Reactor heat exchanger unit

Abstract

The invention relates to a cylindrical reactor (1) having: channels (20, 20P, 20W) arranged in a fan shape, which are adjacent to one another in the radial circumferential direction and which extend in an axial direction (2) and can be permeated by a flow medium, wherein the reactor (1) is divided in the axial direction (2) into a central reaction section (30) and two outer adjacent heat-exchanger sections (33, 36), wherein a reaction of products from the material flow (53, 63) can take place in the reaction section (30), wherein the channels (20, 20W, 20P) are used as product channels (20P) either for material flows (53, 63) or as heat channels (20W) for heat flows (41, 42), wherein the heat flows (41, 42) in the heat channels (20W) can deliver the required energy (TH) for a reaction of the starting products in the material flow (53, 63) in the product channel (20P) in the reaction section (30).

Description

[0001] Reactor heat exchanger unit

[0002] The invention relates to a design of a ceramic reactor heat exchanger unit, in particular for hydrogen (H2) production.

[0003] In many areas of chemical process engineering, reactors, catalysts, heat exchangers and evaporators are used to split or synthesize substances.

[0004] The basic principle of such plants is based on the spatial separation of material flows and the transfer of thermal energy through the reactor structure. High temperatures, possibly elevated pressures, and the presence of a catalyst are often required to activate these processes.

[0005] Two examples of such chemical processes are steam reforming and ammonia splitting to produce hydrogen (H2) from hydrocarbons such as methane (CH4) and ammonia (NH3).

[0006] In steam reforming, hydrocarbons are broken down into methane, hydrogen, carbon monoxide, and carbon dioxide in a pre-reformer using steam at a temperature of 723K–773K and a pressure of 2.5 MPa–3 MPa. In a second step, the methane and steam are converted into carbon monoxide and hydrogen in a reformer at a temperature of 1073K–1173K and a pressure of 2.5 MPa–3 MPa over a nickel catalyst.

[0007] In ammonia cracking, ammonia is evaporated, heated and split into hydrogen and nitrogen in a reactor (cracker) at a temperature of 1193K and a pressure of > 0.1 MPa, preferably using a nickel catalyst.

[0008] For both of these endothermic processes, heat energy must be supplied through electrical heating or an integrated burner. Both examples are high-temperature processes, where efficiency depends on heat losses and heat management.

[0009] The corrosion attack by the starting media (hydrocarbons, water vapor, ammonia) and by the reaction products (hydrogen, carbon, nitrogen) poses a particular challenge to the corrosion resistance of the reactor materials used.

[0010] If the heat input is not achieved by electrical heating, heating by a burner results in the additional requirement of resistance to oxidising atmospheres.

[0011] Plants for ammonia cracking currently only exist in the capacity range < 100kg H2 / h and are constructed similarly to steam reformers.

[0012] Metal-based steam reforming plant concepts are typically operated with beds of extruded ceramic profiles (pellets) coated or vapor-deposited with the catalyst material. Due to the flow through such randomly arranged catalyst beds, the catalysts exhibit significant flow resistance and pressure losses due to the (design-intentional) turbulence.

[0013] The pellet beds are typically housed in externally heated tubes or internally heated double tubes. These designs exhibit an unfavorable ratio of the internal reactor surface to the external shell surface. The heat transfer from the heated tube to the pellet bed, which is required to maintain the endothermic fission reaction, is impaired due to the inherently small contact area.

[0014] It is therefore an object of the invention to solve the above-mentioned problem.

[0015] The object is achieved by a reactor with improved heat transfer according to claim 1. The subclaims list further advantageous measures which can be combined with one another as desired to achieve further advantages.

[0016] It shows

[0017] Figure 1 is a plan view of a reactor,

[0018] Figure 2 Flow channels of a reactor,

[0019] Figure 3 shows a division of the reactor into its

[0020] Function sections,

[0021] Figure 4 Flow pattern of a heat flow channel Figure 5 , 6 Flow patterns of the material flow

[0022] Figure 7 , 8 Arrangement of the heat flow and material flow channels,

[0023] Figure 9 a 2D top view of channels .

[0024] The figures and the description represent only exemplary embodiments of the invention.

[0025] The goal or main requirement is to achieve an adapted heat transfer performance with the highest possible efficiency and the lowest possible flow resistance or pressure loss.

