EP4134609A1 - Steam creation device - Google Patents

Abstract

The present invention relates to a steam generator which has a housing, a first heat exchange element arranged in the housing and through which a heat exchange fluid can flow, and at least one second heat exchange element arranged in the housing through which water can flow to generate steam. The steam generator further includes a heat transfer medium disposed within the housing for transferring heat from the heat exchange fluid flowing through the first heat exchange element to the water flowing through the second heat exchange element to generate steam, the heat transfer medium being a salt bath.

Description

TECHNICAL AREA

The present invention relates to a steam generator for generating steam for power generation, for example by means of a steam engine or a steam turbine. For this purpose, the steam generator can be connected to a biomass furnace, biogas plant or a pellet heater, for example.

BACKGROUND

Steam generators are generally used to generate steam. These steam generators usually 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 required heat. This heat in the form of a heat transfer medium is guided past a heat exchanger, for example, in order to evaporate water flowing in the heat exchanger. The water vapor thus generated can then be used to generate energy, for example in a steam engine.

Efficient steam and energy generation requires high pressures and the associated high temperatures. This leads to thermal expansion of the heat exchanger and stresses in the material of the heat exchanger.

In the prior art, for example, from the DE 10 2010 046 804 A1 a tube bundle heat exchanger with a Multiplicity of tube windings, which emanate from a common outlet space for a heat exchange medium and open into a common outlet space, each tube winding comprising an alternating sequence of tube sections and tube bends and the tube bends being designed as deflections by 180° with respect to an associated bend axis and having the same bending radii , out. This tube bundle heat exchanger is characterized in that along each tube winding the arc axes of tube bends which are connected to the same tube section are at an angle to one another and the arc axes of tube bends between which a tube section, a tube bend and another tube section are arranged in direct succession, run parallel.

However, the efficiency in this case depends strongly on the distance of the tube bundle heat exchanger to the housing and strongly on the flow type of the heat exchange fluid in the tube bundles to the thermal energy generated by fuel. This means that wall losses that are generated by a flow past between the shell-and-tube heat exchanger and a surrounding housing without the heat exchanger being flowed through cannot be prevented in such a configuration. Thus, the heat exchange efficiency is not optimal.

Furthermore, according to such an embodiment, it is not possible to compensate for stresses in the tube bundles due to thermal expansion that is generated by the high temperatures of the heat exchange fluid.

Also the DE 20 2007 017 403 U1 discloses a tube bundle heat exchanger, in particular for the heat exchange from heating gas to heating water or drinking water, the tube bundle heat exchanger having a water space through which a heating water flow or drinking water flow can flow and a water space of having a heating gas flow through which the heating gas space can flow. In this case, the heating gas pipes forming the heating gas can be flown through in parallel or in series.

Here, too, the problems described above occur, and in addition, the efficiency of heat exchange is low because it is co-current.

In addition, when generating steam with biomass in previously known steam generators, it is particularly critical to compensate for an undefined and possibly fluctuating energy content of the fuel mass (in contrast to, for example, coal) and thus the fluctuating steam parameters during steam generation. If this cannot be adequately compensated for, the steam temperature will fluctuate, which—for example when steam turbines are used—can lead to impairment or even damage to these steam turbines.

For this reason, previously known configurations use an additional steam storage tank in order to achieve low pressure losses and to counteract the fluctuation.

However, such a configuration can no longer be used at high pressures, for example above 250 bar, since there is a high risk of destruction, for example in the form of an explosion.

Thus, there has been a previous need for a solution for a steam generator when used with biomass and high pressures, which is not only resistant to high pressure, but can also be implemented easily and inexpensively.

PRESENTATION OF THE INVENTION

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

This object is solved by a device having the features of claim 1. Preferred configurations can be found in the further claims of the following description and the drawings.

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

Here, the heat exchange fluid can be the waste heat originating from a biomass furnace, biogas plant or a 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, corresponding to steam generation.

A heat transfer medium is further disposed within the hollow housing for transferring heat from the heat exchange fluid flowing through the first heat exchange element to the water flowing through the second heat exchange element to generate steam. The heat transfer medium is a salt bath.

Accordingly, the steam generator is able to exchange 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 low pressures between four and ten bar steam pressure can be generated.

