Undisturbed purging detection method and system for pressure measuring point of coal mill

Abstract

The invention provides an undisturbed purging detection method and system for a pressure measuring point of a coal mill, and the system comprises a purging execution device which comprises an instrument gas source, a purging loop, a pressure measuring loop and a measuring loop which are connected through a pipeline. The purging loop is provided with a purging electromagnetic valve and a purging pressure monitoring transmitter; the measurement loop is provided with a measurement isolation electromagnetic valve and a mill group monitoring transmitter; the pressure tapping loop is provided with a pressure tapping switching electromagnetic valve which is communicated with the purging loop or the measuring loop in a switching manner; the control device executes a time sequence control program comprising the steps of isolation, purging and recovery, detects faults in each step and generates fault prompt information, so that the real-time measured value of the mill group monitoring transmitter is kept in a logic value register during purging for logic protection and regulation, and the service life of the mill group monitoring transmitter is prolonged. The method can effectively prevent high-pressure air flow from directly impacting a measurement loop during purging to cause transmitter damage or measurement value jump, and meanwhile, fault second-level response can be realized through multi-dimensional pressure monitoring and intelligent fault-tolerant logic.

Description

Technical Field

[0001] This invention relates to the field of coal mill technology, and in particular to a non-disruptive purging detection method and system for pressure tapping points in a coal mill. Background Technology

[0002] In the pulverizing system of thermal power plants, the pressure tapping points of coal mills are in a high-concentration gas-solid two-phase flow condition for a long time. They are easily affected by factors such as changes in coal quality, coal powder adhesion, and ash content in the air duct, which can lead to blockage of the pressure tapping circuit, resulting in measurement deviations, bad values, and other problems.

[0003] Existing manual and automatic purging methods have many limitations: manual purging operations are high-risk, labor-intensive, and prone to equipment damage; traditional automatic purging devices use side-station integrated control, which has problems such as single communication interface, high risk of solenoid valve failure, lack of effective fault monitoring, and high cost.

[0004] Therefore, there is an urgent need for a system that can perform online, non-disruptive purging and has full-process fault detection capabilities. Summary of the Invention

[0005] This invention provides a non-disruptive purging detection method and system for pressure tapping points in coal mills, which solves the defects of high risk of solenoid valve failure, lack of effective fault monitoring, and high cost in existing automatic purging devices.

[0006] On one hand, the present invention provides a non-disruptive purging detection system for pressure tapping points in a coal mill, comprising: The purging actuator includes an instrument air source, a purging circuit, a pressure tapping circuit, and a measurement circuit connected by pipelines; the purging circuit is equipped with a purging solenoid valve and a purging pressure monitoring transmitter; the measurement circuit is equipped with a measurement isolation solenoid valve and a grinding mill monitoring transmitter; the pressure tapping circuit is equipped with a pressure tapping switching solenoid valve for switching between the purging circuit and the measurement circuit. The control device is used to execute a timing control program that includes isolation, purging and recovery steps, and to detect faults in the isolation, purging and recovery steps and generate fault prompt information. Specifically, after issuing a purging command, the logic value involved in the protection and calculation logic is maintained at the current value output by the mill monitoring transmitter at the moment the purging command is issued. The measurement circuit is isolated, and the purging circuit is connected to the pressure tapping circuit to perform purging. After issuing a purging end command, the purging circuit is isolated, and the measurement circuit is connected to the pressure tapping circuit to resume measurement. Furthermore, after detecting the fault indication information, purging is interrupted, and a reset command is sent to the purging solenoid valve, the measurement isolation solenoid valve, and the pressure tapping switching solenoid valve.

[0007] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill, wherein the control device executes a timing control program including isolation, purging, and recovery steps through the following purging mode: The measurement point selection purging mode responds to the operator station's manual purging command for the selected measurement point; The pre-start purging mode of the grinding unit is triggered when the signal for the opening of the hot primary air damper of the coal mill is received; The abnormal fluctuation purging mode is triggered when the fluctuation rate of the pressure measuring point exceeds a preset threshold. The periodic purging mode is triggered when the mill runs continuously for more than the set period and the unit load is stable.

[0008] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill is provided, wherein the abnormal fluctuation purging mode includes: Calculate the standard deviation and peak-to-peak value of the pressure values ​​of the mill monitoring transmitter within the set sampling time; When the standard deviation is greater than a first preset threshold and the peak-to-peak value is greater than a second preset threshold, it is determined to be an abnormal fluctuation.

[0009] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill is provided, wherein the control device is further used for: The abnormal fluctuation determination is delayed during the operation of the hot and cold air dampers of the grinding unit.

