A device for measuring and controlling the primary air volume of a lignite blended coal mill and its control method

Abstract

The present invention relates to a primary air volume anti-blocking measuring device for a lignite blended coal mill and a control method thereof, comprising a DCS control system, three sets of primary air volume purge sampling pipelines and a compressed air pipeline; each set of primary air volume purge sampling pipelines comprises a primary air volume differential pressure transmitter, a standard differential pressure throttling orifice plate, a positive pressure side solenoid valve, a positive pressure side compressed air purge valve, a positive pressure side three-way joint, a positive pressure side sampling tube, a negative pressure side solenoid valve, a negative pressure side compressed air purge valve, a negative pressure side three-way joint and a negative pressure side sampling tube; all the solenoid valves, purge valves and primary air volume differential pressure transmitters in the three sets of primary air volume purge sampling pipelines are connected to the DCS control system for communication; the DCS control system controls the three sets of primary air volume purge sampling pipelines to perform purge work. In the present application, only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time, ensuring that the coal mill primary air volume automatic adjustment system will not exit the automatic control state due to the purge state.

Description

Technical Field

[0001] The invention relates to the technical field of thermal automatic control of coal-fired power plants, and in particular to a primary air volume anti-blocking measuring device for a lignite blended coal mill and a control method thereof. Background Art

[0002] Coal pulverizer is an extremely important equipment in coal-fired power plants, which grinds raw coal into fine coal powder required for entering the furnace. The primary air of the coal pulverizer is used as the conveying power to carry the coal powder in the coal pulverizer into the furnace. The accurate measurement and automatic adjustment and control of the primary air volume are of great significance to the safety and stability of the unit. In actual production, due to the large amount of dust particles in the working environment of the coal pulverizer, it is very easy for coal powder dust to block the sampling pipeline for measuring the primary air volume of the coal pulverizer. The primary air volume sampling pipeline of the coal pulverizer of most power plants needs to be manually purged at least once or twice a day according to the coal type and working conditions. When manually purging the sampling tube, it is necessary to first prompt the operating personnel to exit the automatic state of the DCS system coal pulverizer primary air volume adjustment system, and then go to the site to remove the connection joint between the transmitter and the sampling tube, and connect the compressed air hose for purging to the sampling pipeline. Frequent disassembly and installation will cause damage to the joint, and in severe cases, the transmitter will be unable to continue to be used. In recent years, in order to save the cost of coal-fired power generation, power generation companies have been operating in different degrees of lignite blending, which has caused different frequencies and severity of blockage of the primary air volume measurement pipeline of the coal mill under the three different working conditions of bituminous coal, lignite, and lignite blending. Therefore, the development of a coal mill primary air volume measurement device that can automatically purge and prevent the sampling pipeline from being blocked under lignite blending conditions has a wide range of application value.

[0003] In recent years, only a few scholars in China have studied the automatic purge device of differential pressure gas flowmeter. For example, the patent with publication number CN208902204U: an automatic purge device of differential pressure gas flowmeter, the automatic purge device includes a differential pressure transmitter, a three-valve group, a first connector, a three-way valve, and a stop valve. The three-way valve is a one-inlet and two-outlet three-way valve, one outlet end is connected to the differential pressure transmitter through the first connector, the other outlet end is connected to the pressure air intake line, the inlet end is connected to one end of the pressure pipe, the other end of the pressure pipe is connected to the stop valve through the second connector, and the stop valve is connected to the standard throttling device.

[0004] Another example is the patent with publication number CN204855079U: an automatic purge device for measuring pressure and differential pressure, which includes a purge pressure pipe, a purge pipeline, a pressure pipeline, a transmitter and an air source. The purge pressure pipe is a three-way pipe, and the purge pressure pipe is provided with a pressure inlet, a bypass purge port and a pressure outlet. The bypass purge port is connected to the air source through the purge pipeline, and the pressure outlet is connected to the transmitter through the pressure pipeline. The pressure pipeline includes a U-shaped tube.

[0005] The structure of the automatic purge device disclosed in the above patents is relatively complicated. When adding a bypass purge port or using a three-way valve, it is unnecessary to add a stop valve at the throttling device. In particular, there is no special description of the purge process of the primary air volume of the coal mill and a detailed explanation of the purge method. The primary air volume of the coal mill is an important automatic adjustment parameter of the pulverizing system. When the measuring device is automatically purged to prevent blockage, it must be interlocked with each other in the DCS system in combination with the thermal automatic adjustment logic. There is a major safety hazard that the automatic adjustment system of the primary air volume at the coal mill inlet fails when the primary air volume is automatically purged. The greater technical defect is that the purge device disclosed in the above patents cannot successfully solve the automatic purge and anti-blockage function of the primary air volume measuring device of the coal mill under the condition of lignite blending.

[0006] Therefore, it is necessary to design a DCS-integrated, low-cost, effective, and highly reliable primary air volume anti-blocking measuring device and control method for a lignite blended coal mill. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a device for preventing primary air volume blocking of a lignite blended coal mill with reasonable design, low cost, good effect and high reliability, and to give a control method thereof.

