A phase change heat transfer type solid particle heat exchange system and a photo-thermal power generation system

Abstract

The application discloses a phase change heat exchange type solid particle heat exchange system and a photo-thermal power generation system, wherein the heat exchange system comprises a particle feeding device, a first heat exchanger and a second heat exchanger; a first outlet of the particle feeding device is communicated with a particle inlet of the first heat exchanger; the first heat exchanger is used for heat exchange between high-temperature particles and phase change medium, and is used for converting the phase change medium from a liquid phase into a gaseous phase; a phase change medium outlet of the first heat exchanger is communicated with a phase change medium inlet of the second heat exchanger; a phase change medium outlet of the second heat exchanger is communicated with a phase change medium inlet of the first heat exchanger; and the second heat exchanger is used for heat exchange between gaseous phase change medium and power generation working medium. The phase change medium is used as an intermediate heat exchange medium between the high-temperature particles and the power generation working medium, the problems of low heat exchange coefficient, poor heat exchange performance, thick heat exchange surface wall and easy abrasion are overcome, and thus the particle heat exchange system with high efficient heat exchange capacity is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of particle heat exchange, and particularly relates to a phase-change heat exchange type solid particle heat exchange system and a photo-thermal power generation system. BACKGROUND

[0002] In the existing tower type photo-thermal power generation technology, a liquid is usually used as a heat storage and exchange medium, and the most typical one is molten salt, but the molten salt has problems such as high corrosion, low energy storage temperature, small available temperature difference, high energy storage cost, and freezing risk.

[0003] The solid particle heat storage technology is a new type of solar thermal power generation technology, and since the particle heat absorption temperature is high and the price is low, it is an ideal high-temperature heat absorption and storage medium. In the solar photo-thermal power generation technology, the heat stored by the solid particles also needs to be transferred to the circulating working medium of the power generation system through a heat exchanger. The current heat exchanger for the solid particles and the circulating working medium of the power generation system mainly researches in the aspects of plate heat exchangers and fluidized bed heat exchangers. Overall, the existing particle heat exchanger research is basically concentrated in the direct contact heat exchange between the circulating working medium and the particles. However, the direct contact heat exchange of high-temperature particles will cause serious wear of the heat exchange surface, and risks such as local rupture and pipe burst of the heat exchange surface; on the other hand, the heat exchange coefficient is low and the heat exchange effect is poor. SUMMARY

[0004] To solve the above technical problems, the present application provides a phase-change heat exchange type solid particle heat exchange system and a photo-thermal power generation system, which uses a phase-change medium as an intermediate heat exchange medium for high-temperature solid particles and the circulating working medium of the power generation system, and uses the phase change process of the phase-change medium to exchange heat with the particles and the circulating working medium of the power generation system, thereby overcoming the problems of low heat exchange coefficient, poor heat exchange performance, large wall thickness of the heat exchange surface and easy wear of the existing particle heat exchange system, and realizing a particle heat exchange system with high efficient heat exchange capacity.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows:

[0006] A phase-change heat exchange type solid particle heat exchange system, comprising a particle feeding device, a first heat exchanger, a second heat exchanger,

[0007] The bottom of the particle feeding device has a first outlet, the first outlet is in communication with the particle inlet of the first heat exchanger, and the first heat exchanger is used for directly transferring the heat of high-temperature particles to the phase-change medium, and converting the phase-change medium from a liquid phase to a gas phase.

[0008] The phase change medium outlet of the first heat exchanger is connected to the phase change medium inlet of the second heat exchanger, and the phase change medium outlet of the second heat exchanger is connected to the phase change medium inlet of the first heat exchanger. The power generation system circulating working fluid side of the second heat exchanger is connected to the power generation system. The second heat exchanger is used to transfer the heat of the gaseous phase change medium to the circulating working fluid of the power generation system.

[0009] In one embodiment of the present invention, the heat exchange system further includes a solid-liquid separation device, the inlet of which is connected to the particle outlet of the first heat exchanger, for separating the phase change medium carried by the low-temperature particles.

