A system and method for reducing flue gas temperature of a medium speed coal mill

Abstract

The present application relates to coal mill drying agent temperature control technical field, disclose a kind of for reducing the system and method of medium-speed coal mill exhaust gas temperature, system includes: according to the result of temperature detection system to mill drying agent temperature detection, target drying agent temperature is obtained by calculation;Primary fan will part of the cold primary air prepared to air preheater;And in the air preheater, by rotary air preheating technology and to cold section shell opening temperature wind technology, respectively output hot primary air and target temperature wind;Target temperature wind, hot primary air and another part of the cold primary air prepared by primary fan are sent into basic coal mill system by corresponding air duct, so that mill drying agent reaches target drying agent temperature.The present application achieves unexpected technical effect: in actual application, by using the technical scheme of the present application, under the same air preheater regenerative sheet consumption weight, exhaust gas temperature can be reduced by about 3.5℃, and boiler efficiency is affected by about 0.15 percentage points.

Description

Technical Field

[0001] This invention relates to the field of coal mill desiccant temperature control technology, specifically to a system and method for reducing the flue gas temperature of a medium-speed coal mill. Background Technology

[0002] The pulverizing system is one of the most important systems in a thermal power plant, responsible for the preparation and transportation of pulverized coal in the boiler. Currently, the most widely used pulverizing system is the direct-fired medium-speed coal mill system. Traditionally designed boilers burning lean or bituminous coal typically require a desiccant temperature of 250-300℃ at the pulverizer inlet due to the generally lower moisture content of the raw coal (below 15%). However, the hot primary air at the air preheater outlet reaches temperatures above 330℃. Therefore, a mixture of hot primary air (above 330℃) and cold primary air (20-30℃) is needed to adjust the pulverizer inlet temperature to 250-300℃ to ensure the safe operation of the pulverizing system. Because the mixed cold air bypasses the air preheater, the amount of air flowing through it is reduced, leading to a 3-5℃ increase in flue gas temperature. This reduces boiler efficiency by 0.15-0.25 percentage points and increases coal consumption by 0.45-0.75 g / kWh.

[0003] In addition, using bypass ventilation to control temperature in traditional technical solutions is one of the important technical means in this field. For example, technical solution 1) divides the output hot air of the air preheater into two parts: one part is bypass hot air, and the other part is input to the medium-speed coal mill, and the coal mill outputs over-grind hot air. The over-grind hot air and bypass hot air form high-temperature primary air and are sent into the boiler furnace. By increasing the temperature of the primary air entering the boiler, the pulverized coal combustion rate is improved, thereby achieving the technical objective of reducing the flue gas temperature. However, the increased temperature leads to a decrease in safety. Technical solution 2) uses bypass cold air and over-grind hot air to form high-temperature primary air and is sent into the medium-speed coal mill. By precisely controlling the temperature of the primary air entering the medium-speed coal mill, such as the above solutions, the temperature of the desiccant at the coal mill inlet can be precisely adjusted, thereby ensuring the safe operation of the pulverizing system. However, the flue gas temperature increases, and the boiler efficiency decreases. Based on this, those skilled in the art urgently need to improve the above-mentioned direct-fired medium-speed coal mill system to reduce the flue gas temperature while ensuring safety, thereby improving boiler efficiency. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects existing in the prior art, thereby providing a system and method for reducing the flue gas temperature of a medium-speed coal mill.

[0005] A system for reducing the flue gas temperature of a medium-speed coal mill includes an air preheater, a basic coal mill system, a temperature detection system, and a primary air fan;

[0006] The target desiccant temperature is calculated based on the temperature detection results of the desiccant in the grinding mill by the temperature detection system.

[0007] The primary air fan delivers all of the produced cold primary air to the air preheater;

[0008] Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening of the cold section shell to extract warm air;

[0009] The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

[0010] Preferably, the heat storage plates inside the air preheater are, from top to bottom, hot section heat storage plates, warm section heat storage plates, and cold section heat storage plates;

[0011] In this process, a portion of the 20-30°C cold primary air produced by the primary air fan flows into the air preheater from the bottom of the primary or secondary air side, passes through the traditional cold section heat storage plates to the warm section heat storage plates, and at the same time, hot flue gas flows into the air preheater from the top of the flue gas side, passes through the traditional hot section heat storage plates, the warm section heat storage plates and the traditional cold section heat storage plates and flows out, so that the warm section heat storage plates connected to the air intake produce a target temperature air of 90-120°C.

[0012] Preferably, the heat storage plate in the hot section generates hot primary air at a temperature of 330°C or higher.

[0013] A method for reducing the flue gas temperature of a medium-speed coal mill includes the following steps:

[0014] The target desiccant temperature is calculated based on the results of the desiccant temperature detection in the grinding mill.

