A rotary air preheater capable of preventing ammonium bisulfate blocking

Abstract

The application discloses a rotary air preheater capable of preventing ammonium bisulfate blockage, wherein a flue gas flow area of the rotary air preheater is divided into a plurality of flue gas sub-areas; a gas burner is arranged in each flue gas sub-area; the gas burner is ignited regularly during normal operation of the rotary air preheater; high-temperature flue gas generated by the gas burner is used for heating heat storage elements in a flue gas heat exchange area; the temperature gradually increases to 260-270 DEG C; ammonium bisulfate adhered to the heat storage elements in the heat exchange sub-area is decomposed into gas at the temperature, so that the heat storage elements in the area are dredged. The heat exchange area in the rotary air preheater is heated to increase the temperature, decompose ammonium bisulfate, clean blockage on line in each load section, and the difference between the primary hot air temperature, the secondary hot air temperature and the flue gas discharge temperature and the design value is small, so that the boiler combustion and the subsequent dust collector of the air preheater are not adversely affected.

Description

Technical Field

[0001] This invention belongs to the field of rotary air preheaters for boilers, and specifically relates to a rotary air preheater that can prevent ammonium bisulfate blockage. Background Technology

[0002] As NOx emission standards for boilers become increasingly stringent, boilers are being designed or retrofitted with flue gas SCR (Selective Catalytic Reduction) denitrification devices. Under the action of a catalyst, nitrogen oxides are decomposed into nitrogen and water. However, a small amount of sulfur dioxide inevitably oxidizes to sulfur trioxide, which reacts with escaped ammonia that did not participate in the denitrification reaction at suitable temperatures to form ammonium bisulfate. Ammonium bisulfate is a highly viscous substance that readily adheres to the heat exchange surfaces of the air preheater and captures dust particles in the flue gas, thus clogging the air preheater.

[0003] Rotary air preheaters are a common type of air preheater equipment used in power plant boilers. If ammonium bisulfate adheres to the surface of the heat storage elements, it can easily clog the flue gas duct. As more and more heat storage elements become clogged, the pressure difference between the inlet and outlet of the rotary air preheater becomes too large. Due to the lack of an effective rotary air preheater soot blower, the boiler will be forced to shut down for cleaning.

[0004] Currently, there is no good solution for ammonium bisulfate blockage in rotary air preheaters; the usual approach is to shut down the boiler for cleaning. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a rotary air preheater that can prevent ammonium bisulfate blockage.

[0006] The present invention is achieved using the following technical solution:

[0007] A rotary air preheater that can prevent ammonium bisulfate blockage includes a rotary air preheater heat exchange zone and a rotary air preheater flow guide zone. The rotary air preheater heat exchange zone is equipped with heat storage elements. Both the rotary air preheater flow guide zone and the rotary air preheater heat exchange zone are separated by baffles into corresponding primary air zone, secondary air zone and flue gas zone.

[0008] A further improvement of the present invention is that, after the high-temperature flue gas enters the flue gas region of the guide zone of the rotary air preheater from the flue gas inlet, it enters the flue gas region of the heat exchange zone of the rotary air preheater. After transferring heat to the heat storage element in the region, the temperature of the high-temperature flue gas decreases and it leaves the rotary air preheater from the flue gas outlet. During this process, the temperature of the heat storage element in the flue gas region increases.

[0009] A further improvement of the present invention is that the cold primary air enters the primary air area of ​​the heat exchange zone of the rotary air preheater from the primary air inlet. In the primary air area, it exchanges heat with the heat storage element of the primary air area. After the temperature of the cold primary air rises, it enters the primary air area of ​​the flow guide zone of the rotary air preheater and leaves the rotary air preheater from the primary air outlet. During this process, the temperature of the heat storage element in the primary air area decreases.

[0010] A further improvement of the present invention is that the cold secondary air enters the secondary air area of ​​the heat exchange zone of the rotary air preheater from the secondary air inlet. In the secondary air area, it exchanges heat with the heat storage element of the secondary air area. After the temperature of the cold secondary air rises, it enters the secondary air area of ​​the flow guide zone of the rotary air preheater and leaves the rotary air preheater from the secondary air outlet. During this process, the temperature of the heat storage element in the secondary air area decreases.

[0011] A further improvement of the present invention is that the flue gas area of ​​the rotary air preheater's intake zone is divided into several sub-areas by a flue gas zone baffle. Each sub-area is equipped with a gas burner, and gas and combustion air are sent to the gas burner through a gas pipeline.

