Electric heating steam furnace and using method thereof

Abstract

The invention discloses an electric heating steam furnace and a using method thereof. The electric heating steam furnace comprises a heating medium heating part and a shell-and-tube heat exchanger. The heat medium heating part comprises a three-column iron core, a primary winding arranged on the primary side, a secondary pipe set arranged on the secondary side and an external power source connected with the primary winding side. The secondary pipe group comprises three metal pipe sections coated with heat preservation layers and insulating layers; the metal pipe sections are respectively wound on secondary side positions of three iron core columns of the three-column iron core in a winding manner; the heat exchange agent inlets of the metal pipe sections are connected in parallel and then are communicated with the heat exchange agent outlet of the shell-and-tube heat exchanger through the first pipe section; the heat exchange agent outlets of all the metal pipe sections are connected in parallel and then communicate with the heat exchange agent inlet of the shell-and-tube heat exchanger through the second pipe section. The electric heating steam boiler can effectively reduce the generation of scale, thereby reducing the reduction of heat transfer efficiency caused by the scale, and further improving the energy conversion efficiency of the electric heating steam boiler.

Description

Technical Field

[0001] The invention relates to the field of water gasification, and in particular to an electric heating steam furnace and a use method thereof. Background Art

[0002] In the fields of petroleum refining, chemical production, and crude oil mining and exploration, boilers are widely used to heat raw materials, and there are many working conditions that require gas-liquid two-phase mixing and heating. At present, in industrial sites such as refineries and chemical plants that require a large amount of high-temperature steam, steam is mostly vaporized by burning fossil fuels in coal-fired furnaces and gas-fired furnaces to vaporize water.

[0003] As the country's energy structure continues to transform toward non-fossil energy and the proportion of clean energy installed capacity increases significantly, energy consumption in refining and chemical production processes will continue to develop in the direction of low carbonization and electrification in the future.

[0004] Based on the development trend of clean energy, a technical solution has emerged in the prior art to directly heat water with a resistive heater (commonly known as a hot plate) to vaporize water.

[0005] The inventor has found through research that the technology of vaporizing water using a resistive heater in the prior art has at least the following defects:

[0006] During the production process, scale is easily formed on the surface of the heating tube of the resistive heater, which leads to a decrease in heat transfer efficiency and thus lower energy conversion efficiency.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment 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

[0008] The main purpose of the present invention is to improve the energy conversion efficiency of a steam furnace for gasifying water.

[0009] The present invention provides an electrically heated steam furnace, comprising a heat medium heating part and a shell and tube heat exchanger;

[0010] The heat medium heating part includes a three-column iron core, a primary winding arranged on the primary side, a secondary tube group arranged on the secondary side, and an external power supply connected to the primary winding side;

[0011] The secondary tube group includes three metal tube sections covered with a thermal insulation layer and an insulating layer; each of the metal tube sections is respectively wound around the secondary side positions of the three core columns of the three-column core in a winding manner; the heat exchanger inlets of each of the metal tube sections are connected in parallel and communicated with the heat exchanger outlet of the shell and tube heat exchanger through a first tube section; the heat exchanger outlets of each of the metal tube sections are connected in parallel and communicated with the heat exchanger inlet of the shell and tube heat exchanger through a second tube section.

[0012] Preferably, in the present invention, it further comprises: the first pipe section and the second pipe section are grounded and connected respectively.

[0013] Preferably, in the present invention, it further comprises: a ventilation sleeve for heat dissipation is sleeved on the primary side of the heat medium heating unit.

[0014] Preferably, in the present invention, the cross-section of the core column is elliptical.

[0015] Preferably, in the present invention, the heat exchanger inlet of the metal pipe segment is located below the heat exchanger outlet of the metal pipe segment.

[0016] Preferably, in the present invention, a ventilation gap of 3-5 mm is left between the ventilation sleeve and the primary winding.

[0017] Preferably, in the present invention, the heat exchange agent includes heat transfer oil.

