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

Abstract

The utility model discloses a modularized air preheater capable of realizing heating furnace flue gas limit heat recovery, which relates to waste heat recovery and utilization technology and comprises a shell, a high-temperature module group and a low-temperature module group are arranged in the shell, a first flue gas inlet is arranged on the upper portion of one side of the high-temperature module group, and the lower shell side of the high-temperature module group is communicated with the shell side of the low-temperature module group. 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 utility model relates to a waste heat recovery and utilization technology, in particular to a modular air preheater capable of realizing extreme heat recovery of flue gas from a heating furnace. Background Art

[0002] Air preheater is a common furnace auxiliary equipment that recovers flue gas waste heat, increases the air temperature entering the furnace, reduces furnace fuel consumption, and improves combustion conditions. Air preheaters are widely used in many different industrial fields, including power plants, chemical plants, and manufacturing industries. At present, the heat exchanger structures commonly used in thermal furnaces of domestic and foreign steel enterprises are mainly round tube heat exchangers with internal plug-ins and cross-flow plate heat exchangers. Compared with rotary air preheaters, traditional tubular air preheaters are less prone to leakage and easier to replace and repair. Due to the use of cross-flow heat exchange and the limitations of on-site site conditions, tubular air preheaters often encounter problems of excessive resistance during operation. On the other hand, the cross-flow heat exchange method causes the heat exchange tubes on the flue gas inlet side to be easily carbonized or even leak due to high-temperature thermal shock, while the flue gas outlet side may leak and block due to low-temperature corrosion; and the cross-flow heat exchange method has a large high-temperature end difference, which is not conducive to improving the overall thermal efficiency of the hot blast furnace. The difference between high and low temperature fields is large, which seriously affects the service life and safe operation of the equipment. Traditional tubular air preheaters generally use straight round tubes, which have low heat exchange efficiency and large size. In addition, since most heat exchangers are arranged in a cross-flow pattern, a lower flue gas velocity is generally used to reduce the flow resistance on the flue gas side outside the tube. On the one hand, the overall heat exchange coefficient of the heat exchanger is reduced. On the other hand, the cross-flow pattern is limited by the heat exchange temperature difference, and the air preheater exhaust temperature is high, which not only reduces the energy utilization efficiency, but also forms local thermal pollution, which is not conducive to carbon reduction and emission reduction, and fails to achieve the maximum recovery of flue gas waste heat. The fully welded plate type has the problem of easy leakage in high temperature occasions and uneven temperature field, which easily forms local dead corners. Also, due to the cross-flow structure, it is difficult to achieve maximum heat recovery. Utility Model Content

[0003] In order to overcome the shortcomings of large resistance of traditional tubular air preheaters and low heat recovery efficiency of traditional tubular and plate air preheaters, the utility model provides a modular air preheater for realizing extreme heat recovery of heating furnace flue gas, which can effectively reduce inlet and outlet resistance and improve heat recovery efficiency of heating furnace flue gas.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A modular air preheater, comprising: a shell, a high temperature module group and a low temperature module group are arranged in the shell, a first smoke 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 parallel to the one side of the low temperature module group, a second smoke outlet is arranged at the upper part of the other side of the low temperature module group, a smoke communication port is arranged at the lower part of the side where the high temperature module group and the low temperature module group are parallel, a plurality of heat exchange tubes are vertically arranged in the high temperature module group and the low temperature module group, and a bottom wind box is arranged at the bottom of the high temperature module group and the low temperature module group;

[0006] Among them, the flue gas enters from the first flue gas inlet on the shell side of the high-temperature module group, passes through the flue gas connecting 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; the air enters the heat exchange tube from the top of the low-temperature module group, passes through the bottom bellows, and is discharged from the heat exchange tube at the top of the high-temperature module group, thereby forming a U-shaped air flow channel on the tube side.

[0007] In 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 counterflow.

[0008] The modular air preheater as described above, further, the top ends and bottom ends of the plurality of heat exchange tubes have straight round tube sections, and the straight round tube sections are airtightly connected to the top and bottom of the shell.

