High-efficiency combined preheater system for boiler of thermal power plant
By adopting a combination design of tubular and rotary air preheaters in thermal power plant boilers, primary and secondary air are heated independently, and feedwater is heated using high-temperature flue gas. This solves the problems of high air leakage rate and air temperature mismatch, thereby improving system efficiency and extending catalyst life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHINA POWER ENG CONSULTING GRP CORP EAST CHINA ELECTRIC POWER DESIGN INST
- Filing Date
- 2025-04-25
- Publication Date
- 2026-05-26
AI Technical Summary
Existing air preheaters in thermal power plants suffer from high air leakage rates, high energy consumption, losses due to mismatch with coal mill air temperature requirements, and catalyst blockage.
The system employs a combination of tubular and rotary air preheaters to heat primary and secondary air respectively, utilizes high-temperature flue gas to heat feedwater, controls primary air temperature by adjusting feedwater flow and temperature, and independently heats denitrification and dilution air, thereby optimizing flue gas heat utilization.
It reduces primary air leakage rate, reduces power consumption, improves system efficiency, extends catalyst life, saves standard coal, increases boiler efficiency by approximately 0.7%, reduces power consumption of fans and dust collectors, and prevents catalyst blockage.
Smart Images
Figure CN224284585U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of thermal power equipment technology, specifically relating to a high-efficiency combined preheater system for thermal power plant boilers. Background Technology
[0002] Currently, coal-fired power plants generally use Junkers rotary air preheaters, which utilize metal heat storage elements to achieve heat exchange between flue gas and the primary and secondary air entering the furnace. Its advantages include low metal consumption and small heat exchange differential. The disadvantage is high energy consumption due to air leakage in the preheater. Because the operating pressure of the primary air in the preheater is much higher than that of the secondary air and flue gas, the leakage on the primary air side is significant. This leakage results in high power consumption for the primary air fan, and also increases the burden on the induced draft fan and the dust removal and desulfurization system, as well as increasing the investment in these systems and the plant's power consumption.
[0003] Furthermore, from a boiler combustion perspective, the final required heating temperatures for primary and secondary air differ. However, current thermal power plant preheaters typically heat both primary and secondary air simultaneously to approximately 350°C. For the primary air system, different coal types have significantly different requirements for the mill inlet temperature. Most coal types, except for lignite, require mill inlet air temperatures between 200 and 280°C. Therefore, to meet the mill inlet air temperature requirements, the common practice is to mix approximately 20°C of cold air into the hot air at the mill inlet until the required temperature is achieved. During this process, the direct mixing of hot and cold air with a temperature difference exceeding 320°C leads to significant [temperature variations / problems]. loss. Utility Model Content
[0004] The purpose of this invention is to address the defects and shortcomings in the existing technology by designing a high-efficiency combined preheater system for thermal power plant boilers that can reduce air leakage rate, reduce power consumption, and improve system efficiency.
[0005] To achieve the above objectives, the technical solution adopted by this utility model is: a high-efficiency combined preheater system for thermal power plant boilers, including a tubular air preheater for heating primary air and a rotary air preheater for heating secondary air, both located at the tail end of the boiler. The flue gas inlets of the tubular air preheater and the rotary air preheater are connected to the flue gas outlet of the denitrification system. The flue gas outlets of the tubular air preheater and the rotary air preheater are both connected to a dust collector. Furthermore, a feedwater heat exchanger is provided between the flue gas inlet of the tubular air preheater and the flue gas outlet of the denitrification system.
[0006] Preferably, the primary air inlet of the tubular air preheater is connected to a primary air fan.
[0007] Preferably, the primary air outlet of the tubular air preheater is connected to the coal mill and the denitrification dilution air system.
[0008] Preferably, the temperature of the hot primary air entering the coal mill from the tubular air preheater is 200-280℃.
[0009] Preferably, the hot primary air from the tubular air preheater enters the denitrification dilution air system through a clean air duct.
[0010] Preferably, the flue outlet of the denitrification system is equipped with a staged economizer, the inlet of the feedwater heat exchanger has a temperature and flow regulating device, and the outlet of the feedwater heat exchanger is connected to the staged economizer.
