Uniform air distribution device and method for rotating air ring of medium-speed coal mill

Abstract

According to the uniform air distribution device and method for the rotating air ring of the medium-speed coal mill, the rotation-starting air distribution ring and the multiple specially-designed rotation-starting nozzles are coaxially arranged in the outer air chamber, and a unique flow channel from outside to inside is constructed, so that primary air enters the outer air chamber in the tangential direction to be preliminarily distributed, and then secondary air enters the outer air chamber in the tangential direction; the air flow is guided into the inner air chamber by the swirling nozzle and forms a swirling air flow with controllable strength; according to the method, by accurately matching the angular velocity of the rotating airflow with the angular velocity of the rotating air ring of the coal mill, primary air tends to have no relative motion with the dynamic rotating air ring flow channel in the horizontal direction when entering the dynamic rotating air ring flow channel, so that the air inlet condition of any position in the circumferential direction of the air ring is fundamentally ensured to be consistent; the core purposes of remarkably improving the primary air distribution uniformity, effectively restraining local high-speed abrasion of the air ring and improving the pebble coal discharging effect are achieved, and meanwhile the running stability and economical efficiency of the coal mill are improved.

Description

Technical Field

[0001] This invention relates to the field of high-speed coal mill technology in coal-fired power plant boiler pulverizing systems, and particularly to a device and method for uniform air distribution via a rotating air ring in a medium-speed coal mill. Background Technology

[0002] The pulverizing system is one of the important auxiliary equipment in coal-fired boilers. With years of development, the medium-speed coal mill has become the most widely used pulverizing equipment. According to the basic working principle of the medium-speed coal mill, hot primary air is sent into the lower air chamber of the mill, passes through the rotating air ring, and comes into contact with the raw coal. On the one hand, the hot primary air heats the raw coal and dries it, making it easier to grind and crush. On the other hand, the hot primary air carries the coal powder to the separator at the top of the mill for separation. Qualified coal powder is carried out of the mill by the hot primary air, while unqualified coal powder is returned to the mill for further grinding.

[0003] The outlet velocity of the hot primary air nozzle ring in currently operational medium-speed coal mills is generally controlled between 70 and 90 m / s, maintaining a relatively high level. The hot primary air nozzle ring rotates with the mill disc, and the hot primary air channel formed by the nozzle ring forms a certain angle with the horizontal plane. This results in significant differences in the entry angle of the hot primary air into the nozzle ring flow channel at different locations within the air chamber: at some locations, the initial flow direction of the airflow is at an acute angle to the flow channel, while at others it is at an obtuse angle. These different flow channel angles inevitably lead to varying resistance to the airflow entering the flow channel, resulting in different air intake volumes at different locations and thus uneven flow velocity at the nozzle ring outlet. At higher airflow velocities, this uneven flow causes varying wear conditions at different locations within the coal mill, with significantly higher wear in high-velocity regions, leading to equipment failure.

[0004] Localized wear caused by uneven airflow distribution inside medium-speed coal mills is a common phenomenon in the industry.

[0005] Furthermore, the nozzle ring structure also serves as the channel for discharging coke and gravel from the medium-speed coal mill. The relatively high hot primary air velocity at the nozzle ring outlet is designed to prevent the accidental discharge of pulverized coal or small coal particles, ensuring that only larger coke and gravel particles are discharged. However, uneven flow distribution within the nozzle ring can lead to a decrease in the hot primary air outlet velocity at certain locations, which is detrimental to preventing the accidental discharge of pulverized coal and small coal particles.

[0006] The above analysis shows that the uniformity of the hot primary air distribution in the nozzle ring of a medium-speed coal mill is crucial for improving the discharge efficiency of coke and suppressing localized wear. However, existing designs of the hot primary air chamber in coal mills cannot guarantee the uniform distribution of hot primary air. To overcome this problem, this invention proposes a uniform air distribution device and design method for a rotating air ring in a medium-speed coal mill. The device design fully relies on the basic principles of fluid mechanics, utilizing the guiding effect of geometric mechanisms on airflow to ensure that the hot primary air flows at nearly the same rotational speed as the nozzle ring. This guarantees that the angle between the hot primary air inlet direction at any position of the nozzle ring and the flow channel direction of the nozzle ring is consistent, thereby greatly improving the uniformity of the hot primary air distribution and solving the problem of hot primary air distribution deviation. Summary of the Invention

