Optimization method for hydrogen energy steelmaking production scheduling

Abstract

The invention discloses a hydrogen energy steelmaking production scheduling optimization method which comprises the following steps: determining a system structure covering key links of power generation, hydrogen production and steelmaking on the basis of the development trend of a hydrogen energy steelmaking process; the method comprises the following steps of: establishing a whole-process mathematical model comprehensively considering energy flow and material flow according to energy consumption characteristics and material conversion relations of each production process of hydrogen energy steelmaking; a target system of hydrogen energy steelmaking optimization is determined, corresponding constraint conditions are established based on safe operation constraints and coupling among all working procedures, and a production scheduling optimization model capable of reflecting the flexibility of an electricity-hydrogen-steel whole link is constructed; according to actual process technical parameters, a specific operation case and a production scene are designed, and Matlab software and a Yalmip toolbox are utilized to carry out numerical solution on an optimization problem. According to the method, the flexibility and controllability of a hydrogen energy steelmaking process are utilized, the electricity utilization characteristic of steel production is optimized, and the absorption capacity of a power grid to renewable energy sources is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking process and energy management, and in particular to an optimization method for hydrogen energy steelmaking production scheduling. Background Art

[0002] With the advancement of the global dual carbon goals, my country's power system is at a critical stage of transformation to clean energy. In this process, it is necessary not only to ensure electricity demand and improve the level of electrification, but also to meet the challenge of decarbonizing electricity. As an important pillar of the national economy, the steel industry accounts for 15% of the country's total carbon emissions, which plays a decisive role in achieving the dual carbon goals. At present, steel companies are facing the difficulty of strategic choice on the road to decarbonization. Hydrogen steelmaking technology, with its flexibility, controllability and high coupling with electricity in its production process, is regarded as a promising energy-saving and emission reduction solution. This technology can not only reduce carbon emissions, but also adapt to the volatility of renewable energy, providing new ideas for peak and frequency regulation of power grids.

[0003] However, the promotion of hydrogen steelmaking technology still faces technical barriers such as industrial hydrogen production and storage, and has not yet achieved large-scale commercial application. Existing theoretical research on hydrogen steelmaking technology focuses on supporting renewable energy installed capacity planning and carbon emission potential assessment. There is still a lack of theoretical research and application exploration on how hydrogen steelmaking technology can adapt to the uncertainty of renewable energy output. Summary of the invention

[0004] The purpose of the present invention is to provide a method for optimizing hydrogen steelmaking production scheduling, which utilizes the flexibility and controllability of the hydrogen steelmaking process to optimize the electricity consumption characteristics of steel production, maximize the economic benefits of steel enterprises, and enhance the power grid's ability to absorb renewable energy.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for optimizing hydrogen energy steelmaking production scheduling, the method comprising:

[0007] Step 1: Based on the development trend of hydrogen steelmaking technology, determine the system structure covering the key links of power generation, hydrogen production and steelmaking;

[0008] Step 2: Based on the energy consumption characteristics and material conversion relationships of each production process of hydrogen steelmaking, a mathematical model of the whole process that comprehensively considers energy flow and material flow is established;

[0009] Step 3: Define the target system for hydrogen steelmaking optimization, and establish corresponding constraints based on the safety operation constraints and coupling between each process, and build a production scheduling optimization model that can reflect the flexibility of the entire electricity-hydrogen-steel process;

[0010] Step 4: Based on the actual process technical parameters, design specific operation cases and production scenarios, and use Matlab software and Yalmip toolbox to numerically solve the production scheduling optimization model constructed in step 3 to achieve the optimization of hydrogen steelmaking production scheduling.

[0011] It can be seen from the technical solution provided by the present invention that the above method utilizes the flexibility and controllability of the hydrogen steelmaking process to optimize the electricity consumption characteristics of steel production, maximize the economic benefits of steel enterprises, enhance the grid's ability to absorb renewable energy, and provide strong technical support for the green transformation of the steel industry and the sustainable development of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0013] Figure 1 A schematic diagram of a process flow of a hydrogen energy steelmaking production scheduling optimization method provided by an embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of the structure of the hydrogen steelmaking system according to an embodiment of the present invention;

[0015] Figure 3 A schematic diagram of the coupling relationship between various production processes of hydrogen steelmaking provided by the present invention;

[0016] Figure 4 This is a schematic diagram of the distribution of electricity prices during the study period of the example given in the present invention;

[0017] Figure 5 The production plan arrangement curve of the molten steel in each period of the example of the present invention;

[0018] Figure 6 A schematic diagram of the working current density of the electrolytic cell at each time period according to the example of the present invention;

[0019] Figure 7 This is a schematic diagram of the pressure change curve of the hydrogen storage tank in the example of the present invention. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] like Figure 1 The figure shows a schematic flow chart of a method for optimizing hydrogen steelmaking production scheduling provided by an embodiment of the present invention, wherein the method comprises:

[0022] Step 1: Based on the development trend of hydrogen steelmaking technology, determine the system structure covering the key links of power generation, hydrogen production and steelmaking;

[0023] In this step, the system architecture of existing hydrogen steelmaking plants at home and abroad is investigated, relevant data is collected and analyzed, and the structure and operating characteristics of the existing systems are understood; based on the investigation, combined with the future development trend of hydrogen steelmaking technology, a hydrogen steelmaking system structure with development prospects is constructed.