[0015] The primary air fan delivers a portion of the produced cold primary air to the air preheater;

[0016] Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening of the cold section shell to extract warm air;

[0017] The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

[0018] Preferably, the heat storage plates inside the air preheater are composed of hot section heat storage plates, warm section heat storage plates and cold section heat storage plates from top to bottom;

[0019] In this process, a portion of the 20-30°C cold primary air produced by the primary air fan flows into the air preheater from the bottom of the primary or secondary air side, passes through the traditional cold section heat storage plates to the warm section heat storage plates, and at the same time, hot flue gas flows into the air preheater from the top of the flue gas side, passes through the traditional hot section heat storage plates, the warm section heat storage plates and the traditional cold section heat storage plates and flows out, so that the warm section heat storage plates connected to the air intake produce a target temperature air of 90-120°C.

[0020] Preferably, the heat storage plate in the hot section generates hot primary air at a temperature of 330°C or higher.

[0021] The technical solution of this invention has the following advantages:

[0022] Compared to other existing technical solutions, this invention is simpler to operate and implement, and achieves unexpected technical effects: In practical applications, by adopting the technical solution of this invention, with the same weight of air preheater regenerator fins consumed, the flue gas temperature can be reduced by approximately 3.5°C, affecting boiler efficiency by approximately 0.15 percentage points. Based on an annual power generation of 2.5 billion kWh for a 660MW unit, this translates to an annual reduction in coal consumption costs of 1.125 million yuan. Simultaneously, under the premise of unchanged flue gas temperature, the design of a 660MW unit can reduce the consumption of cold section regenerator fins by approximately 145 tons, reducing project costs by approximately 3 million yuan. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 A diagram showing the relationship between the operation mode of a traditional medium-speed coal mill pulverizing system and the air source of a rotary air preheater.

[0025] Figure 2 This diagram illustrates the relationship between the operation mode of a medium-speed coal mill pulverizing system and the air source of the rotary air preheater in this embodiment of the invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Example 1

[0031] A system for reducing the flue gas temperature of a medium-speed coal mill includes an air preheater, a basic coal mill system, a temperature detection system, and a primary air fan;

[0032] In this embodiment, the basic coal mill system includes: a raw coal bunker, a coal feeder, and a coal mill;

[0033] like Figure 2 As shown, the raw coal in the raw coal bunker is conveyed to the coal drop pipe of the coal mill by the coal feeder, and then enters the coal mill through the coal drop pipe; after the coal mill is successfully pulverized, it is output from the top of the coal mill to the furnace burner.

[0034] Specifically:

[0035] The target desiccant temperature is calculated based on the temperature detection results of the temperature detection system on the pulverizer desiccant. In practical applications, the temperature monitoring system uses methods for detecting the temperature of the pulverizer desiccant, including but not limited to calculating the temperature of the pulverizer inlet desiccant based on the pulverizer outlet temperature.

[0036] like Figure 2 The primary air fan delivers a portion of the produced cold primary air to the air preheater;

[0037] Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening the cold section shell to extract warm air;

[0038] The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

[0039] In this embodiment, the rotary air preheater disclosed in publication number CN116025923A, entitled "A Rotary Air Preheater for a Pulverizing System Boiler with Exhaust Gas Feeding and Storage," is used. Figure 1 As shown; the heat storage plates inside the air preheater are, from top to bottom, hot section heat storage plates, warm section heat storage plates and cold section heat storage plates; by cutting the outer ring of the cold section heat storage plates, an air volume space is created, and an air intake port is provided on the side wall of the air preheater;

[0040] In this system, a portion of the generated 20-30°C cold primary air flows into the air preheater from the bottom of the primary or secondary air side, passing through the traditional cold section heat storage plates to the warm section heat storage plates. Simultaneously, hot flue gas flows in from the top of the air preheater's flue gas side, passing through the traditional hot section heat storage plates, warm section heat storage plates, and traditional cold section heat storage plates, resulting in the warm section heat storage plates connected to the air intake generating a target temperature air of 90-120°C. This 90-120°C target temperature air enters the coal mill through the inlet warm air door.

[0041] In this embodiment, the hot section heat storage plate generates hot primary air at a temperature of 330°C or higher. The hot primary air at a temperature of 330°C or higher enters the coal mill from the hot air inlet door, so that the target temperature air of 90~120°C and the hot primary air at a temperature of 330°C or higher are mixed to reach 250~330°C, which meets the target desiccant temperature.

[0042] In addition, in this embodiment, by introducing another portion of the cold primary air produced by the primary air fan into the coal mill through the cold air inlet damper, the initial start-up safety of the coal mill is ensured. This design not only improves the safety of the coal mill start-up but also helps to improve the efficiency and stability of the entire system.

