Thermal oxidisers are also known as afterburners. They break down odour and hazardous gases at high temperatures to produce carbon dioxide and water.
There are several types of thermal oxidisers and a variety of sizes. They can range from large-scale for industrial use to small-scale for small business, such as a coffee roaster.
Type of control
- Physical
- Chemical
When to use thermal oxidising
Use a thermal oxidiser if your business or site produces waste gas that contains hydrocarbon-based odours.
A thermal oxidiser is suitable for:
- hydrocarbon-based hazardous air pollutants (HAPs)
- volatile organic compounds (VOCs).
Examples of industries that use thermal oxidisers include:
- coating and laminating
- coffee roasting
- fibreglass manufacturing
- metal finishing
- polystyrene manufacturing and recycling
- printing.
Considerations and requirements
There are 3 factors to consider when deciding the type and size of your thermal oxidiser:
- Temperature – it needs to be high enough to ignite the waste gas (generally above 760°C).
- Residence time – this is how long the gas needs to remain in the thermal oxidiser for complete combustion. Size the equipment to suit the optimal airflow.
- Turbulence – this is the amount of oxygen that needs to mix with the gas during combustion to make sure VOCs and HAPs break down.
For more information on requirements for managing odour, visit Control odour from your business.
Types of thermal oxidisers
Choose a type of thermal oxidiser that meets your requirements.
An expert can help you select the appropriate type of odour control for your business. For more information, visit Work with a consultant.
Afterburner
An afterburner is also known as a direct-fired thermal oxidiser. An afterburner is best used when your waste gas has a very high concentration of VOCs or HAPs.
The gas is pumped into a burner that operates at 980°C to 1200°C. Airflow rates are between 0.24 m3 and 24 m3 per second.
This type of thermal oxidiser is common.
Regenerative thermal oxidiser
A regenerative thermal oxidiser (RTO) uses a ceramic bed that preheats gases. Preheating partially oxidises the waste gas. To preheat the gas, the RTO uses the heat from the previous oxidisation cycle. This makes it energy efficient.
The partially oxidised gas then enters the main burner area. Operating temperatures are from 760°C to 820°C and up to 1100°C. Airflow rates are between 2.4 m3 and 240 m3 per second.
An RTO is versatile and efficient.
Flameless thermal oxidiser
In a flameless thermal oxidiser (FTO), waste gas is pre-mixed with oxygen and fuel before being fed through a preheated, inert ceramic media bed. The oxidisation reaction produces the heat, which heats the ceramic media bed.
An FTO is safe and reliable, but it is not suitable in all circumstances. It's important to understand the gas your business or site produces before you select an FTO.
Catalytic thermal oxidiser
A catalytic oxidiser uses a catalyst to increase the rate of oxidisation. With a catalyst, the oxidisation reaction happens at a lower temperature, generally around 340°C to 540°C. This can reduce operating costs.
However, a catalytic oxidiser is not suitable for all circumstances – for example, when the air stream has high levels of particles or chemicals such as silicone, phosphorous and halogens. These can poison the catalyst, which is very expensive to replace.
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