Electric heating salt dissolving device

Abstract

The utility model relates to an electric heating salt dissolving device which comprises a salt dissolving tank, a resistance heating pipe group, a fused salt circulating pump and a feeding mechanism, wherein the resistance heating pipe group is arranged on the salt dissolving tank and used for primary salt dissolving; the fused salt circulating pump is arranged on the salt dissolving tank and used for conveying high-temperature liquid fused salt; and the feeding mechanism is arranged on the salt dissolving tank and used for adding granular fused salt. Compared with natural gas salt melting, carbon dioxide emission is reduced, and compared with a mirror field salt melting scheme, a heating pipeline is simple, and starting is convenient; jet flow heat exchange is adopted in fused salt melting, and convective heat transfer is strengthened through impact of fluid. And a net basket convenient to replace and clean is arranged in the heat exchange melting area, so that solid caked molten salt is prevented from entering molten liquid molten salt to affect the salt melting efficiency, and insoluble large impurities can also be prevented from entering a molten salt pump and blocking a pipeline.

Description

Technical Field

[0001] The utility model relates to the technical field of molten salt energy storage, in particular to a molten salt melting system for a solar thermal power station, and particularly to an electric heating salt melting device. Background Art

[0002] The power generation of new energy power stations such as photovoltaic and wind power is affected by factors such as light, climate, season, and region, resulting in poor continuity and insufficient stability of solar energy utilization. In order to achieve the continuous availability of solar power generation, new energy power stations need to be equipped with energy storage regulation systems. The molten salt heat storage system has outstanding advantages in terms of heat storage capacity, large-scale construction and operation costs, service life, safety, and power generation power. Especially for absorbing the installed capacity output of intermittent new energy (wind power, photovoltaic, etc.), it plays an important role in building a new power system with new energy as the main body and ensuring the safe and stable operation of the power system, and is the backbone of large-scale energy storage. At present, the initial salt melting amount in the newly built or already built solar thermal power stations is more than ten thousand tons. With the development of new energy power plants, there is a large market demand for salt melting devices and services. Molten salt melting, that is, the initial melting of molten salt, is a key process before the molten salt heat storage system enters commissioning operation. Through this process, the molten salt changes from a solid state to a high-temperature liquid molten salt and enters the system to start circulating, and remains in a liquid state throughout the life cycle of the entire power station. The existing molten salt melting and storage system consists of a molten salt melting system, a molten salt storage system, and a conveying pipeline connecting the two. The solid granular molten salt is first heated to a high-temperature liquid state in the molten salt melting system, and then the high-temperature liquid molten salt is pumped through the conveying pipeline to the high-temperature molten salt tank by a molten salt pump.

[0003] The main salt melting method in the market is natural gas heating salt melting. However, using natural gas combustion as the heat source supply has a large carbon dioxide emission, and is restricted by carbon emission indicators. In the later stage, it will be changed to electric heating salt melting. Currently, binary molten salt is mostly used in solar thermal power stations. The binary molten salt consists of 60% (mass percentage) NaNO 3 and 40% (mass percentage) KNO 3 Before the operation of the molten salt heat storage system, it is necessary to heat and melt the molten salt and then input it into the molten salt tank. The main salt melting methods include natural gas heating salt melting and using the solar energy of the solar thermal mirror field to heat and melt. It has the following disadvantages:

[0004] 1. Natural gas salt melting uses natural gas combustion as the heat source supply, and there is a large amount of CO 2 emission during the whole process;

[0005] 2. The existing solar energy concentrating salt melting device uses the solar energy of the solar thermal power station mirror field as the heat source, and the salt melting is greatly affected by sunlight conditions and has poor controllability;

