Inlet air duct of coal mill
By adjusting the layout of the coal mill inlet air duct and the design of the mixing air duct, the problem of inaccurate air volume measurement was solved, and accurate air volume measurement was achieved, ensuring the stable operation and control of the coal mill and boiler.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-03
- Publication Date
- 2026-03-20
AI Technical Summary
The flow field at the inlet of the coal mill in an existing boiler often contains eddies, which leads to inaccurate air volume measurement and affects the operation and automatic control of the pulverizing system.
By changing the layout of the coal mill inlet duct, the connection between the hot air header and the cold air duct is placed above the boiler operating level. The length and diameter ratio of the mixing duct are adjusted so that the cold air and hot air mix to form a near-parallel flow field condition to meet the requirements of air volume measurement.
It enables accurate measurement of the inlet air volume of the coal mill, ensuring the stable, safe, and economical operation of the coal mill and boiler, and providing a basis for the automatic control of the appropriate air-coal ratio and pulverizing system.
Smart Images
Figure CN224010016U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of boiler medium flow measurement technology, specifically to a coal mill inlet air duct. Background Technology
[0002] In coal-fired power plants, the coal mill is the core equipment of the pulverizing system, responsible for grinding raw coal into pulverized coal for boiler combustion. The cold air duct and hot air duct at the inlet of the coal mill play a key role in the pulverizing system, directly affecting the operating efficiency of the coal mill and the combustion performance of the boiler.
[0003] The cold and hot air ducts at the inlet of the coal mill in existing boilers are usually designed and arranged according to the principle of convenience. The design rarely considers how to accurately measure the air volume at the coal mill inlet. However, eddies often exist in the flow field at the air volume measuring device or measuring point at the coal mill inlet, which makes it impossible to accurately measure the air volume at the coal mill inlet.
[0004] To address the aforementioned problems, existing technologies, without altering the coal mill inlet duct and its layout, employ flow equalization and rectification methods to mitigate the vortex-induced flow field under current conditions. Alternatively, multi-point measurement methods are used to compensate for errors caused by uneven flow field distribution. However, none of these approaches have achieved the desired results, and accurate measurement of the coal mill inlet airflow remains impossible. Clearly, the large measurement error in the coal mill inlet airflow poses significant challenges to the operation and automatic control of the pulverizing system. Utility Model Content
[0005] The purpose of this utility model is to provide a coal mill inlet air duct to overcome the problems existing in the prior art. This utility model can make the medium flow field at the flow device in the coal mill inlet air duct meet the requirements of air volume measurement, which facilitates accurate measurement of the inlet air volume of the coal mill.
[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:
[0007] A coal mill inlet air duct includes a hot air header, a hot air duct installed in the middle or bottom of the hot air header, a cold air duct installed on one side of the bottom of the hot air duct, a cold air header installed at the end of the cold air duct away from the hot air duct, the connection between the hot air duct and the cold air duct is located in the upper part of the boiler operating layer, a mixing air duct is installed at the bottom of the hot air duct, and an air volume device is installed on the mixing air duct.
[0008] Furthermore, the mixing duct includes an upper mixing duct installed at the bottom of the boiler operating layer, a middle mixing duct installed at the bottom of the upper mixing duct via an air volume device, and a lower mixing duct installed at the bottom of the middle mixing duct.
[0009] Furthermore, the upper mixing duct and the middle mixing duct have the same cross-section and the same hydraulic diameter d;
[0010] Furthermore, the length L1 of the upper mixing duct satisfies: L1≥5d;
[0011] Furthermore, the length L2 of the intermediate mixing duct satisfies: d≤L2≤2d;
[0012] Furthermore, the total length L of the upper mixing duct and the middle mixing duct satisfies: L = L1 + L2, L ≥ 6d;
[0013] Furthermore, the hot air duct includes a hot air duct body, on which a hot air shut-off door and a hot air regulating door are installed from top to bottom; a cold air duct is installed on one side of the hot air duct body, the connection between the hot air duct body and the cold air duct is located at the upper part of the boiler operating layer, and a mixing air duct is installed at the bottom of the hot air duct body.
[0014] Furthermore, the cold air duct includes a cold air duct body, on which a cold air shut-off valve and a cold air regulating valve are installed from the cold air header to the hot air duct body; the cold air duct body is installed on one side of the hot air duct body, and the connection between the hot air duct body and the cold air duct body is located at the upper part of the boiler operating layer.
