A steam air preheater

Abstract

The present invention relates to a steam air preheater, which comprises a preheater box body with an air inlet and an air outlet respectively arranged on both sides, a heat pipe in a subcooling section of condensate, a secondary steam condensation heat exchange pipe, a low-pressure condensation heat exchange pipe, a high-pressure condensation heat exchange pipe, a condensate channel and a continuous flash chamber; the heat pipe in the subcooling section of condensate, the secondary steam condensation heat exchange pipe, the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are sequentially arranged from the air inlet to the air outlet; the upper ends of the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are respectively communicated with a low-pressure steam header and a high-pressure steam header provided, and the lower ends are communicated with the condensate channel; the upper end of the secondary steam condensation heat exchange pipe is communicated with the continuous flash chamber and the high-pressure steam header, and the lower end is communicated with the condensate channel; the condensate channel is communicated with the continuous flash chamber; the continuous flash chamber is communicated with the subcooling section box body where the heat pipe in the subcooling section of condensate is located. Compared with the prior art, the present invention has the advantages of preventing pipeline erosion, high heat utilization rate and high safety.

Description

Technical Field

[0001] The present invention relates to the technical field of air preheaters, and particularly to a steam air preheater for municipal solid waste incineration. Background Art

[0002] Compared with conventional fuels, municipal solid waste is characterized by high moisture content and low calorific value. To enable better combustion of the waste, an air preheater is required to heat the combustion-supporting air, dry the waste, and improve the combustion efficiency. Generally, there are two types: a flue gas air preheater that uses flue gas for heating and a steam air preheater that uses steam for heating. Since the flue gas after waste incineration contains a large amount of water vapor and acidic gases, low-temperature corrosion is relatively serious. Therefore, at present, steam air preheaters are increasingly applied in waste incineration power plants.

[0003] Currently, the common air preheater in waste incineration power plants is a two-stage series-connected primary air steam air preheater, which is divided into a low-pressure steam heat exchange section and a high-pressure steam heat exchange section. The heat source for the low-pressure section is the first extraction steam of the steam turbine, and the heat source for the high-pressure section is the saturated steam extracted from the boiler steam drum. The heat exchange tubes in both sections are of a vertical arrangement serpentine tube structure. Under the action of the blower, the cold air from the waste pit is sent into the furnace after being heated in two sections. The high- and low-pressure steam condenses into high- and low-pressure drain water after heat exchange and is discharged through the drain pipe to the deaerator.

[0004] From the current operating conditions, the following problems exist:

[0005] 1. Low heat utilization rate and serious heat loss;

[0006] 2. The equipment is prone to leakage, especially in the lower area of the preheater;

[0007] 3. Sometimes abnormal noises occur during the operation of the equipment, especially in the drain pipeline;

[0008] 4. Severe cavitation erosion in the drain pipeline, short pipeline life, and frequent replacement are required;

[0009] 5. The high-temperature and high-pressure drain water is directly discharged, making it difficult to recover the heat and affecting the safe operation of subsequent process equipment. Summary of the Invention

[0010] The purpose of the present invention is to provide a steam air preheater to overcome the defects existing in the above-mentioned prior art.

[0011] The purpose of the present invention can be achieved through the following technical solutions:

[0012] The present invention provides a steam-air preheater, which includes a preheater box body with an air inlet and an air outlet provided on both sides respectively. Inside the preheater box body, there are a hydrophobic subcooling section heat pipe, a secondary steam condensation heat exchange pipe, a low-pressure condensation heat exchange pipe, a high-pressure condensation heat exchange pipe, a hydrophobic channel and a continuous expansion chamber;

[0013] The hydrophobic subcooling section heat pipe, the secondary steam condensation heat exchange pipe, the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are arranged in sequence from the air inlet to the air outlet direction;

[0014] The upper ends of the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are respectively communicated with a low-pressure steam header and a high-pressure steam header provided, and the lower ends are communicated with the hydrophobic channel; the upper end of the secondary steam condensation heat exchange pipe is communicated with the continuous expansion chamber and the high-pressure steam header, and the lower end is communicated with the hydrophobic channel;

[0015] The hydrophobic channel is communicated with the continuous expansion chamber; the continuous expansion chamber is communicated with the subcooling section box body where the hydrophobic subcooling section heat pipe is located.