[0024] like Figure 2 The figure shows a schematic diagram of the structure of the hydrogen steelmaking system according to an embodiment of the present invention. In the hydrogen steelmaking process, the electrolytic cell, electric heating and electric arc furnace constitute energy-intensive key links. The electrolytic cell generates hydrogen through water electrolysis reaction, providing a clean hydrogen reducing agent for steel production, and the excess hydrogen is stored in a hydrogen storage tank for later use. Before the hydrogen enters the direct reduction vertical furnace (DRIF), it is first preheated in an electric heating device to ensure that the reduction reaction in the vertical furnace can obtain the necessary heat energy. In the DRIF, hydrogen acts as a reducing agent to chemically react with solid iron ore to generate sponge iron, which provides raw materials for the subsequent refining process of the electric arc furnace. The electric arc furnace uses the high heat provided by the electric energy to complete the refining of the molten steel.

[0025] Therefore, the system structure covering the key links of power generation, hydrogen production and steelmaking includes the following components:

[0026] Renewable energy generation system: Use wind and solar energy to generate electricity and provide clean electricity for the hydrogen steel plant;

[0027] Large power grid: Provides a stable power supply to hydrogen steel plants when the renewable energy power generation system is insufficient;

[0028] Electrolyzer: Use water electrolysis technology to produce hydrogen, providing a hydrogen source for the steelmaking process;

[0029] Hydrogen storage tank: stores excess hydrogen produced by electrolysis to ensure the stability and continuity of hydrogen supply during the steelmaking process;

[0030] Electric heating equipment: provides the heat required in the steelmaking process;

[0031] Direct reduction shaft furnace: used to reduce iron ore to sponge iron, providing raw materials for electric arc furnace steelmaking;

[0032] Electric arc furnace: used for molten steel production and provides raw materials for the production of various steel products.

[0033] Step 2: Based on the energy consumption characteristics and material conversion relationships of each production process of hydrogen steelmaking, a mathematical model of the whole process that comprehensively considers energy flow and material flow is established;

[0034] In this step, the electricity required for hydrogen steelmaking comes from renewable energy generation and auxiliary power supply from the large power grid. The renewable energy generation part considers two forms: wind power and photovoltaic power. Wind power generation is related to wind speed. Therefore, a power generation model that can characterize the uncertainty of wind power output is first established. The function expression is:

[0035]

[0036] Where v is the wind speed; f(v) is the wind speed probability density function; k is the shape parameter; λ is the scale parameter; μ1 and σ1 are the mean and standard deviation of the samples; γ is the gamma function;

[0037]

[0038] Where Pwind(t) is the wind turbine output during period t; vt is the wind speed during period t; v wr is the rated wind speed of the fan; v in is the cut-in wind speed; v out is the cut-out wind speed; P wr is the rated power of the fan;

[0039] Photovoltaic power generation is related to the intensity of solar radiation, so a power generation model that can characterize the uncertainty of photovoltaic output is established. The function expression is:

[0040]

[0041] Among them, I t is the solar radiation intensity during period t; μ t is the expected value of period t; σ t is the standard deviation of period t; m t 、n t is the mean and variance of the lognormal random variable in period t;

[0042]

[0043] Where Ppv(t) is the photovoltaic output during period t; It is the solar radiation intensity during period t; I sis the solar radiation intensity under standard conditions; r c is the specific solar radiation intensity; W sr is the rated power of the photovoltaic;

[0044] The electrolyzer uses electrical energy to electrolyze water to produce hydrogen. According to Faraday's law, the amount of hydrogen produced by the electrolyzer is proportional to the total electrolysis current. Therefore, within the normal working range, the hydrogen production flow rate (i.e., hydrogen production) of the electrolyzer can be adjusted by adjusting the input current. Assuming that the connection between the small chambers of the electrolyzer is in series, combined with the classic Ulleberg empirical model, an electrolyzer model that can characterize the coupling relationship between hydrogen production and power consumption is established. The function expression is:

[0045]

[0046] in, is the molar flow rate of hydrogen; is the volume flow rate of hydrogen; n cell is the number of chambers in the electrolytic cell; I cell is the electrolytic cell current; A cell is the effective surface area of ​​a single cell electrode; F is the Faraday constant; f1 and f2 are Faraday efficiency parameters; U cell is the working voltage of the chamber; T cell is the temperature; r1 and r2 are the ohmic resistance parameters related to temperature; s is the overvoltage coefficient; t1, t2, t3 are the overvoltage coefficients; ΔG cell is the Gibbs free energy change of the battery reaction under standard conditions (for the chemical reaction of generating water, it is equal to 236.483 kJ / mol); z is the number of electrons required to produce 1 mol of hydrogen, which is equal to 2; P el The electrical power consumed by the electrolyzer;

[0047] The hydrogen storage tank is used to store hydrogen in the hydrogen energy steelmaking system to ensure the stability and continuity of hydrogen supply during the steelmaking process. However, as a storage device, its internal pressure has certain constraints. According to the ideal gas state equation, a hydrogen storage tank model is established to characterize the relationship between the internal pressure and the molar amount of hydrogen in the tank. The function expression is:

[0048]

[0049] Among them, P tank is the internal pressure of the hydrogen storage tank; R is the gas molar constant; T tank is the temperature of the hydrogen storage tank; V tank is the volume of the hydrogen storage tank; is the molar amount of hydrogen inside the hydrogen storage tank; is the molar amount of hydrogen in the hydrogen storage tank at time t0; is the net inflow molar flow rate of hydrogen; are the hydrogen molar flow rates at the inlet and outlet of the hydrogen storage tank respectively; τ is the variable in the integral formula;

