Laboratory Investigations in Support of Carbon Dioxide Limestone Sequestration in the Ocean. Semi Annual Technical Progress Report for the period 01/09/2005 thru 07/08/2005.
This semi-annual progress reports includes further findings on CO2-in-Water (C/W) emulsions stabilized by fine particles. In previous semi-annual reports we described the formation of stable C/W emulsions using pulverized limestone (CaCO3), flyash, beach sand, shale and lizardite, a rock rich in magnesium silicate. For the creation of these emulsions we used a High-Pressure Batch Reactor (HPBR) equipped with view windows for illumination and video camera recording. For deep ocean sequestration, a C/W emulsion using pulverized limestone may be the most suitable. (a) Limestone (mainly CaCO3) is cheap and plentiful; (b) limestone is innocuous for marine organisms (in fact, it is the natural ingredient of shells and corals); (c) it buffers the carbonic acid that forms when CO2 dissolves in water. For large-scale sequestration of a CO2/H2O/CaCO3 emulsion a device is needed that mixes the ingredients, liquid carbon dioxide, seawater, and a slurry of pulverized limestone in seawater continuously, rather than incrementally as in a batch reactor. A practical mixing device is a Kenics-type static mixer. The static mixer has no moving parts, and the shear force for mixing is provided by the hydrostatic pressure of liquid CO2 and CaCO3 slurry in the delivery pipes from the shore to the disposal depth. This semi-annual progress report is dedicated to the description of the static mixer and the results that have been obtained using a bench-scale static mixer for the continuous formation of a CO2/H2O/CaCO3 emulsion. The static mixer has an ID of 0.63 cm, length 23.5 cm, number of baffles 27. Under pressure, a slurry of CaCO3 in artificial seawater (3.5% by weight NaCl) and liquid CO2 are co-injected into the mixer. From the mixer, the resulting emulsion flows into a Jerguson cell with two oblong windows on opposite sides, then it is vented. A fully ported ball valve inserted after the Jerguson cell allows the emulsion to be stopped in the cell. In such a manner the emulsion can be photographed while it is flowing through the cell, or after it has stagnated in the cell. A slurry of 10 g/L CaCO3 (Sigma Chemicals C-4830 reagent grade) in artificial seawater, co-injected into the static mixer at a rate of 1.5 L/min with liquid CO2 at a rate of 150 mL/min, at temperature 5-10DGC, pressure 10 MPa, produced an emulsion with mean globule diameter in the 70 100 im range. In a HPBR, using the same materials, proportions, temperature and pressure, mixed with a magnetic stir bar at 1300 rpm, the mean globule diameter is in the 200 300 im range. Evidently, the static mixer produces an emulsion with smaller globule diameters and narrower distribution of globule diameters than a batch reactor.
PDF
download
878987797
028-85220240
