Air heater for preventing low-temperature sulfuric acid corrosion of char black tail gas boiler
Patent Information
- Application Number
- CN202522050578.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-24
- Publication Date
- 2026-09-18
- Estimated Expiration
- 2035-09-24
AI Technical Summary
导致锅炉不能安全正常运行
[0018] 1. In this invention, the medium inside the phase change heat pipe is as follows: In the flue gas channel, the flue gas releases heat, heating the medium inside the pipe until its temperature reaches above 130°C. The medium absorbs latent heat of vaporization and boils, and the boiling vapor flows upward into the air channel. In the air channel, the air absorbs heat, the boiling vapor releases heat and condenses into a liquid state, the latent heat of vaporization heats the cold air, the medium temperature is maintained at 130°C but condenses into a saturated liquid state, and the liquid medium flows downward along the inner wall of the pipe back into the flue gas channel. This achieves repeated circulation of the heat exchange medium.
Smart Images
Figure CN224771558U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of heat exchanger technology, and in particular to an air heater that prevents low-temperature sulfuric acid corrosion in boilers burning carbon black tail gas. Background Technology
[0002] Factory boilers burning carbon black exhaust gas require air at a certain temperature for combustion, so air heaters are installed in the flue gas duct at the boiler's tail end. Because the carbon black exhaust gas contains SO2 and moisture after combustion, the flue gas temperature in the air heater area may be lower than the acid dew point temperature. This can cause sulfuric acid corrosion on the heat exchange metal surfaces of the air heaters. Calculations show the acid dew point temperature is approximately 119.7℃. If a conventional air preheater is used, the air temperature at the preheater inlet is at room temperature (16℃). When the exhaust gas temperature is 130℃, the average metal wall temperature is 73℃, far below the acid dew point temperature. This will inevitably cause corrosion of the heat exchange tubes, preventing the boiler from operating safely and normally.
[0003] Based on this, an air heater is proposed to prevent low-temperature sulfuric acid corrosion in carbon black tail gas boilers. Utility Model Content
[0004] The purpose of this invention is to address the problems existing in the background technology by proposing an air heater to prevent low-temperature sulfuric acid corrosion in boilers producing carbon black tail gas.
[0005] The technical solution of this utility model is an air heater for preventing low-temperature sulfuric acid corrosion in a boiler that produces carbon black tail gas. It includes a phase change heat pipe and a partition plate. The partition plate is divided into an upper partition plate, a middle partition plate, and a lower partition plate. The three sets of partition plates work together to form an installation platform at the tail gas discharge end of the boiler.
[0006] The partition has a pre-drilled through hole for the installation of the phase change heat pipe; the phase change heat pipe is tilted at a certain angle and installed in conjunction with the partition; the middle part of the phase change heat pipe passes through the middle partition, and the two ends are inserted into the through holes of the upper and lower partitions respectively; the upper and lower partitions are equipped with limiters for fixing the phase change heat pipe, and openable maintenance doors are installed at the upper and lower partitions.
[0007] The upper, middle and lower sets of baffles are combined at the exhaust end to form a flue gas passage and an air passage; the phase change heat pipe runs across the flue gas passage and the air passage; the phase change heat pipe absorbs heat in the flue gas passage and releases heat in the air passage; the phase change material circulates inside the phase change heat pipe.
[0008] Preferably, the partition is provided with an insulation layer at the installation position of the phase change heat pipe to reduce heat exchange between the phase change heat pipe and the external environment.
[0009] Preferably, the bottom of the partition is provided with multiple sets of steel frames for support.
[0010] Preferably, the length of the inclined phase change heat pipe in the flue gas channel is greater than its length in the air channel.
[0011] Preferably, in the inclined phase change heat pipe, the upward-inclined end is placed in the air channel, and the downward-inclined end is placed in the flue gas channel.
[0012] Preferably, a sealing element that mates with the phase change heat pipe is provided at the through hole of the partition plate to seal the gap between the phase change heat pipe and the through hole.
[0013] Preferably, locking devices are provided on the upper and lower partitions for locking and fixing with the phase change heat pipe.
[0014] Preferably, the outer periphery of the phase change heat pipe is provided with an extended heating surface that extends outward.
[0015] Preferably, the heat exchangers are arranged in a quincunx pattern.
[0016] Preferably, the metal wall temperature at the outlet of the phase change heat pipe is more than 5°C higher than the acid dew point temperature.
[0017] Compared with the prior art, the present invention has the following beneficial technical effects:
[0018] 1. In this invention, the medium inside the phase change heat pipe is as follows: In the flue gas channel, the flue gas releases heat, heating the medium inside the pipe until its temperature reaches above 130°C. The medium absorbs latent heat of vaporization and boils, and the boiling vapor flows upward into the air channel. In the air channel, the air absorbs heat, the boiling vapor releases heat and condenses into a liquid state, the latent heat of vaporization heats the cold air, the medium temperature is maintained at 130°C but condenses into a saturated liquid state, and the liquid medium flows downward along the inner wall of the pipe back into the flue gas channel. This achieves repeated circulation of the heat exchange medium.
