Anti-blocking method for tubular air preheater

Abstract

The application discloses a kind of methods for preventing blockage of tubular air preheater, the intermediate passage of tubular air preheater shell is divided into one virtual heat exchange sub-region by virtual partition, gas burner is arranged in each virtual heat exchange sub-region, in the normal operation process of tubular air preheater, gas burner is ignited regularly and burns, heat tubular air preheater heat exchange tube, temperature will gradually increase to 300-340 DEG C, at the temperature, the ammonium bisulfate adhered to the inner wall of heat exchange tube in the sub-region will be decomposed into gas, so that the heat exchange tube of the region blockage is dredged.The application can realize that each load section can be cleaned on line by heating the heat exchange region in tubular air preheater to increase temperature and decompose ammonium bisulfate, and the difference between primary hot air temperature, secondary hot air temperature, exhaust gas temperature and design value is not large, which will not cause adverse effects on boiler combustion and subsequent dust collector of air preheater.

Description

Technical Field

[0001] This invention belongs to the field of boiler tubular air preheaters, and specifically relates to a method for preventing blockage in tubular air preheaters. 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] Tubular air preheaters are a common type of air preheater equipment used in power plant boilers. Due to the narrow flow area of ​​flue gas inside the tubes, if ammonium bisulfate adheres to the inner wall of the tubes, it is very easy to clog the heat exchange tubes. As more and more heat exchange tubes become clogged, the pressure difference between the inlet and outlet of the tubular air preheater becomes too large. Due to the lack of an effective tubular 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 tubular air preheaters; the usual method is to shut down the furnace for cleaning. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a method for preventing blockage in a tubular air preheater.

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

[0007] A method for preventing blockage in a tubular air preheater, the tubular air preheater including an air preheater shell, heat exchange tubes arranged inside the air preheater shell, the tubular air preheater being divided into a primary virtual heat exchange sub-region by a virtual partition in the middle of the tubular air preheater shell; the air to be heated enters the shell side of the tubular air preheater through the air inlet and exits from the air outlet of the tubular air preheater, and high-temperature flue gas enters the tube side of the tubular air preheater through the flue gas inlet and exits from the flue gas outlet of the tubular air preheater.

[0008] A further improvement of the present invention is that, in the tubular air preheater, the heat exchange region perpendicular to the airflow direction is divided into several virtual heat exchange sub-regions by virtual baffles.

[0009] A further improvement of the present invention is that a gas burner is arranged in each virtual heat exchange sub-region.

[0010] A further improvement of the present invention is that the gas pipeline delivers gas and combustion air to the gas burner.

[0011] A further improvement of the present invention is that, during normal operation of the tubular air preheater, the gas burner is periodically ignited and combusted, heating the heat exchange tubes in the tubular air preheater, and the temperature will gradually rise to 300-340℃.

[0012] A further improvement of the present invention is that, at a temperature of 300-340°C, the ammonium bisulfate adhering to the inner wall of the heat exchange tube in the virtual heat exchange sub-region will decompose into gas, thereby clearing the blockage of the heat exchange tube in the region.

[0013] A further improvement of the present invention is that the gas burners are evenly arranged in the virtual heat exchange sub-region of the tubular air preheater, and their heating range should cover all the heat exchange tubes.

[0014] A further improvement of this invention is that, at a temperature of 300-340℃, the ammonium bisulfate adhering to the inner wall of the heat exchange tubes in all virtual heat exchange zones is decomposed, ensuring that all heat exchange tubes of the entire tubular air preheater are not blocked.

[0015] A further improvement of the present invention is that the gas burners adjacent to the wall surface are started in each heating cycle to avoid fluctuations in the temperature of the air to be heated on the shell side of the tubular air preheater.

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

[0017] The present invention provides a method for preventing blockage in a tubular air preheater. By covering the heat exchange area inside the tubular air preheater with a gas burner, which is ignited and burned at a certain cycle to heat the heat exchange tubes, the ammonium bisulfate on the inner wall of the heat exchange tubes is decomposed. This method can achieve 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 it will not 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 top view of a method for preventing blockage in a tubular air preheater according to the present invention;

[0019] Figure 2 This is a side view of a method for preventing blockage in a tubular air preheater according to the present invention;

[0020] Explanation of reference numerals in the attached figures:

[0021] 1 is the air preheater shell; 2 is the heat exchange tube; 3 is the gas burner; 4 is the virtual baffle; 5 is the air inlet; 6 is the air outlet; 7 is the flue gas inlet; 8 is the flue gas outlet; 9 is the gas pipeline. Detailed Implementation

[0022] 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.

[0023] like Figures 1 to 2 As shown, this invention provides a method for preventing blockage in a tubular air preheater. The tubular air preheater includes an air preheater shell 1, with heat exchange tubes 2 arranged inside the shell 1. A virtual partition 4 divides the tubular air preheater into a primary virtual heat exchange sub-region within the shell 1. Air to be heated enters the shell side of the tubular air preheater through the air inlet 5 and exits from the air outlet 6. High-temperature flue gas enters the tube side of the tubular air preheater through the flue gas inlet 7 and exits from the flue gas outlet 8.

[0024] In the tubular air preheater, the heat exchange area is divided into several virtual heat exchange sub-regions perpendicular to the airflow direction by virtual baffles 4.

[0025] In each virtual heat exchange sub-region, a gas burner 3 is arranged, and a gas pipeline 9 delivers gas and combustion air to the gas burner 3.

