Method and apparatus for removing solid catalyst

Abstract

Used catalyst (500) is removed from the process microchannels (310) of a Fischer-Tropsch reactor by directing air jets (4) from air knives (1) through slots of guard elements (2). The air knives traverse the continuous process microchannels (310) in direction A. The spacing elements (2) protect the internal microchannel structure (315) of the process microchannels from damage by air jets (4) that can approach or exceed the speed of sound when directed into the process microchannels.

Description

Technical Field

[0001] This invention relates to a method for removing spent catalyst from a microchannel reactor. Specifically, but not exclusively, this invention relates to a method for removing spent Fischer-Tropsch catalyst from process microchannels in a Fischer-Tropsch reactor. Background Technology

[0002] The Fischer-Tropsch process is widely used to produce fuels from carbon monoxide and hydrogen, and can be expressed by the following formula:

[0003] (2n+1)H2 + nCO → C n H 2n+2 +nH2O

[0004] The reaction is highly exothermic and is catalyzed by a Fischer-Tropsch catalyst (typically a cobalt-based catalyst) under elevated temperature (typically at least 180 °C, e.g., 200 °C or higher) and pressure (e.g., at least 10 bar). A product mixture is obtained, and n typically ranges from 1 to about 90. Minimizing methane selectivity, i.e., minimizing the proportion of methane (n=1) in the product mixture, and maximizing selectivity for C5 and higher (n≥5) alkanes, typically to a level of 90% or higher, is desirable. Maximizing carbon monoxide conversion is also desired. Preferably, at least about 70% w / w of the product mixture is distributed between n=10 and n=30.

[0005] Hydrogen and carbon monoxide are typically used as feedstocks for synthesis gas.

[0006] In the Fischer-Tropsch reaction, the catalyst gradually degrades, thereby reducing its effectiveness and requiring a gradual increase in temperature to maintain an acceptable carbon monoxide conversion. This is described in Steynberg et al., “Fischer-Tropsch catalyst deactivation in commercial microchannel reactor operation,” Catalysis Today 299 (2018), pp. 10–13.

[0007] Catalysts can be regenerated periodically over a period of time, which can be done in situ by subjecting them to processes such as dewaxing, oxidation, and reduction. However, during the catalyst's lifespan, there are times when the accumulation of non-renewable poisons (such as sulfur) and other non-renewable deactivation mechanisms (such as sintering) render the catalyst unviable. At this point, the catalyst must be removed from the reactor and replaced with fresh catalyst.

[0008] Many different reactor types are known for Fischer-Tropsch synthesis, including fixed-bed reactors, slurry-bubbling-bed reactors (SBCR), and microchannel reactors (Rytter et al., “Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts-AMini-Review” Catalysts 2015, 5, pp478-499 at pp482-483).

[0009] Microchannel reactors are disclosed in our WO2016201218, which is incorporated herein by reference, and similarly in LeViness et al., “Velocys Fischer-Tropsch Synthesis Technology - New Advances on State-of-the-Art”, Top Catal 2014, pp. 5718-525. Such reactors offer a particular advantage in heat removal due to the high ratio of heat exchange surface area to microchannel (and therefore catalyst) volume.

[0010] However, microchannel reactors present unique challenges when catalyst removal is required. This is especially true for used catalysts that may have undergone thousands of hours of equipment operation and deteriorated within the microchannels.

[0011] This invention relates, in particular but not specifically, to the removal of used catalyst from microchannel reactors. Microchannel reactors typically comprise a process layer containing microchannel structures, for example, in the form of wavy ripples within the process layer, which effectively divide the process layer into a linear array of process channels (process microchannels). The microchannel structures are typically thinner than the pressure boundary (and may be made of a different material), and are more susceptible to damage under harsh physical conditions, such as when it may be necessary to remove used catalyst from the microchannels.

[0012] It has been found that it is difficult to remove used catalyst from the microchannels of such reactors because of their relatively small cross-sections. As described in our US2009252658, attempts to remove used catalyst by mechanical means (e.g., hammering) or with steam or high-pressure hot water result in poor catalyst recovery, typically 50% or less of the original catalyst loading.

[0013] It is also known from US2009252658 that used catalyst can be removed from the microchannels of a Fischer-Tropsch reactor by placing an ultrasonic generating head in contact with the acoustic waves of the microchannels and applying ultrasonic energy to the microchannels. However, this method also has some practical drawbacks. In particular, existing ultrasonic equipment and techniques have been found to remove used catalyst from the microchannels too slowly and / or incompletely. Summary of the Invention

[0014] The present invention provides a method for removing particulate catalyst from a packed catalyst bed within a process channel of a microchannel reactor. The method includes hermetically sealing the distal end of a linear array of process channels to form a blocked process channel in the array, and directing a high-velocity gas flow into the open proximal end of the process channel, the gas flow velocity being sufficient to raise the pressure in at least the partially blocked process channel to at least about 5 psig (gauge pressure 34,473 Pa), thereby generating a pressure gradient within the catalyst bed and / or between the catalyst bed and any open space adjacent to the catalyst bed within the blocked process channel that effectively expels the particulate catalyst from the catalyst bed.

