The
gasification of refuse-derived fuel (RDF) in a fluidized bed
gasifier followed by a high-temperature filter was investigated in
a bench-scale plant. The tests were performed at a fixed reactor (bed
and freeboard) temperature of 850 °C and filter temperatures
of 450 and 550 °C using air–N2 and air–steam
mixtures as gasification agents with equivalence ratios (ER) in the
range of 0.24–0.32 and sand and sand/dolomite mixtures as bed
material. The influence of these parameters on the gasification performance
was studied with the primary objective of understanding the fate of
fuel–N, fuel–S, fuel–Cl, and the distribution
of fuel–trace elements into the gas and ash streams (both filter
and bottom ashes). It was found that steam addition, besides increasing
the yield of H2, promoted the yields of NH3,
H2S, and tars. The catalytic effect of dolomite on decreasing
tar production was not observed in our experiments. Fuel–N
and fuel–S were mainly converted into ammonia (≥40%)
and H2S (≥20%). Most of fuel–Cl was measured
in the filter ash, whereas only a minor fraction of the fuel-S was
detected in this solid fraction, especially at low temperature. The
distribution of trace elements into the filter and bottom ashes was
consistent with their inherent volatile behavior, although precise
quantification was difficult due to the heterogeneity of the fuel.
Preliminary assessment of utilization/disposal options of the filter
and bottom ashes generated was made by studying the enrichment factor.