Multi-stage ORC-TEG combined cooling, heating and power generation system and method using geothermal energy and liquefied natural gas

Abstract

A multi-stage ORC-TEG combined heat, cooling and power generation system and method utilizing geothermal energy and liquefied natural gas belongs to the technical field of geothermal energy and liquefied natural gas cold energy recovery and utilization. The present invention solves the problems of insufficient utilization of existing geothermal energy and LNG cold energy and large exergy loss caused by large temperature difference between geothermal and LNG. The geothermal well and the heat source heat exchanger and the geothermal well and the heat supply heat exchanger are respectively connected by pipelines to form a geothermal system; the heat source heat exchanger, the first expander, the first evaporator and the first pump body are connected by pipelines in sequence to form a primary ORC circulation system; the heat source heat exchanger, the second expander, the second evaporator and the second pump body are connected by pipelines in sequence to form a secondary ORC circulation system; the LNG storage tank, the third pump body, the first evaporator, the fourth pump body, the second evaporator, the third expander and the air cooler are connected by pipelines in sequence to form an LNG delivery system. Multi-stage compression is adopted to reduce the temperature difference between the refrigerant and LNG and improve the exergy efficiency of the system.

Description

Technical Field

[0001] The invention relates to a multi-stage ORC-TEG combined cooling, heating and power generation system and method utilizing geothermal energy and liquefied natural gas, belonging to the technical field of geothermal energy and liquefied natural gas cold energy recovery and utilization. Background Art

[0002] With the increasing awareness of environmental protection and the shortage of traditional energy, people are in urgent need of fully developing and utilizing new energy. There is abundant heat underground that can be used for power generation and heating. Similarly, liquefied natural gas (LNG) has a large amount of cold energy due to its temperature as low as -162℃. However, the utilization of LNG cold energy is relatively rough. If the huge temperature difference of up to 260℃ or more between geothermal and LNG is used to generate electricity, it will achieve very high efficiency. Therefore, providing LNG cold energy to ORC can improve the utilization efficiency of geothermal energy and realize the preheating process of LNG at the same time.

[0003] At present, the cold energy utilization of LNG is usually to use expanders to generate electricity. This technology is limited by the small temperature difference and has low efficiency. For the joint utilization of geothermal and LNG, ORC (Organic Rankine Cycle) is usually used for power generation. The heat and cold energy are not fully utilized, and the large temperature difference between geothermal and LNG will cause huge exergy losses. Summary of the invention

[0004] The present invention aims to solve the problems of insufficient utilization of existing geothermal energy and LNG cold energy and large exergy loss caused by large temperature difference between geothermal energy and LNG, and further provides a multi-stage ORC-TEG combined heat, cooling and power generation system and method utilizing geothermal energy and liquefied natural gas.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A multi-stage ORC-TEG combined heat, cooling and power generation system using geothermal energy and liquefied natural gas, comprising a geothermal well, a heat source heat exchanger, a heat supply heat exchanger, first to third expanders, a first evaporator, a second evaporator, an LNG storage tank, an air cooler and first to fourth pump bodies, wherein:

[0007] The geothermal well and the heat source heat exchanger as well as the geothermal well and the heat supply heat exchanger are connected by pipelines to form a geothermal system;

[0008] The heat source heat exchanger, the first expander, the first evaporator and the first pump body are connected in sequence through pipelines to form a primary ORC circulation system;

[0009] The heat source heat exchanger, the second expander, the second evaporator and the second pump body are connected in sequence through pipelines to form a secondary ORC circulation system;

[0010] The LNG storage tank, the third pump body, the first evaporator, the fourth pump body, the second evaporator, the third expander and the air cooler are sequentially connected through pipelines to form an LNG delivery system;

[0011] The heating heat exchanger supplies heat to the heating terminal through pipeline connection;

[0012] The first expander, the second expander and the third expander are respectively connected to the power supply terminal through the circuit to supply power;

[0013] The natural gas outlet of the air cooler is connected to the gas supply terminal through a pipeline for natural gas supply;

[0014] The air outlet of the air cooler is connected to the cooling terminal through a pipeline for cooling.

