A geothermal fluid circulation device and a combined cycle system for a thermoelectric power generation - organic Rankine combined cycle system

Abstract

The present invention provides a geothermal fluid circulation device and a combined cycle system for a thermoelectric power generation - organic Rankine combined cycle system. The thermoelectric power generation - organic Rankine combined cycle system is used for medium - low temperature geothermal fluid. The geothermal fluid circulation device includes a production well, an injection well, an evaporator, a pre - heater, a supply pump, an expander, a generator and a thermoelectric power generation module. The present invention applies the thermoelectric power generation - organic Rankine combined cycle to medium - low temperature geothermal power generation. In the case of introducing TEG, the overall impact of TEG on the system is minimized as much as possible, so that each part of the power generation technology is in the optimal working range, greatly improving the power generation efficiency and the system life. At the same time, by using the TEG component to supply power to the supply pump, the system is "self - sufficient", ensuring passive safety to the greatest extent in case of emergency, and providing an effective reference for applying the thermoelectric power generation - organic Rankine combined cycle system to other working conditions in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermodynamic cycle structure design, especially focuses on the geothermal power generation technology field, and particularly relates to a geothermal fluid circulation device and a combined cycle system of a thermoelectric generation - organic Rankine combined cycle system. Background Art

[0002] The thermoelectric generation - organic Rankine combined cycle (TEG - ORC) has the advantages of higher efficiency and a wider operating temperature range compared with the traditional organic Rankine cycle, and is suitable for environmentally friendly heat energy utilization scenarios such as geothermal power generation and waste heat recovery from ship exhaust gas. With the rapid improvement of the thermoelectric material performance of TEG, the TEG - ORC combined cycle has received more and more attention. The specific structure design of this system can be divided into a heat source part, an organic Rankine cycle part, and a thermoelectric generator device. In the current common structure design of the thermoelectric generation - organic Rankine combined cycle system, when the heat source is relatively high in temperature, such as internal combustion engine exhaust gas, the TEG in the TEG - ORC combined cycle is mainly placed before the ORC cycle to reduce the heat source temperature to the suitable range for ORC, as Figure 1 shown. However, after introducing TEG into this system, it will affect the performance of the original ORC system. To improve the performance of TEG, it is necessary to improve the heat exchange capacity at both its hot and cold ends. Enhancing the heat exchange capacity of TEG usually increases the flow resistance. In the TEG - ORC combined cycle, it will increase the flow resistance of the ORC working fluid and the energy consumption of the circulation pump, and the overall life and passive safety of the system in case of emergency need to be improved. At the same time, for the thermoelectric generation - organic Rankine combined cycle based on medium - low temperature (90 - 200 °C) geothermal fluid, since the heat source temperature is already within the feasible temperature range of the ORC working fluid, there is no need to pre - place TEG to cool down the medium - low temperature heat source. Applying the thermoelectric generation - organic Rankine combined cycle to medium - low temperature geothermal power generation can achieve cascaded utilization of energy and improve the power generation efficiency. In addition, through the combination and optimization of the cycle structure, each power generation technology can be in a relatively optimal temperature working range, which can improve the overall life and passive safety of the system. In view of this, it is necessary to propose a new type of thermoelectric generation - organic Rankine combined cycle system based on medium - low temperature geothermal fluid. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems in the prior art, and a geothermal fluid circulation device and a combined cycle system of a thermoelectric generation - organic Rankine combined cycle system are proposed.

[0004] The present invention is realized through the following technical solutions. The present invention proposes a geothermal fluid circulation device of a thermoelectric generation - organic Rankine combined cycle system. The thermoelectric generation - organic Rankine combined cycle system is used for medium - low temperature geothermal fluid. The geothermal fluid circulation device includes a production well, an injection well, an evaporator, a pre - heater, a supply pump, an expander, a generator, and a thermoelectric generation module;

[0005] The production well: used for drilling in areas rich in geothermal resources, and pumping medium and low temperature geothermal fluid through a circulation pump;

[0006] The reinjection well: used for reinjecting geothermal water underground through a working fluid pump after multi-stage energy utilization to ensure the quality and quantity of underground water resources;

