Device for heat recovery, a use of a storage body in a device for heat recovery and a method for heat recovery

Abstract

Heat recovery device with a chamber (1) through which a gas can flow in one flow direction, wherein in the chamber (1) several storage bodies (2) are arranged one behind the other in the flow direction such that free flow sections are formed between the storage bodies, wherein in each of the storage bodies (2) there are several flow sections arranged next to one another and running in the direction of flow, wherein the flow sections present in the storage bodies (2) are formed by means of tubular passages (4) through the storage bodies (2), wherein the tubular passages are surrounded by inner walls of the storage body, wherein the inner wall surrounding a tubular passage forms a honeycomb, and wherein the entirety of the inner walls of the storage body surrounding the passages forms a honeycomb structure.

Description

[0001] The invention relates to a device for heat recovery, a use of a storage body in a device for heat recovery and a method for heat recovery.

[0002] Thermal processing plants, particularly high-temperature processing plants such as those used for melting, heating, and heat treating steel, non-ferrous metals, glass, ceramics, and other products, have a furnace heated by burners. The burners can combust fuel gas with combustion air and, in part, with the furnace atmosphere drawn in. A significant portion of the input energy is lost to the process via the high-temperature exhaust gas. One way to reduce these losses is through efficient heat recovery, in which the heat still present in the exhaust stream can be used, for example, to preheat the combustion media (preheat combustion air). A thermal regenerator (recuperator) can be used for this purpose.

[0003] A (thermal) regenerator is a short-term heat storage device that is also used for heat transfer. The hot exhaust gas and then the fuel to be preheated, or the combustion air, flow through a storage mass of the regenerator. The storage mass can be arranged in a chamber that has an inlet and an outlet for the exhaust gas, as well as an inlet and an outlet for the fuel to be preheated. The outlet for the exhaust gas can at least partially form the inlet for the fuel to be preheated.

[0004] From DE 199 33 513 C1 a regenerator for heat recovery is known in which a housing is provided, in the interior of which a substantially dimensionally stable storage mass rests on a support area.

[0005] DE 20 2009 009 101 U1 discloses a heat storage device that can be designed as a cross-flow heat storage device, wherein fluid flows of different temperatures intersect, preferably without mixing. A storage element designed as a brick with perforations is used. The fluids of different temperatures thus flow either internally through at least one storage element or externally around the circumference or casing of the storage element. As a result, a flow is guided either through the perforation or externally around the storage element.

[0006] EP 0 472 605 B1 discloses a system and method for thermal exhaust gas treatment. Heat storage masses with heat storage bodies formed with a specific surface area between 200 m2 and 1,000 m2 / m3 and whose channels have a hydraulic diameter of 2 mm to 12 mm are described.

[0007] A disadvantage of the regenerators known to date is that the regenerators cannot be adapted to different requirements and are relatively inflexible in design.

[0008] The object of the present invention is therefore to enable a more compact regenerator design which can be used more flexibly and to provide a storage body with the largest possible surface area along which hot exhaust gas and / or fuel medium to be preheated can flow.

[0009] The problem is solved by the subject matter of the independent patent claims 1, 9, and 10. Advantageous further developments of the subject matter of the independent patent claims are the subject matter of the respective dependent patent claims and emerge from the following description.

[0010] The core idea of ​​the invention is to form a flow section that is a free flow section between flow sections in or on a storage body. This makes it possible to achieve variability in terms of power density by varying the storage body and / or the free flow sections. The flow sections in or on the storage body can be varied in terms of their geometry, their dimensions and / or the material of the storage body, so that a variable or adapted storage capacity can be set. The dimensions of the free flow sections can also be varied. It is possible to provide essentially identical flow sections in or on the storage body within the device, in particular spaced apart in the direction of flow of the fluid, between which essentially identical, free flow sections are arranged.A modular design of a regenerator is possible in which the flow sections are essentially decoupled from one another. Several storage bodies can be arranged one above the other or next to the other at a distance from one another. The flow sections in or on a storage body can each be assigned to a storage body. The free flow sections can cause cross-mixing between the flow sections in or on the storage body. This can achieve a higher power density. An increase in convective heat transfer can be achieved by disrupting the laminar flow between two consecutive flow sections on the storage body with essentially laminar flow using a free flow section. By disrupting the laminar flow, a short-term improvement in convective heat transfer (increase in the Nusselt number) can occur.It may be possible that this increase, while maintaining the same heat transfer performance, allows the heat-transferring surface of the storage body to be made smaller, thus making the entire regenerator more compact. The more compact regenerator thus requires less space and can be used more flexibly. The heat transfer present in the flow sections on the storage body (laminar flow) can be increased by a region of turbulent flow between two flow sections, particularly at the transitions. The inventors have recognized that the initially seemingly contradictory approach of providing at least one flow section that does not run along a storage body but is essentially free, can nevertheless increase the power density.

