An electrode boiler for heating molten salt

Abstract

The present invention discloses an electrode boiler for heating molten salt, comprising: a shell, formed with a receiving cavity; a low-temperature molten salt distribution header, extending into the receiving cavity and arranged vertically and capable of spraying molten salt in at least one direction; an electrode heating unit, comprising an electrode plate capable of being connected to electricity, the electrode plate being arranged in the receiving cavity along a direction substantially parallel to the low-temperature molten salt distribution header, the electrode plate being capable of connecting and heating the molten salt when the molten salt is sprayed thereon, and being capable of disconnecting and stopping heating when no molten salt is sprayed thereon. The present invention uses molten salt as a conductive medium and a technology and equipment for directly heating the molten salt, which can effectively meet the heating requirements in the field of energy storage applications.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and more specifically, to an electrode boiler for heating molten salt, which provides the possibility of large-scale heat storage of electrically heated molten salt. Background Art

[0002] As the installed power of unstable power sources such as wind power and photovoltaic power generation in my country is increasing, while the installed capacity of coal-fired power generators is limited, the output of unstable and discontinuous power sources in the entire power grid has increased significantly year by year. This situation will firstly pose a great threat to the safe operation of the power grid, and secondly, when the load on the power consumption side increases, the power on the power generation side cannot keep up, resulting in insufficient power supply capacity. The current response measures are to use coal-fired power plants to peak or add a large number of wind power and photovoltaic installations. However, when the installed capacity of wind power and photovoltaic power exceeds the regulation capacity of the power grid, they are forced to abandon wind and photovoltaic power. In order to reduce the phenomenon of abandoning wind and photovoltaic power, people have proposed to absorb the abandoned wind and photovoltaic power through various energy storage methods such as batteries, pumping, and compressed air. However, there are problems with the life and safety of battery energy storage technology, and the energy storage cost is still extremely high, which does not meet the conditions for large-scale application. Pumped storage has a low cost and mature technology, but the construction site is restricted by water resources and geographical conditions, and its promotion and application are limited. Compressed air energy storage is expensive and does not have engineering promotion and application.

[0003] Molten salt energy storage has the advantages of flexible site selection, high heat storage efficiency, and large heat storage capacity. The use of molten salt energy storage can effectively overcome the problems faced by the above-mentioned other energy storage technologies. However, the use of molten salt energy storage requires the use of abandoned wind and solar power sources to heat the molten salt for storage and backup. According to different methods of electric energy conversion, it can be divided into resistance heating, induction heating, arc heating, electron beam heating, infrared heating, and dielectric heating.

[0004] At present, electrode boilers are usually used to heat water / steam. Due to the physical parameters of water vapor and equipment manufacturing, and the fact that the temperature of the heating medium usually does not exceed 250°C, they are usually used in heating systems, resulting in poor economic efficiency in the use of abandoned wind and solar power sources to store heat and regenerate electricity, and their promotion and application are limited. In addition, mechanical seals such as sealing rings and spring washers are usually used between the insulators of the existing jet electrode boiler insulation sleeves. As the operating time increases, the molten salt of this sealing method fails. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes an electrode boiler that can heat molten salt using the electrode method. The use of this technology can effectively solve the problem of low heating temperature of current electrode boilers, and provides a practical technology and equipment for large-scale heat storage of electrically heated molten salt.

[0006] The present invention provides an electrode boiler for heating molten salt, comprising:

[0007] A housing, forming a receiving cavity;

[0008] A low-temperature molten salt distribution header extends into the accommodating cavity, is arranged vertically and is capable of spraying molten salt in at least one direction;

[0009] The electrode heating unit comprises an electrode plate capable of being connected to electricity, wherein the electrode plate is arranged in a receiving cavity along a direction substantially parallel to a low-temperature molten salt distribution header, wherein the electrode plate can be connected and heat the molten salt when the molten salt is sprayed thereon, and can be disconnected and stop heating when no molten salt is sprayed thereon.

[0010] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the input end of the low-temperature molten salt distribution manifold is connected to the molten salt pump and the low-temperature molten salt storage tank through a low-temperature molten salt flow control valve, and the output end of the low-temperature molten salt distribution manifold extends from the bottom of the shell into the accommodating cavity to spray molten salt.

[0011] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the output end of the low-temperature molten salt distribution header has at least one row of nozzles arranged along the length direction, and the at least one row of nozzles can spray molten salt in at least one direction.