[0026] Further essential requirements for the design and properties of a reactor arise from a structural and process-related perspective. High efficiency is promoted by a high thermal conductivity of the reactor material and a large internal heat exchanger surface (heat transfer) with the smallest possible external surface (heat loss through radiation and convection), as well as the requirement for the lowest possible heat loss through the effluent reaction products.

[0027] A 3D-printed ceramic reactor heat exchanger unit is proposed. The development progress of 3D printing with ceramic materials makes it possible to use their advantageous properties, particularly under high operating temperatures and under the influence of corrosive atmospheres, for components with specific geometric degrees of freedom. 3D printing offers process-specific geometric degrees of freedom that cannot be achieved using conventional manufacturing methods. 3D printing appears to be particularly advantageous for the production of a reactor / heat exchanger structure consisting of many flow channels. This makes it possible to realize large internal reactor surfaces, e.g. with round (as in a tube bundle heat exchanger) or rectangular (as in a plate heat exchanger) flow cross-sections. The defined flow guidance results in low flow resistance. a small pressure loss.

[0028] To increase heat transfer, turbulators can be implemented within the flow channels during the manufacturing process.

[0029] The manufacturing process offers the possibility of producing the reactor (i.e., the material flows) and the upstream heat exchanger (i.e., the heat flows) as an integrated unit. One of the main advantages of this design is the favorable ratio of the inner reactor and heat exchanger surface to the outer shell surface.

[0030] Figure 1 schematically shows a reactor 1. The reactor 1 has an axial direction 2. The reactor 1 has an outermost shell 13, in particular in the form of a tube.

[0031] The reactor 1 and thus the outermost shell 13 preferably have a cylindrical shape.

[0032] Other shapes, especially elongated shapes, are conceivable.

[0033] The largest part of the reactor 1 is formed by the fan-shaped flow channels 20 within the outermost shell 13, which are shown in more detail in Figure 2.

[0034] The flow channels 20 extend in the axial direction 2. Figure 2 shows a partial cross-section (perpendicular to the axial direction 2) of Figure 1 and shows very schematically the operating principle of a reactor 1 with integrated heat transfer.

[0035] Shown are flow channels 20 : 20W, 20P, ..., which also extend in radial direction 3 .

[0036] The flow channels 20 are preferably arranged next to one another in a fan shape, here around an inner discharge pipe 7.

[0037] A heat channel 20W transports heat in the axial direction 2 into the interior of the reactor 1 .

[0038] This heat is absorbed by the starting products in product channel 20P. Heat is also released by the final products.

[0039] The concept is based on a reactor 1 with radially arranged flow channels 20 which are plate-shaped or wedge-shaped.

[0040] The flow channels 20 carrying heat and product flow are preferably arranged alternately.

[0041] In the axial direction 2, the reactor 1 is divided into a reactor section 30 in the middle and two heat transfer sections 33, 36 to the left and right of the reactor section 30, i.e. at both ends (Figure 3).

[0042] The heat transfer sections 33, 36 are preferably of equal length.

[0043] The ratio of the size ( length ) of the reactor section 30 compared to one or more of the heat transfer sections 33 , 36 depends on the thermal design .

[0044] Figure 4 shows the flow pattern of a heat channel 20W carrying heat flow.

[0045] The reactor 1 has an inner feed pipe 4 and inner discharge pipes 7 : 7 ' , 7 '' surrounding the inner feed pipe 4 .

[0046] The inner feed pipe 4 preferably extends in the axial direction 2 and preferably over the entire length of the reactor 1.

[0047] The inner supply pipe 4 is preferably arranged centrally with respect to the cross section of all channels 20.

[0048] The inner discharge pipes 7', 7'' extend only along the respective heat transfer sections 33 (discharge pipe 7''), 36 (discharge pipe 7').

[0049] The tubes 4, 7 are preferably cylindrical. In a one-piece form of the reactor 1, especially when the reactor 1 is printed, the tubes 4, 7 are formed integrally with the other structures of the reactor 1 and are no longer recognizable separately, but only in their function.

[0050] This results in two flow channels (Fig. 4):

[0051] An inner supply channel 5 in the inner supply pipe 4 and inner discharge channels 8' (heat transfer section 36), 8'' (heat transfer section 33) between the inner supply pipe 4 and respective inner discharge pipes 7', 7'', which are thereby particularly annular.

