Device and method for heating molten salt

Abstract

The present invention relates to a device and method for heating molten salt. The device comprises: a salt solution tank; at least one group of molten salt electrodes, each group of molten salt electrodes comprises a plurality of molten salt electrode boxes; at least one group of electrode insulation pipes; and a power supply device, which comprises multi-phase alternating current and the number of phases of the multi-phase alternating current is the same as the number of the plurality of molten salt electrode boxes, and each phase of the multi-phase alternating current of the power supply device is electrically connected to a corresponding one of the plurality of molten salt electrode boxes.

Description

Technical Field

[0001] The present invention relates to the field of molten salt heating, and more particularly to a device and method for heating molten salt using electrodes. Background Art

[0002] Molten salt is a heat transfer and heat storage medium with extremely good fluidity. It has the characteristics of low vapor pressure, wide applicable temperature range, stable chemical properties, large heat capacity, non-combustibility, low cost and easy preparation. It has broad application prospects in the field of heat storage, especially in the field of medium and high temperature heat storage.

[0003] At present, molten salt electric heating mostly adopts indirect heating by heat conduction using electric heating rods. The higher the working temperature of the heating wire, the shorter the service life. The better the insulation between the heating wire and the outer sleeve, the worse the heat transfer. Therefore, it is not conducive to the application of high-temperature and high-power electric heating of molten salt.

[0004] The electrode heating method is that electric current directly passes through molten salt to generate heat. The molten salt itself is a heating element, and there is no problem caused by indirect heating. However, due to the high electrical conductivity of molten salt, previous electrode heating technical means cannot control the current density on the electrode surface within a reasonable range, and it is difficult to avoid corrosion of the electrode material and electrolysis of the molten salt.

[0005] The information disclosed in this Background of the Invention section is only intended to enhance understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The purpose of the present invention is to provide a device and method for heating molten salt using electrodes. The present invention can successfully solve the technical problem of realizing low current density operation of electrodes in various ion conductors at any voltage, and is not only applicable to electrode heating of molten salt, but also to electrode heating of other ion conductors with fluidity. By using the present invention, molten salt electric heating equipment of various power sizes suitable for various voltage ranges can be designed and manufactured.

[0007] To achieve the above-mentioned object, the present invention provides a device for heating molten salt, which comprises: a salt solution tank; at least one group of molten salt electrodes, each group of molten salt electrodes comprises a plurality of molten salt electrode boxes; at least one group of electrode insulating pipes, the number of pipes in each group of electrode insulating pipes is the same as the number of a plurality of molten salt electrode boxes in each group of molten salt electrodes, a first end of the electrode insulating pipe is fluidically connected to the salt solution tank, a second end of the electrode insulating pipe is fluidically connected to a corresponding one of the plurality of molten salt electrode boxes, and the first end of the electrode insulating pipe is arranged at a higher position than the second end of the electrode insulating pipe so that the molten salt can flow through the electrode insulating pipe; and a power supply device, which comprises multi-phase alternating current and the number of phases of the multi-phase alternating current is the same as the number of the plurality of molten salt electrode boxes, and each phase of the multi-phase alternating current of the power supply device is electrically connected to a corresponding one of the plurality of molten salt electrode boxes.

[0008] In the above-mentioned device for heating molten salt, the plurality of molten salt electrode boxes of each group of molten salt electrodes may be three, the multi-phase alternating current may be three-phase alternating current, and each group of electrode insulating pipes may include three electrode insulating pipes.

[0009] In the above-mentioned device for heating molten salt, the molten salt flowing in each pipe in each set of electrode insulating pipes generates resistors with the same resistance value.

[0010] In the above-mentioned device for heating molten salt, the electrode insulating pipes are arranged at a specific angle with the horizontal plane, the angles of each pipe in each group of electrode insulating pipes relative to the horizontal plane are the same, the lengths of each pipe in each group of electrode insulating pipes are the same, and the flow cross-sectional areas of each pipe in each group of electrode insulating pipes are the same, so as to ensure that the flow rates of each pipe in each group of electrode insulating pipes are the same.

