Biogas deep cleaning step for trace pollutants removal using
iron oxide based sorbents and activated carbon
The configuration of the biogas deep cleaning step consisted of
(i) iron-based adsorbent, (ii) biogas drying with refrigeration to 5 C
and (iii) activated carbon. Two beds of each adsorbent material
were placed in series with reversing capability (lead-lag operation).
The iron-based adsorbent consisted of a regenerable pelleted ironbased adsorbent (diameter 2e4 mm and bed density 840 kg m3
).
Since the upstream BTF could be very sensitive to H2S load fluctuations and could provide not stable performance in terms of
removal efficiency, the iron sponge was designed to allow conservative retention times of 25e35 s (75 kg per vessel) to achieve H2S
concentrations below 0.5 ppmv (maximum concentration accepted
by the SOFC). Each vessel had a volume of 83 L (0.4 m diameter and
0.66 m height) and was operated at linear velocities of
1.3e2 cm s1
.