A new method has been developed to predict the horizontal jet penetration of gas-liquid sprays injected into gas-solid fluidized beds. The technique involves combining a theoretical model to predict the momentum flux of two-phase sprays with the Benjelloun et al. (1995) correlation for gas jets. Following this treatment, a generalized version of the jet penetration correlation has been developed, which includes the effect of nozzle geometry. The correlation predictions are in very good agreement with the experimental data for a wide range of nozzle geometries, nozzle scales, and jet fluids.
The injection of a gas−liquid spray jet into a fluidized bed of particles is used in many applications
such as fluid catalytic cracking or fluid coking. In such applications uniform contact of the liquid
droplets and entrained particles is essential for high yields. The objective of this study is to
measure the quality of the solid−liquid mixing when a gas−liquid jet is injected into a fluidized
bed of coke particles. A quick method has been developed to determine the local quality of solid−liquid mixing on a short time scale. The measuring technique uses temperature to characterize
the solid−liquid mixing. Cold ethanol is injected into the fluidized bed via a two-phase spray
nozzle and is mixed with the heated fluidized coke particles. An assembly of fast response
thermocouples, located downstream of the gas−liquid spray jet, provides instantaneous
temperature readings over the liquid spray jet cross section at different axial positions along
the length of the jet. In the case of perfect mixing, the temperature should be the same at each
radial position. From the variations of the time-averaged temperature, contour plots of the liquid/solid distribution within the cross-sectional area of the jet are created. This technique is used
to compare solid−liquid mixing for two cases: when the spray is introduced as a free jet and
when a draft tube is placed downstream of the gas−liquid spray. The use of a draft tube is
found to improve liquid/solid mixing. The measurement technique has proven to be a reliable
method to determine the liquid/solid distribution in the cross section of the jet. It shows that
very good and rapid contact between sprayed droplets and particles can be achieved by using a
draft tube mixer.
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 8C 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 8C 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.
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