Hard rock fracturing device

Abstract

The application belongs to the technical field of mine exploitation equipment, and particularly relates to a hard rock fracturing device for falling ore from hard ore body. The hard rock fracturing device comprises a fracturing rod, and a cylindrical shell with an open end. Two arc-shaped members are symmetrically arranged in the shell at a certain distance and closely adhere to the inner wall of the shell. A guide groove is arranged between the two arc-shaped members. The shell is filled with expandable graphite. The outer wall of the shell is provided with a groove one along the axial direction and a groove two in a straight line. An induction coil is spirally wound on the outer periphery of the shell from the outer end of the shell to the inner end of the shell and located in the groove one, and then led out from the groove two to the outer end. The device further comprises a power supply system for supplying power to the fracturing rod, which is used for converting direct current into high-frequency high-voltage current and then supplying power to the induction coil. The application uses the high-temperature expansion characteristics of the expandable graphite to fracture the ore body, uses eddy current heating, has high heating efficiency, and the heating process and fracturing pressure are controllable.

Description

Technical Field

[0001] This invention belongs to the technical field of mining equipment, specifically a hard rock fracturing device for extracting ore from hard ore bodies. Background Technology

[0002] During mining operations, when hard rock intrusions or faults appear in front of the working face during hard rock mining, using mechanical rock breaking methods such as coal mining machines for forced mining is inefficient and causes severe equipment wear. Therefore, it is necessary to first weaken the strength of the hard rock by fracturing before using mechanical rock breaking. If the overlying strata of the stope are hard roofs, and a long-distance overhang and fracture of the roof occurs behind the goaf during mining, resulting in severe mine pressure, the safety of the working face cannot be guaranteed. It is necessary to forcefully release the exposed roof to ensure timely roof collapse. In projects involving roof cutting and goaf retention or narrow pillar excavation along the goaf, it is necessary to pre-fracture and relieve pressure on the roof of the mining roadway. Among the currently known methods for roof fracturing, traditional chemical blasting generates a large amount of dust, is easily limited by underground ventilation and gas conditions, and poses significant safety hazards. For non-explosive rock fracturing, the most representative methods are hydraulic fracturing, carbon dioxide phase change blasting, and static blasting. Hydraulic fracturing is overly complex, affecting mining progress and incurring high construction costs. Carbon dioxide phase change fracturing involves complex blasting cartridge loading and on-site construction, requiring high-quality boreholes. Static fracturing is low-cost, but its slow reaction time can easily lead to blowouts if the reaction rate is too fast. Therefore, there is an urgent need for a safe, efficient, and low-cost hard rock fracturing device for widespread application in hard rock fracturing to ensure safe and efficient mine production.

[0003] Expandable graphite is a novel functional carbon material widely used in environmental protection, sealing, biomedicine, high-energy batteries, phase change thermal storage, and fire safety. It can expand its volume instantaneously by 150 to 300 times at high temperatures and possesses high resilience and plasticity. Eddy current heating enables a rapid, uniform, and high-temperature controllable heating process, offering advantages such as efficient energy conversion and non-contact heating. Accordingly, this invention provides a simple-to-operate, rapidly responsive, and effectively directional fracturing device for extracting ore from hard ore bodies. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a hard rock fracturing device that utilizes the high-temperature expansion characteristics of expandable graphite to fracture ore bodies. Specifically, the hard rock fracturing device includes a fracturing rod, the main body of which is a cylindrical shell with one open end and a matching shell cover. Two arc-shaped components, spaced a certain distance apart and tightly fitted to the inner wall of the shell, are symmetrically arranged inside the shell. A groove along the axial direction of the shell is formed on the inner wall between the two arc-shaped components, which, together with the space between the two arc-shaped components, constitutes a guide groove. The shell is filled with expandable graphite. A first groove is spirally arranged along the axial direction on the outer wall of the shell, and a second groove is arranged horizontally. An induction coil spirally winds around the outer circumference of the shell from the outer end of the shell opening side until it reaches the inner end of the shell and is located within the first groove, then extends from the second groove to the outer end. The device also includes a power supply system for supplying power to the fracturing rod, which converts direct current into high-frequency, high-voltage electricity to supply power to the induction coil.

