Chemical reactor with heat exchanger

Abstract

A chemical reactor (10) comprising a catalytic bed (7) and a heat exchanger (15) arranged to transfer heat from a first fluid (2) as an effluent of the catalytic bed to a second fluid (3) as a cooling or heating medium wherein the heat exchanger (15) comprises a structure (1) made by an additive manufacturing process, the structure is a triple periodic minimal curved surface (TPMS) structure having a first side and a second side through which a heat exchange fluid can pass, and the heat exchanger comprises a set of boundary elements (5), the boundary elements are arranged to supply and collect the first fluid (2) and the second fluid (3) to the channels of the first side and the channels of the second side of the structure.

Description

Technical Field

[0001] The invention belongs to the field of catalytic reactors with heat exchangers inside. Background Art

[0002] Many chemical reactions of great industrial importance require a reactor comprising one or more heat exchangers which can carry away the heat of reaction in the case of exothermic reactions or provide the heat of reaction in the case of endothermic reactions.

[0003] A notable example is the synthesis of ammonia or methanol, which are strongly exothermic. Such reactions are carried out in a reactor comprising one or more catalytic beds. Due to the exothermic nature, the effluents of the catalytic beds are usually at high temperatures, and it is intentional to remove heat from such effluents to preheat another process stream or to generate steam, as well as to appropriately cool the effluent for subsequent reaction steps.

[0004] The most common heat exchanger used in chemical reactors is the shell and tube heat exchanger. In a shell and tube heat exchanger, the first fluid passes through the tubes and the second fluid circulates around the tubes, confined by the shell. Typically, the inside of the tubes is called the tube side and the space around the tubes is called the shell side.

[0005] One notable example is the inter-bed heat exchanger of a multi-bed ammonia reactor. In a multi-bed reactor, the conversion is typically carried out in a plurality (e.g., two or more, typically three or four) of catalytic beds arranged in series so that the effluent from one bed is further reacted in the next bed. The inter-bed exchanger cools the effluent from one bed before it enters the next bed. In the common case, the catalytic bed has an annular shape so that a shell and tube exchanger can be accommodated in the central cavity of the bed.

[0006] In most applications, the tubes are of considerable length and are therefore subject to vibrations. In addition, it is desirable that the airflow in the shell side is perpendicular to the tubes to maximize heat exchange. For this purpose, shell and tube heat exchangers include transverse baffles that are arranged to dampen vibrations and increase vortex in 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 exchanger (e.g., the diameter of the shell); the eddy currents caused by the baffles are confined to a small area near the baffles; and the baffles increase cost and complexity.

[0008] A chemical reactor comprising a catalytic bed and a heat exchanger is described in DE 10 2015 114201. A heat exchanger with a gyroid minimal surface is described in US20200033070 or EP 4 033 193. An integral bicontinuous core (MBC) structure for a heat exchanger is described in US20180187984. Systems and methods for reactors, distributors, contactors and heat exchangers based on periodic nodal surfaces are described in US2022 0003503. Summary of the invention

[0009] The present invention aims to solve the above-mentioned disadvantages of heat exchangers installed in chemical reactors. The object of the present invention is to provide a new chemical reactor that solves the above-mentioned problems.

[0010] The present invention uses a triply periodic minimal surface (TPMS) structure made by additive manufacturing as a heat exchanger in a chemical reactor. The structure has interesting properties for heat exchange, including periodicity and the ability to generate diffusion vortices. The TPMS structure can also be considered as a TPMS lattice.

[0011] The TPMS structure inherently defines two sides, which may 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 that is traversed by a fluid having a higher temperature ("hot fluid"), and "cold side" refers to the side that is traversed by a fluid at a lower temperature ("cold fluid").

[0012] In the present invention, a set of suitable boundary elements distributes hot and cold fluids to and collects hot and cold fluids from the respective sides of the TPMS structure. In the structure, the two sides are completely separated, which means that the hot and cold fluids do not contact and exchange heat indirectly through the structure.

[0013] The objects of the invention are therefore achieved with a chemical reactor according to claim 1. Preferred features are stated in the dependent claims.

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

[0015] The heat exchanger can be realized without baffles but with channels of small dimensions. Thus, the Reynolds number of the fluid passing through the channels is increased and the effect of the high specific pressure drop is reduced due to the shorter length of the exchanger. The thickness of the walls forming the channels of the heat exchanger can be minimized, which increases the heat transfer coefficient.

[0016] Additive manufacturing offers several advantages, including rapid and cost-effective production, and the possibility to print heat exchangers on demand with extensive customizability in size and shape.

