Study on mineral carbonation of heat activated lizardite at pilot and laboratory scale

This investigation examines the experimental data obtained from a 30 L pilot batch reactor, used for single stage aqueous carbonation and for the dissolution of heat activated lizardite and compares this data to the laboratory scale data obtained under similar reaction conditions. Two mineral feeds, heat activated lizardite produced in large quantities in a gas fired industrial kiln (P.H.A) and heat activated lizardite sample synthesised in a laboratory kiln (L.H.A) were characterised and their reactivity was compared. Characterisation of the two heat activated samples showed that the P.H.A material contained relatively high concentrations of crystalline phases and a lower proportion of amorphous magnesium silicate, as well as a higher average particle size compared to L.H.A. These properties resulted in a reduction in magnesite yield and extent of magnesium extraction when P.H.A samples were used for carbonation and dissolution experiments, compared to the results obtained with L.H.A. as feed. The results of aqueous carbonation experiments in the pilot and the laboratory scale reactors using P.H.A exhibited less than 5% variation in repeat experiments. Results indicate that the magnesite yield obtained in the pilot batch reactor was 35 +/- 2% higher than that produced in the laboratory scale reactor. The higher yield was attributed to improved mixing in the pilot batch reactor compared to the laboratory scale reactor and consequent removal of the precipitated phases on the surface of heat activated particles in the pilot reactor. The yield of magnesite in mineral carbonation experiments using demineralised water and tap water was almost identical. Undertaking reaction in 1 M NaCl solution did not have a significant effect, but adding 0.64 M sodium bicarbonate had a notable effect on magnesite yield. Low pressure, low temperature dissolution experiments using L.H.A sample displayed similar rates of magnesium extraction in the pilot and the laboratory scale reactors.