[0011] Preferably, the secondary air inlet of the rotary air preheater is connected to a blower.
[0012] Preferably, the temperature of the hot secondary air at the secondary air outlet of the rotary air preheater is 350°C.
[0013] Preferably, the outlet of the dust collector is connected to an induced draft fan.
[0014] After adopting the above technical solution, the high-efficiency combined preheater system for thermal power plant boilers provided by this utility model has the following beneficial effects:
[0015] (1) This utility model constructs a combined preheater system, making the primary air heating and secondary air heating processes independent of each other. The use of a tubular air preheater can minimize the primary air leakage rate and reduce primary air power consumption. The feedwater is heated by the high-temperature flue gas section on the flue gas side of the primary air circuit. The heat absorption of the primary air preheater is controlled by controlling the feedwater flow rate and inlet water temperature, thereby regulating the primary air temperature and avoiding the mixing of cold air. This reduces losses and improves system efficiency. In addition, using dust-free hot primary air as denitrification dilution air can improve catalyst clogging problems.
[0016] (2) The use of this utility model can make more rational and effective use of the heat of the flue gas at the tail of the boiler. For projects where the inlet air temperature required by the coal mill is 200℃, the boiler efficiency can be increased by about 0.7%. Based on the standard coal consumption of 300g / kwh and 5000 hours of operation per year, each 1000MW coal-fired power unit can save 10,500 tons of standard coal per year.
[0017] (3) By adopting this utility model, the power consumption of the primary air fan in a 1000MW coal-fired power unit can be reduced. Based on the leakage of 40Kg / S on the primary air side of the rotary preheater, the power consumption of the primary air fan can be reduced by about 800kW. At the same time, the power consumption of the dust collector, desulfurization island and induced draft fan can also be reduced.
[0018] (4) All primary air in this utility model undergoes heat exchange through a tubular air preheater, which improves the mismatch between the heat of flue gas and cold air and increases the utilization rate of waste heat from flue gas.
[0019] (5) In this utility model, the dilution air for denitrification ammonia can be directly used as hot primary air, without worrying about the blockage of the catalyst in the SCR zone, which reduces the workload of SCR catalyst maintenance and improves catalyst life. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the structure of a high-efficiency combined preheater system for a thermal power plant boiler according to the present invention.
[0021] Among them: 1. Boiler; 2. Tubular air preheater; 3. Rotary air preheater; 4. Denitrification system; 5. Dust collector; 6. Feedwater heat exchanger; 7. Primary air fan; 8. Coal mill; 9. Denitrification dilution air system; 10. Staged economizer; 11. Forced draft fan; 12. Exhaust draft fan. Detailed Implementation
[0022] The present invention will now be described in further clear and complete detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.
[0025] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.
[0026] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.
[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.
[0028] This utility model discloses a high-efficiency combined preheater system for thermal power plant boilers, such as... Figure 1 As shown, for new units or retrofit projects using single or double reheat, a combined integrated design of tubular air preheater 2 and rotary air preheater 3 is adopted at the tail end of boiler 1 to separate the heating paths of primary and secondary air. Specifically, the flue gas inlet of the tubular air preheater 2 is connected to the flue outlet of the denitrification system 4, and a staged economizer 10 is installed at the flue outlet of the denitrification system 4. The primary air inlet of the tubular air preheater 2 is connected to the primary air fan 7, and the primary air outlet of the tubular air preheater 2 is connected to the coal mill 8 and the denitrification dilution air system 9. The flue gas outlet of the tubular air preheater 2 is connected to the dust collector 5. A feedwater heat exchanger 6 is also provided between the flue gas inlet of the tubular air preheater 2 and the flue outlet of the denitrification system 4. The feedwater heat exchanger 6 has a temperature and flow rate regulating device at its inlet and a staged economizer 10 at its outlet. By setting a serpentine tube bundle feedwater heat exchanger 6 in the flue upstream of the tubular air preheater 2, a portion of the high-pressure feedwater can be heated by high-temperature flue gas (e.g., from 200℃ to 330℃). Thus, the temperature of the flue gas upstream of the tubular air preheater 2 can be controlled by the feedwater flow rate, thereby regulating the temperature of the hot primary air and achieving the best utilization of flue gas heat.
