Through-flow structure and flue gas waste heat recovery device comprising same

Abstract

The utility model discloses a through-flow structure and a flue gas waste heat recovery device comprising the through-flow structure, and relates to the technical field of waste heat recovery equipment, the through-flow structure comprises an inlet section, a middle section and an outlet section which are connected in sequence, and the sectional area of the middle section of a second straight section is larger than that of a fluid inlet and a fluid outlet of the second straight section. A heat exchange part of the heat exchanger is arranged in the middle section of the second straight section; the flow guide plate is used for guiding fluid of the inlet section to the middle section in a distributed manner. The through-flow structure comprising the inlet section, the middle section and the outlet section which are sequentially connected is arranged, and the sectional area of the middle section is larger than that of the fluid inlet section, so that when flue gas flows into the middle section from the inlet section, the flow area is increased, and the pressure of the flue gas is reduced; therefore, violent scouring of the flue gas in the flue to the heat exchange part of the heat exchanger is relieved. And by arranging the guide plates, on one hand, a flue gas corridor can be prevented from being formed, and on the other hand, flue gas flow field distribution of the heating surface of the heat exchanger in the flue can be improved, so that the heat exchange effect is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of waste heat recovery equipment, in particular to a flow-through structure and a flue gas waste heat recovery device including the same. Background Art

[0002] The use of coal-fired boilers in the launch site mainly meets the daily life of the apartment area in the launch site, and thus serves the front-line staff. Obviously, its stable operation reliability and high efficiency directly affect the quality of life of front-line workers, and thus indirectly affect the combat ability of launch missions. Currently, the heat exchangers widely used in the waste heat recovery system of coal-fired boilers in the launch site are mainly low-temperature economizers. The heating surface of the low-temperature economizer is generally a serpentine tube screen, which is arranged along the width direction of the boiler in the tail flue. There is a certain gap between the pipe elbow and the wall surface of the tail flue, and the flue gas can directly flow through these gaps. The area where such flue gas short-circuit occurs is called the "flue gas corridor". The long-term erosion and abrasion of the "flue gas corridor" will cause the wall thickness of the heat exchange tube of the low-temperature economizer to decrease, and then lead to the occurrence of tube explosion and leakage accidents. The above accidents account for more than one-third of the total tube explosion and leakage accidents of the "four tubes" of the boiler.

[0003] Therefore, there is an urgent need for a solution that can weaken the influence of directly installing the heat exchanger in the tail flue on the flue gas flow field distribution, eliminate the "flue gas corridor" effect formed between the heat exchanger and the flue wall surface, and improve the uniformity of the flue gas flow field distribution on the heating surface of the heat exchanger. Content of the Utility Model

[0004] The purpose of the utility model is to provide a flow-through structure and a flue gas waste heat recovery device including the same, so as to solve the problems existing in the above-mentioned prior art, weaken the influence of directly installing the heat exchanger in the tail flue on the flue gas flow field distribution, eliminate the "flue gas corridor" effect formed between the heat exchanger and the flue wall surface, and improve the uniformity of the flue gas flow field distribution on the heating surface of the heat exchanger.

[0005] To achieve the above purpose, the utility model provides the following solution:

[0006] A flow-through structure includes an inlet section, an intermediate section, and an outlet section connected in sequence. The cross-sectional area of the intermediate section is larger than that of the inlet section and the outlet section. The heat exchange part of the heat exchanger is arranged in the intermediate section; it also includes a guide plate for dispersedly guiding the fluid in the inlet section to the intermediate section.

[0007] In an exemplary embodiment, the cross-sectional areas of the inlet section and the outlet section both gradually increase in the direction close to the intermediate section.

[0008] In an exemplary embodiment, the inlet section includes a first straight section and a divergent section, and the outlet section includes a second straight section and a convergent section.

[0009] In an exemplary embodiment, the expansion angle of the expansion section is 70°, and the contraction angle of the contraction section is 90°.

[0010] In an exemplary embodiment, there are a plurality of uniformly distributed flow guiding plates. Both side edges of the plurality of flow guiding plates are fixedly installed on the inner wall of the inlet section, and one end of the plurality of flow guiding plates away from the inlet section extends radially towards the middle section.

[0011] In an exemplary embodiment, the number of the flow guiding plates is 6.

[0012] The present utility model also provides a flue gas waste heat recovery device, including the above-mentioned flow-through structure.

[0013] In an exemplary embodiment, it further includes a separated phase change heat exchanger. The separated phase change heat exchanger includes an evaporator, a condenser, a liquid storage device, and a circulation pump that are connected in sequence to form a cycle. The fluid flow path in the flow-through structure intersects with the medium flow path in the evaporator.

[0014] In an exemplary embodiment, a safety pressure reducing device is provided between the evaporator and the condenser.

