Cost-efficient operation of a dri system and of additional sub-systems of an overall system

Abstract

The invention relates to an overall system which comprises, as sub-systems, a DRI system (1), an electrolysis system (4), a hydrogen store (6) and a supply device (7). The DRI system (1) and the electrolysis system (4) are connected to an electricity-supply network (2) for receiving electricity, the DRI system (1), the electrolysis system (4) and the hydrogen store (6) are interconnected for transferring hydrogen, and the DRI system (1) and the supply device (7) are interconnected for supplying the DRI system (1) with natural gas and / or ammonia. Information about current states (Z1, Z4, Z6, Z7) of the sub-systems (1, 4, 6, 7); at least one desired production plan (PP) for the DRI system (1) for a forecast horizon (PH); a cost (B1) for electricity received via the electricity-supply network (2) which cost can at least be expected; and a cost (P2, B3) for the natural gas and / or ammonia which cost can at least be expected, is obtained by a controller (8). The controller (8) calculates operating modes (B1, B4, B6, B7) for the sub-systems (1, 4, 6, 7) for the forecast horizon (PH) and determines final states (Z1', Z4', Z6', Z7') that can be expected for the sub-systems (1, 4, 6, 7) on the basis of the current states (Z1, Z4, Z6, Z7) and the operating modes (B1, B4, B6, B7). The controller (8) varies the calculated operating modes (B1, B4, B6, B7) for the forecast horizon (PH) and varies, on the basis thereof, the final states (Z1', Z4', Z6', Z7') that can be expected so as to minimize a cost function (K). The costs for receiving electricity from the electricity-supply network (2) and for consuming natural gas and / or ammonia, and losses of hydrogen located in the hydrogen store (6) enter into the cost function (K). The operating modes (B1, B4, B6, B7) of the sub-systems (1, 4, 6, 7) and / or assessments of the expected final states (Z1', Z4', Z6', Z7') of the sub-systems (1, 4, 6, 7) which final states can be expected also enter into the cost function (K). The productivity of the DRI system (1) also enters into the cost function (K). The controller (8) operates the sub-systems (1, 4, 6, 7) according to the varied operating modes (B1, B4, B6, B7) at least for the beginning of the forecast horizon (PH).

Description

[0001] Description

[0002] Title of the invention

[0003] Cost-efficient operation of a DRI system and other subsystems of an overall system

[0004] field of technology

[0005] The present invention is based on an operating method for an overall system,

[0006] - the overall system comprises a DRI plant, an electrolysis plant and a hydrogen storage facility as subsystems,

[0007] - the DRI plant and the electrolysis plant are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy,

[0008] - whereby the DRI plant, the electrolysis plant and the hydrogen storage facility for the transfer of hydrogen are directly or indirectly connected to each other.

[0009] The present invention is further based on a control program for a control device for an overall system,

[0010] - the overall system comprises a DRI plant, an electrolysis plant and a hydrogen storage facility as subsystems,

[0011] - the DRI plant and the electrolysis plant are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy,

[0012] - the DRI plant, the electrolysis plant and the hydrogen storage facility for the transfer of hydrogen are directly or indirectly connected to each other,

[0013] - wherein the control program comprises machine code that can be processed by the control device,

[0014] - wherein the processing of the machine code by the control device causes the control device to control the entire system according to such an operating method.

[0015] The present invention is further based on a control device for an overall system,

[0016] - the overall system comprises a DRI plant, an electrolysis plant and a hydrogen storage facility as subsystems,

[0017] - the DRI plant and the electrolysis plant are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy,

[0018] - the DRI plant, the electrolysis plant and the hydrogen storage facility for the transfer of hydrogen are directly or indirectly connected to each other,

[0019] - wherein the control device is programmed with such a control program, so that the control device, when executing the machine code of the control program, controls the entire system according to such an operating method. The present invention is further based on an overall system,

[0020] - the overall system comprises a DRI plant, an electrolysis plant and a hydrogen storage facility as subsystems,

[0021] - the DRI plant and the electrolysis plant are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy,

[0022] - the DRI plant, the electrolysis plant and the hydrogen storage facility for the transfer of hydrogen are directly or indirectly connected to each other,

[0023] - wherein the overall system comprises such a control device which, when executing the machine code of such a control program, controls the overall system according to such an operating method.

[0024] State of the art

[0025] The items mentioned are known - however, not specifically for a DRI plant, but only for other plants in the steel industry - for example from the article "Green Energy Supply for the Steel Industry", Stahl und Eisen, August 2022, pages 22 to 24.

[0026] KR 2019 0136300 A describes an industrial process associated with an energy storage system. The industrial process can be a more or less complex technical process comprising several subprocesses that build on each other and interact with each other. The industrial process has various types of loads, namely loads that must always be supplied with energy, loads that can be switched off, and loads whose energy consumption is adjustable. The actual energy consumption of the various components of the industrial plant is determined. The operation of the industrial plant and the energy storage system are coordinated to minimize costs.

[0027] US Pat. No. 10,354,297 B2 discloses an arrangement comprising a domestic consumer, an energy generator, and an energy storage device. The operation of the energy storage device can be determined taking into account the consumer's planned energy consumption. Furthermore, weather data can also be utilized. Price information for purchasing electrical energy from a utility grid and for feeding electrical energy into the utility grid can also be considered.

[0028] It is known from TW 201 235 124 A that the energy consumption of a steel industry plant—specifically, a rolling mill—can be predicted with good accuracy given the plant's known operating mode. US Pat. No. 8,288,888 B2 discloses an electrolysis plant coupled to a wind farm. Additional loads and energy sources may also be present. These additional loads and energy sources may also take the form of electrical energy storage devices. The hydrogen produced by the electrolysis plant can be fed to an affiliated chemical plant or refinery.

[0029] WO 2021 / 183 022 A1 discloses an operating method for an overall system comprising a DRI system, an electrolysis system, a hydrogen storage system, and a supply system as subsystems. The DRI system and the electrolysis system are connected to an electrical supply grid. Furthermore, the DRI system, the electrolysis system, and the hydrogen storage system are interconnected for the transfer of hydrogen, and the DRI system and the supply system are interconnected for supplying an additional gas to the DRI system. The additional gas is a synthesis gas, which is generated by another electrolysis system and, if necessary, temporarily stored.

[0030] US 2015 / 0 259 760 A1 discloses an operating method for an overall system, wherein the overall system comprises a DRI system, an electrolysis system, a hydrogen storage system, and a supply system as subsystems. The DRI system, the electrolysis system, and the hydrogen storage system are directly or indirectly connected to each other for the transfer of hydrogen. Furthermore, the DRI system and the supply system are connected to supply natural gas and / or ammonia to the DRI system. The overall system is controlled by a predictive controller.

[0031] Summary of the invention

[0032] In the past, the costs incurred in determining the operation of steel industry plants – including the energy costs incurred in this regard – were taken into account when determining the operating costs. This applies equally to DRI plants and other steel industry plants. However, this was only taken into account in the sense that the total electrical energy demand and the resulting costs for electrical energy were taken into account. As the shift towards renewable energies progresses, the availability of electrical energy (including the temporal fluctuations in the costs incurred for electrical energy) must be considered to a much greater extent, as the availability and thus also the costs of electrical energy will be subject to significantly greater fluctuations in the future than in the past.

[0033] However, the costs of operating the entire system are determined by a multitude of other factors. The state-of-the-art approaches are therefore suboptimal. While the aforementioned paper states that the steel industry plant, the electrolysis plant, and an electrical energy storage system are controlled and operated using an intelligent energy management system, it does not provide any further details on the implementation of the intelligent energy management system.

[0034] The object of the present invention is to create possibilities by means of which a cost-efficient operation of an overall system is achieved, which comprises as subsystems a DRI plant, an electrolysis plant and a hydrogen storage system.

[0035] The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject of dependent claims 2 to 8.