[0006] 3. In existing solar thermal salt melting devices, due to the low energy density of solar energy, the molten salt pipelines in high-power solar thermal mirror fields are very long. Liquid molten salt needs to meet the minimum circulation volume to use a molten salt pump to pump the circulation. The molten salt circulates in the pipeline to absorb heat and increase in temperature. These minimum starting amounts of liquid molten salt need to be melted by a small-power resistance heater. When the minimum starting amount is relatively large, the start-up preparation work of the solar thermal salt melting device is complex;

[0007] 4. The existing salt melting method of the salt melting device is to add granular molten salt from above into the liquid molten salt, and then add a stirring device to accelerate heat exchange to achieve melting. However, this solution requires adding a set of stirring devices to accelerate melting. Utility Model Content

[0008] In view of this, the present utility model proposes an electric heating salt melting device, aiming to solve the problems existing in the prior art.

[0009] Specifically, an electric heating salt melting device of the present utility model includes a salt melting tank, on which a resistance heating tube group for primary salt melting is provided, a molten salt circulation pump for transporting liquid molten salt is provided on the salt melting tank, and a feeding mechanism for adding granular molten salt to jet heat exchange with high-temperature liquid molten salt is provided on the salt melting tank.

[0010] On the basis of the above solution, it further includes: a high-voltage electromagnetic molten salt heater for secondary heating of low-temperature molten salt; the input end of the high-voltage electromagnetic molten salt heater is connected to the molten salt circulation pump through an input pipeline, and the output end of the high-voltage electromagnetic molten salt heater is connected to the feeding mechanism through an output pipeline.

[0011] On the basis of the above solution, the feeding mechanism includes: a feeding box, a belt feeder for transporting materials provided on the feeding box, a salt melting wire basket for realizing jet heat exchange between granular molten salt and high-temperature liquid molten salt provided on the salt melting tank, a feeding funnel for guiding and transporting materials from the belt feeder to the salt melting wire basket provided on the salt melting wire basket, and a collection hood for collecting nitrogen oxide gases provided on the feeding funnel.

[0012] On the basis of the above solution, the salt melting wire basket includes a fixed beam, and a standby wire basket and a working wire basket slidably arranged on the fixed beam.

[0013] On the basis of the above solution, a standby working position, a working position and a cleaning position are sequentially arranged on the fixed beam; in the initial stage, the standby wire basket is arranged at the standby working position, and the working wire basket is arranged at the working position.

[0014] Based on the above solution, it further includes: a combined partition plate arranged in the salt dissolving tank for distinguishing the salt dissolving area and the salt discharging area, and the combined partition plate includes a lower partition plate arranged at the bottom of the salt dissolving tank for isolating the solid impurity precipitation area and an upper partition plate arranged at the top of the salt dissolving tank for separating the upper liquid molten salt.

[0015] Based on the above solution, it further includes: a mixing temperature measuring thermocouple arranged on the salt dissolving tank for measuring the temperature of the low-temperature liquid molten salt formed after the high-temperature molten salt and the particulate molten salt are mixed and melted to control the feeding speed of the solid particulate salt, a float level gauge arranged on the salt dissolving tank for measuring the liquid level value, a salt discharging temperature measuring thermocouple arranged on the salt dissolving tank for measuring the temperature of the molten salt after mixing evenly and stably, and a hot salt temperature measuring thermocouple arranged on the high-voltage electromagnetic molten salt heater for measuring the temperature of the molten salt output by the high-voltage electromagnetic molten salt heater.

[0016] Based on the above solution, it further includes: a salt discharging molten salt pump arranged on the salt dissolving tank for outputting the molten salt to the molten salt tank.