[0016] The low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are single-pass spiral finned tube bundles vertically arranged with the upper ends fixed inside the preheater box body;

[0017] The upper ends of the tube bundles of the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe are respectively communicated with the low-pressure steam header and the high-pressure steam header through connecting pipes;

[0018] The hydrophobic channel is a channel separated by a tube sheet inside the preheater box body and is located below the low-pressure condensation heat exchange pipe and the high-pressure condensation heat exchange pipe.

[0019] The hydrophobic subcooling section heat pipe is a heat pipe bundle arranged vertically;

[0020] The middle of the hydrophobic subcooling section heat pipe uses a partition to divide the subcooling section box body where it is located into an upper half and a lower half, which are respectively the heat release area and the heat absorption area of the hydrophobic subcooling section heat pipe 2; the heat absorption area where the lower half is located is communicated with the continuous expansion chamber.

[0021] An electric control valve for adjusting the liquid level height of the heat absorption area is also provided at the lower half of the subcooling section box body.

[0022] The continuous expansion chamber is a gradually expanding space separated inside the preheater box body, and an anti-impulse baffle with uniformly distributed small holes is arranged therein.

[0023] Preferably, an inlet header communicated with the secondary steam condensation heat exchange pipe is also provided inside the preheater box body;

[0024] The continuous expansion chamber and the high-pressure steam header are connected to the inlet header through a heat pump type steam ejector provided.

[0025] Preferably, the secondary steam condensation heat exchange tube is a serpentine tube structure arranged at a preset angle to the horizontal direction;

[0026] Both ends of the tube bundle of the secondary steam condensation heat exchange tube are fixed in the preheater box, the inlet end is connected to the inlet header, and the outlet end is connected to the outlet header provided on the upper part of the continuous expansion chamber; the outlet header includes a connected inclined section and a horizontal section, and the horizontal section is connected to the drain channel.

[0027] Preferably, the preset angle between the secondary steam condensation heat exchange tube and the horizontal direction is 3°~5°.

[0028] Preferably, a low-pressure stop valve and a high-pressure stop valve are respectively provided on the high-pressure steam inlet pipeline and the low-pressure steam inlet pipeline connecting the low-pressure steam header and the high-pressure steam header with the outside.

[0029] Preferably, the preheater box is placed at a preset angle to the horizontal ground, wherein the air outlet end of the preheater box is higher than the air inlet end.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1) The steam air preheater designed in the present invention realizes four-stage air preheating of the water trap subcooling section, secondary steam condensation heat exchange tube, low-pressure condensation heat exchange tube and condensation heat exchange tube, which fully utilizes steam condensation to realize heat exchange; the water trap circulates inside the preheater until it is fully subcooled, and the heat exchange sections are all arranged in the heat exchanger box, which reduces external pipelines and equipment, has a more compact structure, reduces the heat loss of external pipelines, effectively recovers the heat of high-temperature water traps, and has high energy utilization efficiency;

[0032] 2) The high-pressure condensation heat exchange tube and the low-pressure condensation heat exchange tube used in the present invention are vertically arranged heat tube bundles, and the secondary steam condensation heat exchange tube is a serpentine tube arranged at 3° to 5° with the horizontal direction. Condensate is not easy to deposit in the heat exchange tube, solving the leakage problem in the lower area of ​​the original two-stage preheater;

[0033] 3) The air preheater box is placed at a certain angle to the horizontal ground. The water in the heat exchange tube and the drain channel flows under the action of gravity, and no drain valve is required, saving energy;