[0010] One embodiment of the present invention further includes an anti-backflow bypass, used to provide positive pressure to the particle feeding device, ensuring that the high-temperature particles in the high-temperature feeding device stably enter the first heat exchanger, and preventing the pressure increase caused by the vaporization of the phase change medium in the first heat exchanger from causing the gaseous phase change medium to flow back.

[0011] In one embodiment of the present invention, the anti-backflow bypass includes a third heat exchanger, which is used for heat exchange between high-temperature particles and phase change medium. The liquid outlet of the solid-liquid separation device is connected to the phase change medium inlet of the third heat exchanger, the phase change medium outlet of the third heat exchanger is connected to the inlet of the particle feeding device, and the particle inlet of the third heat exchanger is connected to the second outlet of the particle feeding device.

[0012] In one embodiment of the present invention, a first booster pump is provided on the pipeline connecting the phase change medium outlet of the third heat exchanger and the inlet of the particle feeding device, and / or a first regulating valve is provided on the pipeline connecting the liquid outlet of the solid-liquid separation device and the phase change medium inlet of the third heat exchanger.

[0013] In one embodiment of the present invention, a second regulating valve is provided at the first outlet and / or a third regulating valve is provided at the second outlet.

[0014] In one embodiment of the present invention, a distributor is provided inside the first heat exchanger to uniformly distribute the high-temperature particles flowing into the first heat exchanger.

[0015] In one embodiment of the present invention, a filter screen is provided in the first heat exchanger to prevent particles from being carried away by the vaporized phase change medium.

[0016] In one embodiment of the present invention, a second booster pump is provided on the pipeline connecting the phase change medium outlet of the second heat exchanger and the phase change medium inlet of the first heat exchanger.

[0017] One embodiment of the present invention further includes a high-temperature particle storage tank and a low-temperature particle storage tank. The outlet of the high-temperature particle storage tank is connected to the inlet of the particle feeding device, and the inlet of the low-temperature particle storage tank is connected to the particle outlet of the solid-liquid separation device and the particle outlet of the third heat exchanger, respectively.

[0018] In one embodiment of the present invention, a fourth regulating valve is provided on the pipeline connecting the high-temperature particle storage tank and the particle feeding device.

[0019] Based on the same inventive concept, the present invention also provides a solar thermal power generation system, including the phase change heat exchange solid particle heat exchange system described above.

[0020] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art:

[0021] This invention employs a first heat exchanger and a second heat exchanger. The first heat exchanger facilitates direct heat exchange between high-temperature particles and the phase change medium, causing the liquid phase change medium to vaporize into a gaseous phase change medium. The second heat exchanger facilitates heat exchange between the gaseous phase change medium and the circulating working fluid of the power generation system. After heat exchange, the gaseous phase change medium condenses back into a liquid phase change medium, which then re-enters the first heat exchanger for direct heat exchange with the high-temperature particles. Therefore, this invention utilizes the phase change medium as an intermediate heat exchange medium between the high-temperature solid particles and the circulating working fluid of the power generation system. The direct heat exchange between the high-temperature solid particles and the phase change medium significantly improves the heat exchange capacity of the particles while avoiding wear on the heat exchange surface caused by direct heat exchange between the particles and the circulating working fluid of the power generation system.

[0022] In addition, the heat exchange method that involves direct contact between high-temperature solid particles and phase change media utilizes the phase change process of the phase change material for heat exchange, eliminating the need for large-area heat exchange walls as in traditional structures, thus significantly reducing the cost of the heat exchange system.

[0023] This invention also includes a backflow prevention bypass to provide positive pressure to the pellet feeder, ensuring that the high-temperature solid particles can stably enter the first heat exchanger. This prevents the pressure increase caused by the vaporization of the phase change medium in the first heat exchanger, which could lead to backflow of the gaseous phase change medium or blockage of the pipeline. Preferably, the high-temperature particles in the pellet feeder exchange heat with the liquid phase change medium separated by the solid-liquid separation device. The liquid phase change medium is heated and vaporized into a gaseous phase change medium that enters the pellet feeder, providing positive pressure to the pellet feeder and preventing backflow of the gaseous phase change medium formed in the first heat exchanger in the loop. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the phase change heat exchange system for solid particles according to Embodiment 1 of the present invention.

