A method and device for measuring the concentration of pulverized coal in a pulverizing system of a coal-fired power plant

Abstract

The present invention belongs to the field of gas-solid two-phase flow measurement, specifically, a method and device for measuring the concentration of primary air pulverized coal in a pulverizing system of a coal-fired power plant. The device of the present invention includes a stagnation tube, a dust collecting bin, a compressed air tank, a differential pressure sensor, a temperature and humidity sensor, a data acquisition card, a computer, and an anemometer. The pulverized coal in the primary air pulverized coal airflow enters the stagnation tube and decelerates under the action of gas drag, thereby increasing the static pressure of the gas in the stagnation tube. The concentration of pulverized coal is calculated by quantitatively measuring the increase in the static pressure. The momentum of pulverized coal is directly related to its mass concentration and movement speed, and is basically unrelated to the composition (coal quality) of pulverized coal. Compared with measurement methods that rely on characteristics and indicators such as static electricity, electromagnetic waves, and capacitance, the principle of the method of the present invention is more intrinsic, more reliable, and has fewer interference factors. It does not rely on complex electronic equipment, so the cost is lower.

Description

Technical Field

[0001] The invention belongs to the field of gas-solid two-phase flow measurement, and specifically, relates to a method and a device for measuring the primary air pulverized coal concentration of a pulverizing system of a coal-fired power plant. Background Art

[0002] In coal-fired power plants, the pulverizing system grinds coarse coal blocks / coal particles into finer coal powder and uses airflow to transport it into the furnace for combustion. The parameters of coal powder (such as fineness and uniformity) have a direct and significant impact on its combustion process. For a direct-blowing pulverizing system, there may be more than 20 to 30 pulverizing pipelines for a single unit. The pulverized coal flow rate of each pulverizing pipe generally has a large deviation, resulting in the aerodynamic field and combustion conditions in the furnace deviating from the design conditions, causing a series of problems such as incomplete combustion, high NOx generation rate, water-cooled wall scouring / coking, heat exchange surface overheating / tube bursting, and high cooling water consumption. In order to improve combustion efficiency and operational safety and reduce the formation of pollutants, online measurement of pulverized coal concentration in the pulverizing system (especially the direct-blowing pulverizing system) (as well as subsequent equipment and operation control based on this parameter) is very necessary.

[0003] At present, most coal-fired power plants are not equipped with coal powder concentration measurement devices. A few power plants have installed traditional sampling tube measurement systems (such as flute sampling tubes) on the separation outlet pipeline of the pulverizing system, and manually extract, collect and weigh the coal powder to convert it into coal powder concentration. The device is simple and low-cost, but there are problems such as poor sampling representativeness and serious wear and damage of the sampling tube. In addition, the accuracy, reliability and repeatability of its manual operation are difficult to guarantee. Even fewer power plants have adopted electrostatic measurement devices to infer coal powder concentration by sensing and measuring the charge state of coal powder particles. However, the main disadvantage is that its measurement signal has only relative significance (the signal cannot establish a quantitative relationship with the absolute concentration of coal powder), and the measurement accuracy is greatly affected by wind and powder parameters such as moisture and coal quality. It is difficult to adapt to the actual production situation of coal-fired power plants with variable coal quality, and the investment cost is too high. It is difficult to promote and apply it under the current situation where coal-fired power plants are in difficult operation.

[0004] In view of the above situation and taking into full consideration the actual needs of the power plant, the present invention proposes a method and device for measuring the concentration of pulverized coal by relying on the momentum of the pulverized coal. Summary of the invention

[0005] In order to solve the problem that the existing pulverizing system lacks effective means for measuring coal powder concentration, the present invention provides a method and device for measuring the coal powder concentration in the pulverizing system of a coal-fired power plant, based on the physical mechanism that the momentum of the particle phase (coal powder) can be converted into the static pressure energy of the gas phase (air).