[0015] Furthermore, a first TEG module is arranged on the pipeline between the third pump body and the first evaporator.

[0016] Furthermore, a second TEG module is provided on the pipeline between the fourth pump body and the second evaporator.

[0017] Further, the refrigerant saturation temperature in the secondary ORC cycle system is higher than the refrigerant saturation temperature in the primary ORC cycle system;

[0018] Furthermore, the medium for exchanging heat with the geothermal water in the heat supply heat exchanger is air or water.

[0019] A combined heat and power method using the above combined heat and power system, in which, in the geothermal system, water passes through the geothermal well and fully absorbs heat underground, then flows to the heat source heat exchanger and the heat supply heat exchanger respectively, and then flows back to the underground after sufficient heat exchange, forming a circulation loop;

[0020] The heating medium exchanges heat with the water from the geothermal system in the heat exchanger, and after reaching the heating temperature, it enters the heating terminal for heating;

[0021] In the primary ORC circulation system, the refrigerant absorbs heat from the heat source heat exchanger, then generates electricity through the first expander. After expansion, the temperature and pressure of the refrigerant decrease, and then it enters the first evaporator to condense and exchange heat with LNG, and then it is pressurized by the first pump body and returns to the heat source heat exchanger for heating and evaporation.

[0022] In the secondary ORC circulation system, the refrigerant with a higher atmospheric saturation temperature than the primary ORC circulation system absorbs heat from the heat source heat exchanger, and then generates electricity through the second expander. The refrigerant condenses and exchanges heat with LNG in the second evaporator at a condensation temperature higher than that in the primary ORC circulation system. The condensed refrigerant is pressurized by the second pump body and heated and evaporated in the heat source heat exchanger.

[0023] In the LNG delivery system, LNG is pumped out from the LNG storage tank by the third pump body, enters the first evaporator to exchange heat with the refrigerant, and the temperature of LNG rises. After passing through the fourth pump body, the internal energy of LNG increases, and then enters the second evaporator to exchange heat with the refrigerant again to increase the temperature. Then, after the LNG is expanded and generated by the third expander, the pressure drops to the required pressure of the terminal, and after passing through the air cooler to exchange heat with the air, it reaches normal temperature and is supplied with natural gas.

[0024] The air exchanges heat with LNG in the air cooler to form cold air for cooling.

[0025] Compared with the prior art, the present invention has the following effects:

[0026] The present application adopts multi-stage compression to reduce the temperature difference between the refrigerant and the LNG and improve the exergy efficiency of the system.

[0027] The present application adopts two-stage ORC and three-stage power generation in series-parallel form to form a geothermal energy cascade utilization system. The system can better utilize the cold energy of LNG and the thermal energy of geothermal energy, reduce the fire loss caused by the huge temperature difference between the two, and improve the efficiency of fire use. The use of a two-stage ORC cycle can effectively divide the huge temperature difference between geothermal and LNG into two smaller temperature differences, thereby reducing the fire loss of the system. At the same time, the use of two-stage compression on the LNG side can improve the efficiency of the pump and reduce the power consumption of the pump on the one hand, and effectively control the temperature difference between LNG and ORC working fluid on the other hand, further improving the fire efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of a multi-stage ORC-TEG combined heat, cooling and power system utilizing geothermal energy and liquefied natural gas for this application. DETAILED DESCRIPTION

[0029] Specific implementation method 1: Combination Figure 1 The present embodiment is described as a multi-stage ORC-TEG combined heat, cooling and power generation system using geothermal energy and liquefied natural gas, comprising a geothermal well 1, a heat source heat exchanger 2, a heat supply heat exchanger 3, first to third expanders, a first evaporator 7, a second evaporator 8, an LNG storage tank 9, an air cooler 10 and first to fourth pump bodies, wherein:

[0030] The geothermal well 1 and the heat source heat exchanger 2 as well as the geothermal well 1 and the heat supply heat exchanger 3 are connected by pipelines to form a geothermal system;

