A carbon dioxide quasi-closed integrated energy supply system suitable for remote mines and a method for operating the same

Abstract

This invention discloses a semi-closed integrated carbon dioxide power supply system suitable for remote mines. A high-pressure power supply pipe (7.2~7.3MPa) drives a pneumatic compressor to supply air to all pneumatic equipment in the mine, replacing the electric air compressor. Simultaneously, the working fluid, after throttling and expansion, provides a 5~10℃ cold source underground, replacing the electric refrigeration unit, achieving zero power consumption for both the air compressor and refrigeration. The low-pressure return pipe only recovers waste gas and performs safety functions, achieving decoupling of the working fluid flow. Waste heat from the turbine outlet is used in stages to supply heat for shaft antifreeze, employee bathing, surface building heating, and mine water treatment. Carbon dioxide capture and reinjection in the flue gas achieves self-circulation of the working fluid. This invention replaces six separate sets of equipment—electric air compressor, electric refrigeration unit, boiler, fire fighting, inerting, and rescue—with a single system. It is decoupled from the power grid, inherently safe, and explosion-proof, making it suitable for remote mines and off-grid mining areas.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive energy utilization and safety technology in mining, specifically involving a quasi-closed integrated energy supply system using carbon dioxide as the unified working fluid. It is applicable to deep well heat hazard control and off-grid mining areas in various underground mines (including coal mines, metal mines, non-metal mines, chemical mines, etc.).

[0002] Terminology Definition

[0003] (1) Equivalent condensing pressure: A unified pressure reference based on thermodynamic optimization of the reverse Carnot cycle of carbon dioxide. The critical pressure of carbon dioxide is 7.3773 MPa. This invention preferably uses 7.10 MPa as the equivalent condensing pressure, corresponding to a saturation temperature of approximately 29.3 °C, as the pressure reference point for the user-side cooling mode. In actual operation, this pressure fluctuates within the range of ±0.1 MPa and is dynamically adjusted by the PID controller to maintain it near the target value.

[0004] (2) Turbine-boosting coaxial device: A coaxial device consisting of a compression section and an expansion section rigidly connected by the same rotating shaft. The mechanical work output by the expansion section directly drives the compression section, achieving energy self-sufficiency and eliminating the need for external power to drive the compressor. The compression section is a multi-stage centrifugal compression structure, equipped with interstage extraction ports and intermediate stage gas supply ports.

[0005] (3) Quasi-closed circulation: A circulation system in which the working fluid flows continuously back and forth in a closed pipeline network. The system allows for the consumption of the working fluid in identifiable and measurable special consumption scenarios such as inerting and fire fighting. The working fluid is dynamically replenished through the flue gas carbon dioxide capture and reinjection module to maintain a constant total amount in the system. The system does not consume carbon dioxide working fluid due to the daily use of pneumatic equipment, which is driven by an independent compressed air circuit. Background Technology

[0006] As mining of various mineral resources extends to deeper levels, heat hazards in mines have become a widespread problem. Deep mining of coal, metal, and non-metal mines also faces the challenge of working face temperatures exceeding 30°C. Electric air compressors and electric refrigeration systems are the two largest power-consuming components in a mine—electric air compressors account for 10% to 35% of the total mine power consumption and operate continuously year-round; electric refrigeration units have an installed capacity of several thousand kilowatts, consuming approximately 1 million kilowatt-hours per month in summer, and main fan ventilation energy consumption accounts for approximately 14% to 30% of the total mine power consumption. Together, these two systems account for 30% to 60% of the total mine power consumption and are entirely dependent on the power grid.

[0007] Meanwhile, issues such as deep well heat hazards, gas explosion prevention, fire protection, heating, and mine drainage are addressed independently, resulting in redundant equipment, large investments, and complex operation and maintenance. Furthermore, grid connection costs are high for remote mines, and the risk of power outages remains constant.

[0008] Existing mine carbon dioxide refrigeration systems are all electrically driven compression systems, essentially following the "grid → electric compression → refrigeration" technical path, and still dependent on the power grid. Safety functions such as carbon dioxide inerting, fire fighting, and rescue each require independent carbon dioxide gas sources, leading to unreliable supply in remote mines. There is an urgent need for a comprehensive mine system that does not rely on the power grid and uses a single working fluid to simultaneously address issues related to compressed air power, refrigeration, heating, and drainage. Summary of the Invention

[0009] 3.1 Purpose of the Invention

[0010] This invention aims to provide a quasi-closed integrated carbon dioxide energy supply system suitable for remote mines. Using carbon dioxide as the unified working fluid, the core objective is to use the pressure energy from the high-pressure supply pipe, after depressurization, to uniformly drive all pneumatic equipment in the mine, completely replacing the mine's largest power-consuming equipment—the electric air compressor (accounting for 10%~35% of the mine's total power consumption), thus reducing the air compressor's power consumption to zero. Simultaneously, the working fluid in the high-pressure supply pipe, after throttling and expansion, provides a 5~10℃ cold source for the underground working face and surface buildings, completely replacing the electric refrigeration unit and reducing refrigeration power consumption to zero. The low-pressure return gas pipe only handles waste gas recovery and unified distribution for safety functions, achieving decoupling of the working fluid flow between the refrigeration cycle and the pneumatic air supply. Waste heat from the turbine outlet is used in a cascaded manner for shaft antifreeze, employee bathing hot water, surface building heating, and mine water treatment heat. Flue gas carbon dioxide capture and reinjection achieve self-circulation of the working fluid. This single system simultaneously solves the three major energy-consuming areas of air compression, refrigeration, and heating, replacing six separate sets of equipment: electric air compressor + electric refrigeration unit + boiler + fire fighting + inerting + rescue.

