A method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater.

Abstract

This invention relates to a method for adjusting the load of a rotary air preheater based on the temperature distribution characteristics of an air preheater, relating to the field of air preheaters. The method includes the following steps: obtaining the real-time temperature distribution inside the air preheater through digital twin calculations; obtaining the cold end temperature of the air preheater based on temperature sensors; obtaining the deposition temperature of ammonium bisulfate in real time based on a monitoring device; comparing the cold end temperature with the acid dew point temperature; and adjusting the opening degree of the air preheater to change the temperature distribution of the heat transfer elements in the air preheater, ensuring that not only the cold end temperature is higher than the acid dew point temperature, but also that the temperature of the hot end of the cold section heat transfer elements is higher than the deposition temperature of ammonium bisulfate. This invention has the advantages of accurately sensing the ash accumulation trend of the air preheater and simultaneously feeding back to the air preheater to adjust the air intake, achieving stable, safe, and economical operation of the rotary air preheater during boiler wide-load peak shaving.

Description

Technical Field

[0001] This invention relates to the field of air preheater technology, and in particular to a method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater. Background Technology

[0002] Rotary air preheaters are widely used in coal-fired power plants. The preheater can heat the primary and secondary air sent into the furnace by flue gas, thereby providing furnace temperature, improving combustion conditions, and ensuring the stability of ignition under low load.

[0003] Because the flue gas after SCR denitrification contains excessive amounts of ammonia, sulfur trioxide, and water vapor, ammonium bisulfate easily forms in the narrow slits of the corrugated plates in the rotary air preheater, causing more fly ash to adhere and leading to channel blockage. As ash accumulation increases, the heat transfer capacity between the flue gas, air, and heat storage elements decreases, reducing heat transfer efficiency. Simultaneously, ash accumulation increases flow resistance, severely affecting the flow of flue gas and air. By promptly monitoring the ash accumulation within the preheater, soot blowing and downtime for maintenance can be more effectively controlled.

[0004] Adding an external air heater to the air preheater can raise the temperature of the air entering the preheater, thereby increasing the preheater wall temperature and providing a higher overall cold-end temperature. This, in turn, facilitates the timely melting of ammonium bisulfate, preventing low-temperature corrosion. Currently, power plants often rely on worker experience to judge ash blockage, making it difficult to accurately detect the blockage trend. This leads to inaccurate load adjustment of the air heaters, resulting in poor performance of the heaters.

[0005] Currently, monitoring of ash accumulation in air preheaters and load regulation control of air heaters are mainly based on monitoring the cold end wall temperature. However, the cold end wall temperature can only reflect the degree of sulfuric acid deposition and not the deposition of ammonium bisulfate. If the air heaters are not put into operation in a timely manner, their operating effect will be weakened; or if they are over-operated, the unit's economic efficiency will be reduced.

[0006] Therefore, to address the above shortcomings, it is necessary to provide a method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] The technical problem to be solved by this invention is the difficulty in accurately detecting the ash blockage trend in air preheaters.

[0009] (II) Technical Solution

[0010] To address the aforementioned technical problems, this invention provides a method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater, comprising the following steps:

[0011] I. Obtain the real-time temperature distribution inside the air preheater through digital twin calculation, and obtain the cold end temperature of the air preheater based on the temperature sensor;

[0012] II. The deposition temperature of ammonium bisulfate is obtained in real time based on the monitoring device;

[0013] III. Compare the cold end temperature with the acid dew point temperature, and compare the internal temperature distribution of the air preheater with the deposition temperature of ammonium bisulfate: if the cold end temperature is lower than the acid dew point temperature and the internal temperature of the air preheater is higher than the deposition temperature of ammonium bisulfate, increase the opening of the heater; otherwise, decrease the opening of the heater.

[0014] As a further explanation of the present invention, preferably, the heater is provided with a first temperature measuring device to measure the outlet temperature of the heater in real time, and the heater is provided with a first monitoring device to monitor the sulfur volume fraction of the flue gas at the outlet of the heater in real time.

[0015] As a further explanation of the present invention, preferably, the air preheater is provided with a second temperature measuring device to measure the flue gas temperature at each location of the air preheater in real time, and the air preheater is provided with a second monitoring device to monitor the flue gas pressure difference in the air preheater in real time.

[0016] As a further explanation of the present invention, preferably, the acid dew point temperature T is calculated based on the data measured by the first monitoring device and the raw data. p Specifically

[0017]

[0018] in,

[0019] This represents the volume fraction of water in the high-temperature flue gas.

[0020] This represents the volume fraction of sulfur trioxide in high-temperature flue gas.

