System and method for reducing exhaust gas temperature of medium-speed coal mill

Abstract

The invention relates to the technical field of coal mill desiccant temperature control, and discloses a system and method for reducing the exhaust gas temperature of a medium-speed coal mill, and the system comprises the steps: calculating the target desiccant temperature according to the detection result of a temperature detection system on the desiccant temperature of the coal mill; the primary air fan conveys all part of cold primary air to the air preheater; in the air preheater, hot primary air and target warm air are respectively output through a rotary air preheating technology and a cold section shell tapping warm air taking technology; and the target warm air, the hot primary air and the other part of cold primary air produced by the primary air fan are fed into the basic coal mill system through corresponding air ducts, so that the drying agent of the flour mill reaches the target drying agent temperature. According to the invention, the unexpected technical effect is achieved: in practical application, by adopting the technical scheme provided by the invention, the exhaust gas temperature can be reduced by about 3.5 DEG C and the boiler efficiency is influenced by about 0.15% under the condition of the same consumed weight of the heat storage sheet of the air pre-heater.

Description

Technical Field

[0001] The invention relates to the technical field of coal mill desiccant temperature control, and in particular to a system and method for reducing the exhaust temperature of a medium-speed coal mill. Background Art

[0002] The pulverizing system is one of the most important systems in a thermal power plant, responsible for the preparation and transportation of boiler pulverized coal. The most widely used pulverizing system is the direct-blowing medium-speed pulverizer system. For traditional boilers designed to burn lean coal and bituminous coal, the moisture content of the raw coal is generally less than 15%, so the required temperature of the desiccant at the inlet of the pulverizer is generally 250~300℃, while the temperature of the hot primary air at the outlet of the air preheater reaches above 330℃. Therefore, it is necessary to use a mixture of hot primary air above 330℃ and cold primary air at 20~30℃ to adjust the desiccant temperature at the inlet of the pulverizer to 250~300℃ to ensure the safe operation of the pulverizing system. At this time, since the mixed cold air does not pass through the air preheater for heat exchange, the amount of air flowing through the air preheater is reduced, resulting in an increase in the exhaust gas temperature of about 3~5℃, affecting the boiler efficiency by 0.15~0.25 percentage points, and affecting the increase in coal consumption for power generation by 0.45~0.75g / kWh.

[0003] In addition, the use of bypass air to control temperature in traditional technical solutions is one of the important technical means in this field. For example, in technical solution 1, the output hot air of the air preheater is divided into two parts, one part is the bypass hot air, and the other part is input to the medium-speed coal mill, and the coal mill outputs the over-milled hot air; the over-milled hot air and the bypass hot air form a high-temperature primary air and are sent to the boiler furnace. By increasing the temperature of the primary air entering the boiler, the coal powder burnout rate is improved, and the technical purpose of reducing the exhaust gas temperature is achieved, but the safety is reduced due to the increase in temperature; technical solution 2) bypass cold air and over-milled hot air are used to form a high-temperature primary air and send it to the medium-speed coal mill. By controlling the temperature of the primary air entering the medium-speed coal mill, the temperature of the primary air entering the medium-speed coal mill is accurately controlled, such as the above solution, to achieve accurate adjustment of the coal mill inlet desiccant temperature, thereby ensuring the safe operation of the pulverizing system, but the exhaust gas temperature increases and the boiler efficiency decreases. Based on this, those skilled in the art urgently need to improve the defects of the above-mentioned direct-blowing medium-speed coal mill system, while ensuring safety, reduce the exhaust gas temperature, and thus improve the 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 above-mentioned prior art, thereby providing a system and method for reducing the exhaust temperature of medium-speed coal mill.

