. 
     The tube bundle and the tubes may be arranged such that a cross-sectional area of the tubes relative to a cross-sectional area of the catalyst is improved for even heat and flow distribution without interfering with the structural and modularity features of the tube bundle. 
     The reactor embodiments are further configured to reduce the incidence of blockages, eddies, and/or uneven areas of reactants within the reactor body and accompanying hot spots by providing for an improved distribution of catalyst, reactor internals, and reactants during the course of a reaction. 
     The reactor embodiments of the present disclosure further address the disadvantages of existing reactor designs regarding process control and temperature measurement. In embodiments, the reactor is configured to provide one or more thermowells configured to receive one or more respective thermocouples. The thermocouples may be configured to measure a temperature of the reactor interior at a plurality of locations using respectively a single thermowell arranged axially or longitudinally relative to the reactor body. 
     An example embodiment according to the present disclosure may be directed to a reactor, comprising: a shell defining an internal space; at least one inlet nozzle; and a tube bundle comprising one or more tubes. 
     An embodiment may further comprise a catalyst support plate. 
     An embodiment may further comprise at least one tube support plate. 
     An embodiment may further comprise a gas inlet plate. 
     An embodiment may further comprise a top plate. 
     An embodiment may further comprise a top plate and tube support plate. 
     An embodiment may further be configured where the shell is configured to receive at least one catalyst. 
     In an embodiment, the at least one catalyst is a solid catalyst. Such catalyst may comprise balls of a first diameter. 
     In an embodiment the solid catalyst comprises balls of a second diameter. 
     In embodiment the shell is configured to receive at least one solid catalyst. Such solid catalyst may comprise a shape defining at least one of pellets, rings, tablets, or spheres. 
     In an embodiment, the catalyst support plate is configured to support a height of the solid catalyst. 
     In an embodiment, the catalyst support plate defines one or more apertures. 
     In an embodiment, the one or more apertures comprise a plurality of apertures of a first size and a plurality of apertures of a second size, the apertures extending through at least part of a thickness of the catalyst support plate. 
     In an embodiment, the first size corresponds to a circumference of at least one tube of the tube bundle. 
     In an embodiment, the second size is smaller than the first size. 
     In an embodiment, the second size is a function of the thickness of the catalyst support plate. 
     In an embodiment, the apertures of the first size are defined through the catalyst support plate according to an arrangement of the plurality of tubes. 
     In an embodiment, the gas inlet plate comprises a plurality of apertures defined through a thickness of the gas inlet plate. 
     In an embodiment, the plurality of apertures are circular apertures defined through the gas inlet plate according to the arrangement of the plurality of tubes. 
     In an embodiment, the gas inlet plate further comprises a second plurality of apertures defined through the thickness of the gas inlet plate, the second plurality of apertures comprising a different size and/or shape than the plurality of circular apertures. 
     In an embodiment, the shell defines an outlet nozzle. 
     In an embodiment, the outlet nozzle is located at a side portion of the shell. 
     In an embodiment, the inlet nozzle is located proximate a bottom portion of the shell. 
     In an embodiment, the inlet nozzle is arranged transverse to a direction of flow through the shell. 
     In an embodiment, the inlet nozzle is arranged substantially parallel to a direction of flow through the shell. 
     In an embodiment, the gas inlet plate is arranged proximate the inlet nozzle. 
     In an embodiment, the at least one tube support plate comprises at least one circumferential band. 
     In an embodiment, the at least one circumferential band comprises at least one bracket configured to extend about a portion of a tube of the tube bundle. 
     In an embodiment, the at least one bracket extends about an entirety of the tube. 
     In an embodiment, the shell defines a startup nozzle configured for the provision of a heating fluid. 
     In an embodiment, the reactor further comprises at least one catalyst unloading nozzle. 
     In an embodiment, the reactor further comprises a hand hole. 
     In an embodiment, the at least one tube support plate defines a plurality of concentric circumferential bands. 
     In an embodiment, the tube bundle comprises at least one tube of a first size and at least one tube of a second size. 
     In an embodiment, the inlet nozzle is arranged below the gas inlet plate. 
     In an embodiment, the shell defines an outlet nozzle, and wherein the outlet nozzle is arranged below the catalyst support plate. 
     In an embodiment, catalyst (e.g., balls) of the first size (e.g., diameter) and the catalyst (e.g., balls) of the second size (e.g., diameter) are arranged in discrete, respective layers proximate the catalyst support plate. 
     In an embodiment, the shell is configured to receive at least one solid catalyst, wherein the catalyst defines a first height within the shell in an unreduced state and a second height within the shell in a reduced state (e.g., due to settling that may occur during operation). 
     In an embodiment, the second height is lower than the first height. 
     In an embodiment, the at least one tube support plate defines at least one radial strut connected to at least one of the plurality of circumferential bands. 
     In an embodiment, the at least one radial strut connects to at least one of the circumferential bands and to an outer support band. 
     In an embodiment, an innermost circumferential band of the at least one tube support plate comprises a number of brackets (e.g., six) configured respectively to correspond to a ring of the same number of innermost tubes of a first size. 
     In an embodiment, a second circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  10 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the second concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a third circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  14 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the third concentric band or ring of tubes. Such tubes may be of the second size. 
     In an embodiment, a fourth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  18 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the fourth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a fifth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  22 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the fifth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a sixth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  26 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the sixth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a seventh circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  30 ) brackets configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the seventh concentric band or ring of tubes. Such tubes may be of the second size. 
     In an embodiment, an eighth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  34 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the eighth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a ninth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  36 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the ninth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a tenth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  42 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the tenth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, an eleventh circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  46 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the eleventh concentric band or ring of tubes. Such tubes may be of the second size. 
     In an embodiment, a twelfth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  50 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the twelfth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a thirteenth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band (e.g.,  54 ) configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the thirteenth concentric band or ring of tubes. Such tubes may be of the first size. 
     In an embodiment, a fourteenth circumferential band of the at least one tube support plate comprises an equal or greater number of brackets than the previous band configured respectively to correspond to a concentric band (e.g., ring) of the same number of tubes of the tube bundle located in the fourteenth concentric band or ring of tubes. Such tubes may be of the second size. 
     It will be apparent that any number of circumferential bands may be provided. 
     In an embodiment, any of the circumferential bands of the at least one tube support plate further comprises brackets corresponding to at least one thermocouple insertion tube, the at least one thermocouple insertion tube. Such thermocouple insertion tube may be similarly sized relative to the tubes of the tube bundle (e.g., of the first or second size). 
     In an embodiment, at least four tube support plates are arranged longitudinally along the tube bundle. 
     In an embodiment, at least one tube support plate is arranged longitudinally along the tube bundle, wherein a circumferential band of the at least one tube support plate further comprises brackets corresponding to at least one thermocouple insertion tube, wherein the at least one thermocouple insertion tube is configured to receive a temperature measurement device. 
     In an embodiment, the temperature measurement device is configured to obtain a temperature at a plurality of longitudinal locations within the reactor. 
     In an embodiment, the temperature measurement device is configured to obtain a temperature at a plurality of locations (e.g., at least eight different locations), e.g., longitudinally along the reactor. 
     In an embodiment, the shell defines at least one flange facilitating attachment and detachment of an upper portion of the shell from a main body portion of the shell. 
     In an embodiment, the shell is configured to attach to a skirt at a bottom portion of the shell. 
     In an embodiment, the skirt defines an aperture configured to receive an inlet spool. 
     In an embodiment, the at least one tube support plate defines at least one radial strut connected to at least one of a plurality of circumferential bands of the tube support plate, wherein the at least one radial strut of the at least one tube support plate aligns axially with at least one radial strut of another tube support plate. 
