Nitrogen-assisted pneumatic directional drilling equipment and drilling slag removal methods for soft coal seams

Abstract

This invention discloses a nitrogen-driven pneumatic directional drilling equipment for downhole cuttings removal in soft coal seams, comprising a nitrogen drive mechanism and a directional drilling rig. The directional drilling rig has a directional drill string assembly structure, which includes a drill rod. A probe outer tube is coaxially sleeved inside the drill rod, and a measuring probe is coaxially sleeved inside the probe outer tube. The measuring probe is used to measure the gas flow rate and pressure in the borehole. An annular downward air chamber for nitrogen gas flow is formed between the inner wall of the probe outer tube and the outer wall of the measuring probe. An air inlet is opened on the outer wall of the drill rod at the lower part, and an annular upward air chamber for nitrogen gas flow is formed between the inner wall of the drill rod above the air inlet and the outer wall of the probe outer tube. A trumpet-shaped wind shield, wider at the bottom and narrower at the top, is connected to the outer wall of the drill rod above the air inlet. This invention also discloses a corresponding borehole cuttings removal method. This invention significantly reduces the resistance to airflow, achieving faster drilling speeds and removing more cuttings under the same air volume and pressure.

Description

Technical Field

[0001] This invention relates to the field of coal mine operation technology, and more particularly to borehole nitrogen slag removal technology. Background Technology

[0002] Coal is my country's primary energy source, and high-gas and gas-outburst mines account for about one-third of my country's coal production. The vast majority of these mines have soft, fractured coal seams. Gas control in soft, fractured coal seams is a crucial factor affecting safe coal production and stable energy supply in my country.

[0003] Drilling extraction is an effective measure for the prevention and comprehensive utilization of gas accidents in soft coal seams. However, due to the fractured coal body in soft coal seams, problems such as hole collapse and drill jamming, shallow hole depth, and low drilling efficiency exist during drilling, which restricts the efficient management of gas in the mining area.

[0004] Drilling through fractured and soft coal seams requires addressing key issues such as insufficient driving force, the impact of vibration on equipment lifespan, dust pollution, and safety hazards. The existing drilling technology suffers from the following problems:

[0005] ① During drilling and slag removal, the coal wall of the borehole has great resistance to coal dust and other slag due to its own properties, while the maximum air supply pressure that the underground explosion-proof air compressor can provide is 1.25 MPa, resulting in insufficient power for pneumatic drilling and slag removal.

[0006] ② Drilling tools generate strong periodic vibrations. Pneumatic screw drills and electromagnetic wave measurement-while-drilling instruments are easily fatigued and damaged by the alternating stress caused by vibration and impact. Impact has a great impact on the life of pneumatic screw drills and electromagnetic wave measurement-while-drilling instruments.

[0007] ③ It generates a large amount of dust, resulting in serious dust pollution in the drilling site.

[0008] ④ Compressed air drilling also carries the risk of borehole fire, posing a significant safety hazard during construction. Existing technologies include nitrogen drilling. Summary of the Invention

[0009] The purpose of this invention is to provide a nitrogen-driven directional drilling equipment for soft coal seams. By designing a non-rotating drill pipe body and an internal slag removal structure, the slag removal resistance is reduced, and the power requirements for pneumatic drilling and pneumatic slag removal can be met without improving the performance of the air compressor.

[0010] To achieve the above objectives, the nitrogen-driven directional drilling equipment for soft coal seams includes a nitrogen drive mechanism and a directional drilling rig. The directional drilling rig has a directional drilling tool assembly structure. The nitrogen drive mechanism is connected to a nitrogen outlet pipe, the nitrogen outlet pipe is connected to an air supply device, and the air supply device is connected to the directional drilling tool assembly structure.

[0011] The directional drilling assembly includes a drill pipe, a probe outer tube coaxially sleeved inside the drill pipe, and a measuring probe coaxially sleeved inside the probe outer tube. The measuring probe is used to measure the gas flow rate and pressure in the borehole. An annular downward gas chamber for nitrogen gas flow is formed between the inner wall of the probe outer tube and the outer wall of the measuring probe. The upper end of the annular downward gas chamber is connected to a blower and used to input high-pressure nitrogen gas.