[0031] The heat source heat exchanger 2, the first expander 4, the first evaporator 7 and the first pump body 11 are connected in sequence through pipelines to form a primary ORC circulation system;

[0032] The heat source heat exchanger 2, the second expander 5, the second evaporator 8 and the second pump body 12 are sequentially connected through pipelines to form a secondary ORC circulation system;

[0033] The LNG storage tank 9, the third pump body 13, the first evaporator 7, the fourth pump body 14, the second evaporator 8, the third expander 6 and the air cooler 10 are sequentially connected through pipelines to form an LNG delivery system;

[0034] The heat supply heat exchanger 3 supplies heat to the heating terminal through a pipeline connection;

[0035] The first expander 4, the second expander 5 and the third expander 6 are respectively connected to the power supply terminal through circuits for power supply;

[0036] The natural gas outlet of the air cooler 10 is connected to the gas supply terminal through a pipeline for natural gas supply;

[0037] The air outlet of the air cooler 10 is connected to a cooling terminal through a pipeline for cooling.

[0038] The heating terminal, power supply terminal, cooling terminal and gas supply terminal described in this application may be the same or different buildings or any other equipment with heating, power supply, cooling or gas supply needs.

[0039] The geothermal system provides heat source for other systems. Water is used as the working fluid inside the geothermal system. After fully absorbing heat underground through the geothermal well 1, the water flows to the heat source heat exchanger 2 and the heat supply heat exchanger 3 respectively. After sufficient heat exchange, it flows back to the underground to form a circulation loop.

[0040] After the air or water exchanges heat with the hot water flowing in from the geothermal well 1 in the heat exchanger 3, it enters the heat supply terminal for heating. The heat supply terminal can be a building such as a residential building.

[0041] The LNG in the LNG storage tank 9 increases in pressure after passing through the third pump body 13, enters the first evaporator 7 to evaporate and absorb heat, and then enters the second evaporator 8 after being compressed by the fourth pump body 14 to evaporate and absorb heat at a higher saturation temperature. The LNG is then expanded and depressurized to the required pressure by the third expander 6, and finally enters the air cooler 10 to exchange heat with the air and is then sent to terminals such as residential buildings for natural gas supply;

[0042] During the natural gas supply process, the third expander 6 is used to generate electric energy again to supply power to power supply terminals such as residential buildings;

[0043] The air reaches a very low temperature after heat exchange with the low-temperature LNG in the air cooler 10, and is connected to the cooling terminal such as the residential building through a pipeline for cooling;

[0044] Both the primary ORC cycle and the secondary ORC cycle obtain geothermal heat from the heat source heat exchanger 2. After leaving the heat source heat exchanger 2, the refrigerant passes through the first expander 4 and the second expander 5 to perform work, and then enters the first condenser and the second condenser respectively, and then is pressurized by the first pump body 11 and the second pump body 12 respectively, and flows back to the heat source heat exchanger 2 again.

[0045] The electric energy generated by the first expander 4 and the second expander 5 after working is respectively transmitted to power supply terminals such as residential buildings for power supply.

[0046] The present application adopts multi-stage compression to reduce the temperature difference between the refrigerant and the LNG and improve the exergy efficiency of the system.

[0047] The present application adopts two-stage ORC and three-stage power generation in series-parallel form to form a geothermal energy cascade utilization system. The system can better utilize the cold energy of LNG and the thermal energy of geothermal energy, reduce the fire loss caused by the huge temperature difference between the two, and improve the efficiency of fire use. The use of a two-stage ORC cycle can effectively divide the huge temperature difference between geothermal and LNG into two smaller temperature differences, thereby reducing the fire loss of the system. At the same time, the use of two-stage compression on the LNG side can improve the efficiency of the pump and reduce the power consumption of the pump on the one hand, and effectively control the temperature difference between LNG and ORC working fluid on the other hand, further improving the fire efficiency.

