Chemical reactor with heat exchanger

Abstract

A chemical reactor (10) is provided, comprising a catalyst bed (7) and a heat exchanger (15) arranged to transfer heat from a first fluid (2), which is an effluent of the catalyst bed, to a second fluid (3), which is a heating or cooling medium, the heat exchanger (15) comprising an additively manufactured structure (1), the structure being a triple periodic minimal surface TPMS having first and second faces through which a heat exchanger fluid can pass, the heat exchanger including a set of boundary elements (5) arranged to supply and collect the first fluid (2) and the second fluid (3) between channels on the first face and channels on the second face of the structure.

Description

[Technical Field]

[0001] The present invention relates to the field of catalytic reactors with internal heat exchangers. [Background technology]

[0002] Many chemical reactions of considerable industrial importance require a reactor containing one or more heat exchangers that can remove the heat of reaction in the case of exothermic reactions or provide the heat of reaction in the case of endothermic reactions.

[0003] Notable examples are the synthesis of ammonia or methanol, which are highly exothermic. Such reactions are carried out in reactors containing one or more catalyst beds. Due to their exothermic nature, the effluent from the catalyst beds is typically at high temperatures, and in addition to removing heat from such effluents to preheat other process streams or to produce steam, it is important to adequately cool the effluent for subsequent reaction steps.

[0004] The most common heat exchanger for use in chemical reactors is the shell-and-tube heat exchanger. In a shell-and-tube heat exchanger, the tubes are traversed by a first fluid, and a second fluid circulates around the tubes, which are surrounded by a shell. Conventionally, the inside of the tubes is referred to as the tube side, and the space around the tubes is referred to as the shell side.

[0005] A prominent example is represented by the interbed heat exchangers in a multi-bed ammonia reactor. In a multi-bed reactor, the conversion is usually carried out in several (two or more, typically three or four, etc.) catalyst beds arranged in series, whereby the effluent from one bed is further reacted in the next bed. The interbed heat exchangers cool the effluent of one bed before it enters the next bed. In the general case, the catalyst beds have an annular shape so that a shell-and-tube heat exchanger can be accommodated in the central cavity of the bed.

[0006] In most applications, the tubes are quite long and therefore susceptible to vibration. Furthermore, to maximize heat exchange, it is desirable for the gas flow on the shell side to be perpendicular to the tubes. To this end, shell-and-tube heat exchangers are equipped with transverse baffles positioned to suppress vibration and increase vorticity on the shell side.

[0007] However, conventional shell-and-tube heat exchangers with baffles still have limitations: the heat exchange surface is relatively small compared to the overall size of the heat exchanger, such as the diameter of the outer shell, and the baffle-induced vortices are limited to a small area near the baffle. Baffles increase cost and complexity.

[0008] A chemical reactor with a catalyst bed and a heat exchanger is described in German Patent Application Publication No. 10 2015 114201. A heat exchanger with a gyroid minimally curved surface is described in US Patent Application Publication No. 2020 0033070 or European Patent Application Publication No. 4 033 193. US Patent Application Publication No. 2018 0187984 describes a monolithic bi-continuous core (MBC) structure for a heat exchanger. US Patent Application Publication No. 2022 0003503 describes systems and methods for periodic nodal surface-based reactors, distributors, contactors, and heat exchangers. Summary of the Invention

[0009] The present invention aims to solve the above-mentioned drawbacks of heat exchangers installed in chemical reactors, and to provide a novel chemical reactor that solves the above-mentioned problems.

[0010] The present invention uses additively manufactured triply periodic minimal surface TPMS structures as heat exchangers in chemical reactors. The structures have interesting properties for heat exchange, including periodicity and the ability to generate diffuse vorticity. The TPMS structures can also be considered as TPMS lattices.

[0011] A TPMS structure essentially defines two sides, which can be considered a first side and a second side, or in heat exchange applications, a hot side and a cold side. The term hot side refers to the side of the structure traversed by a hotter fluid ("hot fluid"), and the term cold side refers to the side of the structure traversed by a cooler fluid ("cold fluid").

[0012] In the present invention, a set of appropriate boundary elements distributes hot and cold fluids to and collects them from each side of the TPMS structure, where the two sides are completely separated, meaning that the hot and cold fluids do not come into contact with each other but exchange heat indirectly through the structure.

[0013] The object of the present invention is therefore achieved by a chemical reactor according to claim 1. Preferred features are set out in the dependent claims.

[0014] The advantages of the present invention are as follows:

[0015] Heat exchangers can be realized without baffles and with small channel sizes. This increases the Reynolds number of the fluid passing through the channels, and reduces the effect of high specific pressure losses by shortening the length of the heat exchanger. The wall thickness of the heat exchanger channels can be minimized, thereby increasing the heat transfer coefficient.

