Air preheater resistant to low-temperature dew point corrosion

Abstract

The invention relates to the technical field of air preheaters, in particular to a low-temperature dew point corrosion resistant air preheater which comprises a shell and a heat exchange tube positioning mechanism. A partition plate is arranged in the shell and divides the inner space of the shell into an air heating chamber located on the upper portion and a smoke circulation chamber located on the lower portion, heat exchange pipe holes which are evenly distributed are formed in the middle of the partition plate, heat exchange pipes are assembled in the heat exchange pipe holes, and a plurality of upper heat exchange pieces are distributed on the outer side of the upper portion of each heat exchange pipe. Ceramic sealing rings are fixedly connected to the outer sides of the middles of the heat exchange pipes, annular assembling grooves are formed in the outer sides of the middles of the ceramic sealing rings, and detachable lower heat exchange pieces are arranged on the lower portions of the heat exchange pipes. And the heat exchange tube positioning mechanism is used for positioning and releasing the heat exchange tube. According to the air preheater resistant to low-temperature dew point corrosion, the single heat exchange pipe and the lower heat exchange piece can be replaced conveniently, the shutdown maintenance time is shortened, and long-term efficient operation of equipment is guaranteed by optimizing sealing and heat distribution and reducing the risk of low-temperature dew point corrosion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air preheater, in particular to an air preheater resistant to low-temperature dew point corrosion. BACKGROUND

[0002] In the field of energy utilization and industrial production, air preheater as an important energy-saving equipment is widely used in boiler systems of power, chemical, metallurgical and other industries. Its core function is to use the high-temperature flue gas waste heat discharged by the boiler to preheat the cold air entering the boiler, thereby reducing the exhaust gas temperature, improving the fuel combustion efficiency, reducing energy consumption and pollutant emissions. With the continuous improvement of global energy saving and emission reduction requirements, the operation efficiency and service life of air preheater directly affect the economy and environmental protection of industrial system, so the requirements for its performance optimization and corrosion resistance are increasingly stringent.

[0003] The air preheater in the prior art is usually composed of a shell, heat exchange pipes, a partition plate, and auxiliary heat exchange fins. The inside of the shell is divided into a flue gas channel and an air channel by the partition plate. The heat exchange pipes are arranged through the partition plate, with one end in the flue gas channel to absorb high-temperature flue gas heat and the other end in the air channel to release heat and heat cold air. To enhance the heat exchange efficiency, auxiliary heat exchange fins are usually arranged on the surface of the heat exchange pipes to increase the heat exchange area. During operation, high-temperature flue gas flows through the flue gas side auxiliary heat exchange fins of the heat exchange pipes, and the heat is transferred to the air side through the heat exchange pipes. Cold air absorbs heat when flowing through the air side auxiliary heat exchange fins to complete preheating, and finally realizes the recycling of flue gas waste heat.

[0004] However, the existing air preheater has some problems in long-term operation: first, the connection between the heat exchange pipes and the partition plate is usually a fixed structure. When the heat exchange pipes are damaged due to low-temperature dew point corrosion (such as the corrosion of the heat exchange pipes by acid substances condensed in the flue gas) or long-term use, the heat exchange pipes cannot be individually disassembled and replaced, and the entire device must be disassembled. This non-replaceable design not only significantly prolongs the downtime maintenance time, increases the loss of production interruption, but also may cause secondary damage to surrounding components during disassembly, further reducing the overall service life and operation stability of the equipment. Second, the flue gas side auxiliary heat exchange fins are easily covered with dust or corroded due to long-term contact with dusty and acidic flue gas, but the fixed structure makes it difficult to individually disassemble and replace the auxiliary heat exchange fins, thereby reducing the heat exchange efficiency. Third, the partition plate and surrounding structure are prone to form low-temperature areas due to uneven local heat distribution, causing acid condensate to accumulate and accelerating equipment corrosion, thereby shortening the overall service life. Therefore, we propose an air preheater resistant to low-temperature dew point corrosion. SUMMARY

[0005] The present application provides an air preheater resistant to low-temperature dew point corrosion, which can be individually and conveniently disassembled, and simultaneously distribute and transfer heat from the flue gas side, effectively solving the problems in the background art.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] The air preheater resistant to low-temperature dew point corrosion comprises a shell and a heat exchange pipe positioning mechanism.