[0036] First, the overall system comprises – in addition to the subsystems mentioned above – a supply facility as a (further) subsystem. The DRI plant and the supply facility are connected to supply natural gas and / or ammonia to the DRI plant. Furthermore, an operating method of the type mentioned above is designed in such a way that

[0037] - that a control device controlling the entire system knows the current system status of the DRI system, the current electrolysis status of the electrolysis system, the current hydrogen storage status of the hydrogen storage system and the current supply status of the supply device,

[0038] - that the control device knows at least one desired production plan of the DRI plant, at least one expected price for electrical energy purchased via the electrical supply network and at least one expected price for natural gas and / or ammonia for a forecast horizon,

[0039] - that the control system sets operating modes for the forecast horizon and determines expected final states for the end of the forecast horizon,

[0040] - that the operating modes include a plant operating mode for the DRI plant, an electrolysis operating mode for the electrolysis plant, a hydrogen storage operating mode for the hydrogen storage facility and a supply operating mode for the supply facility,

[0041] - that the expected final states comprise a final plant state determined by taking into account the current plant state and the assumed plant operating mode, an expected final electrolysis state determined by taking into account the current electrolysis state and the assumed electrolysis operating mode, an expected final hydrogen storage state determined by taking into account the current hydrogen storage state and the assumed hydrogen storage operating mode, and an expected final supply state determined by taking into account the current supply state and the assumed supply operating mode, - that the control device varies the assumed operating modes and, based on these, the expected final states for the forecast horizon, so that a cost function is minimized,

[0042] - that the cost function includes the costs for the purchase of electrical energy from the electrical supply network, for the consumption of natural gas and / or ammonia and losses of hydrogen in the hydrogen storage facility and further includes the operating modes of the DRI plant, the electrolysis plant, the hydrogen storage facility and the supply facility and / or assessments of the expected final states and further includes a productivity of the DRI plant and

[0043] - that the control device operates the subsystems according to the respective varied operating mode, at least for the beginning of the forecast horizon.

[0044] The invention is based on the finding that a DRI plant can be operated alternatively with hydrogen, natural gas or ammonia and consequently the consumption of natural gas and ammonia and the associated costs as well as the costs for the operation of the corresponding supply facility can be included in the optimization.

[0045] The supply facility can be configured as needed. For example, if natural gas is involved, the supply facility may include a tank for the natural gas and / or be connected to a gas supply network. Alternatively or additionally, if ammonia is involved, the supply facility may include an ammonia production facility. However, this is not mandatory. An ammonia storage facility is also possible.

[0046] The plant status of the DRI plant describes the condition of the DRI plant to the extent necessary. The plant status can include, for example, which materials are currently in the DRI plant and in what condition, as well as the condition of the DRI plant's components.

[0047] The current electrolysis state of the electrolysis plant can, for example, include the temperature of the electrolysis plant, provided that the efficiency of hydrogen production is dependent on the electricity consumption. The electrolysis state can also include other variable parameters, such as electrolyte concentrations.

[0048] A current hydrogen storage status describes the condition of the hydrogen storage device to the extent required. The hydrogen storage status can, in particular, include a fill level or level, i.e., the extent to which (percentage and / or absolute) the hydrogen storage device is filled. The current supply status describes the condition of the supply device to the extent required. If the supply device has tanks, the status can, for example, include fill levels or levels of the tanks – analogous to the hydrogen storage device. If necessary, further data such as maximum filling or withdrawal rates, loss rates, or delivery rates can also be defined. The supply status can also include a degree of wear of the supply device.

[0049] The production plan for the DRI plant specifies the amount of iron or sponge iron to be produced by the DRI plant. If necessary, the production plan also specifies which intermediate products are to be produced. Furthermore, the production plan can also specify planned downtimes of the DRI plant or parts of the DRI plant. A planned downtime may be necessary, for example, for maintenance purposes.

[0050] The phrase that the prices for electrical energy, natural gas, and / or ammonia are "at least expected" encompasses, on the one hand, the case where it is an estimate based on known actual facts. Such known actual facts can, for example, be historical data from previous comparable periods or—particularly for electrical energy—a weather forecast. However, it can also be an actually known price, so that the price is not only expected but also actually given.

[0051] The plant operating mode for the DRI plant is different from the production plan. In particular, the plant operating mode defines how the DRI plant is operated (= controlled) at any given point in time. The plant operating mode is therefore continuous over time ("at 5:52:43 p.m. the DRI plant is operated in control state A, at 5:52:44 p.m. in control state B, at 5:52:45 p.m. in control state C," etc.). The plant operating mode must, of course, be defined in such a way that the specifications of the production plan are met.

[0052] The electrolysis operating mode for the electrolysis plant defines how the electrolysis plant is operated (= controlled) at any given time. The electrolysis operating mode is therefore – analogous to the plant operating mode – continuous over time. The electrolysis operating mode determines the amount of electricity required by the electrolysis plant and the amount of hydrogen produced by the electrolysis plant.

[0053] The DRI plant consumes hydrogen and / or natural gas and / or ammonia. The electrolysis plant produces hydrogen. If there are no other producers or consumers of hydrogen besides the DRI plant and the electrolysis plant, the hydrogen storage mode of operation for the hydrogen storage is a dependent mode of operation, as it must simply absorb or release the difference between the hydrogen required by the DRI plant and the hydrogen produced by the electrolysis plant. When determining the plant operating mode and the electrolysis operating mode, it is only necessary to note that the hydrogen storage will not be completely empty, has only a limited capacity, and only certain amounts of hydrogen can be stored in or withdrawn from the hydrogen storage per unit of time.

[0054] The supply operating mode for the supply facility defines in an analogous manner for each point in time how the supply facility is operated (= controlled).

[0055] The control system determines the expected final states for the end of the forecast horizon based on the respective current states by updating them according to the respective operating mode.

[0056] Varying the applied operating modes with the goal of minimizing the cost function is a typical optimization problem. Optimization problems as such, the way in which optimization problems are applied, and the way in which optimization problems are solved are known to experts. Purely as an example,

[0057] - Fletcher, R.: Practical Methods on Optimization. 2 nd ed., John Wiley Inc., Cichester, New York 1987,

[0058] - Hintermüller, M.; Stadler, G.: A semi-smooth Newton methods for linear-quadratic control problems, Journal of Applied Mathematics and Mechanics (ZAMM) 83-4, 219 - 237, (2003) or

[0059] - Ito, K.; Kunisch, K.: Semi-smooth Newton methods for state-constrained optimal control problems, Systems and Control Letters, 50, 221 - 228, (2003). The sources mentioned also provide information on how boundary conditions to be met can be formulated, for example, the performance limits of a DRI plant. Other issues relevant to the formulation of optimization problems are also known from the sources mentioned. One example of such issues is the way in which deviations from preferred operating states can be penalized. Another example is the way in which conditions to be met can be formulated (using equality constraints). For example, conditions to be met can enforce the state of subsystems of the overall system at the end of the forecast horizon.In the case of the hydrogen storage device, such a state can be, for example, the amount of hydrogen stored there.

[0060] The term “cost function” has a clearly defined meaning for those skilled in the field of optimization problems. It can indeed be intended in the sense of an economic evaluation. However, this is not necessarily the case. In this case, various variables can be included in the cost function. Firstly, the cost function includes the costs for purchasing electrical energy from the supply grid. The costs for purchasing electrical energy are self-explanatory. It is merely pointed out that the costs can be negative in individual cases, namely when the purchase price for electrical energy becomes temporarily negative, for example due to a temporary oversupply. Furthermore, the cost function includes the costs for the consumption of natural gas and / or ammonia. The cost function also includes losses of hydrogen stored in the hydrogen storage facility (6).The latter takes into account the fact that significant losses occur during long-term storage of hydrogen. Depending on the storage method, the loss rate is at least 0.1% of the stored hydrogen per day and can be as high as 0.5% per day.

[0061] The cost function also includes the operating modes of the various subsystems and / or assessments of the expected final states. The assessment of the expected final plant state may include costs related to wear and tear on the DRI plant. Furthermore, the assessment of the expected final plant state may include a component determined, for example, by utilizing an energetic state or a phase state of products in the DRI plant. A similar assessment is possible for the electrolysis plant. With regard to the hydrogen storage system and the supply system, wear and tear may be considered, in particular.Furthermore, the assessment of the expected final hydrogen storage condition may include a portion determined by taking into account any degradation of the hydrogen storage caused by the hydrogen storage mode of operation, i.e., a deterioration in the performance of the hydrogen storage. The same applies to any storage facilities of the supply facility.