[0009] The modular air preheater as described above, further, the plurality of heat exchange tubes are airtightly connected to the top and bottom of the shell using a tube sheet structure.

[0010] As described above, in the modular air preheater, 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] In the modular air preheater as described above, further, adjacent twisted elliptical three-dimensional deformed heat exchange tubes contact each other at the maximum diameter change convex point to form a self-supporting structure, and are assisted by external bundling to form a heat exchange tube cluster.

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

[0013] Compared with the prior art, the utility model has the following beneficial effects:

[0014] 1. The double-tube-pass and double-shell-pass structure is adopted, which is divided into two large module groups, the high-temperature module group and the low-temperature module group. Each large module group is a modular multi-channel combination consisting of multiple small modules and multiple flue gas channels. The small module adopts a side-inlet and side-outlet inlet and outlet arrangement to reduce the inlet and outlet wind speed, reduce the number of lateral flushing tube rows, and effectively reduce the inlet and outlet resistance; the air goes through the tube pass and the flue gas goes through the shell pass, and by adjusting the number of tube rows of the high-temperature module group to ensure that the air side matches a higher flow rate, it can effectively reduce the tube wall temperature and reduce the risk of high-temperature carbonization of the heat exchange tube; the number of tube rows of the low-temperature module group is adjusted to ensure that the air side flow rate is more matched with the flue gas side flow rate, and to avoid low-temperature corrosion, so that ordinary carbon steel pipes can be used as heat exchange tube materials to reduce the material cost of the air preheater; the pure countercurrent heat exchange of the high and low temperature module group can achieve the maximum flue gas temperature drop, thereby obtaining the maximum energy-saving benefits and realizing the ultimate heat recovery of the flue gas of the heating furnace.

[0015] 2. When using twisted elliptical three-dimensional deformed heat exchange tubes as heat exchange elements, they are tightly fixed with external bundling to maximize the flow rate inside and outside the tube and strengthen the heat exchange inside and outside the tube while completely eliminating the hidden danger of vibration; thereby improving the overall heat exchange effect and heat recovery level, reducing the comprehensive cost of waste heat recovery, and achieving better energy saving 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 utility model, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the main plane view of the air preheater of the utility model;

[0018] Figure 2 The diagram is a schematic diagram of the module piping method, with the high-temperature module group on the top and the low-temperature module group on the bottom;

[0019] Figure 3 Marking and elevation of smoke inlet and outlet channels between small modules

[0020] Explanation 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 plate; 6. lower tube plate; 7. second flue gas outlet; 8. low-temperature module group; 9. heat exchange tube; 10. shell; 11. bottom bellows. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] Example:

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the utility model described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" in the embodiments of the utility model and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] In the description of the present invention, "multiple" means at least two, such as two, three, etc., unless otherwise clearly defined. In addition, unless otherwise clearly defined and defined, 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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] See also Figures 1 to 3 The embodiment of the utility model provides a modular air preheater which can realize the extreme heat recovery of flue gas from a heating furnace, and has two tube passes and two shell passes, including 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, a heat exchange tube 9, a bottom wind box 11, an upper tube plate 5, a lower tube plate 6 and a shell 10; the shell 10 is divided into a high-temperature module group 2 and a low-temperature module group 8 which are connected at the bottom, a flue gas inlet section is provided on the left side of the top of the high-temperature module group 2, a flue gas outlet section is provided on the right side of the bottom, and a flue gas outlet section is provided on the right side of the top of the low-temperature module group 8; a flue gas inlet section is provided on the left side of the bottom, and the flue gas outlet section on the right side of the bottom of the high-temperature module group 2 is connected to 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 a plurality of heat exchange tubes 9 bundled into a heat exchange tube cluster and provided with flow isolation side plates. The space between the small modules can constitute an air flow channel. The small module adopts a side-inlet and side-outlet inlet and outlet arrangement, which can reduce the inlet and outlet wind speed, reduce the number of lateral flushing tube rows, and effectively reduce the inlet and outlet resistance.

