Molten salt energy storage device and electric furnace waste heat recovery device

Abstract

The utility model provides a fused salt energy storage device and an electric furnace waste heat recovery device, and belongs to the technical field of electric furnace waste heat recovery. A heat storage unit, a heat storage pipeline and a heat release pipeline are arranged between a waste heat boiler and steam utilization equipment; high-parameter steam generated by the waste heat boiler is guided into a coil pipe of the heat storage unit through a boiler steam conveying pipe, heat storage is conducted on the high-parameter steam in a box body through a low-temperature fused salt medium, and steam condensation water serves as waste heat boiler water through a boiler water supply pipe; when heat energy in the heat storage unit is used, condensed water of the steam utilization equipment is conveyed into the coil pipe of the heat storage unit through the condensed water conveying pipe, the high-temperature fused salt medium in the box body exchanges heat with the condensed water in the coil pipe, and formed high-parameter steam is supplied to the steam utilization equipment through the steam conveying pipe. The modularized heat storage structure effectively solves the problems that in an existing double-tank technology, waste heat integration and control are difficult, stability is poor, and the molten salt corrosion leakage risk is high.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of electric furnace waste heat recovery, more specifically, to a molten salt energy storage device and an electric furnace waste heat recovery device. BACKGROUND

[0002] Electric furnace flue gas has a high temperature, which contains a large amount of waste heat resources. The electric furnace flue gas exchanges heat with water through the heat exchange surface of a waste heat boiler, so that the water is evaporated into steam for power generation, heating or other industrial production processes. In recent years, with the development of short process steelmaking technology, the waste heat recovery and utilization technology of electric furnace flue gas has attracted the attention of major steel enterprises, and various electric furnace flue gas waste heat recovery and utilization systems and processes have been designed to improve energy utilization efficiency.

[0003] During the smelting process, the flow, temperature and dust content of the flue gas generated by the electric furnace show periodic fluctuations. Due to the intermittent nature of high-temperature flue gas from the electric furnace, the existing technology usually uses a traditional waste heat boiler combined with a regenerator to recover waste heat resources to ensure a continuous and stable supply of steam. However, the steam produced is only medium or low pressure saturated steam, and the waste heat is not fully utilized.

[0004] With the maturity of molten salt energy storage technology and the commercialization of its industrial chain, molten salt energy storage is gradually being transferred and applied in the process of steel energy transformation from solar thermal power generation, thermal power flexibility modification and other fields. Due to its high energy storage density, good stability and no geographical restrictions, molten salt energy storage has become a reasonable and effective means to improve the utilization efficiency of waste heat resources in the steel industry.

[0005] However, the current application of molten salt energy storage in the steel industry is mainly focused on processes with continuous heat sources, and the technology for recovering electric furnace waste heat is mainly based on a double-tank molten salt heat storage system. From a technical perspective, the intermittent and fluctuating nature of electric furnace flue gas directly affects the efficient use of molten salt heat exchangers. The molten salt system needs to be coordinated with the operation of the electric furnace, which brings certain difficulties to the integration and control of the system. From a safety perspective, the electric furnace flue gas has a high dust content, and long-term contact with the heat exchange equipment and pipelines of the heat storage system in a high-temperature environment poses a risk of molten salt corrosion and leakage. If a fault occurs, it may affect the normal operation of the entire system. Designing a stable and efficient molten salt flue gas heat exchanger is a major technical challenge for this process. In addition, the initial investment and maintenance costs of the double-tank molten salt system are high, which increases the difficulty of commercialization of this technology. SUMMARY

[0006] In view of the above problems, the utility model aims at providing a molten salt energy storage device and electric furnace waste heat recovery device to solve the problems of the existing technology, such as the influence of the intermittent and fluctuation characteristics of the electric furnace flue gas on the double-tank molten salt heat storage system, the difficulty of waste heat integration and control, poor stability, the contact with the high-temperature environment of the electric furnace flue gas with high dust content for a long time, and the risk of molten salt corrosion and leakage.