[0062] Furthermore, the cost function includes the productivity of the DRI system.

[0063] Preferably, the overall system comprises, as a further subsystem, an electrical energy storage device, which is directly or indirectly connected to the DRI system, the electrolysis system, and the electrical supply grid for transmitting electrical energy. In this case, the control device knows a current storage state of the electrical energy storage device as a further current state, and the operating modes set and varied by the control device additionally include a storage operating mode for the electrical energy storage device. The expected final states also additionally include a final storage state determined by utilizing the current storage state and the set storage operating mode. Finally, the control device also varies the storage operating mode and, based on this, the expected final storage state.

[0064] The provision of an electrical energy storage device and its integration into the optimization process significantly improves the flexibility with which the supply of electrical energy from the supply grid can be controlled. This is because the efficient use of the electrical energy storage device and the hydrogen storage device within the scope of the present invention is dependent on, on the one hand, the expected future electrical energy demand of the DRI system and, on the other hand, the expected future price for electrical energy drawn from the supply grid.

[0065] The energy storage state describes—similar to the other states—the state of the electrical energy storage device to the required extent. The energy storage state can, for example, include the extent to which (percentage and / or absolute) the energy storage device is charged and the temperature of the energy storage device's storage cells. Furthermore, the energy storage state can also include the wear status of the energy storage device or parts of the energy storage device. Furthermore, the energy storage state can, in principle, include maximum possible and currently maximum possible operating variables, such as charging and discharging currents.

[0066] The energy storage mode for the electrical energy storage system determines the rate at which the electrical energy storage system should be charged and discharged. Similar to the system's operating mode, the energy storage system operates continuously. The electrical energy extracted from the electrical energy storage system can, of course, only temporarily, even be so large that it exceeds the energy requirements of the DRI system and the electrolysis system, resulting in electrical energy being fed into the grid.

[0067] The expected price for electrical energy drawn from the grid can be set for different periods of time in different ways. On a spot market, the price is often fixed for a relatively limited period of time, for example, only 24 hours in advance. Here, specific energy quantities are traded for fixed periods of time at a specific spot market price. However, there are also contracts with longer-term commitments, such as a fixed price for a specific power level one year in advance. These two examples are, of course, not the only possible ones.

[0068] However, the billing for the actual power consumed from the grid often deviates from a previously agreed rate, namely when a different amount of power is consumed than the previously purchased amount. For example, while energy is purchased from the spot market by the hour, billing is done by the quarter-hour. If the previously purchased amount of energy is consumed, the agreed rate is also billed. However, if more or less energy is consumed than was previously purchased on the spot market, the actual price for electrical energy drawn from the grid depends on a variety of factors.The actual price shall in particular take into account whether and, if so, at what cost additional electrical energy had to be procured by the grid operator or whether and, if so, at what cost electrical energy purchased but not used by the grid operator could be used for other purposes.

[0069] To reliably determine costs, the forecast horizon is preferably divided into a number of early time periods and a number of late time periods. The number of early and late time periods can be determined as needed. For example, if purchases are made 24 hours in advance and billed by the quarter-hour, the duration of a single time period is 15 minutes, with the forecast horizon comprising 96 early and 4 late time periods.

[0070] For the early time periods, the control device determines the storage operating mode such that the overall system draws a predetermined amount of electrical energy from the electrical grid during the early time periods. This enables a reliable, advance determination of the costs for the electrical energy supply for the early time periods. Furthermore, the control device also varies the storage operating mode, at least for the later time periods, and, based on this, the expected final storage state.

[0071] The procedure just explained demonstrates its full advantages when the control system specifies the quantities of electrical energy to be drawn from the electrical grid during the later periods. This ensures that the energy purchased, for example, on a spot market—neither more nor less—is actually needed and consumed, even during the later periods.

[0072] The determination can be made, for example, based on the operating modes of the other subsystems (i.e., without the electrical energy storage device) during the later time periods, a target storage state of the electrical energy storage device, and a deviation from an expected storage state at the time of the transition from the earlier time periods to the later time periods. The determination can also include, in particular, the price of electrical energy, and possibly even the price of the fossil fuel. If necessary, the control device can also actively intervene in the pricing process. See the applicant's patent application, filed on the same day as the present application, entitled "Cost-efficient operation of a steel industry plant and other subsystems of an overall system."

[0073] When varying the operating mode, the control device preferably takes into account a minimum and a maximum charge level of the electrical energy storage device and / or an average charge level of the electrical energy storage device. By taking such variables into account - either as boundary conditions to be observed or by directly incorporating them into the cost function - it can be ensured that the electrical energy storage device has a certain capacity at all times and in both directions - both for absorbing electrical energy and for releasing electrical energy - so that disruptions in the operation of the DRI system and / or the electrolysis system - possibly also in the event of disruptions in the supply grid or other facilities - can be responded to by changing the operating mode of the electrical energy storage device.

[0074] In some cases, the overall system includes a power generation device as a further subsystem, by means of which electrical energy can be generated in a regenerative manner. In this case, the power generation device for transmitting electrical energy is connected directly or indirectly to the DRI system, the electrolysis system, and the electrical supply grid, and usually also to the electrical energy storage system. The power generation device can be designed, in particular, as a wind turbine or a photovoltaic system. The operating method, if a power generation device is present, is designed as follows:

[0075] - that the control device additionally knows an expected electrical energy that can be generated by the power generation device for the forecast horizon and

[0076] - that the control device takes into account the expected electrical energy that can be generated by the power generating device when varying the operating modes.

[0077] This enables even further optimization of the operation of the entire system.

[0078] When varying the operating modes, the control device preferably takes into account a minimum and a maximum fill level of the hydrogen storage and / or an average fill level of the hydrogen storage. By taking such variables into account – either as boundary conditions to be observed or by directly incorporating them into the cost function – it can be ensured that the hydrogen storage has a certain capacity at all times and in both directions – both for absorbing hydrogen and for releasing hydrogen – so that disruptions in the operation of the DRI system and / or the electrolysis system – possibly also in the event of disruptions in the supply grid or other facilities – can be responded to by changing the operating mode of the hydrogen storage.

[0079] It may be advantageous if the supply facility comprises a generating facility for generating ammonia, with or without an associated ammonia storage facility. In this case, the generating facility is directly or indirectly connected to the DRI plant, the electrolysis plant, and the electrical supply grid for transmitting electrical energy. Furthermore, in this case, the current supply state comprises a current operating state of the generating facility, the supply operating mode comprises the operating mode of the generating facility, and the final expected supply state comprises an expected final operating state of the generating facility. The final expected operating state of the generating facility is determined by the control facility by updating the current operating state in accordance with the operating mode of the generating facility.Thus, varying the supply mode of operation also includes varying the mode of operation of the generating facility.

[0080] The object is further achieved by a control program having the features of claim 9. According to the invention, the controlled overall system comprises—in addition to the subsystems mentioned above—a supply device as a (further) subsystem. The DRI system and the supply device are connected to supply natural gas and / or ammonia to the DRI system. Furthermore, the processing of the machine code by the control device causes the control device to control the overall system according to an operating method according to the invention.

[0081] The object is further achieved by a control device having the features of claim 10. According to the invention, the controlled overall system comprises—in addition to the subsystems mentioned above—a supply device as a (further) subsystem. The DRI system and the supply device are connected to supply natural gas and / or ammonia to the DRI system. Furthermore, the control device is programmed with a control program according to the invention, so that when the machine code of the control program is executed, the control device controls the overall system according to an operating method according to the invention.

[0082] The object is further achieved by an overall system having the features of claim 11. According to the invention,

[0083] - that the controlled overall system - in addition to the subsystems mentioned above - includes a supply facility as a (further) subsystem,

[0084] - that the DRI plant and the supply facility for supplying natural gas and / or ammonia to the DRI plant are interconnected and

[0085] - that the control device is designed as a control device according to the invention which, when the machine code of the control program is executed, controls the entire system according to an operating method according to the invention.

