Recent Example of Model Building and Application Radioactive

Recent Example of Model Building and Application Radioactive Tracer Studies in Bubble Columns for Dimethyl Ether (DME) Synthesis P. Chen, P. Gupta, M. P. Duduković, B. A. Toseland Tracer 3 International Conference Ciechocinek, Poland June 22 – 24, 2004 Full paper submitted to Chemical Engineering Science http: //crelonweb. wustl. edu

Radioactive Tracer Studies in Bubble Columns for Dimethyl Ether (DME) Synthesis P. Chen, P. Gupta and M. P. Duduković Chemical Reaction Engineering Laboratory Washington University, St. Louis, USA Bernard. A. Toseland Air Products & Chemicals, Inc. , USA Tracer 3 June 22 – 24, 2004 Ciechocinek, Polland

Objectives Æ Determine the extent of liquid and gas backmixing in a pilot plant bubble column for DME synthesis Æ Determine the motion of dispersed catalyst relative to liquid Æ Evaluate the ability of phenomenological models developed in CREL to predict slurry and gas flow patterns and mixing

Reactions and Operating Condition Dual-catalyst system containing a commercial proprietary methanol synthesis catalyst and a commercial dehydration material Operating Temperature (K) 523. 0 Operating Pressure (MPa) 5. 27 Inlet Superficial Gas Velocity (m/s) 0. 17 Outlet Superficial Gas Velocity (m/s) 0. 13 Change in Flowrate (%) 21. 6 Average Superficial Gas Velocity (m/s) 0. 15 Liquid/Slurry Superficial Velocity (m/s) 0. 0

Reactor Set-up and Schematic Location of Scintillation Detectors Center injection point N Sidewall injection point W E Injection line S Syngas/Products Out DET 7 DET 6 DET 5 DET 4 DET 3 DET 2 DET 1 DET 0. 46 m 1. 52 m 9. 66 m 1. 83 m N 1 2. 74 m 13. 25 m DET 2. 74 m Liquid/Catalyst Injection to Wall (N 1 -Sidewall) 3. 56 m Liquid/Catalyst Injection to Center (N 2 -Center) N 2 Liquid/Catalyst Injection to Wall (N 2 -Sidewall) 0. 61 m 1. 74 m Liquid/Catalyst Injection to Center (N 1 -Center) DET 1. 52 m Fresh Feed Recycle DET Syngas Gas Tracer Injection

Individual detector responses to N 2 Center and Sidewall injections N 2 Center N 2 Sidewall

Schematic representation of the experimentally observed phenomena in bubble columns and the basis for the gasliquid mixing model with interphase mass transfer 1 -e. L(r) Gas Velocity Profile Dxx Liquid Velocity Profile Gas Holdup Profile r' u. L (r) r'' 0 Drr R Liquid Velocity Profile -R 0 R

Sample of model equations

Determination of model parameters Two-fluid hydrodynamic model - Continuity Equation - Momentum Equation - Mixing length closure (Kumar et al. , 1995) - Drag force (Tomiyama et al. , 1997) Liquid velocity profile Gas velocity profile Bubble diameter

Determination of model parameters n Average gas/liquid velocity and holdup in compartment n n Eddy diffusivity n n From Degaleesan’s (1997) correlation Interfacial area concentration n n From velocity and holdup profile of gas and liquid phases From gas holdup and bubble diameter Mass transfer coefficient n From molecular diffusivity, bubble diameter and gasliquid slip velocity in compartment

Gas and liquid backmixing parameters used in model predictions

Reproducibility of gas and liquid tracer responses N 2 center

Comparison of model prediction and experimental data for N 2 Center and Sidewall injections of “liquid” and catalyst tracers liquid catalyst

Comparison of model prediction and experimental data for N 1 Center and Sidewall injections of catalyst tracer

Conclusions n n n The pseudo-homogeneous assumption is valid. “Liquid” and catalyst tracers exhibit the same dynamics. The gas and liquid re-circulation with mixing model is able to predict the characteristic features of the experimental responses observed for gas, slurry powder and catalyst tracers at different reactor elevations. This model offers a relatively simple tool for assessing mixing and transport in bubble columns for a variety of gas conversion processes and provides a phenomenological framework for bubble column reactor modeling and design.