[0017] Furthermore, cost-effective production can be achieved, as less material (e.g. alloy) is required to manufacture the heat exchanger compared to conventional methods. Less material waste is also generated during the manufacturing process.

[0018] Due to the higher heat transfer coefficient, the heat exchanger can be manufactured with compact dimensions. This is particularly advantageous because the volume occupied by the heat exchanger in the catalytic reactor can be reduced and the volume allocated to the catalytic bed can be increased.

[0019] The invention is particularly useful in the field of plants for the production of one or more synthetic reagents using renewable energy sources.

[0020] The present invention provides a compact heat exchanger that can typically save 50% to 90% of space compared to a conventional baffle rod type heat exchanger.

[0021] Another advantage is associated with the construction of the TPMS heat exchanger comprising boundary elements having thin walls but capable of withstanding high external pressures and preventing buckling phenomena.

[0022] Another noteworthy aspect of the present invention solves the problem of how to connect the TPMS lattice with a conventional collector such as a tube. This task is challenging due to the complex shape of the TPMS lattice. The present invention solves this problem by providing a connecting portion formed together with the TPMS lattice and a transition zone located between the TPMS lattice and the connecting portion, wherein the shape of the TPMS lattice is gradually modified to match the collector. The connecting portion can advantageously be formed integrally with the TPMS lattice. Therefore, the present invention provides a heat exchanger based on the TPMS lattice, which can be seamlessly connected to a conventional distribution pipe or collection pipe.

[0023] Yet another aspect of the present invention relates to a parallel-connected heat exchanger produced by an additive manufacturing method. Summary of the invention

[0025] The chemical reactor of the present invention comprises a heat exchanger having a structure made by additive manufacturing (AM), the structure being a triply periodic minimal surface (TPMS) structure. The term "TPMS" means a non-intersecting 3D surface characterized in that the average curvature value at each point of the surface is zero. The TPMS surface is defined by mathematical functions known in the art and is therefore not discussed in detail herein. The term "TPMS lattice" may also be used to represent the structure.

[0026] The TPMS structure (TPMS lattice) can be considered as a part of the internal volume of the chemical reactor, which performs the function of a heat exchanger. The TPMS structure defines two sides suitable for being traversed by hot and cold media, respectively, so it can actually act as a heat exchanger.

[0027] The TPMS structure can be described mathematically by suitable equations. Preferably, the TPMS structure is defined by an implicit function of the following form:

[0028]

[0029] Where X represents a set of suitable parameters, including spatial coordinates and one or more parameters defining the characteristics of the TPMS structure, such as shape and thickness. For example, the above function may take the following form:

[0030] G(x,y,z,S,k)=0

[0031] where z, y, z are spatial coordinates; S is a set of one or more parameters describing the TMPS structure; and k is a parameter defining the thickness of the structure.

[0032] In addition, the shape of the heat exchanger can be modeled by combining the TPMS structure with other shapes using operators such as Boolean operators. For example, by subtracting a cylinder from the TPMS structure, a hole passing through the TPMS structure can be relatively easily defined. More formally, assuming that A represents a TPMS in a given spatial region and B represents a cylindrical tube passing through the TPMS, the operation (ANOT B) will produce a TPMS with a through hole.

[0033] The mathematical description of the TPMS structure provides input for the design of the structure. Suitable references on the mathematical description of the TPMS and methods of modeling it by the marching cubes method can be found in:

[0034] -Manuscripta Mathematica, Volume 64, 1989, Springer;

[0035] -Marching cubes: a high resolution 3D surface construction algorithm, William E. Lorensen and Harvey E. Cline, Computer Graphics, Vol. 21, No. 4, July 1987, pp. 163-169;

[0036] -Surface curvature in triply-periodic minimal surface architecturesasa distinct design parameter in preparing advanced tissue engineeringscaffold,

[0037] Sébastien Blanquer,Maike Werner,Markus Hannula,Shahriar Sharifi,Guillaume Lajoinie,David Eglin,Jari Hyttinen,André Poot,Dirk Grijpma,IOPPublishing,2017,9(2),page 025001.10.1088 / 1758-5090 / aa6553

[0038] hal-02336718.

[0039] The TPMS structure of the heat exchanger has a first side and a second side, wherein the first side and the second side define a first path and a second path, respectively, through which a heat exchange medium and / or a reagent gas mixture can pass. The first side can be traversed, for example, by a coolant medium such as water, and the second side can be traversed, for example, by a reactant gas mixture.

[0040] The first path and the second path are separated from each other, so that the heat exchange medium flowing through the TPMS structure through the first path does not directly contact the medium passing through the second path.

