An Optimization Study by Response Surface Methodology (RSM) on Viscosity Reduction of Residue Fuel Oil Exposed Ultrasonic Waves and Solvent Injection

In this study, response surface methodology (RSM) based on central composite design (CCD) was applied for investigation of the effects of ultrasonic waves, temperature and solvent concentration on viscosity reduction of residue fuel oil (RFO). Ultrasonic irradiation was employed at low frequency of 24 kHz and power of 280 W. The results showed that the combination of ultrasonic waves and solvent injection caused viscosity to further reduce. To obtain optimum conditions and significant parameters, the results were analyzed by CCD method. In this method, maximum viscosity reduction (133 cSt) was attained in ultrasonic irradiation for 5 min, temperature of 50°C and acetonitrile volumetric concentration of 5% by means of experimental and three dimensional response surface plots. The kinematic viscosity decreased from 494 cSt to 133 cSt at the optimum conditions. In addition, a multiple variables model was developed by RSM, wherebythe second-order effect of ultrasonic irradiation time was significant on viscosity reduction of FRO. Finally, a comparison between the RSM and artificial neural network (ANN) was applied. The results demonstrated that both models, RSM and ANN, with R2 more than 0.99 were powerful in prediction of kinematic viscosity of RFO.