[0016] Additive manufacturing techniques offer several advantages, including fast and cost-effective production, and the ability to print heat exchangers on demand with a wide range of customization in terms of size and shape.

[0017] Furthermore, less material, such as alloys, is required to manufacture the heat exchanger compared to conventional methods, allowing for more cost-effective production. Material waste generated during the manufacturing process is also reduced.

[0018] The higher heat transfer coefficient allows the heat exchanger to be manufactured in a compact size, which is particularly advantageous as it reduces the volume occupied by the heat exchanger in the catalytic reactor and allows more volume to be allocated to the catalyst bed.

[0019] The invention may be used, inter alia, in the field of plants that exploit renewable energy sources to produce one or more of the reagents for synthesis.

[0020] The present invention provides a compact heat exchanger that can typically provide 50% to 90% space savings compared to conventional rod-baffle heat exchangers.

[0021] Another advantage is associated with the structure of the TPMS heat exchanger, which has boundary elements with thin walls, yet is able to withstand high external pressures and avoid buckling phenomena.

[0022] Another salient aspect of the present invention addresses the challenge of how to connect a TPMS grid to a conventional collector, such as a pipe. This task is difficult due to the complex geometry of the TPMS grid. The present invention addresses this challenge by providing a connection section formed with the TPMS grid and a transition region between the TPMS grid and the connection section, where the shape of the TPMS grid gradually changes to match the collector. Advantageously, the connection section can be formed integrally with the TPMS grid. Thus, the present invention provides a TPMS grid-based heat exchanger that can be seamlessly connected to conventional distribution or recovery pipes.

[0023] Yet another aspect of the present invention relates to a parallel-connected heat exchanger fabricated by additive manufacturing. [Brief explanation of the drawings]

[0024] The invention is further illustrated by the following drawings.

[0025] [Figure 1] 1 illustrates a heat exchanger body according to an embodiment of the present invention. [Figure 2] 2A-2C illustrate boundary elements that can be used with the heat exchanger body of FIG. 1. [Figure 3] 3 illustrates the heat exchanger body of FIG. 1 equipped with the boundary element of FIG. 2. [Figure 4] FIG. 1 is a schematic diagram of a cross-sectional view of a catalytic reactor according to an embodiment. [Figure 5] 1 compares a cross-sectional view of a catalytic reactor according to an embodiment of the prior art with a cross-sectional view of a catalytic reactor according to an embodiment of the present invention. [Figure 6] 1 illustrates further embodiments of the present invention, as described in more detail below. [Figure 7] 1 illustrates further embodiments of the present invention, as described in more detail below. [Figure 8] 1 illustrates further embodiments of the present invention, as described in more detail below. [Figure 9]1 illustrates further embodiments of the present invention, as described in more detail below. [Figure 10] 1 illustrates further embodiments of the present invention, as described in more detail below. [Figure 11] 1 illustrates further embodiments of the present invention, as described in more detail below. DETAILED DESCRIPTION OF THE INVENTION

[0026] The chemical reactor of the present invention includes a heat exchanger having a structure fabricated by additive manufacturing (AM). The heat exchanger is a triply periodic minimal surface (TPMS). The term TPMS refers to a non-intersecting 3D surface characterized by a mean curvature value of zero at each point on the surface. TPMS surfaces are defined by mathematical functions known in the art and will not be discussed in detail herein. The term TPMS lattice may also be used to refer to the structure.

[0027] The TPMS structure (TPMS grid) can be considered as part of the internal volume of a chemical reactor with the function of a heat exchanger. The TPMS structure defines two surfaces that are configured to be passed by a hot medium and a cold medium, respectively. Therefore, the TPMS structure can actually function as a heat exchanger.

[0028] The TPMS structure can be mathematically described by suitable equations. Preferably, the TPMS structure is defined by an implicit function having the following form:

number

number

[0029] Furthermore, the TPMS structure can be combined with other shapes using operators such as Boolean operators to model the shape of a heat exchanger. For example, a hole through the TPMS structure can be easily defined by subtracting a cylinder from the TPMS structure. More formally, assuming A denotes the TPMS in a given spatial region and B denotes a cylindrical pipe that cuts through the TPMS, the operation (A NOT B) produces a TPMS with a through hole.

