Molten salt tower heat absorber and working method thereof, process coupling control method

Abstract

The application relates to the technical field of solar photo-thermal power generation, in particular to a molten salt tower heat absorber, a working method thereof, and a flow coupling control method. The molten salt tower heat absorber comprises a plurality of molten salt tower heat absorber single-piece structures arranged in a circumferential shape, which comprises a lower header tank with a first molten salt interface communicated with a molten salt tank arranged at the bottom; an upper header tank arranged directly above the lower header tank, with a second molten salt interface communicated with another molten salt tank arranged at the top; a plurality of heat collecting pipes arranged at intervals between the upper header tank and the lower header tank, with two ends communicated with the upper header tank and the lower header tank respectively; and a filler outer cylinder sleeved outside each heat collecting pipe, with a heat-conducting filler layer filled in the gap between the filler outer cylinder and the heat collecting pipe. The molten salt tower heat absorber can avoid direct reflection of light on the heat collecting pipe, so that the heat collecting pipe can be gently heated and cooled, thereby avoiding the generation of large thermal stress due to the sharp change of the pipe wall temperature of the heat collecting pipe, and reducing the pipe explosion probability of the heat collecting pipe.

Description

Technical Field

[0001] This invention relates to the field of solar thermal power generation technology, specifically to a molten salt tower receiver and its working method and process coupling control method. Background Technology

[0002] Against the backdrop of "carbon neutrality and carbon peaking," and with the large-scale development of intermittent and unstable renewable energy sources such as photovoltaic and wind power, the proportion of traditional coal-fired power units is gradually decreasing, the existing peak-shaving capacity of the power grid is gradually reaching its limit, and various energy storage technologies each have their own advantages and disadvantages. Therefore, solar thermal power generation, which has the characteristics of traditional synchronous power sources, is ushering in greater development opportunities. Currently, there is a call to actively develop solar thermal power generation and promote the establishment of integrated renewable energy power generation bases that complement and regulate solar thermal, photovoltaic, and wind power.

[0003] Currently, during the operation of conventional tubular receivers, the surface heat flow changes are usually affected by incoming clouds. When the system is shut down and unloading salt due to unmet operating conditions, the receiver absorbs heat from the heliostat when the clouds disperse, causing a sharp rise in temperature and resulting in thermal shock to the receiver. This can cause the receiver surface to overheat, leading to the rupture of the collector tubes and ultimately affecting the normal operation of solar thermal power generation. Summary of the Invention

[0004] The purpose of this invention is to provide a molten salt tower absorber, its working method, and a process coupling control method.

[0005] To address the aforementioned technical problems, this invention provides a molten salt tower receiver, comprising: a plurality of molten salt tower receiver monolithic structures arranged in a circumferential pattern, each comprising: a lower header with a first molten salt interface at its bottom communicating with a molten salt tank; an upper header positioned directly above the lower header with a second molten salt interface at its top communicating with another molten salt tank; a plurality of heat collection tubes spaced apart between the upper and lower headers, with both ends communicating with the upper and lower headers respectively; and a packing outer cylinder fitted over the outside of each heat collection tube, the gap between the outer cylinder and the heat collection tubes being filled with a thermally conductive packing layer.

[0006] Furthermore, the heat collection pipe includes: a first straight pipe section, which is offset outward from the line connecting the upper and lower headers and is set at a deflection angle, with its upper end connected to the upper header; a second straight pipe section, which is set along the line connecting the upper and lower headers, with its upper end connected to the lower end of the first straight pipe section; and a third straight pipe section, with its upper end connected to the lower end of the second straight pipe section and its lower end connected to the lower header.

[0007] Furthermore, each of the second straight pipe sections is located on the outer side of the molten salt tower receiver.

[0008] Furthermore, the deflection angle is 45° to 75°.

[0009] Furthermore, each of the aforementioned heat collection tubes is equipped with an electric heat tracing cable.

[0010] Furthermore, the thermally conductive filler layer is made of a material with high thermal conductivity and stable physical properties.

[0011] Furthermore, the lower header, heat collection pipe, and upper header are welded together.

[0012] In another aspect, the present invention also provides a method for operating a molten salt tower-type heat absorber, comprising: feeding low-temperature molten salt into the heat collection tubes; reflecting sunlight onto the outer cylinder of the packing, heating the low-temperature molten salt in each heat collection tube to a high-temperature molten salt at a preset temperature through the thermally conductive packing layer; and discharging the high-temperature molten salt from the heat collection tubes.