This means that such an arrangement can be used particularly flexibly due to the heat-transferring salt bath and both low pressures in the range of, for example, seven bar for food production, and high-pressure steam flows in the range of 500 to 800 bar can be generated without the fluctuating Energy content of the biomass would be critical for the device itself. A complex arrangement with an additional dam storage tank to achieve low pressure losses is also unnecessary in such a configuration. Thus, not only a particularly flexible, but also a cost-effective device for generating steam can be realized.

In addition, destruction or explosion can be reliably avoided, since the salt is crystalline in the idle state and is liquefied by being heated 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 the salt is thus heated liquefied and absorbing energy.

That is, the salt bath acts as a liquid salt, such as a molten nitrate, and thus improves heat transfer from the heat exchange fluid to the water.

According to such an embodiment, not only one can A particularly flexible system can be realized, which can generate steam pressure of up to 800 bar at a wide variety of pressures, but also a particularly reliable steam generator can be achieved.

The heat exchange fluid can flow through the first heat exchange element in a first flow direction from an inlet of the housing to an outlet of the housing.

This means that the first direction of flow corresponds to a direction of flow of the heat exchange fluid through the heat exchanger arranged in the housing. If, for example, the housing has an elongated shape, this first direction of flow corresponds to a longitudinal extension of the housing.

As mentioned above, the heat exchange fluid can be, for example, a combustion gas from the combustion of a fuel, for example in the form of undried, low-grade biomass, in a combustion chamber of an already known moving grate furnace or the exhaust gas of a biogas plant. This means that electricity can be generated from residues. Depending on the heat exchange fluid, different temperature ranges can occur in the steam generator.

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 produced in the steam generator by burning pellets, this is usually 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., usually occur in the steam generator. Salts can also be used which already at 130°C - 150°C change from a crystalline to a liquid state of aggregation, ie an operating state.

The flexibility of the steam generator is particularly advantageous here, and the generation of the desired steam pressure is particularly easy to control.

Due to the high energy storage capabilities of the salt bath used, it is possible to regulate the pressure to be generated only via the flow rate of the water flowing through the second heat exchange element. This can be done with a simple pump.

For example, if required, pressures of seven bar can be used (e.g. for the food industry) 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 Configurations must be provided.

A particularly flexible device for generating steam that can be used multiple times can thus be provided with just one compact device and one housing.

The heat exchange fluid can be flue gas.

In the present case, the generation of steam is independent of the heat source. Thus, the heat exchange fluid can not only be present as flue gas through the combustion of biomass, but the heat exchange fluid can also be generated, for example, through the combustion of fossil fuels, such as coal or natural gas. This heat exchange fluid can then flow analogous to flue gas through the first heat exchange element.

Furthermore, the first heat exchange element can have a multiplicity of tubes which extend along the first flow direction.

According to such an embodiment, the heat exchange fluid, for example flue gas, may enter the housing at an inlet through the plurality of tubes and flow through the housing through the tubes, preferably straight tubes, along the first flow direction.

In other words, the housing has a plurality of tubes through which the heat exchange fluid flows. As a result, the surface area for heat transfer to the heat transfer medium and thus to the water in the second heat exchange elements is increased and reliable shielding of the heat exchange fluid from the salt bath is ensured. This reduces or prevents ignitability in the event of leaks or the like and thus increases the (long-term) operational reliability of the steam generator.

Furthermore, the water can flow through the second heat exchange element in a second flow direction. In this case, the first flow direction and the second flow direction can run essentially perpendicularly or essentially parallel to one another.

That is, the second flow direction corresponds to a flow direction of the water through the housing.

As described above, the plurality of tubes of the first heat exchange element may extend from the inlet of the housing to the outlet housing of the housing. Thus, for example, with an arrangement of the heat exchange elements running essentially parallel to one another, the second heat exchange element also extends from an inlet to an outlet of the housing essentially parallel to the plurality of tubes of the heat exchange element.

The term "substantially" is to be understood here in such a way that, for example, turns, windings or the like, which are used to enable a maximum tube length of the second heat exchange element in the housing, are not used when evaluating the parallelism and/or perpendicular arrangement the first direction of flow and the second direction of flow should be taken into account in relation to one another.

