A high-efficiency heat exchange system and method for preventing and treating heat exchanger ash deposition

Abstract

The application provides a high-efficiency heat exchange system and method for preventing and treating dust blocking of a heat exchanger, and belongs to the technical field of thermal power generation heat energy recovery, and is used for solving the technical problem of dust blocking of a secondary heat exchange component caused by the decrease of flue gas temperature and the generation of ammonium bisulfate. The system comprises a high-temperature heat exchanger, a low-temperature heat exchanger, a main flue, a gasification flue and an air flow channel. The high-temperature heat exchanger and the low-temperature heat exchanger are connected in series in the main flue, and the high-temperature heat exchanger is located at the inlet end of the main flue. The low-temperature heat exchanger is internally partitioned into multiple independent gasification areas, and the main flue and the air flow channel exchange heat in each gasification area and can be independently opened and closed. The gasification flue is connected to the inlet end of the high-temperature heat exchanger, and the outlet end is provided with a connecting nozzle capable of spraying high-temperature flue gas towards any gasification area. The system can realize online removal of ammonium bisulfate dust of the secondary heat exchange component, and can guarantee normal operation of the equipment without shutdown.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation heat recovery technology, specifically to a high-efficiency heat exchange system and method for preventing heat exchanger ash blockage. Background Technology

[0002] Thermal power generation is a major source of electricity supply, and the high-temperature flue gas generated during the operation of its units contains a large amount of recoverable heat energy. To improve energy utilization efficiency, modern thermal power plants generally adopt multi-stage heat exchange systems to recover flue gas heat energy in stages, while simultaneously combining this with environmental protection facilities such as denitrification, dust removal, and desulfurization to purify the flue gas. By setting up high-temperature heat exchangers and low-temperature heat exchangers in series, heat exchange between flue gas can be achieved in different temperature ranges, which not only reduces the exhaust temperature and heat loss, but also creates conditions for the stable operation of subsequent environmental protection equipment. This process route, which combines heat recovery and flue gas treatment, has become an important means of energy conservation and emission reduction for thermal power units.

[0003] However, in the process of cascade utilization of flue gas thermal energy, secondary heat exchange components face severe operational problems. As the flue gas temperature decreases, ammonia escape intensifies during the denitrification process, and sulfur trioxide in the flue gas reacts with ammonia to form ammonium bisulfate. This substance is in a viscous molten state within a specific temperature range, readily combining with fly ash, significantly increasing the adhesion of ash particles, leading to severe ash blockage in the heat exchange channels. This ash blockage not only drastically reduces heat exchange efficiency and increases exhaust gas temperature, but also increases induced draft fan energy consumption, and in severe cases, even forces the unit to operate at reduced load or shut down for cleaning, directly affecting the unit's safety, stability, and economic efficiency. Existing ash removal methods are mostly post-treatment, making it difficult to achieve efficient cleaning without shutting down the unit. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a high-efficiency heat exchange system and method for preventing ash blockage in heat exchangers. This system addresses the technical problem of ash blockage in heat exchange channels caused by the lower flue gas temperature and reduced denitrification efficiency in the secondary heat exchange components of multi-stage heat exchange systems used in thermal power generating units for flue gas heat recovery and exhaust gas treatment. This results in the formation of substances such as ammonium bisulfate in the flue gas, which significantly increases the viscosity of fly ash.

[0005] The technical solution adopted in this invention is a high-efficiency heat exchange system and method for preventing ash blockage in heat exchangers.

[0006] One of the high-efficiency heat exchange systems for preventing heat exchanger ash blockage includes: High-temperature heat exchanger, low-temperature heat exchanger, main flue, gasification flue, and air flow channel; The high-temperature heat exchanger and the low-temperature heat exchanger are connected in series in the main flue, and the high-temperature heat exchanger is located at the inlet of the main flue. The low-temperature heat exchanger is internally divided into multiple independent vaporization zones. The main flue and air flow channel exchange heat in each of the vaporization zones, and the main flue and air flow channel of each of the vaporization zones can be opened and closed independently. The gasification flue inlet is connected to the inlet of the high-temperature heat exchanger, and the gasification flue outlet is provided with a connecting nozzle. The connecting nozzle is located in the low-temperature heat exchanger and can spray high-temperature flue gas toward any of the gasification zones.

[0007] Optionally, each of the gasification zones is provided with a first valve at its inlet. The airflow channel includes multiple parallel air branches. Each air branch exchanges heat with the flue gas in each of the gasification zones. Each air branch is opened and closed independently through a second valve. The orientation of the nozzle connected to the end of the gasification flue can be changed, and the opening of the nozzle can face any of the gasification zones.

[0008] Optionally, each of the gasification zones is provided with a first valve at its inlet, the airflow channel includes multiple parallel air branches, each air branch exchanges heat with the flue gas in each of the gasification zones, and each air branch is opened and closed independently through a second valve; the gasification flue includes multiple gasification branches that correspond one-to-one with the gasification zones, the connecting nozzles of each gasification branch are respectively oriented towards the corresponding gasification zone, and each gasification branch is opened and closed independently through a third valve.