[0041] The heat exchanger further comprises a set of boundary elements, which are configured such that the first medium is distributed only into the first side and collected from the first side, and the second medium is distributed only into the second side and collected from the second side. For example, the first medium is the effluent of the catalytic bed and the second medium is a heating medium or a cooling medium. In a reactor for exothermic reactions, the first medium is the hot effluent of the catalytic bed, from which heat is taken away, and the second medium is a cooling medium, such as water, steam or a process gas to be preheated.

[0042] The set of boundary elements is configured so that the effluent from the catalytic bed can pass through the TPMS structure via a first path, and the heating or cooling medium can pass through the structure via a second path to obtain indirect heat transfer from the effluent to the cooling medium or from the heating medium to the effluent depending on the enthalpy of the chemical reaction (i.e., whether the reaction is exothermic or endothermic).

[0043] The provision of boundary elements solves the challenging problem of how to distribute heat exchange fluid to and collect heat exchange fluid from the TPMS structure.

[0044] According to an interesting application, the set of boundary elements is also produced by additive manufacturing. Advantageously, a high degree of flexibility can be achieved in the design and production of the heat exchanger.

[0045] The set of boundary elements may include one or more surface elements having a permeable pattern configured to match the pattern of input or output ports in the TPMS structure. In some embodiments, the set of boundary elements may include one or more cylindrical shells. In some embodiments, the boundary elements may have different shapes, such as plates or rings, depending on the geometry of the heat exchanger.

[0046] The TPMS structure of the heat exchanger may have any suitable shape. In one embodiment of the invention, the TPMS structure has an annular shape and one side of the structure is radially traversed and the set of boundary elements comprises an inner cylindrical shell around the inner surface of the bed and / or an outer cylindrical shell around the outer portion of the bed to distribute the effluent or the heating or cooling medium to and / or collect the effluent or the heating or cooling medium from the radially traversed side of the TPMS structure.

[0047] In a preferred embodiment, the catalytic bed has an annular shape and is arranged around the TPMS structure. Thus, the outer cylindrical housing can serve as a boundary element of the TPMS structure and as a retaining wall for the catalyst particles forming the catalytic bed.

[0048] In one embodiment, the TPMS structure, transition zone, and boundary elements are placed below the catalytic bed.

[0049] In a particular configuration of the aforementioned embodiment, the TPMS structural heat exchanger is arranged to support the weight of the catalytic bed.

[0050] In one embodiment, the catalytic bed and the TPMS structure have an annular shape, and the TPMS structure is coaxially disposed outside or inside the catalytic bed.

[0051] In one embodiment, the TPMS structure has an annular shape and is penetrated radially by one fluid and axially by another fluid. The boundary element may preferably include a first annular shaped boundary element placed above the structure and a second annular shaped element placed below the structure to distribute and collect the fluid passing through the structure in the axial direction.

[0052] In another embodiment, the TPMS structure has an annular shape, and the set of boundary elements includes a first surface extending on a portion of the inner surface or the outer surface of the TPMS structure and a second surface arranged around a different another portion of the inner surface or the outer surface, so that a fluid can enter the TPMS structure and leave the TPMS structure through different portions of the inner surface or the outer surface.

[0053] Preferably, the first side and the second side comprise a plurality of channels in the TPMS structure. The channels of the heat exchanger may have an almost circular cross section. Preferably, the cross section has a hydraulic diameter in the range of 2 mm to 20 mm and more preferably in the range of 5 mm to 15 mm.

[0054] The surface of the TPMS structure is preferably selected from the group consisting of a Gyroid surface, a Schwarz minimal surface and a Neovius surface. In the embodiment with a Schwarz minimal surface, the surface is preferably a Schwarz-P surface or a Schwarz-D (diamond) surface.

[0055] The TPMS structure and / or the set of boundary elements may be made of any suitable material capable of withstanding the operating conditions of the synthesis reactor. Preferably, the material is Inconel, particularly preferably Inconel 625 or Inconel 718 or a combination thereof.

[0056] Any additive manufacturing method may be used to manufacture the heat exchanger and the set of boundary elements, as long as the selected technology is suitable for manufacturing the structure of the heat exchanger or boundary elements. Preferably, the technology is one of the following: powder bed fusion, such as any of direct metal laser sintering, electron beam melting, selective thermal sintering, selective laser melting and selective laser sintering; binder jetting; stereolithography; fused deposition modeling; digital light processing; multi-jet fusion; polymer jetting; direct energy deposition.

[0057] The inner surface of the heat exchanger according to the present invention follows the TPMS surface. As mentioned above, the TPMS surface is mathematically described, while the physical (real) surface is different from the mathematical surface and has a non-zero thickness. The minimum required thickness of the real surface can be determined by a person skilled in the art based on the manufacturability, stress conditions and characteristics of the material.

