Load-adjustable green electricity electric furnace smelting device and method

Abstract

The application discloses a green electricity electric furnace smelting device and method with adjustable load, which comprises an electric furnace body, a plasma arc heating device, an electromagnetic induction coil, a direct reduced iron feeding and preheating system, a rotary material distribution system, a temperature measuring optical fiber and a data processing unit. The plasma arc heating device is used for main heating of the molten pool by green electricity. The electromagnetic induction coil is arranged outside the electric furnace body and is used for non-contact induction heating of the molten pool when the plasma arc heating device is disconnected due to green electricity fluctuation, so as to maintain the continuity of heat input in the smelting process. The direct reduced iron feeding and preheating system comprises a preheating storage bin for preheating of direct reduced iron, and the preheating time of the preheating storage bin is adjustable. The application combines the plasma arc main heating and the electromagnetic induction compensation heating when the arc is disconnected, so that the heat input continuity of the molten pool is maintained under the condition of green electricity fluctuation, and the stability and controllability of the smelting process are improved.

Description

Technical Field

[0001] This invention relates to the field of electric furnace smelting technology, and more specifically, to a green electric furnace smelting apparatus and method with adjustable load. Background Technology

[0002] Against the backdrop of energy transition and the ongoing pursuit of carbon peaking and carbon neutrality goals, the installed capacity of renewable energy sources such as wind power and solar power is continuously increasing, and the total supply of green electricity is on the rise. However, due to the intermittent and fluctuating nature of renewable energy, its power generation is significantly affected by factors such as weather, day and night, and seasons. Furthermore, with insufficient grid peak-shaving capacity, inter-regional absorption capacity, and energy storage configuration, some regions still experience insufficient green electricity absorption and curtailment of wind and solar power, resulting in a waste of electrical resources.

[0003] Electric arc furnace steelmaking is a typical high-power industrial process, characterized by large single-furnace power and concentrated electrical load, making it a potential participant in green energy consumption and grid flexibility regulation. However, traditional electric arc furnace smelting processes typically rely on a stable and continuous power supply, with a relatively fixed matching relationship between smelting power, heating rhythm, and charging cycle. When there are significant fluctuations in green energy supply, the electric furnace struggles to adjust its load in line with the power supply capacity, easily leading to instability in the smelting process and even production interruptions or reduced energy efficiency.

[0004] Currently, existing electric furnaces still have shortcomings in adapting to fluctuations in green electricity. When there are large fluctuations in voltage or current in the power grid, arc instability or arc breakage can easily occur, leading to interruption of heat input to the molten pool and affecting the continuity and controllability of the smelting process. Summary of the Invention

[0005] In order to solve at least one of the technical problems in the background art, the present invention proposes a green electric furnace smelting apparatus and method with adjustable load.

[0006] One aspect of the present invention provides a load-adjustable green electric furnace smelting apparatus, the apparatus comprising: The electric furnace body, within which a molten pool is formed for melting direct reduced iron; A plasma arc heating device is used to primarily heat the molten pool using green electricity; An electromagnetic induction coil is installed on the outside of the electric furnace body to perform non-contact induction heating on the molten pool when the plasma arc heating device is interrupted due to green electricity fluctuations, so as to maintain the continuity of heat input in the smelting process. The direct reduced iron feeding and preheating system includes a preheating silo for preheating the direct reduced iron, wherein the preheating time of the preheating silo is adjustable to dynamically adjust the furnace temperature of the direct reduced iron entering the furnace according to the green electricity supply status. A rotating feeding system is used to uniformly disperse preheated direct reduced iron into the molten pool, and to lay direct reduced iron crushed powder or mineral powder on the surface of the molten pool to achieve submerged arc heating. A temperature-measuring optical fiber is embedded in the refractory material near the molten pool in the furnace body of the electric furnace, and is used to collect temperature information reflecting the thermal state of the molten pool. The data processing unit is connected to the temperature-measuring optical fiber, the plasma arc heating device, the electromagnetic induction coil, and the direct reduced iron (DRI) feeding and preheating system, respectively. It is used to evaluate the thermal state of the molten pool based on the temperature information, combined with the DRI addition amount and flue gas temperature information. Based on the molten pool thermal state evaluation results, it outputs control commands to adjust the heating power of the plasma arc heating device, control the start / stop state of the electromagnetic induction coil, and adjust the preheating time of the DRI, thereby maintaining the continuity of heat input in the smelting process under fluctuating green electricity conditions.

[0007] Optionally, the preheating silo is equipped with a stirring blade to stir the direct reduced iron during the preheating process, so as to improve the preheating uniformity. The preheating silo is configured to shorten the preheating time of direct reduced iron under conditions of sufficient green electricity supply, so as to reduce the furnace temperature of direct reduced iron entering the furnace.

[0008] Optionally, the rotating feeding system includes a feeding channel, a sliding track, and a telescopic feeding port; the feeding channel is configured to move along the sliding track to directly above the furnace cover feeding port on the electric furnace cover, and is used to introduce direct reduced iron into the molten pool; the telescopic feeding port is configured to communicate with the furnace cover feeding port when the feeding channel is in place, so as to provide a material channel during the feeding process; The furnace cover is equipped with a scale-shaped sensor door at the feeding port. The scale-shaped sensor door is configured to open automatically when the feeding channel is in place and feeding is carried out, and to remain closed when not feeding, so as to prevent the flue gas inside the furnace from overflowing during the smelting process.

[0009] Optionally, the data processing unit is specifically used to calculate the molten steel temperature based on the temperature information and the temperature gradient in the refractory material; and to calculate the electric furnace smelting load based on the molten steel temperature, the amount of direct reduced iron added, and the flue gas temperature, combined with the material balance and energy balance model, so as to generate the control command according to the smelting load.

[0010] Optionally, the data processing unit is specifically configured to control the electromagnetic induction coil to start induction heating when the plasma arc heating device experiences arc interruption due to green electricity fluctuations, and to perform a prediction of the power grid's replenishment power to determine whether the power grid has dispatchable power; after the induction heating continues for a preset time, if the prediction result indicates that the power grid has dispatchable power, then the plasma arc heating device is controlled to continue arc heating; if the prediction result indicates that the power grid does not have dispatchable power, then the induction heating is controlled to continue through the electromagnetic induction coil.

[0011] Optionally, the data processing unit is specifically used to maintain the temperature of the molten pool at 1550°C to 1580°C by outputting control commands during plasma arc heating or electromagnetic induction heating, so that the iron phase in the direct reduced iron melts while the slag phase remains in an incompletely melted state, thereby promoting slag-iron separation.

[0012] Optionally, the direct reduced iron (DRI) feeding and preheating system further includes a feeding belt conveyor and a pull-out grid valve located at the bottom of the preheating silo; the feeding belt conveyor is used to transport room-temperature DRI to the preheating silo; the pull-out grid valve is used to discharge the preheated DRI from the preheating silo and into the feeding channel of the rotary fabric distribution system when opened.

[0013] Optionally, the load-adjustable green electric furnace smelting device further includes a flue gas waste heat recovery system, which includes a waste heat boiler, a gas filter, and an exhaust fan. The exhaust fan is used to guide the flue gas generated during the smelting process through the gas filter and into the waste heat boiler for waste heat recovery, thereby enabling secondary utilization of heat.

