Electrolysis system and method for operating at least one electrical heating element of the electrolysis system

Abstract

The invention relates to a method for operating at least one electrical heating element (10a, 12a, 14a; 10b) of an electrolysis system (16a; 16b), which comprises at least one electrolysis cell unit (18a) and at least one supply path (20a, 22a; 20b) for supplying the electrolysis cell unit (18a) with at least one reactant, wherein, in at least one operating state, the at least one electrical heating element (10a, 12a, 14a; 10b) heats, in particular vaporises, the at least one reactant. According to the invention, in at least one method step, a power parameter (L) of the at least one electrical heating element (10a, 12a, 14a; 10b) is set using a combination of feedforward control (24a; 24b) and a closed control loop (26a; 26b).

Description

[0001] R.413539

[0002] - 1 -

[0003] Description

[0004] Electrolysis system and method for operating at least one electrical heating element of the electrolysis system

[0005] State of the art

[0006] A method for operating at least one electrical heating element of an electrolysis system, comprising at least one electrolysis cell unit and at least one supply path for supplying the electrolysis cell unit with at least one reactant, has already been proposed, wherein the at least one electrical heating element heats, in particular evaporates, the at least one reactant in at least one operating state.

[0007] Disclosure of the invention

[0008] The invention relates to a method for operating at least one electrical heating element of an electrolysis system, which comprises at least one electrolysis cell unit and at least one supply path for supplying the electrolysis cell unit with at least one reactant, wherein the at least one electrical heating element heats the at least one reactant in at least one operating state, in particular by evaporating it.

[0009] It is proposed that in at least one process step of the process, a performance parameter of the at least one electrical heating element is set using a combination of feedforward control and closed-loop control. The at least one electrolysis cell unit preferably comprises at least one electrolysis cell, and in particular a plurality of identical electrolysis cells, which are preferably connected electrically in series and fluidically in parallel for common operation. The electrolysis system can have several R.413539

[0010] - 2 -

[0011] The electrolysis cell units are connected in series or parallel with the at least one electrolysis cell unit, either fluidically and / or electrically. The at least one electrolysis cell is preferably a solid oxide electrolysis cell, or alternatively a polymer electrolyte electrolysis cell, a phosphoric acid electrolysis cell, a molten carbon electrolysis cell, or the like. The electrolysis system is designed, for example, to produce hydrogen and / or carbon monoxide from water and / or carbon dioxide as a reactant.

[0012] The at least one electrolysis cell preferably comprises at least one anode, at least one cathode, and at least one electrolyte arranged between them. The at least one supply path is preferably connected to the cathode. The anode can be connected in parallel to the cathode to the at least one supply path or to a further supply path of the electrolysis system that is fluidically separate from the supply path. Preferably, the electrolysis system includes a cathode-side preheater with an electric heating element in the supply path to heat the reactant before it enters the cathode. Preferably, the electrolysis system includes an anode-side preheater with a further electric heating element in the further supply path to heat a further reactant before it enters the anode.In a configuration with a common supply path to the anode and cathode, the cathode-side preheater and the anode-side preheater can be implemented by the same component upstream of a branch of the common supply path or by separate components downstream of the branch. The electrolysis system preferably comprises an evaporator with an additional electric heating element for vaporizing the reactant. The evaporator is preferably arranged upstream of the cathode-side preheater in the supply path. The electrolysis system preferably comprises at least one control unit for controlling the electric heating element in the cathode-side preheater, in the anode-side preheater, and / or in the evaporator. A "control unit" is understood to mean, in particular, a unit with at least one control electronics module. A "control electronics module" is understood to mean, in particular, a unit with ei-R.413539.

[0013] - 3 -

[0014] The control unit can be understood as comprising a processor unit, a memory unit, and an operating program stored in the memory unit. The control unit preferably includes the feedforward control and the closed-loop control system. Preferably, in at least one process step, the control unit adjusts the power parameter of the at least one electrical heating element.

[0015] The power parameter preferably describes or characterizes the heating power of the at least one electrical heating element. For example, an electrical power consumption, an electrical current flow, an electrical voltage drop through / across the electrical heating element, or the like is used as a power parameter. Particularly preferably, the control electronics control the at least one electrical heating element by means of pulse width modulation, especially by means of a solid-state relay, wherein a pulse width ratio of the pulse width modulation is preferably used as the power parameter.

[0016] The feedforward control and the closed-loop control system preferably perform temperature control of the reactant, which can preferably be activated or deactivated. The power parameter preferably acts as the manipulated variable for the temperature control. The temperature control is specifically designed to set an operating temperature of the reactant, particularly to a predetermined operating temperature of the electrolysis cell unit. Preferably, the feedforward control determines a feedforward value of the power parameter as a function of an input temperature of the reactant upstream of the electrical heating element and / or as a function of an output temperature of the reactant downstream of the electrical heating element. The input temperature and / or the output temperature is preferably detected by means of an input temperature sensor or an output temperature sensor of the electrolysis system.Preferably, the closed-loop control system adjusts the input signal based on a control deviation of the output temperature. Preferably, the closed-loop control system, particularly in an activated state of temperature control, transmits the adjusted input signal to the control electronics to set the heating power of the electric heating element. In a deactivated state of temperature control, the control unit preferably transmits an externally specified value of the power parameter to the control electronics to set the heating power of the electric heating element. R.413539.

[0017] - 4 -

[0018] The design according to the invention allows for a response time (t₉₀) to the intended operating temperature, which can be advantageously kept short. Furthermore, the risk of overheating of the electrical heating element can be advantageously minimized. An electrolysis system operated with this method can be started up particularly quickly and exhibits an advantageously low wear rate.