[0012] According to an embodiment of the electrode boiler for heating molten salt according to the present invention, the electrode heating unit also includes a high-voltage bushing joint arranged on the shell, and the high-voltage bushing joint has a power access end located outside the shell, an electrode plate access end located inside the shell, and an intermediate connecting section connecting the power access section and the electrode plate access end.

[0013] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the power supply access end of the high-voltage bushing joint is connected to the abandoned wind and solar power source, and the electrode plate is connected to the electrode plate access end of the high-voltage bushing joint.

[0014] According to an embodiment of an electrode boiler for heating molten salt according to the present invention, the electrode plate includes a positive electrode plate and a negative electrode plate and a guide groove separating the positive electrode plate and the negative electrode plate, and the guide groove can receive the molten salt sprayed from the low-temperature molten salt distribution header and connect the positive electrode plate with the negative electrode plate to form a molten salt flow heating path.

[0015] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the middle connecting section of the high-voltage bushing joint includes an electrode introduction end and an insulating bushing arranged outside the electrode introduction end, and the insulating bushing includes an external insulator, an intermediate insulator and an internal insulator; a vent pipe seat for introducing gas inward is also provided on the power supply access end of the high-voltage bushing joint.

[0016] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the electrode boiler further comprises a counter electrode plate disposed below the electrode plate of the electrode heating unit and used to prevent breakdown by discharge, and the counter electrode plate is grounded.

[0017] According to an embodiment of the electrode boiler for heating molten salt of the present invention, a high-temperature molten salt outlet pipe is provided at the bottom of the shell, and the high-temperature molten salt outlet pipe is connected to the high-temperature molten salt storage tank through a high-temperature molten salt liquid level control valve.

[0018] According to an embodiment of the electrode boiler for heating molten salt of the present invention, the shell is also provided with a shell charging pipe seat for introducing internal pressure into the accommodating chamber and a shell venting pipe seat for relieving pressure in the accommodating chamber, and the shell is also provided with a liquid level meter.

[0019] Compared with the prior art, the electrode boiler for heating molten salt of the present invention can effectively solve the problems of slow start-up and low power density of the existing electric boilers. At the same time, it solves the problem of insufficient heating temperature by extending the flow channel, adopts gas voltage stabilization technology to ensure the stability of the molten salt jet path, and uses gas sealing to solve the solidification jamming problem during molten salt operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of an electrode boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0021] Figure 2 A schematic structural diagram of a high-voltage bushing joint in an electrode-type boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0022] Figure 3 A schematic structural diagram of an electrode plate in an electrode boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0023] Description of reference numerals:

[0024] 1-shell, 2-electrode plate, 3-low-temperature molten salt, 4-counter-electrode plate, 5-high-temperature molten salt, 6-high-temperature molten salt outlet pipe, 7-high-temperature molten salt level control valve, 8-low-temperature molten salt flow control valve, 9-nozzle, 10-low-temperature molten salt distribution header, 11-shell charging pipe seat, 12-liquid level gauge, 13-shell venting pipe seat, 14-high-voltage bushing joint, 15-vent pipe seat, 16-external insulator, 17-intermediate insulator, 18-internal insulator, 19-electrode introduction end. DETAILED DESCRIPTION

[0025] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0026] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0027] Molten salt has a very low vapor pressure (about several Pa), and can be heated at high temperature under normal pressure, which makes it possible to scale up and heat electric boilers. At the same time, the technology and equipment for heating molten salt using abandoned wind and abandoned solar power need to meet the requirements of large heating power (tens of MW level), high heating power density, uniform heating temperature, wide load adjustment range, fast load response speed, long service life, and high heating efficiency. Therefore, the present invention adopts the technology and equipment of resistive direct heating of molten salt to meet the heating requirements in the field of energy storage applications.

[0028] Specifically, resistance heating uses the Joule effect of electric current to convert electrical energy into thermal energy. Resistance heating is the most widely used and most mature electric heating method. It is usually divided into direct heating and indirect heating. Direct heating is to directly heat the object to be heated by voltage. When current flows through, the heated object itself acts as a resistor to generate heat. Since the heat is generated in the heated object itself, it is internal heating and has a higher heating efficiency. Indirect resistance heating requires a special heating element, which generates heat energy and then transfers it to the heated object through radiation, convection, conduction and other methods.

