A Novel Method for Evaluation of the Flow Field Effects on Mean Drop Size in a Multiphase CFB

Abstract

Prompt evaporation of injected liquid drops near the injectors locating in the FCC unit riser reactor has considerable impacts on the gas–solid mixing phenomena. To investigate influencing various parameters on the injected liquid species in the riser, conservation equations are primarily needed. A novel model to predict droplet mean diameter (DMD) due to computing penetration depth of the jet flowing through the riser was proposed. The proposed model is able to indirect predict DMD based on direct computation of spray tip penetration (STP). The model has been validated by some empirical correlations. In this study, influencing gas superficial velocity, liquid injection velocity, jet angle and nozzle diameter on DMD were investigated. The results for both concurrent and counter-current flows showed that the decrease of jet angle and injection velocity improves DMD. In addition, increasing orifice diameter (as a structural parameter) arising mean drop size can decline performance of atomizing. It also displayed close agreement between the model predictions and experimental data. In this work, the measurement error associated with STP was determined up to 2.7 mm, and the mean relative error with respect to detecting STP is 4.3%.