LIQUID CARBON DIOXIDE/PULVERIZED LIMESTONE GLOBULSION DELIVERY SYSTEM FOR DEEP OCEAN STORAGE

摘要

When liquid or supercritical CO_2 is mixed with a slurry of finely pulverized limestone (CaCO_3) in pure or seawater, a macro-emulsion is formed consisting of CO_2 droplets coated with a sheath of CaCO_3 particles dispersed in water. The sheathed droplets are called globules, and the dispersion of globules in water is called a globulsion. Using a Kenics-type static mixer and pulverized limestone with median particle size of 6 μm, monodisperse globules with average diameter of about 200 μm can be produced. Assuming a monolayer of 6 μm pulverized limestone around the globules, the specific gravity of each globule is greater than that of seawater. For complete encapsulation of liquid CO_2 about 0.6 t of limestone is needed per ton of CO_2. The globulsion has a slightly alkaline pH.rnA practical delivery system for the underwater creation of the globulsion is described. Liquid CO_2 is piped to about 500 m depth, which is below the flash point of liquid CO_2 into vapor. A slurry of pulverized limestone in seawater is separately piped to this depth. A static mixer is mounted at the end of the pipes. Three fluids are entering the mixer: (1) Liquid CO_2; (2) slurry of pulverized limestone; and (3) ambient seawater pumped into the mixer by a turbine. The globulsion exits from the other end of the mixer and sinks like a dense plume to greater depths while entraining ambient seawater until neutral buoyancy is achieved in the density and temperature stratified ocean. After equilibration, the CaCO_3-coated globules will "rain out" from the plume toward the ocean bottom. With this method of discharging CO_2, the ocean will not be acidified.