Comprehensive treatment method for outlet temperature deviation of coal mill

Abstract

The present application relates to the technical field of thermal power generating unit, especially relates to a coal mill outlet temperature deviation comprehensive treatment method, six symmetrical and uniform temperature measuring points arranged at the coal mill outlet are compared by arbitrary deviation calculation, and the maximum temperature deviation calculation measuring point display is added in the DCS (Distributed Control System) pulverizing monitoring picture; meanwhile, the coal layer thickness is judged according to the coal mill current and three mill roller lifting switch position measuring point signals, and the coal mill is always controlled to run under the best working condition; at the same time, the dynamic ring blade shape is optimized and the Venturi effect technology is adopted, and a more efficient air power field is established, so that the internal flow field of the coal mill is improved. The method adopts the coal mill outlet temperature deviation control as the target, and adopts the coal mill current and the coal layer thickness as the reference new adjustment control strategy, at the same time, the dynamic ring blade shape is optimized, the Venturi effect technology is adopted, and the high-efficiency air power field is established, so that the coal mill output is ensured, and the problems such as the powder pipe blockage, the boiler combustion deviation and the water cooling wall over-temperature are avoided.

Description

Technical Field

[0001] This invention relates to the field of thermal power generating unit technology, and in particular to a comprehensive method for controlling temperature deviation at the outlet of a coal mill. Background Technology

[0002] Currently, the outlet temperature monitoring of coal mills in large thermal power generating units is generally accomplished by three sets of temperature sensing elements symmetrically and evenly arranged at 120 degrees on the top of the mill shell. Each set of sensing elements consists of two thermocouples. Typically, the inlet primary air volume is regulated by a hot air damper, and the outlet temperature is regulated by a cold air damper. The mixed hot and cold primary air entering the coal mill is used for drying and conveying pulverized coal. The setpoint of the primary air volume is a function of the coal feed rate. If the primary air volume is greater than the setpoint, the hot air damper will close slightly; if the primary air volume is less than the setpoint, the hot air damper will open wider. This change in air volume simultaneously causes a synchronous change in the cold air damper through a coupling relationship to maintain a constant outlet temperature. Conversely, if the coal mill outlet temperature is higher than the setpoint, the cold air damper will open wider; if the outlet temperature is lower than the setpoint, the cold air damper will close slightly. This temperature change simultaneously causes a synchronous change in the hot air damper through a coupling relationship to maintain a constant outlet temperature.

[0003] However, in actual operation, the coal mill grinds complex and varied coal types with large differences in grindability coefficients. Affected by internal resistance, coal bed thickness and dynamic airflow, the internal flow field is complex, and the outlet temperature deviation is large (the maximum temperature deviation reaches 25℃). The temperature deviation is closely related to the uniformity of the internal flow field. When the temperature deviation is large, the uneven distribution of powder in each branch pipe is more serious, which can easily cause problems such as powder pipe blockage, boiler combustion deviation and water-cooled wall overheating, affecting the safe operation of the boiler. Summary of the Invention

[0004] The main objective of this invention is to overcome the problems of large temperature deviation at the coal mill outlet and uneven powder distribution in the branch pipes in the prior art, and to provide a comprehensive method for controlling the temperature deviation at the coal mill outlet. This method adopts a new control strategy with the coal mill outlet temperature deviation as the target, supplemented by adjustments to the coal mill current and coal bed thickness as references. Simultaneously, it optimizes the shape of the moving ring blades and employs Venturi action technology to establish a highly efficient aerodynamic field. This ensures the output of the coal mill while avoiding problems such as powder pipe blockage, boiler combustion deviation, and water-cooled wall overheating.

[0005] The technical solution adopted by this invention to achieve its technical objective is: a comprehensive method for controlling temperature deviation at the outlet of a coal mill, specifically comprising the following steps:

[0006] S1. Six temperature measuring points are symmetrically and evenly arranged at the outlet of the coal mill for arbitrary deviation calculation and comparison, and the maximum temperature deviation calculation measuring point is displayed on the DCS pulverizing monitoring screen.

[0007] S2. During normal operation, the outlet temperature deviation should not exceed 5℃. When the outlet temperature deviation exceeds 10℃, the DCS will issue a color-changing alarm to remind the operators to intervene and adjust the control in time.

[0008] S3. When the temperature deviation at the coal mill outlet is greater than 5℃, it indicates that the internal flow field is becoming more uneven, suggesting that the primary air velocity and air volume are too high. By reducing the hot primary air volume of the coal mill through offsetting, the air-coal ratio can be controlled (generally 2), thereby adjusting the drying output of the coal mill, improving the internal flow field, and increasing the uniformity of the outlet air-coal mixture.

