Steam creation device

Abstract

The present invention relates to a steam generator comprising a housing, a first heat exchanger element arranged in the housing through which a heat exchange fluid flows, and at least one second heat exchanger element arranged in the housing through which water flows for the purpose of generating steam. Furthermore, the steam generator comprises a heat transfer medium arranged in the housing to transfer heat from the heat exchange fluid flowing through the first heat exchanger element to the water flowing through the second heat exchanger element for the purpose of generating steam, wherein the heat transfer medium is a salt bath.

Description

TECHNICAL AREA

[0001] The present invention relates to a steam generator for producing steam for energy generation, for example by means of a steam engine or a steam turbine. For this purpose, the steam generator can be coupled, for example, to a biomass combustion system, biogas plant, or a pellet heater. BACKGROUND

[0002] Steam generators are generally used to produce steam. These generators typically have a combustion chamber (the furnace) in which fuel is heated or burned to generate heat. Alternatively, the still-hot exhaust gas from a biogas plant can be used to provide the necessary heat. This heat, in the form of a heat transfer medium, is passed, for example, through a heat exchanger to evaporate the water flowing within it. The resulting steam can then be used to generate energy, for example, in a steam engine.

[0003] Efficient steam and energy generation requires high pressures and, consequently, high temperatures. This leads to thermal expansion of the heat exchanger and stresses in the heat exchanger material.

[0004] In the prior art, for example, DE 10 2010 046 804 A1 discloses a shell-and-tube heat exchanger with a plurality of tube windings radiating from and into a common outlet space for a heat exchange medium, wherein each tube winding comprises an alternating sequence of tube sections and tube bends, and wherein the tube bends are designed as deflections by 180° with respect to an associated bend axis and have the same bend radii. This shell-and-tube heat exchanger is characterized in that, along each tube winding, the bend axes of tube bends connected to the same tube section are at an angle to each other, and the bend axes of tube bends between which a tube section, a tube bend, and another tube section are arranged in immediate succession run parallel.

[0005] However, the efficiency here depends heavily on the distance between the shell-and-tube heat exchanger and the casing, and also strongly on the flow pattern of the heat exchange fluid within the tube bundles relative to the heat energy generated by the fuel. This means that wall losses caused by fluid flowing past the shell-and-tube heat exchanger without passing through the heat exchanger itself cannot be prevented in this design. Therefore, the heat exchange efficiency is not optimal.

[0006] Furthermore, according to such a design, it is not possible to compensate for stresses in the tube bundles caused by thermal expansion resulting from the high temperatures of the heat exchange fluid.

[0007] DE 20 2007 017 403 U1 also discloses a shell-and-tube heat exchanger, in particular for the heat exchange of heating gas to heating water or drinking water, wherein the shell-and-tube heat exchanger has a water space through which a heating water flow or drinking water flow can pass and a heating gas space through which a heating gas flow can pass. The heating gas tubes forming the heating gas can be flowed through in parallel or in series.

[0008] The problems described above also occur here, and furthermore the efficiency of the heat exchange is low because it is operated in direct current.

[0009] Furthermore, when generating steam with biomass in currently known steam generators, it is particularly critical to compensate for the undefined and potentially fluctuating energy content of the fuel (unlike, for example, coal) and thus the fluctuating steam parameters during steam generation. If this cannot be adequately compensated, fluctuations in the steam temperature occur, which – for example, when using steam turbines – can lead to impairment or even damage of these turbines.

[0010] Previously known designs therefore use an additional steam storage boiler in order to achieve low pressure losses and counteract the fluctuation.

[0011] However, such a design is no longer applicable at high pressures, for example above 250 bar, because there is a high risk of destruction, for example in the form of an explosion.

[0012] Furthermore, US 2012 / 0067551 A1 discloses an energy storage device according to the preamble of claim 1, which serves to store energy obtained from solar power in a heat storage medium in order to be able to use the stored energy for electricity generation even in phases without solar radiation.

[0013] Further previously known configurations are shown in EP 3 809 084 A1, EP 2 369 288 A1, WO 2013 / 097031 A2 and US 2011 / 226780 A1.

[0014] Therefore, there is a current need for a solution for a steam generator for use with biomass and high pressures, which is not only high-pressure resistant, but also simple and cost-effective to implement. PRESENTATION OF THE INVENTION

[0015] It is therefore an object of the present invention to provide an efficient device for steam generation (a steam generator) in which, with a simple design and even with fluctuating energy content of the fuel, reliable operation can be ensured and high efficiency achieved, and the above disadvantages can be reduced or even prevented.

[0016] This problem is solved by a device having the features of claim 1. Preferred embodiments are found in the further claims of the following description and in the drawings.

