CFD Characerization of Monolithic Reactors for Kinetic Studies

Artikel i vetenskaplig tidskrift, 2014

A laboratory reactor for kinetic studies has been simulated using computational fluid dynamics (CFD). Analysis of temperature distribution within the system shows that adding an inert monolith upstream the catalyst enhances heat conduction and therefore significantly reduces radial temperature gradients. Adjustment of the heating coil plays an important role as well by allowing the gas phase to smooth out the radial temperature profile. Radiative heat transfer and its effects on both the heat losses from the catalyst and on the measurements with an unprotected thermocouple have been particularly investigated. In order to prevent both the falsifying effect of radiation and the influences from the ongoing reaction, thermocouples should be placed and shielded inside a clogged channel. An inert monolith that is placed downstream the catalyst effectively serves as a radiation shield and drastically reduces both axial and radial gradients. Studies of the dispersion in the system reveal that the FTIR's gas cell is the most important source of the overall broadening in the concentration signal, with the reactor tube being the next major source of the distortion. An algorithm based on the Tikhonov regularization method has been developed for calculating the deconvolution of the concentration data, which has refined the time-resolution in transient experiments from 20 to 2 s.