A coal mine respirable dust inertial impact continuous separation system

Abstract

This invention belongs to the field of coal mining technology. It relates to a continuous inertial impact separation system for respirable dust in coal mines, comprising a dust separation unit, a liquid supply unit, a liquid discharge unit, a control unit, and a sampling unit. The liquid supply unit, liquid discharge unit, and sampling unit are all connected to and controlled by the control unit. The dust separation unit is equipped with a dust collection port, a liquid supply port, a liquid discharge port, and a sampling port. The sampling unit is connected to the sampling port. Respirable dust enters the dust separation unit through the dust collection port for inertial separation and then enters the sampling unit for sampling and detection. The liquid supply unit is connected to the liquid supply port, and the liquid discharge unit is connected to the liquid discharge port. The dust accumulated in the dust separation unit is washed by the liquid provided by the liquid supply unit and discharged through the liquid discharge unit to release the dust collection capacity. The separation system of this invention does not require the application of an adhesive substance, enabling continuous separation of respirable dust while improving separation accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coal mines, and relates to a respiratory dust inertia impact continuous separation system for coal mines. BACKGROUND

[0002] Accurate measurement of the concentration of respiratory dust in a coal mine underground is an important basis for evaluating the exposure level of miners and the dust prevention and control effect, and the separation of respiratory dust is the key to realizing dust information measurement. However, at the present stage, the separation of respiratory dust still adopts a manual sampling mode. Inertia impact is the most commonly used respiratory dust separation mode. Due to the existence of a dust collecting impact plate, a sticky substance needs to be applied on the impact plate to adsorb dust, so that the dust capacity of this kind of separation device is very limited, and it is easy to cause dust overload, rebound and other situations, and frequent maintenance is required. Especially in the high dust concentration environment of coal mines, it is more difficult to continuously separate particles such as PM2.5 and PM10 in the atmospheric environment. The development of intelligent coal mines puts forward higher requirements for the separation of respiratory dust. Only by continuously prolonging the maintenance-free period of the separation device can online measurement of the concentration of respiratory dust be realized, so as to achieve the goal of less people and no people in dust monitoring.

[0003] At present, the research on inertia impact separation devices mainly focuses on reducing the use cost, expanding the application range, improving the separation performance, reducing the particle loss and the like. For example, a Chinese patent with publication number CN111999221A discloses an inertia impactor with adjustable impact distance and a dust concentration measurement method, which solves the problem that the existing inertia impactor can only be used to measure the dust concentration of a single PM value, thereby causing the dust measuring instrument to carry too many components in actual use, resulting in inconvenience in carrying and increase in use cost. A Chinese patent with publication number CN105013251A discloses an inertia impactor with enhanced separation effect, which increases the penetration rate of the flow into the medium sheet, and thereby provides improved performance by intercepting, colliding, and diffusing to enhance particle capture. Sun Maowen of Chongqing Jiaotong University carried out research on an impact collector based on the principle of inertia, taking a new type of inertia impactor as the research object, and carried out research on the design of key structural parameters of the internal flow channel of the new type of inertia impactor, analysis of flow field characteristics, influence law of different factors on separation characteristics, and dynamic optimization design. The highest separation efficiency and the least wall loss of the new type of inertia impactor are taken as the optimization objectives, and each sampling flow and different design parameters are taken as the design variables. The central composite design method is used to design the test, the computational fluid dynamics theory is combined, the response surface optimization model of the new type of inertia impactor is established for dynamic optimization, and the new type of inertia impactor obtained by optimization is modeled and numerically simulated and analyzed. It can be seen that the research on inertia impact devices at the present stage still has not solved the problem of frequent maintenance, and it is difficult to realize continuous separation of dust. SUMMARY

[0004] In view of this, the purpose of this invention is to provide a continuous inertial impact separation system for respirable dust in coal mines, which can continuously separate respirable dust in underground coal mines, with less dust rebound and less risk of separator overload, greatly reducing maintenance frequency, and laying the foundation for online continuous measurement of dust concentration and online analysis of its composition.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A continuous inertial impact separation system for respirable dust in coal mines includes a dust separation unit, a liquid supply unit, a liquid discharge unit, a control unit, and a sampling unit; the liquid supply unit, the liquid discharge unit, and the sampling unit are all connected to and controlled by the control unit.