     In an embodiment, the at least one radial strut of the at least one tube support plate is offset axially relative to at least one radial strut of an adjacent tube support plate. 
     In an embodiment, the at least one tube support plate defines a plurality of radial struts arranged symmetrically about a longitudinal axis of the reactor. 
     In an embodiment, the at least one tube support plate defines at least one radial strut connected to at least one of a plurality of circumferential bands of the tube support plate, wherein the at least one circumferential band of the at least one tube support plate is removably secured to the at least one radial strut. 
     In an embodiment, at least one tube of the tube bundle defines a uniform thickness longitudinally within the reactor. 
     In an embodiment, at least one tube of the tube bundle defines a tapered thickness longitudinally within the reactor. 
     In an embodiment, at least one tube of the tube bundle is configured to facilitate a greater degree of heat transfer proximate a bottom portion of the reactor relative to a top portion of the reactor. 
     Any of the features noted above, or other features described herein may be used in combination with one another, alone, or in combination with other features. 
     Other methods, embodiments, and variations of the system are described in greater detail in the following discussion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become readily apparent and better understood in view of the following description, appended claims, and accompanying drawings. 
         FIG. 1A  is a perspective view of a reactor according to an embodiment of the present disclosure. 
         FIG. 1B  is a rotated perspective view of the reactor according to the embodiment of  FIG. 1A . 
         FIG. 2  is a plan view of the reactor according to the embodiment of  FIG. 1A . 
         FIG. 3  is a cutaway elevational view of the reactor and reactor internals of the embodiment of  FIG. 1A  taken along the line  1 A- 1 A. 
         FIG. 4  is a cutaway elevational view of the reactor and catalyst bed and catalyst support layers of the embodiment of  FIG. 1A  taken along the line  1 A- 1 A. 
         FIG. 5A  is a close-up elevational cutaway view of the reactor of the embodiment of  FIG. 1A  according to the detail IV. 
         FIG. 5B  is a close-up elevational cutaway view of the reactor of the embodiment of  FIG. 1A  according to the detail III. 
         FIG. 6  is a perspective view of a tube bundle for use with a reactor according to the embodiment of  FIG. 1A . 
         FIG. 7  is an elevational view of the tube bundle of the embodiment of  FIG. 6 . 
         FIG. 8  is a perspective view of a tube bundle and tube support plate according to the embodiment of  FIG. 6 . 
         FIG. 9  is a plan view of atop and feed tube support plate according to the reactor of the embodiment of  FIG. 1A . 
         FIG. 10A  is a plan view of the tube support plate according to the embodiment of  FIG. 6 . 
         FIG. 10B  is a plan view of a tube support plate according to another embodiment. 
         FIG. 11  is a plan view of a gas inlet plate according to the reactor of the embodiment of  FIG. 1A . 
         FIG. 12  is a plan view of a catalyst support plate according to the reactor of the embodiment of  FIG. 1A . 
         FIG. 13  is a close-up plan view of a catalyst support plate according to the detail XII. 
         FIG. 14  is a perspective exploded view of a top plate and reactor according to the embodiment of  FIG. 1A . 
         FIG. 15  is a plan view of the top plate of the embodiment of  FIG. 14 . 
         FIG. 16  is a close-up perspective exploded view of a top plate for use with the reactor of the embodiment of  FIG. 1A  according to the view XIV. 
         FIG. 17  is an elevational cutaway view of a retaining plate for use with a nozzle of a reactor according to the embodiment of  FIG. 1A  taken along the line  16 A- 16 A. 
         FIG. 18  is an elevational view of the retaining plate and nozzle according to the embodiment of  FIG. 17 . 
         FIG. 19  is a perspective view of the retaining plate and nozzle according to the embodiment of  FIG. 17 . 
         FIG. 20  is a cutaway elevational view of a reactor, catalyst bed, and thermocouple insertion tube according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     A better understanding of different embodiments of the invention may be had from the following description read with the accompanying drawings in which like reference characters refer to like elements. 
     While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are shown in the drawings and will be described below. It should be understood, however, there is no intention to limit the disclosure to the embodiments disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure and defined by the appended claims. 
     It will be understood that, unless a term is defined in this patent to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning. 
     Turning to  FIG. 1A , a reactor  100  according to embodiments of the present disclosure is shown. The reactor  100  comprises a shell  102  defining an internal space  103  ( FIG. 4 ) and comprising at least one inlet nozzle  120 . The reactor  100  is configured to receive and cooperate with at least one reactor internal component, such as a tube bundle  130  ( FIG. 3 ) comprising one or more tubes  131 . The reactor  100  extends longitudinally about an axis  1 A- 1 A from a top end  105  to a bottom end  107  and may define a substantially cylindrical shape. 
     The inlet nozzle  120  is arranged generally proximate the bottom end  107  such that one or more reactants may enter through the inlet nozzle  120  and then travel upwardly in a direction F 1  ( FIG. 4 ) through the internal space  103  of the reactor  100  within the one or more tubes  131  before exiting the tubes  131  proximate the top end  105  and diverting downward in a direction F 2  toward an outlet nozzle  124  which defines a corresponding flange  125 . As the reactants travel upwardly through the one or more tubes  131 , the reactants exchange heat with the catalyst and the reactants and products traveling downwardly in the direction F 2  ( FIG. 4 ). 
     In exothermic reactions such as methanol synthesis, the reactants advantageously absorb heat generated by the reaction within the tubes  131  to pre-heat the reactants prior to delivering the reactants to a catalyst bed  140 . This also advantageously mitigates the formation of catalyst hotspots and associated catalyst sintering and product degradation. This also reduces the likelihood of a runaway reaction, as the reactants define a heat exchange medium for removing heat from the catalyst bed. Due to the distribution of the tubes  131 , the reactants form a much more effective heat-exchange modality than, for example, a cooling-water sleeve surrounding the reactor  100 . 
     The reactor  100  may define, in addition to the inlet nozzle  120  and the outlet nozzle  124 , one or more catalyst unloading nozzles  116  and/or one or more hand holes  118  through which the internal space  103  is accessible. The one or more catalyst unloading nozzles  116  may be angled downwardly so as to facilitate gravity-based removal of the catalyst from the catalyst bed  140 , for example when removing and recharging spent catalyst. The one or more hand holes  118  may facilitate maintenance by allowing a technician to insert a hand, tool, or instrument into the internal space  103  proximate the catalyst support plate  154 , the catalyst bed  140 , or at any other suitable location. 
     As seen in  FIGS. 1A and 1B , the reactor  100  defines a startup nozzle  110  configured for the provision of a heating fluid. During a startup operation, when the reaction has not yet reached steady-state operation, the reactants may not receive a necessary amount of pre-heat as they travel in the direction F 1  in the tube bundle  130 . The startup nozzle  110  may receive a heating fluid such as an inert gas, like heated nitrogen gas, that may pass through the internal space  103  and provides enough enthalpy to achieve steady-state operation without adversely affecting the yield of the reaction. 
     The shell  102  further may define at least one thermocouple port  106 . Each thermocouple port  106  may facilitate the insertion of a temperature measurement device into the reactor  100  and in embodiments into the tube bundle  130  in an axial or longitudinal direction. By positioning the thermocouple port  106  at a top portion  105  of the reactor  100 , a single temperature measurement device, such as a thermocouple, may be inserted therethrough with the ability to measure temperature at a plurality of locations. In embodiments, the temperature measurement device may extend in an elongate manner and comprise a plurality of measurement devices such as thermocouples thereon at predetermined distances such that the reactor conditions at each of said predetermined distances may be measured for improved control of the reaction. 