[0011] 3.2 Technical Solution

[0012] (I) System Overall Architecture

[0013] The system of this invention consists of a local energy station, a waste heat power generation section, a waste heat utilization section, a regenerator, a high-pressure power supply pipe, a low-pressure return gas pipe, an equivalent condensing pressure regulating unit, and a control unit. The local energy station is located on the surface, the high-pressure power supply pipe extends to each energy consumption area underground and each gas consumption area on the surface, and the low-pressure return gas pipe returns to the surface from each area underground and on the surface.

[0014] The decoupling design of the high-pressure power supply pipe and the low-pressure return pipe is the core architectural feature of this invention. The high-pressure power supply pipe simultaneously handles the delivery of two working fluids:

[0015] One path of air enters the underground refrigeration terminal and the surface building air conditioning terminal via a throttling valve to evaporate and absorb heat, providing a 5-10°C cold source; the other path drives the pneumatic compressor to perform work via a pressure reducing branch. The pneumatic compressor draws in air from the roadway, compresses it, and supplies it to the underground and surface pneumatic equipment. After the compressed air performs work, it is discharged into the roadway. The carbon dioxide exhaust gas from the pneumatic compressor and the evaporation return gas from the refrigeration terminal merge in the low-pressure return gas pipe, and together they are preheated by the regenerator before returning to the compressor inlet.

[0016] The two working fluids are split on the high-pressure side and merge on the low-pressure side. The evaporator flow rate and the gas consumption of the pneumatic equipment in the refrigeration cycle are independent and do not interfere with each other.

[0017] (ii) Loop Path

[0018] The working fluid runs along the main circulation path: compression section → cold side of preheater → carbon dioxide heating device → expansion section → hot side of preheater → waste heat power generation section → waste heat utilization section → hot side of regenerator → high pressure energy supply tank → high pressure energy supply → (branch 1: downhole refrigeration terminal / surface air conditioner → low pressure return gas pipe; branch 2: after the pneumatic compressor does work → low pressure return gas pipe) → deep dryer filter → low pressure return gas tank → cold side of regenerator → compression section.

[0019] (III) Functions of each component

[0020] Compression and Expansion Sections: The carbon dioxide working fluid is pressurized from 3.6~3.98MPa to 10~12MPa in the compression section, preheated to approximately 200℃ by a preheater, and then heated to 500~650℃ by a carbon dioxide heating device. It then expands to 7.2~7.3MPa in the expansion section, with an outlet temperature of 350~420℃, coaxially driving the compression section to achieve energy self-sufficiency. The compression section is a multi-stage centrifugal compression structure, equipped with interstage extraction ports and intermediate stage make-up ports.

[0021] Preheater: Utilizes the waste heat from turbine exhaust to preheat the compressed working fluid from 65°C to approximately 200°C.

[0022] Carbon dioxide heating device: It uses mine gas, coalbed methane, diesel or biomass fuel as heat source. Taking mine gas as an example, when the gas concentration is ≥30%, combustion produces high-temperature flue gas of 1200~1700℃, which is heated to 500~650℃ by the carbon dioxide working medium through a heat exchanger.

[0023] Waste heat power generation section: Its inlet is connected to the hot-side outlet of the preheater, recovering the waste heat (400~450℃) released by the preheater after the turbine outlet to generate electricity, while the working fluid temperature drops to 100~200℃. The waste heat power generation section maintains the system's thermal balance by adjusting the heat extraction ratio—increasing the heat extraction when the user-side heat load decreases to maintain thermal balance, and decreasing the heat extraction when the heat load increases to meet user demand. The generated electricity supplies control units, sensors, solenoid valves, auxiliary motors, lighting, and communication equipment.

[0024] Waste heat utilization section: The working fluid after heat extraction in the waste heat power generation section enters this unit and is divided into three branches according to user needs: well shaft antifreeze branch, domestic heating branch, and production heating branch, as detailed below:

[0025] • Wellbore antifreeze branch: Heat exchange generates 45~60℃ hot air to supply the wellhead for antifreeze, preventing the wellbore from freezing in winter;

[0026] • Domestic heating branch: Heat exchange produces hot water at 45~60℃, which is given priority to employees for bathing throughout the year (the mine has the largest and most stable heat load, operating continuously for 365 days). The remaining heat is used for heating ground buildings such as office buildings, dormitories, canteens, bathrooms, and dispatch centers in winter.

[0027] • Production heating branch: Provides heat source for mine water treatment system (for processes such as high-salt wastewater concentration and evaporation), and provides heat for production processes such as mineral drying, replacing coal-fired boilers;

[0028] Regenerator: Located within the local energy station, its hot-side inlet connects to the waste heat recovery section outlet, and its cold-side inlet connects to the low-pressure return gas pipe. It utilizes 5-10°C low-pressure return gas to cool the high-pressure working fluid to 35°C, while simultaneously preheating the low-pressure return gas to reduce power consumption in the compression section. The regenerator is a key component for achieving equivalent condensing pressure lock-in and a 30%-35% COP increase—the high-pressure working fluid, after being cooled by the regenerator, enters the high-pressure power supply tank, providing a stable 35°C working fluid inlet condition for the subsequent equivalent condensing pressure regulation unit, ensuring that the recooler can further subcool the working fluid to no higher than 29.8°C.

[0029] High-pressure energy supply tank: Located between the hot side outlet of the regenerator and the inlet of the high-pressure energy supply pipe, it is used to buffer and maintain the energy supply pressure (7.2~7.3MPa) of the high-pressure energy supply pipe.

