CN114111072A - Device and method for extracting medium-deep geothermal energy through circulating carbon dioxide phase change - Google Patents
Device and method for extracting medium-deep geothermal energy through circulating carbon dioxide phase change Download PDFInfo
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- CN114111072A CN114111072A CN202111402497.6A CN202111402497A CN114111072A CN 114111072 A CN114111072 A CN 114111072A CN 202111402497 A CN202111402497 A CN 202111402497A CN 114111072 A CN114111072 A CN 114111072A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
- F24T10/00—Geothermal collectors
- F24T10/10—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground
- F24T10/13—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground using tube assemblies suitable for insertion into boreholes in the ground, e.g. geothermal probes
- F24T10/17—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground using tube assemblies suitable for insertion into boreholes in the ground, e.g. geothermal probes using tubes closed at one end, i.e. return-type tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
- F24T10/00—Geothermal collectors
- F24T10/40—Geothermal collectors operated without external energy sources, e.g. using thermosiphonic circulation or heat pipes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
- F25B1/047—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of screw type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/40—Fluid line arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
- F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/10—Geothermal energy
Abstract
The invention relates to a device and a method for extracting medium-deep geothermal energy by circulating carbon dioxide phase change, belonging to the technical field of new energy. The technical scheme is as follows: the composite pipe system is positioned in the underground well completion casing (6) and is suspended at a ground wellhead by a wellhead device; the composite pipe system comprises an injection pipe unit (7) and a discharge pipe unit (3), a composite pipe annulus (2) is arranged between the injection pipe unit and the discharge pipe unit, the diameter of the injection pipe unit is smaller than that of the discharge pipe unit, and the injection pipe unit and the discharge pipe unit are concentrically arranged in the completion casing; the heat exchange and storage system is located on the ground and comprises a heat insulation pipeline (21), a first heat exchanger (10), a screw compressor (11), a second heat exchanger (12), a refrigerating machine (13), a storage tank (14) and a booster pump (16). The carbon dioxide working medium efficiently extracts geothermal energy from a single straight well or inclined well through phase change, and the carbon dioxide working medium is in closed circulation without contacting a stratum, so that the requirement of heat extraction without water extraction is met.
Description
Technical Field
The invention relates to a device and a method for extracting medium-deep geothermal energy by circulating carbon dioxide phase change, belonging to the technical field of new energy.
Background
Geothermal energy is taken as energy from the earth interior, has cleanness and renewability, is abundant in reserves, receives more and more attention at home and abroad, and how to efficiently and environmentally exploit and utilize the geothermal energy is the primary problem of the current geothermal energy technology. The medium-depth stratum refers to a stratum 2-3 kilometers below the ground, and the temperature interval of the medium-depth stratum is generally not more than 100 ℃ according to a geothermal gradiometer with the temperature rising of hectometer at 3 ℃. Currently, there are four main modes for exploiting geothermal heat in the middle and deep layers. Firstly, the hot mode is got to the water production, directly extracts the hot water that the stratum itself contains, and this mode leads to the ground subsides, the problem such as the water level descending funnel appears, recharge difficulty, and the restriction is adopted, is forbidden to adopt even the shutdown measure in China. And secondly, an enhanced geothermal mode of a geothermal reservoir is formed artificially, high-pressure water is injected into the stratum to fracture the rock, so that the rock flows through the dry-hot rock to obtain heat, and then the heat is pumped back to the ground from a heat flow outlet. Thirdly, an indirect heat exchange mode of the buried pipe is realized, a closed metal buried pipe is installed in the drill hole, the outer wall of the pipe body is in contact with underground heat storage, and a flowing working medium in the pipe flows through the buried pipe to take heat but is not in contact with the heat storage stratum, namely 'heat taking and water taking'. At present, the ground heat exchangers for extracting the geothermal heat of the middle and deep layers all use water as a heat transfer working medium, the