[0010] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill is provided, wherein the control device is further used for: After the measuring isolation solenoid valve is closed, if the pressure value of the mill monitoring transmitter is greater than the first fault threshold, the measuring isolation solenoid valve will be closed and a fault will be output. After the pressure switching solenoid valve is switched to the purge position, if the pressure value of the purge pressure monitoring transmitter does not rise to the second fault threshold, the purge position fault of the pressure switching solenoid valve will be output. After the purge solenoid valve is opened, if the pressure value of the purge pressure monitoring transmitter is lower than the third fault threshold, the open fault of the purge solenoid valve will be output. After the purge solenoid valve is closed, the pressure value of the purge pressure monitoring transmitter is higher than the fourth fault threshold, and outputs a fault indicating that the purge solenoid valve is closed. After the pressure switching solenoid valve is switched to the measurement position, if the pressure value of the purge pressure monitoring transmitter is higher than the fifth fault threshold, the measurement position fault of the pressure switching solenoid valve will be output. After the measuring isolation solenoid valve is opened, if the pressure value of the mill monitoring transmitter is lower than the sixth fault threshold, the open fault of the measuring isolation solenoid valve will be output.

[0011] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill is provided, wherein the control device is further used for: In response to feedback from operators confirming that the real-time measured values ​​of the monitoring points are stable, the logical value is restored.

[0012] According to the present invention, a non-disruptive purging detection system for pressure tapping points in a coal mill is provided, wherein the timing control program includes: After the purging command is issued, there is a first preset time delay, and the measuring isolation solenoid valve is energized and closed to isolate the mill group monitoring transmitter. After the measuring isolation solenoid valve is energized and closed, a second preset time delay is applied, and the pressure tapping switching solenoid valve is energized and switched to connect the pressure tapping circuit with the purging circuit. After connecting the pressure tapping circuit and the purging circuit, and delaying for a third preset time, the purging solenoid valve is energized and opened to establish a purging path and measure the purging pressure through the monitoring transmitter. After the purge solenoid valve is opened, purge for a fourth preset time, then close the purge solenoid valve to stop purge. After the purge solenoid valve closes, there is a fifth preset time delay; the pressure tapping switching solenoid valve is de-energized and reset; the purge circuit is depressurized to the air; and the pressure tapping circuit is connected to the measurement circuit. After the pressure tapping circuit is connected to the measurement circuit, after a sixth preset time delay, the measurement isolation solenoid valve is de-energized and opens, restoring the pressure tapping of the mill monitoring transmitter. After the measuring isolation solenoid valve opens, a seventh preset time is elapsed before sending a "purge complete" feedback message.

[0013] According to the present invention, a non-disruptive purging detection system for pressure tapping points of a coal mill is provided, wherein the purging solenoid valve is a direct-acting normally closed two-position two-way solenoid valve. The measuring isolation solenoid valve is a direct-acting normally open two-position two-way solenoid valve. The pressure-tapping switching solenoid valve is a direct-acting two-position five-way solenoid valve. Its purge position connects the pressure-tapping circuit and the purge circuit, and its measurement position connects the pressure-tapping circuit and the measurement circuit.

[0014] The non-disruptive purging detection system for pressure tapping points in a coal mill provided by the present invention further includes: The human-machine interface is used to display the purging status, fault alarms, real-time values ​​and logic values ​​of measuring points; and provides operation interfaces for manual purging triggering, automatic mode activation, purging interruption and fault reset.

[0015] On the other hand, the present invention also provides a method for undisturbed purging detection of pressure tapping points in a coal mill, which is applied to the undisturbed purging detection system for pressure tapping points in a coal mill as described in any of the above claims, the method comprising: After issuing the purging command, the measurement circuit of the purging actuator is isolated, and the purging circuit of the purging actuator is connected to the pressure tapping circuit of the purging actuator to perform purging; After issuing the purging end command, the purging circuit is isolated, and the measurement circuit of the purging actuator is connected to the pressure tapping circuit to restore measurement; Upon detecting the fault message, the purging process is interrupted, and a reset command is sent to the purging solenoid valve, the measurement isolation solenoid valve, and the pressure switching solenoid valve of the purging actuator.

[0016] The present invention provides a non-disruptive purging detection method and system for pressure tapping points in a coal mill. It includes an instrument gas source, a purging circuit, a pressure tapping circuit, and a measurement circuit connected by pipelines. A purging solenoid valve and a purging pressure monitoring transmitter are installed in the purging circuit. A measurement isolation solenoid valve and a mill monitoring transmitter are installed in the measurement circuit. A pressure tapping switching solenoid valve is installed in the pressure tapping circuit to switch between the purging circuit and the measurement circuit. A control device executes a timing control program including isolation, purging, and recovery steps. It also detects faults during the isolation, purging, and recovery steps and generates fault warning information. This system maintains the real-time measurement value of the mill monitoring transmitter in a logic value register during purging for use by protection and regulation logic. It effectively prevents high-pressure airflow from directly impacting the measurement circuit during purging, which could damage the transmitter or cause measurement value jumps. Furthermore, multi-dimensional pressure monitoring and intelligent fault-tolerant logic enable second-level fault response. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the non-disruptive purging detection system for pressure tapping points in a coal mill provided in an embodiment of the present invention; Figure 2 It is a specific flowchart of a timing control program; Figure 3 This is a schematic flowchart of the non-disruptive purging detection method for pressure tapping points in a coal mill provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] Figure 1 This is a schematic diagram of the non-disruptive purging detection system for pressure tapping points in a coal mill provided in an embodiment of the present invention.