[0052] The flow channels 20: 20W, 20P fulfill two tasks:

[0053] 1. to conduct a heat flow 41, 42 supplied from the outside (axially) and

[0054] 2. material flows 53, 63 supplied from the outside (axially) (Fig.

[0055] 5, 6) and product streams 54, 64 (Fig. 5, 6).

[0056] The inner feed pipe 4 and thus the inner feed channel 5 is thus preferably continuous over the length of the reactor 1.

[0057] The inner supply channel 5 can preferably also have an inner partition wall 14 in the center of the reactor section 30 to better redirect the heat flows 41, 42. The inner discharge pipes 7', 7'' and thus the inner discharge channels 8', 8'' each extend only over the length of the heat transfer sections 33, 36.

[0058] The reactor section 30 can optionally be divided into two parts or halves, each of which is separately supplied with the heat flows 41 and 42 from the inner feed pipe 4. This can preferably be ensured by an outer partition 12 in the reactor section 30 in the heat channel 20W, which extends as an inner partition 14, possibly also in the inner feed pipe 4.

[0059] From the inner supply channel 5, heat channels 20W for the heat flows 41, 42 extend preferably in a fan shape in the radial direction 3 in the circumferential direction around the inner supply channel 5.

[0060] In the heat channels 20W for heat transfer, the supplied heat flows 41, 42 run in the axial direction 2 in the inner feed pipe 4 from the outside to the inside to the reactor section 30 (Figure 3) and are introduced for the first time into the flow channels 20W in the radial direction 3 in the reactor section 30 (Figure 4).

[0061] For this purpose, opening(s) or slots are provided in the inner feed pipe 4 in the reactor section 30 such that the heat flow 41, 42 from the inner feed pipe 4 can only flow into the respective heat channels 20W in the reactor section 30.

[0062] The 20W heat channels are surrounded by an outer shell 10.

[0063] The purpose of this guidance of the incoming heat flows 41, 42 is to heat the reactor section 30 and, after flowing through, to use the residual heat for the preheating (Fig. 5, 6) of the material flows 53, 63.

[0064] In the heat channels 20W, channel walls 11: 11', 11'' are preferably present for the heat flow, which extend in the radial direction 3.

[0065] The channel walls 11 are present between reactor section 30 and respective heat transfer sections 33, 36 or at the axial height of the end of the inner discharge pipes 7. With the channel walls 11', 11'', which do not extend to the outer shell 10, gaps 6: 6', 6'' result between reactor section 30 and the heat transfer sections 33, 36.

[0066] Thus, the heat flow 41, 42 (Fig. 4) flows from the inner supply channel 5 into the heat channels 20W in the reactor section 30, first only in the radial direction 3 outwards and then through the gaps 6', 6'' into the respective heat transfer section 33, 36 in the radial direction 3 inwards.

[0067] Through opening(s) or slots in the inner discharge pipes 7', 7'', the outgoing heat flow 44, 46 flows back outwards in the axial direction 2 in the inner discharge channels 8', 8''.

[0068] The heat for the heat flow 41, 42 is supplied from both end faces of the reactor 1 in the directions (parallel to the axial direction 2) of the reactor 1.

[0069] Figure 5 shows the flow pattern of the material stream 53 in a product channel 20P, which runs in an axial direction 2.

[0070] On both end faces of the reactor 1 there are supply and discharge channels 16: 16', 16'', through which the material flows 53 and 63 (Fig. 6) are introduced into the reactor 1 from both sides, which represent annular channels between the two shells 10, 13.

[0071] The material stream 53, here preferably the ammonia, is first introduced into the heat transfer section 36 on one side through a feed channel 16', then flows through both the reactor 30 and the subsequent heat transfer section 33 and exits again on the other side through the discharge channel 16' as product stream 54, here preferably nitrogen and hydrogen.

[0072] At one end of the reactor 1, the cold starting product, preferably cold ammonia, is fed into the preferably outer annular channel 16', wherein the ammonia is heated in the heat transfer section 36 and then reacts in the reactor section 30 and is split here preferably into the products hydrogen and nitrogen.

[0073] The reactor 1 is surrounded on the outside by the completely closed outermost shell 13 .