[0030] High-pressure power supply pipeline: Extending to various gas-using areas underground and on the surface, with a pressure of 7.2~7.3MPa. The high-pressure power supply pipeline has multiple pressure-reducing branches, extending to various working faces underground and various gas-using areas on the surface (including anti-freezing dampers at the mine entrance, heating regulating valves, pneumatic equipment in office and living areas, etc.), driving pneumatic compressors after pressure reduction. The pneumatic compressors draw air from the roadway, compress it to 0.2~0.8MPa, and then supply it to the pneumatic equipment, completely replacing the mine's electric air compressors and compressed air pipeline network. The high-pressure power supply pipeline uses carbon dioxide as the working fluid to simultaneously drive the throttling expansion of the refrigeration terminal and the pneumatic compressor. The two working fluids are split on the high-pressure side and then converge in the low-pressure return gas pipeline. The pneumatic compressor draws air from the roadway, compresses it, and supplies it to the pneumatic equipment. The carbon dioxide working fluid does not enter the pneumatic equipment, and the gas consumption of the pneumatic branches does not affect the working fluid balance of the carbon dioxide cycle. Meanwhile, the high-pressure power supply pipe expands through throttling to provide a 5-10°C cooling source for the underground working face and surface buildings (office buildings, dormitories, canteens, etc.), completely replacing the mine's electric-driven refrigeration unit and ground split air conditioner.

[0031] Equivalent condensing pressure regulating unit: Located at the end of the high-pressure power supply pipe and before the refrigeration terminal, it includes a recooler, pressure sensor, temperature sensor, and PID control valve. The working fluid supplied by the high-pressure power supply pipe is locked to 7.10 MPa ± 0.1 MPa by the equivalent condensing pressure regulating unit, and then enters the refrigeration terminal for evaporation and heat absorption via a throttling valve. The cold side of the recooler is circulated with low-temperature return gas diverted from the outlet of the downhole refrigeration terminal, subcooling the high-pressure working fluid to no higher than 29.8℃. The PID controller automatically adjusts the valve opening based on the dual constraints of the equivalent condensing pressure and the recooler outlet temperature, keeping the terminal refrigeration pressure constant at 7.10 MPa ± 0.1 MPa. This locking mechanism improves the system COP by 30%~35% compared to a system without subcooling.

[0032] Low-pressure return gas pipe: pressure 3.6~3.98MPa, temperature 5~10℃. Its inlet connects to the underground refrigeration terminal, the surface building air conditioning terminal, and the carbon dioxide exhaust outlet after each pneumatic compressor has performed work. The outlet connects to the low-pressure return gas tank through a deep drying filter. The low-pressure return gas pipe only undertakes the pressure energy transmission and distribution for exhaust gas recovery and safety functions (firefighting, inerting, rescue), and is not used as a gas source for pneumatic equipment.

[0033] Low-pressure return gas tank: Located between the deep dryer filter and the cold side inlet of the regenerator, it is used to collect the working fluid returned by the low-pressure return gas pipe and stabilize the inlet pressure of the compressor section. Its pressure serves as the feedback quantity of the quality closed-loop control module.

[0034] Deep drying filter: installed between the low-pressure return gas pipe and the low-pressure return gas tank, used to remove moisture and solid impurities from the working fluid, and to prevent water-containing carbon dioxide corrosion and compressor wear.

[0035] Integrated security protection branch line:

[0036] • Fire branch lines: These originate from the low-pressure return gas pipe and are equipped with distributed fire buffer tank assemblies located near each fire compartment. Normally, they are replenished with gas and energy from the low-pressure return gas pipe, maintaining a pressure of no less than 2.5 MPa within the tanks. In case of fire, carbon dioxide is released first for extinguishing the fire; if insufficient, gas is continuously replenished from the pipeline network. Each fire compartment is equipped with pneumatic temperature sensors and pneumatic logic valve assemblies, automatically arranging complete fire-fighting action sequences without the need for a power controller. When a pneumatic temperature sensor activates, the gas pressure signal is transmitted through the low-pressure return gas pipe to the pneumatic logic valve assembly, automatically executing the following interlocking actions based on the protected area type: closing the emergency shut-off valve of the high-pressure power supply pipe, switching the corresponding extinguishing medium to the fire nozzle, closing the ventilation and exhaust valves, opening the ejector device for smoke exhaust, cutting off the pneumatic terminal power supply to the area, and opening the pneumatic fire water valve. In areas unsuitable for water-based firefighting, such as underground electromechanical chambers, substations, material warehouses, grease warehouses, and explosive material warehouses, modular fire-fighting carbon storage cylinders are used for carbon dioxide extinguishing or total flooding inerting. In areas such as coal mining faces, tunneling faces, belt conveyor roadways, refuge chambers, and rescue chambers, pneumatic water pumps driven by low-pressure return air pipes or by opening water supply butterfly valves are used for water spraying, fine water mist, or pneumatic fire monitors. In surface buildings such as mine shaft houses, winch rooms, ground office buildings, canteens, bathrooms, and material storage yards, pneumatic fire pumps driven by low-pressure return air pipes are used for water spraying or fire hydrant extinguishing. All actions are completed within milliseconds after being triggered by a pneumatic pressure signal. The entire process requires no electrically driven components or electronic controllers, and the fire-fighting function is completely unaffected by power outages, covering all underground fire zones and various surface buildings.

