Plate heat exchanger

Abstract

The invention relates to a plate heat exchanger and to a process engineering system comprising the plate heat exchanger.

Description

[0001] Plate heat exchanger

[0002] Subject matter of the invention

[0003] The invention relates to a plate heat exchanger and a process engineering plant comprising the plate heat exchanger.

[0004] Background of the invention

[0005] A heat exchanger is a device or system used to transfer thermal energy from a source to a destination. This transfer can occur between two media without them coming into direct contact, or directly from a heating element to a surrounding fluid. Heat exchangers are available in many shapes and sizes and are found in a wide variety of applications, from heating, ventilation, and air conditioning (HVAC) systems to industrial processes.

[0006] In indirect heat transfer, the media between which heat is transferred are separated by a solid wall to prevent mixing. Heat transfer occurs through conduction across the separating material. Typical examples include plate heat exchangers, shell and tube heat exchangers, and finned tube heat exchangers.

[0007] In direct heat transfer, heat is transferred directly from a heating element (such as a heating coil or heating rod) to a surrounding fluid (such as a gas, a liquid, especially water, or another fluid). This transfer occurs through convection and partly through radiation. Examples include water heaters, radiators, and air heaters.

[0008] Heat exchangers are commonly used in the chemical, pharmaceutical, steel, semiconductor, solar, and environmental industries, as well as many other sectors. They are frequently used to heat a fluid using hot, pressurized steam. However, this process has significant drawbacks, particularly in applications involving the heating of corrosive fluids.

[0009] Even with proper system design, corrosive fluids in particular can place significant stress on the heat exchanger material over time. The use of steam can exacerbate this, especially if the steam also contains impurities that can have a corrosive effect. Steam is generally used at higher temperatures, meaning that the temperature difference between the corrosive fluid and the steam is typically high. This can lead to increased thermal stress on the heat exchanger material, which in turn can shorten its service life. Furthermore, the need to use materials that are resistant to both the corrosive fluid and the high temperatures and pressures of the steam can limit the material selection and thus increase costs.

[0010] Furthermore, precise temperature control can be difficult when using steam or hot water as the heating fluid. This can be particularly problematic if the corrosive fluid cannot tolerate high temperatures, as this could lead to damage or reduced efficiency of the processes the fluid undergoes. The use of steam also necessitates appropriate safety precautions, as steam poses a particular hazard at high pressures. If the heat exchanger is damaged, especially by corrosion, this can lead to leaks or, in the worst case, equipment failure. The use of steam also carries the risk of pressure surges within the system. These can quickly lead to component breakage, particularly with brittle ceramic materials, and thus to unit failure.

[0011] TASK

[0012] Against this background, the object of the present invention was therefore to provide a heat transfer device that is easy to construct, enables heating with the highest possible efficiency and safety, is versatile and also offers significantly greater flexibility and service life.

[0013] Description of the invention

[0014] This problem is solved according to the invention by a plate heat exchanger for heating and / or cooling a preferably corrosive fluid comprising

[0015] ■ two or more plates, o which are in a stacked arrangement so that they form a stack of plates, o wherein each plate of the two or more plates has two opposite flat sides,

[0016] ■ a housing structure that holds the two or more plates in the stacked arrangement, ■ a flow space arranged between two flat sides of two plates of the two or more plates with a flow obstruction,

[0017] ■ an inlet opening for feeding the preferably corrosive fluid into the flow chamber of the plate heat exchanger, and

[0018] ■ an outlet opening for draining the preferably corrosive fluid from the flow chamber of the plate heat exchanger, wherein

[0019] ■ at least one of the two or more plates of the plate heat exchanger can be heated or cooled directly or indirectly using electricity.

[0020] The heat exchanger according to the invention enables direct heat transfer from one of the plates (hereinafter also referred to as "heat exchanger plates") to a preferably corrosive fluid, without the need for a second fluid for heat exchange. The fluids can preferably be either gases or liquids.

[0021] A plate is a body in which two dimensions (length and width) are significantly larger than the third dimension (thickness). The flat surfaces extending along the length and width dimensions constitute the largest surfaces of the plate and, in the context of a plate heat exchanger, are the primary surfaces for interaction with the preferably corrosive fluid.

[0022] Apart from the structurally provided flow obstruction, which serves to control the fluid flow, the plates are preferably completely flat to ensure efficient heat transfer and a uniform flow distribution.

[0023] The flow space (also called the "intermediate space") located between the two flat surfaces of two plates defines the space in which the fluid can flow and heat is transferred from the plate(s) to the fluid. The flow space is preferably the entire space located between the two flat surfaces of two plates. Naturally, a plate heat exchanger preferably comprises several such flow spaces, as it typically has significantly more than two plates. For the sake of simplicity, the term "flow space" will be used hereafter, even though several such intermediate spaces may be present.

[0024] A flow restriction within a heat exchanger is an element designed to influence the flow of a fluid through the flow space between heat exchanger plates. The restriction can take various forms, including but not limited to fins, ribs, baffles, or guide structures. The primary function of a flow restriction is to alter, branch, or lengthen the fluid's flow paths to increase the fluid's contact time with the heat-transferring surfaces, induce turbulence, or ensure a specific flow path, thereby improving heat exchange between the fluid and the plate surfaces. Flow restrictions are crucial for increasing the efficiency of the heat transfer rate and can be optimized in shape to direct the flowing fluid as desired without causing excessive pressure loss.The flow obstruction, or at least one or more of its elements, is / are preferably connected to one or more of the two or more plates by a material, form, or force-fit connection; a material-fit connection is particularly preferred. A monolithic design of the flow obstruction and plate(s) is particularly preferred. The flow obstruction, or one or more of its elements, can be manufactured, for example, from a block by subtractive manufacturing. Alternatively, the flow obstruction (or one or more of its elements) can also be obtained by pressing a mass in a mold. Monolithic designs of the plate with the obstruction can also be manufactured by additive or subtractive manufacturing or by pressing.