The second heat exchange element can have a plurality of tube windings, such that the second heat exchange element extends essentially perpendicularly or essentially parallel to the first flow direction from the inlet of the housing to the outlet of the housing.

That is, in a "box-like" configuration, i.e. in a substantially elongated shape of a housing, the tubes of the first heat exchange element described above can extend along this longitudinal direction and the second heat exchange element can have a tube which has a plurality of tube windings . A large surface area of the second heat exchange element can thus be achieved, and thus a large surface area can be provided for heat transfer.

This pipeline of the second heat exchange element can be essentially parallel to the extension of the housing, ie for example mostly horizontally through the box-like housing described as an example, or in the Substantially perpendicular to the extension of the housing, so for example mostly extend vertically through the box-like housing described as an example.

The second heat exchange element can have a plurality of U-shaped tube coils.

Thus, with a parallel arrangement of the first flow direction to the second flow direction (and thus a parallel arrangement of the plurality of tubes of the first heat exchange element to the second heat exchange element), the tube of the second heat exchange element can run essentially in a parallel direction to the plurality of tubes of the first heat exchange element will be realized. As a result of the U-shaped pipe windings, the pipe can be “snaked” as frequently as possible from the inlet to the outlet and from this outlet back to the inlet and back again from the inlet to the outlet, etc.

Conversely, this means that with a perpendicular arrangement of the first flow direction to the second flow direction, the tube of the second heat exchange element achieves as many windings as possible from the inlet to the outlet of the housing with the U-shaped tube windings with a predominant extension in the vertical direction.

In the example of a box-like housing with a substantially elongated shape already outlined several times above, this means that the multiple tubes of the first heat exchange 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 exchange element , essentially in a perpendicular, i.e. vertical in this example, direction to the elongation of the housing.

Alternatively, the second heat exchange element may comprise a plurality of tube coils extending in circles or in a helical configuration.

That is, the plurality of tube coils extending in circles or helices can lie in the salt bath located in the housing and due to the circular shape or helix shape maximize the surface area of the second heat exchange element, e.g. a tube through which water flows, and thus the heat transfer from the allow first heat exchange element on the salt bath or directly on the second heat exchange element.

The second heat exchange element may include a plurality of helical coils of tubing such that the second heat exchange element extends substantially perpendicularly or substantially parallel to the first flow direction from the inlet of the housing to the outlet of the housing. Here, the helical tube windings are arranged helically between or around the tubes.

That is, the tubes extending from the inlet of the housing to the outlet of the housing through which the heat exchange fluid, e.g. flue gas, passes may be directly wrapped by the tube coils or may have the tube coils between the tubes.

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

The second heat exchange element can be located between the tubes in the housing extend.

According to such a configuration, the tubes of the first heat exchange element can extend from the inlet of the housing to the outlet of the housing and have tube windings of the second heat exchange element arranged therein, for example in the vertical and/or horizontal direction in the interstices thereof. This enables an arrangement that is as compact as possible with a maximum heat exchange surface at the same time.

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

Such a configuration enables not only the heat transfer from the first heat exchange element to the salt bath and from the salt bath to the second heat exchange element (i.e. an indirect heat transfer by means of the salt bath heat storage medium), but also the most direct possible heat transfer from the first to the second heat exchange element can be made possible. This increases the efficiency of heat transfer.

A multiplicity of second heat exchange elements can preferably be arranged in the housing.

As described at the beginning, the salt bath serves as a heat transfer medium and can also store thermal energy. By using a large number of second heat exchange elements, a large number of steam pressures can thus be generated simultaneously in the steam generator with the same heat transfer medium and independently of its temperature or the combusted material with the same arrangement be generated.

Such a configuration is particularly advantageous since it allows a large number of vapor pressures to be generated with the same compact configuration—and without the structure of the system having to be changed in the process.

In addition, due to the energy storage capacity of the heat transfer medium, i.e. the salt bath, an extremely rapid adjustment of the steam generation is possible. This means that simply by controlling the flow rate in the second heat exchange element, it is possible to switch from low pressure (e.g. seven bar) to high pressure (500 to 800 bar) within a few minutes with the same reliable and efficient device.

According to a further aspect, the steam generator can also have at least one pump which is arranged in the housing and is designed to circulate the salt bath.

