Combined air preheater

Abstract

The utility model relates to air preheater technical field, concretely is combined air preheater, including support, the inside fixed connection of support has flue, the top of flue is provided with flue gas inlet, and the bottom fixed connection has liquid collecting tank, the side of liquid collecting tank is provided with flue gas outlet, the inside bottom fixed mounting of liquid collecting tank has condensate neutralizer, the outside of liquid collecting tank is connected with condensate neutralizer, the inside upper portion fixed mounting of liquid collecting tank has demister, the inside upper portion fixed mounting of liquid collecting tank has demister, the flue from top to bottom is installed first heat exchange module, second heat exchange module and third heat exchange module, the side on flue lower extreme is fixed with the air inlet of third heat exchange module intercommunication, this combined air preheater, can keep stable performance in long -term operation, will not appear premature damage because of local material mismatch, reduced the downtime due to equipment failure, has guaranteed the continuous stable operation of heating furnace system, improved overall production efficiency.

Description

Technical Field

[0001] This utility model relates to the field of air preheater technology, specifically a combined air preheater. Background Technology

[0002] An air preheater is a heat exchange surface in the boiler tail flue that preheats the air entering the boiler to a certain temperature through internal heat dissipation fins. It is a device used to improve the heat exchange performance of the boiler and reduce energy consumption.

[0003] Existing equipment often uses heat exchange elements made of a single material, making it difficult to handle the temperature gradient changes along the flue gas flow path (typically from 600-750℃ at the inlet to 100-150℃ at the outlet). For example, carbon steel is prone to high-temperature oxidation above 300℃, while stainless steel oxidizes at lower temperatures (<150℃) due to the presence of SO2 and NO in the flue gas. x The resulting acidic condensate will cause intergranular corrosion, shortening the equipment lifespan to 1-2 years. Furthermore, to improve heat recovery efficiency, the flue gas temperature needs to be reduced. However, when the temperature is below the flue gas acid dew point (typically 100-150℃), corrosive liquids such as sulfuric acid and nitric acid will form on the low-temperature heat exchange surfaces. When using a traditional tubular preheater, although reducing the flue gas temperature from 180℃ to 120℃ increases thermal efficiency by 4.2%, the corrosion rate in the low-temperature section increases from 0.3 mm / year to 1.8 mm / year, leading to increased equipment maintenance frequency.

[0004] These problems make it difficult for traditional equipment to achieve a balance in overall performance. It either sacrifices efficiency for lifespan or increases operating costs due to frequent maintenance. Therefore, there is an urgent need for a new type of combined air preheater that can achieve temperature zone adaptation and high efficiency and corrosion resistance. Utility Model Content

[0005] In view of the problems existing in the prior art, this utility model discloses a combined air preheater. The technical solution adopted includes a support frame, a flue fixedly connected inside the support frame, a flue gas inlet at the top of the flue gas inlet, a liquid collection tank fixedly connected at the bottom, a flue gas outlet on the side of the liquid collection tank, a condensate neutralizer fixedly installed at the bottom of the liquid collection tank, the condensate neutralizer communicating with the outside of the liquid collection tank, a demister fixedly installed at the upper part of the liquid collection tank, and a first heat exchange module, a second heat exchange module, and a third heat exchange module installed sequentially from top to bottom inside the flue gas inlet. The lower side of the flue gas inlet... An air inlet connected to the third heat exchange module is fixedly installed on the upper side of the flue. An air outlet connected to the first heat exchange module is fixedly installed on the side of the upper end of the flue. Two U-shaped connecting pipes are fixedly installed on the side of the flue. The two ends of the two connecting pipes are respectively connected to the first heat exchange module, the second heat exchange module, the third heat exchange module, and the air inlet, the two connecting pipes, the air outlet, the first heat exchange module, the second heat exchange module, and the third heat exchange module form an S-shaped air channel in the flue. The first heat exchange module, the second heat exchange module, and the third heat exchange module have the same structure but different materials.

[0006] The first heat exchange module includes a sealing plate, a heat exchange tube, and heat exchange plates. There are two sealing plates, and the opposite sides of the two sealing plates are fixedly connected to the two ends of a plurality of heat exchange tubes. The side of the heat exchange tube is provided with a through hole that matches the sealing plate. The two sealing plates are fixedly installed in the through grooves on opposite sides of the flue. A plurality of heat exchange plates are fixedly installed on the heat exchange tube.

[0007] As a preferred technical solution of this utility model, the flue gas temperature in the flue is below 130 degrees Celsius, and the heat exchange tube is a high borosilicate glass flat tube or round tube.