[0037] • Inerting branch: Leading out from the outlet of the capture unit and the inlet of the purification unit of the flue gas carbon dioxide capture and purification module, the captured but unpurified carbon dioxide is directly sent into the goaf to maintain the carbon dioxide concentration in the goaf at not less than 23%;

[0038] • Rescue branch: Continuously supply pressure energy to the rescue chamber to enable long-term continuous standby for rescue.

[0039] Thermal compensation loop (optional expansion for winter operation in northern regions): Located between the heating user outlet and the intermediate stage gas supply interface of the compressor, it is only activated during winter heating operations. The working fluid, cooled to 40-50℃ after heating, returns directly to the intermediate stage of the compressor, merging into the compression process at a pressure higher than that of the low-pressure return gas pipe, maintaining the system's mass flow balance and pressure stability during winter heating. The thermal compensation loop and the low-pressure return gas pipe return independently and are not interconnected.

[0040] Optional expansion of the electric compressor (engineering adaptability): The compressor unit can be connected in parallel with an electric storage compressor unit for auxiliary power drive when the mine power grid is available, reducing fuel consumption; or it can serve as a temporary alternative power source during maintenance of the turbine-boosting coaxial unit. This option is an optional additional function and does not affect the independent protection scope of this invention, which is based on heat source self-sustaining drive as its core technical feature. Even during power grid interruptions, the turbine-boosting coaxial unit can still independently maintain the full functionality of the system.

[0041] The flue gas carbon dioxide capture and purification module is located on the exhaust pipe of the carbon dioxide heating device and includes a capture unit and a purification unit. After pretreatment (dust removal and cooling), the flue gas enters the capture unit, where carbon dioxide is separated from the flue gas using at least one of the following methods: chemical absorption (amine method, suitable for low-concentration flue gas of 10%~18%), pressure swing adsorption (solid adsorbent material, low energy consumption, fast start-up and shutdown), or membrane separation, to obtain carbon dioxide-rich gas. A diversion valve is installed at the outlet of the capture unit, one path of which sends the carbon dioxide-rich gas to the purification unit, and the other path is directly connected to the inerting branch for inerting in the goaf. The purification unit purifies the carbon dioxide-rich gas to a purity of ≥99.5% (meeting the industrial-grade carbon dioxide standard GB / T6052 and the requirements of the refrigerant). The purified carbon dioxide is pressurized by a pneumatic booster pump (a multi-stage booster structure, using the pressure energy of the low-pressure return gas pipe as the power source) and then reinjected into the system through the make-up gas branch, realizing a quasi-closed-loop self-sustaining working fluid cycle.

[0042] The three-level metering leak location module: the first meter at the local energy station outlet, the second meter at the entrance of each regional branch road, and the third meter at each end user collect mass flow data in real time. When the deviation exceeds 3%, a leak is detected and remotely isolated.

[0043] (iv) Control Logic:

[0044] The system of this invention is controlled by a three-level global control platform, including three independent control channels for heat balance, pressure balance, and mass balance.

[0045] (1) Heat balance control: The system achieves tiered heat absorption through the coordination of the waste heat power generation section and the waste heat utilization section. The waste heat power generation section maintains the system's heat balance by adjusting the heat extraction ratio—when the user's heat load decreases, the heat extraction ratio is increased to convert excess heat into electricity; when the heat load increases, the heat extraction ratio is decreased to prioritize the supply of heat to users. After heat extraction in the power generation section, the working fluid temperature drops to 100~200℃ and enters the waste heat utilization section, supplying heat as needed for shaft antifreeze, employee bathing hot water, ground building heating, and mine water treatment. After heat extraction, the working fluid enters the regenerator, where it is further cooled from 5~10℃ low-pressure return gas to 35℃. The three heat treatment links constitute a complete heat balance chain: high-temperature heat extraction (power generation section) → medium-temperature absorption (waste heat utilization section) → low-temperature fine adjustment (regenerator), none of which can be omitted.

[0046] (2) Pressure balance control: The thermal closed-loop control module uses the outlet pressure of the compression section as feedback and maintains the outlet pressure of the compression section at 10~12MPa by adjusting the fuel supply. When the user load changes and causes pressure fluctuations, the fuel supply adjustment responds first. When the load transient exceeds the fuel adjustment capacity (there is thermal inertia, and the response time is about 2~3 minutes), the auxiliary motor is driven by the power generated by the waste heat power generation section to supplement the power to the coaxial shaft system within milliseconds, forming a dual actuator collaborative architecture of "fuel adjustment (coarse adjustment) + auxiliary motor (fine adjustment)".

[0047] (3) Mass balance control: The mass closed-loop control module uses the low-pressure return gas tank pressure as feedback quantity and is linked with the gas replenishment valve of the gas replenishment branch. When the return gas pressure drops due to the consumption of working fluid such as fire fighting and inerting, the gas replenishment valve is opened to replenish carbon dioxide working fluid and restore the return gas pressure to the set value. This channel maintains the total amount of working fluid in the system, which is constrained by thermodynamic mass conservation.

[0048] The three control channels are decoupled on a time scale: mass balance adjustment takes about 10 seconds, pressure balance adjustment (fuel) takes about 2 to 3 minutes, and auxiliary motor adjustment takes milliseconds—they do not interfere with each other and work together to maintain the stable operation of the system.