[0034] 4) The saturated drain is separated into steam and water in the continuous expansion chamber, and the drain flowing into the supercooling section is fully supercooled and discharged under the liquid level adjustment of the electric regulating valve, which recovers the heat of the drain and prevents erosion of the subsequent drain pipeline;

[0035] 5) The steam air preheater of the present invention eliminates the original high and low pressure section drain pipes and uses the drain channel in the preheater box instead to prevent the steam-water flushing problem that is easy to occur on the high temperature and high pressure drain pipes;

[0036] 6) The steam-air preheater of the present invention cancels the high- and low-pressure section drain pipelines and flash tanks outside the original equipment, and instead arranges a drain channel and a continuous flash chamber inside the box body. Moreover, the two are directly connected. The anti-scour baffle in the continuous flash chamber effectively slows down the flow rate, separates steam and water, and then recovers the secondary steam, solving the erosion problem that is likely to occur in the original high- and low-pressure section drain pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of the steam-air preheater for preventing pipeline erosion of the present invention;

[0038] Figure 2 is Figure 1 a partial enlarged schematic diagram of the horizontal section of the outlet header at position A in

[0039] Figure 3 is a schematic diagram of the internal system of the box body of the present invention;

[0040] Among them, 1 - preheater box body; 2 - heat pipe for drain subcooling section; 3 - secondary steam condensation heat exchange pipe; 4 - low-pressure condensation heat exchange pipe; 5 - high-pressure condensation heat exchange pipe; 6 - connecting pipe; 7 - low-pressure steam header; 8 - high-pressure steam header; 9 - drain channel; 10 - continuous flash chamber; 11 - anti-scour baffle with evenly distributed small holes; 12 - inlet header; 13 - outlet header; 14 - heat pump steam ejector; 15 - low-pressure stop valve; 16 - high-pressure stop valve; 17 - electric control valve. SPECIFIC EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment

[0043] As Figure 1 and Figure 2 shown, this embodiment provides a steam-air preheater, including a preheater box body 1 provided with an air inlet and an air outlet on both sides, and inside it are provided a heat pipe for drain subcooling section 2, a secondary steam condensation heat exchange pipe 3, a low-pressure condensation heat exchange pipe 4, a high-pressure condensation heat exchange pipe 5, a drain channel 9 and a continuous flash chamber 10; the heat pipe for drain subcooling section 2, the secondary steam condensation heat exchange pipe 3, the low-pressure condensation heat exchange pipe 4, and the high-pressure condensation heat exchange pipe 5 are arranged in sequence from the air inlet to the air outlet direction.

[0044] The upper ends of the low-pressure condensation heat exchange tubes 4 and the high-pressure condensation heat exchange tubes 5 are respectively connected to the provided low-pressure steam header 7 and high-pressure steam header 8, and the lower ends are connected to the drain channel 9; low-pressure stop valves 15 and high-pressure stop valves 16 are respectively provided on the high-pressure steam inlet pipe and the low-pressure steam inlet pipe through which the low-pressure steam header 7 and the high-pressure steam header 8 are connected to the outside.

[0045] The upper end of the secondary steam condensation heat exchange tube 3 is connected to the continuous flash chamber 10 and the high-pressure steam header 8, and the lower end is connected to the drain channel 9.

[0046] The drain channel 9 is connected to the continuous flash chamber 10; the continuous flash chamber 10 is connected to the subcooling section box body where the drain subcooling section heat pipe 2 is located.

[0047] The low-pressure condensation heat exchange tubes 4 and the high-pressure condensation heat exchange tubes 5 are single-pass spiral finned tube bundles vertically arranged with the upper ends fixed in the preheater box body 1; the upper ends of the tube bundles are respectively connected to the low-pressure steam header 7 and the high-pressure steam header 8 through connecting pipes 6; the drain channel 9 is a channel separated by a tube sheet inside the preheater box body 1 and is located below the low-pressure condensation heat exchange tubes 4 and the high-pressure condensation heat exchange tubes 5. The drain vaporizes and reduces pressure in the continuous flash chamber 10, the steam flows to the secondary steam condensation heat exchange section, and the drain flows to the subcooling section.