[0015] In an exemplary embodiment, a non-condensable gas removal device is provided between the evaporator and the condenser.

[0016] The present utility model has achieved the following technical effects compared with the prior art:

[0017] By providing a flow-through structure including an inlet section, a middle section, and an outlet section that are connected in sequence, and making the cross-sectional area of the middle section larger than that of the inlet section and the outlet section, when the flue gas flows from the inlet section into the middle section, due to the increase in the flow area of the flue gas, the pressure of the flue gas is reduced, thereby alleviating the intense erosion of the heat exchange part of the heat exchanger by the flue gas in the flue. Also, by providing flow guiding plates that dispersedly guide the fluid in the inlet section to the middle section, the velocity distribution of the fluid flow field in the flue is made more uniform, the flow velocity near the flue wall surface can be effectively reduced, and the situation where the flue gas concentrates to flow between the pipe elbow and the tail flue wall surface is avoided, thereby avoiding the formation of a "flue gas corridor". In addition, the flow guiding plates have the effect of making the velocity distribution of the fluid flow field in the flue more uniform, and can further improve the flue gas flow field distribution on the heat receiving surface of the heat exchanger in the flue, thereby improving the heat exchange effect.

[0018] Other technical solutions of the present utility model have achieved the following technical effects:

[0019] By adopting a separated phase change heat exchanger, taking the wall temperature as the first design parameter for thermal design, and by changing the matching of the heat transfer areas on the cold and hot sides, the wall temperature of the metal heating surface is maintained at a relatively high temperature level, which is always higher than the acid dew point, fundamentally avoiding acid dew point corrosion, condensation corrosion and the resulting fouling, reducing the maintenance cost of the equipment, and efficiently recovering the waste heat of the flue gas. It is a new type of high-efficiency energy-saving technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic structural diagram of the flow-through structure disclosed by the present invention;

[0022] Figure 2 It is the velocity contour of the symmetric cross-section of the flow-through structure with 2 guide plates;

[0023] Figure 3 It is the velocity contour of the cross-section at the inlet of the heat exchanger with 2 guide plates;

[0024] Figure 4 It is the velocity contour of the symmetric cross-section of the flow-through structure with 4 guide plates;

[0025] Figure 5 It is the velocity contour of the cross-section at the inlet of the heat exchanger with 4 guide plates;

[0026] Figure 6 It is the velocity contour of the symmetric cross-section of the flow-through structure with 6 guide plates;

[0027] Figure 7 It is the velocity contour of the cross-section at the inlet of the heat exchanger with 6 guide plates;

[0028] Figure 8 It is a schematic structural diagram of the flue gas waste heat recovery device disclosed by the present invention;

[0029] Among them, 1. Flow-through structure; 2. Inlet section; 3. Intermediate section; 4. Outlet section; 5. First straight section; 6. Expansion section; 7. Guide plate; 8. Contraction section; 9. Second straight section; 10. Evaporator; 11. Safety decompression device; 12. Non-condensable gas removal device; 13. Condenser; 14. Liquid storage equipment; 15. Circulation pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. People familiar with the art can easily understand the other advantages and functions of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification, so as to facilitate understanding and reading by those familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented, and therefore have no technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical content disclosed in this utility model without affecting the effects and objectives that can be achieved by the present utility model. In the description of this utility model, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the utility model, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the present utility model. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0032] It should also be noted that in the embodiments of the present application, the same figure mark represents the same component or the same part.

[0033] The purpose of the utility model is to provide a flue gas waste heat recovery device including a flow structure thereof, so as to solve the problems existing in the prior art, weaken the influence of the heat exchanger directly installed in the tail flue on the flue flow field distribution, eliminate the "flue gas corridor" effect formed between the heat exchanger and the flue wall, and improve the uniformity of the flue gas flow field distribution on the heated surface of the heat exchanger.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0035] Example 1

[0036] Please refer toFigure 1 , this embodiment provides a flow-through structure 1. The flow-through structure 1 is the main flue through which flue gas flows starting from the boiler tail, including an inlet section 2, an intermediate section 3, and an outlet section 4 connected in sequence. The inlet section 2 is connected to the tail flue of the boiler, the outlet section 4 is connected to the external flue, and the heat exchange part of the heat exchanger is arranged in the intermediate section 3. The cross-sectional area of the intermediate section 3 is set to be larger than that of the inlet section 2 and the outlet section 4. When the flue gas flows from the inlet section 2 into the intermediate section 3, due to the increase in the flue gas flow area, the pressure of the flue gas decreases, thereby alleviating the intense erosion of the heat exchange part of the heat exchanger in the flue - generally the heat exchange tubes. It also includes a deflector 7 that dispersedly guides the fluid in the inlet section 2 to the intermediate section 3, which can make the velocity distribution of the fluid flow field in the flue more uniform, effectively reduce the flow velocity near the flue wall surface, and avoid the concentrated flow of flue gas between the pipe elbow and the tail flue wall surface, thereby avoiding the formation of a "flue gas corridor". In addition, the deflector 7 has the effect of making the velocity distribution of the fluid flow field in the flue more uniform, and can further improve the flue gas flow field distribution on the heat receiving surface of the heat exchanger in the flue, thereby improving the heat exchange effect.