[0012] An air screw motor is connected to the lower end of the drill rod. The lower end of the annular downward air chamber is connected to the air screw motor. The rotor of the air screw motor is connected to a directional drill bit. The drill bit of the air screw motor is provided with an air hole for blowing high-pressure nitrogen into the bottom of the borehole.

[0013] An air inlet is provided on the outer wall of the drill rod at the lower part. The inner wall of the drill rod above the air inlet and the outer wall of the probe tube form an annular upward air chamber for the passage of nitrogen gas.

[0014] A funnel-shaped baffle, wider at the bottom and narrower at the top, is connected to the outer wall of the drill rod at the upper end of the air inlet. The bottom of the baffle matches the drilling radius of the directional drill bit. The baffle allows the upward-reversing airflow from the borehole to enter the annular upward air chamber through the air inlet. Both the inner wall of the drill rod and the outer wall of the probe tube are smooth surfaces. The top of the annular upward air chamber is higher than the borehole opening and is used to discharge the slag-laden airflow.

[0015] It also includes dust collection mechanisms with orifices;

[0016] A dust collection hood is installed above the borehole opening. The drill rod passes through the dust collection hood and is sealed to it. The top of the annular upward air chamber has an opening that communicates with the dust collection hood. The dust collection hood is connected to a dust collector through a pipeline. The dust collector is connected to a gas extraction pipe through a pipeline. A shut-off valve is installed on the pipeline between the gas extraction pipe and the dust collector.

[0017] The nitrogen-driven mechanism includes an air compressor, the air compressor's outlet pipe of which is connected to a cooling device, which has an air inlet, an air outlet, a water inlet, and a water outlet.

[0018] The air inlet of the cooling device is connected to the air outlet pipe of the air compressor.

[0019] The outlet of the cooling device is connected to the inlet of the membrane separation nitrogen generator via a pipeline;

[0020] The cooling unit's water inlet is connected to an external water source.

[0021] The outlet of the cooling device is connected to the underground drainage system;

[0022] The nitrogen outlet of the membrane separation nitrogen generator is connected to the nitrogen outlet pipe;

[0023] The air inlet and outlet of the cooling device are connected by a first set of Tesla valves;

[0024] The inlet and outlet of the cooling device are connected by a second Tesla valve;

[0025] The first set of Tesla valves and the second set of Tesla valves are placed close together and used for water-air heat exchange;

[0026] The air inlet and water outlet of the cooling device are located at the same end of the cooling device, which is called end A, and the opposite end of end A is called end B; the air outlet and water inlet of the cooling device are located at end B of the cooling device.

[0027] The inlet of the membrane separation nitrogen generator is connected to a membrane module, and the nitrogen outlet end of the membrane module is connected to the nitrogen outlet pipe as the nitrogen outlet; the nitrogen outlet or the nitrogen outlet pipe is also connected to a nitrogen concentration sensor.

[0028] The air screw motor includes a stator, an impeller is provided in the air inlet end of the stator, the impeller is connected to a rotor, and the rotor rotates with the stator; the lower end of the rotor extends out of the stator and is connected to the directional drill bit; the stator has an annular chamber arranged around the rotor, the outline of the annular chamber is a logarithmic helical tooth profile, and the helix angle is the same at any point on the tooth direction line of the logarithmic helical tooth profile.

[0029] It also includes an explosion-proof industrial control computer, a measuring probe connected to the directional drilling rig, and a display screen connected to the explosion-proof industrial control computer; the explosion-proof industrial control computer is connected to the nitrogen concentration sensor, the blower, the air compressor, and the directional drilling rig via wiring.

[0030] This invention also discloses a drilling and slag removal method for the above-mentioned nitrogen-assisted directional drilling equipment for soft coal seams, which is carried out according to the following steps:

[0031] The first step is connection and debugging. Connect the nitrogen drive mechanism, air supply, directional drilling tool assembly structure and wellhead dust removal mechanism, and confirm that the entire drilling equipment is working properly through debugging.

