Gas-electricity synergistic steel melting method and device

Abstract

The invention discloses a gas-electricity synergetic steel melting method and device, which are characterized in that after waste steel is partially melted into molten steel, the surface of the molten steel and the exposed waste steel are heated by adopting a gas combustion mode, and the molten steel is heated by adopting an electromagnetic induction mode; the steel scrap softening critical temperature is broken through in a short time through central heating of the gas burner; and then accurate melting of the waste steel is achieved through electromagnetic induction targeted heat compensation, so that the heating melting efficiency of the whole waste steel is greatly improved, and energy consumption is also greatly reduced. In addition, cooperative control over natural gas and electric power is achieved based on energy price sensitivity analysis, the gas-electricity proportion is dynamically distributed through an established real-time optimization model based on energy price and equipment efficiency, and therefore the purpose of achieving rapid melting of waste steel at low cost is achieved. The method and the device have the advantages of being short in process, simple in structure, convenient and fast to operate and control and the like.

Description

Technical Field

[0001] The present invention relates to a steel smelting process, and in particular to a gas-electricity coordinated steel melting method and device, belonging to the technical field of steel smelting. Background Art

[0002] Currently, there are two distinct steelmaking processes: the long converter (BOF) process and the short electric furnace (EAF) process. The long converter process primarily uses molten iron produced from ore and coal coke as raw material, offering a short smelting cycle, high production efficiency, and low cost per ton of steel. However, its drawback is that the production of molten iron involves sintering and pelletizing processes, as well as blast furnace operations. This results in high carbon emissions and severe environmental pollution, which is inconsistent with the national strategy of achieving carbon peak and carbon neutrality. The short electric furnace process primarily uses recycled, crushed, and sorted scrap steel as raw material, without involving other processes. This reduces carbon emissions and environmental pollution. However, its drawbacks are a long smelting cycle, low production efficiency, and high cost per ton of steel. Scrap steel is a cleaner resource than ore and can be recycled endlessly. Compared to using ore and coke to produce steel, using scrap steel in steelmaking significantly reduces emissions of waste gas, wastewater, and waste residue. The "Steel Industry Adjustment Policy" also clearly states that "by 2025, the proportion of scrap steel in steelmaking by Chinese steel enterprises will be no less than 30%."

[0003] With the annual increase in domestic scrap steel resources, increasing scrap utilization is gaining increasing attention among steelmakers, both in the short EAF process and the long BOF process. For the long process, increasing the scrap ratio significantly reduces carbon emissions while also improving resource efficiency and significantly lowering production costs. For the short process, increasing the scrap ratio or even using only scrap steel for smelting aligns with the dual carbon policy. Increasing scrap preheating can significantly reduce production costs and enhance the competitiveness of the short process.

[0004] In the existing technology, the temperature of the scrap steel after preheating is generally far from its melting temperature, so it is necessary to continue to heat and raise the temperature in the steel melting furnace until it melts into molten steel. The heating method of the existing steel melting furnace is mainly gas combustion heating. The temperature of the scrap steel can be easily reached to about 1000°C by using burner combustion to heat the scrap steel. However, if the scrap steel temperature is to exceed 1000°C and reach the melting point temperature and then melt the scrap steel into molten steel, the gas consumption will increase greatly, and the temperature will rise slowly, the scrap steel will be severely oxidized, and the high-temperature flue gas cannot be effectively utilized. The energy utilization efficiency is not high, the melting efficiency is low, and the melting cost will be significantly increased. Summary of the Invention

[0005] In view of the shortcomings of the prior art in which scrap steel is melted only by gas combustion, such as low melting efficiency and low energy utilization efficiency, the present invention provides a gas-electricity coordinated steel melting method and device. After partially melting the scrap steel into molten steel, the surface of the molten steel and the exposed scrap steel are heated by gas combustion, and the molten steel is heated by electromagnetic induction. The combustion heating can quickly heat the scrap steel to about 1000°C. At this temperature, electromagnetic induction can efficiently transfer heat through the existing molten steel, and then quickly heat the scrap steel to about 1500~1600°C and melt it into molten steel. In other words, the present invention achieves rapid melting of scrap steel through the means of gas combustion coupled with electric heating, and at the same time, the energy utilization efficiency is also greatly improved.

[0006] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows: According to a first embodiment of the present invention, a gas-electricity coordinated steel melting method is provided: A gas-electricity coordinated steel melting method, the method comprising the following steps: 1) Initial melting stage: Steel is added to the steel melting furnace, and the gas burner and / or electromagnetic induction heater are started to heat and melt the steel until molten steel is obtained.

[0007] 2) Continued melting stage: Continue adding steel to the steel melting furnace, use gas burners to heat the surface of the molten steel and the steel exposed on the surface of the molten steel, and use electromagnetic induction heaters to heat the molten steel and the scrap steel submerged in the molten steel until the steel is melted into molten steel and repeat step 2).

[0008] Preferably, the method further comprises: 3) Use the high-temperature flue gas generated in the steel melting furnace to preheat the steel to be melted in the furnace.

[0009] Preferably, the average temperature of the steel after preheat treatment is not less than 300°C, preferably not less than 400°C.

[0010] Preferably, during the continued melting stage, a gas and electricity supply distribution model is established under target working conditions using energy consumption cost as an independent variable, and the real-time energy supply ratios of gas and electricity are calculated based on the distribution model, thereby achieving low-cost steel melting. The energy supply distribution model is as follows: (I).

[0011] In formula (I), x It is the ratio of the energy supplied by gas to the total energy required for the target working condition. S gas The real-time unit price of gas is RMB / m³. S elecis the real-time unit price of electricity, RMB / (kW·h). elec is the thermal efficiency of the electromagnetic induction heater. gas is the thermal efficiency of the gas burner. H gas is the calorific value of gas, MJ / m³. The real-time energy supply ratio of gas under different energy consumption costs is calculated by formula (I), and the real-time energy supply ratio of electricity is (1- x ).

[0012] As a preference, the real-time operating power of the gas burner is adjusted according to the real-time energy supply ratio of the gas to meet the working conditions. The actual minimum operating power of a single gas burner under the current working conditions should satisfy the following formula: P gas = xMC ( T obje -T 0 ) / ( nt γ gas ) (II).

[0013] In formula (II), P gas The actual minimum operating power of a single gas burner, MW. M is the mass of steel to be melted in the current steel melting furnace, kg. C is the specific heat capacity of steel, kJ / (kg·℃). T obje is the target melting temperature in the steel melting furnace, ℃. T 0 The temperature of the steel when it enters the steel melting furnace, ℃. n The number of gas burners opened, pcs. t is the melting cycle of steel, s. Under the current working conditions, the lowest real-time working power of a single gas burner is adjusted to the value calculated by formula (II) P gas So that the real-time energy supply ratio of gas is x .

[0014] As a preference, the real-time operating power of the electromagnetic induction heater is adjusted according to the real-time energy supply ratio demand to meet the working conditions. Under the current working conditions, the actual minimum operating power of the electromagnetic induction heater should satisfy the following formula: P elec =(1- x ) MC ( T obje -T 0 ) / ( t γelec ) (III).

