thyssenkrupp Uhde Chlorine Engineers (Japan) Ltd. and the Tosoh Co., Ltd. have jointly developed a series bipolar ion-exchange membrane process electrolyzer - BiTAC - since 1990. Nanyo factory of Tosoh Co., Ltd. is the largest electrolysis plant in Japan, with annual caustic soda production capacity of more than 1.1 million tons per year, operating every generation of BiTAC family – “BiTAC®,” “n-BiTAC” and “nx-BiTAC.”
Through the joint development, significant performance improvements were achieved:
Improvements realized in n-BiATC from BiTAC®
1. Reduction in liquid and structural resistances
- Improvement in the zero gap system (adoption of cathode spring and fine cathode mesh)
- Increased number of anode conductor ribs (Increased by 1.5 times compared that of BiTAC®)
2. More stable operation at higher current density
- Adoption of down comer plate for improved uniformity in brine concentration and distribution
- Redesigning the top chamber structure for reduction in pressure fluctuations caused by the gas and liquid separation
With these improvements, n-BiTAC, compared to BiTAC®, has proven substantial enhancement in voltage (△ 150mV) and lower chances of mechanical damages in the ion exchange membranes. After confirming these advantages, Tosoh Nanyo factory commenced the commercial operation of the n-BiTAC in 2007.
Operating n-BiTAC at current density below 8kA/m2 for more than four years, Tosoh inspected the electrolyzer by dismantling the electrolyzer and confirmed minimal amount of pinholes, blisters and wrinkles in the membranes, furthermore, element gaskets showed remaining life of more than 80% and so it was confirmed that a longer operation was possible.
Tosoh now operates their n-BiTAC electrolyzers for more than 6 years in continuous operation at 8kA/m2 without membrane renewal, and since 2014, they have kept steady operation of nx-BiTAC (the 3rd generation of BiATC family), which has further improvements such as the enhanced uniformity of electrical distribution by the modification in anode and cathode mechanisms and even lower pressure fluctuation due to the modification in the design of top chamber.