[0032] The second step is nitrogen drilling. The high-temperature, high-pressure gas provided by the air compressor exchanges heat with water when passing through the cooling device to obtain room-temperature, high-pressure air. The room-temperature, high-pressure air is then separated into nitrogen and oxygen by a membrane separation nitrogen generator. The separated nitrogen is sent into the annular downward air chamber through the nitrogen outlet pipe and the blower, driving the impeller and rotor of the air screw motor to rotate, which in turn drives the directional drill bit to rotate and drill a hole. During the drilling process, the drill rod is lowered along the borehole to continue drilling.

[0033] The third step is nitrogen slag removal; after passing through the annular chamber of the air screw motor, the nitrogen is discharged to the bottom of the borehole. When it carries the drill cuttings in the borehole upwards along the annular gap between the outer wall of the drill rod and the borehole, it is blocked by the wind shield and enters the annular upward air chamber through the air inlet. The airflow carrying the drill cuttings enters the dust collector after passing through the annular upward air chamber and the dust collection hood. After dust removal, it is discharged into the environment.

[0034] The present invention has the following advantages:

[0035] To achieve pneumatic drilling, the downward airflow must flow inside the drill rod (flowing outside the drill rod cannot drive the air screw motor), while the upward airflow needs to flow on the outer wall of the drill rod (the airflow blowing to the bottom of the hole returns upward through the annular gap between the drill rod and the inner wall of the borehole). The upward airflow carries drill cuttings, and when it comes into contact with the coal wall in the borehole, there is significant resistance due to the physical properties of the coal wall (the coal wall blocks a large amount of drill cuttings), resulting in a small amount of cuttings being discharged, which is not conducive to the purpose of cuttings discharge such as preventing hole blockage and drill sticking.

[0036] The present invention has a simple structure and simple steps. Its outstanding advantage is that the slag-carrying airflow goes upward through the annular upward air chamber, thereby greatly reducing the contact area between the slag-carrying airflow and the borehole coal wall. Compared with the prior art in which the airflow flows along the borehole coal wall, the resistance of the airflow is greatly reduced. After the pressure loss of the airflow is greatly reduced, a faster drilling speed (higher rotation speed of the directional drill bit) can be achieved under the same air volume and air pressure, and more drill cuttings can be discharged.

[0037] With the structure of this invention, when the slag (coal powder, etc.) at the bottom of the borehole moves upward along the borehole with the airflow, it enters the annular upward air chamber through the air inlet under the restriction of the wind shield and flows upward. When the slag flows upward in the annular upward air chamber, it does not come into contact with the borehole wall, i.e., the coal wall. The flow resistance is greatly reduced, avoiding the need for increased air pressure due to the high resistance of the coal wall to the slag and coal powder, and avoiding the problem of insufficient power for pneumatic drilling and slag removal.

[0038] In the nitrogen-driven mechanism, the Tesla valve serves both unidirectional flow (an inherent function of Tesla valves) and water-gas heat exchange. Unidirectional flow makes the system more stable (Tesla valves are inherently more stable than ordinary check valves). Heat exchange is achieved through two sets of Tesla valves in counter-current flow, resulting in fewer components (eliminating the need for check valves and counter-current heat exchange piping) and easier connection. Nitrogen concentration sensor.

[0039] The existing air screw motor uses a cycloidal tooth profile for its annular chamber. This invention improves upon this by using a logarithmic spiral tooth profile. Utilizing the characteristic that the helix angle is the same at any point on the tooth line of a logarithmic spiral tooth profile, the stability of air flow within the annular chamber is increased, resulting in more uniform stress on the stator tooth profile surface. This reduces vibration damage to detection equipment and other devices during operation, and extends the service life of measuring probes and other devices. The change from a cycloidal tooth profile to a logarithmic spiral tooth profile in the annular chamber of the air screw motor is the second major innovation of this invention. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the underground nitrogen slag removal pneumatic directional drilling equipment for soft coal seams of the present invention;

[0041] Figure 2 This is a structural diagram of a directional drilling assembly;

[0042] Figure 3 This is a schematic diagram of the cooling device.

