Modularized air preheater capable of achieving heating furnace flue gas limit heat recovery

Abstract

The invention discloses a modular air preheater capable of achieving heating furnace flue gas limit heat recovery, and relates to the waste heat recycling technology. The modular air preheater comprises a shell, a high-temperature module set and a low-temperature module set are arranged in the shell, a first flue gas inlet is formed in the upper portion of one side of the high-temperature module set, and the shell side of the lower portion of the high-temperature module set communicates with the shell side of the low-temperature module set; a second flue gas outlet is formed in the upper part of the other side of the low-temperature module group, a plurality of heat exchange tubes are vertically arranged in the high-temperature module group and the low-temperature module group, and bottom air boxes are arranged at the bottoms of the high-temperature module group and the low-temperature module group; flue gas enters from a first flue gas inlet in the high-temperature module shell side, passes through a flue gas communicating opening and is exhausted from a second flue gas outlet in the low-temperature module shell side, and therefore a U-shaped flue gas flowing channel is formed. Air enters the heat exchange pipes from the top of the low-temperature module set, passes through the bottom air box and is exhausted from the tops of the heat exchange pipes of the high-temperature module set, and therefore a U-shaped air flowing channel is formed. And the flow direction of smoke and the flow direction of air form a countercurrent double-U channel.

Description

Technical Field

[0001] The present invention relates to the technology of waste heat recovery and utilization, and particularly to a modular air preheater capable of realizing the ultimate heat recovery of the flue gas of a heating furnace. Background Art

[0002] An air preheater is a common auxiliary device for furnaces that recovers the waste heat of flue gas, raises the temperature of the air entering the furnace, reduces the fuel consumption of the furnace, and improves the combustion condition. Air preheaters are widely used in many different industrial fields, including power plants, chemical plants, and manufacturing industries. At present, the main heat exchanger structure types commonly used in the thermal furnaces of domestic and foreign steel enterprises are mainly round tube heat exchangers with internal inserts and cross-flow plate heat exchangers, etc. The traditional tubular air preheater has the characteristics of being less likely to leak and being easy to replace and repair compared with the rotary wheel air preheater. Moreover, due to the cross-flow heat transfer form and the limitation of the on-site site conditions, the traditional tubular air preheater often encounters the problem of too high resistance during operation. On the other hand, the cross-flow heat transfer method causes the heat exchange tubes on the flue gas inlet side to be subjected to large high-temperature thermal shocks and are prone to carbonization and even leakage, while the flue gas outlet side may be leaked and blocked due to low-temperature corrosion; and the high-temperature terminal difference of the cross-flow heat transfer method is relatively large, which is not conducive to improving the overall thermal efficiency of the hot blast stove, and the high and low temperature fields are very different, seriously affecting the service life and safe operation of the equipment. The traditional tubular air preheater generally uses straight round tubes, with low heat exchange efficiency and large volume; and because most of the heat exchangers are arranged in a cross-flow manner, in order to reduce the flow resistance on the outside of the tubes of the flue gas side, a relatively low flue gas flow rate is generally adopted. On the one hand, this reduces the overall heat transfer coefficient of the heat exchanger, and on the other hand, the cross-flow arrangement is limited by the heat transfer temperature difference, and the exhaust gas temperature of the air preheater is high, which not only reduces the energy utilization efficiency, but also forms local thermal pollution, is not conducive to carbon reduction and emission reduction, and fails to achieve the maximum recovery of the waste heat of the flue gas. The all-welded plate type has the problems of being prone to leakage in high-temperature occasions and uneven temperature fields being prone to forming local dead corners, and also because of the cross-flow structure form, it is difficult to achieve the maximum heat recovery. Summary of the Invention