[0017] The molten salt melting of the present utility model adopts jet flow heat exchange to strengthen the convective heat transfer by the impact of the fluid; in addition, a wire basket that is convenient for replacement and cleaning is arranged in the heat exchange melting area, which can prevent the solid agglomerated molten salt from entering the melted liquid molten salt and affecting the salt dissolving efficiency, and can also prevent the insoluble large impurities from entering the molten salt pump and blocking the pipeline. At the same time, the electric energy is used to realize the melting and temperature increase of the molten salt through the high-voltage electromagnetic molten salt heater, which reduces carbon dioxide emissions compared with natural gas salt dissolving, and has a simple heating pipeline and convenient startup compared with the mirror field salt dissolving scheme. Description of the Drawings

[0018] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present utility model. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0019] Figure 1 is a schematic structural diagram of the electric heating salt dissolving device in the present utility model;

[0020] Figure 2 is a schematic structural diagram of the salt dissolving wire basket in the present utility model. Detailed Embodiments

[0021] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] Embodiment 1

[0023] As Figure 1 shown, the present application provides a specific implementation manner of an electric heating salt melting device. The electric heating salt melting device includes a salt melting tank 1, on which a resistance heating tube group for primary salt melting is provided, a molten salt circulation pump 3 for transporting high-temperature liquid molten salt is provided on the salt melting tank 1, and a feeding mechanism for adding granular molten salt and performing jet heat exchange with high-temperature liquid molten salt is provided on the salt melting tank 1 and connected to a high-voltage electromagnetic molten salt heater 5. Specifically, the resistance heating tube group includes a first resistance heating tube 2-1 and a second resistance heating tube 2-2 respectively provided in the salt melting tank 1.

[0024] Among them, a lower partition 1-1 and an upper partition 1-2 are provided in the salt melting tank 1. Specifically, the inner lower partition 1-1 in the salt melting tank 1 isolates the bottom of the salt melting tank 1 to form a solid impurity precipitation area, and the inner upper partition 1-2 in the salt melting tank 1 separates the upper liquid molten salt, which can block the floating impurities remaining during the salt melting process from entering the salt discharging area (the left side of the salt melting tank 1). The melted molten salt flows into the salt discharging area through the gap between the upper partition 1-2 and the lower partition 1-1. When solid molten salt melts, nitrogen oxide gas and solid precipitate magnesium oxide are generated. The gas is collected by a nitrogen oxide gas collection hood 4-5 and then enters a special treatment device for treatment; solid precipitates such as magnesium oxide precipitate in the solid impurity precipitation area of the melting tank and are regularly and quantitatively cleaned through a precipitate discharge port 1-3.

[0025] As a specific implementation, it further includes a precipitate discharge port 1-3 for discharging precipitates and a molten salt discharge port 1-4 for discharging molten salt provided at the bottom of the salt melting tank 1.

[0026] As a specific implementation, it further includes: a high-voltage electromagnetic molten salt heater 5 for heating low-temperature molten salt (heating a certain flow rate of low-temperature molten salt into high-temperature molten salt). The input end of the high-voltage electromagnetic molten salt heater 5 is connected to the molten salt circulation pump 3 through an input pipeline, and the output end of the high-voltage electromagnetic molten salt heater 5 is connected to the feeding mechanism through an output pipeline. The high-voltage electromagnetic heater 5 needs to be preheated before starting. In addition, the high-voltage electromagnetic molten salt heater 5 can be replaced by other forms of electric heating equipment such as a resistance heater or an electrode heater.

[0027] As a specific implementation, the feeding mechanism includes a feeding box 4-1, a belt feeder 4-2 arranged on the feeding box 4-1 for transporting materials (granular molten salt), a salt melting basket 4-3 arranged on the salt melting tank 1 for realizing jet heat exchange between granular molten salt and high-temperature liquid molten salt, a feeding funnel 4-4 arranged on the salt melting basket 4-3 for guiding and transporting materials from the belt feeder 4-2 to the salt melting basket 4-3, and a collecting hood 4-5 arranged on the feeding funnel 4-4 for collecting nitrogen oxide gases.

[0028] To better realize the jet heat exchange between granular molten salt and high-temperature liquid molten salt, it further includes: a high-temperature molten salt nozzle 11 arranged at the end of the output pipeline of the high-voltage electromagnetic molten salt heater.

