Heat exchange structure and boiler flue gas waste heat recovery device

Abstract

The invention relates to the field of boiler waste heat recovery, in particular to a heat exchange structure and a boiler flue gas waste heat recovery device. The cold source part is arranged at the upper part of the heat source part; the heat conduction part comprises a heat conduction piece with an inner cavity, the inner cavity of the heat conduction piece is closed, the lower end of the heat conduction piece is located in the heat source part, and the upper end of the heat conduction piece is located in the cold source part; due to the fact that the heat source medium and the cold source medium are adopted for indirect heat exchange through the heat-conducting medium, leakage of the cold source medium cannot be caused after leakage of the heat-conducting piece is caused by scouring and corrosion of the heat source medium, and harm caused by leakage of the cold source medium is avoided. After the boiler adopts the heat exchange structure, only a small amount of water serving as a heat-conducting medium leaks to the flue when the heat-conducting piece is scoured and corroded by high-temperature flue gas and leaks, and condensed water cannot leak, so that the problems that the flue gas resistance is increased, an ash hopper is blocked and the flue is corroded and blocked due to the fact that the condensed water enters the flue are solved.

Description

Technical Field

[0001] The present invention relates to the field of boiler waste heat recovery, and in particular to a heat exchange structure and a boiler flue gas waste heat recovery device. Background Art

[0002] When the boiler is running, a large amount of high-temperature flue gas is generated. The heat in the high-temperature flue gas is recovered and utilized through the low-temperature economizer. The low-temperature economizer is installed in the flue duct at the rear of the boiler (usually after the outlet of the air preheater and before the inlet of the dust collector). The waste heat of the flue gas is used to heat the boiler feed water. By lowering the exhaust gas temperature and increasing the feed water temperature, the overall thermal efficiency of the boiler is improved and coal consumption is reduced.

[0003] Heat exchange tubes are arranged inside the low-temperature economizer. Condensate passes through the heat exchange tubes. When the high-temperature flue gas passes through the low-temperature economizer, it exchanges heat with the condensate to achieve heat recovery of the high-temperature flue gas. However, due to the scouring and corrosion of the high-temperature flue gas, the heat exchange tubes will leak. The leakage causes condensate to enter the flue, increasing the flue gas resistance, which may cause the induced draft fan current to increase, stall, and even form a positive pressure in the furnace, requiring shutdown for treatment; at the same time, the leaked condensate mixes with dust to form lumps, which block the ash hopper, resulting in poor ash conveying or ash falling, and the condensate accumulates in the flue, aggravating flue corrosion and blockage. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is: how to prevent condensed water from leaking into the flue during the heat exchange process.

[0005] The above technical problems are solved by the following technical solutions: The present invention proposes a heat exchange structure, including a heat source part; a cold source part, the cold source part is arranged at the upper part of the heat source part; a heat conducting part, the heat conducting part includes a heat conducting part with an inner cavity, the inner cavity of the heat conducting part is closed, the lower end of the heat conducting part is inside the heat source part, and the upper end of the heat conducting part is inside the cold source part; wherein, there is a heat conducting medium in the inner cavity of the heat conducting part, and the heat conducting medium can change between liquid and vapor states, the liquid heat conducting medium exchanges heat with the heat source part at the lower end of the heat conducting part and is vaporized, the vaporized heat conducting medium rises to the upper end of the heat conducting part, the vaporized heat conducting medium exchanges heat with the cold source part at the upper end of the heat conducting part and is liquefied, and the liquefied heat conducting medium flows back to the lower end of the heat conducting part.

[0006] In a preferred embodiment of the heat exchange structure of the present invention: the heat conducting portion further includes a flow guiding member arranged at the upper end of the heat conducting member, and the flow guiding member extends obliquely downward from the inner wall of the heat conducting member to the axis of the inner cavity.

[0007] In a preferred embodiment of the heat exchange structure of the present invention, there are multiple flow guide members, which are spirally arranged up and down along the inner cavity of the heat conducting member.

[0008] In a preferred embodiment of the heat exchange structure of the present invention: the heat conductor is a circular tube structure with closed ends, the flow guide is in the shape of an arc plate, and the flow guide gradually narrows from the side close to the inner wall of the heat conductor to the side close to the axis of the inner cavity of the heat conductor.