heat storage temperature cannot reach the vaporization temperature of the water, and the high-efficiency heat exchange cannot be realized through medium phase change; in order to improve the heat extraction power of the ground heat exchanger, horizontal wells and butt wells are developed in recent years, the heat exchange efficiency is improved by prolonging the heat exchange section in a geothermal reservoir, and the drilling difficulty and the drilling cost are both greatly improved. And fourthly, in the mode of the ultra-long gravity heat pipe, geothermal energy is extracted by utilizing the phase change of the working medium, but the upward flowing steam in the heat pipe and the downward flowing liquid are in reverse contact to generate a carrying limit, so that the flow of the steam in the heat pipe is limited, and the heat extraction efficiency of the gravity heat pipe is further reduced. How to efficiently, environmentally, conveniently, economically and sustainably extract the geothermal energy of the middle and deep layers is a technical problem to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a device and a method for extracting medium-deep geothermal energy through circulating carbon dioxide phase change, which can finish medium-deep stratum heat extraction and ground heat release through carbon dioxide phase change, can efficiently, reasonably and environmentally develop 60-100 ℃ geothermal resources, broadens the available field of geothermal exploitation, efficiently extract geothermal energy from a single straight well or inclined well through phase change by a carbon dioxide working medium, meet the requirement of 'heat extraction without water extraction' by closed circulation of the carbon dioxide working medium and no contact with a ground layer, and solve the technical problems in the prior art.
The technical scheme of the invention is as follows:
a device for extracting medium-deep geothermal energy by circulating carbon dioxide phase change comprises a composite pipe system for extracting geothermal energy underground and a ground heat exchange storage system;
the composite pipe system is positioned in the underground well completion casing pipe and is suspended at a ground well head by a well head device; the composite pipe system comprises an injection pipe unit and a discharge pipe unit, a composite pipe annulus is arranged between the injection pipe unit and the discharge pipe unit, the diameter of the injection pipe unit is smaller than that of the discharge pipe unit, and the injection pipe unit and the discharge pipe unit are concentrically arranged in the completion casing; the injection pipe unit comprises an injection pipe inlet, an injection pipe and an injection pipe outlet, the composite pipe annulus comprises an annulus evaporation section, an annulus heat preservation section and an annulus outlet, and the injection pipe inlet, the injection pipe outlet, the annulus evaporation section, the annulus heat preservation section and the annulus outlet form a working medium underground circulation loop in sequence;
the heat exchange storage system is positioned on the ground and comprises a heat insulation pipeline, a first heat exchanger, a screw compressor, a second heat exchanger, a refrigerator, a storage tank and a booster pump; an annular outlet of the composite pipe system is sequentially connected with an inlet of the heat exchanger I, the screw compressor, the heat exchanger II, the refrigerating machine, the storage tank and the booster pump through heat insulation pipelines, and an outlet of the booster pump is connected with an inlet of an injection pipe of the composite pipe system through the heat insulation pipeline to form a ground circulation loop of the working medium.
The discharge pipe unit comprises a discharge pipe heat-taking unit at the lower part and a discharge pipe heat-preserving unit at the upper part, an annular evaporation section is arranged between the discharge pipe heat-taking unit and the injection pipe unit, and an annular heat-preserving section is arranged between the discharge pipe heat-preserving unit and the injection pipe unit.
And the injection pipe unit and the discharge pipe heat insulation unit are both provided with heat insulation layers.
And a first valve is arranged on a heat insulation pipeline between the storage tank and the booster pump.
And a second valve, a pressure gauge, a thermometer and a second valve are sequentially arranged on the heat insulation pipeline between the annular outlet of the composite pipe system and the first heat exchanger, and a flow meter, a thermometer, a pressure gauge and a second valve are sequentially arranged on the heat insulation pipeline between the outlet of the booster pump and the inlet of the injection pipe of the composite pipe system.
The lower part of the well completion casing is positioned in a heat extraction stratum, and the position of the heat extraction stratum corresponds to a heat extraction unit of a discharge pipe.