[0007] The molten salt energy storage device is arranged between a waste heat boiler and a steam utilization equipment, comprising a heat storage unit, a heat storage pipeline and a heat release pipeline.

[0008] The heat storage unit comprises a heat storage module; the heat storage module comprises a box body, and a coil pipe and a molten salt medium arranged inside the box body; a molten salt outlet is arranged at one end of the box body, and a molten salt inlet is arranged at the other end; a molten salt circulating pipe is arranged between the molten salt outlet and the molten salt inlet; a molten salt pump is arranged on the molten salt circulating pipe; first and second reversing three-way pipes are respectively connected to both ends of the coil pipe.

[0009] The heat storage pipeline comprises a boiler steam conveying pipe connected to a steam outlet of the waste heat boiler at one end and a boiler feed water pipe connected to a feed water inlet of the waste heat boiler at one end; the other end of the boiler steam conveying pipe is connected to the first reversing three-way pipe through a first branch pipe; the other end of the boiler feed water pipe is connected to the second reversing three-way pipe through a second branch pipe.

[0010] The heat release pipeline comprises a steam conveying pipe connected to a steam inlet of the steam utilization equipment at one end and a condensate conveying pipe connected to a condensate outlet of the steam utilization equipment at one end; the other end of the steam conveying pipe is connected to the first reversing three-way pipe through a third branch pipe; the other end of the condensate conveying pipe is connected to the second reversing three-way pipe through a fourth branch pipe.

[0011] First, second, third and fourth control valves are respectively arranged on the first, second, third and fourth branch pipes.

[0012] In addition, preferably, the number of the heat storage units is at least two; each of the heat storage units is arranged in parallel between the boiler steam conveying pipe and the boiler feed water pipe and between the steam conveying pipe and the condensate conveying pipe.

[0013] In addition, preferably, the heat storage unit is formed by at least two heat storage modules connected in series; in the series-connected heat storage modules, the ports of the coil pipes of adjacent heat storage modules are connected through a coil pipe connecting pipe, and the external ports of the coil pipes at both ends are respectively connected to the first and second reversing three-way pipes; the coil pipe connecting pipe is arranged outside the box body.

[0014] Further, preferably, in the series of heat storage modules, the molten salt outlet of each heat storage module is connected to the molten salt circulation pipe through a molten salt outlet pipe, and the molten salt inlet of each heat storage module is connected to the molten salt circulation pipe through a molten salt inlet pipe.

[0015] Further, preferably, a drain port is arranged at the steam inlet end of the coil, a drain pipe is connected to the drain port, and the outlet of the drain pipe is arranged outside the box.

[0016] Further, preferably, a molten salt pipe is arranged at the end of the box where the molten salt outlet is arranged.

[0017] Further, preferably, a first check valve is arranged on the boiler feed water pipe.

[0018] Further, preferably, a second check valve is arranged on the steam conveying pipe.

[0019] Further, preferably, the steam utilization equipment is a steam turbine.

[0020] The electric furnace waste heat recovery device provided by the utility model has the molten salt energy storage device arranged between the waste heat boiler and the steam utilization equipment, so that the high-parameter steam generated by the waste heat boiler in the electric furnace smelting process can be introduced into the coil of the heat storage unit through the boiler steam conveying pipe, the heat storage of the high-parameter steam can be completed by the low-temperature molten salt medium in the box, the condensed steam after heat storage can be used as the water for the waste heat boiler, and when the heat energy in the heat storage unit needs to be used, the condensed water generated by the steam utilization equipment can be sent into the coil of the heat storage unit through the condensed water conveying pipe, the high-temperature molten salt medium in the box can be heat-exchanged with the condensed water in the coil, the water can be evaporated into high-parameter steam by absorbing heat, and the high-parameter steam can be supplied to the steam utilization equipment through the steam conveying pipe.