[0048] A first TEG module 15 is provided on the pipeline between the third pump body 13 and the first evaporator 7. The TEG module described in the present application is a temperature difference power generation module, such as a temperature difference power generation sheet. During the supply of natural gas, the temperature difference between LNG and air is used by the first TEG module 15 to generate electricity, thereby supplying power to power supply terminals such as residential buildings. At the same time, TEG is used to recover LNG cold energy, thereby improving energy utilization efficiency. The first TEG module 15 and the third expander 6 can respectively utilize the cold energy before LNG enters the first evaporator 7 and between the second evaporator 8 and the air cooler 10, which is usually not available in the prior art.

[0049] A second TEG module 16 is provided on the pipeline between the fourth pump body 14 and the second evaporator 8. With such a design, during the natural gas supply process, the temperature difference between LNG and air is used in stages by the first TEG module 15 and the second TEG module 16 to generate electricity, and the third expander 6 is used to generate electricity again to supply power to power supply terminals such as residential buildings. The first TEG module 15, the second TEG module 16 and the third expander 6 can respectively utilize the cold energy before LNG enters the first evaporator 7, between the first evaporator 7 and the second evaporator 8, and between the second evaporator 8 and the air cooler 10, which is usually not available in the prior art.

[0050] The saturation temperature of the refrigerant in the secondary ORC cycle system is higher than that in the primary ORC cycle system; the refrigerant in the primary ORC cycle has a very low saturation temperature under normal pressure, and the saturation temperature of the refrigerant in the secondary ORC cycle is higher than that in the primary ORC cycle.

[0051] The medium for exchanging heat with the geothermal water in the heat exchanger 3 is air or water. With such a design, water or air exchanges heat with the high-temperature water coming out of the geothermal system in the heat exchanger 3, and after reaching the temperature required by the heating terminal such as the building, it enters the heating terminal such as the building to provide heat for the heating terminal.

[0052] A method for cogeneration of heat, cooling and power using the above cogeneration system, in which water in the geothermal system passes through a geothermal well 1, absorbs heat underground, and then flows to a heat source heat exchanger 2 and a heat supply heat exchanger 3, respectively, and then flows back underground after sufficient heat exchange, forming a circulation loop;

[0053] The heating medium exchanges heat with water from the geothermal system in the heating heat exchanger 3, and after reaching the heating temperature, enters the heating terminal for heating;

[0054] In the primary ORC circulation system, the refrigerant absorbs heat from the heat source heat exchanger 2, and then performs work to generate electricity through the first expander 4. After expansion, the temperature and pressure of the refrigerant decrease, and then the refrigerant enters the first evaporator 7 to condense and exchange heat with the LNG, and then is pressurized by the first pump body 11 and returns to the heat source heat exchanger 2 to be heated and evaporated; the refrigerant absorbs heat from the heat source heat exchanger 2 to reach a high temperature and high pressure state.

[0055] In the secondary ORC circulation system, the refrigerant with a higher atmospheric saturation temperature than the primary ORC circulation system absorbs heat from the heat source heat exchanger 2, and then generates electricity through the second expander 5. The refrigerant condenses and exchanges heat with LNG in the second evaporator 8 at a condensation temperature higher than that in the primary ORC circulation system. The condensed refrigerant is pressurized by the second pump body 12 and heated and evaporated in the heat source heat exchanger 2.

[0056] In the LNG transportation system, LNG is pumped from the LNG storage tank 9 by the third pump body 13, enters the first evaporator 7 to exchange heat with the refrigerant, the temperature of LNG rises, and the internal energy of LNG increases after passing through the fourth pump body 14. Then, LNG enters the second evaporator 8 to exchange heat with the refrigerant again to increase its temperature. Then, LNG expands and generates electricity through the third expander 6, and its pressure drops to the required terminal pressure. After passing through the air cooler 10 and exchanging heat with the air, it reaches room temperature and is supplied with natural gas. By setting the first TEG module 15 on the pipeline between the third pump body 13 and the first evaporator 7, the LNG in the pipeline can be heated to a temperature 10 degrees lower than the condensation temperature of the refrigerant in the first evaporator 7.