[0021] like Figure 1 As shown, the coal mill pressure tapping point undisturbed purging detection system provided in this embodiment of the invention may include a purging execution device 11 and a control device 12.

[0022] The purging actuator 11 may include an instrument air source G, a purging circuit L1, a pressure tapping circuit L3, and a measurement circuit L2 connected by pipelines; the purging circuit L1 is equipped with a purging solenoid valve D1 and a purging pressure monitoring transmitter P1; the measurement circuit L2 is equipped with a measurement isolation solenoid valve D2 and a mill monitoring transmitter P2; the pressure tapping circuit L3 is equipped with a pressure tapping switching solenoid valve D3, used to switch between connecting the purging circuit L1 and the measurement circuit L2.

[0023] See also Figure 1 The purging actuator 11 may further include a first needle valve S1 and an air source filter E installed in the purging circuit L1, a second needle valve S2 installed in the measuring circuit L2, and a third needle valve S3 installed in the pressure tapping circuit L3. The first needle valve S1, the second needle valve S2, and the third needle valve S3 are manual isolation valves for the purging circuit L1, the measuring circuit L2, and the pressure tapping circuit L3, respectively, used to isolate the air path in case of equipment failure.

[0024] In one specific implementation, the purging solenoid valve D1 is a direct-acting normally closed two-position two-way solenoid valve, which is energized and opened during purging to allow the instrument's air to purge. The measuring isolation solenoid valve D2 is a direct-acting normally open two-position two-way solenoid valve, which is energized and closed during purging to isolate the grinding mill monitoring transmitter P2. The pressure tapping switching solenoid valve D3 is a direct-acting two-position five-way solenoid valve, whose purging position connects the pressure tapping circuit L3 and the purging circuit L1, and its measuring position connects the pressure tapping circuit L3 and the measuring circuit L2. When purging is initiated, it is energized and switched to connect the pressure tapping circuit and the purging circuit L1; when purging is completed, it is de-energized and switched to connect the pressure tapping circuit and the measuring circuit L2.

[0025] In a specific implementation process, the purging actuator 11, manual isolation valve (three needle valves), two transmitters and purging circuit L1 can be integrated into the purging protection cabinet of the grinding group measuring point. The existing grinding group measuring point transmitters can be reused and installed. A prefabricated connector for the sampling tube is left outside the cabinet to connect with the original grinding group measuring point pressure tapping circuit. A prefabricated connector for the purging tube is left outside the cabinet to connect with the instrument gas supply line. The instrument gas line is equipped with a filter and a high-pressure drain valve. A 220V power supply circuit breaker is left inside the cabinet to supply power to the solenoid valve.

[0026] The original mill set measuring point instrument protection cabinet can be removed, while retaining the original distributed control system (DCS) to transmitter control lines; install the mill set measuring point purging protection cabinet and connect the corresponding prefabricated connectors outside the cabinet; lay cables from the DCS room to the mill set measuring point protection cabinet, respectively for the switching signals of the solenoid valve and the analog signals of the monitoring transmitter; take a 220V power supply from the thermal control safety power cabinet in the power distribution room to drive the solenoid valve switching; complete the DCS logic configuration and screen configuration; and perform live commissioning of the system.

[0027] In one specific implementation, the control device 12 is used to execute a timing control program that includes isolation, purging and recovery steps, and to detect faults in the isolation, purging and recovery steps and generate fault prompt information.

[0028] After issuing a purging command, the logic value involved in the protection and calculation logic is maintained at the current value output by the mill monitoring transmitter P2 at the moment the purging command is issued. The measurement circuit L2 is isolated by controlling the purging solenoid valve D1, the measurement isolation solenoid valve D2, and the pressure tapping switching solenoid valve D3, while the purging circuit L1 is connected to the pressure tapping circuit L3 for purging. After issuing a purging end command, the purging circuit L1 is isolated by controlling the purging solenoid valve D1, the measurement isolation solenoid valve D2, and the pressure tapping switching solenoid valve D3, while the measurement circuit L2 is connected to the pressure tapping circuit L3 to restore measurement. Furthermore, upon detecting the fault indication information, purging is interrupted, and a reset command is sent to the purging solenoid valve D1, the measurement isolation solenoid valve D2, and the pressure tapping switching solenoid valve D3. Simultaneously, the operator can input feedback confirming the stability of the real-time measurement value at the measuring point. Upon receiving this feedback, a response can be initiated to restore the logic value.

[0029] In this embodiment, during soot blowing, the logic value involved in protection and calculation logic is maintained at the current value output by the mill monitoring transmitter P2 at the moment the purging command is issued, so as to avoid protection malfunction caused by purging. After the soot blowing ends, the operator inputs and confirms that the real-time measurement value of the measuring point is stable, and then uses the real-time value collected by the mill monitoring transmitter P2 to restore the logic value, so as to avoid step fluctuations in the control quantity and achieve disturbance-free soot blowing.