[0005] Preferably, the guide groove has a narrow bottom and a wide opening, and is spaced apart from the groove.

[0006] Preferably, the shell is made of 99.5% alumina ceramic strip steel, and yttrium oxide stabilizer is added during the molding process; the arc-shaped component is made of iron.

[0007] Preferably, the expandable graphite is low-temperature, high-expansion expandable graphite prepared by chemical oxidation, and the mass ratio of intercalating agent is natural flake graphite:KMnO4:HClO4:NH4NO3 = 1:0.45:8:0.12.

[0008] Preferably, the power supply system includes an LC oscillation circuit, which includes a transistor. The upper end of the transistor is the collector, the lower end is the emitter, and the left end is the base. A resistor is connected from the base of the transistor, and a resistor is connected from the emitter of the transistor. A capacitor is connected in parallel with the resistor. The lower ends of the capacitor, resistor, and resistor are grounded, and the grounding voltage is determined as the reference voltage. A resistor is connected from the upper end to the power supply VCC and from the lower end to the base of the transistor. A frequency selection network is connected from the collector of the transistor. The other end of the frequency selection network is connected to the power supply VCC. The frequency selection network is composed of an inductor and capacitors 2 and 3 connected in parallel. Capacitors 2 and 3 are connected in series. A wire is led out from the middle of capacitors 2 and 3 to the emitter of the transistor to form a feedback path. Wires are led out from both ends of capacitors 2 and 3 to serve as output ports.

[0009] Preferably, the power supply system further includes a non-inverting operational amplifier circuit, which includes an operational amplifier with an inverting input and a non-inverting input on its left side, with the inverting input on top and the non-inverting input on the bottom, and the right side being the output. The operational amplifier has two power interfaces, with power supplies VEE and VDD connected to them. A resistor four is connected to the non-inverting input of the operational amplifier, which is then connected to a signal source. A resistor five is connected to the inverting input of the operational amplifier and grounded, together with the feedback resistor, determining the circuit's amplification factor. The left end of the feedback resistor is connected to the inverting input of the operational amplifier, and the right end is connected to the output of the operational amplifier. A capacitor four is connected to the output of the operational amplifier, followed by a resistor six in series, and finally grounded. The two ends of the capacitor four are connected to the induction coil as the output, and a switch is connected in parallel with the resistor six. The output power of the non-inverting operational amplifier circuit is adjusted by the opening and closing of the switch.

[0010] The beneficial effects achieved by this invention are as follows: 1. This invention utilizes the high-temperature expansion characteristics of expandable graphite for ore body fracturing, employing eddy current heating, which offers high heating efficiency, controllable heating process, and controllable fracturing pressure; continuous and rapid fracturing is achieved by varying the power supply system; directional fracturing is achieved by carving guide grooves on the outer shell of the fracturing rod and assembling arc-shaped components internally. 2. The fracturing device of this invention is lightweight, made of environmentally friendly materials, and highly applicable to various rock engineering applications; the components of the fracturing device are low-cost, can be pre-assembled for transportation, and the process is simple; expandable graphite has high stability, ensuring stability and reliability during transportation; low-voltage DC power is used as the driving force, resulting in a high safety factor during fracturing. The fracturing device of this invention is simple to operate and can perform efficient fracturing work in a short time. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0012] Figure 1 These are the front and side views of the fracturing rod in an embodiment of a hard rock fracturing device according to the present invention;

[0013] Figure 2 This is an LC oscillation circuit diagram in an embodiment of a hard rock fracturing device of the present invention;