[0029] As Figure 2 shown, specifically, the salt melting basket 4-3 includes a standby working position 4-3-1-1, a working position 4-3-1-2, and a cleaning position 4-3-1-3 arranged in sequence within a fixed beam 4-3-1. Among them, in the initial stage, a standby basket 4-3-2 is arranged at the standby working position 4-3-1-1, and a working basket 4-3-3 is arranged at the working position 4-3-1-2. Among them, when the working basket 4-3-3 is located at the working position 4-3-1-2, the granular molten salt and the high-temperature liquid molten salt perform jet heat exchange, and after melting, it flows into the salt melting tank 1 from the working basket 4-3-3. Among them, insoluble impurities will accumulate in the working basket 4-3-3. When the accumulation reaches a certain amount, the standby basket 4-3-2 is horizontally moved to the working position 4-3-1-2, and the working basket 4-3-3 with accumulated undissolved impurities will be pushed to the cleaning position 4-3-1-3. After taking out the working basket 4-3-3, cleaning the impurities and then putting it back to the standby working position 4-3-1-1, and performing reciprocating cyclic operation, the salt melting basket 4-3 can be quickly cleaned.

[0030] As a specific embodiment, it further includes: a mixing temperature measuring thermocouple 6 provided on the salt melting tank 1 for measuring the temperature of the low-temperature molten salt formed after the high-temperature molten salt and the particulate molten salt are mixed and melted to control the feeding speed of the solid particulate salt, a float level gauge 7 for measuring the liquid level value, an outlet salt temperature measuring thermocouple 8 for measuring the temperature of the molten salt after mixing evenly and stably (the outlet salt temperature measuring thermocouple 8 is close to the outlet molten salt pump 10, and measures the temperature of the molten salt after mixing evenly and stably. If the outlet temperature requirement is met, it can be output to the molten salt tank through the outlet molten salt pump 10), and a hot salt temperature measuring thermocouple 9 on the high-voltage electromagnetic molten salt heater 5 for measuring the temperature of the molten salt output by the high-voltage electromagnetic molten salt heater 5 (measuring the temperature of the molten salt at the outlet of the high-voltage electromagnetic molten salt heater 5, and judging whether the flow rate of the circulation pump 3 is appropriate according to the outlet temperature. The outlet temperature is initially set to 550 °C. If the outlet temperature is low, the molten salt circulation flow rate is reduced and the outlet temperature is increased until the outlet temperature is close to 550 °C).

[0031] As a specific embodiment, it further includes: an outlet molten salt pump 10 provided on the salt melting tank 1 for outputting molten salt to the molten salt tank.

[0032] Embodiment 2

[0033] As Figure 1 As shown, in this embodiment, based on the electric heating salt melting device in Embodiment 1, a specific implementation manner is provided. Taking a 10 MW salt melting device as an example, during the initial salt melting, first add granular solid molten salt into the salt melting tank and spread it evenly on the bottom layer with a height of about 0.5 m, completely covering the first resistance heating tube 2-1 and the second resistance heating tube 2-2. The first batch of added molten salt is completely melted, and then salt is continuously added, with a total of about 6 t of salt added until the liquid level of the molten salt reaches the lowest circulation liquid level, and then continue to heat up to about 320 °C. The heating power of the first resistance heating tube 2-1 and the second resistance heating tube 2-2 is designed according to 150 kW, and it is expected that the initial salt melting process will take 30 h. Three hours before the end of the initial salt melting, start the high-voltage electromagnetic molten salt heater 5 and enter the low-power preheating mode. At the same time, start the electric tracing of the molten salt pipeline connected to the high-voltage electromagnetic molten salt heater 5 and preheat it to 320 °C.

[0034] After the cyclic heating is available, cut off the first resistance heating tube 2-1 and the second resistance heating tube 2-2, turn on the molten salt circulation pump 3. There is about 1.5 t of salt in total in the high-voltage electromagnetic molten salt heater 5 and the pipeline. The liquid level of the molten salt drops to 0.4 m, and the bottom inlet of the molten salt circulation pump 3 is 0.2 m below the liquid level, which can ensure the stable operation of the molten salt circulation.

