Hydrothermal Carbonation of K–Rich Ash, Value Added Energy Engineering and CO2 Mineral Sequestration

In this paper, hydrothermal carbonation of raw K–rich ash derived from a palm oil plant factory in West Kalimantan, Indonesia had been studied and evaluated at varying temperatures of 50 °C to 300 °C, initial CO2 pressure at between 2 MPa to 2.5 MPa and a maximum final pressure of 8.5 MPa and a residence time of 30 min. The yield of the solid products was about between 47 wt% and 66 wt% and the effective CO2 content which was captured by hydrothermally solid products was between 0.057 ton · ton–1 and 0.115 ton · ton–1 following hydrothermal carbonation. In addition, dehydration of solid product occurred at mostly 300 °C, while oxidation was started at 50 °C. Obviously, both the sorption–dissociation of CO2 in the solution and hydrothermal carbonation process produce a global pressure drop in the system resulting in CO2 mineral sequestration. The carbonation efficiency of solid–fluid interactions at 25 °C and after 24 h period was 25.36% and 0.05 954 mol of CO2 were consumed by the carbonation process. At the condition applied, observed several possibilities were observed such as: the pH (alkalinity), total inorganic carbon, direct precipitation of carbonates minerals as well as crystallization of carbonates in the solution and solid products.