[0009] In a preferred embodiment of the heat exchange structure of the present invention: the heat source portion includes a first container, the first container contains a heat source medium, and the lower end of the heat conductor extends into the first container and contacts the heat source medium.

[0010] In a preferred embodiment of the heat exchange structure of the present invention: the cold source part includes a second container arranged directly above the first container, the second container has a cold source medium inside, and the upper end of the heat conductor extends into the second container and contacts the heat source medium.

[0011] In a preferred embodiment of the heat exchange structure of the present invention, a gap is provided between the first container and the second container, and a portion of the heat conducting member between the first container and the second container is wrapped with a heat insulating member.

[0012] In a preferred embodiment of the heat exchange structure described in the present invention: the heat-conducting part also includes an isolating member arranged inside the heat-conducting member, the isolating member is located between the first container and the second container, the isolating member is a cylindrical structure with an open lower end and a closed upper end, a reflux channel is provided between the outer wall of the isolating member and the inner wall of the heat-conducting member, an exhaust pipe is provided at the upper end of the isolating member, the air inlet end of the exhaust pipe is located inside the isolating member, and the air outlet end of the exhaust pipe is located at the upper end position inside the heat-conducting member.

[0013] In a preferred embodiment of the heat exchange structure described in the present invention: the isolation member is made of heat insulating material, the upper end of the isolation member is umbrella-shaped, the exhaust pipe is a spiral coil, the outlet end of the exhaust pipe is in contact with the inner wall of the heat conductor, and the exhaust direction of the exhaust pipe is inclined upward.

[0014] A boiler flue gas waste heat recovery device includes a heat exchange structure, wherein the boiler flue gas system is a heat source part, and the boiler flue gas system has a horizontal section; the boiler condensate system is a cold source part, and some pipes of the boiler condensate system are arranged in parallel just above the horizontal section of the boiler flue gas system, and multiple groups of heat conducting parts are arranged between the horizontal section of the boiler flue gas system and the condensate pipe above it, the upper ends of the heat conducting parts extend into the condensate pipe, and the lower ends of the heat conducting parts extend into the horizontal section of the boiler flue gas system; the multiple groups of heat conducting parts are independent of each other; the flue gas flow direction in the horizontal section of the boiler flue gas system is opposite to the condensate flow direction in the condensate pipe.

[0015] The beneficial effects of the present invention are as follows: since the heat source medium and the cold source medium are indirectly exchanged through the heat conducting medium, leakage of the cold source medium will not be caused by the scouring and corrosion of the heat source medium, thereby avoiding the harm caused by leakage of the cold source medium; after the boiler adopts the above-mentioned heat exchange structure, when the heat conducting part is scoured and corroded by the high-temperature flue gas and leaks, only a small amount of water as the heat conducting medium leaks into the flue, and condensed water will not leak, thereby avoiding the problems of increased flue gas resistance, ash hopper blockage and flue corrosion blockage caused by condensed water entering the flue. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Among them:

[0017] Figure 1 The overall structural diagram of the heat exchange structure of the present invention is shown;

[0018] Figure 2 Shows a right side view of the heat exchange structure of the present invention;

[0019] Figure 3 The present invention is shown Figure 2 AA section view;

[0020] Figure 4 A schematic diagram of the internal structure of the heat conducting member of the present invention is shown;

[0021] Figure 5 Shows a schematic structural diagram of the drainage member of the present invention;

[0022] Figure 6 A schematic structural diagram of the isolation element of the present invention is shown. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings.

[0024] The terms used in the present invention are those commonly used in the art in view of the functions of the present invention, but these terms may vary according to the intentions of those skilled in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be understood as simple names, but rather as the meanings of the terms and the overall description of the present invention.

[0025] Reference Figures 1 to 3 , this embodiment provides a heat exchange structure, including,

[0026] The heat source part 1 includes a first container 11, and the first container 11 contains a heat source medium;

[0027] The cold source part 2 is arranged on the upper part of the heat source part 1. Specifically, the cold source part 2 includes a second container 21. The second container 21 is arranged just above the first container 11. The second container 21 has a cold source medium inside.

