A system and method for in-situ pyrolysis and waste heat recovery of oil-rich coal

Abstract

The invention discloses an in-situ pyrolysis and waste heat recovery system and method for oil-rich coal. The other end of a cooler is connected to the input end of a first compressor, the output end of the first compressor is connected to the input end of a four-way reversing valve, the first output end of the four-way reversing valve is connected to one end of a heater, the other end of the heater is connected to one end of a first oil separator, the other end of the first oil separator is connected to an injection well, the injection well is connected to a production well through coal seam fractures, the production well is connected to one end of a second oil separator, the other end of the second oil separator is connected to the second output end of the four-way reversing valve, one end of an absorption refrigeration unit is connected to the third output end of the four-way reversing valve, and the other end of the absorption refrigeration unit is connected to the input end of the first compressor; the cooling medium output end of the cooler is connected to the cooling medium input end of the absorption refrigeration unit, and the cooling medium output end of the absorption refrigeration unit is connected to the cooling medium input end of the cooler.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ pyrolysis and waste heat recovery, and in particular relates to an in-situ pyrolysis and waste heat recovery system and method for oil-rich coal. Background Art

[0002] Oil-rich coal refers to coal with a tar yield between 7% and 12%. Western China has large reserves of oil-rich coal, with Shaanxi Province alone containing 155.03 billion tons. Previous studies have shown that the pyrolysis of one ton of oil-rich coal produces about 10% oil and 500 cubic meters of combustible gas, as well as semi-coke that can replace anthracite and coke. Based on a 10% oil content, the potential oil resources extracted from oil-rich coal in Shaanxi Province can reach 15.503 billion tons. Under the constraints of the "dual carbon" goal, how to efficiently and cleanly utilize coal resources has become an urgent problem to be solved.

[0003] Coal exists in solid form in its natural state and cannot be mined like natural gas in reservoirs. Only after pyrolysis can it be converted into products such as tar and pyrolysis gas. The dry distillation technology currently used in the coal chemical industry is mainly ground dry distillation technology, which involves building large-scale facilities and systems on the ground to create a high-temperature anaerobic environment. The coal mined from underground is crushed to a certain size, sent to the dry distillation system on the ground, and then dry distilled to obtain products such as tar and coal gas. This dry distillation technology has many problems, such as large area occupation, low efficiency and environmental pollution.

[0004] Another technology is in-situ pyrolysis technology, which is to drill a well from the ground into the ore deposit and provide additional heat in the stratum, such as electric heat or heat-carrying fluid, so that the coal can be pyrolyzed in situ to produce products such as tar and gas. This technology can be applied to deep ore deposits. In addition, this technology avoids pollution from chemical residues and has significant advantages over ground distillation technology. At present, this technology is mainly used in the field of oil shale mining, and there is no case of applying it to oil-rich coal. Oil-rich coal and oil shale have similar mineral conditions. Applying this technology to the pyrolysis of oil-rich coal has broad application prospects.

[0005] The in-situ pyrolysis process requires a large amount of energy input. However, the current in-situ pyrolysis technology does not recycle the heat in the ore deposit after in-situ pyrolysis, which not only causes a large amount of energy waste, but also causes thermal pollution to the environment. Therefore, it is of great significance to recycle the waste heat in the ore deposit after in-situ pyrolysis. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an in-situ pyrolysis and waste heat recovery system and method for oil-rich coal to solve the problems of waste heat waste and environmental thermal pollution in the ore deposit after in-situ pyrolysis of oil-rich coal.

[0007] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0008] An oil-rich coal in-situ pyrolysis and waste heat recovery system, comprising a cooler, a first compressor, a four-way reversing valve, a heater, a first oil separator, an injection well, a production well, a second oil separator and an absorption refrigeration unit, wherein one end of the cooler is used to input a gas working medium, the other end of the cooler is connected to the input end of the first compressor, the output end of the first compressor is connected to the input end of the four-way reversing valve, the first output end of the four-way reversing valve is connected to one end of the heater, the other end of the heater is connected to one end of the first oil separator, and the other end of the first oil separator is connected to the The injection well is connected, the injection well is connected with the production well through coal seam fractures, the production well is connected with one end of the second oil separator, the other end of the second oil separator is connected with the second output end of the four-way reversing valve, one end of the absorption refrigeration unit is connected with the third output end of the four-way reversing valve, and the other end of the absorption refrigeration unit is connected with the input end of the first compressor; the cooling medium output end of the cooler is connected with the cooling medium input end of the absorption refrigeration unit, and the cooling medium output end of the absorption refrigeration unit is connected with the cooling medium input end of the cooler.

