Effect of heat transfer on the pressurization, extraction, and depressurization stages of a supercritical CO2 extraction process. 1. Development and validation of the heat transfer model

Abstract

We modeled and simulated the heat and mass transfer in the depressurization, pressurization, and extraction stages of a supercritical CO2 extraction process. Parameters of a Nusselt correlation for convective wall-to-fluid heat transfer coefficient were best fitted to experimental temperatures during the depressurization of vessels packed with different materials. Heat transfer in the pressurization and extraction stages was simulated predictively using this correlation and compared with literature laboratory-scale, pressurization, and extraction data. In depressurization, simulated temperature, pressure, and vented mass flow profiles agreed reasonably well with experimental values, as the calculated Mean Absolute Percent Error (MAPE) was 1.8% for the temperature. For pressurization, simulated values of final temperatures and pressures fell within a standard deviation of experimental data, estimating a MAPE of 3.9% for temperature and 5.2% for pressure. In the extraction stage, including radial and axial temperature gradients in the mass transfer model reduced the error (about 2%) of simulated cumulative extraction curves against experimental values compared to those obtained when neglecting radial variations in temperature. These results are significant because they prove that heat transfer phenomena may impact industrial more considerably than laboratory-scale processes.