[0029] Hereinafter, the electrode boiler for heating molten salt according to the present invention will be described in detail.

[0030] Figure 1 A schematic structural diagram of an electrode boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0031] like Figure 1 As shown, according to an exemplary embodiment of the present invention, the electrode boiler for heating molten salt mainly includes a shell 1, a low-temperature molten salt distribution header 9 and an electrode heating unit. The shell 1 is the main structural component of the boiler and is used to contain molten salt and install other main components. The low-temperature molten salt distribution header 9 is used to input and distribute low-temperature molten salt into the shell. The electrode heating unit uses abandoned wind and solar power or other energy sources to heat the low-temperature molten salt into high-temperature molten salt.

[0032] Specifically, the housing 1 forms a containing chamber having a predetermined volume to contain the molten salt.

[0033] The low-temperature molten salt distribution header 8 extends into the accommodating cavity and is arranged vertically and can spray molten salt in at least one direction. Figure 1As shown, the input end of the low-temperature molten salt distribution manifold 8 is connected to the molten salt pump and the low-temperature molten salt storage tank (not shown) through the low-temperature molten salt flow control valve 8, and the output end of the low-temperature molten salt distribution manifold 8 extends from the bottom of the shell 1 into the accommodating cavity to spray the low-temperature molten salt 3. Preferably, the low-temperature molten salt distribution manifold 8 is an L-shaped structure, and the output end has a certain length and is vertically arranged in the accommodating cavity. Specifically, the amount of low-temperature molten salt entering the low-temperature molten salt distribution manifold 8 and the parameters such as pressure and height can be controlled by the molten salt pump and the low-temperature molten salt capacity control valve 8, thereby realizing the injection control of molten salt at different heights and different amounts.

[0034] Among them, the output end of the low-temperature molten salt distribution manifold 9 has at least one row of nozzles 9 arranged along the length direction, and the at least one row of nozzles can spray molten salt in at least one direction. For example, 2 to 5 rows of nozzles arranged along the length direction can be provided, each row includes 10 to 20 nozzles, different rows of nozzles can spray molten salt in different directions, and different nozzles in each row can spray molten salt at different heights. Specifically, a molten salt pump is used to deliver low-temperature molten salt 3 having a higher melting point than the molten salt into the low-temperature molten salt distribution manifold 10, and the molten salt is input into the containing cavity by spraying out from the low-temperature molten salt distribution manifold 10.

[0035] The electrode heating unit specifically includes an electrode plate 2 that can be connected to electricity, and the electrode plate is arranged in the accommodating cavity along a direction substantially parallel to the low-temperature molten salt distribution header 10. The electrode plate 2 can be connected and heat the molten salt when the molten salt is sprayed thereon, and can be disconnected and stop heating when no molten salt is sprayed thereon. That is, when the low-temperature molten salt 3 is sprayed from the low-temperature molten salt distribution header 10 onto the electrode plate 2 located inside the shell, since the molten salt is a conductor, the sprayed low-temperature molten salt connects the electrode plate and flows through the electrode plate 2 from top to bottom. The low-temperature molten salt 3 is gradually heated to the required temperature by relying on the resistance of the molten salt itself during the flow process, and the heated high-temperature molten salt 5 flows out by its own weight and is sent to the collection tank and other equipment.

[0036] When the low-temperature molten salt distribution header 9 has multiple rows of nozzles spraying in different directions, multiple groups of electrode heating units should be provided correspondingly to achieve efficient heating of the molten salt.

[0037] Figure 2 A schematic structural diagram of a high-voltage bushing joint in an electrode-type boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0038] like Figure 2As shown, the electrode heating unit of the present invention also includes a high-voltage bushing joint 14 arranged on the shell 1, and the high-voltage bushing joint 14 has a power access end located outside the shell 1 and an electrode plate access end located inside the shell 1, and an intermediate connecting section connecting the power access section and the electrode plate access end. Specifically, the intermediate connecting section of the high-voltage bushing joint 14 includes an electrode lead-in end 19 and an insulating bushing arranged outside the electrode lead-in end. Since the high-voltage bushing joint 14 assumes the function of power access, in order to avoid the electrodes being connected through the boiler cylinder, the insulating bushing is required to have a good insulating function. The insulating bushing of the present invention includes an external insulator 16, an intermediate insulator 17 and an internal insulator 18 to achieve high-quality sealing as much as possible.