[0086] Short description of the drawings

[0087] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in conjunction with the drawings. FIG. 1 shows an overall system,

[0088] FIG 2 a flow chart,

[0089] FIG 3 another complete system

[0090] FIG 4 a flow chart,

[0091] FIG 5 a timeline,

[0092] FIG 6 a flow chart and

[0093] FIG 7 a flow chart.

[0094] Description of the embodiments

[0095] According to FIG. 1, an overall system includes a DRI plant 1 (DRI = direct reduction of iron) as a subsystem. In DRI plant 1, sponge iron is produced from iron ore. Depending on production, DRI plant 1 requires a continuous supply of hydrogen, natural gas, and / or ammonia, as well as electrical energy.

[0096] The DRI system 1 can obtain electrical energy from an electrical supply network 2, to which the DRI system 1 is connected directly (not shown) or indirectly (e.g., via a converter 3). The supply network 2 is typically a three-phase network and thus a multi-phase supply network. The three-phase network is often operated at a medium voltage in the range of 20 kV to 30 kV or at a high voltage of 110 kV.

[0097] The overall system includes an electrolysis system 4 as a further subsystem. The electrolysis system 4 also consumes electrical energy during its operation. The electrolysis system 4 is therefore also connected to the supply grid 2. The electrolysis system 4 requires a direct voltage for its operation. A rectifier 5 is therefore usually arranged upstream of the electrolysis system 4, so that only an indirect connection to the supply grid 2 exists. The DRI system 1 and the electrolysis system 4 are directly or indirectly connected to one another for the transfer of hydrogen. Any pumps, valves, and the like are not shown in FIG. 1.

[0098] The overall system comprises a hydrogen storage unit 6 as a further subsystem. The hydrogen storage unit 6 can be designed as a storage unit in the narrower sense, i.e. as a dedicated hydrogen storage unit. However, the pipeline network through which hydrogen is transported also has a certain storage capacity and can serve as a hydrogen storage unit 6 within the meaning of the present invention. In the case of a separate, dedicated storage unit, the storage unit can alternatively be arranged above ground or underground. The hydrogen storage unit 6 is connected directly or indirectly to the electrolysis system 4 for absorbing hydrogen and directly or indirectly to the DRI system 1 for releasing hydrogen. Due to the hydrogen storage unit 6, the operation of the DRI system 1 and the electrolysis system 4 can be designed more flexibly.

[0099] It is possible for the hydrogen produced by electrolysis plant 4 to be continuously fed to hydrogen storage 6, and for the hydrogen required by DRI plant 1 to be continuously supplied by hydrogen storage 6, so that hydrogen storage 6 serves as a transfer station for the hydrogen. However, a direct connection between DRI plant 1 and electrolysis plant 4 is also possible.

[0100] The overall system includes a supply facility 7 as a further subsystem. The DRI plant 1 and the supply facility 7 are connected to supply natural gas and / or ammonia to the DRI plant 1.

[0101] FIG 1 shows a simple embodiment of the supply device 7, in which a storage device 7a, 7b is provided for storing natural gas and ammonia. However, alternative embodiments are also possible. For example, the supply device 7 can have a connection to a natural gas supply network. In this case, the storage device 7a can be omitted - but not necessarily. The supply device 7 can also have a generation device for generating ammonia. In this case, the storage device 7b can be omitted - but not necessarily. FIG 1 also shows an embodiment of the supply device 7 that can supply the DRI system 1 with both natural gas and ammonia. However, it is also possible for the supply device 7 to supply the DRI system 1 only with either natural gas or ammonia.

[0102] If the generating facility for producing ammonia includes a generating facility for transmitting electrical energy, the generating facility is generally also directly or indirectly connected to the DRI plant 1, the electrolysis plant 4, and the electrical supply grid 2. It is possible that this generating facility for producing ammonia from nitrogen and hydrogen is connected to the electrolysis plant 4 and / or the hydrogen storage facility 6.

[0103] The overall system further comprises a control device 8. The control device 8 is programmed with a control program 9. The control program 9 comprises machine code 10 that can be processed by the control device 8. Due to the programming with the control program 9, the control device 8 processes the machine code 10. The processing of the machine code 10 by the control device 8 causes the control device 8 to control the overall system according to an operating method that is explained in more detail below in connection with FIG 2. Before the operating method according to the invention is explained, however, it should be noted that the control device 8 is explained below as a uniform control device 8 that jointly controls the subsystems 1, 4, 6 and 7 of the overall system. However, the control device 8 can also have its own sub-control device for controlling each of the subsystems 1, 4, 6 and 7.In this case, appropriate information exchange and coordination must take place between the sub-control devices.

[0104] According to FIG. 2, a current state Z of the overall system is known to the control device 8 in a step S1. The current state Z comprises a current partial state Z1, Z4, Z6, Z7 for each of the subsystems 1, 4, 6, and 7. The number of the respective current partial state Z1, Z4, Z6, Z7 corresponds to the reference symbol of the respective subsystem 1, 4, 6, and 7.

[0105] For example, sub-state Z1 can include the production progress of DRI plant 1. Sub-state Z1 can also include which materials are currently in which state in DRI plant 1.

[0106] The partial state Z4 can, for example, include a temperature and a chemical composition of the electrolysis liquid of the electrolysis system 4 and a wear state of the electrolysis system 4.

[0107] The partial state Z6 includes at least the fill level of the hydrogen storage 6, i.e., the extent to which the hydrogen storage 6 is filled. The partial state Z6 can also include other variables, for example, a temperature and / or a gas pressure of the hydrogen storage 6 or a maximum possible or permissible flow of hydrogen during filling and emptying of the hydrogen storage 6.

[0108] Similar statements may apply to the partial state Z7 of the supply facility 7. If the supply facility 7 includes the generating facility for generating ammonia, the current supply state Z7 also includes a current operating state of the generating facility.

[0109] In a step S2, the control device 8 is informed of a desired production plan PP of the DRI system 1. For example, the production plan PP can be specified for the control device 8 by an operator (not shown). The production plan PP specifies which end products are to be produced by the DRI system 1 from which starting materials, and which properties the end products should have. As a rule, the production plan PP also specifies which intermediate products are to be produced and by when a certain product is to be produced. The production plan PP extends over a forecast horizon PH. The forecast horizon PH is usually at least several hours, often even in the range of several days. For example, the production plan PP can comprise a quantity of pig iron that is to be produced per hour or per day using the DRI system 1.The production plan PP may also specify the minimum amount of carbon that should be contained in the pig iron or sponge iron produced and / or the maximum amount of nitrogen that should be contained in the pig iron or sponge iron produced.

[0110] In a step S3, data D is made known to the control device 8. Data D determines at least an expected price P1 for electrical energy for the forecast horizon PH, provided the electrical energy is drawn from the supply grid 2. Data D also determines at least expected prices P2, P3 for natural gas and / or ammonia. Prices P1 to P3 are defined at least as a function of time t. They may also depend on other circumstances.

[0111] If necessary, the production plan PP and the data D for the prices P1 to P3 can initially be made known to the control device 8 in steps S2 and S3 for different time horizons. In this case, the forecast horizon PH is determined by the shortest of the time horizons.

[0112] In a step S4, the control device 8 sets an operating mode B for the overall system for the forecast horizon PH. The operating mode B comprises - analogous to the current state Z - a partial operating mode B1, B4, B6, B7 for each of the subsystems 1, 4, 6 and 7. The partial operating modes B1, B4, B6, B7 define for each point in time how the respective subsystem 1, 4, 6, 7 is operated (= controlled). The partial operating modes B1, B4, B6, B7 can be time-resolved to the second. The set operating modes B, B1, B4, B6, B7 are initially only provisional.

[0113] Partial operating mode B1 for DRI plant 1—hereinafter also referred to as plant operating mode B1—is determined by control device 8 in such a way that the specifications of the production plan PP are met. In particular, plant operating mode B1 can control the quantities of materials and energy supplied to DRI plant 1, for example, the quantity of iron ore, the quantity of hydrogen, the quantity of natural gas, the quantity of ammonia, and the quantity of electrical power.