[0014] Optionally, direct reduced iron is preheated in the preheating silo using flue gas generated during the smelting process; under conditions of sufficient green electricity supply, a first preheating time is used to preheat the direct reduced iron; under conditions of insufficient green electricity supply, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time. When preheating is performed using the first preheating time, the exhaust fan operates at a first set speed to recover flue gas from the preheating storage bin to the waste heat boiler; when preheating is performed using the second preheating time, the exhaust fan operates at a second set speed for flue gas recovery or without flue gas recovery, wherein the first set speed is greater than the second set speed. Another aspect of the present invention provides a green electric furnace smelting method with adjustable load, the method comprising: Direct reduced iron at room temperature is fed into a preheating silo for preheating, and the preheating time is adjusted according to the green electricity supply status. After preheating, the pull-out grid valve at the bottom of the preheating storage bin is opened to allow the preheated direct reduced iron to enter the rotating feeding system and then be added to the molten pool inside the electric furnace through the furnace cover charging port. After adding preheated direct reduced iron, the direct reduced iron crushed powder or mineral powder is dispersed and distributed on the surface of the molten pool through the rotary feeding system to form submerged arc heating conditions. The molten pool is heated by a green electric plasma arc heating device, and the temperature information of the refractory material in the furnace body is collected by a temperature measuring fiber. Based on the temperature information and the temperature gradient in the refractory material, the temperature of the molten steel is calculated. The molten steel temperature is calculated in real time by combining the amount of direct reduced iron added, the flue gas temperature and the molten steel temperature. The smelting load of the electric furnace is calculated in real time using a material balance and energy balance model. Based on this, control commands are output to adjust the plasma arc heating power and the preheating time of direct reduced iron. When the green electricity fluctuation causes the plasma arc to break, the electromagnetic induction coil is activated to heat the molten pool induction and the power grid is predicted to replenish the power. After the induction heating continues for a preset time, depending on whether the power grid has dispatchable power, it is selected to continue heating by plasma arc or continue heating by electromagnetic induction. After smelting is completed, steel is tapped and slag is removed.

[0015] Optionally, adjusting the preheating time according to the green electricity supply status includes: When the supply of green electricity is sufficient, a first preheating time is used to preheat the direct reduced iron; when the supply of green electricity is insufficient, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time.

[0016] Optionally, the load-adjustable green electric furnace smelting method further includes: When the direct reduced iron is preheated in the preheating silo, the direct reduced iron is stirred by the stirring blade in the preheating silo to improve the uniformity of preheating.

[0017] The beneficial effects of this invention are as follows: This invention, through its embodiment, simultaneously incorporates a plasma arc heating device driven by green electricity as the main heating source within the molten pool heating path of the electric furnace body. When green electricity fluctuations cause arc interruption, an electromagnetic induction coil provides non-contact compensatory heating to the molten pool. This is complemented by a direct reduced iron (DRI) feeding and preheating system with adjustable preheating time, and a rotating material distribution system that uniformly disperses and surfaces DRI and crushed powder or mineral powder. A data processing unit assesses the molten pool's thermal state based on temperature information collected by a temperature-sensing fiber optic cable, the amount of DRI added, and the flue gas temperature, and outputs control commands. This allows for the maintenance of continuous heat input to the molten pool and stable controllability of the smelting process even under conditions of fluctuating green electricity supply, especially with the risk of arc interruption. It reduces the impact of arc instability or interruption caused by power supply fluctuations on smelting continuity, making the electric furnace more suitable for load-following and stable smelting under green electricity conditions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a first schematic diagram of a green electric furnace smelting device with adjustable load according to an embodiment of the present invention; Figure 2 This is a second schematic diagram of the green electric furnace smelting device with adjustable load according to an embodiment of the present invention; Figure 3 This is a third schematic diagram of the green electric furnace smelting device with adjustable load according to an embodiment of the present invention; Figure 4 This is a flowchart of the green electric furnace smelting method with adjustable load according to an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 and Figure 2 As shown, in one embodiment of the present invention, the load-adjustable green electric furnace smelting apparatus of the present invention includes: The electric furnace body, within which a molten pool is formed for melting direct reduced iron; A plasma arc heating device is used to primarily heat the molten pool using green electricity; An electromagnetic induction coil is installed on the outside of the electric furnace body to perform non-contact induction heating on the molten pool when the plasma arc heating device is interrupted due to green electricity fluctuations, so as to maintain the continuity of heat input in the smelting process. The direct reduced iron feeding and preheating system includes a preheating silo for preheating the direct reduced iron, wherein the preheating time of the preheating silo is adjustable to dynamically adjust the furnace temperature of the direct reduced iron entering the furnace according to the green electricity supply status. A rotating feeding system is used to uniformly disperse preheated direct reduced iron into the molten pool, and to lay direct reduced iron crushed powder or mineral powder on the surface of the molten pool to achieve submerged arc heating. A temperature-measuring optical fiber is embedded in the refractory material near the molten pool in the furnace body of the electric furnace, and is used to collect temperature information reflecting the thermal state of the molten pool. The data processing unit is connected to the temperature-measuring optical fiber, the plasma arc heating device, the electromagnetic induction coil, and the direct reduced iron (DRI) feeding and preheating system, respectively. It is used to evaluate the thermal state of the molten pool based on the temperature information, combined with the DRI addition amount and flue gas temperature information. Based on the molten pool thermal state evaluation results, it outputs control commands to adjust the heating power of the plasma arc heating device, control the start / stop state of the electromagnetic induction coil, and adjust the preheating time of the DRI, thereby maintaining the continuity of heat input in the smelting process under fluctuating green electricity conditions.

[0023] It should be noted that DRI in the specification and drawings of this invention refers to direct reduced iron.

[0024] In one embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the load-adjustable green electric furnace smelting device has an electric furnace body as its main structure. Inside the electric furnace body, a molten pool is formed for melting direct reduced iron. Above the molten pool is the furnace space, which is used to accommodate the electric arc heating zone and the material dropping area between the charging channel and the molten pool.

[0025] The plasma arc heating device is located at the top of the electric furnace body and is used to primarily heat the molten pool using green electricity. During operation, the plasma arc heating device inputs heat into the molten pool to achieve the melting process of direct reduced iron. Due to fluctuations in the green electricity supply, the plasma arc heating device may experience arc interruption when the green electricity supply fluctuates significantly. To ensure uninterrupted heat input during the smelting process, the electromagnetic induction coil is located on the outside of the electric furnace body at a height corresponding to the molten pool. This coil is used for non-contact induction heating of the molten pool in the event of arc interruption, thereby maintaining continuous heat input during periods of unstable arc heating and allowing the smelting process to continue.

[0026] The direct reduced iron (DRI) feeding and preheating system is used to supply DRI to the electric furnace and preheat it. The system includes a preheating silo to hold the DRI to be fed into the furnace and to heat it before it enters the furnace, thus changing the DRI's entry temperature. The preheating time of the preheating silo is an adjustable parameter, used to dynamically adjust according to the green electricity supply status. When the green electricity supply status changes, adjusting the preheating time can change the temperature rise of the DRI before it enters the furnace, allowing the DRI entering the molten pool to have different entry temperatures, thereby matching the green electricity supply capacity and facilitating load regulation.

[0027] The rotating material distribution system is used to evenly disperse preheated direct reduced iron (DRI) into the molten pool, preventing DRI from concentrating and accumulating in the pool. It also serves to spread DRI crushed powder or mineral powder on the surface of the molten pool, creating submerged arc heating conditions. When the DRI crushed powder or mineral powder is located on the surface of the molten pool, it forms a covering layer in the arc action area, keeping the arc heating in a submerged state, improving the stability of the heating process, and cooperating with the plasma arc heating device to complete the main heating process.

[0028] The temperature-sensing optical fiber is embedded in the refractory material near the molten pool within the electric furnace body to collect temperature information reflecting the thermal state of the molten pool. The temperature information from the optical fiber reflects the thermal change trend in the molten pool region, serving as the basic data source for thermal state assessment. The temperature information collected by the optical fiber is transmitted to a data processing unit for analysis and processing.

[0029] like Figure 3As shown, in one embodiment of the present invention, the temperature-measuring optical fiber is arranged in a spiral manner along the thickness direction of the refractory material, thereby forming multiple temperature measuring points at different positions for real-time acquisition of temperature information of the refractory material above the furnace shell; the temperature-measuring optical fiber is connected to a demodulator, which demodulates the temperature measurement signal of the temperature-measuring optical fiber and outputs temperature information, which is transmitted to a data processing unit. The data processing unit evaluates the thermal state of the molten pool by combining the temperature of the refractory material and its temperature gradient, and outputs control commands accordingly to adjust the plasma arc heating power and the start and stop of the electromagnetic induction coil, thereby improving the smelting stability of the device under green electricity fluctuation conditions.