[0028] The heat conducting portion 3 includes a heat conducting member 31 having an inner cavity. The inner cavity of the heat conducting member 31 is closed and contains a heat conducting medium 32. The lower end of the heat conducting member 31 is located inside the heat source portion 1, and the upper end of the heat conducting member 31 is located inside the cold source portion 2. Specifically, the lower end of the heat conducting member 31 extends into the first container 11 and contacts the heat source medium, and the upper end of the heat conducting member 31 extends into the second container 21 and contacts the heat source medium.

[0029] Among them, the heat conducting medium 32 can change between liquid and vapor states. The liquid heat conducting medium 32 exchanges heat with the heat source part 1 at the lower end of the heat conducting member 31 and vaporizes. The vaporized heat conducting medium 32 rises to the upper end of the heat conducting member 31. The vaporized heat conducting medium 32 exchanges heat with the cold source part 2 at the upper end of the heat conducting member 31 and liquefies. The liquefied heat conducting medium 32 flows back to the lower end of the heat conducting member 31.

[0030] In the upper heat exchange structure, the heat source medium and the cold source medium indirectly exchange heat through the heat conducting medium 32. After the heat conducting member 31 leaks due to the scouring and corrosion of the heat source medium, it will not cause the cold source medium to leak, thereby avoiding the harm caused by the leakage of the cold source medium. Specifically, the second container 21 containing the cold source medium is arranged on the upper part of the first container 11 containing the heat source medium, preferably at the top. The heat conducting member 31 is vertically arranged between the first container 11 and the second container 21, and the upper and lower ends of the heat conducting member 31 extend into the second container 21 and the first container 11 respectively and contact the cold source medium and the heat source medium. During the initial heat exchange, the heat conducting medium 32 is liquid and is at the lower end position inside the heat conducting member 31 due to the action of gravity. At the end, the heat-conducting medium 32 exchanges heat with the heat source medium, so that the heat-conducting medium 32 is heated and vaporized, and the vaporized heat-conducting medium 32 rises along the inner cavity to the upper end of the heat-conducting part 31. At the upper end of the heat-conducting part 31, the vaporized heat-conducting medium 32 exchanges heat with the cold source medium, so that the heat-conducting medium 32 condenses into a liquid. The condensed liquid heat-conducting medium 32 flows back downward along the inner wall of the heat-conducting part 31 to the lower end of the heat-conducting part 31 to exchange heat with the heat source medium. This cycle process is repeated to realize indirect heat exchange between the heat source medium and the cold source medium. Since the heat-conducting part 31 is filled with the heat-conducting medium 32, when the heat-conducting part 31 leaks due to scouring and corrosion of the heat source medium, the heat-conducting medium 32 leaks to the heat source part 1 instead of the cold source medium leaking to the heat source part 1.

[0031] The heat conducting medium 32 is specifically determined according to the temperature of the heat source medium and the cold source medium. For example, when the heat exchange structure is applied to a low-temperature economizer, the heat conducting medium 32 can be selected from methanol or water, preferably water. Of course, the heat conducting member 31 is made of a heat conducting material. In order to reduce the impact of leakage of the heat conducting member 31, the heat conducting member 31 is designed to be multiple when it is arranged. Each heat conducting member 31 is independently arranged between the first container 11 and the second container 21. When a heat conducting member 31 leaks due to erosion and corrosion, it will only cause the heat conducting medium 32 inside the heat conducting member 31 to leak, and will not affect other heat conducting members 31. The amount of heat conducting medium 32 in a single heat conducting member 31 is very limited, and the impact after leakage is small.

[0032] In some embodiments, reference Figure 4 and Figure 5 The heat-conducting portion 3 further includes a flow-guiding member 33 disposed at the upper end of the heat-conducting member 31 . The flow-guiding member 33 extends obliquely downward from the inner wall of the heat-conducting member 31 to the axis of the inner cavity.