[0039] Preferably, in order to prevent gas exchange between the inside and outside of the boiler and avoid the problem of easy failure of mechanical seals, the present invention seals the insulating bushing by filling pressurized gas between the insulators. Specifically, a vent pipe seat 15 for introducing gas inward is provided on the power supply access end of the high-voltage bushing joint 14, and the electrode boiler is isolated from the inside and outside by introducing appropriate pressure gas, which plays a further sealing role.

[0040] The power supply access end of the high-voltage bushing joint 14 of the present invention can be connected to the abandoned wind and solar power source, and the electrode plate 2 is connected to the electrode plate access end of the high-voltage bushing joint 14 .

[0041] Figure 3 A schematic structural diagram of an electrode plate in an electrode boiler for heating molten salt according to an exemplary embodiment of the present invention is shown.

[0042] like Figure 3 As shown, according to a preferred embodiment of the present invention, the electrode plate 2 includes a positive plate and a negative plate and a guide groove separating the positive plate and the negative plate, and the guide groove can receive the molten salt sprayed from the low-temperature molten salt distribution header and connect the positive plate with the negative plate to form a molten salt flow heating path. Among them, the setting of the guide groove can extend the time for the low-temperature molten salt to be heated, for example, the guide groove is set to an S-shaped or zigzag shape. The positive plate and the negative plate are not connected at the beginning, but once the molten salt is sprayed to the guide groove of the electrode plate, the molten salt acts as a conductor to connect the positive plate and the negative plate to form a path, and the molten salt itself becomes a resistor and is heated.

[0043] In addition, the electrode boiler may further include a counter electrode plate 4 disposed below the electrode plate 2 of the electrode heating unit and used to prevent breakdown by discharge. The counter electrode plate 4 is grounded to protect the safety of people and equipment.

[0044] A high-temperature molten salt outlet pipe 6 is provided at the bottom of the shell 1, and the high-temperature molten salt outlet pipe 6 is connected to a high-temperature molten salt storage tank (not shown) through a high-temperature molten salt liquid level control valve 7. The liquid level of the high-temperature molten salt 5 in the shell 1 can be adjusted by the high-temperature molten salt liquid level control valve 7, and the liquid level feedforward signal is provided by a liquid level meter 12 arranged on the shell 1.

[0045] The shell 1 of the present invention is also provided with a shell charging pipe seat 11 for introducing internal pressure into the accommodating chamber and a shell venting pipe seat 13 for relieving pressure in the accommodating chamber. In order to ensure that the outlet pressure of the molten salt is constant and the low-temperature molten salt jet meets the design requirements, a certain internal pressure needs to be applied in the shell 1, and the internal pressure is introduced by the shell charging pipe seat 11. When the molten salt in the shell 1 needs to be discharged, the gas source on the shell charging pipe seat 11 is closed and the shell venting pipe seat 13 is connected to the atmosphere.

[0046] In order to ensure that the low-temperature molten salt 3 does not cause thermal shock to the electrode boiler under cold start conditions, the electrode boiler needs to be preheated. The preheating method is to heat the pressurized water in the electrode boiler to 220-260°C, drain the water in the shell, and then add the low-temperature molten salt 3 to heat and increase the temperature.

[0047] The low-temperature molten salt 3 to be heated enters the low-temperature molten salt distribution manifold 10 through the low-temperature molten salt flow control valve 7. The molten salt in the low-temperature molten salt distribution manifold 10 is ejected after reaching a certain liquid level. The low-temperature molten salt 3 forms a passage when flowing through the electrode plate 2. The low-temperature molten salt becomes a resistor and is heated. The liquid level of the low-temperature molten salt 3 in the low-temperature molten salt distribution manifold 10 is adjusted by the low-temperature molten salt flow control valve 8, thereby changing the contact between the low-temperature molten salt 3 and the electrode plate 2 and realizing the adjustment of the electrode boiler power. The heated low-temperature molten salt 3 is collected into the shell 1 along the electrode plate 2 by gravity to become the high-temperature molten salt 5. The liquid level of the high-temperature molten salt 5 in the shell 1 is adjusted and output by the high-temperature molten salt level control valve 7.

[0048] The present invention will be further described below in conjunction with the embodiments.