[0009] Optionally, multiple vaporization zones are arranged in parallel within the cross-section of the low-temperature heat exchanger, multiple connecting nozzles are arranged on the sidewall of the low-temperature heat exchanger, and guide plates are provided between the vaporization zones and the connecting nozzles.

[0010] Optionally, the main flue also includes a dust collector, an induced draft fan, an end heat exchanger, a desulfurization tower, and a chimney, which are sequentially arranged at the rear end of the low-temperature heat exchanger; the air flow channel includes an inlet air temperature distribution unit, an air heater, the low-temperature heat exchanger, an air cooler, and the high-temperature heat exchanger, which are connected in series along the air flow direction; at the low-temperature heat exchanger and the high-temperature heat exchanger, the main flue and the air flow channel can exchange heat.

[0011] Optionally, the inlet air temperature control unit includes an air intake channel and a temperature detection device; the air intake channel can take in air through a first air intake port and / or a second air intake port, the air intake ratio of the first air intake port and the second air intake port can be adjusted, the temperature detection device is located at the output end of the air intake channel, and the output end of the air intake channel is connected to the input end of the air heater; the first air intake port is an atmospheric air intake port, and the second air intake port is an indoor air-cooled tower air intake port.

[0012] Optionally, in the low-temperature heat exchanger, the main flue and the air flow channel exchange heat through heat exchange tubes, and the heat exchange tubes are provided with spirally arrayed protruding fins.

[0013] Optionally, it also includes a temperature detection matrix covering the flue gas outlet section of the low-temperature heat exchanger, with multiple thermometers arranged in a matrix on the temperature detection matrix to measure the temperature distribution of the flue gas outlet section of the low-temperature heat exchanger.

[0014] One efficient heat exchange method for preventing ash blockage in heat exchangers includes the following steps: High-temperature flue gas exchanges heat through a series of high-temperature heat exchangers and low-temperature heat exchangers. Multiple independent vaporization zones are set up inside the low-temperature heat exchanger. Each vaporization zone is equipped with an independent air flow channel for heat exchange with flue gas. When ash blockage occurs in a certain vaporization zone, the air flow channel of the current vaporization zone is closed to block the flue gas heat exchange. High-temperature flue gas is introduced from the inlet end of the high-temperature heat exchanger and passes through the current vaporization zone. The ash blockage components react with the high-temperature flue gas and leave the current vaporization zone, thereby achieving anti-blocking of the low-temperature heat exchanger.

[0015] Optionally, the outlet flue gas temperature of the low-temperature heat exchanger is set to 110℃-130℃; the outlet flue gas temperature of the high-temperature heat exchanger is set to 180-200℃.

[0016] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows: This system achieves precise zonal control of the heat exchange process by dividing the low-temperature heat exchanger into multiple independent gasification zones and configuring them with independently openable and closable main flue and airflow channels. Based on this, high-temperature flue gas from the inlet side of the high-temperature heat exchanger is drawn to the low-temperature heat exchanger via the gasification flue and precisely delivered to any gasification zone requiring cleaning through connecting nozzles. This high-temperature flue gas rapidly raises the temperature of the heat exchange tube wall in that zone to the temperature range required for the gasification and decomposition of ammonium bisulfate, promoting the full gasification of sticky ash deposits, thus enabling online cleaning of the low-temperature heat exchanger without shutting down the unit. Simultaneously, a small amount of high-temperature flue gas containing ammonium bisulfate vapor, after gasification, mixes with the mainstream low-temperature flue gas and is rapidly cooled, causing the ammonium bisulfate to recrystallize and adhere to the fly ash surface, which is then effectively removed by subsequent dust collectors, forming a complete synergistic pollution control pathway. This system transforms the traditional reactive ash removal into proactive online prevention and control, effectively avoiding problems such as decreased heat exchange efficiency, increased flue gas temperature, and reduced unit load operation caused by ash blockage. It significantly improves the operational stability and equipment availability of the heat exchange system, providing a reliable guarantee for the safe, efficient, and long-term operation of thermal power generating units. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0018] Figure 1 This is a schematic diagram of the overall system structure.

[0019] Figure 2 This is a schematic diagram of the ash blockage cleaning structure.

[0020] Figure 3 for Figure 2 A magnified view of a portion of point A in the middle.

[0021] Figure 4 This is a schematic diagram of the nozzle connection.

[0022] Figure 5 This is a schematic diagram of a temperature detection matrix.

[0023] Figure 6 This is a schematic diagram of the inlet air temperature control unit.

[0024] Figure 7 This is a schematic diagram showing the coordination of the high-temperature heat exchanger, the low-temperature heat exchanger, and the inlet air temperature control unit.