[0003] In order to overcome the deficiencies such as the relatively large resistance of the traditional tubular air preheater and the relatively low heat recovery efficiency of the traditional tubular and plate air preheaters, the present invention provides a modular air preheater capable of realizing the ultimate heat recovery of the flue gas of a heating furnace, which can effectively reduce the inlet and outlet resistance and improve the heat recovery efficiency of the flue gas of the heating furnace.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A modular air preheater, comprising: a housing, a high-temperature module group and a low-temperature module group are arranged in the housing, a first flue gas inlet is arranged at the upper part of one side of the high-temperature module group, the other side of the high-temperature module group is arranged side by side with one side of the low-temperature module group, a second flue gas outlet is arranged at the upper part of the other side of the low-temperature module group, a flue gas communication port is arranged at the lower part of the side where the high-temperature module group and the low-temperature module group are arranged side by side, and a plurality of heat exchange tubes are vertically arranged in the high-temperature module group and the low-temperature module group, and a bottom air box is arranged at the bottom of the high-temperature module group and the low-temperature module group;

[0006] Wherein, flue gas enters from the first flue gas inlet on the shell side of the high-temperature module group, passes through the flue gas communication port, and is discharged from the second flue gas outlet on the shell side of the low-temperature module group, thereby forming a U-shaped flue gas flow channel on the shell side; air enters the heat exchange tubes from the top of the low-temperature module group, passes through the bottom air box, and is discharged from the heat exchange tubes at the top of the high-temperature module group, thereby forming a U-shaped air flow channel on the tube side.

[0007] For the modular air preheater as described above, further, the flue gas flow direction of the U-shaped flue gas flow channel on the shell side and the air flow direction of the U-shaped air flow channel on the tube side form a countercurrent.

[0008] For the modular air preheater as described above, further, the top and bottom ends of the plurality of heat exchange tubes have straight circular tube sections, and the straight circular tube sections are hermetically connected to the top and bottom of the housing.

[0009] For the modular air preheater as described above, further, the plurality of heat exchange tubes are hermetically connected to the top and bottom of the housing by a tube sheet structure.

[0010] For the modular air preheater as described above, further, the plurality of heat exchange tubes are twisted elliptical three-dimensional deformed heat exchange tubes or other forms of finless high specific surface heat exchange tubes.

[0011] For the modular air preheater as described above, further, adjacent twisted elliptical three-dimensional deformed heat exchange tubes are in contact with each other at the maximum diameter-changing convex point to form a self-supporting structure, and are supplemented with external bundling to form a heat exchange tube cluster.

[0012] For the modular air preheater as described above, further, the plurality of heat exchange tubes are arranged in a distribution mode from triangular distribution to rectangular distribution.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. It adopts a double-tube-pass and double-shell-pass structure, which is divided into two large module groups: a high-temperature module group and a low-temperature module group. Each large module group is composed of multiple small modules and multiple flue gas channels in a modular multi-channel combination. The small modules adopt side-inlet and side-outlet arrangements for the inlets and outlets, reducing the inlet and outlet air velocities, the number of tube rows scoured transversely, and effectively reducing the inlet and outlet resistances. The air flows through the tube passes and the flue gas flows through the shell passes. By adjusting the number of tube rows in the high-temperature module group, it is ensured that the air side matches a higher flow velocity, which can effectively reduce the tube wall temperature and the risk of high-temperature carbonization of the heat exchange tubes. By adjusting the number of tube rows in the low-temperature module group, it is ensured that the air-side flow velocity is more matched with the flue gas-side flow velocity and low-temperature corrosion is avoided. Thus, ordinary carbon steel pipes can be used as the heat exchange tube materials, reducing the material cost of the air preheater. The pure countercurrent heat exchange of the high- and low-temperature module groups can achieve the maximum flue gas temperature drop, thereby obtaining the maximum energy-saving benefit and realizing the ultimate heat recovery of the heating furnace flue gas.