[0021] From the above technical solution, it can be known that the molten salt energy storage device and the electric furnace waste heat recovery device provided by the utility model have the heat storage unit, the heat storage pipeline and the heat release pipeline arranged between the waste heat boiler and the steam utilization equipment, and the molten salt heat storage and heat release are designed in a unit modular structure, in the electric furnace smelting process, the high-parameter steam generated by the waste heat boiler can be introduced into the coil of the heat storage unit through the boiler steam conveying pipe, the heat storage of the high-parameter steam can be completed by the low-temperature molten salt medium in the box, the condensed steam after heat storage can be cooled and condensed and used as the water for the waste heat boiler, when the heat energy in the heat storage unit needs to be used, the condensed water generated by the steam utilization equipment can be sent into the coil of the heat storage unit through the condensed water conveying pipe, the high-temperature molten salt medium in the box can be heat-exchanged with the condensed water in the coil, the water can be evaporated into high-parameter steam by absorbing heat, and the high-parameter steam can be supplied to the steam utilization equipment through the steam conveying pipe. BRIEF DESCRIPTION OF DRAWINGS

[0022] Other objects and results of the present application will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 Structure diagram of a molten salt energy storage device according to an embodiment of the present application;

[0024] Figure 2 Structure diagram of a heat storage unit according to an embodiment of the present application;

[0025] Figure 3 Structure diagram of heat storage modules connected in series according to an embodiment of the present application;

[0026] Figure 4 Structure diagram of a heat storage process of a heat storage module according to an embodiment of the present application;

[0027] Figure 5 Structure diagram of a heat release process of a heat storage module according to an embodiment of the present application;

[0028] Figure 6 Structure diagram of a waste heat recovery device of an electric furnace according to an embodiment of the present application.

[0029] In the drawings, 1 - molten salt energy storage device, 11 - heat storage unit, 111 - heat storage module, 1111 - box body, 1112 - coil pipe, 1113 - molten salt medium, 1114 - molten salt circulation pipe, 1115 - molten salt pump, 1116 - coil pipe connecting pipe, 1117 - molten salt outlet pipe, 1118 - molten salt inlet pipe, 112 - first reversing tee, 113 - second reversing tee, 114 - drain pipe, 115 - salt drain pipe, 121 - boiler steam delivery pipe, 122 - boiler feed water pipe, 123 - first branch pipe, 124 - second branch pipe, 125 - first check valve, 131 - steam delivery pipe, 132 - condensate water delivery pipe, 133 - third branch pipe, 134 - fourth branch pipe, 135 - second check valve, 14 - first control valve, 15 - second control valve, 16 - third control valve, 17 - fourth control valve, 2 - waste heat boiler, 3 - steam utilization equipment, 4 - electric furnace, 5 - settling chamber.

[0030] The same reference numbers in all the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0031] In view of the foregoing, in the prior art, the double-tank molten salt heat storage system is affected by the intermittent and fluctuating characteristics of the electric furnace flue gas, and has the problems of difficult waste heat integration and control, poor stability, long-term contact with the high-temperature environment of the electric furnace flue gas with high dust content, and the risk of molten salt corrosion and leakage. A molten salt energy storage device and an electric furnace waste heat recovery device are provided.

[0032] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0033] In order to illustrate the molten salt energy storage device and the electric furnace waste heat recovery device provided by the present application, Figure 1 The structure of the molten salt energy storage device according to an embodiment of the present application is shown. Figure 2 The structure of the heat storage unit according to an embodiment of the present application is shown. Figure 3 The structure of the heat storage module in series according to an embodiment of the present application is shown. Figure 4 The structure of the heat storage process of the heat storage module according to an embodiment of the present application is shown. Figure 5 The structure of the heat release process of the heat storage module according to an embodiment of the present application is shown. Figure 6 The structure of the electric furnace waste heat recovery device according to an embodiment of the present application is shown.