[0008] The technical solution adopted by the present invention to solve the above-mentioned problem is: a primary air volume anti-blocking measuring device for a lignite blending pulverizer, including a DCS control system, characterized in that it also includes three sets of primary air volume purge sampling pipelines and a compressed air pipeline; each set of primary air volume purge sampling pipelines includes a primary air volume differential pressure transmitter, a standard differential pressure throttling orifice plate, a positive pressure side solenoid valve, a positive pressure side compressed air purge valve, a positive pressure side three-way joint, a positive pressure side sampling tube, a negative pressure side solenoid valve, a negative pressure side compressed air purge valve, a negative pressure side three-way joint and a negative pressure side sampling tube; the standard differential pressure throttling orifice plate is fixed on the primary air volume pipeline of the pulverizer; one end of the positive pressure side sampling tube is connected to the positive pressure side of the standard differential pressure throttling orifice plate, the other end of the positive pressure side sampling tube is connected to the first port of the positive pressure side three-way joint, the second port of the positive pressure side three-way joint is connected to the positive pressure side solenoid valve, and the positive pressure side solenoid valve is connected to the primary air volume differential pressure transmitter. The positive pressure side three-way joint is connected to the compressed air pipeline through the positive pressure side purge pipeline, and the positive pressure side compressed air purge valve is installed on the positive pressure side purge pipeline; one end of the negative pressure side sampling tube is connected to the negative pressure side of the standard differential pressure throttling orifice plate, and the other end of the negative pressure side sampling tube is connected to the first port of the negative pressure side three-way joint, and the second port of the negative pressure side three-way joint is connected to the negative pressure side solenoid valve, and the negative pressure side solenoid valve is connected to the primary air volume differential pressure transmitter; the third port of the negative pressure side three-way joint is connected to the compressed air pipeline through the negative pressure side purge pipeline, and the negative pressure side compressed air purge valve is installed on the negative pressure side purge pipeline; all the solenoid valves, purge valves and primary air volume differential pressure transmitters in the three sets of primary air volume purge sampling pipelines are connected to the DCS control system in communication; the DCS control system controls the three sets of primary air volume purge sampling pipelines to perform purge work.

[0009] Preferably, the positive-pressure side solenoid valve and the negative-pressure side solenoid valve are both isolation valves that are electrically closed; and the positive-pressure side compressed air purge valve and the negative-pressure side compressed air purge valve are both purge valves that are electrically opened.

[0010] Preferably, the standard differential pressure throttling orifice plate is fixed to the primary air volume pipeline of the coal mill by welding.

[0011] Preferably, an air filter is provided on the compressed air pipeline.

[0012] The present invention also provides a control method for a primary air volume anti-blocking measuring device of a lignite blended coal mill, which sets: three sets of primary air volume purge sampling pipelines are numbered in sequence as a first set of primary air volume purge sampling pipelines, a second set of primary air volume purge sampling pipelines, and a third set of primary air volume purge sampling pipelines; the working state of the primary air volume purge sampling pipelines when not purging is: the positive pressure side solenoid valve and the negative pressure side solenoid valve are in an open state, and the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are in a closed state.

[0013] The control method is:

[0014] Step 1: Initialization: Connect the compressed air pipeline to the compressed air source. The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in each set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control; the measurement points of the three primary air volume differential pressure transmitters are introduced into the DCS control system, and then the median of the three is used for automatic adjustment of the primary air volume of the coal mill;

[0015] Step 2: The three sets of primary air volume purge sampling pipelines work in sequence: First, the first set of primary air volume purge sampling pipelines starts to work, and the positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the first set of primary air volume purge sampling pipelines are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T11 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T12 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T13 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T14 seconds, and then the second set of primary air volume purge sampling pipelines are triggered to start working;

[0016] in,

[0017] Parameter T11 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0018] Parameter T12 is the purge time of the first set of primary air volume purge sampling pipeline;

[0019] Parameter T13 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0020] Parameter T14 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0021] Step 3: The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the second set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T21 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T22 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T23 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T24 seconds, and then the third set of primary air volume purge sampling pipeline is triggered to start working;

[0022] in,

[0023] Parameter T21 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0024] Parameter T22 is the purge time of the second set of primary air volume purge sampling pipeline;

[0025] Parameter T23 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0026] Parameter T24 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0027] Step 4: The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the third set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T31 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T32 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T33 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T34 seconds, and the automatic purge of the coal mill primary air volume measurement sampling pipeline in this cycle is reset to end;

[0028] in,

[0029] Parameter T31 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0030] Parameter T32 is the purge time of the third set of primary air volume purge sampling pipeline;