[0030] The data processing unit is connected to the temperature-measuring fiber optic cable, the plasma arc heating device, the electromagnetic induction coil, and the direct reduced iron (DRI) feeding and preheating system. Based on the temperature information collected by the temperature-measuring fiber optic cable, and combined with the DRI addition amount and flue gas temperature information, the data processing unit evaluates the thermal state of the molten pool. Based on the evaluation results, the data processing unit outputs control commands. These commands are used to adjust the heating power of the plasma arc heating device, control the start / stop status of the electromagnetic induction coil, and adjust the preheating time of the preheating storage tank. Through these adjustments, the device can achieve coordinated control of heat input under fluctuating electricity conditions, establishing a cooperative relationship between plasma arc heating and electromagnetic induction heating. Simultaneously, by adjusting the preheating time, the furnace temperature of the DRI entering the furnace is changed, thereby maintaining the continuity of heat input during the smelting process and improving the stability and adjustability of the smelting process.

[0031] In one embodiment of the present invention, the preheating storage silo is provided with a stirring blade for stirring the direct reduced iron during the preheating process to improve the uniformity of preheating.

[0032] In one embodiment of the invention, the preheating silo is configured to shorten the preheating time of direct reduced iron under conditions of sufficient green electricity supply, so as to reduce the furnace temperature of the direct reduced iron entering the furnace.

[0033] In one embodiment of the present invention, such as Figure 2 As shown, the preheating silo is used to contain and preheat direct reduced iron (DRI). To improve the uniformity of the preheating process, a stirring blade is installed inside the preheating silo. Located within the storage area of ​​the silo, the stirring blade agitates and disturbs the DRI within the silo during preheating, causing the DRI in different locations to interchange positions and reducing the accumulation of temperature differences caused by uneven heating in certain areas. Through the stirring action of the stirring blade, the DRI is heated more evenly within the preheating silo, resulting in a more consistent temperature distribution of the material entering the furnace, which is beneficial to the stability of the subsequent furnace feeding process.

[0034] In one embodiment of the invention, the preheating time of the preheating silo is an adjustable parameter, and the preheating silo is configured to shorten the preheating time of direct reduced iron (DRI) under conditions of sufficient green electricity supply, thereby reducing the DRI's entry temperature into the furnace. Specifically, when green electricity supply is sufficient, the equipment side prioritizes using available electricity for the main heating process on the electric furnace side. To match this power supply status and reduce the heat occupation of the preheating stage, the preheating silo adopts a shorter preheating time, allowing the DRI to enter the molten pool at a relatively low entry temperature. This configuration enables a load distribution relationship between the preheating stage and the main heating stage of the electric furnace, facilitating the coordination of heat input between the preheating side and the smelting side when the green electricity supply status changes, thereby achieving more flexible smelting load adjustment.

[0035] In one embodiment of the present invention, the rotating feeding system includes a feeding channel, a sliding track, and a telescopic feeding port; the feeding channel is configured to move along the sliding track to directly above the furnace cover feeding port on the electric furnace cover, and is used to introduce direct reduced iron into the molten pool; the telescopic feeding port is configured to communicate with the furnace cover feeding port when the feeding channel is in position, so as to provide a material channel during the feeding process.

[0036] In one embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the rotating material feeding system is used to transport preheated direct reduced iron from the preheating silo side and introduce it into the molten pool inside the electric furnace. The rotating material feeding system includes a feeding channel, a sliding track, and a telescopic charging port. The feeding channel forms a material transport path; one end engages with the discharge side of the preheating silo, and the other end faces the furnace cover area. The sliding track is located near the furnace cover charging port, allowing the feeding channel to move along it, ensuring alignment and facilitating stable material entry into the furnace.

[0037] In one embodiment of the invention, a telescopic feeding port is used to establish a connecting channel with the furnace cover feeding port after the feeding channel is in place. The telescopic feeding port is located near the furnace cover feeding port and can extend upwards or downwards when the feeding channel is in place, allowing the telescopic feeding port to fit or connect with the furnace cover feeding port, thereby forming a continuous material channel. During the feeding process, direct reduced iron enters the telescopic feeding port along the feeding channel and then enters the molten pool through the furnace cover feeding port. Through the guiding positioning of the sliding track and the connecting connection of the telescopic feeding port, the opening and closing of the feeding channel is more controllable, and the material landing point is more stable, which helps to reduce scattering and deviation during the feeding process.

[0038] In one embodiment of the present invention, a scale-like sensing door is provided at the feeding port of the furnace cover. The scale-like sensing door is configured to automatically open when the feeding channel is in place and feeding is carried out, and to remain closed when not feeding, so as to prevent the flue gas inside the furnace from overflowing during the smelting process.

[0039] In one embodiment of the present invention, such as Figure 1 As shown, the electric furnace cover is equipped with a furnace cover charging port, and a scale-like sensor door is installed at the furnace cover charging port. The scale-like sensor door is used to control the opening and closing of the furnace cover charging port, so that the furnace cover charging port is in different sealed states during the charging stage and the non-charging stage. The scale-like sensor door can adopt a scale-like structure to form a door body shielding surface. When the door body is closed, it covers the furnace cover charging port, thereby shielding the space inside the furnace and reducing the possibility of flue gas escaping from the furnace cover charging port.

[0040] In one embodiment of the present invention, the scale-like sensor door is configured to automatically open when the feeding channel is in position and feeding begins. Specifically, when the feeding channel moves along the sliding track to directly above the furnace cover charging port and meets the feeding conditions, the scale-like sensor door triggers an opening action based on its position, keeping the furnace cover charging port open and allowing direct reduced iron to enter the molten pool through the furnace cover charging port. After feeding is completed, or when the feeding channel leaves its position, the scale-like sensor door remains or returns to a closed state, keeping the furnace cover charging port closed. Through this automatic opening and closing coordination, the furnace cover charging port remains closed during non-feeding phases, which helps reduce the leakage of flue gas from the furnace during smelting, improving the sealing performance of the smelting process and the effectiveness of on-site environmental control.

[0041] In one embodiment of the present invention, the scale-like sensor door can be composed of multiple overlapping scale units. When closed, these scale units overlap to form a continuous shielding surface, used to seal the furnace cover's charging port. When open, the scale units open under a driving or linkage action, creating an opening through which materials can pass. The sensing function in the scale-like sensor door is used to identify whether the feeding channel is in place and whether it is in a feeding state, thereby achieving linkage control with the feeding action. The advantages of this scale-like sensor door are that it can limit the opening period of the furnace cover's charging port to the short time required for feeding, keeping it closed during non-feeding stages, improving the sealing of the furnace cover's charging port, and reducing the risk of high-temperature flue gas overflowing from the charging port during smelting. Simultaneously, the scale-like door body has relatively relaxed alignment requirements during opening and closing, suitable for docking with the feeding channel, facilitating automatic opening and automatic reset, reducing manual intervention, and improving the controllability and stability of the feeding process.

[0042] In one embodiment of the present invention, the data processing unit is specifically used to calculate the temperature of molten steel based on the temperature information and in combination with the temperature gradient in the refractory material; and to calculate the electric furnace smelting load based on the molten steel temperature, the amount of direct reduced iron added and the flue gas temperature information, in combination with the material balance and energy balance model, so as to generate the control command according to the smelting load.

[0043] In one embodiment of the present invention, the data processing unit can be implemented by an industrial computer or a programmable logic controller (PLC). The data processing unit is connected to a demodulator and data collector corresponding to the temperature-sensing optical fiber, and is used to receive temperature information of the refractory material. The temperature-sensing optical fiber is embedded in the refractory material near the molten pool area, forming multiple temperature measurement points along the circumference or height of the furnace body. The data processing unit periodically reads the temperature of each measurement point to obtain a curve showing the temperature change of the refractory material over time.