[0007] The dust separation unit is equipped with a dust collection port, a liquid supply port, a liquid discharge port, and a sampling port; the sampling unit is connected to the sampling port, and respirable dust enters the dust separation unit through the dust collection port for inertial separation, and then enters the sampling unit for sampling and detection;

[0008] The liquid supply unit is connected to the liquid supply port, and the liquid discharge unit is connected to the liquid discharge port; the dust accumulated in the dust separation unit is washed by the liquid provided by the liquid supply unit and discharged through the liquid discharge unit to release the dust collection capacity.

[0009] Furthermore, the dust separation unit includes a housing and a dust collection assembly; the dust collection assembly is disposed inside the housing; the dust collection assembly includes a dust collection base, a liquid collection tank baffle ring, an impact plate, and a rinsing umbrella;

[0010] The dust collection base is fixedly installed inside the housing and located between the dust collection port and the sampling port, dividing the housing into an upper cavity and a lower cavity; the dust collection port communicates with the upper cavity, and the sampling port communicates with the lower cavity;

[0011] The dust collection base is provided with a boss; the impact plate is fixedly provided on the boss and located below the dust collection port; the flushing umbrella is provided on the impact plate and is provided with a flushing hole; the liquid collection tank baffle is annular and is provided on the outside of the impact plate, forming an annular liquid collection tank with the boss.

[0012] The dust collection base is provided with a rinsing channel, a drain channel, and an airflow passage hole; one end of the rinsing channel is connected to the liquid supply port, and the other end is connected to the rinsing hole on the rinsing umbrella; the drain channel is located in the liquid collection tank and is connected to the drain port; the airflow passage hole is located on the outside of the liquid collection tank baffle ring and passes through the dust collection base, connecting the upper cavity and the lower cavity.

[0013] Dust-laden airflow enters the housing at a certain velocity and impacts the impact plate. Due to inertia, larger dust particles are more likely to be captured by the impact plate because of their greater inertia, while smaller dust particles are less likely to be captured because of their lower inertia. The captured dust accumulates in the impact plate, while the uncaptured dust enters the lower cavity through the airflow holes, achieving inertial separation of dust. The separation efficiency meets the sampling rules for respirable dust, i.e., it satisfies the BMRC curve, ACGIH curve, or EN481 curve.

[0014] Furthermore, the impact plate is made of porous metal material in a stacked mesh process, which increases the dust holding area and reduces particle rebound.

[0015] Furthermore, the impact plate is disc-shaped, thick in the middle and thin at the edges, and its dust-facing surface is arc-shaped.

[0016] Furthermore, the airflow holes are arranged in a circular array centered on the axis of the dust collection base.

[0017] Furthermore, the liquid supply unit includes a pressure regulating valve, a water filter, a magnetized water preparation device, and a flow controller connected in series via pipelines. The front end of the pressure regulating valve is connected to the water supply to adjust the water pressure to a suitable value. The water filter is used to remove impurities from the water, protecting downstream equipment and reducing interference from impurities to dust. The magnetized water preparation device generates active magnetized water by adding an activator and performing magnetization treatment. The active magnetized water is used to wash away the dust accumulated on the impact plate and simultaneously wet the impact plate, increasing its dust-capturing ability.

[0018] Furthermore, the sampling unit includes a sampling pump, a flow controller, a filter, and an analysis and measurement device connected in series; the sampling pump is used to provide suction power to draw the dust-laden airflow into the dust separation unit for inertial separation, and to transport the separated dust to the analysis and measurement device; the analysis and measurement device is connected to the sampling port and is used to analyze and measure the separated dust.

[0019] Furthermore, the housing includes an upper cover and a lower cover, which are connected by threads. The dust collection port is located on the upper cover, and the sampling port is located on the lower cover. The dust collection port is funnel-shaped, with its larger end located on the outside of the upper cover and its smaller end equipped with an accelerating nozzle. The accelerating nozzle is a cylindrical shape with a smooth inner cavity, which rectifies the dust-laden airflow accelerated by the dust collection port. The funnel-shaped dust collection port, with its larger end facing outward, allows for better suction of dust into the housing. Simultaneously, it accelerates the suction-laden airflow, enabling the dust to reach a preset speed with relatively low suction power.

[0020] Furthermore, the rinsing umbrella is mushroom-shaped, including an umbrella handle and an umbrella cap; the umbrella cap is fixedly disposed at one end of the umbrella handle, and the other end of the umbrella handle is fixedly connected to the impact plate; the rinsing hole is disposed at one end of the umbrella handle near the umbrella cap, and passes through the umbrella and communicates with the rinsing channel; the opening of the rinsing hole faces the impact plate.