[0007] A first aspect of this disclosure provides a rotary air ring uniform air distribution device for a medium-speed coal mill, comprising: An external air chamber, which is annular in shape, has at least one primary air inlet on its side wall for receiving primary air from the primary air duct of the coal mill. A swirling air distribution ring is coaxially disposed inside the outer air chamber. Its outer wall and the inner wall of the outer air chamber together define a primary airflow channel, and its inner wall constitutes an inner air chamber. The inner air chamber is an annular air chamber formed by the inner wall of the rotating air distribution ring, and its top is provided with an air chamber outlet for connecting with the inlet of the rotating air ring of the coal mill. Multiple swirling nozzles are disposed through the swirling air distribution ring. Their inlets are connected to the outer air chamber, and their outlets are connected to the inner air chamber. They are used to guide primary air from the outer air chamber into the inner air chamber and form a rotating airflow.

[0008] In conjunction with the first aspect, two primary air inlets are provided on the side wall of the external air chamber, and the two primary air inlets are arranged symmetrically about the central axis of the coal mill.

[0009] In conjunction with the first aspect, the central axis of the primary air inlet forms an acute angle with the flow direction of the primary air in the outer air chamber.

[0010] In conjunction with the first aspect, the plurality of swirling nozzles are evenly distributed along the circumference of the swirling air distribution ring, and the central axis of the plurality of swirling nozzles forms a fixed angle with the radial direction of the swirling air distribution ring.

[0011] In conjunction with the first aspect, the cross-sectional areas of the plurality of swirling nozzles are not equal. Their specific area values ​​are determined by matching the changes in flow rate and pressure parameters of the primary air during the flow of the swirling air distribution ring, so as to ensure that the primary air at the outlet of each swirling nozzle has equal rotational angular velocity and ventilation volume. When the rated flow of primary air passes through, it can make the primary air flowing out of each swirling nozzle form a uniform rotating flow field in the inner air chamber.

[0012] In conjunction with the first aspect, the structural parameters of the plurality of swirling nozzles are configured such that, under the rated ventilation capacity of the coal mill, the rotational angular velocity of the primary airflow in the inner air chamber is equal to the rotational angular velocity of the rotating air ring of the coal mill, and the rotational directions are consistent.

[0013] A second aspect of this disclosure provides a method for uniform air distribution in a rotating air ring of a medium-speed coal mill, comprising the following steps: Determine the target angular velocity of the rotating air ring of the coal mill. V m ; Based on the rated ventilation volume and primary air parameters of the coal mill, calculate the volumetric flow rate of the primary air passing through the swirling air distribution ring. Q ; To satisfy the average angular velocity of the primary airflow in the inner air chamber V PA Equal to the target angular velocity V m As a design criterion, the total flow area of ​​the swirl-inducing nozzles on the swirl-inducing air distribution ring is determined. A and structural parameters; Wherein, the average angular velocity V PA Volumetric flow rate Q With total flow area A The following relationship must be satisfied: Q / A = π • d • V PA / 60, of which, d The inner diameter of the swirling air distribution ring is given.

[0014] In conjunction with the second aspect, when determining the total flow area A Subsequently, based on the flow rate and pressure distribution of the primary air during its flow through the swirling air distribution ring, the individual cross-sectional area of ​​each swirling nozzle is designed to be non-equivalent, so as to ensure that the primary air at the outlet of each swirling nozzle has equal rotational angular velocity and ventilation volume.

[0015] A third aspect of this disclosure provides an electronic device comprising: One or more processors; A storage unit is used to store one or more programs, which, when executed by one or more processors, enable the one or more processors to implement the uniform air distribution method of the rotating air ring of the medium-speed coal mill.

[0016] A fourth aspect of this disclosure provides a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, enables the uniform air distribution method of the rotating air ring of the medium-speed coal mill.