[0114] Partial operating mode B4 for electrolysis plant 4 – hereinafter also referred to as electrolysis operating mode B4 – can often be determined independently and relatively flexibly by control device 8. Control device 8 only needs to ensure that the hydrogen demand of DRI plant 1 is met, that the fill level of hydrogen storage 6 does not fall below 0% or exceed 100%, and that the design limits of electrolysis plant 4 are otherwise observed. As an alternative to a virtually free approach for electrolysis operating mode B4, it is also possible to specify a production plan for electrolysis plant 4, which must be taken into account when determining electrolysis operating mode B4. Depending on the specific circumstances of the individual case, more or less consistent operation of electrolysis plant 4 may be expedient.However, it may also be useful to vary the operation of the electrolysis plant 4 over time, especially if the costs for electrical energy fluctuate greatly.

[0115] The partial operating mode B6 for the hydrogen storage unit 6 – hereinafter also referred to as hydrogen storage operating mode B6 – can usually no longer be freely determined by the control device 8. Rather, it is determined by the plant operating mode B1 (and thus the consumption of hydrogen) and the electrolysis operating mode B4 (and thus the production of hydrogen). However, the hydrogen storage unit 6 enables, at least to a certain extent, the decoupling of the operation of the DRI plant 1 and the electrolysis plant 4 from each other, thus enabling the flexible operation of the electrolysis plant 4.

[0116] The partial operating mode B7 for the supply facility 7 - hereinafter also referred to as supply operating mode B7 - may also include the operating mode of the generating facility.

[0117] In a step S5, the control device determines an expected final overall state Z' for the end of the forecast horizon PH. The expected final overall state Z' comprises - analogous to the current state Z - an expected final partial state ZT, Z4', Z6', Z7' for each of the subsystems 1, 4, 6 and 7. The respective expected final partial state ZT, Z4', Z6', Z7' is determined using the respective current partial state Z1, Z4, Z6, Z7 and the respective partial operating mode B1, B4, B6, B7. Specifically, the control device 8 determines the respective expected final partial state ZT, Z4', Z6', Z7' by updating the respective current partial state Z1, Z4, Z6, Z7 based on the respective partial operating mode B1, B4, B6, B7. The expected final partial state Z7' may also include an expected final operating state of the generating facility.The expected final operating state is determined, if necessary, by the control device 8 by updating the current operating state in accordance with the operating mode of the generating device.

[0118] In a step S6, the control device 8 determines the value of a cost function K. Various cost factors can be included in the cost function K. The cost function K is defined as a weighted or unweighted sum of the individual cost factors. Cost factors include, for example, the costs for purchasing electrical energy from the supply network 2 and for the consumption of natural gas and / or ammonia. Furthermore, the operating modes B1, B4, B6, B7 of the subsystems 1, 4, 6, 7 also represent such cost factors. Alternatively or in addition to the operating modes B1, B4, B6, B7 of the subsystems 1, 4, 6, 7, evaluations of the expected final states ZT, Z4', Z6', Z7' can also be considered. Finally, the productivity of the DRI plant 1 also represents such a cost factor. In addition to the quantity of pig iron or sponge iron produced, the productivity of the DRI plant 1 can also be determined by quality characteristics of the pig iron or sponge iron produced.sponge iron.

[0119] To determine the costs for purchasing electrical energy from the supply network 2, the control device 8 can, for example, use the determined partial operating modes B1, B4, B6, B7 to determine the amount of electrical energy purchased from the supply network 2 and, based on this in conjunction with the known price P1, determine the associated costs. The determination can be made with the same time resolution as the partial operating modes B1, B4, B6, B7, for example, to the second. The determination can also be made with a coarser time resolution, for example with a resolution of 1 minute or 15 minutes. It is also possible to initially work with a high time resolution, for example to the second, but then to build on this and carry out statistical evaluations for longer periods of time (for example 1 minute, 5 minutes, 15 minutes), for example to determine mean values, maximum values, minimum values, dispersion, etc.

[0120] Plant operating mode B1 can, for example, be evaluated in terms of productivity, resource-efficient operation, an assessment of wear and tear on DRI plant 1, etc. Similar evaluations are also possible for electrolysis operating mode B4, hydrogen storage operating mode B6, and supply operating mode B7.

[0121] The assessment of the expected final plant state ZT can include a portion that is determined, for example, by utilizing the energy state of the DRI plant 1—this also includes the energy state of products located in the DRI plant 1. This enables the control device 8 to determine the assessment of the expected final plant state ZT by taking into account the amount of energy that must be generated during the subsequent operation of the DRI plant 1 beyond the forecast horizon PH.

[0122] In the assessment of the expected final plant condition ZT, the wear and tear incurred during the operation of DRI plant 1 can also be taken into account, i.e. the costs due to the wear and tear that occurs during the production horizon PH due to the plant operating mode B1.

[0123] The assessment of the expected final electrolysis state Z4' may also include a component determined by utilizing the energetic state of the electrolysis system 4—particularly for an electrolysis system 4 operating at a high temperature. Concentrations of electrolyte fluids and wear conditions may also be included in the assessment.

[0124] The assessment of the expected final hydrogen storage state Z6' is usually very simple.

[0125] Typically, this is simply a constant. The evaluation of the expected final supply state Z7' is also usually very simple. Analogous to the final hydrogen storage state Z6', this is usually simply a constant.

[0126] Evaluating the productivity of DRI Plant 1 is also usually relatively simple. It is generally better (i.e., the corresponding cost factor is lower) the larger the quantity of output product produced in a given unit of time. In the simplest case, the corresponding cost factor is proportional to the time required to produce a previously determined quantity of output product.

[0127] The cost function K also includes costs that account for the losses of hydrogen in the hydrogen storage facility 6. An analogous approach is also possible for the supply facility 7, if necessary.

[0128] Other cost factors can also be included in the cost function K. Some possible additional cost factors are discussed below as examples.

[0129] For example, a cost factor can be considered that represents the costs for other operations of DRI Plant 1, i.e., the costs resulting from the forecast horizon PH under consideration, but excluding the costs for electrical energy. The costs for other operations of DRI Plant 1 can include, for example, the costs for other required input materials (starting materials) or the costs for the treatment of process media or costs due to environmental impacts, such as the costs for CO2 taxes. The cost factor for other operations of DRI Plant 1 can also include depreciation.

[0130] In an analogous manner, cost factors can also be taken into account which represent the costs for the other operation of the electrolysis plant 4 and the hydrogen storage 6.

[0131] Furthermore, other costs of the overall system can also be taken into account, provided such costs arise. Examples of such costs include environmental taxes or government subsidies.

[0132] As a result, all free control variables for all subsystems 1, 4, 6, 7 are included in the cost function K. In particular, the quantities of hydrogen and / or natural gas and / or ammonia and the associated costs are also included in the cost function K.

[0133] In a step S7, the control device 8 solves an optimization problem. The solution to the optimization problem is the combination of those partial operating modes B1, B4, B6, B7 - each considered over the production horizon PH - for which the cost function K is minimal overall. The cost function K is thus a functional that is to be minimized and is calculated on the basis of an initial value problem with end conditions. In the context of solving the optimization problem, the control device 8 varies the assumed partial operating modes B1, B4, B6, B7 for the forecast horizon PH. The variation takes place taking into account the production plan PP and other boundary conditions such as the design limits of the various subsystems 1, 4, 6, 7. This also applies in particular to the operating limits of the supply facility 7, for example the possibilities for generating, storing and supplying ammonia.If specified, a production plan for the electrolysis plant 4 is also taken into account. Furthermore, when solving the optimization problem, the control device 8 takes into account that the speeds at which the proportions of hydrogen, natural gas, and ammonia supplied to the DRI plant 1 can be changed are limited. The control device 8 therefore takes into account that changes to these proportions require a certain amount of time. In principle, however, any distribution into hydrogen, natural gas, and ammonia is possible. Furthermore, the control device 8 can take into account that a change in the distribution of hydrogen, natural gas, and ammonia can influence the proportion of carbon in the sponge iron produced by the DRI plant 1, thereby affecting subsequent processes, for example thermally, and thus particularly in terms of their energy requirements. It is often advantageous to use a minimum proportion of natural gas.This can be ensured by an appropriate inequality constraint. Where applicable, varying the supply operating mode B7 also includes varying the operating mode of the generating facility.