[0058] In particularly interesting applications, the reactor of the invention is used for the synthesis of ammonia or methanol.

[0059] The preferred configuration includes: an inter-bed heat exchanger for cooling the hot effluent from the catalytic bed prior to the subsequent catalytic bed; a preheater configured to preheat the synthesis gas directed to the catalytic bed; and a steam superheater configured to generate steam above its saturation temperature by heat exchange with the hot reaction gas generated in the chemical reactor.

[0060] Another application of the present invention is a retrofit process, wherein a conventional heat exchanger, such as a shell and tube heat exchanger, inside a chemical reactor is replaced by installing a heat exchanger comprising a structure made by additive manufacturing, which is a triply periodic minimal surface (TPMS) structure and a set of boundary elements as described above.

[0061] In another aspect of the present invention, in addition to the TPMS structure, the heat exchanger further comprises at least one collector portion and a transition zone between the TPMS structure and the collector portion. In the transition zone, the shape of the TPMS structure continuously changes according to the shape of the collector portion.

[0062] According to the local coordinates, the transition zone starts at a first position and ends at a second position. Generally, it is useful to assume that the transition zone starts at a first coordinate z=0 and ends at a second coordinate z=L, wherein the coordinate z is taken along the central main axis of the heat exchanger. Preferably, the axis is the main 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 can be a radially symmetrical axis. See, for example, axis AA of Figure 9 or Figure 10.

[0063] In the above transition zone, the shape of the heat exchanger gradually evolves from the TPMS structure to the shape of the collector part. Preferably, the transition zone is mathematically described by the following equation:

[0064] G(x,y,z,S,k)*w1(z)+C(x,y,z,R,t)*w2(z)=0 (Equation 1)

[0065] in:

[0066] The equation G(x,y,z,S,k)=0 is the above equation describing the structure of TPMS,

[0067] The equation C(x,y,z,R,t)=0 describes the connection part,

[0068] R is a set of one or more parameters that define the shape of the collector in equation C,

[0069] t is a parameter defining the thickness of the connecting part,

[0070] x, y, and z are spatial coordinates as described above,

[0071] w1(z) and w2(z) are weight functions that satisfy the following conditions:

[0072] w1(0) = 1 and w1(L) = 0;

[0073] w2(0) = 0 and w2(L) = 1;

[0074] For any z in the range 0 < z < L, 0 < w1(z) < 1 and 0 < w2(z) < 1.

[0075] The above equations for the TPMS structure and the current collector part are represented by the short symbols G = 0 and C = 0.

[0076] The TPMS structure (or TPMS lattice) is mathematically described by the equation G = 0, which means that the points whose spatial coordinates x, y, and z satisfy the equation G = 0 are all and only the points belonging to the TPMS surface. Similarly, the equation C = 0 describes the current collector part in the sense that the points whose coordinates x, y, z satisfy the equation are the points of the current collector part.

[0077] Depending on the shape of the current collector, the set R can include one or more parameters. For example, in a simple embodiment, the current collector is a cylindrical tube, and R is the average radius of the cylindrical tube. In other embodiments, the current collector has a more refined shape, and R contains the parameters necessary to define the shape. For example, R can contain two parameters to define a tube with an elliptical cross-section.

[0078] The functions w1(z) and w2(z) are continuous in the range of z from 0 to L. More preferably, one or both of the functions w1 and w2 are monotonic in the range 0 < z < L. Due to the boundary values at z = 0 and z = L, the monotonic property causes the function w1(z) to decrease monotonically in the range 0 < z < L, and the function w2(z) to increase monotonically in the same range.

[0079] In a preferred embodiment, both weight functions w1 and w2 are linear functions. Examples of the functions w1 and w2 being linear are embodiments in which:

[0080] w1(z) = 1 – z / L;

[0081] w2(z) = z / L.

[0082] Linearity of the weight functions is generally preferred to provide a gradual transition between the connector and the TPSM structure; however, linearity is not required, and in other embodiments, the functions w1 and / or w2 can be non-linear functions, such as quadratic or higher-order functions with respect to the variable z, or periodic functions, such as sine functions.

[0083] The TPMS defined by the above equation G=0 is preferably selected from the group consisting of a Gyroid surface, a Schwarz minimal surface and a Neovius surface. More preferably, the structure defined by the equation G=0 is a helical surface.