[0025] Advantageously, the flow space is limited by external side walls, for example, by the outer side walls of a housing structure. The plate heat exchanger is preferably constructed to be fluid-tight.

[0026] "Directly or indirectly electrically heated or cooled" refers to the property of a plate or its components (including connected components such as connected heating elements) that their thermal states—that is, the temperature of their components—can be manipulated by electrical energy either directly or indirectly, for example, by induction. This involves a conversion of electrical energy into heat energy.

[0027] Direct electrical heating or cooling means that electrical energy is converted directly into heat or cold, preferably within one of the plates or one of their components. Examples include heating elements such as resistance heaters, which are embedded in or attached to the plate and heat the fluid via the Joule effect (current flow through an electrical resistance generates heat), or Peltier elements, which cool directly via the thermoelectric effect. Preferably, the heating or cooling element is in direct contact with the plate to be heated or cooled, or by means of a thermally conductive layer, for example, a graphite foil, a thermal paste, or a thermal oil. The thermally conductive layer preferably has a thermal conductivity > 1 W / m K, more preferably > 10 W / m K, and most preferably > 50 W / m K.

[0028] Indirect electrical heating or cooling uses electrical energy to generate or remove heat elsewhere. An example of indirect heating is electromagnetic induction heating, where heat is generated in the plate by means of induced eddy currents.

[0029] Direct or indirect electrical heating or cooling also includes heating or cooling elements directly or indirectly connected to the plate, which heat and / or cool at least one of the two or more plates.

[0030] The combination of the terms "heatable or coolable" describes the possibility of temperature control in both directions—both heating and cooling—which gives the device flexible adaptability to different operating conditions and process requirements. For this purpose, the device can have one or more heating and / or cooling elements with which at least one of the two or more plates of the plate heat exchanger is heated and / or cooled during its operation.

[0031] In the case of a heating element, it can have different technical designs. Electric heating elements are particularly preferred, such as:

[0032] • Resistance heating elements (e.g. heating wires, heating coils),

[0033] • Surface heaters (e.g. heating films or flexible heating mats),

[0034] • Heating cartridges or embedded heating elements,

[0035] • Induction heater (e.g. inductive heating of a thermally conductive component, in particular a thermally conductive component with a thermal conductivity > 1 W / m K, preferably > 10 W / m K and most preferably > 50 W / m K, such as a metallic component),

[0036] • Dielectric, radiant or high-frequency heating.

[0037] The thickness of the plates in a plate heat exchanger is a crucial parameter that influences both mechanical stability and thermal efficiency. For ceramic or carbon materials, the plate thickness is preferably in the range of 1 mm to 20 mm to ensure an optimal balance between strength and heat transfer performance. A plate thickness of 3 mm to 10 mm is particularly preferred, as this range offers high thermal conductivity combined with sufficient mechanical strength. For applications with particularly high mechanical demands, such as in large-scale industrial or high-pressure chemical processes, the plate thickness can more preferably be 8 mm to 16 mm. In the case of metallic materials used as plate material, the thickness can be significantly lower, for example, in the range of 0.1 mm to 10 mm, preferably 0.1 mm to 5 mm.

[0038] The housing structure serves to hold the two or more plates in a stacked, preferably parallel arrangement and to at least partially, preferably completely surround them, thereby creating together with the plates an arrangement in which the fluid can flow, preferably completely sealed to the outside.

[0039] Preferably, the heat exchanger is corrosion-resistant, i.e., the component sections that come into contact with the fluid are made of a material that is resistant to acids with a pK s< 7, preferably < 2, even more preferably < 0 and most preferably < -2 and bases with a pKb < 7, preferably < 2, even more preferably < 0 and most preferably < -2, is stable under standard conditions (STP, IIIPAC), i.e., it shows no significant decomposition, in particular no material loss; or reduction in performance. Particularly preferably, the material used is stable even at temperatures up to 80°C, preferably 150°C or even 200°C.

[0040] Exemplary materials that can be used, particularly as sheet material, are selected from the group consisting of: carbon materials, preferably graphite; ceramics, preferably carbides, oxides or nitrides such as silicon carbide, aluminum oxide, mullite, titanium nitride or aluminum nitride; plastics, preferably PTFE, PVDF, PFA, PEEK; glass, glass-ceramics, enamel, niobium, tantalum, stainless steel and combinations of the aforementioned. Carbon materials and ceramics are particularly preferred.

[0041] However, materials that are essentially free of fluoropolymers, i.e., have a fluoropolymer content of less than 1% by weight, are also preferred. This allows for a particularly advantageous design from an environmental perspective.

[0042] Particularly preferred are carbon materials, especially resin-impregnated carbon materials; and silicon carbide. Composite materials, such as composites of carbon materials and fiber materials and / or fluoropolymers, or coated materials, for example, metals with a fluoropolymer coating, can also be used advantageously. Metals (e.g., steel) with a coating or cladding of a special metal such as tantalum or niobium can also be used advantageously. Composite materials comprising carbon materials and fluoropolymers are particularly preferred due to their excellent density and stability.

[0043] The materials are particularly preferred for their stability against strong acids such as HCl, HNO3, HF, H3PO4, H2SO4 and / or strong alkalis such as NaOH, especially at temperatures up to 150°C or even 200°C.

[0044] Stability against hydrochloric acid with an HCI concentration of 35% at a temperature of 110 °C, preferably 150 °C, even more preferably 180 °C or 200 °C, is particularly advantageous.

[0045] Preferably, the heat exchanger is pressure-stable in a range of -1 to 20 bar, more preferably e to 15 bar, and most preferably 1 to 11 bar or 1 to 10 bar.

[0046] Preferably, the maximum working pressure ASME / PED is > 3 bar, more preferably > 5 bar and most preferably > 6 or > 6.5 bar.