[0030] The mathematical description of the TPMS structure provides the input for the design of the structure. Suitable references for the mathematical description of the TPMS and how to model the TPMS using the Marching Cubes method can be found at: - Manuscripta Mathematica, Volume 64, 1989, Springer; - Marching cubes: a high resolution 3d surface construction algorithm, William E. Lorensen and Harvey E. Cline, Computer Graphics Vol. 21 , No. 4, July 1987, 163-169; - Surface curvature in tri-periodic minimal surface architectures as a distinct design parameter in preparing advanced tissue engineering scaffold, Sebastien Blanquer, Maike Werner, Markus Hannula, Shahriar Sharifi, Guillaume Lajoinie, David Eglin, Jari Hyttinen, Andre Poot, Dirk Grijpma, IOP Publishing, 2017,9(2), pp.025001. 10.1088 / 1758-5090 / aa6553hal-02336718

[0031] The TPMS structure of the heat exchanger has a first surface and a second surface, wherein the first surface and the second surface define a first passage and a second passage, respectively, through which a heat exchange medium and / or a reagent gas mixture can pass, such as a cooling medium, e.g., water, through the first surface, and a reactant gas mixture, e.g., can pass through the second surface.

[0032] The first path is separated from the second path so that the heat exchange medium moving through the TPMS structure via the first path does not come into direct contact with the medium moving through the second path.

[0033] The heat exchanger also includes a set of boundary elements. The set of boundary elements is configured such that a first medium is distributed to and collected from only the first surface, and a second medium is distributed to and collected from only the second surface. For example, the first medium may be effluent from a catalyst bed, and the second medium may be a heating or cooling medium. In a reactor for an exothermic reaction, the first medium may be a hot effluent from the catalyst bed from which heat is removed, and the second medium may be a cooling medium such as water, steam, or a process gas to be preheated.

[0034] The set of boundary elements is configured to allow effluent from the catalyst bed to pass through the TPMS structure through a first path, and a heating or cooling medium to pass through the structure through a second path. Depending on the enthalpy of the chemical reaction, i.e., whether the reaction is exothermic or endothermic, heat is transferred indirectly from the effluent to the cooling medium or from the heating medium to the effluent.

[0035] By providing boundary elements, the difficult problem of how to distribute and collect heat exchange fluid to and from the TPMS structure is solved.

[0036] According to an interesting application, the set of boundary elements can also be produced by additive manufacturing, which has the advantage of allowing a high degree of flexibility in the design of the heat exchanger.

[0037] The set of boundary elements can include one or more surface elements having a gas permeable pattern configured to match the inflow or outflow pattern in the TPMS structure. In certain embodiments, the set of boundary elements can include one or more cylindrical shells. In certain embodiments, the boundary elements can have various shapes, such as plates or rings, depending on the geometry of the heat exchanger.

[0038] The TPMS structure of the heat exchanger can have any suitable shape. In an embodiment of the present invention, the TPMS structure has an annular shape. One face of the structure is radially passed through. The set of boundary elements includes an inner cylindrical shell disposed around the inside of the bed and / or an outer cylindrical shell disposed around the outside of the bed. The set of boundary elements is used to distribute effluent or heating or cooling medium to and / or collect effluent or heating or cooling medium from the radially passed face of the TPMS structure.

[0039] The catalyst bed in a preferred embodiment has an annular shape and is disposed around the TPMS structure, so that the outer cylindrical shell can function as a boundary element for the TPMS structure and as a retaining wall for the catalyst granules that form the catalyst bed.

[0040] In one embodiment, the TPMS structure, transition element and boundary element are positioned below the catalyst bed.

[0041] In certain configurations of the foregoing embodiments, the heat exchanger of the TPMS structure is positioned to support the weight of the catalyst bed.

[0042] In one embodiment, the catalyst bed and TMPS structure have an annular shape, with the TMPS structure coaxially positioned outside or inside the catalyst bed.

[0043] In one embodiment, the TPMS structure has an annular shape and is radially traversed by one fluid and axially traversed by another fluid. The boundary elements may preferably include a first ring-shaped boundary element disposed above the structure and a second ring-shaped element disposed below the structure. The boundary elements distribute and collect the fluid passing axially through the structure.

[0044] In another embodiment, the TPMS structure has an annular shape, and the set of boundary elements includes a first surface extending across a portion of an inner or outer surface of the TPMS structure and a second surface disposed around a different portion of the inner or outer surface, such that one fluid enters the TPMS structure and exits the TPMS structure through a different portion of the inner or outer surface.

[0045] Preferably, the first and second surfaces include a plurality of channels within the TPMS structure. The heat exchanger channels may have a substantially circular cross section. Preferably, the hydraulic diameter of the cross section is in the range of 2 mm to 20 mm, more preferably in the range of 5 mm to 15 mm.