Because of this pump, a circulation can be generated which increases the forced convection, since the salt bath is conveyed past the tubes of the first heat exchange element and the tube or the tube windings of the second heat exchange element and thus the heat-storing heat transfer medium in the form of a salt bath facilitates the heat transfer drastically increased.

According to a further aspect, the steam generator can be divided into several segments along the first flow direction. In this case, the segments are connected to one another in such a way that the heat exchange fluid can flow through the segments from the inlet of the housing to the outlet of the housing along the first flow direction. In each segment of the housing can be at least a second heat exchange element can be provided and the second heat exchange elements in the segments of the housing are connected to one another in a fluid-tight manner.

In other words, this configuration is to be understood in such a way that the heat transfer medium can flow through each segment along the first flow direction, for example through a large number of tubes, and in each of these segments heat is transferred to a second heat exchange element for generating steam by means of the salt bath.

In this case, the number of tubes of the first heat exchange element in a first segment does not have to correspond to the number of tubes in a further segment. Rather, this configuration is to be understood such that a heat exchange fluid flow can be realized through all segments along the first flow direction, but more tubes can be provided in a particularly hot area/segment than in an area with a lower temperature. It is therefore sufficient that the incoming heat exchange fluid can flow through the housing with the multiple segments.

In addition, it is conceivable that the heat exchange elements provided in each segment have different configurations. For example, a second heat exchange element in a first segment of the housing can have U-shaped tube windings, whereas a second heat exchange element can be configured in a helical shape in a further segment of the housing. There are no limitations with regard to the variation of the tube windings, as long as there is at least one overall tube through which the water for steam generation can flow within the housing.

It is further understood that a pump as described above may be provided in each of these segments.

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

Furthermore, the steam generator can be designed in such a way 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.

Thus, for example, a pure countercurrent can be generated, i.e. the heat exchange fluid flows from an inlet of the housing to an outlet of the housing, whereas the water for generating steam flows "from the back to the front", i.e. from an outlet to an inlet of the housing .

In addition, the water can thus be preheated at the coldest point, that is to say when it enters the last segment of the housing, in order then to be flown into a front part of the housing of the steam generator for overheating.

The segments can be 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 can be prevented.

The term "oxidizable material" can be understood, for example, as residues from biomass combustion, which are transported, for example, in the flue gas. In this case, for example, grids or the like can be provided so that the oxidizable material cannot flow from segment to segment.

Such a configuration can preferably also be provided in front 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.

Such arrangements are advantageous for operational safety, since a leak and the associated contact of flammable, oxidizable material with the salt bath can be prevented.

Furthermore, the salt bath can contain a nitrate salt.

This is not only particularly cost-effective, but can also be used to store energy at high temperatures of the heat transfer medium, for example in the case of flue gas at up to 900° C., without chemical decomposition. A configuration of the steam generator which is as operationally reliable and efficient as possible is thus implemented.

At least two different salt baths can be provided in the segments, which are stored separately from one another in the segments.

According to such an embodiment, a salt bath can be used that is as efficient as possible and adapted to the temperatures prevailing in the respective segments.

For example, in a first salt bath in a first segment along the first direction of flow, 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 direction of flow at a specific salt bath temperature from 150°C to 400°C without becoming crystalline or thermally decomposing.

The salt bath may contain potassium sodium nitrate.

The salt bath in the last segment in the first flow direction can have potassium sodium calcium nitrate and the salt bath in at least one further segment can have potassium sodium nitrate.

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 the at least one other segment is particularly temperature-stable and thus for efficient heat transfer and heat storage suitable for overheating.

This means that even if the steam temperature is between 180°C and 200°C at the back, the potassium-sodium-calcium nitrate provided in the last segment is still liquid, whereas the potassium-sodium nitrate in at least one further segment would already be solid. Thus, with an arrangement in which the water flows first into the last segment, efficient heat transfer and storage of the heat in the potassium-sodium-calcium nitrate is also possible there.

According to such an embodiment, 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 at a correct salt bath temperature of 350 °C to 550°C can be operated.

