A tubular air preheater and flue gas preheating system

Abstract

The utility model relates to flue gas treatment equipment technical field, concretely relates to a tubular air preheater and flue gas preheating system. The utility model provides a tubular air preheater, including lower plate body, upper plate body and a plurality of preheating tubes, be equipped with a plurality of first round hole on the lower plate body, be equipped with a plurality of second round hole on the upper plate body, the gas outlet end of preheating tube inserts into the first round hole of lower plate body, and its air inlet end passes through the second round hole of upper plate body, the air inlet end of preheating tube is equipped with the turbulence structure, and the turbulence structure is used for inhibiting the vortex in the inner wall of preheating tube air inlet end. Utilize turbulence structure to eliminate the huge energy loss caused by vortex, thereby reduce the energy consumption of induced draft fan, because eliminate the backflow vortex of carrying particulate matter, the local concentrated wear and tear problem of preheating tube inlet section is radically solved, prolongs the equipment life, improves flow distribution.

Description

Technical Field

[0001] This utility model relates to the technical field of flue gas treatment equipment, specifically to a tubular air preheater and a flue gas preheating system. Background Technology

[0002] The flue gas preheating system includes flue ducts, tubular air preheaters, and air ducts. The tubular air preheater, for example... Figure 1 As shown, it includes an upper plate 102, a lower plate 101, and a preheating pipe 103 disposed between the upper plate 102 and the lower plate 101. The upper plate 102 and the lower plate 101 are parallel. Flue gas in the flue pipe flows through the preheating pipe 103, and the flue gas in the preheating pipe 103 exchanges heat with the air in the flue pipe to reduce the temperature of the flue gas. Currently, when the flue gas in the flue pipe enters from the flue gas inlet of the preheating pipe 103, an asymmetric annular backflow vortex is generated near the inner wall of the flue gas inlet of the preheating pipe 103 close to the upper plate 102. Its shape can be understood as "a semi-annular vortex region attached to the inner wall of the inlet of the preheating pipe 103 and bulging in the direction of flue gas flow". The formation and morphology of this vortex are determined by fluid inertia and wall constraints. Its specific characteristics can be understood from the following two aspects:

[0003] 1. Core morphological characteristics of eddies:

[0004] The attachment position is fixed: the vortex is not suspended in the center of the flow channel, but firmly attached to the inner wall of the preheating pipe 103 inlet, forming a "wall-attached" vortex region; the vortex shape is semi-circular. From the cross-section (perpendicular to the flue gas flow direction), the vortex is not a complete circle, but a semi-circular shape with its opening facing upstream of the main flow; from the longitudinal section (parallel to the flue gas flow direction), it is a crescent-shaped region bulging towards the flue gas flow direction. The size of the vortex is not fixed and varies with the inlet Reynolds number (flow velocity, pipe diameter, fluid viscosity). The faster the flow velocity and the larger the pipe diameter abrupt change ratio (larger pipe / smaller pipe diameter), the larger the vortex region is usually.

[0005] 2. The formation mechanism of eddies:

[0006] When fluid flows from the large pipe (flue gas pipe) into the small pipe (preheating pipe 103), due to inertia, it cannot immediately change its flow direction following the sudden contraction of the pipe wall. It will continue to maintain its original linear motion trend, thus forming a low-pressure blank area between the inlet wall of the preheating pipe 103 and the flue gas. In order to fill this blank area, the surrounding fluid will flow in the opposite direction and rotate, eventually forming a stable reflux vortex.

[0007] The resulting eddy current phenomenon can cause the following problems: First, eddies are violent turbulent flows that require the mechanical energy of the fluid to maintain. This energy loss directly manifests as an increase in local resistance loss in flue gas flow. To overcome the increased resistance and ensure the designed flue gas flow rate, the power of the induced draft fan must be increased accordingly, leading to increased system operating energy consumption. Second, the high velocity and turbulent direction of the core eddy current region can pick up fly ash and particulate matter carried in the flue gas. Driven by the eddy current, these solid particles will continuously and at high speed impact and grind a specific area (i.e., the eddy current attachment zone) of the inlet section of the preheating tube 103. This localized concentrated wear is far more harmful than uniform wear and can easily cause the preheating tube 103 wall to thin and perforate in a short period of time, resulting in flue gas leakage. Third, in the low-speed return zone of the eddy current, the flue gas flow energy is low and insufficient to carry fly ash forward. This will cause fly ash particles to deposit and adhere in this area, forming ash accumulation. Ash accumulation will further reduce the flow area and exacerbate the flow resistance. Utility Model Content

[0008] (I) The problem to be solved by this utility model is that the inner wall of the inlet end of the preheating tube of the air preheater in the traditional flue gas preheating system is prone to eddy current phenomenon.