[0007] The evaporator: used for the organic working fluid to undergo non-mixed high-temperature heat exchange with the geothermal fluid in the evaporator and transform from a liquid into a gas that can drive the expander;

[0008] The preheater: used for the geothermal fluid that has undergone high-temperature heat exchange in the evaporator to perform non-mixed low-temperature heat exchange on the organic working fluid in front of the evaporator to achieve the preheating effect and simultaneously realize multi-stage energy utilization;

[0009] The supply pump: used to provide circulating power for the organic working fluid in the organic Rankine cycle;

[0010] The expander: used for the gaseous organic working fluid to release heat by expanding and reducing pressure, output mechanical work, and simultaneously reduce the gas temperature to make it into exhausted steam;

[0011] The generator: used to drive power generation by using the mechanical work output by the expander and output power outward;

[0012] The thermoelectric generation module: composed of thermoelectric generation units, realizing thermoelectric generation, further realizing multi-stage energy utilization, reducing the temperature of the organic working fluid, and outputting power outward.

[0013] Further, the medium and low temperature is 90 - 200 °C.

[0014] Further, geothermal water circulation is carried out in the geothermal fluid circulation device. Specifically: geothermal water is pumped out from the production well through a circulation pump, and after undergoing high-temperature heat exchange and low-temperature heat exchange in the evaporator and the preheater respectively, it is reinjected underground by the circulation pump through the reinjection well again.

[0015] Further, organic working fluid circulation is carried out in the geothermal fluid circulation device. Specifically: the organic working fluid increases the pressure through the supply pump and simultaneously obtains circulating power, vaporizes after undergoing low-temperature heat exchange and high-temperature heat exchange in the preheater and the evaporator respectively, outputs mechanical work after undergoing pressure reduction, heat release, and work done by the expander, and then serves as the heat source of the thermoelectric generation module to further realize multi-stage energy utilization.

[0016] Further, power output is carried out in the geothermal fluid circulation device, and the thermoelectric generation module supplies energy to the supply pump.

[0017] Furthermore, the thermoelectric power generation module uses the exhausted steam after the expander as the heat source and gas or cold water as the cold source.

[0018] Furthermore, the two heat exchange processes and the work process of the expander follow the following formula:

[0019]

[0020] Where Q is the heat input from the geothermal fluid to the organic working fluid, W is the mechanical work generated by the organic working fluid, is the flow rate of the organic working fluid, and h1 and h2 are the enthalpy values of the outflowing working fluid and the inflowing working fluid respectively.

[0021] The present invention also proposes a thermoelectric power generation - organic Rankine combined cycle system based on medium - low temperature geothermal fluid. The combined cycle system includes the geothermal fluid circulation device, the organic Rankine cycle device, and the thermoelectric power generation device described above.

[0022] Furthermore, the exhausted steam flows along the pipeline to the thermoelectric power generation module as the heat source, and air or cold water is used as the cold source in the cooling cycle for thermoelectric power generation, further reducing the temperature of the exhausted steam and achieving multi - level energy utilization. The heat flow relationship between the hot and cold ends of the TEG component is:

[0023]

[0024]

[0025] The relationship between the internal heat field and the electric field in the TEG is as follows:

[0026]

[0027]

[0028] The TEG power output is:

[0029] P = (α H T H - α C T C )I - RI 2

[0030] The TEG efficiency is:

[0031]

[0032] Furthermore, the electric energy generated by the thermoelectric power generation module will be used to supply the energy consumption of the pump to ensure the independence of the system energy consumption and enhance its passive safety in emergency situations. Finally, the exhausted steam is pressurized again by the working fluid pump and enters the subsequent cycle.