[0074] The outer shell 10 has openings or slots in the region of the heat transfer sections 36 through which the material flow 53, in particular the ammonia, can flow into the product channels 20P in the region of the heat transfer section 36, here in Figure 5 into a product channel 20P.

[0075] The hot reaction products then flow further after the reaction section 30 as product stream 54 and then release their heat in the following and further heat transfer section 33.

[0076] The product channel 20P carrying the product stream 54 with the reaction products opens into the outer discharge channel 16 ' ' through which the product stream 54 flows out of the reactor 1 .

[0077] The product stream 54 then flows again through openings or slots in the outer shell 10 in the region of the heat transfer section 33 into the outer discharge channel 16 ' ' on the other end face and flows out on this end face of the reactor 1 as product stream 54.

[0078] Figure 6 shows the flow pattern of the material flow 63 in direction 42 .

[0079] A material stream 63 is introduced into the heat exchanger 33 at the outlet side of product stream 54 through an external feed channel 16, flows through the reactor 30 and the heat exchanger 36 and exits again through a channel on the other side.

[0080] At this end, cold ammonia is also supplied as material stream 63, which is heated in the other heat transfer section 33, i.e., among other things, by the warm product stream 54 mentioned in Fig. 5, and is then split into hydrogen and nitrogen in the reactor section 30.

[0081] A material flow 53, 63 is thus guided in both axial directions through the reactor heat exchanger sections, in the direction of the heat flow 41 and opposite thereto or in the direction of the heat flow 42 and opposite thereto.

[0082] The hot reaction products then give off their heat in the heat transfer sections 33, 36 to the other material flows 53, 63 and flow out on the other end side as product flow 54, 64.

[0083] The heat transfer performance is influenced by adjusting the structural length of the heat exchangers. From a design perspective, the length of the heat exchangers must be selected such that the thermally induced stresses resulting from the temperature difference between the incoming "cold" process gas and the outgoing "hot" reaction products, as well as the residual heat from the reactor, do not exceed the strength limit of the ceramic material. Furthermore, the heat exchanger surface must be dimensioned such that the outgoing reaction gases have the temperature level required for a potential post-treatment step (filter stage).

[0084] Figure 7 shows a section and plan view along the line VI I-VI I in Figures 4 , 5 .

[0085] A heat flow 46 is guided through the heat transfer section 33 via a heat channel 20W after it has passed through the reactor section 30 and has been cooled there.

[0086] The flow is guided in such a way that the heat flow 42 introduced axially through the inner feed pipe 4 is guided inside the reactor section 30.

[0087] Since the heat channels 20W in the reactor section 30 are spatially connected radially outwardly with the two heat transfer sections 33, 36, the heat flow is first guided radially outward and then counter to the (axial) inflow direction into the heat transfer section 33.

[0088] Next to the heat flow channels 20W are the product channels 20P carrying material flow 63 and material flow 54. Product flow 54 flows axially through reactor section 30 as material flow 53.

[0089] The material flows 53, 63 are each introduced into the heat exchanger at the front via the outer ring channels, the supply channels 16', 16''.

[0090] When flowing through the heat transfer sections 33, 36, the residual heat from the reactor section 30 as well as the heat of the reaction products of the respective counterflow is transferred to the inflowing medium.

[0091] Subsequently, the preheated material streams 53, 63 flow through the reactor section 30, in which the heat required for the endothermic reaction is supplied and the decomposition reaction takes place on the catalytically coated surface of the reactor.

[0092] Figure 8 shows a section along the line VIII-VIII in Figures 4, 5.

[0093] In the inner supply channel 5, the heat flow 41 flows, which then flows into the reactor section 30 into the heat channel 20W.

[0094] There it heats the reaction products and flows through the gap 6' back into the heat transfer section 36.

[0095] Material stream 53 used this residual heat, among other things, to preheat itself.

[0096] The substance then flows through the reaction section 30.

[0097] Figure 9 shows a two-dimensional view of the flow channels 20. In the center is a product channel 20P, in which the material stream 53 flows from right to left. The starting materials in this product channel 20P are initially "cold," i.e., they have a low temperature T c on .

[0098] Already in the heat transfer section 36 of the product channel 20, the material flow 53 is preheated by the cooled outgoing heat flow 44 in the adjacent heat flow channel 20W.