[0008] A partition is arranged in the shell, and the partition divides the internal space of the shell into an air heating chamber located at the upper side and a flue gas flow chamber located at the lower side. An air duct is arranged at the side of the shell located in the air heating chamber, and the air duct is in communication with the air heating chamber. A flue gas duct is arranged at the side of the shell located in the flue gas flow chamber, and the flue gas duct is in communication with the flue gas flow chamber. Uniformly distributed heat exchange pipe holes are formed in the middle part of the partition, and heat exchange pipes are assembled in the heat exchange pipe holes. The heat exchange pipes are perpendicular to the partition. The upper part of the heat exchange pipes is located in the air heating chamber, and the lower part of the heat exchange pipes is located in the flue gas flow chamber. A plurality of upper heat exchange fins are arranged at the outer side of the upper part of the heat exchange pipes. Ceramic sealing rings are fixedly connected to the outer side of the middle part of the heat exchange pipes. Annular assembly grooves are formed in the outer side of the middle part of the ceramic sealing rings. Lower heat exchange fins are arranged at the lower part of the heat exchange pipes. A receiving groove adapted to the lower end of the heat exchange pipes is arranged in the bottom wall of the shell.

[0009] The heat exchange pipe positioning mechanism is used for positioning and releasing the heat exchange pipes.

[0010] Further, the upper heat exchange fins are fixed to the upper part of the heat exchange pipes. The upper heat exchange fins adopt an annular structure arranged at intervals or a continuous spiral structure. The lower heat exchange fins are detachably mounted at the lower part of the heat exchange pipes through a lower heat exchange fin assembly component. The lower heat exchange fin assembly component comprises two hingedly connected semi-arc copper plates. The lower heat exchange fins are welded or tightly inserted into the outer side of the semi-arc copper plates. A stop ring is arranged at the outer side of the lower end of the heat exchange pipes. The outer diameter of the stop ring is smaller than the inner diameter of the heat exchange pipe hole. The semi-arc copper plates are located above the stop ring. The two semi-arc copper plates are assembled on the outer side of the heat exchange pipes through a clamp.

[0011] Further, a detachable upper cover plate is arranged at the upper end of the shell. A lifting ring or a handle is arranged at the outer side of the upper cover plate. The upper cover plate is used for mounting or replacing the heat exchange pipes.

[0012] Further, an inspection door is arranged at the lower end of the front side wall of the shell through a bolt. The inspection door is used for mounting or replacing the lower heat exchange fins.

[0013] Further, the heat exchange pipe positioning mechanism comprises horizontal sliding grooves, an assembly plate and mounting columns. The horizontal sliding grooves are located in the partition plate and communicate with the heat exchange pipe holes. Two graphite sealing plates are slidably connected in each horizontal sliding groove. The graphite sealing plates are in arc-shaped structure. The two graphite sealing plates in each horizontal sliding groove are symmetrically arranged on the two sides of the ceramic sealing ring in the heat exchange pipe hole communicating with the horizontal sliding groove. The position of the horizontal sliding groove corresponds to the annular assembly groove. When the graphite sealing plate moves towards the ceramic sealing ring in the horizontal direction, the graphite sealing plate can be inserted into the annular assembly groove. When the graphite sealing plate moves away from the ceramic sealing ring in the horizontal direction, the graphite sealing plate is moved out of the annular assembly groove.

[0014] Further, the two graphite sealing plates in the same horizontal sliding groove are inserted and matched. A slot is arranged on the end face of one of the graphite sealing plates, and a boss matched with the slot is arranged on the end face of the other graphite sealing plate.

[0015] Further, the assembly plate is located in the horizontal sliding groove. Two assembly holes are symmetrically arranged on the assembly plate. A driving rod is slidably connected in the assembly hole. One end of the driving rod is fixedly connected with the graphite sealing plate. A ball is arranged on the other end of the driving rod. A limiting ring is fixedly connected on the outer side of the other end of the driving rod away from the graphite sealing plate. A return spring is sleeved on the outer side of the driving rod, and the return spring is located between the assembly plate and the limiting ring.

