A supercritical carbon dioxide heat conversion device of pseudo-boiling state heat-carrying particles

Abstract

The present application belongs to the technical field of circulating solar power generation, and particularly relates to a supercritical carbon dioxide heat conversion device with pseudo-boiling state heat-carrying particles. The device comprises a shell inlet and a shell outlet arranged at the upper and lower ends of a shell body for the heat-carrying particles to enter and exit the shell body, and a heat exchange core formed by a heat exchange pipe and a circulating gas pipe wound on a central air duct. The heat exchange pipe is connected to a supercritical carbon dioxide circulating device outside the shell body, and the circulating gas pipe is connected to an air inlet device outside the shell body. The pipe wall of the circulating gas pipe is provided with air outlet holes for uniformly supplying air to the heat exchange core. The central air duct is provided with air inlet holes for receiving and discharging the circulating air blown from the air outlet holes to the heat exchange space. When the heat-carrying particles enter the gap of the heat exchange core, the heat-carrying particles are simultaneously subjected to the action of gravity and buoyancy, and form pseudo-boiling motion under the action of air flow, thereby significantly improving the heat exchange efficiency with the heat exchange pipe. Meanwhile, the falling speed of the heat-carrying particles is slowed down, and the heat exchange time is prolonged.

Description

A pseudo-boiling state heat transfer particle supercritical carbon dioxide thermal conversion device Technical Field

[0001] This invention belongs to the field of cyclic solar power generation technology, specifically relating to a supercritical carbon dioxide thermal conversion device with pseudo-boiling state heat-carrying particles. Background Technology

[0002] Currently, power generation still relies primarily on thermoelectric power (TEP), which uses fossil fuels and nuclear energy to generate heat to heat water, which then becomes the steam working fluid driving turbine generators. However, this TEP based on the Rankine cycle of steam has a conversion efficiency of less than 40%. Future solar thermal power generation technology will employ supercritical carbon dioxide Brayton cycles to achieve a TEP of 50% or even higher. High-temperature sintered particles capable of withstanding 1000℃ will be used as the heat transfer medium to transfer ultra-high-temperature solar thermal energy to supercritical carbon dioxide, generating a high-temperature, high-pressure working fluid for power generation. Currently, only a few designs based on traditional concepts, such as fluidized bed heat exchangers and shell-and-tube / plate moving bed heat exchangers, have been publicly reported to enable this high-temperature heat-carrying particle and supercritical carbon dioxide heat transfer working fluid generation.

[0003] Fluidized bed heat exchangers have an air chamber or wind box at the bottom of the heat exchange chamber. Fluidizing air is supplied to the fluidized bed through through-holes and wind caps on a plate-type air distributor. The fluidizing air heats up to a high temperature as it passes through the bed, and when it is discharged, it carries away heat from the particles, resulting in heat loss. Furthermore, the relatively low temperature of the fluidizing air is detrimental to maintaining the bed temperature. Therefore, fluidized bed heat exchangers have inherent flaws in the design of the fluidizing air distribution and the design of the fluidizing air source. Since all particles in the bed are fluidized by cold air blown in from the bottom of the bed, the gas entering the bottom of the fluidized bed at the same time does not reach the top simultaneously, resulting in unequal flow velocities across the flow cross-section. The flow direction of particles at the edge of the heat exchange chamber is not synchronized with the mainstream direction. The chaotic movement of particles causes the particle-carrying airflow to mix in various directions, causing the actual temperature field to deviate from the designed temperature gradient direction. Therefore, fluidized bed heat exchangers have inherent problems in the design of heat exchange flow field uniformity. Because fluidization requires a large amount of aerodynamic energy, the increased bed size after the device is scaled up further exacerbates energy consumption. In some cases, the bed is too large to achieve sufficient fluidization, which leads to uneven heat exchange. Moreover, when the operating temperature and pressure of the working fluid are increased to more efficient supercritical parameters, thermal deviation of the high-temperature heating surface of the heat exchange tube will cause a decline in the performance and reliability of the device. Therefore, fluidized bed heat exchangers lose their competitive advantage in terms of energy saving, high efficiency, high reliability, and ease of scaling up.