[0025] Explanation of reference numerals in the attached drawings: 1-High-temperature particle storage tank; 2-Fourth regulating valve; 3-Particle feeding device; 4-Filter screen; 5-Equalizer; 6-First heat exchanger; 7-Solid-liquid separation device; 8-Second booster pump; 9-Second heat exchanger; 10-Second regulating valve; 11-Third regulating valve; 12-First regulating valve; 13-Low-temperature particle storage tank; 14-Third heat exchanger; 15-First booster pump; Detailed Implementation

[0026] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a phase-change heat exchange system for solid particles and a solar thermal power generation system based on the present invention. The advantages and features of the present invention will become clearer from the following description.

[0027] Example 1

[0028] See Figure 1 A phase change heat exchange system for solid particles is applied to a solar thermal power plant. It includes a particle feeding device 3, a first heat exchanger 6, and a second heat exchanger 9. The bottom of the particle feeding device 3 has a first outlet, which is connected to the particle inlet of the first heat exchanger 6. The first heat exchanger 6 is used to directly transfer the heat of the high-temperature particles to the phase change medium, thereby converting the phase change medium from a liquid phase to a gas phase.

[0029] The phase change medium outlet of the first heat exchanger 6 is connected to the phase change medium inlet of the second heat exchanger 9, and the phase change medium outlet of the second heat exchanger 9 is connected to the phase change medium inlet of the first heat exchanger 6. The power generation system circulating working fluid side of the second heat exchanger 9 is connected to the power generation system. The second heat exchanger 9 is used to transfer the heat of the gaseous phase change medium to the circulating working fluid of the power generation system. Preferably, a second booster pump 8 is installed on the pipeline connecting the phase change medium outlet of the second heat exchanger 9 and the phase change medium inlet of the first heat exchanger 6 to provide pressure for the phase change medium circulation.

[0030] The high-temperature particles in the particle feeding device 3 can be directly derived from the high-temperature particles heated by the solar thermal power plant's solar absorber (in other application environments, the particle heating device can be an electric heater or other heating methods). Preferably, the heated high-temperature particles are stored first, and then a fixed amount of high-temperature particles are added to the particle feeding device 3 as needed. The low-temperature particles after heat exchange in the first heat exchanger 6 can directly enter the absorber to absorb heat. Since the high-temperature particles exchange heat with the phase change medium in the first heat exchanger 6 through contact, what is released from the first heat exchanger 6 is a mixture of particles and phase change medium. Therefore, the heat exchange system preferably also includes a solid-liquid separation device 7. The low-temperature particles flowing out of the particle outlet of the first heat exchanger 6 first flow into the solid-liquid separation device 7. The low-temperature particles separated by the solid-liquid separation device 7 can directly enter the absorber to absorb heat. The separated low-temperature particles are preferably stored first. Therefore, the heat exchange system in this embodiment also includes a high-temperature particle storage tank 1 and a low-temperature particle storage tank 13. The high-temperature particle storage tank 1 is connected to the particle feeding device 3, and the low-temperature particle storage tank 13 is connected to the particle outlet of the solid-liquid separation device 7.

[0031] Preferably, a fourth regulating valve 2 is installed on the pipeline connecting the high-temperature particle storage tank 1 and the particle feeding device 3 to regulate the flow rate of high-temperature particles added to the particle feeding device 3.