[0012] A further improvement of the present invention is that the flue gas area of ​​the rotary air preheater's intake zone is divided into 4-12 sub-regions by a flue gas zone baffle.

[0013] A further improvement of the present invention is that the gas burner in the flue gas side region of the inlet zone of the rotary air preheater is periodically ignited to generate high-temperature flue gas, which flows from the flue gas side region of the inlet zone to the flue gas region of the heat exchange zone of the rotary air preheater, heating the heat storage element in this region to 260-270°C. At this temperature range, the ammonium bisulfate adhering to the heat storage element in this region decomposes into gas and leaves the rotary air preheater from the flue gas outlet along with the high-temperature flue gas.

[0014] A further improvement of the present invention is that, during normal operation, the flow inlet area of ​​the rotary air preheater remains stationary while the heat exchange area rotates, thereby causing the heat storage elements in the heat exchange area to be heated in turn by the high-temperature flue gas generated by the combustion of the gas burner in the flue gas side sub-area, and decomposing the ammonium bisulfate adhering to the heat storage elements therein, thereby preventing the rotary air preheater from being blocked by ammonium bisulfate.

[0015] A further improvement of the present invention is that the gas burners adjacent to the wall are started in each heating cycle to avoid fluctuations in the flue gas heat exchange of the rotary air preheater.

[0016] The present invention has at least the following beneficial technical effects:

[0017] This invention provides a rotary air preheater that can prevent ammonium bisulfate blockage. By arranging several gas burners in the flue gas side guide zone of the rotary air preheater, and igniting and burning them at a certain cycle, the heat storage elements are heated, thereby decomposing the ammonium bisulfate on the surface of the heat storage elements. This allows for online cleaning of blockages in each load section, and the primary hot air temperature, secondary hot air temperature, and flue gas temperature are not much different from the design values, so as not to have an adverse effect on boiler combustion and the subsequent dust collector of the air preheater. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a rotary air preheater that can prevent ammonium bisulfate blockage according to the present invention;

[0019] Explanation of reference numerals in the attached figures:

[0020] 1-Rotary air preheater heat exchange zone;

[0021] 2-Rotary air preheater intake area;

[0022] 3-Heat storage element;

[0023] 4- Primary air inlet;

[0024] 5 - Primary air outlet;

[0025] 6-Secondary air inlet;

[0026] 7-Secondary air outlet;

[0027] 8- Flue gas inlet;

[0028] 9- Flue gas outlet;

[0029] 10 - Flue gas partition;

[0030] 11-Gas burner;

[0031] 12-Gas pipeline. Detailed Implementation

[0032] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1As shown, the present invention provides a rotary air preheater that can prevent ammonium bisulfate blockage. The rotary air preheater includes a rotary air preheater heat exchange zone 1 and a rotary air preheater flow guide zone 2, with a heat storage element 3 arranged in the rotary air preheater heat exchange zone 1. The rotary air preheater flow guide zone 2 and the rotary air preheater heat exchange zone 1 are both separated by partitions into corresponding primary air zone, secondary air zone, and flue gas zone.

[0034] After the high-temperature flue gas enters the flue gas region of the rotary air preheater's inlet 8, it enters the flue gas region of the rotary air preheater's heat exchange zone 1. In this region, the heat is transferred to the heat storage element, and the temperature of the high-temperature flue gas decreases. It then leaves the rotary air preheater from the flue gas outlet 9. During this process, the temperature of the heat storage element in the flue gas region increases.

[0035] Cold primary air enters the primary air zone of the rotary air preheater heat exchange zone 1 from the primary air inlet 4. In this zone, it exchanges heat with the heat storage element of the zone. After the temperature of the cold primary air rises, it enters the primary air zone of the rotary air preheater guide zone 2 and leaves the rotary air preheater from the primary air outlet 5. During this process, the temperature of the heat storage element in the primary air zone decreases.

[0036] Cold secondary air enters the secondary air area of ​​the rotary air preheater heat exchange zone 1 from the secondary air inlet 6. In this area, it exchanges heat with the heat storage element of the zone. After the temperature of the cold secondary air rises, it enters the secondary air area of ​​the rotary air preheater flow zone 2 and leaves the rotary air preheater from the secondary air outlet 7. During this process, the temperature of the heat storage element in the secondary air area decreases.

