A tube-and-box type air preheater

Abstract

This utility model discloses a tube-and-box type air preheater, relating to the field of air preheater technology. It includes a housing, a flue gas passage mechanism, an air passage mechanism, heat exchange tubes, a hot air duct, a soot blowing mechanism, and a controller. The heat exchange tubes are arranged in a staggered matrix within the housing and installed between the flue gas inlet chamber and the flue gas outlet chamber. The soot blowing mechanism is located at the bottom of the side wall of the flue gas inlet chamber, directly opposite the heat exchange area of ​​the heat exchange tubes. The hot air duct is installed on the upper part of the outer wall of the housing, with one end connected to the flue gas outlet chamber and the other end connected to external high-temperature air. The controller is fixed to the outer wall of the housing. The flue gas passage mechanism and the air passage mechanism are vertically staggered. The controller is electrically connected to the soot blowing mechanism. This utility model, employing the above-mentioned tube-and-box type air preheater, effectively solves the problems of frequent low-temperature corrosion and severe ash accumulation and blockage, thereby improving the equipment's corrosion resistance and self-cleaning ability.

Description

Technical Field

[0001] This utility model relates to the field of air preheater technology, and in particular to a tube-box type air preheater. Background Technology

[0002] Tube-type air preheaters, as core components of thermal equipment such as boilers and industrial kilns, function to recover waste heat and improve system thermal efficiency through heat exchange between flue gas and air. However, in actual operation, frequent low-temperature corrosion and severe ash accumulation and blockage are two key challenges restricting their reliability and economy.

[0003] Against the backdrop of a diversified energy structure, the widespread use of high-sulfur coal, biomass fuels, and industrial waste gas has led to an increase in the content of acidic gases in flue gas. When the flue gas temperature drops below 400℃, SO3 combines with water vapor in the flue gas to form sulfuric acid vapor. As the flue gas temperature further decreases, the sulfuric acid vapor condenses and gradually solidifies into a liquid. Due to the presence of the liquid sulfuric acid, on the one hand, dust in the flue gas will adhere and become difficult-to-clean wet ash and scale, causing blockage of the flue gas passage of the air preheater; on the other hand, the liquid sulfuric acid itself will also corrode the equipment body, leading to chemical corrosion of the steel structure.

[0004] In existing technologies, conventional carbon steel heat exchange tubes corrode rapidly in acidic environments, resulting in a short service life. Although anti-corrosion measures such as stainless steel or enamel coatings can be used, stainless steel is expensive and has limited high-temperature oxidation resistance, while enamel coatings are prone to damage during transportation and accelerated corrosion after local failure. Some enterprises attempt to avoid dew point corrosion by increasing flue gas temperature, but this leads to a decrease in boiler thermal efficiency, violating energy conservation and emission reduction targets. Since refineries inevitably contain small amounts of sulfur in their fuel oil or fuel gas, sulfur combustion produces SO2, which further oxidizes to SO3.

[0005] However, improvements targeting individual problems have failed to form a systemic solution, resulting in persistent difficulties in improving the operational reliability of tube-and-box air preheaters under high-sulfur and dusty conditions. Therefore, there is an urgent need for a tube-and-box air preheater structure that combines efficient corrosion resistance and self-cleaning capabilities to address the synergistic challenges of low-temperature corrosion and dust accumulation in existing technologies. Utility Model Content

[0006] The purpose of this invention is to provide a tube-and-box type air preheater that effectively solves the problems of frequent low-temperature corrosion and severe dust accumulation and blockage in the prior art, thereby improving the equipment's corrosion resistance and self-cleaning ability.

[0007] To achieve the above objectives, this utility model provides a tube-and-box type air preheater, comprising: Box; The flue gas passage mechanism includes a flue gas inlet, a flue gas inlet chamber, a flue gas passage, a flue gas outlet chamber, and a flue gas outlet connected in sequence. An air passage mechanism, comprising an air inlet, an air passage, and an air outlet connected in sequence; The heat exchange tubes are arranged in a staggered matrix inside the box and installed between the flue gas inlet chamber and the flue gas outlet chamber; A soot blowing mechanism is installed in the heat exchange area at the bottom of the side wall where the flue gas enters the room and directly opposite the heat exchange tube; A hot air duct is installed on the upper part of the outer wall of the housing, with one end connected to the flue gas exhaust chamber and the other end connected to the outside air; The controller is fixed to the outer wall of the housing; The flue gas passage mechanism and the air passage mechanism are arranged in a vertically staggered manner; The controller is electrically connected to the soot blowing mechanism.