[0046] The surface of the TPMS structure is preferably selected from the group consisting of a gyroid, a Schwartz minimal surface, and a Neovius surface. In embodiments having a Schwartz minimal surface, the surface is preferably a Schwartz P surface or a Schwartz D (diamond) surface.

[0047] The TPMS structure and / or the set of boundary elements can be made of any suitable material that can withstand the operating conditions of the synthesis reactor, preferably Inconel, particularly preferably Inconel 625 or Inconel 718, or a combination thereof.

[0048] Any additive manufacturing technique can be used to manufacture the heat exchanger and the set of boundary elements, provided that the selected technique is suitable for producing the structure of the heat exchanger or boundary elements. Preferably, the technique is one of direct metal laser sintering, electron beam melting, selective thermal sintering, selective laser melting, selective laser sintering, powder bed fusion, binder jetting, stereolithography, fused deposition modeling, digital light processing, multi-jet fusion, polyjet, and directed energy deposition.

[0049] The inner surface of the heat exchanger according to the present invention is formed according to a TPMS curved surface. As mentioned above, the TPMS curved surface is mathematically described, but the physical (real) surface, unlike the mathematical surface, has a non-zero thickness. The minimum thickness required for the real surface can be determined by one skilled in the art based on manufacturability, stress conditions, and material characteristics.

[0050] In a particularly interesting application, the reactor of the present invention is used for the synthesis of ammonia or methanol.

[0051] A preferred configuration includes an interbed heat exchanger used to cool the hot effluent from the catalyst bed prior to the subsequent catalyst bed, a preheater configured to preheat the synthesis gas directed to the catalyst bed, and a steam superheater configured to generate steam above the saturation temperature by heat exchange with the hot reaction gas produced in the chemical reactor.

[0052] A further application of the present invention is the retrofit procedure of conventional heat exchangers inside chemical reactors, such as shell-and-tube heat exchangers, where they are replaced by installing a heat exchanger comprising an additively manufactured triply periodic minimal surface (TPMS) structure and a set of boundary elements as described above.

[0053] In a further aspect of the invention, the heat exchanger includes, in addition to the TPMS structure, at least one collector portion and a transition region between the TPMS structure and the collector portion, where the shape of the TPMS structure continuously changes to match the shape of the collector portion.

[0054] The transition region starts at a first location and ends at a second location according to local coordinates. For convenience, it is useful to assume that the transition region starts at a first coordinate z=0 and ends at a second coordinate z=L, where the coordinate z is set along the central major axis of the heat exchanger. Preferably, the axis is the major axis of the chemical reactor, typically the vertical central axis in a vertical reactor or the horizontal central axis in a horizontal reactor. The axis may also be a radial symmetry axis. See, for example, axis AA in FIG. 9 or FIG. 10.

[0055] In the transition region defined above, the shape of the heat exchanger gradually and continuously changes from the TPMS structure to the collector shape. Preferably, the transition region is mathematically described by the following equation:

number

[0056] The equations of the above TPMS structure and the collector part are represented by the abbreviated notations G = 0 and C = 0.

[0057] The TPMS structure (or TPMS lattice) is mathematically described by the equation G = 0. This means that all points with spatial coordinates x, y, and z that satisfy the equation G = 0 are the only points belonging to the TPMS surface. Similarly, the equation C = 0 describes the above collector part in the sense that points having coordinates x, y, z that satisfy the equation are points of the collector part.

[0058] The set R may include one or more parameters depending on the shape of the collector. For example, in a simple embodiment, the collector is a cylindrical pipe and R is the average radius of the cylindrical pipe. In other embodiments, the collector has a more elaborate shape and R includes the parameters necessary to define that shape. For example, R may include two parameters to define a pipe having an elliptical cross-section.

[0059] The above functions w1(z) and w2(z) are continuous in the z range from 0 to L. More preferably, one or both of the functions w1 and w2 are monotonic in the range 0 < z < L. According to the boundary values at z = 0 and z = L, as a result of monotonicity, the above function w1(z) monotonically decreases in the range 0 < z < L, and the above function w2(z) monotonically increases in the same range.

[0060] In a preferred embodiment, both of the weight functions w1 and w2 are linear functions. Examples where the above functions w1 and w2 are linear are the following embodiments. w1(z)=1 - z / L w2(z)=z / L

[0061] The linearity of the weight function generally is preferable to bring about a gradual transition between the connection part and the TPSM structure, but linearity is not essential. In other embodiments, the above functions w1 and / or w2 may be non-linear functions of higher order such as quadratic functions with respect to the variable z, or periodic functions such as sine functions.

