[SGC49-P01] Particle size control of olivine alteration pathway and rate for simultaneous H2 generation and CO2 storage
Keywords:Olivine, grain size, hydrogen, carbon storage
In this study, three experiments with olivine particles of 28-53, 53-90 and 90-160 µm were conducted in 0.5 mol/L NaHCO3 solution at 300 °C for 72 h. Olivine alteration rate (r, wt%/h) was closely related to its geometric surface area (GS, m2/g), with the linear relationship of r=4.097GS. H2 production was much higher with the simultaneous CO2 storage [in magnesite, (Mg,Fe)CO3] in the experiment with an olivine grain size of 28-53 µm than those with larger olivine grain sizes. The highest cumulative H2 yield was 118 mmol/kgolivine in 72 h. The inhibited magnesite precipitation in experiments with olivine grain size >53 µm was attributed to the low Mg concentrations caused by the slow olivine dissolutions. The results also suggest olivine serpentinization proceeded faster than carbonation, and the covering of olivine with serpentines [(Mg,Fe)3Si2O5(OH)4] may inhibited further olivine alteration and H2 production.
Therefore, decrease the olivine grain size to < 53 µm is an efficient way not only to enhance olivine alteration with H2 production but also to realize simultaneous H2 production and CO2 storage during H2O-olivine-CO2 reaction.