[0008] Preferably, the flue gas inlet is located at the lower left corner of the housing; the flue gas inlet chamber is located at the bottom of the housing; the flue gas passage is the internal flow channel space of the heat exchange tube; the flue gas outlet chamber is located at the top of the housing; and the flue gas outlet is located at the upper right corner of the housing.

[0009] Preferably, the air inlet is located at the lower right corner of the housing, the air channel is a surrounding flow channel outside the heat exchange tube, and the air outlet is located at the upper left corner of the housing.

[0010] Preferably, several longitudinal fins with the same structure are vertically installed on the outer wall of the heat exchange tube. The length of the longitudinal fins is the same as the length of the heat exchange tube and they are evenly distributed along the axis of the tube. Several transverse fins with the same structure are vertically installed on the inner wall of the heat exchange tube. The transverse fins are arranged in a staggered matrix and their edges form a preset angle with the flue gas flow direction.

[0011] Preferably, the upper wall of the flue gas inlet chamber and the lower wall of the flue gas outlet chamber are each provided with a plurality of heat exchange tube connection holes that match the heat exchange tubes.

[0012] Preferably, the soot blowing mechanism includes: a sound wave generator and two steam soot blowers with the same structure; the sound wave generator and the steam soot blowers are both located at the bottom of the side wall of the flue gas inlet chamber, the two steam soot blowers are symmetrically arranged on both sides of the sound wave generator, and the controller is electrically connected to the sound wave generator and the steam soot blowers respectively.

[0013] Preferably, a temperature sensor is installed on the inner wall of the flue gas outlet, and two differential pressure transmitters are installed on the inner walls of the flue gas inlet and outlet respectively. The controller is electrically connected to the temperature sensor and the differential pressure transmitter respectively.

[0014] Preferably, a first solenoid valve is installed inside the flue gas outlet, a second solenoid valve is installed inside the hot air duct, and the controller is electrically connected to the first solenoid valve and the second solenoid valve respectively.

[0015] Therefore, the present invention employs the above-mentioned tube-box type air preheater, and its technical effects are as follows: (1) The three-dimensional inner and outer fin heat exchange tube with staggered matrix arrangement has longitudinal fins on the outer wall to expand the heat exchange area on the air side and guide the flow evenly. The transverse fins on the inner wall disturb the flue gas and destroy the laminar boundary layer, which significantly improves the heat exchange effect on both sides. The overall heat transfer efficiency is much higher than that of traditional bare tubes.

[0016] (2) The acoustic generator at the bottom of the flue gas chamber works in conjunction with the symmetrical steam soot blower. The acoustic pre-loosening combined with the precise steam blowing covers the different types of ash removal needs, resulting in a significant ash removal effect, a substantial reduction in ash thickness, an effective extension of the ash removal cycle, and a significant reduction in the frequency of manual maintenance.

[0017] (3) The composite coating on the surface of the heat exchange tube forms a dual barrier against high-temperature oxidation and dew point corrosion. Combined with the air replenishment and heating function of the hot air duct, it greatly reduces the risk of low-temperature corrosion and significantly extends the service life of the heat exchange tube.

[0018] (4) The controller monitors in real time through temperature sensors, differential pressure transmitters, etc., and dynamically adjusts the frequency of the soot blowing mechanism and the opening of the solenoid valve to achieve stable air outlet temperature, reduce exhaust heat loss, and automatically start anti-corrosion protection under low load to ensure efficient and stable operation of the system under all working conditions.

[0019] (5) The vertical crossflow layout of the flue gas passage mechanism and the air passage mechanism forms a reasonable airflow stroke ratio, and the power consumption of the fan is reduced by utilizing the thermal pressure effect; the staggered tube array design reduces the flow resistance of flue gas, and the system energy consumption is significantly reduced.

[0020] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an embodiment of the tube-box type air preheater of this utility model; Figure 2 This is a longitudinal sectional view of an embodiment of the tube-box type air preheater of this utility model; Figure 3 This is a cross-sectional view of an embodiment of the tube-box type air preheater of this utility model; Figure 4 This is a schematic diagram of the flue gas inlet chamber structure of this utility model; Figure 5 This is a schematic diagram of the heat exchange tube of this utility model.

