NaClO Generator System

Description of electrolysis system
The NaClO Generator System consists of electrolyzers, a catholyte circulation system, an anolyte circulation system, associated piping and instrumentation, and a D. C. Power supply.

1. Features of electrolyzer
1) With a production capacity of 50~3, 000 kg/d-Cl2
2) Using ionic membrane
3) Low Power Consumption
4) High Current Density Operation, can be operated safely at 6 kA/m2 of current density
5) Concentration of sodium hypochlorite can up to 12%
6) Durable Materials of Construction
By adopting a titanium for its anode and Ni for its cathode.
7) The design is optimized for on-site sodium hypochlorite generation unit
8) It is simple to control, operation and maintenance.

2. Principles

1) A modern bipolar type electrolyzer is made up of an alternating series of anode and cathode elements with a cation selective semi-permeable membrane between each anode and cathode. The membrane selectively permits the passage of sodium ions from the anode compartment to the cathode compartment where, in combination with hydroxyl ions, sodium hydroxide is formed. The membrane inhibits the diffusion of negative chloride ions from the anode compartment into the product sodium hydroxide, as well as preventing the migration of negative hydroxyl ions from the cathode compartment to the anode compartment.

2) Anolyte Circulation System
Super-purified brine, whose residual hardness has been removed by chelate ion exchange resin, is pumped to the electrolyzers. Depleted brine, containing free chlorine (HClO + dissolved Cl2), flows from the electrolyzers to the anolyte tank. Hydrochloric acid can be added to the depleted brine to recover the chlorine gas by reaction: HClO + HCl -> Cl2 + H2O. The depleted brine is then pumped on level control to the brine dechlorinator for further chlorine removal. The chlorine gas generated at the anolyte tank is piped back to the chlorine main header piping from the electrolyzers, and is transferred to the chlorine handling area.

The depleted brine from the anolyte receiver is pumped to the dechlorination section by level controller. Some of depleted brine in the anolyte receiver is recycled to the electrolyzers by mixing with the fresh super-purified brine.

3) Catholyte System
The catholyte circulation system consists of the catholyte tank, catholyte pump and catholyte heat exchanger. The circulated sodium hydroxide from the tank is cooled or heated in the catholyte heat exchanger and then fed to the catholyte. In circulated sodium hydroxide system, demineralized water is added to the circulating sodium hydroxide to maintain the product strength.