Appia Energy uses bubbling fluidised bed technology, which optimises RDF energy conversion and permits to comply with the most stringent emission limits stated by National and European legislation.

Fluidised bed system allows the RDF burning into a fluidised sand layer. Fluidisation is obtained by air blown from the furnace at the bottom. This combustion mechanism allows the full control of RDF combustion and pollutants removal.

The advantages of fluidised bed combustion

High combustion efficiency (over 99%) thanks to simultaneous control of temperature, turbulence and residence time.
High combustion stability when fuel characteristics changes, thanks to the sand thermal “fly wheel” effect.
Low combustion temperature, with consequent reduction of NOx.


Pollutants abatement

The first step in pollutants abatement takes place inside the furnace:

• abatement of nitrogen oxides (NOx) throughout a Selective Non Catalitic Reduction system (SNCR), with ammonia hydrate injection;
• partial absorbing of acid gases with limestone or dolomia injection;
• partial absorbing of acid gases with limestone or dolomia injection;.

Final removal of acids, metals and particulate takes place into the flue gas treatment system installated downstream the boiler.

Considering the flue gas temperature when leaving the boiler (170°C) and the required high removal efficiency, the treatment system installed is a “dry” type with a reactor and a final bag filter: micronized sodium bicarbonate (NaHCO3) and activated carbons are injected into the flue gas stream. The activated carbons remove the residual traces of heavy metals, PCDD/F if any, and other micropollutants.

Pollutants removal is completed by gas particulate abatement in the baghouse filter, whose efficiency is exceeding 99.9%.

In the baghouse filter acid gases neutralisation is completed. Acids are forced to pass through a cake deposted on the bags containing non-reacted sorbents by increasing the contact time and surface between the sorbents and the acids themselves.