[0018] Preferably, in the present invention, the minimum gap between the core column and the secondary tube group is set to 5-10 cm.

[0019] Preferably, the present invention further comprises: the power regulator adjusts the input power of the external power supply to the device by introducing a 4-20 mA signal.

[0020] Preferably, in the present invention, it further comprises: a thermocouple for collecting temperature data is provided on the metal outer wall of the metal pipe section.

[0021] Preferably, in the present invention, the material of the metal pipe segment includes carbon steel or stainless steel.

[0022] In another aspect of the present invention, a method for using an electric heating steam furnace is also provided, which is suitable for the above-mentioned electric heating steam furnace, and the method comprises the steps of:

[0023] Using a star-delta starting method to start the electrically heated steam boiler;

[0024] The step of stopping the operation of the electric heating steam furnace comprises:

[0025] Under the condition that the heat exchange agent, water and cooling air are continuously supplied and circulated, the temperature of the secondary tube group is gradually reduced by reducing the output power of the external power supply;

[0026] When the electric heating steam furnace cools down to a preset safety temperature, turning off the external power supply;

[0027] stopping the circulation of the heat exchange agent;

[0028] Stop the supply of circulating water;

[0029] Stop the cooling air.

[0030] Preferably, the present invention includes: in the star-delta starting method, the holding period of the star power supply stage includes 2-20 minutes.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The electric heating steam furnace in the present invention borrows the principle of induced current generated by the transformer. After the primary winding is connected to the power supply, an induced current can be generated in the metal pipe section wound on the secondary side; in this way, the heat exchanger flowing in the metal pipe section can be heated due to the thermal effect of the current, thereby realizing the energy conversion from electrical energy to thermal energy; then, the heat exchange between the high-temperature heat exchanger and the heated water is realized through the shell and tube heat exchanger, thereby completing the heating and gasification of the water.

[0033] In the present invention, the heat exchanger is first heated by the thermal effect of electric current, and then the high-temperature heat exchanger heats the heated water through a shell and tube heat exchanger, thereby avoiding direct contact between the heating electrical elements (such as heating resistors) and the heated water. Therefore, the generation of scale can be effectively reduced, thereby reducing the decrease in heat transfer efficiency caused by this, and thus improving the energy conversion efficiency.

[0034] In addition, since the electrical components and the heated water are completely isolated in the present invention, the potential safety hazard caused by the failure of the electrical heating components can be effectively reduced, making the electric heating steam boiler safer.

[0035] Furthermore, in the present invention, the input power of the external power supply can be adjusted by providing a power regulator in the power supply, thereby achieving precise adjustment of the heat output of the electric heating steam furnace according to the load requirements under different working conditions.

[0036] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 It is a structural schematic diagram of the electric heating steam furnace described in the present invention;

[0039] Figure 2 It is another structural schematic diagram of the electric heating steam furnace described in the present invention. DETAILED DESCRIPTION

[0040] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0041] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0042] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different orientations of the object in use or operation in addition to the orientation depicted in the figure. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both below and above. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0043] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0044] In order to improve the energy conversion efficiency of the steam boiler, refer to Figure 1 and Figure 2 , an electric heating steam furnace provided by an embodiment of the present invention comprises a heat medium heating part 01 and a shell and tube heat exchanger 02;

[0045] The heat medium heating part 01 includes a three-column iron core 11, a primary winding 12 arranged on the primary side, and a secondary tube group 13 arranged on the secondary side; the secondary tube group 13 includes three metal pipe sections 31 covered with a thermal insulation layer and an insulating layer; each metal pipe section 31 is respectively wound on the secondary side of the three core columns of the three-column iron core 11 in a winding manner; the heat exchanger inlet of each of the metal pipe sections 31 is connected in parallel and communicated with the heat exchanger outlet 21 of the shell and tube heat exchanger 02 through the first pipe section 14; each of the metal pipe sections 31 is connected in parallel and communicated with the heat exchanger inlet 22 of the shell and tube heat exchanger 02 through the second pipe section 15.