[0030] In one specific implementation, the timing control program includes: After the purging command is issued, there is a first preset time delay, and the measuring isolation solenoid valve D2 is energized and closed to isolate the mill group monitoring transmitter. After the measuring isolation solenoid valve D2 is energized and closed, a second preset time is delayed, and the pressure tapping switching solenoid valve is energized and switched to connect the pressure tapping circuit with the purging circuit L1. After connecting the pressure tapping circuit and the purging circuit L1, and delaying for a third preset time, the purging solenoid valve D1 is energized and opened, establishing a purging path and measuring the purging pressure through the monitoring transmitter. After the purge solenoid valve D1 is opened, purge for a fourth preset time, then close the purge solenoid valve D1 to stop purge. After the purge solenoid valve D1 is closed, there is a fifth preset time delay. The pressure tapping switching solenoid valve is de-energized and reset. The purge circuit L1 is depressurized to the air. The pressure tapping circuit is connected to the measurement circuit L2. After the pressure tapping circuit is connected to the measurement circuit L2, after a sixth preset time delay, the measurement isolation solenoid valve D2 is de-energized and opens, restoring the pressure tapping of the mill monitoring transmitter. After the measurement isolation solenoid valve D2 opens, a seventh preset time is elapsed before sending a "purge complete" feedback message.

[0031] Specifically, see Figure 2 , Figure 2 It is a specific flowchart of a timing control program, such as Figure 2 As shown, the purging procedure employs timing control, utilizing a delay logic timeline to execute a step-by-step control strategy of isolation followed by purging: a. After a 5-second delay following the issuance of the purging command, the measuring isolation solenoid valve D2 is energized and closed, and the isolation mill monitoring transmitter P2 is activated. b. After a 5-second delay, if the measuring isolation solenoid valve D2 does not fail to close, the pressure switching solenoid valve D3 is energized and switched, connecting the pressure tapping circuit to the purging circuit L1. If the measuring isolation solenoid valve D2 fails to close, the fault protection is activated (the measuring isolation solenoid valve D2 is de-energized, causing it to open). c. After a 5-second delay, if the pressure switching solenoid valve D3 does not experience a switching fault, the purging solenoid valve D1 will be energized and opened, establishing the purging path. The purging pressure monitoring transmitter P1 will measure the purging pressure. If the pressure switching solenoid valve D3 experiences a switching fault, fault protection will be activated (the measuring isolation solenoid valve D2 will be de-energized, causing it to open; the pressure switching solenoid valve D3 will be de-energized and reset, restoring it to its measuring position). d. Purge for 20 seconds (i.e., Figure 2 After a 20-second delay, the high-pressure purging ends, the purging solenoid valve D1 is de-energized and closes, and the purging stops. During the purging process, if the purging solenoid valve D1 does not experience an opening fault, the purging continues for 20 seconds, and then the purging solenoid valve D1 is de-energized and closes. If the purging solenoid valve D1 experiences an opening fault, fault protection is activated (the measuring isolation solenoid valve D2 is de-energized, causing it to open; the pressure tapping switching solenoid valve D3 is de-energized and reset, restoring it to its measuring position; the purging solenoid valve D1 is de-energized, causing it to close). e. After a 5-second delay, if the purge solenoid valve D1 does not fail to close, the pressure tapping switching solenoid valve D3 is de-energized and reset, the purge circuit L1 is depressurized to air, and the pressure tapping circuit is connected to the measurement circuit L2. If the purge solenoid valve D1 fails to close, the fault protection is executed (the measurement isolation solenoid valve D2 is de-energized, causing it to open; the pressure tapping switching solenoid valve D3 is de-energized and reset, causing it to return to the measurement position; the purge solenoid valve D1 is de-energized, causing it to close). f. After a 5-second delay, if the pressure switching solenoid valve D3 does not experience a switching fault, the measuring isolation solenoid valve D2 will be de-energized and open, and the mill monitoring transmitter P2 will resume measurement. If the pressure switching solenoid valve D3 experiences a switching fault, the fault protection will be executed (the measuring isolation solenoid valve D2 will be de-energized, causing it to open; the pressure switching solenoid valve D3 will be de-energized and reset, causing it to return to the measuring position). g. After a 5-second delay, if the measuring isolation solenoid valve D2 does not show a closing fault, send a "purge complete" feedback and send it to the human-machine operation window for further confirmation; if the measuring isolation solenoid valve D2 shows a closing fault, execute the fault protection (the measuring isolation solenoid valve D2 is de-energized, causing the measuring isolation solenoid valve D2 to open).

