The Study of Parameters in Supercritical Carbon Dioxide Extraction of Oil by Response Surface Methodology

Response surface methodology was applied in this study to optimize the operating
parameters of supercritical carbon dioxide (SC-CO2) extraction of wheat bran oil
(WBO) and rice bran oil (RBO). The effect of operating temperature, pressure and
carbon dioxide (CO2) mass on the oil yield were studied. First, the design was carried
out following a Box-Behnken design of experiment for the WBO, the independent
variables were the temperature (40, 50 and 60 oC), pressure (10, 20 and 30 MPa) and
CO2 mass (400, 1825 and 3250 g). Second, 3-level factorial design for RBO, the
independent variables were the temperature (45, 65 and 85 oC) and pressure (20, 27.5
and 35 MPa). The study showed that the second-order polynomial model was
sufficient to be used and best fit of the data. The optimal conditions predicted within
these experimental ranges were at 29.4 oC, 60 MPa and 3250 g, the maximum oil
yield was 2.97 g/12g of wheat bran for the WBO. The operating temperature,
pressure and CO2 mass proved significant effect in increasing the yield of WBO
while these parameters increased. For the RBO, optimal conditions were at 45 oC and
35 MPa, the maximum oil yield predicted was 0.23 kg/kg of rice bran for RBO. The
operating temperature increase effect in decreasing the yield of RBO while the
pressure has the significant effect in increasing the RBO yield.
From the result, the extraction process has not been optimized yet because the
optimal operating conditions were predicted at the maximum value of each
parameter. However, the suggestion is to further conduct the additional experiments
in a wider range of parameters in order to get the best result and more accurate
optimum value of parameters. Lastly the economic feasibility study was conducted
for the supercritical carbon dioxide extraction of RBO plant and it is economically
justified.