[0015] On the other hand, the present invention provides a method for removing particulate catalyst from a process channel of a microchannel reactor, the method comprising hermetically sealing the distal end of a linear array of process channels to form a blocked process channel in the array, and directing a high-velocity gas flow into the open proximal end of the process channel, the gas flow velocity being sufficient to raise the pressure in at least a portion of the blocked process channel to at least about 5 psig (gauge pressure 34,473 Pa), and:

[0016] i. Then remove the gas flow, allowing the accompanying pressure release from the sealed process channel to effectively expel the particulate catalyst from the process channel; and / or

[0017] ii. In the partially discharged catalyst channel, a pressure difference is generated between the undischarged channel section and the discharged channel section by airflow to effectively expel the particulate catalyst from the undischarged channel section into the discharged channel section.

[0018] A device for directing high-speed airflow into an open proximal end of a process channel may be conveniently referred to as an "air knife," and the term should not be construed as limiting in any way.

[0019] An air knife can be deployed at either end of a process channel and can be repositioned from one end to the other. The "proximal end" of the process channel is the end where the air knife is deployed (and into which a high-speed airflow is guided), while the "distal end" is the end sealed by an airtight seal. By definition, when the air knife is redeployed from one end of the process channel to the other, the positions of these ends are reversed.

[0020] Ideally, step i) can be initially deployed when the process channel is completely or at least largely undischarged; while step ii) is subsequently deployed appropriately, and the particulate catalyst is loosely introduced into the discharge channel portion for subsequent removal from the process channel. Step ii) is considered effective in removing particulate catalyst from a partially discharged process channel because applying the gas flow to the channel causes the pressure within the undischarged portion of the channel to rise above the pressure in the (downstream, substantially empty) discharge channel portion. This pressure difference causes the packed catalyst in the undischarged channel portion to be loosely introduced into the (downstream, substantially empty) discharge channel portion, from which it can then be easily removed.

[0021] In the method of the present invention, unexhausted process channels can be partially discharged by including step i) and subsequently further discharged by including step ii). In this case, the method may include hermetically sealing the end of the process channel array opposite to the sealed end in step i) in step ii), and guiding a high-speed airflow into the process channel at the end opposite to the end in step i).

[0022] In some aspects of the invention, the gas flow rate is sufficient to raise the pressure in at least a portion of the sealed process channel to about 5 to about 20 psig, preferably about 8 to about 15 psig, and for example, at least about 10 psig. The pressure in the process channel will be uneven unless it at least substantially completely removes the catalyst.

[0023] The relative rate of pressure increase (and / or subsequent release) in the sealed process channel between the filled catalyst bed and any open spaces adjacent to the catalyst bed can also be an important factor in the successful expulsion of used catalyst from the channel. Preferably, in the method of the invention, the pressure increase in the sealed process channel is at least about 0.01 psi / ms, more preferably in the range of about 0.05 to about 0.5 psi / ms. When the gas flow described in step i) above is removed, the pressure in any open portion of the process channel can similarly decrease rapidly—for example, at least about 0.01 psi / ms, more preferably in the range of about 0.05 to about 0.5 psi / ms—thereby promoting the expulsion of catalyst particles due to the pressure difference generated between the slowly depressurized portion of the process channel (in the catalyst bed) and the rapidly depressurized portion of the process channel (in any open spaces adjacent to the catalyst bed). When the airflow is directed into the channel as in step ii) above, causing the pressure in the unexhausted portion of the channel to rise above the pressure in the (downstream, essentially empty) exhaust portion of the channel, this pressure difference can be gradually generated by the pressure increase in the catalyst bed before any accompanying pressure increase in the open space downstream of the applied airflow adjacent to the end of the catalyst bed.

[0024] It is believed that the mechanism of spent catalyst expulsion is at least in part related to the inherent resistance of the gas flow through tightly packed particles. Once high pressure is reached in the process channel, the removal of the high-velocity gas source creates a tendency for pressurized gas to leave the channel. The inherent flow resistance of the catalyst bed generates a pressure gradient across the catalyst particles, which exerts a force on the particles in the gas escape direction, thereby causing catalyst expulsion.

[0025] In step i), once the high-pressure gas has infiltrated the packed arrangement, it will tend to escape from the arrangement (towards the proximal end) once the pressurized gas source is removed. This escape tendency, combined with the resistance to flow from the closely packed particle arrangement, leads to catalyst expulsion as the high-pressure gas attempts to escape the closely packed particle arrangement at a rate higher than what the natural escape path through the closely packed arrangement could accommodate. This can be most readily understood by considering a process channel that is half-expelled (with catalyst particles remaining only towards the unexpelled distal end). As the gas flow is applied to the half-expelled channel, the pressure increases throughout the channel, including through its unexpelled portion. As the gas flow is removed, the pressure is immediately released from the proximal end of the channel, and the gas subsequently escapes from the unexpelled distal end, resulting in the expulsion as described above.