[0021] As a further explanation of the present invention, preferably, the ammonium bisulfate deposition temperature P is calculated based on the data measured by the second monitoring device and the original data. NH3 (atm)·P SO3 (atm), specifically

[0022]

[0023] in,

[0024] R is the universal gas constant (1.987 cal / K-mol);

[0025] T represents temperature in Kelvin (K).

[0026] As a further explanation of the present invention, preferably, when the outlet temperature of the heater and the temperature of the air preheater are below 150°C, the opening degree of the heater is increased.

[0027] As a further explanation of the present invention, preferably, when the outlet temperature of the heater is higher than 230°C, the opening degree of the heater is reduced.

[0028] As a further explanation of the present invention, preferably, the first temperature measuring device, the first monitoring device, the second temperature measuring device, and the second monitoring device are all electrically connected to the data storage device to store the measured data and the calculated acid dew point temperature and ammonium bisulfate deposition temperature.

[0029] As a further explanation of the present invention, preferably, a temperature display device is electrically connected to the data storage device to display the temperature at each location, and a calculation device is connected to calculate the range for increasing or decreasing the heating air opening.

[0030] As a further explanation of the present invention, preferably, both the temperature display device and the calculation device are electrically connected to the control system, the control system is electrically connected to the heater, and the control system receives signals from the temperature display device and the calculation device to control the opening degree of the heater.

[0031] (III) Beneficial Effects

[0032] The above-described technical solution of the present invention has the following advantages:

[0033] This invention achieves real-time monitoring and analysis of temperature and pressure changes within the air preheater through intelligent detection of temperature and side pressure difference. It can accurately and timely control the opening degree of the corresponding air heater, thus ensuring high feasibility, stability, and accuracy of the solution while meeting low cost requirements. It solves the problem of difficulty in accurately detecting the ash blockage trend of the air preheater, while ensuring the stable, safe, and economical operation of the rotary air preheater during boiler peak load regulation. Attached Figure Description

[0034] Figure 1 This is the adjustment logic diagram of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] A method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater, such as... Figure 1 As shown, it includes the following steps:

[0037] I. Based on actual field data, construct a digital twin model of the air preheater within a computer to reflect its physical characteristics and operational behavior. The model uses computational fluid dynamics and other simulation methods to model the temperature distribution and fluid flow within the air preheater.

[0038] The system includes a first temperature measuring device inside the air heater to measure the outlet temperature in real time, and a first monitoring device inside the air heater to monitor the sulfur volume fraction of the flue gas at the outlet in real time. The air preheater includes a second temperature measuring device to measure the flue gas temperature at various locations within the air preheater in real time, and a second monitoring device inside the air preheater to monitor the flue gas pressure difference on the inside of the air preheater in real time. The real-time temperature distribution inside the air preheater is obtained through digital twin calculations, and the cold end temperature of the air preheater is obtained based on temperature sensors.

[0039] II. Calculate the acid dew point temperature T based on the data measured by the first monitoring device and the raw data. p Specifically:

[0040]

[0041] in,

[0042] This represents the volume fraction of water in the high-temperature flue gas.

[0043] This represents the volume fraction of sulfur trioxide in high-temperature flue gas.

[0044] By calculating the acid dew point temperature, the formation of sulfuric acid can be predicted. In conjunction with increasing the opening of the heater, the sulfuric acid that has already formed or the sulfur elements that have not yet formed sulfuric acid can be blown away from the air preheater as soon as possible to avoid corrosion of the corrugated plate and affect the service life of the air preheater.

[0045] Based on the data measured by the second monitoring device and the raw data, the ammonium bisulfate deposition temperature P was calculated. NH3 (atm)·P SO3 (atm), specifically

[0046]

[0047] in,

[0048] R is the universal gas constant (1.987 cal / K-mol);

[0049] T represents temperature in Kelvin (K).

[0050] Based on past control experience, the decreasing trend between the ammonium bisulfate deposition temperature and the flue gas side pressure difference is adjusted. This eliminates the need to detect factors affecting the ammonium bisulfate deposition temperature, such as air velocity, gas temperature, gas composition, and content. The current deposition temperature of ammonium bisulfate is calculated using empirical formulas, allowing for control of the heater opening. This ensures the flue gas temperature is higher than the deposition temperature, preventing ammonium bisulfate from solidifying while increasing airflow velocity to blow away liquefied ammonium bisulfate. Maintaining the temperature of the hot end of the cold section heat transfer element higher than the ammonium bisulfate deposition temperature ensures that ammonium bisulfate deposition occurs only within the cold section heat transfer element channel, preventing cross-layer deposition. This improves the effectiveness of steam soot blowing and prevents other solid powder particles from adhering and sticking to the corrugated plate.

