Abstract This work represents the extraction of oilsand free fatty acids from the spent bleaching earth using sub-critical water as a solvent in pilot scale batch reactors. Prior to using the pilot scale reactors, the extraction conditions were optimized using laboratory small batch reactor of 34 cm3 volume. The optimization of the extraction condition showed that the optimum temperature, feed to solvent ratio, and extraction time were 270 °C, 1:3(the solvent is just water), 20 min. The obtained data were used to design tubularreactor with 7 Kg capacity heated with an electric heater. The extraction was carried out using 750 grams of the spent bleaching earth with 1:3 ratio. The results showed that more than 95% of the oil absorbed in the spent bleaching earth was recovered under 210 0C. The heating up period was 72 minutes with holding extraction time of 20 minutes at 210 0C and cooling down for 25 minutes.