[0011] The invention provides a device for heat recovery, particularly in a thermal processing system, comprising a chamber through which a gas, particularly an exhaust gas, can flow, wherein at least one storage body is formed in the chamber. Two flow sections are provided on a storage body, between which a free flow section is formed. The formation of a free flow section is achieved by providing a region that essentially has no storage body.

[0012] A flow section is formed by several tubular passages through the storage body. A tubular passage through the storage body is easy to manufacture.

[0013] Within the meaning of the invention, a tubular passage can have any cross-sectional diameter. The tubular passage can, in particular, have a circular, elliptical, or polygonal cross-section. The cross-section of the tubular passage can be symmetrical. In a preferred embodiment, the tubular passage can have a polygonal cross-section, in particular a quadrangular cross-section, in particular a square cross-section. A uniform design of the tubular passage can improve the production and handling of the storage body.

[0014] A substantially laminar flow can form at the flow sections on the storage body, which can be interrupted by a region with substantially turbulent flow, in particular at the transitions to the free flow section.

[0015] A series connection of flow sections on a storage body and free flow sections in the chamber can be created. The series connection or series connection essentially occurs in the direction of flow. Flow sections on a storage body and free flow sections can alternate and be traversed successively in the direction of flow, which can in particular correspond to the longitudinal axis of the chamber.

[0016] Where the terms “laminar flow” and “turbulent flow” are used here, it can be understood that the use of one of the two terms does not completely exclude the other type of flow. For the purposes of the invention, the two terms refer to two extremes which, however, do not have to be completely mutually exclusive. For the purposes of the invention, laminar flow is essentially characterized by the fact that it essentially follows the course of the flow channel or section and essentially does not break off or become turbulent. Small proportions of turbulent flow or the presence of small vortices in laminar flow do not, for the purposes of the invention, lead to the flow being regarded as turbulent. Laminar flow can have components of turbulent flow; in laminar flow, however, the laminar character of the flow predominates.Turbulent flow can have elements of a laminar flow; however, in turbulent flow, the turbulent nature of the flow predominates. The term "laminar flow" thus encompasses a flow that is as little turbulent or has as few turbulences as possible. The term "turbulent flow" encompasses a flow characterized by turbulence. A laminar flow is therefore a flow with little turbulence or a quasi-laminar flow. "Turbulent flow" is the movement of a gas in which turbulences occur over a wide area; the observable flow shape is characterized by a mostly three-dimensional flow field with a component that appears to vary randomly in time and space.

[0017] The term "chamber" within the meaning of the invention is a volume formed by a wall and / or within a body, which can also be referred to as a hollow volume. The chamber within the meaning of the invention has one or more, in particular two, openings that can serve to admit and discharge a fluid flow, in particular a gas flow. The storage mass, to which the hot exhaust gas transfers the heat and from which the heat can be transferred in turn to another fluid, in particular a fuel to be preheated, is located in the chamber.