[0050] The electric heating equipment uses the electric heat conversion mechanism to preheat the iron ore and hydrogen to provide the heat required for the reduction reaction in the direct reduction shaft furnace. Therefore, the electric heating model should reflect the energy balance relationship between electric energy and thermal energy. According to the first law of thermodynamics, an electric heating model that can characterize the balance relationship between electric energy and thermal energy is established. The function expression is:

[0051]

[0052] Among them, Q elec The heat required for electric heating; W elec is the heat equivalent electrical energy; c is the specific heat capacity of the preheated object; m is the mass of the preheated object; T0 is the initial temperature of the preheated object; T1 is the target temperature of the preheated object;

[0053] The direct reduction vertical furnace is a countercurrent solid-gas reactor. The preheated iron ore pellets are fed from the top and undergo a reduction reaction with the hydrogen flow with a certain physical heat entering from the bottom of the reactor, producing sponge iron with a certain temperature and sending it to the electric arc furnace. At the same time, waste gas is generated to take away some of the heat. Iron ore is the main raw material for producing molten steel. The amount of iron ore added is determined according to the molten steel production plan and the iron content of the iron ore. The hydrogen in the vertical furnace participates in the reduction reaction of the iron ore as a reducing agent. Due to objective issues such as hydrogen utilization, there are certain requirements for the hydrogen flow rate. At the same time, in order to meet the thermal balance inside the vertical furnace, there are certain constraints on the hydrogen flow rate. Therefore, a direct reduction vertical furnace model that can characterize thermal balance and material balance is established, and the function expression is:

[0054]

[0055] in, is the volume flow rate of hydrogen required to produce one ton of sponge iron; λ is the ratio of the mass flow rate of hydrogen required for the reduction reaction to the volume flow rate, which is 1.5; is the proportion of iron in iron ore; is the utilization rate of hydrogen in the reduction reaction, which is 0.65; The mass of hydrogen required for heat balance; is the specific heat capacity of hydrogen; C pore is the specific heat capacity of iron ore; η SF is the thermal efficiency of the vertical furnace, which takes a value of 0.9; is the hydrogen inlet temperature; T ore is the iron ore inlet temperature; T out,t is the furnace top gas temperature; is the enthalpy of the reduction reaction in the shaft furnace; M Fe is the mass of sponge iron; More To produce M Fe The mass of iron ore required to produce a ton of sponge iron; T Fe is the temperature of metallic iron; is the specific heat capacity of metallic iron; α is the metallization rate of sponge iron; is the mass of total iron in the sponge iron entering the furnace;

[0056] In the specific implementation, it is assumed that the iron content in the iron ore is 80%, the temperature of the hydrogen flowing into the shaft furnace is 1173K, the temperature of the iron ore flowing into the shaft furnace is 973K, the temperature inside the shaft furnace is 1123K, the temperature of the gas flowing out of the top of the shaft furnace is 623K, and the production target is 1 ton of sponge iron. The volume of hydrogen required for the reduction reaction is calculated by formula (6) to be 516Nm 3 , the volume of hydrogen required to meet the thermal balance is 738Nm 3 This means that when the preheating temperature of the input material of the shaft furnace is determined, the heat balance requirement cannot be met when only the reduction reaction is considered to control the hydrogen flow rate in the shaft furnace. In order to avoid the waste of hydrogen resources, the preheating temperature of iron ore and hydrogen is adjusted to ensure the heat balance in the shaft furnace while meeting the hydrogen volume required for the reduction reaction. That is, the two equations for the calculation of hydrogen volume in formula (6) are combined, and it can be found that a two-variable first-order equation is formed. Without setting other conditions, this equation has infinite solutions.

[0057] The electric arc furnace uses electric energy to refine molten steel. Its smelting cycle is related to the input electric energy. At the same time, since the input material has a certain amount of physical heat, the chemical reaction in the furnace produces a certain amount of chemical heat. Therefore, based on the principle of energy conservation, an electric arc furnace model is established to characterize the relationship between the smelting cycle, chemical energy, physical energy and input electric energy. The function expression is:

[0058]

[0059] Among them, τ is the arc furnace smelting cycle, that is, the time between the first steel tapping and the second steel tapping; τ′ is the power-on time; τ″ is the non-power-on time; M is the weight of the molten steel; P E is the apparent input electrical power; η is the electrical efficiency; is the power factor; P C P is the electrical power converted from chemical heat; P is the electrical power converted from physical heat; C is the smelting power consumption; C C Power saving due to chemical heat; C P Power saving due to physical heat; C E C C and C P The effective power consumption when it is 0;

[0060] When hot sponge iron is used as the raw material of an electric arc furnace, it brings in a certain amount of physical heat. However, since sponge iron contains a small amount of FeO, it absorbs a large amount of heat during the reduction reaction. In addition, the increase in the amount of slag in the electric arc furnace due to FeO will also lead to physical heat loss ΔQ. el Increase, so each ton of sponge iron in the electric arc furnace needs to consume electricity W arc The calculation expression is:

[0061]

[0062] Where ΔQ el is the physical heat loss; C pFe is the constant pressure specific heat capacity of Fe element in sponge iron; T Fe is the temperature of sponge iron entering the furnace; T steel is the temperature of the molten steel; N is the mass of all iron in the sponge iron entering the furnace; FeO is the proportion of FeO in sponge iron; N vs is the proportion of gangue in sponge iron; N Fe is the proportion of total iron in sponge iron; P Fe is the proportion of metallic iron in sponge iron; W arc It is the amount of electricity consumed after each ton of sponge iron enters the electric arc furnace.

