LNG cold energy and geothermal energy combined power generation system

Abstract

This utility model discloses a combined LNG cold energy and geothermal energy power generation system, compared to existing technologies. It includes an LNG cold energy recovery subsystem, a geothermal circulation subsystem, and a cooling water system. The LNG cold energy recovery subsystem includes an LNG storage tank, an LNG cryogenic pump, a downstream user terminal, a second evaporator, a preheater, a second working fluid pump, a second turbine generator set, and a second condenser. The geothermal circulation subsystem includes a water extraction well, a geothermal water pump, a reinjection well, a first evaporator, a first working fluid pump, and a first turbine generator set. The cooling water system includes a cooling water pump and a first condenser. This utility model combines LNG cold energy power generation with geothermal power generation, effectively improving energy utilization while avoiding the limitations of a single energy source. Utilizing the cold energy from LNG vaporization lowers the condensation temperature of the ORC system, increases the system temperature difference, and improves power generation efficiency. Geothermal energy provides a heat source for LNG vaporization, reducing the environmental impact of traditional seawater heating.

Description

Technical Field

[0001] This utility model relates to the field of comprehensive energy utilization technology, specifically to a combined LNG cold energy and geothermal energy power generation system. Background Technology

[0002] Current Status of LNG Cold Energy Utilization: Existing standalone LNG cold energy power generation systems mostly use a single working fluid, which is difficult to fully adapt to the wide temperature range of LNG cold energy from -160℃ to room temperature. This results in poor cascade utilization of cold energy, with a cold energy utilization rate of only about 40%. Furthermore, the accompanying heat exchangers are usually simple in structure and have low heat exchange efficiency, resulting in significant energy loss during heat exchange, further reducing the utilization efficiency of cold energy.

[0003] In geothermal power generation technology, traditional ORC systems often suffer from inaccurate matching between the critical temperature of the working fluid and the geothermal water temperature. A significant difference between these temperatures prevents the working fluid from fully absorbing geothermal energy in the evaporator, resulting in limited enthalpy increase and consequently impacting the turbine's work capacity. Furthermore, the condenser relies on a cooling tower or ambient water source, and the cooling tower's heat dissipation efficiency is significantly affected by ambient temperature. In high summer temperatures, the condensation temperature rises, leading to a decrease in the system's thermodynamic efficiency. Moreover, existing geothermal power generation systems often fail to adequately consider the characteristics of geothermal water in their heat exchanger design. For example, the presence of minerals and other impurities in the geothermal water can easily cause scaling on the heat exchanger, affecting heat exchange performance and further reducing power generation efficiency.

[0004] Existing technological shortcomings:

[0005] 1. LNG cold energy power generation is greatly affected by ambient temperature, and its efficiency drops significantly in winter. Because the evaporation process of traditional LNG cold energy power generation systems relies on seawater to remove heat, the temperature of the seawater decreases in winter, leading to a smaller temperature difference between the LNG cold energy and the condensing medium. This reduces the utilization efficiency of the cold energy and significantly decreases the power generation efficiency.

[0006] 2. Geothermal power generation systems rely on cooling towers or ambient water sources for condensation. High condensation temperatures reduce thermodynamic efficiency. The cooling tower's heat dissipation effect is affected by factors such as ambient humidity and wind speed. Under unfavorable environmental conditions, the condensation temperature is difficult to reduce effectively, resulting in a decrease in the pressure ratio of the ORC system, a drop in turbine output power, and a decrease in the system's thermodynamic efficiency.

[0007] 3. Independent utilization of the two energy sources fails to create a synergistic effect. In existing technologies, the utilization systems for LNG cold energy and geothermal energy operate independently, failing to achieve complementary utilization of the two energy sources. For example, the LNG gasification process consumes a large amount of heat, traditionally using seawater as a heat source. This not only has a certain impact on the environment but also fails to utilize the valuable geothermal energy resource. Simultaneously, the condensation side of the geothermal power generation system does not utilize the cold energy of LNG to lower the condensation temperature, wasting LNG cold energy resources, resulting in low utilization efficiency for both energy sources. Utility Model Content