[0018] The term "storage body" in the sense of the invention comprises a storage mass, in particular a ceramic one, to which the heat can be transferred first from the exhaust gas to the storage mass and then again to a fluid later flowing along the storage mass. In contrast to a pure bulk material, the storage body has a fixed shape. The storage body in the sense of the invention therefore has a predefined geometric configuration. A fixed shape makes it possible to change the relative position of the chamber without having to influence the arrangement of the storage bodies. However, the (additional) provision of bulk material as (supplementary) storage mass alongside the storage body, which has a fixed shape, is not excluded. The "storage body" in the sense of the invention can be formed from one or more elements. In particular, one or more storage bodies can be assigned to a flow section on a storage body.In order to be able to manufacture the device simply and compactly, one storage body can be provided for each flow section on or in a storage body. One or more storage bodies of one flow section can be positioned or fixed in their relative position to one another by one or more storage bodies of another flow section by means of spacers in the chamber. The length of a spacer in the direction of the two storage bodies can essentially correspond to the length of a free flow section. The heat-transfer surface on the storage body can be different for the flow sections within a chamber. Different storage bodies can be used within the chamber. This makes it possible to connect flow sections on the storage body and a free flow section in series or one behind the other.The same storage body or the same structural design of the storage body does not have to be present for the flow sections on the storage body. For the storage bodies of different flow sections, the pitch dimension in particular can vary. The pitch dimension determines the free flow cross-section in a honeycomb body, which can be specified as the sum of the channel width and the wall thickness of a honeycomb body channel. A smaller pitch dimension can lead to an increase in the specific surface area of ​​the honeycomb body. Channel widths of a honeycomb body can vary in the range from 2 mm to 30 mm. The wall thickness of a honeycomb body can vary in the range from 0.5 mm to 3 mm. A pitch dimension, which is specifically described here, is a channel width of 3 mm to 9 mm with a wall thickness of between 0.5 mm and 2 mm.

[0019] The term “free flow section” as used in the description comprises a region in the chamber in which the gas can flow essentially freely, such that essentially no solid material is present in the free flow section. The term “free flow section” comprises a section in the longitudinal direction of the chamber in which the chamber has no solid material over more than half of its cross-section, in particular has no solid material over more than 60% of its cross-section, particularly preferably has no solid material over more than 70% of its cross-section, particularly preferably has no solid material over more than 80% of its cross-section, and very particularly preferably has no solid material over more than 90% of its cross-section. In particular, the central region of the chamber in the region of the free flow section may have no solid material.However, it can also be provided that the spacer has a spacer element arranged centrally to the storage body in the chamber, which can be present alone or together with an edge-side spacer element.

[0020] The preposition "on" when designating that a flow section is formed on a storage body encompasses the possibility that the flow section is formed in the storage body, but also on it, in particular in an edge region of the storage body. For example, several storage bodies can be arranged next to one another in order to form a flow section between the storage bodies. The two storage bodies placed next to one another can, for example, each have one half of the flow section in the longitudinal direction of the same. The flow through the flow section of a storage body can be a flow through the storage body. The essential feature of the flow of the gas with respect to the storage body is that the gas flows along the storage body.

[0021] The term “thermal processing plant” in the sense of the invention generally includes high-temperature process furnaces, in particular industrial furnaces, for example reheating furnaces, heat treatment furnaces, forging furnaces, ladle furnaces, continuous furnaces, batch furnaces, rolling mill furnaces and melting furnaces.

[0022] According to the present invention, the device is of modular construction such that storage bodies are arranged one behind the other in the flow direction in the chamber and a free flow section is formed between the storage bodies. In a preferred embodiment, the dimensions of the storage bodies can be adapted such that the extension in one direction can essentially correspond to the extension of the chamber transverse to the flow direction. It can be provided that the storage body has a contact section on the edge for contacting or making contact with the chamber. This edge region can be structured or designed differently than the non-edge region of the storage body. For example, few or no flow sections for the fluid can be formed in the edge region compared to the non-edge region of the storage body, i.e. in particular the central region of the storage body.For the area of ​​the free flow section, a spacer can be provided which is adapted to the dimensions of the chamber such that the spacer has a contact surface or a surface that faces the inner wall of the chamber transversely to the flow direction of the fluid. Essentially, the contour of the spacer for the free flow section can be adapted to the inner contour of the chamber. The storage bodies and the spacer(s) can have contact surfaces in a transverse direction to the contact surfaces or the surfaces facing the inner wall of the chamber, with which contact can be made with the respective other body in the flow direction. The spacer and storage bodies can be brought into contact with one another in the chamber. This contact can occur directly or indirectly. It can also be provided that two storage bodies are arranged directly one behind the other.Several spacers can also be arranged in direct succession, for example, to increase the flow section on the storage body and / or to increase the flow section that is freely formed. For example, storage bodies of a specific size can be provided that are adapted to the requirements such that an arrangement in the chamber is achieved. Spacers of a predetermined size for arrangement in the chamber with the dimension along the flow direction can also be provided.