[0011] In the above-mentioned device for heating molten salt, the first end of the electrode insulating pipe is arranged inside the salt solution tank, near the bottom of the salt solution tank, and the electrode insulating pipe passes through the side wall of the salt solution tank.

[0012] In the above-mentioned device for heating molten salt, the first end of the electrode insulation pipe is connected to the bottom of the salt solution tank.

[0013] In the above-mentioned device for heating molten salt, the electrode insulating pipe is arranged vertically.

[0014] In the above-mentioned device for heating molten salt, the molten salt electrode box can be made of corrosion-resistant and high-temperature resistant metal materials to form a container with a specific inner surface area, and has an electrode insulating pipe connection port, and the second end of the electrode insulating pipe can be fluidically connected to the electrode insulating pipe connection port of the corresponding molten salt electrode box; the outer wall of the molten salt electrode box can be connected to a conductive copper busbar.

[0015] According to the device for heating molten salt of the present invention, it further comprises: at least one preheater, which is arranged in the salt solution tank and is used to heat the salt in the salt solution tank; at least one group of flow control valves, which are arranged on the electrode insulating pipe between the salt solution tank and the molten salt electrode, the number of the flow control valves is equal to the number of the electrode insulating pipes, and the flow control valves are arranged in the corresponding electrode insulating pipes; and a controller, which is electrically connected to the preheater, the power supply device and the flow control valve to control the opening or closing of the preheater, the power supply or power off of the power supply device and the opening degree of the flow control valve.

[0016] The present invention further provides a method for heating molten salt, which uses the above-mentioned device for heating molten salt, and the method comprises the following steps: using a preheater to heat the salt in a salt solution tank, and heating the salt to a molten state capable of flowing; after the salt is in a molten state capable of flowing, closing the preheater; adjusting a flow control valve to allow the molten salt in the salt solution tank to flow to the molten salt electrode through an electrode insulating pipe; after the molten salt flowing through the electrode insulating pipe enters the molten salt electrode box, turning on a power supply device to supply power, thereby heating the molten salt.

[0017] Through the above-mentioned exemplary embodiments, the advantages of the present invention are: the electrode insulation pipe and the molten salt electrode can be designed according to any power supply voltage and heating power to form a suitable molten salt heating device. The device and method of electrode-type heating of molten salt of the present invention use the molten salt itself as a heating element, without heat conduction loss and no risk of dry burning of the heating wire. The most important thing is that the present invention successfully solves the technical problem of realizing low current density operation of electrodes in various high conductivity ion conductors at any working voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of an apparatus for heating molten salt according to an exemplary embodiment of the present invention.

[0019] Figure 2 is a perspective view of an apparatus for heating molten salt according to an exemplary embodiment of the present invention.

[0020] Figure 3 is a schematic diagram of an apparatus for heating molten salt according to another exemplary embodiment of the present invention.

[0021] It should be understood that the drawings are not drawn to scale, but show various features that illustrate the basic principles of the invention in a slightly simplified manner. In the drawings of the present invention, the same reference numerals represent the same or equivalent parts of the present invention. DETAILED DESCRIPTION

[0022] Reference will be made in detail to various embodiments of the present invention, examples of which are shown in the accompanying drawings and are described below. Although the present invention will be described in conjunction with exemplary embodiments of the present invention, it will be understood that this specification is not intended to limit the present invention to those exemplary embodiments. On the contrary, the present invention is intended to cover not only the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments included within the spirit and scope of the present invention as defined in the appended claims.