[0004] In shell-and-tube moving bed heat exchangers, the high-temperature particles above the heat exchange tubes are trapped and cooled, isolating fresh heat-carrying particles, and the particles below the heat exchange tubes may not even come into contact with each other. As a result, the heat exchange effect is poor, and the overall heat transfer coefficient is inevitably low.

[0005] In plate-and-shell moving bed heat exchangers, the particles and heat exchange surfaces in the heat exchange chamber are still in near-static contact, resulting in conductive heat exchange. Although the gap between the heat exchange plates is smaller than that in shell-and-tube moving bed heat exchangers, the particle layer close to the heat exchange plate still presents heat transfer resistance that hinders conductive heat exchange. Therefore, moving bed heat exchangers have inherent defects in the design of the heat-carrying particle movement state. Uneven particle distribution in the inter-plate channels is not conducive to heat transfer, and the reliability of the plates also has inherent defects. Although the plates can be reduced in size and stacked to reduce plate distortion, the numerous pipes and extremely complex connections make it difficult to achieve large-scale production, causing the product to lose its competitiveness in terms of energy saving, high efficiency, high reliability, and ease of large-scale production.

[0006] Since this device, which transfers heat energy between heat-carrying particles and supercritical carbon dioxide, is essentially a generator for the working fluid of a power generation turbine, achieving a solar-thermal-electric conversion efficiency of 50% or even higher requires compatibility with different power generation turbines and various supercritical carbon dioxide Brayton cycle process requirements. Clearly, with the continuous improvement of solar thermal power generation system processes, the device needs to constantly add or modify process interfaces and corresponding structural functional modules to accommodate new material flows. Existing device designs are ill-suited to this need. Therefore, the design of heat-carrying particle supercritical carbon dioxide working fluid generators urgently requires innovation to achieve competitive advantages such as energy saving, high efficiency, high reliability, ease of scaling, modularity, and high compatibility. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a sand bath type solid particle heat exchanger.

[0008] The present invention adopts the following technical solution:

[0009] A pseudo-boiling state supercritical carbon dioxide heat conversion device for heat-carrying particles includes a shell, a shell-side inlet, a shell-side outlet, and a heat exchange section. The shell-side inlet and outlet are respectively located at the upper and lower ends of the shell for the heat-carrying particles to enter and exit the shell. The shell has a heat exchange space to accommodate the heat exchange section. The heat exchange section is a heat exchange core formed by heat exchange tubes and circulating air pipes wound around a central air duct. The heat exchange tubes are connected to a supercritical carbon dioxide circulation device outside the shell to form a first tube side, and the circulating air pipes are connected to an air inlet device outside the shell to form a second tube side. The first and second tube sides exchange heat separately. The tube wall of the circulating air pipe is covered with air outlets. One end of the upper central air duct is fixedly connected to the shell to form a shell-side air outlet. The wall of the central air duct has air holes to receive circulating air blown from the air outlets of the circulating air pipes to the heat exchange space.

[0010] Preferably, the heat exchange core is a multi-layer heat exchange structure formed by the spiral winding of heat exchange tubes and circulating air pipes arranged radially along the central air duct. The spiral winding means that both the heat exchange tubes and circulating air pipes are spirally wound upward along the lower end of the central air duct, and each layer of the heat exchange core is composed of heat exchange tubes and / or circulating air pipes; there is a gap between each heat exchange tube and the circulating air pipe in the heat exchange core.

[0011] Preferably, the front ends of the heat exchange tubes are connected in parallel and connected to the supercritical carbon dioxide circulation device outside the shell through a tube box; the ends of the heat exchange tubes are assembled and connected to the tube-side outlet pipe provided on the shell.