[0019] 2. During the circulation process, the temperature of the medium inside the phase change heat pipe remains at its saturation temperature under a certain pressure. At this point, the temperature of the outer wall of the heat exchange pipe is basically the same as the saturation temperature of the medium inside the pipe, that is, the temperature of the outer metal wall of the pipe is ≥130℃. This temperature is the acid dew point temperature of the high-pressure flue gas. Therefore, the outer metal wall of the phase change heat pipe will not be corroded.
[0020] 3. Through the phase change heat transfer process, the flue gas is cooled while the air is heated. This improves the boiler's thermal efficiency and stabilizes the combustion of carbon black exhaust gas. It also avoids the problem of low-temperature dew point corrosion on the boiler's tail-end heating surface (air heater). Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the external structure of the device according to an embodiment of the present utility model;
[0022] Figure 2 This is a top view of the heat exchanger in an embodiment of the present invention.
[0023] Figure 3 This is a schematic diagram of the phase change heat pipe in an embodiment of the present invention;
[0024] Figure 4 This is a schematic diagram of the structure of an air preheater in the prior art;
[0025] Figure 5 This is a schematic diagram of the phase change heat pipe in an embodiment of this utility model;
[0026] Figure 6 This is a cross-sectional view of the phase change heat pipe in an embodiment of this utility model.
[0027] Reference numerals: 1. Inspection door; 2. Insulation layer; 3. Phase change heat pipe; 31. Extended heating surface; 32. Heat exchange base pipe; 4. Partition plate; 5. Sealing element; 6. Locking element; 7. Supporting steel frame; 8. Connecting box. Detailed Implementation
[0028] Example 1
[0029] like Figure 4 The diagram shows the structure of a traditional boiler tail-end air preheater; it is typically a tube-and-box type indirect heat exchanger. Flue gas flows outside the tubes, while air flows inside. The heat from the flue gas outside the tubes is conducted to the internal air through the metal of the tubes, gradually heating the air inside. The upper and lower sets of tubes are connected by a connecting box 8. This heat exchange method, where heat is transferred from the flue gas outside the tubes to the air inside by the metal of the tubes, is called indirect heat exchange. The metal wall temperature is the average temperature of the medium inside and outside the tubes. Therefore, in flue gas containing corrosive components such as SO2, when using this type of heat exchanger, the metal wall temperature of the heat exchanger must be higher than the acid dew point temperature; otherwise, tube corrosion will occur, causing the heat exchanger to fail and affecting the normal operation of the boiler.
[0030] This implementation example Figure 1 As shown, an air heater for preventing low-temperature sulfuric acid corrosion in a coal black flue gas boiler is proposed, comprising a phase change heat pipe 3 and a partition 4. The partition 4 is divided into an upper partition, a middle partition, and a lower partition. The three sets of partitions 4 cooperate to form an installation platform at the boiler's exhaust gas discharge end. Multiple sets of steel frames 7 are provided at the bottom of the partition 4 for support. Through the support of the steel frames 7, and the partition 4 forming a relatively isolated flue gas passage and air passage in the exhaust gas passage, the partition 4 has a pre-reserved through hole for installing the phase change heat pipe 3. The phase change heat pipe 3 is inclined at a certain angle and installed in conjunction with the partition 4. The middle part of the phase change heat pipe 3 passes through the middle partition, and its two ends are inserted into the through holes of the upper and lower partitions, respectively. Limiters for fixing the phase change heat pipe 3 are provided on both the upper and lower partitions, and openable maintenance doors 1 are installed at the upper and lower partitions.
[0031] The upper, middle and lower sets of baffles are combined at the exhaust end to form a flue gas passage and an air passage; the phase change heat pipe 3 runs through the flue gas passage and the air passage; the phase change heat pipe 3 absorbs heat in the flue gas passage and releases heat in the air passage; the phase change material circulates in the phase change heat pipe 3.
[0032] The technical measure adopted by this utility model to solve the above-mentioned technical problems is as follows: The heat of the flue gas in the flue gas channel is used to heat the heat-absorbing section of the phase change heat pipe. The absorbed heat is then transferred to the air in the air channel. The phase change heat pipe is a separate heat transfer element. Its interior is under vacuum and filled with a medium mainly composed of pure water. Under vacuum conditions at room temperature and below atmospheric pressure, the boiling point of the medium is only 70℃~80℃. When the pipe exchanges heat with flue gas above 130℃, the medium inside the pipe boils and vaporizes, losing the vacuum and acquiring a certain internal pressure. This internal pressure ensures that the boiling point of the medium is 130℃ (or above). The boiling vapor rises to the upper end of the pipe, exchanges heat with the cold air, releases the latent heat of vaporization, and its state becomes a liquid saturated medium again. The liquid medium flows down the inner wall of the pipe into the flue gas channel, where it continues to be heated by the flue gas and vaporizes. This cycle of heat absorption and release achieves the effect of cooling the flue gas and heating the air. The principle of the phase change heat pipe 3 is as follows: Figure 5 As shown.