[0023] Hereinafter, various exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0024] Figure 1 and Figure 2 An apparatus 100 for heating molten salt according to an exemplary embodiment of the present invention is shown, which may include:

[0025] A salt solution tank 10, which is made of a high temperature resistant and corrosion resistant material and is grounded, and at least one preheater 11 is arranged inside the salt solution tank 10;

[0026] At least one group of molten salt electrodes 20, each group of molten salt electrodes 20 comprising a plurality of molten salt electrode boxes;

[0027] At least one group of electrode insulating pipes 30, the number of pipes in each group of electrode insulating pipes is the same as the number of multiple molten salt electrode boxes in each group of molten salt electrodes, the first end of the electrode insulating pipe 30 is fluidically connected to the salt solution box 10, the second end of the electrode insulating pipe 30 is fluidically connected to a corresponding molten salt electrode box 20 in the multiple molten salt electrode boxes, and the first end of the electrode insulating pipe 30 is arranged at a higher position than the second end of the electrode insulating pipe 30, so that the molten salt can flow through the electrode insulating pipe 30;

[0028] A power supply device 40, which includes a multi-phase alternating current, and the number of phases of the multi-phase alternating current is the same as the number of the plurality of molten salt electrode boxes, each phase of the multi-phase alternating current of the power supply device 40 is electrically connected to a corresponding one of the plurality of molten salt electrode boxes;

[0029] At least one preheater 11 is disposed in the salt solution tank 10. Figure 1 In the embodiment shown, the position where the preheater 11 is arranged is only schematic. In a specific implementation, the preheater 11 can be arranged near the middle of the bottom of the salt solution tank 10 and near the electrode insulating pipe 30 to preheat the salt in the salt solution tank 10 and the salt in the electrode insulating pipe 30.

[0030] At least one set of flow control valves 12, which are arranged on the electrode insulation pipes between the salt solution tank 10 and the molten salt electrode 20, the number of the flow control valves is equal to the number of the electrode insulation pipes, and the flow control valves are arranged in the corresponding electrode insulation pipes to control the flow of molten salt in the electrode insulation pipes; and

[0031] The controller 50 is electrically connected to the preheater 11 , the power supply device 40 and the flow control valve 12 to control the opening or closing of the preheater 11 , the power supply or power off of the power supply device 40 and the opening degree of the flow control valve 12 .

[0032] Specifically, in the present exemplary embodiment, the plurality of molten salt electrode boxes of each group of molten salt electrodes 20 is three (in Figure 2 The multiphase alternating current is a three-phase alternating current (denoted by L1, L2, L3), and each set of electrode insulating pipes 30 includes three electrode insulating pipes (in Figure 2 31, 32, 33 are used in the figure to represent respectively). Specifically, each phase L1, L2, L3 of the three-phase alternating current is electrically connected to three molten salt electrode boxes 21, 22, 23 respectively. It can be understood by those skilled in the art that the three-phase alternating current is only an example, and alternating current with more or fewer phases is also feasible, for example, two-phase alternating current is also feasible.

[0033] exist Figure 2 In the illustrated embodiment, only one group of molten salt electrodes 20 is shown, but those skilled in the art will appreciate that two, three or more groups of molten salt electrodes 20 may be provided, and each group of molten salt electrodes 20 includes a plurality of molten salt electrode boxes (illustrated as each group of molten salt electrodes 20 includes three molten salt electrode boxes 21, 22, 23). Accordingly, taking three-phase alternating current as an example, in the case of three groups of molten salt electrodes 20, the L1 phase of the three-phase alternating current is electrically connected to the first molten salt electrode box 21 of each group of molten salt electrodes 20, the L2 phase of the three-phase alternating current is electrically connected to the second molten salt electrode box 22 of each group of molten salt electrodes 20, and the L3 phase of the three-phase alternating current is electrically connected to the third molten salt electrode box 23 of each group of molten salt electrodes 20. Furthermore, Figure 2 Only one set of electrode insulating pipes 30 is shown, that is, one set of electrode insulating pipes 30 is provided for one set of molten salt electrodes 20. However, those skilled in the art will appreciate that, as required, two or more sets of electrode insulating pipes 30 arranged in parallel may be provided for one set of molten salt electrodes 20.

[0034] Specifically, in the present exemplary embodiment, the molten salt flowing in each pipe in each group of electrode insulating pipes 30 generates the same resistance value, that is, the resistance values ​​generated by the molten salt flowing in each electrode insulating pipe 31, 32, 33 are the same as each other.