[0084] In a particularly preferred embodiment, the reactor of the invention comprises concentric tubes connected to the TPMS structure of the heat exchanger in the manner described above. In more detail, in this embodiment, the reactor has a first tube and a second tube, wherein the first tube is coaxial with the second tube; the heat exchanger is preferably connected to the tubes by welding; the tube interface is connected to the heat exchanger core (with the TPMS lattice) through a transition zone described by the equation EQ1 according to the local coordinate system.

[0085] In particular, the first interface has a first transition zone with a TPMS structure, and the second interface has a second transition zone with a TPMS. The first transition zone and the second transition zone can be located at different positions, and therefore the first transition zone can be described with equation EQ1 and using a first coordinate system, and the second transition zone can be described with the same equation EQ1 but using a second coordinate system. The first coordinate system and the second coordinate system can have different origins, so for example the first transition zone is described with coordinate z1 by equation EQ1 and the second transition zone is described with second coordinate z2. The extensions of the transition zones can be different, so the first transition zone can extend from z1=0 to z1=L1, and the second transition zone can extend from z2=0 to z2=L2.

[0086] Another aspect of the invention is the modularity of the TPMS based heat exchanger. Modularity is advantageous when the desired size of the heat exchanger is larger than the optimal size for additive manufacturing methods.

[0087] The compact heat exchanger according to the present invention can replace the baffled rod type heat exchanger. The baffled rod type heat exchanger usually has multiple tubes with a length of about 4 to 10 times the diameter of the tube sheet, which means that the length is the main dimension of the exchanger. In some cases, the TPMS-based compact heat exchanger may not have the same longitudinal extension because the pressure drop will be too large and / or the length may exceed the manufacturing capabilities.

[0088] The applicant has found that, particularly for service as an exchanger, the preferred shape of the compact exchanger according to the invention is cylindrical, with a height of about 1 to 4 times the diameter. A longer height will result in a higher pressure drop, while a larger diameter may result in a lower Reynolds number, thus reducing the effectiveness of the heat exchanger.

[0089] A possible solution to overcome the above limitations is proposed. The solution consists of moving the exchanger below the bed and making the heat exchanger modular. The heat exchanger can be composed of many parts welded together at transverse linear boundaries. A related advantage is that the bed can be shortened in the axial direction and, therefore, the pressure vessel can be shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The present invention is further illustrated by the following drawings:

[0091] FIG. 1 shows a heat exchanger body according to an embodiment of the present invention,

[0092] FIG. 2 shows a boundary element that can be used with the heat exchanger body of FIG. 1 ,

[0093] FIG. 3 shows the heat exchanger body of FIG. 1 with the boundary element of FIG. 2 ,

[0094] FIG4 is a schematic diagram of a cross-sectional view of a catalytic reactor according to one embodiment,

[0095] FIG5 is a cross-sectional view comparing a catalytic reactor according to an embodiment of the prior art and a catalytic reactor according to an embodiment of the present invention,

[0096] 6 to 11 illustrate other embodiments of the present invention, as described in detail below. DETAILED DESCRIPTION

[0097] The following terms may be used to better understand the present invention.

[0098] The TPMS lattice represents a lattice structure that divides a spatial region into two separate sub-sections. In operation, each sub-section can be traversed by a heat exchange medium.

[0099] The term "core section" refers to a heat exchanger comprising a TPMS lattice and at least one shell. In a common embodiment, the core section comprises a TPMS lattice and two coaxial shells, an outer shell and an inner shell. The outer shell and the inner shell are preferably cylindrical.

[0100] The term "transition lattice" may be used to refer to the transition portion described by equation EQ1 above.

[0101] The term "transition section" denotes that part of a heat exchanger which is formed by the transition section and one or more shells of the heat exchanger.

[0102] The term "collector" denotes a piping element that feeds fluid to a heat exchanger or collects fluid from a heat exchanger.

[0103] The heat exchanger is essentially formed by a core section and one or two transition sections. Preferably, the assembly of the core section and any transition sections is integrally printed as a one-piece component.

[0104] The term "interface" refers to the connection between the transition section and the collector. At the interface, the heat exchanger is connected to the collector. The connection can be achieved by welding or other techniques such as flanges.

[0105] Turning to the drawings, Figure 1 shows a TPMS lattice 1 and an inner shell 4. According to a preferred embodiment, the lattice 1 is of the spiral type.

[0106] The lattice 1 is axially penetrated by a first fluid 2 and radially penetrated by a second fluid 3. For example, fluid 2 is the effluent of an upstream catalytic bed and fluid 3 is the fresh gas to be preheated. This example shows an inward radial flow, but in other embodiments, an outward radial flow may also be provided.