[0033] Since the vaporized heat-conducting medium 32 exchanges heat with the cold source medium at the inner wall position of the upper end of the heat-conducting member 31, the condensed liquid heat-conducting medium 32 flows back downward along the inner wall of the heat-conducting member 31, and a liquid film is formed on the inner wall of the heat-conducting member 31. The liquid film will block the heat exchange between the vaporized heat-conducting medium 32 and the cold source medium to a certain extent. The thickness of the liquid film directly affects the heat exchange efficiency between the vaporized heat-conducting medium 32 and the cold source medium. The thicker the liquid film, the lower the heat exchange efficiency. By arranging a guide member 33 on the inner wall of the heat-conducting member 31, the liquid heat-conducting medium 32 flowing back from the inner wall of the heat-conducting member 31 is guided to the middle position of the inner cavity of the heat-conducting member 31 and then continues to flow back downward, thereby reducing the thickness of the liquid film on the inner wall of the heat-conducting member 31 and improving the heat exchange efficiency between the vaporized heat-conducting medium 32 and the cold source medium.

[0034] As an optional embodiment, refer to Figure 4 and Figure 5 The heat conducting member 31 is a circular tube structure with closed ends, the flow guiding member 33 is an arc-shaped plate, and the flow guiding member 33 gradually narrows from the side close to the inner wall of the heat conducting member 31 to the side close to the axis of the inner cavity of the heat conducting member 31. There are multiple flow guiding members 33 and they are spirally arranged up and down along the inner cavity of the heat conducting member 31.

[0035] During the design, the guide member 33 is specifically an arc plate structure formed by bending the fan-shaped plate toward the middle. The end of the guide member 33 away from the inner wall of the heat-conducting member 31 has an outlet. With a curved arc structure, the guided liquid heat-conducting medium 32 is not easy to flow out from the side of the guide member 33, which is conducive to concentrating the liquid heat-conducting medium 32 to the axial position of the heat-conducting member 31 and flowing back downward. The outer arc end of the guide member 33 is fixed or integrally connected to the inner wall of the heat-conducting member 31, and the outer arc end of the guide member 33 is directed toward the axial direction of the heat-conducting member 31. The flow piece 33 is arranged downwardly at an angle to facilitate the downward backflow of the liquid heat-conducting medium 32. The guide piece 33 is specifically designed to be multiple and spirally arranged up and down along the inner cavity of the heat-conducting piece 31, that is, adjacent guide pieces 33 are spaced apart in the vertical direction and have staggered angles in the horizontal direction to provide a spiral upward steam channel. The vaporized heat-conducting medium 32 spirally rises along the steam channel, thereby improving the contact between the vaporized heat-conducting medium 32 and the inner wall of the heat-conducting piece 31, thereby improving the heat exchange efficiency between the heat-conducting medium 32 and the cold source medium.

[0036] In one embodiment provided in this application, referring to Figures 1 to 3 There is a gap between the first container 11 and the second container 21 , and the outer portion of the heat conducting member 31 between the first container 11 and the second container 21 is wrapped with a heat insulating member 34 .

[0037] When the first container 11 and the second container 21 are separated by a certain distance due to space or other restrictions, the portion of the heat conducting member 31 between the first container 11 and the second container 21 is insulated by the heat insulating member 34 to prevent the vaporous heat conducting medium 32 from exchanging heat with the external atmosphere when rising through this section, thereby reducing heat loss.

[0038] In some embodiments, reference Figure 4 and Figure 6 The heat-conducting part 3 also includes an isolating member 35 arranged inside the heat-conducting member 31. The isolating member 35 is located between the first container 11 and the second container 21. The isolating member 35 is a cylindrical structure with an open lower end and a closed upper end. A reflux channel is provided between the outer wall of the isolating member 35 and the inner wall of the heat-conducting member 31. An exhaust pipe 36 is provided at the upper end of the isolating member 35. The air inlet end of the exhaust pipe 36 is located inside the isolating member 35, and the air outlet end of the exhaust pipe 36 is located at the upper end of the heat-conducting member 31.