[0015] 2. When using twisted elliptical three-dimensional deformed heat exchange tubes as heat exchange elements, supplemented by tightly fixed external bundling, it can maximize the flow velocities inside and outside the tubes and enhance the heat transfer inside and outside the tubes while completely eliminating the vibration hazards. Thus, it improves the overall heat transfer effect and the heat recovery level, reduces the comprehensive cost of waste heat recovery, and achieves better energy conservation and emission reduction effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a front view plane schematic diagram of the air preheater of the present invention;

[0018] Figure 2 It is a schematic diagram of the tube layout method of the module. The high-temperature module group is above and the low-temperature module group is below;

[0019] Figure 3 It is the flue gas inlet and outlet channel identification and elevation view between small modules

[0020] Description of the reference numerals: 1. First flue gas inlet; 2. High-temperature module group; 3. First flue gas outlet; 4. Second flue gas inlet; 5. Upper tube sheet; 6. Lower tube sheet; 7. Second flue gas outlet; 8. Low-temperature module group; 9. Heat exchange tube; 10. Shell; 11. Bottom air box. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0022] Embodiment:

[0023] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" in the embodiments of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0024] In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] See Figures 1 to 3 , the embodiment of the present invention provides a modular air preheater that can achieve the ultimate heat recovery of the flue gas of a heating furnace, which has two tube passes and two shell passes, and includes a high-temperature module group 2 composed of a plurality of small modules, a low-temperature module group 8 composed of a plurality of small modules, heat exchange tubes 9, a bottom air box 11, an upper tube sheet 5, a lower tube sheet 6, and a housing 10; the housing 10 is divided into a high-temperature module group 2 and a low-temperature module group 8 that communicate at the bottom. The left side of the top of the high-temperature module group 2 is provided with a flue gas inlet section, and the right side of the bottom is provided with a flue gas outlet section. The right side of the top of the low-temperature module group 8 is provided with a flue gas outlet section; the left side of the bottom is provided with a flue gas inlet section, and the flue gas outlet section on the right side of the bottom of the high-temperature module group 2 communicates with the flue gas inlet section on the left side of the bottom of the low-temperature module group 8.

[0026] It should be noted that the small module refers to multiple heat exchange tubes 9 bundled into a heat exchange tube cluster respectively and provided with baffle side plates. The space between the small modules can form an air flow channel. The small modules adopt side-in and side-out inlet and outlet arrangements, which can reduce the inlet and outlet air speeds, reduce the number of tube rows scoured transversely, and effectively reduce the inlet and outlet resistances.

[0027] In the above embodiment, there are multiple heat exchange tubes 9, which are vertically arranged at intervals inside the housing 10. And the heat exchange tubes 9 located in the high-temperature module group 2 and the low-temperature module group 8 adopt a tube-sheet structure and a form of expanding and welding the tubes and the tube sheets to improve the tube sealing reliability; the gaps between the heat exchange tubes 9 form a flue gas flow channel, and the inside of the heat exchange tubes 9 forms an air flow channel.

[0028] In this way, the flue gas flow path is in a U shape, and the air flow paths in the heat exchange tubes 9 in the two large module groups inside the housing 10 are also in a U shape. The flue gas flow path and the air flow path form a double-U countercurrent channel, and the flue gas can perform pure countercurrent heat exchange with the air in the heat exchange tubes 9. At the same time, the small modules in the high-temperature module group 2 and the low-temperature module group 8 adopt side-in and side-out inlet and outlet arrangements, which reduce the inlet and outlet air speeds, reduce the number of tube rows scoured transversely, and effectively reduce the inlet and outlet resistances.

[0029] Furthermore, air enters the low-temperature module group 8 from the top of the heat exchange tubes 9 and enters the high-temperature module group 2 from the bottom inside the heat exchanger. In this way, both the high-temperature module group 2 and the low-temperature module group 8 are of countercurrent heat exchange type, which expands the heat transfer temperature difference between the media on both sides of the wall of the heat exchange tubes 9, helps to reduce the heat exchange area of the air preheater. The air flows through the tube side and the flue gas flows through the shell side, and by adjusting the number of tube rows of the high and low temperature small modules, it is ensured that a higher flow rate is matched on the air side in the high-temperature section, which can effectively reduce the tube wall temperature and reduce the risk of high-temperature carbonization of the heat exchange tubes 9 in the high-temperature section; at the same time, it is also convenient to adjust the flue gas and air flow rates in the low-temperature module section. When there is a risk of low-temperature corrosion, a lower air-side flow rate is adopted to increase the tube wall temperature and avoid low-temperature corrosion.