[0006] The technical solution adopted by the present invention to solve the above-mentioned problem is: a method for measuring the pulverized coal concentration of a pulverizing system of a coal-fired power plant, characterized in that the process is as follows: a stagnation tube is placed in a main pipeline, one end of the stagnation tube is an open end and faces the flow direction of the primary air pulverized coal, the other end of the stagnation tube is a closed end and is connected to a dust collecting bin, a static pressure measuring hole is opened at the other end of the stagnation tube and the main pipeline and a No. 1 differential pressure sensor is connected; an anemometer is installed on the main pipeline, and the anemometer is connected to a No. 2 differential pressure sensor; the No. 1 differential pressure sensor and the No. 2 differential pressure sensor are both connected to a data acquisition card and to a computer; the pulverized coal in the primary air pulverized coal airflow enters the stagnation tube and is decelerated under the action of gas drag, thereby increasing the static pressure of the gas in the stagnation tube, and the pulverized coal concentration is calculated according to the following formula by quantitatively measuring the increase in static pressure:

[0007]

[0008] Among them, △p s is the difference between the static pressure at the closed end of the stagnation tube and the static pressure of the main pipeline airflow, u0 is the flow rate of the main pipeline airflow, ρ g is the density of the main pipeline gas, k is the pressure head conversion factor, and k is the core parameter of the calculation method, which is preferably obtained through experimental calibration.

[0009] The velocity of the main pipeline air flow is measured by a wind velocity tube that is not affected by coal powder. The wind velocity tube preferably adopts a BS-I type velocity measuring tube; the static pressure of the main pipeline gas is measured by a static pressure hole opened on the main pipeline, or by a static pressure tube arranged "back to back" with the stagnation tube.

[0010] The dust collecting bin is opened with a hole and connected to a compressed air back-blowing system. When the dust collecting bin is connected to compressed air, the airflow blows up the coal powder in the dust collecting bin and sends it back to the main pipeline through the open end of the stagnation pipe, thereby cleaning the dust collecting bin.

[0011] The temperature and humidity sensor is connected to the main pipeline to measure the temperature and relative humidity of the gas in the main pipeline for subsequent calculation of gas parameters.

[0012] The device in the method for measuring the pulverized coal concentration in the pulverizing system of a coal-fired power plant is characterized in that it includes a stagnation tube, a dust collecting bin, a compressed air tank, a No. 1 differential pressure sensor, a data acquisition card, a computer, a wind speed tube and a No. 2 differential pressure sensor, wherein the stagnation tube is arranged in the main pipeline, one end of the stagnation tube is an open end and is arranged toward the flow direction of the primary air pulverized coal, the other end of the stagnation tube is a closed end and is connected to the dust collecting bin, static pressure measuring holes are provided on the other end of the stagnation tube and the main pipeline and are respectively connected to the No. 1 differential pressure sensor through the stagnation tube static pressure guide pipe and the main pipeline static pressure guide pipe; a wind speed tube is installed on the main pipeline, and the wind speed tube is connected to the No. 2 differential pressure sensor; a backflush pipe is provided on the dust collecting bin, the backflush pipe is connected to the compressed air tank, and a stop valve is installed on the backflush pipe; the No. 1 differential pressure sensor and the No. 2 differential pressure sensor are both connected to the data acquisition card, and the data acquisition card is connected to the computer.

[0013] The stagnation tube can be a straight tube or a curved tube, and its opening can be a straight opening or a bell-mouth structure.

[0014] Compared with the prior art, the present invention has the following advantages and effects: the momentum of coal powder is directly related to its mass concentration and movement speed, and is basically unrelated to the composition (coal quality) of the coal powder. Compared with the measurement methods that rely on characteristics and indicators such as static electricity, electromagnetic waves, and capacitance, the principle of the method of the present invention is more intrinsic, more reliable, has fewer interference factors, and does not rely on complex electronic equipment, thus lowering the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0016] Figure 2 Schematic diagram of the measurement principle of an embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram of the structure of the measuring head of the straight tube type stagnation tube with a dust collecting bin according to an embodiment of the present invention (front view, left view).

[0018] Figure 4 It is a schematic structural diagram of a measuring head of a curved tube type stagnation tube with a dust collecting bin according to an embodiment of the present invention.

[0019] Figure 5 It is a schematic diagram of the structure of a stagnation tube with an opening end being a "bell mouth" according to an embodiment of the present invention.

[0020] Figure 6 It is a schematic diagram of the back-to-back design structure of the main pipeline static pressure guiding pipe and the stagnation pipe in an embodiment of the present invention.

[0021] In the figure: main pipeline 1, stagnation pipe 2, dust collection bin 3, compressed air tank 4, stagnation pipe static pressure guide pipe 5, main pipeline static pressure guide pipe 6, No. 1 differential pressure sensor 7, data acquisition card 8, computer 9, wind speed tube 10, No. 2 differential pressure sensor 11, backflush pipe 12, stop valve 13, temperature and humidity sensor 14. DETAILED DESCRIPTION

[0022] 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.

