Analysis of the kinetics of regeneration of bidispersed activated granular carbon, by supercritical carbon dioxide

A desorption of m-xylene by supercritical CO2 under different temperatures (40, 50 and 60 °C) and pressures (80, 100 and 128 bar) has been modelled using the analytical solution expressing the desorption yield for bidisperse granular activated carbon. This solution is in the form of an infinite double series. The coefficients of which were calculated by solving the transcendental equation using the method of Newton–Raphson. Solutions of first and second order of this equation determine the coefficients of the analytical solution. The results of this modelling, including macropore and micropore diffusion, show very good concordancy between experimental and simulated data for all operating conditions, which confirms the appropriateness of this model for this type of adsorbent considered. Only the equilibrium adsorption constant “KC” was used as adjustable parameter. The values of KC varied between 13.32 and 121.33 and the maximum average deviation between estimated and fitted values not exceeding 6.54%. On the other hand, it has been particularly highlighted for the experimental conditions studied, that the contribution of resistance due to external transfer and axial dispersion were negligible and that the resistance due to macropore diffusion was consistent and it was possible to reduce the time of desorption by reducing the size of the grain.