     While two thermocouple ports  106  are shown in  FIGS. 1A and 1B  on opposite sides of the startup nozzle  110 , it will be appreciated that more or fewer thermocouple ports  106  may be provided at any suitable location. By providing the temperature measurement devices through the thermocouple ports  106 , the reactor  100  advantageously allows for measurement of reactor conditions at different elevational locations in the reactor while minimizing the number of thermocouple joints, thereby facilitating improved process control and throughput while minimizing the risk of leaks, either into or out of the shell  102 . The location of the thermocouple ports  106  further allows for sampling the reactor conditions at desired radial locations of the reactor  100  regardless of the size of the reactor  100 , in contrast to existing reactor designs in which the thermocouples are inserted radially, such that larger reactors are sampled disproportionately close to the shell. 
     Turning to  FIG. 4 , the shell  102  may define an inlet nozzle  120  with a corresponding flange  121  arranged a distance below a gas inlet plate  156  and both arranged proximate the bottom end  107  of the reactor  100 . The inlet nozzle  120  may be arranged transverse relative to a longitudinal extension direction of the reactor  100 , such that as the reactants enter through the inlet nozzle  120  in a flow direction F 4 , the reactants change direction and enter into one or more tubes  131  of the tube bundle  130  through the gas inlet plate  156  in the direction F 1 . 
     The inlet nozzle  120  may be arranged as shown to optimize a distance between the inlet nozzle  120  and a bottom of the tube bundle  130  and to evenly distribute the reactants to the tubes  131  such that eddies that result in blockages, hot spots, and uneven flow are avoided. The flange  121  may be configured to facilitate attachment of a reactant feed line to the nozzle  120 . While the inlet nozzle  120  has been shown and described, it will be appreciated that the distance between the inlet nozzle  120  and the bottom of the tube bundle  130  may be greater or smaller as suitable. 
     Additionally or as an alternative, the shell  102  further defines a secondary inlet nozzle  132  with a corresponding flange  133  as shown in  FIG. 5A . The flange  133  may be configured to facilitate attachment of a reactant feed line to the nozzle  132 . The secondary inlet nozzle  132  is arranged to deliver the reactants vertically in a direction F 3 , which may correspond to or be parallel with the flow direction F 1  upwardly through the tubes  131 . 
     The reactor shell  102  may be secured with a skirt  108  which may define through a thickness thereof an aperture  122  configured to receive an inlet spool  135  connecting to the secondary inlet nozzle  132 . 
     The skirt  108  may be cylindrical in shape and extend substantially coextensively with the reactor shell  102  downwardly from the bottom end  107 . The skirt  108  may define a ring  109  at grade securing the reactor  100  and the skirt  108  in position. The inlet spool  135  may be curved such that the reactants are fed toward the reactor  100  in a flow direction generally transverse to the flow direction F 3 , for example in a direction substantially parallel to the direction F 4  of the inlet nozzle  120 . The inlet nozzle  120  and the secondary inlet nozzle  132  may be configured to operate simultaneously or independently of each other. While a skirt has been shown and described, any suitable support may be utilized, and the disclosure is not limited to the use of a skirt. 
     In embodiments, a diverter  137  may be removably arranged within the secondary inlet nozzle  132  or the shell  102  for directing a flow direction of the reactants when the secondary inlet nozzle  132  is in use. The diverter  137  may define a shape that distributes a portion of the flow of reactants from the secondary inlet nozzle  132  radially outward such that the flow is evenly distributed between the central tubes, which are generally aligned with the secondary inlet nozzle  132 , and outer tubes. While the diverter  137  has been shown and described, it will be appreciated that any suitable structure, configuration, or arrangement may be utilized. In embodiments, the diverter  137  defines a plurality of apertures and/or protrusions configured for distributing the flow of the reactants entered through the nozzle  132 . 
     Turning to  FIG. 5B , the reactor  100  may further comprise a domed head portion  104  that is detachable from the shell  102  and is releasably attached thereto at flanges  112 ,  114  which may comprise any suitable modality for attaching the domed head portion  104  and the shell  102 , such as apertures and corresponding fasteners. The domed head portion  104  may define a space  113  above a top extent of the tube bundle  130 . The space  113  provides a space for the pre-heated reactants to mix and divert back downwardly through the catalyst bed  140 . The nozzle  110  may be defined through a thickness of the domed head portion  104  to allow for the addition of a heating medium during start-up operation, as described previously. 
     While a domed head portion releasably securable to a shell has been shown and described, it will be appreciated that the disclosure is not limited thereto, and for any size of reactor, a fixed head, for example comprising a flanged manhole, may be utilized instead. 
     The thermocouple ports  106  may be aligned with respective thermocouple insertion tubes  126 , which may extend a distance above the top extent of the tube bundle  130 . The thermocouple ports  106  may extend through a part or an entirety of a thickness of the domed head portion  104  to allow access to the reactor interior  103 . The thermocouple ports  106  may facilitate access to the reactor interior  103  in any suitable way, such as by defining an aperture of a size that is configured to be flush with a surface of the temperature measurement device such that pressure may be maintained within the reactor interior  103 , by cooperating with a gasket seal, combinations thereof, or any other suitable means. Any suitable modality may be used. By extending a distance above the top extent of the tube bundle  130 , the thermocouple insertion tubes  126  are configured to be more easily identified during installation of the thermocouple, particularly as access is limited when the domed head portion  104  is in place. The thermocouple insertion tubes  126  may extend along a length of the reactor  100  substantially parallel to or aligned with the feed tubes  131 . 
     The reactor  100  further may comprise one or more of a catalyst support plate  154 , at least one tube support plate  162 ,  163 ,  164 ,  165 , a gas inlet plate  156 , a top and feed tube support plate  150 , and/or a top plate  190 , the provision of which advantageously facilitates securing the tube bundle  130  within the shell  102  while allowing for access to the reactor interior  103  as necessary for maintenance or other purposes. The gas inlet plate  156  and the catalyst support plate  154  may advantageously be welded to an interior surface of the shell  102  to secure the tube bundle  130  therewithin. 
     The tubes  131  of the tube bundle  130  may be welded to the gas inlet plate  156 , the top and feed tube support plate  150 , and/or to the at least one tube support plate  162 ,  163 ,  164 ,  165 . In embodiments, only the gas inlet plate  156  is welded or otherwise secured to the interior surface of the reactor shell  102 , with the top and feed tube support plate  150  and the at least one tube support plate  162 ,  163 ,  164 ,  165  being unsecured so as to accommodate thermal expansion of the tubes  131 . 
     Turning to  FIG. 4 , the catalyst bed  140  may comprise one or more sections of catalyst, such as solid catalyst. The catalyst bed  140  may also or alternatively comprise one or more inert sections  142 ,  144 , which sections may comprise support ceramic balls of a first diameter, such as 1-30 mm, more specifically 5-20 mm, or in embodiments 9 mm. The catalyst bed  140  may also comprise support ceramic balls of a second diameter, such as 1-30 mm, more specifically 10-25 mm, or in embodiments 19 mm. The catalyst bed  140  may define distinct sections  142 ,  144  corresponding to ceramic balls comprising substantially only balls of a single size. 
     For example, in the depicted embodiment the section  142  comprises substantially only balls having a diameter of 9 mm while the section  144  comprises only balls having a diameter of 19 mm. The sections  142 ,  144  may have any suitable height within the reactor  100 , such as 5-500 mm, more specifically 100-300 mm, or in embodiments 200 mm for each of the sections  142 ,  144 . The height of sections  142 ,  144  may the same, or different from one another. The catalyst bed  140  may additionally or alternatively comprise solid catalyst having a shape defining at least one of pellets, rings, tablets, or spheres. The sections  142 ,  144  may be arranged proximate (e.g., above, or directly above) the catalyst support plate  154  and below a section  141  comprising substantially only solid catalyst of a different shape and/or size than the support ceramic balls of sections  142 ,  144 . 