[0015] In formula (III), P elec is the actual minimum operating power of the electromagnetic induction heater, MW. M is the mass of steel to be melted in the current steel melting furnace, kg. C is the specific heat capacity of steel, kJ / (kg·℃). T obje is the target melting temperature in the steel melting furnace, ℃. T 0 The temperature of the steel when it enters the steel melting furnace, ℃. t is the melting cycle of steel, s. Under the current working conditions, the real-time working power of the electromagnetic induction heater is adjusted to the lowest value calculated by formula (III) P elec So that the real-time energy supply ratio of electric energy is (1- x ).

[0016] As a preferred option, the minimum operating power of a single gas burner when the energy required for steel melting is all supplied by gas is set to P allgas , then when the calculated value x When <0.1, the actual minimum working power of a single gas burner P gas =(0.05~0.15) P allgas .

[0017] As a preferred method, the minimum operating power of the electromagnetic induction heater when the heat required for steel melting is all supplied by electricity is set to P allelec , then when the calculated value (1- x )<0.05, the actual minimum working power of the electromagnetic induction heater P elec =(0.05~0.1) P allelec , preferably when the calculated value (1- x )<0.05, P elec The value ranges from 40000 to 60000W, for example, 50000W.

[0018] According to a second embodiment of the present invention, a gas-electricity coordinated steel melting device is provided: A gas-electricity-coordinated steel melting device, or a steel melting device used in the method described in the first embodiment, comprises a steel melting furnace, a gas heating mechanism, and an electric heating mechanism. The steel melting furnace comprises a furnace shell and a furnace chamber, with a charging channel connected to the furnace chamber at the upper portion of the furnace shell. The gas heating mechanism is disposed at the upper portion of the furnace chamber, and the electric heating mechanism is disposed at the lower portion of the furnace chamber. A molten steel outlet is provided at the bottom of the furnace chamber.

[0019] Preferably, the gas heating mechanism includes a burner and an air inlet pipe. The combustion end of the burner extends through the furnace shell near the charging channel and into the furnace. The air inlet end of the burner is connected to the air inlet pipe, through which gas and auxiliary gas are transported to the burner for combustion and heating. Preferably, a gas flow regulating valve is also provided on the air inlet pipe.

[0020] Preferably, the electric heating mechanism is an electromagnetic induction coil, which is arranged in a surrounding manner in the furnace shell.

[0021] Preferably, a thermal imager is also provided at the top of the furnace cavity.

[0022] Preferably, the feeding channel is one of a horizontal channel, a vertical channel and an inclined channel.

[0023] Preferably, the feeding channel is an inclined channel, and a partition is provided in the inclined channel to separate the inclined channel from top to bottom into a material storage area and a preheating area. A material blocking claw is provided at the bottom end of the preheating area, and a smoke outlet is also provided at the upper end of the preheating area.

[0024] Preferably, a thermocouple and a pressure sensor are provided in the smoke outlet duct, and a speed-regulating fan is connected to the smoke outlet of the smoke outlet duct.

[0025] Preferably, one end of the partition passes through the top wall of the feeding channel and is connected to a lifting drive motor arranged outside, and the lifting drive motor drives the partition to rise and fall, thereby realizing the opening and closing of the partition.

[0026] Preferably, a rotary drive motor connected to the material blocking claw is provided at the bottom end of the preheating zone, and the rotary drive motor drives the material blocking claw to be lifted and lowered in a swinging arc (for example, the top end of the material blocking claw is hinged to the feeding channel by a bearing and a rotating shaft, and the material blocking claw can swing in an arc shape up and down under the support of the hinge. The rotary drive motor drives the material blocking claw to rotate and swing upward to open the material blocking claw, and the scrap steel can slide downward along the feeding channel; the rotary drive motor drives the material blocking claw to rotate and swing downward to close the material blocking claw, and the scrap steel is blocked by the material blocking claw), thereby realizing the opening and closing of the material blocking claw.

[0027] Preferably, a cooling medium channel and a cooling medium inlet and a cooling medium outlet connected to the cooling medium channel are further provided inside the material blocking claw.

[0028] Preferably, the steel melting device also includes a controller, which is respectively associated with the gas heating mechanism, the electric heating mechanism thermocouple, the pressure sensor, the speed regulating fan, the lifting drive motor, the rotation drive motor, and the thermal imager and comprehensively controls their working states.

[0029] In the prior art, preheating and melting scrap steel using burners alone can easily reach a preheating temperature of around 1000°C, resulting in relatively low overall costs. However, if the scrap steel is to be melted into molten steel at a temperature of 1500-1600°C, gas consumption will increase significantly, the temperature rise will be slow, the scrap steel will be severely oxidized, and the high-temperature flue gas cannot be effectively utilized, resulting in low energy efficiency and high costs. While electromagnetic induction heating alone can be highly energy efficient for preheating and melting scrap steel, it has a slow temperature rise rate at relatively low scrap temperatures (below 800°C), consumes a large amount of electricity, and has high heating costs. Therefore, the present invention couples gas burner heating with electromagnetic induction heating, utilizing gas combustion to rapidly raise the temperature of the molten steel liquid level and exposed scrap steel, while simultaneously utilizing electromagnetic induction to further raise the temperature of the liquid below the molten steel liquid level and the scrap steel, thereby efficiently and quickly melting the scrap steel. That is to say, in the process of heating and melting scrap steel, gas combustion is used to quickly and cheaply raise the scrap steel temperature to above 800°C, and then electromagnetic induction is used to further heat and melt the scrap steel. When the scrap steel temperature exceeds its melting point and becomes liquid, the comprehensive thermal efficiency of electromagnetic induction heating will be further improved due to the electromagnetic stirring effect (heat transfer efficiency is increased by 15~20%), and the melting efficiency will be further improved, while the cost can be reduced again.

[0030] In this invention, the integrated utilization of gas and electricity for scrap melting significantly reduces the impact of market energy price fluctuations or climate change (primarily electricity prices) compared to single-energy sources. This effectively avoids the high-cost constraints of using a single energy source, which can be forced to maintain production when prices rise. Furthermore, this invention utilizes a synergistic gas and electricity melting process, allowing for coordinated allocation of both energy usage based on price fluctuations. This minimizes unit production costs while meeting scrap melting requirements, significantly improving the economic benefits of production.

