Experiment And CFD Numerical Simulation Study Of Hydrodynamics And Mixing Characteristics Of Slight Expanded Bed Reactor

The slight expanded bed reactor is a new one used in residue hydro-treating. It has some advantages compare with trickle bed reactor, such as lower growth rate of pressure drop, longer operation period, and better flexibility of crude material. But there are also some problems emerged in industrial operation, such as coke, hot point, temperature runway. So, it is greatly significant to study slight expanded bed reactor for finding out the causes of the problems and proposing solutions.Experiments are operated in a laboratory slight expanded bed reactor. Water and air are used as liquid phase and gas phase, three different catalysts, sphere, toothed ball and cloverleaf, are used as packed particles. Superficial gas velocity ranges from0.0088m/s to0.0531m/s, superficial liquid velocity ranges from0.0018m/s to0.0053m/s. Parameters, such as flow regime, pressure drop, expansion ratio, gas holdup and axial dispersion, are investigated. The main conclusions are as follows.1.The flow regimes of gas and liquid phase are bubble flow, water is the continuous phase, air passes though the water as bubbles. The bottom part of the bed is stationary, and the top part of the bed is slightly expanded or fluidized.2.Pressure drop decreases along with increasing axial height. Total bed pressure drop of the three kinds of catalysts are in the order of:sphere> toothed ball> cloverleaf. The correlation for calculating pressure drop is:3.Bed expansion ratio of the three kinds of catalysts are in the order of: cloverleaf> toothed ball> sphere. The correlations for calculating expansion ratios are:(1) sphere catalyst:φ=720.5uG131uL0.21(2) toothed ball catalyst:φ=888.9uG142uL0.15(3) cloverleaf catalyst:φ=812.4uG133uL0.154.Gas holdup of the three kinds of catalysts are in the order of: cloverleaf> toothed ball> sphere. The correlation for calculating gas holdup is:5.Pe number decreases along with increasing axial height. Total Pe number of the three kinds of catalysts are in the order of:sphere> toothed ball> cloverleaf. The correlation for calculating total Pe number is:6.The results of CFD simulation are in accordance with the experimental phenomena and can provide explanations for the results of the experiments.