Hydrodynamic models for slurry bubble column reactors. final technical report211 also includes the quarterly technical report for the period 01/01/1997-03/31/1997

摘要

The objective of this study is to develop a predictive experimentally verified211u001ecomputational fluid dynamic (CFD) three phase model. It predicts the gas, liquid 211u001eand solid hold-ups (volume fractions) and flow patterns in the industrially 211u001eimportant bubble-coalesced (churn-turbulent) regime. The input into the model can 211u001ebe either particulate viscosities as measured with a Brookfield viscometer or 211u001eeffective restitution coefficient for particles. A combination of x-ray and 211u001e(gamma)-ray densitometers was used to measure solid and liquid volume fractions. 211u001eThere is a fair agreement between the theory and the experiment. A CCD camera was 211u001eused to measure instantaneous particle velocities. There is a good agreement 211u001ebetween the computed time average velocities and the measurements. There is an 211u001eexcellent agreement between the viscosity of 800 (micro)m glass beads obtained 211u001efrom measurement of granular temperature (random kinetic energy of particles) and 211u001ethe measurement using a Brookfield viscometer. A relation between particle 211u001eReynolds stresses and granular temperature was found for developed flow. Such 211u001emeasurement and computations gave a restitution coefficient for a methanol 211u001ecatalyst to be about 0.9. A transient, two-dimensional hydrodynamic model for 211u001eproduction of methanol from syn-gas in an Air Products/DOE LaPorte slurry bubble 211u001ecolumn reactor was developed. The model predicts downflow of catalyst at the 211u001ewalls and oscillatory particle and gas flow at the center, with a frequency of 211u001eabout 0.7 Hertz. The computed temperature variation in the rector with heat 211u001eexchangers was only about 5 K, indicating good thermal management. The computed 211u001eslurry height, the gas holdup and the rate of methanol production agree with 211u001eLaPorte's reported data. Unlike the previous models in the literature, this model 211u001ecomputes the gas and the particle holdups and the particle rheology. The only 211u001eadjustable parameter in the model is the effective particle restitution 211u001ecoefficient.