Method and system for monitoring the functionality of electrolysis cells

Abstract

Method and system for monitoring the functionality of electrolysis cells for use in chlor-alkali electrolysis. The method uses the analysis of the current/voltage characteristic of the cells in relation to an AC voltage overlaid on the operating voltage

1 . Method for monitoring the functionality of multiple electrolysis cells of a membrane electrolysis facility, which multiple electrolysis cells are operated simultaneously in production, wherein the current/voltage curve of an AC voltage overlaid on the electrolysis voltage is measured and compared to the predefined characteristic values of a functional electrolysis cell and the comparison value is detected. 
     
     
         2 . Method according to  claim 1 , wherein the electrolysis cells are provided in an electrolyzer having bipolar interconnection of the electrolysis cells. 
     
     
         3 . Method according to  claim 1 , wherein the harmonic wave AC voltage of the rectifier is used as the AC voltage for the generation of the electrolysis voltage. 
     
     
         4 . Method according to  claim 3 , wherein the possible interfering components in the AC voltage signal and/or alternating current signal are filtered out before or after the detection of the signal. 
     
     
         5 . Method according to  claim 1 , wherein the alternating current/AC voltage components are measured at a sampling rate of at least 10 kHz. 
     
     
         6 . Method according to  claim 1 , wherein the measurement of the alternating current component at the current supply to the electrolysis cell is performed inductively, with use of a Rogowski coil. 
     
     
         7 . Method according to  claim 1 , wherein the slope in a derived current density-voltage characteristic curve is used as a characteristic value for the functionality of the individual electrolysis cells to identify electrical contact faults and/or membrane damage. 
     
     
         8 . Method according to  claim 1 , wherein the extrapolated axis section of the characteristic curve for the current density zero in a derived current density-voltage characteristic curve is used as a characteristic value for the functionality of the individual electrolysis cells to identify leaks in the ion exchange membrane in membrane electrolyzers or to identify electrode flaws. 
     
     
         9 . Method according to  claim 1 , wherein the changes of the hysteresis of the characteristic curve are used as a characteristic value for the functionality of the individual electrolysis cells in a derived current density-voltage characteristic curve. 
     
     
         10 . Method according to  claim 1 , wherein the method is combined with the monitoring of the single cell voltage of the electrolysis cells. 
     
     
         11 . Method according to  claim 1 , wherein, if a predefined number of electrolysis cells which are impaired in their functionality is exceeded based on the measured value detection, a warning signal is generated, which is used for informing the operating personnel or for automatically taking the individual electrolysis cells or the entire electrolyzer out of operation. 
     
     
         12 . Method according to  claim 1 , wherein the method is operated in an electrolysis facility for electrolysis of alkali chloride solutions or hydrochloric acid. 
     
     
         13 . System for monitoring the functionality of electrolysis cells of an electrolysis facility having multiple electrolysis cells, comprising a voltage generator ( 1 ) for generating an AC voltage overlaid on the electrolysis DC voltage, a voltage measuring unit ( 5 ) connected to measure the DC voltage component and the AC voltage component over the individual electrolysis cells ( 4 ), at least one current measuring unit ( 6 ,  7 ) for measuring the direct current component and the alternating current component of the electrical current, which flows to the electrolysis cells, and a data processing unit ( 8 ), which records the measured values of the DC voltage components, the AC voltage components, the direct current, and the alternating current component, generates a current/voltage curve and compares the current/voltage curve of the individual electrolysis cells to the predefined characteristic values of a functional electrolysis cell. 
     
     
         14 . System according to  claim 13 , having current and voltage measuring units for electrolysis cells in an electrolyzer having bipolar interconnection of the electrolysis cells. 
     
     
         15 . System according to  claim 14 , wherein the AC voltage generator is formed by a rectifier for generating the electrolysis voltage from AC voltage, which has a harmonic wave AC voltage in operation. 
     
     
         16 . System according to  claim 13 , comprising electronic filters for possible interfering components in the AC voltage signal upstream of the detection unit of the data processing unit. 
     
     
         17 . System according to  claim 13 , wherein the unit for measuring the alternating current component is an inductive alternating current measuring unit and comprises a Rogowski coil as a measured value sensor. 
     
     
         18 . System according to  claim 13 , wherein the data processing unit has an output unit having signal generator. 
     
     
         19 . System according to  claim 18 , wherein the signal generator is electrically connected to an optical and/or acoustic warning device and/or to the facility controller for the operation of the individual electrolysis cells, or selected cell stacks, or the entire electrolyzer. 
     
     
         20 . System according to  claim 13 , wherein the electrolysis facility is a facility for the electrolysis of alkali chloride solutions or hydrochloric acid.