[0026] The same principle can be applied to step ii), except that it may not be necessary to remove the gas flow to induce expulsion. Once the channel has been partially evacuated in the manner of step i) (or by some other means), it provides a channel that is tightly packed with catalyst at one end but substantially empty (exhausted) at the other end. The hermetically tight seal of the substantially empty end and the application of gas flow to the filled end cause pressure to build up in the filled catalyst relative to the downstream empty channel portion. This pressure differential causes the filled catalyst in the unexhausted channel portion to be loosely expelled into the (downstream, substantially empty) exhaust channel portion, from which it can then be easily removed.

[0027] Microchannel reactors typically include intricate structures within process channels, such as wave-like structures that accommodate particulate catalysts. In such cases, to prevent or minimize damage to the process channel structure, the process of the present invention may include positioning an opening at the proximal end of a linear array of spacer elements adjacent to the process channel, wherein the spacer elements have at least one hole or gap covering the opening, and guiding a high-speed gas flow through at least one hole or gap into the process channel.

[0028] Microchannel reactors typically consist of microchannel structures that form a linear array of process channels.

[0029] Typically, the particulate catalyst removed in the method of this invention is the spent catalyst.

[0030] Preferably, the reactor comprises layers of process channels. Where the process channels include fine microchannel structures and therefore require spacer elements, preferably, each process channel layer is provided with said spacer element extending across the entire width of the layer. These features facilitate rapid and efficient catalyst removal.

[0031] Preferably, the gas flow moves laterally across the openings of a continuous process channel layer. This feature facilitates rapid and efficient catalyst removal.

[0032] Preferably, the airflow is generated by elongated slot openings. These slot openings can be elongated in the direction of the linear array of process channels and extend over two or more, preferably ten or more, more preferably twenty or more, and most preferably all process channel openings in the process channel layer. This feature balances the pressure within the process channel and thus balances the forces acting on its walls, thereby tending to protect the walls from damage by the airflow.

[0033] The lateral dimension of the slot opening can be smaller than the corresponding lateral dimension of the hole or gap of the spacer element (when present). This feature further enhances the protection of the process channel walls.

[0034] In some aspects of the invention, the spacer element provides important technical protection. In the absence of a spacer element, the direct flow of high-speed airflow through the process channels tends to damage any microchannel structure within those channels. Therefore, for example, if the microchannel structure comprises corrugated inserts or waveforms, such as those described in our WO2008030467 and incorporated herein by reference, these could be damaged if the spacer element used in the method of the invention is omitted.

[0035] A linear array of process channels constitutes a process layer. Process layers typically have length, height, and width, and a rectangular configuration. Typical lengths are approximately 100 mm to approximately 1000 mm, or approximately 200 mm to approximately 600 mm. Typical heights are approximately 3 mm to approximately 10 mm, or approximately 5 mm to approximately 7 mm. Typical widths are approximately 50 mm to approximately 800 mm, or approximately 100 mm to approximately 300 mm. Microchannel structures within the process layer typically produce a linear array of process channels (process microchannels) with approximately 0.5 to 2 mm or 0.75 to 1.5 mm widths and roughly the same length and height as the process layer. Channels with widths of 2 mm or less are generally considered microprocess channels or microchannels, possessing a particularly high surface area to volume ratio, which facilitates heat exchange with the reactor during production and is beneficial for process control and selectivity.

[0036] Preferably, the velocity of the airflow entering the open proximal end of the process channel or the orifice or gap of the spacer element is at least about 250 m / s, preferably at least about 300 m / s, most preferably at least about 330 m / s, and may be supersonic. These values ​​have been found to result in rapid and efficient pressure build-up within the process channel, facilitating efficient and rapid removal of the catalyst from these channels upon pressure release; and in some aspects of the invention, the presence of the spacer element prevents damage to the microchannel structure of the process channel.

[0037] The process channel is closed at its distal end. This causes the pressure within the process channel to increase as airflow enters the channel at its proximal end. Typically, the pressure within the process channel will be ambient pressure, i.e., atmospheric pressure, prior to operation of the method of the present invention. The pressure within the process channel typically rises from ambient pressure to above 5 psig (gauge pressure 34,473.5 Pa) during the application of the airflow, preferably up to or above 20 psig (gauge pressure 137,895 Pa).

[0038] The remote end can be sealed by any suitable method, such as heavy-duty aluminum adhesive or other sealants.

[0039] Preferably, the airflow is air, but any other suitable gas can be used, preferably an inert gas.

[0040] The process channel openings are arranged in a linear array. Preferably, the airflow is generated through nozzles having elongated openings parallel to the linear array and mounted for linear movement in the lateral direction on a carriage supported by the reactor. This feature enables a relatively compact device that can be easily connected to and removed from the reactor.

[0041] The present invention also provides a microchannel reactor comprising a linear array of process channels containing particulate catalyst, the linear array having means for hermetically sealing the process channels at its distal end, and having an opening at its proximal end (of which a spacer element having at least one orifice or gap covers the opening) and means for movably mounting a nozzle for guiding a high-speed gas flow through at least one orifice or gap into the process channels.