[0062] The TPMS defined by the above equation G = 0 is preferably selected from the group of gyroid surfaces, Schwarz minimal surfaces, and Neovius surfaces. More preferably, the above structure defined by the equation G = 0 is a gyroid surface.

[0063] In a particularly preferred embodiment, the reactor of the present invention includes concentric pipes connected to the TPMS structure of the heat exchanger by the above method. More specifically, in this embodiment, the reactor has a first pipe and a second pipe. Here, the first pipe is coaxial with the second pipe. The heat exchanger is preferably connected to these pipes by welding. The pipe interface is connected to the heat exchanger core (equipped with a TPMS lattice) by the transition region described by the above equation EQ1 according to the local coordinate system.

[0064] In particular, the first interface has a first transition region with a TPMS structure, while the second interface has a second transition region with a TPMS. The first and second transition regions may be located at different positions. As a result, the first transition region may be described by equation EQ1 using a first coordinate system, and the second transition region may be described by the same equation EQ1 but using a second coordinate system. The first and second coordinate systems may have different origins. So, for example, the first transition region may be described by equation EQ1 using coordinate z1, and the second transition region may be described using coordinate z2. The extension lengths of the transition regions may be different. So, the first transition region may extend from z1=0 to z1=L1, and the second transition region may extend from z2=0 to z2=L2.

[0065] A further aspect of the present invention is the modularity of the TPMS-based heat exchanger. Modularity is advantageous when the desired size of the heat exchanger is larger than is optimal for additive manufacturing.

[0066] The compact heat exchanger of the present invention can be an alternative to rod-baffle type heat exchangers. Rod-baffle heat exchangers typically have multiple pipes whose length is approximately 4 to 10 times the diameter of the tubesheet, meaning that length is the dominant dimension of the exchanger. TPMS-based compact heat exchangers may not have the same longitudinal extension. This is because pressure loss may be excessive and / or the length may exceed manufacturing capabilities.

[0067] Applicant has discovered that a preferred shape for a compact exchanger according to the invention, particularly for service as an exchanger, is a cylinder having a height of about 1 to 4 times its diameter. Greater heights result in higher pressure losses, while larger diameters can result in lower Reynolds numbers and reduced effectiveness of the heat exchanger.

[0068] Possible solutions are presented to overcome the above-mentioned limitations. Solutions include moving the exchanger below the floor and modularizing the heat exchanger. The heat exchanger can be made up of multiple parts welded together at lateral linear boundaries. A related advantage is the possible axial shortening of the floor and therefore the pressure vessel.

[0069] To better understand the present invention, the following terms may be used.

[0070] A TPMS lattice refers to a lattice structure that divides a spatial region into two separate sub-portions, each of which may be passed by a heat exchange medium during operation.

[0071] The term core refers to a heat exchanger that includes a TPMS grid and at least one shell. In a typical embodiment, the core includes a TPMS grid and two coaxial shells, an outer shell and an inner shell, which are preferably cylindrical.

[0072] The term transition grating may be used to refer to the transition portion described by equation EQ1 above.

[0073] The term transition section refers to the portion of the heat exchanger formed by the transition section and one or more shells of the heat exchanger.

[0074] The term collector refers to a piping element that supplies fluid to or collects fluid from a heat exchanger.

[0075] The heat exchanger is essentially formed by a core section and one or two transition sections, and preferably the core and transition section assembly is printed integrally as a single part.

[0076] The term interface refers to the connection between the transition and the collector. At the interface, the heat exchanger is connected to the collector. The connection can be made by welding or other techniques such as flanges.

[0077] Turning to the drawings, Figure 1 illustrates a TPMS grid 1 and inner shell 4. The grid 1 is of the gyroid type according to a preferred embodiment.

[0078] The grid 1 is passed axially by a first fluid 2 and radially by a second fluid 3. For example, fluid 2 is the effluent from an upstream catalyst bed and fluid 3 is fresh gas to be preheated. While this example illustrates a radially inward flow, other embodiments may provide a radially outward flow.

[0079] The flow of fluid 2 and the flow of fluid 3 are directed into different channels in the structure of body 1. An inner shell 4 integrally formed in body 1 collects the radial flow of fluid 3.

[0080] 2 illustrates a boundary element in the form of an outer shell 5. The outer shell 5 has a cylindrical surface with a pattern of gas permeable regions 6. The gas permeable regions 6 coincide with an inlet on one face of the body 1, e.g., the face through which the radial flow of fluid 3 passes. The gas permeable regions 6 have a pattern of small holes for retaining granular catalyst.

