Two-dimensional heterogeneous pseudocontinuous models are effectively used to simulate the performances of honeycomb structured catalysts in non-adiabatic reactors. The quality of the simulations, however, strongly relies on the ability to correctly predict the effective axial and radial thermal conductivities of the structured support, as well as the wall heat transfer coefficient. In this paper, literature correlations for the calculation of the effective radial conductivity of honeycomb monoliths are critically reviewed. It is shown that all of them result in predicted values of the effective radial conductivity that may differ from the exact value even significantly. An engineering correlation recently proposed by our group overcome this issue. Since most of the simulation papers reported in the literature are based on previous effective radial conductivity models, it is essential to verify the extent of the deviations between the temperature profiles simulated with our new model and with previous models. To this purpose, a direct comparison is herein carried out by using a relevant case study, i.e. the simulation of an innovative reactor for the Fischer-Tropsch synthesis based on highly conductive honeycomb monoliths, washcoated with a cobalt-based catalyst. It is shown that in the case of highly conductive honeycomb monoliths the wall heat transfer coefficient is the limiting factor in the overall heat transfer performances of the reactor. Accordingly, the scatter in the predictions of the effective radial conductivity by different models only results in minor variations of the simulated thermal behavior of the reactor.
On the effective radial conductivity of highly conductive honeycomb structured catalysts
VISCONTI, CARLO GIORGIO;GROPPI, GIANPIERO;TRONCONI, ENRICO
2013-01-01
Abstract
Two-dimensional heterogeneous pseudocontinuous models are effectively used to simulate the performances of honeycomb structured catalysts in non-adiabatic reactors. The quality of the simulations, however, strongly relies on the ability to correctly predict the effective axial and radial thermal conductivities of the structured support, as well as the wall heat transfer coefficient. In this paper, literature correlations for the calculation of the effective radial conductivity of honeycomb monoliths are critically reviewed. It is shown that all of them result in predicted values of the effective radial conductivity that may differ from the exact value even significantly. An engineering correlation recently proposed by our group overcome this issue. Since most of the simulation papers reported in the literature are based on previous effective radial conductivity models, it is essential to verify the extent of the deviations between the temperature profiles simulated with our new model and with previous models. To this purpose, a direct comparison is herein carried out by using a relevant case study, i.e. the simulation of an innovative reactor for the Fischer-Tropsch synthesis based on highly conductive honeycomb monoliths, washcoated with a cobalt-based catalyst. It is shown that in the case of highly conductive honeycomb monoliths the wall heat transfer coefficient is the limiting factor in the overall heat transfer performances of the reactor. Accordingly, the scatter in the predictions of the effective radial conductivity by different models only results in minor variations of the simulated thermal behavior of the reactor.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
