GRUNDFOS allDOS Selcoperm

The Selcoperm electrolysis principle

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:

2 Nacl + 2 H2o g 2 NaoH + cl

2 + H

2

The chlorine produced reacts immediately with the caustic soda solution also formed, resulting in a hypochlorite solution:

cl2 + 2 NaoH D Nacl + Naclo + H

2o

The solution generated has a pH value between 8 and 8.5, and a maximum equivalent chlorine concentration of less than 8 g/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 correc-tion is necessary, as it is often required in electrolysis according to the membrane principle. The sodium hypochlorite solution reacts in a balance reaction, resulting in hypochlorous acid, the efficient disinfectant:

Naclo + H2o D NaoH + Hclo

The dosing quantity depends on the application as well as the local regulations. In general, the concentration after the injection unit is 0.3 to 2 ppm chlorine equivalent.

The benefits of the electrolytic chlorination method• Common salt is the base material – it is nontoxic and easy to

store.

• Only water, common salt and electricity is needed for the elec-trolysis – low operating costs, world-wide use.

• Fresh hypochlorite is always on hand – the disinfectant solution does not dissociate like commercial hypochlorite solutions. Lower formation of chlorate as a by-product.

• Approved disinfection method complying with the DWI drinking water regulations – an alternative with less safety requirements to chlorine-gas-based systems.

• Robust and elementary components – low-maintenance and a long service life, compared with the membrane cell electrolysis

The applications

Typical disinfection applications for Selcoperm systems are above all the• drinking water treatment and

• swimming pool water treatment.

The systems are a good alternative to chlorine-gas-based systems.

The composition of the Selcoperm systems

Key components in the Selcoperm unit include an electrolysis sys-tem, storage tanks for the saturated salt solution and product so-lution, an exhaust fan for removing any hydrogen produced, and dosing pumps for the product solution. The concept is rounded off with a measuring and control unit for chlorine dosing.

The electrolysis system is supplied as a turn-key solution. Only the pipework for the water supply, the connections of the salt and product storage tanks as well as the exhaust pipe have to be installed. The size of the storage tanks depends on the capac-ity level of the system and the amount of disinfectant solution required.

Selcoperm electrolytic chlorination systemSafe and simple production of hypochlorite solution

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Technical Data

electrical connection 185 - 265 V or 380 - 440 V, 50/60 Hz

power consumption Approx. 4.5 kW per kg of prepared chlorine

Water quality Good water quality, preferably drinking water

Water consumption 125 litres of water per kg of prepared chlorine

Water pressure Pressure range: from 2.5 to 10.0 bars.For lower water pressures, booster pumps are available.

Water inlet temperature Temperature range: from 5°C to 20°C

Salt quality Food-grade common salt. For drinking water disinfection salt with a low bromide concentration must be used.

Salt consumption 3 to 3.5 kg of salt per kg of prepared chlorine

Drain An on-site drain for the regeneration water of the water softener is necessary.

exhaust air • The outlet of the exhaust air has to be as close as possible to the electrolysis system.• In addition, natural air supply via a ventilation hole in the room is required.

preparation capacity Type capacity/hour capacity/day

Selcoperm 125 125 g Cl2 3 kg Cl

2

Selcoperm 250 250 g Cl2 6 kg Cl

2

Selcoperm 500 500 g Cl2 12 kg Cl

2

Selcoperm 1000 1000 g Cl2 24 kg Cl

2

Selcoperm 2000 2000 g Cl2 48 kg Cl

2

Functional scheme

cathode anode

NaCl +H2O

NaClOsolution

H2

H2ONaCl

NaClO

H+

NaOH

Na+

OH–

Cl2

Cl–

Generation of chlorine from a common salt solution using electricity