[0026] During normal operation of the tubular air preheater, the gas burner 3 is periodically ignited and burned, heating the heat exchange tube 2 in the tubular air preheater. The temperature will gradually rise to 300-340℃. At this temperature, the ammonium bisulfate adhering to the inner wall of the heat exchange tube 2 in this heat exchange sub-region will decompose into gas, thereby clearing the blockage of the heat exchange tube 2 in this region.

[0027] The gas burners 3 are evenly arranged in the virtual heat exchange sub-region of the tubular air preheater, and their heating range should cover all the heat exchange tubes 2.

[0028] At 300-340℃, ensure that the ammonium bisulfate adhering to the inner wall of heat exchange tube 2 in all virtual heat exchange zones is decomposed, and ensure that all heat exchange tubes 2 of the entire tubular air preheater are not blocked.

[0029] Each heating cycle should start the gas burner adjacent to the wall to avoid fluctuations in the temperature of the air to be heated on the shell side of the tubular air preheater.

[0030] Example

[0031] The air preheater in a certain power plant is a tubular air preheater. In recent years, with the improvement of environmental emission standards and the increasing requirements for flexible operation, in order to ensure that NOx emissions do not exceed the standard, the power plant injects NH3 into the denitrification facility to react with ammonium bisulfate in the flue gas to generate ammonium bisulfate. This ammonium bisulfate adheres to the heat exchanger surface of the tubular air preheater along with dust in the flue gas and is difficult to blow off. Over time, this can easily cause blockage of the air preheater, affecting the normal production process of the power plant.

[0032] To prevent blockage of the tubular air preheater, the power plant modified the air preheater as follows:

[0033] (1) The tubular air preheater is divided into 6 primary virtual heat exchange sub-regions in the middle of the shell by a virtual partition. The air to be heated enters the shell side of the tubular air preheater through the air inlet and exits from the air outlet. The high-temperature flue gas enters the tube side of the tubular air preheater through the flue gas inlet and exits from the flue gas outlet.

[0034] In the tubular air preheater, the heat exchange area is divided into six virtual heat exchange sub-regions perpendicular to the airflow direction by virtual baffles. A gas burner is arranged in each virtual heat exchange sub-region, and gas pipelines deliver gas and combustion air to the gas burner. The gas burners are evenly distributed within the virtual heat exchange sub-regions of the tubular air preheater, and their heating range should cover all heat exchange tubes.

[0035] During normal operation of the tubular air preheater, six gas burners are ignited in turn at regular intervals to heat the heat exchange tubes. The first gas burner ignites and burns for 10 minutes. During this time, the temperature of the heated surface in this section gradually rises to 300-340℃. At this temperature, the ammonium bisulfate adhering to the inner wall of the heat exchange tubes in this heat exchange sub-region decomposes into gas, thereby clearing any blockages in the heat exchange tubes. After the first gas burner stops burning for 10 minutes, the second burner ignites and begins burning. After the second burner has burned for 10 minutes, the third gas burner is started, and so on.

[0036] The above methods ensure that ammonium bisulfate adhering to the heating surfaces of each part of the tubular air preheater is decomposed sequentially, guaranteeing the cleanliness of the entire heating surface. Furthermore, since only one gas burner is running at any given time, the temperature of the air to be heated on the shell side of the tubular air preheater will not fluctuate in a way that would affect safety or production.

[0037] After the power plant carried out anti-clogging modifications on the tubular air preheater, the tubular air preheater operated continuously for a year, and the pressure difference between the inlet and outlet of the flue gas side did not increase significantly, demonstrating a good anti-clogging effect.

[0038] 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 method for preventing blockage in a tubular air preheater, characterized in that, The tubular air preheater includes an air preheater shell (1), heat exchange tubes (2) are arranged in the internal space of the air preheater shell (1), and the tubular air preheater is divided into a primary virtual heat exchange sub-region in the middle of the tubular air preheater shell (1) by a virtual partition (4); the air to be heated enters the shell side of the tubular air preheater through the air inlet (5) and is discharged from the air outlet (6); the high temperature flue gas enters the tube side of the tubular air preheater through the flue gas inlet (7) and is discharged from the flue gas outlet (8). In the tubular air preheater, the heat exchange area is divided into several virtual heat exchange sub-regions perpendicular to the air flow direction by virtual baffles (4); Each virtual heat exchange sub-region is equipped with a gas burner (3); gas pipelines (9) deliver gas and combustion air to the gas burner (3).

2. The anti-clogging method for a tubular air preheater according to claim 1, characterized in that, During normal operation of the tubular air preheater, the gas burner (3) is periodically ignited and burned, heating the heat exchange tubes (2) in the tubular air preheater, and the temperature will gradually rise to 300-340℃.

3. The anti-clogging method for a tubular air preheater according to claim 2, characterized in that, At a temperature of 300-340℃, the ammonium bisulfate adhering to the inner wall of the heat exchange tube (2) in the virtual heat exchange sub-region will decompose into gas, thereby clearing the blockage of the heat exchange tube (2) in the region.

4. The anti-clogging method for a tubular air preheater according to claim 3, characterized in that, The gas burner (3) is evenly arranged in the virtual heat exchange sub-region of the tubular air preheater, and its heating range should cover all heat exchange tubes (2).

5. The anti-clogging method for a tubular air preheater according to claim 3, characterized in that, At a temperature of 300-340℃, ensure that the ammonium bisulfate adhering to the inner wall of the heat exchange tubes (2) in all virtual heat exchange zones is decomposed, and ensure that all heat exchange tubes (2) of the entire tubular air preheater are not blocked.

6. The anti-clogging method for a tubular air preheater according to claim 5, characterized in that, During each heating cycle, adjacent gas burners on the wall are activated to avoid fluctuations in the temperature of the air to be heated on the shell side of the tubular air preheater.

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