[0008] The purpose of this invention is to address the shortcomings of the existing independent utilization of cold energy and geothermal energy, which fails to form a synergistic effect, resulting in the waste of cold energy resources and low utilization rates of both energy sources. To address these shortcomings, an LNG cold energy and geothermal energy combined power generation system is proposed.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An LNG cold energy and geothermal energy combined power generation system includes an LNG cold energy recovery subsystem, a geothermal circulation subsystem, and a cooling water system. The LNG cold energy recovery subsystem includes an LNG storage tank, an LNG cryogenic pump, a downstream user terminal, a second evaporator, a preheater, a second working fluid pump, a second turbine generator set, and a second condenser. The geothermal circulation subsystem includes a water extraction well, a geothermal water pump, a reinjection well, a first evaporator, a first working fluid pump, and a first turbine generator set. The cooling water system includes a cooling water pump and a first condenser.

[0011] Among them, high-temperature power generation: geothermal water enters the first evaporator through a geothermal water pump to exchange heat with liquid organic working fluid, causing the liquid organic working fluid to vaporize. After vaporization, it enters the first turbine generator to generate electricity. The gaseous organic working fluid after doing work enters the first condenser to exchange heat with cooling water and liquefy. Then, it enters the first evaporator through the first working fluid pump to circulate and generate electricity at high temperature.

[0012] Low-temperature power generation: After geothermal water vaporizes and exchanges heat with liquid organic working fluid in the first evaporator, it enters the second evaporator to exchange heat with liquid mixed working fluid, causing the mixed working fluid to vaporize. After vaporization, it enters the second turbine to generate electricity. The gaseous mixed working fluid after doing work enters the second condenser to exchange heat with LNG. The LNG changes from liquid to gas, absorbs heat, and releases cold energy, causing the gaseous mixed working fluid to liquefy. It then enters the preheater through the second working fluid pump to exchange heat with cooling water, cooling the cooling water. Subsequently, it enters the second evaporator to exchange heat with the geothermal water after heat exchange, and the cycle continues to generate electricity at low temperature.

[0013] As a further preferred embodiment of this invention, both the first evaporator and the second evaporator are configured as spiral tube heat exchangers.

[0014] As a further preferred embodiment of this invention, both the first evaporator and the second evaporator are made of stainless steel.

[0015] The LNG cold energy and geothermal energy combined power generation system proposed in this utility model has the following advantages compared with the prior art:

[0016] 1. This utility model combines LNG cold energy power generation with geothermal power generation, which can effectively improve energy utilization while avoiding the limitations of a single energy source;

[0017] 2. This utility model utilizes the cold energy of LNG vaporization to reduce the condensation temperature of the original ORC system to -30℃, thereby increasing the system temperature difference and improving power generation efficiency;

[0018] 3. This utility model uses geothermal energy to replace the traditional seawater heating method, providing a heat source for LNG gasification, reducing the impact on the marine environment, realizing the synergistic utilization of cold and heat energy, and forming an efficient and environmentally friendly energy utilization system.

[0019] 4. A mixed working fluid is used in the cryogenic power generation system to match the LNG cold energy temperature range (-160℃ to room temperature) to achieve efficient utilization of cold energy;

[0020] 5. This utility model adopts a spiral tube heat exchanger, which has a large heat exchange area, effectively improving the heat exchange rate and reducing energy loss. It can also effectively reduce the deposition of minerals and other impurities in geothermal water, reduce the possibility of scaling, and extend the service life of the heat exchanger.

[0021] 6. The evaporator is made of stainless steel, which can adapt to the special environment of geothermal water and LNG, improving the reliability of the equipment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the connection structure of an LNG cold energy and geothermal energy combined power generation system, which is related to this utility model.

[0023] The meanings of the labels in the attached diagram are as follows: 1. Water intake well; 2. Recharge well; 3. First evaporator; 4. First turbine generator; 5. First condenser; 6. First working fluid pump; 7. Cooling water pump; 8. Preheater; 9. Second evaporator; 10. Second turbine generator; 11. Second condenser; 12. Second working fluid pump; 13. LNG cryogenic pump; 14. LNG storage tank; 15. Downstream user end; 16. Geothermal water pump. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention discloses a combined LNG cold energy and geothermal energy power generation system. By using the cold energy from the LNG vaporization process to lower the condensation temperature of the geothermal Organic Rankine Cycle (ORC) system, and simultaneously utilizing geothermal energy to provide a heat source for LNG vaporization, the system achieves synergistic utilization of cold and heat energy. This system can significantly improve geothermal power generation efficiency and LNG cold energy utilization rate, and is suitable for areas where LNG receiving terminals and geothermal resources coexist.