[0031] In this invention, in order to maximize the benefits of gas-electricity synergistic melting, it is necessary to adjust the burner power and electromagnetic induction power in real time according to energy prices during the scrap steel melting process, thereby reducing the total energy consumption. Therefore, the first thing to determine is the total energy required to heat a certain weight (single charge amount or single furnace charge amount) of scrap steel to a certain temperature: set the total energy demand as Q total, then each ton of scrap steel is melted to a temperature of T obje The energy required is Q=C × △T ,in △T = T obje - T 0 , T 0 is the initial temperature of the scrap entering the furnace (generally the temperature of the scrap after being efficiently preheated by the process flue gas and then entering the steel melting furnace). If the capacity of the steel melting furnace is A M Tons, the total energy requirement is Q total = M × Q = M × C ×( T obje -T 0 ). Then ensure that the energy supply meets Q total Under the premise of dynamically adjusting the use ratio of gas and electricity according to the fluctuating energy prices, assuming that natural gas burners are used (taking two as an example), the melting cycle of t a for t 1 , thermal efficiency is γ gas The calorific value of natural gas is H gas , then the power of a single burner is P gas ≥ Q total / (2 t 1 γ gas ),in P gas Rounded value, including redundancy. Assume that the melting cycle of the electromagnetic induction system (taking one set as an example) is t a for t 2 , the electrothermal efficiency of the electromagnetic induction system is γ elec , then the power of the electromagnetic induction system is P elec ≥ Q total / ( t 2 γ elec ),in P elecRounded values, including redundancy. Then, during the real-time adjustment process, by dynamically adjusting the ratio of natural gas to electricity usage, and taking advantage of the price fluctuations between the two, the total smelting cost is minimized: (i) Total energy demand Q total Allocated proportionally to natural gas and electricity: Q total = Q gas + Q elec ;in, Q gas = xQ total , Q elec =(1- x ) Q total , x The energy supply share of natural gas.

[0032] (ii) Set the real-time natural gas price to S gas , the real-time electricity price is S elec , then: Total cost = Q gas S gas / (γ gas H gas )+ Q elec S elec / γ elec , substitute Q gas and Q elec Then we have: Total cost = Q total [ xS gas / (γ gas H gas )+(1- x ) S elec / 3.6γ elec ].

[0033] (iii) Derivative the total cost function and set the derivative to zero, solving for x : .

[0034] , .

[0035] The energy supply distribution model of the two energy sources can be obtained by integrating them: (I).

[0036] In formula (I), x It is the ratio of the energy supplied by gas to the total energy required for the target working condition. S gas The real-time unit price of gas is RMB / m³. S elec is the real-time unit price of electricity, RMB / (kW·h). elec is the thermal efficiency of the electromagnetic induction heater. gas is the thermal efficiency of the gas burner. H gas is the calorific value of gas, MJ / m³. The real-time energy supply ratio of gas under different energy consumption costs is calculated by formula (I), and the real-time energy supply ratio of electricity is (1- x ).Proportion x Determined by the current energy price: when the natural gas price is low, increase the burner power; when the electricity price is low, increase the electromagnetic induction power.

[0037] (iv) The adjustment of the energy supply ratio of gas and electricity is mainly achieved by adjusting the real-time working power of the gas burner and the electromagnetic induction heater: According to the real-time gas energy supply ratio demand, the real-time working power of the gas burner is adjusted to meet the working conditions. Under the current working conditions, the actual minimum working power of a single gas burner should meet the following formula: P gas = xMC ( T obje -T 0 ) / ( nt γ gas ) (II).

[0038] In formula (II), P gas The actual minimum operating power of a single gas burner, MW. M is the mass of steel to be melted in the current steel melting furnace, kg. C is the specific heat capacity of steel, kJ / (kg·℃). T obje is the target melting temperature in the steel melting furnace, ℃. T 0 The temperature of the steel when it enters the steel melting furnace, ℃. n The number of gas burners opened, pcs. tis the melting cycle of steel, s. Under the current working conditions, the lowest real-time working power of a single gas burner is adjusted to the value calculated by formula (II) P gas So that the real-time energy supply ratio of gas is x .

[0039] According to the real-time energy supply ratio of electric energy, the real-time working power of the electromagnetic induction heater is adjusted to meet the working conditions. Under the current working conditions, the actual minimum working power of the electromagnetic induction heater should meet the following formula: P elec =(1- x ) MC ( T obje -T 0 ) / ( t γ elec ) (III).

[0040] In formula (III), P elec is the actual minimum operating power of the electromagnetic induction heater, MW. M is the mass of steel to be melted in the current steel melting furnace, kg. C is the specific heat capacity of steel, kJ / (kg·℃). T obje is the target melting temperature in the steel melting furnace, ℃. T 0 The temperature of the steel when it enters the steel melting furnace, ℃. t is the melting cycle of steel, s. Under the current working conditions, the real-time working power of the electromagnetic induction heater is adjusted to the lowest value calculated by formula (III) P elec So that the real-time energy supply ratio of electric energy is (1- x ).

[0041] In the present invention, the real-time function flow of adjusting the gas burner and electromagnetic sensor is as follows: First, real-time data input: real-time update and input of natural gas price S gas and electricity prices elec Then calculate the optimal ratio: Dynamically calculate the ratio of natural gas to electricity according to formula (I) x and (1- x ). Finally, the execution strategy: when the electricity price is low, reduce x , increase the proportion of electricity use (1- x ); When natural gas prices are low, increase x , increase the proportion of natural gas use (1- x). Specific adjustment: The adjustment of the gas burner is mainly achieved by continuously adjusting the gas flow through the proportional valve to achieve precise control of the total power; if the gas energy supply after adjustment accounts for x i <0.1, the actual working power of the two gas burners after adjustment P gas1-i = ‌P gas2-i =0.1 ‌P allgass ( P allgas The minimum operating power of a single gas burner when the energy required for steel melting is all supplied by gas to prevent flameout or unstable combustion. x i ≥0.1, then P gas1-i = ‌P gas2-i = x i ‌P allgass ‌ The regulation of the electromagnetic induction system is mainly to dynamically adjust its actual working power with the fluctuation of electricity price under the premise of maintaining basic operation. If the actual energy supply after adjustment accounts for (1- x i )≥0.05, then the actual working power of the electromagnetic induction system after adjustment P elec-i =(1-xi) P allelec ( P allelec is the minimum working power of the electromagnetic induction heater when the energy required for steel melting is all supplied by electricity), if (1- x i )<0.05, then P elec-i =(0.05~0.1) P allelec =40~60kW, which puts the electromagnetic induction system into standby mode to avoid complete shutdown.

