CN218816722U

CN218816722U - Dry heat rock heat utilization system for cogeneration

Info

Publication number: CN218816722U
Application number: CN202222593028.3U
Authority: CN
Inventors: 许刚; 李建华; 焦扬; 王哲; 魏大福; 许亮; 于春堂; 许嵩峰; 刘昭勇
Original assignee: Zibo Zhongji Energy Technology Co ltd
Current assignee: Zibo Zhongji Energy Technology Co ltd
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2023-04-07
Anticipated expiration: 2032-09-29

Abstract

The utility model discloses a combined heat and power generation's hot dry rock heat utilization system belongs to the electricity generation technology field. The technical scheme is as follows: the device comprises a water filtering device, wherein a water inlet pipe of the water filtering device is connected with a water pool, a water outlet of the water filtering device is connected with a siphon, and electromagnetic valves are respectively arranged at the water inlet end and the water outlet end of the water inlet pipe and the siphon; the siphon is connected with a water diversion bucket through a water diversion pipe, the water diversion pipe is connected with an exhaust pipe, and the water diversion pipe and the exhaust pipe are provided with electromagnetic valves; the siphon pipe stretches into the shaft, a plurality of hydraulic power generation mechanisms are sequentially arranged below a water outlet of the siphon pipe along the height direction of the shaft, each hydraulic power generation mechanism comprises a hydraulic generator, a water falling hopper is arranged below the hydraulic generator, a water outlet of the water falling hopper is connected with a water falling pipe, and the hydraulic generator is connected with the power transmission and transformation device through cables. The utility model discloses utilize the siphon principle to realize the coupling of hot dry rock heat recovery and gravitational potential energy hydroelectric power generation, whole production process does not have the input of external energy, and no pump is carried, can realize zero carbon combined heat and power, greatly reduced the energy consumption.

Description

Dry heat rock heat utilization system for cogeneration

Technical Field

The utility model relates to a power generation technical field, concretely relates to combined heat and power's hot dry rock heat utilization system.

Background

The petrochemical mobile energy is in vicious circle in energy crisis and environmental pollution all the time, and common new energy such as wind power, photoelectricity and tidal power are extremely unstable energy forms. The development of dry hot rock which is a natural energy source with abundant resources and stable output is concerned by the energy source field, the dry hot rock resources in China are abundant and have huge reserves, the discovered dry hot rock resources are equivalent to 8.56 million tons of standard coal, and the energy of the dry hot rock resources is enough to be self-sufficient for 4000 years according to the calculation of the current energy consumption. The dry hot rock is a typical renewable clean energy source, so the dry hot rock will become one of the important resources in the future.

The hydraulic potential energy power generation is the most safe and environment-friendly clean renewable energy and is also a stable output energy, so if the dry-hot rock heat energy and the hydraulic potential energy power generation can be combined to realize the co-production of heat energy and electric energy, the energy consumption can be greatly reduced.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is: the defects of the prior art are overcome, the dry hot rock heat utilization system for cogeneration is provided, the coupling of dry hot rock heat collection and gravitational potential energy hydroelectric generation is realized by utilizing a siphon principle, no external energy source is input in the whole production process, no pump is used for conveying, zero-carbon cogeneration can be realized, and the energy consumption is greatly reduced.

The technical scheme of the utility model is that:

