Eggshell as a potential CO2 sorbent in the calcium looping gasification of biomass

Abstract

This work presents an investigation into the potential use of eggshell as a CO₂ sorbent in the calcium looping gasification of biomass to enhance carbon negativity. Calcination reaction was studied in a quartz wool matrix reactor and a thermogravimetric analyser coupled with a Fourier transform infrared spectroscopy. The resulting sorbent was characterised with a scanning electron microscope, colourimeter, inductively coupled plasma optical emission spectroscopy, and nitrogen sorption analyser. The pore structures of the samples are of Type II isotherm. Results show that increasing the calcination temperature enhances decomposition and improves the calcium content and specific surface area of the sorbent. As compared to nitrogen, calcination in a CO₂ environment is not effective due to the increased CO₂ partial pressure. Samples with low particle size displayed higher carbonation conversion. Increasing the carbonation temperature to an extent enhances the carbonation conversion. The carbonation conversion by the sorbent in multiple calcination-carbonation cycles was also studied. Initial CO₂ uptake by the sorbent was highly encouraging. A conversion of 76.41% was realized after the first cycle, but due to sintering and attrition, the conversion reduced with increasing cycle. The sorbent exhibited a low conversion of 18% after the seventh cycle and this corresponds to a decay extent of 76.65%.

Keywords: CO(2) sorbent; Calcination; Carbonation; Characterization; Eggshell; Gasification.