The whole process of the injection pipe unit is insulated, and the thermal resistance of the pipe wall of the unit length of the injection pipe unit is lower than 0.35 m.k/W; the discharge pipe heat taking unit is a steel coiled tubing; the whole course of the discharge pipe heat preservation unit is heat preserved, and the heat resistance of the pipe wall in unit length is lower than 0.55 m.k/W; the outlet of the annular evaporation section is an inlet of the annular heat preservation section, and the temperature of the annular outlet corresponding to the stratum is not lower than 70 ℃.
The pressure of the storage tank is not lower than 6MPa, and the temperature is not higher than-20 ℃; the pressure head of the booster pump is not lower than 6MPa, and the flow rate is adjustable; the pressure bearing capacity of the first heat exchanger is not lower than 5MPa, and the outlet temperature can be reduced to be lower than 30 ℃; the output working pressure of the screw compressor is not lower than 6 MPa; the pressure bearing capacity of the heat exchanger II is not lower than 6MPa, and the outlet temperature is reduced to be lower than 5 ℃; the pressure bearing capacity of the refrigerating machine is not lower than 6MPa, and the outlet temperature can be reduced to be lower than-20 ℃.
A method for extracting medium-deep geothermal energy by circulating carbon dioxide phase change comprises the following steps:
after the booster pump boosts the liquid carbon dioxide in the storage tank, the liquid carbon dioxide enters the injection pipe from the inlet of the injection pipe;
secondly, the liquid carbon dioxide descends to the outlet of the injection pipe in the injection pipe, is kept in a liquid state in the whole process and then enters an annular evaporation section;
absorbing heat of a heat-taking stratum to vaporize and continuously raise the temperature in the ascending process of the liquid carbon dioxide in the annular evaporation section until the carbon dioxide steam reaches the annular heat-preservation section, and continuously raising the carbon dioxide steam along the annular heat-preservation section until the carbon dioxide steam reaches an annular outlet of the composite pipe system;
after flowing out of an annular outlet of the composite pipe system, the carbon dioxide steam enters a first heat exchanger through an insulating pipeline for heat exchange to provide heat energy for a heat-taking user, and the temperature of the carbon dioxide steam is reduced to below 30 ℃ after flowing out of the first heat exchanger;
the carbon dioxide steam flows out of the heat exchanger and enters a screw compressor for pressurization, the pressure of the pressurized carbon dioxide steam reaches more than 4.5MPa, so that the liquefaction temperature of the carbon dioxide steam is increased to more than 10 ℃, and the temperature of the carbon dioxide steam is increased while the pressure is increased;
after the pressure is increased and the temperature is raised by the screw compressor, the carbon dioxide steam enters a second heat exchanger for heat exchange, the temperature of the carbon dioxide after flowing out of the second heat exchanger is reduced to below 10 ℃, the carbon dioxide is in a liquid state by phase change, and the released latent heat of vaporization is provided for a heat-taking user;
seventhly, the liquid carbon dioxide flowing out of the heat exchanger II enters a refrigerator to reduce the temperature of the liquid carbon dioxide;
and allowing the liquid carbon dioxide flowing out of the refrigerator to enter the storage tank, and repeating the steps to realize exploitation and utilization of geothermal energy.
The depth of the heat taking stratum is 1.0 km-3.5 km.