[0009] Furthermore, the gas working medium is air;

[0010] It also includes an air separator and a first heat exchanger, wherein the air separator is used to separate oxygen and nitrogen in the air, the other end of the cooler is connected to the input end of the air separator, the nitrogen output end of the air separator is connected to one end of the first heat exchanger, and the other end of the first heat exchanger is connected to the input end of the first compressor.

[0011] Furthermore, it also includes a second heat exchanger and an oxygen collecting device, the oxygen output end of the air separator is connected to one end of the second heat exchanger, and the other end of the second heat exchanger is connected to the oxygen collecting device.

[0012] Furthermore, a pipe network for forming a freezing wall is arranged around the injection well and the production well, and the pyrolysis area; the cooling medium output end of the first heat exchanger and the cooling medium output end of the second heat exchanger are respectively connected to one end of the pipe network, and the other end of the pipe network is respectively connected to the cooling medium input end of the first heat exchanger and the cooling medium input end of the second heat exchanger.

[0013] Furthermore, it also includes an air storage tank, the output end of the first compressor is connected to the input end of the air storage tank, and the output end of the air storage tank is connected to the input end of the four-way reversing valve.

[0014] Furthermore, it also includes a second compressor, the input end of the second compressor is used to input gas working medium, and the output end of the second compressor is connected to one end of the cooler.

[0015] Furthermore, the absorption refrigeration unit adopts a lithium bromide absorption refrigeration unit.

[0016] Furthermore, the set temperature of the heater during heating is 500° C. to 650° C.; the set pressure of the first compressor during pressurization is 2 MPa to 20 MPa.

[0017] A method for in-situ pyrolysis and waste heat recovery of oil-rich coal, using the system, comprising:

[0018] A cooling medium is introduced into the cooling medium input end of the cooler, and a gaseous working medium is input into the cooler. The gaseous working medium cooled by the cooler is pressed into the four-way reversing valve through the first compressor, and the second output end and the third output end of the four-way reversing valve are controlled to be connected. The gaseous working medium is output from the first output end of the four-way reversing valve and then enters the heater. The gaseous working medium heated by the heater enters the injection well after passing through the first oil separator, and heats the oil-rich coal seam through the coal seam fracture. The heated gaseous working medium carries the product oil after pyrolysis into the production well, and the production well collects After the product oil is produced, the heated gaseous working medium enters the second oil separator. After the second oil separator separates the heated gaseous working medium into oil and gas, the heated gaseous working medium enters the absorption refrigeration unit as a heat source to drive the absorption refrigeration unit, and is input into the first compressor. At the same time, the cooling medium carrying heat output from the cooling medium output end of the cooler enters from the cooling medium input end of the absorption refrigeration unit, and the refrigerated cooling medium is input from the cooling medium output end of the absorption refrigeration unit to the cooling medium input end of the cooler. The gaseous working medium is continuously circulated to complete the in-situ pyrolysis of the oil-rich coal.

[0019] When the in-situ pyrolysis of the oil-rich coal is completed, the heater is turned off, and the first output end and the third output end of the four-way reversing valve are controlled to be connected. The gaseous working medium output from the first compressor is output from the second output end of the four-way reversing valve and enters the production well through the second oil separator, and enters the coal seam fracture through the production well to exchange heat with the oil-rich coal seam after the in-situ pyrolysis. The gaseous working medium after the heat exchange carries the residual product oil through the injection well and enters the first oil separator. After the first oil separator separates the gaseous working medium carrying the residual product oil from oil and gas, the gaseous working medium after the oil separation passes through the heater and the four-way reversing valve, and the gaseous working medium carrying the residual heat enters the absorption refrigeration unit as a heat source to drive the absorption refrigeration unit, and then enters the first compressor to complete the waste heat recovery cycle after the in-situ pyrolysis of the oil-rich coal.