[0019] It is further proposed that in at least one process step, the adjustable range of the power parameter is limited as a function of a flow parameter of the at least one reactant. Preferably, the control unit specifies a maximum adjustable value of the power parameter as a function of the flow parameter. Preferably, the control unit increases the maximum adjustable value of the power parameter, particularly monotonically, with increasing flow parameter. The increase in the maximum adjustable value of the power parameter preferably occurs proportionally with the flow parameter, or alternatively in steps. For example, a volumetric flow rate, a mass flow rate, a substance flow rate of the reactant, or the like can be used as the flow parameter. The flow parameter is preferably detected by a flow sensor of the electrolysis system, particularly upstream of the electrical heating element.Preferably, the control unit sets the power parameter to zero as long as the flow parameter is below a predetermined minimum flow value. The minimum flow value is preferably greater than zero. Preferably, the control unit sets the power parameter to a permissible maximum heating value as long as the flow parameter is above a predetermined maximum flow value. The permissible maximum heating value is preferably less than a possible maximum value of the power parameter. The permissible maximum heating value is preferably a value at which continuous operation of the electric heating element is possible. The maximum flow value is preferably less than a maximum possible value of the flow parameter, which is, in particular, predetermined by a feed unit of the electrolysis system. The design according to the invention allows the electrical power input of the heating element to be advantageously and reliably matched to the heat output to the feedstock.R.413539.

[0020] - 5 -

[0021] It is further proposed that in at least one process step, the feedforward control calculates a feedforward value of the power parameter as a function of an enthalpy balance of the supply path. Preferably, the feedforward control calculates the feedforward value as the sum of at least the significant enthalpy inflows and outflows into / out of a partial volume that includes at least the electrical heating element. The significant inflows and outflows include, in particular, at least the enthalpy change associated with the movement of the reactant along the supply path, as well as the electrical energy input from the operation of the electrical heating element. In a more precise and advantageous development, waste heat can also be taken into account. In the simplest case, the partial volume comprises only the electrical heating element.Alternatively, the partial volume comprises the electric heating element and at least one heat exchanger, in particular a gas-liquid separator, of the electrolysis system, which is designed to preheat the at least one reactant. In this case, the essential inlets and outlets preferably also include an inlet and outlet for the enthalpy changes associated with the movement of a medium through a primary side of the heat exchanger, in particular the enthalpy change associated with the movement of a gaseous medium and a condensate. The inventive design allows the pre-control value to be advantageously determined precisely.

[0022] It is further proposed that in at least one step of the process, the closed-loop control system includes a proportional-integral controller with prioritization to adjust the performance parameter. The modified input value transmitted to the control electronics preferably comprises the input value plus a proportional component and an integral component. The total sum of the input value, proportional component, and integral component is preferably limited. A respective portion of the input value, the proportional component, and the integral component is preferably dynamically adjusted by the control unit, particularly depending on whether the temperature control is in a steady state, a transition state, and / or a change between a steady state and a transition state. Preferably, when adjusting the respective portions of the R.413539

[0023] - 6 -

[0024] The input value is prioritized over the proportional component. Preferably, the proportional component is prioritized over the integral component when adjusting the respective components. Similarly, a maximum rate of change of the power parameter is preferably divided and prioritized among the input value, a proportional element of the closed-loop control system, and an integral element of the closed-loop control system. The rate of change is preferably a time-dependent rate of change and can be specified, in particular, as a time derivative, a time difference quotient, or a time-averaged rate of change of the power parameter. The inventive design allows the response time to be advantageously kept short. Furthermore, the degree of overshoot and undershoot in dynamic phases of temperature control can be advantageously kept low.

[0025] It is further proposed that in at least one process step, the feedforward control calculates a feedforward value of the power parameter under the assumption that the reactant is at least substantially monophasic. "Monophasic" preferably means that the reactant, upon entering the evaporator, the cathode-side preheater, and / or the anode-side preheater, is in a single state of matter, for example, existing only as a liquid or only as a gas. "Substantially monophasic" fluid means that the fluid comprises a monophasic main phase, which comprises at least 90%, preferably at least 95%, and particularly at least 99% of the total volume of the fluid. Preferably, the feedforward control of the evaporator assumes that the reactant is essentially monophasic as a liquid.Preferably, the feedforward control of the cathode-side preheater and / or the feedforward control of the anode-side preheater assumes that the reactant is essentially monophasic as a gas. Preferably, in the case of an essentially monophasic reactant, the feedforward control calculates the enthalpy balance for the partial volume that comprises only the corresponding electrical heating element. Whether the feedforward control assumes that the reactant is essentially monophasic can be stored as a fixed value in the control unit and / or can be set by an operator and / or installer (R.413539).

[0026] - 7 -

[0027] The electrolysis system's pre-control value can be adjusted. Thanks to the inventive design, the pre-control value can be determined advantageously in a resource-efficient manner, particularly with advantageously few measured values ​​and calculation steps.

[0028] Furthermore, it is proposed that in at least one process step, an electrical heating element of a cathode-side inlet of the electrolysis cell unit and / or an electrical heating element of an anode-side inlet of the electrolysis cell unit is controlled by means of a combination of feedforward control and a closed-loop control system. Preferably, the control unit comprises a feedforward control and a closed-loop control system, as described above, which control the electrical heating element of the cathode-side preheater. Preferably, the control unit also comprises a feedforward control and a closed-loop control system, as described above, which control the electrical heating element of the anode-side preheater. The design according to the invention allows for advantageously precise adjustment of the operating temperature of the electrolysis cell unit.Furthermore, the operating temperature of the electrolysis cell unit can be reached advantageously quickly, especially without risk of overheating the respective electrical heating elements.