[0032] Because the liquid phase change medium in the first heat exchanger 6 absorbs heat from the high-temperature particles and vaporizes into a gaseous phase change medium, the pressure inside the first heat exchanger 6 increases, which may cause gas backflow into the particle feeding device 3. To avoid backflow of the gaseous phase change medium, the heat exchange system in this embodiment also includes an anti-backflow bypass, which provides positive pressure to the particle feeding device 3 to ensure that the high-temperature particles in the high-temperature feeding device stably enter the first heat exchanger 6, preventing the pressure increase caused by the vaporization of the phase change medium in the first heat exchanger 6 from causing the gaseous phase change medium to flow back.

[0033] Positive pressure is provided into the pellet feeding device 3, and inert gas can be introduced into it. Preferably, the high-temperature pellets of this system and the liquid phase change medium separated by the solid-liquid separation device 7 are used. Furthermore, considering cost savings, system simplification, and optimization of circulation path, and in combination with the existing structure, the backflow prevention bypass includes a third heat exchanger 14. The third heat exchanger 14 is used for heat exchange between the high-temperature pellets and the liquid phase change medium. The liquid outlet of the solid-liquid separation device 7 is connected to the phase change medium inlet of the third heat exchanger 14. The phase change medium outlet of the third heat exchanger 14 is connected to the inlet of the pellet feeding device 3. The pellet inlet of the third heat exchanger 14 is connected to the second outlet of the pellet feeding device 3. The pellet outlet of the third heat exchanger 14 is connected to the low-temperature pellet storage tank 13.

[0034] Preferably, a first booster pump 15 is installed on the pipeline connecting the phase change medium outlet of the third heat exchanger 14 and the inlet of the particle feeding device 3. The gaseous phase change medium after vaporization enters the particle feeding device 3 under the action of the first booster pump 15. A first regulating valve 12 is installed on the pipeline connecting the liquid outlet of the solid-liquid separation device 7 and the phase change medium inlet of the third heat exchanger 14 to regulate the liquid phase change medium entering the third heat exchanger 14.

[0035] A second regulating valve 10 is installed at the first outlet of the pellet feeding device 3, and a third regulating valve 11 is installed at the second outlet to regulate the flow rate of high-temperature particles entering the first heat exchanger 6 and the third heat exchanger 14.

[0036] The first heat exchanger 6 is equipped with a distributor 5, such as a distribution plate, to evenly distribute the high-temperature particles flowing into the first heat exchanger 6, so that the high-temperature particles can uniformly contact and exchange heat with the liquid phase change medium. The first heat exchanger 6 is also equipped with a filter screen 4 to prevent the particles from being carried away by the vaporized phase change medium. The mesh diameter of the filter screen is smaller than the particle size.

[0037] The specific workflow of the heat exchange system in this embodiment is as follows:

[0038] High-temperature particles in high-temperature particle storage tank 1 enter particle feeding device 3 through fourth regulating valve 2. Under the action of gravity, the particles enter first heat exchanger 6 through first outlet and third heat exchanger 14 through second outlet. The high-temperature particles in first heat exchanger 6 are evenly distributed by distributor 5 and directly contact the liquid phase change medium for heat exchange. After heat exchange, the low-temperature particles carry part of the liquid phase change medium into solid-liquid separation device 7 for separation. The particles enter low-temperature particle storage tank 13. The liquid phase change medium enters third heat exchanger 14 through first regulating valve 12 and exchanges heat with the high-temperature particles from particle feeding device 3. The low-temperature particles after heat exchange enter low-temperature particle storage tank 13. The heated gaseous phase change medium enters particle feeding device 3 under the action of first booster pump 15, providing positive pressure to particle feeding device 3 to ensure that the high-temperature particles can stably enter first heat exchanger 6 and prevent the pressure increase caused by the vaporization of phase change medium in first heat exchanger 6 from causing backflow of gaseous phase change medium or blockage of pipeline. The gaseous phase change medium after the liquid phase change medium in the first heat exchanger 6 is vaporized enters the phase change medium side of the second heat exchanger 9 under pressure, and transfers heat to the low-temperature power generation system circulating working medium that enters from the power generation working medium inlet of the second heat exchanger 9. The heated power generation circulating working medium flows out from the power generation working medium outlet of the second heat exchanger 9 and enters the power generation system to generate electricity, while the condensed liquid phase change medium enters the first heat exchanger 6 under the action of the second booster pump 8 to complete the cycle.