[0020] Furthermore, cooling medium is introduced into the cooling medium input end of the first heat exchanger and the cooling medium input end of the second heat exchanger. After the air separator separates the air into nitrogen and oxygen, the nitrogen and oxygen are respectively heat exchanged through the first heat exchanger and the second heat exchanger. The cooling medium with cold capacity is input into one end of the pipeline through the cooling medium output end of the first heat exchanger and the cooling medium output end of the second heat exchanger to cool the oil-rich coal seam, thereby forming the freezing wall, and then enters the cooling medium input end of the first heat exchanger and the cooling medium input end of the second heat exchanger.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: the present invention provides an in-situ pyrolysis and waste heat recovery system for oil-rich coal. When in use, a cooling medium is introduced into the cooling medium input end of the cooler, and a gaseous working medium is input into the cooler. The gaseous working medium cooled by the cooler is pressed into the four-way reversing valve through the first compressor, and the second output end and the third output end of the four-way reversing valve are controlled to be connected. The gaseous working medium is output from the first output end of the four-way reversing valve and then enters the heater. The gaseous working medium heated by the heater enters the injection well after passing through the first oil separator, and heats the oil-rich coal seam through the coal seam fractures. The heated gaseous working medium carries the product oil after pyrolysis into the production well. After the production well collects the product oil, the heated gaseous working medium enters the second oil separator. After the second oil separator separates the heated gaseous working medium into oil and gas, the heated gaseous working medium enters the absorption refrigeration unit as a heat source to drive the absorption refrigeration unit, and is input into the first compressor. At the same time, the gaseous working medium carrying heat output from the cooling medium output end of the cooler A large amount of cooling medium enters from the cooling medium input end of the absorption refrigeration unit, and the refrigerated cooling medium is input from the cooling medium output end of the absorption refrigeration unit to the cooling medium input end of the cooler, and the gaseous working medium circulates continuously to complete the in-situ pyrolysis of the oil-rich coal; when the in-situ pyrolysis of the oil-rich coal is completed, the heater is turned off, and the first output end and the third output end of the four-way reversing valve are controlled to be connected. The gaseous working medium output from the first compressor is output from the second output end of the four-way reversing valve and then enters the production well through the second oil separator, and enters the coal seam fracture through the production well to exchange heat with the oil-rich coal seam after in-situ pyrolysis. The gaseous working medium after heat exchange carries the residual product oil through the injection well and enters the first oil separator. After the first oil separator separates the gaseous working medium carrying the residual product oil from oil and gas, the gaseous working medium after oil separation passes through the heater and the four-way reversing valve, and the gaseous working medium carrying the residual heat enters the absorption refrigeration unit as a heat source to drive the absorption refrigeration unit, and then enters the first compressor to complete the waste heat recovery and utilization cycle after the in-situ pyrolysis of the oil-rich coal. It can be seen that the present invention utilizes cold fluid in the coal seam fracture flow channel to exchange heat with the coal seam after in-situ pyrolysis by means of convection heat transfer, thereby recycling the waste heat, and after a certain waste heat recovery cycle, the device is placed in the next production well and injection well to continue to recover waste heat. This method can recover most of the heat after in-situ pyrolysis of the coal seam, save energy, improve energy utilization efficiency, and does not pollute the environment.

[0022] Furthermore, the gaseous working medium carrying waste heat is used as a heat source to drive the lithium bromide absorption refrigeration unit. The cooling medium enters the cooler after obtaining cold energy through the lithium bromide absorption refrigeration unit, precools the air before entering the air separator, and is sent back to the lithium bromide absorption refrigeration unit through a pipeline to complete the air precooling cycle. The entire system realizes the cascade utilization of energy, with high energy utilization efficiency and low environmental pollution.

