Modelling mass transfer from a packed bed by fluid extraction

A mathematical model describing the erosion or leaching of a solid material by flowing fluid in column is developed. This involves an advection-diffusion equation coupled to linear kinetic reaction mass transfer between and fluid. Two specific cases are analysed, first where extracted has same saturation solubility rate throughout process, second switches after certain amount erosion. In case there only two unknowns, coefficient, third unknown, solubility. Exploiting fact that slow process (relative flow rate) perturbation solution based on smallness removed developed describe concentration radius column. From this analytical expression for fraction obtained. The large section which results simple calculation estimate initial from very few even single data point. remaining unknowns may also be easily calculated formula later points. numerical solution, using finite differences, verify solution. verified against experimental removal lanolin wool fibres with supercritical CO2/ethanol solvent. Values solubilities obtained different pressures shown provide excellent agreement series fraction.