[0039] In this embodiment, a phase change medium is used as an intermediate heat exchange medium between high-temperature solid particles and power generation working fluid. The phase change medium does not decompose at high temperatures and does not react with particles. Suitable materials include heat transfer oil and liquid sodium metal.

[0040] Example 2

[0041] The present invention also provides a solar thermal power generation system, including the phase change heat exchange system of solid particles of Embodiment 1, a heat collection system and a power generation system. The heat collection system is used to heat low-temperature particles by solar radiation. The low-temperature particle storage tank 13 is connected to the inlet of the heat collection system, the high-temperature particle storage tank is connected to the particle outlet of the heat collection system, and the working fluid side of the second heat exchanger 9 is connected to the power generation system.

[0042] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A phase-change heat exchange system for solid particles, characterized in that, Includes a pellet feeding device, a first heat exchanger, and a second heat exchanger. The bottom of the particle feeding device has a first outlet, which is connected to the particle inlet of the first heat exchanger. The first heat exchanger is used to directly transfer the heat of the high-temperature particles to the phase change medium, thereby converting the phase change medium from a liquid phase to a gas phase. The phase change medium outlet of the first heat exchanger is connected to the phase change medium inlet of the second heat exchanger, and the phase change medium outlet of the second heat exchanger is connected to the phase change medium inlet of the first heat exchanger. The second heat exchanger is used to transfer the heat of the gaseous phase change medium to the circulating working fluid of the power generation system. The heat exchange system further includes a solid-liquid separation device, the inlet of which is connected to the particle outlet of the first heat exchanger; It also includes a backflow prevention bypass for providing positive pressure to the pellet feeding device; The anti-backflow bypass includes a third heat exchanger, which is used for heat exchange between high-temperature particles and phase change medium. The liquid outlet of the solid-liquid separation device is connected to the phase change medium inlet of the third heat exchanger, the phase change medium outlet of the third heat exchanger is connected to the inlet of the particle feeding device, and the particle inlet of the third heat exchanger is connected to the second outlet of the particle feeding device.

2. The phase change heat exchanger system for solid particles according to claim 1, characterized in that, It also includes a high-temperature particle storage tank and a low-temperature particle storage tank. The outlet of the high-temperature particle storage tank is connected to the inlet of the particle feeding device, and the inlet of the low-temperature particle storage tank is connected to the particle outlet of the solid-liquid separation device and the particle outlet of the third heat exchanger, respectively.

3. The phase change heat exchanger system for solid particles according to claim 1, characterized in that, A first booster pump is installed on the pipeline connecting the phase change medium outlet of the third heat exchanger and the inlet of the particle feeding device, and / or a first regulating valve is installed on the pipeline connecting the liquid outlet of the solid-liquid separation device and the phase change medium inlet of the third heat exchanger.

4. The phase-change heat exchange system for solid particles according to claim 1, characterized in that, A second regulating valve is provided at the first outlet and / or a third regulating valve is provided at the second outlet.

5. The phase-change heat exchange system for solid particles according to claim 2, characterized in that, A fourth regulating valve is installed on the pipeline connecting the high-temperature particle storage tank and the particle feeding device.

6. The phase-change heat exchange system for solid particles according to claim 1, characterized in that, A material distributor is installed inside the first heat exchanger.

7. The phase change heat exchanger system for solid particles according to claim 1, characterized in that, A filter screen is installed inside the first heat exchanger.

8. The phase-change heat exchange system for solid particles according to claim 1, characterized in that, A second booster pump is installed on the pipeline connecting the phase change medium outlet of the second heat exchanger and the phase change medium inlet of the first heat exchanger.

9. A solar thermal power generation system, characterized in that, Includes the phase change heat exchange system for solid particles as described in any one of claims 1-8.

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