[0047] In a preferred embodiment of the invention, the plate heat exchanger is a heat exchanger. A plate heat exchanger is a heat exchanger used to transfer heat between two fluids without them coming into direct contact. In the heat exchanger, two or more fluids are alternately passed through the spaces between the plates, so that one fluid flows through every other space and the other fluid flows through the remaining spaces. In this case, the plate heat exchanger is preferably designed to operate according to the counterflow principle, thereby ensuring maximum thermal efficiency through the continuous heat exchange between the opposing media. In another preferred embodiment of the invention, the plate heat exchanger is not a heat exchanger.

[0048] For the supply and discharge of the preferably corrosive fluids, such a heat exchanger has several inlet and outlet openings. Due to the high turbulence in the flow through the narrow gaps and the large surface area of ​​the plates available for heat exchange, the heat transfer between the fluids in a plate heat exchanger is very efficient. In this embodiment, the invention can enable heat exchange between the media in addition to indirect or direct electrical heating or cooling. Alternatively, heat transfer (partial or complete) can also occur from one of the two or more plates, which can be heated or cooled electrically, directly or indirectly, to a first fluid, which in turn then heats or cools a second fluid. In the heat exchanger embodiments, the electrical heating or cooling according to the invention is thus preferably combined with heat transfer between two or more fluids.

[0049] Preferably, a seal is inserted between each of the two or more plates, preferably a seal comprising PTFE and / or graphite. This seals the system and prevents the escape of the preferably corrosive fluid, especially at higher pressures. Alternatively and / or additionally, the plates can be welded together (especially in metallic versions) or bonded together (especially in carbon and composite material versions).

[0050] The present invention offers significant advantages over traditionally used heat exchangers. Electric heating enables higher efficiency compared to conventional methods by allowing for more precise, i.e., more spatially and temporally directed and faster, heat transfer. Losses from the use of fossil fuels and an additional heating fluid are avoided. More efficient use of the heat transfer surfaces leads to a reduction in the required size of the heat exchanger, resulting in cost and space savings.

[0051] The possibility of continuous heating and rapid start-up and shut-down contributes to process flexibility and can reduce operating costs. Compared to the use of heat transfer media such as steam, which are introduced into the system at high temperature and lose heat during transit, electric heating enables a constant heat transfer rate, if desired, regardless of the position within the heat exchanger. Furthermore, electric heating allows for the use of individual heating sources for different plates in the system, ensuring a uniform and defined temperature distribution, which optimizes heat transfer and enables a more homogeneous heat flow.

[0052] Furthermore, by eliminating steam as a heat transfer medium, the aforementioned problems regarding material selection, process reliability, and the service life of a corresponding system can be solved.

[0053] In a preferred embodiment of the invention, the inlet opening for supplying the preferably corrosive fluid and / or the outlet opening for draining the preferably corrosive fluid from the flow chamber is formed by a through-opening, like a hole, extending through the flat sides of one of the two or more plates.

[0054] Integrating the inlet and / or outlet openings directly into the flat sides of one of the two or more plates offers several significant advantages. Firstly, this design promotes a compact and stable structure, as separate connectors or fittings that would otherwise need to be attached externally to the housing structure are eliminated. This can reduce both material costs and assembly effort, and leads to increased structural integrity of the heat exchanger.

[0055] Furthermore, this through-hole, integrated directly into the plate, allows for improved flow dynamics of the preferably corrosive fluid. Since disruptive flow interruptions and dead spaces, which often occur at the transitions between external connections and the internal flow chamber, are reduced, optimized heat transfer efficiency is achieved.

[0056] Directly routing the inlet and / or outlet openings through the flat surfaces of the plates can also contribute to a more homogeneous heat distribution. This allows the corrosive fluid to flow through the plate heat exchanger at a more uniform temperature, resulting in higher thermal efficiency of the system.

[0057] In a preferred embodiment, the flow obstruction is designed in such a way that it divides a preferably corrosive fluid guided through the flow space into two or more, at least sectionally, separate material flows.

[0058] This type of flow restriction design results in a targeted division of the fluid flow, thus contributing to improved heat distribution and heat transfer by optimizing the fluid flow across the heat exchanger plates. This targeted flow guidance can increase the contact time of the fluid with the heat-transferring surfaces and thereby enhance the thermal performance of the plate heat exchanger.

[0059] Distributing the preferably corrosive fluid into separate flows can also lead to more efficient utilization of the available flow volume by minimizing pressure drop and achieving a more uniform fluid distribution. Such a design can also offer advantages in avoiding temperature spikes (hotspots) and minimizing corrosion, as a uniform temperature distribution throughout the flow chamber is ensured. In particular, combined with the ability of the plate(s) as heat exchanger to transfer heat more quickly and in a more spatially and temporally focused manner, highly customized and optimized heat transfer scenarios can be implemented, enabling the heat exchanger to be used extensively in demanding industrial environments.

[0060] In a preferred embodiment, the flow obstruction is designed such that it allows at least partial, preferably complete, immersion in a preferably corrosive fluid. Preferably, the flow element comprises one or more elements that are completely accessible to the fluid from all sides, for example, ribs or pins that can be surrounded by the fluid from all sides.

[0061] The possibility of complete immersion ensures that all areas of the surfaces are uniformly reached by the preferably corrosive fluid, promoting a homogeneous temperature distribution and thus uniform heat transfer. This continuous and uniform exposure of the surfaces to the fluid reduces the risk of temperature spikes (hotspots) and can extend the service life of the plates by preventing uneven stress.

[0062] Complete fluid circulation can also help minimize deposits and contaminants on the plate surfaces, as the continuous flow of fluid can lead to a self-cleaning effect. This simplifies maintenance and ensures that the heat exchanger's performance is maintained even during long-term operation in corrosive environments.