[0023] Furthermore, it also includes a second heat exchanger and an oxygen collecting device. The oxygen output end of the air separator is connected to one end of the second heat exchanger, and the other end of the second heat exchanger is connected to the oxygen collecting device. The collected oxygen can be used for other purposes.

[0024] Furthermore, the cooling medium after obtaining cold enters the pipeline around the pyrolysis area, exchanges heat with the coal seam, and forms a freezing wall, thereby achieving the purpose of preventing groundwater from infiltrating into the pyrolysis area and oil and gas from seeping out. The cooling medium after heat exchange is then returned to the first heat exchanger and the second heat exchanger through the pipeline, completing the refrigeration cycle of the freezing wall.

[0025] Furthermore, it also includes a gas storage tank, the output end of the first compressor is connected to the input end of the gas storage tank, and the output end of the gas storage tank is connected to the input end of the four-way reversing valve, so as to facilitate the storage and utilization of the gas working medium.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic diagram of an oil-rich coal in-situ pyrolysis and waste heat recovery system of the present invention;

[0029] Figure 2a and 2b This is the fluid flow diagram in the four-way reversing valve.

[0030] 1-second compressor; 2-cooler; 3-air separator; 4-second heat exchanger; 5-first heat exchanger; 6-first compressor; 7-gas storage tank; 8-four-way reversing valve; 9-heater; 10-first oil separator; 11-injection well; 12-coal seam fracture; 13-production well; 14-second oil separator; 15-absorption refrigeration unit; 16-freezing wall; 17-oxygen collection device. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] As a specific embodiment of the present invention, Figure 1 As shown, an oil-rich coal in-situ pyrolysis and waste heat recovery system includes a second compressor 1, a cooler 2, an air separator 3, a second heat exchanger 4, a first heat exchanger 5, a first compressor 6, a gas storage tank 7, a four-way reversing valve 8, a heater 9, a first oil separator 10, an injection well 11, a production well 13, a second oil separator 14, an absorption refrigeration unit 15, a freezing wall 16 and an oxygen collection device 17. A pipe network for forming a freezing wall 16 is arranged around the pyrolysis area where the injection well 11 and the production well 13 are located. The air separator 3 is used to separate oxygen and nitrogen in the air. The absorption refrigeration unit 15 adopts a lithium bromide absorption refrigeration unit.

[0033] The input end of the second compressor 1 is used to input a gaseous working medium, which is air. The output end of the second compressor 1 is connected to one end of the cooler 2, the other end of the cooler 2 is connected to the input end of the air separator 3, the oxygen output end of the air separator 3 is connected to one end of the second heat exchanger 4, and the other end of the second heat exchanger 4 is connected to the oxygen collection device 17. The nitrogen output end of the air separator 3 is connected to one end of the first heat exchanger 5, the other end of the first heat exchanger 5 is connected to the input end of the first compressor 6, the output end of the first compressor 6 is connected to the input end of the gas storage tank 7, the output end of the gas storage tank 7 is connected to the input end of the four-way reversing valve 8, the first output end of the four-way reversing valve 8 is connected to one end of the heater 9, the other end of the heater 9 is connected to one end of the first oil separator 10, the other end of the first oil separator 10 is connected to the injection well 11, the injection well 11 is connected to the production well 13 through the coal seam fracture 12, the production well 13 is connected to one end of the second oil separator 14, the other end of the second oil separator 14 is connected to the second output end of the four-way reversing valve 8, one end of the absorption refrigeration unit 15 is connected to the third output end of the four-way reversing valve 8, and the other end of the absorption refrigeration unit 15 is connected to the input end of the first compressor 6.

[0034] The cooling medium output end a1 of the cooler 2 is connected to the cooling medium input end a2 of the absorption refrigeration unit 15 , and the cooling medium output end b1 of the absorption refrigeration unit 15 is connected to the cooling medium input end b2 of the cooler 2 .

[0035] The cooling medium output end c1 of the first heat exchanger 5 and the cooling medium output end c2 of the second heat exchanger 4 are respectively connected to one end c3 of the pipe network, and the other end d1 of the pipe network is respectively connected to the cooling medium input end d2 of the first heat exchanger 5 and the cooling medium input end d3 of the second heat exchanger 4.