[0035] In order to make the resistance values ​​generated by the molten salt flowing in each electrode insulating pipe 31, 32, 33 the same, the electrode insulating pipe can have a cross-section of a circular, elliptical, rectangular, hexagonal or other closed shape, each insulating pipe is a complete pipe or is composed of multiple short pipes, and each group of electrode insulating pipes has the same flow cross-sectional area and the same length, so as to ensure that each pipe of each group of electrode insulating pipes has the same resistance value after being filled with molten salt liquid. Further, the electrode insulating pipe is inclined at a specific angle to the horizontal plane to ensure that the molten salt flowing by gravity has enough flow to take out all the heat, and the angles of each pipe in each group of electrode insulating pipes relative to the horizontal plane are the same, so as to ensure that each group of electrode insulating pipes has the same flow cross-sectional area and the same length, so as to ensure that each pipe of each group of electrode insulating pipes has the same resistance value after being filled with molten salt liquid.

[0036] The present invention utilizes the principle of thermal convection. Thermal convection is caused by uneven pressure or density in the fluid due to uneven temperature, which leads to circulating flow. The density of molten salt is inversely proportional to temperature. The higher the temperature of the molten salt, the lower the density. When the molten salt in the molten salt electrode is heated, its density decreases, and the molten salt with a relatively low temperature in the salt solution tank will flow into the molten salt electrode through the electrode insulation pipe due to gravity due to its relatively high density, and then be heated in the molten salt electrode. The heated high-temperature molten salt will be "squeezed" out of the molten salt electrode by the low-temperature molten salt with a larger density that flows into the molten salt electrode due to its decreased density, and rise through the electrode insulation pipe into the salt solution tank, thereby forming convection motion. The convection motion will increase with the increase of the temperature difference between the molten salt electrode and the salt solution tank, and decrease with the decrease of the temperature difference.

[0037] exist Figure 2 In the illustrated embodiment, the first end of the electrode insulating tube 30 is disposed inside the saline tank 10 and near the bottom of the saline tank, and the electrode insulating tube 30 passes through the side wall of the saline tank 10 .

[0038] In an exemplary embodiment of the present invention, the molten salt electrode boxes 21, 22, and 23 are containers made of corrosion-resistant and high-temperature-resistant metal materials with a specific inner surface area, and have an electrode insulation pipe connection port, and the second end of the electrode insulation pipe is fluidically connected to the electrode insulation pipe connection port of the corresponding molten salt electrode box. Further, the outer wall of the molten salt electrode box is connected with a conductive copper busbar (not shown).

[0039] Figure 3 1 is a schematic diagram of an apparatus for heating molten salt according to another exemplary embodiment of the present invention. The first end of the electrode insulating pipe 30 is connected to the bottom of the salt solution tank 10, and the electrode insulating pipe 30 is inclined at a specific angle to the horizontal plane or vertically arranged. Figure 3In the embodiment, the electrode insulating pipe 30 is vertically arranged relative to the horizontal plane. It is ensured that each group of electrode insulating pipes has the same flow cross-sectional area and the same length, so as to ensure that each pipe of each group of electrode insulating pipes has the same resistance value after being filled with molten salt liquid. In this exemplary embodiment, flow control valves 12a, 12b and 12c are respectively arranged on the electrode insulating pipes 31, 32 and 33, and the flow control valves 12a, 12b and 12c are located on the electrode insulating pipe 30 between the salt solution tank 10 and the molten salt electrode 20, near the position of the outlet of the salt solution tank 10.

[0040] The following is a specific description of a method for heating molten salt using the above-mentioned device for heating molten salt, the method comprising the following steps: using a preheater 11 to heat the salt in the salt solution tank 10, and heating the salt to a molten state capable of flowing; after the salt is in a molten state capable of flowing, closing the preheater 11; opening the flow control valve 12, so that the molten salt in the salt solution tank 10 flows to the molten salt electrode 20 through the electrode insulating pipe 30; after the molten salt flowing through the electrode insulating pipe 30 enters the molten salt electrode box 20, turning on the power supply device 40 to supply power, thereby heating the molten salt.