According to the configurations described above, a particularly efficient and cheap, as well as flexible steam generation can be realized, because the salt bath allows a high heat transfer at different temperatures and also has a "high forgiving" with regard to temperature fluctuations and fluctuating energy contents. This means that the salt bath enables high heat homogeneity and can thus counteract the problems described above of the different steam temperatures and the variable energy content of the biomass used, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

• Figur 1: eine perspektivische Darstellung eines Dampferzeugers gemäß einer beispielhaften Ausführungsform.
• Figur 2: eine schematische Querschnittsdarstellung des Wärmetauschers aus Figur 1.

A steam generator according to an exemplary embodiment is described below with reference to schematic drawings. Such steam generators are used, for example, to generate steam for generating energy, for example in a steam engine or a steam engine. Show it:

• figure 1 1: a perspective representation of a steam generator according to an exemplary embodiment.
• figure 2 : a schematic cross-sectional view of the heat exchanger figure 1 .

DESCRIPTION OF THE PREFERRED EMBODIMENT

the inside figure 1 Steam generator 1 shown comprises a housing 2 in which a first heat exchange element 3 and a second heat exchange element 4 are arranged.

A heat exchange fluid can flow through the first heat exchange element 3 . In the following description of an embodiment, flue gas 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.

The flue gas is fed to the steam generator 1 via a funnel 13 . In particular, 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 . In the embodiment described, this direction of flow is referred to as “first direction of flow 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.

In the embodiment shown, the first heat exchange element 3 has a multiplicity of tubes 8 which extend along the direction in which the housing 2 extends, ie from the inlet 6 to the outlet 7 of the housing 2 .

In the embodiment of the steam generator 1 shown, the housing 2 has a “box-like” design, that is to say it extends essentially along a depth direction of the housing 2 and has a rectangular cross section. However, the width and/or height and the depth of the housing 2 are not limiting for steam generation and can be configured according to space requirements and/or desired configurations. In the embodiment shown, the first flow direction 5 corresponds to the longitudinal extent of the housing 2.

In this embodiment, water flows through the second heat exchange element 4 to generate steam. In other words, the water in the second heat exchange element 4 is heated by the flue gas flowing from the first heat exchange element 3 or the flue gas flowing therein and is thus brought from a liquid state to a vapor state. This steam can then be used to generate electricity, for example. Here, the current can be used in a steam engine and/or a steam turbine, which are fed with the generated steam. In the embodiment shown, the second heat exchange element 4 is designed as a single tube 8 which extends through the housing 2 of the steam generator 1 with windings.

At this point it should be noted that, for purposes of illustration, the cover of the housing 2 (at an upper side thereof) in figure 1 has not been shown, so that the inner workings of the housing 2 in the isometric view of figure 1 is recognizable.

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

As can be seen from the figures, the second heat exchange element 4 in the form of a tube 8 has a multiplicity of tube windings 10 . These tube windings 10 are, as in figure 2 recognizable, arranged in the housing 2 in such a way that the second heat exchange element 4 extends essentially perpendicularly to the first flow direction 5 from the inlet 6 of the housing 2 to the outlet 7 of the housing 2 and with U-shaped tube winding sections along the largest possible tube length and thus tube surface its extension from the inlet 6 to the outlet 7 of the housing 2 is achieved.

That is, while the tubes 8 of the first heat exchange element 3 extend in a straight line from the inlet 6 to the outlet 7 of the housing 2, the tube 8 of the second heat exchange element 4 has a large number of tube sections running vertically in the embodiment shown, so that the U-shaped Tube coil sections connected tube coils 10 extend substantially perpendicular to the first flow direction 5 from the inlet 6 to the outlet 7 of the housing 2.

According to a further embodiment that is not shown, however, it is also possible for the first direction of flow 5 and the second direction of flow 9 to run essentially parallel to one another.

In addition, the shape of the U-shaped tube windings 10 (cf. figure 2 ) not limited to this.

Likewise, in an embodiment that is not shown, the second heat exchange element 4 can have a multiplicity of tube windings 10 extending in circles or in the shape of a snail.

It is the same in another, not shown Embodiment possible that the second heat exchange element 4 has a plurality of helical tube windings 10, which extend substantially perpendicularly or parallel to the first flow direction 5 from the inlet 6 to the outlet 7 of the housing 2 and between the tubes 8 or around them helically.

figure 1 also illustrates that the second heat exchange element 4 with the U-shaped tube windings 10 extends between the tubes 8 in the housing 2 .