[0046] In the embodiment of the present invention, the three metal pipe sections 31 , the first pipe section 14 and the second pipe section 15 in the secondary pipe group 13 are made of conductive metal materials; preferably, the materials may be carbon steel or stainless steel.

[0047] The three metal pipe segments 31 in the embodiment of the present invention are arranged in a manner similar to the secondary winding of a transformer, and are wound around the secondary side of the three-column iron core 11. In practical applications, the specific number of turns of the metal pipe segment 31 can be determined by technicians in this field based on experience according to actual needs, or through a limited number of experiments, and is not specifically limited here.

[0048] The inventive concept of the embodiment of the present invention includes: after the metal pipe segment on the secondary side generates an induced current, the heat exchanger in the metal pipe segment will be heated due to the thermal effect of the current; in view of this, in the embodiment of the present invention, the metal pipe segment 31 needs to be coated with an insulating layer like the secondary winding on the one hand, and on the other hand, it is also necessary to provide a thermal insulation layer to avoid waste of heat energy; therefore, the metal pipe segment 31 of the embodiment of the present invention includes a metal pipe, a thermal insulation layer arranged on the outer wall of the metal pipe, and an insulating layer arranged on the outermost layer.

[0049] In the embodiment of the present invention, a three-column iron core 11 is adopted, so the number of metal pipe segments 31 is also three, which are respectively wound on the three core columns of the three-column iron core 11; the two ends of the metal pipe segment 31, one end is a pipe segment inlet for connecting the cooled heat exchanger, and the other end is a pipe segment outlet for outputting the heated heat exchanger; the pipe segment inlet of the metal pipe segment 31 is connected to the heat exchanger outlet 21 of the shell and tube heat exchanger 02; the pipe segment outlet of the metal pipe segment 31 is connected to the heat exchanger inlet 22 of the shell and tube heat exchanger 02; in this way, when the primary winding 12 is connected to the external power supply, the heat exchanger flowing into the metal pipe segment 31 from the heat exchanger inlet 22 will be heated to become a high-temperature heat exchanger due to the thermal effect of the current, and the high-temperature heat exchanger is transported to the shell and tube heat exchanger 02 through the pipe segment outlet to heat the vaporized water; after the heat exchanger that has undergone heat exchange is cooled, it flows into the metal pipe segment 31 again through the heat exchanger outlet 21 for heating, thereby forming a continuous cycle of energy conversion and heat exchange. Preferably, the heat exchange agent in the embodiment of the present invention may specifically be heat transfer oil.

[0050] In practical applications, the pipe section inlet of the metal pipe section 31 in the embodiment of the present invention is located below the pipe section outlet, that is, the heat exchanger enters from the pipe section inlet at the lower end of the metal pipe section 31, and is transported to the shell and tube heat exchanger 02 from the pipe section outlet at the upper end after being heated.

[0051] In the embodiment of the present invention, the heat exchange power of the shell and tube heat exchanger 02 can be set to be no higher than the total power of the electric heating steam furnace, and the closer to the total power of the electric heating steam furnace, the better. In a specific example, when the power of the electric heating steam furnace is 50kW, the heat exchange power of the shell and tube heat exchanger 02 is 50kW, the heat exchanger is heated to 350°C, and under the calculated flow rate, the temperature difference between the inlet and outlet temperatures of the heat exchanger is 50°C, and the steam outlet of the shell and tube heat exchanger 02 can well produce high-temperature steam.

[0052] Preferably, in order to further improve the safety of the electric heating steam furnace and reduce potential safety hazards of electrical equipment, in an embodiment of the present invention, the first pipe section and the second pipe section may be grounded respectively.