[0037] The cross-sectional area change of the inlet section 2, the intermediate section 3, and the outlet section 4 of the flow-through structure 1 can be a stepped change or a gradual change, that is, the cross-sectional areas of the inlet section 2 and the outlet section 4 both gradually increase along the direction close to the intermediate section 3. The specific structure can be: the inlet section 2 includes a first straight section 5 and an expansion section 6, the outlet section 4 includes a second straight section 9 and a contraction section 8, the first straight section 5 is connected to the tail flue of the boiler, the expansion section 6 is connected to one end of the intermediate section 3, the other end of the intermediate section 3 is connected to the contraction section 8, and the second straight section 9 is connected to the external flue.

[0038] Combined with the actual site conditions of the coal-fired boiler in the launch site and relevant research results, the design of the flow-through structure 1 in this embodiment mainly considers influencing factors such as the elevation angles of the expansion section 6 and the contraction section 8 and the number of internal deflectors 7.

[0039] According to the actual space conditions of the site, the expansion angle of the expansion section 6 is set to 70°, at this time the elevation angle of the side wall of the expansion section 6 is 35°, the contraction angle of the contraction section 8 is 90°, and at this time the elevation angle of the side wall of the contraction section 8 is 45°, which is in line with the actual space conditions of the site.

[0040] The deflectors 7 in the flow-through structure 1 are multiple and evenly distributed. The two side edges of the multiple deflectors 7 are fixedly installed on the inner wall of the inlet section 2, and the ends of the multiple deflectors 7 far from the inlet section 2 extend radially towards the intermediate section 3.

[0041] On this basis, using the fluent numerical simulation calculation method, the improvement effects of 2, 4, and 6 deflectors 7 on the uniformity of the flow field velocity distribution in the flow-through structure 1 are calculated and simulated respectively, as Figures 2 - 7As shown in the figure. It can be found from the velocity distribution nephogram at the symmetric cross-section of each flue that the fluid is divided into multiple branch flows by the deflector 7 and flows towards the heat receiving surface of the heat exchanger. When 6 deflectors 7 are installed in the flow-through structure 1, the velocity distribution of the fluid flow field in the flue is more uniform, and the flow velocity distribution near the flue wall surface can be effectively improved. Therefore, in order to further improve the flow field distribution of the flue gas on the heat receiving surface of the heat exchanger in the flue and thus improve the heat exchange effect, 6 deflectors 7 are provided at the inlet section 2 of the flow-through structure 1 of the heat exchanger.

[0042] Embodiment 2

[0043] Please refer to Figure 8 , this embodiment provides a flue gas waste heat recovery device, including the flow-through structure 1 described in Embodiment 1.

[0044] In the traditional flue gas waste heat recovery device using a low-temperature economizer, due to factors such as the fluctuation of the coal-fired boiler load and the change of operating conditions, the low-temperature economizer at the end of the tail flue is prone to ash accumulation, and in severe cases, large-area ash blockage, acid dew point corrosion, and wear may occur. To solve the above problems, in this embodiment, the traditional low-temperature economizer is replaced with a separated phase change heat exchanger.

[0045] Specifically, the separated phase change heat exchanger includes an evaporator 10, a condenser 13, a liquid storage device 14, and a circulation pump 15 that are connected in sequence to form a cycle. Among them, the evaporator 10 is arranged in the middle section 3 of the flow-through structure 1, and the fluid flow path in the flow-through structure 1 intersects with the medium flow path in the evaporator 10.

[0046] As a preferred solution of this embodiment, a safety pressure reducing device 11 is provided between the evaporator 10 and the condenser 13.

[0047] As a preferred solution of this embodiment, a non-condensable gas removal device 12 is also provided between the evaporator 10 and the condenser 13.