[0017] Beneficial Effects: The present disclosure provides a uniform air distribution device and method for a rotating air ring in a medium-speed coal mill. By coaxially setting a swirling air distribution ring and multiple specially designed swirling nozzles in the outer air chamber, a unique flow channel from the outside to the inside is constructed. After the primary air is initially distributed through the tangentially entering outer air chamber, it is guided by the swirling nozzles to the inner air chamber and forms a rotating airflow with controllable intensity. This method precisely matches the angular velocity of this rotating airflow with the angular velocity of the rotating air ring of the coal mill, so that when the primary air enters the dynamically rotating air ring flow channel, there is almost no relative motion between them in the horizontal direction. This fundamentally ensures that the air intake conditions are consistent at any position in the circumference of the air ring, achieving the core objectives of significantly improving the uniformity of primary air distribution, effectively suppressing local high-speed wear of the air ring, and improving the discharge effect of gravel and coal. At the same time, it enhances the stability and economy of the coal mill operation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a rotating air ring uniform air distribution device for a medium-speed coal mill according to an embodiment of the present disclosure; Figure 2 This is a schematic flowchart of a method for uniform air distribution in a rotating air ring of a medium-speed coal mill, according to an embodiment of the present disclosure. Figure 3 An electronic device according to an embodiment of this disclosure. Detailed Implementation

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those disclosed herein.

[0020] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0021] Figure 1 This is a schematic flowchart of a method for uniform air distribution via a rotating air ring in a medium-speed coal mill, according to an embodiment of the present disclosure. The method includes a coal-fired power generation unit, a solar thermal energy storage unit, and an industrial steam supply unit. External air chamber 2, the external air chamber is annular, and at least one primary air inlet is provided on its side wall for receiving primary air from the primary air duct of the coal mill; The swirling air distribution ring 4 is coaxially disposed inside the outer air chamber. Its outer wall and the inner wall of the outer air chamber together define a primary airflow channel, and its inner wall constitutes an inner air chamber. The inner air chamber 5 is an annular air chamber formed by the inner wall of the rotating air distribution ring 4, and its top is provided with an air chamber outlet for connecting with the inlet of the rotating air ring of the coal mill. Multiple swirling nozzles are disposed through the swirling air distribution ring. Their inlets are connected to the outer air chamber 2, and their outlets are connected to the inner air chamber 5. They are used to guide primary air from the outer air chamber 2 into the inner air chamber 5 and form a rotating airflow.

[0022] Preferably, the side wall of the outer air chamber 2 is provided with two primary air inlets, primary air inlet 1 and primary air inlet 6, and the two primary air inlets are arranged symmetrically about the central axis of the coal mill.

[0023] The airflow entering the coal mill is split in two, cutting in from two completely symmetrical points. This symmetrical design is the primary prerequisite for ensuring the uniformity of the subsequent flow field. It can balance the pressure distribution in the air chamber from the source, prevent airflow bias caused by unilateral air intake, and lay a structural foundation for establishing a uniform flow field in the entire annular space.

[0024] Furthermore, the central axis of the primary air inlet forms an acute angle with the flow direction of the primary air within the outer air chamber. .

[0025] The acute angle This ensures that the primary airflow does not rush directly into the outer air chamber, but rather cuts in along the annular wall of the air chamber in a certain tangential direction. This air intake method utilizes the guidance of the wall to generate a circumferential momentum in the airflow as soon as it enters the outer air chamber, forming a preliminary rotational tendency around the central axis, which prepares for the subsequent formation of a strong rotating flow field in the inner air chamber.

[0026] The plurality of swirl-initiating nozzles are evenly distributed along the circumference of the swirl-initiating air distribution ring, as shown in the figure as swirl-initiating nozzle 101, swirl-initiating nozzle 102, swirl-initiating nozzle 103, and swirl-initiating nozzle 104.

[0027] The central axis of the multiple swirling nozzles forms a fixed angle with the radial direction of the swirling air distribution ring.

[0028] Uniform distribution ensures the continuity of the point of action and prevents dead zones in the flow. The fixed angle formed by the nozzle's central axis and the radial direction essentially imparts a tangential velocity component to the airflow. When the airflow exits from these nozzles with a uniform angle, it converges in the inner air chamber, superimposing to form a uniformly oriented, stably rotating "gas vortex," which is the key flow pattern for achieving uniform air distribution.

[0029] Furthermore, the cross-sectional area 3 of the plurality of swirling nozzles is not equal. Its specific area value is determined by matching the changes in flow rate and pressure parameters of the primary air during the flow of the swirling air distribution ring, so as to ensure that the primary air at the outlet of each swirling nozzle has equal rotational angular velocity and ventilation volume. When the rated flow of primary air flows through, it can make the primary air flowing out from each swirling nozzle form a uniform rotating flow field in the inner air chamber.