[0042] Within the scope of this invention, it is also contemplated that multiple high-speed gas flow nozzles can be used simultaneously. When multiple nozzles are used simultaneously, they can be used together to discharge catalyst from a single core of the reactor and / or they can be used to discharge catalyst from multiple cores of the reactor simultaneously.

[0043] The airflow through the nozzle can be pulsed or continuous.

[0044] Other preferred features are defined in the dependent claims. Attached Figure Description

[0045] Please refer to the attached diagram below. Figures 1 to 7 Preferred embodiments of the invention are described by way of example only, wherein:

[0046] Figure 1 This is a schematic perspective view of the microchannel reactor used in the preferred embodiment;

[0047] Figure 2 yes Figure 1 A schematic perspective view of the reactor core used in the reactor.

[0048] Figure 3 It is included Figure 1 and 2 A schematic perspective view of a portion of the process channel of the microchannel structure used in the reactor core;

[0049] Figure 4 It is used from Figure 3 A schematic perspective view of the gas knife and isolation element used to remove used catalyst in the reactor core;

[0050] Figure 5 This is a view from below showing the crossing. Figure 2 The process microchannel layer of the reactor core Figure 4 A schematic front view of an air knife;

[0051] Figure 6 It shows crossing Figure 2 The process microchannel layer of the reactor core Figure 4 A schematic side view of an air knife;

[0052] Figure 7 This is shown from below. Figure 2 A schematic perspective view of the spacer element mounted on the lower side of the reactor core;

[0053] Figure 8 It is installed on the linear bracket assembly Figure 4 and 6 A schematic perspective view of an air knife;

[0054] Figure 9 It is installed in Figure 2 A schematic perspective view of the linear support assembly on the underside of the reactor core, in a retracted configuration, and

[0055] Figure 10 It is installed in Figure 2 A schematic perspective view of the linear support assembly on the underside of the reactor core, in an extended configuration. Detailed Implementation

[0056] The following is for reference. Figures 1 to 3 Details of a suitable microchannel Fischer-Tropsch reactor that can remove catalysts by the method according to the invention are given.

[0057] refer to Figure 1 The microchannel reactor 200 includes a containment vessel 210 containing or accommodating three microchannel reactor cores 220. In other embodiments, the containment vessel 210 may be used to contain or accommodate one to about 16 microchannel reactor cores, one to about 8 microchannel reactor cores, or one to about 4 microchannel reactor cores. The containment vessel 210 may be a pressurized vessel. The containment vessel 210 includes an inlet and an outlet 245, allowing reactant streams to flow into and out of the microchannel reactor cores 220. Heat exchange fluids are supplied to the microchannel reactor cores through an inlet 230 and recovered from outlets similarly arranged on opposite sides of the reactor.

[0058] Inlet 245 may be connected to a manifold or manifold (not shown) that provides flow of reactants into the process microchannels in each microchannel reactor core. Inlet 230 may be connected to a manifold or manifold (not shown) that provides flow of heat exchange fluid (e.g., saturated water) into the heat exchange channels in each microchannel reactor core. One of outlets 245 is connected to a manifold or footer (not shown) that provides product flow out of the process microchannels in each microchannel reactor core. One of the heat exchange fluid outlets 230 may be connected to a manifold or footer (not shown) for heat exchange fluid flow out of the heat exchange channels in each microchannel reactor core.

[0059] The containment vessel 210 can be constructed using any suitable material sufficient to withstand the operating pressures that may arise within the microchannel reactor core. For example, the shell 240 and reinforcing ribs 242 of the containment vessel 210 can be constructed of cast steel or stainless steel. For example, flanges, fittings, and piping can be constructed of stainless steel. The containment vessel 210 can, for example, have a diameter of 1.5 m. For each reactor core located therein, the axial length of the containment vessel 210 can, for example, be 1.5 m, i.e., 5.5 m for a four-core reactor.

[0060] refer to Figure 2 The microchannel reactor core 220 comprises a stack of alternating laminar flow units 300 of process microchannels 310 and laminar flow units 350 of heat exchange channels 355.

[0061] The microchannel reactor core 220 may optionally include multiple plates in a stack defining multiple process layers and multiple heat exchange layers, each plate having a peripheral edge, the peripheral edge of each plate or a gasket welded to the peripheral edge of the next adjacent plate to provide a peripheral seal for the stack. This is shown in US20120095268, which is incorporated herein by reference.

[0062] The microchannel reactor core 220 may optionally be in the form of a three-dimensional module having six sides of a square or rectangle. The microchannel reactor core 220 may optionally have a uniform cross-section along its length. The microchannel reactor core 220 may optionally be in the form of a parallel or cubic module or prism. The microchannel reactor core 220 may have, for example, a length, width, and height of 1 m.

[0063] The Fischer-Tropsch catalyst 500 is located in the process microchannel 310 and can be in any suitable form, such as a fixed bed of particulate solids.

