Surplus ozone, what’s that? You’ll find more information about surplus ozone, what it is and how to get rid of it on this page.
Surplus ozone the ozone that isn’t used in your ozone reactor. In an ozone reactor, water and gas (in this case ozone) are mixed using a venturi or air stone. After it’s don’t it’s job, the gas stream leaves the ozone reactor via an outlet. An ozone reactor can’t make all the ozone react with the water because the efficiency isn’t 100%, more likely between 10% and 80%.
This means that part of the ozone that was put in is also in the outgoing gas stream, this is called surplus ozone. The gas concentration in this stream is often high enough to be dangerous to humans and animals. This is why we use an ozone destroyer: to bring the ozone concentration down to an acceptable level.
Breaking down surplus ozone with a surplus ozone destroyer can be done a couple different ways. There are different versions with their own pro’s and cons. A couple different ways to break down ozone can be found below.
Breaking down ozone using activated carbon
A surplus ozone destroyer based on activated carbon is undoubtedly the best known destroyer. Ozone is an unstable gas that wants to decay into oxygen. One of the ways to do this is to make sure it can oxidise something. A carbon source (for example activated carbon) is oxidised very fast by ozone and makes it fall back into oxygen.
Heat is released during this reaction, carbon is oxidised (burnt) after all. This is the reason activated carbon can only be used for surplus ozone with a low ozone concentration. If the concentration is too high, enough heat can be released to make the carbon ignite spontaneously. This is why there’s a simple rule: activated carbon can only be used in systems where ozone is generated using air.
The ozone concentration and fire risk are simply too high in ozone systems that use pure oxygen to make ozone.
A practical tip: always hang your activated carbon filter in such a way that the ozone ‘sinks’ through the activated carbon. This means you inject the ozone on the top and the outlet will be on the bottom. This is because ozone is heavier than air so it will move down to the lowest point of the filter. If you hang it upside down, the ozone will collect in the activated carbon filter which can result in extra risk of fire due to more heat being produced in the smaller filters.
Advantages:
- Cheap
- Simple
Disadvantages:
- Looses its function when there’s (too) much moisture in the surplus ozone
- There’s a fire risk when there’s a high ozone concentration
Breaking down ozone with manganese dioxide
This method is comparable to the activated carbon based one. The big advantage when using manganese however, is that the fire risk is much smaller.
Advantages:
- No risk of fire
- Simple
Disadvantages:
- Looses its function when there’s (too) much moisture in the surplus ozone
- Relatively expensive
Breaking down ozone with heat
Ozone decays into ozone by itself, the rate at which this happens depends mostly on the temperature of the ozone gas. For example, the half-life is about 72 hours at 20 degrees Celsius, but only one and a half seconds at 250 degrees Celsius! Surplus ozone is heated to about 275 degrees Celsius in a thermal ozone destroyer, this causes the ozone to decay into oxygen very quickly.
Advantages:
- Can also be used with moist surplus ozone
- Maintenance free
Disadvantages:
- A minimal contact time is needed, which makes the selection of a destroyer more of a precise job. Part of the ozone won’t be converted into oxygen when the contact time is too short.
- Uses quite a lot of energy
Breaking down ozone with manganese dioxide and heat
Tol Watertechniek uses ozone destroyers that consist of cartridges filled with manganese dioxide. These cartridges are then heated to 50~100 degrees Celsius. This way, both heat and a substance that can be oxidised is used. The advantages of both methods are also combined: this type of destroyer is less sensitive to moisture and selecting the proper type is less of a problem.
Advantages:
- Can be used when there’s moisture in the surplus ozone
- Maintenance free
- Very reliable
Disadvantages:
- Uses quite a lot of energy
Breaking down ozone with UV light
Ozone decays into oxygen under the influence of UV light as well. UV-C lamps with a wavelength of +/- 254nm can be used to do this. However, this method is barely used because of its very high energy consumption and the big size. This is why we’re not explaining this method any further here.© Tol Watertechniek