[0107] The flows of fluids 2 and 3 are directed to different channels of the structure of the body 1 . The radial flow of fluid 3 is collected by an inner casing 4 , which is integrated into the body 1 .

[0108] Figure 2 shows a boundary element in the form of a housing 5. The housing 5 has a cylindrical surface with a pattern of gas permeable areas 6. The gas permeable areas 6 match the inlet of one side of the body 1, e.g. the side through which the radial flow of the fluid 3 passes. The gas permeable areas 6 have a pattern of small holes for retaining a granular catalyst.

[0109] Figure 3 shows the core section of a heat exchanger 15 formed by the lattice 1, the inner shell 4 and the outer shell 5. In this embodiment, the fluid 3 is distributed by the outer shell 5 into one side of the lattice 1 and, after passing through the lattice, it is collected by the inner shell 4. Similarly, suitable distributors and collectors can be provided for the axial flow 2.

[0110] Figure 4 shows a catalytic reactor 10 comprising a heat exchanger 15 according to one embodiment of the present invention. In particular, Figure 4 discloses a possible arrangement of a heat exchanger located below the catalytic bed according to the present invention.

[0111] Figure 4 shows the following items:

[0112] Heat exchanger 15

[0113] TPMS Lattice 1

[0114] Catalytic bed 7

[0115] Internal Collector 4

[0116] Entrance board 9

[0117] Exit plate 11

[0118] Entrance ring 12

[0119] Exit ring 13

[0120] Sealing ring 14.

[0121] The catalytic bed 7 is arranged inside the catalytic reactor. The heat exchanger 15 is arranged below the catalytic bed 7 and is defined by an inlet ring 12 on the central bottom side and an outlet ring 13 located on the central top of the heat exchanger.

[0122] The inlet ring 12 and the outlet ring 13 are part of a set of boundary elements together with a sealing ring 14 arranged between the two rings 12 and 13. The set of boundary elements also comprises an inlet plate 9 and an outlet plate 11 arranged above and below the heat exchanger 15, respectively.

[0123] The inlet ring 12 and the outlet ring 13 have a hole pattern arranged to match a first side of the lattice 1 , whereas the inlet plate 9 and the outlet plate 11 have a hole pattern arranged to match a second side of the lattice 1 .

[0124] A reactant gas mixture (not shown) is delivered to the catalytic bed where it reacts on the catalyst to generate a hot effluent 2. The hot effluent 2 axially passes through the inlet plate 9 and enters the first side of the heat exchanger body 1, where it indirectly exchanges heat with a cold stream 3 passing through the second side of the heat exchanger body 1. After exchanging heat with the cold stream 3, the reaction effluent 2 leaves the heat exchanger via the outlet plate 11.

[0125] The cold stream 3 enters the second side of the heat exchanger 15 via the inlet ring 12 and returns to the internal collector via the outlet ring 13 after exchanging heat with the hot effluent 2 .

[0126] The sealing ring 14 prevents the cold flow 3 from entering the first side of the heat exchanger body 1 through which the hot effluent 2 passes.

[0127] Fig. 5 shows a comparison with the prior art. Fig. 5(a) shows a cross-sectional view of a catalytic reactor according to one embodiment of the prior art, and Fig. 5(b) shows a cross-sectional view of a catalytic reactor according to one embodiment of the present invention.

[0128] The prior art catalytic reactor comprises a catalytic bed 7, a shell and tube heat exchanger 17 and a start-up heater 18. As can be seen in the figure, the start-up heater 18 is arranged adjacent (usually concentrically) to the shell and tube heat exchanger 17. The heat exchanger may be a baffle rod type heat exchanger.

[0129] In the catalytic reactor 10 of the present invention, the shell and tube heat exchanger 17 is replaced by a heat exchanger 15, which is made by additive manufacturing and includes a TPMS lattice as described above. The heat exchanger 15 provides a greater heat transfer coefficient than the shell and tube heat exchanger of the prior art, and for this reason it can be made into a compact design and arranged below the start-up heater 18, as shown. This arrangement frees up space for more catalyst. Advantageously, the size of the catalytic bed 7 can be increased, which brings huge advantages to the process, such as higher productivity.

[0130] 6 shows an embodiment of the transition between a spiral lattice 100 and a cylinder 101. The transition starts at the axial coordinate z=0 and is completed at the axial coordinate z=L. In the transition region 102, the shape of the structure is described by equation EQ1 as described above. Thus, the structure evolves from the lattice interface 100 to the circular interface 101.

[0131] FIG. 7 shows the transition from FIG. 6 in a perspective view.