[0023] The method for measuring the pulverized coal concentration of the pulverizing system of a coal-fired power plant in this embodiment is as follows: a stagnation tube 2 is placed in the main pipeline 1, one end of the stagnation tube 2 is an open end and faces the flow direction of the primary air pulverized coal, the other end of the stagnation tube 2 is a closed end and connected to the dust collecting bin 3, a static pressure measuring hole is opened at the other end of the stagnation tube 2 and the main pipeline 1 and connected to a No. 1 differential pressure sensor 7; an anemometer 10 is installed on the main pipeline 1, and the anemometer 10 is connected to a No. 2 differential pressure sensor 11; the No. 1 differential pressure sensor 7 and the No. 2 differential pressure sensor 11 are both connected to a data acquisition card 8 and to a computer 9; the pulverized coal in the primary air pulverized coal airflow enters the stagnation tube 2 and is decelerated under the action of gas drag, thereby increasing the static pressure of the gas in the stagnation tube 2, and the pulverized coal concentration is calculated according to the following formula by quantitatively measuring the increase in the static pressure:

[0024]

[0025] Among them, △p s is the difference between the static pressure at the closed end of the stagnation tube 2 and the static pressure of the airflow in the main pipe 1, u0 is the flow velocity of the airflow in the main pipe 1, ρ g is the density of the gas in the main pipeline 1, k is the pressure head conversion factor, and k is the core parameter of the calculation method, which is preferably obtained through experimental calibration.

[0026] The velocity of the air flow in the main pipeline 1 is measured by a wind velocity tube 10 which is not affected by coal powder, preferably a BS-I type velocity measuring tube; the static pressure of the gas in the main pipeline 1 is measured by a static pressure hole opened on the main pipeline 1, or by a static pressure tube arranged "back to back" with the stagnation tube 2.

[0027] The dust collecting bin 3 is opened with a hole and connected to a compressed air back-blowing system. When the dust collecting bin 3 is connected to compressed air, the airflow blows up the coal powder in the dust collecting bin 3 and sends it back to the main pipeline 1 through the open end of the stagnation pipe 2, thereby cleaning the dust collecting bin 3.

[0028] The device in the above-mentioned method for measuring the coal powder concentration of the pulverizing system of a coal-fired power plant comprises a stagnation pipe 2, a dust collecting bin 3, a compressed air tank 4, a No. 1 differential pressure sensor 7, a data acquisition card 8, a computer 9, a wind speed tube 10 and a No. 2 differential pressure sensor 11. The stagnation pipe 2 is arranged in the main pipeline 1, one end of the stagnation pipe 2 is an open end and is arranged in the direction of the flow of the primary air coal powder, the other end of the stagnation pipe 2 is a closed end and is connected to the dust collecting bin 3, and the other end of the stagnation pipe 2 and the main pipeline 1 are provided with static The pressure measuring hole is connected to the No. 1 differential pressure sensor 7 through the stagnation tube static pressure guide pipe 5 and the main pipeline static pressure guide pipe 6 respectively; the main pipeline 1 is equipped with a wind speed tube 10, and the wind speed tube 10 is connected to the No. 2 differential pressure sensor 11; the dust collecting bin 3 is provided with a backblowing pipe 12, the backblowing pipe 12 is connected to the compressed air tank 4, and a stop valve 13 is installed on the backblowing pipe 12; the No. 1 differential pressure sensor 7 and the No. 2 differential pressure sensor 11 are both connected to the data acquisition card 8, and the data acquisition card 8 is connected to the computer 9.

[0029] The core device of the present invention is a stagnation tube 2, which is placed in the primary air powder delivery pipeline (referred to as the main pipeline 1), and its opening faces the incoming flow. When the coal powder, which is driven by the airflow and moves at a relatively high speed (20m / s to 40m / s), approaches the pipe mouth of the stagnation tube 2, it cannot bypass it due to its large inertia and "collides" into the pipe from the pipe mouth of the stagnation tube 2. The coal powder particles entering the stagnation tube 2 are decelerated by the drag of the gas in the pipe (close to a static state). Due to the interaction of forces, the gas is also simultaneously subjected to the force from the particles, causing its static pressure to increase. The higher the concentration of coal powder, the greater the increase in static pressure. The concentration of coal powder can be calculated by measuring the difference between the static pressure of the gas at the tail of the stagnation tube 2 and the static pressure of the gas in the main pipeline 1 (mainstream), the flow rate and temperature of the gas in the main pipeline 1, and combining the theoretical principles with the actual calibration formula.