[0025] Reference numerals: High-temperature heat exchanger 111, Low-temperature heat exchanger 112, Main flue 110, Gasification flue 121, Connecting nozzle 125, First valve 122, Second valve 124, Third valve 123, Guide plate 126, Dust collector 113, Exhaust fan 114, Terminal heat exchanger 115, Desulfurization tower 116, Chimney 117, Inlet air temperature control unit 140, Air heater 131, Air cooler 130, Air intake duct 141, Temperature detection element 144, First air intake 142, Second air intake 143, Temperature detection matrix 151, Thermometer 152, Plate heat exchanger 400, First low-pressure heater 410, Second low-pressure heater 420. Detailed Implementation

[0026] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] One of the high-efficiency heat exchange systems for preventing heat exchanger ash blockage is described in the appendix.Figure 1 One possible implementation includes: a high-temperature heat exchanger 111, a low-temperature heat exchanger 112, a main flue 110, a gasification flue 121, and an air flow channel; the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112 are connected in series in the main flue 110, where high temperature and low temperature are relative terms; the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112 are also connected in series in the air flow channel, the airflow direction of the air flow channel and the main flue 110 is opposite, and heat exchange is carried out in different temperature ranges in the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112, respectively; the high-temperature heat exchanger 111 is located at the inlet of the main flue 110, and the flue gas in the high-temperature heat exchanger 111 has a higher temperature. Typically, in the main flue gas duct 110, the outlet temperature of the economizer, which is also the inlet temperature of the high-temperature heat exchanger 111, is approximately 300℃-400℃, and the outlet temperature is controlled at 180℃-200℃. The gas then enters the low-temperature heat exchanger 112, whose outlet temperature is controlled at 110℃-130℃. The low-temperature heat exchanger 112 is internally divided into multiple independent gasification zones. In a preferred embodiment, the number of gasification zones is no less than 20 to enhance the gasification intensity of the flue gas, ensure temperature rise within the gasification zones, and facilitate rapid cooling at the outlet of the gasification zones. The baffle plate on the flue gas inlet side of each gasification zone is increased by a predetermined distance (preferably 500mm) to improve the gasification intensity and isolation effect of that zone. The gasification zone can be understood as multiple independent flue gas sub-channels. For example, the entire space of the heat exchanger is divided by multiple parallel baffles. The main flue duct 110 and the air flow channel exchange heat in each gasification zone. That is, heat exchange tubes are set in each flue gas sub-channel for heat exchange. The heat exchange tubes are equipped with spiral array-distributed protruding fins to enhance heat exchange. The air in the air flow channel absorbs the heat of the flue gas in the main flue duct 110. The main flue duct 110 and the air flow channel of each gasification zone can be opened and closed independently. That is, the flue gas sub-channels and / or air flow channels of one or more gasification zones can be selectively closed. When only the flue gas sub-channel of the corresponding gasification zone is closed, the flue gas cannot pass through the current gasification zone; when only the air flow channel of the corresponding gasification zone is closed, the air used for heat exchange cannot pass through the gasification zone, but the flue gas can still pass through the current gasification zone. However, since the flue gas in the current gasification zone cannot dissipate heat, its temperature will be higher than that of the surrounding gasification zones. The inlet end of the gasification flue 121 is connected to the inlet end of the high-temperature heat exchanger 111, with a temperature of about 300℃-400℃. The outlet end of the gasification flue 121 is provided with a connecting nozzle 125, which is located in the low-temperature heat exchanger 112 and can spray high-temperature flue gas toward any gasification zone.

[0029] Corresponding to the above-mentioned high-efficiency heat exchange system for preventing heat exchanger ash blockage, a possible implementation method for preventing heat exchanger ash blockage is as follows, including the following steps: High-temperature flue gas undergoes heat exchange through a series of high-temperature heat exchangers 111 and 112, with the corresponding heat exchangers maintained within a suitable temperature range. The outlet flue gas temperature of the low-temperature heat exchanger 112 is set to 110℃-130℃; the outlet flue gas temperature of the high-temperature heat exchanger 111 is set to 180-200℃; and the temperature of the original flue gas is approximately 300℃-400℃. The outlet flue gas temperatures of the low-temperature heat exchanger 112 and the high-temperature heat exchanger 111 can be controlled by adjusting the heat exchange efficiency, for example, by changing the airflow rate and the initial air temperature.

[0030] Multiple independent vaporization zones are set up in the low-temperature heat exchanger 112. Each vaporization zone has an independent air flow channel for heat exchange with flue gas. When ash blockage occurs in a certain vaporization zone, the air flow channel of the current vaporization zone is closed to block the heat exchange of flue gas. The current vaporization zone loses the heat exchange function of the air flow channel, and its temperature will be higher than that of the other vaporization zones. At the same time, high-temperature flue gas is introduced from the inlet end (300℃-400℃) of the high-temperature heat exchanger 111, and the flue gas is appropriately temperature controlled so that the high-temperature flue gas passes through the current vaporization zone, and the temperature of the current vaporization zone is kept in the range of 200℃-220℃ for no less than 30 minutes. This temperature allows the deposited ammonium bisulfate to be fully vaporized and decomposed. The ash blockage components react with the high-temperature flue gas and leave the current vaporization zone. Once they leave the current vaporization zone, they mix with the mainstream low-temperature flue gas, cool down rapidly, and recrystallize to form ammonium bisulfate, which enters the subsequent filtration stage with the flue gas dust. This process realizes the anti-clogging of the low-temperature heat exchanger 112.