The working principle of the invention is as follows: drilling a heat-taking stratum with the depth of 1.0 km-3.5km by using a drilling machine, installing a well completion sleeve matched with the depth of the heat-taking stratum in a drill hole, installing a concentric composite pipe system in the well completion sleeve, and injecting low-temperature liquid carbon dioxide from an injection pipe inlet of the composite pipe system at a certain pressure; in the descending process of the liquid carbon dioxide along the injection pipe unit, gravitational potential energy is converted into pressure potential energy and the on-way energy loss is overcome, the on-way energy loss of the liquid carbon dioxide in the injection pipe unit is controlled by controlling the mass flow of the injected liquid carbon dioxide, so that when the liquid carbon dioxide reaches the outlet of the injection pipe, the pressure is higher than the vaporization pressure but lower than the critical point pressure by 7.38MPa, the carbon dioxide in the injection pipe is ensured to be in a liquid state in the whole process, and the liquid carbon dioxide can be vaporized after entering the annular space of the composite pipe to absorb heat. After the liquid carbon dioxide flows out of the outlet of the injection pipe, the liquid carbon dioxide enters an annular evaporation section; the carbon dioxide goes upward in the annular evaporation section and extracts geothermal energy, and the processes of liquid carbon dioxide heating to the vaporization temperature, phase change vaporization and carbon dioxide steam heat absorption heating are sequentially carried out; and the carbon dioxide steam enters the annular heat preservation section after passing through the annular evaporation section and continues to move upwards to an annular outlet of the composite pipe system, so that the phase change efficient heat extraction process of converting the carbon dioxide from a liquid state to a gaseous state is completed. After the carbon dioxide steam flows out of an annular outlet of the composite pipe system, part of heat energy is released through the first heat exchanger, and the temperature is reduced; then, the pressure of the carbon dioxide steam is increased through a screw compressor so as to obtain higher liquefaction temperature, and meanwhile, the temperature is increased; the temperature of the pressurized and heated carbon dioxide steam is reduced to be below the saturation temperature through the second heat exchanger, the carbon dioxide steam is in a liquid state through phase change, heat energy absorbed by the carbon dioxide steam in the annular evaporation section is rapidly released, and the heat energy can be supplied to heat-taking users through equipment such as a heat pump; then the liquid carbon dioxide further reduces the temperature through a refrigerator and then enters a storage tank to finish the circulation process of underground heat extraction-ground heat release.
The invention has the beneficial effects that: the medium-depth stratum heat taking and ground heat release are completed through carbon dioxide phase change, the high-efficiency, reasonable and environment-friendly development of geothermal resources at the temperature of 60-100 ℃ can be realized, the utilizable field of geothermal exploitation is widened, the carbon dioxide working medium efficiently extracts geothermal energy from a single straight well or inclined well through phase change, the carbon dioxide working medium is in closed circulation and does not contact with a ground layer, the requirement that no water is taken when heat is taken is met, the utilization cost of geothermal energy is saved, and the method has good economic application prospect and technical applicability.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of the present invention;
in the figure: the system comprises the ground 1, a composite pipe annulus 2, an annulus heat preservation section 2-1, an annulus evaporation section 2-2, an annulus outlet 2-3, a discharge pipe unit 3, a discharge pipe heat preservation unit 3-1, a discharge pipe heat taking unit 3-2, a heat taking stratum 4, stratum water 5, a well completion casing 6, an injection pipe unit 7, an injection pipe inlet 7-1, an injection pipe outlet 7-2, liquid carbon dioxide 8, carbon dioxide steam 9, a heat exchanger I10, a screw compressor 11, a heat exchanger II 12, a refrigerator 13, a storage tank 14, a valve I15, a booster pump 16, a flowmeter 17, a thermometer 18, a pressure gauge 19, a valve II 20, a heat insulation pipeline 21 and a heat taking user 22.
Detailed Description
The present invention will be further described by way of examples with reference to the accompanying drawings.
A device for extracting medium-deep geothermal energy by circulating carbon dioxide phase change comprises a composite pipe system for extracting geothermal energy underground and a ground heat exchange storage system;
the composite pipe system is positioned in the underground well completion casing 6 and is suspended at a ground wellhead by a wellhead device; the composite pipe system comprises an injection pipe unit 7 and a discharge pipe unit 3, a composite pipe annulus 2 is arranged between the injection pipe unit 7 and the discharge pipe unit 3, the diameter of the injection pipe unit is smaller than that of the discharge pipe unit, and the injection pipe unit and the discharge pipe unit are concentrically arranged in a completion casing 6; the injection pipe unit 7 comprises an injection pipe inlet 7-1, an injection pipe and an injection pipe outlet 7-2, the composite pipe annulus 2 comprises an annulus evaporation section 2-2, an annulus heat preservation section 2-1 and an annulus outlet 2-3, and the injection pipe inlet 7-1, the injection pipe outlet 7-2, the annulus evaporation section 2-2, the annulus heat preservation section 2-1 and the annulus outlet 2-3 sequentially form a working medium underground circulation loop;
the heat exchange storage system is positioned on the ground and comprises a heat insulation pipeline 21, a first heat exchanger 10, a screw compressor 11, a second heat exchanger 12, a refrigerator 13, a storage tank 14 and a booster pump 16; an annulus outlet 2-3 of the composite pipe system is sequentially connected with inlets of a first heat exchanger 10, a screw compressor 11, a second heat exchanger 12, a refrigerator 13, a storage tank 14 and a booster pump 16 through an insulated pipeline 21, and an outlet of the booster pump is connected with an inlet 7-1 of an injection pipe of the composite pipe system through the insulated pipeline 21 to form a ground circulation loop of working media.