[0029] It is further proposed that in at least one process step, an electrical heating element, in particular the aforementioned one, of an evaporator of the electrolysis system, in particular the aforementioned one, is controlled by means of the combination of feedforward control and closed-loop control, as described in particular above. The design according to the invention allows the evaporator to be operated advantageously and efficiently, in particular without the risk of overheating.

[0030] It is further proposed that in at least one process step, the feedforward control calculates a feedforward value of the power parameter based on a specified phase ratio of the reactant. The phase ratio preferably defines, describes, or characterizes the ratio of the gaseous and liquid phases of the reactant upon entry into the evaporator. For example, a concentration or a relative volume can be used as the phase ratio. R.413539

[0031] - 8 -

[0032] A vapor pressure, a partial flow of the substance, or the like can be used. The control unit queries the phase ratio, for example, from an operator of the electrolysis system, from a higher-level control system of the electrolysis system, or from another source. Alternatively, the phase ratio is stored in a memory of the control unit during the manufacture, installation, and / or maintenance of the electrolysis system. The design according to the invention allows the power consumption of the electrical heating element to be advantageously and precisely adapted to a phase mixture of the reactant.

[0033] It is further proposed that in at least one process step, the feedforward control calculates a feedforward value of the power parameter as a function of a measurement of the phase ratio of the reactant. The measurement of the phase ratio is preferably indirect, particularly since operating conditions upstream of the electrical heating element are unfavorable for commercially available sensors. The feedforward control preferably uses the enthalpy balance of the partial volume, which includes the electrical heating element and the heat exchanger, in particular the gas-liquid separator, to calculate the feedforward value. The primary side of the heat exchanger is preferably connected to a cathode outlet of the electrolysis cell unit. The medium on the primary side of the heat exchanger is preferably a mixture of reactant residues and a product formed from the reactant in the electrolysis cell unit.Preferably, the feedforward control infers the phase ratio of the reactant from the composition of the primary-side medium, particularly based on particle number conservation and / or mass conservation. The composition of the primary-side medium can be measured directly, for example, using a humidity sensor of the electrolysis system, or indirectly, for example, using a temperature sensor and a pressure sensor of the electrolysis system. The inventive design allows the feedforward value to be advantageously calculated precisely as a function of the actual phase mixture of the reactant. In particular, it is advantageous to react quickly to fluctuations in the composition of the reactant. R.413539.

[0034] - 9 -

[0035] It is further proposed that in at least one process step, the measurement is carried out using at least two humidity sensors of the electrolysis system. If the heat exchanger is configured as a gas-liquid separator, the composition of the primary-side medium is measured upstream of an inlet and downstream of a gas outlet of the gas-liquid separator in order to determine the phase ratio of the reactant. Preferably, one humidity sensor is arranged upstream of the inlet and one downstream of the gas outlet. The design according to the invention advantageously allows the use of otherwise known quantities, in particular measured variables and / or manipulated variables, to solve the enthalpy balance. In particular, a preferably precise feedforward value can be calculated.

[0036] It is further proposed that in at least one process step, the measurement is carried out using at least one humidity sensor of the electrolysis system and at least one soft sensor. The humidity sensor is preferably arranged downstream of the gas outlet of the gas-liquid separator. Preferably, the feedforward control determines the composition of the medium upstream of the inlet of the gas-liquid separator as a function of a conversion rate of the electrolysis cell unit and, in particular, as a function of a proportion, especially a recirculation proportion, of the product upon entry of the reactant into the electrolysis cell unit. The conversion rate and / or the proportion of the product is preferably queried by the control unit from a higher-level control system of the electrolysis system, which sets an operating point for the electrolysis cell unit.The design according to the invention allows the phase ratio of the reactant to be measured advantageously and cost-effectively, in particular with only one humidity sensor.

[0037] It is further proposed that in at least one process step of the process, the feedforward control determines the phase ratio of the reactant based on a saturation vapor pressure curve. Preferably, the temperature and pressure of the primary-side medium downstream of the gas outlet are measured by a temperature sensor and a pressure sensor of the electrolysis system. Preferably, the feedforward control calculates the composition of the primary-side medium.

[0038] - 10 -

[0039] The phase ratio of the reactant is determined downstream of the outlet using the measured temperature, pressure, and saturation vapor pressure curve. The inventive design allows for a more cost-effective measurement of the reactant's phase ratio, particularly without the need for humidity sensors.

[0040] Furthermore, an electrolysis system is proposed comprising at least one electrolysis cell unit for the electrolysis of at least one reactant, at least one supply path for supplying the electrolysis cell unit with at least one reactant, at least one electrical heating element in the supply path for heating, in particular vaporizing, the at least one reactant, and at least one control unit for carrying out a process according to the invention. The inventive design allows for the provision of an electrolysis system that can be advantageously put into operation quickly and exhibits an advantageously low risk of wear.