[0033] The beneficial effects of the present invention are:

[0034] The present invention applies the thermoelectric power generation - organic Rankine combined cycle to medium - low temperature geothermal power generation. When introducing the TEG, the overall impact it brings to the system is minimized as much as possible, enabling each part of the power generation technology to be in the optimal working range, greatly improving the power generation efficiency and the system life. At the same time, by using the TEG components to power the supply pump, the system becomes "self - sufficient", ensuring passive safety to the greatest extent in case of emergencies, and providing an effective reference for applying the thermoelectric power generation - organic Rankine combined cycle system to other working conditions in the future. Brief Description of the Drawings

[0035] Figure 1 It is a structural diagram of a common thermoelectric power generation - organic Rankine combined cycle system;

[0036] Figure 2 It is a structural diagram of the thermoelectric power generation - organic Rankine combined cycle system based on medium - low temperature geothermal fluid in the present invention. Detailed Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Combined with Figure 2 , the present invention proposes a geothermal fluid circulation device for a thermoelectric power generation - organic Rankine combined cycle system. The thermoelectric power generation - organic Rankine combined cycle system is used for medium - low temperature geothermal fluid. The geothermal fluid circulation device includes a production well, an injection well, an evaporator, a pre - heater, a supply pump, an expander, a generator, and a thermoelectric power generation module;

[0039] The production well: used for drilling in areas rich in geothermal resources to extract medium - low temperature geothermal fluid through a circulation pump;

[0040] The injection well: used for injecting the geothermal water back into the ground through a working fluid pump after multi - stage energy utilization to ensure the quality and quantity of underground water resources;

[0041] The evaporator: used for the organic working fluid to undergo non - mixing high - temperature heat exchange with the geothermal fluid in the evaporator and transform from a liquid into a gas that can drive the expander;

[0042] The pre - heater: used for the geothermal fluid that has undergone high - temperature heat exchange in the evaporator to perform non - mixing low - temperature heat exchange on the organic working fluid before the evaporator to achieve the pre - heating effect and simultaneously realize multi - stage energy utilization;

[0043] The supply pump: used to provide circulating power for the organic working fluid in the organic Rankine cycle;

[0044] The expander: used for the gaseous organic working fluid to release heat through expansion and pressure reduction, output mechanical work outward, and at the same time reduce the gas temperature to make it into exhaust steam;

[0045] The generator: used to drive power generation by using the mechanical work output by the expander and output power outward;

[0046] The thermoelectric generation module: composed of thermoelectric generation units, realizes thermoelectric generation, further realizes multi-stage energy utilization, reduces the temperature of the organic working fluid, and outputs power outward.

[0047] The medium and low temperature is 90 - 200 °C.

[0048] In the geothermal fluid circulation device, geothermal water circulation is carried out. Specifically: the geothermal water is pumped out from the production well through a circulation pump, and after high-temperature heat exchange and low-temperature heat exchange with the organic working fluid in the evaporator and the preheater respectively, it is reinjected into the ground by the circulation pump through the injection well again.

[0049] In the geothermal fluid circulation device, organic working fluid circulation is carried out. Specifically: the organic working fluid increases the pressure through the supply pump and at the same time obtains circulating power, vaporizes after low-temperature heat exchange and high-temperature heat exchange in the preheater and the evaporator respectively, outputs mechanical work after pressure reduction, heat release and work done by the expander, and then serves as the heat source of the thermoelectric generation module to further realize multi-stage energy utilization.

[0050] In the geothermal fluid circulation device, power output is carried out, and the thermoelectric generation module supplies energy for the supply pump.

[0051] The thermoelectric generation module uses the exhaust steam after passing through the expander as the heat source and gas or cold water as the cold source.

[0052] The two heat exchange processes and the work process of the expander follow the following formula:

[0053]

[0054] Where Q is the heat input of the geothermal fluid to the organic working fluid, W is the mechanical work generated by the organic working fluid, is the flow rate of the organic working fluid, and h1 and h2 are the enthalpy values of the outflowing working fluid and the inflowing working fluid respectively.

[0055] The present invention also proposes a thermoelectric generation - organic Rankine combined cycle system based on medium and low temperature geothermal fluid. The combined cycle system includes the geothermal fluid circulation device, the organic Rankine cycle device and the thermoelectric generation device described above.