The discharge pipe unit 3 comprises a discharge pipe heat-taking unit 3-2 at the lower part and a discharge pipe heat-preserving unit 3-1 at the upper part, an annular evaporation section 2-2 is arranged between the discharge pipe heat-taking unit 3-2 and the injection pipe unit 7, and an annular heat-preserving section 2-1 is arranged between the discharge pipe heat-preserving unit 3-1 and the injection pipe unit 7.
And the injection pipe unit 7 and the discharge pipe heat insulation unit 3-1 are both provided with heat insulation layers.
And a first valve 15 is arranged on the heat insulation pipeline 21 between the storage tank 14 and the booster pump 16.
And a second valve 20, a pressure gauge 19, a thermometer 18 and a flowmeter 17 are sequentially arranged on a heat insulation pipeline 21 between the annular outlet 2-3 of the composite pipe system and the first heat exchanger 10, and the flowmeter 17, the thermometer 18, the pressure gauge 19 and the second valve 20 are sequentially arranged on the heat insulation pipeline 21 between the outlet of the booster pump and the inlet 7-1 of the injection pipe of the composite pipe system.
The lower part of the well completion casing 6 is positioned in the heat extraction stratum 4, and the position of the heat extraction stratum 4 corresponds to the position of the heat extraction unit 3-2 of the discharge pipe.
The whole process of the injection pipe unit 7 is insulated, and the thermal resistance of the pipe wall of the unit length is lower than 0.35 m.k/W; the discharge pipe heat taking unit 3-2 is a steel coiled tubing; the whole course of the discharge pipe heat preservation unit 3-1 is heat preserved, and the thermal resistance of the pipe wall in unit length is lower than 0.55 m.k/W; the outlet 2-2 of the annular evaporation section is the inlet of the annular heat preservation section 2-1, and the temperature of the formation corresponding to the annular outlet 2-3 is not lower than 70 ℃.
The pressure of the storage tank 14 is not lower than 6MPa, and the temperature is not higher than-20 ℃; the pressure head of the booster pump 16 is not lower than 6MPa, and the flow rate is adjustable; the pressure bearing capacity of the first heat exchanger 10 is not lower than 5MPa, and the outlet temperature can be reduced to be lower than 30 ℃; the output working pressure of the screw compressor 11 is not lower than 6 MPa; the pressure bearing capacity of the second heat exchanger 12 is not lower than 6MPa, and the outlet temperature is reduced to be lower than 5 ℃; the pressure bearing capacity of the refrigerating machine 13 is not lower than 6MPa, and the outlet temperature can be reduced to be lower than-20 ℃.