[0014] Figure 3 This is a circuit diagram of an in-phase proportional operational amplifier in an embodiment of a hard rock fracturing device of the present invention;

[0015] Figure 4This is a schematic diagram of the borehole arrangement for fracturing in an embodiment of a hard rock fracturing device of the present invention;

[0016] In the diagram: 1. Drill hole; 2. Initial crack; 3. Fracture crack; 41. Capacitor 1; 42. Resistor 1; 43. Resistor 2; 44. Resistor 3; 45. Transistor; 46. Inductor; 47. Capacitor 2; 48. Capacitor 3; 49. Power supply VCC; 50. Output port; 51. Signal source; 52. Ground; 53. Resistor 4; 54. Resistor 5; 55. Operational amplifier; 56. Feedback resistor; 57. Capacitor 4; 58. Resistor 6; 59. Switch S; 61. Power supply VEE; 62. Power supply VDD; 7. Induction coil; 8. Groove 1; 9. Groove 2; 10. Guide groove; 11. Arc-shaped component; 12. Housing. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The present invention proposes a hard rock fracturing device comprising a fracturing rod, such as... Figure 1 As shown, the fracturing rod body is a cylindrical shell 12 with one open end and a shell cover for sealing the opening of the shell 12; two arc-shaped members 11 are symmetrically arranged inside the shell 12, spaced a certain distance apart and tightly fitted to the inner wall of the shell 12; the shell 12 between the two arc-shaped members 11 has a groove on its inner wall along the axial direction of the shell 12, which together with the space between the two arc-shaped members 11 forms a guide groove 10, the guide groove 10 being narrow at the bottom and wide at the opening; the shell 12 is filled with expandable graphite (not shown in the figure); the outer wall of the shell 12 is spirally arranged with a groove 8 along the axial direction, and the outer wall of the shell 12 is straightly arranged with a groove 9 along the axial direction; the induction coil 7 starts from the outer end (open side) of the shell 12 and spirally winds around the outer circumference of the shell 12 until the inner end of the shell 12 and is located in the groove 8, and then leads out from the groove 9 to the outer end; the two ends of the induction coil 7 are respectively provided with wiring ( Figure 1 Induction coil 7 is not shown in the diagram. Figure 4The groove 9 and the guide groove 10 are spaced apart; the shell 12 is made of 99.5% alumina ceramic strip steel, and yttrium oxide stabilizer is added during the forming process; the arc-shaped component 11 is made of iron, and iron has a higher electrical conductivity than graphite, which can accelerate the eddy current heating speed and increase the strength of the shell 12 near the arc-shaped component 11, so that the shell 12 breaks at the guide groove 10, thereby achieving directional cracking; the expandable graphite is low-temperature high-ratio expandable graphite, prepared by chemical oxidation method, and the mass ratio of intercalating agent is natural flake graphite:KMnO4:HClO4:NH4NO3 = 1:0.45:8:0.12, wherein the natural flake graphite is 50 mesh.

[0019] It also includes a power supply system that supplies power to the fracturing rod. The power supply system converts direct current into high-frequency high-voltage electricity and then supplies power to the induction coil 7. The induction coil 7 generates a changing magnetic field, and the expandable graphite with high conductivity generates eddy current heating.

[0020] like Figure 2 As shown, the power supply system includes an LC oscillation circuit for generating high-frequency sine waves. The LC oscillation circuit includes a frequency selection network and an amplifier circuit. The frequency selection network consists of inductor 46, capacitor 47, and capacitor 48, which separates signals within a certain frequency range from signals of other frequencies. The amplifier circuit uses resistors 42, 43, and 44 to set the static operating point, ensuring that transistor 45 in the amplifier circuit amplifies AC signals without distortion when carrying them. AC signals refer to signals whose current direction changes, also known as oscillation signals. Transistor 45 amplifies the feedback signal, ultimately generating a sine wave oscillation. The LC oscillation circuit utilizes the energy storage characteristics of capacitors and inductors, allowing electrical and magnetic energy to alternately convert. Both electrical and magnetic energy have maximum and minimum values, resulting in oscillation. However, this is only an ideal situation. In reality, all electronic components will have losses. During the process of energy conversion between capacitors and inductors, energy is either lost or leaked to the outside, and the energy will continuously decrease. Therefore, actual LC oscillation circuits need an amplifying element, such as transistors, integrated operational amplifiers, and other digital LC circuits. Using this amplifying element, various signal feedback methods are used to amplify the continuously consumed oscillation signal, thereby ultimately outputting a signal with relatively stable amplitude and frequency.

