A salt melting system for a solar thermal power station based on a natural gas heat transfer oil furnace

Abstract

A solar thermal power plant salt melting system based on a natural gas heat-conducting oil furnace belongs to the technical field of solar thermal salt melting production. The present invention aims to shorten the salt melting cycle and reduce the salt melting cost. The present invention includes a salt melting furnace, a heat exchanger, and a molten salt storage tank. The salt melting furnace is connected to the low-temperature molten salt inlet of the heat exchanger through a molten salt pipeline. The salt melting furnace is connected to the molten salt storage tank through a delivery pump. The high-temperature molten salt outlet of the heat exchanger is connected to the salt melting furnace. The heat exchanger is connected to a natural gas heat-conducting oil furnace, and the natural gas heat-conducting oil furnace is used to provide a heat exchange heat source for the heat exchanger. The heat exchanger can be an oil-salt heat exchanger, can be replaced by an electric heater, or can be a solar thermal direct heating molten salt collector system. The present invention realizes salt melting by a solar thermal method, and its salt melting speed is significantly improved. Moreover, the system has a simple structure, is easy to operate, has high safety, is energy-saving, environmentally friendly, clean, and efficient.

Description

Technical Field

[0001] The present invention relates to a salt melting system for a solar thermal power station based on a natural gas heat-conducting oil furnace, belonging to the technical field of salt melting systems. Background Art

[0002] Before molten salt is put into a solar thermal power station, it is mainly supplied in solid form (because molten salt is solid at normal temperature), and supplying in solid form is convenient for the transportation and storage of molten salt. When molten salt needs to be put into the solar thermal power station for heat storage, a large amount of solid molten salt needs to be converted into high-temperature liquid molten salt. The method is to preliminarily melt the molten salt. The preliminary melting of molten salt is a key procedure before the molten salt heat storage system of the solar thermal power station enters commissioning operation. Through this process, the molten salt changes from solid to high-temperature liquid molten salt and enters the system to start circulating, and remains in liquid state throughout the life cycle of the entire power station.

[0003] In existing solar thermal power stations, there are generally two schemes for realizing salt melting. One is to use an electric heater to initialize the salt, and then use a molten salt circulation pump to pump the low-temperature liquid molten salt into a natural gas salt melting furnace. The molten salt in the coil in the salt melting furnace is heated to a high temperature state by the high-temperature flue gas generated by burning natural gas, and then transported back to the molten salt tank. Sodium nitrate and potassium nitrate (solid molten salt) are added to the molten salt tank in proportion. When the temperature of the molten salt in the molten salt tank meets the requirements, the molten salt is transported to the molten salt tank by another molten salt transfer pump; the other is that sodium nitrate and potassium nitrate are crushed and mixed in proportion and then directly enter the natural gas salt melting furnace. Heat exchange coils are arranged in the furnace chamber, and high-temperature flue gas is contained in the pipes, and its flow direction is opposite to the stirring direction of the liquid in the furnace. The melted liquid molten salt overflows into the buffer tank through the overflow pipe, and then is pumped into the molten salt tank from the buffer tank. The above two traditional salt melting methods both use the flue gas after burning natural gas as the heat source for heating solid molten salt particles, and a large amount of natural gas is consumed during the salt melting process. Due to the technical limitations of the natural gas furnace itself and for safety considerations, the salt melting speed is about 30 - 40 t / h. After the salt melting is completed, the supporting salt melting equipment has no use value in this project and can only be used for salt melting again in the next project or left unused and wasted.

[0004] In addition to the above statements, the conventional salt melting methods also have the following disadvantages:

[0005] 1. For a salt melting furnace system that realizes salt melting by using a natural gas heating method, its cost is relatively high. After one-time salt melting, when the molten salt is put into the solar thermal system for use, there is no need for salt melting again. Therefore, the supporting natural gas salt melting furnace system equipment cannot be reasonably used;

[0006] 2. When using a natural gas salt melting furnace system to realize salt melting, natural gas needs to be burned, and in a large-scale molten salt project of a solar thermal power station with tens of thousands of tons, the cost of natural gas consumed is relatively high;

[0007] 3. The amount of carbon dioxide emitted by burning natural gas in the natural gas salt melting furnace system is relatively large, which has a certain degree of pollution to the environment;

[0008] 4. The heating-up capacity of the natural gas salt melting furnace system is limited. In the molten salt project of a large-scale solar thermal power station with a capacity of several hundred thousand tons, its salt melting speed is slow and the salt melting cycle is long.