[0013] Thirdly, the present invention also provides a process coupling control method for a molten salt tower receiver, comprising: pre-setting the minimum operating temperature of the thermally conductive packing. Minimum cooling rate of thermally conductive filler Temperature difference threshold between molten salt inlet and outlet Determine the clear sky factor based on weather conditions. And obtain the real-time temperature of the thermally conductive packing under actual operating conditions. and real-time cooling rate and the temperature difference between the inlet and outlet of the molten salt The main controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt and the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers.

[0014] Furthermore, the central controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt And the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers, including: when the clear sky factor... When the molten salt tower absorber is shut down and the salt is unloaded; when the clear sky factor... At that time, if ,or, And simultaneously satisfy and If the molten salt tower absorber is shut down and the salt is unloaded, then the molten salt flow rate is reduced and the molten salt temperature is controlled; or the molten salt flow rate is reduced and the electric heat tracing is activated to control the molten salt temperature. When the clear sky factor... At that time, if And simultaneously satisfy and Then, control the molten salt tower receiver to operate normally; if only the following conditions are met... Or, only satisfying at the same time and If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature; Clear Sky Factor If at the same time, and Then control the molten salt tower receiver to operate normally, if and only satisfy or If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature.

[0015] The beneficial effect of the present invention is that the outer cylinder of the packing and each heat collection tube are filled with a thermally conductive packing layer, which can prevent reflected light from directly hitting the heat collection tube, allowing the heat collection tube to heat up and cool down slowly, thereby avoiding the large thermal stress caused by the rapid change in the tube wall temperature of the heat collection tube and reducing the probability of the heat collection tube bursting.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a top view of the molten salt tower receiver of the present invention, which is composed of single molten salt tower receivers connected in series or in parallel.

[0020] Figure 2 This is a front view of the single-piece structure of the molten salt tower absorber of the present invention;

[0021] Figure 3 This is a side view of the monolithic structure of the molten salt tower absorber of the present invention.

[0022] In the picture:

[0023] Molten salt tower type heat absorber single-piece structure 1, lower header 11, first molten salt interface 111, upper header 12, second molten salt interface 121, heat collection tube 13, first straight pipe section 131, second straight pipe section 132, third straight pipe section 133, packing outer cylinder 14, heat-conducting packing layer 15. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] like Figure 1 and Figure 2 As shown, this embodiment provides a molten salt tower receiver, including: a plurality of molten salt tower receiver single-piece structures 1 arranged in a circumferential shape, each including: a lower header 11, the bottom of which has a first molten salt interface 111 communicating with a molten salt tank; an upper header 12, located directly above the lower header 11, the top of which has a second molten salt interface 121 communicating with another molten salt tank; a plurality of heat collection tubes 13, spaced apart between the upper header 12 and the lower header 11, with both ends communicating with the upper header 12 and the lower header 11 respectively; and a packing outer cylinder 14, sleeved on the outside of each heat collection tube 13, the gap between the outer cylinder and the heat collection tube 13 being filled with a thermally conductive packing layer 15.

[0027] In some applications, the surface heat flux of conventional tubular receivers is often affected by cloud cover during normal operation. When the system is shut down and unloading salt due to unmet operating conditions, the receiver absorbs heat from the heliostats as the clouds disperse, causing a rapid temperature rise and thermal shock. This can lead to overheating of the receiver surface and rupture of the collector tubes, ultimately affecting the normal operation of solar thermal power generation. Therefore, the material requirements for the receiver's collector tubes are relatively high, and the delivery cycle for these materials is typically 6-9 months. Adding the 3-4 months required for receiver manufacturing and transportation, the overall delivery cycle for the receiver is approximately 9-12 months. This results in a long construction period, and in the event of a tube rupture, repair or replacement of the receiver requires a significant amount of time.

[0028] In this embodiment, a thermally conductive filler layer 15 is filled between the outer packing cylinder 14 and each heat collection tube 13. This can prevent reflected light from directly hitting the heat collection tube 13, allowing the heat collection tube to heat up and cool down smoothly. It can also prevent the heat collection tube wall temperature from changing drastically and generating large thermal stress, thereby reducing the probability of the heat collection tube bursting.

[0029] like Figure 3 As shown, in this embodiment, the heat collection pipe 13 includes: a first straight pipe section 131, which is biased towards the line connecting the upper header 12 and the lower header 11 and is set at a deflection angle, with its upper end connected to the upper header 12; a second straight pipe section 132, which is set along the line connecting the upper header 12 and the lower header 11, with its upper end connected to the lower end of the first straight pipe section 131; and a third straight pipe section 133, whose upper end is connected to the lower end of the second straight pipe section 132 and whose lower end is connected to the lower header 11.

