Following a heat treatment, pollutants may be present in gaseous effluents (CO, Volatile Organic Compounds – VOCs -….).
These pollutants come from:
- Products of gaseous fuel combustion for lean gas such as biogas (resulting from methanation of organic waste). Indeed, biogas contains between 20 and 70% of methane according to its production mode (methanizer, technical landfill …), the remaining being HCl, CO2, silanes, CO leading to Volatile organic compounds after combustion.
- Products which undergo the heat treatment themselves. For example, some ceramic parts contain a large amount of organic binders, often necessary for shaping. During the temperature rise, the organic binders have an incomplete (non-stoichiometric) combustion leading to the formation of Volatile Organic Compounds in the furnace – debinding phase.
During debinding phase, it is therefore necessary:
1/ To prevent any explosion hazard related to a VOC concentration that would be greater than the lower explosive limit. This is why Ceritherm kilns can be equipped with safety systems according to the principles of EN 1539 or NFPA 86A application fields of industrial kilns – technical ceramics
2/ To respect the regulations on air emissions for VOCs.
For this, thermal effluent oxidation systems also called post-combustion are defined by the European Union as the best available technique (BAT) for the “ceramic” industries.
The principle is to thermally oxidize VOCs in post-combustion to transform it into non-harmful substances (mainly water and CO2).
In order to allow this combustion, the effluents from the kiln or from the oven must reach a high temperature (higher than the self-ignition temperature) during enough time enable complete oxidation in an oxidizing atmosphere.
There are no regulations on post-combustion design. The Ceritherm post-combustion design is based on huge knowledge of our team and on the rules of the art – the 3T rule:
- Temperature: it must be higher than the self-ignition temperature of the components to destroy. Usually 850°C.
- Residence time: the gases residence time must be adjusted according to kinetics of thermal oxidation of components to be treated. Usually from 1 to 2 s.
- Turbulence: mixture of pollutants and quantity of oxygen must be sufficient.
Ceritherm has developed post combustion concepts to meet your needs:
- Energy saving: heat exchanger, direct hot air recovery, use of kiln fuel gases as combustion air for the afterburner
- Ultra-fast heating (850°C) to facilitate your workflows. Ceritherm post combustion does not need to be started before the kiln. The design allows to be at operating temperature before the kiln cycle reached the debinding temperature
- Very robust: Ceritherm design for refractory insulation gives the post combustion a very low thermal inertia, a great resistance to chemical attacks and a very great resistance to mechanical erosion linked to the flows.
- Pressure control in the kiln
- Compact design
- Outdoor Installation:
Ceritherm post-combustion combines with debinding kilns, sintering or debinding heat chambers.