[0009] Based on the above situation, carrying out research on the salt melting technical solution is of great significance for shortening the salt melting cycle, reducing the salt melting cost, increasing the salt melting speed and quality, and ensuring both solar thermal power generation and salt melting without interference. Summary of the Invention

[0010] The present invention aims to shorten the salt melting cycle and reduce the salt melting cost. The following gives a brief overview of the present invention to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0011] Technical solution of the present invention:

[0012] A molten salt system for a solar thermal power station based on a natural gas heat-conducting oil furnace, comprising a salt melting furnace, a heat exchanger, a molten salt storage tank and a natural gas heat-conducting oil furnace. The heat exchanger has a molten salt inlet, a molten salt outlet, a heat source outlet and a heat source inlet. The salt melting furnace is connected to the molten salt inlet of the heat exchanger through a molten salt pipeline. The salt melting furnace is connected to the molten salt storage tank through a delivery pump. The molten salt outlet of the heat exchanger is connected to the salt melting furnace through a first pipeline. A connection relationship is established between the heat source outlet and the heat source inlet of the heat exchanger and the natural gas heat-conducting oil furnace. The natural gas heat-conducting oil furnace is used to provide a heat exchange heat source for the heat exchanger.

[0013] Preferably: It further includes an auxiliary electric heater. The inlet of the auxiliary electric heater is connected to the molten salt pipeline, and the outlet of the auxiliary electric heater is connected to the salt melting furnace through a second pipeline.

[0014] Preferably: Valves and temperature measuring instruments are respectively installed on the first pipeline and the second pipeline.

[0015] Preferably: The electric energy used in the auxiliary electric heater is sourced from abandoned wind power, abandoned photovoltaic power or off-peak electricity.

[0016] Preferably: The number of the heat exchangers is multiple, and the multiple heat exchangers are installed in parallel.

[0017] Preferably: The number of the heat exchangers is multiple, and the multiple heat exchangers are installed in series.

[0018] Preferably: Adjacent two heat exchangers are connected through a secondary molten salt pipeline.

[0019] Preferably, a valve and a temperature measuring instrument are installed on the secondary molten salt pipeline.

[0020] Preferably, the heat exchanger is a shell-and-tube heat exchanger, a tubular heat exchanger or a plate heat exchanger.

[0021] The present invention has the following beneficial effects:

[0022] 1. In the salt melting system of the present invention, the problem that the solid molten salt of a conventional solar thermal power station is melted through a dedicated natural gas salt melting furnace system is solved. When the conventional dedicated natural gas salt melting furnace realizes the salt melting process, it is restricted by factors such as the heating capacity of the furnace and the consumption of natural gas, resulting in low salt melting efficiency, inability to guarantee the entire salt melting cycle, and high fuel cost for salt melting.

[0023] 2. The present invention uses the solar thermal power generation system for salt melting work, so that power generation and salt melting do not interfere with each other, and the salt melting capacity is much greater than that of a dedicated natural gas salt melting furnace system;

[0024] 3. When there is sunlight during the day in the present invention, solar thermal energy is used for salt melting. When there is no sunlight at night, electric heating is used to absorb abandoned electricity or valley electricity for salt melting, effectively shortening the salt melting cycle.

[0025] 4. Compared with the conventional salt melting method, the present invention realizes salt melting through the solar thermal method, with significantly increased salt melting speed, and the system is simple, easy to operate, highly safe, energy-saving and environment-friendly.