[0042] The steel melting device provided in the present invention is primarily a steel melting furnace, comprising a furnace shell and a furnace chamber. Within the furnace chamber are located gas-fired heating burners (i.e., gas-fired heating mechanisms, such as gas burners) for rapidly heating scrap steel, and electromagnetic heaters (i.e., electric heating mechanisms, such as electromagnetic induction coils) for rapidly melting the scrap steel. The gas burners are used to rapidly heat the scrap steel entering the furnace chamber (particularly scrap steel accumulated above molten steel; during continuous production, a certain amount of molten steel is typically reserved within the furnace chamber). They utilize a preheating structure, including a combustion air casing and a gas casing. A tubular heat exchanger can be provided at the front end of the combustion air chamber, utilizing high-temperature flue gas to preheat the combustion air and conserve energy. A gas-fired heating burner is typically positioned on either side of the scrap steel landing area within the furnace chamber, each burner having specific horizontal and vertical deflection angles. Electromagnetic induction coils are primarily used to rapidly melt scrap steel in molten steel. They utilize electromagnetic induction to heat the molten steel, rapidly melting the scrap through heat transfer from the molten steel. The alternating magnetic field generated by electromagnetic induction induces a current in the molten steel, which in turn generates heat through the resistance of the molten steel, thereby heating both the molten steel and the scrap. Specifically, when preheated scrap enters the melting furnace, it accumulates below the gas burners, with scrap at higher preheat temperatures accumulating below and scrap at lower preheat temperatures accumulating above. In a steel retention operation (reserving molten steel), hot scrap enters the furnace from the bottom, where the electromagnetic induction heater transfers heat from the molten steel to the scrap, achieving rapid melting. The purpose of steel retention is to maintain the molten steel in a liquid state. The electromagnetic force causes the molten steel to rotate and flow, allowing heat to be transferred more quickly to the scrap submerged in the molten steel, accelerating its temperature rise and melting. However, the cooler scrap accumulated above, unable to reach the molten steel, heats up more slowly due to electromagnetic induction heating alone. At this time, turn on the gas burner and use the heat generated by the combustion of natural gas to quickly preheat the low-temperature scrap steel above the molten steel, or even locally heat and directly melt the scrap steel, allowing the scrap steel to be immersed in the molten steel faster, thus greatly reducing the scrap steel heating time.

[0043] In this invention, the melting furnace adopts a dump-free tapping method, facilitating continuous production. The molten steel outlet is designed as a step. During normal steel retention, the molten steel level is lower than the tapping step. During tapping, a ladle is placed below the molten steel outlet. Acetylene is used to burn through the molten steel outlet, allowing molten steel to flow into the ladle. When the molten steel level falls below the tapping step, tapping is stopped and the molten steel outlet is blocked with drainage sand. The tapping step has a specific height (designed according to actual operating conditions).

[0044] In the present invention, a large amount of high-temperature flue gas (approximately 1200°C) is generated during the melting of scrap steel. This flue gas contains a large amount of waste heat, which can be used to preheat the scrap steel, thereby increasing the scrap steel entry temperature to improve melting efficiency and reduce melting energy consumption. Therefore, the steel melting method of the present invention also includes a step of using the high-temperature flue gas generated in the steel melting furnace to preheat the steel to be melted in the furnace. Similarly, the steel melting device of the present invention also includes a feed and preheating channel for adding scrap steel to the steel melting furnace and preheating it. The feed and preheating channel is separated by a partition into an upper storage area and a lower preheating area. A material blocking claw is provided at the connection between the lower preheating area and the furnace of the steel melting furnace, and a smoke outlet is provided at the upper end of the lower preheating area. The upper storage area and the lower preheating area are connected and isolated by the lifting and lowering of the partition, allowing the scrap steel temporarily retained in the upper storage area to enter the lower preheating area. The scrap steel is allowed to stay in the lower preheating area by the lowering and closing of the blocking claw. At the same time, the high-temperature flue gas from the furnace enters the lower preheating area and exchanges heat with the scrap steel in countercurrent before being discharged from the flue gas outlet. The blocking claw is then raised and opened to allow the preheated scrap steel to enter the furnace for melting. In other words, the three steps of scrap steel temporary retention, preheating, and melting are integrated to achieve continuous scrap steel melting production.

[0045] Furthermore, a flue gas temperature and pressure detector (such as a thermocouple and a pressure sensor) is provided at the smoke outlet to detect the temperature of the exhaust flue gas and the pressure at the smoke outlet in real time, and to predict and judge the utilization efficiency of the flue gas waste heat and the preheating effect of the scrap steel according to the change of the flue gas temperature at the smoke outlet. The preheating temperature of scrap steel is related to many factors, and it is difficult to predict and control the preheating temperature of scrap steel. The influence of various factors on the preheating temperature of scrap steel is analyzed below: First, the inclination angle α of the feed and preheating channel affects the state of the scrap steel in the channel, and thus affects the contact area A between the scrap steel and the flue gas. The contact area A can be expressed as A=A0(1+k A α), where k A is the contact area influence coefficient (experience value, generally 0.01~0.1), A0 is the contact area in the horizontal state. Secondly, the distance d between the blocking claws and the negative pressure P at the smoke outlet out Affects flue gas flow rate v g , which in turn affects heat transfer. The combined effect of the two factors leads to the flue gas velocity v g It can be expressed as , where k3 is the flue gas velocity influence coefficient (empirical value, generally 0.8~2.0), γ is the flue gas resistance coefficient, ρ g is the flue gas density. The steel melting furnace adopts a slightly negative pressure operation, preferably negative pressure P out Controlled within the range of 0 to -100 Pa. Again, it is also affected by the outlet flue gas temperature T out , inlet flue gas temperature T inInfluence: When the working condition of the steel melting furnace is stable, it can be considered that the inlet flue gas temperature T in Keep constant, generally believed to be up to 1200℃; outlet flue gas temperature T out The flue gas temperature at the outlet should not be too high, as it will result in low heat utilization rate. It is usually controlled at T out -T obj ≤50℃ is appropriate (T obj is the target preheating temperature of scrap steel). In addition, according to the heat balance, within a certain time t, the heat absorbed by the scrap steel is equal to the heat transferred to the scrap steel by the flue gas. Therefore, the scrap steel preheating temperature T s (Assuming the scrap temperature is uniform, the average scrap temperature is used instead) The calculation formula is as follows: .

[0046] From this we can get: .

[0047] In the above formula, k3 is the flue gas velocity influence coefficient, which ranges from 0.8 to 2.0. h is the heat transfer coefficient between scrap steel and flue gas, ranging from 15 to 80 W / (m 2 ·K). d is the distance between two adjacent retaining claws, cm. out is the negative pressure at the smoke outlet, Pa. γ is the smoke resistance coefficient. ρ g is the smoke density, g / cm 3 D is the diameter of the smoke outlet, cm. p is the specific heat capacity of flue gas, J / (kg·k). t is the duration of the unit time period, ranging from 60 to 600 seconds. in is the initial temperature of the flue gas, °C. out is the flue gas temperature at the smoke outlet, °C. m s is the mass of steel, kg. C s T is the specific heat capacity of steel, J / (kg·k). s,i T is the temperature of scrap steel before the current time period, ℃. s,i+1 is the temperature of scrap steel after the current time period, ℃ (i is an integer greater than or equal to 0, and T s,0 The above formula can be used to calculate the real-time preheating temperature of steel after different time periods. The specific scrap steel preheating temperature control process is as follows: Step 1: Input various parameters, including: the inclination angle α of the feeding and preheating channels, the distance d between the blocking claws, the heat transfer coefficient between the scrap steel and the flue gas h , scrap steel and flue gas contact area A0, scrap steel mass m s , scrap steel specific heat capacity C s, smoke outlet flue diameter D, flue gas specific heat capacity C p , steel size influence coefficient k1, flue gas velocity influence coefficient k3, flue gas resistance coefficient γ, flue gas density ρ g , adjust the pressure difference △P=10Pa, time interval △t=60s, inlet flue gas temperature T in =1200℃, initial scrap temperature T s,0 =25℃.