[0016] Further, the mounting column is arranged on the partition plate. A through hole is arranged on the partition plate and communicates with the horizontal sliding groove. The mounting column is slidably arranged in the through hole. An auxiliary heat exchange fin is arranged on the upper end of the mounting column. The auxiliary heat exchange fin is in fish fin shape. The arrangement of the auxiliary heat exchange fin is parallel to the air flow direction. A driving slope is arranged on the lower end of the mounting column. When the mounting column penetrates through the horizontal sliding groove downward, the driving slope cooperates with the ball to push the driving rod and the graphite sealing plate to move towards the annular assembly groove. When the mounting column moves out of the horizontal sliding groove upward, the mounting column and the driving slope are separated from the ball. The return spring pushes the driving rod and the graphite sealing plate to separate from the annular assembly groove.

[0017] Further, in the air heating chamber, the heat exchange area of the auxiliary heat exchange fin at the middle position of the shell is greater than that of the auxiliary heat exchange fin close to the side wall of the shell. The width of the auxiliary heat exchange fin close to the side wall of the shell is greater than that of the auxiliary heat exchange fin at the middle position of the shell. The height of the auxiliary heat exchange fin at the middle position of the shell is greater than that of the auxiliary heat exchange fin close to the side wall of the shell. In the flue gas flow chamber, the heat exchange area of the copper heat conduction plate at the middle position of the shell is greater than that of the copper heat conduction plate close to the side wall of the shell.

[0018] Further, the outer side of the mounting column is coaxially fixedly connected with an outer threaded sleeve. An inner thread matched with the outer threaded sleeve is arranged in the through hole. A limiting plate is arranged on the outer side of the upper end of the outer threaded sleeve. When the outer threaded sleeve cooperates with the inner thread, the limiting plate is in contact with the upper end face of the partition plate.

[0019] Further, the heat exchange pipe positioning mechanism further comprises copper heat plates, the copper heat plates are fixedly connected to the lower surface of the partition plate, blind holes are arranged in the copper heat plates, and the lower ends of the mounting columns are inserted into the blind holes.

[0020] Compared with the prior art, the air preheater with low-temperature dew point corrosion resistance has the beneficial effects that:

[0021] 1. The air preheater with low-temperature dew point corrosion resistance disclosed by the application can be conveniently and efficiently replaced by only rotating the auxiliary heat exchange sheet at the upper end of the mounting column, disengaging the external thread sleeve from the internal thread at the top of the through hole, and pulling the auxiliary heat exchange sheet upward, at this time, the graphite sealing plate is driven to move in a centrifugal manner under the action of the return spring, and the heat exchange pipe can be pulled out from the shell, the whole process does not need to disassemble the equipment as a whole, the replacement of a single heat exchange pipe is convenient and efficient, the downtime for maintenance can be greatly reduced, meanwhile, the annular assembly groove of the graphite sealing plate and the ceramic sealing ring is in contact and cooperation, the basic sealing performance after the installation of the heat exchange pipe is guaranteed, the corrosion of acid medium (such as acid mist formed by sulfur oxide) in flue gas can be resisted, and the risk of sealing failure caused by low-temperature dew point corrosion can be significantly reduced.

[0022] 2. The air preheater with low-temperature dew point corrosion resistance disclosed by the application adopts a detachable design for the lower heat exchange sheet assembly component, the lower heat exchange sheet on the semicircular copper plate increases the contact area between the lower end of the heat exchange pipe and flue gas, and enhances the heat absorption capacity, the high thermal conductivity of the copper material further improves the heat exchange efficiency, the detachable connection realized by the clamp enables the lower heat exchange sheet to be quickly disassembled and replaced when corrosion or ash accumulation occurs, the maintenance time is greatly shortened, and efficient operation of the equipment is ensured.

[0023] 3. The air preheater with low-temperature dew point corrosion resistance disclosed by the application has optimized heat distribution and stable structure design, prolongs the overall service life of the equipment, the copper heat plate can quickly spread the locally concentrated heat on the lower side of the partition plate, avoids the formation of a low-temperature zone to gather acidic condensate due to uneven temperature distribution, reduces the corrosion of the partition plate and the surrounding structure, and improves the heat recovery rate through the contact and conduction of the copper mounting column and the heat plate.