[0031] As a specific implementation method of the above-mentioned scheme, the ash blockage in each gasification zone can be periodically cleaned during the operation of the high-efficiency heat exchange system, or the ash blockage in a specific gasification zone can be cleaned in a targeted manner according to the ash blockage situation.

[0032] As a preferred option, only one zone is used for gasification at a time, while the other zones are not gasified. The total number of gasification zones in the heat exchanger is n≥(t1-t2) / (140-t2), where t1 is the outlet flue gas temperature of the gasification zone and t2 is the outlet flue gas temperature of the non-gasification zone. This ensures that the ammonium bisulfate gas released during gasification can be rapidly cooled to below 140℃ and recrystallized after mixing with the mainstream flue gas, and then captured by the subsequent dust collector 113.

[0033] The above solution addresses the problem of severe ammonium bisulfate ash buildup and blockage in air preheaters and waste heat recovery systems of existing coal-fired boilers under conditions such as frequent peak shaving, excessive ammonia escape, and high-sulfur coal. Traditional technologies can only alleviate the problem, not cure it, and can transfer the blockage to downstream equipment. Furthermore, when existing systems add low-temperature economizers for waste heat recovery on the flue gas side, they are prone to low-temperature corrosion due to flue gas temperatures below the acid dew point. It is also difficult to accurately control the outlet flue gas temperatures of the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112 based on coal quality fluctuations and unit load changes, leading to decreased heat exchange efficiency and poor operational stability. In addition, traditional systems lack online methods for cleaning ash buildup in the low-temperature heat exchanger 112; cleaning requires shutdown, affecting the unit's continuous operation capability.

[0034] To address the aforementioned issues, this solution utilizes a flue gas gasification unit. High-temperature flue gas from the inlet side of the high-temperature heat exchanger 111 is used to locally gasify and clear blockages in each independent gasification zone of the low-temperature heat exchanger 112. The wall temperature is maintained at 200℃-220℃ for at least 30 minutes, allowing ammonium bisulfate to fully gasify and decompose. The blockage ash in the localized gasification zones is then mixed with the mainstream flue gas and rapidly cooled, causing ammonium bisulfate to crystallize and adhere to fly ash, which is then simultaneously removed by the dust collector 113. This achieves online blockage clearing and coordinated pollutant treatment without shutting down the system. The heat exchange efficiency is adjusted by an air-side control unit, combined with a graded temperature control strategy, ensuring that the outlet flue gas temperature of the high-temperature heat exchanger 111 is 180℃-200℃ and the outlet flue gas temperature of the low-temperature heat exchanger 112 is 110℃-130℃. This keeps the equipment operating above the acid dew point. Furthermore, the operating conditions are comprehensively classified based on indicators such as the sulfur content, ash content, moisture content, and NOx content of the coal, precisely matching different coal qualities and unit loads to suppress low-temperature corrosion.

[0035] In the above embodiments, in order to detect the ash blockage or heat exchange efficiency of each gasification zone, in one possible implementation, refer to the appendix. Figure 5 It also includes a temperature detection matrix 151 covering the flue gas outlet section of the low-temperature heat exchanger 112. Multiple thermometers 152 are arranged in a matrix on the temperature detection matrix 151 to measure the temperature distribution at the flue gas outlet section of the low-temperature heat exchanger 112 and identify local areas with ash blockage or faults. The control module determines the location of ash blockage by analyzing the temperature uniformity of each temperature measurement point: when the temperature of a certain local area is significantly higher than the surrounding area, it indicates that heat accumulation is caused by ash blockage. At the same time, it identifies fault points by recognizing sudden drops in local temperature: when the temperature of a certain area suddenly drops, it indicates that the heat exchange tube may have leaked or other faults, thereby realizing the location and early warning of ash blockage and faults.

[0036] To achieve unblocking of specific gasification zones without shutting down the system, in one possible implementation, see Appendix Figure 2Each gasification zone is equipped with a first valve 122 at its inlet. The air flow channel includes multiple parallel air branches. Each air branch exchanges heat with the flue gas in each gasification zone. Each air branch is opened and closed independently through a second valve 124. The orientation of the nozzle 125 connected to the end of the gasification flue 121 can be changed, that is, the nozzle 125 can be rotated and the opening of the nozzle 125 can face any gasification zone.