[0064] Figure 3 A corrugated sheet 315 is shown sandwiched between plates 316 and 317, defining a microchannel structure of process microchannels 310 on either side of sheet 315. For clarity, Fischer-Tropsch catalyst 500 is shown in only one of these microchannels, but in practice each microchannel 310 will be filled with Fischer-Tropsch catalyst 500. Further details of the construction are disclosed in WO2008030467, which is incorporated herein by reference.

[0065] The Fischer-Tropsch catalyst 500 may optionally contain cobalt and a support. The catalyst may optionally have a cobalt loading of about 10 to about 60 wt%, or about 15 to about 60 wt%, or about 20 to about 60 wt%, or about 25 to about 60 wt%, or about 30 to about 60 wt%, or about 32 to about 60 wt%, or about 35 to about 60 wt%, or about 38 to about 60 wt%, or about 40 to about 60 wt%, or about 40 to about 55 wt%, or about 40 to about 50 wt%.

[0066] The Fischer-Tropsch catalyst 500 may optionally further comprise a noble metal. The noble metal may be, for example, one or more of Pd, Pt, Rh, Ru, Re, Ir, Au, Ag, and Os. The noble metal may be one or more of Pt, Ru, and Re. The noble metal may be Ru. Alternatively or additionally, the noble metal may be Pt. The Fischer-Tropsch catalyst may optionally comprise a total of about 0.01 to about 30% noble metal (based on the total weight of all present noble metals, as a percentage of the total weight of the catalyst precursor or activated catalyst), or optionally a total of about 0.05 to about 20% noble metal, or optionally a total of about 0.1 to about 5% noble metal, or optionally a total of about 0.2% noble metal.

[0067] The Fischer-Tropsch catalyst 500 may optionally include one or more other metal-based components as promoters or modifiers. These metal-based components may also optionally be present as carbides, oxides, or elemental metals in the catalyst precursor and / or activated catalyst. Suitable metals for one or more other metal-based components may be, for example, one or more of Zr, Ti, V, Cr, Mn, Ni, Cu, Zn, Nb, Mo, Tc, Cd, Hf, Ta, W, Re, Hg, Tl, and 4f-block lanthanides. Suitable 4f-block lanthanides may be La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and / or Lu. Metals for one or more other metal-based components may be, for example, one or more of Zn, Cu, Mn, Mo, and W. Metals for one or more other metal-based components may be, for example, one or more of Re and Pt. The catalyst may optionally contain a total of about 0.01 to about 10% of other metals (as a percentage of the total weight of all other metals, based on the total weight of all other metals, as a catalyst precursor or activated catalyst), or optionally a total of about 0.1 to about 5% of other metals, or optionally a total of about 3% of other metals.

[0068] The Fischer-Tropsch catalyst 500 may optionally be derived from a catalyst precursor that can be activated to produce a Fischer-Tropsch catalyst, for example by heating the catalyst in hydrogen and / or hydrocarbon gases (e.g., methane) or in hydrogen and / or hydrocarbon gases diluted with another gas such as nitrogen and / or methane, to convert at least some carbides or oxides into an elemental metal. In the active catalyst, cobalt may optionally be at least partially in the form of its carbides or oxides.

[0069] The Fischer-Tropsch catalyst 500 may optionally include a catalyst support. The support may optionally comprise a refractory metal oxide, carbide, carbon, nitride, or a mixture of two or more thereof. The support may optionally comprise alumina, zirconium oxide, silica, titanium dioxide, or a mixture of two or more thereof. The surface of the support may optionally be modified by treatment with silica, titanium dioxide, zirconium oxide, magnesium oxide, chromium oxide, alumina, or a mixture of two or more thereof. The material used for the support and the material used for modifying the support may be different. The support may optionally comprise silica, and the surface of the silica may optionally be treated, for example, with a refractory oxide solid oxide such as titanium dioxide. The material used to modify the support can be used to increase the stability of the supported catalyst (e.g., by reducing deactivation).

[0070] The catalyst support may optionally contain, for example, up to about 30 wt% of an oxide (e.g., silica, titanium dioxide, magnesium oxide, chromium oxide, alumina, zirconium oxide, or a mixture of two or more thereof) for surface modification of the support, or about 1 wt% to about 30 wt%, or about 5 wt% to about 30 wt%, or about 5 wt% to about 25 wt%, or about 10 wt% to about 20 wt%, or about 12 wt% to about 18 wt%. The catalyst support may optionally be in the form of a structured shape, pellets, or powder. The catalyst support may optionally be in the form of a particulate solid. While not wishing to be bound by theory, it is believed that the surface treatments provided herein help prevent Co from sintering during Fischer-Tropsch process operations.

[0071] The deactivation rate of the Fischer-Tropsch catalyst 500 can optionally allow it to be used in Fischer-Tropsch synthesis for more than about 300 hours, or more than about 3,000 hours, or more than about 12,000 hours, or more than about 15,000 hours before the catalyst reactivation or regeneration is required.