[0015] The above technical solution has the following advantages or beneficial effects:
[0016] This utility model provides a coal mill inlet air duct. By changing the traditional arrangement of the hot air header at the coal mill inlet from below the boiler operating level to above the boiler operating level, and also placing the connection between the cold air duct and the hot air duct at the coal mill inlet above the boiler operating level, the overall length L of the mixed cold and hot air to the upper and middle mixing air ducts satisfies L≥6d with respect to the hydraulic diameter d of the upper and middle mixing air ducts. Furthermore, the length L1 of the upper mixing air duct satisfies L1≥5d with respect to the hydraulic diameter d of the upper and middle mixing air ducts. The length L2 and the hydraulic diameter d of the upper and middle mixing ducts satisfy the condition that d≤L2≤2d, which can form a near-parallel or parallel flow field condition. This ensures that the medium flow field at the air volume device (or measuring point) at the coal mill inlet is uniform, thus meeting the measurement requirements and obtaining an accurate coal mill inlet air volume. This lays the foundation for controlling the appropriate air-coal ratio of the coal mill during operation, controlling the reasonable primary air rate of the boiler, and the automatic control of the pulverizing system. This utility model can change the situation where the coal mill inlet air volume is often inaccurate, creating conditions for operators to control the coal mill ventilation volume normally and reasonably, and for the safe, stable, and economical operation of the coal mill and boiler. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of the inlet air duct of a coal mill according to the present invention;
[0018] In the diagram, 1-Hot air main pipe; 2-Cold air main pipe; 3-Hot air duct body; 31-Hot air shut-off valve; 32-Hot air regulating valve; 4-Upper mixing air duct; 5-Middle mixing air duct; 6-Cold air duct body; 61-Cold air shut-off valve; 62-Cold air regulating valve; 7-Boiler operating layer; 8-Air volume device; 9-Lower mixing air duct. Detailed Implementation
[0019] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.
[0020] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to 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 of this utility model.
[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.
[0022] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0025] See Figure 1 This utility model provides a coal mill inlet air duct, including a hot air main pipe 1, a cold air main pipe 2, a cold air duct, a hot air duct, a mixing air duct, a boiler operating layer 7, and an air volume device 8; the hot air duct includes a hot air duct body 3, a hot air stop valve 31, and a hot air regulating valve 32; the cold air duct includes a cold air duct body 6, a cold air stop valve 61, and a cold air regulating valve 62; the mixing air duct includes an upper mixing air duct 4, a middle mixing air duct 5, and a lower mixing air duct 9;
[0026] The hot air duct body 3 is installed in the middle or bottom of the hot air header 1. A hot air stop valve 31 and a hot air regulating valve 32 are installed on the hot air duct body 3 from top to bottom. The cold air duct body 6 is installed on the bottom side of the hot air duct body 3. The cold air header 2 is installed at the end of the cold air duct body 6 away from the hot air duct body 3. A cold air stop valve 61 and a cold air regulating valve 62 are installed on the cold air duct body 6 from the cold air header 2 to the hot air duct body 3. The connection between the hot air duct body 3 and the cold air duct body 6 is located at the upper part of the boiler operating layer 7. The mixing air duct is installed at the bottom of the hot air duct. An air volume device 8 is installed on the mixing air duct. The upper mixing air duct 4 is installed at the bottom of the boiler operating layer 7. The bottom of the upper mixing air duct 4 is connected to the middle mixing air duct 5 through the air volume device 8. The lower mixing air duct 9 is installed at the bottom of the middle mixing air duct 5. The upper mixing air duct 4 and the middle mixing air duct 5 have the same cross-section and the same hydraulic diameter d.
[0027] Specifically, the air volume device 8 can also be called the air volume measuring point;
[0028] Specifically, d = 4 × area of upper mixing duct 4 or middle mixing duct 5 / wet perimeter of upper mixing duct 4 or middle mixing duct 5;
[0029] Specifically, the length L1 of the upper mixing duct 4 satisfies: L1≥5d; the length L2 of the middle mixing duct 5 satisfies: d≤L2≤2d; the total length L of the upper mixing duct 4 and the middle mixing duct 5 satisfies: L= L1+ L2, L≥6d;
[0030] In a preferred minimum requirement of this utility model, the hydraulic diameters of the upper mixing duct 4 and the middle mixing duct 5 are d=1 m, the total length of the upper mixing duct 4 and the middle mixing duct 5 is L=6 m, satisfying L=6d; the length of the upper mixing duct 4 is L1=5 m, satisfying L1=5d; and the length of the middle mixing duct 5 is L2=1 m, satisfying L2=d.
[0031] Preferably, in one embodiment of the present invention, the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 is 1 m, the total length L of the upper mixing duct 4 and the middle mixing duct 5 is 7 m, satisfying L=7d; the length L1 of the upper mixing duct 4 is 6 m, satisfying L1=6d; and the length L2 of the middle mixing duct 5 is 1 m, satisfying L2=d.
[0032] Preferably, in one embodiment of the present invention, the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 is 1 m, the total length L of the upper mixing duct 4 and the middle mixing duct 5 is 8 m, satisfying L=8d; the length L1 of the upper mixing duct 4 is 7 m, satisfying L1=7d; the length L2 of the middle mixing duct 5 is 1 m, satisfying L2=d.
[0033] Preferably, in one embodiment of the present invention, the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 is 1 m, the total length L of the upper mixing duct 4 and the middle mixing duct 5 is 9 m, satisfying L=9d; the length L1 of the upper mixing duct 4 is 8 m, satisfying L1=8d; and the length L2 of the middle mixing duct 5 is 1 m, satisfying L2=d.
