Oxidative dehydrogenation of butane in an interconnected fluidized-bed reactor

The use of an internal circulating fluidized bed (ICFB) is proposed for the oxidative dehydrogenation of butane. The reactor consists of two adjacent Zones, separated by a wall. In the oxidizing zone the catalyst is oxidized and in the reducing zone the butane is dehydrogenated by reaction with the oxygen from the catalyst lattice. The circulation between both zones is produced by the different bed porosity, which originates a pressure difference between the two zones at the communication orifice at the bottom of the vessel. The design of this reactor is studied in a cold model. An image analysis technique was applied to measure solid circulation rates between the different regions in the reactor, by using a solid coated with a long afterglow phosphor as a tracer. The solid circulation rates through the orifices were found to correlate reasonably well with a previously developed correlation for the orifice drag coefficient. The model for solid circulation between fluidized regions was then integrated in the overall mathematical model for the ICFB reactor system to incorporate the effect of design and operating conditions on the catalyst circulation rates between compartments. A good correlation between the experimentally obtained values of conversion and selectivity anti those predicted by the model is obtained. Improvements in selectivity to olefins are obtained, compared with conventional fluidized-bed reactors with cofeeding of reactants. (C) 2004 American Institute of Chemical Engineers.