[0072] The Fischer-Tropsch catalyst 500 can optionally be used for extended time periods (e.g., >300 hours) where the deactivation rate is less than about 1.4% / day, or less than about 1.2% / day, or between about 0.1% / day and about 1% / day, or between about 0.03% / day and about 0.15% / day.

[0073] The Fischer-Tropsch catalyst 500 can have any size and geometry adapted within the process microchannel 310. The catalyst can optionally be in the form of particulate solids (e.g., pellets, powders, fibers, etc.) having a median particle size of about 1 to about 1000 μm, or about 10 to about 750 μm, or about 25 to about 500 μm. The median particle size can optionally be in the range of 50 to about 500 μm, or about 100 to about 500 μm, or about 125 to about 400 μm, or about 170 to about 300 μm. In one embodiment, the catalyst can be in the form of a fixed bed of particulate solids.

[0074] The microchannel reactor core 220 may, for example, comprise a layer 350 containing six heat exchange channels 355.

[0075] refer to Figure 3 Each process microchannel 310 may, for example, have a height (h) of 6.35 mm and a width (w) of 1 mm. The length of each process microchannel may, for example, be 610 mm.

[0076] Each unit or layer 300 of the process microchannel 310 may, for example, have hundreds of process microchannels 310. The process microchannels 310 may have a cross-section of any shape, such as square, rectangular, circular, semi-circular, etc. The internal height of each process microchannel 310 can be considered as the smaller of the internal dimensions perpendicular to the flow direction of reactants and products through the process microchannel.

[0077] Each unit or layer 350 of the heat exchange channel 355 may, for example, have hundreds of heat exchange channels. The heat exchange channels 355 may be microchannels or they may have a larger size that classifies them as not microchannels.

[0078] The microchannel reactor core 220 can be made of any material that provides sufficient strength, dimensional stability, and heat transfer properties to allow operation of the desired process. These materials can include, for example, aluminum; titanium; nickel; platinum; rhodium; copper; chromium; alloys of any of the above metals; brass; steel (e.g., stainless steel); quartz; silicon; or combinations of two or more thereof. Each microchannel reactor can optionally be constructed of stainless steel, with one or more copper or aluminum corrugations used to form the channels.

[0079] The microchannel reactor core 220 can optionally be manufactured using known techniques, including, for example, wire electro-discharge machining, conventional machining, laser cutting, photochemical machining, electrochemical machining, molding, water jetting, stamping, etching (e.g., chemical, photochemical, or plasma etching), and combinations thereof.

[0080] The microchannel reactor core 220 can optionally be constructed by forming plates in which portions are removed to allow for fluid flow channels. For example, stacks of plates can be assembled to form an integrated device by diffusion bonding, laser welding, diffusion brazing, conventional welding, additive manufacturing, and similar methods. The microchannel reactor can be assembled, for example, using a combination of plates and partial plates or strips. In this approach, channels or void regions can be formed by assembling strips or partial plates to reduce the amount of material required.

[0081] The microchannel reactor core 220 may optionally include multiple plates in a stack defining multiple process layers and multiple heat exchange layers, each plate having a peripheral edge, the peripheral edge of each plate or a gasket being welded to the peripheral edge of the next adjacent plate to provide a peripheral seal for the stack. This is shown in US20120095268, which is incorporated herein by reference.

[0082] The containment 210 may optionally include control mechanisms to maintain the pressure within the containment at a level at least as high as the internal pressure within the microchannel reactor core 220. The internal pressure within the containment 210 may optionally range from about 10 to about 60 atmospheres, or from about 15 to about 30 atmospheres, during operation of the syngas conversion process (e.g., Fischer-Tropsch process). The control mechanisms for maintaining the pressure within the containment may optionally include check valves and / or pressure regulators. The check valves or regulators may optionally be programmed to activate at any desired internal pressure within the containment. Either or both may be used in conjunction with systems such as piping, valves, controllers, etc., to ensure that the pressure within the containment 210 is maintained at a level at least as high as the internal pressure within the microchannel reactor core 220. This is done in part to protect the welds used to form the microchannel reactor core 220. A significant decrease in pressure within the containment 210 without a corresponding decrease in the internal pressure within the microchannel reactor core 220 could lead to costly rupture of the welds within the microchannel reactor core 220. The control mechanism may optionally be designed to allow the transfer of one or more process gases into the containment vessel in the event of a pressure reduction imposed by the containment gases.

[0083] Now refer to Figures 4 to 10 An apparatus and method are described for removing used Fischer-Tropsch catalyst from the process microchannel 310 of the reactor described above.

[0084] refer to Figure 4 The diagram shows an air knife 1, which is connected to a compressed air source (not shown) and has a slit with a width approximately equal to the width of a cell or layer 300 of the process microchannel, thereby defining a high-speed air jet 4.