[0051] III. Compare the cold end temperature with the acid dew point temperature, and compare the internal temperature distribution of the air preheater with the deposition temperature of ammonium bisulfate. If the cold end temperature is lower than the acid dew point temperature and the internal temperature of the air preheater is higher than the deposition temperature of ammonium bisulfate, increase the opening of the air heater; conversely, decrease the opening of the air heater. Additionally, when the outlet temperature of the air heater and the air preheater temperature are below 150°C, increase the opening of the air heater. When the outlet temperature of the air heater is above 230°C, decrease the opening of the air heater. However, if the differential pressure increases non-linearly, the opening of the air heater needs to be further increased to raise the flue gas temperature above 300°C, vaporizing the ammonium bisulfate. Combined with a large air volume and high flow rate, this will blow the material away from the air preheater, ensuring the air preheater can operate normally.

[0052] like Figure 1 As shown, the first temperature measuring device, the first monitoring device, the second temperature measuring device, and the second monitoring device are all electrically connected to a data storage device to store the measured data and the calculated acid dew point temperature and ammonium bisulfate deposition temperature. A temperature display device is electrically connected to the data storage device to display the temperature at each location, and a calculation device is connected to calculate the range for increasing or decreasing the heater opening. Both the temperature display device and the calculation device are electrically connected to the control system, which is electrically connected to the heater. The control system receives signals from the temperature display device and the calculation device to control the heater opening.

[0053] Compared to traditional methods that involve complex and multi-parameter detection, this invention only retains measurements of volume fraction, temperature, and pressure difference. Based on extensive work experience, a set of judgment criteria has been summarized. By controlling the opening of the heater through this criterion, sulfuric acid condensation and ammonium bisulfate deposition can be avoided, heater wear can be reduced, and economic efficiency can be improved. It also avoids the problems of complex algorithms and difficult-to-fix bugs caused by detecting multiple indicators, making it more user-friendly for ordinary technicians to operate and maintain.

[0054] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An air heater load adjustment method based on the temperature distribution characteristics of an air preheater, characterized by: Includes the following steps, Ⅰ. The heater is equipped with a first temperature measuring device to measure the outlet temperature of the heater in real time, and a first monitoring device is equipped in the heater to monitor the sulfur volume fraction of the flue gas at the outlet of the heater in real time. The air preheater is equipped with a second temperature measuring device to measure the flue gas temperature at various locations in the air preheater in real time, and a second monitoring device to monitor the flue gas pressure difference in the air preheater in real time; the real-time temperature distribution inside the air preheater is obtained through digital twin calculation of the air preheater, and the cold end temperature of the air preheater is obtained based on the temperature sensor. II. Calculate the acid dew point temperature based on the data measured by the first monitoring device and the raw data. Specifically in, This represents the volume fraction of water in the high-temperature flue gas. This represents the volume fraction of sulfur trioxide in high-temperature flue gas. The ammonium bisulfate deposition temperature was calculated based on the data measured by the second monitoring device and the raw data. Specifically in, It is the universal gas constant (1.987 cal / K-mol); Temperature is expressed in Kelvin (K). III. Compare the cold end temperature with the acid dew point temperature, and compare the internal temperature distribution of the air preheater with the deposition temperature of ammonium bisulfate. If the cold end temperature is lower than the acid dew point temperature and the internal temperature of the air preheater is higher than the deposition temperature of ammonium bisulfate, increase the opening of the heater; otherwise, decrease the opening of the heater. In addition, when the outlet temperature of the heater and the air preheater temperature are lower than 150°C, increase the opening of the heater; when the outlet temperature of the heater is higher than 230°C, decrease the opening of the heater. However, if the differential pressure increases non-linearly, further increase the opening of the heater so that the flue gas temperature is higher than 300°C to vaporize the ammonium bisulfate.

2. The method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater according to claim 1, characterized in that: The first temperature measuring device, the first monitoring device, the second temperature measuring device, and the second monitoring device are all electrically connected to the data storage device to store the measured data and the calculated acid dew point temperature and ammonium bisulfate deposition temperature.

3. The method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater according to claim 2, characterized in that: Temperature display devices are electrically connected to the data storage device to display the temperature at each location, and a calculation device is connected to calculate the range for increasing or decreasing the heating air opening.

4. The method for adjusting the load of a heater based on the temperature distribution characteristics of an air preheater according to claim 3, characterized in that: The temperature display device and the calculation device are both electrically connected to the control system. The control system is electrically connected to the heater. The control system receives signals from the temperature display device and the calculation device to control the opening degree of the heater.

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