[0048] Step 2: According to the monitoring equipment, obtain the outlet negative pressure P after the time interval △t=60s out , outlet flue gas temperature T out , calculate the scrap preheating temperature T s,i , and calculate the difference between the scrap preheating temperature and the target preheating temperature, that is, △T=T s,it -T obj .

[0049] Step 3: If △T≤0, the average temperature of the scrap steel is lower than the target value and needs to be heated. At this time, first determine whether the outlet flue gas temperature is overheated to avoid heat loss. out -T obj ≤50℃, indicating that the outlet flue gas temperature is not over-temperature. At this time, adjust the fan power of the flue gas outlet to increase the outlet negative pressure, that is, P out,i+1 =P out,i -△P. The flue gas flow rate increases, and the heat transferred to the scrap steel in a certain period of time increases, which is conducive to the temperature rise of the scrap steel. It should be noted that in order to maintain low negative pressure operation, if the negative pressure P out,i+1 ≤-100Pa, then take P out,i+1 =-100Pa; if T out -T obj >50℃, indicating that the outlet flue gas temperature is over-temperature. At this time, adjust the fan power to reduce the outlet negative pressure, that is, P out,i+1 =P out,i +△P. The flue gas flow rate is reduced, and after the scrap steel absorbs heat, the outlet flue gas temperature naturally decreases. Similarly, in order to maintain a slightly negative pressure operation, if P out,i+1 >0Pa, then take P out,i+1 =-10Pa.

[0050] Step 4: If △T>0, the average temperature of the scrap steel has reached the target value, and only the temperature needs to be kept warm, and the preheated scrap steel is ready to be added to the melting furnace. At this time, set P out,i+1 =-10Pa and remain stable until the preheating of the scrap steel heat is completed. It should be noted that the numerical values ​​in the above statements are only exemplary values ​​for the convenience of explaining the technical solution, and are not limitations on the technical solution claimed in the present invention.

[0051] In the prior art, traditional preheating devices mostly adopt a simple horizontal or vertical structure, which has many shortcomings in terms of material transportation. For example, in horizontal preheating devices, scrap steel is transported by mechanical push, and the start-up and shutdown response is slow. It is difficult to accurately control the feeding amount and time interval, and the material transportation is often excessive or insufficient. In the present invention, the feeding and preheating channels with a certain inclination angle are preferably used to feed the steel melting furnace and preheat the scrap steel. The inclined feeding and preheating channels cleverly use gravity as the power for transporting different types of scrap steel by adjusting the inclination angle. They can slide down at a stable speed under the action of gravity, ensuring that the amount of scrap steel transported each time is accurately controlled, effectively solving the problem of the difficulty in controlling the material transportation rhythm of traditional devices. Compared with the traditional horizontal preheating device that relies on mechanical push to load materials, the loading efficiency of the inclined feeding and preheating channels is increased by 30~50%, which greatly shortens the loading time and improves the overall production efficiency. In addition, when high-temperature flue gas is used to preheat scrap steel in the inclined feeding and preheating channels, the contact area and contact time with the flue gas are greatly increased, and the utilization efficiency of the heat in the flue gas and the preheating temperature of the scrap steel are significantly improved.

[0052] In the present invention, when the scrap steel is loaded and preheated using an inclined feeding and preheating channel, the scrap steel will continue to slide downward under the action of its own gravity, and the length of the inclined feeding and preheating channel is generally fixed, that is, the time for the scrap steel to slide through the inclined feeding and preheating channel is generally relatively short. In this process, it is difficult to preheat the scrap steel to the target temperature. At the same time, it takes a certain amount of time for the scrap steel in the steel melting furnace to melt into molten steel. Therefore, it is impossible to continuously add scrap steel through the inclined feeding and preheating channel indefinitely. Therefore, intermittent addition is generally adopted, that is, by arranging a blocking claw at the bottom end of the inclined feeding and preheating channel to retain the scrap steel in the inclined feeding and preheating channel for a certain period of time. After the scrap steel is preheated to the target temperature, the blocking claw is opened to slide the preheated scrap steel into the steel melting furnace. At this time, the scrap steel of the previous batch in the steel melting furnace is basically melted into molten steel.

[0053] It should be noted that in the present invention, the inclined feeding and preheating channels are usually made of high-temperature resistant and wear-resistant alloy materials, which can withstand the erosion of high-temperature flue gas and the friction when the scrap steel slides. The inclined feeding and preheating channels serve as the main channels for the scrap steel to slide and exchange heat with the high-temperature flue gas. The use of gravity allows the scrap steel to slide naturally, reducing additional power consumption and greatly improving the feeding efficiency. At the same time, the inclined design increases the contact time and area between the scrap steel and the high-temperature flue gas, which is beneficial to improving the heat exchange efficiency. In addition, in order to better realize the waste heat of the scrap steel, the inclination angle α of the inclined feeding and preheating channels is not fixed, but is closely related to the characteristics of the scrap steel to be processed. That is to say, for different scrap steel, the inclination angle of the inclined feeding and preheating channels will also change accordingly. When preheating the scrap steel, determine the optimal inclination angle α It is very important to improve the preheating effect of scrap steel. Different types of scrap steel have differences in size, density, porosity, etc. These factors will affect the sliding characteristics of scrap steel, the force of the retaining claws, the permeability of flue gas and the heat exchange efficiency. Therefore, for the optimal inclination angle α The determination of scrap steel length should take into account the factors such as the scrap steel sliding speed and the force on the blocking claws. Assuming that the average length of scrap steel is l 0 (unit: m), the average width is w 0 (unit: m), the average thickness is h 0 (unit: m), then the motion equations of the sliding speed v (unit: m / s) of scrap steel of different sizes are as follows: (1-1).

[0054] In formula (1-1), g is the acceleration due to gravity, which is generally taken as 9.8m / s 2 μ is the friction coefficient between the scrap and the feed and preheating channels, ranging from 0.2 to 0.6. k1 is the influence factor of steel size, ranging from 0.1 to 5.0. In other words, according to Equation (1-1), the sliding speed of the scrap at different inclination angles can be calculated.

[0055] When the scrap steel's sliding speed v is known, the impact force F (unit: N) on the stop claw when the scrap steel contacts it can be calculated using the following formula: (1-2).

[0056] In formula (1-2), m s is the mass of the steel, kg (generally, the mass of the steel can be obtained by weighing directly or by calculation: m s =ρ l 0 w 0 h 0, ρ is the density of steel, kg / m 3Δt is the collision time between the steel and the retaining claw (an empirical estimate, generally ranging from 0.01 to 1 second). k2 is the force coefficient of the retaining mechanism, ranging from 10 to 100. In other words, using formula (1-2), we can calculate the impact force on the retaining claw of the breathable retaining mechanism at different sliding speeds.

[0057] To determine the optimal tilt angle α , introduce the comprehensive evaluation factor E: (1-3).