[0030] Furthermore, the heat exchange tubes 9 are twisted elliptical three-dimensional deformed heat exchange tubes or other forms of finless high-specific-surface heat exchange tubes 9. In this way, the heat exchange tubes 9 are formed by spirally twisting elliptical tubes, which can effectively enhance the external flow disturbance and the internal swirl flow of the tubes, realize double-sided enhanced heat exchange, and improve the convective heat transfer coefficients inside and outside the tubes.

[0031] Furthermore, a certain length of straight circular tube sections are reserved at both ends of the twisted elliptical three-dimensional deformed heat exchange tubes or other forms of finless high-specific-surface heat exchange tubes 9 for airtight connection with the top and bottom of the housing 10.

[0032] Furthermore, adjacent twisted elliptical three-dimensional deformed heat exchange tubes are in contact with each other at the maximum diameter-changing convex points to form a self-supporting structure and are supplemented with external bundling. In this way, the flow rates inside and outside the tubes can be maximally increased, the characteristics of a three-dimensional variable space and variable flow field can be formed between the tube bundles, and at the same time, the risk of vibration wear can be effectively eliminated.

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0034] As Figure 1 shown, a modular air preheater capable of realizing the ultimate heat recovery of the flue gas of a heating furnace has two tube passes and two shell passes, and includes a first flue gas inlet 1; a high-temperature module group 2; a first flue gas outlet 3; a second flue gas inlet 4; a lower tube sheet 5; an upper tube sheet 6; a second flue gas outlet 7; a low-temperature module group 8; heat exchange tubes 9; a housing 10; and a bottom air box 11.

[0035] The housing 10 is the main body of the air preheater. The high-temperature module group 2 and the low-temperature module group 8 are vertically arranged in the housing 10, and the bottoms of the high- and low-temperature modules communicate with each other. The first flue gas inlet 1 is arranged at the upper left of the housing 10 and communicates with the high-temperature module group 2. The first flue gas outlet 3 is arranged at the lower right of the high-temperature module group 2. The second flue gas inlet 4 is arranged at the lower left of the low-temperature module group 8 and communicates with the first flue gas outlet 3 at the lower right of the high-temperature module group 2. The second flue gas outlet 7 is arranged at the upper right of the housing 10 and communicates with the low-temperature module group 8, forming a U-shaped pure countercurrent flow space with two shell passes and two tube passes.

[0036] The heat exchange tubes 9 are vertically and spacedly laid inside the housing 10. The gaps between the heat exchange tubes 9 form a flue gas flow channel, and the inside of the heat exchange tubes 9 forms an air flow channel. In order to improve the comprehensive heat exchange performance of the air preheater, the heat exchange tubes 9 are three-dimensional deformed tubes formed by spirally twisting elliptical tubes, and straight pipe sections are provided at both ends thereof to facilitate welding with the upper and lower end faces of the housing 10.

[0037] During operation, air enters the heat exchange tubes 9 in the low-temperature module group 8 from the top of the air preheater, flows from top to bottom, passes through the bottom inside the housing 10, and then enters the heat exchange tubes 9 in the high-temperature module group 2 from bottom to top, showing a U-shaped flow. The flue gas flowing in from the first flue gas inlet 1 flows downward along the high-temperature module group 2 in a countercurrent manner, flows out from the first flue gas outlet 3 at the bottom, enters the low-temperature module group 8 from the second flue gas inlet 4 and turns upward, at this time, it exchanges heat with the air in the tube in a countercurrent manner, and finally flows out through the second flue gas outlet 7.