[0005] A system for reducing the exhaust gas temperature of a medium-speed coal mill, comprising an air preheater, a basic coal mill system, a temperature detection system and a primary fan; According to the result of the temperature detection system detecting the temperature of the grinding mill desiccant, the target desiccant temperature is calculated; The primary fan delivers all the produced partially cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the cold section shell opening technology for taking warm air; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

[0006] Preferably, the heat storage plates inside the air preheater are respectively a hot section heat storage plate, a warm section heat storage plate and a cold section heat storage plate from top to bottom; Among them, the primary fan will make a part of the 20~30℃ cold primary air flow into the bottom of the primary air side or secondary air side of the air preheater, pass through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows into the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate and flows out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target temperature air.

[0007] Preferably, the hot section heat storage sheet generates hot primary air above 330°C.

[0008] A method for reducing the exhaust temperature of a medium-speed coal mill comprises the following steps: According to the results of the mill desiccant temperature detection, the target desiccant temperature is calculated; The primary fan delivers all of the produced cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the cold section shell opening technology for taking warm air; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

[0009] 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; Among them, the primary fan will make a part of the 20~30℃ cold primary air flow into the bottom of the primary air side or secondary air side of the air preheater, pass through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows into the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate and flows out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target temperature air.

[0010] Preferably, the hot section heat storage sheet generates hot primary air above 330°C.

[0011] The technical solution of the present invention has the following advantages: Compared with other existing technical solutions, the present invention is simpler to operate and implement, and has achieved unexpected technical effects: in actual application, by adopting the technical solution of the present invention, under the condition of the same air preheater heat storage plate consumption weight, the exhaust gas temperature can be reduced by about 3.5°C, affecting the boiler efficiency by about 0.15 percentage points, and according to the annual power generation of 2.5 billion kWh of the 660MW unit, the coal consumption cost can be reduced by 1.125 million yuan per year. At the same time, under the premise of unchanged exhaust gas temperature, the design of the 660MW unit can reduce the consumption of cold section heat storage plates by about 145 tons, reducing the project cost by about 3 million yuan. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 This is the relationship diagram between the operation mode of the traditional medium-speed coal mill pulverizing system and the wind source of the rotary air preheater; Figure 2 This is a diagram showing the relationship between the operation mode of a medium-speed coal mill pulverizing system and the wind source of a rotary air preheater in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0016] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] In addition, 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.

[0018] Example 1 A system for reducing the exhaust gas temperature of a medium-speed coal mill, comprising an air preheater, a basic coal mill system, a temperature detection system and a primary fan; Among them, in this embodiment, the basic coal mill system includes: a raw coal bunker, a coal feeder and a coal mill; like Figure 2 As shown, the raw coal in the raw coal bin is transported to the coal drop pipe of the coal mill through the coal feeder, and enters the coal mill through the coal drop pipe; after the coal mill is pulverized successfully, it is output from the top of the coal mill to the furnace burner.

[0019] Specifically: The target desiccant temperature is calculated based on the results of the temperature detection system detecting the mill desiccant temperature. In actual application, the temperature monitoring system uses a method for detecting the mill desiccant temperature, including but not limited to estimating the mill inlet desiccant temperature based on the mill outlet temperature.

[0020] like Figure 2 The primary fan delivers all of the produced cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the hot air taking technology of opening holes in the shell of the cold section; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

[0021] In this embodiment, the rotary air preheater disclosed in the publication number CN116025923A, entitled A rotary air preheater for a boiler in a pulverizing system with exhaust gas feeding and storage, is used. Figure 1 As shown; the heat storage plates inside the air preheater are respectively hot section heat storage plates, warm section heat storage plates and cold section heat storage plates from top to bottom; the volume space of air is established by cutting the outer circle part of the cold section heat storage plates, and an air intake port is provided on the side wall of the air preheater; Among them, the primary fan will make a part of the 20~30℃ cold primary air flow into the bottom of the primary air side or secondary air side of the air preheater, pass through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows in from the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate to flow out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target warm air. The 90~120℃ target warm air enters the coal mill from the coal mill inlet warm air door; In this embodiment, the hot section heat storage plate generates hot primary air above 330°C; the hot primary air above 330°C enters the coal mill from the hot air door at the coal mill inlet, so that the target warm air of 90~120°C and the hot primary air above 330°C are mixed to reach 250~330°C, meeting the target desiccant temperature.