[0022] Figure Labels 1. Housing; 2. Heat exchanger tubes; 201. Longitudinal fins; 202. Transverse fins; 3. Flue gas inlet; 4. Flue gas inlet chamber; 5. Flue gas passage; 6. Flue gas outlet chamber; 7. Flue gas outlet; 8. First solenoid valve; 9. Air inlet; 10. Air passage; 11. Air outlet; 12. Soot blowing mechanism; 1201. Acoustic wave generator; 1202. Steam soot blower; 13. Hot air duct; 14. Second solenoid valve; 15. Temperature sensor; 16. Differential pressure transmitter; 17. Controller; 18. Heat exchanger tube connection hole. Detailed Implementation

[0023] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] Example 1 like Figures 1-5 The tube-type air preheater includes: Box 1 serves as the carrier and mounting base for various functional components, providing structural support and forming a closed heat exchange space. It is connected to external pipes through flexible expansion joints, and the joints are filled with sealing material.

[0026] The flue gas passage mechanism consists of a flue gas inlet 3, a flue gas inlet chamber 4, a flue gas passage 5, a flue gas outlet chamber 6, and a flue gas outlet 7, which are connected in sequence to form a dedicated flue gas flow channel, realizing the orderly introduction, heat exchange, and discharge of high-temperature flue gas. Solid arrows indicate the movement path of the flue gas.

[0027] The air passage mechanism consists of an air inlet 9, an air channel 10, and an air outlet 11 connected in sequence, forming a heating path for the low-temperature air and creating a highly efficient heat exchange loop with the flue gas passage mechanism. The dashed arrows indicate the air movement path.

[0028] The heat exchange tubes 2 are densely arranged in a staggered matrix inside the housing 1, between the flue gas inlet chamber 4 and the flue gas outlet chamber 6, maximizing space utilization and enhancing turbulence, thus significantly improving the heat exchange efficiency per unit volume. The heat exchange tubes 2 are coated with an Al2O3 and TiO2 composite coating to prevent corrosion and significantly extend their service life.

[0029] The soot blowing mechanism 12 is located at the bottom of the inner wall of the flue gas inlet chamber 4 and directly opposite the heat exchange area of ​​the heat exchange tube 2. By periodically removing the ash accumulated on the tube surface, it avoids the increase of thermal resistance and ensures long-term stable operation.

[0030] Hot air duct 13 is installed on the upper part of the outer wall of the housing 1. One end is connected to the flue gas exhaust chamber 6, and the other end is connected to an external high-temperature air source (such as primary air or steam). By introducing an auxiliary heat source, low-temperature corrosion is prevented and the system operation stability is maintained.

[0031] The controller (PLC control system) 17 is fixed to the outer wall of the housing 1, serving as the intelligent control hub and integrating data acquisition, logic operation and equipment control functions.

[0032] The flue gas passage mechanism and the air passage mechanism are vertically staggered to form a cross-flow heat exchange mode, which significantly improves heat exchange efficiency.

[0033] The controller 17 establishes an electrical connection with the soot blowing mechanism 12, and automatically triggers the soot blowing action through a preset program or real-time monitoring signal to realize intelligent control of the soot cleaning process.

[0034] Flue gas passage mechanism: Flue gas inlet 3 is located at the lower left corner of housing 1, adopting a low-position air intake design. It utilizes gravity settling of flue gas to initially separate large dust particles, reducing wear on heat exchange tubes. Flue gas inlet chamber 4 is installed at the bottom of housing 1, serving as a flue gas buffer chamber to balance airflow distribution and reduce flow velocity, avoiding localized erosion and wear. Flue gas passage 5 is the internal flow channel space of heat exchange tube 2. High-temperature flue gas exchanges heat with the air on the outer wall as it flows inside the tube. The transverse fins 202 on the inner wall further agitate the airflow, enhancing convective heat transfer within the tube. Flue gas exhaust chamber 6 is installed at the top of housing 1, collecting the low-temperature flue gas after heat exchange and discharging it at a high position through flue gas outlet 7, utilizing thermal pressure to reduce exhaust resistance. Flue gas outlet 7 is located at the upper right corner of housing 1, forming a diagonal layout with the inlet, extending the flow path of flue gas within the housing and fully releasing residual heat.

[0035] Airflow Mechanism: Air inlet 9 is located at the lower right corner of housing 1, diagonally opposite to the flue gas inlet, forming a completely cross-flow heat exchange structure to maximize the temperature difference for heat transfer. Air channel 10 is a surrounding flow channel outside the heat exchange tube 2, where low-temperature air is laterally swept outside the tube, and the longitudinal fins 201 on the outer wall significantly expand the heat exchange area while guiding the airflow to a uniform distribution. Air outlet 11 is located at the upper left corner of housing 1, collecting the heated air at a high position for easy connection to subsequent process piping and reducing power consumption.