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 a first flow direction 5 runs in a vertical direction and the second flow direction 9 runs essentially in a horizontal direction. If the space requirement requires this, an inclined arrangement of the housing 2 is also conceivable.

in the in figure 1 and in figure 2 In the illustrated embodiment, the second heat exchange element 4 extends along several levels in a width direction, because the tube windings 10 of the second heat exchange element 4 extend essentially perpendicularly to the first flow direction 5. Detached from this, however, it is also possible for the tube windings 10 of the second heat exchange element 4 to along a vertical direction in different planes in a height direction of the casing 2 between the tubes 8 of the first heat exchange element 3 or a mixture thereof inside the casing 2 between the tubes 8 of the first heat exchange element 3 .

In this case, 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 .

The embodiment shown in the figures is also divided along the first flow direction 5 into a plurality of segments 11, 12, two segments 11, 12 here by way of example. However, using more than two segments 11, 12 is also conceivable without problems.

The segments 11, 12 are connected to one another in such a way that the flue gas can flow along the first flow direction 5 through the segments 11, 12 from the inlet 6 to the outlet 7 of the housing 2 and in each segment 11, 12 of the housing 2 at least one second heat exchange element 4 is provided. As can be seen in FIG. 1, a connecting pipe 14 is provided between the two second heat exchange elements 4 in the segments 11, 12 of the housing 2, so that the second heat exchange elements 4 are connected to one another in a fluid-tight manner and water can flow through the entire housing 2 to generate steam.

It is also possible that not only a single second heat exchange element 4 is provided in each segment 11, 12 of the housing 2 and/or that a plurality of segments 11, 12 have to be provided at all. In a further embodiment that is not shown, it is also possible for the steam generator 1 to have only a single segment with a first heat exchange element 3 and a second heat exchange element 4 .

As described, it is also possible to use a large number of second heat exchange elements 4 in at least one segment 11, 12 to arrange. Different steam pressures can thus be generated, controlled by the fluid flow rate of the water for steam generation, with only one flue gas flow as the heat transfer medium.

Regardless of the number of second heat exchange elements 4 in the housing 2 or in the segments 11, 12 of the housing 2, the water, as in figure 1 and figure 2 shown, first flowed through the last segment 11 in the first flow direction 5 and then flowed through the first segment 12 in the first flow direction 5 . In this way, the water can first be preheated and then overheated. This means that the water enters the steam generator 1 on an outlet side of the housing 2, flows against the first flow direction 5 of the flue gas in the last segment 11 in the first flow direction 5 and is then conveyed via the connecting pipe 14 to an inlet side of the first segment 12 in flows in a flow direction of the housing 2 (see figure 2 ).

A heat transfer medium is arranged in the housing 2 in order 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 in order to generate steam. Here, the heat transfer medium is a salt bath covering the first heat exchange element 3 and the second heat exchange element 4 .

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 thus increase forced convection.

In the embodiment formed with segments 11, 12 and shown in the figures, 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, which upon contact with the salt bath, for example in the event of a leak, from one segment 12 can be prevented in a further segment 11 along the first flow direction 5. This can be done, for example, via a lattice arrangement, not shown, which prevents the entry of flammable material into one of the segments 11, 12.

As in figure 1 and figure 2 shown, this salt bath can be filled into the housing 2 via the inlet connection 15 . Thus, the salt bath fills the gaps between the first heat exchange element 3 and the second heat exchange element 4 in the housing 2 and can fill it completely. Accordingly, this salt bath can serve as a heat transfer medium and energy store in order to increase the homogeneity of the energy transfer.

The salt bath can contain a nitrate salt, in particular a potassium sodium nitrate.

In the illustrated embodiment, at least two different salt baths can be provided in the respective segments 11, 12 separately from each other. A suitable nitrate salt can thus be used, adapted to the prevailing temperatures 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.

Thus, the flue gas occurs as a heat exchange fluid over the Funnel 13 enters the housing 2 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.

Meanwhile, the heat exchange fluid transfers the heat to the salt bath filling the casing 2 as a heat transfer medium and a heat storage medium. This arrangement then heats the water present in the pipes of the second heat exchange element 4 and thus generates steam.

According to such an embodiment, problems due to fluctuating steam parameters, which can be attributed, for example, to non-constant fuel or its calorific value, can be counteracted even at supercritical pressures of over 350 bar.

