Numerical integration strategies of PFR dynamic models with axial dispersion and variable superficial velocity: the case of CO2 capture by a solid sorbent

In order to integrate mole balances (partial differential equations) of an Axial Dispersion Plug Flow Reactor (ADPFR) model, the overall superficial velocity is usually considered constant, a hypothesis which fits well only null or negligible variations of volumetric flow rate, e.g. feeding flow strongly diluted by inert species. This work proposes a numerical-integration approach (based on the method of lines) for ADPFR dynamic modelling, applied to simulate the CO2 capture in an isothermal-isobaric packed bed, made of purposely synthesized and experimentally characterized CaO-mayenite sorbent particles. This approach proved to be suitable for both constant and variable superficial velocity with respect to time and space. With the latter option, velocity profiles agreed with simulated reactive phenomena, while discrepancies between solutions from the two options became increasingly evident as dilution of inlet CO2 decreased. N2 flow rate and CO2 mole balances obtained from numerical-integrations with variable superficial velocity appeared as the most physicochemically reasonable.