[0053] When the primary winding 12 of the embodiment of the present invention is connected to an external power supply, some heat will be generated on the primary side. If the heat is not dissipated in time, the normal operation of the electric heating steam furnace may be affected. Therefore, it is preferred that Figure 2 As shown, in the embodiment of the present invention, a ventilation sleeve 03 for heat dissipation can also be provided at the primary side of the heat medium heating part; thus, by connecting the cooling air, cooling can be performed on the primary side to take away the heat generated by the three-column iron core 11 itself. In practical applications, a ventilation gap of 3-5 mm can be left between the ventilation sleeve 03 and the primary winding to keep the cooling air flowing normally to improve the heat dissipation effect.

[0054] In order to facilitate the processing and manufacturing of the secondary tube group 13, in the embodiment of the present invention, the minimum gap between the core column and the secondary tube group 13 can be set to 5-10cm; in this way, sufficient process error margin can be left to conveniently install the three-column core 11 in the circle surrounded by the metal tube segment 31, and the thermal energy conversion rate of the thermal effect will not be affected due to the metal tube segment 31 being too far away from the core column.

[0055] Preferably, in the embodiment of the present invention, in order to more easily maintain a set distance from the core column when the metal tube segment 31 is enclosed in a winding, the cross-section of the core column in the embodiment of the present invention can be set to an elliptical shape.

[0056] The electric steam boiler in the embodiment of the present invention can match the heat output of the electric steam boiler with the load requirements of the actual working conditions by power regulating the external power supply connected to the primary winding 12; for this purpose, in the embodiment of the present invention, a power regulator can also be provided on the external power supply; in actual application, the power regulator can adjust the input power of the external power supply to the device by introducing a 4-20 mA signal, so that the heat output of the electric steam boiler can be accurately adjusted within the operating load variation range of 20%-100%.

[0057] Preferably, in the present invention, the metal outer wall of the metal pipe segment may also be provided with one or more thermocouples for collecting temperature data; thus, the operating condition of the electric heating steam furnace can be monitored according to the real-time temperature of the metal pipe segment, or corresponding temperature control adjustments can be made according to the temperature data.

[0058] In practical applications, the pipe wall temperature can be monitored and the equipment can be protected by means of a thermocouple + transmitter set on the metal outer wall; in addition, the heat exchanger temperature can be monitored by a thermocouple set at the heat exchanger inlet of the shell and tube heat exchanger 02 to adjust the power and protect the equipment accordingly.

[0059] In summary, the electric heating steam boiler in the embodiment of the present invention borrows the principle of the induced current generated by the transformer. After the primary winding is connected to the power supply, an induced current can be generated in the metal pipe section wound on the secondary side; in this way, the heat exchanger flowing in the metal pipe section can be heated due to the thermal effect of the current, thereby realizing the energy conversion from electrical energy to thermal energy; then, the heat exchange between the high-temperature heat exchanger and the heated water is realized through the shell and tube heat exchanger, thereby completing the heating and gasification of the water.

[0060] In the embodiment of the present invention, the heat exchanger is first heated by the thermal effect of electric current, and then the high-temperature heat exchanger heats the heated water through a shell and tube heat exchanger, thereby avoiding direct contact between the heating electrical elements (such as heating resistors) and the heated water. Therefore, the generation of scale can be effectively reduced, thereby reducing the decrease in heat transfer efficiency caused by this, and thus improving the energy conversion efficiency.

[0061] In addition, since the electrical components and the heated water are completely isolated in the embodiment of the present invention, the potential safety hazard caused by the failure of the electrical heating components can be effectively reduced, making the electric heating steam boiler safer.

[0062] Furthermore, in the embodiment of the present invention, the input power of the external power supply can be adjusted by providing a power regulator in the power supply, thereby achieving precise adjustment of the heat output of the electric heating steam boiler according to the load requirements under different working conditions.