[0081] 3 illustrates the core of a heat exchanger 15 formed by a grid 1, an inner shell 4, and an outer shell 5. In this example, fluid 3 is distributed to one side of the grid 1 by the outer shell 5, passes through the grid, and is collected by the inner shell 4. Similarly, suitable distributors and collectors can be provided for axial flow 2.

[0082] Figure 4 shows a catalytic reactor 10 including a heat exchanger 15 according to an embodiment of the present invention. In particular, Figure 4 discloses a possible arrangement of a heat exchanger according to the present invention located below the catalyst bed.

[0083] Figure 4 shows the following items: heat exchanger 15 TPMS lattice 1 catalyst bed 7 Inner collector 4 Entrance Plate 9 Exit Plate 11 Entrance Ring 12 Exit Ring 13 Sealing Ring 14

[0084] A catalyst bed 7 is disposed inside the catalytic reactor. A heat exchanger 15 is disposed below the catalyst bed 7. The heat exchanger 15 is bounded by an inlet ring 12 located at the top center of the heat exchanger and an outlet ring 13 located at the bottom center of the heat exchanger.

[0085] The inlet ring 12 and the outlet ring 13 are part of a set of boundary elements together with a sealing ring 14 located between the two rings 12 and 13. The set of boundary elements also includes an inlet plate 9 and an outlet plate 11 located above and below the heat exchanger 15, respectively.

[0086] The inlet ring 12 and the outlet ring 13 have a pattern of openings arranged to match the first face of the grid 1, while the inlet plate 9 and the outlet plate 11 have a pattern of openings arranged to match the second face of the grid 1.

[0087] A reagent gas mixture (not shown) is conveyed to the catalyst bed and reacts on the catalyst to produce a hot effluent 2. The hot effluent 2 passes axially through an inlet plate 9 and enters a first face of the heat exchanger body 1 where it indirectly exchanges heat with a cold stream 3 passing through a second face of the heat exchanger body 1. After exchanging heat with the cold stream 3, the reacted effluent 2 exits the heat exchanger via an outlet plate 11.

[0088] The cold stream 3 enters the second face of the heat exchanger 15 through the inlet ring 12 and exchanges heat with the hot effluent 2 before returning to the internal collector through the outlet ring 13 .

[0089] The sealing ring 14 prevents the cold stream 3 from entering the first face of the heat exchanger body 1 through which the hot effluent 2 passes.

[0090] A comparison with the prior art is shown in Figure 5. Figure 5(a) illustrates a cross-sectional view of a catalytic reactor according to an embodiment of the prior art, and Figure 5(b) illustrates a catalytic reactor according to an embodiment of the present invention.

[0091] The prior art catalytic reactor comprises a catalyst bed 7, a shell-and-tube heat exchanger 17, and a start-up heater 18. As can be seen in the drawing, the start-up heater 18 is positioned adjacent (usually concentrically) to the shell-and-tube heat exchanger 17. The heat exchanger may be of the rod baffle type.

[0092] In the catalytic reactor 10 of the present invention, the shell-and-tube heat exchanger 17 is replaced with a heat exchanger 15 fabricated by additive manufacturing and including a TPMS grid, as described above. The heat exchanger 15 provides a greater heat transfer coefficient than prior art shell-and-tube heat exchangers. As such, it can be manufactured in a compact design and placed below the start-up heater 18, as shown in the drawings. This arrangement frees up space for more catalyst. Advantageously, the size of the catalyst bed 7 can be increased, providing significant benefits to the process, including higher production rates.

[0093] 6 illustrates an embodiment of a transition between a gyroid lattice 100 and a cylinder 101. The transition begins at axial coordinate z=0 and completes at axial coordinate z=L. In the transition region 102, the shape of the structure is described by equation EQ1 discussed above. As a result, the structure continuously evolves from the lattice interface 100 to the circular interface 101.

[0094] FIG. 7 is a perspective view illustrating the transition of FIG.

[0095] 8 illustrates an embodiment in which a gyroid lattice 100 is housed within an outer tube 112. The lattice 100 has a first transition section 120 that forms a pipe 110 for connecting to a collector that separates the inlet gas flow from the outlet gas flow. The lattice 100 also has a second transition section 122 with the outer tube 112. A central bypass pipe 114 is also illustrated. The bypass pipe 114 passes through the lattice 100 and can formally be obtained by removing a cylinder (Boolean operation) from the structure of the lattice 100.

[0096] 8, it can be seen that the cylindrical sections 110, 112 represent suitable connections to conventional (cylindrical) pipes. The connections 110, 112 can be formed by additive manufacturing together with the lattice 100 and can be connected (e.g., welded) to the conventional pipes.

[0097] The transition regions 120, 122 can be mathematically defined by equation EQ1, provided that the appropriate coordinate z (local coordinate) is employed.