[0029] Furthermore, the temperature of the hot primary air entering the coal mill 8 from the tubular air preheater 2 is 200-280℃. The hot primary air from the tubular air preheater 2 enters the denitrification dilution air system 9 through a clean air channel. That is, the dust-free clean primary hot air obtained by heating through the tubular air preheater 2 is used in the denitrification dilution air system 9.
[0030] The flue gas inlet of the rotary air preheater 3 is also connected to the flue outlet of the denitrification system 4. The secondary air inlet of the rotary air preheater 3 is connected to the blower 11. The hot secondary air temperature at the secondary air outlet of the rotary air preheater 3 is 350°C. The flue gas outlet of the rotary air preheater 3 is also connected to the dust collector 5. Furthermore, the outlet of the dust collector 5 is connected to the induced draft fan 12.
[0031] In the application of this utility model, a high-efficiency combined preheater system for thermal power plant boilers allows for online optimization of the flue gas flow distribution between the primary and secondary air systems at the boiler tail denitrification system 4 outlet, based on operational needs. All primary air destined for the coal mill 8 enters the tubular air preheater 2, with the primary air heating temperature determined by the coal mill 8's requirements. The heated primary air can then directly enter the coal mill 8 without temperature adjustment. By integrating a feedwater heat exchanger 6 upstream of the tubular air preheater 2 in the high-temperature flue gas section, high thermal efficiency can be achieved. This technology can be used for primary air temperature control. Specifically, primary air temperature control includes coarse adjustment and fine adjustment. Coarse adjustment determines the required primary air volume of the coal mill 8 based on the number of operating coal mills 8, coal quality, and unit load rate. It controls the amount of flue gas entering the primary air system according to the optimal heat exchange ratio with the primary air to achieve the best heat exchange effect of the primary air duct air preheater 2. Fine adjustment controls the temperature of the hot primary air by adjusting the feed water flow rate of the feed water heat exchanger 6 to control the flue gas temperature upstream of the primary air duct air preheater 2, based on the required air temperature at the inlet of the coal mill 8.
[0032] In summary, the high-efficiency combined preheater system for thermal power plant boilers provided by this utility model can further improve the operating efficiency of coal-fired power plants and solve the problems of high air leakage in traditional rotary preheaters. It addresses issues of loss and catalyst blockage, while also offering energy efficiency, economy, and reliability, meeting the technical requirements for efficient and clean operation of thermal power plants.
[0033] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. A high-efficiency combined preheater system for thermal power plant boilers, characterized in that: It includes a tubular air preheater (2) installed at the tail of the boiler (1) for heating primary air and a rotary air preheater (3) for heating secondary air. The flue gas inlets of the tubular air preheater (2) and the rotary air preheater (3) are connected to the flue outlet of the denitrification system (4). The flue gas outlets of the tubular air preheater (2) and the rotary air preheater (3) are connected to the dust collector (5). A feedwater heat exchanger (6) is also provided between the flue gas inlet of the tubular air preheater (2) and the flue outlet of the denitrification system (4).
2. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The primary air inlet of the tubular air preheater (2) is connected to the primary air fan (7).
3. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The primary air outlet of the tubular air preheater (2) is connected to the coal mill (8) and the denitrification dilution air system (9).
4. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 3, wherein: The temperature of the hot primary air entering the coal mill (8) from the tubular air preheater (2) is 200-280℃.
5. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 3, wherein: The hot primary air from the tubular air preheater (2) enters the denitrification dilution air system (9) through a clean air duct.
6. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The denitrification system (4) is equipped with a graded economizer (10) at the flue outlet, the feedwater heat exchanger (6) has a temperature and flow regulating device at the inlet, and the feedwater heat exchanger (6) is connected to the graded economizer (10) at the outlet.
7. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The secondary air inlet of the rotary air preheater (3) is connected to the blower (11).
8. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The temperature of the hot secondary air at the secondary air outlet of the rotary air preheater (3) is 350°C.
9. A high efficiency combined preheater system for a boiler of a thermal power plant as claimed in claim 1, wherein: The outlet of the dust collector (5) is connected to the induced draft fan (12).