[0012] The coiled ends of the circulating air pipe form a collection and are connected to the outlet pipe of the second tube side provided on the housing; the coiled front ends of the circulating air pipe are connected in parallel and are connected to the air intake device outside the housing through the pipe box.

[0013] Preferably, the lower end of the central air duct is open, and the upper end is connected to the shell-side air outlet through an air outlet pipe. A particle separator is provided at the connection between the central air duct and the air outlet pipe.

[0014] Preferably, the air vents are located on the portion of the central air duct where the heat exchange core is wound.

[0015] Preferably, a distribution disk is also provided inside the shell side inlet. The distribution disk is umbrella-shaped, and the upper surface of the distribution disk is fixedly connected to the periphery of the shell side inlet through a connector. There is a gap between the outer periphery of the distribution disk and the shell, and the gap is adapted to the position of the heat exchange core below the distribution disk.

[0016] Preferably, the ratio of heat exchange tubes to circulating air tubes in the heat exchange core is 1:0.5-2, and the heat exchange tubes and circulating air tubes have the same diameter.

[0017] Preferably, the tube box is located on the outside of the shell and connected to the shell through a connecting cylinder. Inside the tube box, a tube plate is also provided on the side near the shell. Through holes are opened on the tube plate, and each through hole is connected to a circulating gas pipe or heat exchange pipe to realize the parallel connection of the circulating gas pipe or heat exchange pipe.

[0018] Preferably, the heat exchange tube and the circulating gas tube are fixed together by pipe clamps and limiting components.

[0019] Preferably, the shell is cylindrical, a support member is provided on the outside of the shell, and a heat exchange core fixing device is provided inside the shell.

[0020] The beneficial effects of this invention are as follows:

[0021] 1) In the second tube of the present invention, the circulating gas tube is adjacent to and intertwined with the heat exchange tube in the first tube. Each circulating gas tube is covered with through holes, which can uniformly circulate gas to all parts of the heat exchange core, so that the heat exchange surface on all heat exchange tubes is in the uniform boiling environment of particles created by the circulating gas tube.

[0022] 2) The heat exchanger core of this invention can also realize more tube-pass modules and can be expanded to connect multiple different material flows to adapt to the needs of different supercritical carbon dioxide cycle thermoelectric conversion processes. Since the numerous tube heads of multiple tube-pass modules can be concentrated in their respective small tube boxes, the number of tube box connections does not change when the device is enlarged. When the process becomes more complex, the number of connections increases synchronously with the number of tube passes, which can avoid the generation of complicated pipelines. Therefore, the device of this invention has the characteristics of high reliability, high compatibility, easy enlargement, and modularity.

[0023] 3) In the second tube of this invention, numerous circulating gas pipes discharge hot gas flow, generating buoyancy force on the high-temperature heat-carrying particles. The heat-carrying particles are simultaneously subjected to gravity and buoyancy force, and when they pass through the gaps in the winding tube group, they are suspended and fall, resulting in a pseudo-boiling state gas-solid two-phase flow. On the one hand, this can avoid the solid particles from accumulating and being obstructed when moving downwards, which is conducive to the uniform settling of the particles. On the other hand, it can make the particles dynamically contact the heat exchange surface and fully exchange heat. Therefore, the device of this invention has the beneficial effects of energy saving, high efficiency, high reliability, high compatibility, easy large-scale and modularization. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the structure of the present invention;

[0025] Figure 2 is a schematic diagram of the air inlet holes on the central air duct;

[0026] Figure 3 is a schematic diagram of the tube box structure;

[0027] Figure 4 is a schematic diagram of the heat exchange tubes and circulating air pipes being intertwined on the central air duct;

[0028] Figure 5 is a schematic diagram of an air outlet on a circulating air duct.