[0063] Step 3: Define the target system for hydrogen steelmaking optimization, and establish corresponding constraints based on the safety operation constraints and coupling between each process, and build a production scheduling optimization model that can reflect the flexibility of the entire electricity-hydrogen-steel process;

[0064] In this step, in the steel production process, each production link is interconnected through key parameters such as power consumption, material balance, heat balance and electricity cost, forming a highly coupled system. Figure 3 The figure shows the schematic diagram of the coupling relationship between the various production processes of hydrogen steelmaking provided by the present invention. The steel production of the electric arc furnace and its operating status are the key factors that determine the electricity demand of the enterprise. It not only directly affects the power consumption of the electric arc furnace itself, but also indirectly affects the power consumption of electric heating through material balance and heat balance. In addition, the steel production of the electric arc furnace not only determines the working current density of the electrolytic cell, but also affects the hydrogen reserve and pressure regulation of the hydrogen storage tank. The total electricity consumption of the enterprise and the electricity price signal work together to affect the electricity cost of the entire production system, and the electricity cost in turn affects the time distribution characteristics of the steel production of the electric arc furnace. It can be seen that the interaction and dependence between the various production links constitute a complex coupling network in steel production. By optimizing these coupling relationships, the production efficiency and electricity cost of the enterprise can be effectively improved.

[0065] Therefore, the lowest enterprise electricity cost is taken as the objective function, and the function expression is:

[0066]

[0067] in, is the amount of electricity purchased from the power grid in period t; is the grid electricity price in the tth period; N is the total number of study periods;

[0068] Determine the equation constraints for system operation, including power balance constraints, material balance constraints, and heat balance constraints. The power consumption links in the hydrogen steelmaking system include electrolyzers, electric heating, and electric arc furnaces. The power sources include wind and solar power generation from self-provided power plants and power supply from large power grids. Therefore, the function expression of the power balance constraint is:

[0069]

[0070] In the formula, is the electric power purchased from the grid in period t; is the wind power output in period t; is the photovoltaic output in period t; is the operating power of the electrolytic cell during the t period; is the operating power of the electric heating device in period t; is the operating power of the arc furnace in the tth period;

[0071] Hydrogen is an important gas base in the steelmaking process. If the hydrogen production rate of the electrolyzer and the hydrogen reserve in the hydrogen storage tank cannot meet the steelmaking needs, it will seriously affect the sustainability of the entire production process of the steel plant. Considering that there is an upper limit to the hydrogen production rate of the electrolyzer, in order to ensure that the production plan of each period is completed on time and does not affect the plan of the next period, the remaining volume of hydrogen at the end of the current period plus the hydrogen production of the next period is greater than the volume of hydrogen required to produce molten steel in the next period. The function expression is:

[0072]

[0073] In the formula, is the volume of hydrogen produced by electrolysis of hydrogen in period t+1; is the volume of hydrogen in the hydrogen storage tank at time period t; The volume of hydrogen required to produce one ton of molten steel; The molten steel production plan for period t;

[0074] The inlet temperature of the material in the direct reduction shaft furnace is the key to determining its thermal balance state, and it is also an important factor affecting the electric energy demand of the electric heating device. Under the premise of meeting the amount of hydrogen used in molten steel production, the thermal balance in the furnace can be effectively reduced by adjusting the material inlet temperature. Therefore, the functional expression of the thermal balance constraint is:

[0075]

[0076] In the formula, is the physical heat brought by the hydrogen flow in period t; is the physical heat brought by the iron ore in period t; is the heat removed by the exhaust gas in period t; is the heat consumed by the reduction reaction in the furnace during the t period; is the physical heat taken away by the sponge iron in period t;

[0077] Then, the inequality constraints of the system operation are determined, including renewable energy power generation constraints, production index constraints, electrolyzer operation constraints, and hydrogen storage tank pressure constraints; among which:

[0078] Renewable energy generation constraints: Wind power generation systems and photovoltaic power generation systems can only output electrical energy, and the actual output level at any time cannot exceed the maximum output, expressed as:

[0079]

[0080] In the formula, is the actual output of the wind power generation system in period t; is the maximum power that the wind power generation system can generate in the t period; is the actual output of the photovoltaic power generation system in the t period; is the maximum power that the photovoltaic power generation system can generate in the t period;

[0081] Production index constraint: The quantitative index of the production target of a steel enterprise is the amount of steel produced within a specified time. In order to avoid frequent cold starts of electric arc furnaces, the difference in production plans for adjacent periods is constrained within a reasonable range, expressed as:

[0082]

[0083] In the formula, M is the total production index; max is the upper limit of the difference between production plans in adjacent periods; is the production plan for period t; is the production plan for the t+1 period; N is the total number of research periods;

[0084] Electrolyzer operation constraints: The electrolytic hydrogen production equipment can flexibly control the hydrogen production of the electrolyzer through continuous adjustment of the input current. The operation constraints of the electrolyzer are expressed as the working range of the input current density, specifically:

[0085]

[0086] In the formula, is the input current density of the electrolytic cell in the tth period; Enter the lower limit of the current density for the electrolyzer; Enter an upper limit on the current density for the electrolyzer;

[0087] Hydrogen storage tank pressure constraint: The pressure of the hydrogen storage tank is used to characterize the storage capacity of hydrogen. The change at adjacent moments is related to the net inflow of hydrogen. In order to ensure the safety and stability of the hydrogen storage tank, its pressure should meet the upper and lower limit constraints, specifically:

[0088]

[0089] In the formula, is the pressure of the hydrogen storage tank at time period t; They respectively represent the lower and upper pressure limits of the hydrogen storage tank.