     The support ceramic balls sections  142 ,  144  advantageously support a weight of the catalyst in the catalyst bed while promoting effective and even flow distribution. By providing distinct first and second sections  142 ,  144 , the flow of reactants, products, and byproducts through the reactor interior  103  toward the outlet nozzle  124  is improved as the flow of gases is allowed between the catalyst particles in the catalyst bed  140 , between the support ceramic balls of the first, smaller diameter in the first section  142 , and finally between the support ceramic balls of the second, larger diameter in the second section  144  prior to passing through the catalyst support plate  154 . The support ceramic balls may advantageously be inert and configured to resist thermal shock and corrosion from various reactants, products, and/or byproducts. While support ceramic balls have been described, it will be appreciated that the sections  142 ,  144  may have more or fewer sections and may comprise differently shaped or sized support structures, such as rings, cylinders, polygons, or otherwise. 
     In embodiments, the section  141  of the catalyst bed  140  may have or define a first height  148  corresponding to an unreduced catalyst height, and a second height  146  corresponding to a reduced catalyst height. 
     While the section  141  of the catalyst bed  140  may comprise catalyst particles of a single size and/or shape, it will be appreciated that distinct sections within the catalyst bed  140  of differently sized and/or shaped catalyst particles are contemplated within the scope of the present disclosure. The catalyst particles may have any suitable shape or configuration, such as spheres, pellets, cylinders, trilobes, quadralobes, pyramids, cones, stars, or otherwise, and may have any suitable number and size of apertures defined therethrough and/or notches or grooves defined on a portion of the surface thereof. Distinct sections corresponding to a single, different type of catalyst size and/or shape may be provided in the catalyst bed  140 , for example as axial or radial layers or pockets. In embodiments different sizes and shapes of catalyst particles may be provided and mixed together within the catalyst body in any suitable configuration. 
     The catalyst particles in the catalyst bed  140  may be a function of and cooperative with the support ceramic balls in the sections  142 ,  144 , or vice versa. In embodiments the catalyst particles are selected independently of the support ceramic balls. 
     A tube bundle  130  according to an embodiment is shown in  FIGS. 6 and 7 . The tube bundle  130  is configured to extend substantially longitudinally about the axis  1 A- 1 A within the shell  102  and is maintained by, in order from top to bottom, a top plate and tube support plate  150 , a plurality of tube support plates  162 ,  163 ,  164 ,  165 , a catalyst support plate  154 , and a gas inlet plate  156 . A distance  161  between the top plate and tube support plate  150  and the tube support plate  162  and between the tube support plates  162 ,  163 ,  164 , and  165  may be uniform along a length of the tube bundle  130 . In embodiments the distance  161  may vary. A distance  167  between the tube support plate  165  and the catalyst support plate  154  may be greater than the distance  161 . A distance  169  between the catalyst support plate  154  and the gas inlet plate  156  may be smaller than the distance  167 . It will be appreciated that the depicted embodiment is merely exemplary and any arrangement of the tube bundle  130  may be used. 
     The tubes  131  may define a uniform thickness and diameter along a longitudinal length of the tube bundle  130 . In embodiments, the tubes  131  have a tapered thickness along the length of the tube bundle, with increased thickness and/or diameter proximate one or more of the plates  150 ,  162 ,  163 ,  164 ,  165 ,  154 ,  156  in order to support the plates. 
     In embodiments, one or more of the tubes  131  of the tube bundle  130  may have an increased thickness relative to other tubes  131  for increased structural support. For example, tubes  131  that extend closer to a center or an outer edge of the tube bundle  130  may have an increased thickness relative to the other tubes of, for example, 10%, 20%, 25%, 33%, 50%, or any other suitable thickness. That is, the walls of such tubes  131  may have an increased thickness while in embodiments maintaining a same internal diameter. This advantageously allows the tubes  131  with the increased thickness to convey reactants while supporting the tube bundle  130 , thereby freeing up cross-sectional area for increased catalyst loading and more evenly distributed catalyst relative to other structural arrangements. 
     In embodiments, the tubes  131  have a reduced thickness and/or increased diameter proximate a bottom portion of the reactor  100 , for example to facilitate more-efficient heat transfer at the bottom portion of the reactor  100  compared to the top portion of the reactor  100 . Alternatively, one or more of the tubes  131  of the tube bundle  130  may comprise internal tube rods configured to increase a velocity of the reactants being preheated therein. The internal tube rods may extend a partial or entire distance from a bottom of the tubes  131  to a top of the tubes  131 . 
     The tube bundle  130  and the reactor  100  generally are advantageously configured for modularity in design and implementation. Whereas existing shell-and-tube-type reactors are not easily scalable due to the significant rework that must be completed to properly balance the tube length and diameters, the catalyst bed, the shell, and other components, the design of the reactor  100  advantageously allows for scaling up or down based on the arrangement of the concentric bands of tubes  131  on the tube bundle  130 . The tube bundle  130  is arranged such that whether circumferential bands of tubes  131  are added (to increase the capacity of the reactor design for larger throughput or during a debottleneck effort) or removed (for scaling down the capacity of the reactor design), other geometric features of the reactor may remain unchanged. As a result extensive redesign work can be avoided. 
     The tube bundle  130  may be configured such that one or more geometric constraints or ratios are maintained in any design, regardless of whether the reactor and tube bundle are configured for reduced throughput or for increased throughput in various designs. To ensure that a tube density is improved, an average tube pitch (i.e. a center-to-center distance between tubes) of the tube bundle may be substantially constant throughout the tube bundle, with the circumferential bands and tubes defining the same being spaced so as to maintain a constant tube pitch. 
     As another example, the tube bundle  130  advantageously achieves a desired ratio of a cumulative cross-sectional area of the catalyst bed when viewing the reactor according to a plan view relative to a cumulative cross-sectional area of the tubes  131  (i.e. the total radial surface area of the tubes taken together) according to the same plan view. In embodiments, the ratio of the cumulative cross-sectional area of the catalyst relative to the cumulative cross-sectional area of the tubes is in a range between 2 and 20, more specifically between 5 and 12. 
     Regardless of a circumferential band of tubes  131  being added to or removed from the tube bundle  130  design, the cross-sectional area of the tubes  131  relative to the catalyst bed may be simply and easily adjusted so as to remain within a suitable bound, such that the performance of the reactor, and in particular its safety profile, are suitable. In an embodiment, adding or removing one or more circumferential bands of tubes may not substantially change the cumulative cross-sectional area of the catalyst relative to the cumulative cross-sectional area of the tubes. In other embodiments, the tube bundle  130  may be designed such that any other geometric or process-related parameter is targeted such that removal or addition of circumferential bands of tubes do not entail extensive redesign but rather allow an engineer to simply and easily adjust the reactor to a new, required capacity or other requirement. By providing a tube bundle  130  with the specified relation between the cross-sectional areas of the tubes and the catalyst bed, heat distribution is improved, which reduces the likelihood of runaway reactions by reducing hotspots and improving overall throughput through the reactor  100 . 
     The reactor  100  may be controlled and maintained during operation to control one or more features of the catalyst bed  140  and/or the tube bundle  130 . In some embodiments, the reactor  100  is configured to utilize the temperature measurement devices to evaluate a distribution of heat throughout the cross-sectional area of the catalyst bed. In particular, the reactor  100  may be controlled by assessing a radial temperature gradient within the reactor according to depth and/or assessing a growth of the gradient according to depth within the reactor  100  (from the top end  105  toward the bottom end  107 ). 