[0026] Example 1: Combining Figure 1 An LNG cold energy and geothermal energy combined power generation system includes an LNG cold energy recovery subsystem, a geothermal circulation subsystem, and a cooling water system. The LNG cold energy recovery subsystem includes an LNG storage tank 14, an LNG cryogenic pump 13, a downstream user terminal 15, a second evaporator 9, a preheater 8, a second working fluid pump 12, a second turbine generator set 10, and a second condenser 11. The geothermal circulation subsystem includes a water extraction well 1, a geothermal water pump 16, a reinjection well 2, a first evaporator 3, a first working fluid pump 6, and a first turbine generator set 4. The cooling water system includes a cooling water pump 7 and a first condenser 5.

[0027] Geothermal water circulation loop: Geothermal water in well 1 enters the first evaporator 3 via geothermal pump 16, undergoes primary heat exchange, then enters the second evaporator 9, undergoes secondary heat exchange, and finally enters the reinjection well 2; For example... Figure 1 The red route in the middle.

[0028] High-temperature power generation connection structure: The inlet of the geothermal water pump 16 is connected to the water well 1, the outlet of the geothermal water pump 16 is connected to the inlet of the first evaporator 3, the working fluid inlet of the first evaporator 3 is connected to the outlet of the first working fluid pump 6, the inlet of the first working fluid pump 6 is connected to the working fluid outlet of the first condenser 5, the working fluid outlet of the first evaporator 3 is connected to the inlet of the first turbine generator 4, and the outlet of the first generator is connected to the working fluid inlet of the first condenser 5.

[0029] High-temperature power generation: Geothermal water, output from a geothermal well at 100℃, enters the first evaporator 3 via geothermal water pump 16 to exchange heat with liquid organic working fluid, causing the liquid organic working fluid to vaporize. The working fluid is heated to 84℃ and then enters the first turbine generator 4 to generate electricity, producing 50kW. The geothermal water temperature drops to 87℃, and the gaseous organic working fluid, after performing work, enters the first condenser 5 to exchange heat with cooling water, liquefying it. It then enters the first evaporator 3 via the first working fluid pump 6, circulating for high-temperature power generation. Figure 1 The magenta route on the left.

[0030] Low-temperature power generation connection structure: The outlet of the first evaporator 3 is connected to the inlet of the second evaporator 9, the outlet of the second evaporator 9 is connected to the reinjection well 2, the working fluid inlet of the second evaporator 9 is connected to the working fluid outlet of the preheater 8, the working fluid outlet of the second evaporator 9 is connected to the inlet of the second turbine motor, the outlet of the second turbine motor is connected to the working fluid inlet of the second condenser 11, the working fluid outlet of the second condenser 11 is connected to the inlet of the second working fluid pump 12, and the outlet of the second working fluid pump 12 is connected to the working fluid inlet of the preheater 8.

[0031] Low-temperature power generation: After geothermal water vaporizes and exchanges heat with liquid organic working fluid in the first evaporator 3 (at which point the geothermal water temperature is 87°C), it enters the second evaporator 9 to exchange heat with the liquid mixed working fluid, causing the mixed working fluid to vaporize. After vaporization, it enters the second turbine to generate electricity. The gaseous mixed working fluid after generating power enters the second condenser 11 to exchange heat with LNG. The LNG changes from liquid to gas, absorbing heat and releasing cold energy, causing the gaseous mixed working fluid to liquefy. It then enters the preheater 8 through the second working fluid pump 12 to exchange heat with cooling water, cooling the cooling water. Subsequently, it enters the second evaporator 9 to exchange heat with the geothermal water after heat exchange, circulating for low-temperature power generation. The low-temperature stage generates 55kW of power. Figure 1 The magenta route on the right.

[0032] The high-temperature stage power generation uses conventional organic working fluids (such as R245fa and R1233zd(E)); the low-temperature stage circulation uses a mixed working fluid (propane + CO2), with a volume ratio of propane to CO2 of 7:3. This mixed working fluid has a critical temperature 10 to 20°C lower than the hot water temperature, allowing for better matching with the hot water temperature and maximizing heat absorption in the evaporator, thus increasing the enthalpy of the working fluid. Simultaneously, the mixed working fluid has a wide boiling point range, adapting to the temperature range of LNG cold energy from -160°C to ambient temperature, enabling cascaded utilization of cold energy. This allows the entire system to operate efficiently over a wide temperature range, improving energy utilization efficiency.