[0017] According to one aspect, the steam generator has a casing, a first heat exchanger element arranged in the casing through which a heat exchange fluid can flow, and at least one second heat exchanger element arranged in the casing through which water can flow to generate steam.

[0018] The heat exchange fluid can be waste heat from a biomass combustion plant, biogas plant, or pellet heating system, which can flow through the first heat exchange element and thus through the steam generator. The second heat exchange element is water, used for steam generation.

[0019] Furthermore, a heat transfer medium is arranged within the hollow housing to transfer heat from the heat exchange fluid flowing through the first heat exchange element to the water flowing through the second heat exchange element for steam generation. The heat transfer medium is a salt bath.

[0020] Accordingly, the steam generator is capable of exchanging heat. In the present heat exchange arrangement of the steam generator, pressures between 50 and 800 bar, preferably 30 to 500 bar, particularly preferably 30 to 180 bar, but also lower pressures between four and ten bar steam pressure can be generated.

[0021] This means that such an arrangement, due to the heat-transferring salt bath, is particularly versatile and can generate both low pressures, for example around seven bar for food production, and high-pressure steam streams in the range of 500 to 800 bar, without the fluctuating energy content of the biomass being critical for the device itself. A complex arrangement with an additional storage tank to minimize pressure losses is also unnecessary in this design. Thus, a particularly flexible and cost-effective steam generation device can be implemented.

[0022] Furthermore, destruction or explosion can be reliably avoided because the salt is crystalline in its resting state and is liquefied by heating with or via the first heat exchange element, through which the heat exchange fluid can flow, so that the molten salt is heated by the heat exchange fluid and thus the salt liquefies and absorbs energy.

[0023] This means that the salt bath acts as a liquid salt, for example as a nitrate melt, and thus improves the heat transfer from the heat exchange fluid to the water.

[0024] According to such a design, not only can a particularly flexible system be realized which can generate steam pressure up to 800 bar at a wide variety of pressures, but also a particularly reliable steam generator can be achieved.

[0025] The first heat exchange element can be permeated by the heat exchange fluid in a first flow direction from an inlet of the housing to an outlet of the housing.

[0026] This means that the first flow direction corresponds to the flow direction of the heat exchange fluid through the heat exchanger located in the housing. For example, if the housing has an elongated shape, this first flow direction corresponds to the longitudinal extent of the housing.

[0027] As mentioned earlier, the heat exchange fluid can be, for example, combustion gas from the combustion of a fuel, such as undried, low-grade biomass, in the combustion chamber of a conventional grate-fired boiler, or the exhaust gas from a biogas plant. This allows electricity to be generated from residual materials. Depending on the heat exchange fluid, different temperature ranges can occur in the steam generator.

[0028] Depending on the heat exchange fluid, different temperature ranges can occur in the steam generator. If the heat exchange fluid, also known as heating fluid, is generated by pellet combustion in the steam generator, it typically has a temperature between 600°C and 1000°C, preferably 900°C. If exhaust gas from a biogas plant is used as the heat exchange fluid, temperatures of 450°C to 500°C, preferably 470°C, typically occur in the steam generator. Furthermore, salts can be used that transition from a crystalline to a liquid state at temperatures as low as 130°C to 150°C. . transition to an operating state.

[0029] The flexibility of the steam generator proves particularly advantageous in this context, and the generation of the desired steam pressure is particularly easy to control.

[0030] Due to the high energy storage capacity of the salt bath used, the pressure to be generated can be regulated solely by the flow rate of the water flowing through the second heat exchanger element. This can be achieved using a simple pump.

[0031] For example, pressures of seven bar (e.g., for the food industry) can be used if required, and shortly thereafter, by increasing the flow rate, pressures of up to 800 bar can be generated without the need for other, additional, or different resistant materials, configurations, or designs.

[0032] Thus, a particularly flexible and multi-application device for steam generation can be provided with just one compact device and one housing.

[0033] The heat exchange fluid can be flue gas.

[0034] In this case, steam generation is independent of the heat source. Therefore, the heat exchange fluid can be produced not only from the combustion of biomass as flue gas, but also, for example, from the combustion of fossil fuels such as coal or natural gas. This heat exchange fluid can then flow through the first heat exchange element, similar to flue gas.

[0035] Furthermore, the first heat exchanger element can have a multitude of tubes extending along the first flow direction.

[0036] According to such a design, the heat exchange fluid, for example flue gas, can enter the housing at an inlet through the multitude of tubes and flow through the housing along the first flow direction through the tubes, preferably straight tubes.