[0044] In one embodiment of the present invention, the data processing unit calculates the molten steel temperature based on the temperature gradient within the refractory material. Here, the temperature gradient can be understood as the ratio of the temperature difference at different locations within the refractory material to the corresponding distance. This can be achieved by having a temperature-measuring optical fiber cover at least two different depths along the thickness direction of the refractory material. The data processing unit simultaneously reads the temperature values ​​near the hot surface and near the cold surface, calculating the temperature gradient of the refractory material. The data processing unit pre-stores a correspondence table obtained from heat transfer calculations. This correspondence table takes the temperature gradient and the cold surface temperature of the refractory material as input, and the molten steel temperature as output. The table can be established during the equipment commissioning phase. During commissioning, reference values ​​for the molten steel temperature can be obtained under several typical smelting conditions. These reference values ​​can be obtained using commonly used temperature guns or by measuring the temperature at the tapping point. The data processing unit establishes a mapping at these reference points. During operation, the data processing unit looks up the table to obtain the estimated molten steel temperature. This method enables online calculation without requiring the placement of easily damaged probes inside the furnace.

[0045] In one embodiment of the present invention, the data processing unit can also use the heat flux trend reflected by the temperature gradient to assess the thermal state of the molten pool. An increasing temperature gradient indicates enhanced heat transfer towards the furnace shell, resulting in higher heat input or greater heat dissipation from the molten pool. A decreasing temperature gradient indicates weakened heat transfer outwards, resulting in lower heat input or a drop in the molten pool temperature. The data processing unit combines this trend with the estimated molten steel temperature to generate a real-time assessment of the molten pool's thermal state, which is then used for subsequent load calculation and control.

[0046] In one embodiment of the present invention, the data processing unit acquires information on the amount of direct reduced iron added and the flue gas temperature. The amount of direct reduced iron added can be provided by the metering device of the feeding system. The flue gas temperature can be collected by a flue gas temperature sensor or by a temperature point in the extraction channel. The data processing unit aligns the added amount and flue gas temperature over time to form input data within the same calculation cycle.

[0047] In one embodiment of the present invention, the data processing unit calculates the electric furnace smelting load based on a material balance and energy balance model. The material balance component describes the change in the amount of metal formed after the added direct reduced iron enters the molten pool. The energy balance component describes the heat balance of the molten pool. The data processing unit calculates the required net heat input in each calculation cycle. Net heat input includes the heat required to heat the direct reduced iron to a molten state, the heat required to raise the molten steel temperature from the current estimate to the target range, and heat loss from the molten pool towards the refractory material and flue gas. The data processing unit also considers the sensible heat level of the flue gas reflected by the flue gas temperature to correct for heat dissipation or energy utilization. The calculated net heat input is then converted into electrical power demand to obtain the smelting load. The smelting load can be understood as the effective heat input capacity required by the electric furnace in the current time period, corresponding to a target power or target energy input rate.

[0048] In one embodiment of the present invention, the data processing unit generates control commands based on the smelting load. The control commands include at least the power setting value of the plasma arc heating device, the start / stop status of the electromagnetic induction coil, and the preheating time setting value of the preheating silo. This can be implemented using closed-loop regulation. The data processing unit uses the estimated molten steel temperature as feedback and the target temperature range as the control objective, outputting an arc power adjustment amount. The data processing unit uses the temperature gradient or its rate of change as auxiliary feedback to limit excessively high furnace lining heat load. The data processing unit determines the upper limit of the arc power based on the smelting load and the available green electricity power. If the available green electricity power is lower than the smelting load, the data processing unit reduces the arc power setting value, extends the preheating time, and increases the direct reduced iron temperature entering the furnace, using the preheating side to share some of the heat demand. If the available green electricity power is higher than the smelting load, the data processing unit can shorten the preheating time and reduce the direct reduced iron temperature entering the furnace, allowing the electric furnace side to bear more heat input and improving the green electricity absorption capacity.

[0049] In one embodiment of the present invention, control under arc-interruption conditions can be implemented as follows: The data processing unit continuously monitors the operating status signal of the plasma arc heating device. Upon detecting arc interruption, the data processing unit issues a start command to activate the electromagnetic induction coil. Simultaneously, the data processing unit continues to collect temperature information from the temperature-measuring fiber optic cable, updating the estimated steel temperature and temperature gradient. Based on this, the data processing unit adjusts the induction heating duration or power to maintain the molten pool temperature near a set range. The data processing unit also performs a prediction of the replenishment of power from the power grid. The prediction result is used to determine whether to switch back to arc heating or continue induction heating. If the prediction result indicates that the power grid has dispatchable power, the data processing unit issues a recovery command when the arc recovery conditions are met, and the plasma arc heating device is reactivated. If the prediction result indicates that the power grid does not have dispatchable power, the data processing unit keeps the electromagnetic induction coil operational until green electricity is restored or smelting enters the next stage.

[0050] In one embodiment of the present invention, the data processing unit is specifically configured to control the electromagnetic induction coil to start induction heating when the plasma arc heating device experiences arc interruption due to green electricity fluctuations, and to perform a prediction of the power grid replenishment to determine whether the power grid has dispatchable power; after the induction heating continues for a preset time, if the prediction result indicates that the power grid has dispatchable power, the plasma arc heating device is controlled to continue arc heating; if the prediction result indicates that the power grid does not have dispatchable power, the induction heating is controlled to continue through the electromagnetic induction coil.

[0051] In one embodiment of the present invention, a data processing unit is electrically connected to the plasma arc heating device and the electromagnetic induction coil. This unit acquires the operating status information of the plasma arc heating device and performs heating mode switching control when green electricity fluctuations cause arc interruption, thereby maintaining the continuity of heat input to the molten pool. Specifically, the data processing unit can determine whether arc interruption has occurred based on the current, voltage, and power feedback signals of the plasma arc heating device, or based on the arc voltage stability signal. When arc interruption is detected, the data processing unit outputs a start command, activating the electromagnetic induction coil to inductively heat the molten pool. Induction heating is a non-contact heating method, capable of continuously inputting heat to the molten pool during periods of arc instability or interruption, thereby reducing the impact of arc interruption on the smelting process.

[0052] In one embodiment of the present invention, the data processing unit, while controlling the electromagnetic induction coil to start, performs a prediction of the supplementary power supply to the power grid to determine whether the power grid has dispatchable power. The prediction can be based on at least one of the following: available power information from the green electricity supply side, instantaneous voltage and current fluctuation amplitude, and short-term power change trend information. The data processing unit uses the prediction result as a basis for subsequent heating mode selection, determining whether to switch back to arc heating after induction heating has been maintained for a period of time.

[0053] In one embodiment of the present invention, after the electromagnetic induction coil is activated, the data processing unit controls the induction heating to continue for a preset time. The preset time can be a fixed duration or set according to the actual smelting cycle. After the preset time is reached, if the prediction result indicates that the power grid has dispatchable power, the data processing unit controls the plasma arc heating device to continue arc heating, so that the smelting process returns to the main heating mode dominated by the arc. If the prediction result indicates that the power grid does not have dispatchable power, the data processing unit controls the induction heating to continue through the electromagnetic induction coil, so that the molten pool still maintains heat input during the stage when the arc cannot be stably maintained, thereby ensuring the continuity and controllability of the smelting process.

[0054] In one embodiment of the present invention, the data processing unit is specifically used to maintain the temperature of the molten pool at 1550°C to 1580°C by outputting control commands during plasma arc heating or electromagnetic induction heating, so that the iron phase in the direct reduced iron melts while the slag phase is in an incompletely melted state, thereby promoting slag-iron separation.

[0055] In one embodiment of the present invention, a data processing unit is connected to both a plasma arc heating device and an electromagnetic induction coil, and is used to output control commands in both arc heating mode and induction heating mode to adjust the heat input of the molten pool. The data processing unit uses the molten pool thermal state assessment results as the control basis, and adjusts the plasma arc heating power and / or controls the operating state of the electromagnetic induction coil to maintain the molten pool temperature within the target range of 1550°C to 1580°C.