[0032] In a specific implementation process, the logic for the whole-process fault self-check is as follows: After the measuring isolation solenoid valve D2 is closed, if the pressure value of the mill monitoring transmitter P2 is greater than the first fault threshold, it will output a fault indicating that the measuring isolation solenoid valve D2 is closed. After the pressure switching solenoid valve D3 is switched to the purge position, if the pressure value of the purge pressure monitoring transmitter P1 does not rise to the second fault threshold, the purge position fault of the pressure switching solenoid valve D3 will be output. After the purge solenoid valve D1 is opened, if the pressure value of the purge pressure monitoring transmitter P1 is lower than the third fault threshold, the open fault of the purge solenoid valve D1 will be output. After the purge solenoid valve D1 is closed, if the pressure value of the purge pressure monitoring transmitter P1 is higher than the fourth fault threshold, it will output a fault indicating that the purge solenoid valve D1 is closed. After the pressure switching solenoid valve D3 is switched to the measurement position, if the pressure value of the purge pressure monitoring transmitter P1 is higher than the fifth fault threshold, the measurement position fault of the pressure switching solenoid valve D3 will be output. After the measuring isolation solenoid valve D2 is opened, if the pressure value of the mill monitoring transmitter P2 is lower than the sixth fault threshold, the open fault of the measuring isolation solenoid valve D2 will be output.

[0033] Specifically, (1) After the measuring isolation solenoid valve D2 is energized and closed, the measuring circuit L2 should be at low static pressure. If the measured value of the mill monitoring transmitter P2 is still greater than 1 kPa at this time, an alarm “D2 closed fault” will be issued. (2) When the pressure switching solenoid valve D3 is switched on and the pressure tapping circuit is connected to the purging circuit L1, if the pressure tapping circuit is not completely blocked (the measured value of the mill monitoring transmitter P2 is greater than 1 kPa when the measuring isolation solenoid valve D2 is not closed), the measured value of the purging pressure monitoring transmitter P1 should be greater than 1 kPa. Otherwise, an alarm will be issued for "D3 purging position fault". (3) After the purge solenoid valve D1 is energized and opened, the purge passage is established. If the measured value of the purge pressure monitoring transmitter P1 is less than 20 kPa, an alarm “D1 open fault” will be issued. (4) When the purging solenoid valve D1 is de-energized and closed, purging stops. At this time, the purging pressure monitoring transmitter P1 measures the pressure at the grinding unit measuring point. If the measured value is greater than 10 kPa, an alarm “D1 closed fault” will be issued. (5) When the pressure switching solenoid valve D3 is de-energized and reset, the pressure tapping circuit is connected to the measurement circuit L2, and the purging circuit L1 is depressurized to the air. If the measured value of the purging pressure monitoring transmitter P1 is greater than 1 kPa at this time, an alarm "D3 measurement position fault" will be issued. (6) When the isolation solenoid valve D2 is de-energized and opens, the mill monitoring transmitter P2 resumes measurement. If the measured value of P2 is less than 1 kPa, an alarm for "D2 opening fault" will be issued. When a fault is detected in any step, an alarm for "purge fault" will be issued and the purging main program will be reset.

[0034] The undisturbed purging detection system for the coal mill pressure tapping point in this embodiment is configured with an instrument gas source G, a purging circuit L1, a pressure tapping circuit L3, and a measurement circuit L2 connected by pipelines. A purging solenoid valve D1 and a purging pressure monitoring transmitter P1 are installed in the purging circuit L1; a measurement isolation solenoid valve D2 and a mill monitoring transmitter P2 are installed in the measurement circuit L2; and a pressure tapping switching solenoid valve D3 is installed in the pressure tapping circuit L3 to switch between the purging circuit L1 and the measurement circuit L2. A timing control program including isolation, purging, and recovery steps is executed by the control device 12. Faults during the isolation, purging, and recovery steps are detected, and fault prompts are generated. This system maintains the real-time measurement value of the mill monitoring transmitter P2 in a logic value register during purging for use by protection and regulation logic. It effectively prevents high-pressure airflow from directly impacting the measurement circuit L2 during purging, which could damage the transmitter or cause measurement value jumps. Furthermore, multi-dimensional pressure monitoring and intelligent fault-tolerant logic enable second-level fault response.

[0035] In one specific implementation, the control device 12 executes a timing control program that includes isolation, purging, and recovery steps through the following purging mode: The measurement point selection purging mode responds to manual purging commands from the operator station for selected measurement points. In other words, operators can independently select mill measurement points in the mill purging window on the unit's DCS operator station screen for sequential purging or perform individual purging of a single measurement point. This mode offers operators greater autonomy, allowing them to focus on purging key measurement points based on different mill coal blending characteristics, such as susceptibility to clogging or ignition. This results in high monitoring efficiency and aligns with the current need for implementing "one mill, one policy" measures.

[0036] The pre-start purging mode of the mill is triggered when the hot primary air damper of the coal mill is opened. In other words, when the mill is shut down, the different opening and closing states of the mill outlet door and the hot and cold primary air dampers create turbulence within the mill, causing coal dust and ash to accumulate at the sampling ports. Before starting the mill, the hot primary air needs to be turned on for preheating to increase the coal mill outlet temperature. With the automatic purging function of this mill in operation, the opening signal of the hot primary air damper of the coal mill is used as the pre-start signal, and a comprehensive purging of the sampling ports is performed before the mill starts, which greatly reduces abnormal fluctuations in the sampling ports during mill operation.