     Turning to  FIGS. 12 and 13 , the catalyst support plate  154  is configured to support a total height of the solid catalyst, such as a height of the sections  142 ,  144  combined with the height of the section  141 . The catalyst support plate  154  further advantageously supports forces due to differential pressure over the catalyst bed  140 . The catalyst support plate  154  may be arranged within the shell  102  proximate the catalyst unloading nozzle  116  and/or the hand hole  118 . The catalyst support plate  154  may define one or more apertures  180 ,  181 . The apertures  180 ,  181  may comprise or define apertures comprising a plurality of apertures of a first size corresponding to the apertures  180  and a plurality of apertures of a second size corresponding to the apertures  181 , the apertures extending through at least part of a thickness of the catalyst support plate  154 . 
     The first size of the apertures  180  may correspond to a circumference of at least one tube  131  of the tube bundle  130 . In embodiments, the first size of the apertures  180  is larger than a circumference of the tubes  131  to allow for a degree of movement and/or thermal expansion of the tubes within the aperture  180 . The apertures  180  may be defined through the catalyst support plate  154  according to an arrangement of the plurality of tubes  131  in the tube bundle  130 . The second size of the apertures  181  may be smaller than the first size of the apertures  180 , the second size of the apertures  181  serving to allow for flow of reactants, reaction products, and reaction byproducts therethrough en route to the outlet nozzle  124 . 
     In embodiments, one or more of the apertures  180  may define a terminus for a temperature measurement device. The apertures  182  may be sized and configured to receive a thermocouple insertion tube  126  and to terminate an extension of the thermocouple insertion tubes  126  ( FIG. 7 ). The apertures  182  may in embodiments extend only partly into the thickness of the catalyst support plate  154 . In embodiments the thermocouple insertion tubes  126  may be welded to the catalyst support plate  154  and plugged thereat. The tubes  131  may not be welded to the catalyst support plate  154  to allow for the effects of thermal expansion. 
     The size of the apertures  181  and/or the average distance between the apertures  181  may be a function of the thickness of the catalyst support plate  154 , such that the size of the apertures  181  is proportional to a thickness of the catalyst support plate  154  and/or the distance between the apertures  181  is inversely proportional to the thickness of the catalyst support plate  154 . That is, the greater the thickness of the catalyst support plate  154 , the greater the diameter of the apertures  181  and/or the smaller the distance between the apertures  181 . In embodiments, the catalyst support plate  154  may have a thickness of between 20 and 500 mm, more specifically between 50 and 300 mm, and in embodiments 110 mm, while the apertures  181  may have a diameter of 1-50 mm, more specifically 5-25 mm, and in embodiments 10 mm. 
     As seen in the close-up view of  FIG. 13 , the apertures  180  may extend in a pattern or arrangement corresponding to an arrangement of tubes  131  in the tube bundle  130  as will be discussed in greater detail herein. The apertures  181  may extend between each of the apertures  180 . The apertures  181  may define any suitable pattern or arrangement, such as an extension direction  183 A and/or a transverse extension direction  183 B, the extension directions  183 A,  183 B defining straight lines. Other patterns or arrangements of the apertures  181  are contemplated within the scope of the disclosure. The apertures  181  may be spaced apart from each other by any suitable distance, including in embodiments by a distance of 1-30 mm from center to center of adjacent apertures  181 , more specifically from 5-20 mm from center to center, and in embodiments 15 mm from center to center of adjacent apertures  181  along one or both of the directions  183 A,  183 B. The distance from center to center of adjacent apertures  181  need not be uniform across an entirety of the surface of the catalyst support plate  154  but rather may vary as suitable. 
     The catalyst support plate  154  may define at an outer periphery a band  184  of material forming the catalyst support plate  154  that does not define any of the apertures  180 ,  181 . The band  184  may extend partially or wholly about the periphery of the catalyst support plate  154  and advantageously facilitates welding or other suitable attachment of the catalyst support plate  154  to the interior surface of the shell  102 . In embodiments, the band  184  may extend into and then be welded to a recess defined by the inner surface of the shell  102 . The band  184  may extend any suitable distance such as 5 mm radially. 
     Turning to  FIG. 11 , the gas inlet plate  156  may be arranged below the catalyst support plate  154 , and may comprise a plurality of apertures  155  defined through at least part of a thickness of the gas inlet plate  156 . The plurality of apertures  155  may be circular apertures defined through the gas inlet plate  156  according to the arrangement of the plurality of tubes  131  of the tube bundle  130 , and aligning with an arrangement of the apertures  180  of the catalyst support plate  154 . In an embodiment, the gas inlet plate  156  is substantially solid and devoid of openings outside of the plurality of apertures  155  so as to force the incoming reactants into the tubes  131 . The plurality of tubes  131  may be seal welded and/or strength welded to the gas inlet plate  156 . It will be appreciated that where a component is discussed herein as being welded to another component, seal welding, strength welding, a combination thereof, or any other type of attachment is contemplated. 
     Turning to  FIGS. 8-9 , the reactor  100  may further comprise at least one tube support plate  150 ,  162 ,  163 ,  164 ,  165  which may be arranged longitudinally spaced apart along an axial or longitudinal length of a tube bundle  130 . The tube support plates  150 ,  162 ,  163 ,  164 ,  165  are shown and described, but it will be appreciated that more or fewer support plates may be provided. The top and feed tube support plate  150  may be substantially the same as the tube support plates  162 ,  163 ,  164 ,  165  and may include or omit one or more features. For example, the top and feed tube support plate  150  may have the same features as the tube support plates  162 ,  163 ,  164 ,  165  and may further include one or more spacers configured to cooperate with a top plate, as will be described in greater detail below. 
     The tube support plate  150 ,  162 ,  163 ,  164 ,  165  may comprise at least one circumferential band  168  configured to maintain a position of the at least one tube  131 . The at least one circumferential band  168  comprises at least one bracket  172  configured to extend about a portion of a tube  131  of the tube bundle  130 . In embodiments, the at least one bracket  172  extends about an entirety of the tube  131 . The bracket  172  may be configured to releasably attach to the tube  131 . 
     In embodiments, the bracket  172  may extend about only a portion rather than an entirety of the tube. The bracket  172  may advantageously cooperate with a beam  173  that extends between the bracket  172  and an adjacent bracket  172  attached to an adjacent tube  131 . The bracket  172  may be connected releasably or non-releasably with the beam  173  and may define a filleted connection, for example. A circumferential band  168  may be defined by a series of connected brackets  172  and beams  173  defining a substantially circumferential arrangement with corresponding tubes  131 . 
     The circumferential band  168  may be concentrically arranged with adjacent circumferential bands  168  of the tube support plate  150 ,  162 ,  163 ,  164 ,  165 , with the circumferential bands  168  optionally centered on the longitudinal axis  1 A- 1 A of the reactor. The cooperation of brackets  172 , beams  173 , radial struts  166 , and circumferential bands  168  together define a tube support plate. While the circumferential bands  168  have been shown and described, it will be appreciated that any suitable configuration may be used, including asymmetric, offset, or non-circumferential arrangements. While the cooperation of various components is described as defining a tube support plate, it will be appreciated that a tube support plate may take any suitable configuration and is not limited hereby. 
     The at least one tube support plate  150 ,  162 ,  163 ,  164 ,  165  defines at least one radial strut  166  connected to the at least one circumferential band  168  at an attachment point  169  and/or to an outer support band  170  at an attachment point  171 . The tube support plate may define a plurality of radial struts  166  arranged radially symmetrically, for example at 22.5° increments, at 30° increments, at  450  increments, at 90° increments, at  1200  increments, at  1800  increments, another increment evenly divisible by 360°, or otherwise. In other embodiments, the radial struts  166  are arranged asymmetrically in any suitable manner. 