[0056] In one embodiment of the present invention, the data processing unit can calculate the molten steel temperature based on the refractory material temperature information collected by the temperature-measuring optical fiber and combined with the temperature gradient. The calculated molten steel temperature is then compared with a target range. When the molten steel temperature is below the lower limit of the target range, the data processing unit increases the heating power of the plasma arc heating device, or, if the arc is limited, activates an electromagnetic induction coil for compensatory heating to increase the heat input to the molten pool. When the molten steel temperature is above the upper limit of the target range, the data processing unit reduces the plasma arc heating power, or controls the electromagnetic induction coil to stop working, to suppress further increases in the molten pool temperature. Through these methods, the molten pool temperature is maintained within the target range during the smelting process.

[0057] Controlling the molten pool temperature between 1550℃ and 1580℃ has clear smelting significance. Within this temperature range, the iron phase in direct reduced iron can melt and enter the molten steel, while the melting of the slag phase is relatively delayed. The slag layer is more likely to maintain a certain viscosity and morphological stability, resulting in clearer stratification between the molten steel and the slag layer, which is beneficial for subsequent slag-iron separation. By controlling the molten pool temperature within a range through a data processing unit, more suitable thermal conditions for slag-iron separation can be created while ensuring the melting of direct reduced iron, thereby improving the controllability and stability of the smelting process.

[0058] In one embodiment of the present invention, the direct reduced iron feeding and preheating system further includes a feeding belt conveyor and a pull-out grid valve disposed at the lower part of the preheating silo; the feeding belt conveyor is used to transport direct reduced iron at room temperature to the preheating silo; the pull-out grid valve is used to discharge the preheated direct reduced iron from the preheating silo and into the feeding channel of the rotary fabric distribution system when opened.

[0059] In one embodiment of the present invention, such as Figure 2 As shown, the direct reduced iron (DRI) feeding and preheating system, in addition to the preheating silo, also includes a feeding belt conveyor and a pull-out gate valve located at the bottom of the preheating silo. The feeding belt conveyor continuously or intermittently transports ambient-temperature DRI to the preheating silo, allowing the DRI to enter its storage space. The conveying method of the feeding belt conveyor facilitates matching with the production cycle, enabling it to replenish the preheating silo at a set feeding speed, thereby ensuring that the preheating silo has sufficient DRI to meet the requirements of a single feeding operation.

[0060] In one embodiment of the invention, a pull-out grid valve is installed at the lower discharge position of the preheating silo to control the discharge process of the preheating silo. When closed, the pull-out grid valve blocks the discharge port of the preheating silo, keeping the preheated direct reduced iron (DRI) within the silo, facilitating the completion and maintenance of the preheating process. When open, the pull-out grid valve opens the discharge channel, allowing the preheated DRI to be discharged from the preheating silo under its own weight and enter the feed channel of the rotating material feeding system, subsequently being guided into the molten pool inside the electric furnace. By controlling the opening and closing of the pull-out grid valve, the preheating and discharge processes can be managed separately, allowing the preheating silo to maintain a relatively closed heat storage state during the preheating stage and quickly switch to the discharge state during the feeding stage, thereby improving the controllability and stability of the feeding process.

[0061] In one embodiment of the present invention, the device further includes a flue gas waste heat recovery system, which includes a waste heat boiler, a gas filter, and an exhaust fan; the exhaust fan is used to guide the flue gas generated during the smelting process through the gas filter and into the waste heat boiler for waste heat recovery, thereby enabling secondary utilization of heat.

[0062] In one embodiment of the present invention, such as Figure 2 As shown, the load-adjustable green electric furnace smelting device also includes a flue gas waste heat recovery system. This system collects and recovers waste heat from the high-temperature flue gas generated during the smelting process, converting the heat carried by the flue gas into reusable thermal energy, reducing energy waste in the smelting process, and improving energy utilization.

[0063] In one embodiment of the present invention, the flue gas waste heat recovery system includes a waste heat boiler, a gas filter, and an exhaust fan. The exhaust fan is connected to the flue gas discharge side of the electric furnace and is used to draw and transport the flue gas, ensuring a stable flow path for the flue gas generated during the smelting process. The gas filter is installed in the extraction path of the exhaust fan and is used to remove dust or filter impurities from the flue gas, reducing the risk of particulate matter in the flue gas entering subsequent equipment and improving the reliability of system operation. The waste heat boiler is connected downstream of the gas filter and is used to perform heat exchange and recovery on the filtered flue gas, absorbing the heat in the flue gas and converting it into usable thermal energy, thereby achieving secondary heat utilization. Through the above configuration, the flue gas generated during the smelting process passes sequentially through the gas filter and the waste heat boiler under the guidance of the exhaust fan, achieving both orderly emission and purification of the flue gas and recovery and utilization of waste heat from the flue gas, which is beneficial to improving the overall energy efficiency of the electric furnace smelting process.

[0064] In one embodiment of the present invention, direct reduced iron is preheated in the preheating storage silo by the flue gas generated during the smelting process; under the condition of sufficient green electricity supply, a first preheating time is used to preheat the direct reduced iron; under the condition of insufficient green electricity supply, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time. When preheating is performed using the first preheating time, the exhaust fan is operated at a first set speed to recover flue gas from the preheating storage bin to the waste heat boiler; when preheating is performed using the second preheating time, the exhaust fan is operated at a second set speed to recover flue gas or not to recover flue gas, wherein the first set speed is greater than the second set speed.

[0065] In one embodiment of the present invention, the heat source for the preheating storage bin can preferentially utilize the waste heat from the flue gas generated during the electric furnace smelting process. Specifically, the high-temperature flue gas generated during electric furnace smelting is introduced into the heat exchange area of ​​the preheating storage bin through a flue gas channel. The flue gas exchanges heat with the direct reduced iron (DRI) in the preheating storage bin, causing the DRI to heat up. Simultaneously, the preheating storage bin can be equipped with stirring blades or a flow guiding structure to ensure more uniform heating of the DRI during preheating, avoiding localized overheating or insufficient temperature rise. In some embodiments, the preheating storage bin can also be equipped with an auxiliary preheating device as a supplementary heat source, used to supplement the heating of the DRI when the waste heat from the flue gas is insufficient or when a rapid preheating target needs to be achieved, thereby improving the adaptability and controllability of the preheating process.

[0066] In one embodiment of the present invention, the flue gas waste heat recovery system includes an exhaust fan, a gas filter, and a waste heat boiler. The inlet of the exhaust fan is connected to the exhaust of the preheating storage chamber. The exhaust fan is used to extract the flue gas after it has passed through the preheating storage chamber and guide it to the gas filter. After removing particulate matter such as dust, the flue gas enters the waste heat boiler for waste heat recovery. The waste heat boiler is used to exchange heat with the incoming flue gas, converting the heat carried by the flue gas into usable thermal energy, such as generating steam for power generation or heating, thereby achieving secondary utilization of heat.

[0067] In one embodiment of the invention, the preheating time of the preheating silo is linked to the waste heat recovery process of the flue gas and corresponds to the green electricity supply status. When the green electricity supply is sufficient, a first preheating time is used to preheat the direct reduced iron (DRI). This first preheating time is relatively short, resulting in a relatively lower DRI temperature entering the furnace and a relatively reduced occupation of flue gas heat during the preheating stage. At this time, the exhaust fan operates at a first set speed to enhance the extraction of flue gas from the preheating silo, allowing the flue gas after preheating to more fully enter the waste heat boiler for waste heat recovery, thereby increasing the recoverable heat level. When the green electricity supply is insufficient, a second preheating time is used to preheat the DRI. This second preheating time is longer than the first preheating time, allowing more flue gas heat to be used for the heating and holding of the DRI, reducing the electric furnace's immediate dependence on green electricity for main heating. At this time, the exhaust fan operates at a second set speed, which is lower than the first set speed, thereby reducing the extraction intensity of flue gas into the waste heat boiler and prioritizing the preheating needs of the preheating silo. When preheating requirements or operational needs are met, the exhaust fan can be adjusted to operate at a low speed to maintain a small amount of flue gas recovery. Through this method, a dynamic match between preheating requirements and waste heat recovery is achieved under different green electricity supply conditions, improving the system's adaptability to green electricity fluctuations and enhancing the overall utilization efficiency of flue gas waste heat.