[0030] Although the airflow undergoes pre-swirl in the outer air chamber, slight pressure and flow rate reductions still occur during the flow process. If all nozzle areas are equal, the outflow from the nozzles downstream will differ from that upstream. By using a non-uniform cross-section design—that is, tailoring different flow areas to the specific location of each nozzle on the circumference—this flow loss can be precisely compensated for, ensuring that the airflow exiting each nozzle has exactly the same flow rate and rotational momentum, ultimately forming an extremely uniform and symmetrical rotating flow field in the inner air chamber.

[0031] Furthermore, the structural parameters of the plurality of swirl nozzles are configured such that, under the rated ventilation capacity of the coal mill, the rotational angular velocity of the primary airflow in the inner air chamber is equal to the rotational angular velocity of the rotating air ring of the coal mill, and the rotational directions are consistent.

[0032] Through the combined effect of the aforementioned measures (symmetrical air intake, tangential pre-rotation, angled nozzles, and non-uniform cross-sections), the "synchronous rotation" of the airflow and mechanical components is ultimately achieved. When there is almost no relative velocity between the rotating air ring and the airflow it is about to receive in the horizontal direction, the air intake conditions at any position on the circumference of the air ring become completely uniform, thereby fundamentally eliminating the problems of local eddies, high-speed impacts, and uneven flow, and achieving the ideal effect of suppressing wear and optimizing slag discharge.

[0033] Figure 2 This is a schematic flowchart of a combined heat and power (CHP) steam supply method for coupled dual-tank active solar thermal energy storage according to an embodiment of the present disclosure, including: S1: Determine the target angular velocity of the coal mill rotating air ring. V m ; S2: Based on the rated ventilation volume and primary air parameters of the coal mill, calculate the volumetric flow rate of the primary air passing through the swirling air distribution ring. Q ; S3: To satisfy the average angular velocity of the primary airflow in the inner air chamber V PA Equal to the target angular velocity V m As a design criterion, the total flow area of ​​the swirl-inducing nozzles on the swirl-inducing air distribution ring is determined. A and structural parameters, wherein the average angular velocity V PA Volumetric flow rate Q With total flow area A The following relationship must be satisfied: Q / A = π • d • V PA / 60, of which, d The inner diameter of the swirling air distribution ring is given.

[0034] First, step S1, "determining the target angular velocity of the coal mill's rotating air ring," is the starting point of the design. It comes directly from the inherent operating parameters of the coal mill and clarifies the mechanical rotation reference that the airflow needs to match.

[0035] Next, step S2, "Calculate the volumetric flow rate of the primary air flowing through the swirling air distribution ring based on the rated ventilation volume and primary air parameters of the coal mill," transforms the system's operating conditions into key design boundary conditions, providing accurate flow input for subsequent calculations.

[0036] The final S3 step is crucial. It proposes "using the average angular velocity of the primary airflow in the inner air chamber to equal the target angular velocity as the design criterion." This formally establishes the inventive concept of "synchronous gas-solid rotation" as the design principle and provides the specific mathematical tool for realizing this principle—namely, the relational formula. Q / A = π • d • V PA / 60.

[0037] This formula connects the design objectives, known conditions, and the core structural parameters to be determined (total flow area), enabling the design process to move from the conceptual level to the precisely calculable engineering level.

[0038] Furthermore, in determining the total flow area ASubsequently, based on the flow rate and pressure distribution of the primary air during its flow through the swirling air distribution ring, the individual cross-sectional area of ​​each swirling nozzle is designed to be non-equivalent, so as to ensure that the primary air at the outlet of each swirling nozzle has equal rotational angular velocity and ventilation volume.

[0039] By "tailor-making" different cross-sectional areas for the swirling nozzles at different locations along the airflow path, this flow non-uniformity can be actively compensated for. The ultimate goal is to "ensure that the primary air at the exit of each swirling nozzle has equal rotational angular velocity and ventilation volume." This means that the "contribution" of the airflow ejected from each nozzle to the formation of the overall rotating flow field in the inner air chamber is completely equal, thus ensuring the uniformity and stability of the rotating flow field from the source. This allows the theoretical design criteria in step S3 to be realized most accurately in the actual device.

[0040] Electronic device 300 can be a desktop computer, laptop, handheld computer, cloud server, or other electronic device. Electronic device 300 may include, but is not limited to, processor 301 and memory 302. Those skilled in the art will understand that... Figure 3 This is merely an example of electronic device 300 and does not constitute a limitation on electronic device 300. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device may also include input / output devices, network access devices, buses, etc.