[0034] As Figures 1 to 6 As shown in the drawings, the molten salt energy storage device 1 provided by the present application is arranged between the waste heat boiler 2 and the steam utilization equipment 3, and includes a heat storage unit 11, a heat storage pipeline and a heat release pipeline. The heat storage unit 11 includes a heat storage module 111. The heat storage module 111 includes a box body 1111, and a coil pipe 1112 and a molten salt medium 1113 arranged inside the box body 1111. A molten salt outlet is arranged at one end of the box body 1111, and a molten salt inlet is arranged at the other end. A molten salt circulating pipe 1114 is arranged between the molten salt outlet and the molten salt inlet, and a molten salt pump 1115 is arranged on the molten salt circulating pipe 1114. First and second reversing three-way pipes 112 and 113 are respectively connected to both ends of the coil pipe 1112.

[0035] The heat storage pipeline includes a boiler steam conveying pipe 121 connected to the steam outlet of the waste heat boiler 2 at one end, and a boiler feed water pipe 122 connected to the feed water inlet of the waste heat boiler 2 at one end. The other end of the boiler steam conveying pipe 121 is connected to the first reversing three-way pipe 112 through a first branch pipe 123. The other end of the boiler feed water pipe 122 is connected to the second reversing three-way pipe 113 through a second branch pipe 124.

[0036] The heat releasing pipeline comprises a steam conveying pipe 131 connected at one end with the steam inlet of the steam utilization device 3 and a condensate conveying pipe 132 connected at one end with the condensate outlet of the steam utilization device 3; the other end of the steam conveying pipe 131 is connected with the first reversing three-way pipe 112 through a third branch pipe 133; the other end of the condensate conveying pipe 132 is connected with the second reversing three-way pipe 113 through a fourth branch pipe 134;

[0037] The first control valve 14, the second control valve 15, the third control valve 16 and the fourth control valve 17 are respectively arranged on the first branch pipe 123, the second branch pipe 124, the third branch pipe 133 and the fourth branch pipe 134.

[0038] By arranging the heat storage unit 11, the heat storage pipeline and the heat releasing pipeline and the molten salt heat storage and heat releasing in a unit modular structure between the waste heat boiler 2 and the steam utilization device 3, during the smelting process of the electric furnace 4, the high-parameter steam generated by the waste heat boiler 2 is introduced into the coil 1112 of the heat storage unit 11 through the boiler steam conveying pipe 121, and the heat storage of the high-parameter steam is completed by the low-temperature molten salt medium 1113 in the box 1111, and the cooled and condensed steam is used as the water for the waste heat boiler 2 through the boiler feed water pipe 122; when the heat energy in the heat storage unit 11 needs to be used, the condensate water generated by the steam utilization device 3 is sent into the coil 1112 of the heat storage unit 11 through the condensate conveying pipe 132, the high-temperature molten salt medium 1113 in the box 1111 exchanges heat with the condensate water in the coil 1112, the water absorbs heat to evaporate into high-parameter steam, and the steam is supplied to the steam utilization device 3 through the steam conveying pipe 131 for reutilization; the modular heat storage structure directly converts into stable and sustainable high-quality steam without affecting the normal production of the electric furnace 4, greatly improves the energy utilization efficiency of the steam utilization device 3, effectively solves the problems of waste heat integration and control difficulty, poor stability and high risk of molten salt corrosion and leakage of the double-tank technology, fully utilizes the advantages of molten salt heat storage, and improves the reliability and flexibility of waste heat utilization.

