What should the redox potential of the filtered brine discharged each time be controlled at?
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For the chelating resin used in the secondary brine treatment for ion-exchange membrane caustic soda production, it is required that there be no free chlorine in the filtered brine. Generally, online measurement of the redox potential is employed to control the amount of sodium sulfite added, thereby eliminating the sodium hypochlorite introduced during the primary brine purification process. So, what should the redox potential of the filtered, purified brine exiting the primary treatment stage be set at, in order to ensure that no free chlorine remains in the brine?
-50 MV; generally, analysis should be relied upon, as instruments sometimes have errors
Plus or minus 50 millivolts: A positive value that’s too high indicates excessive oxidativity and the presence of free chlorine; a negative value that’s too low indicates excessive reductivity and an over-addition of sodium sulfite
This brine process helps to control any excess sodium sulfite; generally, the value is negative. At our E-153 point, the online reading is -150 mV; sometimes it rises to around -70 mV. However, there’s no issue with free chlorine levels, as they remain at 0
We rely on laboratory analysis; we haven’t installed any online ORP detection systems. Laboratory tests remain the primary method of testing