[0031] Parameter T33 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0032] Parameter T34 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0033] Step 5: Optimize the control logic of the automatic adjustment system of the primary air volume of the coal mill. When the first set of primary air volume purge sampling pipelines is being purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter in the first set of primary air volume purge sampling pipelines is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the first set of primary air volume purge sampling pipelines in the purging state exits the automatic adjustment of the three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge, but temporarily uses the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines to take the average value; when the second set of primary air volume purge sampling pipelines is being purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines in the purging state exits the automatic adjustment of the three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge, but temporarily uses the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines to take the average value; when the second set of primary air volume purge sampling pipelines is being purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines in the purging state The device exits the automatic adjustment of three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; when the third set of primary air volume purge sampling pipeline is purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter in the third set of primary air volume purge sampling pipeline is forced to be "1" to bad quality, so that the primary air volume differential pressure transmitter in the third set of primary air volume purge sampling pipeline in the purge state exits the automatic adjustment of three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; prevent the inaccurate automatic adjustment of the primary air volume of the coal mill caused by the distortion of the primary air volume measurement point of the sampling pipeline in the purge state;

[0034] Step 6: Only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time. The three sets of primary air volume purge sampling pipelines are purged in turn to form a purge cycle. According to the purge frequency set in the DCS control system and the purge duration of each set of primary air volume purge sampling pipelines, the three sets of primary air volume purge sampling pipelines are purged.

[0035] Step 7: According to the coal type and working conditions of the coal mill, optimize the setting of different purge frequencies and the purge duration of each set of primary air volume purge sampling pipelines.

[0036] The core idea of ​​the present invention is that the three redundant sets of primary air volume purge sampling pipelines are all provided with positive pressure side solenoid valves and negative pressure side solenoid valves that are electrically closed, as well as positive pressure side compressed air purge valves and negative pressure side compressed air purge valves that are electrically opened. During purge, the positive pressure side solenoid valve and the negative pressure side solenoid valve must be closed at the same time, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time to purge the sampling pipeline with compressed air; after the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve must be closed at the same time, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve can be opened at the same time; only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time; when the pipeline is purged, the quality state of the primary air volume measuring point of the sampling pipeline is forced to be "1", ensuring that the primary air volume regulation system of the coal mill will not exit the automatic control state due to the purge state; according to the coal type and working condition of the coal mill, different automatic purge frequencies and sampling pipeline purge durations are optimally set.

[0037] Compared with the prior art, the present invention has the following advantages and effects: (1) a positive pressure side solenoid valve and a negative pressure side solenoid valve which are powered on and closed are provided, as well as a positive pressure side compressed air purge valve and a negative pressure side compressed air purge valve which are powered on and opened are provided, so as to ensure that the measurement sampling channel is unobstructed when the control power supply fails and the purge channel is closed, and the normal measurement of the primary air volume is not affected; (2) only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time. When the pipeline is purged, the quality status of the primary air volume measurement point of the sampling pipeline is forced to be "1", which ensures that the automatic adjustment system of the primary air volume of the coal mill will not exit the automatic control state due to the purge state; (3) according to the lignite blending operation, different automatic purge frequencies and purge durations are reasonably set. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 It is a structural schematic diagram of a primary air volume anti-blocking measurement device according to an embodiment of the present invention.

[0040] Figure 2 It is a logic diagram of the automatic purge control method for three sets of primary air volume purge sampling pipelines in an embodiment of the present invention.

[0041] Figure 3 It is a flow chart of optimizing the selection of three median values ​​of primary air volume in an embodiment of the present invention.

[0042] Description of reference numerals:

[0043] Figure 1 middle:

[0044] Air filter 51; Compressed air pipeline 52;

[0045] The first set of primary air volume purge sampling pipeline: primary air volume differential pressure transmitter 10, positive pressure side solenoid valve 11, positive pressure side compressed air purge valve 12, positive pressure side three-way joint 13, positive pressure side sampling tube 14, negative pressure side solenoid valve 15, negative pressure side compressed air purge valve 16, negative pressure side three-way joint 17, negative pressure side sampling tube 18, standard differential pressure throttle orifice plate 19;

[0046] The second set of primary air volume purge sampling pipeline: primary air volume differential pressure transmitter 20, positive pressure side solenoid valve 21, positive pressure side compressed air purge valve 22, positive pressure side three-way joint 23, positive pressure side sampling tube 24, negative pressure side solenoid valve 25, negative pressure side compressed air purge valve 26, negative pressure side three-way joint 27, negative pressure side sampling tube 28, standard differential pressure throttle orifice plate 29;

[0047] The third set of primary air volume purge sampling pipeline: primary air volume differential pressure transmitter 30, positive pressure side solenoid valve 31, positive pressure side compressed air purge valve 32, positive pressure side three-way joint 33, positive pressure side sampling tube 34, negative pressure side solenoid valve 35, negative pressure side compressed air purge valve 36, negative pressure side three-way joint 37, negative pressure side sampling tube 38, standard differential pressure throttle orifice plate 39;

[0048] Figure 2 middle:

[0049] 100-automatic purge interval;

[0050] 111- maximum value of closing travel time of solenoid valve 11 and solenoid valve 15;