[0057] The air exchanges heat with the LNG in the air cooler 10 to form cold air for cooling.

Claims

1. A multi-stage ORC-TEG combined heat, cooling and power system using geothermal energy and liquefied natural gas, characterized by: The invention comprises a geothermal well (1), a heat source heat exchanger (2), a heat supply heat exchanger (3), first to third expanders, a first evaporator (7), a second evaporator (8), an LNG storage tank (9), an air cooler (10) and first to fourth pump bodies, wherein: The geothermal well (1) and the heat source heat exchanger (2) as well as the geothermal well (1) and the heat supply heat exchanger (3) are connected via pipelines to form a geothermal system; The heat source heat exchanger (2), the first expander (4), the first evaporator (7) and the first pump body (11) are connected in sequence through pipelines to form a primary ORC circulation system; The heat source heat exchanger (2), the second expander (5), the second evaporator (8) and the second pump body (12) are connected in sequence through pipelines to form a secondary ORC circulation system; The LNG storage tank (9), the third pump body (13), the first evaporator (7), the fourth pump body (14), the second evaporator (8), the third expander (6) and the air cooler (10) are connected in sequence through pipelines to form an LNG transportation system; The heating heat exchanger (3) supplies heat to the heating terminal via a pipeline connection; The first expander (4), the second expander (5) and the third expander (6) are respectively connected to the power supply terminal through a circuit to supply power; The natural gas outlet of the air cooler (10) is connected to the gas supply terminal via a pipeline for natural gas supply; The air outlet of the air cooler (10) is connected to a cooling terminal via a pipeline for cooling; A first TEG module (15) is provided on the pipeline between the third pump body (13) and the first evaporator (7); A second TEG module (16) is provided on the pipeline between the fourth pump body (14) and the second evaporator (8); The refrigerant saturation temperature in the secondary ORC circulation system is higher than the refrigerant saturation temperature in the primary ORC circulation system; The medium for exchanging heat with the geothermal water in the heat supply heat exchanger (3) is air or water.

2. A method for cogeneration of heat, cooling and power using the cogeneration system of claim 1, characterized in that: In the geothermal system, water passes through the geothermal well (1) and absorbs sufficient heat underground, then flows to the heat source heat exchanger (2) and the heat supply heat exchanger (3), respectively, and then flows back to the underground after sufficient heat exchange, forming a circulation loop; The heating medium exchanges heat with water from the geothermal system in the heating heat exchanger (3), and after reaching the heating temperature, enters the heating terminal for heating; In the primary ORC circulation system, the refrigerant absorbs heat from the heat source heat exchanger (2), then generates electricity through the first expander (4), after which the temperature and pressure of the refrigerant decrease, and then enters the first evaporator (7) to condense and exchange heat with LNG, and then is pressurized by the first pump body (11) and returns to the heat source heat exchanger (2) to be heated and evaporated; In the secondary ORC circulation system, the refrigerant having a higher atmospheric pressure saturation temperature than the primary ORC circulation system absorbs heat from the heat source heat exchanger (2), then generates electricity through the second expansion machine (5), and the refrigerant condenses and exchanges heat with LNG in the second evaporator (8) at a condensation temperature higher than that in the primary ORC circulation system, and the condensed refrigerant is pressurized by the second pump body (12) and heated and evaporated in the heat source heat exchanger (2); In the LNG delivery system, LNG is pumped from the LNG storage tank (9) by the third pump body (13), enters the first evaporator (7) to exchange heat with the refrigerant, and the temperature of the LNG rises. After passing through the fourth pump body (14), the internal energy of the LNG increases, and the LNG enters the second evaporator (8) to exchange heat with the refrigerant again to increase the temperature. After the LNG is expanded and generates electricity through the third expander (6), the pressure is reduced to the pressure required by the terminal, and after passing through the air cooler (10) to exchange heat with the air, the pressure reaches normal temperature, and the natural gas is supplied; The air exchanges heat with the LNG in the air cooler (10) to form cold air for cooling.

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