[0021] The specific LC oscillation circuit includes a transistor 45, with the upper end being the collector, the lower end the emitter, and the left end the base. A resistor 42 is connected from the base of the transistor, and a resistor 43 is connected from the emitter. A capacitor 41 is connected in parallel with the resistor 42. The lower ends of the capacitor 41, resistor 42, and resistor 43 are grounded, and the grounding voltage is determined as the reference voltage. A resistor 44 is connected from the upper end to the power supply VCC49 and from the lower end to the transistor base. A frequency selection network is connected from the collector of the transistor, and the other end of the frequency selection network is connected to the power supply VCC49. The frequency selection network is composed of an inductor 46 and capacitors 47 and 48 connected in parallel. Capacitors 47 and 48 are connected in series, and a wire is led out from the middle of capacitors 47 and 48 to the emitter of the transistor to form a feedback path. Wires are led out from both ends of capacitors 47 and 48 to serve as output ports 50. The power supply VCC 49 is a 36V DC power supply; resistors 42, 43, and 44 have a resistance of 1kΩ; transistor 45 is a 2N2925; inductor 46 has an inductance of 1μH; capacitor 41 has a capacitance of 1μF; and capacitors 47 and 48 have a capacitance of 0.4μF. The LC oscillation circuit composed of these components, measured using Multisim simulation software, can output a 351kHz sine wave at output port 50. Figure 2 The output port 50 of the LC oscillation circuit is used as the signal source 51.

[0022] like Figure 3 As shown, the power supply system also includes a non-inverting operational amplifier circuit, which includes an operational amplifier 55. The left end of the operational amplifier 55 has an inverting input and a non-inverting input, with the inverting input on top and the non-inverting input on the bottom. The right end is the output. The operational amplifier 55 has two power interfaces, connected to power supplies VEE61 and VDD62 to power it and enable its operation. The non-inverting input of the operational amplifier is connected to a resistor 53, which is then connected to a signal source 51 (in practical applications, this should be replaced by the output port 50 of an LC oscillator circuit). Figure 3The signal source is positioned such that the upper end of output port 50 is replaced with the positive terminal of the signal source, and the lower end is replaced with the negative terminal of the signal source. The inverting input of the operational amplifier is connected to resistor 54 and then grounded, which, together with the feedback resistor 56, determines the circuit's amplification factor. The left end of the feedback resistor 56 is connected to the inverting input of the operational amplifier, and the right end is connected to the output of the operational amplifier. The output of the operational amplifier is connected to capacitor 57, then in series with resistor 58, and finally grounded. The two ends of capacitor 57 serve as the output, and are connected in parallel to induction coil 7 through the wiring of induction coil 7. Switch S59 is connected in parallel with resistor S58. The output power of the non-inverting proportional operational amplifier circuit is adjusted by closing and opening switch S59. The signal source 51 operates at 21V and 351kHz. Resistors 53 and 54 have a resistance of 10kΩ, and feedback resistor 56 has a resistance of 100kΩ. Operational amplifier 55 amplifies the input signal by 11 times, transforming the sine wave output from the LC oscillation circuit into a high-voltage sine wave that acts on induction coil 7. Power supplies VEE61 and VDD62 provide 5V power to operational amplifier 55. Feedback resistor 56 introduces voltage negative feedback to stabilize the output voltage and achieve the operational relationship. Capacitor 57 has a capacitance of 0.1μF to improve the power factor and reduce reactive power loss in the circuit. Using Multisim simulation software, when switch S59 is open, the voltage of induction coil 7 is 260V, a high-frequency current of 90A flows at 351kHz, and the average power is 4kW. When switch S59 is closed, resistor 58 has a resistance of 5Ω, and the measured voltage is 360V, the current is 90A, and the average power is 10kW.