[0051] 112-Purge time of the first set of primary air volume purge sampling pipeline;

[0052] 113 - maximum value of the closing stroke time of purge valve 12 and purge valve 16;

[0053] 114-the maximum value of the opening stroke time of the solenoid valve 11 and the solenoid valve 15;

[0054] 121-the maximum value of the closing stroke time of the solenoid valve 21 and the solenoid valve 25;

[0055] 122-Purge time of the second set of primary air volume purge sampling pipeline;

[0056] 123-the maximum value of the closing stroke time of the purge valve 22 and the purge valve 26;

[0057] 124-the maximum value of the opening stroke time of the solenoid valve 21 and the solenoid valve 25;

[0058] 131 - maximum value of closing travel time of solenoid valve 31 and solenoid valve 35;

[0059] 132-Purge time of the third set of primary air volume purge sampling pipeline;

[0060] 133 - maximum value of the closing stroke time of the purge valve 32 and the purge valve 36;

[0061] 134-The maximum value of the opening stroke time of the solenoid valve 31 and the solenoid valve 35. DETAILED DESCRIPTION

[0062] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0063] Example

[0064] See also Figures 1 to 3 .

[0065] This embodiment discloses a primary air volume anti-blocking measuring device for a lignite blended coal mill, comprising a DCS control system, three sets of primary air volume purging sampling pipelines, and a compressed air pipeline 52. An air filter 51 is provided on the compressed air pipeline 52, and the air filter 51 can effectively filter impurities and moisture in the compressed air to prevent water accumulation or dust impurities after the sampling tube is purged.

[0066] In this embodiment, each set of primary air volume purge sampling pipeline includes a primary air volume differential pressure transmitter, a standard differential pressure throttling orifice plate, a positive pressure side solenoid valve, a positive pressure side compressed air purge valve, a positive pressure side three-way joint, a positive pressure side sampling tube, a negative pressure side solenoid valve, a negative pressure side compressed air purge valve, a negative pressure side three-way joint and a negative pressure side sampling tube.

[0067] See also Figure 1The first set of primary air volume purge sampling pipeline includes a primary air volume differential pressure transmitter 10, a standard differential pressure throttling orifice plate 19, a positive pressure side solenoid valve 11, a positive pressure side compressed air purge valve 12, a positive pressure side three-way joint 13, a positive pressure side sampling tube 14, a negative pressure side solenoid valve 15, a negative pressure side compressed air purge valve 16, a negative pressure side three-way joint 17 and a negative pressure side sampling tube 18.

[0068] See also Figure 1 The second set of primary air volume purge sampling pipeline includes a primary air volume differential pressure transmitter 20, a standard differential pressure throttling orifice plate 29, a positive pressure side solenoid valve 21, a positive pressure side compressed air purge valve 22, a positive pressure side three-way joint 23, a positive pressure side sampling tube 24, a negative pressure side solenoid valve 25, a negative pressure side compressed air purge valve 26, a negative pressure side three-way joint 27 and a negative pressure side sampling tube 28.

[0069] See also Figure 1 The third set of primary air volume purge sampling pipeline includes a primary air volume differential pressure transmitter 30, a standard differential pressure throttling orifice plate 39, a positive pressure side solenoid valve 31, a positive pressure side compressed air purge valve 32, a positive pressure side three-way joint 33, a positive pressure side sampling tube 34, a negative pressure side solenoid valve 35, a negative pressure side compressed air purge valve 36, a negative pressure side three-way joint 37 and a negative pressure side sampling tube 38.

[0070] In this embodiment, the connection relationship of each component in each set of primary air volume purge sampling pipeline is as follows: the standard differential pressure throttling orifice is fixed on the primary air volume pipeline of the coal mill by welding; one end of the positive pressure side sampling tube is connected to the positive pressure side of the standard differential pressure throttling orifice, and the other end of the positive pressure side sampling tube is connected to the first port of the positive pressure side three-way joint, the second port of the positive pressure side three-way joint is connected to the positive pressure side solenoid valve, and the positive pressure side solenoid valve is connected to the primary air volume differential pressure transmitter; the third port of the positive pressure side three-way joint is connected to the compressed air pipe through the positive pressure side purge pipeline The positive-pressure side sampling tube is connected to the negative-pressure side of the standard differential pressure throttling orifice plate, and the other end of the negative-pressure side sampling tube is connected to the first port of the negative-pressure side three-way joint, and the second port of the negative-pressure side three-way joint is connected to the negative-pressure side solenoid valve, and the negative-pressure side solenoid valve is connected to the primary air volume differential pressure transmitter; the third port of the negative-pressure side three-way joint is connected to the compressed air pipeline 52 through the negative-pressure side purge pipeline, and the negative-pressure side compressed air purge valve is installed on the negative-pressure side purge pipeline.

[0071] In this embodiment, all solenoid valves, purge valves, and primary air volume differential pressure transmitters in the three sets of primary air volume purge sampling pipelines are communicatively connected to the DCS control system; the DCS control system controls the three sets of primary air volume purge sampling pipelines to perform the purge work.