the dry hot rock heat utilization system for cogeneration comprises a water filtering device, wherein a water inlet pipe of the water filtering device is connected with a water pool, a water outlet of the water filtering device is connected with a siphon, and electromagnetic valves are respectively arranged at the water inlet pipe, the water inlet end and the water outlet end of the siphon; the siphon is connected with a water diversion bucket through a water diversion pipe, the water diversion pipe is connected with an exhaust pipe, and the water diversion pipe and the exhaust pipe are provided with electromagnetic valves; the siphon pipe extends into the vertical shaft, a plurality of hydraulic power generation mechanisms are sequentially arranged below the water outlet of the siphon pipe along the height direction of the vertical shaft, each hydraulic power generation mechanism comprises a hydraulic generator, a water falling hopper is arranged below each hydraulic generator, the water outlet of each water falling hopper is connected with a water falling pipe, and each hydraulic generator is connected with the power transmission and transformation device through a cable; a water outlet of the downpipe at the lowest end is connected with a medium pipe, the medium pipe penetrates through the bottom of the vertical shaft and extends into the hot dry rock vertical shaft below the vertical shaft, and a well plug is arranged at the joint of the vertical shaft and the hot dry rock vertical shaft; in the dry hot rock shaft, a plurality of nozzles or spray holes are arranged on the medium pipe, the side surface of the dry hot rock shaft is communicated with a steam inclined shaft, a steam outlet of the steam inclined shaft extends out of the ground and is connected with a steam pipe, the steam pipe is connected with a heat-utilizing device through a steam outlet pipe, and an electromagnetic valve is arranged on the steam outlet pipe; the condensed water of the heat utilization device is connected with the water storage tank through a condensed water discharge pipe, the siphon pipe is connected with the water storage tank through a circulating pipe, and the electromagnetic valve is arranged on the condensed water discharge pipe and the circulating pipe.

Preferably, the side surface of the dry hot rock vertical shaft is communicated with a plurality of steam inclined shafts.

Preferably, the steam pipe is connected with an emptying pipe, and a steam emptying valve is installed on the emptying pipe.

Preferably, the bottom of the dry hot rock vertical shaft is communicated with a plurality of horizontal wells.

Preferably, the water storage tank and the steam pipe are externally provided with a first heat preservation layer.

Preferably, the first heat preservation layer is made of silica aerogel.

Preferably, the upper surface and the lower surface of the well plug are compounded with heat insulation layers.

Preferably, the heat insulation layer on the upper surface of the well plug is made of a PU foam composite board, and the heat insulation layer on the lower surface of the well plug is made of heat insulation aerogel.

Preferably, a second insulating layer is arranged outside the circulating pipe.

Preferably, the second heat-insulating layer is made of PU materials.

Compared with the prior art, the utility model, following beneficial effect has: the utility model discloses a combined heat and power's hot dry rock heat utilization system utilizes the siphon principle to realize hot dry rock and adopts heat and the coupling of gravitational potential energy hydroelectric generation, and whole production process does not have external energy input, and no pump is carried, can realize zero carbon combined heat and power, greatly reduced the energy consumption.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a schematic structural view of the vertical shaft, the dry hot rock vertical shaft and the steam inclined shaft of the utility model.

In the figure, 1, a water filtering device; 2. a water inlet pipe; 3. a water pool; 4. a siphon tube; 5. an electromagnetic valve; 6. a water conduit; 7. a water diversion hopper; 8. an exhaust pipe; 9. a shaft; 10. a hydro-generator; 11. a water falling hopper; 12. a downpipe; 13. a cable; 14. a power transmission and transformation device; 15. a medium pipe; 16. a hot dry rock shaft; 17. plugging a well; 18. a nozzle; 19. steam inclined shaft; 20. a steam pipe; 21. a vapor outlet pipe; 22. a heat-using device; 23. a condensed water discharge pipe; 24. a water storage tank; 25. a circulation pipe; 26. emptying the pipe; 27. a steam evacuation valve; 28. and a horizontal well.

Detailed Description

In order to make the technical solutions in the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall belong to the protection scope of the present invention.

As shown in fig. 1-2, the utility model provides a combined heat and power's hot dry rock heat utilization system, including water filter equipment 1, water filter equipment 1's inlet tube 2 is connected with pond 3, and the delivery port is connected with siphon 4, and solenoid valve 5 is installed respectively to inlet tube 2, siphon 4's the end of intaking and play water end. Water filter equipment 1 filters the water source in 3 ponds and purifies, can adopt equipment such as anion and cation resin, electron ultrasonic wave, belongs to comparatively ripe device among the prior art, and its specific structure is no longer repeated. The treatment capacity of the water filtering device 1 is determined according to the evaporation capacity of the heat collecting area of the dry hot rock shaft 16, for example, after physical filtration by adopting a plurality of layers of steel meshes, quartz sand and ceramsite, the water is treated by an ultrasonic composite filter, and the treatment flow is 25000T/h; the filter is filtered by anion and cation resin combined with adsorbing materials such as activated carbon, molecular sieve and the like, and the purification flow is 15000T/h.