[0039] During the heat storage of the heat storage unit 11, the third control valve 16 and the fourth control valve 17 are in a closed state, i.e., the steam conveying pipe 131 and the condensate conveying pipe 132 are in a non-flowing state; the first control valve 14 and the second control valve 15 are opened, i.e., the boiler steam conveying pipe 121 and the boiler feed water pipe 122 are in a flowing state; during the heat release of the heat storage unit 11, the third control valve 16 and the fourth control valve 17 are in an open state, i.e., the steam conveying pipe 131 and the condensate conveying pipe 132 are in a flowing state, and the first control valve 14 and the second control valve 15 are closed, i.e., the boiler steam conveying pipe 121 and the boiler feed water pipe 122 are in a non-flowing state. The heat storage and heat release of the heat storage unit 11 are adjusted by the above-mentioned valve control, so that the device has high flexibility.

[0040] The molten salt medium 1113 is preferably but not limited to a binary molten salt (such as NaNO3-KNO3), and the utility model does not make special limitation thereto.

[0041] As a preferred scheme of the utility model, the number of the heat storage units 11 is at least two; each heat storage unit 11 is arranged in parallel between the boiler steam conveying pipe 121 and the boiler feed water pipe 122 and between the steam conveying pipe 131 and the condensate conveying pipe 132.

[0042] Specifically, the heat storage units 11 are independently operated in parallel, and the waste heat storage, heat release and heat exchange processes of the electric furnace 4 are completed by each heat storage unit 11 through the control valve. Finally, the steam temperature and pressure are improved, and the steam utilization equipment 3 is better driven to work.

[0043] It should be noted that the number of the heat storage units 11 can be set according to actual needs, and can be one, two, three (such as Figure 1 as shown), four and the like, and the utility model does not make special setting thereto.

[0044] As a preferred scheme of the utility model, the heat storage unit 11 is formed by at least two heat storage modules 111 in series; in the series-connected heat storage modules 111, the ports of the adjacent coil pipes 1112 of the adjacent heat storage modules 111 are connected through the coil pipe connecting pipe 1116, and the external ports of the coil pipes 1112 at both ends are connected with the first reversing three-way pipe 112 and the second reversing three-way pipe 113 respectively; the coil pipe connecting pipe 1116 is arranged outside the box body 1111.

[0045] Specifically, the adjacent ports of the coil pipes 1112 between the series-connected heat storage modules 111 are connected through the coil pipe connecting pipe 1116, the external ports of the coil pipes 1112 of the heat storage modules 111 at both ends are used for being connected with the first reversing three-way pipe 112 and the second reversing three-way pipe 113 respectively, and the coil pipe connecting pipe 1116 is arranged outside the box body 1111. The coil pipe connecting pipe 1116 can be covered with an outer shell outside the series-connected heat storage modules 111, or can not be covered with an outer shell. When the outer shell is arranged, the coil pipe connecting pipe 1116 is arranged inside the outer shell, and the first reversing three-way pipe 112 and the second reversing three-way pipe 113 are arranged outside the outer shell.

[0046] It should be noted that the number of the heat storage modules 111 can be set according to actual needs, and can be one, two, three, four and the like, and the utility model does not make special setting thereto.

[0047] As a preferred embodiment of the present invention, in the series-connected thermal storage modules 111, the molten salt outlet of each thermal storage module 111 is connected to the molten salt circulation pipe 1114 through the molten salt outlet pipe 1117, and the molten salt inlet of each thermal storage module 111 is connected to the molten salt circulation pipe 1114 through the molten salt inlet pipe 1118.

[0048] Specifically, the thermal storage unit 11 may include only one thermal storage module 111. In this case, the two ends of the molten salt circulation pipe 1114 are connected to the molten salt outlet through the molten salt outlet pipe 1117 and to the molten salt inlet through the molten salt inlet pipe 1118, respectively. The thermal storage unit 11 may also include multiple thermal storage modules 111 connected in series. In this case, the molten salt outlet of each thermal storage module 111 is connected to the molten salt circulation pipe 1114 through the molten salt outlet pipe 1117, and the molten salt inlet of each thermal storage module 111 is connected to the molten salt circulation pipe 1114 through the molten salt inlet pipe 1118, so that the molten salt flows in the thermal storage modules 111 connected in series and undergoes forced convection heat exchange with water or steam in the tank 1111 through the molten salt pump 1115. Each thermal storage module 111 integrates heat storage, heat release and heat exchange.