[0058] In formula (III), v smax F is the maximum sliding speed of steel allowed by the working conditions, m / s. max is the maximum load of the breathable material retaining mechanism (101) allowed by the working conditions, N. S=( l 0+ w 0+ h 0) / ( l 0 w 0 h 0), S opt It is the optimal comprehensive parameter of steel size under ideal production conditions, and its value ranges from 5 to 50. v is the weight of the steel decline rate, w F is the weight of the force on the retaining claw, w S is the weight of the steel size factor, where: w v +w F +w s =1,w v 、w F 、w s are all greater than 0 and less than 1. In other words, according to formula (1-3), different tilt angles are calculated α The corresponding comprehensive evaluation factor value. α The value is the inclination angle of the inclined material feeding and preheating channel under the current working condition. The steps to obtain the maximum value of the comprehensive evaluation factor are as follows: Set the inclination angle adjustment range of the inclined material feeding and preheating channel to 30~60°, then first give an initial inclination angle of 30°, then α 1=0.524 (30° converted to radians is constrained to 0.524). Then, according to the above formulas (1-1) and (1-2), we can calculate α 1=0.524 corresponding to v s1 and F1, and then calculate the corresponding E1 according to formula (1-3). Finally, increase the tilt angle by a certain step size (such as 0.01 radians) to obtain α 2= α1+0.01, and then calculate again according to formulas (1-1), (1-2), and (1-3) α 2= α 1+0.01=0.524+0.01 corresponds to v s2 , F2 and E2; repeat the above process until all the comprehensive evaluation factor E values ​​corresponding to the entire tilt angle range of 30~60° (0.524~1.047 radians) are traversed, and then compare all the calculated E values ​​to find the tilt angle that makes E reach the maximum value α b ,this α b That is, the inclination angle of the inclined feeding and preheating channel corresponding to the current optimal comprehensive conditions of steel.

[0059] It should be noted that all formulas in the present invention are obtained by fitting by the inventors based on experiments and engineering applications, and all calculations are numerical values ​​converted according to prescribed units, and are obtained by substituting the converted numerical values ​​into the formulas (after converting the units, only the numerical values ​​are substituted into the formulas for calculation, without substituting the units; the units are only used to adjust the size of the numerical values).

[0060] In the present invention, the number of gas heating mechanisms is 1-20, preferably 2-30, more preferably 3-20. The thickness of the furnace shell is 1-300 cm, preferably 5-200 cm, more preferably 10-100 cm. The volume of the furnace is 0.3-100 m 3 , preferably 0.5~50m 3 , more preferably 0.8~30m 3 .

[0061] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1: This invention breaks through the traditional single energy reliance model. Through the coupling synergy of natural gas burners (rapid heating) and electromagnetic inductors (precise melting), the critical softening temperature of scrap steel can be broken through in a short period of time through centralized heating by gas burners. Then, electromagnetic induction targeted heating is used to achieve precise melting of the scrap steel, which greatly improves the heating and melting efficiency of the entire scrap steel and significantly reduces energy consumption.

[0062] 2: The present invention also achieves coordinated control of natural gas and electricity based on energy price sensitivity analysis. By tracking energy prices in real time and dynamically allocating the gas-to-electricity ratio through a real-time optimization model based on energy prices and equipment efficiency, the rigidity loss of the traditional fixed ratio mode is avoided. That is, through the dynamic gas-to-electricity ratio optimization algorithm, the cost savings under all operating conditions can be as high as 13.5%.

[0063] 3: The present invention not only couples the rapid heating of the gas burner with the precise melting of the electromagnetic inductor, but also uses flue gas waste heat recovery to efficiently preheat the scrap steel, thereby realizing the cascade utilization of energy. The flue gas burned by the burner can efficiently preheat the scrap steel to above 400°C, further reducing the subsequent melting energy consumption and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The figure is a schematic diagram of the control flow of adjusting the melting power of a steel-melting furnace based on energy price fluctuations according to the present invention.

[0065] Figure 2 It is a structural schematic diagram of the steel melting furnace of the present invention.

[0066] Figure 3 This is a structural schematic diagram of the steel melting furnace of the present invention having an inclined charging channel.

[0067] Figure 4 It is a structural schematic diagram of the material blocking claw of the present invention.

[0068] Attached markings: 1: steel melting furnace; 101: furnace shell; 102: furnace chamber; 103: molten steel outlet; 2: gas heating mechanism; 201: burner; 202: air inlet pipe; 203: gas flow regulating valve; 3: electric heating mechanism; 4: feeding channel; 401: partition; 402: storage area; 403: preheating area; 404: material blocking claw; 4041: cooling medium channel; 4042: cooling medium inlet; 4043: cooling medium outlet; 405: flue; 406: thermocouple; 407: pressure sensor; 408: speed regulating fan; 409: lifting drive motor; 410: rotation drive motor; 5: thermal imager. DETAILED DESCRIPTION

[0069] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0070] A gas-electricity-coordinated steel melting device includes a steel melting furnace 1, a gas heating mechanism 2, and an electric heating mechanism 3. The steel melting furnace 1 comprises a furnace shell 101 and a hearth 102. A charging channel 4 is located in the upper portion of the furnace shell 101 and communicates with the hearth 102. The gas heating mechanism 2 is located in the upper portion of the hearth 102, and the electric heating mechanism 3 is located in the lower portion of the hearth 102. A molten steel outlet 103 is located at the bottom of the hearth 102.

[0071] Preferably, the gas heating mechanism 2 includes a burner 201 and an air inlet pipe 202. The combustion end of the burner 201 extends through the furnace shell 101 near the charging channel 4 and into the furnace 102. The air inlet end of the burner 201 is connected to the air inlet pipe 202, through which gas and auxiliary gas are delivered to the burner 201 for combustion and heating. Preferably, a gas flow regulating valve 203 is also provided on the air inlet pipe 202.

[0072] Preferably, the electric heating mechanism 3 is an electromagnetic induction coil, which is arranged in a surrounding manner in the furnace shell 101.

[0073] Preferably, a thermal imager 5 is also provided at the top of the inner cavity of the furnace 102 .

[0074] Preferably, the feeding channel 4 is one of a horizontal channel, a vertical channel and an inclined channel.

[0075] Preferably, the feeding channel 4 is an inclined channel, and a partition 401 is provided in the inclined channel to separate the inclined channel from top to bottom into a material storage area 402 and a preheating area 403. A material blocking claw 404 is provided at the bottom end of the preheating area 403, and a smoke outlet 405 is also provided at the upper end of the preheating area 403.

[0076] Preferably, a thermocouple 406 and a pressure sensor 407 are further provided in the smoke outlet 405. A speed-regulating fan 408 is further connected to the smoke outlet of the smoke outlet 405.

[0077] Preferably, one end of the partition 401 passes through the top wall of the feeding channel 4 and is connected to a lifting drive motor 409 arranged outside. The lifting drive motor 409 drives the partition 401 to rise and fall, thereby realizing the opening and closing of the partition 401.