[0026] 5. Adopting the salt melting scheme of the present invention, sodium nitrate and potassium nitrate are crushed and then transported into the salt melting furnace in proportion. After initial salt melting with an electric heater, the low-temperature liquid molten salt in the salt melting furnace is pumped into the oil-salt heat exchanger by a molten salt circulation pump. The molten salt in the oil-salt heat exchanger is heated to a high temperature state by a natural gas heat transfer oil furnace and then transported back to the salt melting furnace. The high-temperature liquid salt is mixed with the solid molten salt to form a low-temperature liquid molten salt above 270 °C, and is transported and stored in a molten salt storage tank.

[0027] Since the present invention utilizes the original heat exchange equipment of the solar thermal power station, the construction cost is saved. After salt melting is completed, the supporting feeding system can be disassembled, recycled and reused. The salt melting furnace and the electric heater can be directly converted into a high-temperature energy storage system for absorbing abandoned wind and light to realize energy storage.

[0028] 6. Adopting the salt melting system of the present invention, the salt melting speed exceeds 210 tons per hour, which is five times faster than the traditional salt melting speed. It can exceed 4000 tons per day, which is more than four times the previous single-day salt melting world record. If 70,000 tons of salt are continuously melted, it only takes two and a half weeks, which is two months faster than the traditional salt melting method, saving tens of millions of yuan in fossil fuels for salt melting, and the equipment investment is also 20% less than that of the traditional salt melting system. Calculated according to a 100 MW 10-hour energy storage solar thermal power station, realizing energy storage power generation two months in advance can create a power generation income of 60 million kWh. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. 1 is a schematic diagram of a salt melting system based on a natural gas heat transfer oil furnace;

[0030] Figure 2 FIG. 2 is a composition diagram of the salt melting system in the second specific embodiment;

[0031] Figure 3 FIG. 3 is a composition diagram of the salt melting system of the heat exchanger in the second specific embodiment;

[0032] Figure 4 FIG. 4 is a schematic diagram showing the relationship between the salt melting amount and the salt melting cycle of the traditional salt melting method and the salt melting method of the present invention;

[0033] In the figures, 1 - salt melting furnace, 2 - heat exchanger, 3 - molten salt storage tank, 4 - molten salt pipeline, 5 - transfer pump, 6 - natural gas heat transfer oil furnace, 7 - secondary molten salt pipeline, 8 - valve, 9 - temperature measuring instrument, 10 - auxiliary electric heater, 11 - first pipeline, 12 - second pipeline, 21 - molten salt inlet, 22 - molten salt outlet, 23 - heat source outlet, 24 - heat source inlet, 14 - circulation pump. SPECIFIC EMBODIMENTS

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention. Specific Embodiment 1:

[0036] Referring to Figure 1 FIG. 1, this embodiment provides a solar thermal power plant salt melting system based on a natural gas heat transfer oil furnace, including a salt melting furnace 1, a heat exchanger 2, a molten salt storage tank 3 and a natural gas heat transfer oil furnace 6. The heat exchanger 2 has a molten salt inlet 21, a molten salt outlet 22, a heat source outlet 23 and a heat source inlet 24. The salt melting furnace 1 is connected to the molten salt inlet 21 of the heat exchanger 2 through a molten salt pipeline 4. The salt melting furnace 1 is connected to the molten salt storage tank 3 through a transfer pump 5. The molten salt outlet 22 of the heat exchanger 2 is connected to the salt melting furnace 1 through a first pipeline 11. A connection relationship is established between the heat source outlet 23 and the heat source inlet 24 of the heat exchanger 2 and the natural gas heat transfer oil furnace 6. The natural gas heat transfer oil furnace 6 is used to provide a heat exchange heat source for the heat exchanger 2.