The siphon 4 is connected with a water diversion bucket 7 through a water diversion pipe 6, the water diversion pipe 6 is connected with an exhaust pipe 8, and the water diversion pipe 6 and the exhaust pipe 8 are provided with electromagnetic valves 5. The water diversion mechanism consisting of the water diversion hopper 7, the water diversion pipe 6 and the exhaust pipe 8 has the functions of mainly leading the siphon 4 and the water filtering device 1 to be full of water diversion in all devices and pipelines of the water pool 3 and discharging air in the devices and pipelines on the premise of closing the electromagnetic valve 5 at the water outlet end of the siphon 4 so as to prepare for subsequent siphoning. The position of the catchment 7 is higher than the position of all relevant devices. The water diversion hopper 7 can be made of engineering plastics, metal and the like, and has the specification of DN1500 and the height of 3000mm; the water conduit 6 can adopt SUS304 pipe of DN 76.

The siphon 4 extends into the shaft 9, a plurality of hydraulic power generation mechanisms are sequentially arranged below a water outlet of the siphon 4 along the height direction of the shaft 9, each hydraulic power generation mechanism comprises a hydraulic generator 10, a water falling hopper 11 is arranged below the hydraulic generator 10, a water outlet of the water falling hopper 11 is connected with a water falling pipe 12, and the hydraulic generator 10 is connected with a power transmission and transformation device 14 through a cable 13; a water outlet of the downpipe 11 at the lowest end is connected with a medium pipe 15, the medium pipe 15 penetrates through the bottom of the vertical shaft 9 and extends into a dry hot rock vertical shaft 16 below the vertical shaft, and a well plug 17 is arranged at the joint of the vertical shaft 9 and the dry hot rock vertical shaft 16; in the dry hot rock vertical shaft 16, a plurality of nozzles 18 or spray holes are arranged on the medium pipe 15, a plurality of steam inclined shafts 19 are communicated with the side surface of the dry hot rock vertical shaft 16, steam outlets of the steam inclined shafts 19 extend out of the ground and are connected with steam pipes 20, the steam pipes 20 are connected with emptying pipes 26, and steam emptying valves 27 are arranged on the emptying pipes 26; the steam pipe 20 is connected with a useful heat device 22 through a steam outlet pipe 21, and the electromagnetic valve 5 is arranged on the steam outlet pipe 21; the condensed water of the heat utilization device 22 is connected with a water storage tank 24 through a condensed water discharge pipe 23, the siphon 4 is connected with the water storage tank 24 through a circulating pipe 25, a second heat insulation layer is arranged outside the circulating pipe 25, and the second heat insulation layer can be made of PU materials; the electromagnetic valve 5 is installed on the condensed water discharge pipe 23 and the circulation pipe 25.

Hydraulic generator 10 is the utility model discloses a produce the equipment of electric energy, many hydraulic generator 10 can be installed to the direction from top to bottom in shaft 9. Because the hydro-generator 10 is installed in the vertical shaft 9, the hydro-generator 10 with high water head, small flow and slender equipment can be selected due to the restriction of the well diameter, such as a through-flow turbine, an axial flow turbine, a bulb turbine, a pelton turbine and the like of the vertical shaft 9. The design vertical shaft 9 has the well depth of 1000m and the well diameter of 1000mm, four hydraulic generators 10 can be installed, the model is an axial flow water turbine water head 200m, the power is 90kw, the total power generation power is 360kw, and the daily power generation quantity is 8640kwh. The design shaft 9 has the well depth of 1200m and the well diameter of 1200mm, three shaft 9 through-flow turbines and one pelton turbine can be installed, the installed power is 75kw and 200kw respectively, the total power is 425kw, and the power generated each day is 10200kwh.