[0049] 4. Beneficial effects

[0050] 1. A single system simultaneously addresses three major energy-consuming areas: air compression, refrigeration, and heating. High-pressure power supply pipes, after pressure reduction, uniformly drive all pneumatic compressors in the mine, replacing electric air compressors (which account for 10%~35% of total mine power consumption), eliminating power consumption for air compressors. Simultaneously, the working fluid in the high-pressure power supply pipes, after throttling and expansion, provides a 5~10℃ cold source for underground working faces and surface buildings, replacing electric refrigeration units, eliminating refrigeration power consumption. Waste heat from the turbine outlet is used in a cascade system for shaft antifreeze, employee hot water for showers, surface building heating, and mine water treatment, eliminating heating power consumption. A single carbon dioxide pipeline network simultaneously provides air compression power, underground refrigeration, surface air conditioning, shaft antifreeze, surface heating, mine water treatment heating, fire extinguishing, carbon dioxide inerting, and rescue support, replacing six independent systems: electric air compressors + electric refrigeration units + boilers + fire fighting + inerting + rescue.

[0051] 2. Decoupling of refrigeration and pneumatic working fluid flow, resulting in high temperature control accuracy: The pneumatic compressor draws gas from the high-pressure power supply pipe to perform work, while the low-pressure return gas pipe only recovers carbon dioxide waste gas. There is no mass competition between the refrigeration evaporator flow and the gas consumption of the pneumatic compressor, and fluctuations in pneumatic load do not affect refrigeration stability. The equivalent condensing pressure is locked at 7.10MPa±0.1MPa. In conjunction with the regenerator, the low-pressure return gas is used to cool the high-pressure working fluid to achieve subcooling. The system COP is improved by 30%~35% compared to the scheme without subcooling, the terminal temperature control accuracy is stable within ±0.5℃, and the compression power consumption is reduced by 5%~10%.

[0052] 3. Decoupling of waste heat utilization from the power grid: The heat from the turbine outlet is used for heat extraction and power generation in the waste heat power generation section and for cascade heating in the waste heat utilization section. The overall primary energy utilization rate reaches 75%~85%, and it is completely independent of the external power grid.

[0053] 4. Elimination-type Intrinsically Safe Explosion-Proof (Eliminating Two Major Risk Chains at the Root): Electrical ignition sources are the primary cause of gas explosions (accounting for 48.1%). This invention completely replaces the electric drive of all underground pneumatic equipment and core circulation with pressure energy, physically eliminating the conditions for the generation of electrical sparks. Simultaneously, traditional mine safety is highly dependent on the reliability of the power grid—power outages mean ventilation stoppage and gas accumulation; power restoration means ignition and gas explosion. This invention does not rely on power grid operation, physically eliminating both the "power outage leading to gas accumulation" and the "power restoration generating electrical sparks igniting explosion"—two fatal risk chains—achieving a leap from "limited intrinsic safety" to "elimination-type intrinsic safety."

[0054] 5. Long-distance non-powered transportation: The resistance along the path of supercritical carbon dioxide is much lower than that of water systems, and it can cover tens of kilometers of mining area without the need for intermediate booster pump stations; the vertical static pressure is only 1 / 3 to 1 / 2 of that of water systems.

[0055] 6. Co-treatment of working fluid and waste heat and wastewater: Carbon dioxide (ODP=0, GWP=1) completely eliminates Freon; waste heat from turbine outlet provides a heat source for mine water treatment (such as high-salt wastewater concentration and evaporation), realizing the co-treatment of waste heat and wastewater and reducing coal or electricity consumption in mine water treatment.

[0056] 7. Integrated fire protection and distributed buffer protection: The low-pressure return gas pipe also serves as a unified fire protection gas source for the entire mining area, and the distributed buffer tank group achieves a second-level response, so the fire protection function is not affected when the mains power is interrupted.

[0057] 8. Modular and detachable with continuous excavation: The high-pressure power supply pipe and the low-pressure return gas pipe adopt a segmented modular structure. The pipe segments are connected by a detachable connection structure. As the mine excavation face advances, the pipe segments are dismantled and recycled in the completed mining area and moved to the new working face for reinstallation and use. The equipment has a high reuse rate and significantly reduces long-term investment. Attached Figure Description

[0058] Figure 1 is a schematic diagram of the overall structure of the system of the present invention. Detailed Implementation

[0059] Example 1: Remote deep mines – Elimination of electric air compressors and electric refrigeration

[0060] A remote, deep mine, at a depth of 1200m, with a working face temperature of 38℃, has no power grid connection. The original system configuration included: an electric air compressor with a power of 800kW (accounting for 25% of the mine's total electricity consumption), consuming approximately 7 million kWh annually, with annual electricity costs of approximately 4.9 million yuan; and an electric chiller unit with an installed capacity of 1500kW, consuming approximately 1 million kWh per month in summer and approximately 4 million kWh during the four-month cooling season, with annual electricity costs of approximately 2.8 million yuan; the combined annual electricity costs for both were approximately 7.7 million yuan. In addition, a coal-fired boiler and an independent fire-fighting system were also configured, each operating independently.

[0061] Install one system of this invention, and the local energy station uses coal mine gas as fuel. A certain high-gas mine has a sufficient annual coal mine gas extraction capacity (≥50 million m³). 3 The system's annual gas consumption is approximately 200,000 m³. 3 This accounts for only 0.4% of the extracted gas, ensuring a sufficient and reliable gas supply.

[0062] Core replacement effect – elimination of electric air compressor and electric refrigeration: The high-pressure power supply pipe maintains a pressure of 7.2~7.3MPa, which drives the pneumatic compressor through the pressure reducing branch. The pneumatic compressor compresses the intake air to 0.5~0.7MPa and supplies it to all underground and surface pneumatic equipment in the mine. The original 800kW electric air compressor is completely decommissioned and dismantled, and the power consumption of the air compressor is reduced to zero.