[0041] Furthermore, it is proposed that the electrolysis system comprises at least one input temperature sensor upstream of the electric heating element and at least one output temperature sensor downstream of the electric heating element. The temperature sensors are preferably designed to determine an enthalpy change along the supply path. In an embodiment with a known phase ratio of the reactant, particularly an at least substantially monophasic reactant, the input temperature sensor is preferably arranged directly upstream of the electric heating element. When measuring the phase ratio of the reactant, the input temperature sensor is preferably arranged directly upstream of the heat exchanger, particularly the evaporator, in the supply path.The term "arranged immediately before / after a component" is understood to mean, in particular, without any other intervening components that would cause a temperature change and / or composition of the reactant during normal operation of the electrolysis system, before / after the component. Notwithstanding this, other sensors, safety shut-off valves, or the like may be arranged between the electrical heating element and the corresponding temperature sensor. The input temperature sensor R.413539 is a prime example.

[0042] - 11 -

[0043] The output temperature sensor is arranged between the electric heating element and the heat exchanger, in particular the evaporator, or between the heat exchanger, in particular the evaporator, and the reactant conveying unit. Preferably, the output temperature sensor is arranged between the electric heating element and the electrolysis cell unit, in particular between the evaporator and a discharge point of a recirculation line of the electrolysis system. The design according to the invention allows for advantageously reliable, fast, and low-wear control of the operation of the electric heating element.

[0044] The method and / or the electrolysis system according to the invention are not to be limited to the application and embodiment described above. In particular, the method and / or the electrolysis system according to the invention may, in order to achieve a functionality described herein, comprise a different number of individual elements, components, units, and process steps than that specified herein. Furthermore, values ​​within the specified limits of the value ranges stated in this disclosure shall also be considered disclosed and freely usable.

[0045] Drawings

[0046] Further advantages become apparent from the following description of the drawings. The drawings illustrate two main embodiments with a total of five variants of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0047] They show:

[0048] Fig. 1 shows a schematic fluid circuit diagram of an electrolysis system according to the invention.

[0049] Fig. 2 shows a schematic block diagram of a control unit of the electrolysis system according to the invention, R.413539

[0050] - 12 -

[0051] Fig. 3 shows a schematic saturation profile of a performance parameter manipulated by the control unit.

[0052] Fig. 4 shows a section of a schematic fluid circuit diagram of an alternative embodiment of the electrolysis system according to the invention and

[0053] Fig. 5 shows a schematic block diagram of a control unit of the electrolysis system according to the invention in the alternative configuration.

[0054] Description of the exemplary implementations

[0055] Figure 1 shows an electrolysis system 16a. The electrolysis system 16a comprises at least one electrolysis cell unit 18a for the electrolysis of at least one reactant. The electrolysis cell unit 18a preferably comprises a plurality of electrolysis cells, in particular solid oxide electrolysis cells. The electrolysis cell unit 18a is shown here functionally as a single electrolysis cell. The electrolysis cell unit 18a comprises at least one cathode 44a, at least one anode 46a, and an electrolyte arranged between them. The electrolysis cell unit 18a is designed for the electrochemical conversion of the at least one reactant into at least one product. An exemplary embodiment of the electrolysis system 16a for the electrolysis of water as reactant into hydrogen as product is shown here. The electrolysis system 16a comprises at least one supply path 20a for supplying the electrolysis cell unit 18a with the at least one reactant, in particular water.The electrolysis system 16a comprises at least one further supply path 22a for supplying the electrolysis cell unit 18a with a further reactant, here by way of example air. The supply path 20a is preferably connected to an inlet of the cathode 44a. The further supply path 22a is preferably connected to an inlet of the anode 46a. The electrolysis system 16a preferably comprises a cathode-side product removal path 48a, which is connected to an outlet of the cathode 44a, and an anode-side product removal path 50a, which is connected to an outlet of the anode 46a. R.413539.

[0056] - 13 -

[0057] The cathode-side supply path 22a comprises, for example, in particular in this order, a cathode-side reactant inlet, a cathode-side reactant conditioning unit 52a, a cathode-side reactant conveying unit 54a, in particular a pump, a heat exchanger designed as a gas-liquid separator 56a, an evaporator 42a, a heat exchanger designed as a cathode-side product recuperator 58a, and / or a cathode-side preheater 60a. The cathode-side product discharge path 48a comprises, for example, in particular in this order, a primary side of the cathode-side product recuperator 58a and / or a primary side of the gas-liquid separator 56a. A liquid outlet of the gas-liquid separator 56a is preferably connected to the cathode-side reactant preparation unit 52a.The cathode-side product discharge path 48a comprises, downstream of a gas outlet of the gas-liquid separator 56a, for example, and in particular in this order, a branch of a recirculation path 62a of the electrolysis system 16a, a product post-treatment unit 64a, a product storage unit 66a, and / or a cathode-side product outlet. The recirculation path 62a preferably opens downstream of the evaporator 42a and upstream of the cathode-side product recuperator 58a into the cathode-side supply path 20a. The recirculation path 62a comprises, for example, a recirculation pumping unit, in particular a blower or compressor, a shut-off valve, and a recirculation heat exchanger, the primary side of which is connected, by way of example, to the anode-side product discharge path 50a.

[0058] The anode-side supply path 22a comprises, for example, and in particular in this order, an anode-side reactant inlet, here in particular with an air filter, an anode-side reactant conveying unit 68a, in particular a blower or compressor, an anode-side product recuperator 70a and / or an anode-side preheater 72a. The anode-side product discharge path 50a comprises, for example, and in particular in this order, a primary side of the anode-side product recuperator 70a, a primary side of the recirculation heat exchanger and an anode-side product outlet.