[0009] S4. While controlling the temperature deviation at the coal mill outlet, determine the coal seam thickness based on the coal mill current and the signals from the measuring points at the positions of the three grinding roller lifting switches.

[0010] When the current of the coal mill is found to be too low or too high, the signal of the grinding roller descending or rising to the correct position can be used to clearly determine the amount of coal inside the coal mill, thereby allowing for further analysis and determination of the coal bed thickness.

[0011] By adjusting the loading force through offset, the coal mill is always kept in optimal operating condition.

[0012] S5. To address the issue of uneven airflow field in the moving ring of the coal mill, the nozzle outlet velocity can be increased with the same primary air volume by modifying the moving ring blades and adopting a Venturi air passage. This reduces the retention of coal powder in the inert region, lowers ventilation resistance, and gradually increases the air velocity from the nozzle inlet to the outlet, reaching its maximum at the nozzle throat. This creates a more efficient aerodynamic field and further improves the uniformity of the internal flow field of the coal mill.

[0013] Preferably, in step S4, the coal mill current is normally controlled between 60% and 80% of the rated current.

[0014] Preferably, the optimal operating condition of the coal mill output in step S4 is controlled between 60% and 80%.

[0015] Preferably, in step S5, the air outlet of the moving ring blade is configured to be curved, so that the airflow direction is variable.

[0016] Preferably, in step S5, the Chinese Qiuli air passage is configured as a low-resistance curved torsion channel, and is used in conjunction with a moving ring blade.

[0017] Preferably, the moving ring blade in step S includes an inner ring and an outer ring, and an air outlet ring is fixedly disposed between the inner ring and the outer ring;

[0018] The air outlet ring is angled and has multiple air outlets that are bent inside it.

[0019] The air outlet ring has multiple air outlets interconnected by through holes inside.

[0020] Preferably, an inner upper stop block is integrally connected to one side of the top of the inner ring, and the inner upper stop block limits and blocks the upper right side of the air outlet ring;

[0021] An inner lower stop block is integrally connected to one side of the bottom end of the inner ring, and the inner lower stop block limits and blocks the lower right side of the air outlet ring;

[0022] A support plate is integrally connected to one side of the top of the outer ring. An outer upper first stop block is fixedly connected above the support plate, and an outer upper second stop block is fixedly connected above it. The outer upper first stop block and the outer upper second stop block together limit and block the upper left side of the air outlet ring.

[0023] An outer lower stop block is integrally connected to one side of the bottom end of the outer ring, and the outer lower stop block limits and blocks the lower left side of the air outlet ring.

[0024] Compared with the prior art, the beneficial effects of this invention are as follows: This comprehensive method for controlling the outlet temperature deviation of a coal mill addresses the problems of large outlet temperature deviation and uneven powder distribution in each branch pipe. It innovatively adopts a new control strategy that aims to control the outlet temperature deviation of the coal mill, improves the internal flow field, and enhances the uniformity of the outlet air and powder. At the same time, it uses the coal mill current and coal bed thickness as references to adjust the control strategy, keeping the coal mill output at the optimal operating condition. Furthermore, it technically modifies and optimizes the shape of the moving ring blades, adopts Venturi action technology, and establishes an efficient aerodynamic field to make the airflow field of the moving ring uniform, avoiding the formation of stagnation zones for coal powder. This ensures the output of the coal mill while avoiding problems such as powder pipe blockage, boiler combustion deviation, and water-cooled wall overheating. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the front cross-sectional structure of the moving ring blade.

[0026] Figure 2 This is a top view of the moving ring blade.

[0027] Figure 3 This is a schematic diagram of the Venturi airway's main structure.

[0028] in:

[0029] 1-Inner ring; 2-Outer ring; 3-Inner upper stop block; 4-Inner lower stop block; 5-Outer upper first stop block; 6-Outer upper second stop block; 7-Outer lower stop block; 8-Air outlet ring; 801-Air outlet; 802-Through hole. Detailed Implementation

[0030] 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, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and 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 this invention. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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.

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention. Example 1:

[0033] Please see Figure 1-2 The comprehensive method for addressing the temperature deviation at the coal mill outlet is as follows:

[0034] S1. Six temperature measuring points are symmetrically and evenly arranged at the outlet of the coal mill for arbitrary deviation calculation and comparison, and the maximum temperature deviation calculation measuring point is displayed on the DCS pulverizing monitoring screen.