[0037] The flue gas area of ​​the rotary air preheater 2 is divided into 4-12 sub-areas by the flue gas partition 10. Each sub-area is equipped with a gas burner 11, and gas and combustion air are sent to the gas burner 11 through the gas pipeline 12.

[0038] The gas burner 11 in the flue gas side sub-region of the rotary air preheater's inlet zone 2 is periodically ignited to generate high-temperature flue gas, which flows from the flue gas side sub-region of the rotary air preheater's inlet zone 2 to the flue gas region of the rotary air preheater's heat exchange zone 1, heating the heat storage element 3 in this region to 260-270°C. At this temperature range, the ammonium bisulfate adhering to the heat storage element in this region decomposes into gas and leaves the rotary air preheater from the flue gas outlet 9 along with the high-temperature flue gas.

[0039] During normal operation, the flow inlet zone 2 of the rotary air preheater remains stationary, while the heat exchange zone 1 rotates. This causes the heat storage elements in the heat exchange zone 1 to be heated in turn by the high-temperature flue gas generated by the combustion of the gas burner 11 in the flue gas side sub-zone, and decomposes the ammonium bisulfate adhering to the heat storage elements 3, thereby preventing the rotary air preheater from being blocked by ammonium bisulfate.

[0040] Each heating cycle should start the gas burner adjacent to the wall to avoid fluctuations in flue gas heat exchange in the rotary air preheater.

[0041] Example

[0042] A power plant originally had a three-compartment rotary air preheater. In recent years, with stricter environmental emission standards and increased demands for flexible operation, the power plant, in order to ensure that NOx emissions do not exceed limits, injects NH3 into the denitrification system to react with ammonium bisulfate in the flue gas, generating ammonium bisulfate. This ammonium bisulfate, along with dust in the flue gas, adheres to the surface of the heat exchange elements in the rotary air preheater and is difficult to remove. Over time, this easily causes blockage of the air preheater, affecting the power plant's normal production process. The power plant attempted to address this through online water flushing and shutdown cleaning, but the results were unsatisfactory, and the air preheater developed severe blockages again after a period of operation.

[0043] During a recent technical upgrade, the power plant replaced the entire air preheater with a rotary air preheater to prevent clogging by ammonium bisulfate, as detailed below:

[0044] The rotary air preheater includes a rotary air preheater heat exchange zone and a rotary air preheater flow inlet zone, with heat storage elements arranged in the rotary air preheater heat exchange zone. Both the rotary air preheater flow inlet zone and the rotary air preheater heat exchange zone are separated by partitions into corresponding primary air zone, secondary air zone, and flue gas zone.

[0045] After the high-temperature flue gas enters the flue gas area of ​​the rotary air preheater's inlet, it enters the flue gas area of ​​the rotary air preheater's heat exchange zone. In this zone, the high-temperature flue gas transfers heat to the heat storage element, causing the temperature of the flue gas to decrease. Then, it leaves the rotary air preheater from the flue gas outlet. During this process, the temperature of the heat storage element in the flue gas area increases.

[0046] Cold primary air enters the primary air zone of the rotary air preheater heat exchange area from the primary air inlet. In this zone, it exchanges heat with the heat storage elements. After the temperature of the cold primary air rises, it enters the primary air zone of the rotary air preheater guide zone and leaves the rotary air preheater from the primary air outlet. During this process, the temperature of the heat storage elements in the primary air zone decreases.

[0047] Cold secondary air enters the secondary air zone of the rotary air preheater's heat exchange area from the secondary air inlet. In this zone, it exchanges heat with the heat storage elements. After the temperature of the cold secondary air rises, it enters the secondary air zone of the rotary air preheater's flow guide zone and leaves the rotary air preheater from the primary air outlet. During this process, the temperature of the heat storage elements in the secondary air zone decreases.

[0048] The flue gas area of ​​the rotary air preheater's intake zone is divided into 8 sub-zones by a flue gas zone baffle. Each sub-zone is equipped with a gas burner, and gas and combustion air are sent to the gas burner through a gas pipeline.

[0049] The gas burners in each flue gas side sub-region of the rotary air preheater's inlet zone are periodically ignited to generate high-temperature flue gas, which flows from the flue gas side sub-region of the rotary air preheater's inlet zone to the flue gas region of the rotary air preheater's heat exchange zone, heating the heat storage elements in that region to 300-340°C. At this temperature range, the ammonium bisulfate adhering to the heat storage elements in that region decomposes into gas and leaves the rotary air preheater from the flue gas outlet along with the high-temperature flue gas.