[0063] In a preferred embodiment, the flow obstruction is designed such that it is at least partially in the form of several ribs, between which channels are formed in which the preferably corrosive fluid can be guided through the flow space.

[0064] The specific arrangement of the ribs, which act as flow restrictors, ensures the formation of defined flow channels through which the preferably corrosive fluid can be effectively guided. These ribs contribute to defining the structure of the flow chamber and directing the flow of the preferably corrosive fluid, minimizing the formation of dead spaces and optimizing heat transfer across the entire surface of the plates. The ribs may be interrupted, i.e., not continuous. The rib design also enhances the mechanical stability of the plates, which is particularly important in corrosive applications, as it ensures the longevity and reliability of the heat exchanger even under demanding conditions.

[0065] In a preferred embodiment, the ribs are designed to form two or more flow channels, the ribs forming channel walls which in turn completely or partially define the channel grooves of the flow channels.

[0066] By guiding the fluid in the channels between the fins, the heat exchanger can operate even more efficiently.

[0067] The local width Bb of the bottom of the channel troughs of the flow channel and the local width B sp of a plateau of a channel rib of a flow channel on the side facing away from the bottom of the channel of the flow channel - in each case measured perpendicular to the local direction of flow of the flow channel - a ratio Bb:B can be determined. sp exhibiting ratios of 10:3, such that the relationship 10:15 < Bb:B sp < 10:2 is fulfilled. These conditions are particularly preferred when the floor and the channel wall formed by the rib are at a 90° angle to each other.

[0068] The local latitude B S b the base of the channel bridge of the flow channel at the level of the bottom of the channel trough of the flow channel and the local width B sp of the plateau of the channel rib of the flow channel on the side facing away from the bottom of the channel trough of the flow channel - each measured perpendicular to the local direction of flow of the flow channel - a ratio B S b:B sp in the range of 1:1 to 4:2, preferably 4:3, such that the relationship 4:2 < B S b:B sp < 1 :1 is fulfilled.

[0069] Preferably, the channel walls of a flow channel enclose an angle α with the normal to the bottom of the channel trough of the flow channel, which is in the range of more than 0° and less than 60°, preferably less than 30°, preferably at 15°± 5°, such that the relationship 0° < a < 60° or preferably the relationship a = 15°± 5° is satisfied.

[0070] The local width Bb of the channel bed of the flow channel – measured perpendicular to the local direction of flow of the flow channel – and the depth t of the channel bed of the flow channel – measured perpendicular to the channel bed of the flow channel – have a ratio Bbl in the range of 10:10 to 10:4, preferably 10:4, such that the relationship 10:20 < Bbl < 10:4 is satisfied. These ratios are particularly preferred when the bed and the channel wall formed by the rib are at a 90° angle to each other.

[0071] In a further preferred embodiment, the flow channels can have different geometries depending on their proximity to the inlet and outlet openings. In a preferred embodiment, the plate heat exchanger is characterized in that the channels formed between the fins of the flow restrictor run parallel, at least in sections.

[0072] This parallel arrangement of the channels ensures a uniform flow of the corrosive fluid through the flow chamber and contributes to efficient and homogeneous heat transfer. The parallel routing of the flow channels minimizes the risk of dead zones, which is particularly advantageous with regard to the durability and efficiency of the heat exchanger.

[0073] Furthermore, the parallel alignment of the channels can lead to simplified manufacturing and increased reproducibility of flow characteristics across different heat exchangers. This not only facilitates the maintenance and cleaning of the heat exchanger components but also enables more precise design for specific applications, particularly in corrosive environments.

[0074] For direct or indirect electrical heating or cooling, the plate heat exchanger can have a heating or cooling element, such as a resistance heater or an induction heater, which is partially, preferably completely, arranged in or outside one of the two or more plates.

[0075] In a particularly preferred embodiment of the plate heat exchanger, a heating or cooling element, preferably an electric heating or cooling element, is arranged at least partially, preferably completely, in or on at least one of the two or more plates of the plate heat exchanger.

[0076] In another preferred embodiment of the plate heat exchanger, at least one electrical heating or cooling element is arranged at least partially, preferably completely, directly or indirectly (for example, via a thermally conductive film or paste) in contact with at least one of the two or more plates, i.e., directly or indirectly connected to it. Such a connection can be, for example, form-fit, material-fit, or force-fit.

[0077] The two or more plates can have different functions. For example, one plate can be solely a heating plate, while another solely conducts the preferably corrosive fluid. However, the functions can also be combined in such a plate; that is, the plate conducts the fluid and simultaneously serves for heating because a heating element is at least partially arranged in or on the plate. For example, such a plate can be made of graphite and have the media guide on one flat side, while on the opposite side, strands for inductive heating are provided, preferably embedded.

[0078] A heating element is an electrically driven resistor used to convert electrical energy into heat energy. Heating elements come in various shapes and designs, depending on their application, including but not limited to: wire coils, metal foils, ceramic or quartz bodies, or PTC (Positive Temperature Coefficient) elements.

[0079] The heating element serves to selectively influence the temperature of the preferably corrosive fluid passed through the stack of plates, which can lead to an increase or maintenance of the desired operating temperature.

[0080] The heating element is preferably designed to apply locally varying heating power, allowing the fluid passing through the plate stack to be heated to different degrees at various points. This not only enables precise adjustment of the temperature distribution along the plate stack but also facilitates the implementation of a counterflow principle. At the same time, this flexibility allows deviations from this principle to meet specific thermal requirements or process conditions, for example, through targeted local temperature increases or decreases.

[0081] In a preferred embodiment, the plate heat exchanger has a heating element comprising a planar electrical conductor, for example made of metal or graphite, and one or more insulated electrical conductors, such as a stranded wire, which is or are able to generate an alternating magnetic field in order to generate heat in the planar electrical conductor.