[0035] S2. During normal operation, the outlet temperature deviation should not exceed 5℃. When the outlet temperature deviation exceeds 10℃, the DCS will issue a color-changing alarm to remind the operators to intervene and adjust the control in time.

[0036] S3. When the temperature deviation at the coal mill outlet is greater than 5℃, it indicates that the internal flow field is becoming more uneven, suggesting that the primary air velocity and air volume are too high. By reducing the hot primary air volume of the coal mill through offsetting, the air-coal ratio can be controlled (generally 2), thereby adjusting the drying output of the coal mill, improving the internal flow field, and increasing the uniformity of the outlet air-coal mixture.

[0037] S4. While controlling the temperature deviation at the coal mill outlet, the coal layer thickness is determined based on the coal mill current and the signals from the measuring points at the positions of the three grinding roller lifting switches. The coal mill current is normally controlled between 60% and 80% of the rated current.

[0038] When the current of the coal mill is found to be too low or too high, the signal of the grinding roller descending or rising to the correct position can be used to clearly determine the amount of coal inside the coal mill, thereby allowing for further analysis and determination of the coal bed thickness.

[0039] By adjusting the loading force through offset, the coal mill is always kept in optimal operating condition; the optimal operating condition for the coal mill output is controlled between 60% and 80%.

[0040] S5. To address the issue of uneven airflow field in the moving ring of the coal mill, the moving ring blades are modified and a Venturi air passage is adopted. The air outlet of the moving ring blades is designed as a curved flow, which makes the airflow direction more variable. The Venturi air passage is designed as a low-resistance curved and torsional channel. When used in conjunction with the moving ring blades, the nozzle outlet velocity can be increased with the same primary air volume, reducing the retention of coal powder in the inert region and reducing ventilation resistance. The air velocity gradually increases from the nozzle inlet to the outlet, reaching its maximum at the nozzle throat, which can establish a more efficient aerodynamic field and further improve the uniformity of the internal flow field of the coal mill.

[0041] In step S5 above, the modification of the moving ring blades and the adoption of the Venturi air passage structure are as follows: Figure 1 As shown, the modification of the moving ring blades changes the original direct-flow airflow to a curved-flow airflow, resulting in more variable airflow direction; for example... Figure 2 As shown, in conjunction with the Venturi air passage design, the nozzle velocity is increased. Compared with the direct flow pipe, the low-resistance curved and torsional channel has a variable airflow direction, and the coal powder is retained in the inert region to form an inert region, which reduces the retention of coal powder and can carry away the coal powder in time, thereby reducing the overall resistance of the coal mill.

[0042] Specifically, six symmetrically and evenly arranged temperature measuring points at the coal mill outlet are used for arbitrary deviation calculation and comparison, and the maximum temperature deviation calculation measuring point is added to the DCS pulverizing monitoring screen. While controlling the coal mill outlet temperature deviation, the coal bed thickness is judged based on the coal mill current and the signals from the three grinding roller lifting switch position measuring points. The coal mill current is normally controlled between 60% and 80% of the rated current. By adjusting the loading force through offset adjustment, the coal mill is always kept running under optimal conditions (60% to 80% output). At the same time, the shape of the moving ring blades is optimized using Venturi effect technology to establish a more efficient aerodynamic field, thereby improving the internal flow field of the coal mill. By adopting the above comprehensive treatment methods, the problems of large coal mill outlet temperature deviation and uneven powder output are solved. Example 2:

[0043] Please see Figure 1-2The method for comprehensively controlling the outlet temperature deviation of the coal mill includes an inner ring 1 and an outer ring 2. An air outlet ring 8 is fixedly installed between the inner ring 1 and the outer ring 2. The air outlet ring 8 is obliquely arranged and has multiple air outlets 801 that are opened through it. The air outlets 801 are bent. The multiple air outlets 801 are interconnected by through holes 802 inside the air outlet ring 8.

[0044] Furthermore, an inner upper baffle 3 is integrally connected to one side of the top of the inner ring 1, which limits and blocks the upper right side of the air outlet ring 8; an inner lower baffle 4 is integrally connected to one side of the bottom of the inner ring 1, which limits and blocks the lower right side of the air outlet ring 8.

[0045] A support plate is integrally connected to one side of the top of the outer ring 2. An upper outer first stop block 5 is fixedly connected above the support plate, and an upper outer second stop block 6 is fixedly connected above it. The upper outer first stop block 5, together with the upper outer second stop block 6, limits and blocks the upper left of the air outlet ring 8. An lower outer stop block 7 is integrally connected to one side of the bottom of the outer ring 2. The lower outer stop block 7 limits and blocks the lower left of the air outlet ring 8.

