05 Nuclear fuels (scientific, technical) from FTIR. Solid samples collected during the bio-sludge combustion process were analysed with SEM, wavelength-dispersive and energydispersive X-ray spectrometry and electron probe microanalysis to determine morphology, particle size, composition and metals distribution in ash particles. The bio-sludge combustion process could be divided into four stages. (1) Initial burning (T < 600ยฐC) dominated by moisture evaporation, fibres volatilization and pyrolysis.
(2) Biosludge/ash transition (600 < T < 1100ยฐC) dominated by char oxidation, metals reduction and AI-Si spine1 formation. (3) Solid particle sintering (1100 < T < 1400ยฐC) dominated by mullite formation, ash softening and metals segregation.
(4) Ash melting (T > 1400ยฐC). However, it is difficult to accurately establish a clear boundary between these stages because the regimes of volatiles release, char combustion and ash transformation are overlapping. Ash formed during quenching was a condensed and packed substance while during natural cooling it revealed dendritic character with needle-like features present on the particle surface. The former structure is better from the environmental point of view because it would not allow for leaching of toxic metals if ash was disposed of in a sanitary landfill. 02lOO439