[0078] Preferably, a rotary drive motor 410 connected to the material blocking claw 404 is provided at the bottom end of the preheating zone 403 , and the rotary drive motor 410 drives the material blocking claw 404 to be lifted and lowered in an arc-shaped manner, thereby realizing the opening and closing of the material blocking claw 404 .

[0079] Preferably, a cooling medium channel 4041 and a cooling medium inlet 4042 and a cooling medium outlet 4043 connected to the cooling medium channel 4041 are further provided inside the material blocking claw 404 . Example 1

[0080] like Figure 2-4As shown, a gas-electric coordinated steel melting device comprises a steel melting furnace 1, a gas heating mechanism 2, and an electric heating mechanism 3. The steel melting furnace 1 comprises a furnace shell 101 and a furnace chamber 102. A charging channel 4 is provided in the upper portion of the furnace shell 101 and communicates with the furnace chamber 102. The gas heating mechanism 2 is provided in the upper portion of the furnace chamber 102, and the electric heating mechanism 3 is provided in the lower portion of the furnace chamber 102. A molten steel outlet 103 is provided at the bottom of the furnace chamber 102. Example 2

[0081] Example 1 is repeated, except that the gas heating mechanism 2 includes a burner 201 and an air inlet pipe 202. The combustion end of the burner 201 penetrates the furnace shell 101 near the side of the charging channel 4 and extends into the furnace 102. The air inlet end of the burner 201 is connected to the air inlet pipe 202, and the air and supporting gas are transported to the burner 201 through the air inlet pipe 202 for combustion and heating. Example 3

[0082] The second embodiment is repeated, except that a gas flow regulating valve 203 is further provided on the air inlet pipe 202 . Example 4

[0083] The third embodiment is repeated, except that the electric heating mechanism 3 is an electromagnetic induction coil, which is disposed in a surrounding manner in the furnace shell 101 . Example 5

[0084] Example 4 is repeated, except that a thermal imager 5 is further provided on the top of the inner cavity of the furnace 102 . Example 6

[0085] Example 5 was repeated, except that the feeding channel 4 was a horizontal channel. Example 7

[0086] Example 5 was repeated, except that the feeding channel 4 was a vertical channel. Example 8

[0087] Example 5 was repeated, except that the feeding channel 4 was an inclined channel. A partition 401 was provided in the inclined channel to separate the inclined channel from top to bottom into a material storage area 402 and a preheating area 403. A material blocking claw 404 was provided at the bottom end of the preheating area 403, and a smoke outlet 405 was also opened at the upper end of the preheating area 403. Example 9

[0088] The embodiment 8 is repeated except that a thermocouple 406 and a pressure sensor 407 are further provided in the smoke outlet 405. A speed-adjustable fan 408 is also connected to the smoke outlet of the smoke outlet 405. Example 10

[0089] Example 9 is repeated, except that one end of the partition 401 passes through the top wall of the feeding channel 4 and is connected to the lifting drive motor 409 provided on the outside, and the lifting drive motor 409 drives the partition 401 to rise and fall, thereby realizing the opening and closing of the partition 401. Example 11

[0090] Example 10 is repeated, except that a rotary drive motor 410 connected to the material blocking claw 404 is further provided at the bottom end of the preheating zone 403, and the rotary drive motor 410 drives the material blocking claw 404 to swing up and down to realize the opening and closing of the material blocking claw 404. Example 12

[0091] Example 11 is repeated, except that a cooling medium channel 4041 and a cooling medium inlet 4042 and a cooling medium outlet 4043 connected to the cooling medium channel 4041 are further provided inside the material blocking claw 404 . Example 13

[0092] The steel melting device described in Example 12 is used to melt scrap steel: First, 10 tons of scrap steel is fed into the furnace 102 of the steel melting furnace 1 through the feeding channel 4. Then, the gas heating mechanism 2 (composed of two gas burners located on either side of the scrap landing point) is activated to heat and melt the steel until it becomes molten steel. During the melting process, 10 tons of scrap steel is added to the preheating zone 403 of the feeding channel 4 for preheating (and 10 tons of scrap steel is added to the storage zone 402 for temporary storage). After melting is complete, approximately 60% of the molten steel is discharged through the molten steel outlet 103.

[0093] Open the retaining claw 404 and feed 10 tons of scrap steel, which has been preheated to a temperature of approximately 500°C, into the furnace 102 of the steel melting furnace 1. Then close the retaining claw 404 and open the baffle 401 to add another 10 tons of scrap steel to the preheating zone 403. Then close the baffle 401 and continue to add 10 tons of scrap steel to the storage zone 402 for temporary storage. Simultaneously, start the gas heating mechanism 2 and the electric heating mechanism 3 (electromagnetic inductor) to melt the scrap steel. Under the current working conditions: natural gas price S gas 4 yuan / m 3 , electricity price S elec The thermal efficiency of the gas burner is γ gas The thermal efficiency of the electromagnetic induction heater is 0.7. elec The calorific value of gas is 0.9. H gas The specific heat capacity of steel is 35MJ / m³. C is 0.65kJ / (kg·℃), and the melting target temperature is T objeThe temperature is 1500℃ and the melting period t is 2 hours (7200s). Under the current working conditions: Total energy requirement Q total = MC ( T obje -T 0 )=10×0.65×(1500-500)=6500MJ.

[0094] Energy proportional coefficient K=3.6γ elec / (γ gas H gas )=3.6×0.9÷0.7÷35≈0.1322.

[0095] Optimal natural gas usage ratio x =1 / (1+K S gas / S elec )=1÷(1+0.1322×4÷0.8)≈0.602.

[0096] The actual minimum operating power of two gas burners: P gas-1 = P gas-2 = xMC ( T obje -T 0 ) / ( nt γ gas )=0.602×6500÷2÷7200÷0.7≈0.38820MW.

[0097] The actual minimum operating power of the electromagnetic inductor: P elec =(1- x ) MC ( T obje -T 0 ) / ( t γ elec )=(1-0.602)×6500÷7200÷0.9≈0.39923MW.

[0098] Under the current working conditions, the air inlet valves of the two gas burners are adjusted so that their actual working power is 388.20kW, and the actual minimum working power of the battery sensor is adjusted to 399.23kW.

[0099] The total cost of melting 10 tons of scrap steel at 500°C under current conditions is: Q total [ xS gas / (γ gas H gas )+(1- x ) S elec / 3.6γ elec ]=6500×[0.602×4÷0.7÷35+(1-0.602)×0.8÷3.6÷0.9]≈1278 yuan.

[0100] In summary, when the natural gas price is 4 yuan / m 3 When the electricity price is 0.8 yuan / / (kW·h), the optimal energy distribution ratio is 60.2% for natural gas and 39.8% for electricity. The actual working power of the two gas burners is 388.20 kW, the actual working power of the electromagnetic inductor is 399.23 kW, and the total melting cost is about 1,278 yuan.