[0037] When a specific gasification zone needs to be cleared, firstly, the second valve 124 corresponding to that gasification zone is closed, cutting off the airflow to that zone and depriving it of air-side cooling. Simultaneously, the first valve 122 corresponding to that gasification zone is closed, blocking the main flue gas from entering the zone. Then, the outlet of the gasification flue 121 is directed towards the gasification zone via the connecting nozzle 125, and the valve of the gasification flue is opened, introducing high-temperature flue gas (300℃-400℃) from the inlet side of the high-temperature heat exchanger 111. This gas is then directionally injected into the gasification zone via the connecting nozzle 125. Without cooling air, the heat exchange tube wall temperature in this zone rises rapidly. The control module precisely maintains the gasification wall temperature at 200℃-220℃ for at least 30 minutes, allowing the deposited ammonium bisulfate to fully vaporize and decompose. Once it leaves the gasification zone, it immediately mixes with the mainstream low-temperature flue gas and cools, recrystallizing into a solid and entering the next stage with the flue gas dust. After the blockage is cleared, the gasification flue valve is closed, and the first valve 122 and the second valve 124 are opened to restore the normal flue gas and air heat exchange process in the area. The system can sequentially clear blockages in each gasification zone, enabling online blockage clearing of the low-temperature heat exchanger 112 without shutting down the system.

[0038] As an alternative to the above embodiments, in order to enable the opening of the connecting nozzle 125 to face any vaporization zone, in one possible implementation, a first valve 122 is provided at the inlet of each vaporization zone, the air flow channel includes multiple parallel air branches, each air branch exchanges heat with the flue gas in each vaporization zone, and each air branch is opened and closed independently through a second valve 124; the vaporization flue 121 includes multiple vaporization branches corresponding one-to-one with the vaporization zones, the connecting nozzle 125 of each vaporization branch faces the corresponding vaporization zone, and each vaporization branch is opened and closed independently through a third valve 123.

[0039] More specifically, multiple gasification zones are arranged in parallel within the cross-section of the low-temperature heat exchanger 112, and multiple connecting nozzles 125 are arranged on the sidewall of the low-temperature heat exchanger 112. Guide plates 126 are provided between the corresponding gasification zones and the connecting nozzles 125. The end of the connecting nozzle 125 that connects to the gasification flue 121 is circular, and the end that connects to the main flue / injects towards the low-temperature heat exchanger 112 is rectangular. (See reference...) Figure 4This forms a "round sky and square earth" structure. The width of its rectangular end is the same as the width of a gasification zone, and it is angled downwards towards the gasification zone of the low-temperature heat exchanger 112, ensuring that the ejected high-temperature gasification flue gas can cover approximately 30% of the heat exchange tubes on the cold air side of this zone (where dust accumulation is most severe). The tail angle of the guide plate 126 is consistent with the incident angle of the gasification flue 121, while the head angle is aligned with the line connecting the corresponding target tube bundle, thereby uniformly and accurately guiding the high-temperature flue gas to the target tube bundle. Assuming the pressure difference of the high-temperature heat exchanger is ΔP, the number of low-temperature heat exchanger tubes covered is m, the tube bundle diameter of the low-temperature heat exchanger is d, the density of the flue gas is ρ, and the diameter D of the circular gasification flue duct satisfies the following formula: .

[0040] The width of the second end of the connecting nozzle is the same as the width 'a' of a single vaporization zone in the cryogenic heat exchanger, and the height 'b' of the connecting nozzle satisfies the following formula: .

[0041] The design method for connecting nozzle 125 is as follows: (1) The nozzle sprays downward at an angle, and the sprayed high-temperature flue gas covers 30% of the heat exchange tubes in the target gasification area of ​​the low-temperature heat exchanger that are close to the cold air side. (2) The incident angle of the gasification flue 121 is the same as the first end angle of the outermost guide plate inside the nozzle. (3) A guide plate 126 is provided inside the nozzle. The guide plate 126 is an arc-shaped plate. The angle of the tail end of the guide plate is the same as the incident angle of the gasification flue, and the angle of the first end is the line connecting the corresponding pipe row and the guide plate, to ensure that the sprayed hot flue gas is evenly distributed.

[0042] When a specific gasification zone needs to be cleared, firstly, the second valve 124 corresponding to that gasification zone is closed, cutting off the airflow to that zone and depriving it of air-side cooling. Simultaneously, the first valve 122 corresponding to that gasification zone is closed, preventing main flue gas from entering the zone. Then, the third valve 123 on the gasification branch corresponding to that zone is opened, introducing high-temperature flue gas (300℃-400℃) from the inlet side of the high-temperature heat exchanger 111. This gas is then directionally injected into the corresponding gasification zone through the connecting nozzle 125 of the gasification branch. The connecting nozzle 125 is located on the side wall of the low-temperature heat exchanger 112, and its internal guide plate 126 evenly guides the high-temperature flue gas to the heat exchange tube bundle of the gasification zone. Without cold air cooling, the heat exchange tube wall temperature in that zone rises rapidly. The control module precisely maintains the gasification wall temperature at 200℃-220℃ for at least 30 minutes, allowing the deposited ammonium bisulfate to fully vaporize and decompose. After unblocking is completed, the third valve 123 is closed, and the first valve 122 and the second valve 124 are opened to restore the normal flue gas and air heat exchange process in this area. Since multiple gasification branches correspond one-to-one with multiple gasification zones, the system can sequentially unblock each gasification zone in turn, realizing online unblocking of the low-temperature heat exchanger 112 without shutting down the system. It can also perform online unblocking of multiple gasification zones simultaneously.