[0043] Figure 4 This is a schematic diagram of a membrane separation nitrogen generator;

[0044] Figure 5 This is a schematic diagram of the stator and rotor of an air screw motor. Detailed Implementation

[0045] like Figures 1 to 5 As shown, the nitrogen-driven directional drilling equipment for soft coal seams of the present invention includes a nitrogen drive mechanism 1 and a directional drilling rig 2. The directional drilling rig 2 has a directional drilling tool assembly structure. The nitrogen drive mechanism 1 is connected to a nitrogen outlet pipe 134, the nitrogen outlet pipe 134 is connected to an air supply device 14, and the air supply device 14 is connected to the directional drilling tool assembly structure.

[0046] The directional drilling assembly includes a drill rod, which is preferably divided into three sections from top to bottom: a cable-guided drill rod section 41, an upper non-magnetic drill rod 42, and a lower non-magnetic drill rod 43. A probe outer tube 34 is coaxially sleeved inside the drill rod, and a measuring probe is coaxially sleeved inside the probe outer tube 34. The measuring probe is used to measure the gas flow rate and pressure in the borehole. The measuring probe is obscured by the probe outer tube 34 in the figure and is not shown.

[0047] An annular downward gas chamber for passing nitrogen gas flow is formed between the inner wall of the outer tube 34 and the outer wall of the measuring probe; the upper end of the annular downward gas chamber is connected to the blower 14 and used to input high-pressure nitrogen gas.

[0048] An air screw motor 44 is connected to the lower end of the drill rod. The lower end of the annular downward air chamber is connected to the air screw motor 44. The rotor (rotating part) of the air screw motor 44 is connected to a directional drill bit 45. The drill bit of the air screw motor 44 is provided with an air hole for blowing high-pressure nitrogen into the bottom of the borehole. The air hole is a conventional technology and is not shown in the figure.

[0049] An air inlet 33 is provided on the outer wall of the drill rod at the lower part (at the lower non-magnetic drill rod 43). An annular upward air chamber 79 for passing nitrogen gas flow is formed between the inner wall of the drill rod above the air inlet 33 and the outer wall of the probe outer tube 34.

[0050] A funnel-shaped baffle 46, wider at the bottom and narrower at the top, is connected to the outer wall of the drill rod at the upper end of the air inlet 33. The bottom end of the baffle 46 matches (is the same as or slightly smaller than) the drilling radius of the directional drill bit 45. The baffle 46 is used to allow the upward-reversing airflow from the borehole to enter the annular upward air chamber 79 through the air inlet. The inner wall of the drill rod and the outer wall of the probe tube 34 are both smooth surfaces. The top of the annular upward air chamber 79 is higher than the borehole opening and is used to discharge the slag-laden airflow.

[0051] With the structure of the present invention, when the slag (coal powder, etc.) at the bottom of the borehole moves upward along the borehole with the airflow, it enters the annular upward air chamber 79 through the air inlet under the restriction of the wind shield 46 and flows upward. When the slag flows upward in the annular upward air chamber 79, it does not come into contact with the borehole wall, i.e., the coal wall, and the flow resistance is greatly reduced. This avoids the need to increase the air pressure due to the high resistance of the coal wall to the slag and coal powder, and avoids the problem of insufficient power for pneumatic drilling and slag discharge.

[0052] It also includes an orifice dust removal mechanism 5; a dust collection hood 52 is provided above the borehole opening, the drill rod passes through the dust collection hood 52 and is sealed to the dust collection hood 52 (e.g., a sealing ring is provided on the contact surface of the two), the top of the annular upward air chamber 79 is provided with an opening communicating with the dust collection hood 52 (this opening is provided on the drill rod); the dust collection hood 52 is connected to a dust collector 53 through a pipeline, the dust collector 53 is connected to a gas extraction pipe 56 through a pipeline, and a shut-off valve 57 is provided on the pipeline between the gas extraction pipe 56 and the dust collector 53.

[0053] The nitrogen-driven mechanism 1 includes an air compressor 11 (preferably a mobile air compressor), the air compressor 11 has an air outlet pipe connected to a cooling device 12, and the cooling device 12 has an air inlet, an air outlet, a water inlet and a water outlet.

[0054] The air inlet of the cooling device 12 is connected to the air outlet pipe of the air compressor 11.

[0055] The outlet of the cooling device 12 is connected to the inlet of the membrane separation nitrogen generator 13 via a pipeline;

[0056] The inlet of the cooling device 12 is connected to an external water source (such as an underground water supply pipeline or a municipal water supply network).