[0037] Among them, in the salt dissolving furnace 1, after the solid salt and the high-temperature molten salt are mixed in the salt dissolving furnace 1, a medium-temperature liquid molten salt is formed. A part of the medium-temperature liquid molten salt is sent into the molten salt storage tank 3 for storage through the transfer pump 5, and the other part is pumped into the heat exchanger 2 through the circulation pump. The heat exchanger 2 is used to heat the medium-temperature molten salt to high-temperature molten salt, and then the high-temperature molten salt is transported into the salt dissolving furnace 1 through the circulation pump and used for salt dissolving work again, thus forming a cyclic salt dissolving process;

[0038] In this embodiment, the heat exchanger 2 is a heat-conducting oil heat exchanger. When the system conducts salt dissolving work, the solid salt is mixed with the high-temperature molten salt at 300 - 400 °C in the salt dissolving furnace 1 to form a medium-temperature liquid molten salt at 280 - 340 °C. One part of the formed medium-temperature liquid molten salt is sent into the molten salt storage tank 3 for storage through the transfer pump 5, and the other part is pumped into the heat exchanger 2 from the molten salt inlet 21 through the circulation pump. At the same time, the natural gas heat-conducting oil furnace 6 is connected to the heat source outlet 23 and the heat source inlet 24 of the heat exchanger 2, and the high-temperature heat-conducting oil that absorbs heat in the natural gas heat-conducting oil furnace 6 is transported into the heat exchanger 2. Inside the heat exchanger 2, the high-temperature heat-conducting oil transfers heat to the medium-temperature molten salt entering the heat exchanger 2, so that the temperature of the medium-temperature molten salt (280 - 340 °C) reaches the high-temperature molten salt (300 - 400 °C). Subsequently, the high-temperature molten salt is transported into the salt dissolving furnace 1 through the first pipeline 11 for completing the salt dissolving work again. The transported amount ensures that the solid molten salt newly added to the salt dissolving furnace 1 can reach a certain temperature and melts the solid molten salt. Repeating the above steps realizes the cyclic salt dissolving process.

[0039] The salt dissolving system in this embodiment solves the problem that in a conventional solar thermal power station, the solid molten salt is dissolved through a natural gas salt dissolving furnace system. However, for the conventional natural gas salt dissolving furnace to realize the salt dissolving process, it is restricted by factors such as the heating capacity of the furnace and the consumption of natural gas. The entire salt dissolving cycle is relatively long, and the construction and operation costs of the salt dissolving are relatively high.

[0040] Adopting the salt dissolving system of this embodiment, this system uses the power generation and heat storage system of the solar thermal power station to conduct salt dissolving work, so that power generation and salt dissolving do not interfere with each other, and the salt dissolving capacity is much greater than that of the traditional natural gas salt dissolving furnace system;

[0041] Inside the heat exchanger 2, the high-temperature heat-conducting oil transfers heat to the medium-temperature molten salt entering the heat exchanger 2, so that the temperature of the medium-temperature molten salt reaches the high-temperature molten salt, and the heat-conducting oil comes from the natural gas heat-conducting oil furnace 6. The heat-conducting oil in the heat exchanger 2 comes from the natural gas heat-conducting oil furnace.

[0042] In this embodiment, the salt dissolving furnace 1 is used to convert the crushed solid molten salt into liquid melt. The salt dissolving furnace 1 is a container for realizing salt dissolving; the heat exchanger 2 is a shell-and-tube heat exchanger, a tubular heat exchanger or a plate heat exchanger. Specific Embodiment Two:

[0044] Reference Figure 1 and Figure 2 On the basis of the first specific embodiment, it further includes an auxiliary electric heater 10. The inlet of the auxiliary electric heater 10 is communicated with the molten salt pipeline 4, and the outlet of the auxiliary electric heater 10 is communicated with the salt melting furnace 1 through the second pipeline 12;

[0045] Specifically: A part of the medium-temperature molten salt in the salt melting furnace 1 flows into the heat exchanger 2 and / or the auxiliary electric heater 10. The heat exchanger 2 and / or the auxiliary electric heater 10 are used to heat the medium-temperature molten salt to high-temperature molten salt, and then the high-temperature molten salt is transported to the salt melting furnace 1 through the circulation pump 14 to realize the cyclic salt melting operation;

[0046] When the system performs the salt melting operation, the solid salt is mixed with the high-temperature molten salt at 300 - 400 °C in the salt melting furnace 1 to form a medium-temperature liquid molten salt at 280 - 340 °C. One part of the formed medium-temperature liquid molten salt is sent to the molten salt storage tank 3 for storage through the transfer pump 5, and the other part is pumped into the heat exchanger 2 or the auxiliary electric heater 10 through the circulation pump 14. After passing through the heat exchanger 2 or the auxiliary electric heater 10, the medium-temperature liquid molten salt (280 - 340 °C) is heated and converted into high-temperature liquid molten salt (300 - 400 °C). Subsequently, the high-temperature molten salt is transported into the salt melting furnace 1 to realize cyclic salt melting. The transported amount ensures that the newly added solid molten salt in the salt melting furnace 1 can reach a certain temperature and melts the solid molten salt.