[0008] As a preferred technical solution of this utility model, the flue gas temperature in the flue is between 130-200 degrees Celsius, and the heat exchange plate is one of low alloy graphene ductile iron double-sided fins, low alloy graphene ductile iron plain plate, and ND steel thin plate.

[0009] As a preferred technical solution of this utility model, the flue gas temperature in the flue is between 200-330 degrees Celsius, and the heat exchange plate is a cold-rolled carbon steel sheet.

[0010] As a preferred technical solution of this utility model, the flue gas temperature in the flue is between 330 and 450 degrees Celsius, and the heat exchange plate is made of 304 cold-rolled stainless steel plate.

[0011] As a preferred technical solution of this utility model, the flue gas temperature in the flue is between 450-650 degrees Celsius, and the heat exchange plate is made of 316 cold-rolled stainless steel sheet.

[0012] As a preferred technical solution of this utility model, the flue gas temperature of the flue is between 650-750 degrees Celsius, and the heat exchange plate is a 06Cr25Ni20 cold-rolled stainless steel sheet.

[0013] The beneficial effects of this utility model are as follows: 1. This utility model adopts a three-stage heat exchange module made of different materials, which can accurately cope with the temperature gradient change of flue gas from 600-750℃ at the inlet to 50-100℃ at the outlet. For the high-temperature section, a material resistant to high-temperature oxidation is selected, avoiding the problem of high-temperature oxidation of carbon steel above 300℃; in the low-temperature section, a material resistant to acidic condensate corrosion is used, solving the problem of stainless steel being corroded by SO2 and NO at <150℃. x The problem of intergranular corrosion caused by the acidic condensate has been solved, which greatly extends the service life of the equipment, far exceeding that of traditional equipment.

[0014] 2. Through reasonable material selection and S-shaped air channel design, it effectively resists corrosion while improving heat recovery efficiency. It can both reduce flue gas temperature to improve thermal efficiency and cope with corrosive liquids such as sulfuric acid and nitric acid generated when the temperature is below the flue gas acid dew point (100-150℃). Compared with traditional tubular preheaters, while achieving improved thermal efficiency by reducing flue gas temperature, it can significantly reduce the corrosion rate in the low-temperature section, reducing equipment maintenance frequency and breaking the dilemma of traditional equipment either sacrificing efficiency for lifespan or increasing costs due to maintenance.

[0015] 3. Each heat exchange module is precisely matched with materials for different temperature ranges, and the S-shaped air channel allows for full contact and heat exchange between air and flue gas. The equipment can maintain stable performance during long-term operation and will not be damaged prematurely due to local material incompatibility. This reduces downtime caused by equipment failure, ensures the continuous and stable operation of the heating furnace system, and improves overall production efficiency.

[0016] 4. A condensate neutralizer installed at the bottom of the collection tank ensures that the pH value of the discharged flue gas condensate meets the standard and does not corrode public pipelines. A demister installed at the top of the collection tank removes moisture from the flue gas, reducing its moisture content and ensuring that the flue gas does not corrode the flue gas duct, induced draft fan impeller, and bearings. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 1 ;

[0018] Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 2 ;

[0019] Figure 3 This is a cross-sectional three-dimensional structural diagram of the present invention;

[0020] Figure 4 This is a schematic diagram of the flat tube structure of the heat transfer module of this utility model;

[0021] Figure 5 This is a schematic diagram of the internal structure of the liquid collection tank of this utility model.

[0022] In the diagram: 1. Support frame, 2. Flue, 3. Flue gas inlet, 4. Liquid collection tank, 5. Air inlet, 6. Connecting pipe, 7. Air outlet, 8. First heat exchange module, 81. Sealing plate, 82. Heat exchange tube, 83. Heat exchange plate, 9. Second heat exchange module, 10. Third heat exchange module, 11. Flue gas outlet, 12. Condensate neutralizer, 13. Demister. Detailed Implementation