[0034] Preferably, in one embodiment of the present invention, the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 is 1 m, the total length L of the upper mixing duct 4 and the middle mixing duct 5 is 10 m, satisfying L=10d; the length L1 of the upper mixing duct 4 is 8 m, satisfying L1=8d; and the length L2 of the middle mixing duct 5 is 2 m, satisfying L2=2d.
[0035] Preferably, in one embodiment of the present invention, the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 is 1 m, the total length L of the upper mixing duct 4 and the middle mixing duct 5 is 8 m, satisfying L=8d; the length L1 of the upper mixing duct 4 is 6.5 m, satisfying L1=6.5d; the length L2 of the middle mixing duct 5 is 1.5 m, satisfying L2=1.5d.
[0036] The structure and working principle of this utility model will be further explained below:
[0037] The purpose of this utility model is to provide a coal mill inlet air duct. By changing the traditional arrangement of the hot air header 1 at the coal mill inlet from below the boiler operating layer 7 to above the boiler operating layer 7, and by also arranging the connection between the cold air duct and the hot air duct at the coal mill inlet above the boiler operating layer 7, the arrangement elevation and position of the hot air header 1, cold air duct, and hot air duct are changed so that the total length L of the cold and hot air after mixing to the upper mixing air duct 4 and the middle mixing air duct 5 satisfies L≥6d with respect to the hydraulic diameter d of the upper mixing air duct 4 and the middle mixing air duct 5. The length L1 and the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 satisfy L1≥5d, and the length L2 of the middle mixing duct 5 and the hydraulic diameter d of the upper mixing duct 4 and the middle mixing duct 5 satisfy: d≤L2≤2d. This can form a flow field condition that is close to parallel flow or parallel flow, so that the medium flow field at the air volume device 8 (or measuring point) at the coal mill inlet is uniform, so as to meet the measurement requirements and obtain accurate coal mill inlet air volume. This lays the foundation for controlling the appropriate air-coal ratio of the coal mill in operation, controlling the reasonable primary air rate of the boiler, and the automatic control of the pulverizing system.
[0038] This invention can change the situation where the inlet air volume of a coal mill is often inaccurate, creating conditions for operators to control the ventilation volume of the coal mill normally and reasonably, and for the safe, stable and economical operation of the coal mill and boiler.
[0039] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0040] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of this utility model and should not be used to limit the scope of protection of this utility model. Any modifications made to the technical solutions based on the technical concept proposed by this utility model shall fall within the scope of protection of the claims of this utility model.
Claims
1. A coal mill inlet air duct, characterized in that, It includes a hot air header (1), a hot air duct is installed in the middle or bottom of the hot air header (1), a cold air duct is installed on one side of the bottom of the hot air duct, a cold air header (2) is installed at the end of the cold air duct away from the hot air duct, the connection between the hot air duct and the cold air duct is located at the upper part of the boiler operating layer (7), a mixing air duct is installed at the bottom of the hot air duct, and an air volume device (8) is installed on the mixing air duct.
2. The coal mill inlet air duct according to claim 1, characterized in that, The mixing duct includes an upper mixing duct (4) installed at the bottom of the boiler operating layer (7), a middle mixing duct (5) installed at the bottom of the upper mixing duct (4) via an air volume device (8), and a lower mixing duct (9) installed at the bottom of the middle mixing duct (5).
3. The coal mill inlet air duct according to claim 2, characterized in that, The upper mixing duct (4) and the middle mixing duct (5) have the same cross-section and the same hydraulic diameter d.
4. The coal mill inlet air duct according to claim 3, characterized in that, The length L1 of the upper mixing duct (4) satisfies: L1≥5d.
5. The coal mill inlet air duct according to claim 4, characterized in that, The length L2 of the mixed air duct (5) satisfies: d≤L2≤2d.
6. A coal mill inlet air duct according to claim 5, characterized in that, The total length L of the upper mixing duct (4) and the middle mixing duct (5) satisfies: L = L1 + L2, L ≥ 6d.
7. The coal mill inlet air duct according to claim 1, characterized in that, The hot air duct includes a hot air duct body (3), on which a hot air shut-off door (31) and a hot air regulating door (32) are installed from top to bottom; the hot air duct body (3) is installed in the middle or bottom of the hot air header (1), the cold air duct is installed on one side of the hot air duct body (3), the connection between the hot air duct body (3) and the cold air duct is located at the upper part of the boiler operating layer (7), and the mixing air duct is installed at the bottom of the hot air duct body (3).
8. The coal mill inlet air duct according to claim 7, characterized in that, The cold air duct includes a cold air duct body (6), and a cold air stop valve (61) and a cold air regulating valve (62) are installed on the cold air duct body (6) from the cold air header (2) to the hot air duct body (3); the cold air duct body (6) is installed on one side of the hot air duct body (3), and the connection between the hot air duct body (3) and the cold air duct body (6) is located at the upper part of the boiler operating layer (7).