Technical Information

Basic Chemistry

Liquid Chlorine New Zealand’s range of onsite sodium hypochlorite generators, Hypogen® can produce up to 48kg per day of chlorine and are designed as an alternative to chlorine gas or commercial sodium hypochlorite.

The Hypogen® system is made up of the following components:

The Process

  • Salt (NaCl) is dissolved in a tank to form a concentrated (32%) brine solution.
  • The brine solution is reduced in concentration with softened water.
  • The diluted brine solution is pumped through the electrolytic cell. The cell consists of numerous titanium plates packed into an equal number of plates acting as anodes and cathodes.
  • DC power is applied to the cell. Chemically, chlorine is evolved at the anode surface, while hydrogen is evolved at the cathode surface. The secondary reaction of chlorine, sodium and the hydroxyl ion results in sodium hypochlorite up to 2.4% solution.
  • The sodium hypochlorite solution then flows into a bulk chlorine storage tank.
  • A metering pump then delivers the disinfectant (chlorine) to the required ejection point.
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Advanced Chemistry

In additional to the basic chemistry to produce salt generated chlorine, as shown above, the follow goes into greater detail explaining the chemical reactions involved.

With electrolysis, chlorine is produced directly from a solution of common salt using electricity, without creating any notable by-products. The following reactions take place in the electrolytic cell:
2NaCl + 2H2O → 2NaOH + Cl2 + H2

The chlorine produced reacts immediately with the caustic soda solution also formed, resulting in a sodium hypochlorite solution:
Cl2 + 2NaOH ↔ NaCl + NaClO + H2O

When the Hypogen S model is used (non-membrane cell), the solution generated has a pH value between 8.5 and 9.5, and an equivalent chlorine concentration of 10g/l. It has a very long half-life which makes it ideal for storage in a buffer tank.

After dosing the solution into the water flow, no pH value correction or very little is necessary, as is often required in membrane electrolysis. The sodium hypochlorite solution reacts in a balance reaction, resulting in hypochlorous acid, the efficient disinfectant:
NaClO + H2O ↔ NaOH + HClO