[0063] At the same time, the high-pressure power supply pipe delivers carbon dioxide to the underground and surface buildings. After being locked at an equivalent condensation pressure of 7.10 MPa, it expands and throttles to provide a 5-10°C cold source for the underground working face and the surface office building, dormitory, and canteen. The working face temperature drops from 38°C to below 18°C. The original 1500kW electric-driven refrigeration unit and the ground split air conditioner are completely shut down and dismantled, and the refrigeration power consumption is reduced to zero.

[0064] As a preferred option, the gas source for the high-pressure power supply pipe can also be drawn from the intermediate stage of the compressor section, cooled and depressurized before being supplied with gas, which can further reduce the load on the final stage of the compressor section by about 5% to 10%.

[0065] Simultaneously, waste heat is utilized in a cascade manner: waste heat from the turbine outlet is used for power generation in the power generation section (generating approximately 80,000 kWh annually, used for control systems, sensors, lighting, etc.). The waste heat utilization section supplies antifreeze hot air to the shaft (in winter), hot water for employee showers (year-round), heating for ground buildings (in winter), and heat for mine water treatment (year-round). The original coal-fired boiler and electric heating equipment for mine water treatment are decommissioned.

[0066] Simultaneously, it provides integrated safety protection: carbon dioxide inerting in the goaf, continuous power supply to the rescue chamber, and fire protection coverage throughout the entire mine area (underground + surface), ensuring that all functions remain unaffected during power outages.

[0067] Summary of economic benefits:

[0068] • Eliminating the electric air compressor: annual electricity cost savings of approximately 4.9 million yuan.

[0069] • Eliminating electric-driven chiller units and floor-mounted split air conditioners: annual electricity savings of approximately 2.8 million yuan.

[0070] • Eliminating coal-fired boilers: Annual savings of approximately 800,000 yuan in coal and environmental protection costs.

[0071] • Eliminating the independent fire protection and inerting system: Annual maintenance cost savings of approximately 300,000 yuan.

[0072] • Annual total savings: approximately 8.8 million yuan

[0073] • Equipment investment payback period: approximately 3-4 years

[0074] Example 2: Gas-driven solution

[0075] In a high-gas mine, extracted methane gas (methane concentration ≥30%) is used as fuel. The methane is continuously supplied by the mine's extraction system, eliminating the need for external fuel. Compared to diesel-powered operation, fuel costs are reduced by more than 60%.

[0076] Example 3: Multi-stage preheating optimization

[0077] After adding multi-stage preheating units, fuel consumption is reduced by about 15% to 20%.

[0078] Example 4: Modular Excavation Follow-up and Flue Gas Capture and Reinjection

[0079] In a certain mine, the strike length of the mining area is 2000m. The high-pressure power supply pipe and the low-pressure return gas pipe are connected using standard pipe sections with a detachable connection structure. The system extends segment by segment as the working face advances, with the mined areas being dismantled and recycled section by section, achieving a recovery rate of over 95%, which is then reused in the next mining area. The flue gas carbon dioxide capture and purification module recovers carbon dioxide from the exhaust gas and reinjects it through a pneumatic booster pump system, recovering approximately 150 tons of carbon dioxide annually, meeting the needs for inerting and fire-fighting fluid consumption.

[0080] Example 5: Emergency Rescue Situation

[0081] The simulation addresses a complex disaster scenario involving a mine power outage, a sudden rise in working face temperature, and methane accumulation. After the mains power is interrupted, the turbine-boost coaxial unit maintains thermal circulation by continuously supplying heat from a heat source. High-pressure carbon dioxide is continuously delivered to the disaster area through a high-pressure power supply pipe. After being locked at equivalent condensation pressure, the carbon dioxide expands and throttles, providing an emergency cooling source of 5-10°C to the high-temperature area. A low-pressure return gas pipe drives a pneumatic fan for localized forced ventilation, diluting harmful gases. Simultaneously, the low-pressure return gas pipe injects carbon dioxide into the goaf and methane accumulation areas through an inerting branch, maintaining the carbon dioxide concentration in the disaster area above 23% and actively suppressing the risk of methane explosion. Rescue personnel, carrying lightweight pneumatic rescue tools supplied by the low-pressure return gas pipe, enter the disaster area to carry out rescue operations.