[0059] The electrolysis system 16a includes at least one electric heating element 10a as part of the evaporator 42a in the supply path 20a for the evaporation of the R.413539

[0060] - 14 -

[0061] The electrolysis system 16a comprises at least one electric heating element 12a as part of the preheater 60a in the supply path 20a for heating the cathode-side reactant. The electrolysis system 16a comprises at least one electric heating element 14a as part of the anode-side preheater 72a in the anode-side supply path 22a for heating the anode-side reactant. The electrolysis system 16a comprises at least one control unit 36a for controlling the heating elements 10a, 12a, 14a, which is described in Figure 2. Preferably, the electrolysis system 16a comprises one control unit 36a for each heating element 10a, 12a, 14a, wherein the different control units 36a can be designed as independent components or integrated into one another.The electrolysis system 16a comprises, for each control unit 36a, an input temperature sensor upstream of the electrical heating element 10a, 12a, 14a assigned to the control unit 36a, and at least one output temperature sensor downstream of the corresponding electrical heating element 10a, 12a, 14a. The control units 36a assigned to the heating elements 10a, 12a, 14a are preferably identical in construction and function. Therefore, for the sake of simplicity, we will henceforth refer only to the heating element 10a, 12a, 14a, the control unit 36a, the reactant, the input temperature sensor, the output temperature sensor, etc.

[0062] Figure 2 shows a block diagram of the control unit 36a. The control unit 36a preferably comprises a feedforward control 24a and a closed-loop control system 26a. The control unit 36a is designed to implement a method for operating the electric heating element 10a, 12a, 14a. In at least one operating state, the at least one reactant is heated, in particular vaporized, by the electric heating element 10a, 12a, 14a. The control unit 36a is designed to control the heating power supplied to the reactant by means of the electric heating elements 10a, 12a, 14a using a power parameter L. The heating element 10a, 12a, 14a is preferably controlled by the control unit 36a using pulse width modulation, wherein the power parameter L is, for example, a pulse width ratio of the pulse width modulation. In particular, the power parameter L can assume values ​​between 0 and 100% of the maximum electrical power consumption of the heating element 10a, 12a, 14a.Alternatively, the performance parameter L is an absolute value. R.413539.

[0063] - 15 -

[0064] The power parameter L of the electric heating element 10a, 12a, 14a is set by a combination of the feedforward control 24a and the closed-loop control 26a. The feedforward control 24a preferably calculates a feedforward value 30a of the power parameter. The closed-loop control 26a comprises a proportional-integral controller with prioritization to set the power parameter L. The closed-loop control 26a preferably includes a proportional element 76a, which determines a proportional component 80a of the power parameter L, and an integral element 78a, which determines an integral component 82a of the power parameter L. Preferably, the control unit 36a forms a sum 84a from the input control value 30a, the proportional component 80a and the integral component 82a, which it transfers to an actuating element, in particular as an actuating variable or setpoint, of the heating element 10a, 12a, 14a.The closed-loop control 26a preferably has as its input signal a control deviation 88a resulting from an output temperature TEd.aus measured by the output temperature sensor element and a predefined setpoint 7'Ed,aus,soii for this temperature. Preferably, the integral element 78a has as a further input signal a maximum permissible limit 90a and a maximum permissible rate of change 92a for the integral element 78a, which is preferably defined by the proportional element 76a. Preferably, the proportional element 76a has as a further input signal a maximum permissible limit 90a' and a maximum permissible rate of change 92a' for the proportional part 80a, which is preferably defined by the feedforward control 24a. Preferably, the proportional element 76a outputs its limit 90a' and its maximum permissible rate of change 92a' minus the proportional component 80a, respectively.The corresponding rate of change is passed to the integral element 78a as a limit value 90a and a maximum permissible rate of change 92a. Preferably, the feedforward control has as an input signal a maximum permissible limit value 90a” and a maximum permissible rate of change 92a” for the feedforward value 30a. Preferably, the feedforward control 24a passes its limit value 90a” and its maximum permissible rate of change 92a” minus the feedforward value 30a or the corresponding rate of change as a limit value 90a' and maximum permissible rate of change 92a' to the proportional element 76a. The maximum permissible rate of change 92a” of the feedforward control is preferably stored in a memory of the control unit 36a or is queried by an operator of the electrolysis system 16a. The limit value 90a” of the feedforward control 24a is preferably set in a limit setting step 86a of the method inR.413539.

[0065] - 16 -

[0066] The dependence on a flow parameter S of the reactant, as well as, for example, a minimum flow value 98a and a maximum flow value 102a, is determined. The limit setting step 86a is explained in more detail in Figure 3.

[0067] The feedforward control 24a includes as a further input signal an input temperature T measured by the input sensor element. Ed,ein , the setpoint of the output temperature T Ed,aus,soll and a setpoint S sollof the flow parameter. Depending on the design of the electrolysis system 16a, the feedforward control unit 24a can additionally have a phase ratio XGas of the reactant as an input signal. The feedforward control unit 24a calculates the feedforward value 30a of the power parameter L as a function of an enthalpy balance of the supply path 20a, 22a in which the heating element 10a, 12a, 14a is arranged. The enthalpy balance is preferably considered to be a steady-state balance of a temporal enthalpy change in a partial volume that includes, in particular only, the electric heating element 10a, 12a, 14a. Preferably, the feedforward control unit determines the feedforward value 30a based on the following balance:

[0068] Ḣ Ed,ein + P Heiz − Ḣ Ed,aus = 0

[0069] where Ḣ Ed,ein the enthalpy inflow carried by the reactant at the inlet of the heating element 10a, 12a, 14a, Ḣ Ed,austhe enthalpy dissipation carried by the reactant at the outlet of heating element 10a, 12a, 14a and P Heiz The heating power of heating element 10a, 12a, 14a is given. If necessary, an additional term for heat losses Q can be added. ioss to be added. The enthalpy inflow Ḣ ein is preferably used with Ḣ Ed,ein = ṅ Ed · h Ed,p (T Heiz,ein ) is set. Here, n Ed of the flow parameter S expressed as mass flow and h Ed p A molar enthalpy of the reactant as a function of the inlet temperature, where the subscript p indicates the state of matter of the reactant. The enthalpy flow Ḣ aus is preferably used with Ḣ aus = ṅ Ed · h Ed,p (T Heiz,aus ) as a function of the initial temperature. The heating power can be expressed as P. Heiz = P el,max · L · η, where P el,maxthe maximum absorbable electrical power and η is an efficiency of the heating element 10a, 12a, 14a, which are stored as parameters in a memory of the control unit 36a.

[0070] In the simplest case, the feedforward control 24a calculates the feedforward value 30a of the power parameter L under the assumption that the input is at least in We-R.413539

[0071] - 17 -

[0072] The reactant is essentially monophasic. In particular, the reactant is substantially entirely gaseous (p=Gas) upon entering the preheater 60a, 72a. In particular, depending on the configuration of the electrolysis system 12a, the reactant can be at least substantially entirely liquid (p=Fl) upon entering the evaporator 42a. The feedforward control 24a preferably determines the feedforward value 30a of the power parameter L for an at least substantially monophasic reactant using the following calculation method:

[0073]

[0074] The flow parameter S is preferably recorded by a flow meter of the electrolysis system 16a or queried by the reactant conveying unit 54a, 68a. A dependence of the molar enthalpies h Ed aus , h Ed ein The input temperature or the output temperature is preferably stored in a memory of the control unit 36a, in particular as a regression function, alternatively as a table.

[0075] In an advantageous further development of the control unit 36a, the feedforward control 24a determines the feedforward value 30a of the power parameter L of the heating element 10a of the evaporator 42a preferably on the basis of the extended calculation rule:

[0076]

[0077] using the phase ratio x Gas, which here is explicitly used as the concentration of a gas phase of the reactant. Due to the extended calculation method, the feedforward control 24a can also be advantageously used in electrolysis systems 16a in which the reactant enters the evaporator 42a partly in liquid and partly in gaseous form. The phase ratio x Gas The control unit 36a queries, for example, a higher-level control unit of the electrolysis system 16a and / or an operator. The calculation rule can also be used by the feedforward controls 24a of the heating elements 12a, 14a of the preheaters 60a, 72a by adjusting the phase ratio x Gas = 0 is set. R.413539

[0078] - 18 -

[0079] Preferably, the control of the heating element 10a, 12a, 14a can be switched off. The above explanations apply in the case where a switching state 94a of the control is positive, i.e., the control is activated. In the case of a negative switching state 94a of the control, a signal input of the feedforward control 24a is preferably deviated from the setpoint T. Ed,aus,soll the initial temperature to the actual value T Ed,ausThe control deviation 88a is preferably set to zero in the negative switching state 94a. In the negative switching state 94a, an externally specified value 96a is preferably output as a power parameter L to the heating element 10a, 12a, 14a. The externally specified value can be, for example, a predefined standard value stored in the control unit or a user input. In the negative switching state 94a, the integral component 82a is preferably maintained at a difference between the externally specified value 96a and the feedforward value 30a. Upon switching to the positive switching state 94a, the integral component 82a is reinitialized with the result of the last executed determination of the integral component 82a, so that the proportional-integral controller has a continuous output signal.When switching to the positive switching state 94a, the control deviation 88a is no longer artificially held at zero, so the proportional element 76a operates normally. When switching to the positive switching state 94a, the feedforward control 24a outputs a continuous feedforward value 30a, since in the negative switching state 94a it is connected to the actual value of the output temperature T. Ed, aus will continue to operate.

[0080] Figure 3 shows a diagram on which the power parameter L is plotted against the flow parameter S. The diagram illustrates an example of the limit value 90a” as it is set in the limit setting step 86a as a function of a measured value of the flow parameter. Preferably, the control unit 36a sets the limit value 90a” to zero as long as the flow parameter S is below the predetermined minimum flow value 98a. The minimum flow value 98a is preferably greater than zero. Preferably, the control unit 36a sets the limit value 90a” to a permissible maximum heating value 100a as long as the flow parameter S is above the predetermined maximum flow value 102a. The permissible maximum heating value 100a is preferably less than a possible maximum value R.413539

[0081] - 19 -

[0082] of the performance parameter, in particular less than 100%. The maximum flow value 102a is preferably less than a maximum possible value 104a of the flow parameter S, which is in particular specified by the feed unit 54a, 68a.

[0083] Figures 4 and 5 show a further embodiment of the invention. The following descriptions and drawings are essentially limited to the differences between the embodiments, whereby with regard to identically designated components, in particular components with the same reference numerals, reference may also be made to the drawings and / or the description of the other embodiments, especially Figures 1 to 3. To distinguish the embodiments, the letter a is appended to the reference numerals of the embodiment in Figures 1 to 3. In the embodiments of Figures 4 to 5, the letter a is replaced by the letter b.