[0030] The stagnation tube can be a straight tube or a curved tube, and its opening can also be a bell-mouth structure.

[0031] The device is composed of the following core components: stagnation pipe 2 and its compressed air backflush system, wind speed tube 10, temperature and humidity sensor 14, multiple pressure sensors and differential pressure sensors, data acquisition card 8, computer 9. The main pipeline 1 and its compressed air backflush system are the main innovations, and the remaining instruments, equipment, sensors and technical process links can adopt mature products and technical solutions on the market.

[0032] The temperature and humidity sensor 14 is connected to the main pipeline 1 to measure the temperature and relative humidity of the gas in the main pipeline 1, which will be used for calculating gas parameters (density, viscosity, etc.) later.

[0033] The data acquisition card 8 collects the analog signals from each sensor in real time and converts them into digital signals, which are transmitted to the computer 9 for data processing and conversion, and the final measurement result, namely the coal powder concentration, is obtained.

[0034] The wind speed tube 10 should preferably use a BS-I type speed measuring device (refer to the industry standard "Performance Test of Power Plant Coal Mill and Pulverizing System: DL / T467-2004"), which has the advantages of directly obtaining the air flow velocity (the measurement signal is independent of the coal powder concentration), simple structure and low cost.

[0035] The technical principle of the present invention is described as follows:

[0036] Under pure air flow, the static pressure p in the stagnation tube 2 is s The total pressure is equal everywhere and equal to the incoming flow (mainstream), that is:

[0037]

[0038] Where: p s,0 is the static pressure in the stagnation pipe 2 under the condition of pure gas flow without coal powder (unit: Pa), p g is the static pressure of the mainstream gas (unit: Pa); ρ g The mainstream gas density (unit: kg / m 3 ), with static pressure p g The temperature and relative humidity of the mainstream gas measured by the temperature and humidity sensor 14 are used as known quantities and calculated based on the ideal gas state equation; u0 is the mainstream gas flow rate (unit: m / s, through Figure 1 Measured by the air velocity tube 10 in the air velocity tube).

[0039] When the airflow contains coal powder, due to its large particle size and high movement speed, only a small amount of the coal powder particles moving towards the mouth of the stagnation tube 2 will bypass the stagnation tube 2 with the gas when passing through the front end of the stagnation tube 2 and continue to move downstream. Most of the coal powder particles enter the stagnation tube 2 from the open end of the stagnation tube 2 and gradually slow down under the action of the airflow drag. The coal powder particles also exert a reaction force on the gas in the tube, causing the static pressure in the tube to increase, and the closer to the closed section (the bottom of the tube), the higher the static pressure.

[0040] thereby:

[0041]

[0042] Where: p s (c) is the static pressure in the stagnation tube 2 in the presence of coal powder (unit: Pa), c is the mass concentration of coal powder particles, k is called the pressure head conversion factor, which represents the ratio of the coal powder momentum converted into the increase in the static pressure of the gas in the stagnation tube 2, and is related to the structural design, material, coal powder particle size and other factors of the stagnation tube 2.

[0043] Substituting formula (1) into formula (2) yields:

[0044]

[0045] thereby:

[0046]

[0047] △p s for Figure 1 The differential pressure measured by differential pressure sensor No. 1 7 is shown. It can be seen that once the pressure head conversion factor k is determined, the mass concentration c of the coal powder can be calculated in combination with other parameters (obtained by measurement).

[0048] Under certain ideal conditions, the theoretical value of k can be derived, including: 1) when the stagnation tube 2 is a straight tube, the coal powder inertia is very small and can completely follow the fluid movement, k = 1; 2) when the stagnation tube 2 is a straight tube, the coal powder inertia is large and the stagnation tube 2 is long enough, k = 2. In actual situations, the k value cannot be known in advance and must be calibrated to obtain it.

[0049] The calibration method of k is: at the production site of the pulverizing system or in a laboratory simulation environment, c is obtained by standard means such as the isokinetic sampling and weighing method (such as the international standard ISO 9931 "Coal--Sampling of pulverized coal conveyed by gases indirect fired coal systems"), and k can be calculated by formula (4). When the actual operating conditions and the coal powder fineness are slightly different from the calibration state, the calibrated k value can be used for real-time online measurement of c. The calibration of k is not the core of the present invention. It is easy to implement in principle and technology, so the detailed process is not repeated here.