[0134] When varying the operating modes B1, B4, B6, B7, the control device 10 can also take additional conditions into account. Examples of such conditions can be, for example, specifications for the expected final partial states ZT, Z4', Z6', Z7'. For example, it can be specified as a specification that the hydrogen storage device 6 has a very specific fill level at the end of the forecast horizon PH or that the fill level of the hydrogen storage device 6 lies within a predetermined range at the end of the forecast horizon PH. Analogous specifications are also possible for the supply device 7 if necessary. Such conditions can be taken into account in particular by so-called equality constraints and / or inequality constraints.Other conditions are also possible, for example that the energy drawn from supply network 2 does not exceed a specified maximum value or that the production of certain products is completed at a specified time.

[0135] Optimization problems as such, their approach, and procedures for solving such optimization problems are known to those skilled in the art. They are also approached in this way in the aforementioned prior art. Upon execution of step S7, the varied and thus optimized partial operating modes B1, B4, B6, B7 are determined. Therefore, in a step S8, the control device 8 can operate the subsystems 1, 4, 6, 7 according to the varied partial operating modes B1, B4, B6, B7. This is initially performed for the beginning of the forecast horizon PH.

[0136] In step S9, the control device 8 checks whether new information is available. If this is not the case, the control device 8 returns to step S8. When step S8 is executed again, the control device 8 continues to operate the subsystems 1, 4, 6, and 7 according to the varied partial operating modes B1, B4, B6, and B7. In doing so, it takes into account the progress over time t.

[0137] If new information is available to the control device 8, the control device 8 proceeds to step S10. In step S10, the control device 8 checks whether the information is a command to terminate the operation of the entire system. If this is the case, the control device 8 terminates the operation of the entire system in step S11. Otherwise, the control device 8 returns to step S1. Depending on the type of new information, the control device 8 can alternatively return to step S2 or step S3.

[0138] As a result, the procedure shown in FIG. 2 repeatedly determines the partial operating modes B1, B4, B6, and B7 with a specific forecast horizon PH. The determination is thus carried out as a permanent forecast and is continuously adjusted to the expected price P and the production plan PP.

[0139] The overall system of FIG 3 has the same components as the overall system of FIG

[0140] 1. In addition, however, the overall system comprises an electrical energy storage device 11, as shown in FIG. 3. The energy storage device 11 is connected directly or indirectly to the supply network 2, at least for absorbing electrical energy, and possibly also for discharging electrical energy. The energy storage device 11 is also connected to the DRI system 1 and the electrolysis system 4 for discharging electrical energy.

[0141] If the energy storage unit 11 absorbs electrical energy, it is always taken from the supply network

[0142] 2. If the energy storage device 11 supplies electrical energy, it is used primarily to meet the needs of the DRI system 1 and the electrolysis system 4 and only secondarily for feeding into the supply grid 2. As a result, depending on whether the electrical energy supplied by the energy storage device 11 is greater or lesser than the electrical energy consumed by the DRI system 1 and the electrolysis system 4, electrical energy can be temporarily fed into the supply grid 2 or drawn from the supply grid 2.

[0143] It must be possible to adjust whether and to what extent electrical energy is supplied to the energy storage device 11, or whether and to what extent the electrical energy storage device 11 releases electrical energy. For this purpose, a bidirectionally operable converter unit is generally present. This converter unit is not shown in FIG. 1. Rather, it is considered a component of the energy storage device 11.

[0144] The precise nature of the electrical connection between the DRI system 1, the electrolysis system 4, and the energy storage system 11 and the supply grid 2 is of secondary importance. In particular, rectifiers 5, inverters, and other converters 3 can be assigned to the various subsystems 1, 4, and 11 as required. However, it should be ensured that a transfer of electrical energy from the energy storage system 11 to the DRI system 1 and the electrolysis system 4 is possible without a detour via the supply grid 2.

[0145] The electrical energy storage device 11 is a further subsystem of the overall system and is treated as such by the control device 8. The integration of the electrical energy storage device 11 into the operating process is shown in FIG. 4.

[0146] Steps S21 to S31 of FIG. 4 correspond in principle to steps S1 to S11 of FIG. 2. However, according to the illustration in FIG. 4, the control device 8 knows a current storage state Z11 of the electrical energy storage device 11 as a further current state Z11. The partial state Z11 comprises at least the charge state of the energy storage device 11, i.e., the extent to which the energy storage device 11 is charged. The partial state Z11 can also comprise further variables, for example a temperature of the energy storage device 11 or a maximum possible or permissible charging and discharging current. Furthermore, the partial state Z11 can comprise a wear state of the energy storage device 11.

[0147] For the same reasons, the operating modes set and varied by the control device 8 additionally include a storage operating mode B11 for the electrical energy storage device 11. The partial operating mode B11 for the energy storage device 11—hereinafter also referred to as energy storage operating mode B11—can often also be determined independently and relatively flexibly by the control device 8 in some cases. The control device 8 only needs to ensure that the state of charge of the energy storage device 11 does not fall below 0% and does not rise above 100%, and that the design limits of the energy storage device 11 (e.g., the maximum charging current and the maximum discharging current) are observed.

[0148] Likewise, the expected final states additionally include a final storage state Z1 T determined using the current storage state Z11 and the assumed storage operating mode B11.

[0149] Finally, as part of the optimization, the control device 8 also varies the storage operating mode B11 and, based thereon, the expected final storage state Z11'. When varying the partial operating modes B1, B4, B6, B7, B11, the control device 8 preferably also takes into account a minimum and a maximum state of charge of the electrical energy storage device 11 and / or an average state of charge of the electrical energy storage device 11. This can be taken into account by weighting deviations from the average state of charge with a - albeit relatively small - factor in the cost function K and thus "penalizing" them. It can also be required that no energy is fed into the supply grid 2 or that the energy drawn from the supply grid 2 does not exceed a predetermined maximum value.The evaluation of the expected final energy storage state Z1 T may include a portion that takes into account the wear and tear incurred by the operation of the energy storage device 11, i.e. the costs due to the wear and tear that occurs during the production horizon PH due to the storage operating mode B11.

[0150] A particularly advantageous embodiment of the present invention is explained below in conjunction with FIGS. 5 and 6. Within the scope of this embodiment, the energy storage device 11 is required.

[0151] According to FIG. 5, the forecast horizon PH is divided into a number of early time periods 12 and a number of late time periods 13. For a typical forecast horizon PH of 24 hours, for example, the time periods 12 and 13 can each have a duration of 15 minutes, and there can also be 92 early time periods 12 and 4 late time periods. However, the stated duration and the stated number of early and late time periods 12 and 13 are purely exemplary.

[0152] In the case of a division of the forecast horizon PH into early and late time periods 12, 13, step S26 of FIG. 4 can be designed as shown in FIG. 6.

[0153] According to FIG 6, step S26 of FIG 4 is divided into steps S41 and S42. In step S41, the control device 8 optimizes the operating modes B1, B4, B6, B7, B11 for the early time periods 12. In step S42, the control device 8 optimizes the operating modes B1, B4, B6, B7, B11 for the late time periods 13. The difference between steps S41 and S42 is that when optimizing step S41, the control device 8 takes into account the additional boundary condition that the overall system draws a predetermined amount E12 of electrical energy from the electrical supply network 2 during the early time periods 12 for the respective early time period 12. The amount E12 can indeed be determined individually for the respective early time period 12. However, it is known.The operating mode B11 of the electrical energy storage device 11 is therefore determined such that the respective amount E of electrical energy drawn from the supply network 2 during the respective early time period 12 corresponds to this value. In step S42, however, no such boundary condition is taken into account. The amount of electrical energy that the entire system draws from the electrical supply network 2 is therefore adjusted during the later time periods 13 in accordance with the optimization of the operating modes B1, B4, B6, B7, B11. Thus, as part of the optimization for the later time periods 13, the control device 8 also varies the storage operating mode B11 and, based on this, the expected final storage state Z11'.

[0154] The late time periods 13 are often so far in the future that specific energy quantities can be ordered from an energy exchange for the late time periods 13. It is therefore possible to supplement the procedure of FIG. 6 with steps S43 and S44. In step S43, the control device 8 orders energy quantities for the late time periods 13 from an energy exchange. In step S44, the control device 8 assigns the corresponding energy quantities to the corresponding late time periods 13, thus specifying the corresponding quantities of electrical energy for the late time periods 13 that are to be drawn from the electrical supply grid 2 during the last time periods 13.