[0047] The number of the auxiliary electric heaters 10 is multiple, and the multiple auxiliary electric heaters 10 are arranged in parallel or in series in the entire salt melting system;

[0048] In this embodiment, the salt melting system of this embodiment is adopted. Its salt melting speed exceeds 210 tons per hour, which is five times faster than the traditional salt melting speed. It can exceed 4000 tons per day, which is more than four times the previous single-day salt melting world record. If 70,000 tons of salt are continuously melted, it only takes two and a half weeks, which is two months faster than the traditional salt melting method. It can realize the power generation of the heat storage island in advance and save tens of millions of yuan of fossil fuels for salt melting. The equipment investment is also 20% less than that of the traditional salt melting system. The specific comparison is shown in the figure:

[0049] Table 1. Comparison between the solar thermal salt melting system and the traditional salt melting system

[0050]

[0051] It should be noted that in solar power generation projects, currently, conventional salt melting systems internationally all use natural gas salt melting furnaces, and the flue gas after natural gas combustion is used to provide heat to melt the solid molten salt into a liquid state.

[0052] When a solar power generation project requires salt melting, the conventional method is to purchase a molten salt furnace and then use the flue gas after natural gas combustion to provide heat to melt the solid molten salt into a liquid state;

[0053] Different from the conventional salt melting method, in this embodiment, the original equipment of the solar power plant is used for salt melting operations. For example, the heat exchanger 2 and the natural gas heat-conducting oil furnace 6 used in this embodiment are both existing equipment in the power plant. The original function of this equipment is for solar power generation. In this embodiment, according to the cooperation and connection methods of the technical features in this embodiment, a salt melting system is formed, and this system is used to achieve salt melting. In this way, the cost of purchasing and building a natural gas salt melting furnace is saved, the carbon dioxide emissions during the salt melting process are reduced, and the method of using existing equipment to achieve salt melting improves the salt melting speed and salt melting cycle (as Figure 4 shown);

[0054] It should be noted that: the heat storage medium used in the solar thermal power station project is high-temperature molten salt. Taking the 100MW trough-type heat-conducting oil solar thermal power generation project in Wulate Zhongqi as an example, the power station is equipped with a high-temperature molten salt heat storage system. The high-temperature molten salt used in this system is a mixture of potassium nitrate with a mass fraction of 40% and sodium nitrate with a mass fraction of 60%. Before the molten salt energy storage system is put into operation, the solid molten salt must be melted and injected into the cold salt tank first. This step (salt melting) is crucial for the smooth development and formal operation of the heat storage system debugging. Currently, conventional salt melting systems internationally all use natural gas salt melting furnaces, and use the flue gas after natural gas combustion to provide heat to melt the solid molten salt into a liquid state. This conventional salt melting system not only has a low salt melting rate and cannot put the heat storage system into normal operation in a short time, but also consumes a large amount of fossil fuels, which is contrary to the "dual carbon" commitment. And limited by the characteristics of high molten salt melting temperature and many technical difficulties in the salt melting system, the practical exploration of high-speed and low-carbon new salt melting technologies at home and abroad is almost zero.

