Rheological Properties and Stability Characteristics of Biochar-Algae-Water Slurry Fuels Prepared by Wet Milling

This study was aimed to understand the rheological properties and stability characteristics of biochar-algae-water (BAW) slurry fuels prepared by wet milling. A pine sawdust biochar and a chlorella vulgaris algae were used in preparing the slurry fuels. The BAW slurries were formulated by mixing the biochar, algae, de-ionized water, lignosulfonic acid sodium salt, and then the mixture was ball-milled for various times. The BAW slurries with a constant solid loading of 45 wt % were prepared with varied algae proportion in algae/biochar mixture. The apparent viscosity and stability of BAW slurries were measured. It was found that D₅₀ of the particles of the solid in the slurries decreased with increasing milling time. The viscosity of the slurries decreased first and then increased as milling time increased, reaching a minimal value when D₅₀ of the solid was between 3 and 7 μm. The lowest viscosity of BAW slurries achieved at a given solid loading increased with increasing the algae proportion in the solid. The BAW slurries showed better stability at higher algae proportions due to enhanced flocculation.