[0024] 4. The low-temperature dew point corrosion resistant air preheater disclosed in this invention has the following characteristics: Since the gas flow rate near the middle of the shell is greater than that near the sidewall of the shell, the heat exchange area of ​​the auxiliary heat exchange fins near the middle of the shell is greater than that near the sidewall of the shell. Considering the actual space configuration within the shell, the auxiliary heat exchange fins near the sidewall of the shell are arranged in a single row without interference, and their width is designed to be greater than the width of the auxiliary heat exchange fins in the middle of the shell. Since the auxiliary heat exchange fins in the middle of the shell are compact and prone to interference, their height is designed to be greater than the height of the auxiliary heat exchange fins near the sidewall of the shell. This achieves the goal of having a larger heat exchange area near the middle of the shell than near the sidewall of the shell, thereby achieving balanced heat dissipation. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an air preheater resistant to low-temperature dew point corrosion, as shown in the example.

[0026] Figure 2 This is a schematic diagram of the internal structure of an air preheater resistant to low-temperature dew point corrosion, as shown in the example.

[0027] Figure 3 This is a schematic diagram of the structure of a single heat exchange tube in an embodiment.

[0028] Figure 4 This is a schematic diagram of the structure of the heat exchange tube in the embodiment;

[0029] Figure 5 This is a partial cross-sectional view of the partition of the present invention;

[0030] Figure 6 for Figure 5 Enlarged view of section A (labeled A);

[0031] Figure 7 This is a schematic diagram of the graphite sealing plate of the present invention;

[0032] Figure 8 This is a schematic diagram showing a partial cross-section of the copper heat sink in an embodiment.

[0033] In the diagram: 101-shell, 102-partition, 103-air duct, 104-flue gas duct, 105-heat exchanger tube hole, 106-heat exchanger tube, 107-upper heat exchanger plate, 108-ceramic sealing ring, 109-annular assembly groove, 110-lower heat exchanger plate, 111-accommodating groove, 112-semi-arc copper plate, 113-retaining ring, 114-clamp, 115-upper cover plate, 116-handle, 117-inspection door.

[0034] 201-horizontal sliding slot, 202-assembly plate, 203-mounting column, 204-graphite sealing plate, 205-slot, 206- boss, 207-assembly hole, 208-driving rod, 209-rolling ball, 210-limiting ring, 211-return spring, 212-assisted heat exchange fin, 213-driving slope, 214-external threaded sleeve, 215-limiting plate, 216-copper heat sink, 217-blind hole. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] Please refer to Figures 1-8 The embodiment provides a low-temperature dew point corrosion resistant air preheater, which comprises a shell 101 and a heat exchange pipe positioning mechanism.

[0037] A partition plate 102 is arranged in the shell 101, the partition plate 102 divides the internal space of the shell 101 into an air heating chamber A located at the upper portion and a flue gas flow chamber B located at the lower portion, an air duct 103 is arranged at the side portion of the shell 101 located in the air heating chamber A, the air duct 103 is in communication with the air heating chamber A, a flue gas duct 104 is arranged at the side portion of the shell 101 located in the flue gas flow chamber B, the flue gas duct 104 is in communication with the flue gas flow chamber B, a plurality of heat exchange pipe holes 105 are arranged in the middle portion of the partition plate 102, the heat exchange pipe holes 105 are assembled with heat exchange pipes 106, the heat exchange pipes 106 are perpendicular to the partition plate 102, the upper portion of the heat exchange pipes 106 is located in the air heating chamber A, and the lower portion of the heat exchange pipes 106 is located in the flue gas flow chamber B, a plurality of upper heat exchange fins 107 are arranged on the outer side of the upper portion of the heat exchange pipes 106, ceramic sealing rings 108 are fixedly connected to the outer side of the middle portion of the heat exchange pipes 106, annular assembly grooves 109 are arranged in the middle portion of the ceramic sealing rings 108, detachable lower heat exchange fins 110 are arranged on the lower portion of the heat exchange pipes 106, and a containing groove 111 matched with the lower end of the heat exchange pipes 106 is arranged on the bottom wall of the shell 101.

[0038] As a preferred scheme of the embodiment, the upper heat exchange fins 107 are fixed on the upper part of the heat exchange pipes 106, and the upper heat exchange fins 107 adopt a ring structure arranged at intervals or a continuous spiral structure, and the spiral structure is adopted in the description of the drawings in the embodiment, the lower heat exchange fins 110 are detachably installed on the lower part of the heat exchange pipes 106 through a lower heat exchange fin assembly, the lower heat exchange fin assembly includes two hinged semi-arc copper plates 112, the lower heat exchange fins 110 are welded or tightly inserted on the outside of the semi-arc copper plates 112, the lower end of the heat exchange pipes 106 is provided with a retaining ring 113, the semi-arc copper plates 112 are located above the retaining ring 113, and the two semi-arc copper plates 112 are assembled on the outside of the heat exchange pipes 106 through a clamp 114.

