LABORATORY INVESTIGATIONS IN SUPPORT OF CARBON DIOXIDE-LIMESTONE SEQUESTRATION IN THE OCEAN

This semi-annual progress reports includes further findings on CO{sub 2}-in-Water (C/W) emulsions stabilized by fine particles. In previous reports we described C/W emulsions using pulverized limestone (CaCO{sub 3}), flyash, and a pulverized magnesium silicate mineral, lizardite, Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}, which has a similar composition as the more abundant mineral, serpentine. All these materials formed stable emulsions consisting of droplets of liquid or supercritical CO{sub 2} coated with a sheath of particles dispersed in water. During this semi-annual period we experimented with pulverized beach sand (10-20 {micro}m particle diameter). Pulverized sand produced an emulsion similar to the previously used materials. The globules are heavier than water, thus they accumulate at the bottom of the water column. Energy Dispersive X-ray (EDX) analysis revealed that the sand particles consisted mainly of SiO{sub 2}. Sand is one of the most abundant materials on earth, so the economic and energy penalties of using it for ocean sequestration consist mainly of the cost of transporting the sand to the user, the capital and operating costs of the pulverizer, and the energy expenditure for mining, shipping and grinding the sand. Most likely, sand powder would be innocuous to marine organisms if released together with CO{sub 2} in the deep ocean. We examined the effects of methanol (MeOH) and monoethanolamine (MEA) on emulsion formation. These solvents are currently used for pre- and post-combustion capture of CO{sub 2}. A fraction of the solvents may be captured together with CO{sub 2}. A volume fraction of 5% of these solvents in a mix of CO{sub 2}/CaCO{sub 3}/H{sub 2}O had no apparent effect on emulsion formation. Previously we have shown that a 3.5% by weight of common salt (NaCl) in water, simulating seawater, also had no appreciable effect on emulsion formation. We investigated the formation of inverted emulsions, where water droplets coated with pulverized materials are dispersed in liquid or supercritical CO{sub 2}. This is a Water-in-CO{sub 2} emulsion (W/C) stabilized by particles. For a W/C emulsion it is necessary to employ hydrophobic particles, where the particles are primarily wetted by CO{sub 2}. We used the following hydrophobic particles: carbon black, coal dust, and Teflon. All materials were either obtained as fine particles or ground to 10-20 {micro}m size. All these hydrophobic particles produced a stable W/C emulsion