[0039] In order to make the liquid heat-conducting medium 32 reflux along the inner wall of the heat-conducting member 31 at the lower end of the heat-conducting member 31 and improve the heat exchange efficiency of the refluxed liquid heat-conducting medium 32 and the heat source medium, an isolating member 35 is provided inside the heat-conducting member 31. The isolating member 35 is coaxially arranged inside the heat-conducting member 31. The upper end of the isolating member 35 is closed. The liquid heat-conducting medium 32 refluxed downward from the upper end axial position of the heat-conducting member 31 falls on the top of the isolating member 35 and then flows along the reflux channel between the side wall of the isolating member 35 and the inner wall of the heat-conducting member 31. The heat-conducting medium 32 vaporized by exchanging heat with the heat source medium returns to the lower end of the heat-conducting member 31 and rises along the inside of the isolation member 35. The isolation member 35 isolates the returning liquid heat-conducting medium 32 and the rising vapor heat-conducting medium 32, reducing the entrainment of the liquid heat-conducting medium 32 by the vapor heat-conducting medium 32 during its rise, thereby further improving the heat exchange efficiency. When the heat-conducting medium 32 vaporized by exchanging heat with the heat source medium rises along the inside of the isolation member 35 to the top of the isolation member 35, it is discharged from the exhaust pipe 36 to the upper end of the heat-conducting member 31.

[0040] As an optional embodiment, refer to Figure 4 and Figure 6 The exhaust pipe 36 is a spiral coil, and the outlet end of the exhaust pipe 36 is in contact with the inner wall of the heat conductor 31, and the exhaust direction of the exhaust pipe 36 is inclined upward. The exhaust pipe 36 adopts a spiral coil and exhausts tangentially along the inner wall of the heat conductor 31, so that the vaporous heat conductor 32 spirals up after being discharged from the exhaust pipe 36, increasing the contact between the vaporous heat conductor 32 and the inner wall of the heat conductor 31, thereby improving the heat exchange efficiency. In order to adapt to the amount of vaporous heat conductor 32, multiple exhaust pipes 36 can be arranged circumferentially on the top of the isolation member 35. Part of the side wall of the isolation member 35 extends to the heat conductor 31 and is fixed on the heat conductor 31 to achieve the fixation of the isolation member 35.

[0041] A boiler flue gas waste heat recovery device includes a heat exchange structure, wherein:

[0042] The boiler exhaust system is the heat source part 1, and the boiler exhaust system has a horizontal section;

[0043] The boiler condensate system is the cold source part 2. Part of the boiler condensate system pipeline is arranged in parallel just above the horizontal section of the boiler exhaust system. Multiple groups of heat conducting members 31 are arranged between the horizontal section of the boiler exhaust system and the condensate pipeline above it. The upper end of the heat conducting member 31 extends into the condensate pipeline, and the lower end of the heat conducting member 31 extends into the horizontal section of the boiler exhaust system. Water is contained in the heat conducting pipe as the heat conducting medium 32.

[0044] The multiple groups of heat conducting members 31 are independent of each other;

[0045] The flue gas flow direction in the horizontal section of the boiler exhaust system is opposite to the condensate flow direction in the condensate pipe. The high-temperature flue gas and condensate form a countercurrent, which is conducive to heat exchange.

[0046] For ease of layout, a heat source box can be set on the horizontal section of the boiler exhaust system, and the lower end of the heat conductor 31 extends to the bottom position inside the heat source box. The boiler flue gas passes through the heat source box. A cold source box is arranged on the upper part of the heat source box. The condensed water passes through the cold source box, and the upper end of the heat conductor 31 extends to the top position inside the cold source box.

[0047] During operation, even if a single set of heat conducting parts 31 leaks due to scouring and corrosion by high-temperature flue gas, it will not cause condensed water to leak into the flue, and the amount of heat conducting medium 32 in the single set of heat conducting parts 31 is very limited, and will not react with the fly ash in the flue to worsen ash accumulation.

[0048] Finally, it should be pointed out that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways without departing from the scope of the present invention.