[0155] FIG 3 also shows a further extension of the overall system of FIG 1. According to FIG 3, the overall system has a power generation device 14 as a further subsystem. By means of the power generation device 14, electrical energy can be generated in a regenerative manner - i.e. using sunlight or wind power, possibly also using hydropower or geothermal energy. In this case, the power generation device 14 is connected directly or indirectly to the other subsystems 1, 4, 11 that absorb or emit electrical energy and also to the electrical supply network 2 for the transmission of electrical energy. A converter, which is usually required for the power generation device 14, can be regarded as a component of the power generation device 14. It is not shown in FIG 3. Preferably, the supply of electrical energy from the power generation device 14 to the subsystems 1, 4, 11 is possible without a detour via the supply network 2.

[0156] If the power generation device 14 is present, the procedure of FIG. 4 is initially modified according to FIG. 7 in that a step S51 is additionally provided. Step S51 precedes step S24. It can be preceded directly by step S24 as shown in FIG. 7. However, this is not absolutely necessary. In step S51, the control device 8 is informed of an electrical energy for the forecast horizon PH that can (presumably) be generated by the power generation device 14. Such a forecast can be made, for example, using a local weather forecast for the location of the power generation device 14.

[0157] Furthermore, the procedure of FIG. 4 is modified in that, in step S26, the expected electrical energy that can be generated by the power generation device 14 is taken into account in the cost function K. This results in other partial operating modes B1, B4, B6, B7, B11 in step S27, for which the cost function K is minimal.

[0158] Below, possible models that can be used to determine the respective cost factor for the DRI system 1, the electrolysis system 4 (including the hydrogen storage system 6), and the power generation system 14 are explained. These models are implemented within the control device 8 and are evaluated by the control device 8 in step S6 and step S26, respectively.

[0159] For DRI plant 1, a function v and a target electrical power P* are assumed, each for the forecast horizon PH. The function v is a function of time t. The target power P* can be a constant. The target power P* is multiplied by the function v. The result is the actual electrical power P at which DRI plant 1 is operated:

[0160] P = v(t)P*. (1)

[0161] The function v is defined for positive values ​​of time t and has a value range from vmin to 1, where vmin in turn has a value between 0 and 1. vmin is a function of the state of the DRI system 1. The current value of vmin takes into account that it is not possible to arbitrarily reduce the actual power P in every state of the DRI system 1. This depends rather on the state of the DRI system 1. The state of the DRI system 1 must therefore be known to the control device 8. As a rule, an attempt is made to operate the DRI system 1 as evenly as possible. The value of vmin will usually be just below 1.

[0162] The total electrical energy demand of the DRI system 1 is a function of the course of the function v. It is possible for the control device 8 to independently determine the total electrical energy demand of the DRI system 1. Alternatively, the total electrical energy demand of the DRI system 1 can be specified, for example, or determined via the energy balance (radiation) of the DRI system 1.

[0163] The function v can be used by the control device 8 to influence the operation of the DRI system 1. Naturally, the extent to which sponge iron is produced decreases if the function v has a value below 1. The control device 8 can therefore determine the associated time delay T and evaluate it accordingly:

[0164] Ka = k1 + k2T. (2) k1 is a constant with the unit "currency," for example, 2000 euros. k2 is a constant with the unit "currency per time," for example, 1000 euros per minute. T is the time difference by which the production of DRI plant 1 is reduced to produce a certain amount of sponge iron, for example, in minutes.

[0165] However, the cost factor Ka is offset by a significant potential for energy savings, provided that it is possible to shift the high electrical energy consumption of the DRI system 1 to times when the electrical energy drawn from the supply grid 2 is cost-effective. This is where the advantages of the present invention become apparent, i.e., when the operation of the DRI system 1, the electrolysis system 4, the hydrogen storage device 6, the supply device 7, and optionally also the electrical energy storage device 11 are jointly optimized. The advantages can be even greater if electricity can also be generated independently using the power generation device 14.

[0166] The cost share Kb, which is caused by the supplied electrical energy for DRI plant 1, can be determined by integrating the respective instantaneous costs over the production horizon PH. The instantaneous costs can be determined as k3(t)P(t) (3). Here, k3 is a factor that depends at least on time t and reflects the costs of purchasing electrical energy from the supply grid 2.

[0167] In an analogous manner, further cost components Kc, Kd and Ke can be determined, which are caused for the DRI plant 1 due to the supplied hydrogen, natural gas and ammonia.

[0168] Furthermore, direct reduction also produces carbon dioxide, which often requires certificates when released into the environment. This cost component should also be considered.

[0169] The total cost share determined for DRI Annex 1 is the sum of the cost shares explained above.

[0170] The electrolysis plant 4 produces and releases hydrogen, while the hydrogen storage plant 6 absorbs and releases hydrogen. It is taken into account that some of the stored hydrogen escapes. As already mentioned, these losses can amount to up to 0.5% of the stored amount of hydrogen per day. Furthermore, energy is required to pressurize the hydrogen into the hydrogen storage plant 6. This energy can usually not be recovered when the hydrogen is removed from the hydrogen storage plant 6. The joint costs for operating the electrolysis plant 4 and the hydrogen storage plant 6 can be determined, for example, by integrating the respective instantaneous costs over the production horizon PH. The instantaneous costs can be calculated as k3(t)P'(t) + k4H'(t) (4). Here, k3 is the factor already explained in connection with equation 3. P' is the electrical energy drawn from the supply grid 2.In the simplest case, the factor k5 is a constant. If necessary, the factor k5 can also be time-dependent. H' is the amount of hydrogen currently being lost, i.e., the derivative of the amount of stored hydrogen as a function of time t. If necessary, the wear and tear of the electrolysis plant 4 can also be taken into account in the costs.

[0171] In a similar way, the costs for producing ammonia from hydrogen and for storing the ammonia can also be considered. It is important to note that ammonia production not only requires energy but also consumes hydrogen. The required nitrogen can usually be extracted from the air. However, costs may arise for removing oxygen and other gases from the air. Any wear and tear on the production equipment can also be considered.

[0172] If the power generation device 14 is directly assigned to the other subsystems 1, 4, 6, 7, and possibly 11, i.e., in particular, if the electrical energy generated by the power generation device 14 can be supplied to the subsystems 1, 4, 6, 7, and possibly 11 without detouring via the supply grid 2, the generation of electrical energy is free of charge. If it (temporarily) exceeds the electrical energy consumption of the other subsystems 1, 4, 6, 7, and possibly 11, the electrical energy is fed into the supply grid 2. In this case, in particular, the costs for the power generation device 14 may even be negative.

[0173] The present invention offers many advantages. In particular, it enables comprehensive optimization of the operation of the entire system, consisting of subsystems 1, 4, 6, and 7, and possibly also subsystems 11 and 14.