[0037] The abnormal fluctuation purging mode is triggered when the fluctuation rate of the pressure measuring point exceeds a preset threshold.

[0038] In a specific implementation process, the standard deviation and peak-to-peak value of the pressure value of the mill monitoring transmitter P2 within a set sampling time can be calculated; when the standard deviation is greater than a first preset threshold and the peak-to-peak value is greater than a second preset threshold, it is determined to be an abnormal fluctuation.

[0039] Specifically, when the automatic purging function of the mill is in operation, the abnormal fluctuation judgment of the pressure and flow measurement point is introduced. When the abnormal judgment is triggered, the unit's soft light alarm is detected in time, and the corresponding measurement point is purged to restore normal monitoring.

[0040] The judgment of abnormal fluctuations at pressure flow measurement points is based on the dynamic fluctuation rate calculation formula:

[0041] when ,and The judgment was that the measurement points fluctuated greatly, with the standard deviation being particularly high. This reflects the overall fluctuation dispersion of the measuring point within the set sampling time, peak-to-peak value. It reflects the peak value of the instantaneous fluctuation of the measuring point within the set sampling time.

[0042] This represents the i-th pressure sample value (unit: kPa) within the set sampling time. This represents the average pressure value within the set sampling time; n represents the number of sampling points within the set sampling time (e.g., n=300 for a setting of 30 seconds). The standard deviation threshold coefficient is taken as 2%-3% of the measurement range. For example, when the measurement range is 10 kPa, α=0.03 corresponds to 0.3 kPa. This represents the peak-to-peak threshold coefficient (taken as 5%-6% of the measurement range, e.g., when the range is 10 kPa, β=0.06 corresponds to 0.6 kPa). Indicates the measurement range of the measuring point.

[0043] In a specific implementation process, in order to avoid the need to open / close the cold and hot air dampers when the grinding unit undergoes changes in operating conditions such as coal quantity and temperature, and to prevent the actual changes in air volume and air pressure from triggering abnormal fluctuations and purging when adjusting the cold and hot air dampers, it is also necessary to shield the abnormal fluctuations of the pressure measuring points according to the above conditions, that is, to delay the judgment of the abnormal fluctuations during the operation of the grinding unit's cold and hot air dampers.

[0044] Specifically, the system can trigger a delay to shield abnormal fluctuations and initiate purging under conditions such as opening and closing commands for the cold primary air damper and the hot primary air damper, and changes in the opening command of the cold primary air damper exceeding ±5%. This prevents the system from misinterpreting pressure changes caused by normal adjustments as "measuring point blockage or malfunction," thus incorrectly triggering the purging procedure.

[0045] In a specific implementation, the periodic purging mode is triggered when the continuous running time of the grinding mill exceeds the set cycle and the unit load is stable. When the automatic purging function of the grinding mill is in operation, the purging cycle calculation is introduced when the pre-start purging of the grinding mill is completed. The load command sent by the power grid to the unit and the unit response load are taken as feedforwards. When the continuous rate of change of the power grid load command and the unit response load curve is lower than the set value and lasts for 15 minutes, it is considered that the current unit load is stable. When the continuous running time of the grinding mill exceeds the set purging cycle, a full purging of the grinding mill measuring points is performed and a new round of purging cycle is recalculated. This effectively prevents abnormalities in measuring points caused by long-term uninterrupted operation of the bottom and middle layer grinding mills.

[0046] In a specific implementation, the system may also include a human-machine interface for displaying purging status, fault alarms, real-time values ​​and logic values ​​of measuring points; and provide interfaces for manual purging triggering, automatic mode activation, purging interruption and fault reset.

[0047] Specifically, the design can be based on the grinding group screen of the DCS operator station. The measuring point purging window can be brought up from the grinding group screen. The purging window is designed with function blocks such as purging status, fault monitoring, measuring point selection, current measuring point value, measuring point logic value, operator station manual purging, automatic purging activation, interrupted purging, and fault reset. It is also possible to jump to a secondary window in the window to perform purging operation on a single measuring point of the grinding group.

[0048] Among them, the design of the measuring point purging window is as follows: Purging status: Displays whether the purging program is currently running. When automatic purging is started, it displays "Purge in progress" and when it ends, it displays "Purge complete". Fault monitoring: Displays whether the current purging fault self-test program has been triggered. When any fault is triggered, "Purge Fault" is displayed. After the fault is investigated, the thermal engineer confirms the reset and displays "Fault Reset". Measurement point selection: Display the mill group monitoring measurement points as purging options: inlet primary air pressure, inlet primary air volume, upper / lower grinding bowl differential pressure, grinding bowl / sealing air differential pressure, outlet primary air pressure. Select any measurement point and the button will jump to the secondary window; Secondary window: Allows selection of any single measuring point on the grinding assembly for purging operation; Current value at the measuring point: The real-time value converted from the milliampere value sent by the transmitter to the DCS, continuously measured in real time, and not affected by the purging process; Measurement point logic value: The real-time value of the measurement point, after purging and fault signal self-holding calculation, participates in the unit logic holding value; Manual purging at the operator station: Operators can perform purging by selecting measurement points through the purging window frame or by selecting individual measurement points through the secondary window; Automatic purging activation: When the operator activates the automatic purging of the mill's measuring points, the purging process of the measuring points will be automatically executed when conditions such as pre-start purging, abnormal fluctuation purging, and periodic purging are met. Interruption of purging: If the operator encounters an emergency during the purging process and needs to restore the monitoring of the mill's measuring points, the operator can actively interrupt the purging procedure. Fault Reset: After troubleshooting and eliminating the fault, thermal engineers perform a reset procedure.