[0082] This specific heating element enables efficient and uniform heat generation within the plate, which directly contributes to regulating the temperature of the preferably corrosive fluid. The use of an alternating magnetic field to heat the flat electrical conductor represents an inductive heating method characterized by high energy efficiency, rapid response time, and precise local control. This technology allows for accurate and controlled heat distribution within the plate heat exchanger without direct electrical contact with the fluid, thus increasing system safety, particularly in corrosive environments.

[0083] In a preferred embodiment, the plate heat exchanger has a heating element in which the insulated electrical conductor described above runs in a meandering shape, at least in sections.

[0084] The meandering pattern of the insulated electrical conductor enables a uniform propagation of the alternating magnetic field across the entire surface of the conductor. This arrangement contributes to efficient heat generation and ensures a homogeneous temperature distribution in the preferably corrosive fluid flowing through the heat exchanger. The meandering conductor pattern can also improve the efficiency of the inductive heating process by maximizing surface area utilization and reducing response time. This makes the heat exchanger particularly suitable for applications requiring precise and rapid temperature adjustments.

[0085] In general, the heating or cooling element preferably has meandering sections or is entirely meandering. A meandering arrangement also allows for a more homogeneous temperature distribution, for example, in resistance heating.

[0086] A spiral shape for the insulated electrical conductor is also preferable.

[0087] In an alternative embodiment, the plate heat exchanger comprises a resistance heating element, which may have the meandering or spiral shape described above. This element is preferably arranged at least partially within one of the two or more plates.

[0088] In a preferred embodiment, at least one of the plates, preferably all of the two or more plates, comprises or consists of a carbon material, preferably graphite. The use of graphite or another carbon material offers excellent corrosion resistance and enables high thermal and electrical conductivity, which can improve the efficiency of the heat exchanger and significantly increase its service life. The term carbon material also includes partially or fully graphitized or graphitic carbon materials.

[0089] Preferably, the proportion of carbon material in one or more plates is > 40 vol.%, more preferably > 50 vol.%, even more preferably > 70 vol.%, considerably more preferably > 90 vol.%, and most preferably 100 vol.%. The inventors have determined that, above a corresponding carbon content, the chemical and mechanical resistance required for demanding process engineering applications, particularly plants handling corrosive chemicals, is achieved.

[0090] In another preferred embodiment of the plate heat exchanger, the carbon material is a carbon material impregnated with a resin, preferably a phenolic resin, and in particular impregnated graphite. Impregnation of the carbon material with a resin such as phenolic resin can improve the structural integrity of the plates, increase their mechanical strength, and enhance their resistance to corrosive chemicals, thus contributing to the longevity of the plate heat exchanger in demanding operating environments.

[0091] Preferably, one or more plates have a permeability coefficient (gas permeability) of c(perm) < 5 * 10' 4 cm 2 / s, preferred c(perm) < 1 * 10' 4 cm 2 / s, even more preferred c(perm) < 8 * 10' 5 cm 2 / s, even more preferred c(perm) < 5 * 10' 5 cm 2 / s and preferably c(perm) < 2 * 10' 5 cm 2 / s or even < 1 * 10' 5 cm 2 / s or < 1 * 10' 6 cm 2 The inventors discovered that a correspondingly low permeability coefficient improves long-term stability. In particular, this results in high thermal and chemical resistance. Impregnation is preferably carried out with a phenolic or vinyl ester resin, wherein the plate(s) is / are preferably impregnated once, twice, three times, or more. A phenolic or vinyl ester resin is preferably used as the impregnating resin. The above permeability coefficients can be determined using the vacuum decay method according to DIN 51935:2019-07.

[0092] In a preferred embodiment, at least one of the plates, preferably all of the two or more plates, comprises or consists of a metal, preferably a metal selected from the group consisting of tantalum, niobium, zirconium, nickel, titanium, as well as alloys and combinations of the aforementioned, in particular tantalum and nickel-based alloys. Due to its excellent corrosion resistance, even under extreme conditions, tantalum offers high reliability in process engineering applications, especially with corrosive fluids. Tantalum is characterized by its high resistance to acids and other aggressive substances, which extends the service life of the heat exchanger and increases its operational reliability.

[0093] In a preferred embodiment, the preferably corrosion-resistant plate heat exchanger is designed such that the preferably corrosive fluid is in direct contact with at least one of the two or more plates. This enables direct and efficient heat transfer between the corrosive fluid and the plates of the heat exchanger, resulting in increased heat transfer efficiency. The direct contact ensures that the heat is transferred from the plates to the fluid without additional barriers, which is particularly important in applications requiring high precision in temperature control or where maximum energy efficiency is crucial.

[0094] In a preferred embodiment, < 70 vol.%, more preferably < 50 vol.%, even more preferably < 30 vol.%, and particularly preferably < 20 vol.% of the flow chamber is filled with the at least one flow obstruction. This limitation of the volume fraction of the flow obstruction in the flow chamber ensures that sufficient space remains for the effective flow of the preferably corrosive fluid and that a correspondingly high throughput can be achieved.

[0095] Particularly, > 5 vol.%, more preferably > 10 vol.%, and most preferably > 15 vol.% of the flow space is filled with at least one flow obstruction – especially in combination with one of the maximum limits mentioned above. These lower limits for the volume fraction of the flow obstruction in the flow space ensure that good heat transfer can take place and that the formation of flow paths can be sufficiently influenced.

[0096] The plate heat exchanger is dimensioned to meet the requirements of technical, particularly large-scale industrial and chemical processes. The filling volume (media-carrying volume) of the plate heat exchanger can range from 0.6 l to 10 l, with specific volume ranges preferred for different applications.