[0041] By the above-mentioned method of heating molten salt, molten salt flows from the salt solution tank 10 into the molten salt electrode box 20 through the electrode insulation pipe 30 by gravity, and the power supply device 40 is turned on to supply power, so that the molten salt is heated, and then the density of the high-temperature molten salt heated in the molten salt electrode box 20 is reduced, which is less than the density of the low-temperature molten salt in the salt solution tank 10. The salt solution tank 10 and the molten salt electrode box 20 are fluidly connected through the electrode insulation pipe 30, and the high-temperature molten salt and the low-temperature molten salt form thermal convection therein. Specifically, when the density of the molten salt in the molten salt electrode decreases after being heated, and the molten salt with a relatively low temperature in the salt solution tank has a relatively high density, it will flow into the molten salt electrode through the electrode insulation pipe due to gravity, and then be heated in the molten salt electrode. The high-temperature molten salt after being heated is "squeezed" out of the molten salt electrode by the low-temperature molten salt with a larger density flowing into the molten salt electrode due to the decrease in density, and rises into the salt solution tank through the electrode insulation pipe, thereby forming a convection motion. The convection motion will increase with the increase of the temperature difference between the molten salt electrode and the salt solution tank, and decrease with the decrease. During the above circulation, the molten salt in the salt solution tank 10 heats up. When the heating is stopped, the flow control valve 12 is closed and the circulation is stopped.

[0042] The present invention takes three-phase alternating current as an example, and uses electrodes to heat molten salt, which is equivalent to using a star connection of three-phase alternating current. In the star connection, whether the neutral line is connected or not, the current will flow between the phase lines. If the three-phase loads are the same, the vector sum of the three-phase currents is zero, and thus the neutral line current is zero. Therefore, as long as the phase balance between the electrodes is ensured, that is, the molten salt flow rate and flow velocity flowing through the electrodes are the same, and the electrode sizes are the same, the electrodes can heat the molten salt.

[0043] In an exemplary embodiment of the present invention, when heated by the preheater 11, the salt can be heated to 200-275°C to put the salt in a molten state where it can flow, thereby forming the above-mentioned cycle; further, after turning on the power supply device 40, the molten salt can be heated to 300-600°C, or even up to 800°C.

[0044] The molten salt heated by the present invention can be used to provide high-temperature steam for industrial use at different temperatures through a heat exchanger, directly provide high-temperature steam to a power plant turbine, and provide steam at different temperatures for brewing, pharmaceuticals, mining, etc. Furthermore, the present invention can utilize the peak-shaving electricity of a power plant to convert electricity into heat for storage or use. The present invention can also directly utilize the electricity generated by waste clean energy to directly convert it into heat for storage or direct use.

[0045] Through the above-mentioned exemplary embodiments, the advantages of the present invention are: the electrode insulation pipe and the molten salt electrode can be designed according to any power supply voltage and heating power to form a suitable molten salt heating device. The device and method of electrode-type heating of molten salt of the present invention use the molten salt itself as a heating element, without heat conduction loss and no risk of dry burning of the heating wire. The most important thing is that the present invention successfully solves the technical problem of realizing low current density operation of electrodes in various high conductivity ion conductors at any working voltage.

[0046] Finally, in order to more clearly illustrate the present invention, the applicant explains the following with specific examples. The size design of the insulating tube of the present invention is to regard the molten salt flowing through the insulating tube as a cylindrical resistor, whose resistance is R = ρ * L / S, where R is the resistance of the cylindrical resistor, ρ is the conductivity of the molten salt, L is the length of the insulating tube, and S is the inner diameter area of ​​the cross section of the insulating tube. When L / s reaches a certain value, the resistance of the molten salt flowing through the insulating tube can be very large, so after passing through the insulating tube, the molten salt current is very small.

