IMPROVING THE PROCESS OF SUPERCRITICAL CARBON-DIOXIDE-ASSISTED LIQUEFACTION OF BIOMASS FOR THE PRODUCTION OF BIOFUELS

Abstract

The United States has been looking for alternative energy sources to combat energy dependence and carbon emissions. There exists a multitude of methods attempting to achieve this effort while making use of existing infrastructure. One such novel method is the supercritical carbon-dioxide-assisted liquefaction of biomass. This method seeks to exploit a large supply of biomass waste in the US through the use of carbon dioxide, a readily available and nontoxic gas. This paper investigated two potential improvements for liquid yields in the supercritical carbon-dioxide-assisted liquefaction system. Those improvements were the effects of heating on the solid and liquid yields and the efficacy of supercritical carbon dioxide extraction of liquid products. Three specific aspects of heating were investigated: resident time, heating rate, and total time. Resident times of 10 minutes 20 minutes and 60 minutes were tested. High heating rates were achieved via the use of induction heating. Heating rates of 6, 12, and 250 ℃/min were tested. The effects of total reaction time were also investigated; however, this was dependent on the heating rate and resident time, thus it could not be independently controlled. The investigation found that neither resident time nor total reaction time has a significant impact on the solid or liquid yields. The heating rate, on the other hand, showed a good correlation with a proposed relationship of L = 13.01 · H0.1687 and S = 58.57 · H-0.08348, where L is the liquid yield in wt%, S is the solids yield in wt%, and H is the heating rate in ℃/min. This investigation had a stated goal of achieving a liquid yield of over 30% in under 45 minutes while maintaining a solids yield of less than 50%. It achieved this goal with a particular test having a liquid yield of 32% and a solids yield of 40% in under 12 minutes. Supercritical carbon dioxide extraction was proven to be effective at recovering liquid yields. It was not as successful as acetone-aided extraction; however, it shows promise, especially given its potential for overall process integration in the future. sCO2 extraction was seen to be most effective when conducted in conjunction with sCO2 liquefaction.