Statistical testing of input factors in the carbonation of brine impacted fly ash

A D-optimal design was applied in the study of input factors: temperature, pressure, solid/liquid (S/L) ratio and particle size and their influence on the carbonation of brine impacted fly ash (FA) determined. Both temperature and pressure were at two levels (30°C and 90°C; 1 Mpa and 4 Mpa), S/L ratio was at three levels (0.1, 0.5 and 1) while particle size was at 4 levels (bulk ash, <20 μm, 20 μm -150 μm and >150 μm). Pressure was observed to have a slight influence on the % CaCO(3) yield while higher temperatures led to higher percentage CaCO(3) yield. The particle size range of 20 μm - 150 μm enhanced the degree of carbonation of the fly ash/brine slurries. This was closely followed by the bulk ash while the >150 μm particle fraction had the least influence on the % CaCO(3). The effect of S/L ratio was temperature dependent. At low temperature, the S/L ratio of 1 resulted in the highest % CaCO(3) formation while at high temperature, the ratio of 0.5 resulted in the highest percentage CaCO(3) formation. Overall the two most important factors in the carbonation of FA and brine were found to be particle size and temperature.