BiTAC® is a bi-polar type ion exchange membrane electrolyzer jointly developed with Tosoh. It takes advantage of a mono-polar type ion exchange membrane electrolyzer of Chlorine Engineers (CME) and bi-polar type ion exchange membrane electrolyzer of Tosoh (TMB). It is a high performance electrolyzer that breaks through industrial common sense and has attracted attention as a safe and low cost electrolyzer used inside and outside of the industry. The development was started in 1991. When test operation of a pilot electrolyzer succeeded in 1992, the first commercial plant was operated in Korea in 1994. Since then, we received orders from more than 25 plants in 10 countries and our market share including the electrolyzer technology relegated from Asahi Glass is 40%. It looks like a conventional bi-polar type ion exchange membrane electrolyzer but there are many innovations in the internal structure. For BiTAC®, pressed titan pans for the diaphragm of the anode and cathode are connected by using special welding technology and other innovations are applied to realize a low cost and high performance electrolyzer (Figure 7).
Electric current flows from the cathode to anode through the diaphragm inside on element. This electric resistance of the element is also called box resistance and it is one of the reasons for power loss. For the bi-polar type ion exchange membrane electrolyzer, an anode chamber made of titan has six-time larger resistance than a cathode chamber made of nickel. If you narrow the distance between the anode chamber made of titan and diaphragm too much in order to shorten the electric current route, the chlorine gas stays in the anode chamber, and gas resistance and electrolysis pressure increase and therefore power consumption increases. For BiTAC®, the electric current route through titan is shortened by making the diaphragm a wave shape and keeping enough capacity to exhaust chlorine gas, as shown in Figure 1.
Because of this structure, it can be operated with a much lower power unit than a conventional electrolyzer (Figure 8).
The common sense of operation current density (kA/m2) of 3-4 kA/m2 in the industry has become obsolete and high electric density operation with a rated operation electric current density of 5kA/m2 (more than 6kA/m2) becomes possible. The production per reaction area increases by applying more electric current to the same electrolyte reaction area. You can reduce the initial investment to build a smaller electrolysis plant.Tosoh, our joint developer, is running a rated operation at 6.5kA/m2 (Figure 9).
For the ion exchange membrane method salt electrolyzer, it is important that the temperature and density of the electrolyte in the anode/cathode chamber of the element are evenly distributed to maintain high performance for a long period. For BiTAC®, the grooves and projections of the wave shape diaphragm are arranged alternately. Electrolyte supplied from the bottom of the electrolyzer is repeatedly mixed and separated at the edge of the grooves and projects and evenly distributes it on the electrolysis surface (Figure 10).
The system proved with our monopolar type electrolyzer CME is also used for BiTAC®. It is innovative that the electrolyte is smoothly converted to gas-liquid and separated, then exhausted in the nozzle (Figure 11).
Electric current discharged from an anode goes through the electrolyte (Brine solution) in the anode chamber, ion exchange membrane, and electrolyte (caustic) in the cathode chamber, and then flows into the cathode chamber. Although IR loss occurs because of electric resistance of the electrolyte in the anode and cathode chambers, BiTAC® has the spring effect for the cathode mesh. The reaction takes place on the surface of the cathode pan so that the distance between the anode and cathode is close to the size of ion exchange membrane. As a result, the electric resistance is successfully reduced with electrolytes.
The system proved with our monopolar type electrolyzer CME is also used for BiTAC®. It is also innovative that a teflon tube is set longer than CME to make observation easier and the leakage of electric current from electrolyte is reduced (Figures 12 and 13).
As materials for the element, titan is used for the anode and nickel is used for the cathode, and as a result, longer life cycle than with conventional electrolyzers is realized.