[0022] In addition, in this embodiment, the initial startup safety of the coal mill is ensured by passing another part of the cold primary air produced by the primary fan into the coal mill through the cold air door at the coal mill inlet. This design not only improves the safety of coal mill startup, but also helps to improve the efficiency and stability of the entire system.

[0023] It should be noted that the other part of the cold air produced by the primary 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 fan is in a closed state, and only the corresponding air ducts of the target warm air and hot primary air are running.

[0024] It should be noted that the above-mentioned improved air preheater is introduced in this embodiment, and the structural simplification is achieved by redesigning the air path direction. After the structural simplification, the stable operation of the overall powder making system is still guaranteed, the exhaust gas temperature is reduced, and the boiler efficiency is improved.

[0025] Example 2 A method for reducing the exhaust temperature of a medium-speed coal mill comprises the following steps: According to the results of the mill desiccant temperature detection, the target desiccant temperature is calculated; The primary fan delivers all of the produced cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the hot air taking technology of opening holes in the shell of the cold section; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

[0026] Specifically: 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; Among them, the primary fan flows the produced 20~30℃ cold primary air into the bottom of the primary air side or secondary air side of the air preheater, passes through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows into the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate and flows out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target temperature air.

[0027] The hot section heat storage sheet generates hot primary air above 330℃.

[0028] It should be noted that this embodiment can be used to design a boiler unit with a medium-speed coal mill pulverizing system using lean coal, bituminous coal and other low-moisture coal. The present invention is particularly suitable for a building block combination structure of heat storage plates for air preheaters.

[0029] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A system for reducing the exhaust gas temperature of a medium-speed coal mill, comprising an air preheater, a basic coal mill system, a temperature detection system and a primary fan, characterized in that: According to the result of the temperature detection system detecting the temperature of the grinding mill desiccant, the target desiccant temperature is calculated; The primary fan delivers part of the produced cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the cold section shell opening technology for taking warm air; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

2. The system for reducing the exhaust gas temperature of a medium-speed coal mill according to claim 1, characterized in that: The heat storage plates inside the air preheater are respectively a hot section heat storage plate, a warm section heat storage plate and a cold section heat storage plate from top to bottom; Among them, the primary fan will make a part of the 20~30℃ cold primary air flow into the bottom of the primary air side or secondary air side of the air preheater, pass through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows into the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate and flows out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target temperature air.

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

4. A method for reducing the exhaust gas temperature of a medium-speed coal mill, characterized in that: According to the results of the mill desiccant temperature detection, the target desiccant temperature is calculated; The primary fan delivers all of the produced cold primary air to the air preheater; In the air preheater, the hot primary air and the target warm air are output respectively through the rotary air preheating technology and the cold section shell opening technology for taking warm air; The target warm air, hot primary air and another part of cold primary air produced by the primary fan are sent to the basic coal mill system through the corresponding air ducts to make the mill desiccant reach the target desiccant temperature.

5. The method for reducing the exhaust gas temperature of a medium-speed coal mill according to claim 4, characterized in that: The heat storage plates inside the air preheater are respectively a hot section heat storage plate, a warm section heat storage plate and a cold section heat storage plate from top to bottom; Among them, the primary fan will make a part of the 20~30℃ cold primary air flow into the bottom of the primary air side or secondary air side of the air preheater, pass through the traditional cold section heat storage plate to the warm section heat storage plate, and at the same time, the hot flue gas flows into the top of the flue gas side of the air preheater, passes through the traditional hot section heat storage plate, the warm section heat storage plate and the traditional cold section heat storage plate and flows out, so that the warm section heat storage plate connected to the air intake port produces 90~120℃ target temperature air.

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

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