[0039] As a preferred scheme of the embodiment, the upper end of the shell 101 is provided with a detachable upper cover plate 115, the outside of the upper cover plate 115 is provided with a lifting ring or handle 116, and the upper cover plate 115 is used for installing or replacing the heat exchange pipes 106.

[0040] As a preferred scheme of the embodiment, the lower end of the front side wall of the shell 101 is provided with an inspection door 117 installed through bolts, and the inspection door 117 is used for installing or replacing the lower heat exchange fins 110.

[0041] The heat exchange pipe positioning mechanism includes horizontal sliding grooves 201, assembly plates 202 and mounting columns 203, the horizontal sliding grooves 201 are located in the partition plate 102, the horizontal sliding grooves 201 are in communication with the heat exchange pipe holes 105, two graphite sealing plates 204 are slidably connected in each horizontal sliding groove 201, the graphite sealing plates 204 are in an arc structure, the two graphite sealing plates 204 in each horizontal sliding groove 201 are symmetrically arranged on the two sides of the ceramic sealing ring 108 in the heat exchange pipe hole 105 in communication with the horizontal sliding groove 201, and the position of the horizontal sliding groove 201 corresponds to the annular assembly groove 109, when the graphite sealing plate 204 moves towards the ceramic sealing ring 108 in the horizontal direction, the graphite sealing plate 204 can be inserted into the annular assembly groove 109, and when the graphite sealing plate 204 moves away from the ceramic sealing ring 108 in the horizontal direction, the graphite sealing plate 204 moves out of the annular assembly groove 109.

[0042] As a preferred scheme of the embodiment, the two graphite sealing plates 204 located in the same horizontal sliding groove 201 are inserted and matched, specifically, an insertion groove 205 is arranged on the end face of one of the graphite sealing plates 204, and a boss 206 matched with the insertion groove is arranged on the end face of the other graphite sealing plate 204.

[0043] The assembly plate 202 is located in the horizontal sliding groove 201, two assembly holes 207 are symmetrically arranged on the assembly plate 202, a driving rod 208 is slidably connected in the assembly hole 207, one end of the driving rod 208 is fixedly connected with the graphite sealing plate 204, a ball 209 is arranged at the other end of the driving rod 208, a limiting ring 210 is fixedly connected outside the end of the driving rod 208 away from the graphite sealing plate 204, a reset spring 211 is arranged outside the driving rod 208, and the reset spring 211 is located between the assembly plate 202 and the limiting ring 210.

[0044] The mounting column 203 is arranged on the partition plate 102, a through hole is arranged on the partition plate 102 and communicates with the horizontal sliding groove 201, the mounting column 203 is slidably arranged in the through hole, an auxiliary heat exchange fin 212 is arranged at the upper end of the mounting column 203, the auxiliary heat exchange fin 212 is in the shape of a fish fin, the auxiliary heat exchange fin 212 is arranged to be parallel to the air flow direction, and a driving slope 213 is arranged at the lower end of the mounting column 203. When the mounting column 203 penetrates downward through the horizontal sliding groove 201, the driving slope 213 cooperates with the ball 209 to drive the driving rod 208 and the graphite sealing plate 204 to move towards the annular assembly groove 109. When the mounting column 203 moves upward out of the horizontal sliding groove 201, the mounting column 203 and the driving slope 213 are separated from the ball 209, and the reset spring 211 drives the driving rod 208 and the graphite sealing plate 204 to separate from the annular assembly groove 109.

[0045] As a preferred scheme of the embodiment, an outer threaded sleeve 214 is coaxially fixedly connected outside the mounting column 203, an inner thread is arranged in the through hole and matched with the outer threaded sleeve 214, and a limiting plate 215 is arranged outside the upper end of the outer threaded sleeve 214. When the outer threaded sleeve 214 is matched with the inner thread, the limiting plate 215 is in contact with the upper end surface of the partition plate 102.