[0041] Processor 301 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0042] The memory 302 can be an internal storage unit of the electronic device 300, such as a hard disk or RAM of the electronic device 300. The memory 302 can also be an external storage device of the electronic device 300, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the electronic device 300. Furthermore, the memory 302 can include both internal and external storage units of the electronic device 300. The memory 302 is used to store the computer program 303 and other programs and data required by the electronic device. The memory 302 can also be used to temporarily store data that has been output or will be output.

[0043] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure 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. Such 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 this disclosure, and should all be included within the protection scope of this disclosure.

Claims

1. A uniform air distribution device for a rotating air ring in a medium-speed coal mill, characterized in that, include: An external air chamber, which is annular in shape, has at least one primary air inlet on its side wall for receiving primary air from the primary air duct of the coal mill. A swirling air distribution ring is coaxially disposed inside the outer air chamber. Its outer wall and the inner wall of the outer air chamber together define a primary airflow channel, and its inner wall constitutes an inner air chamber. The inner air chamber is an annular air chamber formed by the inner wall of the rotating air distribution ring, and its top is provided with an air chamber outlet for connecting with the inlet of the rotating air ring of the coal mill. Multiple swirling nozzles are disposed through the swirling air distribution ring. Their inlets are connected to the outer air chamber, and their outlets are connected to the inner air chamber. They are used to guide primary air from the outer air chamber into the inner air chamber and form a rotating airflow.

2. The apparatus according to claim 1, characterized in that, Two primary air inlets are provided on the side wall of the external air chamber, and the two primary air inlets are arranged symmetrically about the central axis of the coal mill.

3. The apparatus according to claim 2, characterized in that, The central axis of the primary air inlet forms an acute angle with the flow direction of the primary air in the outer air chamber.

4. The apparatus according to claim 1, characterized in that, The plurality of swirling nozzles are evenly distributed along the circumference of the swirling air distribution ring, and the central axis of the plurality of swirling nozzles forms a fixed angle with the radial direction of the swirling air distribution ring.

5. The apparatus according to claim 4, characterized in that, The cross-sectional areas of the multiple swirl nozzles are not equal. Their specific area values ​​are determined by matching the changes in flow rate and pressure parameters of the primary air during the flow of the swirl air distribution ring, so as to ensure that the primary air at the outlet of each swirl nozzle has equal rotational angular velocity and ventilation volume. When the rated flow of primary air passes through, it can make the primary air flowing out of each swirl nozzle form a uniform rotating flow field in the inner air chamber.

6. The apparatus according to claim 1, characterized in that, The structural parameters of the multiple swirl nozzles are configured such that, under the rated ventilation conditions of the coal mill, the rotational angular velocity of the primary airflow in the inner air chamber is equal to the rotational angular velocity of the rotating air ring of the coal mill, and the rotational directions are consistent.

7. A method for uniform air distribution in a rotating air ring of a medium-speed coal mill, characterized in that, Includes the following steps: Determine the target angular velocity of the rotating air ring of the coal mill. V m ; Based on the rated ventilation volume and primary air parameters of the coal mill, calculate the volumetric flow rate of the primary air passing through the swirling air distribution ring. Q ; To satisfy the average angular velocity of the primary airflow in the inner air chamber V PA Equal to the target angular velocity V m As a design criterion, the total flow area of ​​the swirl-inducing nozzles on the swirl-inducing air distribution ring is determined. A and structural parameters, wherein the average angular velocity V PA Volumetric flow rate Q With total flow area A The following relationship must be satisfied: Q / A = π • d • V PA / 60, of which, d The inner diameter of the swirling air distribution ring is given.

8. The design method according to claim 7, characterized in that, In determining the total flow area A Subsequently, based on the flow rate and pressure distribution of the primary air during its flow through the swirling air distribution ring, the individual cross-sectional area of ​​each swirling nozzle is designed to be non-equivalent, so as to ensure that the primary air at the outlet of each swirling nozzle has equal rotational angular velocity and ventilation volume.

9. An electronic device, characterized in that, include: One or more processors; A storage unit is used to store one or more programs, which, when executed by one or more processors, enable the one or more processors to implement the uniform air distribution method of the rotating air ring of the medium-speed coal mill.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it can realize the method of uniform air distribution of the rotating air ring of the medium-speed coal mill.

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