[0043] In the above embodiments, the temperature control target of the air-side control unit is set in stages according to the operating conditions of the coal-fired unit to match the design requirements of flue gas temperature. The outlet flue gas temperature of the high-temperature heat exchanger 111 is set as follows: 180°C under good operating conditions, 190°C under moderate operating conditions, and 200°C under poor operating conditions. The outlet flue gas temperature of the low-temperature heat exchanger 112 is set as follows: 110°C under good conditions, [missing value]°C under moderate conditions, and 130°C under poor conditions. The levels of operating conditions are determined comprehensively based on at least one of the following indicators: sulfur content, ash content, moisture content of the coal as received, and NOx content at the furnace outlet.

[0044] For example, the outlet flue gas temperature of high-temperature heat exchanger 111 is set according to the following table: The outlet flue gas temperature setting for the low-temperature heat exchanger 112 is based on the following table: The design method for the outer diameter of the heat exchange tubes is as follows: ≥60mm under good conditions, ≥76mm under moderate conditions, and ≥89mm under poor conditions. Three-dimensional finned tubes with excellent heat exchange performance are used, thereby increasing the tube diameter while ensuring heat exchange performance and enhancing the ability to prevent dust blockage.

[0045] The specific control logic is as follows: Cold air is first regulated by the inlet air temperature distribution unit 140, then enters the air heater 131 for preliminary heating (especially to increase air temperature in winter), and then enters the low-temperature heat exchanger 112 to exchange heat with the flue gas, absorbing heat from the flue gas and becoming heated. This hot air then flows through the air cooler 130, releasing the heat it carries to the power plant's regenerative system (through the third low-pressure heater 160 and the fourth low-pressure heater 161), and the air itself is cooled before entering the high-temperature heat exchanger 111. By adjusting the heat exchange capacity of the air cooler 130 and the air heater 131, the outlet flue gas temperature of the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112 can be precisely controlled in reverse, ensuring that it is always above the acid dew point and avoiding low-temperature corrosion. The air heater 131 can transfer excess waste heat from the flue gas to the air side, avoiding the problems of ash blockage, wear, and corrosion that would occur if a low-temperature economizer were installed on the flue gas side.

[0046] In one possible implementation, see Appendix Figure 1 The main flue 110 also includes a dust collector 113, an induced draft fan 114, an end heat exchanger 115, a desulfurization tower 116, and a chimney 117, which are sequentially arranged at the rear end of the low-temperature heat exchanger 112; the air flow channel includes an inlet air temperature distribution unit 140, an air heater 131, a low-temperature heat exchanger 112, an air cooler 130, and a high-temperature heat exchanger 111, which are connected in series along the air flow direction; at the low-temperature heat exchanger 112 and the high-temperature heat exchanger 111, the main flue 110 and the air flow channel can exchange heat.

[0047] The inlet air temperature control unit 140 includes an air intake channel 141 and a temperature detection element 144. The air intake channel 141 can take in air through a first air intake port 142 and / or a second air intake port 143. The air intake ratio of the first air intake port 142 and the second air intake port 143 can be adjusted. The temperature detection element 144 is located at the output end of the air intake channel 141. The output end of the air intake channel 141 is connected to the input end of the air heater 131. The first air intake port 142 is an atmospheric air intake port, and the second air intake port 143 is an indoor air-cooled tower air intake port.

[0048] The system works as follows: The flue gas flows sequentially along the main flue duct 110 through the high-temperature heat exchanger 111, the low-temperature heat exchanger 112, the dust collector 113, the induced draft fan 114, the terminal heat exchanger 115, the desulfurization tower 116, and the chimney 117. The air flows sequentially along the air flow channel through the inlet air temperature control unit 140, the air heater 131, the low-temperature heat exchanger 112, the air cooler 130, and the high-temperature heat exchanger 111. At the low-temperature heat exchanger 112 and the high-temperature heat exchanger 111, the air flows counterclockwise with the flue gas to exchange heat and regulate the outlet temperature of the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112.