[0046] As a preferred scheme of the embodiment, the heat exchange pipe positioning mechanism further comprises copper heat plates 216, the copper heat plates 216 are fixedly connected to the lower surface of the partition plate 102, blind holes 217 are arranged in the copper heat plates 216, and the lower end of the mounting column 203 is inserted into the blind holes 217.

[0047] As a preferred scheme of the embodiment, in the air heating chamber A, the heat exchange area of the auxiliary heat exchange fin 212 at the middle position of the shell 101 is greater than that of the auxiliary heat exchange fin 212 close to the side wall of the shell 101, the width of the auxiliary heat exchange fin 212 close to the side wall of the shell 101 is greater than that of the auxiliary heat exchange fin 212 at the middle position of the shell 101, and the height of the auxiliary heat exchange fin 212 at the middle position of the shell 101 is greater than that of the auxiliary heat exchange fin 212 close to the side wall of the shell 101; in the flue gas flow chamber B, the heat exchange area of the copper heat plate 216 at the middle position of the shell 101 is greater than that of the copper heat plate 216 close to the side wall of the shell 101.

[0048] The air preheater with low-temperature dew point corrosion resistance provided by the application has the following assembly process and spare part replacement process:

[0049] Assembly process:

[0050] First, open the upper cover plate 115, pass the heat exchange pipe 106 (without the lower heat exchange sheet 110) through the heat exchange pipe hole 105 of the partition plate 102 until the lower end of the heat exchange pipe 106 is inserted into the accommodating groove 111 of the bottom wall of the shell 101, and the ceramic sealing ring 108 in the middle of the heat exchange pipe 106 is located in the heat exchange pipe hole 105.

[0051] Then, insert the lower end of the mounting column 203 into the through hole, push the auxiliary heat exchange sheet 212 downward to make the mounting column 203 move downward in the through hole 214, and in the process of moving downward of the mounting column 203, the driving slope 213 at the lower end of the mounting column 203 extrudes the ball 209 at the end of the driving rod 208, the ball 209 drives the driving rod 208 to move centripetally, and then pushes the graphite sealing plate 204 to move inward, in the process, the limiting ring 210 outside the driving rod 208 extrudes the return spring 211, the inner wall of the graphite sealing plate 204 is in close contact with the annular assembly groove 109 of the ceramic sealing ring 108, and the two graphite sealing plates 204 are inserted through the boss 206 and the insertion groove 205 to enhance the sealing stability, the ceramic sealing ring 108 and the graphite sealing plate 204 selected in the scheme both have corrosion resistance and high temperature resistance, and can resist the acid mist formed by the low-temperature condensation of acidic media such as nitrogen oxides and sulfur oxides in flue gas.

[0052] When the outer thread sleeve 214 at the outer arc surface of the mounting column 203 is screwed with the inner thread 213 at the top of the through hole, the installation of the heat exchange pipe 106 is completed, the lower end of the mounting column 203 extends into the blind hole 217 in the middle of the copper heat sink 216 and contacts the inner side of the blind hole 217, and then the upper cover plate 115 is connected with the upper end of the shell 101 through bolts.

[0053] Open the maintenance door 117, paste the semicircular copper plate 112 equipped with the lower heat exchange sheet 110 to the lower end of the heat exchange pipe 106, make the lower end of the semicircular copper plate 112 contact the upper side of the retaining ring 113, fasten the semicircular copper plate 112 by using the clamp 114, and then reconnect the maintenance door 117 with the shell 101 through bolts. The assembly process is completed.