[0057] The outlet of the cooling device 12 is connected to the underground drainage facilities (such as a water tank);

[0058] The nitrogen outlet of the membrane separation nitrogen generator 13 is connected to the nitrogen outlet pipe 134;

[0059] The air inlet 124 and air outlet 125 of the cooling device 12 are connected by a first set of Tesla valves 121;

[0060] The inlet 123 and outlet 122 of the cooling device 12 are connected by a second Tesla valve 121;

[0061] The first set of Tesla valve 121 and the second set of Tesla valve 121 are closely attached together and used for water-air heat exchange;

[0062] The air inlet 124 and the water outlet 122 of the cooling device 12 are located at the same end of the cooling device 12, which is called end A, and the opposite end of end A is called end B; the air outlet 125 and the water inlet 123 of the cooling device 12 are located at end B of the cooling device 12.

[0063] The inlet 131 of the membrane separation nitrogen generator 13 is connected to the membrane module 132, and the nitrogen outlet end of the membrane module 132 is connected to the nitrogen outlet pipe 134 as the nitrogen outlet. The membrane module 132 also has an oxygen outlet end, which is a conventional technology and is not shown in the figure. The nitrogen outlet or nitrogen outlet pipe 134 is also connected to a nitrogen concentration sensor 133.

[0064] In the nitrogen-driven mechanism 1, the Tesla valve 121 serves both unidirectional flow (its inherent function) and water-gas heat exchange. Unidirectional flow makes the system more stable (the Tesla valve 121 itself is more stable than a regular check valve). Through counter-current heat exchange using two sets of Tesla valves 121, the system has fewer components (no need for check valves and counter-current heat exchange piping) and is easy to connect. Nitrogen concentration sensor 133

[0065] The air screw motor 44 includes a stator 444, an impeller 441 is provided in the air inlet end of the stator 444, and a rotor 443 is connected to the impeller 441. The rotor 443 rotates with the stator 444. The lower end of the rotor 443 extends out of the stator 444 and is connected to the directional drill bit 45. The stator 444 has an annular chamber 442 arranged around the rotor 443. The outline of the annular chamber 442 is a logarithmic helical tooth profile, and the helix angle is the same at any point on the tooth direction line of the logarithmic helical tooth profile.

[0066] The existing air screw motor 44 uses a cycloidal tooth profile for its annular chamber 442. This invention improves upon this by using a logarithmic spiral tooth profile. Utilizing the characteristic that the helix angle at any point on the tooth line of a logarithmic spiral tooth profile is the same value, the stability of airflow within the annular chamber 442 is increased. This results in more uniform stress on the stator 444 tooth profile surface, reducing vibration damage to detection equipment and other devices during operation, and extending the service life of measuring probes and other devices. Changing the cycloidal tooth profile of the annular chamber 442 in the air screw motor 44 to a logarithmic spiral tooth profile is another major innovation of this invention.

[0067] The present invention also includes an explosion-proof industrial control computer 31, a measuring probe connected to the directional drilling rig 2, and an explosion-proof industrial control computer 31 connected to a display screen; the explosion-proof industrial control computer is connected to the nitrogen concentration sensor 133, the blower 14, the air compressor 11 and the directional drilling rig 2 via a circuit.

[0068] This invention also provides a drilling and slag removal method for the above-mentioned nitrogen-driven pneumatic directional drilling equipment for underground nitrogen slag removal in soft coal seams, which is carried out according to the following steps:

[0069] The first step is connection and debugging. Connect the nitrogen drive mechanism 1, the air supply unit 14, the directional drilling tool assembly structure and the wellhead dust removal mechanism 5, and confirm that the entire drilling equipment is working normally through debugging.