[0097] 1. Compact design:

[0098] Volumes from 0.6 l to 5 l are particularly suitable for applications with limited space, such as in modular plants or mobile units. This design enables efficient heat transfer with a small footprint and is ideal for smaller chemical processes or pilot plants. 2. Large-format design:

[0099] Volumes from 5 l to 500 l, preferably 10 l to 300 l, particularly preferably 20 l to 300 l, especially suitable for large-scale industrial applications where high throughput rates and maximum heat transfer performance are required. This design is preferably used in the chemical industry, the petrochemical industry, and in large-scale power plants, where high thermal efficiency and robustness are crucial.

[0100] The flexibility in volume dimensioning allows the plate heat exchanger to be adapted to the specific requirements of each process. The volume ranges mentioned above represent preferred designs that ensure optimal performance and efficiency, particularly in large-scale industrial and chemical applications where high demands are placed on thermal stability and process integration.

[0101] The number of plates in a plate heat exchanger can vary in three preferred levels: 2 to 50 plates offer the advantage of a compact design that is space-saving, cost-effective, and easy to maintain, ideal for smaller chemical processes or pilot plants. 51 to 100 plates are characterized by a balanced ratio of heat transfer performance, versatility, and moderate footprint, making them suitable for medium-sized industrial applications such as distillation processes or heat recovery. 101 to 200 plates enable maximum thermal efficiency and high throughput rates, making them particularly well-suited for large-scale industrial applications.

[0102] The maximum heat exchange surface of the plate heat exchanger is preferably in a range of 0.1 to 100 m². 2 Particularly preferred levels are: 4 to 20 m 2, ideal for compact applications with moderate heat transfer requirements, such as in pilot plants or smaller chemical processes; 21 to 50 m 2 , which offer a balanced ratio between heat transfer performance and space requirements and are suitable for medium-sized industrial applications such as distillation processes or heat recovery; as well as 51 to 100 m 2 , which enable maximum thermal efficiency and high throughput rates and are therefore particularly suitable for large-scale industrial applications such as the petrochemical industry or large-scale energy plants.

[0103] The exchange area per plate can range from 0.01 to 1.0 m² 2 lying, preferably 0.01 to 0.1 m 2 or 0.11 to 0.4 m 2 or 0.41 to 0.8 m 2The maximum design temperature (MDT) of the plate heat exchanger is in the range of 120 to 210 °C, preferably 180 to 200 °C. The MDT of a chemical apparatus is the highest temperature at which the apparatus can be operated continuously and safely without compromising the mechanical strength, leak tightness, corrosion resistance, or functional integrity of the materials and components used.

[0104] Exceeding the MDT can lead to material failure, deformation, corrosion damage, or seal loss and is therefore unacceptable during operation. The MDT is a crucial parameter in equipment design, safety assessments, and technical approval.

[0105] The heat exchanger is preferably designed for a maximum flow rate of at least 0.1 m³ / h for a liquid heating fluid. 3Designed for / h. In preferred embodiments, the maximum flow rate is at least 0.5 m³ / h. 3 / h, at least 1 m 3 / h, at least 5 m 3 / h, at least 10 m 3 / h, at least 50 m 3 / h, at least 100 m 3 / h, at least 200 m 3 / h, and particularly preferably at least 300 m 3 / h.

[0106] Higher maximum flow rates enable particularly efficient heat transfer in large-volume processes, such as those found in the chemical industry, petrochemicals, or large-scale energy plants, more efficient temperature control under highly fluctuating load profiles, and the prevention of local overheating or temperature gradients in the medium. Furthermore, high flow rates can increase the overall performance of the heat exchanger and enable operation in processes with high heat transfer requirements, such as in industrial cooling or heating circuits. In addition, they contribute to the optimization of process times and allow for economical scaling for applications with high throughput requirements.

[0107] The invention also relates to a plate heat exchanger according to the invention with a heat transfer fluid arranged therein, wherein the heat transfer fluid preferably comprises or consists of a substance selected from the group consisting of strong acids, such as HCl, HNO3, HF, H3PO4, H2SO4, and strong bases, such as NaOH or KOH. Preferably, the heat transfer fluid arranged in the plate heat exchanger has a temperature > 70°C at least in some sections, more preferably a temperature > 90°C, and most preferably > 100°C or even > 120°C, or a temperature < 0°C. The invention also relates to a process plant, particularly in chemical plants, comprising the heat exchanger according to the invention.

[0108] The robust construction, especially when using corrosion-resistant materials, makes the heat exchanger ideal for critical applications in sectors such as chemical engineering, electronics, biotechnology, steel, semiconductor, solar, pharmaceutical, environmental, food, and energy technology. This enables the construction of process plants with high process stability and reliable operation in a wide variety of industrial environments.

[0109] The invention also relates to methods for heating and / or cooling a fluid using the plate heat exchanger according to the invention. In this method, the fluid flows through the plate heat exchanger.

[0110] The invention also relates to the use of the plate heat exchanger according to the invention in thermal applications in industrial processes, in particular for heating, cooling, evaporation, condensation or heat recovery in a production process, e.g. in the chemical industry, metal processing or food production.

[0111] The invention relates in particular to the use of the plate heat exchanger according to the invention for heat recovery in an industrial process or in an energy plant, such as a power plant.

[0112] EXAMPLES

[0113] The present invention will be explained in more detail below with reference to the embodiment of a plate heat exchanger for heating a corrosive fluid shown in the figures.

[0114] Brief description:

[0115] Fig. 1 shows a side view of a heat exchanger according to the invention.

[0116] Fig. 2 shows a perspective front view of a heat exchanger according to the invention. Fig. 3 shows a perspective rear view of a heat exchanger according to the invention.

[0117] Fig. 4 shows a sectional view of a plate pack of a heat exchanger according to the invention as shown in Figs. 1-3.

[0118] Fig. 5 shows a top view of a front side of a plate for conveying corrosive fluids as used in a plate pack of Fig. 4.

[0119] Fig. 6 shows a top view of the back side of a plate for conveying corrosive fluids as used in a plate pack of Fig. 4.

[0120] Fig. 7 shows a top view of a heating plate as used in a plate pack of Fig. 4.

