Discharge device for electrolyzer and electrolyzer

Abstract

Discharge device for an electrolysis plant (2), comprising a control unit (1), two contact elements (DC+, DC-), wherein one contact element is provided for connection to a DC pole of the electrolysis system (2) and the other contact element is provided for connection to the other DC pole of the electrolysis system (2), wherein a discharge resistor (R1), a switch (S1) which can be controlled by the control unit (1) and a voltage measuring unit (V) which is set up for measuring the voltage between one and the other DC pole of the electrolysis system (2) are arranged between the two contact elements, wherein the control unit (1) is configured to close the switch (S1) in response to a discharge signal as long as the voltage measured by the voltage measuring unit (V) is greater than a first threshold, and to open the switch (S1) when the measured voltage is less than the first threshold.

Description

[0001] The invention relates to a discharge device for an electrolyzer and an electrolyzer with such a discharge device. Problem

[0002] If an electrolyzer is shut down during operation (safety shutdown, shutdown for maintenance and repair, or stopping hydrogen production), the DC voltage between the electrolyzer's poles drops very quickly to the electrolyzer's open-circuit voltage. This can range between 300V and 1000V, depending on the electrolyzer type and manufacturer.

[0003] When the electrolyzer's open-circuit voltage is established, the highly capacitive nature of the electrolyzer takes effect. This capacitive behavior ensures that the voltage decays very slowly. Values ​​measured in the field are approximately 1V / min. This means that after the electrolyzer is shut down, maintenance work can often not be carried out until the next day.

[0004] State-of-the-art solutions accelerate the discharge of the residual voltage in the electrolyzer by creating an island network using the residual voltage at the electrolyzer's poles. In this case, the discharge of the residual voltage occurs via losses through a converter that creates an island network. However, this process can only be carried out up to a certain voltage, for example, 50 V. Once 50 V is reached, the discharge process is stopped.

[0005] Subsequently, the capacitive effect of the electrolyzer again leads to an increase in the residual voltage, although this time the discharge via an island network and the losses of the corresponding converter do not work.

[0006] The task is therefore to reduce an electrolyzer safely and time-efficiently to a residual voltage at which safe maintenance is possible.

[0007] This object is achieved by the unloading device according to the main claim. Aspects and further developments of the invention are the subject of the subclaims and the secondary claim, respectively.

[0008] The discharge device according to the main claim comprises a control unit and two contact elements, one contact element being provided for connection to a direct current pole of an electrolysis system, and the other contact element being provided for connection to the other direct current pole of an electrolysis system. Furthermore, a discharge resistor, a switch that can be controlled by the control unit, and a voltage measuring unit configured to measure the voltage between one and the other direct current pole of an electrolysis system are arranged between the two contact elements. The control unit is configured to close the switch in response to a discharge signal as long as the voltage measured by the voltage measuring unit is greater than a first threshold value, and to open the switch when the measured voltage is less than the first threshold value.

[0009] The discharge device according to the invention can ensure that the residual voltage of the electrolyzer is low. For this purpose, the first threshold can be set to a non-harmful voltage, such as 30V. If the control unit detects a residual voltage greater than the first threshold, and if the discharge of the electrolyzer is initiated by a discharge signal, the control unit controls the switch to close it. The poles of the electrolyzer are now connected via a resistor and are discharged. If the voltage drops below the first threshold, the switch is opened again. In this way, the residual voltage present in the electrolyzer can be safely reduced below a threshold.

[0010] According to one embodiment of the discharge device, the control device is further configured to close the switch again when, after a predetermined time has elapsed after the first threshold value has been undershot, the measured voltage exceeds a second threshold value which is higher than the first threshold value.

[0011] As already described, due to the capacitive properties of the electrolyzer, the residual voltage of the electrolyzer may increase again after discharging below a first threshold. For this reason, a second threshold is defined in this embodiment. This second threshold is higher than the first threshold and is sufficiently large that the voltage at the second threshold is harmless.

[0012] If the residual voltage rises again to a value that is potentially harmful to a maintenance worker, the discharge process is started again by closing the switch.

[0013] According to one embodiment of the discharge device, the control device is further configured to close the switch again when, after falling below the first threshold value, a third threshold value which is lower than the first threshold value is exceeded.

[0014] In this embodiment, a third threshold is defined that is lower than the first threshold. To increase the safety of the discharge, a third threshold can be defined to which the residual voltage is reduced before the discharge process is completed and electrolyzer maintenance can begin.

[0015] According to one embodiment of the discharge device, the control device is further configured to open the switch again when the measured voltage falls below the third threshold value.

[0016] In this embodiment, the end of the temporary discharge is defined such that the switch is opened when the measured voltage falls below the third threshold.

[0017] Electrolysis plant with a discharge device configured as described in the above embodiments.

[0018] The electrolysis plant with such a discharge device can be safely discharged and maintained because the existing residual voltage is sustainably reduced to a low level by the discharge device.

[0019] In the following, the invention is illustrated by means of the figures, where Fig. 1 shows an electrolysis plant with a discharge device according to the invention.

[0020] The figures are explained in detail below.

[0021] In Fig.Figure 1 shows an electrolyzer 2 with a discharge device according to the invention. The discharge device comprises a control unit 1, a voltage measuring unit V, a discharge resistor R1, and a switch S1. List of reference symbols 1 control unit 2 electrolyzer V voltage measurement unit S1 switch R1 discharge resistor DC+, DC- contact elements

Claims

[1] Discharge device for an electrolysis plant (2), comprising a control unit (1), two contact elements (DC+, DC-), one contact element being provided for connection to a direct current pole of the electrolysis system (2) and the other contact element being provided for connection to the other direct current pole of the electrolysis system (2), wherein a discharge resistor (R1), a switch (S1) which can be controlled by the control unit (1), and a voltage measuring unit (V) which is designed to measure the voltage between one and the other direct current pole of the electrolysis system (2) are arranged between the two contact elements, wherein the control unit (1) is configured to close the switch (S1) in response to a discharge signal as long as the voltage measured by the voltage measuring unit (V) is greater than a first threshold value, and to open the switch (S1) when the measured voltage is less than the first threshold value. [2] Discharge device for an electrolysis plant according to claim 1, wherein the control device (1) is further configured to close the switch (S1) again when, after a predetermined time has elapsed after the first threshold value has been undershot, the measured voltage exceeds a second threshold value which is higher than the first threshold value. [3] Discharge device for an electrolysis plant according to claim 2, wherein the control device (1) is further configured to close the switch (S1) again when, after falling below the first threshold value, a third threshold value which is lower than the first threshold value is exceeded. [4] Discharge device for an electrolysis plant according to claim 3, wherein the control device (1) is further configured to open the switch (S1) again when the measured voltage falls below the third threshold value. [5] Electrolysis plant with a discharge device arranged as described in claims 1 to 4.

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