[0090] Step 4: Based on the actual process technical parameters, design specific operation cases and production scenarios, and use Matlab software and Yalmip toolbox to numerically solve the production scheduling optimization model constructed in step 3 to achieve the optimization of hydrogen steelmaking production scheduling.

[0091] In this step, the detailed configuration design of the hydrogen steelmaking system is first carried out based on the actual process technical parameters, and the key configuration parameters of the hydrogen steelmaking system are accurately defined, including the installed capacity of the renewable energy power generation system, the rated input current density of the electrolyzer and its operating range, the volume and pressure limit of the hydrogen storage tank, and the material temperature and rated capacity of the direct reduction shaft furnace and electric arc furnace;

[0092] Then, based on the mathematical model of the whole process established in step 2, a preliminary analysis of the flexibility of the system is conducted. According to the analysis results, a variety of production modes are designed to adapt to different production needs, and the production status is initialized, including the initial pressure of the hydrogen storage tank, steel production, etc.;

[0093] Since the production scheduling optimization model constructed in step 3 is a nonlinear programming problem, its complexity requires the use of advanced mathematical tools to solve it. Therefore, Matlab software is selected in conjunction with the Yalmip toolbox to solve the model and output the sequential production plan for hydrogen production and steelmaking, thereby maximizing the economic benefits of the hydrogen steelmaking plant while ensuring the safe and stable operation of green electricity.

[0094] In a specific implementation, even if other mathematical tools or algorithms are used to solve the optimization problem, as long as these methods are applied to the production scheduling optimization model of the present invention, they also fall within the scope of protection of the present invention.

[0095] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in the field.

[0096] The optimization method described in the embodiment of the present invention is illustrated below with a specific example. In the complex system of steel production, the electric arc furnace is a key link, and its capacity optimization is crucial to the overall efficiency of the steel plant. In view of the large-scale characteristics of the steel plant, the present invention focuses on exploring the coupling between the various links of hydrogen steelmaking, and how to optimize the capacity of the electric arc furnace within the controllable potential of these links. Therefore, in order to improve the feasibility and depth of the research, this example selects the capacity of a single electric arc furnace as the optimization object, and the optimization cycle is 48 time periods. According to the survey information, the smelting cycle of the electric arc furnace in the steel enterprise is usually between 40 minutes and 90 minutes. This example sets the smelting cycle of the electric arc furnace to 1 hour, and cuts the optimization cycle in hours.

[0097] Assuming that the rated capacity of a single electric arc furnace is 100 t / h, according to formula (6), when the electric arc furnace is running at full load, the volume flow rate of hydrogen to be fed into the direct reduction vertical furnace is 7.923×10 4 Nm 3 / h. Referring to the hydrogen production rate of the largest proton exchange membrane electrolysis hydrogen production device in my country, when the rated power of the electrolyzer is 300MW, the hydrogen production rate can reach 4.335×10 4 Nm 3 / h. According to formula (4), the initial pressure of the hydrogen storage tank is set to 17MPa. When the electrolytic cell and the electric arc furnace are running at full load, and the pressure constraint of the hydrogen storage tank is met, about 8 hours of uninterrupted continuous operation can be achieved. However, due to factors such as equipment maintenance and time-of-use electricity prices, it is not realistic for the steel plant to run continuously at full load throughout the entire process. At the same time, in order to ensure that the steelmaking operation can still run continuously for a long time when the electrolytic cell capacity is reduced, the hydrogen storage tank is designed to be 2000m 3 / 30MPa. In addition, according to formulas (5) and (8), the power consumption of a 100t electric arc furnace at full load is about 88MWh, and the power consumed by the electric heating link is about 50MWh. Therefore, the maximum power consumption at full load operation of the entire process is about 440MWh. Considering the limitations of wind and solar resources, the output level of self-owned power plants is generally lower than the installed capacity. At the same time, due to objective factors such as equipment maintenance and hydrogen storage tank capacity limitations, the demand for electricity in steel enterprises also has peaks and valleys. Therefore, in order to make full use of the power generation of self-owned power plants and avoid a high wind and solar abandonment rate, the wind power installed capacity of the self-owned power plant is designed to be 350MW, and the photovoltaic installed capacity is designed to be 100MW.

[0098] In order to achieve the production target, in addition to relying on the electricity provided by the self-provided power plant, it is also necessary to purchase additional electricity from the power grid to ensure the smooth progress of production arrangements. Figure 4The figure shows the distribution of electricity prices during the study period of the example cited in the present invention. During the low-load period at night, the electricity price drops to the lowest point, while during the high-load period during the day, the electricity price reaches the peak. The difference between the peak and valley electricity prices is about 0.7 yuan / kWh. This price fluctuation is consistent with the current electricity price situation of the actual power grid, and can reflect the supply and demand relationship and price mechanism of the electricity market. In order to maximize the economic benefits of the low-price period and take into account the necessity of manual work in the steel production process, this example designs two different operating scenarios: one is a 24-hour uninterrupted continuous operation mode; the other is a production mode limited to daytime working hours. Considering the significance of the demand for hydrogen in the hydrogen energy steelmaking process, the initial reserve of hydrogen has a significant impact on the arrangement of the production plan. Therefore, in order to further explore the impact of hydrogen reserves on the production scheduling of steel enterprises, this example sets the initial pressure of the hydrogen storage tank to the minimum value and the middle value respectively. Table 1 lists the specific settings of the operating scenarios in detail:

[0099] Table 1 Operation scenario settings

[0100]

[0101] The production scheduling optimization model that can reflect the flexibility of the entire electricity-hydrogen-steel link constructed according to step 3 is essentially a nonlinear programming problem. The complexity of the problem requires the use of advanced mathematical tools to solve it. For this reason, this example selects Matlab software with the Yalmip toolbox to build and solve the model. The optimization results are summarized in Table 2. Under the condition of sufficient hydrogen reserves and no restrictions on steel production time periods, the company's electricity purchase cost is the lowest. For scenario 1 that restricts the steel production period, although its purchased electricity is lower than scenario 3, its electricity purchase cost is the highest because it is mainly purchased during periods with higher electricity prices. This result reveals the important impact of hydrogen reserves and production period arrangements on the company's electricity purchase cost. The calculation results obtained based on the optimization method emphasize the importance of reasonable planning of production periods and energy procurement strategies to reduce costs during production scheduling.