[0054] When the high-temperature flue gas enters the flue gas flow passage B from the flue gas pipeline 104 at the lower left end of the shell 101, flows through the lower heat exchange fins 110 at the lower part of the heat exchange tube 106, and the heat in the flue gas is transferred to the upper part of the heat exchange tube 106 through the lower heat exchange fins 110 and the semi-arc copper plate 112, the heat conducting medium in the heat exchange tube 106 absorbs the heat and evaporates into a gaseous state, rises along the inside of the heat exchange tube 106, and preheats the cold air in the air heating chamber A through the upper heat exchange fins 107 at the upper end of the heat exchange tube 106. The liquid state working medium condensed in the heat exchange tube 106 returns to the lower end of the heat exchange tube 106 under the action of gravity or capillary force, and absorbs the heat of the flue gas again to form a "evaporation-condensation" cycle, continuously realizing efficient heat transfer from the flue gas to the air. Among them, the copper heat spreading plate 216 itself has good heat conduction performance, can quickly absorb and conduct the local concentrated heat in the flue gas flow passage B of the partition plate 102 to the auxiliary heat exchange fins 212 in the air heating chamber A, avoid the local overheating or excessive concentration of the partition plate 102 due to uneven distribution of flue gas temperature, and reduce the aggregation of acidic condensate formed due to the local temperature being lower than the dew point, thereby reducing the corrosion risk of the partition plate 102 and the surrounding structure, prolonging the service life of the whole equipment. When the heat is transferred to the auxiliary heat exchange fins 212, the auxiliary heat exchange fins 212 efficiently release the heat to the cold air by increasing the contact area with the air, and assist in improving the preheating temperature of the air. At the same time, the arrangement of the auxiliary heat exchange fins 212 is parallel to the air flow direction, and the fish fin-shaped auxiliary heat exchange fins 212 can reduce the wind resistance and ensure the rapid flow of air.

[0055] Replacement process:

[0056] The components in the flue gas flow passage B, such as the lower heat exchange fins 110, are consumable parts. When the lower heat exchange fins 110 need to be replaced, open the maintenance door 117, loosen the two clamps 114, and remove the semi-arc copper plate 112 together with the lower heat exchange fins 110 from the lower end of the heat exchange tube 106 to complete the disassembly of the lower heat exchange fins 110. Then, use cleaning tools to clean the surface of the lower end of the heat exchange tube 106, mainly to clean the dirt and acidic condensate residues formed by the impurities such as dust and sulfides contained in the flue gas. The cleaning function is to avoid the impurities covering the surface of the heat exchange tube 106, hinder the heat transfer between the heat exchange tube 106 and the flue gas, ensure that the heat exchange tube 106 can efficiently absorb the heat of the flue gas, and prevent the acidic residues from corroding the surface of the lower end of the heat exchange tube 106, thereby prolonging the service life of the heat exchange tube 106. After cleaning, the reverse steps can be used for reinstallation.

[0057] The above description is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. An air preheater resistant to low temperature dew point corrosion, characterized by: The heat exchange tube positioning mechanism comprises a horizontal sliding groove, an assembly plate and a mounting column. The shell is internally provided with a partition plate, which divides the internal space of the shell into an air heating chamber located at the upper portion and a flue gas flow-through chamber located at the lower portion. An air duct is arranged on the side of the shell at the air heating chamber and is in communication with the air heating chamber. A flue gas duct is arranged on the side of the shell at the flue gas flow-through chamber and is in communication with the flue gas flow-through chamber. Uniformly distributed heat exchange tube holes are formed in the middle portion of the partition plate, and heat exchange tubes are assembled in the heat exchange tube holes. The heat exchange tubes are perpendicular to the partition plate. The upper portions of the heat exchange tubes are located in the air heating chamber, and the lower portions of the heat exchange tubes are located in the flue gas flow-through chamber. A plurality of upper heat exchange fins are arranged on the outer side of the upper portions of the heat exchange tubes. Ceramic sealing rings are fixedly connected to the outer sides of the middle portions of the heat exchange tubes. Annular assembly grooves are formed in the outer sides of the middle portions of the ceramic sealing rings. The lower portions of the heat exchange tubes are provided with detachable lower heat exchange fins. The bottom wall of the shell is provided with a receiving groove matched with the lower ends of the heat exchange tubes. The heat exchange tube positioning mechanism is used for positioning and releasing the heat exchange tubes.

2. The low temperature freeze dew point corrosion resistant air preheater of claim 1, wherein: The upper heat exchange fins are fixed to the upper portions of the heat exchange tubes. The upper heat exchange fins adopt an annular structure arranged at intervals or a continuous spiral structure. The lower heat exchange fins are detachably mounted on the lower portions of the heat exchange tubes through a lower heat exchange fin assembly component. The lower heat exchange fin assembly component comprises two hingedly connected semi-arc copper plates. The lower heat exchange fins are welded or tightly inserted on the outer sides of the semi-arc copper plates. A stop ring is arranged on the outer side of the lower end of the heat exchange tube. The outer diameter of the stop ring is smaller than the inner diameter of the heat exchange tube hole. The semi-arc copper plates are located above the stop ring. The two semi-arc copper plates are assembled on the outer side of the heat exchange tube through a clamp.