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

In addition, for example in the food sector a tube 8 for seven bar steam, another tube 8 for 16 bar steam and a fourth tube 8 for high-pressure steam (e.g. 500 bar) for engines and turbines can be produced with the same device. This is controlled by the flow rate in the respective tubes 8 of the second heat exchange element 4 .

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 can be used or liquid up to 400° C. and thus serves as a preheater. The potassium sodium nitrate provided in the at least one further segment 12 becomes liquid from about 200° C. and can be used up to a salt bath temperature of 550° C.

According to such an arrangement, pressureless storage of energy and higher pressures can be realized.

Moreover, due to the use of the heat transfer medium, the net length of the tube 8 is significantly reduced relative to use without such a transfer medium. Such a shortening of the tube reduces the pressure loss in the second heat exchange element 4 and, correspondingly, the pressure itself can in turn be controlled much better.

REFERENCE LIST

1

steam generator

2

Housing

3

first heat exchange element

4

second heat exchange element

5

first direction of flow

6

inlet

7

outlet

8th

Pipe

9

second direction of flow

10

tube windings

11

last segment

12

another segment

13

funnel

14

connecting pipe

15

inlet port

Claims (21)

Steam generator (1), comprising: a housing (2); a first heat exchange element (3) arranged in the housing and through which a heat exchange fluid can flow; and at least one second heat exchange element (4) arranged in the housing, through which water can flow to generate steam, a heat transfer medium which is arranged in the housing (2) in order 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 generate steam, wherein the heat transfer medium is a salt bath. Steam generator (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). Steam generator (1) according to claim 1 or 2, wherein the heat exchange fluid is flue gas. Steam generator (1) according to claim 2 or 3, wherein the first heat exchange element (3) comprises a plurality of tubes (8) extending along the first flow direction (5). Steam generator (1) according to 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 direction of flow (5) and the second direction of flow (9) are essentially perpendicular or essentially parallel to one another. Steam generator (1) according to one of claims 2 to 5, wherein the second heat exchange element (4) has a multiplicity of tube windings (10), so that the second heat exchange element (4) extends essentially perpendicularly or essentially parallel to the first flow direction (5). extends from the inlet (6) of the housing (2) to the outlet (7) of the housing (2). Steam generator (1) according to claim 6, wherein the second heat exchange element (4) comprises a plurality of U-shaped tube coils (10). Steam generator (1) according to claim 6, wherein the second heat exchange element (4) comprises a plurality of tube coils (10) extending in circles or in a helix. Steam generator (1) according to one of claims 4 to 6, wherein the second heat exchange element (4) has a multiplicity of helical tube windings (10), so that the second heat exchange element (4) extends essentially perpendicularly or essentially parallel to the first flow direction (5 ) extends from the inlet (6) of the housing (2) to the outlet (7) of the housing (2), and
the helical tube coils (10) extending helically between or around the tubes (8). Steam generator (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). Steam generator (1) according to one of the preceding claims, wherein the second heat exchange element (4) is arranged 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). . Steam generator (1) according to one of the preceding claims, wherein a plurality of second heat exchange elements are arranged in the housing (2). Steam generator (1) according to one of the preceding claims, wherein the steam generator (1) further comprises at least one pump which is arranged in the housing (2) and is designed to circulate the salt bath. Steam generator (1) according to one of claims 2 to 13, wherein the steam generator (1) is divided into a plurality of 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 flows 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 ) can flow, and at least one second heat exchange element (4) being 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. Steam generator (1) according to claim 14, wherein the steam generator (1) is designed such that the water can flow first through the last segment (11) in the first flow direction (5) and then through the first segment (11) in the first flow direction (5). Segment (12) is flowable. Steam generator (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. Steam generator (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). Steam generator (1) according to any one of the preceding claims, wherein the salt bath comprises a nitrate salt. Steam generator (1) according to claim 18, wherein the salt bath comprises potassium sodium nitrate. Steam generator (1) according to 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). Steam generator (1) according to claim 20, wherein the salt bath in the first flow direction (5) last segment (11) has potassium-sodium-calcium nitrate, and
wherein the salt bath has potassium sodium nitrate in at least one further segment (12).

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