[0036] The present invention discloses an in-situ pyrolysis and waste heat recovery method for oil-rich coal, which uses the system of the present invention, and is specifically as follows:

[0037] The cooling medium is introduced into the cooling medium input end b2 of the cooler 2, and the cooling medium is introduced into the cooling medium input end d2 of the first heat exchanger 5 and the cooling medium input end d3 of the second heat exchanger 4. The gaseous working medium air is input into the cooler 2 through the second compressor 1. The air is separated into nitrogen and oxygen by the air separator 3. The nitrogen and oxygen are respectively heat exchanged through the first heat exchanger 5 and the second heat exchanger 4. The oxygen after heat exchange through the second heat exchanger 4 is collected for other uses. The nitrogen after heat exchange through the first heat exchanger 5 passes through the first compressor 6 and enters the gas storage tank 7 after the pressure is increased.

[0038] When the oil-rich coal is in-situ pyrolysis, the heater 9 is turned on, and the slider in the four-way reversing valve 8 is placed on the right side to control the second output end and the third output end of the four-way reversing valve 8 to be connected. At this time, the flow direction of the working medium in the four-way reversing valve 8 is as follows: Figure 2a As shown, the nitrogen coming out of the gas storage tank 7 enters the four-way reversing valve 8, is output from the first output end of the four-way reversing valve 8 and enters the heater 9. The nitrogen heated by the heater 9 passes through the first oil separator 10 and enters the injection well 11, and passes through the coal seam fracture 12 to heat the oil-rich coal seam. The heated nitrogen carries the product oil after pyrolysis into the production well 13. After the production well 13 collects the product oil, the heated nitrogen enters the second oil separator 14. After the second oil separator 14 separates the heated nitrogen into oil and gas, the heated nitrogen enters the second oil separator 14. The nitrogen after cooling enters the absorption refrigeration unit 15 as a heat source to drive the absorption refrigeration unit 15, and is input into the gas storage tank 7 through the first compressor 6 after heat exchange with the lithium bromide solution; at the same time, the cooling medium carrying heat output from the cooling medium output end a1 of the cooler 2 enters from the cooling medium input end a2 of the absorption refrigeration unit 15, and the cooling medium after cooling is input from the cooling medium output end b1 of the absorption refrigeration unit 15 to the cooling medium input end b2 of the cooler 2, and the gas working medium is continuously circulated to complete the in-situ pyrolysis of the oil-rich coal.

[0039] The nitrogen carrying waste heat is used as a heat source to drive the lithium bromide absorption refrigeration unit. The cooling medium enters the cooler 2 after passing through the lithium bromide absorption refrigeration unit to obtain cold capacity, and precools the air before entering the air separator 3. After precooling, it is sent back to the lithium bromide absorption refrigeration unit through a pipeline to complete the air precooling cycle. The entire system realizes the cascade utilization of energy, with high energy utilization efficiency and low environmental pollution.

[0040] When the in-situ pyrolysis of the oil-rich coal is completed, the heater 9 is turned off, and the slider in the four-way reversing valve 8 is placed on the left side to control the first output end and the third output end of the four-way reversing valve 8 to be connected. At this time, the flow direction of the working medium in the four-way reversing valve 8 is as follows: Figure 2b As shown, the nitrogen output from the gas tank 7 is output from the second output end of the four-way reversing valve 8, enters the production well 13 through the second oil separator 14, and enters the coal seam fracture 12 through the production well 13, and exchanges heat with the oil-rich coal seam after in-situ pyrolysis. The nitrogen after heat exchange carries the residual product oil through the injection well 11 and enters the first oil separator 10. After the first oil separator 10 separates the nitrogen carrying the residual product oil from oil and gas, the nitrogen after oil separation passes through the heater 9 and the four-way reversing valve 8 and enters the absorption refrigeration unit 15. After heat exchange with the lithium bromide solution, it is input into the gas tank 7 through the first compressor 6, completing the waste heat recovery cycle after the in-situ pyrolysis of the oil-rich coal.