[0048] The drain subcooling section heat pipe 2 is a heat pipe bundle arranged vertically; the subcooling section box body where it is located is separated into an upper half and a lower half by a partition, the upper half passes cold air, and the lower half passes the drain, serving as the heat release area and the heat absorption area of the drain subcooling section heat pipe 2; the heat absorption area where the lower half is located is connected to the continuous flash chamber 10. An electric control valve 17 for adjusting the liquid level height of the heat absorption area is also provided in the lower half of the subcooling section box body.

[0049] The continuous flash chamber 10 is an expanding space separated in the preheater box body 1, and an impact-proof baffle 11 with evenly distributed small holes is arranged therein. The continuous flash chamber 10 and the high-pressure steam header 8 are connected to the inlet header 12 communicating with the secondary steam condensation heat exchange tube 3 through a heat pump steam ejector 14 provided.

[0050] The secondary steam condensation heat exchange tube 3 is a serpentine tube structure arranged at an angle of 3° to 5° with the horizontal direction; the two ends of the tube bundle of the secondary steam condensation heat exchange tube 3 are fixed in the preheater box body 1, the inlet end is connected to the inlet header 12, and the outlet end is connected to the outlet header 13 provided at the upper part of the continuous flash chamber 10; the horizontal section of the outlet header 13 is connected to the drain channel 9.

[0051] The preheater box body 1 is placed at a preset angle with the horizontal ground, and the air outlet end of the preheater box body 1 is higher than the air inlet end.

[0052] Combined with Figure 3The working principle of this embodiment is given as follows:

[0053] On the air side, air enters the preheater casing 1 through a fan. First, it absorbs the heat of the hydrophobic subcooling section heat pipe 2 in the upper half of the subcooling section, and then successively passes through the secondary steam condensation heat exchange pipe 3, the low-pressure condensation heat exchange pipe 4, and the high-pressure condensation heat exchange pipe 5 for segmented heating. The heated air is sent into the incineration furnace interior;

[0054] On the steam side, the low-pressure stop valve 15 is in the open state. The low-pressure steam from the turbine extraction enters the low-pressure condensation heat exchange pipe 4 through the low-pressure steam header 7 and the connecting pipe 6, exchanges heat with the air, and then becomes saturated water and enters the drain channel 9; the high-pressure stop valve 16 is in the open state. The high-pressure saturated steam from the steam drum enters the high-pressure condensation heat exchange pipe 5 through the high-pressure steam header 8 and the connecting pipe 6 to heat the air, and the generated saturated drain enters the drain channel 9;

[0055] On the drain side, the drain enters the continuous flash chamber 10 through the drain channel 9 and continuously vaporizes and depressurizes. The anti-impulse baffle 11 with evenly distributed small holes plays a role in slowing down the flow rate and separating steam and water, thereby reducing the steam-water impact. The generated secondary steam is extracted from the outlet of the continuous flash chamber 10 by the heat pump steam ejector 14, enters the secondary steam condensation heat exchange pipe 3 through the inlet header 12, exchanges heat with the air, and then condenses into drain and flows into the drain channel 9 through the outlet header 13 to achieve circulation; the drain of the continuous flash chamber 10 is discharged into the lower half of the subcooling section casing, and the liquid level height of the drain is adjusted by the electric control valve 17 to adjust the heat exchange amount. The drain is fully subcooled under the heat exchange action of the hydrophobic subcooling section heat pipe 2 and is discharged from the bottom outlet of the preheater casing 1 and sent to the deaerator.