[0049] The inlet air temperature distribution unit 140 ensures a suitable air temperature entering the air heater 131, guaranteeing safe system operation under all weather conditions and different unit types. The air output terminal of the inlet air temperature distribution unit 140 is connected to the air input terminal of the air heater 131, and is used to distribute the air temperature entering the air heater 131 according to the power plant unit type. The inlet air temperature distribution unit 140 draws air from the first air intake 142 and / or the second air intake 143 through the air intake channel 141, where the first air intake 142 is an atmospheric air intake, and the second air intake 143 is an indoor air-cooled tower air intake. By adjusting the air intake ratio of the two air intakes, the mixed air temperature in the air intake channel 141 reaches the design value, and the temperature detection element 144 monitors the mixed air temperature in real time. After the mixed air enters the air heater 131 and is initially heated, it flows through the low-temperature heat exchanger 112 to absorb heat from the flue gas. The heated air then enters the air cooler 130 to release heat, and finally enters the high-temperature heat exchanger 111 to exchange heat with the flue gas at a higher temperature, thus completing the stepwise heating process of the air.

[0050] After being cooled by the high-temperature heat exchanger 111, the flue gas enters the low-temperature heat exchanger 112 for further cooling. It then flows sequentially through the dust collector 113 for dust removal, the induced draft fan 114 for pressurization, and the terminal heat exchanger 115 for deep cooling before entering the desulfurization tower 116 for desulfurization. Finally, it is discharged into the atmosphere through the chimney 117. The terminal heat exchanger 115 can be a FUNI tube heat exchanger. The entire system achieves waste heat recovery and utilization, as well as heat exchange temperature control, through counter-current staged heat exchange between flue gas and air. This design can stably reduce the inlet flue gas temperature to approximately 70°C at the desulfurization tower 116, thus deeply recovering waste heat from the flue gas and reducing unit coal consumption. Furthermore, the corrosion-resistant properties of the FUNI tube effectively resist the erosion of the low-temperature, highly corrosive wet flue gas at the desulfurization tower inlet, solving the corrosion and leakage problem of traditional metal heat exchangers at this location. For example, the FUNI tube has a thermal conductivity ≥16 W / (m·K), a friction coefficient ≤0.2, and a corrosion rate in the flue gas condensate ≤0.05 mm / a.

[0051] In summary, this solution has the following beneficial effects: Through the flue gas gasification unit, the high-temperature flue gas at the inlet side of the high-temperature heat exchanger 111 is used to locally gasify and clear blockages in each independent gasification zone of the low-temperature heat exchanger 112, so that ammonium bisulfate is fully gasified and decomposed. After being mixed and rapidly cooled by subsequent flue gas, it is simultaneously removed by the dust collector 113, realizing online clearing without stopping the machine, effectively solving the problem of ammonium bisulfate ash accumulation, and preventing the ash blockage from being transferred to downstream equipment.

[0052] The outlet temperature of the heat exchanger in the flue gas waste heat recovery path is regulated by the air-side control unit. Combined with the graded temperature control strategy, the outlet flue gas temperature of the high-temperature heat exchanger 111 and the low-temperature heat exchanger 112 is always kept above the acid dew point, thus avoiding low-temperature corrosion at the source. At the same time, the flue gas temperature is set according to the coal quality and unit load to improve heat exchange efficiency and operational stability.

[0053] A temperature detection matrix 151 is arranged across the entire cross-section of the flue gas outlet of the low-temperature heat exchanger 112 by the ash blockage and status detection unit 150. Thermometers 152 monitor the temperature distribution in real time. The control module analyzes the temperature uniformity to accurately locate the ash blockage location or fault point, achieving early warning and automatic handling, significantly improving operation and maintenance efficiency and system reliability. It is easy to understand that the control module, as the brain of the system, electrically connects to and coordinates the control of all modules. It receives signals from various sensors such as the temperature detection element 144 and thermometers 152, and automatically controls the opening and closing states of the first valve 122, the second valve 124, and the third valve 123 according to the preset operating condition classification logic and gasification control strategy. It also adjusts the working states of the air cooler 130, the air heater 131, and the plate heat exchanger 400, ensuring that the entire system maintains efficient, stable, and safe operation, comprehensively achieving the goals of anti-blockage, corrosion prevention, deep waste heat recovery, and precise control.

[0054] The inlet air temperature distribution unit 140 employs different air intake strategies for the air-cooled and water-cooled units to ensure that the air temperature entering the air heater 131 is suitable and to prevent icing or corrosion. The terminal heat exchanger 115 exchanges heat with the first low-pressure heater 410 and the second low-pressure heater 420 to deeply recover waste heat from the flue gas and reduce the unit's coal consumption. The third low-pressure heater 160 and the fourth low-pressure heater 161 are linked with the air-side control unit to assist in regulating the air temperature and further optimize the system's energy efficiency.