[0041] The cooling medium that has obtained cold energy is input into one end c3 of the pipe network through the cooling medium output end c1 of the first heat exchanger 5 and the cooling medium output end c2 of the second heat exchanger 4, and then enters the cooling medium input end d2 of the first heat exchanger 5 and the cooling medium input end d3 of the second heat exchanger 4 after heat exchange with the oil-rich coal seam. That is, the cooling medium that has obtained cold energy enters the pipeline around the pyrolysis area, exchanges heat with the coal seam, and forms a freezing wall 16, thereby preventing groundwater from infiltrating into the pyrolysis area and preventing oil and gas from seeping out. The cooling medium that has exchanged heat then returns to the first heat exchanger 5 and the second heat exchanger 4 through the pipeline, completing the refrigeration cycle of the freezing wall.

[0042] The set temperature of the heater 9 of the present invention during heating is 500° C. to 650° C.; the set pressure of the first compressor 6 during pressurization is 2 MPa to 20 MPa.

[0043] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection 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. An oil-rich coal in-situ pyrolysis and waste heat recovery system, characterized in that: The invention comprises a cooler (2), a first compressor (6), a four-way reversing valve (8), a heater (9), a first oil separator (10), an injection well (11), a production well (13), a second oil separator (14) and an absorption refrigeration unit (15), wherein one end of the cooler (2) is used for inputting a gas working medium, the other end of the cooler (2) is connected to the input end of the first compressor (6), the output end of the first compressor (6) is connected to the input end of the four-way reversing valve (8), the first output end of the four-way reversing valve (8) is connected to one end of the heater (9), the other end of the heater (9) is connected to one end of the first oil separator (10), the other end of the first oil separator (10) is connected to the injection well (11), and the injection well (13) is connected to the second oil separator (14). The well (11) is connected to the production well (13) through a coal seam fracture (12); the production well (13) is connected to one end of the second oil separator (14); the other end of the second oil separator (14) is connected to the second output end of the four-way reversing valve (8); one end of the absorption refrigeration unit (15) is connected to the third output end of the four-way reversing valve (8); the other end of the absorption refrigeration unit (15) is connected to the input end of the first compressor (6); the cooling medium output end (a1) of the cooler (2) is connected to the cooling medium input end (a2) of the absorption refrigeration unit (15); and the cooling medium output end (b1) of the absorption refrigeration unit (15) is connected to the cooling medium input end (b2) of the cooler (2).

2. The in-situ pyrolysis and waste heat recovery system of oil-rich coal according to claim 1, characterized in that: The gas working medium is air; It also comprises an air separator (3) and a first heat exchanger (5), wherein the air separator (3) is used to separate oxygen and nitrogen in the air, the other end of the cooler (2) is connected to the input end of the air separator (3), the nitrogen output end of the air separator (3) is connected to one end of the first heat exchanger (5), and the other end of the first heat exchanger (5) is connected to the input end of the first compressor (6).

3. The in-situ pyrolysis and waste heat recovery system of oil-rich coal according to claim 2, characterized in that: It also comprises a second heat exchanger (4) and an oxygen collecting device (17), wherein the oxygen output end of the air separator (3) is connected to one end of the second heat exchanger (4), and the other end of the second heat exchanger (4) is connected to the oxygen collecting device (17).

4. The oil-rich coal in-situ pyrolysis and waste heat recovery system according to claim 3, characterized in that: A pipe network for forming a freezing wall (16) is arranged around the pyrolysis area where the injection well (11) and the production well (13) are located. The cooling medium output end (c1) of the first heat exchanger (5) and the cooling medium output end (c2) of the second heat exchanger (4) are respectively connected to one end (c3) of the pipe network, and the other end (d1) of the pipe network is respectively connected to the cooling medium input end (d2) of the first heat exchanger (5) and the cooling medium input end (d3) of the second heat exchanger (4).

5. The in-situ pyrolysis and waste heat recovery system of oil-rich coal according to claim 1, characterized in that: It also includes an air storage tank (7), the output end of the first compressor (6) is connected to the input end of the air storage tank (7), and the output end of the air storage tank (7) is connected to the input end of the four-way reversing valve (8).