     The outer support band  170  may define a substantially continuous band of support material, such as stainless steel, that provides sufficient rigidity, strength, and/or support to the tube support plate, and/or that facilitates attachment of the outer support band  170  to an inner surface of the reactor shell  102 . While eight radial struts  166  are shown and described regarding the embodiment of  FIGS. 9 and 10 , it will be appreciated that more or fewer radial struts  166  may be provided, and that all of the tube support plates  150 ,  162 ,  163 ,  164 ,  165  need not have a same number or arrangement of radial struts or other components. 
     The radial struts  166  may extend straight outwardly from a center of the tube support plate to the outer support band  170 , or may define a curved, bent, tortuous, or other configuration. The radial struts  166  may be formed of any suitable material, such as stainless steel, and may define heat-resistance properties to retain desired stiffness and strength in the reactor conditions. The radial struts  166  advantageously define attachment points  169  between the circumferential bands  168  and the radial struts  166 . The attachment points  169  may be releasable or non-releasable, and may define any suitable connection, such as being welded together or being attached by a suitable fastener. The tube support plate may be configured to move with the tubes  131  by thermal expansion and contraction, and may be formed of high temperature-resistance materials, such as steel (e.g., stainless steel), ceramics, polymeric materials, composite materials, or otherwise. 
     In embodiments, the tube support plate  150 ,  162 ,  163 ,  164 ,  165  may be fabricated using any suitable means. In embodiments, the tube support plate  150 ,  162 ,  163 ,  164 ,  165  is formed from a single, solid plate from which material is removed for example by water jet cutting. In other embodiments, the radial struts and circumferential bands are independently fabricated and assembled to form the tube support plates. 
     The top and feed tube support plate  150  may additionally define one or more spacers  174  on a top surface thereof. The spacers  174  may be attached to one or more structures of the top and feed tube support plate  150  in any suitable manner, including by welding. The spacers  174  may extend a predetermined height and may define an aperture within a center portion thereof. The aperture may comprise one or more threadings configured to matingly engage with one or more threadings of a fastener, as will be discussed in greater detail herebelow regarding the top plate  190 . The spacers  174  may extend about the top and feed tube support plate  150  in any suitable arrangement and in any suitable number. 
     For instance, the spacers  174  may define three concentric ring patterns  175  ( FIG. 9 ) about the top and feed tube support plate  150  as the spacers  174  attach to radial struts  166 . In an embodiment, the spacers  174  extend along four of the radial struts  166  between the first and second circumferential bands, between the seventh and eighth circumferential bands, and between the thirteenth and fourteenth circumferential bands. A total of four spacers  174  may be arranged on each of the concentric ring patterns  175 , such that a corner portion of each segment of the top plate  190  may be fastened thereto, as will be described herebelow. 
     The arrangement of the radial struts  166  advantageously provides a secure attachment of the tubes  131  of the tube bundle  130  while minimizing interference with the distribution of catalyst as the catalyst is loaded from the top portion  105  of the reactor  100 . For example, as the catalyst particles are poured into the shell  102 , the radial struts  166  are configured to minimize uneven distribution of the catalyst. In embodiments, the radial struts  166  of adjacent tube support plates  162 ,  163 ,  164 ,  165  may align axially along the longitudinal extension length of the reactor  100 . 
     In other embodiments, as shown in  FIG. 10B , the radial struts  167  of adjacent tube support plates may be offset from the radial struts  166  to promote even distribution of the catalyst during loading. The degree of offset may be any suitable degree. In embodiments, the radial struts  167  are offset by a distance corresponding to half the angular distance between the radial struts  166 . In the embodiment of  FIG. 10B , the radial struts  166  are offset by 450 from each other, and the offset of the radial struts  167  is 22.5°. Subsequent tube support plates may alternate in arrangement. The radial struts  166  of adjacent tube support plates may be offset down a longitudinal length of the reactor so as to define a spiral or helix pattern. The depicted embodiment is exemplary, and any other arrangement may be used as suitable. 
     The tube bundle  130  may be arranged such that an innermost circumferential band  168 A of the at least one tube support plate comprises six brackets configured respectively to correspond to a ring of six innermost tubes of a first size. The first size may be, for example, 0.5-3 mm in diameter, more specifically 1-2 mm in diameter, and in embodiments 1.5 mm. A second circumferential band  168 B of the at least one tube support plate comprises 10 brackets configured respectively to correspond to a ring of 10 tubes of the tube bundle of the first size. A third circumferential band  168 C of the at least one tube support plate comprises 14 brackets configured respectively to correspond to a ring of 14 tubes of the tube bundle of a second size. The second size may be, for example, 0.5-5 mm in diameter, more specifically 1-4 mm, and in embodiments 2.5 mm. 
     A fourth circumferential band  168 D of the at least one tube support plate comprises 18 brackets configured respectively to correspond to a ring of 18 tubes of the tube bundle of the first size. A fifth circumferential band  168 E of the at least one tube support plate comprises 22 brackets configured respectively to correspond to a ring of 22 tubes of the tube bundle of the first size. A sixth circumferential band  168 F of the at least one tube support plate comprises 26 brackets configured respectively to correspond to a ring of 26 tubes of the tube bundle of the first size. 
     A seventh circumferential band  168 G of the at least one tube support plate comprises 30 brackets configured respectively to correspond to a ring of 30 tubes of the tube bundle of the second size. An eighth circumferential band  168 H of the at least one tube support plate comprises 34 brackets configured respectively to correspond to a ring of 34 tubes of the tube bundle of the first size. A ninth circumferential band  168 I of the at least one tube support plate comprises 36 brackets configured respectively to correspond to a ring of 36 tubes of the tube bundle of the first size. A tenth circumferential band  168 J of the at least one tube support plate comprises 42 brackets configured respectively to correspond to a ring of 42 tubes of the tube bundle of the first size. 
     An eleventh circumferential band  168 K of the at least one tube support plate comprises 46 brackets configured respectively to correspond to a ring of 46 tubes of the tube bundle of the second size. A twelfth circumferential band  168 L of the at least one tube support plate comprises 50 brackets configured respectively to correspond to a ring of 50 tubes of the tube bundle of the first size. A thirteenth circumferential band  168 M of the at least one tube support plate comprises 54 brackets configured respectively to correspond to a ring of 54 tubes of the tube bundle of the first size. A fourteenth circumferential band  168 N of the at least one tube support plate comprises 58 brackets configured respectively to correspond to a ring of 58 tubes of the tube bundle of the second size. 
     While the first through fourteenth circumferential bands have been shown and described, it will be appreciated that the reactor embodiments of the present disclosure advantageously facilitate a modular reactor construction that accommodates different throughput requirements of different facilities better than existing reactor designs. As needed, for example, an engineer may modify the depicted tube bundle  130  to have more, fewer, and/or different circumferential bands. In order to scale up the tube bundle  130  and the reactor  100  as a whole to accommodate a higher yearly capacity of a plant, such as during a debottlenecking effort, an additional circumferential band may be added to increase the number of tubes and expand the tube bundle outwardly in a simple modification. For example, the attachments  171  between the radial struts  166  and the outer band  170  may be released such that an additional circumferential band may be added to the tube support plate, with the outer band  170  replaced about the new circumferential band. To this end, the outer band  170  may be configured to have an expandable circumference. 
     Conversely, to scale down the reactor  100 , a circumferential band, such as an outermost circumferential band, may be removed to reduce the size of the tube bundle so as to fit a smaller reactor shell and/or to yield a correspondingly lower yearly plant capacity. This may be done, for example, by detaching the attachments  169  between circumferential bands and the radial struts. 
     Moreover, the arrangement of the circumferential bands as shown allows for the addition or removal of circumferential bands and the accompanying brackets and tubes while accommodating the structure of the radial struts. As seen, the circumferential bands increase in number of brackets and tubes such that the tubes are positioned in a substantially even distribution and with sufficient space between the tubes to allow for catalyst and reactant to pass therebetween and for the circumferential bands to be added or removed without disrupting the design of the radial struts and the tube support plate generally. 
