Validation of a population balance model for olivine dissolution

The dissolution of silicate minerals, among them olivine, in water enables its subsequent reaction with carbon dioxide to form magnesium carbonate, a process called aqueous mineral carbonation. A general model for the dissolution of olivine, based on a population balance approach, has been developed. For this purpose, the dissolution rate of olivine has been measured as a function of varying particle size and pH at 120 ^{{ring operator}} C. Three separate particle populations in three different size ranges were used: a sub 90, a 90-180, and a 180-355 μ m size fraction. The pH was varied between 2 and 4.75 using HCl. Experiments were carried out in a flow-through reactor under a nitrogen atmosphere of 20 bar. The dissolution extent varied from 12% up to complete dissolution, depending on experimental conditions. Particle size distributions of the different size fractions were measured with a Coulter Multisizer^®. Using the assumption of a surface controlled reaction, the solution to the population balance equation was coupled with a reactor model. Data were fitted to the model to obtain a shape modulated dissolution rate, k_v^{1 / 3} D, combining the volume shape factor k_v with the dissolution rate D, which has the dimensions of a velocity. Including earlier published dissolution experiments an overall correlation for the dissolution rate was regressed. Using the general model, the limitations of the simplified model employed in an earlier publication are illustrated.