[0056] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A steam air preheater, comprising a preheater casing (1) with an air inlet and an air outlet provided on both sides respectively, characterized in that, a hydrophobic subcooling section heat pipe (2), a secondary steam condensation heat exchange pipe (3), a low-pressure condensation heat exchange pipe (4), a high-pressure condensation heat exchange pipe (5), a hydrophobic channel (9) and a continuous expansion chamber (10) are provided in the preheater casing (1); the hydrophobic subcooling section heat pipe (2), the secondary steam condensation heat exchange pipe (3), the low-pressure condensation heat exchange pipe (4), and the high-pressure condensation heat exchange pipe (5) are arranged in sequence from the air inlet to the air outlet direction; the upper ends of the low-pressure condensation heat exchange pipe (4) and the high-pressure condensation heat exchange pipe (5) are respectively communicated with a provided low-pressure steam header (7) and a high-pressure steam header (8), and the lower ends are communicated with the hydrophobic channel (9); the upper end of the secondary steam condensation heat exchange pipe (3) is communicated with the continuous expansion chamber (10) and the high-pressure steam header (8), and the lower end is communicated with the hydrophobic channel (9); the hydrophobic channel (9) is communicated with the continuous expansion chamber (10); the continuous expansion chamber (10) is communicated with the subcooling section casing where the hydrophobic subcooling section heat pipe (2) is located; the continuous expansion chamber (10) is a gradually expanding space separated in the preheater casing (1), and an impact-proof baffle (11) with uniformly distributed small holes is arranged therein; the hydrophobic subcooling section heat pipe (2) is a heat pipe bundle arranged vertically; the middle of the hydrophobic subcooling section heat pipe (2) divides the subcooling section casing where it is located into an upper half and a lower half, which are respectively the heat release area and the heat absorption area of the hydrophobic subcooling section heat pipe 2; the lower half of the heat absorption area is communicated with the continuous expansion chamber (10).

2. A steam air preheater according to claim 1, characterized in that, the low-pressure condensation heat exchange pipe (4) and the high-pressure condensation heat exchange pipe (5) are single-pass spiral finned tube bundles vertically arranged with the upper ends fixed in the preheater casing (1); the upper ends of the tube bundles of the low-pressure condensation heat exchange pipe (4) and the high-pressure condensation heat exchange pipe (5) are respectively communicated with the low-pressure steam header (7) and the high-pressure steam header (8) through connecting pipes (6); the hydrophobic channel (9) is a channel separated by a tube sheet inside the preheater casing (1) and is located below the low-pressure condensation heat exchange pipe (4) and the high-pressure condensation heat exchange pipe (5).

3. A steam air preheater according to claim 1, characterized in that, an electric control valve (17) for adjusting the liquid level height of the heat absorption area is further provided in the lower half of the subcooling section casing.

4. A steam air preheater according to claim 1, characterized in that, an inlet header (12) communicated with the secondary steam condensation heat exchange pipe (3) is further provided in the preheater casing (1); the continuous expansion chamber (10) and the high-pressure steam header (8) are connected to the inlet header (12) through a provided heat pump steam ejector (14).

5. A steam air preheater according to claim 4, characterized in that, the secondary steam condensation heat exchange pipe (3) is a serpentine tube structure arranged at a preset angle with the horizontal direction; The tube bundles at both ends of the secondary steam condensation heat exchange tubes (3) are fixed inside the preheater casing (1). The inlet end is communicated with the inlet header (12), and the outlet end is communicated with an outlet header (13) provided at the upper part of the continuous flash chamber (10). The outlet header (13) includes a connected inclined section and a horizontal section, and the horizontal section is communicated with the drain channel (9).

6. A steam-air preheater according to claim 1, characterized in that the preset angle of the secondary steam condensation heat exchange tubes (3) with the horizontal direction is 3° to 5°.

7. A steam-air preheater according to claim 1, characterized in that low-pressure stop valves (15) and high-pressure stop valves (16) are respectively provided on the high-pressure steam inlet pipe and the low-pressure steam inlet pipe through which the low-pressure steam header (7) and the high-pressure steam header (8) are communicated with the outside.

8. A steam-air preheater according to claim 1, characterized in that the preheater casing (1) is placed at a preset angle with the horizontal ground, wherein the air outlet end of the preheater casing (1) is higher than the air inlet end.

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