[0070] The second step is nitrogen drilling. The high-temperature, high-pressure gas provided by the air compressor 11 exchanges heat with water in the cooling device 12 to obtain room-temperature, high-pressure air. This room-temperature, high-pressure air is then separated into nitrogen and oxygen by the membrane separation nitrogen generator 13. The separated nitrogen is sent into the annular downward air chamber through the nitrogen outlet pipe 134 and the blower 14, driving the impeller 441 and rotor 443 of the air screw motor 44 to rotate, which in turn drives the directional drill bit 45 to rotate and drill. During drilling, the drill rod is lowered along the borehole to continue drilling. During this step, the operator can monitor the nitrogen concentration in real time through the display screen to avoid safety risks caused by excessively low nitrogen concentration. If the nitrogen concentration is too low, the machine can be stopped immediately for maintenance of the membrane separation nitrogen generator 13. In this step, the nitrogen concentration is preferably controlled above 97% to balance safety and nitrogen production economy (higher concentrations result in higher costs).

[0071] The third step is nitrogen slag removal; after passing through the annular chamber 442 of the air screw motor 44, the nitrogen is discharged to the bottom of the borehole, carrying the drill cuttings (such as coal dust) in the borehole upwards along the annular gap between the outer wall of the drill rod and the borehole. When it is blocked by the wind shield 46, it enters the annular upward air chamber 79 through the air inlet 33. The airflow carrying the drill cuttings enters the dust collector 53 after passing through the annular upward air chamber 79 and the dust collection hood 52. After dust removal, it is discharged into the environment.

[0072] To achieve pneumatic drilling, the downward airflow must flow inside the drill rod (flowing outside the drill rod cannot drive the air screw motor 44), while the upward airflow needs to flow on the outer wall of the drill rod (the airflow blowing to the bottom of the hole returns upward through the annular gap between the drill rod and the inner wall of the borehole). The upward airflow carries drill cuttings, and due to the physical properties of the coal wall, there is significant resistance between them when it comes into contact with the borehole coal wall (the borehole coal wall blocks a large amount of drill cuttings), resulting in a small amount of cuttings discharged, which is not conducive to the purpose of cuttings discharge such as preventing hole blockage and drill jamming.

[0073] The present invention has a simple structure and simple steps. Its outstanding advantage is that the slag-carrying airflow ascends through the annular upward air chamber 79, thereby greatly reducing the contact area between the slag-carrying airflow and the borehole coal wall. Compared with the prior art in which the airflow flows along the borehole coal wall, the resistance of the airflow is greatly reduced. After the pressure loss of the airflow is greatly reduced, a faster drilling speed (higher rotation speed of the directional drill bit 45) can be achieved under the same air volume and air pressure, and more drill cuttings can be discharged.

[0074] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A nitrogen-driven directional drilling equipment for underground slag removal in soft coal seams, comprising a nitrogen drive mechanism and a directional drilling rig, wherein the directional drilling rig has a directional drilling tool assembly structure, the nitrogen drive mechanism is connected to a nitrogen outlet pipe, the nitrogen outlet pipe is connected to an air supply device, and the air supply device is connected to the directional drilling tool assembly structure, characterized in that: The directional drilling assembly includes a drill pipe, a probe outer tube coaxially sleeved inside the drill pipe, and a measuring probe coaxially sleeved inside the probe outer tube. The measuring probe is used to measure the gas flow rate and pressure in the borehole. An annular downward gas chamber for nitrogen gas flow is formed between the inner wall of the probe outer tube and the outer wall of the measuring probe. The upper end of the annular downward gas chamber is connected to a blower and used to input high-pressure nitrogen gas. An air screw motor is connected to the lower end of the drill rod. The lower end of the annular downward air chamber is connected to the air screw motor. The rotor of the air screw motor is connected to a directional drill bit. The drill bit of the air screw motor is provided with an air hole for blowing high-pressure nitrogen into the bottom of the borehole. An air inlet is provided on the outer wall of the drill rod at the lower part of the drill rod. An annular upward air chamber for passing nitrogen gas flow is formed between the inner wall of the drill rod above the air inlet and the outer wall of the probe tube. A funnel-shaped baffle, smaller at the top and larger at the bottom, is connected to the outer wall of the drill rod at the upper end of the air inlet. The bottom of the baffle matches the drilling radius of the directional drill bit. The baffle is used to allow the airflow that is deflected upwards through the borehole to enter the annular upward air chamber through the air inlet. The inner wall of the drill rod and the outer wall of the probe tube are both smooth surfaces. The top of the annular upward air chamber is higher than the borehole opening and is used to discharge the slag-laden airflow. The air screw motor includes a stator, an impeller is provided in the air inlet end of the stator, the impeller is connected to a rotor, and the rotor rotates with the stator; the lower end of the rotor extends out of the stator and is connected to the directional drill bit; the stator has an annular chamber arranged around the rotor, the outline of the annular chamber is a logarithmic helical tooth profile, and the helix angle is the same at any point on the tooth direction line of the logarithmic helical tooth profile.