[0037] In other words, the casing features numerous tubes through which the heat exchange fluid flows. This increases the surface area for heat transfer to the heat transfer medium, and thus to the water in the secondary heat exchange elements, while also ensuring reliable separation of the heat exchange fluid from the salt bath. This reduces or prevents flammability in the event of leaks or similar incidents, thereby increasing the (long-term) operational reliability of the steam generator.

[0038] Furthermore, the second heat exchange element can be permeable to water in a second flow direction. The first and second flow directions can be essentially perpendicular or essentially parallel to each other.

[0039] This means that the second flow direction corresponds to a flow direction of the water through the casing.

[0040] As described above, the multiple tubes of the first heat exchanger element can extend from the inlet of the housing to the outlet of the housing. Thus, for example, if the heat exchanger elements are arranged essentially parallel to each other, the second heat exchanger element can also extend from an inlet to an outlet of the housing essentially parallel to the multiple tubes of the heat exchanger element.

[0041] The term "essentially" should therefore be understood to mean that, for example, turns, windings or the like, which are used to enable a maximum pipe length of the second heat exchanger element in the housing, should not be taken into account when assessing the parallelism and / or perpendicular arrangement of the first flow direction and the second flow direction to each other.

[0042] The second heat exchange element can have a plurality of tube windings, such that the second heat exchange element extends substantially perpendicular or substantially parallel to the first flow direction from the inlet of the casing to the outlet of the casing.

[0043] This means that in a "box-like" design, i.e., with a housing that is essentially elongated, the tubes of the first heat exchanger element described above can extend along this longitudinal direction, and the second heat exchanger element can have a tube with a multitude of tube windings. This allows for a large surface area of ​​the second heat exchanger element, and thus a large surface area for heat transfer.

[0044] This piping of the second heat exchanger element can extend essentially parallel to the extent of the housing, i.e., for example, mostly horizontally through the box-like housing described by way of example, or essentially perpendicular to the extent of the housing, i.e., for example, mostly vertically through the box-like housing described by way of example.

[0045] The second heat exchanger element can have a variety of U-shaped pipe windings.

[0046] Thus, with a parallel arrangement of the first flow direction to the second flow direction (and therefore a parallel arrangement of the multiple tubes of the first heat exchanger element to the second heat exchanger element), the path of the second heat exchanger tube can be realized essentially in a parallel direction to the multiple tubes of the first heat exchanger element. The U-shaped tube windings allow for the most frequent possible "winding" of the tube from the inlet to the outlet and from the outlet back to the inlet and back again from the inlet to the outlet, etc.

[0047] Conversely, this means that if the first flow direction is arranged perpendicular to the second flow direction, the pipe of the second heat exchanger element should achieve as many windings as possible from the inlet to the outlet of the housing with the U-shaped pipe windings with a predominant extension in the vertical direction.

[0048] In the example of a box-like housing with an essentially elongated shape, already outlined several times above, this means that the several tubes of the first heat exchanger element extend along the longitudinal extent of the housing, and the tube windings, in particular U-shaped tube windings of the tube of the second heat exchanger element, extend essentially in a perpendicular, i.e., in this example vertical, direction to the elongated extent of the housing.

[0049] Alternatively, the second heat exchanger element can have a multitude of pipe windings extending in circles or spirals.

[0050] This means that the multitude of pipe windings extending in circles or spirals can lie in the salt bath located in the housing and, due to their circular or spiral shape, maximize the surface area of ​​the second heat exchange element, for example a pipe through which water flows, thus enabling heat transfer from the first heat exchange element to the salt bath or directly to the second heat exchange element.

[0051] The second heat exchanger element can have a plurality of helical tube windings, such that the second heat exchanger element extends substantially perpendicular or substantially parallel to the first flow direction from the inlet of the housing to the outlet of the housing. The helical tube windings are arranged helically between or around the tubes.

[0052] This means that the pipes extending from the inlet of the housing to the outlet of the housing, through which the heat exchange fluid, for example flue gas, flows, can be directly wrapped by the pipe windings or can have the pipe windings between the pipes.

[0053] In any case, both the first heat exchange element and the second heat exchange element are completely surrounded by the salt bath.

[0054] The second heat exchanger element can extend between the pipes in the housing.

[0055] According to this design, the tubes of the first heat exchanger element can extend from the inlet to the outlet of the housing and, for example, have tube windings of the second heat exchanger element arranged vertically and / or horizontally in the spaces between them. This allows for the most compact arrangement possible while simultaneously maximizing the heat exchange surface area.

[0056] The second heat exchange element can be arranged in the housing in such a way that it contacts the first heat exchange element at least at one point, preferably at several points in the housing.