[0068] Based on the same inventive concept, this invention also provides a load-adjustable green electric furnace smelting method. This method is applied to the load-adjustable green electric furnace smelting apparatus described in the above embodiments, as illustrated in the following embodiments. Since the principle of the load-adjustable green electric furnace smelting method is similar to that of the load-adjustable green electric furnace smelting apparatus, embodiments of the load-adjustable green electric furnace smelting method can be found in the embodiments of the load-adjustable green electric furnace smelting apparatus; repeated details will not be elaborated further.

[0069] Figure 4 This is a flowchart of the green electric furnace smelting method with adjustable load according to an embodiment of the present invention, as follows: Figure 4 As shown, in one embodiment of the present invention, the load-adjustable green electric furnace smelting method of the present invention includes steps S101 to S106.

[0070] Step S101: Direct reduced iron at room temperature is fed into a preheating storage silo for preheating, and the preheating time is adjusted according to the green electricity supply status.

[0071] In one embodiment of the present invention, this step involves feeding room-temperature direct reduced iron (DRI) into a preheating silo for preheating. The room-temperature DRI can enter the preheating silo via a feeding conveyor structure, where it remains and is heated. The preheating time is an adjustable parameter. The preheating time is adjusted according to the availability of green electricity. When green electricity is sufficient, a shorter preheating time is used, allowing the DRI to enter the electric furnace at a lower inlet temperature, thus reserving more heat input for the main heating process of the electric furnace. When green electricity is insufficient, a longer preheating time is used, increasing the DRI's inlet temperature, reducing the instantaneous heat load demand on the electric furnace side, and facilitating matching of the smelting process with available power supply capacity.

[0072] Step S102: After preheating, open the pull-out grid valve at the bottom of the preheating storage bin to allow the preheated direct reduced iron to enter the rotating feeding system and then be added to the molten pool inside the electric furnace through the furnace cover charging port.

[0073] In one embodiment of the present invention, after preheating, the pull-out grid valve at the bottom of the preheating silo is opened, allowing the preheated direct reduced iron (DRI) to be discharged from the silo and enter the rotary charging system. The preheated DRI is then fed through the rotary charging system into the furnace cover charging port and into the molten pool inside the electric furnace. During the charging process, the rotary charging system forms a stable material channel, enabling the DRI to enter the molten pool at a set charging rhythm, reducing the risk of material accumulation and improving the controllability of the charging process.

[0074] In step S103, after adding preheated direct reduced iron, the crushed direct reduced iron powder or mineral powder is dispersed and distributed on the surface of the molten pool through the rotating feeding system to form submerged arc heating conditions.

[0075] In one embodiment of the present invention, after adding preheated direct reduced iron (DRI), DRI crushed powder or mineral powder is dispersed and distributed on the surface of the molten pool via a rotating material distribution system. The crushed powder or mineral powder forms a covering layer on the surface of the molten pool, thus covering the arc action area and creating submerged arc heating conditions. In the submerged arc state, more arc energy is released in the covering layer and the upper region of the molten pool, which helps to improve the stability of the heating process and reduce the fluctuation effects caused by direct arc exposure.

[0076] Step S104: The molten pool is heated by a green electric plasma arc heating device, and the temperature information of the refractory material in the furnace body is collected by a temperature measuring fiber. Based on the temperature information and the temperature gradient in the refractory material, the temperature of the molten steel is calculated. The molten steel temperature is calculated in real time by combining the amount of direct reduced iron added, the flue gas temperature and the temperature of the molten steel. The smelting load of the electric furnace is calculated in real time using a material balance and energy balance model. Based on this, control commands are output to adjust the plasma arc heating power and the preheating time of direct reduced iron.

[0077] In one embodiment of the present invention, a green electricity-driven plasma arc heating device is used to primarily heat the molten pool, while simultaneously collecting temperature information of the refractory material in the electric furnace body via a temperature-sensing optical fiber. The temperature-sensing optical fiber is embedded in the refractory material near the molten pool, enabling continuous acquisition of refractory material temperature changes. The data processing unit calculates the molten steel temperature based on the refractory material temperature information and the temperature gradient within the refractory material. The calculated molten steel temperature serves as a key characteristic parameter of the molten pool's thermal state. The data processing unit further combines the direct reduced iron (DRI) addition amount, flue gas temperature, and molten steel temperature to calculate the electric furnace smelting load based on a material and energy balance model. The smelting load characterizes the effective heat input level required for the current stage. Based on this, the data processing unit outputs control commands to control the plasma arc heating power and adjust the DRI preheating time accordingly, ensuring that the smelting heat input matches the green electricity supply capacity.

[0078] Step S105: When the green electricity fluctuation causes the plasma arc to break, the electromagnetic induction coil is activated to perform induction heating on the molten pool, and the power grid is predicted to replenish the power. After the induction heating continues for a preset time, depending on whether the power grid has dispatchable power, it is selected to continue heating by plasma arc or continue heating by electromagnetic induction.

[0079] In one embodiment of the present invention, when a fluctuation in green electricity causes the plasma arc to interrupt, an electromagnetic induction coil is activated to induction heat the molten pool. Electromagnetic induction heating is used to continuously input heat into the molten pool during the arc interruption phase, reducing the impact of arc interruption on the continuity of smelting. Simultaneously, the data processing unit performs a prediction of the supplementary power supply from the power grid to determine whether the power grid has dispatchable power. After induction heating continues for a preset time, if the prediction result indicates that the power grid has dispatchable power, the plasma arc heating device is controlled to continue arc heating. If the prediction result indicates that the power grid does not have dispatchable power, induction heating is controlled to continue through the electromagnetic induction coil. This method achieves the switching or maintenance between arc heating and induction heating, maintaining the continuity of heat input in the smelting process.

[0080] Step S106: After smelting is completed, steel is tapped and slag is removed.

[0081] In one embodiment of the present invention, steel and slag are tapped after smelting. The tapping and slag removal are carried out after melting and slag-iron separation to conclude the current smelting process and proceed to the preparation stage for the next heat.

[0082] In one embodiment of the present invention, adjusting the preheating time according to the green electricity supply status in step S101 includes: When the supply of green electricity is sufficient, a first preheating time is used to preheat the direct reduced iron; when the supply of green electricity is insufficient, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time.

[0083] In one embodiment of the present invention, adjusting the preheating time according to the green electricity supply status in step S101 can be achieved by a tiered preheating method. The preheating storage silo is pre-set with at least two selectable preheating durations, namely a first preheating time and a second preheating time. The first preheating time is shorter than the second preheating time. The data processing unit or control system selects between the two preheating durations according to the green electricity supply status, thereby changing the residence time of direct reduced iron in the preheating storage silo, and consequently changing the furnace entry temperature level of the direct reduced iron.

[0084] In one embodiment of the present invention, when the supply of green electricity is sufficient, a first preheating time is used to preheat the direct reduced iron. Because the first preheating time is short, the direct reduced iron experiences less temperature rise in the preheating storage chamber, resulting in a relatively low furnace entry temperature. At this time, the electric furnace can utilize sufficient green electricity for main heating, and the preheating stage does not require excessive heat input. This allows more available electricity to be used for the main heating process of the molten pool by the plasma arc heating device, thereby improving the green electricity utilization capacity.

[0085] In one embodiment of the invention, when the supply of green electricity is insufficient, a second preheating time is used to preheat the direct reduced iron. Because the second preheating time is longer, the direct reduced iron receives a greater temperature rise in the preheating storage bin, resulting in a relatively higher furnace entry temperature. This reduces the amount of heat required from the electric furnace side to heat the direct reduced iron after it enters the molten pool, lowering the main heating load on the electric furnace. This is beneficial for maintaining the continuity and stability of the smelting process when available green electricity is scarce or fluctuates significantly.