[0021] Furthermore, the projected area of ​​the flushing umbrella on the dust-facing surface of the impact plate is no more than 5% of the dust-facing surface area. The flushing umbrella is relatively small in size compared to the impact plate, reducing the impact of the top of the flushing umbrella on dust collection.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. The continuous inertial impact separation system for respirable dust in coal mines in this invention does not require the application of sticky substances, reducing errors caused by manual operation and enabling continuous separation of respirable dust while improving separation accuracy. The dust separation unit adopts a porous metal material stacked mesh impact plate, which has a large dust collection capacity and is easy to clean. The built-in umbrella-shaped flushing component can be automatically flushed using underground production water supply, which is simple, convenient, and provides uniform flushing to ensure flushing effect. The flushing frequency can be set according to the actual use environment.

[0024] 2. The magnetized water preparation device in this invention is used to generate active magnetized water, which is used to wash the dust accumulated on the impact plate, release the dust collection capacity, and at the same time wet the impact plate to increase the impact plate's ability to capture dust.

[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0027] Figure 1 This is a schematic diagram of the overall inertial impact continuous separation system for respirable dust in coal mines in this invention.

[0028] Figure 2 This is a schematic diagram of the dust separation unit in this invention;

[0029] Figure 3 for Figure 2 Schematic diagram of the dust collection base;

[0030] Figure 4 for Figure 3 A half-section view;

[0031] Figure 5 Schematic diagram of the retaining ring for the liquid collection tank;

[0032] Figure 6 This is a schematic diagram of an impact plate;

[0033] Figure 7 This is a diagram of a rinsing umbrella;

[0034] Figure 8 The curves show the comparison of the effects of inertial separation and grading.

[0035] Reference numerals: 1-Dust separation unit; 2-Liquid supply unit; 3-Liquid drainage unit; 4-Sampling unit; 5-Control unit; 6-Dust collection port; 7-Sampling port; 11-Accelerating nozzle; 12-Upper cover; 13-Rinsing umbrella; 14-Impact plate; 15-Liquid collection tank retaining ring; 16-Drainage port; 17-Dust collection base; 18-Lower cover; 19-Liquid supply port; 21-Pressure regulating valve; 22-Water filter; 23-Magnetized water preparation device; 24-Flow controller; 41-Sampling pump; 42-Flow controller; 43-Filter; 44-Analysis and measurement device; 131-Umbrella cap; 132-Umbrella handle; 133-Rinsing hole; 171-Boss; 172-Airflow passage hole; 173-Rinsing channel; 174-Drainage channel. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0038] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0039] Please see Figures 1-7 This is a continuous inertial impact separation system for respirable dust in coal mines, comprising a dust separation unit 1, a liquid supply unit 2, a liquid discharge unit 3, a control unit 5, and a sampling unit 4. The liquid supply unit 2, liquid discharge unit 3, and sampling unit 4 are all connected to and controlled by the control unit 5. The dust separation unit 1 is equipped with a dust collection port 6, a liquid supply port 19, a liquid discharge port 16, and a sampling port 7. The sampling unit 4 is connected to the sampling port 7. Respirable dust enters the dust separation unit 1 through the dust collection port 6 for inertial separation and then enters the sampling unit 4 for sampling and detection. The liquid supply unit 2 is connected to the liquid supply port 19, and the liquid discharge unit 3 is connected to the liquid discharge port 16. The dust accumulated in the dust separation unit 1 is washed away by the liquid supplied by the liquid supply unit 2 to release its dust collection capacity. The liquid discharge unit 3 uses a pumping and drainage device to discharge the magnetized water containing dust after washing out of the dust separation unit 1.

[0040] The dust separation unit 1 includes a housing and a dust collection assembly. The dust collection assembly is disposed inside the housing and includes a dust collection base 17, a liquid collection tank baffle 15, an impact plate 14, and a rinsing umbrella 13. The dust collection base 17 is fixedly disposed inside the housing and located between the dust collection port 6 and the sampling port 7, dividing the housing into an upper cavity and a lower cavity. The dust collection port 6 communicates with the upper cavity, and the sampling port 7 communicates with the lower cavity. A boss 171 is provided on the dust collection base 17. The impact plate 14 is fixedly disposed on the boss 171 and located below the dust collection port 6. The rinsing umbrella 13 is installed on the impact plate 14 and has rinsing holes 133. The liquid collection tank baffle 15 is annular and disposed on the outside of the impact plate 14, forming an annular liquid collection tank with the boss 171. The dust collection base 17 is provided with a rinsing channel 173, a drain channel 174, and an airflow passage 172. One end of the flushing channel 173 is connected to the liquid supply port 19, and the other end is connected to the flushing hole 133 on the flushing umbrella 13. The drain channel 174 is set in the liquid collection tank and is connected to the drain port 16. The airflow passage hole 172 is set on the outside of the liquid collection tank baffle ring 15 and passes through the dust collection base 17, connecting the upper cavity and the lower cavity. The dust-laden airflow enters the shell at a certain flow rate and impacts the impact plate 14. Under the action of inertia, the dust with a larger particle size has a higher probability of being captured by the impact plate 14 due to its greater inertia, while the dust with a smaller particle size has a lower probability of being captured by the impact plate 14 due to its smaller inertia. The captured dust accumulates in the impact plate 14, while the uncaptured dust enters the lower cavity through the airflow passage hole 172, realizing the inertial separation of dust. The separation efficiency meets the sampling rules for respirable dust, that is, it satisfies the BMRC curve, ACGIH curve, or EN481 curve.