[0099] In the reactor section 30, the material flow 53 is heated to reaction temperature T by the hot heat flow 44. H brought .

[0100] After the reactor section 30, the product stream 54 then cools down and has a lower temperature T w because no further active heating takes place. This lower temperature Tw However, this is sufficient to preheat the "cold", counter-flowing product stream 63 in the adjacent product channel 20P, which flows in the direction of the reaction section 30.

[0101] Also shown is the heat flow with the reaction temperature T H through the inner feed pipe 4 , which only flows out in the reaction section 30 in the radial direction 3 .

[0102] With regard to the shape of the flow channels 20, the claim includes not only the plate-shaped geometries shown but also non-planar geometries, in particular wave-shaped flow channels and the integration of turbulators.

[0103] Silicon-infiltrated silicon carbide (SiSiC) is the preferred material base. Other oxide and non-oxide ceramic materials that can be manufactured gas-tight using 3D printing are also possible.

[0104] In addition to the essential property of processability through a 3D printing process, the material must meet a number of requirements with regard to its mechanical, thermal and chemical properties.

[0105] In addition to the strength requirements in the temperature range from RT to 1373K due to the high stationary and unsteady thermal gradients, high oxidation and corrosion resistance, high thermal conductivity and high thermal shock resistance are particularly required.

[0106] Since nickel (Ni) is a preferred and economically viable catalyst material for the production of hydrogen (H2) by splitting, for example, ammonia (NH3), the ceramic material should be able to be coated or wetted with nickel.

[0107] With regard to chemical resistance, ammonia splitting requires high corrosion resistance against the reactant medium ammonia and against the reaction products, in particular against hydrogen and nitrogen in the temperature range of 573K - 1223K and pressures of 0.1MPa to 50MPa.

[0108] For steam reforming, a high corrosion resistance against hydrocarbons, for example methane, and against the reaction products, in particular against hydrogen, carbon and water vapor in the temperature range of 293K - 1123K and pressures of 0.1 MPa to 40MPa is required.

[0109] In order to ensure a material separation of the heat and material flows, the ceramic material must be able to be manufactured in a gas-tight manner.

[0110] Silicon-infiltrated silicon carbide (SiSiC) preferably meets these requirements. Provided that other oxide or non-oxide ceramic materials can be produced gas-tight using 3D printing in the future, they represent a potential alternative material.

[0111] Plants for ammonia cracking currently only exist in the capacity range < 100 kg H2 / h and, as far as is known, are constructed similarly to steam reformers.

[0112] With a 3D printing design of a ceramic reactor-heat exchanger unit, the efficiency can be increased by integrating the reactor and heat exchanger into a thermally insulated and heat flow-optimized system. Ceramic 3D printing makes it possible to utilize the advantageous properties of ceramics, particularly at high operating temperatures and under the influence of corrosive atmospheres, for components with specific geometric degrees of freedom. In the case of ammonia cracking with Ni catalyst and high temperatures, initial test results indicate high corrosion of the metallic reactor materials, caused by the hydrogen and nitrogen atmosphere. The use of corrosion- and high-temperature-resistant ceramic materials offers the potential for significant increases in component service life.

[0113] The main advantages of the proposed design are high efficiency through integration of heat exchanger and reactor and through reduction of heat losses due to small external surface, high power density and high heat transfer per component volume, low pressure loss due to defined flow guidance, rapid heating behavior due to an integrated, compact design and reduced thermal losses and thus a short switch-on delay (enables use in cyclically operated systems), low weight when using SiSiC (enables use for non-stationary applications), high corrosion resistance against a variety of media, in particular against the influence of water vapor, ammonia, hydrogen and nitrogen and the possibility of a modular concept with which scaling for a broad power spectrum is feasible.

Claims

Patent claims 1. Reactor (1), which is in particular cylindrical or cylinder-shaped, comprising: fan-shaped channels (20, 20P, 20W) which are adjacent to one another in the radial circumferential direction and which extend in an axial direction (2), in particular that of the cylinder shape, and through which flow can pass, wherein the reactor (1) is divided in the axial direction (2) into a central reaction section (30) and two outer adjacent heat transfer sections (33, 36), in particular two directly adjacent, outer adjacent heat transfer sections (33, 36), wherein a reaction of products of the material flow (53, 63) can take place in the reaction section (30), wherein the channels (20, 20W, 20P) are used as product channels (20P) either for material flows (53, 63) or for heat channels (20W) for heat flows (41, 42). wherein the heat flows (41, 42) in the heat channels (20W) provide the necessary energy (T H) for a reaction of starting products in the material stream (53, 63) in the product channel (20P) in the reaction section (30).