[0036] The heat exchange tube 2 employs a three-dimensional internal and external finned reinforcement system. Several longitudinal fins 201 of equal length are vertically installed on the outer wall, evenly distributed along the tube's axis. This creates longitudinal turbulence in the external airflow channel, significantly improving the air-side heat transfer coefficient without substantially increasing pressure drop. Transverse fins 202 are vertically installed on the inner wall in a staggered matrix arrangement. The edges of the transverse fins 202 form a pre-defined angle with the flue gas flow direction, forcing periodic turbulence in the flue gas, disrupting the laminar boundary layer, significantly enhancing the heat transfer efficiency on the flue gas side inside the tube, and simultaneously reducing ash accumulation.

[0037] Several heat exchange tube connection holes 18 are opened on the upper wall of the flue gas inlet chamber 4 and the lower wall of the flue gas outlet chamber 6. They are precisely matched with the pipe ends of the heat exchange tube 2 and fixed by welding or expansion joint process to ensure airtightness and withstand thermal expansion and contraction stress, thus ensuring long-term operational reliability.

[0038] The soot blowing mechanism 12 consists of a sound wave generator 1201 and two symmetrically installed steam soot blowers 1202. The sound wave generator 1201 breaks down the ash accumulation structure through high-frequency vibration, suitable for pre-cleaning loose ash layers. The steam soot blowers 1202 use high-temperature, high-pressure steam jets to remove sticky ash. The two methods work together to cover the cleaning needs under different working conditions. The controller 17 establishes control signal connections with the sound wave generator 1201 and the steam soot blowers 1202 respectively. It can trigger the combined soot blowing program based on the flow resistance monitored by the differential pressure transmitter 16 or by timed triggering to achieve a balance between efficient cleaning and energy consumption optimization.

[0039] Temperature sensor 15 is installed on the inner wall of flue gas outlet 7 to monitor the air-side outlet temperature in real time, preventing acid dew point corrosion and providing feedback to adjust the air supply volume of hot air duct 13. Two differential pressure transmitters 16 are installed on the inner walls of the inlet and outlet of flue gas channel 5, respectively, to monitor changes in channel differential pressure. When the differential pressure exceeds a threshold, the soot blowing mechanism is automatically triggered to achieve quantitative monitoring of the degree of ash accumulation. Controller 17 establishes a data acquisition and control connection with temperature sensor 15 and differential pressure transmitters 16 to construct a closed-loop control system. Through a PID algorithm, parameters such as soot blowing frequency and valve opening are dynamically adjusted to ensure that the system always operates in a highly efficient and energy-saving state.

[0040] The flue gas outlet 7 integrates a first solenoid valve 8, which automatically adjusts its opening according to the system load to control the flue gas flow rate to match the air-side heating demand and avoid excessive heat loss from exhaust. The hot air duct 13 integrates a second solenoid valve 14, which opens under low-temperature conditions to introduce high-temperature external air, raising the surface temperature of the heat exchange tubes and preventing low-temperature corrosion caused by sulfuric acid vapor condensation, thus extending equipment life. The first solenoid valve 8 and the second solenoid valve 14 are connected to the controller 17 via control circuitry to achieve automated control of their opening and closing states. Combined with temperature sensor data, this forms an intelligent anti-corrosion protection mechanism.