[0041] The impact plate 14 is made of porous metal material in a stacked mesh process to increase the dust holding area and reduce particle rebound. The impact plate 14 is disc-shaped, thicker in the middle and thinner at the edges, and its dust-facing surface is arc-shaped. The airflow holes 172 are distributed in a circular array with the axis of the dust collection base 17 as the center.

[0042] The liquid supply unit 2 includes a pressure regulating valve 21, a water filter 22, a magnetized water preparation device 23, and a flow controller 24 connected in series via pipelines. The front end of the pressure regulating valve 21 is connected to the water supply to adjust the water pressure to a suitable value. The water filter 22 is used to remove impurities from the water, protect downstream equipment, and reduce the interference of impurities on dust. The magnetized water preparation device 23 generates active magnetized water by adding an activator and performing magnetization treatment. The active magnetized water is used to wash the dust accumulated on the impact plate 14 and wet the impact plate 14, increasing the impact plate 14's ability to capture dust.

[0043] The sampling unit 4 includes a sampling pump 41, a flow controller 42, a filter 43, and an analysis and measurement device 44 connected in series. The sampling pump 41 is used to provide suction power to draw the dust-laden airflow into the dust separation unit 1 for inertial separation and to transport the separated dust to the analysis and measurement device 44. The analysis and measurement device 44 is connected to the sampling port 7 and is used to analyze and measure the separated dust.

[0044] In this embodiment, the housing includes an upper cover 12 and a lower cover 18, which are connected by threads. The dust collection base 17 is threaded into the upper cover 12. A dust collection port 6 is located on the upper cover 12, and a sampling port 7 is located on the lower cover 18. The dust collection port 6 is funnel-shaped, with its larger end located on the outside of the upper cover 12 and its smaller end equipped with an accelerating nozzle 11. The accelerating nozzle 11 is a cylindrical shape with a smooth inner cavity, which rectifies the dust-laden airflow accelerated by the dust collection port 6. The dust collection port 6 is funnel-shaped, with the larger end facing outward, so that dust can be better drawn into the housing. At the same time, it also accelerates the drawn-in dust-laden airflow, so as to achieve the preset movement speed of dust with a small suction force.

[0045] The rinsing umbrella 13 is mushroom-shaped, including a handle 132 and a cap 131. The cap 131 is fixedly disposed at one end of the handle 132, and the other end of the handle 132 is fixedly connected to the impact plate 14. A rinsing hole 133 is disposed at the end of the handle 132 near the cap 131, and extends through the umbrella and communicates with the rinsing channel 173. The opening of the rinsing hole 133 faces the impact plate 14. The projected area of ​​the rinsing umbrella 13 on the dust-facing surface of the impact plate 14 is no more than 5% of the dust-facing surface area.