[0029] The meanings of the symbols marked in the figure are as follows:

[0030] 10-Shell casing 11-Shell-side inlet 12-Shell-side outlet 13-Shell-side air outlet 20-Heat exchange core

[0031] 21-Heat exchanger tube 22-Tube side - Tube box 23-Tube side - Outlet pipe 30-Circulating gas pipe

[0032] 31-Air outlet 32-Pipe-side two-pipe box 33-Pipe-side two-outlet connection 40-Central air duct

[0033] 41-Air inlet 42-Air outlet 50-Particle separator 60-Distribution plate 61-Connector

[0034] 71-Connecting cylinder; 72-Tube sheet; 721-Through hole; 80-Support component; 90-Fixing device; 91-Pipe clamp. Detailed Implementation

[0035] The technical solution of the present invention will be described in more detail below with reference to the accompanying drawings and embodiments:

[0036] As shown in Figures 1-5, a pseudo-boiling state heat transfer device for supercritical carbon dioxide with heat-carrying particles includes a cylindrical shell 10, a shell-side inlet 11, a shell-side outlet 12, and a heat exchange section. The shell-side inlet 11 and the shell-side outlet 12 are respectively located at the upper and lower ends of the shell 10 for the heat-carrying particles to enter and exit the shell 10. The shell 10 has a heat exchange space inside to accommodate the heat exchange section.

[0037] The heat exchange section is a heat exchange core 20 with an inner and outer multi-layer heat exchange structure, formed by heat exchange tubes 21 and circulating air pipes 30 spirally wound around the central air duct 40. The spiral winding means that both the heat exchange tubes 21 and the circulating air pipes 30 are spirally wound upwards along the lower end of the central air duct 40, and each layer of the heat exchange core 20 consists of heat exchange tubes 21 and / or circulating air pipes 30. The ratio of heat exchange tubes 21 to circulating air pipes 30 in the heat exchange core 20 is 1:0.5-2, or the specific number and ratio are determined according to the actual working conditions. The heat exchange tubes 21 and circulating air pipes 30 have the same diameter and are fixed together by pipe clamps 91 and limiting strips. The limiting strips are used to separate adjacent heat exchange structures to form gaps. The pipe clamps 91 fix the heat exchange tubes 21 to the limiting strips, and there is a gap between each heat exchange tube 21 and the circulating air pipe 30.

[0038] The front ends of the heat exchange tubes 21 are connected in parallel on the central air duct 40 and are connected to the supercritical carbon dioxide circulation device outside the shell 10 through the tube-side first tube box 22. The winding ends of the heat exchange tubes 21 on the central air duct 40 form a collection and are connected to the tube-side first outlet pipe 23 provided on the shell 10, constituting the first tube side for forming supercritical carbon dioxide circulation. The front ends of the circulating gas pipes 30 are connected in parallel on the central air duct 40 and are connected to the air inlet device outside the shell 10 through the tube-side second tube box 32. The winding ends of the circulating gas pipes 30 on the central air duct 40 form a collection and are connected to the tube-side second outlet pipe 33 provided on the shell 10, constituting the second tube side for gas circulation. The first tube side and the second tube side have separate flow.

[0039] Furthermore, both the first-pass tube box 22 and the second-pass tube box 32 are located on the outside of the shell 10 and connected to the shell 10 via a connecting sleeve 71. The side of the first-pass tube box 22 and the second-pass tube box 32 closest to the shell 10 is sealed by a tube sheet 72. The tube sheet 72 has through holes 721, each of which is connected to a circulating gas pipe 30 or a heat exchange pipe 21, thus achieving parallel connection of the circulating gas pipes 30 or heat exchange pipes 21. The circulating gas pipes 30 or heat exchange pipes 21 are connected in parallel to the first-pass tube box 22 or the second-pass tube box 32 via the connecting sleeve 71 and the through holes 721.

[0040] Furthermore, the circulating air pipe 30 has air outlet holes 31 all over its pipe wall, and the central air duct 40 has air inlet holes 41 on the part of its pipe wall where the heat exchange core 20 is wound. One end of the central air duct 40 is fixed to the shell 10 to form a shell-side air outlet 13 that penetrates the shell 10. The air inlet holes 41 receive the circulating air blown from the air outlet holes 31 to the heat exchange space and then discharge it from the shell through the shell-side air outlet 13.

