Method for preparing bio-oil from fatty acid with high acid value

A method for producing bio-oil, the method comprising the steps of:

• esterifying a feedstock containing glycerin and fatty acid to afford bio-oil and water in a column-type reactor which has a plurality of trays installed therein to form a plurality of compartments in the vertical direction inside the reactor, the plurality of trays each having an opening formed therein through which vertically adjacent compartments communicate with each other, with the openings in adjacent trays alternately formed in a crisscrossing manner, the feedstock containing glycerin and fatty acid being fed through respective material input ports located at a center of the column-type reactor to conduct the esterification in each tray of a reaction zone;
• obtaining the produced bio-oil through a lower part of the reactor;
• and
• removing the water produced through the esterification by vaporizing the water, moving the resulting water vapor to a distillation zone in an upper part of the reactor, along with effective ingredients including the feedstock and the bio-oil which are converted into vapor upon the vaporization, separating the vapor into water and the effective ingredients including feedstock and bio-oil on each tray in the distillation zone, and allowing the effective ingredients to flow into the reaction zone and the separated water from the vapor to be removed in a vapor state through the upper part of the reactor,
• wherein the bio-oil has an acid value of 30 mgKOH/g or lower, and the esterification reaction is performed at a reaction temperature of 170 to 350° C. under atmospheric pressure without using a catalyst.