[0082] The refuge chamber is continuously supplied with pressurized energy through a low-pressure return pipe to drive the air purification and cooling system, maintaining a life-saving environment for the trapped personnel. The system operated continuously for 72 hours, with all rescue functions functioning normally, without relying on any external power or gas source.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A quasi-closed integrated carbon dioxide energy supply system suitable for remote mines, characterized in that, include: The local energy station is equipped with a turbine-boost coaxial unit, a preheater, and a carbon dioxide heating unit. The turbine-boosting coaxial device includes a compression section and an expansion section rigidly connected coaxially. The outlet of the compression section is connected to the cold-side inlet of the preheater, the cold-side outlet of the preheater is connected to the inlet of the carbon dioxide heating device, and the outlet of the carbon dioxide heating device is connected to the inlet of the expansion section. The expansion section expands and depressurizes, outputting mechanical work to the compression section to achieve energy self-sufficiency. The system relies on a heat source to drive the turbine-boosting coaxial device to maintain the circulating pressure, and normal operation does not require mains power to drive the compression equipment. The heat source of the carbon dioxide heating device is one or more of mine gas, coalbed methane, diesel, or biomass fuel. The waste heat power generation section is located in the local energy station. Its inlet is connected to the hot side outlet of the preheater. It is used to recover the waste heat after the turbine outlet has released heat through the preheater to generate electricity. The generated electricity is supplied to the system's electrical load. The waste heat power generation section maintains the system's thermal balance by adjusting the heat extraction ratio. When the user-side heat load decreases, the heat extraction ratio is increased to absorb the excess waste heat. The waste heat utilization section is located within the local energy station and is connected to the outlet of the waste heat power generation section. It is used to recover waste heat from the turbine outlet and is divided into a shaft anti-freezing branch, a domestic heating branch, and a production heating branch according to user needs. The domestic heating branch prioritizes supplying hot water for employee bathing throughout the year, and the remaining heat is used for winter heating of surface buildings. The production heating branch is used for mine water treatment and mineral drying. The regenerator is installed in the local energy station. Its hot-side inlet is connected to the outlet of the waste heat utilization section, and its cold-side inlet is connected to the low-pressure return gas pipe. It is used to cool the high-pressure side working fluid with low-pressure return gas and preheat the low-pressure return gas. The high-pressure power supply pipe has its inlet connected to the hot-side outlet of the regenerator via a high-pressure power supply tank, extending to various gas-using areas underground and on the surface. The high-pressure power supply pipe has multiple pressure-reducing branches, each of which is connected to a pneumatic compressor to drive it. The outlet of the pneumatic compressor is connected to pneumatic equipment to supply compressed air, replacing the mine's electric air compressor. Simultaneously, the working fluid in the high-pressure power supply pipe expands through throttling to provide a 5-10°C cold source for the underground working face and surface buildings, replacing the electric refrigeration unit. The low-pressure return gas pipe has its inlet connected to the exhaust gas outlet of each gas-using device, and its outlet connected to the cold side inlet of the regenerator via a deep drying filter and a low-pressure return gas tank. It is used to recover exhaust gas and send it to the regenerator for preheating. The low-pressure return gas pipe only undertakes exhaust gas recovery and safety functions and is not used as a gas source for pneumatic equipment. The pressure of the low-pressure return gas pipe is 3.6~3.98MPa. An equivalent condensing pressure regulating unit is installed at the end of the high-pressure power supply pipe and before the refrigeration terminal. It is used to lock the pressure of the high-pressure working fluid entering the refrigeration terminal at 7.10MPa±0.1MPa and then supply it to the refrigeration terminal through a throttling valve. The system includes a control unit and a quality closed-loop control module. The quality closed-loop control module includes a pressure sensor and a gas replenishment valve. The quality closed-loop control module uses the pressure of the low-pressure return gas tank as feedback and is linked with the gas replenishment valve of the gas replenishment branch to maintain a constant total amount of working fluid in the system. When the pressure of the low-pressure return gas tank drops due to the consumption of working fluid by fire fighting or inerting, the gas replenishment valve opens to replenish the working fluid and maintain a constant total amount of working fluid in the system.

2. The system according to claim 1, characterized in that, The compression section pressurizes the carbon dioxide working fluid to 10-12 MPa, preheats it in a preheater, and then sends it to the carbon dioxide heating device. The carbon dioxide heating device heats the working fluid to 500-650°C before sending it to the expansion section. The expansion section expands the working fluid to 7.2-7.3 MPa, with an outlet temperature of 350-420°C. After expansion, the working fluid passes through a preheater (high-temperature side), a waste heat power generation section, and a waste heat utilization section for heat extraction. It is then cooled to approximately 35°C by a regenerator before entering the high-pressure energy supply tank. The pressure of the high-pressure energy supply tank is 7.2-7.3 MPa. The pressure reduction branch reduces the pressure to 0.2-0.8 MPa before connecting it to a pneumatic compressor, which then supplies air to the pneumatic equipment.

3. The system according to claim 1, characterized in that, The control unit is also equipped with a thermal closed-loop control module, which adjusts the fuel supply based on the outlet pressure of the compression section as feedback, maintaining the outlet pressure of the compression section at a stable level of 10~12MPa. The compression section is equipped with an auxiliary motor, which is powered by the waste heat power generation section and is used to establish the initial circulating pressure during cold start of the system and to provide instantaneous power compensation during load transients. The auxiliary motor and the fuel supply regulation form a dual-actuator collaborative architecture, with the fuel supply regulation being a coarse adjustment and the auxiliary motor being a fine adjustment, so that the dynamic deviation of the outlet pressure of the compression section converges from the minute level to within the second level.

4. The system according to claim 1, characterized in that, The waste heat utilization section's shaft antifreeze branch generates 45-60℃ hot air to supply the wellhead for antifreeze; the domestic heating branch is used to supply hot water for employee bathing and heating for ground buildings, with hot water for bathing being supplied continuously throughout the year; the production heating branch is used to provide a heat source for the mine water treatment system and heat for mineral drying.

5. The system according to claim 1, characterized in that, The control unit is equipped with a three-level metering leak location module, including a first metering unit installed at the outlet of the local energy station, a second metering unit installed at the entrance of each regional branch road, and a third metering unit installed at each end user. The three-level metering leak location module collects the mass flow data of each metering point in real time. When the deviation between the second metering unit and the third metering unit exceeds the 3% threshold, it determines that there is a leak in the area and remotely closes the corresponding area solenoid valve to complete the isolation.

6. The system according to claim 1, characterized in that, It also includes a flue gas carbon dioxide capture and purification module, which is installed on the exhaust pipe of the carbon dioxide heating device. The module includes a capture unit and a purification unit. The capture unit is used to separate carbon dioxide-rich gas from the flue gas, and the purification unit is used to purify the carbon dioxide-rich gas to obtain high-purity carbon dioxide. The purified carbon dioxide is reinjected into the system through the make-up gas branch. The outlet of the purification unit is connected to a pneumatic booster pump. The pneumatic booster pump has a multi-stage booster structure and uses the pressure energy of the low-pressure return gas pipe as a power source to boost the purified carbon dioxide and reinject it into the system.