[0050] Table 1 shows the pressure head conversion factors (particle density 2250kg / m 3 , the gas is room temperature air, the mainstream flow rate is 15m / s, and the stagnation tube 2 has a diameter of 10mm and a length of 200mm). Table 1 shows that in a wide particle size range (40-100μm), the variation of k with particle size is small, which means that this method is insensitive to the change of the coal powder particle size distribution range (usually unknown) in the actual production process, which is also one of the key advantages of this method.

[0051] Table 1 CFD verification results of stagnation tube measurement principle

[0052]

[0053] The continuous accumulation of coal powder in the stagnation pipe 2 will cause it to be "blocked" by coal powder, so dust removal measures must be taken. Figure 3The diagram shows a measuring head with a dust collecting bin 3. The measuring head works in the horizontal main pipeline 1, and the coal powder entering the stagnation pipe 2 falls into the dust collecting bin 3 under the action of gravity, thereby preventing the stagnation pipe 2 from being blocked for a period of time.

[0054] Figure 1 The method of using compressed air backblowing to remove accumulated powder is illustrated. When the stop valve 13 is closed, there is no compressed air backblowing, and the measuring device is in normal working condition. When the stop valve 13 is opened, the compressed air from the compressed air tank 4 enters the dust collecting bin 3 at a high flow rate, blows up and takes out the accumulated powder, and blows it into the main pipeline 1 through the pipe opening of the stagnation pipe 2. Through periodic backblowing, the measuring head can maintain a continuous (short interruption during backblowing) measuring state.

[0055] Figure 3 The structural design shown is more suitable for the horizontal section of the main pipeline 1. In the vertical section of the main pipeline 1, the air and powder air flow moves from bottom to top. In order to avoid powder accumulation, a structure with a curved pipe inlet of the stagnation pipe 2 can be adopted ( Figure 4 After the coal powder enters the elbow, part of it can enter the straight pipe section, and the other part collides with the inner wall of the elbow outside the turning radius and changes its movement direction, and then can also enter the straight pipe section. Since the probability of particles colliding with the pipe wall is higher than that of the straight pipe stagnation pipe 2 ( Figure 3 ), resulting in a part of its momentum being lost in the wall collision, so the pressure head conversion factor k in this case is smaller than that of the straight tube stagnation tube 2.

[0056] According to formula (3), a larger k is more beneficial for measurement. The larger k is, the smaller △p is under the same conditions. s The larger the value, the greater the △p s The smaller the relative error of the measurement is, the smaller the error is. In order to increase k, the inlet of the stagnation tube 2 can be designed into a "bell mouth" shape, such as Figure 5 The bell mouth opening diameter D2 is larger than the straight tube diameter D1, which allows more (compared with the straight tube stagnation tube 2) coal powder particles to enter the stagnation tube 2, thereby obtaining a larger △p s and k. Stagnation pipe 2 with elbow inlet ( Figure 4 ) can also use a bell-mouth entrance.

[0057] The measurement of mainstream static pressure can be done by Figure 1 The method of opening a hole in the main pipeline 1 to take pressure can also adopt a more compact "back-to-back" design, that is, a main pipeline static pressure guide pipe 6 for measuring the main static pressure is integrated with the stagnation pipe 2, the stagnation pipe 2 faces the incoming flow and the main static pressure guide pipe faces away from the incoming flow ( Figure 6 ). This form is similar to the common S-type pitot tube (commonly known as backrest tube) used for speed measurement.

[0058] Implementation process: In the horizontal section of the primary air powder delivery pipeline, The straight pipe is used as the stagnation pipe 2, and the stagnation pipe 2 is connected to the dust collecting bin 3, and the combination is as follows Figure 6 The backrest pipe shown (the main pipeline 1 is no longer provided with an additional static pressure measuring hole). The wind speed of the main pipeline 1 is measured using a BS-I type velocity measuring tube. The temperature and humidity of the gas are measured in the main pipeline 1 using a temperature and humidity sensor 14. At the production site of a coal-fired power plant using a direct-blowing pulverizing system, the key parameter k of this method is calibrated using the method specified in the international standard ISO 9931. The data acquisition card 8 transmits the signals measured by each sensor to the computer 9, and the aforementioned signals are analyzed and calculated using the calculation method and formula of the present invention to obtain the coal powder concentration.