[0055] Using the salt melting system of this embodiment can ensure that solar thermal power generation and salt melting do not interfere with each other, and it has very important significance for realizing salt melting in solar thermal power generation projects. Specific Embodiment Three:

[0057] Referring to Figure 1 、 Figure 2 shown, and on the basis of Specific Embodiment One and Specific Embodiment Two, valves 8 and temperature measuring instruments 9 are respectively installed on the first pipeline 11 and the second pipeline 12. The valve 8 is used to control the opening and closing of the pipeline, and the temperature measuring instrument 8 is used to measure the fluid temperature in the pipeline. By using the information interaction of the valve 8 and the temperature measuring instrument 9, the opening and closing of the molten salt in the first pipeline 11 and the second pipeline 12 are monitored in real time to ensure the smooth progress of the salt melting work. Specific Embodiment Four:

[0059] On the basis of the second specific implementation manner, the electric energy used in the auxiliary electric heater 10 is sourced from low-cost electricity such as abandoned wind power, abandoned photovoltaic power, and valley electricity, and the cost of this electric energy is lower than that of the electric energy provided by conventional power stations. Specific implementation manner five:

[0061] Refer to Figure 3 As shown, this implementation manner provides a solar thermal power plant salt melting system based on a natural gas heat transfer oil furnace. Different from the first specific implementation manner, the number of heat exchangers 2 is multiple, and the multiple heat exchangers 2 are installed in parallel. Through the multiple heat exchangers 2 arranged in parallel, medium-temperature liquid molten salt at 280 - 340 degrees can be heated simultaneously to high-temperature molten salt at 300 - 400 degrees. In addition, any one of the heat exchangers 2 can be individually controlled to work / stop without affecting the operation of other heat exchangers 2. In the whole system, the method of using multiple heat exchangers 2 in parallel has the advantages of flexibility, convenient use, and when an accident occurs in a single heat exchanger 2, it does not affect the operation of the entire salt melting system. Specific implementation manner six:

[0063] Refer to Figure 3 As shown, this implementation manner provides a solar thermal power plant salt melting system based on a natural gas heat transfer oil furnace. Different from the first specific implementation manner, the number of the heat exchangers 2 is multiple, and the multiple heat exchangers 2 are installed in series. By using the series-connected heat exchangers 2, the medium-temperature liquid molten salt at 280 - 340 degrees can flow through a path and be heat-exchanged multiple times to reach high-temperature molten salt at 300 - 400 degrees, and in the series connection method, there is only one path in the whole system, which is convenient for switching and controlling the whole system. Specific implementation manner seven:

[0065] Refer to Figure 3 As shown, on the basis of the fifth specific implementation manner, two adjacent heat exchangers 2 are connected through a secondary molten salt pipeline 7. A valve 8 for opening / closing the secondary molten salt pipeline 7 and a temperature measuring instrument 8 for measuring the temperature of the flowing liquid molten salt in the secondary molten salt pipeline 7 are installed on the secondary molten salt pipeline 7. With such a setting, the medium-temperature liquid molten salt at 280 - 340 degrees flowing out of the salt melting furnace 1 enters the heat exchanger 2, and in the heat exchanger 2, the medium-temperature liquid molten salt at 280 - 340 degrees is raised to high-temperature molten salt at 300 - 400 degrees; if the medium-temperature liquid molten salt in the heat exchanger 2 cannot be effectively heat-exchanged to the high-temperature molten salt temperature state, the secondary molten salt pipeline 7 is opened, and the liquid molten salt is transported to another parallel heat exchanger 2 again for further heat-exchange of the liquid molten salt until it reaches the high-temperature molten salt state at 300 - 400 degrees. Specific implementation manner nine:

[0067] Refer to Figure 1 、 Figure 3As shown, on the basis of the fifth specific implementation manner, the heat exchanger 2 is used to heat and convert medium-temperature liquid molten salt (280 - 340 °C) into high-temperature liquid molten salt (300 - 400 °C). The main principle is that the heat exchanger 2 has a molten salt inlet 21, a molten salt outlet 22, a heat source outlet 23, and a heat source inlet 24. The medium-temperature liquid molten salt enters the heat exchanger 2 from the molten salt inlet 21 and exchanges heat with the heat medium (such as heat-conducting oil, hot molten salt) entering from the heat source outlet 23 to heat the medium-temperature liquid molten salt to form high-temperature liquid molten salt, which is transported to the salt melting furnace 1 to melt the solid molten salt in the salt melting furnace 1.