[0050] During normal operation, the flow inlet of the rotary air preheater remains stationary while the heat exchange zone rotates. This causes the heat storage elements in the heat exchange zone to be heated in turn by the high-temperature flue gas generated by the combustion of the gas burner in the flue gas side area, which decomposes the ammonium bisulfate adhering to the heat storage elements, thereby preventing the rotary air preheater from being blocked by ammonium bisulfate.

[0051] Each heating cycle should start the gas burner adjacent to the wall to avoid fluctuations in flue gas heat exchange in the rotary air preheater.

[0052] After the power plant replaced the rotary air preheater with one that has the function of preventing ammonium bisulfate blockage, the air preheater operated normally for one year. During the operation, the pressure difference between the inlet and outlet of the air preheater remained basically unchanged, and no ammonium bisulfate blockage occurred in the air preheater.

[0053] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A rotary air preheater that prevents ammonium bisulfate blockage, characterized in that, The rotary air preheater includes a rotary air preheater heat exchange zone (1) and a rotary air preheater flow guide zone (2). The rotary air preheater heat exchange zone (1) is equipped with heat storage elements (3). The rotary air preheater flow guide zone (2) and the rotary air preheater heat exchange zone (1) are separated by partitions into corresponding primary air zone, secondary air zone and flue gas zone. The flue gas area of ​​the rotary air preheater flow zone (2) is divided into several sub-areas by the flue gas partition (10). Each sub-area is equipped with a gas burner (11), and gas and combustion air are sent to the gas burner (11) through the gas pipeline (12). The gas burner (11) in the flue gas side sub-region of the rotary air preheater (2) is periodically ignited and burns to generate high-temperature flue gas, which flows from the flue gas side sub-region of the rotary air preheater (2) to the flue gas region of the rotary air preheater heat exchange region (1), heating the heat storage element (3) in this region to 260-270°C. At this temperature range, the ammonium bisulfate adhering to the heat storage element in this region decomposes into gas and leaves the rotary air preheater from the flue gas outlet (9) with the high-temperature flue gas. During normal operation, the flow zone (2) of the rotary air preheater remains stationary while the heat exchange zone (1) of the rotary air preheater rotates.

2. A rotary air preheater according to claim 1 that prevents ammonium bisulfate blockage, characterized in that, After the high-temperature flue gas enters the flue gas region of the rotary air preheater priming zone (2) from the flue gas inlet (8), it enters the flue gas region of the rotary air preheater heat exchange zone (1). After transferring heat to the heat storage element (3) in the region, the temperature of the high-temperature flue gas decreases and it leaves the rotary air preheater from the flue gas outlet (9). During this process, the temperature of the heat storage element (3) in the flue gas region increases.

3. A rotary air preheater according to claim 1 that prevents ammonium bisulfate blockage, characterized in that, Cold primary air enters the primary air area of ​​the rotary air preheater heat exchange zone (1) from the primary air inlet (4). In the primary air area, it will exchange heat with the heat storage element (3) of the primary air area. After the temperature of the cold primary air rises, it enters the primary air area of ​​the rotary air preheater flow zone (2) and leaves the rotary air preheater from the primary air outlet (5). During this process, the temperature of the heat storage element (3) in the primary air area decreases.

4. A rotary air preheater according to claim 1 that prevents ammonium bisulfate blockage, characterized in that, Cold secondary air enters the secondary air area of ​​the rotary air preheater heat exchange zone (1) from the secondary air inlet (6). In the secondary air area, it exchanges heat with the heat storage element (3) of the secondary air area. After the temperature of the cold secondary air rises, it enters the secondary air area of ​​the rotary air preheater flow zone (2) and leaves the rotary air preheater from the secondary air outlet (7). During this process, the temperature of the heat storage element (3) in the secondary air area decreases.

5. A rotary air preheater according to claim 1 that prevents ammonium bisulfate blockage, characterized in that, The flue gas area of ​​the rotary air preheater duct (2) is divided into 4-12 sub-areas by the flue gas partition (10).

6. A rotary air preheater according to claim 1 that prevents ammonium bisulfate blockage, characterized in that, Each heating cycle, the gas burners adjacent to the wall are started to avoid fluctuations in flue gas heat exchange in the rotary air preheater.

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