[0035] The inlet molten salt temperature of the 10MW electromagnetic molten salt heater is 320°C, the outlet temperature is 550°C, and the flow rate is about 90t / h. Before starting the electromagnetic molten salt heater, first ensure that the circulating flow rate is greater than 90t / h. According to the temperature display of the mixing temperature measuring thermocouple 6, slowly adjust the frequency of the molten salt circulation pump 3 to achieve flow regulation until the heater outlet temperature is stable at about 550°C. At the same time, start the feeding mechanism so that the granular molten salt enters the salt melting basket 4-3 through the feeding funnel 4-4. The aperture of the basket is designed according to the size of the molten salt particles so that most of the granular molten salt cannot pass through, which is the best. The 550°C high-temperature molten salt impacts and sprays on the granular molten salt through the high-temperature molten salt nozzle 11. The impact spraying has excellent heat exchange effect. After mixing and melting, it passes through the salt melting basket 4-3 and enters the salt melting tank 1. Run according to this process until the molten salt level in the salt melting tank is close to the highest salt outlet level, and then start the salt outlet molten salt pump 10.

[0036] Adjust the salt adding speed of the feeding device according to the temperature of the mixing temperature measuring thermocouple 6 to make the mixing temperature measuring thermocouple 6 stable at about 320°C. Control the start and flow rate of the salt outlet molten salt pump 10 according to the liquid level value measured by the float liquid level gauge 7. When the liquid level is higher than the highest salt outlet level, increase the flow rate of the salt outlet molten salt pump 10. When the liquid level is lower than the lowest salt outlet level, decrease the flow rate of the salt outlet molten salt pump 10 to control the liquid level between the highest and lowest salt outlet levels.

[0037] The lower partition 1-1 in the salt melting tank isolates the bottom of the salt melting tank to form a solid impurity precipitation area. The upper partition 1-2 separates the upper liquid molten salt, which can prevent the residual floating impurities during the salt melting process from entering the salt outlet area. The melted molten salt flows into the salt outlet area through the gap between the upper and lower partitions. When the solid molten salt melts, nitrogen oxide gas and solid precipitate magnesium oxide will be generated. The gas is collected by the collection hood 4-5 and then enters the special treatment device for treatment; solid precipitates such as magnesium oxide precipitate in the solid impurity precipitation area of the melting tank and are regularly and quantitatively cleaned through the precipitate discharge port 1-3.

[0038] When shutting down, first stop the operation of the electromagnetic molten salt heater 5 and the feeding mechanism, and then stop the molten salt circulation pump 3. When the liquid level in the salt melting tank 1 is lower than the lowest salt outlet level, stop the salt outlet molten salt pump 10. The remaining molten salt passes through the molten salt discharge port 1-4. If the temperature in the tank is too low and there is a risk of molten salt condensation, the resistance heating can be started to cooperate with the salt discharge.

[0039] The electric heating salt melting device of the present utility model uses electric energy to achieve the melting and temperature increase of molten salt through an electric heater, reducing carbon dioxide emissions compared to natural gas salt melting, and having a simpler heating pipeline and more convenient startup compared to the mirror field salt melting scheme; the molten salt melting adopts jet flow heat transfer to strengthen convective heat transfer by using the impact of the fluid; a wire basket that is convenient for replacement and cleaning is provided in the heat exchange melting area to prevent solidified molten salt from entering the melted liquid molten salt and affecting the salt melting efficiency; it can also prevent insoluble large impurities from entering the molten salt pump and blocking the pipeline; in addition, a combined baffle is provided inside the salt melting tank, dividing the inside of the tank into two areas, namely a salt melting area (on the right side of the salt melting tank 1) and a salt outlet area (on the left side of the salt melting tank 1). The combined baffle is divided into upper and lower parts, namely the lower partition 1-1 and the upper partition 1-2. The upper partition 1-2 prevents floating impurities from entering the salt outlet area, and the lower partition 1-1 prevents bottom sediment impurities from entering the salt outlet area.