[0063] Embodiment 2

[0064] On the basis of the first embodiment, the embodiment of the present invention further provides a method for using an electric heating steam furnace, that is, the embodiment of the present invention is applicable to the electric heating steam furnace in the first embodiment;

[0065] Using a star-delta starting method to start the electrically heated steam boiler;

[0066] The step of stopping the operation of the electric heating steam furnace comprises:

[0067] Under the condition that the heat exchange agent, water and cooling air are continuously supplied and circulated, the temperature of the secondary tube group is gradually reduced by reducing the output power of the external power supply;

[0068] When the electric heating steam furnace cools down to a preset safety temperature, turning off the external power supply;

[0069] stopping the circulation of the heat exchange agent;

[0070] Stop the supply of circulating water;

[0071] Stop the cooling air.

[0072] In practical applications, the detailed operation process of the present invention may include:

[0073] The inlet terminal of the primary winding side in the electric heating steam boiler is connected to the outlet terminal of the power regulator, and the inlet terminal of the power regulator is connected to the external power supply, and is equipped with necessary electrical switch components.

[0074] Before the system including the electric heating steam boiler is put into operation, it is necessary to fill each pipeline with sufficient heat transfer oil for system circulation; before the system is powered on, the heat transfer oil is first circulated in the system, and after the buffer tank of the shell and tube heat exchanger 02 stores half a tank of water, the water in the buffer tank and the shell and tube heat exchanger 02 are pumped through another circulation.

[0075] After the heat transfer oil and water circulate well, cooling air is introduced. The cooling air cools the upper part of the three-column core 11 through the ventilation gap to take away the heat generated by the three-column core 11 itself. Then, the power is turned on to gradually increase the temperature, and the output power of the primary side is controlled by adjusting the power regulator.

[0076] Since the secondary tube group 13 acts as a cold resistor with a low resistance value at the initial stage of power-on, the coil can have a smooth transition by means of star-delta starting or low-load operation at the initial stage of power-on.

[0077] As the temperature of the secondary tube group 13 gradually increases, the secondary tube group 13 turns into a hot resistor, and its resistance value increases. At this time, the power supply mode is switched to a triangle power supply, or the output power of the power regulator is increased. Since the heat transfer oil has been circulating in the secondary tube group 13 and the temperature is continuously increasing, when it reaches a sufficient temperature, the heat transfer oil enters the shell and tube heat exchanger 02, and the heat transfer oil heats the circulating water to generate a large amount of steam.

[0078] The temperature of the heat transfer oil in the shell and tube heat exchanger 02 decreases after releasing heat. When it circulates to the secondary pipe group 13 again, the heat transfer oil already has a sufficient initial temperature. The energy consumed in this heating is much less than that of the initial heating, thereby ensuring that there is enough heat inside the shell and tube heat exchanger 02 to generate steam. From then on, the outlet end of the shell and tube heat exchanger 02 can continuously generate high-temperature steam.

[0079] When the external steam demand changes, the output power of the secondary tube group 13 is indirectly adjusted by adjusting the output power of the power regulator, thereby achieving control over a wide operating range.

[0080] During the continuous operation of the system, in order to extend the service life of the equipment, the cooling air in the ventilation sleeve 03 should be continuously supplied.

[0081] When the system stops running, the output power of the power regulator is first reduced to gradually cool down the secondary pipe group 13. During the gradual cooling process, the heat transfer oil, circulating water and cooling air are continuously supplied and circulated. After the system cools to a safe temperature, the power supply of the power regulator is turned off. Then the circulation of the heat transfer oil is stopped, and then the supply of circulating water is stopped, and finally the cooling air is stopped.

[0082] It should be noted that, in the embodiment of the present invention, the length of the secondary pipe group can be set according to the operation compliance and working conditions; at the same time, temperature sensors are set at the three-column core, the secondary pipe group, and the primary winding, and regulating valves and other equipment are added externally to facilitate accurate control of the temperature of the circulating heat transfer oil.

[0083] In summary, the embodiment of the present invention heats the electrical heating and the heated material in a manner that is isolated from each other, thereby fundamentally eliminating the potential safety hazard caused by the failure of the electrical heating element. The heating electrical and heating material parts can be disassembled and repaired independently in parts when a failure occurs, and the operating load variation of 20%-100% can be used by setting an external power regulator.