[0084] Figure 4 shows a section of an electrolysis system 16b, which is otherwise constructed identically to that shown in Figure 1. The electrolysis system 16b comprises a cathode-side supply path 20b with a heating element 10b arranged therein for transporting a reactant, in particular water, to an electrolysis cell unit of the electrolysis system 16b, which is designed to electrochemically convert the reactant into a product. The heating element 10b is preferably part of an evaporator 42b of the electrolysis system 16b. The electrolysis system 16b comprises a gas-liquid separator 56b, the secondary side of which is arranged upstream of the evaporator 42b in the supply path 20b. A primary side of the gas-liquid separator 56b is preferably connected to a cathode-side product discharge path 48b of the electrolysis system 16b.The section shown in Figure 4 is preferably the partial volume considered by a feedforward control 24b (see Figure 5) for the purpose of creating an enthalpy balance.

[0085] The electrolysis system 16b preferably comprises an input temperature sensor 38b for measuring an input temperature T Ed, ein of the reactant and a flow meter 114b for measuring a flow parameter S of the reactant, R.413539

[0086] - 20 -

[0087] which are arranged upstream of the gas-liquid separator 56b in the supply path 20b. The electrolysis system 16b preferably includes an output temperature sensor 40b for measuring an output temperature T. Ed, aus of the reactant, which is arranged downstream of the evaporator 42b in the supply path 20b. The electrolysis system 16b preferably includes a product inlet temperature sensor 106b for measuring a product inlet temperature T Pr, ein, which is arranged upstream of the gas-liquid separator 56b in the product discharge path 48b. The electrolysis system 16b preferably includes a product outlet temperature sensor 108b for measuring a product outlet temperature T Pr,aus , which is arranged at a gas outlet of the gas-liquid separator 56b and includes a condensate temperature sensor 110b for measuring a condensate temperature T K, which is arranged at a liquid outlet of the gas-liquid separator 56b. Furthermore, the electrolysis system 16b can include a humidity sensor 34b upstream of the gas-liquid separator 56b in the product discharge path 48b for measuring a residual reactant input molar fraction XRE of an unreacted reactant residue in the product, a humidity sensor 32b for measuring a residual reactant output molar fraction RE of an unreacted reactant residue downstream of the gas outlet of the gas-liquid separator 56b, and / or a pressure sensor 112b for measuring an outlet pressure p. aiiS downstream of the gas outlet of the gas-liquid separator 56b.

[0088] Figure 5 shows a control unit 36b of the electrolysis system 16b with a feedforward control unit 24b and a closed-loop control system 26b for operating the electric heating element 10b of the evaporator 42b by determining a power parameter L. The feedforward control unit 24b preferably determines an unknown phase ratio XGas of the reactant. In addition to the signal inputs shown in Figure 2, the feedforward control unit 24b includes a measured value of the product output temperature T as an additional signal input. Pr,aus , a measured value of the product inlet temperature T Pr, ein and a setpoint of a recirculation flow parameter S re,soll a portion of the product fed back via a recirculation path of the electrolysis system 16b (see Fig. 1). The feedforward control 24b includes an additional signal input 116b, which in particular replaces the signal input for directly setting the phase ratio XGas as shown in Figure 2. R.413539

[0089] - 21 -

[0090] Preferably, the input tax 24b determines the input tax value 30a based on the following balance sheet:

[0091]

[0092] where Ḣ Ed,ein The enthalpy inflow carried by the reactant at the secondary-side inlet of the gas-liquid separator 56b is H E d, from the enthalpy dissipation carried by the reactant at the outlet of the heating element 10b, P Heiz The heating power of heating element 10b is H Pr ,an enthalpy inflow carried by the product at the primary-side inlet of the gas-liquid separator 56b, H Pr ,out, gas of the enthalpy discharge at the gas outlet of the gas-liquid separator 56b and H Pr ,out, Fi is the enthalpy discharge at the liquid outlet of the gas-liquid separator 56b. If necessary, an additional term for heat losses Q can be added. ioss to be added.

[0093] The reactant-side enthalpy inflow H Ed,ein is preferably with H Ed.ein = Ed ■ hEd, Fi( Ed,ein) is set. Here, n Ed the flow parameter S expressed as mass flow and h Ed p A molar enthalpy of the liquid reactant as a function of the reactant's inlet temperature. The reactant-side enthalpy flow H Ed , a us is preferably with H Ed , aus = n Ed ■ h Ed,Gas (T Ed,aus ) set, where h EdiGas The molar enthalpy of the vaporized reactant is given by the formula Pmolar as a function of the initial reactant temperature. The heating power can be expressed as Pheat. Heiz = Pei, max • • T|, where P el,max The maximum absorbable electrical power and r| are the efficiency of the heating element 10b, which are stored as parameters in a memory of the control unit 36b. The product-side enthalpy inflow H Pr , is preferably set with H Pr,ein = ṅ Pr,ein · h Pr,ein (T Pr,ein ), where ṅ Pr,eina material flow of the product at the primary-side inlet of the gas-liquid separator 56b and h Pr ein The molar enthalpy of the product is a function of the product inlet temperature. The enthalpy loss on the product side is H. Pr , out, gas at the gas outlet is preferably supplied with H Pr , a us, Gas = n Pr , a us ■ h P r,aus( pr,aus)> where ṅ Pr,aus a mass flow of the product at the gas outlet and h Pr , from which the molar enthalpy of the product is a function of the product outlet temperature. The product-side enthalpy flow H Pr ,out, Fi at the liquid outlet is preferably set with H Pr,aus,Fl = ṅ K · h Ed,Fl (T K , where ṅ K a material flow of the condensate is and h Ed,Fl the molar enthalpy of the liquid reactant R.413539

[0094] - 22 -

[0095] as a function of the condensate temperature T K The condensate temperature TK is preferably measured by the condensate temperature sensor 110, alternatively by a measured value of the product outlet temperature T Pr aus approached.