     In an embodiment, the ninth circumferential band  168 I (or any other) of the at least one tube support plate further comprises brackets  172  corresponding to at least one thermocouple insertion tube  126 , the at least one thermocouple insertion tube  126  being of the first tube size. The provision of brackets  172  for the thermocouple insertion tube  126  allows for temperature measurement devices to be inserted into the tube bundle, preferably into a region of the tube bundle where the temperature measurement device will be surrounded by catalyst and tubes, for accurate temperature readings along a longitudinal length of the reactor. 
     The top and feed tube support plate, similar to the tube support plates  162 ,  163 ,  164 ,  165 , may comprise one or more radial struts  166 , an outer band  170 , and one or more brackets  172  configured to engage with and/or surround a tube  131  of a tube bundle  130 . 
     The radial struts  166  of the top and feed tube support plate  150  may be arranged analogous or corresponding to the struts  166  of the feed tube support plates  162 ,  163 ,  164 ,  165  and may be divided axially by a suitable angle  176  ( FIG. 9 ), such as 45°. It will be appreciated that other angles or arrangements are contemplated by the present disclosure. 
     The brackets  172  of the top and feed tube support plate  150  may constitute or extend proximate a terminus of the tubes  131 , with the pre-heated reactants exiting the tubes  131  thereat and then flowing in the second direction F 2  downwardly. The thermocouple insertion tubes  126  may extend a distance above a topmost distance or extent of the tubes  131 , this facilitating easier insertion of the temperature measurement devices from the thermocouple port  106  to the thermocouple insertion tube  126 . As with the tube support plates  162 ,  163 ,  164 ,  165 , the top and feed tube support plate  150  may be configured to be expanded or decreased in size as suitable for a desired capacity of the reactor  100 . 
     The arrangement of the tube bundle  130  and the tube support plates  150 ,  162 ,  163 ,  164 ,  165  may advantageously account for heat transfer and reactor kinetics of the reactor. 
     Turning to  FIGS. 14-16 , a top plate  190  is shown. The top plate  190  may be configured to be installed atop or above the top and feed tube support plate  150 . The top plate  190  may be modular in construction and define four distinct segments  192  surrounded by a flange  191 . The top plate  190  may define a plate edge  194 , one or more tube holes  202  defined through at least a partial thickness of the plate  190 , and one or more gas apertures  204  defined through at least a partial thickness of the plate  190 . The tube holes  202  may be configured to align generally with an arrangement of the tubes  131  of the tube bundle  130  and facilitate passage of pre-heated reactants out of the tubes  131  into the space  113  ( FIG. 5B ) of the reactor  100 . 
     The gas apertures  204  facilitate passage of the pre-heated reactant into the catalyst bed  140  and ensure proper flow distribution. The top plate  190  may be configured to create a small pressure drop to make the flow entering the catalyst bed as uniform as possible. The top plate  190  is advantageously configured to achieve improved uniformity of flow distribution using a simplified design as shown and described relative to existing approaches which may utilize heavy and/or complicated designs that are difficult and/or costly to manufacture and/or to manipulate for maintenance purposes. 
     As the top plate  190  may extend outwardly to the flange  191 , the gas apertures  204  may extend substantially to the edge  194  without leaving a gap as in the catalyst support plate  154 . The top plate  190  may have a reduced thickness compared to the catalyst support plate  154 . In embodiments, the top plate  190  has a thickness of between 1 and 25 mm, more specifically between 5 and 15 mm, and in embodiments 8 mm. 
     The top plate  190  is configured to be removably attached to the shell  102  and/or to the top plate and tube support plate  150  by any suitable mechanism, such as by the use of fasteners  196  that cooperate with corresponding apertures  193  ( FIG. 15 ) at the edge of each section of the plate  190 . The fasteners  196  of the top plate  190  may cooperate with one or more of the spacers  174  extending between the top plate  190  and the top and feed tube support plate  150 , and which may be welded, for example tack welded, to the top and tube support plate  150 . 
     In embodiments, the spacers  174  may have a height and/or circumference sufficient to receive a mating end of the fastener  196  within a track or recess defined through a portion of a thickness of the spacer  174 , this allowing a robust attachment of the top plate  190  onto the top and feed tube support plate  150 . The height of the spacer  174  may be between 1 and 30 mm, more specifically between 5 and 20 mm, and in embodiments 15 mm. The spacer  174  may be welded onto a radial strut  166 , a circumferential band  168 , a bracket  172 , or otherwise. As seen, the fasteners  196  and the corresponding spacers  174  may be located such that a fastener and spacer  196 ,  174  is provided in each corner and along interior edges of a section  194  of the top plate  190 . 
     The top plate  190  may further comprise or cooperate with one or more load rings  195 . The load rings  195  may be any suitable component configured to facilitate positioning and/or removal of the section  194  of the top plate  190 . The load rings  195  may attach through one or more of the gas apertures  204  or at any other suitable location and define a component for removably securing to and manipulating the top plate  190 . In embodiments the load rings  195  are configured to allow an operator to grasp the top plate  190  with a tool for lifting the top plate  190  away from the reactor shell  102 . 
     By providing the top plate  190  in a modular fashion, with the distinct sections  194 , the top plate  190  is more easily removable and replaceable during maintenance operations without sacrificing the ability of the top plate  190  to distribute the reactants and secure the catalyst bed  140 . The modular construction of the top plate  190  further makes the manufacturing process less costly and complex, as identical sections  192  may be manufactured rather than plates  190  of unitary construction. One benefit of the arrangement of the top plate  190  is the ability for a plant worker to stand on one of the sections  194  of the top plate  190  while loading catalyst through the opening provided by a section  194  that has been removed. 
     Turning to  FIGS. 17-19 , a retaining plate  210  for use with one or more nozzles of the reactor  100  is shown and described. The retaining plate  210  may secure the catalyst unloading nozzle  116  and/or the hand hole  118 . The retaining plate  210  may comprise a handle  212  and is configured to cooperate with a lip  214  defined by the nozzle  116 . In embodiments, the nozzle  116  defines a plurality of lips  214  arranged circumferentially about an opening of the nozzle in any suitable pattern, with the retaining plate  210  configured to abut an inner surface of the lip  214  as seen in  FIG. 17 . In embodiments, the lips  214  are spaced apart by an angle, such as 15°, 20°, 30°, 45°, 60°, 90°, or otherwise. The arrangement of the lips  214  may be symmetric or asymmetric. The flange  117  of the nozzle  116  may define one or more apertures  211  through which suitable fasteners may be received to connect the nozzle  116  to a suitable spool. 
     In particular embodiments, the plurality of lips  214  do not extend about a bottommost section B of a circumferential aperture defined by the catalyst unloading nozzle  116  or the hand hole  118 . Rather, as seen in  FIG. 19 , the bottommost section B is unobstructed such that catalyst particles may flow freely under the effects of gravity during catalyst unloading. The arrangement of the retaining plate  210  advantageously prevents the catalyst from flowing too fast during catalyst unloading. 
     Turning to  FIG. 20 , a reactor  300  according to an embodiment is shown and described. The “300” series reference numbers may include similar or identical features to those already described with “100” series reference numbers. The reactor  300  comprises a shell  302  in which a tube bundle having a top plate  350  as described above may be received and secured, and defines an inlet nozzle  320  and an outlet nozzle  324 . The shell  302  may further comprise or cooperate with a domed top portion  304  defining and/or supporting a thermocouple insertion nozzle  306 . The domed top portion  304  may be secured to the shell  302  by a flange  312 . The reactor  300  extends longitudinally about an axis  20 A- 20 A. A catalyst bed  340  may extend a suitable height within an internal space defined by the reactor shell  302 . 
