Journal of Supercritical Fluids, Vol.13, No.1, 343-350, 1998
Evaluation of the effects of process variables on the characteristics of the products from SCFE of a Brazilian mineral coal by statistical methods
The influence of some process variables on the productivity of the fractions (liquid yield times fraction per cent) obtained from SCFE of a Brazilian mineral coal using isopropanol and ethanol as primary solvents is analyzed using statistical techniques. A full factorial 2(3) experimental design was adopted to investigate the effects of process variables (temperature, pressure and cosolvent concentration) on the extraction products. The extracts were analyzed by the Preparative Liquid Chromatography-8 fractions method (PLC-8), a reliable, non-destructive solvent fractionation method, especially developed for coal-derived liquids. Empirical statistical modeling was carried out in order to reproduce the experimental data. Correlations obtained were always greater than 0.98. Four specific process criteria were used to allow process optimization. Results obtained show that it is not possible to maximize both extract productivity and purity (through the minimization of heavy fraction content) simultaneously by manipulating the mentioned process variables.
Keywords:SUPERCRITICAL EXTRACTION