[0040] Obviously, those skilled in the art can make various modifications and variations to the present utility model without departing from the spirit and scope of the present utility model. Thus, if these modifications and variations of the present utility model fall within the scope of the claims of the present utility model and their equivalent technologies, the present utility model is also intended to include these modifications and variations.

Claims

1. An electric heating salting device, comprising a salting tank (1), characterized in that: The salt-making tank (1) is provided with a resistance heating tube group for initial salt-making, the salt-making tank (1) is provided with a molten salt circulation pump (3) for conveying liquid molten salt, and the salt-making tank (1) is provided with a feeding mechanism for adding granular molten salt; It also includes: a high-pressure electromagnetic molten salt heater (5) for reheating the low-temperature molten salt; the input end of the high-pressure electromagnetic molten salt heater (5) is connected to the molten salt circulation pump (3) through an input pipeline, and the output end of the high-pressure electromagnetic molten salt heater (5) is connected to a feeding mechanism through an output pipeline; The feeding mechanism comprises: a feeding box (4-1), a belt feeding machine (4-2) arranged on the feeding box (4-1) for conveying materials, a salt-forming net basket (4-3) arranged on the salt-forming tank (1) for realizing jet heat exchange between granular molten salt and high-temperature liquid molten salt, a feeding funnel (4-4) arranged on the salt-forming net basket (4-3) for guiding and conveying materials from the belt feeding machine (4-2) to the salt-forming net basket (4-3), and a collecting hood (4-5) arranged on the feeding funnel (4-4) for collecting nitrogen oxide gas; The salt-making net basket (4-3) comprises a fixed beam (4-3-1) and a standby net basket (4-3-2) and a working net basket (4-3-3) which are slidably arranged on the fixed beam (4-3-1).

2. The electric heating salt-making device according to claim 1, characterized in that: A standby station (4-3-1-1), a working station (4-3-1-2) and a cleaning station (4-3-1-3) are sequentially arranged on the fixed beam (4-3-1); in an initial stage, the standby net basket (4-3-2) is arranged on the standby station (4-3-1-1), and the working net basket (4-3-3) is arranged on the working station (4-3-1-2).

3. The electric heating salt-making device according to claim 1, characterized in that: Also includes: A combined partition plate is arranged in the salt-forming tank (1) for distinguishing a salt-forming area from a salt-discharging area, the combined partition plate comprising a lower partition plate (1-1) arranged at the bottom of the salt-forming tank (1) for isolating a solid impurity precipitation area, and an upper partition plate (1-2) arranged at the top of the salt-forming tank (1) for isolating an upper liquid molten salt.

4. The electric heating salt-making device according to claim 1, characterized in that: Also includes: The salt-forming tank (1) is provided with a mixed temperature measuring thermocouple (6) for measuring the temperature of low-temperature liquid molten salt formed after the high-temperature molten salt and the granular molten salt are mixed and melted to control the feeding speed of the solid granular salt; the salt-forming tank (1) is provided with a float liquid level meter (7) for measuring the liquid level value; the salt-forming tank (1) is provided with a salt outlet temperature measuring thermocouple (8) for measuring the temperature of the molten salt after the mixture is uniformly and stably mixed; and the high-pressure electromagnetic molten salt heater (5) is provided with a hot salt temperature measuring thermocouple (9) for measuring the temperature of the molten salt output by the high-pressure electromagnetic molten salt heater (5).

5. The electric heating salt-making device according to claim 1, characterized in that: Also includes: The salt tank (1) is provided with a molten salt discharge pump (10) for discharging molten salt to the molten salt tank.

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