[0048] Among them, the evaporator 10 is used to recover the waste heat in the flue gas discharged from the coal-fired boiler at the launch site. In this embodiment, the heat exchange tubes of the evaporator 10 adopt a vertical tube structure. Through heat exchange, the water (heat exchange medium) in the vertical tubes undergoes a phase change, changing from a liquid state to a gaseous state - water vapor. The safety pressure reducing device 11 mainly plays a protective role in the pipeline system to prevent safety accidents caused by excessive steam pressure in the pipeline. The non-condensable gas removal device 12 mainly removes the non-condensable gases generated during the evaporation process and due to component process problems in the pipeline to ensure the long-term efficient and stable operation of the heat exchanger. The condenser 13 exchanges heat between the steam inside the tube and the water supply outside the tube, so that the water vapor inside the tube releases latent heat and condenses into liquid water, and the water supply outside the tube obtains heat to complete the preheating treatment of the boiler water supply, improving the heating efficiency of the boiler; the liquid storage device 14 is used to adjust the amount of circulating water in the tube; the circulation pump 15 provides the driving force for the circulating medium in the tube to complete heat transfer.

[0049] The separated phase change heat exchanger takes the wall temperature as the first design parameter for thermal design. By changing the matching of the heat transfer areas on the cold and hot sides, that is, the matching of the heat transfer areas of the evaporator 10 and the condenser 13, the wall temperature of the metal heating surface is maintained at a relatively high temperature level, which is always higher than the acid dew point, fundamentally avoiding acid dew point corrosion, avoiding condensation corrosion and the resulting ash fouling, reducing the maintenance cost of the equipment, and efficiently recovering the waste heat of the flue gas. It is a new type of high-efficiency energy-saving technology.

[0050] In summary, the utility model has the following advantages:

[0051] 1. High heat transfer efficiency: The flow-through structure 1 can optimize the distribution of the flue gas flow on the heat transfer surface of the heat exchanger in the flue through the panel elevation angle and the number of the built-in guide plates 7, thereby improving the heat transfer efficiency of the heat exchanger.

[0052] 2. High safety and stability: First, the design and function realization of the separated phase change heat exchanger can solve the safety problem of acid dew point corrosion in the low-temperature economizer of the coal-fired boiler waste heat recovery system at the launch site; second, with the addition of the flow-through structure 1, the leakage accident problem caused by the "flue gas corridor" effect formed between the heat exchanger and the flue wall can be eliminated.

[0053] In the description of the present application, it should be noted that 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 a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0054] If the utility model discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (such as using bolts or screws for connection), or it can be understood as: an inseparable fixed connection (such as riveting or welding). Of course, the mutual fixed connection can also be replaced by an integral structure (such as being integrally formed by a casting process) (except when it is clearly impossible to adopt the integral forming process).

[0055] In addition, the terms used to represent the positional relationship or shape in any of the technical solutions disclosed by the present utility model, unless otherwise stated, include states or shapes that are approximate, similar, or close to it.

[0056] Any component provided by the utility model can either be assembled from multiple separate components or be a single component manufactured by an integral forming process.

[0057] Adaptations made according to actual requirements are all within the protection scope of the present utility model.

[0058] It should be noted that for those skilled in the art, it is obvious that the present utility model is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present utility model, the present utility model can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present utility model. Any reference signs in the claims should not be construed as limiting the claims involved.

[0059] Specific examples are used in the present utility model to elaborate on the principles and implementation manners of the present utility model. The description of the above embodiments is only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present utility model.

Claims

1. A flow-through structure, characterized in that: It includes an inlet section, a middle section and an outlet section connected in sequence. The cross-sectional area of the middle section is larger than that of the inlet section and the outlet section, and a heat exchange part of a heat exchanger is arranged in the middle section; it also includes a guide plate for dispersedly guiding the fluid in the inlet section to the middle section.

2. The flow-through structure according to claim 1, wherein: The cross-sectional areas of the inlet section and the outlet section both gradually increase in the direction close to the middle section.

3. The flow-through structure according to claim 2, characterized in that: The inlet section includes a first straight section and a diverging section, and the outlet section includes a second straight section and a converging section.

4. The flow-through structure according to claim 3, characterized in that: The diverging angle of the diverging section is 70°, and the converging angle of the converging section is 90°.

5. The flow-through structure according to claim 2, characterized in that: The guide plates are multiple and evenly distributed. Both side edges of the multiple guide plates are fixedly installed on the inner wall of the inlet section, and one end of the multiple guide plates far from the inlet section extends radially towards the middle section.

6. The flow-through structure according to claim 5, characterized in that: The number of the guide plates is 6.

7. A flue gas waste heat recovery device, characterized in that: It includes the flow-through structure according to any one of claims 1-6.

8. The flue gas waste heat recovery device according to claim 7, characterized in that: It further includes a separated phase change heat exchanger, which includes an evaporator, a condenser, a liquid storage device and a circulation pump connected in sequence to form a cycle. The fluid flow path in the flow-through structure intersects with the medium flow path in the evaporator.

9. The flue gas waste heat recovery device according to claim 8, characterized in that: A safety decompression device is arranged between the evaporator and the condenser.

10. The flue gas waste heat recovery device according to claim 8, characterized in that: A non-condensable gas removal device is arranged between the evaporator and the condenser.

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