[0068] In this implementation manner, the temperature of the high-temperature molten salt can fluctuate around 370 degrees, with a fluctuation range of 70 degrees (the maximum does not exceed 600 degrees), and the medium-temperature salt fluctuates around 310 degrees, with a fluctuation range of 30 degrees. Specific implementation manner ten:

[0070] Combined with the first specific implementation manner, the heat exchanger 2 is a shell-and-tube heat exchanger, a tube-and-shell heat exchanger, or a plate heat exchanger.

[0071] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary implementation manners according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0072] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0073] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention; the orientation terms "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0074] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "above-mentioned", etc. can be used here to describe the spatial positional relationship of a device or feature shown in the drawings with other devices or features. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the drawings for the device. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will then be positioned "below" or "beneath" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used here.

[0075] It should be noted that the terms "first", "second", etc. in the specification, claims and above-mentioned drawings of the present application are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0076] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutations and combinations. Therefore, the present invention will no longer describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0077] This embodiment is only an exemplary illustration of the present patent and does not limit its protection scope. Those skilled in the art can also make partial changes to it. As long as it does not exceed the spiritual essence of the present patent, it is within the protection scope of the present patent.

Claims

1. A salt melting system for a solar thermal power station based on a natural gas heat transfer oil furnace, characterized in that: It includes a salt dissolving furnace (1), a heat exchanger (2), a molten salt storage tank (3) and a natural gas heat transfer oil furnace (6). The heat exchanger (2) has a molten salt inlet (21), a molten salt outlet (22), a heat source outlet (23) and a heat source inlet (24). The salt dissolving furnace (1) is connected to the molten salt inlet (21) of the heat exchanger (2) through a molten salt pipeline (4). The salt dissolving furnace (1) is connected to the molten salt storage tank (3) through a delivery pump (5). The molten salt outlet (22) of the heat exchanger (2) is connected to the salt dissolving furnace (1) through a first pipeline (11). A connection relationship is established between the heat source outlet (23) and the heat source inlet (24) of the heat exchanger (2) and the natural gas heat transfer oil furnace (6). The natural gas heat transfer oil furnace (6) is used to provide a heat exchange heat source for the heat exchanger (2). The number of the heat exchangers (2) is multiple, and the multiple heat exchangers (2) are installed in parallel. Two adjacent heat exchangers (2) are connected through a secondary molten salt pipeline (7), and a valve (8) for opening / closing the secondary molten salt pipeline (7) and a temperature measuring instrument (9) for measuring the temperature of the flowing liquid molten salt in the secondary molten salt pipeline (7) are installed on the secondary molten salt pipeline (7). The 280 - 340 °C medium-temperature liquid molten salt flowing out of the salt dissolving furnace (1) enters the heat exchanger (2). In the heat exchanger (2), the 280 - 340 °C medium-temperature liquid molten salt is heated to 300 - 400 °C high-temperature molten salt. If the medium-temperature liquid molten salt in the heat exchanger (2) cannot be effectively heat-exchanged to the high-temperature molten salt temperature state, the secondary molten salt pipeline (7) is opened, and the liquid molten salt is conveyed to another parallel heat exchanger (2) for further heat exchange of the liquid molten salt until it reaches the 300 - 400 °C high-temperature molten salt state. This 300 - 400 °C high-temperature molten salt is conveyed into the salt dissolving furnace (1) to melt the solid molten salt in the salt dissolving furnace (1). It also includes an auxiliary electric heater (10). The inlet of the auxiliary electric heater (10) is connected to the molten salt pipeline (4), and the outlet of the auxiliary electric heater (10) is connected to the salt dissolving furnace (1) through a second pipeline (12).

2. The salt melting system of the solar thermal power station based on the natural gas heat transfer oil furnace according to claim 1, characterized in that: The electric energy used in the auxiliary electric heater (10) comes from abandoned wind power, abandoned photovoltaic power or low-valley electricity.

3. The salt melting system of a solar thermal power station based on a natural gas heat transfer oil furnace according to claim 1, characterized in that: The heat exchanger (2) is a shell-and-tube heat exchanger, a tube-and-shell heat exchanger or a plate heat exchanger.

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