Variables Governing the Initial Stages of the Synergisms of Ultrasonic Treatment of Biochar in Water Saturated with Carbon Dioxide
This work investigates the initial stage of the synergistic processes of acoustic treatment of biochar in water saturated with CO2 (AIChE Journal, 2014;60:1054-1065). Treatments with switchgrass and miscanthus biochars have been conducted to examine the effects of acoustic intensity, biochar/H2O ratio, CO2 concentrations of the solution, and that in the headspace above the solution. The changes in biochars’ heating values, carbon and hydrogen contents, internal surface area, and pore size distribution have significant technological implications and are the focal points of this study. The miscanthus and switchgrass biochars were produced via pyrolysis process at 700 oC and 550 oC, respectively. Stoichiometric ratio of biochar/H2O has the most significant effect on the ratio of energy gained by biochar to ultrasound energy consumed during the treatment. The optimal stoichiometric ratio of miscanthus biochar to water is 0.06 g/ml for which the energy gained by the miscanthus biochar was about 10-fold greater than total ultrasound energy consumed during the treatment. Miscanthus biochar gains 4.6% in heating value (or 328 cal/g of biochar) with a total ultrasound consumption 33 cal/g of biochar. CO2 bubbling into the solution improves the removal of mineral matter from the biochar and thus biochar’s heating value, but CO2 in the headspace during the treatment is detrimental to the increase in heating value. Higher acoustic power does not benefit the heating value of the biochar.
biochar, carbon dioxide, gasification, heating values, Sonochemical, stoichiometric ratio, Chemical Engineering
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