Detecting thermite reactions in an electrolytic cell

Abstract

A method for detecting a thermite reaction in an electrolytic cell comprising an anode assembly of one or more metal-oxide-containing anodes is disclosed. Each anode assembly is powered by a current provided through a distinct anode rod for each anode assembly. The method comprises: measuring a voltage drop using a pair of voltage probes located on the anode rod, the voltage drop corresponding to a current flow in the anode assembly; processing the voltage drop by computing at least one of the voltage drop derivative, the voltage drop variance, and the derivative of the voltage drop variance; and detecting a thermite reaction based on the results of the signal processing, before mitigating and/or suppressing the thermite reaction by adjusting the operational parameters of the electrolytic cell. This method is particularly advantageous as it reduces the number of voltage drops necessary for detecting a thermite reaction by a factor of 10.

1 . A method for detecting a thermite reaction in an electrolytic cell comprising at least one anode assembly of one or more metal-oxide-containing anodes, at least one cathode, an electrolytic bath, and a current supply buss providing a current to the at least one anode assembly through a distinct anode rod for each anode assembly, the method comprising:
 measuring a voltage drop using at least one pair of voltage probes located on the anode rod of each anode assembly, the voltage drop corresponding to a current flow in each anode assembly;   computing from the measured voltage drop at least one of:
 a voltage drop derivative, 
 a voltage drop variance across the one or more anode assemblies; and 
 a derivative of the voltage drop variance across the one or more anode assemblies, 
 wherein the at least one of the voltage drop derivative, the voltage drop variance and the derivative of the voltage drop variance are computed when the electrolytic cell comprises a plurality of anode assemblies; and 
   detecting the thermite reaction upon occurrence of one or more of:
 a voltage drop exceeding at least one voltage threshold level, wherein each voltage threshold level is a predetermined voltage drop previously associated with a thermite reaction; 
 a variation in the voltage drop derivative; 
 a variation in the variance of the voltage drop across the anode assemblies; and 
 a variation in the derivative of the voltage drop variance across the 
   
     
     
         2 . The method of  claim 1 , further comprising, upon detection of the thermite reaction, adjusting at least one operational parameter of the electrolytic cell to mitigate and/or suppress the thermite reaction. 
     
     
         3 . The method of  claim 1 , further comprising sending a signal to an operator of the electrolytic cell upon detection of the thermite reaction. 
     
     
         4 . The method of  claim 1 , wherein the threshold voltage levels are based on past operational data of the electrolytic cell. 
     
     
         5 . The method of  claim 1 , wherein the threshold voltage levels are computer derived threshold levels derived from at least one of past operational data of the electrolytic cell, operation parameters, and composition of the electrolytic cell. 
     
     
         6 . The method of  claim 1 , wherein the thermite reaction is detected when:
 the variation in voltage drop exceeds a threshold variation;   the variation in voltage drop derivative exceeds the threshold variation;   the variation in variance of the voltage drop across the anode assemblies exceeds the threshold variation; and/or   the variation in derivative of the voltage drop across the anode assemblies exceeds the threshold variation.   
     
     
         7 . The method of  claim 1 , wherein adjusting at least one operational parameter of the electrolytic cell to mitigate and/or suppress the thermite reaction comprises one or more of:
 changing an anode to cathode overlap (ACO) of one or more anode assemblies;   removing one or more anode assemblies from the electrolytic bath;   changing the current supplied to at least one of the one or more anode assemblies or the electrolytic cell;   changing a temperature of the electrolytic bath; and   changing a chemistry of the electrolytic bath.   
     
     
         8 . The method of  claim 1 , wherein, when the voltage drop of one of the anode assemblies exceeds the at least one voltage threshold level, adjusting at least one operational parameter of the electrolytic cell takes into account one or more of the exceeded voltage threshold levels. 
     
     
         9 . The method of  claim 1 , wherein, upon detection of the thermite reaction, adjusting at least one operational parameter of the electrolytic cell takes into account:
 a magnitude of the voltage drop;   a magnitude of the voltage drop derivative;   a magnitude of the variance of the voltage drop; and/or   a magnitude of the derivative of the voltage drop variance.   
     