[0085] An elongated protective element or spacer 2 with two parallel slots 3 is shown aligned with the air knife 1, such that the air jet 4 passes through one of the parallel slots. The length of the air knife slot is equal to or slightly greater than the length of the slot 3, and both correspond to the full width W of the reactor core 220. Figure 2 In use, the protective element or spacer 2 is fixed by a row of openings in the process microchannel 310, and the air knife 1 traverses in direction A, allowing the air jet 4 to pass sequentially through each slot 3. Figure 7 As shown in the best embodiment, an array of such protective elements 2 is provided, such that the air jet 4 passes through the successive slots of the continuous protective elements and thereby enters the successive rows of the process microchannels 310 of the reactor core 220.

[0086] like Figure 6As shown in the optimal configuration, the protective element or spacer 2 is located below the coolant plate 350 and its slot is aligned with the process microchannel 310. The coolant plate 350 includes coolant channels (not shown). The length of the spacer strip below the coolant plate extends across all the installed reactor cores, which determine the width of the reactor. The depth of the protective element ( Figure 6 The vertical direction (in the process channel) is appropriately from 10mm to 50mm, for example, 25mm. Alignment between the slot and the process microchannel also creates alignment between the contact points of the spacer strip and the corrugated coolant plate, which in use protects these contact points from the full force of the airflow guided through the body of the slot. The depth of the protective element can also be appropriately selected with reference to this most vulnerable location in the process channel.

[0087] refer to Figure 6A In variants of the protective element, slot 3 can be discarded, and Figure 5 Each protective element 2 shown can be replaced by three narrowly spaced protective elements 2A, 2B and 2C located above the respective coolant layer 350, wherein air jets 4 are guided through the gaps g between them.

[0088] like Figure 5 As shown, the air knife 1 traverses the continuous row of process channel 310 and extrudes the catalyst 500. The width w of the microprocess channel is appropriately 1 mm and the internal height h is appropriately 6.35 mm.

[0089] When air knife 1 is set to align with any given protective element, the distance from the air knife slit to the protective element 2 is kept as small as possible within practical tolerances, typically between 0.5 and 19 mm. For all cores corresponding to the entire reactor width, the length of the air knife slit is equal to or slightly greater than the width of the process layer.

[0090] The size of the air knife slit and the upstream air pressure are set so that air flows through the slit at near or approximately the speed of sound or even supersonic speeds. The slit width is typically in the range of 150 to 180 mm, but can reach or slightly exceed the width of the process layer.

[0091] During use, air knife 1 operates at 0.01 and 0.2 ms. -1 The air knife moves at a speed from one end of the reactor to the other, and after having traversed the entire length or a selected portion of the reactor core 220 below it, returns at a similar speed to its starting position at the other end of the reactor core 220 or a portion of the reactor core. This motion is repeated, allowing a continuous gas flow through the air knife slits until the catalyst stops flowing out of the channel. The reactor is then inspected to determine if complete catalyst removal has been achieved.

[0092] Regarding any unexpelled channel, the method of the present invention can then be deployed in step ii). By opening the sealed end of the process channel and then hermetically sealing the opposite ends of the linear array of process channels to form a blocked process channel in the array, a spacer element is positioned as an opening adjacent to the (currently) unsealed end of the linear array of process channels (where the spacer element has at least one hole or gap covering the opening), and a high-speed gas flow is directed through at least one hole or gap into the process channel. The gas flow velocity is sufficient to raise the pressure in the blocked process channel to at least about 5 psig in at least a portion of the blocked process channel. The accompanying pressure accumulation within the unexpelled catalyst causes the filled catalyst in the unexpelled channel portion to be loosely expelled into the (downstream, substantially empty) discharge channel portion. Preferably, the pressure difference between the pressure within the filled catalyst bed and the unfilled portion of the adjacent process microchannel is at least about 1 psig, preferably at least about 2 psig.

[0093] As an alternative to step ii), the method of the present invention in step i) can be repeated by applying the method of the present invention from the opposite side of the process channel—that is, by opening the sealed end of the process channel and then hermetically sealing the opposite ends of the linear array of the process channel to form a blocked process channel in the array, positioning the opening of the (currently) unsealed end of the linear array of the process channel adjacent to the spacer element (where the spacer element has at least one hole or gap covering the opening), and guiding a high-speed gas flow through the at least one hole or gap into the process channel, the gas flow velocity being sufficient to raise the pressure in the blocked process channel to at least about 5 psig, and then removing the gas flow such that the pressure from the accompanying release of the blocked process channel effectively expels the particulate catalyst from the process channel.

[0094] If there are any remaining channels containing some catalyst, non-automated methods, such as solvent washing and / or mild physical stimulation, can be applied to these channels.

[0095] like Figure 8 As best shown, the air knife 1 is supported on a slide rail 6, which in turn is mounted on four support arms 7. The ends of these support arms have fasteners (e.g., machine screws) for securing the resulting assembly 5 to the underside of the reactor core 220. The protective element 2 is not shown in this figure.

[0096] During operation, as the air knife 1 moves along the length of the reactor, air continuously flows upward through the air knife slits to sequentially guide the airflow into the gaps between the spacers. The air knife slits extend across all the process microchannels 310 in 315.