[0056] The exhausted steam flows along the pipeline to the thermoelectric generation module as the heat source, and air or cold water is used as the cold source in the cooling cycle for thermoelectric generation, further reducing the temperature of the exhausted steam and realizing multi-stage energy utilization. The heat flow relationship between the hot and cold ends of the TEG component is as follows:

[0057]

[0058]

[0059] The relationship between the internal heat field and the electric field in the TEG is coupled as follows:

[0060]

[0061]

[0062] The power output of the TEG is:

[0063] P = (α H T H -α C T C )I - RI 2

[0064] The efficiency of the TEG is:

[0065]

[0066] The electric energy generated by the thermoelectric generation module will be used to supply the energy consumption of the pump to ensure the independence of the system energy consumption and enhance its passive safety in case of emergency. Finally, the exhausted steam is pressurized again by the working fluid pump and enters the subsequent cycle.

[0067] The above has introduced in detail a geothermal fluid circulation device and a combined cycle system of a thermoelectric generation - organic Rankine combined cycle system proposed by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A geothermal fluid circulation device for a thermoelectric power generation - organic Rankine combined cycle system, characterized in that, The thermoelectric power generation - organic Rankine combined cycle system is used for medium - low temperature geothermal fluid. The geothermal fluid circulation device includes a production well, an injection well, an evaporator, a pre - heater, a supply pump, an expander, a generator, and a thermoelectric power generation module; The production well: It is used for drilling in areas rich in geothermal resources and pumping medium - low temperature geothermal fluid through a circulation pump; The injection well: It is used for injecting the geothermal water back into the ground through a working fluid pump after multi - stage energy utilization to ensure the quality and quantity of underground water resources; The evaporator: It is used for the organic working fluid to undergo non - mixed high - temperature heat exchange with the geothermal fluid in the evaporator and transform from a liquid into a gas that can drive the expander; The pre - heater: It is used for the geothermal fluid that has undergone high - temperature heat exchange in the evaporator to conduct non - mixed low - temperature heat exchange with the organic working fluid before the evaporator to achieve the pre - heating effect and simultaneously realize multi - stage energy utilization; The supply pump: It is used to provide circulating power for the organic working fluid in the organic Rankine cycle; The expander: It is used for the gaseous organic working fluid to expand, reduce pressure, release heat, and output mechanical work, while reducing the gas temperature to make it into exhausted steam; The generator: It is used to drive power generation by using the mechanical work output by the expander and output power outward; The thermoelectric power generation module: It is composed of thermoelectric power generation units to achieve thermoelectric power generation, further realize multi - stage energy utilization, reduce the temperature of the organic working fluid, and output power outward; In the geothermal fluid circulation device, the organic working fluid circulates as follows: The organic working fluid increases its pressure through the supply pump and simultaneously obtains circulating power. After undergoing low - temperature heat exchange and high - temperature heat exchange in the pre - heater and the evaporator respectively, it vaporizes. After the expander reduces pressure, releases heat, and does work, it outputs mechanical work, and then serves as the heat source of the thermoelectric power generation module to further realize multi - stage energy utilization.

2. The geothermal fluid circulation device according to claim 1, wherein The medium - low temperature is 90 - 200 °C.

3. The geothermal fluid circulation device according to claim 2, wherein In the geothermal fluid circulation device, the geothermal water circulates as follows: The geothermal water is pumped out from the production well through a circulation pump. After undergoing high - temperature heat exchange and low - temperature heat exchange in the evaporator and the pre - heater respectively, it is reinjected into the ground by the circulation pump through the injection well.

4. The geothermal fluid circulation device according to claim 3, characterized in that, In the geothermal fluid circulation device, power is output. The thermoelectric power generation module supplies energy to the supply pump.

5. The geothermal fluid circulation device according to claim 1, wherein The thermoelectric power generation module uses the exhausted steam after the expander as the heat source and gas or cold water as the cold source.

6. A combined cycle system of thermoelectric power generation - organic Rankine based on medium and low temperature geothermal fluid, characterized in that, The combined cycle system includes the geothermal fluid circulation device, the organic Rankine cycle device, and the thermoelectric power generation device described in claim 1.

7. The combined cycle system according to claim 6, characterized in that, The electric energy generated by the thermoelectric power generation module will be used for the energy consumption of the supply pump to ensure the independence of the system's energy consumption, enhance its passive safety in case of emergency. Finally, the exhausted steam is pressurized again by the working fluid pump and enters the subsequent cycle.

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