[0121] Fig. 8 shows a top view of a frame as used in a heating plate of Fig. 7.

[0122] Fig. 9 shows a top view of a heating unit, as used in a heating plate of Fig. 7.

[0123] Fig. 10 shows a sectional view of a plate pack of a heat exchanger according to the invention with sequential media flow.

[0124] Fig. 11 shows a cross-sectional view of a plate pack of a heat exchanger according to the invention with parallel media routing.

[0125] Detailed description:

[0126] Fig. 1 shows a side view of a heat exchanger according to the invention, which is specifically designed to guide and heat preferably corrosive fluids. The heat exchanger comprises a centrally arranged plate pack 8, a key element of the heat exchanger, which consists of several stacked plates. These plates are designed to reliably guide and simultaneously heat or cool the preferably corrosive fluid during operation.

[0127] The clamping and frame plates 2, 3 made of steel form the frame structure of the heat exchanger and serve as support elements for the central plate package 8. They ensure the necessary stability and the design enables the heat exchanger to safely absorb the loads that occur during operation, such as those caused by the flow of the preferably corrosive fluid or by temperature fluctuations.

[0128] The frame structure formed by the clamping and frame plates 2, 3 is tensioned by compression springs 1. The compression springs serve to exert a uniform and controlled pressure on the plate stack in order to ensure a firm and tight arrangement of the individual plates and to optimize the thermal contact between the plates.

[0129] The clamping plates and the frame plates 2, 3 serve as pressure distribution elements, transferring the force exerted by the springs evenly to the underlying plate stack. A PTFE lining can also be used for improved sealing. This homogeneous pressure distribution is advantageous for efficient heat transfer and for protecting and sealing the heat exchanger against potential damage from uneven loads. Preferably, a seal is inserted between each plate, which is compressed by the applied pressure. This seals the system and prevents the escape of the preferably corrosive fluid, even at higher pressures.

[0130] Figures 2 and 3 show perspective views of the heat exchanger according to the invention shown in Figure 1. The access point for the wiring 4 allows electrical lines, sensors, or control cables to be routed into the interior of the heat exchanger. This connection is essential for the integration of measurement and control technology, which is advantageous for the operation and monitoring of the heat exchanger. Furthermore, this connection supplies energy to the electric heating element.

[0131] The corrosive fluid is introduced into the heat exchanger via the inlet opening 5 located on the frame plate. Its size and position are precisely tailored to the flow rate and the requirements of the specific application. This ensures that the corrosive fluid can be effectively guided through the plate pack of the heat exchanger, where the heat transfer process takes place.

[0132] The optional elements, namely the sealed access point for cabling 6 and the sealed inlet opening 7, allow the heat exchanger to be adapted to various requirements. These sealed access points can be provided for future expansions or upgrades, but are initially not in use and therefore securely sealed to prevent leaks or contamination. The clamping plate 2, opposite the frame plate 3, houses the outlet for cabling 9 and the discharge opening 10 for the preferably corrosive fluid. Depending on the flow direction of the preferably corrosive fluid, the inlet and discharge openings can be reversed. The cabling access point can also be used as an outlet, depending on the application, and vice versa.

[0133] Fig. 4 shows a detailed sectional view of the plate pack of the heat exchanger shown in previous figures. The plate pack comprises plates for conveying preferably corrosive media 19 and heating plates 20. In general, the plates for conveying preferably corrosive media can simultaneously perform the heating or cooling function, i.e., the plate stack is formed from only one type of plate.

[0134] At the center of the cross-sectional view are the plates for guiding the preferably corrosive fluid 19, which define the flow space by means of flow restrictions. These plates are specifically designed to safely guide corrosive liquids or gases. Their special properties and the material from which they are made ensure that they can withstand the aggressive properties of the preferably corrosive fluid. They are made, for example, of graphite, silicon carbide, a fluoropolymer, or tantalum. The design of these plates enables an efficient and controlled flow.

[0135] The heating plates 20, positioned between the plates for conveying corrosive media 19, play a crucial role in the heat transfer process. They are electrically heated and transfer this heat to the plates for conveying the preferably corrosive fluid 19, which in turn transfer the heat to the fluid moving through the flow chamber. In principle, a cooling plate could be used analogously to cool the preferably corrosive fluid instead of a heating plate.

[0136] The end plates 23 are arranged at the end of the plate stack. These serve as the terminal elements of the plate stack and are designed to distribute the pressure evenly within the plate stack to achieve uniform heat transfer. The end plates are also robustly constructed to withstand the mechanical stresses that can arise from the operating pressure of the flowing, preferably corrosive, fluid.

[0137] Figure 5 shows a top view of the front face of a plate for guiding the preferably corrosive fluid, as used in a plate pack according to the illustrations in Figure 4. The inlet opening 5 serves to guide the preferably corrosive fluid, which is to be heated or cooled in the space between the plates, i.e., the flow space.

[0138] A key feature of the plate is the flow obstruction 11, which is designed to control the path taken by the preferably corrosive fluid through the plate and to maximize this path by changing direction. This obstruction allows the flow to be distributed and turbulence to be generated, which increases heat transfer efficiency. It contributes to the fluid contacting a larger surface area of ​​the plate, which improves heat exchange and thus leads to more effective heating.

[0139] Additionally, the plate has feedthroughs for wiring 21. These allow the integration of sensors or other electrical components that may be required for monitoring, regulating, and controlling the heat transfer process. In particular, the electrical supply for the electric heating element can be routed through the feedthroughs and thus made accessible to the heating plate. Fig. 6 shows the flat back side of the plate. Of course, the front and back sides of the plates can also be designed with flow restrictions to guide the preferably corrosive fluid and thereby define the flow space.