A method for extracting medium-deep geothermal energy by circulating carbon dioxide phase change comprises the following steps:
firstly, after the booster pump 16 boosts the liquid carbon dioxide in the storage tank 14, the liquid carbon dioxide enters an injection pipe from an inlet (7-1) of the injection pipe;
secondly, the liquid carbon dioxide 8 descends in the injection pipe to an outlet 7-2 of the injection pipe, keeps in a liquid state in the whole process, and then enters an annular evaporation section 2-2;
thirdly, absorbing heat of the heat-taking stratum 4 to vaporize and continuously raise the temperature in the ascending process of the annular evaporation section 2-2 by the liquid carbon dioxide until the carbon dioxide steam 9 reaches the annular heat-preservation section 2-1, and continuously raising the carbon dioxide steam 9 along the annular heat-preservation section 2-1 until the carbon dioxide steam reaches an annular outlet 2-3 of the composite pipe system;
after flowing out of an annular outlet 2-3 of the composite pipe system, the carbon dioxide steam enters a first heat exchanger 10 through an insulated pipeline 21 for heat exchange to provide heat energy for a heat-taking user 22, and the temperature of the carbon dioxide steam is reduced to be below 30 ℃ after flowing out of the first heat exchanger 10;
the carbon dioxide steam flows out of the first heat exchanger 10 and then enters a screw compressor 11 for pressurization, and the pressure of the pressurized carbon dioxide steam reaches more than 4.5MPa, so that the liquefaction temperature of the carbon dioxide steam is increased to more than 10 ℃, and the temperature of the carbon dioxide steam is increased while the pressure is increased;
sixthly, the carbon dioxide steam after being boosted and heated by the screw compressor 11 enters the second heat exchanger 12 for heat exchange, the temperature of the carbon dioxide after flowing out of the second heat exchanger 12 is reduced to below 10 ℃, the carbon dioxide is in a liquid state by phase change, and the released latent heat of vaporization is provided for a heat user 22;
the liquid carbon dioxide flowing out of the second heat exchanger 12 enters a refrigerating machine 13 to reduce the temperature of the liquid carbon dioxide;
and eighthly, the liquid carbon dioxide flowing out of the refrigerating machine 13 enters the storage tank 14 to reciprocate in this way, so that the exploitation and utilization of geothermal energy are realized.
The depth of the heat-taking stratum 4 is 1.0 km-3.5 km.
In this embodiment, the storage tank 14 storing the low-temperature liquid carbon dioxide is opened, so that the liquid carbon dioxide flows into the booster pump 16, and the liquid carbon dioxide enters the injection pipe from the injection pipe inlet 7-1 at a certain mass flow rate after being boosted; reasonably determining the injection pressure and the injection flow of the liquid carbon dioxide, so that the pressure when the liquid carbon dioxide 8 reaches the outlet 7-2 of the injection pipe is not higher than the critical point pressure of 7.38MPa, and the pressure when the carbon dioxide steam 9 reaches the outlet 2-3 of the annulus is kept between 2.5 MPa and 4.5MPa to adapt to the working parameters of the ground screw compressor 11;
the carbon dioxide steam 9 flows out of the annular outlet 2-3 and enters a first heat exchanger 10 to release heat to a heat taking user 22; then the carbon dioxide enters a screw compressor 11, the outlet pressure of the screw compressor 11 is controlled, so that the carbon dioxide steam is pressurized to 4.5MPa, and the steam temperature is increased; the pressurized and heated carbon dioxide steam enters a second heat exchanger 12, the temperature of the carbon dioxide is reduced to be lower than the saturation temperature, the carbon dioxide steam is changed into liquid, latent heat of phase change is released, and the heat is supplied to a heat-taking user 22 through equipment such as a heat pump; then the liquid carbon dioxide enters the storage tank 14 after further temperature reduction through the refrigerating machine 13, and the process is repeated, so that the high-efficiency exploitation and utilization of geothermal energy are realized.