2. Reactor according to claim 1, wherein the product channels (20P) and heat channels (20W) are arranged relative to one another in such a way that the residual heat in the heat transfer sections (30, 33) is used to preheat adjacent material flows (53, 63) can be used in adjacent channels (20). Reactor according to one or both of claims 1 or 2, which has a particularly central, continuous inner feed pipe (4) for heat flows (41, 42), which forms an inner feed channel (5), which (4) is connected in the reaction section (30) to the radially (3) extending heat channels (20W) in such a way that the heat flows (41, 42) can only flow into the channels (20W) in the reaction section (30). Reactor according to one or more of claims 1, 2 or 3, in which in the reaction section (30) in the heat channels (20W) there is an outer, radially extending partition wall (12) which further divides the reaction section (30). Reactor according to one or more of claims 1, 2, 3 or 4, wherein the inner feed pipe (4) has an inner partition wall (14) in the reaction section (30) which (14) fluidically separates the inner feed pipe (4).Reactor according to one or more of claims 1, 2, 3, 4 or 5, wherein the product channels (20P) run continuously in the axial direction (2), wherein the heat channels (20W) are designed such that the heat flows (41, 42) can be directed such that they can run in cross-flow to the material flows (53, 63). Reactor according to one or more of claims 1, 2, 3, 4 or 6, in which the reactor (1) is delimited on the outside by an outermost shell (13) and has an inner outer shell (10), so that outer supply and discharge channels (16, 16', 16'') are formed in the heat transfer sections (30, 33). Reactor according to claim 7, which has outer supply and discharge channels (16, 16', 16'') extending in the axial direction (2), which are in particular annular, which are also connected to the channels (20), and through which the product streams (54, 64) can flow out of the heat transfer sections (33, 36) and through which the material streams (53, 63) can flow into the heat transfer sections (33, 36).Reactor according to one or more of claims 1, 2, 3, 4, 5, 6, 7 or 8, in which axially extending inner discharge pipes (7', 7") surround the inner feed pipe (4) in the region of the heat transfer sections (33, 36), thus forming inner, in particular annular, discharge channels (8', 8") for the outflowing heat flows (44, 46). Reactor according to one or more of the preceding claims, in which inner, axially extending discharge pipes (7', 7") and a feed pipe (4) are connected to (4, 7) radially (3) extending flow channels (20W, 20P). Reactor according to one or more of the preceding claims, in which the inner channels (5, 8) are formed by tubes (4, 7). Reactor according to one or more of the preceding claims, in which the outer shells (10, 13) are formed by tubes. Reactor according to one or more of the preceding claims, in which a wall (11) is present in the radial direction in the heat channel (20W), which wall forms a gap (6) with the outer shell (10). Reactor according to one or more of the preceding claims, which is of ceramic or metalloceramic construction, in particular is completely ceramic or metalloceramic. Reactor according to one or more of the preceding claims, which has at least one, in particular only one, catalyst on the channel walls in the product channels (20P) in the reaction section (30).Method for operating a reactor (1), in particular according to one or more of the preceding claims, in which a material stream (53) is introduced into a product channel on one side of the reactor (1) and is heated as it flows further through and in a re-. action section (30) is allowed to react to form the starting products, with a further material stream (63) flowing parallel on the other side of the reactor (1) and in the directly adjacent product channel. . Process according to claim 16, wherein the product channels (20P) run continuously in the axial direction (2), while the heat streams (41, 42) in the heat channels (20W) are deflected so that they run in crossflow to the material streams (53, 63). . Process according to one or both of claims 16 or 17, wherein heat streams (41, 42) are introduced into an inner feed pipe (4) from both sides of the reactor (1). . Method according to one or more of the preceding claims 16, 17 or 18, wherein the product channels (20P) run continuously in the axial direction (2), wherein the heat channels (20W) are designed such that the heat flows (41, 42) are directed such that they run in cross-flow to the material flows (53, 63).

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