[0059] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0060] 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 method for measuring the concentration of pulverized coal in a pulverizing system of a coal-fired power plant, characterized in that the process As follows: a stagnation tube (2) is placed in a main pipeline (1), one end of the stagnation tube (2) is an open end and faces the flow direction of primary air pulverized coal, the other end of the stagnation tube (2) is a closed end and is connected to a dust collecting bin (3), a static pressure measuring hole is opened on the other end of the stagnation tube (2) and the main pipeline (1) and a No. 1 differential pressure sensor (7) is connected; an air velocity tube (10) is installed on the main pipeline (1), and the air velocity tube (10) is connected to a No. 2 differential pressure sensor (11); the No. 1 differential pressure sensor (7) and the No. 2 differential pressure sensor (11) are both connected to a data acquisition card (8) and connected to a computer (9); the pulverized coal in the primary air pulverized coal airflow enters the stagnation tube (2) and is decelerated under the action of gas drag, thereby increasing the static pressure of the gas in the stagnation tube (2), and the pulverized coal concentration is calculated according to the following formula by quantitatively measuring the increase in static pressure: Among them, △p s is the difference between the static pressure at the closed end of the stagnation tube (2) and the static pressure of the airflow in the main pipe (1), u0 is the velocity of the airflow in the main pipe (1), and ρ g is the density of the gas in the main pipeline (1), and k is the pressure head conversion factor, which is obtained through experimental calibration.

2. The method for measuring the pulverized coal concentration in the pulverizing system of a coal-fired power plant according to claim 1 is characterized in that: The velocity of the air flow in the main pipeline (1) is measured by a wind velocity tube (10) which is not affected by coal powder. The wind velocity tube (10) adopts a BS-I type velocity measuring tube. The static pressure of the gas in the main pipeline (1) is measured by a static pressure hole opened on the main pipeline (1), or by a static pressure tube arranged in a "back-to-back" manner with the stagnation tube (2).

3. The method for measuring the pulverized coal concentration in the pulverizing system of a coal-fired power plant according to claim 1, characterized in that: The dust collecting bin (3) has a hole formed therein and is connected to a compressed air back-blowing system. When the dust collecting bin (3) is connected to compressed air, the airflow blows up the coal powder in the dust collecting bin (3) and sends it back to the main pipeline (1) through the open end of the stagnation pipe (2), thereby cleaning the dust collecting bin (3).

4. The method for measuring the pulverized coal concentration in the pulverizing system of a coal-fired power plant according to claim 1, characterized in that: A temperature and humidity sensor (14) is connected to the main pipeline (1) to measure the temperature and relative humidity of the gas in the main pipeline (1) for subsequent calculation of gas parameters.

5. A device for use in a method for measuring the pulverized coal concentration in a pulverizing system of a coal-fired power plant according to any one of claims 1 to 4, characterized in that: The invention comprises a stagnation pipe (2), a dust collecting bin (3), a compressed air tank (4), a first differential pressure sensor (7), a data acquisition card (8), a computer (9), a wind speed tube (10) and a second differential pressure sensor (11); the stagnation pipe (2) is arranged in a main pipeline (1); the stagnation pipe (2) is a straight pipe or a curved pipe; one end of the stagnation pipe (2) is an open end and is arranged toward the flow direction of primary air pulverized coal; the other end of the stagnation pipe (2) is a closed end and is connected to the dust collecting bin (3); the other end of the stagnation pipe (2) and the main pipeline (1) are both provided with static pressure measuring holes, which are respectively connected through the static pressure guide pipe (5) of the stagnation pipe and the static pressure guide pipe (5) of the main pipeline. The pressure-guiding pipe (6) is connected to a No. 1 differential pressure sensor (7); a wind speed tube (10) is installed on the main pipeline (1), and the wind speed tube (10) is connected to a No. 2 differential pressure sensor (11); a backflush pipe (12) is provided on the dust collecting bin (3), the backflush pipe (12) is connected to a compressed air tank (4), and a stop valve (13) is installed on the backflush pipe (12); a temperature and humidity sensor (14) is installed on the main pipeline (1), the No. 1 differential pressure sensor (7), the No. 2 differential pressure sensor (11) and the temperature and humidity sensor (14) are all connected to a data acquisition card (8), and the data acquisition card (8) is connected to a computer (9).

6. The device for measuring the pulverized coal concentration in the pulverizing system of a coal-fired power plant according to claim 5 is characterized in that: The opening of the stagnation tube (2) is a straight opening or a bell-mouth structure.

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