[0057] This design allows not only for heat transfer from the first heat exchanger element to the salt bath and from the salt bath to the second heat exchanger element (i.e., indirect heat transfer via the salt bath heat storage medium), but also for the most direct possible heat transfer from the first to the second heat exchanger element. This increases the efficiency of the heat transfer.

[0058] Preferably, a large number of secondary heat exchange elements can be arranged in the housing.

[0059] As described earlier, the salt bath serves as a heat transfer medium and can also store thermal energy. By using a large number of secondary heat exchange elements, a multitude of vapor pressures can be generated simultaneously in the steam generator with the same heat transfer medium and regardless of its temperature or the material being burned, using the same configuration.

[0060] Such a design is particularly advantageous because it allows a large number of vapor pressures to be generated with the same compact design – without having to change the structure of the system.

[0061] Furthermore, due to the energy storage capacity of the heat transfer medium, i.e., the salt bath, extremely rapid adjustment of steam generation is possible. This means that, purely by controlling the flow rate in the second heat exchanger element, it is possible, for example, to switch from low pressure (e.g., seven bar) to high pressure (500 to 800 bar) within a few minutes using the same reliable and efficient device.

[0062] According to another aspect, the steam generator may also have at least one pump arranged in the housing, which is designed to circulate the salt bath.

[0063] This pump creates a circulation that increases forced convection, as the salt bath is pumped past the pipes of the first heat exchanger element and the pipe or pipe windings of the second heat exchanger element, thus drastically increasing the heat transfer of the heat-storing heat transfer medium in the form of a salt bath.

[0064] According to another aspect, the steam generator can be divided into several segments along the first flow direction. These segments are interconnected in such a way that the heat exchange fluid can flow through them along the first flow direction, from the casing inlet to the casing outlet. Each casing segment can contain at least one secondary heat exchange element, and these secondary heat exchange elements are fluid-tightly connected to each other.

[0065] In other words, this design is to be understood as follows: each segment along the first flow direction can be traversed by a multitude of pipes containing the heat transfer medium, and in each of these segments, heat transfer to a second heat exchange element for steam generation is realized using the salt bath.

[0066] The number of tubes in the first heat exchanger element within a first segment does not need to correspond to the number of tubes in a subsequent segment. Rather, this design allows for the flow of heat exchange fluid through all segments along the first flow direction. However, for example, a particularly hot area / segment may have more tubes than an area with a lower temperature. It is sufficient that the incoming heat exchange fluid can flow through the housing containing the multiple segments.

[0067] Furthermore, it is conceivable that the heat exchange elements provided in each segment could have different configurations. For example, a second heat exchange element in a first segment of the housing could have U-shaped pipe windings, while a second heat exchange element in another segment of the housing could have a helical configuration. There are no limitations regarding the variation of the pipe windings, as long as at least one complete pipe is created through which the water can flow for steam generation within the housing.

[0068] Furthermore, it should be understood that a pump as described above may be provided in each of these segments.

[0069] Multiple secondary heat exchange elements can also be provided in one or more segments of the housing. This means that configurations are possible in which a first secondary heat exchange element flows through several segments of the housing for heat exchange, while a second secondary heat exchange element flows through only a single segment of the housing to also generate steam in a second tube.

[0070] Furthermore, the steam generator can be designed so that the water can first flow through the last segment in the first flow direction and then through the first segment in the first flow.

[0071] Thus, for example, a pure counterflow can be generated, meaning that the heat exchange fluid flows from an inlet of the housing to an outlet of the housing, whereas the water for steam generation flows "from back to front", i.e. from an outlet to an inlet of the housing.

[0072] Furthermore, the water can thus enter at the coldest point, i.e. in the last segment of the housing, and be preheated before flowing into a front part of the steam generator housing for superheating.

[0073] The segments can be connected in such a way that the flow of oxidizable material contained in the heat exchange fluid from one segment to another along the first flow can be prevented.

[0074] The term "oxidizable material" can refer, for example, to residues from biomass combustion that are transported in the flue gas. In such cases, screens or similar devices may be used to prevent the oxidizable material from flowing from segment to segment.

[0075] Preferably, such a design can also be provided upstream of the first segment in a first flow direction, so that the oxidizable material contained in the heat exchange fluid can be prevented from entering the housing.

[0076] Such arrangements are advantageous for operational safety, as they prevent leakage and the associated contact of flammable, oxidizable material with the salt bath.

[0077] Furthermore, the salt bath may contain a nitrate salt.

[0078] This is not only particularly cost-effective, but also suitable for energy storage at high temperatures of the heat transfer medium, for example flue gas up to 900 °C, without chemical decomposition. This results in the most reliable and efficient design of the steam generator.

[0079] The segments can contain at least two different salt baths, which are stored separately from each other within the segments.