[0132] FIG8 shows an embodiment in which the spiral lattice 100 is contained within an outer tube 112. The lattice 100 has a first transition section 120 that forms a tube 110 for connection to a collector that separates the inlet gas flow from the outlet gas flow. The lattice 100 also has a second transition section 122 connected to the outer tube 112. A central bypass tube 114 is also shown. The bypass tube 114 passes through the lattice 100 and can be formally obtained by removing a cylinder from the structure of the lattice 100 (Boolean operation).

[0133] As can be seen in Figure 8, cylindrical portions 110, 112 represent suitable connecting portions to a conventional (cylindrical) tube. Connecting portions 110, 112 may be formed with lattice 100 by additive manufacturing and may be connected (eg, welded) to a conventional tube.

[0134] The transition regions 120, 122 can be mathematically defined using equation EQ1, provided that the appropriate coordinate z (local coordinate) is used.

[0135] Figure 9 shows a cross-sectional view of the transition between the lattice 100 and the inner ring 110. Figure 9 also shows the input F1 of heat exchange fluid to the lattice 100 and the output F2 of heat exchange fluid from the lattice 100. The transition zone 120 is easily understood in this figure. Figure 9 also shows the main axis AA of the heat exchanger.

[0136] 10 shows a modular heat exchanger according to an embodiment of the present invention, wherein a compact heat exchanger 200 comprises parallel connected sectors 201. If made of weldable material, the sectors 201 can be welded together to form the exchanger 200. Each sector 201 comprises a TPMS structure according to any of the above-described embodiments.

[0137] Figure 10 shows a preferred shape of the modular heat exchanger 200, which is annular. The area 202 near the main axis AA is the preferred location of the inlet and outlet on both sides of the heat exchanger 200, i.e. one side communicates with the cooling fluid and the heating fluid, and the other side is closed by the boundary of the pressure vessel.

[0138] Fig.11 The heat exchanger 200 of FIG. 10 is shown positioned below the catalytic bed 7 . Fig.11 This allows for an appreciation of the compactness of heat exchanger 200 as compared to conventional longitudinally extending baffle rod type exchangers.

Claims

1. A chemical reactor (10) comprising a catalytic bed (7) suitable for carrying out a catalytic reaction and comprising a heat exchanger (15) arranged to transfer heat from a first fluid (2) being an effluent of the catalytic bed to a second fluid (3) being a heating or cooling medium, wherein: The heat exchanger (15) comprises a heat exchange structure (1) manufactured by an additive manufacturing method, wherein the structure is a triple periodic minimal surface (TPMS) structure; The reactor comprises a set of boundary elements (4, 5, 12, 13) configured to distribute the first fluid and the second fluid to the TPMS structure or to collect the first fluid and the second fluid from the TPMS structure; The TPMS structure (1) has a first side and a second side; The first side defines a first path traversable by a heat exchange medium, The second side defines a second path traversable by a heat exchange medium, The first path and the second path are separated from each other, so that the medium passing through the TPMS structure (1) via the first path does not directly contact the medium in the second path, the set of boundary elements being configured such that the effluent is distributed to and collected from the first side only, and the heating or cooling medium is distributed to and collected from the second side only, The effluent is allowed to pass through the TPMS structure (1) via the first path, and the heating or cooling medium is allowed to pass through the structure via the second path, so as to obtain indirect heat transfer from the effluent to the cooling medium or from the heating medium to the effluent.

2. The reactor according to claim 1, wherein the heat exchanger comprises: at least one connecting portion having a suitable shape for connection with a collecting pipe or a distribution pipe; a transition region between the TPMS structure and the connecting portion; wherein the TPMS structure and the connecting portion are integrally formed into an integrally formed part by an additive manufacturing method; Wherein, in the transition area, the shape of the TPMS structure changes continuously to the shape of the connecting portion.

3. The reactor according to claim 2, wherein the transition zone extends from a starting position at z=0 to an end position at z=L according to a coordinate z along the axis of the heat exchanger; in, In the transition zone defined above, the shape of the heat exchanger is mathematically described by the following equation: G(x,y,z,S,k)*w1(z)+C(x,y,z,R,t)*w2(z)=0 (Equation 1) in: 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 part, S is a set of one or more parameters defining the shape of the TPMS structure, k is a parameter defining the thickness of the TPMS structure, R is a set of parameters that define the shape of the connection part, t is a parameter defining the thickness of the connecting part, x, y and z are spatial coordinates, w1(z) and w2(z) are weight functions satisfying the following conditions: i) w1(0) = 1 and w1(L) = 0; ii) w2(0) = 0 and w2(L) = 1; iii) For any z in the range 0 < z < L, 0 < w1(z) < 1 and 0 < w2(z) < 1.