[0072] In this embodiment, both the positive-pressure side solenoid valve and the negative-pressure side solenoid valve are isolation valves that are electrically closed; an isolation valve that is electrically closed is arranged at the inlet of the primary air volume differential pressure transmitter. The operating principle of the electrically closed valve can ensure that the isolation valve is in an open state when the control power supply fails, and does not affect the normal measurement of the primary air volume.

[0073] In this embodiment, both the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side are energized-open purge valves. The energized-open operation principle ensures that the purge valve is in a closed state when the control power supply fails, without affecting the normal measurement of the primary air volume.

[0074] In the present embodiment, a control method for the primary air volume anti-blocking measuring device of the lignite blending pulverizer is also provided, and it is set that: three sets of primary air volume purge sampling pipelines are numbered as the first set of primary air volume purge sampling pipelines, the second set of primary air volume purge sampling pipelines, and the third set of primary air volume purge sampling pipelines in sequence; the working state of the primary air volume purge sampling pipelines when not purging is: the positive pressure side solenoid valve and the negative pressure side solenoid valve are in the open state, and the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are in the closed state.

[0075] The control method is:

[0076] Step 1: Initialization: Connect the compressed air pipeline 52 to the compressed air source. The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in each set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control; the measuring points of the three primary air volume differential pressure transmitters are introduced into the DCS control system, and then the median of the three is used for automatic adjustment of the primary air volume of the coal mill;

[0077] Step 2: Three sets of primary air volume purge sampling pipelines work in sequence: First, the first set of primary air volume purge sampling pipelines starts to work, and the positive pressure side solenoid valve 11, positive pressure side compressed air purge valve 12, negative pressure side solenoid valve 15, and negative pressure side compressed air purge valve 16 in the first set of primary air volume purge sampling pipelines are connected to the DCS control system for timed automatic purge program control, first close the positive pressure side solenoid valve 11 and the negative pressure side solenoid valve 15 at the same time for T11 seconds, and then open the positive pressure side compressed air purge valve 12 and the negative pressure side compressed air purge valve 16 at the same time for T12 seconds, after the purge is completed, close the positive pressure side compressed air purge valve 12 and the negative pressure side compressed air purge valve 16 at the same time for T13 seconds, and then open the positive pressure side solenoid valve 11 and the negative pressure side solenoid valve 15 at the same time for T14 seconds, and then trigger the second set of primary air volume purge sampling pipelines to start working;

[0078] in,

[0079] Parameter T11 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0080] Parameter T12 is the purge time of the first set of primary air volume purge sampling pipeline;

[0081] Parameter T13 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0082] Parameter T14 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0083] Step 3: The positive pressure side solenoid valve 21, the positive pressure side compressed air purge valve 22, the negative pressure side solenoid valve 25, and the negative pressure side compressed air purge valve 26 in the second set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control. The positive pressure side solenoid valve 21 and the negative pressure side solenoid valve 25 are first closed at the same time for T21 seconds, and then the positive pressure side compressed air purge valve 22 and the negative pressure side compressed air purge valve 26 are opened at the same time for T22 seconds. After the purge is completed, the positive pressure side compressed air purge valve 22 and the negative pressure side compressed air purge valve 26 are first closed at the same time for T23 seconds, and then the positive pressure side solenoid valve 21 and the negative pressure side solenoid valve 25 are opened at the same time for T24 seconds, and then the third set of primary air volume purge sampling pipeline is triggered to start working;

[0084] in,

[0085] Parameter T21 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0086] Parameter T22 is the purge time of the second set of primary air volume purge sampling pipeline;

[0087] Parameter T23 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0088] Parameter T24 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0089] Step 4: the positive pressure side solenoid valve 31, the positive pressure side compressed air purge valve 32, the negative pressure side solenoid valve 35, and the negative pressure side compressed air purge valve 36 in the third set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control, first close the positive pressure side solenoid valve 31 and the negative pressure side solenoid valve 35 at the same time for T31 seconds, and then open the positive pressure side compressed air purge valve 32 and the negative pressure side compressed air purge valve 36 at the same time for T32 seconds, after the purge is completed, close the positive pressure side compressed air purge valve 32 and the negative pressure side compressed air purge valve 36 at the same time for T33 seconds, and then open the positive pressure side solenoid valve 31 and the negative pressure side solenoid valve 35 at the same time for T34 seconds, and reset to end the automatic purge of the coal mill primary air volume measurement sampling pipeline in this cycle;

[0090] in,

[0091] Parameter T31 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place;

[0092] Parameter T32 is the purge time of the third set of primary air volume purge sampling pipeline;

[0093] Parameter T33 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place;

[0094] Parameter T34 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened;