[0084] In addition, the embodiment of the present invention has no risk of coking, thereby improving the operational stability of the equipment. The embodiment of the present invention can cope with continuously changing working conditions by adjusting the power of the electric heating tube through an external power regulator, and ensure that the total steam flow meets the process requirements stably.

[0085] Furthermore, the embodiments of the present invention do not need to use coal-fired or gas-fired boilers to heat materials, which responds to the low-carbon call while improving the electrification rate, automation rate, and intelligence of the equipment. There is no generation of CO2, nitrogen oxides, or sulfides, and the environmental performance is excellent.

[0086] It should be noted that the number of channels and the number of internal components in the present invention are not fixed, and are only described as examples using partial schematic diagrams.

[0087] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. An electrically heated steam furnace, characterized in that: It includes a heat medium heating unit and a shell and tube heat exchanger; The heat medium heating part includes a three-column iron core, a primary winding arranged on the primary side, a secondary tube group arranged on the secondary side, and an external power supply connected to the primary winding side; The secondary pipe group includes three metal pipe sections covered with a thermal insulation layer and an insulating layer; each of the metal pipe sections is wound around the secondary side of the three core columns of the three-column core in a winding manner; the heat exchanger inlets of each of the metal pipe sections are connected in parallel and communicated with the heat exchanger outlet of the shell and tube heat exchanger through a first pipe section; the heat exchanger outlets of each of the metal pipe sections are connected in parallel and communicated with the heat exchanger inlet of the shell and tube heat exchanger through a second pipe section.

2. The electrically heated steam furnace according to claim 1, characterized in that: Also includes: The first pipe section and the second pipe section are grounded respectively.

3. The electrically heated steam furnace according to claim 2, characterized in that: Also includes: A ventilation sleeve for heat dissipation is sleeved on the primary side of the heat medium heating unit.

4. The electrically heated steam furnace according to claim 3, characterized in that: include: The cross section of the core column is elliptical.

5. The electrically heated steam furnace according to claim 4, characterized in that: include: The heat exchanger inlet of the metal pipe section is located below the heat exchanger outlet of the metal pipe section.

6. The electrically heated steam furnace according to claim 5, characterized in that: include: A ventilation gap of 3-5 mm is left between the ventilation sleeve and the primary winding.

7. The electrically heated steam furnace according to claim 6, characterized in that: The heat exchange agent includes heat transfer oil.

8. The electrically heated steam furnace according to claim 7, characterized in that: The minimum gap between the core column and the secondary tube group is set to 5-10 cm.

9. The electrically heated steam furnace according to claim 8, characterized in that: Also includes: The power regulator of the external power supply regulates the input power of the external power supply to the device by introducing a 4-20 mA signal.

10. The electrically heated steam furnace according to claim 9, characterized in that: Also includes: The metal outer wall of the metal pipe section is provided with a thermocouple for collecting temperature data.

11. The electric heating steam furnace according to claim 10, characterized in that: The materials of the metal pipe section include: Carbon steel or stainless steel.

12. A method for using an electric heating steam furnace, suitable for the electric heating steam furnace as claimed in any one of claims 1 to 11, characterized in that: Includes steps: Using a star-delta starting method to start the electrically heated steam boiler; The step of stopping the operation of the electric heating steam furnace comprises: Under the condition that the heat exchange agent, water and cooling air are continuously supplied and circulated, the temperature of the secondary tube group is gradually reduced by reducing the output power of the external power supply; When the electric heating steam furnace cools down to a preset safety temperature, turning off the external power supply; stopping the circulation of the heat exchange agent; Stop the supply of circulating water; Stop the cooling air.

13. The method for using the electric heating steam furnace according to claim 12, characterized in that: include: In the star-delta starting method, the holding period of the star-shaped power supply stage includes 2-20 minutes.

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