Studies On Mass Transfer Characteristics Of Palm Kernel Oil Extraction Using Supercritical Carbon Dioxide

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Date
2005-05
Authors
Ismail, Norhuda
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Universiti Sains Malaysia
Abstract
To exploit further the application of supercritical carbon dioxide (SC-COz) extraction, as a simplified and environmental friendly process, a study on the palm kernel oil yield, fundamental of diffusivity and mass transfer coefficients of palm kernel oil in situation of overall single palm kernel and a packed-bed column of the overall single palm kernels was studied. The study also incorporated mathematical models formulation for describing the mass transfer phenomena of palm kernel oil at the supercritical conditions. Thus, this study has focused on the candidate sample of overall single palm kernels of size 6 mm (outside diameter) by using a laboratory Supercritical Carbon Dioxide (SC-CO2) equipment. The experimental runs of the supercritical conditions considered in this study vary in a range of temperatures and pressures of 40 °C, 50 °C, 60 °C, 70 °C and 80 °C and pressures of 27.6 MPa, 34.5 MPa, 41.4 MPa and 48.3 MPa respectively for an overall single palm kernel, and at a constant temperature of 50 °C, 60 °C and 70 °C and within the same pressure range for a packed bed of overall single palm kernels. The findings of this study on an overall single palm kernel, demonstrated that first, the laboratory SC-CO2 extraction process managed to extract a maximum yield of 5 percent PKO at the best supercritical conditions of temperature 80 °C and pressure 48.3 MPa respectively. Secondly, the solubility of PKO in SC-CO2 increases with temperatures at a particular constant pressure, and likewise increases with pressures at a particular constant temperature. Thirdly, the study shows that the diffusion coefficients of PKO at the supercritical condition, based on an overall single palm kernel, is strongly dependent on pressures from 27.6 MPa to 48.3 MPa, at each constant temperature of 50 °C, and 60 °C. Nevertheless, a weak correlation between diffusion coefficients with pressures was found at each constant temperature of 40 °C, 70 °C and 80 °C. Similarly, findings from this study also showed that at a constant temperature of 50 °C, and 60 °C, the overall mass transfer coefficients increases with pressures from 27.6 MPa to 48.3 MPa. But, at a constant temperature of 40 °C, 70 °C and 80 °C, no increasing trend of the overall mass transfer coefficients of PKO with pressure could be observed.In another SC-CO? studies, for extraction of PKO from a packed bed of palm kernels in a laboratory scale extractor, show that a maximum amount of 15 percent PKO can be extracted at the best supercritical conditions of temperature 70 °C and pressure 48.3 MPa. The studies also demonstrated that the diffusion coefficients of PKO in a packed bed of overall single palm kernels are dependent on pressures rather than temperatures. In a similar study, it was found that the overall mass transfer coefficients of PKO from a packed bed of overall single palm kernels, dependent on both temperatures and pressures at supercritical conditions with temperature range from 50 °C to 70 °C and pressure range from 27.6 MPa to 48.3 MPa respectively. A mass transfer correlation model was developed for palm kernel oil extraction in a packed bed of overall single palm kernels.The mathematical empirical model developed is given by Sh = 0.980 ReSc best-fit equation for correlating the experimental results of the Sherwood, Schmidt and Reynolds numbers for PKO extraction over the entire range of pressures and temperatures of 27.6 MPa to 48.3 MPa and 50 °C to 70 °C respectively.
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