[0023] Example 1

[0024] like Figures 1 to 5 As shown, this utility model discloses a combined air preheater. The technical solution includes a support frame 1, a flue 2 fixedly connected inside the support frame 1, a flue gas inlet 3 at the top of the flue 2, a liquid collection tank 4 fixedly connected at the bottom, a flue gas outlet 11 on the side of the liquid collection tank 4, a condensate neutralizer 12 fixedly installed at the bottom inside the liquid collection tank 4, the condensate neutralizer 12 communicating with the outside of the liquid collection tank 4, a demister 13 fixedly installed at the upper part inside the liquid collection tank 4, a first heat exchange module 8, a second heat exchange module 9, and a third heat exchange module 10 installed sequentially from top to bottom inside the flue 2, an air inlet 5 connected to the third heat exchange module 10 fixedly installed on the side of the lower end of the flue 2, and an air inlet 5 fixedly installed on the side of the upper end of the flue 2. An air outlet 7 is connected to the first heat exchange module 8. Two U-shaped connecting pipes 6 are fixedly installed on the side of the flue 2. The two ends of the two connecting pipes 6 are respectively connected to the first heat exchange module 8, the second heat exchange module 9, and the third heat exchange module 10. The air inlet 5, the two connecting pipes 6, the air outlet 7, the first heat exchange module 8, the second heat exchange module 9, and the third heat exchange module 10 form an S-shaped air channel in the flue. The first heat exchange module 8, the second heat exchange module 9, and the third heat exchange module 10 have the same structure but different materials. The use of three different materials for the heat exchange modules 8 can accurately cope with the temperature gradient change of the flue gas from 600-750℃ at the inlet to 50-100℃ at the outlet. For the high-temperature section, a material resistant to high-temperature oxidation is selected to avoid the problem of high-temperature oxidation of carbon steel above 300℃. For the low-temperature section, a material resistant to acidic condensate corrosion is used to solve the problem of stainless steel being corroded by SO2 and NO at <150℃. x The problem of intergranular corrosion caused by the acidic condensate formed is solved, which greatly extends the service life of the equipment, far exceeding that of traditional equipment.

[0025] The flue gas temperature in flue 2 is below 130 degrees Celsius, and the heat exchange tube 82 is a high borosilicate glass flat tube or round tube. The flue gas temperature in flue 2 is between 130 and 200 degrees Celsius, and the heat exchange fin 83 is one of the following: low-alloy graphene ductile iron double-sided fins, low-alloy graphene ductile iron plain plates, or ND steel thin plates.

[0026] The flue gas temperature in flue 2 is between 200-330 degrees Celsius, and heat exchanger fin 83 is made of cold-rolled carbon steel sheet. The flue gas temperature in flue 2 is between 330-450 degrees Celsius, and heat exchanger fin 83 is made of 304 cold-rolled stainless steel sheet. The flue gas temperature in flue 2 is between 450-650 degrees Celsius, and heat exchanger fin 83 is made of 316 cold-rolled stainless steel sheet. The flue gas temperature in flue 2 is between 650-750 degrees Celsius, and heat exchanger fin 83 is made of 06Cr25Ni20 cold-rolled stainless steel sheet.

[0027] The first heat exchange module 8 includes a sealing plate 81, a heat exchange tube 82, and heat exchange plates 83. There are two sealing plates 81. The opposite sides of the two sealing plates 81 are fixedly connected to the two ends of several heat exchange tubes 82. The side of the heat exchange tubes 82 is provided with through holes that cooperate with the sealing plates 81. The two sealing plates 81 are fixedly installed in the through grooves on opposite sides of the flue 2. Several heat exchange plates 83 are fixedly installed on the heat exchange tubes 82.

[0028] The working principle of this invention is as follows: High-temperature flue gas enters from the flue gas inlet 3 at the top of the flue duct 2, flows sequentially from top to bottom through the first heat exchange module 8, the second heat exchange module 9, and the third heat exchange module 10, and finally exits from the flue gas outlet 11 on the side of the bottom collection tank 4. During this process, the condensate neutralizer 12 neutralizes the condensate in the collection tank 4 and discharges it to the outside, while the demister 13 removes most of the moisture in the flue gas, preventing the moisture in the flue gas from corroding the flue duct 2 and the induced draft fan. The flue gas temperature decreases along the way (from 600-750℃ at the inlet to 50-100℃ at the outlet), and the heat is transferred to the air through each heat exchange module. The preheated cold air enters from the air inlet 5 on the lower side of the flue duct 2, flows sequentially through the third heat exchange module 10, the second heat exchange module 9, and the first heat exchange module 8, and finally exits from the air outlet 7 on the upper side of the flue duct 2, forming hot air. The airflow is achieved by connecting the modules in series through two U-shaped connecting pipes 6, which together with the three heat exchange modules form an S-shaped air channel, extending the contact time between the air and the flue gas and improving the heat exchange efficiency.

[0029] As the flue gas flows from top to bottom, the high-temperature flue gas first comes into contact with the heat exchange plates 83 and heat exchange tubes 82 on the first heat exchange module 8, transferring most of the heat to the air inside the heat exchange tubes 82; the flue gas, after its temperature has decreased, continues to interact with the second heat exchange module 9 and the third heat exchange module 10, gradually releasing the remaining heat; the cold air is heated in the opposite direction in the S-shaped channel, and finally the high-temperature air is discharged from the air outlet 7, thus achieving air preheating.