[0096] The input control 24b particularly preferentially determines an input control value 30b of the power parameter L using the following calculation rule derived from the enthalpy balance:

[0097]

[0098] and where ṅ re,soll the setpoint of the recirculation flow parameter S re,soll expressed as a material flow.

[0099] If the electrolysis system 16b includes the humidity sensors 32b, 34b, measured values ​​from these are supplied to the feedforward control 24b via the additional signal input 116b and are used directly by the feedforward control 24b to evaluate the above calculation rule.

[0100] If the electrolysis system 16b includes the humidity sensor 32b downstream of the gas outlet, the measured value of this sensor is fed to the feedforward control unit 24b via the auxiliary signal input 116b and used directly by the feedforward control unit 24b to evaluate the above calculation formula. The feedforward control unit 24b preferably determines the residual reactant input molar fraction XRE using the following calculation formula:

[0101] x RE,ein = (1 − SU soll ) · (1 − xPr,EZEein,soll) Where SU so u is a setpoint for the reactant utilization or conversion rate of the electrolysis cell unit, and xPr,EZEein,sollein is a setpoint for the product concentration at a cathode input of the electrolysis cell unit. Preferably, the feedforward control 24b queries the reactant utilization and product concentration. R.413539

[0102] - 23 -

[0103] from a higher-level control system of the electrolysis system 16b via the additional signal input 116b.

[0104] If the electrolysis system 16b includes the pressure sensor 112b and, in particular, no humidity sensors, the feedforward control 24b determines the residual reactant output molar fraction x REiaus . based on a saturation vapor pressure curve p sat (T), in particular according to the calculation rule:

[0105]

[0106] The feedforward control 24b preferably determines the residual reactant input molar fraction XRE.ein as described in the last section.

Claims

R.413539 - 24 - Claims 1. A method for operating at least one electric heating element (10a, 12a, 14a; 10b) of an electrolysis system (16a; 16b), comprising at least one electrolysis cell unit (18a) and at least one supply path (20a, 22a; 20b) for supplying the electrolysis cell unit (18a) with at least one reactant, wherein the at least one electric heating element (10a, 12a, 14a; 10b) heats, in particular evaporates, the at least one reactant in at least one operating state, characterized in that in at least one process step a power parameter (L) of the at least one electric heating element (10a, 12a, 14a; 10b) is set with a combination of feedforward control (24a; 24b) and closed-loop control (26a; 26b).

2. Method according to claim 1, characterized in that an adjustment range (28a) of the power parameter (L) is limited as a function of a flow parameter (S) of the at least one reactant.

3. Method according to claim 1 or 2, characterized in that in at least one method step the pre-control (24a; 24b) calculates a pre-control value (30a; 30b) of the power parameter (L) as a function of an enthalpy balance of the supply path (20a, 22a; 20b).

4. A method according to any of the preceding claims, characterized in that the closed-loop control (26a; 26b) comprises a proportional integral controller with prioritization to adjust the performance parameter (L). R.413539 - 25 - 5. Method according to one of the preceding claims, characterized in that in at least one method step the feedforward control (24a) calculates a feedforward value (30a;30b) of the power parameter (L) under the assumption that the reactant is at least substantially monophasic.

6. Method according to one of the preceding claims, characterized in that in at least one method step an electrical heating element (12a) of a cathode-side inlet of the electrolysis cell unit (18a) and / or an electrical heating element (14a) of an anode-side inlet of the electrolysis cell unit (18a) is controlled by means of the combination of the feedforward control (24a) and the closed control loop (26a).

7. Method according to one of the preceding claims, characterized in that in at least one method step an electrical heating element (10a; 10b) of an evaporator (42a; 42b) of the electrolysis system (16a; 16b) is controlled by means of the combination of feedforward control (24a; 24b) and closed control loop (26a; 26b).

8. Method according to claim 7, characterized in that in at least one method step the feedforward control (24a) calculates a feedforward value (30a) of the power parameter (L) by specifying a phase ratio of the reactant.

9. Method according to one of claims 7 or 8, characterized in that in at least one method step the feedforward control (24b) calculates a feedforward value (30b) of the power parameter (L) as a function of a measurement of a phase ratio of the reactant.

10. The method of claim 9, characterized in that in at least one method step the measurement is carried out using at least two humidity sensors (32b, 34b) of the electrolysis system (16b). R.413539 - 26 - 11. Method according to claim 9 or 10, characterized in that in at least one method step the measurement is carried out using at least one moisture sensor (32b) of the electrolysis system (16b) and at least one soft sensor.

12. Method according to one of claims 9 to 11, characterized in that in at least one process step the feedforward control (24b) determines the phase ratio of the reactant on the basis of a saturation vapor pressure curve.

13. Electrolysis system (16a; 16b) comprising at least one electrolysis cell unit (18a) for the electrolysis of at least one reactant, comprising at least one supply path (20a, 22a; 20b) for supplying the electrolysis cell unit (18a) with at least one reactant, comprising at least one electrical heating element (10a, 12a, 14a; 10b) in the supply path (20a, 22a; 20b) for heating, in particular evaporating, the at least one reactant and comprising at least one control unit (36a; 36b) for carrying out a method according to one of the preceding claims.

14. Electrolysis system (16a; 16b) according to claim 13, characterized by at least one input temperature sensor (38b) upstream of the electric heating element (10a, 12a, 14a; 10b) and by at least one output temperature sensor (40b) downstream of the electric heating element (10a, 12a, 14a; 10b).

Images