[0102] Table 2 Comparison of total electricity purchase under three scenarios

[0103]

[0104] The steel production plan is the key to guiding the electricity consumption behavior of enterprises. Figure 5 The following is a production schedule curve of molten steel in each period of the present invention. Figure 5The displayed results show that: the molten steel production activities of scenario 1 are mainly arranged during daytime working hours, while scenarios 2 and 3 try to arrange production during the night when electricity prices are low. However, during the period of high wind and solar power generation with higher electricity prices, the molten steel production plan is still adjusted to avoid the phenomenon of wind and solar power abandonment in self-provided power plants. This shows that the production scheduling optimization method proposed in the present invention can not only improve the economic benefits of the enterprise, but also take into account the problem of renewable energy consumption. Comparing scenarios 2 and 3, when the initial hydrogen reserves are sufficient, the electric arc furnace can operate at full load in the initial period, and gradually reduce the load level as the hydrogen reserves decrease. When the initial hydrogen reserves are insufficient, the electric arc furnace first operates at a low load level, and gradually increases the load level as the hydrogen reserves increase. It can be seen that the production plan calculated based on the optimization method described in the embodiment of the present invention not only takes into account the energy cost, but also ensures the continuity and efficiency of the production process.

[0105] The operating current density of the electrolyzer is a key indicator for hydrogen production planning. Figure 6 The figure shows the working current density of the electrolytic cell in each period of the present invention. Figure 6 Results shown: Since the steel liquid production period in Scenario 1 is more stringent and the initial hydrogen reserve in Scenario 3 is less, in order to ensure the stability and sustainability of the hydrogen supply in each period, the electrolyzer maintains a relatively high load operation level in most periods. The initial hydrogen reserve in Scenario 2 is relatively sufficient. In order to effectively reduce the cost of electricity, the electrolyzer operates at a relatively low load level during the period when steel liquid is not produced and the electricity price is high. In the last few periods of the night, only the wind power part of the self-provided power plant has output power, and all the generated electricity is used for electrolysis and hydrogen production in Scenario 1, realizing full absorption of the self-provided power plant. In the same period, Scenario 2 and Scenario 3 centrally arranged steel liquid production. In order to meet the hydrogen supply required for production, the electrolyzer maintained a high load level. Therefore, based on the optimization method proposed in the present invention, not only the continuous supply of hydrogen is guaranteed, but also the effective control of electricity costs is achieved by optimizing the operating load of the electrolyzer.

[0106] The pressure of the hydrogen storage tank is closely related to the working current density of the electrolytic cell and the steel liquid production plan, such as Figure 7 The figure shows a schematic diagram of the pressure change curve of the hydrogen storage tank in the example of the present invention. Figure 7 It can be seen that: unlike scenario 1, the molten steel production in scenarios 2 and 3 is basically arranged at night. Although the electrolytic cell operates at full load during the same period, the net inflow of the hydrogen storage tank is negative or fluctuates around 0. Therefore, the pressure of the hydrogen storage tank remains at a low level during the night period. During the daytime non-molten steel production period, the pressure of the hydrogen storage tank increases steadily as the electrolytic cell hydrogen production work continues to advance.

[0107] In summary, the method described in the embodiment of the present invention starts from the steel production demand, aims to minimize the enterprise's electricity cost, comprehensively considers the maximization of renewable energy consumption, safety production constraints, and the mutual constraint relationship between hydrogen production and steelmaking, and proposes a production scheduling optimization plan that takes into account the flexibility of the entire electricity-hydrogen-steel link. It can effectively use time-of-use electricity price information to adjust the production plan, and while pursuing maximum economic benefits, it takes into account the transfer characteristics between production processes and the sustainability of the production process.

[0108] The production scheduling optimization method proposed in the present invention can not only improve economic benefits on the basis of ensuring the production indicators of steel enterprises, but also promote the efficient use of renewable energy and the innovative development of hydrogen steelmaking technology, providing strong technical support for the green transformation and sustainable development of the steel industry. In terms of economic benefits, by finely managing production costs and optimizing resource allocation, production costs can be significantly reduced, product competitiveness can be improved, and the economic benefits of steel enterprises can be maximized; in terms of environmental benefits, the present invention integrates renewable energy utilization technologies, such as solar energy, wind energy, etc., and combines them with the steel production process to reduce dependence on traditional fossil energy, reduce carbon emissions, and promote the green transformation of the steel industry.

[0109] In addition, a person skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be implemented by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium. The above-mentioned storage medium can be a read-only memory, a disk or an optical disk, etc.