[0009] (II) Technical Solution

[0010] A tubular air preheater includes a lower plate, an upper plate, and a plurality of preheating tubes. The lower plate has a plurality of first circular holes, and the upper plate has a plurality of second circular holes. The air outlet of the preheating tube is inserted into the first circular hole of the lower plate, and its air inlet passes through the second circular hole of the upper plate.

[0011] The air inlet end of the preheating pipe is provided with a turbulence structure, which is used to suppress eddies on the inner wall of the air inlet end of the preheating pipe.

[0012] As an embodiment of this utility model, the turbulence structure includes a plurality of holes formed on the circumferential surface of the air inlet end of the preheating pipe. The holes are higher than the upper plate, and the ratio of the diameter of the preheating pipe to the distance between the holes and the top surface of the preheating pipe is 1 / 5 to 1 / 2.

[0013] As an embodiment of this utility model, the turbulence structure includes a flared opening located at the air inlet end face of the preheating pipe.

[0014] In one embodiment of this utility model, the lower plate is horizontally arranged, and the upper plate intersects with the lower plate; along the width direction of the tubular air preheater, the first end of the upper plate is higher than its second end.

[0015] As one embodiment of this utility model, the ratio of the diameter of the preheating tube to the distance between the hole and the top surface of the preheating tube is 1 / 3.

[0016] As one embodiment of this utility model, a plurality of the holes are uniformly arranged around the axis of the preheating tube.

[0017] As one embodiment of this utility model, the hole body is any one of a round hole, a square hole, or a regular polygonal hole.

[0018] A flue gas preheating system includes a tubular air preheater, a flue pipe, and an air duct; the flue pipe includes an upper flue pipe and a lower flue pipe, the flue outlet of the upper flue pipe is sealed to the top surface of the upper plate, the flue inlet of the lower flue pipe is sealed to the lower plate, and the air duct is perpendicular to the flue pipe and isolated from the flue pipe;

[0019] The side wall of the upper flue is provided with an ash discharge port, the bottom wall of the ash discharge port is at least not higher than the top surface of the upper plate, and an ash discharge door is installed at the ash discharge port.

[0020] According to one embodiment of the present invention, the ash discharge door is equipped with a door handle.

[0021] The beneficial effects of this utility model are:

[0022] The use of a turbulence structure eliminates the huge energy loss caused by eddies, thereby reducing the energy consumption of the induced draft fan. By eliminating the backflow eddies carrying particulate matter, the problem of localized concentrated wear in the inlet section of the preheating tube is fundamentally solved, extending the equipment life and improving the flow distribution. In addition, it makes the flow into each preheating tube more uniform, which helps to improve the working efficiency and stability of the entire air preheater. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a structural diagram of an existing air preheater;

[0025] Figure 2 A structural diagram of the first type of air preheater provided in this embodiment of the utility model;

[0026] Figure 3 A structural diagram of the second type of air preheater provided in this embodiment of the utility model;

[0027] Figure 4A structural diagram of a third type of air preheater provided in this embodiment of the utility model;

[0028] Figure 5 A schematic diagram of the flue gas preheating system provided in an embodiment of this utility model;

[0029] Figure 6 A top view of a flue gas preheating system with a third type of air preheater provided in an embodiment of this utility model;

[0030] Figure 7 Provided for the embodiments of this utility model Figure 6 Sectional view of AA;

[0031] Figure 8 A schematic diagram of the flue pipe and the third type of air preheater provided for an embodiment of this utility model.

[0032] Icons: 1. Air preheater; 101. Lower plate; 102. Upper plate; 103. Preheating pipe; 104. Hole; 105. Trumpet mouth; 2. Flue pipe; 201. Ash discharge door; 202. Door handle; 3. Air duct pipe. Detailed Implementation

[0033] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0034] like Figures 2-4 As shown, one embodiment of the present invention provides a tubular air preheater, including a lower plate 101, an upper plate 102 and a plurality of preheating tubes 103. The lower plate 101 is provided with a plurality of first circular holes, and the upper plate 102 is provided with a plurality of second circular holes. The air outlet end of the preheating tube 103 is inserted into the first circular hole of the lower plate 101, and its air inlet end passes through the second circular hole of the upper plate 102.

[0035] The air inlet end of the preheating tube 103 is provided with a turbulence structure, which is used to suppress the eddies located on the inner wall of the air inlet end of the preheating tube 103.

[0036] It should be noted that the bottom end of the preheating tube 103 is inserted into the first round hole of the lower plate 101 and is fixedly connected to the first round hole. The top end of the preheating tube 103 passes through the second round hole of the upper plate 102 and the outer circumferential surface of the preheating tube 103 is fixedly connected to the second round hole of the upper plate 102. That is, the top end of the preheating tube 103 is higher than the upper plate 102.

