Effect of compression molding of CaCO3 powder on the kinetics of CO2 capture towards sustainable CO2 capture and sequestration cycle

Abstract

Reducing CO₂ emissions from industrial sectors and motor vehicles is currently receiving much attention. There are different strategies for CO₂ capture, one of which is using calcium oxide (CaO). In our proposed carbon dioxide cycle, limestone is first calcined to get CaO, which is then used to capture CO₂ by converting it to CaCO₃. Next, the released CO₂ could be converted to different organic matter by different sequestration techniques. For this purpose, CaCO₃ discs have been prepared by compression molding to investigate the effect of sintering temperature on the mechanical and chemical properties of CaO carbonation reaction. The aim of this work is to fill the knowledge gap for the effect of the contact profile between CO₂ gas and CaO disc, particularly the effect of reducing the void fraction of CaO on the rate of carbonation reaction. It was found that the flexural strength of the CaO discs was influenced by several factors, such as the calcination temperature, duration of calcination, and pressing pressure. The carbonation step indicated that both CO₂ and H₂O are reacting with CaO simultaneously and progressively, with the progressive reaction of H₂O and CO₂ being a favorable route. The carbonation process happens as a surface reaction-controlled process followed by a slower internal diffusion-controlled process. Additionally, a kinetic study of the competing reactions indicated that two factors are controlling the process: diffusion of gases through the pores and then the reaction rate. Furthermore, our data showed that the CO₂ uptake rate was 1352.34 mg/g CaO, indicating that 566.34 mg of CO₂ was adsorbed inside the pores of the CaO disc. Based on these results, we propose a new mechanism of the sequence of the competing reactions. In summary, the CaO discs revealed a significant removal of CO₂ from stack gases, which will be suitable for removing CO₂ from exhaust gases generated by industrial processes and other sources of emissions such as vehicles and ships.

Keywords: CO2 capture; CO2 reaction kinetics; CaCO3 calcination; CaO discs; Mechanical compression; Sintering.