Steam O2-enriched air gasification of lignite and solid recovered fuel in fluidized bed
Katia Gallucci, Andrea Di Giuliano, Sergio Rapagnà
Abstract
Continuous steady-state gasification tests were performed, in which mixtures of lignite and solid recovered fuel (SRF) were fed to a bench-scale facility at atmospheric pressure, loaded with the bottom product of a high-temperature Winkler gasifier as the fluidized bed material. The O2/fuel and steam/fuel ratios were varied from 0.3 to 0.4 and from 0.25 to 0.35, respectively, and the effects of the temperature were examined at different levels (700, 750, and 800 °C). The objective of the experimental campaign was to evaluate the effects of above mentioned operating conditions on the (i) quality of syngas expressed in terms of gas yield (Ygas), cold gas efficiency (ηCG), and carbon conversion (XC); (ii) effectiveness in tar reduction; and (iii) improvement of the H2/CO molar ratio. Characterization analyses (grain-size distribution, scanning electron microscopy and energy-dispersive X-ray spectroscopy) were performed on the materials before and after the tests. Pressure-fluctuation signals were acquired during the tests to monitor the fluidization quality and diagnose the correlated incipient sintering or agglomeration of the bed particles. At 800 °C, the obtained results (Ygas=1.53;ηCG=79%;XC=92%;tar content = 7.35 g/Nm3; H2/CO molar ratio = 0.96) demonstrated the convenient feasibility of gasification with the SRF–lignite mixture as a fuel (SRF/lignite = 0.5 wt/wt) and helped define the operating conditions for future pilot tests aiming for liquid fuel synthesis, although the best results were obtained at 800 °C with SFR/lignite = 0.2 wt/wt (Ygas=1.79;ηCG=93%;XC=102%;tar content = 0.92 g/Nm3; H2/CO molar ratio = 0.84).