Reactive Precipitation in Gas-Slurry Systems:  The CO₂−Ca(OH)₂−CaCO₃ System

Abstract

The present work examines the chemical absorption of carbon dioxide (CO 2 ) gas in aqueous calcium hydroxide (Ca(OH) 2 ) slurries, which leads to the precipitation of calcium carbonate. Carbonation of the Ca(OH) 2 slurry is an important method for the industrial manufacture of precipitated calcium carbonate (PCC), wherein the hydroxide particles are gradually converted to carbonate. Experimental data have been generated by contacting CO 2 with an aqueous Ca(OH) 2 suspension in a model gas-liquid, stirred contactor, under different operating conditions. It is not possible to distinguish between the different types of particles present in the system (hydroxide, carbonate, mixed particles) "visually". Therefore, the particle size distribution of all the particles present has been obtained using microscopy and optical image analysis techniques. The conversion of hydroxide-to-carbonate is determined by titration. A modeling approach that assumes that the hydroxide particles get converted by the diffusion of dissolved CO 2 into its internal parts (as is observed in a "shrinking core" scenario), coupled with a population balance to describe the size distribution of the unreacted particle cores has been formulated. The experimental and theoretical conversions agree reasonably well.

Effect of particle morphology on mechanical properties of liquid marbles

“…Both spherical and rod-shaped CaCO3nanoparticles (Figures 1 and S1) were kindly donated from Shiraishi Kogyo Kaisha, Ltd (Hyogo, Japan). These nanoparticles were used as a liquid marble stabilizer, which were synthesized by carbonation process in aqueous medium [29,30]. Numberaverage diameter of the spherical CaCO3 particles (C1) was determined to be 80 nm from transmission electron microscopy studies (n=200).…”

Stable Nano Calcite Synthesis

“…For this case, other ions such as Na + and Clplay an important role on crystallization and bigger particles are produced with sizes larger than 3 µm (7). The other method is carbonization method and uses carbon dioxide (CO2) and calcium hydroxide (Ca(OH)2) as the reactants (8)(9)(10). Nano size particles can be produced in carbonization method depending on concentration and temperature of the solution (11).…”

Influence of ethylene glycol on CaCO3 particles formation via carbonation in the gas–slurry system

“…the reaction of CO 2 and Ca(OH) 2 , or as a by-product of some bulk chemical processes, e.g. caustic soda production [22][23][24]. The precipitation in liquid-liquid systems is usually applied in a laboratory study because it is easy to control the process variables [15].…”

“…However, the gas and liquid flows depend on the reactor geometry and its hydrodynamic characteristics. The reaction of CO 2 with Ca(OH) 2 involves the dissolution of the reactant particles while the CaCO 3 particles are simultaneously formed [22]. It means that unreacted dissolved Ca(OH) 2 , product carbonate particles, hydroxide particles coated with the precipitated CaCO 3 as well as complex agglomerates can be present in the reaction mixture.…”