[0110] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for optimizing hydrogen steelmaking production scheduling, characterized in that: The method comprises: Step 1: Based on the development trend of hydrogen steelmaking technology, determine the system structure covering the key links of power generation, hydrogen production and steelmaking; Step 2: Based on the energy consumption characteristics and material conversion relationships of each production process of hydrogen steelmaking, a mathematical model of the whole process that comprehensively considers energy flow and material flow is established; Step 3: Define the target system for hydrogen steelmaking optimization, and establish corresponding constraints based on the safety operation constraints and coupling between each process, and build a production scheduling optimization model that can reflect the flexibility of the entire electricity-hydrogen-steel process; Step 4: Based on the actual process technical parameters, design specific operation cases and production scenarios, and use Matlab software and Yalmip toolbox to numerically solve the production scheduling optimization model constructed in step 3 to achieve the optimization of hydrogen steelmaking production scheduling.

2. The optimization method for hydrogen steelmaking production scheduling according to claim 1 is characterized in that: In step 1, the system architecture includes the following components: Renewable energy generation system: Use wind and solar energy to generate electricity and provide clean electricity for the hydrogen steel plant; Large power grid: Provides a stable power supply to hydrogen steel plants when the renewable energy power generation system is insufficient; Electrolyzer: Use water electrolysis technology to produce hydrogen, providing a hydrogen source for the steelmaking process; Hydrogen storage tank: stores excess hydrogen produced by electrolysis to ensure the stability and continuity of hydrogen supply during the steelmaking process; Electric heating equipment: provides the heat required in the steelmaking process; Direct reduction shaft furnace: used to reduce iron ore to sponge iron, providing raw materials for electric arc furnace steelmaking; Electric arc furnace: used for molten steel production and provides raw materials for the production of various steel products.

3. The optimization method for hydrogen energy steelmaking production scheduling according to claim 1 is characterized in that: In step 2, a power generation model that can characterize the uncertainty of wind power output is first established, and the function expression is: Where v is the wind speed; f(v) is the wind speed probability density function; k is the shape parameter; λ is the scale parameter; μ1 and σ1 are the mean and standard deviation of the samples; γ is the gamma function; Where Pwind(t) is the wind turbine output during period t; vt is the wind speed during period t; v wr is the rated wind speed of the fan; v in is the cut-in wind speed; v out is the cut-out wind speed; P wr is the rated power of the fan; Then, a power generation model that can characterize the uncertainty of photovoltaic output is established, and the function expression is: Among them, I t is the solar radiation intensity during period t; μ t is the expected value of period t; σ t is the standard deviation of period t; m t 、n t is the mean and variance of the lognormal random variable in period t; Where Ppv(t) is the photovoltaic output during period t; It is the solar radiation intensity during period t; I s is the solar radiation intensity under standard conditions; r c is the specific solar radiation intensity; W sr is the rated power of the photovoltaic; An electrolyzer model that can characterize the coupling relationship between hydrogen production and power consumption is established, and the function expression is: in, is the molar flow rate of hydrogen; is the volume flow rate of hydrogen; n cell is the number of chambers in the electrolytic cell; I cell is the electrolytic cell current; A cell is the effective surface area of ​​a single cell electrode; F is the Faraday constant; f1 and f2 are Faraday efficiency parameters; U cell is the working voltage of the chamber; T cell is the temperature; r1 and r2 are the ohmic resistance parameters related to temperature; s is the overvoltage coefficient; t1, t2, t3 are the overvoltage coefficients; ΔG cell is the Gibbs free energy change of the battery reaction under standard conditions; z is the number of electrons required to produce 1 mol of hydrogen, which is equal to 2; P el The electrical power consumed by the electrolyzer; A hydrogen storage tank model is established to characterize the relationship between the internal pressure and the molar amount of hydrogen in the tank. The function expression is: Among them, P tank is the internal pressure of the hydrogen storage tank; R is the gas molar constant; T tank is the temperature of the hydrogen storage tank; V tank is the volume of the hydrogen storage tank; is the molar amount of hydrogen inside the hydrogen storage tank; is the molar amount of hydrogen in the hydrogen storage tank at time t0; is the net inflow molar flow rate of hydrogen; are the hydrogen molar flow rates at the inlet and outlet of the hydrogen storage tank respectively; τ is the variable in the integral formula; An electric heating model that can characterize the balance between electric energy and thermal energy is established, and the function expression is: Among them, Q elec The heat required for electric heating; W elec is the heat equivalent electrical energy; c is the specific heat capacity of the preheated object; m is the mass of the preheated object; T0 is the initial temperature of the preheated object; T1 is the target temperature of the preheated object; A direct reduction shaft furnace model that can characterize heat balance and material balance is established, and the function expression is: in, is the volume flow rate of hydrogen required to produce one ton of sponge iron; λ is the ratio of the mass flow rate of hydrogen required for the reduction reaction to the volume flow rate, which is 1.5; is the proportion of iron in iron ore; is the utilization rate of hydrogen in the reduction reaction, which is 0.65; The mass of hydrogen required for heat balance; is the specific heat capacity of hydrogen; C pore is the specific heat capacity of iron ore; η SF is the thermal efficiency of the vertical furnace, which takes a value of 0.9; is the hydrogen inlet temperature; T ore is the iron ore inlet temperature; T out,t is the furnace top gas temperature; is the enthalpy of the reduction reaction in the vertical furnace; M Fe is the mass of sponge iron; M ore To produce M Fe The mass of iron ore required to produce a ton of sponge iron; T Fe is the temperature of metallic iron; is the specific heat capacity of metallic iron; α is the metallization rate of sponge iron; is the mass of total iron in the sponge iron entering the furnace; An arc furnace model is established to characterize the relationship between smelting cycle, chemical energy, physical energy and input electrical energy. The function expression is: Among them, τ is the arc furnace smelting cycle, that is, the time between the first steel tapping and the second steel tapping; τ′ is the power-on time; τ″ is the non-power-on time; M is the weight of the molten steel; P E is the apparent input electrical power; η is the electrical efficiency; is the power factor; P C P is the electrical power converted from chemical heat; P is the electrical power converted from physical heat; C is the smelting power consumption; C C Power saving due to chemical heat; C P Power saving due to physical heat; C E C C and C P The effective power consumption when it is 0; The calculation expression of electric energy consumed per ton of sponge iron in an electric arc furnace is: Where ΔQ el is the physical heat loss; C pFe is the constant pressure specific heat capacity of Fe element in sponge iron; T Fe is the temperature of sponge iron entering the furnace; T steel is the temperature of the molten steel; N is the mass of all iron in the sponge iron entering the furnace; FeO is the proportion of FeO in sponge iron; N vs is the proportion of gangue in sponge iron; N Fe is the proportion of total iron in sponge iron; P Fe is the proportion of metallic iron in sponge iron; W arc It is the amount of electricity consumed after each ton of sponge iron enters the electric arc furnace.