[0101] Taking a fixed natural gas ratio of 50% as the benchmark operating condition, we analyze the differences in smelting costs under the conditions of fixed natural gas supply ratio and coordinated control of natural gas and electricity when natural gas and electricity prices fluctuate. The specific comparison results are shown in the following table:

[0102] As can be seen from the table above, through dynamic energy ratio gas-electricity coordinated optimization control, compared with a fixed energy ratio (50%), full-operating cost savings of up to 13.5% can be achieved, providing a new solution for fast-response cross-energy coordinated control in the scrap steel preheating industry.

Claims

1. A gas-electricity coordinated steel melting method, characterized by: The method comprises the following steps: 1) Initial melting stage: Steel is added to the steel melting furnace, and the gas burner and / or electromagnetic induction heater are started to heat and melt the steel until molten steel is obtained; 2) Continued melting stage: Continue adding steel to the steel melting furnace, use gas burners to heat the surface of the molten steel and the steel exposed on the surface of the molten steel, and use electromagnetic induction heaters to heat the molten steel and the scrap steel submerged in the molten steel until the steel is melted into molten steel and repeat step 2).

2. The method according to claim 1, wherein: The method further includes: 3) Use the high-temperature flue gas generated in the steel melting furnace to preheat the steel to be melted in the furnace; Preferably, the average temperature of the steel after preheat treatment is not less than 300°C, preferably not less than 400°C.

3. The method according to claim 1 or 2, characterized in that: During the continued melting phase, a gas and electricity supply allocation model is established under target operating conditions using energy consumption cost as the independent variable. The real-time energy supply ratios of gas and electricity are calculated based on this allocation model, thereby enabling steel melting at low cost. The energy supply allocation model is as follows: （I）； In formula (I), x It is the ratio of energy supplied by gas to total energy required under target working condition; S gas is the real-time unit price of gas, RMB / m³; S elec is the real-time unit price of electricity, yuan / (kW·h); γ elec is the thermal efficiency of the electromagnetic induction heater; γ gas is the thermal efficiency of the gas burner; H gas is the calorific value of gas, MJ / m³; the real-time energy supply ratio of gas under different energy consumption costs is calculated by formula (I), and the real-time energy supply ratio of electricity is (1- x ).

4. The method according to claim 3, wherein: The real-time operating power of the gas burner is adjusted according to the real-time energy supply ratio of the gas to meet the working conditions. The actual minimum operating power of a single gas burner under the current working conditions should meet the following formula: P gas = xMC ( T obje -T 0 ) / ( nt c gas ) (II); In formula (II), P gas is the actual minimum operating power of a single gas burner, MW; M is the mass of steel to be melted in the current steel melting furnace, kg; C is the specific heat capacity of steel, kJ / (kg·℃); T obje is the target melting temperature in the steel melting furnace, °C; T 0 is the temperature of the steel when it enters the steel melting furnace, °C; n is the number of gas burners opened, pcs; t is the melting cycle of steel, s; under the current working conditions, the real-time working power of a single gas burner is adjusted to the minimum value calculated by formula (II) P gas So that the real-time energy supply ratio of gas is x .

5. The method according to claim 3 or 4, characterized in that: According to the real-time energy supply ratio of electric energy, the real-time working power of the electromagnetic induction heater is adjusted to meet the working conditions. Under the current working conditions, the actual minimum working power of the electromagnetic induction heater should meet the following formula: P elec =(1- x ) MC ( T obje -T 0 ) / ( t c elec ) (III); In formula (III), P elec is the actual minimum operating power of the electromagnetic induction heater, MW; M is the mass of steel to be melted in the current steel melting furnace, kg; C is the specific heat capacity of steel, kJ / (kg·℃); T obje is the target melting temperature in the steel melting furnace, °C; T 0 is the temperature of the steel when it enters the steel melting furnace, °C; t is the melting cycle of steel, s; under the current working conditions, the real-time working power of the electromagnetic induction heater is adjusted to the lowest value calculated by formula (III) P elec So that the real-time energy supply ratio of electric energy is (1- x ).

6. The method according to any one of claims 3 to 5, characterized in that: When the energy required for steel melting is all supplied by gas, the minimum working power of a single gas burner is recorded as P allgas , then when the calculated value x When <0.1, the actual minimum working power of a single gas burner P gas =(0.05~0.15) P allgas and / or When the heat required for steel melting is fully supplied by electricity, the minimum operating power of the electromagnetic induction heater is P allelec , then when the calculated value (1- x )<0.05, the actual minimum working power of the electromagnetic induction heater P elec =(0.05~0.1) P allelec .

7. A gas-electricity coordinated steel melting device, characterized by: The steel melting device comprises a steel melting furnace (1), a gas heating mechanism (2) and an electric heating mechanism (3); the steel melting furnace (1) comprises a furnace shell (101) and a furnace (102), and a feeding channel (4) communicating with the furnace (102) is provided at the upper part of the furnace shell (101); the gas heating mechanism (2) is arranged at the upper part of the furnace (102), and the electric heating mechanism (3) is arranged at the lower part of the furnace (102); and a molten steel outlet (103) is provided at the bottom of the furnace (102).

8. The steel melting device according to claim 7, characterized in that: The gas heating mechanism (2) comprises a burner (201) and an air inlet pipe (202); the combustion end of the burner (201) penetrates the furnace shell (101) on the side close to the feeding channel (4) and then extends into the furnace (102); the air inlet end of the burner (201) is connected to the air inlet pipe (202), and gas and auxiliary gas are transported to the burner (201) through the air inlet pipe (202) for combustion and heating; preferably, a gas flow regulating valve (203) is further provided on the air inlet pipe (202); and / or The electric heating mechanism (3) is an electromagnetic induction coil, and the electromagnetic induction coil is arranged in a surrounding manner in the furnace shell (101); Preferably, a thermal imager (5) is further provided at the top of the inner cavity of the furnace (102).

9. The steel melting device according to claim 7 or 8, characterized in that: The feeding channel (4) is one of a horizontal channel, a vertical channel, and an inclined channel; Preferably, the feeding channel (4) is an inclined channel, and a partition (401) is provided in the inclined channel to separate the inclined channel from top to bottom into a material storage area (402) and a preheating area (403); a material blocking claw (404) is provided at the bottom end of the preheating area (403), and a smoke outlet (405) is also provided at the upper end of the preheating area (403); Preferably, a thermocouple (406) and a pressure sensor (407) are further provided in the smoke outlet duct (405); and a speed-regulating fan (408) is further connected to the smoke outlet of the smoke outlet duct (405).

10. The steel melting device according to claim 8, characterized in that: One end of the partition (401) passes through the top wall of the feeding channel (4) and is connected to an externally arranged lifting drive motor (409), and the lifting drive motor (409) drives the partition (401) to rise and fall, thereby realizing the opening and closing of the partition (401); and / or A rotary drive motor (410) connected to the material blocking claw (404) is further provided at the bottom end of the preheating zone (403). The rotary drive motor (410) drives the material blocking claw (404) to be raised and lowered in an arc-shaped manner, thereby realizing the opening and closing of the material blocking claw (404); Preferably, a cooling medium channel (4041) and a cooling medium inlet (4042) and a cooling medium outlet (4043) connected to the cooling medium channel (4041) are further provided inside the material blocking claw (404).

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