[0027] In the above embodiment, there are multiple heat exchange tubes 9, which are laid vertically at intervals inside the shell 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 tube-to-tube sheet expansion welding form to improve the tube sealing reliability; the gaps between the heat exchange tubes 9 constitute a flue gas flow channel, and the heat exchange tubes 9 constitute an air flow channel.

[0028] In this way, the flue gas flow is U-shaped, and the air flow in the heat exchange tube 9 in the two large module groups in the shell 10 is also U-shaped. The flue gas flow and the air flow form a double U-countercurrent channel, and the flue gas can perform pure countercurrent heat exchange with the air in the heat exchange tube 9. At the same time, the small modules in the high-temperature module group 2 and the low-temperature module group 8 adopt a side-inlet and side-outlet inlet and outlet arrangement to reduce the inlet and outlet wind speed, reduce the number of lateral flushing tube rows, and effectively reduce the inlet and outlet resistance.

[0029] Furthermore, air enters the low-temperature module group 8 from the top of the heat exchange tube 9 and enters the high-temperature module group 2 from the bottom of the heat exchanger. In this way, both the high-temperature module group 2 and the low-temperature module group 8 are countercurrent heat exchangers, which expands the heat transfer temperature difference of the medium on both sides of the heat exchange tube 9 wall, helps to reduce the heat exchange area of ​​the air preheater, and the air goes through the tube side and the flue gas goes through the shell side. By adjusting the number of high and low temperature small module tube rows to ensure that the high-temperature section air side matches a higher flow rate, the tube wall temperature can be effectively reduced, and the risk of high-temperature carbonization of the heat exchange tube 9 in the high-temperature section can be reduced; at the same time, it is also convenient to adjust the flue gas and air flow rates of the low-temperature module section, and use a lower air side flow rate when there is a risk of low-temperature corrosion, so as to increase the tube wall temperature and avoid low-temperature corrosion.

[0030] Furthermore, the heat exchange tube 9 is a twisted elliptical three-dimensional deformation heat exchange tube or other forms of finless high specific surface heat exchange tube 9. In this way, the heat exchange tube 9 is formed by spirally twisting an elliptical tube, which can effectively enhance the turbulence outside the tube and the swirl inside the tube, realize the enhanced heat exchange on both sides, and improve the convection heat transfer coefficient inside and outside the tube.

[0031] Furthermore, a certain length of straight circular tube sections is retained at both ends of the twisted elliptical three-dimensional deformed heat exchange tube or other forms of finless high specific surface heat exchange tube 9 so as to be airtightly connected to the top and bottom of the shell 10 .

[0032] Furthermore, adjacent twisted elliptical three-dimensional deformed heat exchange tubes contact each other at the maximum diameter change convex point to form a self-supporting structure, and are bundled externally. In this way, the flow velocity inside and outside the tube can be maximized, and the characteristics of a three-dimensional variable space variable flow field can be formed between the tube bundles, while effectively eliminating the risk of vibration wear.

[0033] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] like Figure 1 As shown, a modular air preheater capable of realizing extreme heat recovery of flue gas from a heating furnace has two tube passes and two shell passes, including 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; a heat exchange tube 9; a shell 10; and a bottom wind box 11.

[0035] The shell 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 shell 10. The bottoms of the high and low temperature modules are connected. The first flue gas inlet 1 is arranged at the upper left side of the shell 10 and is connected to the high-temperature module group 2. The first flue gas outlet 3 is arranged at the lower right side of the high-temperature module group 2. The second flue gas inlet 4 is arranged at the lower left side of the low-temperature module group 8 and is connected to the first flue gas outlet 3 at the lower right side of the high-temperature module group 2. The second flue gas outlet 7 is arranged at the upper right side of the shell 10 and is connected to the low-temperature module group 8, forming a U-shaped pure countercurrent flow space with double shell passes and double tube passes.

[0036] The heat exchange tubes 9 are laid vertically and spaced apart inside the shell 10. The gaps between the heat exchange tubes 9 constitute a flue gas flow channel, and the heat exchange tubes 9 constitute 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 spiral twisting of elliptical tubes, and straight tube sections are provided at both ends thereof for easy welding with the upper and lower end faces of the shell 10.