The working principle of the invention is as follows: drilling a heat-taking stratum 4 with the depth of 1.0 km-3.5km by using a drilling machine, installing a well completion sleeve 6 matched with the depth of the heat-taking stratum in a drill hole, installing a concentric composite pipe system in the well completion sleeve 6, and injecting low-temperature liquid carbon dioxide from an injection pipe inlet 7-1 of the composite pipe system at a certain pressure; in the process that the liquid carbon dioxide 8 descends along the injection pipe unit 7, gravitational potential energy is converted into pressure potential energy and the on-way energy loss is overcome, the on-way energy loss of the liquid carbon dioxide in the injection pipe unit 7 is controlled by controlling the mass flow of the injected liquid carbon dioxide, so that when the liquid carbon dioxide 8 reaches the injection pipe outlet 7-2, the pressure is higher than the vaporization pressure but lower than the critical point pressure by 7.38MPa, the carbon dioxide in the injection pipe is ensured to be in a liquid state in the whole process, and the liquid carbon dioxide can be vaporized after entering the composite pipe annulus 2 to absorb heat. After the liquid carbon dioxide flows out of an outlet 7-2 of the injection pipe, the liquid carbon dioxide enters an annular evaporation section 2-2; the carbon dioxide ascends in the annular evaporation section 2-2 and extracts geothermal energy, and the processes of liquid carbon dioxide heating to the vaporization temperature, phase change vaporization and carbon dioxide steam 9 heat absorption heating are sequentially carried out; and the carbon dioxide steam 9 enters the annular heat preservation section 2-1 after passing through the annular evaporation section 2-2 and continues to move upwards to an annular outlet 2-3 of the composite pipe system, so that the phase change efficient heat extraction process of converting the carbon dioxide from a liquid state to a gaseous state is completed. After carbon dioxide steam flows out of an annular outlet 2-3 of the composite pipe system, part of heat energy is released through a first heat exchanger 10, and the temperature is reduced; then the pressure of the carbon dioxide vapor is increased by the screw compressor 11 to obtain a higher liquefaction temperature, while the temperature is increased; the temperature of the pressurized and heated carbon dioxide steam is reduced to be below the saturation temperature through the second heat exchanger 12, the carbon dioxide steam is changed into liquid, heat energy absorbed by the carbon dioxide steam in the annular evaporation section 2-2 is rapidly released, and the heat energy can be supplied to a heat-taking user 22 through equipment such as a heat pump; the liquid carbon dioxide is then passed through a refrigerator 13 to further reduce its temperature and then into a storage tank 14 to complete the heat removal-surface heat release cycle.
Claims (8)
1. The utility model provides a device of middle and deep geothermal energy is drawed in circulation carbon dioxide phase transition which characterized in that: the underground geothermal energy recovery system comprises a composite pipe system for underground geothermal energy extraction and a ground heat exchange storage system;
the composite pipe system is positioned in the underground well completion casing (6) and is suspended at a ground wellhead by a wellhead device; the composite pipe system comprises an injection pipe unit (7) and a discharge pipe unit (3), a composite pipe annulus (2) is arranged between the injection pipe unit (7) and the discharge pipe unit (3), the diameter of the injection pipe unit is smaller than that of the discharge pipe unit, and the injection pipe unit and the discharge pipe unit are concentrically arranged in a well completion casing (6); the injection pipe unit (7) comprises an injection pipe inlet (7-1), an injection pipe and an injection pipe outlet (7-2), the composite pipe annulus (2) comprises an annulus evaporation section (2-2), an annulus heat preservation section (2-1) and an annulus outlet (2-3), and the injection pipe inlet (7-1), the injection pipe outlet (7-2), the annulus evaporation section (2-2), the annulus heat preservation section (2-1) and the annulus outlet (2-3) sequentially form a working medium underground circulation loop;
the heat exchange storage system is positioned on the ground and comprises a heat insulation pipeline (21), a first heat exchanger (10), a screw compressor (11), a second heat exchanger (12), a refrigerator (13), a storage tank (14) and a booster pump (16); an annulus outlet (2-3) of the composite pipe system is sequentially connected with inlets of a heat exchanger I (10), a screw compressor (11), a heat exchanger II (12), a refrigerating machine (13), a storage tank (14) and a booster pump (16) through an insulating pipeline (21), and an outlet of the booster pump is connected with an inlet (7-1) of an injection pipe of the composite pipe system through the insulating pipeline (21) to form a ground circulation loop of working media.
2. The device for extracting geothermal energy in the middle and deep layers by the phase change of the circulating carbon dioxide as claimed in claim 1, wherein: the discharge pipe unit (3) comprises a discharge pipe heat-taking unit (3-2) at the lower part and a discharge pipe heat-preserving unit (3-1) at the upper part, an annular evaporation section (2-2) is arranged between the discharge pipe heat-taking unit (3-2) and the injection pipe unit (7), and an annular heat-preserving section (2-1) is arranged between the discharge pipe heat-preserving unit (3-1) and the injection pipe unit (7).