     
         10 . The method of  claim 1 , further comprising:
 filtering the voltage drop, the voltage drop derivative, the variance of the voltage drop, and/or the derivative of the voltage drop variance.   
     
     
         11 . A system for detecting a thermite reaction in an electrolytic cell comprising at least one anode assembly of one or more metal-oxide-containing anodes, at least one cathode, an electrolytic bath, and a current supply buss providing a current to the at least one anode assembly through a distinct anode rod for each of the at least one anode assembly, the system comprising:
 a measurement module comprising, for each of the at least one anode assembly, a pair of voltage probes located on the anode rod of the anode assembly for measuring a voltage drop, the voltage drop corresponding to a current flow in the anode assembly; and   a processor module configured to:
 compute from the measured voltage drop at least one of:
 a voltage drop derivative; 
 a voltage drop variance across the one or more anode assemblies; and 
 a derivative of the voltage drop variance across the one or more anode assemblies; 
 wherein the at least one of the voltage drop derivative, the voltage drop variance and the derivative of the voltage drop variance are computed when the electrolytic cell comprises a plurality of anode assemblies; and 
 
 detecting the thermite reaction upon occurrence of one or more of:
 a voltage drop exceeding at least one voltage threshold level, wherein each voltage threshold level is a predetermined voltage drop previously associated with a thermite reaction; 
 a variation in voltage drop derivative; 
 a variation in variance of the voltage drop across the anode assemblies; and 
 a variation in derivative of the voltage drop variance across the anode assemblies. 
 
   
     
     
         12 . The system of  claim 11 , further comprising a network interface module operatively connected to the processor module for sending a signal to an operator of the electrolytic cell upon detection of the thermite reaction. 
     
     
         13 . The system of  claim 11 , wherein the threshold voltage levels are based on past operational data of the electrolytic cell. 
     
     
         14 . The system of  claim 11 , wherein the threshold voltage levels are computer derived threshold levels derived from at least one of past operational data of the electrolytic cell, operation parameters, and composition of the electrolytic cell. 
     
     
         15 . The system of  claim 11 , wherein the processor module is configured to detect the thermite reaction when the variation in voltage drop derivative exceeds a threshold variation. 
     
     
         16 . The system of  claim 11 , wherein the processor module is configured to detect the thermite reaction when:
 the variation in voltage drop exceeds a threshold variation;   the variation in voltage drop derivative exceeds the threshold variation;   the variation in variance of the voltage drop across the anode assemblies exceeds the threshold variation; and/or   the variation in derivative of the voltage drop variance across the anode assemblies exceeds the threshold variation.   
     
     
         17 . The system of  claim 11 , further comprising a control module operatively connected to the processor module configured to adjust at least one operational parameter of the electrolytic cell to mitigate and/or suppress the thermite reaction by:
 changing an anode to cathode overlap (ACO) of one or more anode assemblies;   removing one or more anode assemblies from the electrolytic bath;   changing the current supplied to at least one of the one or more anode assemblies or the electrolytic cell;   changing a temperature of the electrolytic bath; and/or   changing a chemistry of the electrolytic bath.   
     
     
         18 . The system of  claim 11 , wherein, when the voltage drop of one of the anode assemblies exceeds the at least one voltage threshold level, the processor module is configured to adjust at least one operational parameter of the electrolytic cell by taking into account one or more of the exceeded voltage threshold levels. 
     
     
         19 . The system of  claim 11 , wherein, upon detection of the thermite reaction, the processor module is configured to adjust at least one operational parameter of the electrolytic cell taking into account:
 a magnitude of the voltage drop;   a magnitude of the voltage drop derivative;   a magnitude of the variance of the voltage drop; and/or   a magnitude of the derivative of the voltage drop variance.   
     
     
         20 . The system of  claim 11 , wherein the processor module is further configured to filter the voltage drop, the voltage drop derivative, the variance of the voltage drop, and/or the derivative of the voltage drop variance. 
     
     
         21 . An electrolytic cell comprising at least one anode assembly of one or more metal-oxide-containing anodes, at least one cathode, an electrolytic bath, and a current supply buss providing a current to the at least one anode assembly through a distinct anode rod for each anode assembly, and the system for detecting a thermite reaction as claimed in  claim 11 .