The bottom of the dry hot rock vertical shaft 16 is communicated with a plurality of branched horizontal wells 28, and spray holes are processed on the medium pipe 15 in the horizontal wells 28. The specification of the medium pipe 15 is DN200 and the material is SUS 316, and the specification of the medium pipe 15 in the horizontal well 28 is DN120 and the material is SUS 316. The nozzle 18 on the medium pipe 15 is made of silicon carbide and stainless steel, the nozzle 18 on the upper part of the dry hot rock shaft 16 is made of SUS 310S, the flow rate is 200kg/h, and the installation density is one per 8 meters; the nozzle 18 at the lower part of the dry hot rock shaft 16 is made of silicon carbide, the flow rate is 220kg/h, and the installation density is one per 5 meters; the flow rate of the spray holes on the medium pipe 15 in the horizontal well 28 is 250kg/h, and the installation density is one spray hole per 3 meters. The connection of the medium pipe 15 can be screw connection or chuck connection, and the elbow part can be metal corrugated pipe connection or carbon fiber high-strength flexible pipe connection.

The well plug 17 is an enclosure for separating the vertical shaft 9 and the dry hot rock vertical shaft 16, and because the temperature and the steam pressure in the dry hot rock vertical shaft 16 are higher, besides the high-strength material plugging, the upper surface and the lower surface of the well plug 17 are compounded with heat insulation layers, for example, the upper surface is compounded with a PU foam composite plate with the thickness of 250mm, and the lower surface of the well plug 17 is compounded with heat insulation aerogel with the thickness of 100 mm. The well plug 17 may be made of SUS304 stainless steel plate 50mm thick, 800X 50 or 700X 50 phi, or concrete 500mm thick.

The vertical shaft 9 and the dry hot rock vertical shaft 16 belong to a one-shaft structure, the vertical shaft 9 is an upper section one-shaft opened well of the shaft, the dry hot rock vertical shaft 16 is a lower section two-shaft opened well of the shaft, the middle part is divided into two spaces through a shaft plug 17, the vertical shaft 9 is an open space, and the dry hot rock vertical shaft 16, the steam inclined shaft 19 and the steam pipe 20 form a closed space.

The diameter and depth of the shaft 9 and the dry hot rock shaft 16 depend on the temperature and design heat of the underground mine of the geographical location of the dry hot rock resource.

The gradient of the dry and hot rock in a certain area is 60 ℃/km, and the design is that the well diameter of a dry and hot rock vertical well 16 is 500mm, the depth is 5500m, the bottom temperature of the well is 330 ℃, the well diameter of the vertical well 9 is 1000mm, and the well depth is 1000m. The bottom of the dry hot rock vertical shaft 16 is provided with two horizontal wells 28, the length of each horizontal well is 400m, and the total length of each horizontal well 28 is 800m. The steam inclined shaft and the dry hot rock vertical shaft 16 are intersected at 1100m, and the well diameter is 400mm.

In a certain dry hot rock resource-rich area, the gradient of dry hot rock is 80 ℃/km, the well diameter of a dry hot rock vertical shaft 16 is 600mm, the depth is 5000m, the bottom temperature is 400 ℃, the well depth of a vertical shaft 9 is 800m, and the well diameter is 1200mm. The bottom of the dry hot rock vertical shaft 16 is provided with three branched horizontal wells 28, the well diameter is 500mm, the length is 500m, and the total length of the horizontal wells 28 is 1500m. The steam inclined shaft 19 is provided with two holes which are respectively crossed at the position 169900 m and the position 950m of the dry hot rock vertical shaft, the well diameter is 400mm, and an EGS energy storage area is established in the heat recovery area of the dry hot rock vertical shaft 16 and the horizontal well 28.

The steam pipe 20 is arranged at the wellhead part of the steam inclined shaft 19 and is in sealing connection; an exhaust valve is installed at the upper part of the steam pipe 20 for use in equipment maintenance; the outer layer of the steam pipe 20 is provided with a first heat preservation layer to prevent heat dissipation loss; the steam pipe 20 is a transfer line between the high-temperature steam from the steam shaft 19 and the heat consuming device 22. The steam pipe 20 may be made of SUS304 pipe of DN300, and coated with a silica aerogel layer of 80mm thickness.

The steam used by the heat utilization device 22 may be industrial steam, steam for turbine power generation, steam for facility building heating and ventilation, etc., and the power of the heat utilization device 22 may be designed according to the temperature, pressure, and volume of the steam.