[0037] In some embodiments, the turbulence structure includes a plurality of holes 104 formed on the circumferential surface of the air inlet end of the preheating pipe 103. The holes 104 are higher than the upper plate 102, and the ratio of the diameter of the preheating pipe 103 to the distance between the holes 104 and the top surface of the preheating pipe 103 is 1 / 5 to 1 / 2. Preferably, the ratio of the diameter of the preheating pipe 103 to the distance between the holes 104 and the top surface of the preheating pipe 103 is 1 / 3.

[0038] It should be noted that the flue pipe 2 includes an upper flue pipe and a lower flue pipe. The outlet of the upper flue pipe is sealed to the top surface of the upper plate 102, and the inlet of the lower flue pipe is sealed to the lower plate 101.

[0039] The upper flue is the source of flue gas and has the highest pressure. The flue gas enters the small-section preheating pipe 103 from the large-section upper flue, and the flow velocity increases sharply. According to Bernoulli's principle, the increase in flow velocity leads to a decrease in static pressure. At the same time, in the vortex region at the inlet of the preheating pipe 103, a low-pressure zone is generated due to flow separation. Therefore, the pressure at the inlet section of the preheating pipe 103 is lower than the pressure in the upper flue. The lower flue is the outlet of flue gas. It has the lowest pressure because it passes through the entire flow resistance of the preheating pipe 103.

[0040] Because multiple holes 104 are opened on the inner wall of the vortex zone of the preheating tube 103, the holes 104 directly connect the low-pressure zone at the inlet of the preheating tube 103 with the upper flue pipe with higher pressure. Due to the existence of a stable pressure difference from high pressure (upper flue pipe) to low pressure (inlet of preheating tube 103), a stable and small jet of airflow will be injected into the preheating tube 103 through the through hole. The direction of this jet of airflow is opposite to the return flow direction inside the vortex. It is like an "energy jet" that directly rushes into and fills the low-pressure vortex zone that was originally occupied by the return fluid, thereby effectively blowing away the return fluid and destroying the rotating structure and pressure conditions on which the vortex depends for survival. As a result, the semi-annular return vortex attached to the wall surface is greatly weakened, making the flue gas flow more adherent to the wall and smoother, thereby effectively suppressing the vortex phenomenon.

[0041] In this embodiment, there are no specific restrictions on the number and shape of the holes 104 on the circumferential surface of the air inlet end of the preheating pipe 103; any reasonable design is acceptable. For example, the holes 104 can be any of the following: round holes, square holes, or regular polygonal holes.

[0042] As a specific embodiment, the hole 104 is a circular hole, and multiple holes 104 are evenly arranged around the axis of the preheating pipe 103.

[0043] In some embodiments, such as Figure 3 As shown, the turbulence structure includes a flared opening 105 located at the air inlet end face of the preheating pipe 103. The diameter of the flared opening 105 gradually decreases from the air inlet end to the air outlet end of the preheating pipe 103.

[0044] It should be noted that the bell mouth 105 provides a smooth, continuously contracting flow channel. As the flue gas flows through the bell mouth 105, the flow area gradually decreases, causing the fluid velocity to gradually increase as well. This process provides sufficient space and time for the fluid to adjust its flow direction, ensuring that its streamlines remain in close contact with the wall of the preheating tube 103, thereby effectively suppressing eddy currents. With the bell mouth 105, pressure changes occur smoothly throughout the contracting section, avoiding drastic pressure fluctuations. The reverse pressure gradient at the inlet of the preheating tube 103 is significantly weakened, preventing strong backflow.

[0045] In summary, in this embodiment, the large energy loss caused by eddies is eliminated by using a turbulence structure, thereby reducing the energy consumption of the induced draft fan. Since the backflow eddies carrying particulate matter are eliminated, the problem of localized concentrated wear in the inlet section of the preheating tube 103 is fundamentally solved, extending the equipment life and improving the flow distribution. In addition, the flow into each preheating tube 103 is made more uniform, which helps to improve the working efficiency and stability of the entire air preheater.

[0046] It should be noted that, as Figure 1 As shown, the upper plate 102 and lower plate 101 of a conventional air preheater are parallel. The inlet end of the preheating tube 103 is fixed in the second circular hole of the upper plate 102. When the flue gas in the flue pipe 2 flows through the preheating tube 103 of the air preheater 1, it is easy to cause dust to accumulate inside the preheating tube 103.

[0047] In some embodiments, in order to suppress dust accumulation, such as Figure 2 As shown, the air inlet end of the preheating pipe 103 passes through the second circular hole of the upper plate 102, that is, the air inlet end of the preheating pipe 103 is higher than the upper plate 102. The lower plate 101 is set horizontally, and the upper plate 102 intersects with the lower plate 101. Along the width direction of the tubular air preheater, the left end of the upper plate 102 is higher than its right end.