[0030] In this embodiment, the first, second, and third straight pipe sections are adapted to protrude outward relative to the line connecting the upper header 12 and the lower header 11, which can increase the distance between adjacent second straight pipe sections 132, so that more heat-conducting filler is filled between adjacent second straight pipe sections 132, so that the low-temperature molten salt in the heat collection pipe 13 can absorb heat evenly and smoothly.

[0031] In this embodiment, each of the second straight pipe sections 132 is located on the outer side of the molten salt tower receiver.

[0032] In this embodiment, the deflection angle is 45° to 75°.

[0033] In this embodiment, the protruding heat collection tube 13 increases the contact area between the outer packing cylinder 14 and the reflected sunlight, resulting in a larger heat collection per unit time, accelerating the heating of the heat-conducting packing, and improving the heat absorption efficiency of the heat collection tube 13.

[0034] In addition, compared with conventional tubular heat absorbers, each molten salt tower heat absorber in this embodiment has a larger number of single-piece connected heat collection tubes 13, a smaller inner diameter of each heat collection tube 13, and the heat collection tube 13 is wrapped with a thermally conductive filler layer 15 for uniform heating, which can significantly improve the heat absorption and temperature rise efficiency of the low-temperature molten salt in each heat collection tube 13.

[0035] In this embodiment, each of the heat collection tubes 13 is equipped with an electric heating cable. When the heat carried by the sunlight reflected by the heliostat is relatively small, and the molten salt cannot be heated to the preset temperature even by reducing the molten salt flow rate, the electric heating cable is activated to control the molten salt temperature to reach the preset temperature, thus ensuring the normal operation of the tower-type molten salt absorber.

[0036] In some application scenarios, due to the large size of the upper and lower headers, the corresponding thermal stress is also large. The upper ends of the upper header 12 and the first straight pipe section 131, as well as the lower ends of the lower header 11 and the third straight pipe section 133, need to be shielded with protective components to prevent the upper and lower headers from being directly exposed to the reflected sunlight, which would cause the temperature of the upper and lower headers to rise sharply.

[0037] In this embodiment, the thermally conductive filler layer 15 is made of a material with high thermal conductivity and stable physical properties, such as a specific metallic filler, amorphous carbon, graphite, silicon carbide, etc.

[0038] In this embodiment, the thermally conductive filler layer 15 is selected from a thermally conductive medium that is stable in physical properties at high temperatures and has a high thermal conductivity. It can absorb the heat reflected by sunlight and make the heat transferred to the heat collector tube 13 more uniform, without causing severe thermal stress, thus increasing the service life of the molten salt tower heat absorber.

[0039] In some embodiments, the lower header 11, the heat collection tube 13, and the upper header 12 are welded together, which can make the structure of the molten salt tower receiver more stable.

[0040] Example 2

[0041] Based on the above embodiment 1, the present invention also provides a working method of a molten salt tower heat absorber, comprising: feeding low-temperature molten salt into the heat collection tube 13; reflecting sunlight onto the outer cylinder 14 of the packing, heating the low-temperature molten salt in each heat collection tube 13 to a high-temperature molten salt at a preset temperature through the thermally conductive packing layer 15; and sending out the high-temperature molten salt in the heat collection tube 13.

[0042] In this embodiment, low-temperature molten salt enters the heat collection tube 13 through a cold salt pump. The heat generated by the reflection of sunlight is evenly and slowly transferred from the outer cylinder 14 of the packing to the outer wall of the heat collection tube 13. The low-temperature molten salt exchanges heat with the inner wall of the heat collection tube 13 and is heated to a preset temperature to form high-temperature molten salt before being sent out of the heat collection tube 13.

[0043] Optionally, the second molten salt interface 121 is connected to a low-temperature molten salt tank, and the first molten salt interface 111 is connected to a high-temperature molten salt tank. The low-temperature molten salt enters the heat collection tube 13 through the upper header 12 from the second molten salt interface 121 to carry away heat and raise the temperature to the preset temperature. Then, it enters the high-temperature molten salt tank through the lower header 11 from the first molten salt interface 111.

[0044] Preferably, the first molten salt interface 111 is connected to a low-temperature molten salt tank, and the second molten salt interface 121 is connected to a high-temperature molten salt tank. The low-temperature molten salt enters the heat collection tube 13 through the lower header 11 from the first molten salt interface 111 to carry away heat and raise the temperature to the preset temperature. Then, it enters the high-temperature molten salt tank through the second molten salt interface 121 via the upper header 12.