[0037] During operation, air enters the heat exchange tube 9 in the low temperature module group 8 from the top of the air preheater, flows from top to bottom through the bottom of the shell 10, and then enters the heat exchange tube 9 in the high temperature module group 2 from bottom to top, forming 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 flows upward, at this time exchanging 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 pressure drop of the inlet and outlet sections and avoid excessive resistance, a small module layout is adopted, such as Figure 2 As shown, the small modules in the high temperature module group 2 and the low temperature module group 8 adopt a side-inlet and side-outlet inlet and outlet arrangement, which reduces the inlet and outlet wind speed, reduces the number of lateral flushing pipe rows, and effectively reduces the inlet and outlet resistance.

[0039] In summary, the utility model is a modular air preheater that can realize the extreme heat recovery of flue gas in a heating furnace. The structural design adopts two large modules, a high-temperature module group and a low-temperature module group, for heat exchange. The high-temperature module group 2 and the low-temperature module group 8 are both arranged in a modular manner. The small module adopts a side-inlet and side-outlet inlet and outlet arrangement to reduce the inlet and outlet wind speed, reduce the number of lateral flushing tube rows, and effectively reduce the inlet and outlet resistance; the entire heat exchanger realizes a countercurrent heat exchange method. The heat exchange tube 9 for flue gas waste heat recovery adopts a twisted elliptical three-dimensional deformation heat exchange tube, which has a good enhanced heat transfer effect. While ensuring the gas flow rate, it is not easy to vibrate and has a strong ability to resist dust accumulation. Compared with the traditional air preheating device, the air preheater of the utility model can achieve a heat exchange end difference of ≤50±5℃, achieve a heat recovery amount that is 40%-50% higher than the current air preheater, and improve the overall thermal utilization efficiency of the heating furnace by 6%-8%, complete the extreme heat recovery of the flue gas in the heating furnace, and thus achieve efficient and energy-saving operation of flue gas waste heat recovery.

[0040] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0041] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0042] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. 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, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0043] The above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable ordinary technicians in the field to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the essence of the content of the utility model should be included in the protection scope of the utility model.

Claims

1. A modular air preheater, characterized in that: include: A shell, wherein a high-temperature module group and a low-temperature module group are arranged in the shell, a first smoke inlet is arranged at an upper portion 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 smoke outlet is arranged at an upper portion of the other side of the low-temperature module group, a smoke communication port is arranged at a lower portion of a side where the high-temperature module group and the low-temperature module group are arranged side by side, a plurality of heat exchange tubes are vertically arranged in the high-temperature module group and the low-temperature module group, and a bottom bellows is arranged at the bottom of the high-temperature module group and the low-temperature module group; The smoke enters from the first smoke inlet on the shell side of the high temperature module group, passes through the smoke communication port, and is discharged from the second smoke outlet on the shell side of the low temperature module group, thereby forming a U-shaped smoke flow channel on the shell side; Air enters the heat exchange tube from the top of the low temperature module group, passes through the bottom wind box, and is discharged from the heat exchange tube 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, characterized in that: The smoke flow direction of the U-shaped smoke flow channel on the shell side and the air flow direction of the U-shaped air flow channel on the tube side form a counterflow.

3. The modular air preheater according to claim 1, characterized in that: The top ends and bottom ends of the plurality of heat exchange tubes are provided with straight round tube sections, and the straight round tube sections are airtightly connected to the top and bottom of the shell.

4. The modular air preheater according to claim 3, characterized in that: The plurality of heat exchange tubes are airtightly connected to the top and bottom of the shell using a tube sheet structure.

5. The modular air preheater according to claim 1, characterized in that: The plurality of heat exchange tubes are twisted elliptical three-dimensional deformed heat exchange tubes.

6. The modular air preheater according to claim 5, characterized in that: The adjacent twisted elliptical three-dimensional deformed heat exchange tubes contact each other at the maximum diameter change convex point to form a self-supporting structure, and are bundled to form a heat exchange tube cluster.

7. The modular air preheater according to claim 1, characterized in that: The plurality of heat exchange tubes are arranged in a distribution pattern ranging from a triangle to a rectangle.

Images