[0095] Step 5: Optimize the control logic of the automatic adjustment system of the primary air volume of the coal mill. When the first set of primary air volume purge sampling pipelines is purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter 10 in the first set of primary air volume purge sampling pipelines is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the first set of primary air volume purge sampling pipelines in the purge state exits the automatic adjustment and takes the median value, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge, but temporarily uses the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines to take the average value; when the second set of primary air volume purge sampling pipelines is purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter 20 in the second set of primary air volume purge sampling pipelines is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines in the purge state exits the automatic adjustment and takes the median value. The transmitter exits the automatic adjustment of three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; when the third set of primary air volume purge sampling pipeline is purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter 30 in the third set of primary air volume purge sampling pipeline is forced to be "1" for bad quality, so that the primary air volume differential pressure transmitter in the third set of primary air volume purge sampling pipeline in the purge state exits the automatic adjustment of three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; prevent the inaccurate automatic adjustment of the primary air volume of the coal mill caused by the distortion of the primary air volume measurement point of the sampling pipeline in the purge state;

[0096] Step 6: Only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time. The three sets of primary air volume purge sampling pipelines are purged in turn to form a purge cycle. According to the purge frequency set in the DCS control system and the purge duration of each set of primary air volume purge sampling pipelines, the three sets of primary air volume purge sampling pipelines are purged.

[0097] Step 7: According to the coal type and working conditions of the coal mill, optimize the setting of different purge frequencies and the purge duration of each set of primary air volume purge sampling pipelines.

[0098] In this embodiment, the three redundant sets of primary air volume purge sampling pipelines are all provided with positive pressure side solenoid valves and negative pressure side solenoid valves that are electrically closed, as well as positive pressure side compressed air purge valves and negative pressure side compressed air purge valves that are electrically opened. During purge, the positive pressure side solenoid valve and the negative pressure side solenoid valve must be closed at the same time before the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time to purge the sampling pipeline with compressed air; after the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve must be closed at the same time before the positive pressure side solenoid valve and the negative pressure side solenoid valve can be opened at the same time; only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time; when the pipeline is purged, the quality state of the primary air volume measurement point of the sampling pipeline is forced to be "1", ensuring that the primary air volume regulation system of the coal mill will not exit the automatic control state due to the purge state; according to the coal type and working condition of the coal mill, different automatic purge frequencies and sampling pipeline purge durations are optimally set.

[0099] In this embodiment, a positive pressure side solenoid valve and a negative pressure side solenoid valve that are powered on and closed are provided, as well as a positive pressure side compressed air purge valve and a negative pressure side compressed air purge valve that are powered on and opened are provided, so as to ensure that the measurement sampling channel is unobstructed when the control power supply fails and the purge channel is closed, and the normal measurement of the primary air volume is not affected. Only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time. When the pipeline is purged, the quality status of the primary air volume measurement point of the sampling pipeline is forced to "1", ensuring that the automatic adjustment system of the primary air volume of the coal mill will not exit the automatic control state due to the purge state. According to the lignite blending work, different automatic purge frequencies and purge durations are reasonably set.

[0100] The following is a specific application analysis: Taking a coal mill primary air volume anti-blocking measuring device with automatic purge and anti-blocking function and its control method for a 660MW ultra-supercritical coal-fired unit in a power plant as an example, the practical application of a lignite blending coal mill primary air volume measuring and anti-blocking device and its control method of the present invention is introduced.

[0101] The unit is equipped with six coal mills, and each coal mill is equipped with three redundant primary air flow measurement points. The primary air volume of a single coal mill is equipped with three Rosemount differential pressure transmitters imported from Germany, six isolation valves with power off, six purge valves with power on, six sets of three-way joints, six sampling tubes, three sets of standard differential pressure throttling orifice plates, and the unit DCS control system adopts the OVATION control system. The above instruments and equipment are installed and named according to the structural diagram of the embodiment. The primary air volume differential pressure transmitters 10, 20, 30, the positive pressure side solenoid valves 11, 21, 31, the negative pressure side solenoid valves 15, 25, 35, the positive pressure side compressed air purge valves 12, 22, 32, and the negative pressure side compressed air purge valves 16, 26, 36 are all connected to the DCS control system for automatic purge control, and the coal mill primary air volume automatic adjustment system is optimized and controlled.

[0102] Each coal mill has a separate automatic purge start-up and exit operation for the primary air volume. However, when the operating personnel manually start the automatic purge function of the primary air volume sampling device, the purge start-up of the six coal mills must be separated by more than 5 to 10 minutes in sequence to ensure that the primary air volume of the six coal mills is not in the automatic purge state to prevent blockage of the sampling pipeline at the same time.

[0103] After multiple manual opening and closing operations in the DCS control system, the full stroke time of the six electrically closed isolation valves from opening to closing or closing to opening is 4 to 5 seconds, and the full stroke time of the six electrically opened purge valves from opening to closing or closing to opening is 3 to 4 seconds. Therefore, the isolation valve closing time parameters T11, T21, and T31 are all set to 7 seconds (conservatively about 2 seconds more than the isolation valve closing stroke time), and the purge time parameters T12, T22, and T32 are automatically switched and selected according to the coal type and operating conditions of the coal mill. The purge valve closing time parameters T13, T23, and T33 are 6 seconds (conservatively about 2 seconds more than the purge solenoid valve closing stroke time), and the isolation valve opening time parameters T14, T24, T34, and T44 are all 7 seconds (conservatively about 2 seconds more than the isolation solenoid valve opening stroke time).