[0049] In a specific implementation process, the non-disruptive purging detection system for coal mill pressure tapping points of the present invention has the following beneficial effects: First, it can take into account the potential dangers of mill production and operation from multiple perspectives, meet the independent needs of operation and maintenance monitoring, fit the operating conditions and interlocking logic of most thermal power plant pulverizing systems, and at the same time make up for the limitations of the current mainstream purging scheme of side-station integrated control.

[0050] Secondly, it has open and reasonable computing logic, relatively uninterrupted program execution, high scalability of main equipment linkage, complete control system algorithm with online parameter adjustment, reliable and intuitive step-by-step fault monitoring, user-friendly human-machine interaction and high adaptability. With the characteristics of distributed deployment of execution and control equipment, it has the features of convenient installation, system stability, strong substitutability and high compatibility, which can significantly reduce installation and debugging costs and reduce manpower maintenance.

[0051] Third, it can significantly improve the accuracy of monitoring points, directly enhance the operational stability of the pulverizing system, and ensure smooth purging execution. Automatic purging, especially pre-start purging and abnormal fluctuation purging, has a significant effect on the prevention of active monitoring point faults, greatly reducing monitoring point defects. Combined with the purging process and pressure algorithm, the fault judgment alarm is accurate, saving thermal engineers time in troubleshooting. Under special operating conditions, the system can decisively reset purging if manually interrupted or automatically interrupted due to purging faults, restoring normal monitoring conditions in the first instance, with timely response and a high safety factor.

[0052] Based on the same general inventive concept, this invention also protects a method for non-disruptive purging detection of pressure tapping points in a coal mill. The non-disruptive purging detection method for pressure tapping points in a coal mill provided by this invention is described below. The non-disruptive purging detection method for pressure tapping points in a coal mill described below can be referred to in correspondence with the non-disruptive purging detection system for pressure tapping points in a coal mill described above.

[0053] Figure 3 This is a flowchart illustrating the non-disruptive purging detection method for pressure tapping points in a coal mill provided in an embodiment of the present invention. The method is applied to the control device within the non-disruptive purging detection system for pressure tapping points in a coal mill. Figure 3 As shown, the undisturbed purging detection method for the coal mill pressure tapping points in this embodiment includes the following steps: 201. After issuing the purging command, the measurement circuit L2 of the purging actuator is isolated, and the purging circuit L1 of the purging actuator is connected to the pressure tapping circuit of the purging actuator to perform purging; 202. After issuing the purging end command, isolate the purging circuit L1 and connect the measurement circuit L2 of the purging actuator to the pressure tapping circuit to restore measurement; 203. Upon detecting the fault message, interrupt the purging process and send a reset command to the purging solenoid valve, the measurement isolation solenoid valve, and the pressure switching solenoid valve of the purging actuator.

[0054] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A non-disruptive purging detection system for pressure tapping points in a coal mill, characterized in that, include: The purging actuator includes an instrument air source, a purging circuit, a pressure tapping circuit, and a measurement circuit connected by pipelines; the purging circuit is equipped with a purging solenoid valve and a purging pressure monitoring transmitter; the measurement circuit is equipped with a measurement isolation solenoid valve and a grinding mill monitoring transmitter; the pressure tapping circuit is equipped with a pressure tapping switching solenoid valve for switching between the purging circuit and the measurement circuit. The control device is used to execute a timing control program that includes isolation, purging and recovery steps, and to detect faults in the isolation, purging and recovery steps and generate fault prompt information. Specifically, after issuing a purging command, the logic value involved in the protection and calculation logic is maintained at the current value output by the mill monitoring transmitter at the moment the purging command is issued. The measurement circuit is isolated, and the purging circuit is connected to the pressure tapping circuit to perform purging. After issuing a purging end command, the purging circuit is isolated, and the measurement circuit is connected to the pressure tapping circuit to resume measurement. Furthermore, after detecting the fault indication information, purging is interrupted, and a reset command is sent to the purging solenoid valve, the measurement isolation solenoid valve, and the pressure tapping switching solenoid valve.

2. The undisturbed purging detection system for pressure tapping points in a coal mill according to claim 1, characterized in that, The control device executes a timing control program that includes isolation, purging, and recovery steps through the following purging mode: The measurement point selection purging mode responds to the operator station's manual purging command for the selected measurement point; The pre-start purging mode of the grinding unit is triggered when the signal for the opening of the hot primary air damper of the coal mill is received; The abnormal fluctuation purging mode is triggered when the fluctuation rate of the pressure measuring point exceeds a preset threshold. The periodic purging mode is triggered when the mill runs continuously for more than the set period and the unit load is stable.