3. The low temperature freeze dew point corrosion resistant air preheater of claim 2, wherein: A maintenance door is bolted to the lower end of the front side wall of the shell. The maintenance door is used for mounting or replacing the lower heat exchange fins.

4. The low temperature freeze dew point corrosion resistant air preheater of claim 1, wherein: The heat exchange tube positioning mechanism comprises a horizontal sliding groove, an assembly plate and a mounting column. The horizontal sliding groove is located in the partition plate and is in communication with the heat exchange tube hole. Two graphite sealing plates are slidably connected in each horizontal sliding groove. The graphite sealing plates are in an arc structure. The two graphite sealing plates in each horizontal sliding groove are symmetrically arranged on the two sides of the ceramic sealing ring in the heat exchange tube hole in communication with the horizontal sliding groove. The position of the horizontal sliding groove corresponds to the annular assembly groove. When the graphite sealing plate moves towards the ceramic sealing ring in the horizontal direction, the graphite sealing plate can be inserted into the annular assembly groove. When the graphite sealing plate moves away from the ceramic sealing ring in the horizontal direction, the graphite sealing plate is removed from the annular assembly groove.

5. The low temperature freeze dew point corrosion resistant air preheater of claim 4, wherein: The two graphite sealing plates in the same horizontal sliding groove are inserted and matched. A slot is arranged on the end face of one of the graphite sealing plates, and a boss matched with the slot is arranged on the end face of the other graphite sealing plate.

6. The low temperature freeze dew point corrosion resistant air preheater of claim 4, wherein: The assembly plate is located in the horizontal sliding groove. Two assembly holes are symmetrically arranged on the assembly plate. A drive rod is slidably connected in the assembly hole. One end of the drive rod is fixedly connected with the graphite sealing plate. The other end of the drive rod is provided with a ball. The outer side of the end of the drive rod away from the graphite sealing plate is fixedly connected with a limiting ring. The outer side of the drive rod is sleeved with a reset spring. The reset spring is located between the assembly plate and the limiting ring.

7. The low temperature freeze dew point corrosion resistant air preheater of claim 4, wherein: The installation column is arranged on the partition plate, the through hole is arranged on the partition plate and communicates with the horizontal sliding groove, the installation column is slidingly arranged in the through hole, the upper end of the installation column is provided with an auxiliary heat exchange fin, the auxiliary heat exchange fin is in the shape of a fish fin, the auxiliary heat exchange fin is arranged to be parallel to the air flow direction, the lower end of the installation column is provided with a driving slope, when the installation column penetrates the horizontal sliding groove downward, the driving slope cooperates with the ball to push the driving rod and the graphite sealing plate to move towards the annular assembly groove, when the installation column moves out of the horizontal sliding groove upward, the installation column and the driving slope are separated from the ball, and the reset spring pushes the driving rod and the graphite sealing plate to separate from the annular assembly groove.

8. The low temperature freeze dew point corrosion resistant air preheater of claim 7, wherein: The outer side of the installation column is coaxially and fixedly connected with an outer threaded sleeve, the through hole is provided with an inner thread matched with the outer threaded sleeve, and the outer side of the upper end of the outer threaded sleeve is provided with a limiting plate.

9. The low temperature freeze dew point corrosion resistant air preheater of claim 8, wherein: The heat exchange pipe positioning mechanism further comprises copper heat plates fixedly connected to the lower surface of the partition plate, and the lower end of the installation column is inserted into the blind hole in the copper heat plate.

10. The low temperature freeze dew point corrosion resistant air preheater of claim 9, wherein: In the air heating chamber, the heat exchange area of the auxiliary heat exchange fin at the middle position of the shell is greater than that of the auxiliary heat exchange fin close to the side wall of the shell, the width of the auxiliary heat exchange fin close to the side wall of the shell is greater than that of the auxiliary heat exchange fin at the middle position of the shell, and the height of the auxiliary heat exchange fin at the middle position of the shell is greater than that of the auxiliary heat exchange fin close to the side wall of the shell. In the flue gas flow chamber, the heat exchange area of the copper heat plate at the middle position of the shell is greater than that of the copper heat plate close to the side wall of the shell.

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