CFD Example 2 Cyclonic Combustion Furnace for Charcoal Chips

The combustion furnace shown below is designed to burn charcoal chips produced from the pyrolysis of waste derived biomass in an associated rotary kiln pyrolyser.

Charcoal is collected from the pyrolysis process, and cooled before storage in a feed hopper. From there the material is picked up by fans and injected into the furnace via two inclined nozzles. Intense turbulent combustion follows at a temperature sufficient to melt the inert ash, which flows down the walls of the cyclone and is extracted as a slag into a water bath below.

The CFD modelling exercise shows that the flow patterns are stable within the furnace and that the gas residence time is consistent and in compliance with regulatory demands under the Waste Incineration Directive. This enables the plant to process material classified as waste, such as RDF.

Hot flue gases from the furnace are used firstly to heat the pyrolysis kiln, and then to generate hot water or steam. Some of this energy is used in fuel pre-treatment.