[0046] Specifically, in use, the inner upper baffle 3 and the outer lower baffle 7 are set as flat plate structures, the inner lower baffle 4 and the outer upper first baffle 5 are set as bent plate structures, and the outer upper second baffle 6 is set as a triangular block structure. Through the cooperation of the above components, the four positions of the air outlet ring 8 are fixed and limited between the inner ring 1 and the outer ring 2. The air outlet ring 8 always flows out in a curved direction. The air outlet ring 8 is set in the Venturi air passage. Due to the change of airflow direction, the retention of coal powder can be reduced, so as to carry away the coal powder in time and reduce the overall resistance of the coal mill.

[0047] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or equivalent structural, procedural, or functional transformations made using the description and drawings of this invention, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of protection of this invention.

Claims

1. A comprehensive method for controlling temperature deviation at the outlet of a coal mill, characterized in that, The specific steps are as follows: S1. Six temperature measuring points are symmetrically and evenly arranged at the outlet of the coal mill for arbitrary deviation calculation and comparison, and the maximum temperature deviation calculation measuring point is displayed on the DCS pulverizing monitoring screen. S2. During normal operation, the outlet temperature deviation should not exceed 5℃. When the outlet temperature deviation exceeds 10℃, the DCS will issue a color-changing alarm to remind the operators to intervene and adjust the control in time. S3. When the temperature deviation at the outlet of the coal mill is greater than 5℃, it indicates that the internal flow field is becoming more uneven, suggesting that the primary air velocity and air volume are too high. By reducing the hot primary air volume of the coal mill through offsetting, the air-coal ratio can be controlled, thereby adjusting the drying output of the coal mill, improving the internal flow field, and increasing the uniformity of the outlet air-coal mixture. S4. While controlling the temperature deviation at the coal mill outlet, determine the coal seam thickness based on the coal mill current and the signals from the measuring points at the positions of the three grinding roller lifting switches. When the current of the coal mill is found to be too low or too high, the signal of the grinding roller descending or rising to the correct position is used to clearly determine the amount of coal inside the coal mill, thereby further analyzing and determining the thickness of the coal bed. By adjusting the loading force through offset, the coal mill is always kept in optimal operating condition. S5. By modifying the moving ring blades and adopting the Venturi air passage, the nozzle outlet velocity is increased under the same primary air volume, reducing the retention of coal powder in the inert area, reducing ventilation resistance, and the air velocity gradually increases from the nozzle inlet to the outlet, reaching the maximum at the nozzle throat, establishing a more efficient aerodynamic field, and further improving the uniformity of the internal flow field of the coal mill. The moving ring blade in step S5 includes an inner ring (1) and an outer ring (2), and an air outlet ring (8) is fixedly arranged between the inner ring (1) and the outer ring (2). The air outlet ring (8) is set at an angle, and multiple air outlets (801) are opened through it. The air outlets (801) are set at a bend. The air outlet ring (8) is internally connected to multiple air outlets (801) through through holes (802); The inner ring (1) is integrally connected to an inner upper stop block (3) on one side of its top end. The inner upper stop block (3) limits and blocks the upper right side of the air outlet ring (8). The inner ring (1) is integrally connected to an inner lower stop block (4) on one side of its bottom end. The inner lower stop block (4) limits and blocks the lower right side of the air outlet ring (8). A support plate is integrally connected to one side of the top of the outer ring (2). An outer upper first stop block (5) is fixedly connected above the support plate, and an outer upper second stop block (6) is fixedly connected above it. The outer upper first stop block (5) cooperates with the outer upper second stop block (6) to limit and block the upper left of the air outlet ring (8). The bottom end of the outer ring (2) is integrally connected to an outer lower stop block (7), which limits and blocks the lower left side of the air outlet ring (8).

2. The comprehensive method for controlling coal mill outlet temperature deviation according to claim 1, characterized in that: In step S4, the current of the coal mill is normally controlled between 60% and 80% of the rated current.

3. The comprehensive method for controlling coal mill outlet temperature deviation according to claim 1, characterized in that: In step S4, the optimal operating condition for the coal mill output is controlled between 60% and 80%.

4. The comprehensive method for controlling coal mill outlet temperature deviation according to claim 1, characterized in that: In step S5, the air outlet of the moving ring blade is set to bend, which makes the airflow direction change.

5. The comprehensive method for controlling coal mill outlet temperature deviation according to claim 1, characterized in that: In step S5, the Chinese-made Qiuli air passage is configured as a low-resistance curved torsion channel and used in conjunction with a moving ring blade.

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