Canadian Journal of Chemical Engineering, Vol.94, No.5, 886-895, 2016
Low-temperature experimental model of liquid injection and reaction in a fluidized bed
In several commercial processes, liquid is injected into a hot fluidized bed, where it undergoes a reaction that generates gases, vapours, and a solid residue. An example is Fluid Coking(TM), where large agglomerates resulting from poor liquid-solid contacting during the liquid injection are undesirable. These agglomerates limit heat and mass transfer, leading to operating problems and a reduction in valuable product yield. Performing experiments in pilot plants for such processes is difficult because of the high required temperature, e.g. 550 degrees C for Fluid Coking. It is very difficult to determine the proportion of fresh coke residue in agglomerates recovered from a pilot plant, which is essential information for understanding agglomerate formation. This study presents a low-temperature experimental model that would be much easier and safer to use than a Fluid Coking pilot plant, while providing more information on agglomerate formation and breakup. A solution comprising Plexiglas(TM) dissolved in acetone and pentane is injected into a fluidized bed of sand particles at 68 degrees C to simulate heavy oil injection which, in Fluid Cokers(TM), gives off gases and vapours, simulated by the vapours from the solvents in the Plexiglas solution, and a solid coke residue, simulated by the Plexiglas deposit on sand particles. The experimental model was tested with three separate methods that have been found to reduce agglomerates in commercial or pilot plant Fluid Cokers: increasing the flowrate of atomization steam in liquid spray nozzles, increasing the fluidization velocity, and increasing the bed temperature.