[0080] According to such a design, the most efficient use of a salt bath, adapted to the temperatures prevailing in the respective segments, can be enabled.

[0081] For example, in a first salt bath in a first segment along the first flow direction, a salt bath can be used which is operated at a salt temperature of 350°C to 550°C, whereas a second salt bath in a further segment along the first flow direction can be used at a specific salt bath temperature of 150°C to 400°C without becoming crystalline or thermally decomposing.

[0082] The salt bath may contain potassium sodium nitrate.

[0083] The salt bath in the last segment in the first flow direction may contain potassium-sodium-calcium nitrate, and the salt bath in at least one further segment may contain potassium-sodium nitrate.

[0084] While the potassium sodium calcium nitrate provided in the last segment liquefies at lower temperatures and can therefore efficiently store and transfer heat, the potassium sodium nitrate provided in at least one further segment is particularly temperature-stable and therefore suitable for efficient heat transfer and heat storage in case of overheating.

[0085] This means that even if the steam temperature at the rear is between 180°C and 200°C, the potassium sodium calcium nitrate in the last segment is still liquid, whereas the potassium sodium nitrate in at least one further segment would already be solid. Therefore, in an arrangement where the water flows into the last segment first, efficient heat transfer and heat storage in the potassium sodium calcium nitrate are possible there.

[0086] According to such a design, the potassium-sodium-calcium nitrate in the last segment can be operated at a specific salt bath temperature of 150°C to 400°C, whereas the potassium-sodium nitrate in at least one further segment can be operated at a correct salt bath temperature of 350°C to 550°C.

[0087] According to the configurations described above, particularly efficient, cost-effective, and flexible steam generation can be achieved, as the salt bath provides high heat transfer at a wide range of temperatures and also exhibits high tolerance to temperature fluctuations and varying energy contents. This means that the salt bath enables high thermal homogeneity and can thus counteract the problems described above regarding varying steam temperatures and the variable energy content of, for example, the biomass used. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The following schematic drawings describe a steam generator according to an exemplary embodiment. Such steam generators are used, for example, to generate steam for energy production, such as in a steam engine or a steam motor. The drawings show: Figure 1: a perspective view of a steam generator according to an exemplary embodiment. Figure 2 : a schematic cross-sectional representation of the heat exchanger made of Figure 1 . DESCRIPTION OF THE PREFERRED EXECUTION FORM

[0089] The in Figure 1 The steam generator 1 shown comprises a housing 2 in which a first heat exchanger element 3 and a second heat exchanger element 4 are arranged.

[0090] The first heat exchange element 3 is permeable to a heat exchange fluid. In the following description of an embodiment, flue gas, which is produced by biomass combustion, is used as an example of such a heat exchange fluid. Another example of such a heat exchange fluid would be the waste heat from a biogas plant.

[0091] The flue gas is guided to the steam generator 1 via a funnel 13. Specifically, the housing 2 of the steam generator 1 has an inlet 6, to which the funnel 13 is connected, and an outlet 7. Accordingly, the flue gas can flow through the housing 2 from the inlet 6 to the outlet 7. This flow direction is referred to in the described embodiment as the "first flow direction 5". That is, the flue gas flows through the housing 2 along the first flow direction 5 from the inlet 6 to the outlet 7 of the housing 2.

[0092] In the embodiment shown, the first heat exchanger element 3 has a plurality of tubes 8 which extend along the direction of extension of the housing 2, i.e. from the inlet 6 to the outlet 7 of the housing 2.

[0093] In the illustrated embodiment of the steam generator 1, the housing 2 is designed in a "box-like" shape, meaning that it extends essentially along one dimension of the housing 2 and has a rectangular cross-section. However, the width and / or height as well as the depth of the housing 2 are not limiting factors for steam generation and can be configured according to space requirements and / or desired design features. In the illustrated embodiment, the first flow direction 5 corresponds to the longitudinal dimension of the housing 2.

[0094] In this embodiment, water flows through the second heat exchanger element 4 to generate steam. In other words, the water in the second heat exchanger element 4 is heated by the first heat exchanger element 3 or the flue gas flowing through it, thus changing from a liquid state to a vaporous state. This steam can then be used, for example, to generate electricity. The electricity can be used in a steam engine and / or a steam turbine, which are powered by the generated steam. In the illustrated embodiment, the second heat exchanger element 4 is designed as a single tube 8, which extends through the housing 2 of the steam generator 1 with windings.

[0095] It should be noted here that, for illustrative purposes, the lid of housing 2 (on one of its top sides) is shown in Figure 1not shown, so the interior of housing 2 is shown in the isometric view of Figure 1 is recognizable.