[0049] Example:

[0050] Taking an electrode boiler with a rated thermal power of 40MW as an example, 300°C low-temperature molten salt 3 is sent to the low-temperature molten salt distribution header 10, and the low-temperature molten salt flow rate is 580kg / s. Three rows of nozzles are arranged on the low-temperature molten salt distribution header, each row has sixteen nozzles 9, the flow rate of each nozzle is 12.08kg / s, the nozzle flow rate is 3m / s, and the radius of each nozzle is 15mm.

[0051] In order to ensure that the high-temperature liquid level in the shell will not be interrupted, the liquid level height in the shell is controlled to be 0.8m and the shell working pressure is 0.1MPa.

[0052] When the electrode boiler is at 50% of the rated power, the flow rate of its low-temperature molten salt is 290kg / s. The liquid level in the distribution manifold is controlled to be sprayed out from the lower eight rows of nozzles*, so that the contact area between the molten salt and the electrode is reduced by half, thereby protecting and maintaining 50% power operation. The power of the molten salt electrode furnace can be steplessly adjusted by the molten salt flow rate.

[0053] In summary, the electrode boiler of the present invention that utilizes the electrode method to heat molten salt can effectively solve the problem of low heating temperature of the current electrode boiler, and provides a practical technology and equipment for large-scale heat storage of electrically heated molten salt; in terms of the insulating sleeve sealing method, the problem of easy failure of mechanical seals can be avoided by filling pressurized gas between the insulators for sealing.

[0054] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. An electrode boiler for heating molten salt, characterized in that: include: A housing, forming a receiving cavity; A low-temperature molten salt distribution header extends into the accommodating cavity, is arranged vertically and is capable of spraying molten salt in at least one direction; An electrode heating unit, comprising an electrode plate capable of being connected to electricity, the electrode plate being arranged in the accommodating cavity along a direction substantially parallel to the low-temperature molten salt distribution header, the electrode plate being capable of being connected and heating the molten salt when the molten salt is sprayed thereon, and being capable of being disconnected and stopping heating when no molten salt is sprayed thereon; The input end of the low-temperature molten salt distribution header is connected to the molten salt pump and the low-temperature molten salt storage tank through a low-temperature molten salt flow control valve, and the output end of the low-temperature molten salt distribution header extends from the bottom of the shell into the accommodating cavity to spray molten salt; The electrode heating unit further comprises a high voltage bushing joint arranged on the shell, wherein the high voltage bushing joint comprises a power supply access end located outside the shell, an electrode plate access end located inside the shell, and an intermediate connection section connecting the power supply access section and the electrode plate access end; The electrode plate comprises a positive electrode plate and a negative electrode plate and a guide groove separating the positive electrode plate and the negative electrode plate, wherein the guide groove can receive the molten salt sprayed by the low-temperature molten salt distribution header and connect the positive electrode plate with the negative electrode plate to form a molten salt flow heating path; The middle connecting section of the high voltage bushing joint includes an electrode introduction end and an insulating bushing arranged outside the electrode introduction end, and the insulating bushing includes an outer insulator, an intermediate insulator and an inner insulator; the power supply access end of the high voltage bushing joint is also provided with a vent pipe seat for introducing gas inwardly; The electrode boiler further includes a counter electrode plate disposed below the electrode plate of the electrode heating unit and used to prevent breakdown by discharge, and the counter electrode plate is grounded.

2. The electrode boiler for heating molten salt according to claim 1, characterized in that: The output end of the low-temperature molten salt distribution header has at least one row of nozzles arranged along the length direction, and the at least one row of nozzles can spray molten salt in at least one direction.

3. The electrode boiler for heating molten salt according to claim 1, characterized in that: The power supply access end of the high-voltage bushing joint is connected to the abandoned wind and solar power source, and the electrode plate is connected to the electrode plate access end of the high-voltage bushing joint.

4. The electrode boiler for heating molten salt according to claim 1, characterized in that: A high-temperature molten salt outlet pipe is provided at the bottom of the shell, and the high-temperature molten salt outlet pipe is connected to the high-temperature molten salt storage tank through a high-temperature molten salt liquid level control valve.

5. The electrode boiler for heating molten salt according to claim 1, characterized in that: The shell is also provided with a shell pressure charging pipe seat for introducing internal pressure into the accommodating chamber and a shell venting pipe seat for relieving pressure in the accommodating chamber. The shell is also provided with a liquid level meter.

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