[0041] The shell-side air outlet 13 is located on the side wall of the shell 10. The lower end of the central air duct 40 is open, and the upper end is tightly connected to the shell-side air outlet 13 through the air outlet pipe 42. A particle separator 50 is installed at the connection between the central air duct 40 and the air outlet pipe 42. The heat-carrying particles brought into the central air duct 40 by the circulating air through the air inlet 41 are blocked and filtered by the particle separator and fall from the lower end of the central air duct 40 to the shell-side outlet 12 for unified discharge without affecting the flow of the circulating air. The particle separator can adopt existing technology.

[0042] Inside the shell 10, a distribution plate 60 is also provided at the shell-side inlet. The distribution plate 60 is umbrella-shaped. The upper surface of the distribution plate 60 is fixedly connected to the shell-side inlet 11 on the periphery of the junction inlet on the shell 10 through a connector 61. The connector 61 is a connecting rod with a certain length and a gap between adjacent connecting rods. Thus, there is a gap between the outer periphery of the distribution plate 60 and the shell 10. The gap is adapted to the position of the heat exchange core 20 below the distribution plate 60 so that the heat-carrying particles can fall from the gap and land exactly on the heat exchange tube of the heat exchange core for heat exchange.

[0043] A support member 80 is provided on the outside of the shell 10, and a heat exchange core fixing device 90 is also provided inside the shell 10.

[0044] During operation, the heat-carrying particles enter the shell 10 through the shell-side inlet 11, are sprayed onto the umbrella-shaped distribution disk 60, and fall through the gaps around the distribution disk 60 to achieve distribution. After distribution, the heat-carrying particles are evenly sprayed onto the surfaces of the heat exchange tubes 21 and the circulating air pipes 30 wound below, and flow from top to bottom along the winding layers of the heat exchange tubes 21 and the circulating air pipes 30 under the action of gravity.

[0045] Supercritical carbon dioxide enters the heat exchange tube 21 from the tube-side first tube box 22, and flows spirally upward along the winding direction of the heat exchange tube 21 in the central air duct 40. Circulating air enters the circulating air pipe 30 from the tube-side second tube box 32, and flows spirally upward along the winding direction of the circulating air pipe 30 in the central air duct 40. Air outlets 31 are opened on the wall of the circulating air pipe 30, and a portion of the circulating air flowing within the circulating air pipe 30 is ejected from the air outlets 31 into the heat exchange space.

[0046] When the heat-carrying particles shower onto the heat exchange tube 21 and the circulating air pipe 30 and fall into the gap between the heat exchange tube 21 and the circulating air pipe 30, they will be simultaneously affected by the circulating air ejected from the circulating air pipe 30 from multiple directions. The heat-carrying particles are agitated under the action of the airflow, forming a pseudo-boiling motion, and exchanging heat with the heat exchange tube 21. At the same time, the falling speed of the heat-carrying particles is slowed down, which prolongs the heat exchange time.