[0038] In order to control the excessive pressure drop at the inlet and outlet sections to avoid too high resistance, small module arrangements are adopted. As Figure 2 shown, the small modules in the high-temperature module group 2 and the low-temperature module group 8 adopt side-in and side-out inlet and outlet arrangements, reducing the inlet and outlet air velocities, reducing the number of tube rows scoured transversely, and effectively reducing the inlet and outlet resistances.

[0039] In summary, for the modular air preheater capable of achieving the ultimate heat recovery of the heating furnace flue gas in the present invention, the structural design adopts two large modules, namely a high-temperature module group and a low-temperature module group, for heat exchange. Both the high-temperature module group 2 and the low-temperature module group 8 adopt a modular layout. The small modules adopt a side-in and side-out inlet and outlet layout, which reduces the inlet and outlet air velocities, reduces the number of tube rows scoured transversely, and effectively reduces the inlet and outlet resistances. The entire heat exchanger achieves a countercurrent heat exchange mode. The heat exchange tubes 9 for flue gas waste heat recovery adopt twisted elliptical three-dimensional deformed heat exchange tubes, which have a good heat transfer enhancement effect. While ensuring the gas flow velocity, they are not prone to vibration and have a strong anti-fouling ability. Compared with the traditional air preheating device, the air preheater of the present invention can achieve a heat transfer end difference of ≤50±5°C, increase the heat recovery amount by 40%-50% compared with the current air preheater, increase the overall heat utilization efficiency of the heating furnace by 6%-8%, complete the ultimate heat recovery of the heating furnace flue gas, and thus achieve the efficient and energy-saving operation of flue gas waste heat recovery.

[0040] It should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0041] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0042] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the essence of the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. A modular air preheater, characterized in that, Including: A housing, within which a high-temperature module group and a low-temperature module group are provided. At the upper part of one side of the high-temperature module group, there is a first flue gas inlet. The other side of the high-temperature module group is arranged side by side with one side of the low-temperature module group. At the upper part of the other side of the low-temperature module group, there is a second flue gas outlet. At the lower part of the side where the high-temperature module group and the low-temperature module group are arranged side by side, there is a flue gas communication port. And within the high-temperature module group and the low-temperature module group, multiple heat exchange tubes are vertically arranged. At the bottom of the high-temperature module group and the low-temperature module group, there is a bottom air box; Among them, flue gas enters from the first flue gas inlet on the shell side of the high-temperature module group, passes through the flue gas communication port, and is discharged from the second flue gas outlet on the shell side of the low-temperature module group, thereby forming a U-shaped flue gas flow channel on the shell side; Air enters the heat exchange tubes from the top of the low-temperature module group, passes through the bottom air box, and is discharged from the heat exchange tubes at the top of the high-temperature module group, thereby forming a U-shaped air flow channel on the tube side.

2. The modular air preheater according to claim 1, wherein The flue gas flow direction of the U-shaped flue gas flow channel on the shell side and the air flow direction of the U-shaped air flow channel on the tube side form a countercurrent.

3. The modular air preheater according to claim 1, wherein, The top and bottom of multiple heat exchange tubes have straight circular tube sections, and the straight circular tube sections are hermetically connected to the top and bottom of the housing.

4. The modular air preheater according to claim 3, wherein Multiple heat exchange tubes are hermetically connected to the top and bottom of the housing by a tube sheet structure.

5. The modular air preheater according to claim 1, characterized in that, Multiple heat exchange tubes are twisted elliptical three-dimensional deformed heat exchange tubes or other forms of finless high specific surface heat exchange tubes.

6. The modular air preheater according to claim 5, characterized in that, Adjacent twisted elliptical three-dimensional deformed heat exchange tubes are in contact with each other at the maximum diameter-changing convex points to form a self-supporting structure, and are supplemented by external bundling to form a heat exchange tube cluster.

7. The modular air preheater according to claim 1, wherein Multiple heat exchange tubes are arranged in a distribution manner ranging from triangular distribution to rectangular distribution.

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