科研之友
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摘要
A multiphase volume of fluid (VOF) model was developed to provide a more detailed understanding of the transient behavior of a laboratory-scale trickle-bed reactor. The gas-liquid flow through a catalytic bed of spherical particles was used to compute velocity field and liquid volume fraction distributions considering interfacial phenomena as well as surface tension effects. The computational model was used to simulate the catalytic wet air oxidation of a phenolic model solution in the multiphase reactor. Several runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the total organic carbon concentration and temperature profiles. In all runs, some level of backmixing was predicted, being lower at high operating temperatures. These axial concentration profiles were then Correlated with the radial ones revealing a poor radial mixing for the simulated flow regime, namely, at the hot spots. The influence of the operating temperature on the thermal profiles illustrated the existence Of Such hot spots located in the first quarter of the axial coordinate with an intensity about 6% higher than the inlet and wall temperatures. The transient radial temperature profiles corresponding to the hot spot showed the same intensity as was found for the axial thermal profiles, indicating the existence of considerable radial gradients that sustained the poor radial mixing in downflow operating mode. Despite the qualitative differences attained for the shapes of the thermal profiles, one should bear in mind that the maximum difference between the computed results and experimental data was lower than 1.5%, which reinforces the validation of the computational fluid dynamics (CFD) approach at reacting flow conditions.
- 出版日期2010-3-17