[0104] The study developed an automatic purge control strategy for a single coal mill grinding bituminous coal, lignite, and lignite blended combustion. In actual operation, it was found that when burning lignite, the period of blockage of the purge sampling pipeline was very short, and an abnormality would occur at the measuring point in about 5-7 hours; when lignite was blended combustion, the period of blockage of the purge sampling pipeline would improve, and an abnormality would occur at the measuring point in about 6-9 hours; when burning bituminous coal, the purge sampling pipeline was not easy to be blocked, and an abnormality would occur at the measuring point in about 14 hours. Combined with the actual operating conditions, the following three purge strategies were developed for the three combustion methods:

[0105] When burning lignite, the purge cycle T51 is set to 6 hours, and the purge time T12, T22, and T32 of each set of sampling pipelines are all 70 seconds (excluding the travel time of about 4 seconds for opening the purge valve, the actual purge time is about 65 seconds);

[0106] When lignite is mixed with coal, the purge cycle T51 is set to 8 hours, and the purge time T12, T22, and T32 of each sampling pipeline are all 60 seconds (excluding the travel time of about 4 seconds for opening the purge valve, the actual purge time is about 55 seconds);

[0107] When burning bituminous coal, the purge cycle T51 is set to 15 hours, and the purge time T12, T22, and T32 of each sampling pipeline are all 45 seconds (excluding the travel time of about 4 seconds for opening the purge valve, the actual purge time is about 40 seconds).

[0108] In the DCS operation screen, after the operator activates the automatic purge function of the primary air volume of each coal mill, the device immediately and orderly performs automatic purge of the three sets of primary air volume sampling pipelines of this coal mill according to the selected coal quality conditions. The automatic purge will be performed periodically every T51 hours. The automatic purge control parameters are shown in Table 1.

[0109] Table 1 Automatic purge control parameters

[0110]

[0111] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the protection scope of the present invention. Any changes and modifications made by any technician familiar with the technology without departing from the concept and scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A device for measuring the primary air volume of a lignite blended coal mill to prevent blockage, including a DCS control system, characterized in that: It also includes three sets of primary air volume purge sampling pipelines and a compressed air pipeline; each set of primary air volume purge sampling pipelines includes a primary air volume differential pressure transmitter, a standard differential pressure throttling orifice plate, a positive pressure side solenoid valve, a positive pressure side compressed air purge valve, a positive pressure side three-way joint, a positive pressure side sampling tube, a negative pressure side solenoid valve, a negative pressure side compressed air purge valve, a negative pressure side three-way joint and a negative pressure side sampling tube; the standard differential pressure throttling orifice plate is fixed on the primary air volume pipeline of the coal mill; One end of the positive pressure side sampling tube is connected to the positive pressure side of the standard differential pressure throttling orifice plate, the other end of the positive pressure side sampling tube is connected to the first port of the positive pressure side three-way joint, the second port of the positive pressure side three-way joint is connected to the positive pressure side solenoid valve, the positive pressure side solenoid valve is connected to the primary air volume differential pressure transmitter; the third port of the positive pressure side three-way joint is connected to the compressed air pipeline through the positive pressure side purge pipeline, and the positive pressure side compressed air purge valve is installed on the positive pressure side purge pipeline; One end of the negative pressure side sampling tube is connected to the negative pressure side of the standard differential pressure throttling orifice plate, the other end of the negative pressure side sampling tube is connected to the first port of the negative pressure side three-way joint, the second port of the negative pressure side three-way joint is connected to the negative pressure side solenoid valve, and the negative pressure side solenoid valve is connected to the primary air volume differential pressure transmitter; the third port of the negative pressure side three-way joint is connected to the compressed air pipeline through the negative pressure side purge pipeline, and the negative pressure side compressed air purge valve is installed on the negative pressure side purge pipeline; All solenoid valves, purge valves and primary air volume differential pressure transmitters in the three sets of primary air volume purge sampling pipelines are connected to the DCS control system; the DCS control system controls the three sets of primary air volume purge sampling pipelines to perform purge work; The positive pressure side solenoid valve and the negative pressure side solenoid valve are both isolation valves that are electrically closed; the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are both purge valves that are electrically opened; An air filter is arranged on the compressed air pipeline.

2. The anti-blocking measuring device for primary air volume of a lignite blended coal mill according to claim 1 is characterized in that: The standard differential pressure throttling orifice plate is fixed on the primary air volume pipeline of the coal mill by welding.