[0098] Figure 9 illustrates a cross-sectional view of the transition between the grid 100 and the inner ring 110. Figure 9 also illustrates the inflow F1 and outflow F2 of the heat exchange fluid to and from the grid 100. The transition region 120 is easily seen in this view. Figure 9 also illustrates the major axis AA of the heat exchanger.

[0099] 10 illustrates a modular heat exchanger according to an embodiment of the present invention, where a compact heat exchanger 200 includes parallel-connected sectors 201. If made of a weldable material, the sectors 201 can be welded together to form the exchanger 200. Each sector 201 includes a TPMS structure according to any of the embodiments described above.

[0100] 10 illustrates a toroidal shape as a preferred shape for modular heat exchanger 200. Region 202 near major axis AA is the preferred location for the inlets and outlets on both sides of heat exchanger 200. The two sides of heat exchanger 200 are those sides that are in communication with the cooling and heating fluids and those sides that are closed by the boundary of the pressure vessel.

[0101] Figure 11 illustrates the heat exchanger 200 of Figure 10 positioned below the catalyst bed 7. In Figure 11, the compactness of the heat exchanger 200 can be appreciated compared to conventional longitudinally extending rod baffle heat exchangers.

Claims

1. A chemical reactor (10) comprising a catalyst bed (7) configured to carry out a catalytic reaction, and a heat exchanger (15) arranged to transfer heat from a first fluid (2) which is the effluent from the catalyst bed to a second fluid (3) which is a heating or cooling medium, The heat exchanger (15) comprises a heat exchange structure (1) produced by additive manufacturing, the structure being a triple periodic minimal surface TPMS; a reactor including a set of boundary elements (4, 5, 12, 13) configured to distribute the first fluid and the second fluid to a TPMS structure and to collect the first fluid and the second fluid from the TPMS structure; The TPMS structure (1) has a first surface and a second surface; the first surface defines a first passageway through which a heat exchange medium may pass; the second surface defines a second passageway through which a heat exchange medium may pass; the first path is separated from the second path, so that a medium passing through the TPMS structure (1) via the first path does not come into direct contact with a medium in the second path; the set of boundary elements is configured such that the effluent is distributed to and collected from only the first surface, and the heating medium or the cooling medium is distributed to and collected from only the second surface; This allows the effluent to pass through the TPMS structure via the first path, and the heating medium or the cooling medium to pass through the structure via the second path, thereby indirectly transferring heat from the effluent to the cooling medium or from the heating medium to the effluent.

2. The heat exchanger is At least one connecting portion having a shape suitable for connection with a collector or distributor pipe; a transition region between the TPMS structure and the connecting portion, the TPMS structure and the connecting portion are integrally fabricated as a single piece by additive manufacturing; The chemical reactor (10) of claim 1, wherein in the transition region, the shape of the TPMS structure continuously changes to match the shape of the connecting portion.

3. the transition region extends according to a coordinate Z along the axis of the heat exchanger from a start position at Z=0 to an end position at Z=L; In the transition region defined above, the geometry of the heat exchanger is mathematically described by the following equation: [Equation 1] where: The equation G(x, y, z, S, k)=0 describes the TPMS structure, The equation C(x, y, z, R, t)=0 describes the connection, S is a set of one or more parameters that define the shape of the TPMS structure; k is a parameter defining the thickness of the TPMS structure; R is a set of parameters defining the shape of the connection portion; t is a parameter defining the thickness of the connection portion, x, y, and z are spatial coordinates; w1(z) and w2(z) satisfy the following conditions: i) w1(0)=1 and w1(L)=0; ii) w2(0)=0 and w2(L)=1; iii) a weighting function that satisfies 0<w1(z)<1 and 0<w2(z)<1 for any z in the range 0<z<L.

4. The chemical reactor (10) of claim 3, wherein the functions w1(z) and w2(z) are continuous and monotonic in the range 0<z<L.

5. The chemical reactor (10) of claim 4, wherein the functions are linear, preferably the functions w1(z)=1-z / L and w2(z)=z / L.

6. 6. The chemical reactor (10) according to any one of claims 2 to 5, wherein the heat exchanger comprises a first connecting portion and a second connecting portion integrally formed with the TPMS structure for connection with two coaxial pipes, each connecting portion being connected to the heat exchanger by a respective transition region described by equation (EQ1) according to a local coordinate system.

7. 7. The chemical reactor (10) of any one of claims 1 to 6, wherein the set of boundary elements comprises one or more surface elements (5) having a gas permeable pattern arranged to match an inflow or outflow pattern in the TPMS structure.