[0049] As a preferred embodiment of this utility model, a drain outlet is provided at the steam inlet end of the coil 1112; a drain pipe 114 is connected to the drain outlet; and the outlet of the drain pipe 114 is located outside the housing 1111.

[0050] Specifically, when the molten salt energy storage device 1 stops operating, the water inside it is discharged through the drain pipe 114.

[0051] As a preferred embodiment of this utility model, a salt-draining pipe 115 is provided at one end of the housing 1111 where the molten salt outlet is located.

[0052] Specifically, when the molten salt energy storage device 1 stops operating, the molten salt medium 1113 inside it is discharged through the salt-draining pipe 115.

[0053] As a preferred embodiment of this utility model, a first check valve 125 is provided on the boiler feedwater pipe 122.

[0054] As a preferred embodiment of this utility model, a second check valve 135 is provided on the steam conveying pipe 131.

[0055] Specifically, by installing a check valve, backflow of water and steam is prevented.

[0056] As a preferred embodiment of this utility model, the steam utilization device 3 is a steam turbine.

[0057] It should be noted that the steam utilization equipment 3 is preferably, but not limited to, a steam turbine.

[0058] The electric furnace waste heat recovery device provided by the utility model, including steam utilization equipment 3, with the flue gas outlet of electric furnace 4 connects the settlement chamber 5 and with settlement chamber 5 connects the waste heat boiler 2, still including the molten salt energy storage device 1 of the utility model as described above.

[0059] High-temperature flue gas discharged from the electric furnace 4 of steelmaking is first collected through a pipeline, and the collected high-temperature flue gas enters the settlement chamber 5, so that some large-particle dust in the flue gas is naturally settled under the action of gravity, and part of the large-particle impurities is preliminarily removed; the flue gas after pretreatment enters the waste heat boiler 2. Various heat exchange pipelines are arranged in the waste heat boiler 2, and the heat of the flue gas is transferred to the water in the pipelines, so that the water is heated and evaporated to form high-temperature and high-pressure steam. The steam generated from the waste heat boiler 2 can be saturated steam or superheated steam, and the temperature and pressure of the steam can have certain fluctuations. In order to make the steam better for power generation, the molten salt energy storage modular structure design of the molten salt energy storage device 1 of the utility model as described above is used to process the steam, so that the steam can be continuously and stably outputted for the steam utilization equipment 3.

[0060] As can be seen from the above specific embodiments, the molten salt energy storage device and the electric furnace waste heat recovery device provided by the utility model are provided with a heat storage unit, a heat storage pipeline and a heat release pipeline and a molten salt heat storage and heat release unit modular structure design between the waste heat boiler and the steam utilization equipment. In the electric furnace smelting process, the high-parameter steam generated by the waste heat boiler is introduced into the coil of the heat storage unit through the boiler steam conveying pipe, and the heat storage of the high-parameter steam is completed in the box through the low-temperature molten salt medium. The condensed steam after heat storage is cooled and condensed and is used as the water of the waste heat boiler through the boiler feed water pipe. When the heat energy in the heat storage unit needs to be used, the condensed water generated by the steam utilization equipment is sent into the coil of the heat storage unit through the condensed water conveying pipe, the high-temperature molten salt medium in the box exchanges heat with the condensed water in the coil, the water absorbs heat and evaporates to become high-parameter steam, and the steam is supplied to the steam utilization equipment through the steam conveying pipe for reutilization. The modular heat storage structure design directly converts into stable and sustainable high-quality steam without affecting the normal production of the electric furnace, greatly improves the energy utilization efficiency of the steam utilization equipment, effectively solves the problems of waste heat integration and control difficulty, poor stability and high risk of molten salt corrosion and leakage of the double-tank technology, fully utilizes the advantages of molten salt heat storage, and improves the reliability and flexibility of waste heat utilization.

