UBC Theses and Dissertations
Comprehensive modelling and its application to simulation of fluidized-bed reactors for efficient production of hydrogen and other hydrocarbon processes Mahecha-Botero, Andrés
A generalized comprehensive model, coupled with experimentation in a pilot reactor, is developed to simulate the performance of fluidized-bed catalytic reactors. The model characterizes multiple phases and regions (low-density phase, high-density phase, staged membranes, freeboard region) in different geometries. It accounts for conventional and balancing interphase transfer, catalytic reaction, solid sorption, change in molar/volumetric flow, temperature and pressure profiles, anisotropic dispersion, hydrodynamic regime variation, catalyst deactivation, energy options, feed distribution along the reactor, selective membranes, fluidization hydrodynamics and dynamic behaviour. It also allows for seamless introduction of features and/or simplifications depending on the system of interest. The literature is comprehensively analyzed, reviewing the most important models proposed since 1952. A systematic algorithm for formulating chemical/biochemical reaction engineering problems is developed for systems of different complexity. Simulations are conducted for specific processes including: 1) steam methane reforming (SMR) for production of ultra-pure hydrogen, 2) oxychlorination of ethylene to ethylene dichloride, 3) partial oxidation of n-butane to maleic anhydride, and 4) partial oxidation of naphthalene to phthalic anhydride. Special emphasis is dedicated to steam reforming in fluidized-bed membrane reactors comparing their performance under bubbling, turbulent and fast fluidization regimes in a variety of configurations. Bubbling regime simulations predict somewhat less hydrogen production due to the effects of conventional and balancing interphase mass transfer. Overall reactor performance is predicted to be best under turbulent fluidization operation. A concomitant experimental program was performed to collect detailed experimental data in a novel pilot scale prototype reactor operated under SMR and auto-thermal reforming (ATR) conditions, without and with membranes of different areas under diverse operating conditions. Hydrogen permeate purity of up to 99.995+% as well as a pure-H₂-to-methanes yield of 2.07 were achieved with only half of the full complement of membrane panels active. A permeate-H₂-to reactor methane feed molar ratio >3 was achieved when all of the membrane panels were installed. The reactor model is tested with no adjustable parameters by comparing predictions against axially distributed concentration in the pilot reactor, leading to reasonable agreement and better understanding of a variety of phenomena.
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