Performance studies of trickle bed reactors.

摘要

A thorough understanding of the interaction between kinetics, transport, and hydrodynamics in trickle bed reactors under different reaction and operating conditions is necessary to design, scale-up, and operate them in such a way as to achieve the best performance. In this study, systematic experimental and theoretical investigations have been carried out to study trickle bed performance in different modes of operation and reaction conditions in order to improve our understanding of the factors governing scale-up and performance.; The first part of this study is focused on comparison of performance of down-flow (trickle bed reactors-TBR) and up-flow reactors (packed bubble columns-PBC) without and with fines to assess their applicability as test reactors for scale-up and scale-down studies for different reaction systems (gas and liquid reactant limited). This has been accomplished by experimentation on hydrogenation of α-methylstyrene to cumene, and, by comparing the predictions of existing models for both modes of operation with each other and with the data. Comparison of results obtained at different pressures, liquid reactant feed concentrations, and gas flow rates has been presented, and differences in performance of the two reactor modes of operation explained on the basis of the observed shift from gas limitation to liquid limitation. Experiments in the bed diluted with fines have been conducted to demonstrate the fact that hydrodynamics and kinetics can be decoupled by using fines. A rigorous steady state model for reactor and pellet scale flow-reaction-transport phenomena based on multicomponent transport is proposed to overcome assumptions in earlier models such as non-volatile reactants, dilute solutions, isothermal, isobaric operation, and constant phase velocities. Predictions of this model are compared against data available in the literature for a system with volatile liquids.; The second part of this study is devoted to investigating the performance of trickle bed reactors under unsteady state liquid flow modulation (periodic operation) for gas and liquid limited reactions. The effect of key parameters such as extent of gas/liquid limitation, total cycle period, cycle split, liquid mass velocity, and liquid-solid contacting have been investigated experimentally to demonstrate the cause-effect relationships in unsteady state operation. Rigorous modeling of the interphase transport of mass and energy based on the Stefan-Maxwell approach at the reactor and catalyst level has been used to simulate the processes occurring under unsteady state conditions for a general multi-component system. Reactor performance results for several flow modulation simulation tests for a hydrogenation reaction have been presented and discussed.