[0041] The working process of this utility model is as follows: High-temperature flue gas first enters from the flue gas inlet 3 at the lower left corner of the housing 1, and after being uniformly regulated and pressure-stabilized in the flue gas inlet chamber 4 at the bottom of the housing 1, it flows into the flue gas channel 5. The transverse fins 202 on the inner wall of the heat exchange tube 2 force the flue gas to generate turbulence and disturbance when flowing in the tube, which enhances convective heat transfer. After releasing heat, the temperature of the flue gas decreases, and after being collected in the flue gas discharge chamber 6 at the top of the housing 1, it is discharged from the flue gas outlet 7 at the upper right corner of the housing 1. Low-temperature air enters from the air inlet 9 at the lower right corner of the housing 1, and passes through the air channel 10. The longitudinal fins 201 on the outer wall of the heat exchange tube 2 significantly improve the heat absorption efficiency of the air side by expanding the heat exchange area and guiding the airflow to be evenly distributed. The heated air is sent to the subsequent process system from the air outlet 11 at the upper left corner of the housing 1. During operation, temperature sensor 15 and differential pressure transmitter 16 transmit pipe wall temperature, flue gas temperature, and flow channel differential pressure signals to controller 17 in real time. When differential pressure transmitter 16 detects that the flow channel differential pressure exceeds the threshold or reaches the preset cycle, controller 17 first activates the acoustic generator 1201 at the bottom of the inner wall of flue gas entering chamber 4 to loosen the ash accumulation on the pipe surface through high-frequency vibration. Subsequently, it triggers the steam soot blowers 1202 symmetrically arranged on both sides of acoustic generator 1201 to remove sticky ash using high-temperature and high-pressure steam jets, achieving composite cleaning of heat exchange tube 2. When temperature sensor 15 detects that the pipe wall temperature is close to the acid dew point, controller 17 opens the second solenoid valve 14 to introduce external high-temperature air to mix with the air outside the pipe, raising the pipe wall temperature to prevent low-temperature corrosion.

[0042] Therefore, this utility model adopts the above-mentioned tube box type air preheater, which effectively solves the problems of frequent low-temperature corrosion and serious dust accumulation and blockage in the prior art, and improves the equipment's corrosion resistance and self-cleaning ability.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solution of this utility model, and these modifications or equivalent substitutions cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of this utility model.

Claims

1. A regenerative air preheater of the channel type, characterized in that, include: Box; The flue gas passage mechanism includes a flue gas inlet, a flue gas inlet chamber, a flue gas passage, a flue gas outlet chamber, and a flue gas outlet connected in sequence. An air passage mechanism, comprising an air inlet, an air passage, and an air outlet connected in sequence; The heat exchange tubes are arranged in a staggered matrix inside the box and installed between the flue gas inlet chamber and the flue gas outlet chamber; A soot blowing mechanism is installed in the heat exchange area at the bottom of the side wall where the flue gas enters the room and directly opposite the heat exchange tube; A hot air duct is installed on the upper part of the outer wall of the housing, with one end connected to the flue gas exhaust chamber and the other end connected to the outside air; The controller is fixed to the outer wall of the housing; The flue gas passage mechanism and the air passage mechanism are arranged in a vertically staggered manner; The controller is electrically connected to the soot blowing mechanism.

2. A regenerative air preheater according to claim 1, wherein The flue gas inlet is located at the lower left corner of the housing; the flue gas inlet chamber is located at the bottom of the housing; the flue gas passage is the internal flow channel space of the heat exchange tube; the flue gas outlet chamber is located at the top of the housing; and the flue gas outlet is located at the upper right corner of the housing.

3. A regenerative air preheater according to claim 1, wherein The air inlet is located at the lower right corner of the housing, the air channel is a surrounding flow channel outside the heat exchange tube, and the air outlet is located at the upper left corner of the housing.

4. A regenerative air preheater according to claim 1, wherein Several identical longitudinal fins are vertically installed on the outer wall of the heat exchange tube. The length of the longitudinal fins is the same as the length of the heat exchange tube and they are evenly distributed along the tube axis. Several identical transverse fins are vertically installed on the inner wall of the heat exchange tube. The transverse fins are arranged in a staggered matrix and their edges form a preset angle with the flue gas flow direction.

5. A regenerative air preheater according to claim 1, wherein The upper wall of the flue gas inlet chamber and the lower wall of the flue gas outlet chamber are each provided with a number of heat exchange tube connection holes that match the heat exchange tubes.

6. A regenerative air preheater according to claim 1, wherein The soot blowing mechanism includes: a sound wave generator and two identical steam soot blowers; the sound wave generator and the steam soot blowers are both located at the bottom of the side wall of the flue gas inlet chamber, and the two steam soot blowers are symmetrically arranged on both sides of the sound wave generator. The controller is electrically connected to the sound wave generator and the steam soot blowers respectively.

7. A regenerative air preheater according to claim 1, wherein A temperature sensor is installed on the inner wall of the flue gas outlet, and two differential pressure transmitters are installed on the inner walls of the flue gas inlet and outlet respectively. The controller is electrically connected to the temperature sensor and the differential pressure transmitter respectively.

8. A regenerative air preheater according to claim 1, wherein A first solenoid valve is installed inside the flue gas outlet, and a second solenoid valve is installed inside the hot air duct. The controller is electrically connected to the first solenoid valve and the second solenoid valve respectively.

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