Hydrogen-Enriched Syngas Production from Steam Gasification of Biomass with Eggshell As a CO2 Sorbent

An investigation into the steam gasification of biomass with an in-situ CO₂ capture was conducted in this study. An enrichment in the hydrogen concentration and a reduction in the carbon dioxide (CO₂) concentration in the gas product was achieved. Sawdust from spruce was utilized as the feedstock while eggshell was used as the CO₂ sorbent material. The gasification experiments were conducted in a bubbling fluidized bed reactor with calcined eggshell as both bed material and CO₂ sorbent. Activation of the eggshell was performed by calcination at 900^oC as thermogravimetric analysis conducted on the eggshell showed that 900^oC is sufficient to fully convert the calcium carbonate in the eggshell to calcium oxide. X-ray diffraction peaks also revealed the complete conversion. Effects of important process parameters, steam to biomass ratio (SBR) and calcined eggshell to biomass ratio (CEBR), were studied. Increasing the CEBR promoted the CO₂ uptake via the carbonation reaction and accordingly enhanced hydrogen enrichment. An increase in SBR improved the hydrogen concentration in the gas stream. A maximum hydrogen concentration of 78% and a minimum CO₂ volumetric concentration of 3.3% were obtained in this study at a temperature of 650^oC, CEBR of 1.0 and SBR of 1.2. Additionally, results revealed that the water gas shift reaction is the most important gasification reaction in the process.