[0046] In the specific implementation process, at 95~100mg / m 3 The total dust concentration in the environment (of which the respirable dust concentration is approximately 22 mg / m³) 3 Taking this as an example, comparing the traditional inertial plate impact method with the present invention, from... Figure 8 It can be seen that, compared with the BMRC standard sampling curve, the two methods are not significantly different within a short sampling time. However, as the sampling time increases, the traditional inertial plate impact method, due to the limited dust capacity of the impact plate, allows some dust to escape with the sampling airflow and be detected by the dust measurement unit, thus increasing the measured concentration of respirable dust. In contrast, the present invention, due to the cleaning of the impact plate, although the measured concentration fluctuates, is significantly better than the traditional inertial plate impact method. Therefore, the present invention is suitable for long-cycle sampling and can meet the requirements for continuous separation of respirable dust.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A continuous inertial impact separation system for respirable dust in coal mines, characterized in that: It includes a dust separation unit, a liquid supply unit, a liquid discharge unit, a control unit, and a sampling unit; the liquid supply unit, the liquid discharge unit, and the sampling unit are all connected to and controlled by the control unit. The dust separation unit is equipped with a dust collection port, a liquid supply port, a liquid discharge port, and a sampling port; the sampling unit is connected to the sampling port, and respirable dust enters the dust separation unit through the dust collection port for inertial separation, and then enters the sampling unit for sampling and detection; The liquid supply unit is connected to the liquid supply port, and the liquid discharge unit is connected to the liquid discharge port; the dust collected in the dust separation unit is washed by the liquid provided by the liquid supply unit and discharged through the liquid discharge unit to release the dust collection capacity; The dust separation unit includes a housing and a dust collection assembly; the dust collection assembly is disposed inside the housing; the dust collection assembly includes a dust collection base, a liquid collection tank baffle ring, an impact plate, and a rinsing umbrella; The dust collection base is fixedly installed inside the housing and located between the dust collection port and the sampling port, dividing the housing into an upper cavity and a lower cavity; the dust collection port communicates with the upper cavity, and the sampling port communicates with the lower cavity; The dust collection base is provided with a boss; the impact plate is fixedly provided on the boss and located below the dust collection port; the flushing umbrella is provided on the impact plate and is provided with a flushing hole; the liquid collection tank baffle is annular and is provided on the outside of the impact plate, forming an annular liquid collection tank with the boss. The dust collection base is provided with a rinsing channel, a drain channel, and an airflow passage hole; one end of the rinsing channel is connected to the liquid supply port, and the other end is connected to the rinsing hole on the rinsing umbrella; the drain channel is located in the liquid collection tank and is connected to the drain port; the airflow passage hole is located on the outside of the liquid collection tank baffle ring and passes through the dust collection base, connecting the upper cavity and the lower cavity; the impact plate is disc-shaped, thick in the middle and thin at the edges, and its dust-facing surface is arc-shaped; the liquid supply unit includes a pressure regulating valve, a water filter, a magnetized water preparation device, and a flow controller connected in series through pipes.

2. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: Dust-laden airflow enters the housing at a certain velocity and impacts the impact plate. Due to inertia, larger dust particles are more likely to be captured by the impact plate because of their greater inertia, while smaller dust particles are less likely to be captured because of their lower inertia. The captured dust accumulates in the impact plate, while the uncaptured dust enters the lower cavity through the airflow holes, achieving inertial separation of dust. The separation efficiency meets the sampling rules for respirable dust, i.e., it satisfies the BMRC curve, ACGIH curve, or EN481 curve.

3. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The impact plate is made of porous metal material in a stacked mesh process to increase the dust holding area and reduce particle rebound.

4. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The airflow holes are arranged in a circular array centered on the axis of the dust collection base.

5. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The pressure regulating valve is connected to the water supply at its front end to adjust the water pressure to a suitable value; the water filter is used to remove impurities from the water, protect downstream equipment, and reduce the interference of impurities on dust; the magnetized water preparation device generates active magnetized water by adding an activator and performing magnetization treatment, and uses the active magnetized water to wash the dust accumulated on the impact plate, while also wetting the impact plate and increasing the impact plate's ability to capture dust.

6. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The sampling unit includes a sampling pump, a flow controller, a filter, and an analysis and measurement device connected in series. The sampling pump provides suction power to draw the dust-laden airflow into the dust separation unit for inertial separation and transports the separated dust to the analysis and measurement device. The analysis and measurement device is connected to the sampling port and is used to analyze and measure the separated dust.

7. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The housing includes an upper cover and a lower cover, which are connected by threads. The dust collection port is located on the upper cover, and the sampling port is located on the lower cover. The dust collection port is funnel-shaped, with its large end located on the outside of the upper cover and its small end equipped with an accelerating nozzle. The accelerating nozzle is a cylindrical shape with a smooth inner cavity, which rectifies the dust-laden airflow accelerated by the dust collection port.

8. The continuous inertial impact separation system for respirable dust in coal mines according to claim 1, characterized in that: The rinsing umbrella is mushroom-shaped and includes a handle and a cap. The cap is fixedly located at one end of the handle, and the other end of the handle is fixedly connected to the impact plate. The rinsing hole is located at the end of the handle near the cap, passes through the umbrella, and communicates with the rinsing channel. The opening of the rinsing hole faces the impact plate.

9. The continuous inertial impact separation system for respirable dust in coal mines according to claim 8, characterized in that: The projected area of ​​the flushing umbrella on the dust-facing surface of the impact plate is no more than 5% of the dust-facing surface area.

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