An emulsion phase condensation model to describe the defluidization behavior for reactions involving gas-volume reduction

The fluidization quality decreases drastically when the reactions involving a gas volume decrease were carried out in a fluidized bed reactor. The model to describe the defluidization behavior for reactions involving gas-volume reduction is highly required to choose proper operation parameters. Herein a phase condensation model is proposed to describe the fluidization and the transfer behavior of the chemical reactions involving a gas volume decrease when they are carried out in a fluidized bed reactor. The phase condensation model concerns an emulsion phase domain. The mass transfer between bubbles and the modeling domain, the governing equations for the hydrodynamics and mass transport, the Brinkman equation, together with the kinetic sub-model are incorporated in the model. The simulation result captures the spatial distribution of reactant concentration and gas velocity which is onion-shaped for the CO2 hydrogenation reaction. The fluidization quality can be predicted by the phase condensation model. The result indicates that lower temperature and higher inert gas content in the feed gas are favorable for good fluidization. A phase diagram of fluidization quality is obtained using temperature and expansion factor as indices. The phase condensation model renders the precise prediction which compares well with published experimental data.

Graphical abstractA phase diagram for fluidization quality in fluidized-bed reactor with reactions involving gas volume reduction carried on is provided by the phase condensation model. The solid line refers to conditions in which the minimum gas velocity in the emulsion phase equals umf. The left side region of the line indicate stable operation conditions while in the above region of the line, poor fluidization even defluidization may occur. Four kinds of fluidization phenomena are observed at different operation parameters in experiments. The experiment results are in good accord with division of operation regions by simulation results, showing the credibility and good prediction of the emulsion phase condensation model.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► An emulsion phase condensation model to describe the fluidization of reactions involving a gas volume decrease. ► Onion-shaped distributions of reactant concentration and gas velocity in the emulsion phase. ► The minimum gas velocity, emulsion phase voidage and the fluidization quality are predicted. ► The prediction of the fluidization quality and the fluidization diagram fit well with the published experiment results.