[0096] In this embodiment, the flow direction of the water in the second heat exchange element 4 is referred to as "second flow direction 9".

[0097] As can be seen from the figures, the second heat exchanger element 4, in the form of a tube 8, has a plurality of tube windings 10. These tube windings 10 are, as shown in Figure 2 recognizably arranged in the housing 2 such that the second heat exchange element 4 extends essentially perpendicular to the first flow direction 5 from the inlet 6 of the housing 2 to the outlet 7 of the housing 2 and achieves the greatest possible pipe length and thus pipe surface area along its extension from the inlet 6 to the outlet 7 of the housing 2 with U-shaped pipe winding sections.

[0098] That is, while the pipes 8 of the first heat exchanger element 3 extend in a straight line from the inlet 6 to the outlet 7 of the housing 2, the pipe 8 of the second heat exchanger element 4 has a plurality of vertically extending pipe sections in the embodiment shown, so that the pipe windings 10 connected with U-shaped pipe winding sections extend substantially perpendicular to the first flow direction 5 from the inlet 6 to the outlet 7 of the housing 2.

[0099] However, according to another embodiment not shown, it is also possible that the first flow direction 5 and the second flow direction 9 run essentially parallel to each other.

[0100] Furthermore, the shape of the U-shaped pipe windings 10 (see Figure 2 ) not limited to that.

[0101] Likewise, in an embodiment not shown, the second heat exchange element 4 can have a plurality of pipe windings 10 extending in circles or spirals.

[0102] Likewise, in another embodiment not shown, it is possible that the second heat exchanger element 4 has a plurality of helical pipe windings 10 which extend substantially perpendicular or parallel to the first flow direction 5 from the inlet 6 to the outlet 7 of the housing 2 and extend helically between or around the pipes 8.

[0103] Figure 1 Figure 1 also illustrates that the second heat exchanger element 4 with the U-shaped tube windings 10 extends between the tubes 8 in the housing 2.

[0104] In the embodiment illustrated in the figures, the first flow direction 5 runs essentially along a horizontal direction, whereas the second flow direction 9 runs essentially vertically. However, it is also possible to arrange the steam generator 1 "upright" so that the first flow direction 5 runs in a vertical direction and the second flow direction 9 runs essentially horizontally. If space constraints require it, an inclined arrangement of the housing 2 is also conceivable.

[0105] In the Figure 1 and in Figure 2In the illustrated embodiment, the second heat exchange element 4 extends along several planes in a lateral direction, since the pipe windings 10 of the second heat exchange element 4 extend essentially perpendicular to the first flow direction 5. However, independently of this, it is equally possible that the pipe windings 10 of the second heat exchange element 4 extend along a vertical direction in different planes in a vertical direction of the housing 2 between the pipes 8 of the first heat exchange element 3, or a mixture thereof, within the housing 2 between the pipes 8 of the first heat exchange element 3.

[0106] Here, the second heat exchange element 4 is arranged in the housing 2 in such a way that it contacts the first heat exchange element 3 in the housing 2.

[0107] The embodiment shown in the figures is further subdivided into several segments 11, 12 along the first flow direction 5, here by way of example two segments 11, 12. However, the use of more than two segments 11, 12 is also conceivable without any problems.

[0108] Here, segments 11 and 12 are connected to each other in such a way that the flue gas can flow along the first flow direction 5 through segments 11 and 12 from the inlet 6 to the outlet 7 of the housing 2, and at least one second heat exchanger element 4 is provided in each segment 11 and 12 of the housing 2. As can be seen in the figure, a connecting pipe 14 is provided between the two second heat exchanger elements 4 in segments 11 and 12 of the housing 2, so that the second heat exchanger elements 4 are fluid-tightly connected to each other and that water can pass through the entire housing 2 for steam generation.

[0109] It is also possible that not only is a single second heat exchanger element 4 provided in each segment 11, 12 of the housing 2, and / or that several segments 11, 12 are required. In a further embodiment not shown, it is also possible that the steam generator 1 has only a single segment with a first heat exchanger element 3 and a second heat exchanger element 4.

[0110] As described, it is also possible to arrange a large number of second heat exchange elements 4 in at least one segment 11, 12. Thus, different steam pressures can be generated using only one flue gas stream as the heat transfer medium, controlled by the fluid flow velocity of the water for steam generation.

[0111] Regardless of the number of second heat exchange elements 4 in housing 2 or in segments 11, 12 of housing 2, the water can, as in Figure 1 and Figure 2As shown, the water first flows through the last segment 11 in the first flow direction 5 and then through the first segment 12 in the first flow direction 5. This allows for initial preheating of the water followed by superheating. That is, the water enters the steam generator 1 at an outlet side of the casing 2, flows counter-clockwise through the last segment 11 in the first flow direction 5 of the flue gas, and then flows via the connecting pipe 14 to an inlet side of the first segment 12 in a flow direction of the casing 2 (see figure). Figure 2 ) .