[0023] The length of the storage bodies is preferably in the range from approximately 50 cm to approximately 450 cm, in particular in the range from approximately 100 cm to approximately 350 cm. It can be provided that, to form the length of an "uninterrupted" flow section on or in the storage body, two storage bodies follow one another essentially directly in the flow direction.

[0024] The length of a free flow section is preferably in the range from approximately 2 cm to approximately 35 cm, in particular in the range from approximately 5 cm to approximately 25 cm. In the region of the free flow section, the chamber can be free essentially over the entire cross-section of the chamber, wherein, particularly in the edge region of the chamber, spacers can be provided as spacing elements between storage bodies. Two or more spacers can also be arranged essentially directly one after the other in the flow direction.

[0025] In a preferred embodiment, the surface of the storage body along which the gas flows can be in the range between 200 m 2 at 1 m 3 and 1,000 m 2 relative to 1 m 3Heat-transfer surfaces, i.e., surfaces along which the gas flows, can be created that are adapted to the specific application. The heat-transfer surface for the individual storage bodies in the chamber can be varied. For example, it can be provided that, in the direction of flow of the hot exhaust gas, a lower or higher heat-transfer surface is provided first, before a lower or higher heat-transfer surface of a storage body following in the direction of flow of the hot exhaust gas.

[0026] In the flow section of the storage body, the storage body can extend substantially over the entire cross-section of the chamber. The chamber can have a cross-sectional area in the range of approximately 350 cm 2 up to about 1,500 cm 2 , especially in the range of approximately 450 cm 2 up to about 1,350 cm 2 .

[0027] In a preferred embodiment, an alternating sequence of flow sections is provided on the storage body with free flow sections. The alternating sequence can have substantially identical dimensions for the storage bodies and the free flow sections in the direction of fluid flow. The manufacture of such a device is simple, and the device can be adapted to requirements. The number of free flow sections is one, two, three, four, or more. Preferably, the number of free flow sections is between one and four, with three or four between storage bodies.

[0028] In a preferred embodiment, spacers are provided between two consecutive storage bodies arranged in the region of a free flow section. This simplifies the manufacture of a device; the storage bodies can be introduced into the device, in particular stacked, and positioned and fixed with respect to their position in the longitudinal direction. By means of appropriate end fixings at the ends of the chamber, the storage bodies can be fastened or fixed in the chamber. When the storage body and / or spacer are fixed in the chamber, the position of the device can also be changed, so that the chamber can also be arranged in a flow path in such a way that the inlet and / or outlet of the device is oriented laterally to the chamber.

[0029] In a preferred embodiment, the at least one flow section formed on or in the storage body runs essentially straight. This simplifies manufacturing. In particular, a storage body can be used that has multiple flow sections that can run essentially straight. A parallel run can increase the number of flow sections passing through the storage body. The flow sections can be formed as non-interfering channels in the storage body, which can ensure laminar flow in the flow section that runs through the storage body. The flow sections can be present in the tubular passages or can be formed in them.

[0030] In a preferred embodiment, the storage body is arranged in the chamber such that the flow section formed on or in the storage body, in particular the plurality of flow sections, encloses an angle of approximately 20° to approximately 160° with the longitudinal axis of the chamber. In a preferred embodiment, several flow sections on a storage body enclose an angle of approximately 70° to approximately 110°, preferably approximately 80° to approximately 100°, particularly preferably approximately 85° to approximately 95° with the longitudinal axis of the chamber. In a particularly preferred embodiment, the plurality of flow sections of a storage body are aligned substantially in the direction of the longitudinal axis of the chamber, in particular substantially parallel to it.

[0031] In a preferred embodiment, the storage body comprises a plurality of storage body elements, each of which contains at least one flow section, in particular a plurality of flow sections arranged adjacent to one another. Providing a plurality of elements forming the storage body can lead to an improved formation of turbulent flow regions by providing a turbulent flow region between the storage body elements of the storage body. Furthermore, multiple elements allow for simplified handling.

