| Drop-in biofuel production for replacing traditional liquid transportation fuel can be accomplished by converting oils and fats, which are composed mostly triglycerides, into high quality free fatty acid (FFA) and then turning the hydrolyzed FFA into long-chain hydrocarbons through deoxygenation. A small scale thermal hydrolysis of fats and oils in continuous mode is presented in this study with high temperature (250°C∼270°C) and with high pressure in order to suppress the vaporization of liquid reactants. Countercurrent water and lipid flows provided mass transfer and enhanced mixing. Preheating water and oil inflow reduced heat exchange between the inflows and the reactants, and this offered 44% more FFA yield than non-preheating. Increasing reaction temperature improved water solubility in lipid phase and accelerated hydrolysis reaction. Higher excess water also provided better replacement for glycerol content in sweet water and resulted in a better FFA yield. The mass yield, calculated from the reactions with commercial off-shelf canola oil, camelina oil as well as algal oil, was approximately 89% ∼ 93%. Moreover, the energy conversion efficiency is determined to be 75.66%.;In order to minimize the energy input and reaction time, and refine the glycerol refinery for use as an energy source, sweet water formed from the continuous hydrolysis process was recovered. Superheated steam, generated by heating the sweet water above the boiling point of water at the reaction pressure, was injected into the hydrolysis system. This resulted in a high yield of FFA without preheating water and oil as well as at low reactor temperatures and low water-to-oil ratios. Within 300 minutes process time, glycerol was concentrated from 2∼3% (from the reactor) to 5.5% (from the glycerol concentrator), and was expected to increase with extended reaction time. The high enthalpy of the steam and refined glycerol gave 78.64% of energy conversion efficiency, which was 2.98% more than the normal water/oil injection method.;The experimental data allowed the use of two famous methods for determining thermochemical properties; Peng-Robinson departure functions and the Joback group contribution method gave the kinetic model of the continuous hydrolysis reaction, including four equilibrium constants and eight rate constants of the reaction steps. The results provided the activation energy for all forward and reverse reactions under a variety of reaction temperatures. In addition, the results indicated that diglycerides (DG) in the lipid feedstock reduce the induction period for hydrolysis. Moreover, mass balance was found to be conserved by observing uniform carbon distribution. The results from kinetic modeling of hydrolysis, coupled with thermophysical and thermochemical properties as well as liquid flow behavior, were used to develop a CFD model using ANSYS-CFX software. By showing good agreements with experimental data, the concentration distribution of every component of hydrolysis was predicted.;FFA product from continuous hydrolysis reaction, composed of palmitic, oleic, linoleic, linolenic, stearic, arachidic and behenic acids, was fed into a catalytic fed-batch deoxygenation process at an average rate of 15.5 mmoles/min. With a constant temperature of 300°C and a constant pressure of 19 bar and 100g of 5% Pd/C catalyst in H2 and He atmosphere, the liquid product, contained mostly heptadecane, was a drop-in replacement for petroleum diesel fuel. |
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