3. A control method for the anti-blocking measuring device of primary air volume of a coal mill for brown coal blending combustion as claimed in claim 1 or 2, characterized in that: Setting: The three sets of primary air volume purge sampling pipelines are numbered as the first set of primary air volume purge sampling pipelines, the second set of primary air volume purge sampling pipelines, and the third set of primary air volume purge sampling pipelines in sequence; the working state of the primary air volume purge sampling pipelines when not purging is: the positive pressure side solenoid valve and the negative pressure side solenoid valve are in the open state, and the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are in the closed state; The control method is: Step 1: Initialization: Connect the compressed air pipeline to the compressed air source. The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in each set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control; the measurement points of the three primary air volume differential pressure transmitters are introduced into the DCS control system, and then the median of the three is used for automatic adjustment of the primary air volume of the coal mill; Step 2: The three sets of primary air volume purge sampling pipelines work in sequence: First, the first set of primary air volume purge sampling pipelines starts to work, and the positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the first set of primary air volume purge sampling pipelines are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T11 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T12 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T13 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T14 seconds, and then the second set of primary air volume purge sampling pipelines are triggered to start working; in, Parameter T11 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place; Parameter T12 is the purge time of the first set of primary air volume purge sampling pipeline; Parameter T13 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place; Parameter T14 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the first set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened; Step 3: The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the second set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T21 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T22 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T23 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T24 seconds, and then the third set of primary air volume purge sampling pipeline is triggered to start working; in, Parameter T21 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place; Parameter T22 is the purge time of the second set of primary air volume purge sampling pipeline; Parameter T23 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both purge valves can be closed in place; Parameter T24 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the second set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened; Step 4: The positive pressure side solenoid valve, positive pressure side compressed air purge valve, negative pressure side solenoid valve, and negative pressure side compressed air purge valve in the third set of primary air volume purge sampling pipeline are connected to the DCS control system for timed automatic purge program control. First, the positive pressure side solenoid valve and the negative pressure side solenoid valve are closed at the same time for T31 seconds, and then the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve can be opened at the same time for T32 seconds. After the purge is completed, the positive pressure side compressed air purge valve and the negative pressure side compressed air purge valve are closed at the same time for T33 seconds, and then the positive pressure side solenoid valve and the negative pressure side solenoid valve are opened at the same time for T34 seconds, and the automatic purge of the coal mill primary air volume measurement sampling pipeline in this cycle is reset to end; in, Parameter T31 is the maximum value of the isolation valve closing stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be closed in place; Parameter T32 is the purge time of the third set of primary air volume purge sampling pipeline; Parameter T33 is the maximum value of the closing stroke time range of the compressed air purge valve on the positive pressure side and the compressed air purge valve on the negative pressure side in the third set of primary air volume purge sampling pipeline, plus 1-4 seconds, to ensure that both purge valves can be closed in place; Parameter T34 is the maximum value of the isolation valve opening stroke time range used by the positive pressure side solenoid valve and the negative pressure side solenoid valve in the third set of primary air volume purge sampling pipeline plus 1-4 seconds to ensure that both isolation valves can be fully opened; Step 5: Optimize the control logic of the automatic adjustment system of the primary air volume of the coal mill. When the first set of primary air volume purge sampling pipelines is being purged, the quality status of the primary air volume monitored by the primary air volume differential pressure transmitter in the first set of primary air volume purge sampling pipelines is set to "1" bad quality, so that the primary air volume differential pressure transmitter in the first set of primary air volume purge sampling pipelines in the purging state exits the automatic adjustment of the three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge, but temporarily uses the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines to take the average value; when the second set of primary air volume purge sampling pipelines is being purged, the quality status of the primary air volume monitored by the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines is set to "1" bad quality, so that the primary air volume differential pressure transmitter in the second set of primary air volume purge sampling pipelines in the purging state The device exits the automatic adjustment of the three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; when the third set of primary air volume purge sampling pipeline is purged, the quality state of the primary air volume monitored by the primary air volume differential pressure transmitter in the third set of primary air volume purge sampling pipeline is set to "1" bad quality, so that the primary air volume differential pressure transmitter in the third set of primary air volume purge sampling pipeline in the purge state exits the automatic adjustment of the three medians, so that the automatic adjustment system of the primary air volume of the coal mill does not need to exit during the automatic purge period, and the primary air volume monitored by the two primary air volume differential pressure transmitters in the other two sets of primary air volume purge sampling pipelines is temporarily used to take the average value; prevent the inaccurate automatic adjustment of the primary air volume of the coal mill caused by the distortion of the primary air volume measurement point of the sampling pipeline in the purge state; Step 6: Only one of the three sets of primary air volume purge sampling pipelines can be purged at the same time. The three sets of primary air volume purge sampling pipelines are purged in sequence to form a purge cycle. According to the purge frequency set in the DCS control system and the purge duration of each set of primary air volume purge sampling pipelines, the three sets of primary air volume purge sampling pipelines are purged; Step 7: According to the coal type and working conditions of the coal mill, optimize the setting of different purge frequencies and the purge duration of each set of primary air volume purge sampling pipelines.

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