7. The system according to claim 1, characterized in that, It also includes a thermal compensation circuit, which is set between the heating user outlet and the intermediate stage gas injection interface of the compressor section. It is used to directly return the working fluid that has cooled down after heating to the intermediate stage of the compressor section during winter heating conditions, so that it can be incorporated into the compression process at a pressure higher than that of the low-pressure return gas pipe, thereby maintaining the mass flow balance and pressure stability of the system during winter heating.

8. The system according to claim 1, characterized in that, The low-pressure return gas pipe is connected to a safety function branch, including: The fire protection branch is equipped with distributed fire-fighting buffer tank groups and pneumatic temperature sensors and pneumatic logic valve groups arranged in each fire compartment. The fire-fighting buffer tank groups are normally replenished with air and stored by low-pressure return air pipes, and the pressure inside the tanks is maintained at no less than 2.5MPa. In case of fire, carbon dioxide in the tanks is released first for fire extinguishing, and if the pressure is insufficient, air is continuously replenished by low-pressure return air pipes. When the pneumatic temperature sensors are activated, the air pressure signal is transmitted to the pneumatic logic valve group through the low-pressure return air pipe, triggering a series of actions: closing the emergency shut-off valve of the high-pressure power supply pipe in the area and the pneumatic terminal power supply in the area, switching the extinguishing medium, closing the ventilation and exhaust valves, opening the jet smoke exhaust, and opening the pneumatic fire water valve. The entire process is driven by no electric drive components. Each fire compartment is equipped with differentiated extinguishing media according to the area type: carbon dioxide extinguishing or inerting is used in areas where water is not suitable, water spray or fine water mist is used in mining faces and transportation tunnels, and fire hydrants or water spray are used in ground buildings. The inerting branch is connected before the outlet of the capture unit and the inlet of the purification unit of the flue gas carbon dioxide capture and purification module. It is used to directly send the captured but unpurified carbon dioxide into the goaf to maintain the inerting environment, and the carbon dioxide concentration in the goaf is maintained at more than 23%. The rescue branch line is used to continuously supply pressure energy to the rescue chamber; the system does not have a dedicated carbon dioxide storage room or an independent fire-fighting pipeline network, and its safety functions are not affected when the mains power is interrupted.

9. The system according to claim 1, characterized in that, The high-pressure power supply pipe and the low-pressure return gas pipe adopt a segmented modular structure, and the pipe segments are connected by a detachable connection structure; the underground cooling terminal adopts a detachable modular structure; the system is laid forward segment by segment along with the mine tunneling face, and the mined area is dismantled and recycled segment by segment, and moved to the new working face for reinstallation and use.

10. A quasi-closed integrated carbon dioxide energy supply method suitable for remote mines, based on the system described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1 Heat source drive and pressure building: Using one or more of mine gas, coalbed methane, diesel or biomass fuel as a heat source, the carbon dioxide heating device is driven to heat the working medium to 500~650℃, the turbine expansion does work to drive the compression section to build up the circulating pressure, and the system enters self-sustaining operation. S2 Waste Heat Cascade Utilization and Heat Balance Regulation: After the working fluid at the turbine outlet releases heat through the preheater, it sequentially passes through the waste heat power generation section for heat extraction and power generation, and the waste heat utilization section for cascade heat supply. After heat extraction, the working fluid is cooled to 35°C by the low-pressure return gas in the regenerator before entering the high-pressure energy supply tank. The waste heat after power generation is supplied as needed for shaft antifreeze hot air, hot water for employee bathing, ground building heating, and mine water treatment. When the user's heat load decreases, the heat extraction ratio of the waste heat power generation section is increased to maintain heat balance; when the heat load increases, the heat extraction ratio of the waste heat power generation section is decreased to meet user demand. S3 replaces the electric air compressor and electric refrigeration: The high-pressure power supply pipe maintains high-pressure energy, which is reduced in pressure by the pressure reducing branch and drives the pneumatic compressor, which supplies air to underground and surface pneumatic equipment. The mine electric air compressor is completely shut down, and the power consumption of the air compressor is zero. At the same time, the working fluid in the high-pressure power supply pipe is expanded by throttling to provide a 5~10℃ cold source for the underground working face and surface buildings. The electric refrigeration unit is completely shut down, and the refrigeration power consumption is zero. S4 Pressure Locking and Cooling: The high-pressure power supply pipe delivers high-pressure carbon dioxide to the well. After being locked to 7.10MPa±0.1MPa by the equivalent condensing pressure regulating unit, it expands and throttles to provide a 5~10℃ cold source for the well working face. S5 Mass conservation gas replenishment and pressure control: The control unit uses the pressure of the low-pressure return gas tank as feedback. When the working fluid in the system decreases, the gas replenishment valve is opened to replenish the working fluid and maintain the total amount of working fluid in the system constant. S6 Power Outage Self-Sustaining Operation: After the mains power is interrupted, the turbine-boost coaxial unit relies on the heat source to continuously supply heat to maintain the thermal cycle; the high-pressure power supply pipe maintains the pressure energy to drive the pneumatic compressor, which supplies air and refrigeration to the pneumatic equipment; the low-pressure return air pipe maintains the safety function; the power generated by the waste heat power generation section supplies the electrical load of the system.

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