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

5. The reactor according to claim 4, wherein the functions are linear, and preferably the functions are w1(z) = 1 – z / L and w2(z) = z / L.

6. The reactor according to any one of claims 2 to 5, wherein the heat exchanger includes a first connecting portion and a second connecting portion integrally formed with the TPMS structure for connecting to two coaxial tubes, and each connecting portion is connected to the heat exchanger through a corresponding transition region described by the equation (Equation 1) according to a local coordinate system.

7. The reactor according to any one of the preceding claims, wherein the set of boundary elements includes one or more surface elements (5), and the surface elements have a breathable pattern which is arranged to match the pattern of the input port or output port in the TPMS structure.

8. The reactor according to any one of the preceding claims, wherein the TPMS structure has an annular shape, and one side of the structure is radially penetrated, and the set of boundary elements includes an inner cylindrical shell and / or an outer cylindrical shell to distribute the effluent or the cooling medium to the radially penetrated side of the TPMS structure and / or collect the effluent or the cooling medium from the radially penetrated side of the TPMS structure.

9. The reactor according to claim 8, wherein the catalytic bed has an annular shape and is arranged around the TPMS structure, and the outer cylindrical shell serves as a boundary element of the TPMS structure and serves as a retaining wall for the catalyst particles forming the catalytic bed.

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

11. The reactor according to any one of the preceding claims, wherein both the catalytic bed and the TPMS structure have an annular shape, and the TMPS structure is coaxially arranged outside or inside the catalytic bed.

12. The reactor according to any one of the preceding claims, wherein: The TPMS structure has an annular shape, The TPMS structure can be axially penetrated by two fluids, The boundary elements include a first annular boundary element (9) placed above the structure and a second annular element (11) located below the structure to distribute and collect the fluids axially penetrating the structure.

13. A reactor according to any one of the preceding claims, wherein the TPMS structure has an annular shape and the set of boundary elements comprises a first element (12) extending over a portion of an inner or outer surface of the TPMS structure (1) and a second element (13) arranged around a different another portion of the inner or outer surface, so that a fluid can enter the TPMS structure (1) and leave the TPMS structure through different portions of the inner or outer surface.

14. The reactor according to any one of the preceding claims, wherein the TPMS structure is selected from the group consisting of Gyroid surfaces, Schwarz minimal surfaces, Neovius surfaces.

15. The reactor according to any of the preceding claims, wherein the heat exchanger including the TPMS structure, the boundary elements and the transition zone is made of Inconel, preferably Inconel 625 or Inconel 718 or a combination thereof.

16. A reactor according to any one of the preceding claims, wherein the additive manufacturing method is any of the following: powder bed fusion, such as any of direct metal laser sintering, electron beam melting, selective thermal sintering, selective laser melting and selective laser sintering; binder jetting; stereolithography; fused deposition modeling; digital light processing; multi-jet melting; polymer jetting; direct energy deposition.

17. A reactor according to any one of the preceding claims, wherein the reactor is configured for the synthesis of ammonia or methanol.

18. The reactor according to any one of the preceding claims, wherein the heat exchanger (15) is an inter-bed heat exchanger, or a preheater, or a steam superheater, or a combination thereof.

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

20. A method for designing and manufacturing a chemical reactor, comprising providing a heat exchanger located inside the reactor, wherein the heat exchanger includes a TPMS lattice structure, the TPMS lattice structure defining two independent heat exchange sides to be passed by a first heat exchange medium and a second heat exchange medium; the reactor also includes at least one connecting portion for connecting to a distribution pipe or a collecting pipe, the distribution pipe or collecting pipe for distributing the heat exchange medium to one heat exchange side of the heat exchanger or collecting the heat exchange medium from one heat exchange side of the heat exchanger, the method comprising modeling a transition zone for connecting between the TPMS lattice structure and the connecting portion according to the following equation EQ1: G(x,y,z,S,k)*w1(z)+C(x,y,z,R,t)*w2(z)=0 (Equation 1) 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 connection part, S is a set of one or more parameters defining the shape of the TPMS lattice structure, R is a set of one or more parameters defining the shape of the connection part, k is a parameter defining the thickness of the TPMS structure, t is a parameter defining the thickness of the connecting part, x, y, and z are spatial coordinates, assuming that the transition region starts at z = 0 and ends at z = L; w1(z) and w2(z) are weight functions satisfying the following conditions: w1(0) = 1 and w1(L) = 0; w2(0) = 0 and w2(L) = 1; for any z in the range 0 < z < L, 0 < w1(z) < 1 and 0 < w2(z) < 1.

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

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

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.

Images