[0030] First heat exchange module 8 (high temperature section): Located at the top of flue 2, it comes into contact with flue gas at 450-750℃. It is made of high-temperature oxidation resistant materials such as 316 stainless steel or 06Cr25Ni20 stainless steel to avoid high-temperature corrosion.

[0031] The second heat exchange module 9 (medium temperature section) is located in the middle of flue 2 and comes into contact with flue gas at 200-450℃. It is made of cold-rolled carbon steel or 304 stainless steel and other materials to balance heat exchange efficiency and cost.

[0032] The third heat exchange module 10 (low-temperature section): Located at the lower part of flue 2, it contacts flue gas at 50-200℃. It is made of acid-resistant materials such as low-alloy graphene ductile iron, ND steel, or high borosilicate glass to resist corrosion from condensate below the acid dew point of the flue gas. When using high borosilicate glass as the heat exchange tube 82, a one-piece molded flat or round glass tube can be used. Figure 4 and Figure 3 As shown.

[0033] Components not described in detail in this article are existing technologies.

[0034] While the specific embodiments of this utility model have been described in detail above, this utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this utility model. Modifications or variations that do not involve creative labor are still within the protection scope of this utility model.

Claims

1. A combined air preheater, characterized in that, The system includes a support frame (1), a flue (2) fixedly connected inside the support frame (1), a flue gas inlet (3) at the top of the flue (2), a liquid collection tank (4) fixedly connected at the bottom, a flue gas outlet (11) on the side of the liquid collection tank (4), a condensate neutralizer (12) fixedly installed at the bottom inside the liquid collection tank (4), the condensate neutralizer (12) communicating with the outside of the liquid collection tank (4), a demister (13) fixedly installed at the upper part inside the liquid collection tank (4), a first heat exchange module (8), a second heat exchange module (9) and a third heat exchange module (10) installed sequentially from top to bottom inside the flue (2), and an air inlet communicating with the third heat exchange module (10) fixedly installed on the side of the lower end of the flue (2). The air inlet (5), the air outlet (7) connected to the first heat exchange module (8) is fixedly installed on the side of the upper end of the flue (2), and two U-shaped connecting pipes (6) are fixedly installed on the side of the flue (2). The two ends of the two connecting pipes (6) are respectively connected to the first heat exchange module (8), the second heat exchange module (9), the second heat exchange module (9), and the third heat exchange module (10). The air inlet (5), the two connecting pipes (6), the air outlet (7), the first heat exchange module (8), the second heat exchange module (9), and the third heat exchange module (10) form an S-shaped air channel in the flue. The first heat exchange module (8), the second heat exchange module (9), and the third heat exchange module (10) have the same structure but different materials. The first heat exchange module (8) includes a sealing plate (81), a heat exchange tube (82), and heat exchange plates (83). There are two sealing plates (81). The opposite sides of the two sealing plates (81) are fixedly connected to the two ends of a plurality of heat exchange tubes (82). The side of the heat exchange tube (82) is provided with a through hole that matches the sealing plate (81). The two sealing plates (81) are fixedly installed in the through grooves on opposite sides of the flue (2). A plurality of heat exchange plates (83) are fixedly installed on the heat exchange tube (82).

2. The combined air preheater according to claim 1, characterized in that: The flue gas temperature in the flue (2) is below 130 degrees Celsius, and the heat exchange tube (82) is a high borosilicate glass flat tube or round tube.

3. The combined air preheater according to claim 1, characterized in that: The flue gas temperature in the flue (2) is between 130 and 200 degrees Celsius, and the heat exchange plate (83) is one of the following: low alloy graphene ductile iron double-sided fins, low alloy graphene ductile iron plain plate, and ND steel thin plate.

4. The combined air preheater according to claim 1, characterized in that: The flue gas temperature in the flue (2) is between 200 and 330 degrees Celsius, and the heat exchange plate (83) is a cold-rolled carbon steel sheet.

5. The combined air preheater according to claim 1, characterized in that: The flue gas temperature in the flue (2) is between 330 and 450 degrees Celsius, and the heat exchange plate (83) is made of 304 cold-rolled stainless steel plate.

6. The combined air preheater according to claim 1, characterized in that: The flue gas temperature in the flue (2) is between 450 and 650 degrees Celsius, and the heat exchange plate (83) is made of 316 cold-rolled stainless steel sheet.

7. The combined air preheater according to claim 1, characterized in that: The flue gas temperature of the flue (2) is between 650 and 750 degrees Celsius, and the heat exchange plate (83) is a 06Cr25Ni20 cold-rolled stainless steel sheet.

Images