3. The device for extracting geothermal energy in the middle and deep layers by the phase change of the circulating carbon dioxide as claimed in claim 2, wherein: and the injection pipe unit (7) and the discharge pipe heat insulation unit (3-1) are both provided with heat insulation layers.
4. The apparatus for extracting geothermal energy in the middle and deep layers by the phase change of the circulating carbon dioxide according to claim 1 or 2, wherein: and a first valve (15) is arranged on the heat insulation pipeline (21) between the storage tank (14) and the booster pump (16).
5. The apparatus for extracting geothermal energy in the middle and deep layers by the phase change of the circulating carbon dioxide according to claim 1 or 2, wherein: and a second valve (20), a pressure gauge (19), a thermometer (18) and a flowmeter (17) are sequentially arranged on the heat insulation pipeline (21) between the annular outlet (2-3) of the composite pipe system and the first heat exchanger (10), and the flowmeter (17), the thermometer (18), the pressure gauge (19) and the second valve (20) are sequentially arranged on the heat insulation pipeline (21) between the outlet of the booster pump and the inlet (7-1) of the injection pipe of the composite pipe system.
6. The apparatus for extracting geothermal energy in the middle and deep layers by the phase change of the circulating carbon dioxide according to claim 1 or 2, wherein: the completion casing (6) is located below the heat extraction formation (4).
7. A method for extracting geothermal energy in a medium depth by cyclic carbon dioxide phase transition using the apparatus defined in any one of claims 1 to 6, comprising the steps of:
firstly, after a booster pump (16) boosts liquid carbon dioxide in a storage tank (14), the liquid carbon dioxide enters an injection pipe from an inlet (7-1) of the injection pipe;
secondly, liquid carbon dioxide (8) descends to an outlet (7-2) of the injection pipe in the injection pipe, is kept in a liquid state in the whole process, and then enters an annular evaporation section (2-2);
liquid carbon dioxide absorbs heat of the heat-taking stratum (4) to be vaporized and continuously heated in the ascending process of the annular evaporation section (2-2) until carbon dioxide steam (9) reaches the annular heat-preservation section (2-1), and the carbon dioxide steam (9) continuously rises along the annular heat-preservation section (2-1) until reaching an annular outlet (2-3) of the composite pipe system;
after flowing out of an annular outlet (2-3) of the composite pipe system, the carbon dioxide steam enters a first heat exchanger (10) through an insulating pipeline (21) for heat exchange to provide heat energy for a heat-taking user (22), and the temperature of the carbon dioxide steam is reduced to below 30 ℃ after flowing out of the first heat exchanger (10);
after flowing out of the first heat exchanger (10), the carbon dioxide steam enters a screw compressor (11) for pressurization, and the pressure of the pressurized carbon dioxide steam reaches more than 4.5MPa, so that the liquefaction temperature of the carbon dioxide steam is increased to more than 10 ℃, and the temperature of the carbon dioxide steam is increased while the pressure is increased;
sixthly, the carbon dioxide steam after being boosted and heated by the screw compressor (11) enters a second heat exchanger (12) for heat exchange, the temperature of the carbon dioxide is reduced to below 10 ℃ after the carbon dioxide flows out of the second heat exchanger (12), the carbon dioxide is changed into liquid, and the released latent heat of vaporization is provided for a heat-taking user (22);
the liquid carbon dioxide flowing out of the second heat exchanger (12) enters a refrigerating machine (13) to reduce the temperature of the liquid carbon dioxide;
and allowing the liquid carbon dioxide flowing out of the refrigerating machine (13) to enter the storage tank (14) and reciprocate in this way, so as to realize exploitation and utilization of geothermal energy.
8. A method for extracting medium-deep geothermal energy by circulating carbon dioxide phase change is characterized by comprising the following steps: the depth of the heat taking stratum (4) is 1.0 km-3.5 km.
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| CN105526726A (en) * | 2015-12-30 | 2016-04-27 | 严建勋 | Efficient terrestrial heat taking well and heat taking method |
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