[0033] Cold energy recovery connection structure: The outlet of LNG storage tank 14 is connected to the inlet of LNG cryogenic pump 13, the outlet of LNG cryogenic pump 13 is connected to the cooling inlet of second condenser 11, and the cooling outlet of second condenser 11 is connected to downstream user terminal 15. Liquid LNG (-162℃) enters second condenser 11 through LNG cryogenic pump 13, vaporizes and absorbs heat, releasing cold energy. This vaporization lowers the condensation temperature of the ORC system from the traditional 40℃ to -30℃ before entering downstream user terminal 15, such as... Figure 1 The cyan line is on the right side of the middle.

[0034] Cooling water circulation connection structure: The cooling water inlet of the first condenser 5 is connected to the outlet of the cooling water pump 7, the inlet of the cooling water pump 7 is connected to the cooling water outlet of the preheater 8, and the cooling water outlet of the first condenser 5 is connected to the cooling water inlet of the preheater 8. The cooling water exchanges heat with the gaseous organic working fluid in the first condenser 5, raising its temperature from 25°C to 30°C. The heated cooling water then enters the preheater 8, where it exchanges heat with the mixed working fluid, cooling down (to 25°C). It then passes through the cooling water pump 7 and enters the first condenser 5, forming a cooling water circulation. Figure 1 The blue route in the middle.

[0035] Both the LNG evaporator and the evaporator in the geothermal circulation subsystem employ high-efficiency spiral tube heat exchangers. These heat exchangers have a large heat exchange area, improving heat exchange efficiency and reducing energy loss. Simultaneously, the spiral tube structure effectively reduces the deposition of minerals and other impurities in the geothermal water, lowering the likelihood of scaling and extending the heat exchanger's service life. The heat exchangers are made of corrosion-resistant stainless steel, adaptable to the special environments of geothermal water and LNG, thus improving equipment reliability.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that the above embodiments do not limit this utility model in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of this utility model.

Claims

1. A combined LNG cold energy and geothermal energy power generation system, characterized in that, The system includes an LNG cold energy recovery subsystem, a geothermal circulation subsystem, and a cooling water system. The LNG cold energy recovery subsystem includes an LNG storage tank, an LNG cryogenic pump, a downstream user terminal, a second evaporator, a preheater, a second working fluid pump, a second turbine generator set, and a second condenser. The geothermal circulation subsystem includes a water extraction well, a geothermal water pump, a reinjection well, a first evaporator, a first working fluid pump, and a first turbine generator set. The cooling water system includes a cooling water pump and a first condenser. Among them, high-temperature power generation: geothermal water enters the first evaporator through a geothermal water pump to exchange heat with liquid organic working fluid, causing the liquid organic working fluid to vaporize. After vaporization, it enters the first turbine generator to generate electricity. The gaseous organic working fluid after doing work enters the first condenser to exchange heat with cooling water and liquefy. Then, it enters the first evaporator through the first working fluid pump to circulate and generate electricity at high temperature. Low-temperature power generation: After geothermal water vaporizes and exchanges heat with liquid organic working fluid in the first evaporator, it enters the second evaporator to exchange heat with liquid mixed working fluid, causing the mixed working fluid to vaporize. After vaporization, it enters the second turbine to generate electricity. The gaseous mixed working fluid after doing work enters the second condenser to exchange heat with LNG. The LNG changes from liquid to gas, absorbs heat, and releases cold energy, causing the gaseous mixed working fluid to liquefy. It then enters the preheater through the second working fluid pump to exchange heat with cooling water, cooling the cooling water. Subsequently, it enters the second evaporator to exchange heat with the geothermal water after heat exchange, and the cycle continues to generate electricity at low temperature.

2. The LNG cold energy and geothermal energy combined power generation system according to claim 1, characterized in that, Both the first evaporator and the second evaporator are configured as spiral tube heat exchangers.

3. The LNG cold energy and geothermal energy combined power generation system according to claim 1, characterized in that, Both the first evaporator and the second evaporator are made of stainless steel.

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