6. The oil-rich coal in-situ pyrolysis and waste heat recovery system according to claim 1, characterized in that: It also comprises a second compressor (1), wherein the input end of the second compressor (1) is used to input a gas working medium, and the output end of the second compressor (1) is connected to one end of the cooler (2).

7. The oil-rich coal in-situ pyrolysis and waste heat recovery system according to claim 1, characterized in that: The absorption refrigeration unit (15) is a lithium bromide absorption refrigeration unit.

8. The oil-rich coal in-situ pyrolysis and waste heat recovery system according to claim 1, characterized in that: The set temperature of the heater (9) during heating is 500° C. to 650° C.; the set pressure of the first compressor (6) during pressurization is 2 MPa to 20 MPa.

9. A method for in-situ pyrolysis of oil-rich coal and waste heat recovery, characterized in that: The system according to claim 4 comprises: A cooling medium is introduced into the cooling medium input end (b2) of the cooler (2), and a gaseous working medium is input into the cooler (2). The gaseous working medium cooled by the cooler (2) is pressed into the four-way reversing valve (8) through the first compressor (6), and the second output end and the third output end of the four-way reversing valve (8) are controlled to be connected. The gaseous working medium is output from the first output end of the four-way reversing valve (8) and then enters the heater (9). The gaseous working medium heated by the heater (9) passes through the first oil separator (10) and then enters the injection well (11), and passes through the coal seam fractures (12) to heat the oil-rich coal seam. After being heated, the gaseous working medium carries the product oil after pyrolysis and enters the production well (13). The production well (13) receives the oil. After collecting the product oil, the heated gaseous working medium enters the second oil separator (14). After the second oil separator (14) separates the heated gaseous working medium from oil and gas, the heated gaseous working medium enters the absorption refrigeration unit (15) as a heat source to drive the absorption refrigeration unit (15), and is input into the first compressor (6). At the same time, the cooling medium carrying heat output from the cooling medium output end (a1) of the cooler (2) enters from the cooling medium input end (a2) of the absorption refrigeration unit (15), and the refrigerated cooling medium is input from the cooling medium output end (b1) of the absorption refrigeration unit (15) to the cooling medium input end (b2) of the cooler (2). The gaseous working medium is continuously circulated to complete the in-situ pyrolysis of the oil-rich coal. When the in-situ pyrolysis of the oil-rich coal is completed, the heater (9) is turned off, and the first output end and the third output end of the four-way reversing valve (8) are controlled to be connected. The gaseous working medium output from the first compressor (6) is output from the second output end of the four-way reversing valve (8) and enters the production well (13) through the second oil separator (14), and enters the coal seam fracture (12) through the production well (13) to exchange heat with the oil-rich coal seam after the in-situ pyrolysis. The gaseous working medium after the heat exchange carries the residual product oil and enters the first oil separator (10) through the injection well (11). The first oil separator (10) separates the gaseous working medium carrying the residual product oil from oil and gas. After the gaseous working medium after the oil separation passes through the heater (9) and the four-way reversing valve (8), the gaseous working medium carrying the residual heat enters the absorption refrigeration unit (15) as a heat source to drive the absorption refrigeration unit (15), and then enters the first compressor (6), completing the waste heat recovery cycle after the in-situ pyrolysis of the oil-rich coal.

10. The method for in-situ pyrolysis and waste heat recovery of oil-rich coal according to claim 9, characterized in that: A cooling medium is introduced into the cooling medium input end (d2) of the first heat exchanger (5) and the cooling medium input end (d3) of the second heat exchanger (4). After the air separator (3) separates the air into nitrogen and oxygen, the nitrogen and oxygen are respectively passed through the first heat exchanger (5) and the second heat exchanger (4) for heat exchange. The cooling medium with cold capacity is input into one end (c3) of the pipe network through the cooling medium output end (c1) of the first heat exchanger (5) and the cooling medium output end (c2) of the second heat exchanger (4) to cool the oil-rich coal seam, thereby forming the freezing wall (16), and then enters the cooling medium input end (d2) of the first heat exchanger (5) and the cooling medium input end (d3) of the second heat exchanger (4).

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