3. The undisturbed purging detection system for coal mill pressure tapping points according to claim 2, characterized in that, In the abnormal fluctuation purge mode: Calculate the standard deviation and peak-to-peak value of the pressure values ​​of the mill monitoring transmitter within the set sampling time; When the standard deviation is greater than a first preset threshold and the peak-to-peak value is greater than a second preset threshold, it is determined to be an abnormal fluctuation.

4. The undisturbed purging detection system for coal mill pressure tapping points according to claim 3, characterized in that, The control device is also used for: The abnormal fluctuation determination is delayed during the operation of the hot and cold air dampers of the grinding unit.

5. The undisturbed purging detection system for coal mill pressure tapping points according to claim 1, characterized in that, The control device is also used for: After the measuring isolation solenoid valve is closed, if the pressure value of the mill monitoring transmitter is greater than the first fault threshold, the measuring isolation solenoid valve will be closed and a fault will be output. After the pressure switching solenoid valve is switched to the purge position, if the pressure value of the purge pressure monitoring transmitter does not rise to the second fault threshold, the purge position fault of the pressure switching solenoid valve will be output. After the purge solenoid valve is opened, if the pressure value of the purge pressure monitoring transmitter is lower than the third fault threshold, the open fault of the purge solenoid valve will be output. After the purge solenoid valve is closed, the pressure value of the purge pressure monitoring transmitter is higher than the fourth fault threshold, and outputs a fault indicating that the purge solenoid valve is closed. After the pressure switching solenoid valve is switched to the measurement position, if the pressure value of the purge pressure monitoring transmitter is higher than the fifth fault threshold, the measurement position fault of the pressure switching solenoid valve will be output. After the measuring isolation solenoid valve is opened, if the pressure value of the mill monitoring transmitter is lower than the sixth fault threshold, the open fault of the measuring isolation solenoid valve will be output.

6. The undisturbed purging detection system for coal mill pressure tapping points according to claim 1, characterized in that, The control device is also used for: In response to feedback from operators confirming that the real-time measured values ​​of the monitoring points are stable, the logical value is restored.

7. The undisturbed purging detection system for coal mill pressure tapping points according to claim 1, characterized in that, The timing control program includes: After the purging command is issued, there is a first preset time delay, and the measuring isolation solenoid valve is energized and closed to isolate the mill group monitoring transmitter. After the measuring isolation solenoid valve is energized and closed, a second preset time delay is applied, and the pressure tapping switching solenoid valve is energized and switched to connect the pressure tapping circuit with the purging circuit. After connecting the pressure tapping circuit and the purging circuit, and delaying for a third preset time, the purging solenoid valve is energized and opened to establish a purging path and measure the purging pressure through the monitoring transmitter. After the purge solenoid valve is opened, purge for a fourth preset time, then close the purge solenoid valve to stop purge. After the purge solenoid valve closes, there is a fifth preset time delay; the pressure tapping switching solenoid valve is de-energized and reset; the purge circuit is depressurized to the air; and the pressure tapping circuit is connected to the measurement circuit. After the pressure tapping circuit is connected to the measurement circuit, after a sixth preset time delay, the measurement isolation solenoid valve is de-energized and opens, restoring the pressure tapping of the mill monitoring transmitter. After the measuring isolation solenoid valve opens, a seventh preset time is elapsed before sending a "purge complete" feedback message.

8. The undisturbed purging detection system for coal mill pressure tapping points according to any one of claims 1-7, characterized in that, The purge solenoid valve is a direct-acting normally closed two-position two-way solenoid valve. The measuring isolation solenoid valve is a direct-acting normally open two-position two-way solenoid valve. The pressure-tapping switching solenoid valve is a direct-acting two-position five-way solenoid valve. Its purge position connects the pressure-tapping circuit and the purge circuit, and its measurement position connects the pressure-tapping circuit and the measurement circuit.

9. The undisturbed purging detection system for coal mill pressure tapping points according to any one of claims 1-7, characterized in that, Also includes: The human-machine interface is used to display the purging status, fault alarms, real-time values ​​and logic values ​​of measuring points; and provides operation interfaces for manual purging triggering, automatic mode activation, purging interruption and fault reset.

10. A method for undisturbed purging and testing of pressure tapping points in a coal mill, characterized in that, The method applied to the undisturbed purging detection system for pressure tapping points of a coal mill according to any one of claims 1-9 includes: After issuing the purging command, the measurement circuit of the purging actuator is isolated, and the purging circuit of the purging actuator is connected to the pressure tapping circuit of the purging actuator to perform purging; After issuing the purging end command, the purging circuit is isolated, and the measurement circuit of the purging actuator is connected to the pressure tapping circuit to restore measurement; Upon detecting the fault message, the purging process is interrupted, and a reset command is sent to the purging solenoid valve, the measurement isolation solenoid valve, and the pressure switching solenoid valve of the purging actuator.

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