[0033] Example 2
[0034] like Figure 2 As shown, the partition 4 has an insulation layer 2 at the installation position of the phase change heat pipe 3 to reduce heat exchange between the phase change heat pipe 3 and the external environment. The inclined phase change heat pipe 3 has a longer length in the flue gas channel than in the air channel. In the inclined phase change heat pipe 3, the upward-sloping end is placed in the air channel, and the downward-sloping end is placed in the flue gas channel. This facilitates the phase change material, after releasing heat in the air channel, to flow back to the heat absorption section of the flue gas channel under the action of gravity.
[0035] A sealing element 5, which mates with the phase change heat pipe 3, is provided at the through hole of the partition 4 to seal the gap between the phase change heat pipe 3 and the through hole. Locking elements 6 are provided on the upper and lower partitions for locking and fixing to the phase change heat pipe 3. Commonly, the locking elements can be bolts, washers, or used in conjunction with springs for locking.
[0036] like Figure 6 As shown, the phase change heat pipe 3 includes an extended heating surface 31 and a heat exchange base pipe 32; wherein, the extended heating surface 31 is formed by extending the heat exchange base pipe 32 outward; and multiple phase change heat pipes 3 are arranged in a quincunx pattern.
[0037] In this embodiment, the metal wall temperature at the outlet of the phase change heat pipe 3 is more than 5°C higher than the acid dew point temperature. The heat-absorbing pipes in the flue gas passage have extended heating surfaces, and the heat-releasing pipes in the air passage have extended heating surfaces. The heat exchangers are arranged in a quincunx pattern. Because the flue gas contains SO2 and a large amount of moisture, the acid dew point temperature reaches 119.7°C. Therefore, the metal surface temperature of the boiler's final stage heat exchange surface must be approximately 5°C higher than the acid dew point temperature, meaning the metal wall temperature at the boiler's final exhaust point must be higher than 125°C to prevent corrosion by sulfuric acid, which could damage the equipment and cause a safety accident. This invention employs phase change heat exchange with extended heating surface technology, ensuring normal operation with a metal wall temperature above 125°C and effectively preventing heat exchanger failure caused by low-temperature acid dew point corrosion.
[0038] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.
Claims
1. An air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler, comprising a phase change heat pipe (3) and a baffle plate (4), characterized in that, The partition (4) is divided into an upper partition, a middle partition and a lower partition; the three sets of partitions (4) work together to form an installation platform at the exhaust gas discharge end of the boiler; A through hole is reserved on the partition (4) for the installation of the phase change heat pipe (3); the phase change heat pipe (3) is tilted at a certain angle and installed in conjunction with the partition (4); the middle part of the phase change heat pipe (3) passes through the middle partition, and the two ends are inserted into the through holes of the upper and lower partitions respectively; a limiter for fixing the phase change heat pipe (3) is provided on both the upper and lower partitions, and an openable maintenance door (1) is installed on the upper and lower partitions; The upper, middle and lower three sets of baffles are combined at the exhaust gas emission end to form a flue gas passage and an air passage; the phase change heat pipe (3) runs through the flue gas passage and the air passage; the phase change heat pipe (3) absorbs heat in the flue gas passage and releases heat in the air passage; the phase change material circulates in the phase change heat pipe (3).
2. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, The partition (4) is provided with an insulation layer (2) at the installation position of the phase change heat pipe (3) to reduce the heat exchange between the phase change heat pipe (3) and the external environment.
3. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, Multiple sets of steel frames (7) are provided at the bottom of the partition (4) for support.
4. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, The length of the inclined phase change heat pipe (3) in the flue gas channel is greater than its length in the air channel.
5. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, In the phase change heat pipe (3) that is set at an angle, the upward-angled end is placed in the air channel and the downward-angled end is placed in the flue gas channel.
6. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, A sealing element (5) is provided at the through hole of the partition (4) to cooperate with the phase change heat pipe (3) and to seal the gap between the phase change heat pipe (3) and the through hole.
7. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, Locking elements (6) are provided on the upper and lower partitions for locking and fixing with the phase change heat pipe (3).
8. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, The outer periphery of the phase change heat pipe (3) is provided with an extended heating surface that extends outward.
9. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, The heat exchangers are arranged in a quincunx pattern.
10. The air heater for preventing low-temperature sulfuric acid corrosion in a carbon black tail gas boiler according to claim 1, characterized in that, The metal wall temperature at the outlet of the phase change heat pipe (3) is more than 5°C higher than the acid dew point temperature.