[0086] In one embodiment of the present invention, the first preheating time and the second preheating time can be preset by the device operating parameters and can be adjusted according to factors such as furnace type, furnace cycle time, direct reduced iron particle size, and oxygen content. The green electricity supply status can be characterized by the available power information or short-term fluctuation level on the power supply side. The control system updates the preheating time selection once before each feeding or at each furnace stage to match the heat input requirements of the electric furnace smelting stage.

[0087] In one embodiment of the present invention, the load-adjustable green electric furnace smelting method of the present invention further includes: When the direct reduced iron is preheated in the preheating silo, the direct reduced iron is stirred by the stirring blade in the preheating silo to improve the uniformity of preheating.

[0088] In one specific embodiment of the present invention, the load-adjustable green electric furnace smelting method of the present invention includes the following steps: Step 1: The exhaust fan is on. After the previous heat of steel and slag is tapped, sand is poured into the tapping port through the charging port on the furnace cover to block the tapping port.

[0089] Step 2: Start the DRI feeding conveyor. Open the top door fulcrum of the gravity-closed door by pushing open the top door rod, allowing the ambient temperature DRI to enter the DRI preheating storage bin.

[0090] Step 3: After feeding is complete, turn off the DRI feeding conveyor, lower the top gate lever, and close the gravity-operated gate. Turn on the stirring blades in the preheating silo to stir the DRI in the preheating silo to improve preheating uniformity.

[0091] Step 4: After the DRI preheating is complete, open the pull-out grid valve to make the preheated DRI ready for feeding.

[0092] Step 5: Drive the rotating material feeding system to move the feeding channel to the corresponding position of the furnace cover loading port. The telescopic loading port extends upward and connects with the feeding channel. The scale sensor door at the furnace cover loading port automatically opens, allowing the preheated DRI to enter the molten pool through the feeding channel.

[0093] Step 6: To prepare the surface material, turn off the exhaust fan. Open the top gate rod and open the pull-out grid valve to allow the DRI crushed powder or mineral powder to be conveyed to the feeding channel via the belt conveyor, and then dispersed on the surface of the molten pool by the rotating material distributor to form submerged arc heating conditions.

[0094] Step 7: After the surface material is laid, close the top door rod, turn on the exhaust fan and power it on to generate a plasma arc in the plasma arc heating device to perform the main heating of the molten pool.

[0095] Step 8: Collect temperature information of the refractory material in the electric furnace body via a temperature-measuring optical fiber. The data processing unit calculates the molten steel temperature based on this temperature information and the temperature gradient within the refractory material. Furthermore, based on the DRI addition amount, flue gas temperature, and molten steel temperature, and combined with a material balance and energy balance model, it calculates the electric furnace smelting load in real time.

[0096] Step 9: When the green electricity fluctuation causes an arc interruption, the electromagnetic induction coil is activated to heat the molten pool, and the data processing unit performs a prediction of the power supply to the power grid.

[0097] Step 10: After electromagnetic induction heating has continued for a preset time, if the prediction result indicates that the power grid has dispatchable power, then switch to continue heating via plasma arc; if the prediction result indicates that the power grid does not have dispatchable power, then continue induction heating via electromagnetic induction coil to maintain continuous heat input.

[0098] Step 11: Control the temperature of the molten pool to be maintained in the range of 1550℃ to 1580℃, so that the iron phase in DRI melts into the molten steel, while the slag phase is in an incompletely melted state, thus promoting slag-iron separation.

[0099] Step 12: After the slag and iron are separated, open the sand baffle and tap the steel.

[0100] Step 13: After tapping the steel, remove the slag to complete the smelting process for this furnace.

[0101] In another specific embodiment of the present invention, based on an 80t electric furnace, the load-adjustable green electric furnace smelting method of the present invention includes the following steps.

[0102] Step 1: The exhaust fan is on. After the previous heat of steel and slag is tapped, sand is poured into the tapping opening through the charging port on the furnace cover to block the tapping opening.

[0103] Step 2: Push the top door lever open the gravity-closed door's top door support point, start the DRI feeding belt conveyor to feed the material at a feeding speed of 10t / min, so that the ambient temperature DRI enters the DRI preheating storage silo.

[0104] Step 3: After feeding for 3 minutes, turn off the feeding conveyor belt, lower the top gate lever, and allow the gravity-operated closing door to close. Turn on the stirring blade to agitate the DRI to ensure uniform preheating. Adjust the preheating time according to the green electricity supply status. When the green electricity supply is sufficient, shorten the preheating time to reduce the DRI inlet temperature; when the green electricity supply is insufficient, extend the preheating time to increase the DRI inlet temperature.

[0105] Step 4: After preheating, open the pull-out grid valve.

[0106] Step 5: Drive the rotating material feeding system to move the feed channel to the corresponding position of the furnace cover charging port. The charging port extends upward and connects with the feed channel, and the scale sensor door opens, allowing the DRI to enter the molten pool.

[0107] Step 6: Turn off the exhaust fan, open the top door rod and open the pull-out grid valve to allow the DRI crushed powder or mineral powder to be conveyed to the feeding channel by the belt conveyor and dispersed on the surface of the molten pool by the rotating cloth to form submerged arc heating conditions.

[0108] Step 7: Close the top door rod, turn on the exhaust fan and power it on to generate a plasma arc in the plasma arc heating device to heat the molten pool.

[0109] Step 8: Collect temperature information of refractory materials in the furnace through fiber optic temperature measurement, and calculate the temperature of molten steel by combining the temperature gradient in the refractory materials; calculate the electric furnace smelting load in real time based on indicators such as DRI addition amount, flue gas temperature and molten steel temperature, combined with material balance and energy balance models.

[0110] Step 9: After 5 minutes of arc heating, the green electricity fluctuations trigger the arc to break, the electromagnetic induction coil is activated for medium-frequency induction heating, and the power grid is replenished.

[0111] Step 10: After 10 minutes of electromagnetic induction heating, if the power grid has no dispatchable power, continue to use electromagnetic induction heating.

[0112] Step 11: Control the electric furnace temperature to maintain it within the range of 1550℃ to 1580℃, so that the iron phase in DRI melts into the molten steel, while the slag phase remains in an incompletely melted state, thus promoting slag-iron separation.

[0113] Step 12: After melting for 20 minutes, it will reach a clear melt state.

[0114] Step 13: Rotate the sand baffle.

[0115] Step 14: Steel tapping and slag removal are completed, thus finishing the smelting process for this furnace.

[0116] As can be seen from the above embodiments, the solution of the present invention has at least the following beneficial effects: 1. This invention combines plasma arc heating with electromagnetic induction heating, which can continue to input heat into the molten pool even when the arc is interrupted due to green power fluctuations, thereby reducing the impact of arc interruption on the continuity of smelting and improving the stable operation capability of the electric furnace under unstable power supply conditions.

[0117] 2. This invention uses a temperature-measuring optical fiber to collect the temperature of the refractory material above the furnace shell in real time, and combines the temperature gradient of the refractory material to calculate the temperature of the molten steel. It also introduces a material balance and energy balance model to calculate the smelting load in real time, so that the smelting process has a basis for load assessment and supports load prediction and adjustment.

[0118] 3. This invention, through the coordination of the adjustable DRI preheating chamber and the belt feeding system, shortens the preheating time and reduces the DRI furnace inlet temperature when there is a surplus of green electricity, so that the furnace heat input demand can be matched with the power supply capacity, thereby improving the flexibility of green electricity consumption.

[0119] 4. This invention guides the heat from the flue gas to a waste heat boiler for recovery, thereby realizing the secondary utilization of waste heat from the smelting process, reducing heat waste, and improving the overall energy efficiency of the system.

[0120] 5. This invention achieves DRI dispersion by combining a preheating chamber with a rotating material feeding system, reducing the risk of low-temperature DRI accumulating in the furnace, mitigating local temperature disturbances in the molten pool, and improving the controllability of the feeding process.

[0121] 6. This invention links the furnace cover feeding scale sensor door with the feeding channel's feeding action, so that the feeding port is only opened during the feeding stage and kept closed during the non-feeding stage, reducing flue gas overflow during smelting and improving the furnace's airtightness and working environment.