[0112] A heat transfer medium is arranged in the housing 2 to transfer heat from the heat exchange fluid (here flue gas) flowing through the first heat exchange element 3 to the water flowing through the second heat exchange element 4 for steam generation. The heat transfer medium is a salt bath that covers both the first heat exchange element 3 and the second heat exchange element 4.

[0113] In this case, at least one pump can be arranged in the housing 2, which is designed to circulate this salt bath in order to increase forced convection.

[0114] In the embodiment formed with segments 11, 12 and shown in the figures, the segments 11, 12 are connected to each other in such a way that the flow of oxidizable material contained in the heat exchange fluid, which, upon contact with the salt bath, for example in the event of a leak, can be prevented from one segment 12 into another segment 11 along the first flow direction 5. This can be achieved, for example, by means of a grid arrangement (not shown) which prevents the entry of flammable material into one of the segments 11, 12.

[0115] As in Figure 1 and Figure 2As shown, this salt bath can be filled into the housing 2 via inlet nozzle 15. The salt bath thus fills the spaces between the first heat exchanger element 3 and the second heat exchanger element 4 in the housing 2, completely filling it. Accordingly, this salt bath can serve as a heat transfer medium and energy storage medium, thereby increasing the homogeneity of the energy transfer.

[0116] The salt bath may contain a nitrate salt, in particular a potassium sodium nitrate.

[0117] In the illustrated embodiment, at least two different salt baths can be provided separately in the respective segments 11, 12. Thus, a suitable nitrate salt can be used, adapted to the temperatures prevailing in the corresponding segments 11, 12 of the housing 2. The use of potassium-sodium-calcium nitrate salt in the last segment 11 in the first flow direction 5 and potassium-sodium nitrate in at least one further segment 12 is particularly preferred.

[0118] Thus, the flue gas enters the housing 2 as a heat exchange fluid via the funnel 13 and flows through the tubes 8 of the first heat exchange element 3 along the first flow direction 5 to the outlet 7 of the housing 2.

[0119] Meanwhile, the heat exchange fluid transfers heat to the salt bath, which acts as both a heat transfer and heat storage medium and fills the housing 2. This arrangement then heats the water in the pipes of the second heat exchange element 4, thus generating steam.

[0120] According to such a design, problems caused by fluctuating steam parameters, which are due, for example, to non-constant fuel or its calorific value, can be counteracted even at supercritical pressures above 350 bar.

[0121] This means that even if, for example, flue gas at a temperature of 900°C enters the steam generator 1, the thermal energy is first transferred to the heat transfer medium in the form of a salt bath. In the case of multiple secondary heat exchange elements 4, it is also possible that one of these heat exchange elements is not supplied with water if it is not currently required. Due to the arrangement of the heat transfer medium within the housing 2 of the steam generator 1, damage to or overheating of the empty tube of the secondary heat exchange element 4 can be prevented, because the salt bath is not only intended as a heat transfer medium, but can also store thermal energy and release it again when needed. Such a salt bath is often also referred to as a "nitrate melt." This can be heated up to 550°C without decomposing.

[0122] Furthermore, for example in the food industry, a pipe 8 for seven bar steam, another pipe 8 for 16 bar steam, and a fourth pipe 8 for high-pressure steam (e.g., 500 bar) for engines and turbines can be generated using the same device. This is controlled by the flow velocity in the respective pipes 8 of the second heat exchanger element 4.

[0123] The potassium-sodium-calcium nitrate described in the last segment 11 in the first flow direction 5 serves as a so-called low-temperature salt and is usable up to 400°C, i.e., liquid, and thus serves as a preheater. The potassium-sodium nitrate provided in at least one further segment 12 becomes liquid from approximately 200°C and is usable up to a salt bath temperature of 550°C.

[0124] According to such an arrangement, pressureless energy storage and higher pressures are feasible.

[0125] Furthermore, due to the use of the heat transfer medium, the length of the tube 8 is significantly reduced compared to its use without such a medium. This shortening of the tube reduces the pressure loss in the second heat exchange element 4, and consequently, the pressure itself becomes much more controllable. REFERENCE MARK LIST

[0126] 1 Steam generator 2 Housing 3 First heat exchanger element 4 Second heat exchanger element 5 First flow direction 6 Inlet 7 Outlet 8 Pipe 9 Second flow direction 10 Pipe windings 11 Last segment 12 Further segment 13 Funnel 14 Connecting pipe 15 Inlet nozzle

Claims

1. A steam creation device (1), having: a housing (2); a first heat exchange element (3), disposed in the housing, through which a heat exchange fluid can flow; and at least one second heat exchange element (4), disposed in the housing, through which water can flow to create steam, a heat transfer medium, disposed in the housing (2), to transfer heat from the heat exchange fluid, flowing through the first heat exchange element (3), to the water, flowing through the second heat exchange element (4), to create steam, characterized in that the heat transfer medium is a salt bath.