8. 8. The chemical reactor (10) of any one of claims 1 to 7, wherein the TPMS structure has an annular shape, one face of the structure is passed radially, and the set of boundary elements includes an inner cylindrical shell and / or an outer cylindrical shell for distributing the effluent or the cooling medium to and / or collecting the effluent or the cooling medium from the radially passed face of the TPMS structure.

9. 10. The chemical reactor (10) of claim 8, wherein the catalyst bed has an annular shape and is disposed around the TPMS structure, and the outer cylindrical shell serves as a boundary element for the TPMS structure and as a retaining wall for catalyst granules forming the catalyst bed.

10. The chemical reactor (10) according to any one of claims 1 to 9, wherein the TPMS structure (1) is arranged below the catalyst bed (7) and is arranged to support the weight of the catalyst bed.

11. 11. The chemical reactor (10) of any one of claims 1 to 10, wherein the catalyst bed and the TPMS structure both have annular shapes, and the TPMS structure is coaxially disposed outside or inside the catalyst bed.

12. the TPMS structure has a ring shape; the TPMS structure is passed axially by both fluids; 12. The chemical reactor (10) according to any one of claims 1 to 11, wherein the boundary elements comprise a first ring-shaped boundary element (9) arranged above the structure and a second ring-shaped element (11) arranged below the structure, for distributing and collecting fluids passing axially through the structure.

13. 13. The chemical reactor (10) of any one of claims 1 to 12, wherein the TPMS structure has an annular shape and the set of boundary elements includes a first element (12) extending across a portion of an inner or outer surface of the TPMS structure (1) and a second element (13) disposed around a different portion of the inner or outer surface, whereby one fluid enters the TPMS structure (1) and exits the TPMS structure through a different portion of the inner or outer surface.

14. The chemical reactor (10) according to any one of claims 1 to 13, wherein the TPMS structure is selected from the group of gyroid surfaces, Schwarz minimal surfaces, and Neobius surfaces.

15. The chemical reactor (10) according to any one of the preceding claims, wherein the TPMS structure, the boundary elements and the heat exchanger including the transitions are made of Inconel, preferably Inconel 625 or Inconel 718, or a combination thereof.

16. 16. The chemical reactor (10) of any one of claims 1 to 15, wherein the additive manufacturing technique is one of powder bed fusion, binder jetting, stereolithography, fused deposition modeling, digital light processing, multi-jet fusion, polyjet, directed energy deposition, such as direct metal laser sintering, electron beam melting, selective thermal sintering, selective laser melting, and selective laser sintering.

17. The chemical reactor (10) of any one of claims 1 to 16, wherein the reactor is configured for the synthesis of ammonia or methanol.

18. The chemical reactor (10) of any one of claims 1 to 17, wherein the heat exchanger (15) is an interbed heat exchanger, a preheater, a steam superheater, or a combination thereof.

19. Use of a reactor according to any one of claims 1 to 18 for the synthesis of ammonia or the synthesis of methanol.

20. 1. A method for designing a chemical reactor, the method comprising: providing a heat exchanger disposed inside the reactor, the heat exchanger comprising a TPMS lattice structure defining two separate heat exchange surfaces passed by a first heat exchange medium and a second heat exchange medium; the reactor further comprising at least one connection portion for connecting a distribution pipe of the heat exchange medium to one surface of the heat exchanger or a collector pipe of the heat exchange medium from said one surface; and modeling a transition region for the connection between the lattice structure and said connection portion according to the following equation EQ1: [Equation 2] where: The equation G(x, y, z, S, k) = 0 describes the TPMS lattice structure, The equation C(x, y, z, R, t) = 0 describes the collector section, S is a set of one or more parameters defining the shape of the TPMS lattice; R is a set of one or more parameters defining the shape of the connection portion; k is a parameter that defines the thickness of the TPMS structure; t is a parameter that defines the thickness of the collector; x, y, and z are spatial coordinates; The transition region is assumed to start at z=0 and end at z=L, w1(z) and w2(z) satisfy the following conditions: w1(0)=1 and w1(L)=0, w2(0)=0 and w2(L)=1, The weighting functions satisfy 0<w1(z)<1 and 0<w2(z)<1 for any z in the range 0<z<L.

21. 21. The method of claim 20, wherein the functions w1(z) and w2(z) are continuous and monotonic in the range 0<z<L.

22. 22. The method of claim 21, wherein the functions are linear, preferably the functions w1(z)=1-z / L and w2(z)=z / L.

23. 23. The method according to any one of claims 20 to 22, wherein the reactor is a reactor for the synthesis of ammonia or methanol.

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