[0048] In this way, when the high-speed flue gas from the upper flue encounters the protruding pipe opening and the inclined upper plate 102, it will naturally branch. Part of the flue gas enters the preheating pipe 103, while the other part directly washes against the inclined top surface of the upper plate 102. The flue gas carrying fly ash directly washes against the inclined top surface of the upper plate 102, which is equivalent to a continuous "purge". Most of the dust in the flue gas cannot enter the small preheating pipe 103 with the airflow due to inertia, but falls directly onto the inclined upper plate 102. Under the combined action of gravity and continuous flue gas purging, the dust will naturally slide down to the lower (right) side, facilitating subsequent collection. This greatly simplifies the dust removal operation, requiring only periodic cleaning of the accumulated dust on the lower part of the top surface of the upper plate 102.

[0049] One embodiment of this utility model provides a flue gas preheating system, including any of the above-mentioned tubular air preheaters, a flue pipe 2, and an air duct 3; the flue pipe 2 includes an upper flue pipe and a lower flue pipe, the flue outlet of the upper flue pipe is sealed to the top surface of the upper plate 102, the flue inlet of the lower flue pipe is sealed to the lower plate 101, and the air duct 3 is perpendicular to the flue pipe 2 and isolated from the flue pipe 2.

[0050] Because the flue gas preheating system is equipped with the aforementioned air preheater, it can effectively suppress the eddy current phenomenon generated at the inlet end of the preheating tube 103, thereby making the flue gas flow more adherent to the wall and smoother.

[0051] As a specific embodiment, when the upper plate 102 of the tubular air preheater is inclined, such as Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, a ash discharge port is provided on the side wall of the upper flue. The bottom wall of the ash discharge port is at least no higher than the top surface of the upper plate 102, that is, the bottom wall of the ash discharge port is lower than the lowest point of the upper plate 102. An ash discharge door 201 is installed at the ash discharge port, and a door handle 202 is installed on the ash discharge door 201. In this way, later, it is only necessary to open the ash discharge door 201 and use tools to clean the accumulated ash on the top surface of the upper plate 102.

[0052] In the description of this utility model, it should be noted that the terms "upper" and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. Furthermore, in the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0054] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A tubular air preheater, comprising a lower plate (101), an upper plate (102), and a plurality of preheating tubes (103), wherein the lower plate (101) is provided with a plurality of first circular holes, and the upper plate (102) is provided with a plurality of second circular holes, characterized in that, The air outlet of the preheating pipe (103) is inserted into the first round hole of the lower plate (101), and its air inlet passes through the second round hole of the upper plate (102). The air inlet end of the preheating pipe (103) is provided with a turbulence structure, which is used to suppress the eddies located on the inner wall of the air inlet end of the preheating pipe (103).

2. A tubular air preheater according to claim 1, characterized in that, The turbulence structure includes a plurality of holes (104) formed on the circumferential surface of the air inlet end of the preheating pipe (103). The holes (104) are higher than the upper plate (102). The ratio of the diameter of the preheating pipe (103) to the distance between the holes (104) and the top surface of the preheating pipe (103) is 1 / 5 to 1 / 2.

3. A tubular air preheater according to claim 1, characterized in that, The turbulence structure includes a flared opening (105) located at the air inlet end face of the preheating pipe (103).

4. A tubular air preheater according to claim 2, characterized in that, The lower plate (101) is horizontally arranged, and the upper plate (102) intersects with the lower plate (101); along the width direction of the tubular air preheater, the first end of the upper plate (102) is higher than its second end.

5. A tubular air preheater according to claim 2, characterized in that, The ratio of the diameter of the preheating tube (103) to the distance between the hole (104) and the top surface of the preheating tube (103) is 1 / 3.

6. A tubular air preheater according to claim 5, characterized in that, The plurality of the holes (104) are evenly arranged around the axis of the preheating tube (103).

7. A tubular air preheater according to claim 2, characterized in that, The hole (104) can be any one of a round hole, a square hole, or a regular polygonal hole.

8. A flue gas preheating system, characterized in that, The invention includes a tubular air preheater, a flue pipe (2), and an air duct pipe (3) as described in any one of claims 1-7; the flue pipe (2) includes an upper flue pipe and a lower flue pipe, the outlet of the upper flue pipe is sealed to the top surface of the upper plate (102), the inlet of the lower flue pipe is sealed to the lower plate (101), and the air duct pipe (3) is perpendicular to the flue pipe (2) and isolated from the flue pipe (2); The side wall of the upper flue is provided with an ash discharge port, the bottom wall of the ash discharge port is at least not higher than the top surface of the upper plate (102), and an ash discharge door (201) is installed at the ash discharge port.

9. A flue gas preheating system according to claim 8, characterized in that, The ash discharge door (201) is equipped with a door handle (202).

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