[0043] It should be noted that the other part of the cold air produced by the primary air fan only runs for a few minutes when the coal mill is started, and the running time is determined according to the actual coal mill. During other working periods, the air duct used to run the other part of the cold air produced by the primary air fan is in a closed state, and only the corresponding air ducts for the target warm air and hot primary air are running.

[0044] It should be noted that in this embodiment, the improved air preheater is introduced and the structure is simplified by redesigning the air path. Even after the simplification, the stable operation of the overall pulverizing system is still guaranteed, as well as the reduction of flue gas temperature and the improvement of boiler efficiency are achieved.

[0045] Example 2

[0046] A method for reducing the flue gas temperature of a medium-speed coal mill includes the following steps:

[0047] The target desiccant temperature is calculated based on the results of the desiccant temperature detection in the grinding mill.

[0048] The primary air fan delivers a portion of the produced cold primary air to the air preheater;

[0049] Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening the cold section shell to extract warm air;

[0050] The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

[0051] Specifically: The heat storage plates inside the air preheater consist of hot section heat storage plates, warm section heat storage plates and cold section heat storage plates from top to bottom;

[0052] The primary air fan draws in the 20-30°C cold primary air from the bottom of the primary or secondary air side of the air preheater, passing through the traditional cold section heat storage plates to the warm section heat storage plates. At the same time, hot flue gas flows in from the top of the flue gas side of the air preheater, passing through the traditional hot section heat storage plates, the warm section heat storage plates, and the traditional cold section heat storage plates, so that the warm section heat storage plates connected to the air intake produce a target temperature air of 90-120°C.

[0053] The hot section heat storage fins generate hot primary air at temperatures above 330°C.

[0054] It should be noted that this embodiment can be used to design boiler units using low-moisture coal such as lean coal and bituminous coal, and equipped with a medium-speed coal mill pulverizing system. This invention is particularly suitable for the modular assembly structure of air preheater regenerator plates.

[0055] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A system for reducing the flue gas temperature of a medium-speed coal mill, comprising an air preheater, a basic coal mill system, a temperature detection system, and a primary air fan, characterized in that: The target desiccant temperature is calculated based on the temperature detection results of the desiccant in the grinding mill by the temperature detection system. The primary air fan delivers a portion of the produced cold primary air to the air preheater; Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening of the cold section shell to extract warm air; The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

2. The system for reducing the flue gas temperature of a medium-speed coal mill according to claim 1, characterized in that, The heat storage plates inside the air preheater, from top to bottom, are hot section heat storage plates, warm section heat storage plates, and cold section heat storage plates; In this process, a portion of the 20-30°C cold primary air produced by the primary air fan flows into the air preheater from the bottom of the primary or secondary air side, passes through the traditional cold section heat storage plates to the warm section heat storage plates, and at the same time, hot flue gas flows into the air preheater from the top of the flue gas side, passes through the traditional hot section heat storage plates, the warm section heat storage plates and the traditional cold section heat storage plates and flows out, so that the warm section heat storage plates connected to the air intake produce a target temperature air of 90-120°C.

3. The system for reducing the flue gas temperature of a medium-speed coal mill according to claim 2, characterized in that, The heat storage plate in the hot section generates hot primary air at a temperature of over 330°C.

4. A method for reducing the flue gas temperature of a medium-speed coal mill, characterized in that: The target desiccant temperature is calculated based on the results of the desiccant temperature detection in the grinding mill. The primary air fan delivers a portion of the produced cold primary air to the air preheater; Furthermore, in the air preheater, hot primary air and target temperature air are output respectively through rotary air preheating technology and opening of the cold section shell to extract warm air; The target temperature air, hot primary air, and another portion of cold primary air produced by the primary air fan are sent into the basic coal mill system through corresponding air ducts so that the desiccant in the mill reaches the target desiccant temperature.

5. The method for reducing the flue gas temperature of a medium-speed coal mill according to claim 4, characterized in that, The heat storage plates inside the air preheater, from top to bottom, are hot section heat storage plates, warm section heat storage plates, and cold section heat storage plates; In this process, a portion of the 20-30°C cold primary air produced by the primary air fan flows into the air preheater from the bottom of the primary or secondary air side, passes through the traditional cold section heat storage plates to the warm section heat storage plates, and at the same time, hot flue gas flows into the air preheater from the top of the flue gas side, passes through the traditional hot section heat storage plates, the warm section heat storage plates and the traditional cold section heat storage plates and flows out, so that the warm section heat storage plates connected to the air intake produce a target temperature air of 90-120°C.

6. The method for reducing the flue gas temperature of a medium-speed coal mill according to claim 5, characterized in that, The heat storage plate in the hot section generates hot primary air at a temperature of over 330°C.

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