2. The steam creation device (1) according to claim 1, wherein the heat exchange fluid can flow through the first heat exchange element (3) in a first flow direction (5) from an inlet (6) of the housing (2) to an outlet (7) of the housing (2).

3. The steam creation device (1) according to claim 1 or 2, wherein the heat exchange fluid is flue gas.

4. The steam creation device (1) according to claim 2 or 3, wherein the first heat exchange element (3) has a plurality of tubes (8) extending along the first flow direction (5).

5. The steam creation device (1) according to any one of claims 2 to 4, wherein the water can flow through the second heat exchange element (4) in a second flow direction (9), and wherein the first flow direction (5) and the second flow direction (9) run substantially perpendicular or substantially parallel to one another.

6. The steam creation device (1) according to any one of claims 2 to 5, wherein the second heat exchange element (4) has a plurality of tube windings (10) such that the second heat exchange element (4) extends substantially perpendicularly or substantially parallel to the first flow direction (5) from the inlet (6) of the housing (2) to the outlet (7) of the housing (2).

7. The steam creation device (1) according to claim 6, wherein the second heat exchange element (4) has a plurality of U-shaped tube windings (10).

8. The steam creation device (1) according to claim 6, wherein the second heat exchange element (4) has a plurality of tube windings (10) extending in circles or helically.

9. The steam creation device (1) according to any one of claims 4 to 6, wherein the second heat exchange element (4) has a plurality of helical tube windings (10) such that the second heat exchange element (4) extends substantially perpendicularly or substantially parallel to the first flow direction (5) from the inlet (6) of the housing (2) to the outlet (7) of the housing (2), and wherein the helical tube windings (10) extend helically between the tubes (8) or around them.

10. The steam creation device (1) according to any one of claims 4 to 8, wherein the second heat exchange element (4) extends between the tubes (8) in the housing (2).

11. The steam creation device (1) according to any one of the preceding claims, wherein the second heat exchange element (4) is disposed in the housing (2) such that it contacts the first heat exchange element (3) at at least one point, preferably at several points, in the housing (2).

12. The steam creation device (1) according to any one of the preceding claims, wherein a plurality of second heat exchange elements is disposed in the housing (2).

13. The steam creation device (1) according to any one of the preceding claims, wherein the steam creation device (1) further has at least one pump, disposed in the housing (2), which is configured to circulate the salt bath.

14. The steam creation device (1) according to any one of claims 2 to 13, wherein the steam creation device (1) is divided into several segments (11, 12) along the first flow direction (5), wherein the segments (11, 12) are connected to one another in such a way that the heat exchange fluid can flow along the first flow direction (5) through the segments (11, 12) from the inlet (6) of the housing (2) to the outlet (7) of the housing (2), and wherein at least one second heat exchange element (4) is provided in each segment (11, 12) of the housing (2), and wherein the second heat exchange elements in the segments (11, 12) of the housing (2) are connected to one another in a fluid-tight manner.

15. The steam creation device (1) according to claim 14, wherein the steam creation device (1) is configured such that the water can first flow through the last segment (11) in the first flow direction (5) and then through the first segment (12) in the first flow direction (5).

16. The steam creation device (1) according to claim 14 or 15, wherein the segments (11, 12) are connected to one another in such a way that a flow of oxidizable material, contained in the heat exchange fluid, from one segment into another segment along the first flow direction (5) is prevented.

17. The steam creation device (1) according to any one of the preceding claims, wherein the heat transfer medium covers at least the first heat exchange element (3) and the second heat exchange element (4).

18. The steam creation device (1) according to any one of the preceding claims, wherein the salt bath has a nitrate salt.

19. The steam creation device (1) according to claim 18, wherein the salt bath has potassium sodium nitrate.

20. The steam creation device (1) according to any one of claims 14 to 19, wherein at least two different salt baths are provided in the segments (11, 12), which are stored separately from one another in the segments (11, 12).

21. The steam creation device (1) according to claim 20, wherein the salt bath in the last segment (11) in the first flow direction (5) has potassium-sodium-calcium nitrate, and wherein the salt bath in at least one further segment (12) has potassium-sodium-nitrate.

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