[0140] Fig. 7 shows a top view of a heating plate, which is an integral part of the plate stack described in Fig. 4. The heating plate includes a feedthrough for the preferably corrosive fluid 22, which allows the preferably corrosive fluid to flow to the plates for the conveyance of the preferably corrosive fluid 19.

[0141] A key component is the frame 14, which has an opening in which the heating element 13 is arranged. The heating element comprises a loop-shaped stranded wire structure, which is arranged within a double-walled structure consisting of two cover steel plates. The loop-shaped stranded wire structure, arranged between the flat plates, inductively heats the steel plates, so that the heating element provides a maximum surface area for heat transfer and thus enables uniform heating of the plates for the conduction of the preferably corrosive fluid.

[0142] Furthermore, the wiring access to the heating element is shown. This access is for the electrical connection of the heating element and allows for the safe and protected routing of the necessary wiring. Through this access, the heating element can be powered and monitored, which is advantageous for maintaining the correct operating temperatures and for the general operation of the heat exchanger. Fig. 8 shows the frame without the heating element installed within it, whereas Fig. 9 shows the heating element on its own (cover plate not shown).

[0143] Fig. 10 shows a sectional view of a plate stack of a heat exchanger according to the invention, as already shown in Fig. 4, revealing a sequential media flow. The preferably corrosive fluid flows through the inlet opening for the corrosive fluid, which is arranged at the first elongated end of the plate, into the first flow chamber formed by the end plate and a first plate for conveying the preferably corrosive fluid. At its opposite elongated end, it is guided through the feedthroughs of the heating plate into the next flow chamber, which is formed by two adjacent plates for conveying corrosive media. This results in a meandering flow through the plate stack.

[0144] In contrast, Fig. 11 shows an arrangement with parallel fluid flow, in which, after entering the stack of plates, a partial flow is supplied to the parallel flow chambers.

[0145] Reference number

[0146] 1 compression spring

[0147] 2 chipboard

[0148] 3. Frame plate

[0149] 4 Access for cabling

[0150] 5 Inlet / outlet opening for supplying the preferably corrosive fluid

[0151] 6 Optional access for cabling (sealed)

[0152] 7. Optional inlet / or outlet opening for supplying the preferably corrosive fluid (sealed)

[0153] 8 Stacked plate package for heating the preferably corrosive fluid

[0154] 9 Output cabling

[0155] 10 Outlet opening for draining the preferably corrosive fluid

[0156] 11 Flow obstruction

[0157] 12 Flat surface

[0158] 13 Heating element

[0159] 14 frames

[0160] 15 Access of the wiring to the heating element

[0161] 16 Access of the wiring to the heating element

[0162] 17 Recess for heating element

[0163] 18 Flow direction of the preferably corrosive fluid

[0164] 19 Plate for guiding the preferably corrosive fluid

[0165] 20 heating plates

[0166] 21. Cabling feedthrough

[0167] 22. Feedthrough for the preferably corrosive fluid

[0168] 23 end plates

[0169] 24 Meandering cabling

Claims

Patent claims 1. Plate heat exchanger for heating and / or cooling a preferably corrosive fluid comprising ■ two or more plates, o which are in a stacked arrangement so that they form a stack of plates, o wherein each plate has two opposite flat sides, ■ a housing structure that holds the two or more plates in the stacked arrangement, ■ a flow chamber arranged between two flat sides of two plates with a flow obstruction, ■ an inlet opening for feeding the preferably corrosive fluid into the flow chamber of the plate heat exchanger, and ■ an outlet opening for draining the preferably corrosive fluid from the flow chamber of the plate heat exchanger, characterized in that ■ at least one of the two or more plates of the plate heat exchanger can be heated or cooled directly or indirectly with electricity.

2. Plate heat exchanger according to claim 1, wherein the inlet and / or outlet opening is formed by a through-opening extending through the flat sides of one of the two or more plates.

3. Plate heat exchanger according to one of the preceding claims, wherein the flow obstruction is designed in such a way that it can divide the fluid that can be conveyed through the flow space into two or more, at least sectionally, separate material flows.

4. Plate heat exchanger according to one of the preceding claims, wherein the flow obstruction is designed in such a way that it allows at least section by section a complete immersion with fluid.

5. Plate heat exchanger according to one of the preceding claims, wherein the flow obstruction is at least partially in the form of several ribs between which channels are formed in which the fluid can be guided through the flow space.

6. Plate heat exchanger according to claim 5, wherein the channels run parallel at least in sections.

7. Plate heat exchanger according to one of the preceding claims, wherein a heating element is arranged in at least one of the two or more plates of the plate heat exchanger.

8. Plate heat exchanger according to claim 7, wherein the heating element comprises a planar electrical conductor, for example made of metal or graphite, and an insulated electrical conductor, such as a stranded wire, which can generate an alternating magnetic field in order to generate heat in the planar electrical conductor.

9. Plate heat exchanger according to claim 8, wherein the insulated electrical conductor is at least partially meandering, spiraling, circular, zigzag, wave-like or grid-like and / or has at least partially parallel sections.

10. Plate heat exchanger according to one of the preceding claims, wherein at least one, preferably all, of the two or more plates comprise or consist of a carbon material, preferably graphite, and / or a ceramic material, preferably SiC ceramic.

11. Plate heat exchanger according to claim 10, wherein at least one of the two or more plates comprises a carbon material and the carbon material is a carbon material impregnated with a resin, preferably a phenolic resin.

12. Plate heat exchanger according to one of the preceding claims, wherein at least one, preferably all, of the two or more plates comprise or consist of a metal, preferably tantalum.

13. Plate heat exchanger according to one of the preceding claims, wherein the plate heat exchanger is designed such that the fluid is in direct contact with at least one of the two or more plates.

14. Plate heat exchanger according to one of the preceding claims, wherein < 50 vol.-% of the flow space is filled with the at least one flow obstruction.

15. Process engineering plant comprising a plate heat exchanger as described in any of the preceding claims.

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