[0122] 7. This invention maintains the plasma arc submerged arc heating conditions by laying DRI crushed powder or mineral powder on the surface of the molten pool to form a covering layer, thereby improving the stability of the arc heating process and reducing the fluctuations caused by exposed arc.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A green electric furnace smelting apparatus with adjustable load, characterized in that, include: The electric furnace body, within which a molten pool is formed for melting direct reduced iron; A plasma arc heating device is used to primarily heat the molten pool using green electricity; An electromagnetic induction coil is installed on the outside of the electric furnace body to perform non-contact induction heating on the molten pool when the plasma arc heating device is interrupted due to green electricity fluctuations, so as to maintain the continuity of heat input in the smelting process. The direct reduced iron feeding and preheating system includes a preheating silo for preheating the direct reduced iron, wherein the preheating time of the preheating silo is adjustable to dynamically adjust the furnace temperature of the direct reduced iron entering the furnace according to the green electricity supply status. A rotating feeding system is used to uniformly disperse preheated direct reduced iron into the molten pool, and to lay direct reduced iron crushed powder or mineral powder on the surface of the molten pool to achieve submerged arc heating. A temperature-measuring optical fiber is embedded in the refractory material near the molten pool in the furnace body of the electric furnace, and is used to collect temperature information reflecting the thermal state of the molten pool. The data processing unit is connected to the temperature-measuring optical fiber, the plasma arc heating device, the electromagnetic induction coil, and the direct reduced iron (DRI) feeding and preheating system, respectively. It is used to evaluate the thermal state of the molten pool based on the temperature information, combined with the DRI addition amount and flue gas temperature information. Based on the molten pool thermal state evaluation results, it outputs control commands to adjust the heating power of the plasma arc heating device, control the start / stop state of the electromagnetic induction coil, and adjust the preheating time of the DRI, thereby maintaining the continuity of heat input in the smelting process under fluctuating green electricity conditions.

2. The load-adjustable green electric furnace smelting apparatus according to claim 1, characterized in that, The preheating silo is equipped with a stirring blade to stir the direct reduced iron during the preheating process, thereby improving the uniformity of preheating. The preheating silo is configured to shorten the preheating time of direct reduced iron under conditions of sufficient green electricity supply, so as to reduce the furnace temperature of direct reduced iron entering the furnace.

3. The load-adjustable green electric furnace smelting apparatus according to claim 1, characterized in that, The rotating feeding system includes a feeding channel, a sliding track, and a telescopic feeding port; the feeding channel is configured to move along the sliding track to directly above the furnace cover feeding port on the electric furnace cover, and is used to introduce direct reduced iron into the molten pool; The telescopic feeding port is configured to communicate with the furnace cover feeding port when the feeding channel is in position, so as to provide a material channel during the feeding process; The furnace cover is equipped with a scale-shaped sensor door at the feeding port. The scale-shaped sensor door is configured to open automatically when the feeding channel is in place and feeding is carried out, and to remain closed when not feeding, so as to prevent the flue gas inside the furnace from overflowing during the smelting process.

4. The load-adjustable green electric furnace smelting apparatus according to claim 1, characterized in that, The data processing unit is specifically used to calculate the molten steel temperature based on the temperature information and the temperature gradient in the refractory material; and to calculate the electric furnace smelting load based on the molten steel temperature, the amount of direct reduced iron added, and the flue gas temperature, combined with the material balance and energy balance model, so as to generate the control command according to the smelting load.

5. The green electric furnace smelting apparatus with adjustable load according to claim 1, characterized in that, The data processing unit is specifically used to control the electromagnetic induction coil to start induction heating when the plasma arc heating device experiences arc interruption due to green electricity fluctuations, and to perform a prediction of the power grid's replenishment power to determine whether the power grid has dispatchable power; after the induction heating continues for a preset time, if the prediction result indicates that the power grid has dispatchable power, the plasma arc heating device is controlled to continue arc heating; if the prediction result indicates that the power grid does not have dispatchable power, the induction heating is controlled to continue through the electromagnetic induction coil.

6. The load-adjustable green electric furnace smelting apparatus according to claim 1, characterized in that, The data processing unit is specifically used to maintain the temperature of the molten pool at 1550°C to 1580°C by outputting control commands during plasma arc heating or electromagnetic induction heating, so that the iron phase in the direct reduced iron melts while the slag phase remains in an incompletely melted state, thereby promoting slag-iron separation.

7. The load-adjustable green electric furnace smelting apparatus according to claim 3, characterized in that, The direct reduced iron (DRI) feeding and preheating system also includes a feeding belt conveyor and a pull-out grid valve located at the bottom of the preheating silo. The feeding belt conveyor is used to transport DRI at room temperature to the preheating silo. The pull-out grid valve is used to discharge the preheated DRI from the preheating silo and into the feeding channel of the rotary fabric distribution system when it is opened.

8. The load-adjustable green electric furnace smelting apparatus according to claim 1, characterized in that, It also includes a flue gas waste heat recovery system, which includes a waste heat boiler, a gas filter, and an exhaust fan; the exhaust fan is used to guide the flue gas generated during the smelting process through the gas filter and into the waste heat boiler for waste heat recovery, so as to use the heat for secondary utilization.

9. The load-adjustable green electric furnace smelting apparatus according to claim 8, characterized in that, In the preheating storage silo, direct reduced iron is preheated by the flue gas generated during the smelting process; under the condition of sufficient green electricity supply, a first preheating time is used to preheat the direct reduced iron; under the condition of insufficient green electricity supply, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time. When preheating is performed using the first preheating time, the exhaust fan is operated at a first set speed to recover flue gas from the preheating storage bin to the waste heat boiler; when preheating is performed using the second preheating time, the exhaust fan is operated at a second set speed to recover flue gas or not to recover flue gas, wherein the first set speed is greater than the second set speed.

10. A method for smelting in a green electric furnace with adjustable load, characterized in that, The method, applied to the load-adjustable green electric furnace smelting apparatus according to any one of claims 1 to 9, comprises: Direct reduced iron at room temperature is fed into a preheating silo for preheating, and the preheating time is adjusted according to the green electricity supply status. After preheating, the pull-out grid valve at the bottom of the preheating storage bin is opened to allow the preheated direct reduced iron to enter the rotating feeding system and then be added to the molten pool inside the electric furnace through the furnace cover charging port. After adding preheated direct reduced iron, the direct reduced iron crushed powder or mineral powder is dispersed and distributed on the surface of the molten pool through the rotary feeding system to form submerged arc heating conditions. The molten pool is heated by a green electric plasma arc heating device, and the temperature information of the refractory material in the furnace body is collected by a temperature measuring fiber. Based on the temperature information and the temperature gradient in the refractory material, the temperature of the molten steel is calculated. The molten steel temperature is calculated in real time by combining the amount of direct reduced iron added, the flue gas temperature and the molten steel temperature. The smelting load of the electric furnace is calculated in real time using a material balance and energy balance model. Based on this, control commands are output to adjust the plasma arc heating power and the preheating time of direct reduced iron. When the green electricity fluctuation causes the plasma arc to break, the electromagnetic induction coil is activated to heat the molten pool induction and the power grid is predicted to replenish the power. After the induction heating continues for a preset time, depending on whether the power grid has dispatchable power, it is selected to continue heating by plasma arc or continue heating by electromagnetic induction. After smelting is completed, steel is tapped and slag is removed.

11. The green electric furnace smelting method with adjustable load according to claim 10, characterized in that, The adjustment of preheating time according to the green electricity supply status includes: When the supply of green electricity is sufficient, a first preheating time is used to preheat the direct reduced iron; when the supply of green electricity is insufficient, a second preheating time is used to preheat the direct reduced iron, wherein the first preheating time is shorter than the second preheating time.

12. The green electric furnace smelting method with adjustable load according to claim 10, characterized in that, Also includes: When the direct reduced iron is preheated in the preheating silo, the direct reduced iron is stirred by the stirring blade in the preheating silo to improve the uniformity of preheating.

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