[0023] An infrared temperature sensor is used to measure the temperature of the fracturing rod during operation. The infrared temperature sensor can be installed at the orifice. An overcurrent protection device is installed between the power supply system and the fracturing rod to prevent the impact force generated by fracturing from damaging the induction coil and causing a short circuit rather than an open circuit. When the short circuit current is too large, the overcurrent protection device automatically disconnects the induction coil from the power supply system to protect the power supply system.

[0024] like Figure 4 As shown, the hard rock fracturing device of the present invention is used as follows:

[0025] Step 1: Use a bench drill to drill holes in the hard rock ore body, hard rock intrusion, or hard rock roof.

[0026] Step 2: Insert the fracturing rod into the borehole 1, with the open end of the housing 12 facing the borehole, lead out the wiring of the induction coil, and seal the hole;

[0027] In step 3, after connecting the power supply system to the fracturing rod, a low-power heating of 4 kW is initially used to maintain the temperature of the expandable graphite inside the fracturing rod at around 300°C. The expansion pressure of the fracturing rod near borehole 1 creates an initial crack 2 in the radial direction. After 15 seconds of heating, the power is switched to a high power of 10 kW, raising the temperature to 400°C. The expandable graphite expands almost completely, with an expansion volume of 430 ml / g. When the strength limit of the shell 12 near the guide groove 10 is reached, the expanded graphite is released from the guide groove 10, further expanding the initial crack 2 and creating a fracture crack 3 in the direction of the guide groove, fully fracturing the hard rock. The induction coil 7 wrapped around the shell is damaged by impact, forming an open circuit to prevent a safety accident. The optimal frequency for eddy current heating of graphite is several hundred kilohertz to several megahertz; in this embodiment, the frequency is tuned to 351 kHz.

[0028] In this embodiment, the fracturing rod is a cylindrical shell 12 with a diameter of 76 mm and a length of 250 mm. It is assumed that the interior is completely filled with expandable graphite, which has a specific heat capacity of 0.7 J / (g·℃) and a density typically between 0.02 and 0.35 g / cm³. 3 The density of expandable graphite is taken as 0.2 g / cm³. 3 If the ambient temperature is room temperature (25℃), when the temperature rises to 300℃, ΔT1 = 275℃, and when it rises from 300℃ to 400℃, ΔT2 = 100℃. Based on these conditions, the mass of expandable graphite can be calculated to be 227.66g. It requires absorbing 42191.1J of heat to reach 300℃, and 15933.8J of heat to rise from 300℃ to 400℃. At a power of 4kW, it takes 10.55s to reach 300℃; when the power is increased to 10kW by closing switch S59, it takes 1.5s to reach 400℃. Considering the electrothermal conversion efficiency and circuit losses, low power heating should be maintained for 15s at the beginning to ensure the initial cracks are fully formed. After that, the temperature should be increased by closing switch S until complete cracking occurs.