The water storage tank 24 is used to collect and store condensed water generated by the operation of the heat utilization device 22, and may also be used as a water source for siphoning by the siphon tube 4. When the siphon 4 is used as the water source, the water storage tank 24 is subjected to the negative pressure of the siphon force, such as the water head height of the siphon 4 is 300m, namely the negative pressure of 3Mpa, and the water storage tank 24 can be 30000m ² The vault tank is made of carbon steel, the wall thickness is 80mm, an epoxy coating in the tank is anticorrosive, and a PU flame-retardant foam heat-insulating material with the thickness of 50mm is arranged outside the tank for heat preservation. In addition, because the condensed water has higher temperature, the heat can be secondarily utilized by the heat exchanger and then siphoned into the vertical shaft 9, so that the heat energy is 'eaten and squeezed out'.

1. The operation method comprises the following steps:

(1) Closing the electromagnetic valve 5 on the water inlet pipe 2 of the water filtering device 1; closing the electromagnetic valve 5 at the water outlet end of the siphon 4 and opening the electromagnetic valve 5 at the water inlet end; the electromagnetic valve 5 on the water conduit 6 and the exhaust pipe 8 is opened.

(2) Fresh water is filled in the water diversion hopper 7, so that gas in the device and the pipeline is emptied through the exhaust pipe 8, the water level in the water hopper does not drop any more, and the electromagnetic valve 5 on the water diversion pipe 6 is closed.

(3) The electromagnetic valve 5 on the water inlet pipe 2 of the water filtering device 1 and the electromagnetic valve 5 on the water outlet end of the siphon 4 are opened.

2. Principle of operation

After the above operation, when the water in the siphon 4 flows out from the water outlet, the siphon 4 will automatically pump the water from the pool 3 into the water filtering device 1 for filtering and purifying under the action of siphon force. The filtered water flows into the siphon 4 and falls into the hydraulic generator 10 below from the water outlet of the siphon 4, and the hydraulic generator 10 is driven to work by utilizing the gravitational potential energy of the water. Then the water falls down into the downpipe 11 and falls onto the next level of hydraulic generator 10 through the downpipe 12 to drive the next level of hydraulic generator 10 to work, so that the multistage hydraulic generator 10 can be driven to generate electricity, and finally the water falling into the downpipe 11 at the lowest end passes through the well plug 17 through the medium pipe 15 to enter the hot dry rock shaft 16. The medium pipe 15 extends to the bottom of the dry hot rock vertical shaft 16, and if a horizontal well 28 is arranged at the bottom of the dry hot rock vertical shaft 16, the medium pipe 15 extends into the horizontal well 28. And a nozzle 18 or spray holes (the nozzle 18 is arranged on a common dry hot rock shaft 16, the spray holes are arranged on a horizontal well 28) are arranged on a corresponding medium pipe 15 entering the heat collecting area of the dry hot rock shaft 16, the medium water is sprayed to the heat collecting area for heat exchange, the water phase is changed into steam, the steam rises to a steam pipe 20 on the ground along a steam inclined shaft 19 under the driving of the ascending of heat power and the expansion pressure of the steam, and finally enters a heat utilization device 22 (the heat utilization device 22 can be a thermal power generation field, an industrial heat device, a food processing device, a steam drying device, a building heat device and the like). The steam phase is changed into condensed water after heat exchange by the heat utilization device 22, and the condensed water is discharged into the water storage tank 24 through the condensed water discharge pipe 23.

Furthermore, the utility model discloses a have two circulation routes among the combined heat and power, when starting promptly, adopt the diversion retaining circulation that the diversion mechanism realized, make and reach the evaporation cycle water storage volume in the water storage tank 24 after, change over to another circulation route, normal work circulation route promptly, close the solenoid valve 5 of siphon 4 intake end, open solenoid valve 5 on the circulating pipe 25, circulate as the water source with the water that stores in the water storage tank 24. When water in the normal working circulation route is consumed, the water diversion and storage circulation route can be properly started, and the siphon 4 can suck water from the water pool 3 to replenish water so as to meet the requirement of water consumption of working circulation evaporation capacity.