[0097] When the airflow crosses the depth of protective element 2 ( Figure 5 and 6Upon reaching the process microchannel 310, an air shock wave impacts the catalyst 500 in each reactor channel, increasing the pressure within the channel (which is sealed at its distal end) to above 5 psig, or as high as or above 10 psig. Once the air knife has passed through the channel, this pressure is released, causing at least some of the catalyst within the channel to be ejected in the released flow. Driven by an automated air knife movement system, the air knife continues to move back and forth along the length of the reactor at a preset speed until no further catalyst is removed from the reactor.

[0098] The ejected catalyst can be collected in a chamber (not shown) installed below the reactor core 200, which is evacuated.

[0099] like Figure 2 , 3 As shown in Figure 5, each row of process microchannels 310 is defined by corrugated sheets 315 located between the opposing walls of adjacent cooling plates 350. The corrugated sheets are made of a thermally conductive material, typically copper, and are shaped to form multiple vertical reactor channels 310. The walls of the cooling plates are typically parallel stainless steel plates. The parallel plates are typically cooled internally by a coolant liquid. In operation, the reactor channels are filled with particulate catalyst material.

[0100] After the used catalyst 500 has been removed, it can be replaced with fresh catalyst.

[0101] The described catalyst removal method can be applied to chemical reactors other than Fischer-Tropsch reactors to remove used catalysts.

[0102] The variants mentioned above can be combined in any combination.

Claims

1. A method for removing catalyst from a packed catalyst bed within a process channel of a microchannel reactor, the method comprising: The distal end of a linear array of hermetically sealed process channels forms a blocked process channel within the array, and a high-speed airflow is directed into the open proximal end of the process channel, the airflow velocity being sufficient to raise the pressure within at least a portion of the blocked process channel to at least 5 psig. i. Remove the gas flow so that the accompanying release of pressure from the blocked process channel effectively expel the particulate catalyst from the process channel; ii. In the partially discharged catalyst channel, the airflow generates a pressure differential between the non-discharge channel portion and the discharge channel portion that effectively expels particulate catalyst from the non-discharge channel portion into the discharge channel portion. This creates a pressure gradient within the catalyst bed and / or between the catalyst bed and any open space adjacent to the catalyst bed within the sealed process channel, effectively expelling particulate catalyst from the catalyst bed. The undischarged process channel is partially discharged by means of step i) and then further discharged by means of step ii); In step ii), the end of the process channel array opposite to the sealed end in step i) is hermetically sealed, and the high-speed airflow is guided into the process channel at the end opposite to the end into which the high-speed airflow was guided in step i).

2. A method for removing particulate catalyst from a process channel of a microchannel reactor, the method comprising: The distal end of a linear array of hermetically sealed process channels forms a blocked process channel within the array, and a high-speed airflow is directed into the open proximal end of the process channel, the airflow velocity being sufficient to raise the pressure within at least a portion of the blocked process channel to at least 5 psig. i. Then remove the gas flow, so that the pressure released from the sealed process channel effectively expel the particulate catalyst from the process channel; ii. In the partially discharged catalyst channel, the gas flow generates a pressure differential between the undischarged channel portion and the discharged channel portion that effectively expels the particulate catalyst from the undischarged channel portion into the discharged channel portion; The undischarged process channel is partially discharged by means of step i) and then further discharged by means of step ii); In step ii), the end of the process channel array opposite to the sealed end in step i) is hermetically sealed, and the high-speed airflow is guided into the process channel at the end opposite to the end into which the high-speed airflow was guided in step i).

3. The method of claim 2, wherein in step ii), the particulate catalyst is expelled in a loose form into the discharge channel portion for subsequent removal from the process channel.

4. The method according to claim 2, wherein a linear array of process channels constitutes a process channel layer, and the airflow moves laterally over the openings of the continuous process channel layer.

5. The method according to claim 2, wherein a linear array of process channels constitutes a process channel layer, and the reactor includes a process channel layer.

6. The method of claim 5, wherein each process channel layer is provided with a spacer extending over the entire width of the layer.

7. The method of claim 2, further comprising positioning a spacer element as an opening at the proximal end of a linear array adjacent to a process channel, wherein the spacer element has at least one hole or gap covering the opening, and guiding the high-speed airflow through the at least one hole or gap into the process channel.

8. The method of claim 7, wherein the airflow is generated by an elongated slot opening, the lateral dimension of which is smaller than the corresponding lateral dimension of the hole or gap of the spacer element.

9. The method of claim 7, wherein the holes or gaps of the spacer element are elongated in the direction of the linear array of process channel openings and extend over two or more of the process channel openings of the process channel layer.

10. The method of claim 2, wherein the velocity of the airflow entering the process channel is at least 250 m / s.

11. The method of claim 2, wherein during the application of the airflow, the pressure within the process channel increases from ambient pressure to as high as or above 20 psig.

12. The method of claim 2, wherein the airflow is generated by a nozzle having an elongated opening of the linear array parallel to the process channel opening and mounted for linear movement in the lateral direction on a bracket, and the bracket is supported by the reactor.

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