[0047] Since solid particles always tend to move downwards under the influence of gravity, after heat exchange is completed, the solid particles fall out of the heat exchange core 20 and finally flow out of the shell 10 from the shell-side outlet 12; the supercritical carbon dioxide in the heat exchange tube 21 absorbs the heat from the heat-carrying particles and flows out of the shell 10 through the tube-side outlet pipe 23 for subsequent use; the circulating air flowing from the air outlet 31 to the heat exchange space enters the central air duct through the air inlet 41 and is discharged through the shell-side air outlet 13, while another part of the circulating air continues to flow out through the tube-side outlet pipe 33.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pseudo-boiling state heat transfer device for supercritical carbon dioxide with heat-carrying particles, comprising a shell (10), a shell-side inlet (11), a shell-side outlet (12), and a heat exchange section, wherein the shell-side inlet (11) and the shell-side outlet (12) are respectively disposed at the upper and lower ends of the shell (10) for the heat-carrying particles to enter and exit the shell (10), and the shell (10) has a heat exchange space inside to accommodate the heat exchange section, characterized in that: The heat exchange section is a heat exchange core (20) formed by heat exchange tubes (21) and circulating air pipes (30) being wound around a central air duct (40). The heat exchange tubes (21) are connected to a supercritical carbon dioxide circulation device outside the shell (10) to form a first tube side, and the circulating air pipes (30) are connected to an air inlet device outside the shell (10) to form a second tube side. The first tube side and the second tube side flow separately. The tube wall of the circulating air pipes (30) is covered with air outlet holes (31). One end of the central air duct (40) is fixedly connected to the shell (10) to form a shell side air outlet (13) that penetrates the shell (10). The tube wall of the central air duct (40) is provided with air inlet holes (41) to receive the circulating air blown from the air outlet holes (31) to the heat exchange space.

2. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 1, characterized in that, The heat exchange core (20) is formed by the rising and winding of heat exchange tubes (21) and circulating air pipes (30) to form a multi-layer heat exchange structure arranged radially along the central air duct (40). The rising and winding means that the heat exchange tubes (21) and circulating air pipes (30) are spirally wound upward along the lower end of the central air duct (40), and each layer of the heat exchange core (20) is composed of heat exchange tubes (21) and / or circulating air pipes (30). There is a gap between each heat exchange tube (21) and the circulating air pipe (30) in the heat exchange core (20).

3. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 2, characterized in that, The front ends of the heat exchange tubes (21) are connected in parallel and are connected to the supercritical carbon dioxide circulation device outside the shell (10) through the tube side one tube box (22); the winding ends of the heat exchange tubes (21) form a collection and are connected to the tube side one outlet pipe (23) provided on the shell (10); the front ends of the circulating gas pipes (30) are connected in parallel and are connected to the air inlet device outside the shell (10) through the tube side two tube box (32); the winding ends of the circulating gas pipes (30) form a collection and are connected to the tube side two outlet pipe (33) provided on the shell (10).

4. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 2, characterized in that, The lower end of the central air duct (40) is open, and the upper end is connected to the shell side air outlet (13) through the air outlet pipe (42). A particle separator (50) is provided at the connection between the central air duct (40) and the air outlet pipe (42).

5. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 2, characterized in that, The air inlet (41) is located on the part of the central air duct (40) around which the heat exchange core (20) is wound.

6. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 1, characterized in that, The shell (10) is also provided with a distribution plate (60) at the shell side inlet. The distribution plate (60) is umbrella-shaped. The upper surface of the distribution plate (60) is fixedly connected to the periphery of the opening of the shell side inlet (11) on the shell (10) through a connector (61). There is a gap between the outer periphery of the distribution plate (60) and the shell (10). The gap is adapted to the position of the heat exchange core (20) below the distribution plate (60).

7. The pseudo-boiling state heat-carrying particle supercritical carbon dioxide thermal conversion device as described in claim 3, characterized in that, The first tube box (22) and the second tube box (32) are both located outside the shell (10) and connected to the shell (10) via a connecting tube (71). The first tube box (22) and the second tube box (32) are both provided with tube sheets (72) on the side closer to the shell (10).

8. The pseudo-boiling state heat transfer particle supercritical carbon dioxide thermal conversion device as described in claim 7, characterized in that, Through holes are provided on the tube sheet (72), and each through hole is connected to a circulating gas pipe (30) or a heat exchange pipe (21) to realize the parallel connection of the circulating gas pipe (30) or the heat exchange pipe (21).

9. A pseudo-boiling state heat transfer particle supercritical carbon dioxide thermal conversion device as described in any one of claims 1-8, characterized in that, The shell (10) is cylindrical, and a support member is provided on the outside of the shell (10). A heat exchange core fixing device (90) is also provided inside the shell (10).

Images