In the cogeneration process, the carbon-free cogeneration of power generation by the hydraulic generator 10 and heat generation by the dry hot rock shaft 16 is realized, no external energy consumption is caused, the environment is protected, and the output is safe and stable, which is a rare natural new energy.

Although the present invention has been described in detail by referring to the drawings in conjunction with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and substance of the present invention, and these modifications or substitutions are intended to be included within the scope of the present invention/any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The dry hot rock heat utilization system for cogeneration is characterized by comprising a water filtering device (1), wherein a water inlet pipe (2) of the water filtering device (1) is connected with a water pool (3), a water outlet is connected with a siphon (4), and electromagnetic valves (5) are respectively arranged at the water inlet end and the water outlet end of the water inlet pipe (2) and the siphon (4); the siphon (4) is connected with a water diversion bucket (7) through a water diversion pipe (6), the water diversion pipe (6) is connected with an exhaust pipe (8), and the water diversion pipe (6) and the exhaust pipe (8) are provided with electromagnetic valves (5); the siphon (4) extends into the vertical shaft (9), a plurality of hydraulic power generation mechanisms are sequentially arranged below a water outlet of the siphon (4) along the height direction of the vertical shaft (9), each hydraulic power generation mechanism comprises a hydraulic generator (10), a water falling hopper (11) is arranged below the hydraulic generator (10), a water outlet of the water falling hopper (11) is connected with a water falling pipe (12), and the hydraulic generator (10) is connected with a power transmission and transformation device (14) through a cable (13); a water outlet of the downpipe (11) at the lowest end is connected with a medium pipe (15), the medium pipe (15) penetrates through the bottom of the vertical shaft (9) and extends into a dry hot rock vertical shaft (16) below the vertical shaft, and a well plug (17) is arranged at the joint of the vertical shaft (9) and the dry hot rock vertical shaft (16); in the dry hot rock vertical shaft (16), a plurality of nozzles (18) or spray holes are arranged on the medium pipe (15), the side surface of the dry hot rock vertical shaft (16) is communicated with a steam inclined shaft (19), a steam outlet of the steam inclined shaft (19) extends out of the ground and is connected with a steam pipe (20), the steam pipe (20) is connected with a heat utilization device (22) through a steam outlet pipe (21), and an electromagnetic valve (5) is arranged on the steam outlet pipe (21); the condensed water of the heat utilization device (22) is connected with the water storage tank (24) through a condensed water discharge pipe (23), the siphon pipe (4) is connected with the water storage tank (24) through a circulating pipe (25), and the electromagnetic valve (5) is arranged on the condensed water discharge pipe (23) and the circulating pipe (25).

2. The cogeneration hot dry rock heat utilization system of claim 1, wherein the hot dry rock shaft (16) is flanked by a plurality of steam slanted wells (19).

3. The cogeneration dry hot rock heat utilization system according to claim 1, wherein a drain pipe (26) is connected to the steam pipe (20), and a steam evacuation valve (27) is installed on the drain pipe (26).

4. The cogeneration dry hot rock heat utilization system of claim 1, wherein the bottom of the dry hot rock shaft (16) is communicated with a plurality of horizontal wells (28).

5. A cogeneration hot dry rock heat utilization system according to claim 1, wherein the water storage tank (24) and the steam pipe (20) are externally provided with a first heat insulating layer.

6. The cogeneration dry hot rock heat utilization system of claim 5, wherein the first insulating layer is made of silica aerogel.

7. The cogeneration hot dry rock heat utilization system of claim 1, wherein the upper and lower surfaces of the well plug (17) are compounded with thermal insulation layers.

8. The cogeneration hot dry rock heat utilization system of claim 7, wherein the thermal insulation layer on the upper surface of the well plug (17) is made of PU foam composite board, and the thermal insulation layer on the lower surface of the well plug (17) is made of thermal insulation aerogel.

9. The cogeneration hot dry rock heat utilization system of claim 1, wherein the circulation pipe (25) is externally provided with a second insulation layer.

10. The cogeneration hot dry rock heat utilization system of claim 9, wherein said second insulating layer is made of PU.