Experimental and Computational Fluid Dynamics Investigations of Light Alkane Dehydrogenation in a Fluidized Bed Reactor

An experimental setup and a three-dimensional computational fluid dynamics (CFD) model are developed for a light alkane (pure propane, iso-butane, n-butane, and their mixtures) dehydrogenation reactor that is a key part of a pilot-scale circulating fluidized bed (CFB) apparatus. Experimental findings indicate that the reaction temperature (T) and the gas hourly space velocity (GHSV) have a significant influence on the dehydrogenation process of the different light alkanes. As for propane and under the optimal conditions of T = 600 °C and GHSV = 2350 h^-1, the conversion of C₃H₈ is 39% and the yield of C₃H₆ is 33%. The conversion of i-C₄H₁₀ is found to be 49%, and a yield of 45% for iso-butane (i-C₄H₈) under the conditions of T = 580 °C and GHSV = 1700 h^-1 is achieved. For n-butane and under the conditions of T = 580 °C and GHSV = 1700 h^-1, the conversion of n-C₄H₁₀ reaches 40% with a yield of 32%. Optimal conditions for the different light alkanes' mixtures are also obtained. A 3D reactive CFD model is built and validated using some of the experimental data. The CFD model validation indicates that the predicted product distributions are in very good agreement with the experimental data. Using the developed CFD model, hydrodynamics and species concentration distributions in the reactor are quantified for better understanding of the performance of the fluidized bed reactor. Using the CFD simulations together with the experimental data, material balance of the pilot-scale CFB unit for propane dehydrogenation is obtained. The CFD methodology, developed in this study, is shown to be capable of helping engineering design and operation optimization of industrial CFB used for the light alkanes' dehydrogenation process.