[0029] While the present invention has been described above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method of using a hard rock fracturing device, the hard rock fracturing device comprising a fracturing rod, the main body of the fracturing rod being a cylindrical shell with one open end and a shell cover matching the shell; two arc-shaped components symmetrically arranged inside the shell, spaced at a certain distance and tightly fitted to the inner wall of the shell; a groove along the axial direction of the shell is formed on the inner wall of the shell between the two arc-shaped components, which together with the space between the two arc-shaped components forms a guide groove; the shell is filled with expandable graphite; a groove one is spirally arranged along the axial direction on the outer wall of the shell, and a groove two is arranged straight; an induction coil is spirally wound around the outer circumference of the shell from the outer end of the shell opening side to the inner end of the shell and located in the groove one, and then led out from the groove two to the outer end; it also includes a power supply system for supplying power to the fracturing rod, the power supply system converting direct current into high-frequency high-voltage current to supply power to the induction coil; in, The shell is made of 99.5% alumina ceramic strip steel, with yttrium oxide stabilizer added during the molding process; the arc-shaped component is made of iron; the expandable graphite is low-temperature high-expansion expandable graphite, prepared by chemical oxidation method, with the mass ratio of intercalating agent being natural flake graphite:KMnO4:HClO4:NH4NO3=1:0.45:8:0.12; Its features include the following steps: Step 1: Use a bench drill to drill holes in the hard rock ore body, hard rock intrusion, or hard rock roof. Step 2: Insert the fracturing rod into the drill hole with the open end of the shell facing the hole, lead out the wiring of the induction coil, and seal the hole; In step 3, after connecting the power supply system to the fracturing rod, a low-power heating of 4kW is initially used to maintain the temperature of the expandable graphite inside the fracturing rod at 300℃. The expansion pressure of the fracturing rod near the borehole generates initial cracks in the radial direction. After heating for 15 seconds, the power is changed to 10kW, and the temperature rises to 400℃. The expandable graphite expands almost completely. When it reaches the strength limit of the shell near the guide groove, the expanded graphite is released from the guide groove, further expanding the initial cracks and generating fracture cracks in the direction of the guide groove, fully fracturing the hard rock. The induction coil wrapped around the shell is damaged by the impact, forming an open circuit and avoiding a safety accident.

2. The method of using the hard rock fracturing device according to claim 1, characterized in that, The guide groove has a narrow bottom and a wide opening, and is spaced apart from the groove.

3. The method of using the hard rock fracturing device according to claim 1 or 2, characterized in that, The power supply system includes an LC oscillation circuit, which includes a transistor. The upper end of the transistor is the collector, the lower end is the emitter, and the left end is the base. A resistor is connected from the base of the transistor, and a resistor is connected from the emitter of the transistor. A capacitor is connected in parallel with the resistor. The lower ends of capacitors 1, 1, and 2 are grounded, and the grounding voltage is determined as the reference voltage. A resistor is connected from the upper end to the power supply VCC and from the lower end to the base of the transistor. A frequency selection network is connected from the collector of the transistor. The other end of the frequency selection network is connected to the power supply VCC. The frequency selection network is composed of an inductor and capacitors 2 and 3 connected in parallel. Capacitors 2 and 3 are connected in series. A wire is led out from the middle of capacitors 2 and 3 and connected to the emitter of the transistor to form a feedback path. Wires are led out from both ends of capacitors 2 and 3 to serve as output ports.

4. The method of using the hard rock fracturing device according to claim 3, characterized in that, The power supply system also includes a non-inverting operational amplifier circuit, which includes an operational amplifier with an inverting input and a non-inverting input on its left side, with the inverting input on top and the non-inverting input on the bottom. The right side is the output. The operational amplifier has two power interfaces, with power supply VEE and power supply VDD connected to them. The non-inverting input of the operational amplifier is connected to a resistor four, which is then connected to a signal source. The inverting input of the operational amplifier is connected to a resistor five and then grounded, which, together with the feedback resistor, determines the circuit's amplification factor. The left end of the feedback resistor is connected to the inverting input of the operational amplifier, and the right end is connected to the output of the operational amplifier. The output of the operational amplifier is connected to a capacitor four, which is then connected in series with a resistor six and finally grounded. The two ends of the capacitor four are connected to the induction coil as the output, and a switch is connected in parallel with the resistor six. The output power of the non-inverting operational amplifier circuit is adjusted by opening and closing the switch.

Images