[0061] The molten salt energy storage device and the electric furnace waste heat recovery device according to the utility model are described above with reference to the accompanying drawings in an exemplary manner. However, those skilled in the art should understand that various improvements can be made to the molten salt energy storage device and the electric furnace waste heat recovery device according to the utility model without departing from the content of the utility model. Therefore, the protection scope of the utility model should be determined by the content of the appended claims.

Claims

1. A molten salt energy storage device, characterized by, The molten salt energy storage device is arranged between the waste heat boiler and the steam utilization equipment, comprising a heat storage unit, a heat storage pipeline and a heat release pipeline; wherein, The heat storage unit comprises a heat storage module; the heat storage module comprises a box body, and a coil and a molten salt medium arranged inside the box body; a molten salt outlet is arranged at one end of the box body, a molten salt inlet is arranged at the other end, a molten salt circulation pipe is arranged between the molten salt outlet and the molten salt inlet, and a molten salt pump is arranged on the molten salt circulation pipe; a first reversing tee and a second reversing tee are respectively connected to both ends of the coil; The heat storage pipeline comprises a boiler steam conveying pipe connected to the steam outlet of the waste heat boiler at one end and a boiler water supply pipe connected to the water supply port of the waste heat boiler at one end; the other end of the boiler steam conveying pipe is connected to the first reversing tee through a first branch pipe; the other end of the boiler water supply pipe is connected to the second reversing tee through a second branch pipe; The heat release pipeline comprises a steam conveying pipe connected to the steam inlet of the steam utilization equipment at one end and a condensate conveying pipe connected to the condensate outlet of the steam utilization equipment at one end; the other end of the steam conveying pipe is connected to the first reversing tee through a third branch pipe; the other end of the condensate conveying pipe is connected to the second reversing tee through a fourth branch pipe; First, second, third and fourth control valves are respectively arranged on the first, second, third and fourth branch pipes.

2. The molten salt energy storage device according to claim 1, wherein, The number of heat storage units is at least two; Each heat storage unit is arranged in parallel between the boiler steam conveying pipe and the boiler water supply pipe, and between the steam conveying pipe and the condensate conveying pipe.

3. The molten salt energy storage device according to claim 1, wherein, The heat storage unit is composed of at least two heat storage modules connected in series; In the series-connected heat storage modules, the ports of the coils of adjacent heat storage modules are connected through a coil connecting pipe, and the external ports of the coils at both ends are respectively connected to the first reversing tee and the second reversing tee; the coil connecting pipe is arranged outside the box body.

4. The molten salt energy storage device according to claim 3, wherein, In the series-connected heat storage modules, the molten salt outlet of each heat storage module is connected to the molten salt circulation pipe through a molten salt outlet pipe, and the molten salt inlet of each heat storage module is connected to the molten salt circulation pipe through a molten salt inlet pipe.

5. The molten salt energy storage device according to claim 1, wherein, A drain port is arranged at the steam inlet end of the coil; A drain pipe is connected to the drain port; The water outlet of the drain pipe is arranged outside the box body.

6. The molten salt energy storage device according to claim 1, wherein, A salt drain pipe is arranged at the end of the box body where the molten salt outlet is arranged.

7. The molten salt energy storage device according to claim 1, wherein, A first check valve is arranged on the boiler water supply pipe.

8. The molten salt energy storage device of claim 1, wherein A second check valve is provided on the steam delivery pipe.

9. The molten salt energy storage device of claim 1, wherein The steam utilization device is a steam turbine.

10. An electric furnace waste heat recovery device comprising a steam utilization equipment, a precipitator connected to a flue gas outlet of an electric furnace, and a waste heat boiler connected to the precipitator, characterized by, Also included is a molten salt energy storage device as in any of claims 1-9.

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