[0047] The above descriptions of the specific exemplary embodiments of the present invention are presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise form disclosed, and it is obvious that many modifications and changes can be made according to the above teachings. The selection and description of the exemplary embodiments are to explain certain principles of the present invention and their practical applications, so that those skilled in the art can make and use various exemplary embodiments of the present invention and their different alternative forms and modified forms. The scope of the present invention is intended to be limited by the appended claims and their equivalents.

Claims

1. A device for heating molten salt, characterized in that: include: Salt tank; At least one group of molten salt electrodes, each group of molten salt electrodes comprising a plurality of molten salt electrode boxes; at least one group of electrode insulating pipes, the number of pipes in each group of electrode insulating pipes is the same as the number of multiple molten salt electrode boxes in each group of molten salt electrodes, the first end of the electrode insulating pipe is fluidically connected to the salt solution box, the second end of the electrode insulating pipe is fluidically connected to a corresponding one of the multiple molten salt electrode boxes, and the first end of the electrode insulating pipe is arranged at a higher position than the second end of the electrode insulating pipe so that molten salt can flow through the electrode insulating pipe; A power supply device, comprising a multi-phase alternating current, wherein the number of phases of the multi-phase alternating current is the same as the number of the plurality of molten salt electrode boxes, each phase of the multi-phase alternating current of the power supply device being electrically connected to a corresponding one of the plurality of molten salt electrode boxes; at least one preheater, which is disposed in the brine tank and is used to heat the salt in the brine tank; At least one set of flow control valves, which are arranged on the electrode insulating pipes between the salt solution tank and the molten salt electrode, the number of the flow control valves is equal to the number of the electrode insulating pipes, and the flow control valves are arranged in the corresponding electrode insulating pipes; as well as a controller electrically connected to the preheater, the power supply device and the flow control valve to control the opening or closing of the preheater, the power supply or power off of the power supply device and the opening degree of the flow control valve; Wherein, each group of molten salt electrodes has three molten salt electrode boxes, the multiphase alternating current is three-phase alternating current, and each group of electrode insulating pipes includes three electrode insulating pipes; The molten salt flowing in each pipe in each set of electrode insulation pipes generates resistors with the same resistance value.

2. The device for heating molten salt according to claim 1, wherein: The electrode insulating pipes are arranged at an angle with the horizontal plane, the angles of the pipes in each group of electrode insulating pipes relative to the horizontal plane are the same, the lengths of the pipes in each group of electrode insulating pipes are the same, and the flow cross-sectional areas of the pipes in each group of electrode insulating pipes are the same, so as to ensure that the flow rates of the pipes in each group of electrode insulating pipes are the same.

3. The device for heating molten salt according to claim 2, wherein: The first end of the electrode insulation pipe is arranged inside the salt solution tank and close to the bottom of the salt solution tank, and the electrode insulation pipe passes through the side wall of the salt solution tank.

4. The device for heating molten salt according to claim 2, wherein: The first end of the electrode insulation pipe is connected to the bottom of the salt solution tank.

5. The device for heating molten salt according to claim 4, wherein: The electrode insulation pipe is arranged vertically.

6. The device for heating molten salt according to claim 1, wherein: The molten salt electrode box is made of corrosion-resistant and high-temperature resistant metal material to form a container with an inner surface area, and has an electrode insulation pipe connection port. The second end fluid of the electrode insulation pipe is connected to the electrode insulation pipe connection port of the corresponding molten salt electrode box; the outer wall of the molten salt electrode box is connected to a conductive copper busbar.

7. A method for heating molten salt, using the device for heating molten salt according to claim 1, the method comprising the following steps: Using a preheater to heat the salt in the salt solution tank and heat the salt to a molten state capable of flowing; After the salt is in a molten state capable of flowing, the preheater is turned off; Adjust the flow control valve to allow the molten salt in the salt solution tank to flow to the molten salt electrode through the electrode insulation pipe; After the molten salt flowing through the electrode insulation pipe enters the molten salt electrode box, the power supply device is turned on to supply power, thereby heating the molten salt.

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