[0045] In this embodiment, the preset temperature can be set to 565°C.

[0046] Example 3

[0047] Based on Embodiments 1 and 2 above, this embodiment also provides a process coupling control method for a molten salt tower receiver, including: pre-setting the minimum operating temperature of the thermally conductive packing. Minimum cooling rate of thermally conductive filler Temperature difference threshold between molten salt inlet and outlet Determine the clear sky factor based on weather conditions. And obtain the real-time temperature of the thermally conductive packing under actual operating conditions. and real-time cooling rate and the temperature difference between the inlet and outlet of the molten salt The main controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt and the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers.

[0048] In this embodiment, the main controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt And the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers, including: when the clear sky factor... When the molten salt tower absorber is shut down and the salt is unloaded; when the clear sky factor... At that time, if ,or, And simultaneously satisfy and If the molten salt tower absorber is shut down and the salt is unloaded, then the molten salt flow rate is reduced and the molten salt temperature is controlled; or the molten salt flow rate is reduced and the electric heat tracing is activated to control the molten salt temperature. When the clear sky factor... At that time, if And simultaneously satisfy and Then, control the molten salt tower receiver to operate normally; if only the following conditions are met... Or, only satisfying at the same time and If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature; Clear Sky Factor If at the same time, and Then control the molten salt tower receiver to operate normally, if and only satisfy or If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature; see Table 1 below for details.

[0049]

[0050] In a specific implementation, the clear sky factor Indicates rainy days, clear sky factor Indicates cloudy weather, clear sky factor Indicates cloudy, clear sky factor It indicates a sunny day.

[0051] Specifically, the actual heat that can be utilized by a molten salt tower receiver is expressed as:

[0052] ;in The heat carried by the light reflected from the heliostat; The composite thermal conductivity of the filler material, the pipe wall, and the molten salt; To absorb direct sunlight on the wall surface area; The emission rate is set to 0.5 under the same conditions, taking into account the actual operating environment on site. Stephen Bolhertz constant ; Ambient temperature; The outer wall temperature of the tower-type molten salt absorber is represented by the real-time temperature of the thermally conductive packing. and the thickness of the thermally conductive filler layer The function of [the function]. The actual usable heat is only related to the clear sky factor. Real-time temperature of thermally conductive filler Related to the real-time cooling rate of the thermally conductive filler. and the temperature difference between molten salt inlet and outlet Irrelevant.

[0053] In this embodiment, by combining structural modifications with system control, the frequency of downtime for salt unloading caused by weather cloud cover at the heliostat plant can be reduced, thus lowering operational risks, minimizing heat loss, and increasing efficiency.

[0054] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A process coupling control method for a molten salt tower receiver, characterized in that, include: Preset the minimum operating temperature of the thermally conductive filler. Minimum cooling rate of thermally conductive filler Temperature difference threshold between molten salt inlet and outlet The molten salt tower type heat absorber includes a packing outer cylinder (14), which is sleeved on the outside of each heat collecting tube (13), and the gap between it and the heat collecting tube (13) is filled with a thermally conductive packing layer (15). Determine the clear sky factor based on weather conditions. And obtain the real-time temperature of the thermally conductive packing under actual operating conditions. and real-time cooling rate and the temperature difference between the inlet and outlet of the molten salt ; The main controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt And the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers; The main controller is based on the clear sky factor. And combined with the temperature difference between the inlet and outlet of the molten salt And the real-time temperature of the thermally conductive filler. and real-time cooling rate Decision-making and control of the operation of molten salt tower receivers, including: When clear sky factor It was raining, so the molten salt tower absorber was shut down and the salt was unloaded. When clear sky factor It was a cloudy day, if ,or, And simultaneously satisfy and If the molten salt tower absorber is shut down and the salt is unloaded, then the molten salt flow rate is reduced and the molten salt temperature is controlled, or the molten salt flow rate is reduced and the electric heat tracing is turned on to control the molten salt temperature. When clear sky factor It was cloudy at the time, if And simultaneously satisfy and Then, control the molten salt tower receiver to operate normally; if only the following conditions are met... Or, only satisfying at the same time and If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature. Clear Sky Factor It was a sunny day, and if all of the following conditions were met... and Then control the molten salt tower receiver to operate normally, if and only satisfy or If the temperature is too high, reduce the molten salt flow rate and control the molten salt temperature; otherwise, reduce the molten salt flow rate and turn on the electric heat tracing to control the molten salt temperature.

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