4. The optimization method for hydrogen steelmaking production scheduling according to claim 1 is characterized in that: The process of step 3 is: Taking the lowest enterprise electricity cost as the objective function, the function expression is: in, is the amount of electricity purchased from the power grid in period t; is the grid electricity price in the tth period; N is the total number of study periods; Determine the equation constraints for system operation, including power balance constraints, material balance constraints, and heat balance constraints. Therefore, the function expression of the power balance constraint is: In the formula, is the electricity purchased from the grid in period t; is the wind power output in period t; is the photovoltaic output in period t; is the operating power of the electrolytic cell during the t period; is the operating power of the electric heating device in period t; is the operating power of the arc furnace in the tth period; Considering that there is an upper limit to the hydrogen production rate of the electrolyzer, in order to ensure that the production plan of each period is completed on time and does not affect the plan of the next period, the remaining volume of hydrogen at the end of the current period plus the hydrogen production of the next period is greater than the volume of hydrogen required to produce molten steel in the next period. The function expression is: In the formula, is the volume of hydrogen produced by electrolysis of hydrogen in period t+1; is the volume of hydrogen in the hydrogen storage tank at time period t; The volume of hydrogen required to produce one ton of molten steel; The molten steel production plan for period t; Under the premise of meeting the hydrogen consumption of molten steel production, the thermal balance in the furnace can be ensured by adjusting the material inlet temperature, which can effectively reduce the electricity cost of the enterprise. Therefore, the functional expression of the thermal balance constraint is: In the formula, is the physical heat brought by the hydrogen flow in period t; The physical heat brought by the iron ore in period t; is the heat removed by the exhaust gas in period t; is the heat consumed by the reduction reaction in the furnace during the t period; is the physical heat taken away by the sponge iron in period t; Then, the inequality constraints of the system operation are determined, including renewable energy power generation constraints, production index constraints, electrolyzer operation constraints, and hydrogen storage tank pressure constraints; among which: Renewable energy generation constraints: Wind power generation systems and photovoltaic power generation systems can only output electrical energy, and the actual output level at any time cannot exceed the maximum output, expressed as: In the formula, is the actual output of the wind power generation system in period t; is the maximum power that the wind power generation system can generate in the t period; is the actual output of the photovoltaic power generation system in the t period; is the maximum power that the photovoltaic power generation system can generate in the t period; Production index constraint: The quantitative index of the production target of a steel enterprise is the amount of steel produced within a specified time. In order to avoid frequent cold starts of electric arc furnaces, the difference in production plans for adjacent periods is constrained within a reasonable range, expressed as: In the formula, M is the total production index; max is the upper limit of the difference between production plans in adjacent periods; is the production plan for period t; is the production plan for the t+1 period; N is the total number of research periods; Electrolyzer operation constraints: The electrolytic hydrogen production equipment can flexibly control the hydrogen production of the electrolyzer through continuous adjustment of the input current. The operation constraints of the electrolyzer are expressed as the working range of the input current density, specifically: In the formula, is the input current density of the electrolytic cell in the tth period; Enter the lower limit of the current density for the electrolyzer; Enter an upper limit on the current density for the electrolyzer; Hydrogen storage tank pressure constraint: The pressure of the hydrogen storage tank is used to characterize the storage capacity of hydrogen. The change at adjacent moments is related to the net inflow of hydrogen. In order to ensure the safety and stability of the hydrogen storage tank, its pressure should meet the upper and lower limit constraints, specifically: In the formula, is the pressure of the hydrogen storage tank at time period t; They respectively represent the lower and upper pressure limits of the hydrogen storage tank.

5. The optimization method for hydrogen steelmaking production scheduling according to claim 1 is characterized in that: In step 4, First, the hydrogen steelmaking system is configured and designed in detail based on the actual process technical parameters, and the key configuration parameters of the hydrogen steelmaking system are accurately defined, including the installed capacity of the renewable energy power generation system, the rated input current density of the electrolyzer and its operating range, the volume and pressure limit of the hydrogen storage tank, and the material temperature and rated capacity of the direct reduction shaft furnace and electric arc furnace; Then, based on the whole process mathematical model established in step 2, a preliminary analysis of the system flexibility is conducted, and according to the analysis results, a variety of production modes are designed to adapt to different production needs, and the production state is initialized and designed; Since the production scheduling optimization model constructed in step 3 is a nonlinear programming problem, Matlab software is selected in conjunction with the Yalmip toolbox to solve the model and output the sequential production plan for hydrogen production and steelmaking, thereby maximizing the economic benefits of the hydrogen steelmaking plant while ensuring the safe and stable operation of green electricity.

Images