[0055] By centrally controlling and coordinating the operation of each module through the control module, a closed-loop control system of "anti-blocking-temperature control-detection-blocking removal" is formed, which significantly extends the service life of the equipment, adapts to different coal qualities and unit load conditions, and has good engineering application and promotion value.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A high-efficiency heat exchange system for preventing ash blockage in heat exchangers, characterized in that, include: The system includes a high-temperature heat exchanger (111), a low-temperature heat exchanger (112), a main flue (110), a gasification flue (121), and an airflow channel. The high-temperature heat exchanger (111) and the low-temperature heat exchanger (112) are connected in series in the main flue (110), with the high-temperature heat exchanger (111) located at the inlet of the main flue (110). The low-temperature heat exchanger (112) is internally divided into multiple independent gasification zones. The main flue (110) and the airflow channel... The flow channels exchange heat in each of the gasification zones, and the main flue (110) and air flow channel of each of the gasification zones can be opened and closed independently; the inlet end of the gasification flue (121) is connected to the inlet end of the high-temperature heat exchanger (111), and the outlet end of the gasification flue (121) is provided with a connecting nozzle (125), which is located in the low-temperature heat exchanger (112) and can spray high-temperature flue gas toward any of the gasification zones.

2. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 1, characterized in that: Each of the gasification zones is provided with a first valve (122) at its inlet. The air flow channel includes multiple parallel air branches. Each air branch exchanges heat with the flue gas in each of the gasification zones. Each air branch is opened and closed independently through a second valve (124). The orientation of the nozzle (125) at the end of the gasification flue (121) can be changed, and the opening of the nozzle (125) can face any of the gasification zones.

3. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 1, characterized in that: Each of the gasification zones is provided with a first valve (122) at its inlet. The air flow channel includes multiple parallel air branches. Each air branch exchanges heat with the flue gas in each of the gasification zones. Each air branch is opened and closed independently through a second valve (124). The gasification flue (121) includes multiple gasification branches that correspond one-to-one with the gasification area. The connecting nozzles (125) of each gasification branch face the corresponding gasification area. Each gasification branch is opened and closed independently through a third valve (123).

4. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 3, characterized in that: Multiple vaporization zones are arranged in parallel within the cross-section of the low-temperature heat exchanger (112), and multiple connecting nozzles (125) are arranged on the sidewall of the low-temperature heat exchanger (112). A guide plate (126) is provided between the vaporization zones and the connecting nozzles (125).

5. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 1, characterized in that: The main flue (110) also includes a dust collector (113), an induced draft fan (114), an end heat exchanger (115), a desulfurization tower (116), and a chimney (117) arranged sequentially at the rear end of the low-temperature heat exchanger (112). The airflow channel includes an inlet air temperature distribution unit (140), an air heater (131), a low-temperature heat exchanger (112), an air cooler (130), and a high-temperature heat exchanger (111) connected in series along the airflow direction. At the low-temperature heat exchanger (112) and the high-temperature heat exchanger (111), the main flue (110) and the air flow channel can exchange heat.

6. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 5, characterized in that: The inlet air temperature control unit (140) includes an air intake channel (141) and a temperature detection element (144); The air intake channel (141) can draw air through the first air intake port (142) and / or the second air intake port (143). The air intake ratio of the first air intake port (142) and the second air intake port (143) can be adjusted. The temperature detection element (144) is located at the output end of the air intake channel (141). The output end of the air intake channel (141) is connected to the input end of the air heater (131). The first air intake (142) is an atmospheric air intake, and the second air intake (143) is an indoor air-cooled tower air intake.

7. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 1, characterized in that: Inside the low-temperature heat exchanger (112), the main flue (110) and the air flow channel exchange heat through heat exchange tubes, and the heat exchange tubes are provided with spirally arrayed protruding fins.

8. The high-efficiency heat exchange system for preventing heat exchanger ash blockage as described in claim 1, characterized in that: It also includes a temperature detection matrix (151) covering the flue gas outlet section of the low-temperature heat exchanger (112), with multiple thermometers (152) arranged in a matrix on the temperature detection matrix (151) to measure the temperature distribution of the flue gas outlet section of the low-temperature heat exchanger (112).

9. A highly efficient heat exchange method for preventing ash blockage in heat exchangers, characterized in that, Includes the following steps: The high-temperature flue gas exchanges heat through a series of high-temperature heat exchangers (111) and low-temperature heat exchangers (112); Multiple independent vaporization zones are set in the low-temperature heat exchanger (112). Each vaporization zone is equipped with an independent air flow channel for heat exchange with flue gas. When ash blockage occurs in a certain vaporization zone, the air flow channel of the current vaporization zone is closed to block the heat exchange of flue gas. High-temperature flue gas is introduced from the inlet end of the high-temperature heat exchanger (111) and passes through the current vaporization zone. The ash blockage components react with the high-temperature flue gas and leave the current vaporization zone, thereby achieving anti-blockage of the low-temperature heat exchanger (112).

10. The efficient heat exchange method for preventing ash blockage in heat exchangers as described in claim 9, characterized in that, The outlet flue gas temperature of the low-temperature heat exchanger (112) is set to 110℃-130℃; the outlet flue gas temperature of the high-temperature heat exchanger (111) is set to 180-200℃.

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