We determined the effect of pressure drop (Delta P) in a 3.6-m tall vessel on the CO2 extraction of Citrus Peel Oil (CPO). We represented mass transfer using a linear-driving-force model and a pseudo-Sips' desorption isotherm for CPO. A single microstructural factor (877) was estimated from literature data on CPO extraction at several extraction conditions. We simulated the effect of Delta P on CPO extraction at 50 degrees C varying particle diameter (0.5 <= d(p) <= 2 mm), bed porosity (0.20 <= epsilon <= 0.35), and inlet CO2 pressure (9 <= P-in <= 10 MPa) under incipient fluidization conditions. The negative effect of Delta P on CPO extraction increased markedly as d(p), or epsilon decreased, or as P-in, increased, with a 1.8 time increase in extraction time as compared to isobaric conditions when using 4.54 kg s(-1)M(-2) of CO2 at 50 degrees C and 10 MPa (d(p)= 0.5 mm and epsilon = 0.30).