Biomass Gasification and BioSNG Production: Use of Sorbents for Simultaneous H2 Enrichment and CO2 Removal for the Conditioning of Gas Composition

Use of sorbents for sorption enhanced water gas shift (SEWGS) were considered to adjust the composition of the product gas obtained from a process of biomass gasification and convert it in BioSNG. To this purpose four sorbents were prepared and tested in experiments of SEWGS with a real gas obtained at a 1000 kWth pilot plant based on the process of steam/oxygen biomass gasification. The selected sorbents were two K-enriched hydrotalcites Mg/Al (HT1K and PMG70/K), a hydrocalumite Ca/Al (HT2) and a mixed hydrotalcite Mg/Ca/Al (HT3). The two Mg/Al materials were selected for cyclic tests of SEWGS at 400 °C (low temperature), the other two for evaluations at 600 °C (high temperature). Based on the experimental results, average and rather stable, CO2-uptake capacities of about 0.9 and 0.7 mmolCO2/gsorbent were respectively evaluated for HT1K and PMG70/K; for HT2 and HT3 the average uptake capacities were correspondingly found to be 2.6 and 3.1 mmolCO2/gsorbent. By comparing the structural properties of the materials before and after tests, no relevant modifications were observed based on results from SEM-EDX and XRD, as well as no presence of residual contaminants from tars were detected based on the FTIR spectrum. Preliminary data from modelling for the processes carried out at 400 °C and 600 °C, indicated a conversion efficiency from biomass to BioSNG up to 56 % and 45 %, respectively.