2. The pneumatic directional drilling equipment for nitrogen slag removal in soft coal seams according to claim 1, characterized in that: It also includes dust collection mechanisms with orifices; A dust collection hood is installed above the borehole opening. The drill rod passes through the dust collection hood and is sealed to it. The top of the annular upward air chamber has an opening that communicates with the dust collection hood. The dust collection hood is connected to a dust collector through a pipeline. The dust collector is connected to a gas extraction pipe through a pipeline. A shut-off valve is installed on the pipeline between the gas extraction pipe and the dust collector.

3. The pneumatic directional drilling equipment for nitrogen slag removal in soft coal seams according to claim 1, characterized in that: The nitrogen-driven mechanism includes an air compressor, the air compressor's outlet pipe of which is connected to a cooling device, which has an air inlet, an air outlet, a water inlet, and a water outlet. The air inlet of the cooling device is connected to the air outlet pipe of the air compressor. The outlet of the cooling device is connected to the inlet of the membrane separation nitrogen generator via a pipeline; The cooling unit's water inlet is connected to an external water source. The outlet of the cooling device is connected to the underground drainage system; The nitrogen outlet of the membrane separation nitrogen generator is connected to the nitrogen outlet pipe; The air inlet and outlet of the cooling device are connected by a first set of Tesla valves; The inlet and outlet of the cooling device are connected by a second Tesla valve; The first set of Tesla valves and the second set of Tesla valves are placed close together and used for water-air heat exchange; The air inlet and water outlet of the cooling device are located at the same end of the cooling device, which is called end A, and the opposite end of end A is called end B; the air outlet and water inlet of the cooling device are located at end B of the cooling device. The inlet of the membrane separation nitrogen generator is connected to a membrane module, and the nitrogen outlet end of the membrane module is connected to the nitrogen outlet pipe as the nitrogen outlet; the nitrogen outlet or the nitrogen outlet pipe is also connected to a nitrogen concentration sensor.

4. The pneumatic directional drilling equipment for nitrogen slag removal in soft coal seams according to claim 3, characterized in that: It also includes an explosion-proof industrial control computer, a measuring probe connected to the directional drilling rig, and a display screen connected to the explosion-proof industrial control computer; the explosion-proof industrial control computer is connected to the nitrogen concentration sensor, the blower, the air compressor, and the directional drilling rig via wiring.

5. The drilling and slag removal method of the nitrogen-assisted directional drilling equipment for soft coal seams as described in claim 4, characterized in that... Follow these steps: The first step is connection and debugging. Connect the nitrogen drive mechanism, air supply, directional drilling tool assembly structure and wellhead dust removal mechanism, and confirm that the entire drilling equipment is working properly through debugging. The second step is nitrogen drilling. The high-temperature, high-pressure gas provided by the air compressor exchanges heat with water when passing through the cooling device to obtain room-temperature, high-pressure air. The room-temperature, high-pressure air is then separated into nitrogen and oxygen by a membrane separation nitrogen generator. The separated nitrogen is sent into the annular downward air chamber through the nitrogen outlet pipe and the blower, driving the impeller and rotor of the air screw motor to rotate, which in turn drives the directional drill bit to rotate and drill a hole. During the drilling process, the drill rod is lowered along the borehole to continue drilling. The third step is nitrogen slag removal; after passing through the annular chamber of the air screw motor, the nitrogen is discharged to the bottom of the borehole. When it carries the drill cuttings in the borehole upwards along the annular gap between the outer wall of the drill rod and the borehole, it is blocked by the wind shield and enters the annular upward air chamber through the air inlet. The airflow carrying the drill cuttings enters the dust collector after passing through the annular upward air chamber and the dust collection hood. After dust removal, it is discharged into the environment.

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