7. Processing products: solid residues, effluents/gas products

7.1 In combustion

The appearance of unburnt carbon in solid combustion residues reflects defects in the mixing and/or aeration of the charge with the combustion air. The fixed carbon content of bottom ash must remain below 2%. If this is not the case, the residence time of the solid charge in the furnace needs to be increased and/or aeration of the charge needs to be improved and/or combustion air needs to be preheated.

In the case of liquid waste, it is often necessary to improve dispersion.

The presence of unburnt CO gas or soot in the flue gases reflects a lack of aeration of the load, but also a limitation in the reoxidation kinetics of CO and C in the gas phase above the furnace. This can be remedied by the use of secondary air and/or...