[0032] According to the invention, the storage body has a honeycomb structure. Several flow sections are formed in the storage body, which pass through the storage body. The inner walls surrounding a flow section in the storage body form a honeycomb, and the entire inner walls of the storage body surrounding the flow sections form a honeycomb structure. This results in a particularly large surface area of ​​the storage body, along which hot exhaust gas and / or fuel to be preheated can flow.

[0033] In a preferred embodiment, the storage body comprises a ceramic. This allows a durable material to be used for storing and dissipating heat.

[0034] The invention also provides for the use of a storage body in a heat recovery device. The device includes a chamber through which exhaust gas can flow and in which the storage body is arranged. The storage body has at least one or more flow sections. A storage body configured in this way is used, which has two flow sections on the storage body, in particular two storage bodies, each with at least one associated flow section, wherein a free flow section arranged between the two flow sections is also used.

[0035] The invention also describes a method for heat recovery, in which the aforementioned device can be used in particular. For this purpose, exhaust gas flows around a storage body, which can be arranged in a chamber. In the described method, a free flow section is formed between the two flow sections.

[0036] The invention also provides a method for heat recovery from a gas, wherein the gas flows through a chamber. In particular, the method can utilize a device as described in the description. According to the invention, two substantially laminar flow sections are formed. A substantially turbulent flow section is formed in the chamber between the two substantially laminar flow sections.

[0037] If numerical data are provided within the scope of the invention, this includes ranges containing the specific numerical data, which are limited by a 10% tolerance above and below the respective specified numerical value. The significance of a range specification, which is attributed to the specific numerical value, takes into account the manufacturing tolerances and / or the measurement accuracy of the respective underlying quantity. The person skilled in the art therefore understands the specifically specified numerical values ​​as approximate.

[0038] The term "have" within the meaning of the invention encompasses both the meaning "have", so that in addition to the specified element, further elements can be provided; however, the term "have" also encompasses, according to the invention, a conclusive concept in the sense of a meaning of "consist of".

[0039] The invention is explained in more detail below with reference to an embodiment shown in the drawings.

[0040] In the drawings shows: Fig. 1 a device according to the invention in a schematic sectional view from the side; and Fig. 2 a schematic representation of a flow between flow sections in an enlarged view.

[0041] Fig. Figure 1 shows a device for heat recovery with a chamber 1 through which an exhaust gas, the flow direction of which is indicated by a downward arrow, and originates from a thermal processing plant (not shown). At least one flow channel is formed in the chamber 1, which runs at least partially along or in a storage body 2. In the Fig. In the embodiment shown in Figure 1, four storage bodies 2 are arranged one behind the other in the longitudinal direction of the chamber 1. The storage bodies 2 are arranged at a distance from one another in the chamber 1, which essentially has a wall 3 formed from a refractory material, which is designed in particular as a fiber molded part.

[0042] Each of the storage bodies 2 has a honeycomb structure, so that tubular passages 4 are formed in a storage body 2, passing through the storage body 2. The tubular passages 4 form flow sections in or on the storage body 2. The tubular passages 4 of a storage body 2 form, when flowing through by a fluid, an area of ​​essentially laminar flow for the fluid, ie the hot exhaust gas, as in Fig. 2 is shown schematically enlarged, flows through the storage body 2 essentially laminarly.

[0043] The storage bodies 2 are arranged at a distance from one another, so that free flow sections 5 exist between two consecutive or adjacent storage bodies. Three free flow sections 5 are formed. Two storage bodies 2 are kept spaced apart by spacers 6 arranged in the chamber 1. The storage bodies 2 and the spacers 6 are fixed by means of fixing elements 7, which act on the ends of a storage body 2 or a spacer 6 in the longitudinal direction of the chamber 1. The fixing element 7 acts on the storage body 2 at least at the edge. The wall 3 surrounds the storage bodies 2 and the free flow sections 5 in a direction that corresponds to the flow direction of the exhaust gas.

[0044] The fixing elements 7, together with the wall 3, form a clamp-like fixing for the storage bodies 2 and the spacers 6. With the clamp-like fixing, the storage body 2 located at each end in the chamber 1 is left freely accessible, so that the storage bodies 2 arranged at each end can essentially be flowed against by the exhaust gas or the exhaust gas can escape from the chamber 1 over the widest possible cross-section.