[0174] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0175] 1 system

[0176] 2 Supply network

[0177] 3 inverters

[0178] 4 Electrolysis plant

[0179] 5 rectifiers

[0180] 6 hydrogen storage

[0181] 7 Supply facility

[0182] 7a, 7b Storage facilities

[0183] 8 Control device

[0184] 9 Control program

[0185] 10 Machine code

[0186] 11 Energy storage

[0187] 12, 13 periods

[0188] 14 Power generation facility

[0189] B, B1, B4, B6, B7, B11 operating modes

[0190] D Data

[0191] E; E12, E13 Amounts of energy

[0192] K cost function

[0193] P1 to P3 prices

[0194] PH forecast horizon

[0195] PP production plan

[0196] S1 to S51 steps t time

[0197] Z, Z1, Z4, Z6, Z7, Z11 current states

[0198] Z', Z1', Z4', Z6', Z7', Z11' expected final states

Claims

Claims 1. Operating procedures for an entire system, - wherein the overall system comprises as subsystems a DRI plant (1), an electrolysis plant (4), a hydrogen storage facility (6) and a supply facility (7), - wherein the DRI plant (1) and the electrolysis plant (4) are connected directly or indirectly to an electrical supply network (2) for the purpose of obtaining electrical energy, - wherein the DRI plant (1), the electrolysis plant (4) and the hydrogen storage facility (6) are directly or indirectly connected to each other for the transfer of hydrogen, - wherein the DRI plant (1) and the supply device (7) for supplying natural gas and / or ammonia to the DRI plant (1) are connected to each other, - wherein a control device (8) controlling the entire system knows as current states a current system state (Z1) of the DRI system (1), a current electrolysis state (Z4) of the electrolysis system (4), a current hydrogen storage state (Z6) of the hydrogen storage (6) and a current supply state (Z7) of the supply device (7), - wherein the control device (8) knows at least one desired production plan (PP) of the DRI plant (1), at least one expected price (P1) for electrical energy obtained via the electrical supply network (2) and at least one expected price (P2, P3) for the natural gas and / or the ammonia for a forecast horizon (PH), - wherein the control device (8) sets operating modes (B1, B4, B6, B7) for the forecast horizon and determines expected final states (ZT, Z4', Z6', Z7') for the end of the forecast horizon (PH), - wherein the operating modes (B1, B4, B6, B7) comprise a plant operating mode (B1) for the DRI plant (1), an electrolysis operating mode (B4) for the electrolysis plant (4), a hydrogen storage operating mode (B6) for the hydrogen storage (6) and a supply operating mode (B7) for the supply device (7), - wherein the expected final states (ZT, Z4', Z6', Z7') comprise a final plant state (ZT) determined by utilizing the current plant state (Z1) and the assumed plant operating mode (B1), an expected final electrolysis state (Z4') determined by utilizing the current electrolysis state (Z4) and the assumed electrolysis operating mode (B4), an expected final hydrogen storage state (B6') determined by utilizing the current hydrogen storage state (Z6) and the assumed hydrogen storage operating mode (B6), and an expected final supply state (Z7') determined by utilizing the current supply state (Z7) and the assumed supply operating mode (B7), - wherein the control device (8) for the forecast horizon (PH) varies the set operating modes (B1, B4, B6, B7) and, based thereon, the expected final states (ZT, Z4', Z6', Z7') so that a cost function (K) is minimized, - wherein the cost function (K) includes the costs for the purchase of electrical energy from the electrical supply network (2), for the consumption of natural gas and / or ammonia and losses of hydrogen in the hydrogen storage facility (6) and further includes the operating modes (B1, B4, B6, B7) of the DRI plant (1), the electrolysis plant (4), the hydrogen storage facility (6) and the supply facility (7) and / or evaluations of the expected final states (ZT, Z4', Z6', Z7') and further includes a productivity of the DRI plant (1) and - wherein the control device (8) operates the subsystems (1, 4, 6, 7) at least for the beginning of the forecast horizon (PH) according to the respective varied operating mode (B1, B4, B6, B7).

2. Operating method according to claim 1, characterized in that - that the overall system comprises an electrical energy storage device (11) as a further subsystem, - that the electrical energy storage device (11) is connected directly or indirectly to the DRI system (1), the electrolysis system (4) and the electrical supply network (2) for the transmission of electrical energy, - that the control device (8) knows a current storage state (Z11) of the electrical energy store (11) as a further current state (Z11) and the operating modes set and varied by the control device (8) additionally comprise a storage operating mode (B11) for the electrical energy store (11), - that the expected final states additionally include a final storage state (Z1 T) determined by using the current storage state (Z11) and the expected storage operating mode (B11), - that the control device (8) also varies the memory operating mode (B11) and, based thereon, the expected final memory state (Z1 T).

3. Operating method according to claim 2, characterized in that - that the forecast horizon (PH) is divided into a number of early time periods (12) and a number of late time periods (13), - that the control device (8) determines the storage mode of operation (B11) for the early time periods (12) in such a way that the overall system draws a predetermined amount (E12) of electrical energy from the electrical supply network (2) for the respective early time period (12) during the early time periods (12), and - that the control device (8) also varies the memory operating mode (B11) and, based thereon, the expected final memory state (Z1 T), at least for the later time periods (13).

4. Operating method according to claim 3, characterized in that the control device (8) determines for the later time periods (13) quantities (E13) of electrical energy which are to be drawn from the electrical supply network (2) during the last time periods (13).

5. Operating method according to claim 2, 3 or 4, characterized in that the control device (8) takes into account a minimum and a maximum charge state of the electrical energy store (11) and / or an average charge state of the electrical energy store (11) when varying the operating modes (B1, B4, B6, B7, B11).

6. Operating method according to one of the above claims, characterized in that - that the overall system has, as a further subsystem, a power generation device (14) by means of which electrical energy can be generated in a regenerative manner, - that the power generation device (14) for transmitting electrical energy is connected directly or indirectly to the DRI plant (1), the electrolysis plant (4) and the electrical supply network (2), - that the control device (8) additionally knows an expected electrical energy that can be generated by means of the power generation device (14) for the forecast horizon (PH) and - that the control device (8) takes into account the expected electrical energy that can be generated by means of the power generation device (14) when varying the operating modes (B1, B4, B6, B7).

7. Operating method according to one of the above claims, characterized in that the control device (8) takes into account a minimum and a maximum filling level of the hydrogen storage (6) and / or an average filling level of the hydrogen storage (6) when varying the operating modes (B1, B4, B6, B7).

8. Operating method according to one of the above claims, characterized in that - that the supply device (7) comprises a generating device for generating ammonia with or without an associated storage device (7b) for ammonia, - that the generating facility for transmitting electrical energy is directly or indirectly connected to the DRI plant (1), the electrolysis plant (4) and the electrical supply network (2), - that the current supply status (Z7) includes a current operating status of the generating facility, - that the supply mode of operation (B7) includes the mode of operation of the generating facility, - that the final expected supply state (Z7') comprises an expected final operating state of the generating device, which is determined by the control device (8) by updating the current operating state in accordance with the operating mode of the generating device, and - that the variation of the supply operating mode (B7) also includes a variation of the operating mode of the generating facility.

9. Control program for a control device (8) for an overall system, - wherein the overall system comprises as subsystems a DRI plant (1), an electrolysis plant (4), a hydrogen storage facility (6) and a supply facility (7), - wherein the DRI plant (1) and the electrolysis plant (4) are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy, - wherein the DRI plant (1), the electrolysis plant (4) and the hydrogen storage facility (6) are directly or indirectly connected to each other for the transfer of hydrogen, - wherein the DRI plant (1) and the supply device (7) for supplying natural gas and / or ammonia to the DRI plant (1) are connected to each other, - wherein the control program comprises machine code (10) which can be processed by the control device (8), - wherein the processing of the machine code (10) by the control device (8) causes the control device (8) to control the overall system according to an operating method according to one of the above claims.

10. Control device for an entire system, - wherein the overall system comprises as subsystems a DRI plant (1), an electrolysis plant (4), a hydrogen storage facility (6) and a supply facility (7), - wherein the DRI plant (1) and the electrolysis plant (4) are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy, - wherein the DRI plant (1), the electrolysis plant (4) and the hydrogen storage facility (6) are directly or indirectly connected to each other for the transfer of hydrogen, - wherein the DRI plant (1) and the supply device (7) for supplying natural gas and / or ammonia to the DRI plant (1) are connected to each other, - wherein the control device is programmed with a control program (9) according to claim 9, so that when the machine code (10) of the control program (9) is processed, the control device controls the entire system according to an operating method according to one of claims 1 to 8.

11. Overall system, - wherein the overall system comprises as subsystems a DRI plant (1), an electrolysis plant (4), a hydrogen storage facility (6) and a supply facility (7), - wherein the DRI plant (1) and the electrolysis plant (4) are directly or indirectly connected to an electrical supply network for the purpose of obtaining electrical energy, - wherein the DRI plant (1), the electrolysis plant (4) and the hydrogen storage facility (6) are directly or indirectly connected to each other for the transfer of hydrogen, - wherein the DRI system (1) and the supply device (7) for supplying natural gas and / or ammonia to the DRI system (1) are connected to one another, - wherein the overall system comprises a control device (8) according to claim 10, which, when the machine code (10) of a control program (9) of claim 9 is executed, controls the overall system according to an operating method according to one of claims 1 to 8.

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