Claims

1. A heat exchange structure, characterized in that: include, Heat source part (1); A cold source part (2), the cold source part (2) being arranged on the upper part of the heat source part (1); A heat conducting part (3), the heat conducting part (3) comprising a heat conducting member (31) having an inner cavity, the inner cavity of the heat conducting member (31) being closed, the lower end of the heat conducting member (31) being located inside the heat source part (1), and the upper end of the heat conducting member (31) being located inside the cold source part (2); The heat conducting element (31) has a heat conducting medium (32) in its inner cavity. The heat conducting medium (32) can change between a liquid state and a vapor state. The liquid heat conducting medium (32) exchanges heat with the heat source part (1) at the lower end of the heat conducting element (31) and is vaporized. The vaporized heat conducting medium (32) rises to the upper end of the heat conducting element (31). The vaporized heat conducting medium (32) exchanges heat with the cold source part (2) at the upper end of the heat conducting element (31) and is liquefied. The liquefied heat conducting medium (32) flows back to the lower end of the heat conducting element (31).

2. The heat exchange structure according to claim 1, characterized in that: The heat-conducting portion (3) further comprises a flow-guiding member (33) arranged at the upper end of the heat-conducting member (31), and the flow-guiding member (33) extends obliquely downward from the inner wall of the heat-conducting member (31) to the position of the inner cavity axis.

3. The heat exchange structure according to claim 2, characterized in that: The flow guide members (33) are multiple and are arranged in a spiral pattern up and down along the inner cavity of the heat conducting member (31).

4. The heat exchange structure according to claim 3, characterized in that: The heat conducting member (31) is a circular tube structure with both ends closed, the flow guiding member (33) is in the shape of an arc plate, and the flow guiding member (33) gradually narrows from the side close to the inner wall of the heat conducting member (31) to the side close to the inner cavity axis of the heat conducting member (31).

5. The heat exchange structure according to claim 4, characterized in that: The heat source part (1) comprises a first container (11), wherein the first container (11) contains a heat source medium, and the lower end of the heat conducting member (31) extends into the first container (11) and contacts the heat source medium.

6. The heat exchange structure according to claim 5, characterized in that: The cold source part (2) includes a second container (21) arranged directly above the first container (11), the second container (21) contains a cold source medium, and the upper end of the heat conducting member (31) extends into the second container (21) and contacts the heat source medium.

7. The heat exchange structure according to claim 6, characterized in that: There is a gap between the first container (11) and the second container (21), and the exterior of the heat-conducting member (31) between the first container (11) and the second container (21) is wrapped with a heat-insulating member (34).

8. The heat exchange structure according to claim 7, characterized in that: The heat-conducting portion (3) further comprises an isolating member (35) arranged inside the heat-conducting member (31), the isolating member (35) being located between the first container (11) and the second container (21), the isolating member (35) being a cylindrical structure with an open lower end and a closed upper end, a reflux channel being provided between the outer wall of the isolating member (35) and the inner wall of the heat-conducting member (31), an exhaust pipe (36) being provided at the upper end of the isolating member (35), an air inlet end of the exhaust pipe (36) being located inside the isolating member (35), and an air outlet end of the exhaust pipe (36) being located at the upper end inside the heat-conducting member (31).

9. The heat exchange structure according to claim 8, characterized in that: The isolating member (35) is made of a heat-insulating material. The upper end of the isolating member (35) is umbrella-shaped. The exhaust pipe (36) is a spiral coil. The outlet end of the exhaust pipe (36) is in contact with the inner wall of the heat-conducting member (31). The exhaust direction of the exhaust pipe (36) is tilted upward.

10. A boiler flue gas waste heat recovery device, characterized by: The heat exchange structure according to any one of claims 1 to 9, wherein: The boiler exhaust system is a heat source part (1), and the boiler exhaust system has a horizontal section; The boiler condensate system is a cold source part (2), and some pipes of the boiler condensate system are arranged in parallel just above the horizontal section of the boiler smoke exhaust system. A plurality of groups of heat conducting members (31) are arranged between the horizontal section of the boiler smoke exhaust system and the condensate pipe above it, and the upper ends of the heat conducting members (31) extend into the condensate pipe, and the lower ends of the heat conducting members (31) extend into the horizontal section of the boiler smoke exhaust system. The multiple groups of heat conducting members (31) are independent of each other; The direction of flue gas flow in the horizontal section of the boiler exhaust system is opposite to the direction of condensate flow in the condensate pipe.

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