[0045] The clamp-like fixing of the storage bodies 2 and the spacers 6 to the wall 3 can, in turn, be carried out as in Fig. 1, can be integrated into the flow path of the exhaust gas by means of an inlet section 8 or inlet and an outlet section 9 or outlet. The inlet section 8 or inlet essentially has a connection for connecting to the chamber 1. The outlet section 9 or outlet also has a connection for connecting to the chamber 1. As outlined with the further possible connections shown in dashed lines, a connection to the exhaust gas flow can be made by means of connections 10, so that a connection is present at the inlet section 8 or inlet which essentially corresponds to the direction in which the flow through the chamber 1 is carried out. A connection 10 can be present at the outlet section 9 or outlet, with which connection the exhaust gas emerging from the chamber 1 is initially guided essentially in the flow direction of the chamber 1.However, connections are also conceivable which may be at an angle, which may in particular be 90°, as is sketched, for example, by the connections 11.

[0046] It can be provided that the inlet section 8 or inlet has both a connection 10 and a connection 11 to allow flexibility for connecting the chamber 1 to the exhaust gas flow. The outlet section 9 or outlet can also have both the connection 10 and the connection 11. Embodiments are also conceivable in which only one of the connections 10, 11 is present.

[0047] As in Fig.As shown in Figure 2, flow separation occurs between the storage bodies 2, generating a turbulent flow. The turbulent flow is essentially limited to the area of ​​an initial or an end region of the free flow section 5 or the flow section in or on the storage bodies 2. In particular, in the central region of the tubular passage 4 on or in the storage bodies 2, a substantially laminar flow exists.

Claims

[1] Device for heat recovery with a chamber (1) through which a gas can flow in one flow direction, wherein in the chamber (1) several storage bodies (2) are arranged one behind the other in the flow direction such that free flow sections are formed between the storage bodies, wherein in each of the storage bodies (2) there are several flow sections arranged next to one another and running in the direction of flow, wherein the flow sections present in the storage bodies (2) are formed by means of tubular passages (4) through the storage bodies (2), wherein the tubular passages are surrounded by inner walls of the storage body, wherein the inner wall surrounding a tubular passage forms a honeycomb, and wherein the entirety of the inner walls of the storage body surrounding the passages forms a honeycomb structure. [2] Device according to claim 1, characterized by that the length of a flow section in the storage bodies (2) is in the range from approximately 50 cm to approximately 450 cm and / or the length of the free flow section (5) is in the range from approximately 2 cm to approximately 35 cm. [3] Device according to claim 1 or 2, characterized by that the surface of a storage body (2) along which the gas flows is in a range between 200 m 2 relative to 1 m 3 Storage body and 1,000 m 2 relative to 1 m 3 storage body. [4] Device according to one of claims 1 to 3, characterized by that there is an alternating sequence of flow sections in the storage bodies (2) with free flow sections (5), the number of free flow sections (5) being equal to or greater than two. [5] Device according to one of claims 1 to 4, characterized bythat spacers (6) are provided between two successive storage bodies (2) which are arranged in the region of a free flow section (5). [6] Device according to one of claims 1 to 5, characterized by that the chamber (1) has a cross-sectional area in the range of approximately 450 cm 2 up to about 1,350 cm 2 has. [7] Device according to one of claims 1 to 6, characterized by that the chamber (1) has two connection options for an inlet (8) and / or an outlet (9), wherein the two connection options enclose an angle of greater than 60°, in particular an angle of approximately 90°, with one another. [8] Device according to one of claims 1 to 7, characterized by that the chamber (1) has a steel housing. [9] Use of several storage bodies (2) in a device according to one of claims 1 to 8 for heat recovery. [10] A method for heat recovery from a gas, comprising a device according to any one of claims 1 to 8, wherein a chamber (1) is flowed through with the gas, the method comprising the following steps: Formation of two essentially laminar flow sections and Forming a substantially turbulent flow section between the two substantially laminar flow sections in the chamber (1), wherein the two substantially laminar flow sections are formed by means of tubular passages (4) through the storage body (2).

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