     The reactor  300  further defines a thermocouple insertion tube  326  extending about or substantially parallel or aligned with the longitudinal axis  20 A- 20 A and through the catalyst bed  340 . The thermocouple insertion tube  326  may be integrated with or independent of a tube bundle as described above. The thermocouple insertion tube  326  is configured to receive a temperature measurement device  310 , which likewise extends about the longitudinal axis  20 A- 20 A. The temperature measurement device  310  may be a multi-element thermocouple. The multi-element thermocouple is configured to obtain a measurement of a temperature at a plurality of locations along the reactor  300 . 
     As seen in  FIG. 20 , the temperature measurement device  310  may comprise eight measurement locations  382 A,  382 B,  382 C,  382 D,  382 E,  382 F,  382 G,  382 H along the length of the reactor  300  and extends to a terminus  327 . The temperature measurement device  310  may have a total length  3301 . The locations  382 A,  382 B,  382 C,  382 D,  382 E,  382 F,  382 G,  382 H may be distanced by, respectively, distances  330 A,  330 B,  330 C,  330 D,  330 E,  330 F,  330 G. The distances  330 A,  330 B,  330 C,  330 D,  330 E,  330 F,  330 G may be a same distance such that the measurement locations are evenly spaced along the reactor  300 , or may be different distances depending on the needs of a particular process. 
     The thermocouple insertion tube  326  may be suitably configured to allow the temperature measurement device  310  to obtain readings at the locations  382 A,  382 B,  382 C,  382 D,  382 E,  382 F,  382 G,  382 H, such as by defining apertures in the thermocouple insertion tube  326  at or proximate the locations  382 A,  382 B,  382 C,  382 D,  382 E,  382 F,  382 G,  382 H to allow the temperature measurement device  310  to gauge the temperature of the reactor interior. While a temperature measurement device has been described, it will be appreciated that the disclosure extends to other types of sensors and is not limited to a multi-element thermocouple. In embodiments, different sensors may be arranged at different locations as necessary. 
     The temperature measurement device  310 , the reactor  300 , and the thermocouple insertion tube  326  advantageously facilitate improved process control by providing granular reactor conditions data at multiple locations within a reactor while simultaneously minimizing the risk of leakage, particularly for high pressure and/or high temperature service and/or for reactions involving hydrogen or catalysts that are sensitive to oxygen, by reducing the number of thermocouple joints. The configuration of the temperature measurement device  310 , the reactor  300 , and the thermocouple insertion tube  326  further improves the scalability of a reactor design, as the arrangement of the thermocouple insertion tube  326  and the temperature measurement device  310  allows for an accurate reading of internal reactor conditions regardless of the size of the reactor, mitigating the difficulty of monitoring reactors in which thermowells are arranged radially from a sidewall surface of the reactor and, for larger reactors, disproportionately measure conditions near the shell rather than near the center of the reactor. 
     Additionally, as seen in at least  FIGS. 2 and 7 , a reactor may comprise a plurality of temperature measurement devices. The temperature measurement devices may be arranged in any suitable configuration relative to the reactor shell and to each other. In the embodiment of  FIGS. 2 and 7 , for example, the temperature measurement devices may be offset from a central longitudinal axis of the reactor by a same distance and arranged opposite each other. The distance between the temperature measurement devices may be configured to minimize interference with or disturbances in the heat distribution within the reactor, particularly the catalyst bed. The distance may be selected to be above a minimum threshold at which a hotspot would develop between or proximate the temperature measurement devices due to the resulting disruption to reactant and product flow and accordingly heat distribution. Arranging the temperature measurement devices above the minimum threshold thereby avoids performance disruptions of the reactor and improves accuracy of the measurement. 
     The temperature measurement devices may serve different purposes and/or may be complementary to each other. In the embodiment of  FIGS. 2 and 7 , the temperature measurement devices are multi-element thermocouples as described regarding  FIG. 20 . One of the multi-element thermocouples may be connected to a process control system, while a second one of the multi-element thermocouples may be connected to a safety instrument system. 
     Providing a plurality of the multi-element thermocouples advantageously confirms the measurement of temperature at a particular location, i.e. elevation, within the reactor. Any difference between the signals obtained from the multi-element thermocouples may be used to determine, for example, the development of a hot spot at a particular elevation, allowing an operator to make adjustments as necessary. It will be appreciated that any suitable number of thermocouples in any suitable configuration may be used. 
     An embodiment of the reactor comprises a plurality of feed tubes extending longitudinally through the reactor and a catalyst bed. A tube bundle may define thermocouple insertion tubes extending parallel to the feed tubes and configured to receive a temperature measurement device such as a multi-element thermocouple therethrough. The thermocouple insertion tubes may be configured to extend at different distances from a center of the reactor. 
     The distances may be configured to allow for measurement of a temperature distribution at different distances from the center. In particular, this may help to validate a design of the reactor at a particular scale, further enhancing the scalability of the reactor of embodiments of the present disclosure. This further enhances the process control of the reactor, with improved granularity of temperature measurement and the ability to tailor the associated responses using the process control system. In embodiments, the radial configuration of the thermocouple insertion tubes may be determined so as to coincide with predicted hotspots. 
     This allows an operator to quickly and accurately determine when a hotspot has formed and to respond accordingly, thereby preventing runaway reactions. The configuration of the thermocouple insertion tubes may further be determined relative to the tube bundle so as to accommodate the size of the reactor shell. In smaller reactors, for example, fewer thermocouple insertion tubes may be utilized, whereas the number of thermocouple insertion tubes, and the complexity of the configuration of the same, may increase in larger reactors. 
     By providing a reactor according to the disclosed embodiments, the problems of existing reactors being difficult to access when maintenance is needed, and reactors being difficult to scale based on the throughput needs of a facility, are addressed. The reactor embodiments of the present disclosure advantageously provide a reactor that comprises robust yet flexible reactor internals that are configured to be modularly arranged based on the throughput needs of a facility design, easily accessible for maintenance and catalyst loading, facilitate improved, even distribution of catalyst, reactants, and heat, and/or provide robust structural support during construction, transportation, installation, and operation. 
     While the reactor has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes, equivalents, and modifications that come within the spirit of the embodiments defined by following claims are desired to be protected. 
     Accordingly, features of the disclosed embodiments may be combined or arranged for achieving particular advantages as would be understood from the disclosure by one of ordinary skill in the art. Similarly, features of the disclosed embodiments may provide independent benefits applicable to other examples not detailed herein. In particular, any feature from one disclosed embodiment may be employed in another disclosed embodiment. 
     It is to be understood that not necessarily all objects or advantages may be achieved under any embodiment of the disclosure. Those skilled in the art will recognize that the reactor may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught without achieving other objects or advantages as taught or suggested. 
     The skilled artisan will recognize the interchangeability of various disclosed features. Besides the variations described, other known equivalents for each feature can be mixed and matched by one of ordinary skill in this art to make or use a reactor under principles of the present disclosure. It will be understood by the skilled artisan that the features described may be adapted to other types of reactors, reaction suites, chemical species, and processes. Hence this disclosure and the embodiments and variations thereof are not limited to methanol synthesis processes or to shell-and-tube reactors, but can be utilized in any chemical process. 
     Although this disclosure describes certain exemplary embodiments and examples of a reactor, it therefore will be understood by those skilled in the art that the present disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the disclosure and obvious modifications and equivalents thereof. It is intended that the present disclosure should not be limited by the particular disclosed embodiments described above. 
     In addition, unless otherwise indicated, numbers expressing quantities, constituents, distances, or other measurements used in the specification and claims are to be understood as optionally being modified by the term “about” or its synonyms. When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 20%, less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition. As used herein, the term “between” includes any referenced endpoints. For example, “between 2 and 10” includes both 2 and 10.