SLURRY BUBBLE COLUMN HYDRODYNAMICS - Progress Report - Novica S. Rados Department of Chemical Engineering, CREL Washington University, St. Louis April 12, 2001

CHEMICAL REACTION ENGINEERING LABORATORY Motivation and Objectives There is a lack of experimental data on slurry bubble columns operated at these conditions. Develop a new CARPT calibration apparatus and scanning procedure that can be used for thick wall high pressure metal vessels. Slurry bubble columns are frequently used type of chemical reactors. They mostly operate in churn turbulent regime and at high pressure. Develop a more robust CARPT tracer particle position reconstruction algorithm that can more accurately resolve arches and other “imperfections” of the CARPT calibration (count vs. distance) curves. Acquire CARPT experimental data of a slurry bubble column operated at a wide range of gas velocities and pressures.

CHEMICAL REACTION ENGINEERING LABORATORY CARPT Calibration Device tracer particle holding rod ass. needle bearing high pressure seals PVDF guides sprocket tripod rod lead screw theta dir. stepper motor axial dir. stepper motor 8:1 gear box

CHEMICAL REACTION ENGINEERING LABORATORY CARPT Calibration Calibration yields count vs. distance curve counts = f (distance, solid angle, wall path, medium) threshold Build-up problems wall path detector crystal solid angle Compton Scattering Photo peaks Threshold = 45 mV

CHEMICAL REACTION ENGINEERING LABORATORY Spectrum Stability Acquisition of the photo peak fraction of the spectrum using a high threshold Stability of the Spectrum ? Spectrum  f (source strength) Gupta: Spectrum = f (distance) Rammohan: Spectrum = f (time) & Spectrum shifted slightly only when: - distance was changed for more than 2 ft. - order of magnitude weaker particle was used - gain wasn’t tuned over several days required nearly ideal conditions

CHEMICAL REACTION ENGINEERING LABORATORY Calibration Curve Detector alignment and pile-up problems Detectors well aligned and further away Threshold = 600 mV G-L: Ug=30cm/s Det #7

CHEMICAL REACTION ENGINEERING LABORATORY Pile Up Limitations Pile up: Detectors are unable to count all incoming photons Detectors too close ! + Distorted Spectrum + Detectors further away ! + Well Shaped Spectrum + When using the photo peak fraction of the spectrum C Max < 1000 detector crystal

CHEMICAL REACTION ENGINEERING LABORATORY Laser Detector Alignment - Posts not firm enough => middle detectors can vibrate / move - Angles between detectors not 45 o => mismatched particle/detector positions All detectors are within 5 degrees

CHEMICAL REACTION ENGINEERING LABORATORY CARPT - Error Analysis => assumed power law dependency error in counts = std. distribution weighing function signal to noise ratio exact error depends on the algorithm and the number of used detectors G-L: Ug=30cm/s Det #3 source strength, sampling time

CHEMICAL REACTION ENGINEERING LABORATORY Particle Position Reconstruction Algorithm Rados beta 1. Find distance using beta spline fit spline fit of the calibration curve. Determine particle location using least square approach. Find distance using power 2. Find distance using power law fit of the several law fit of the several surrounding calib. points. surrounding calib. points. Determine particle location using least square approach. Step 1.    Disadvantages - Only one z level considered - Far points on the same level unnecessarily considered Step 2. improvement Degaleesan qubic 1. Find distance using qubic spline fit spline fit of the calibration curve. Determine particle location using least square approach. 2. Find distance using quadratic fit of all calib. quadratic fit of all calib. points at a single level. points at a single level. Determine particle location using least square approach.

CHEMICAL REACTION ENGINEERING LABORATORY Local Power Law Fitting Counts Distance, cm

CHEMICAL REACTION ENGINEERING LABORATORY Position Reconstruction Rados’ method: more spurious points (using less det.) better centered islands comparable size of the islands to Degaleesan G-L Ug=30cm/s

CHEMICAL REACTION ENGINEERING LABORATORY Position Reconstruction off center ~ 4 (9) mm off center < 3 mm  r ~ 7.5 (10) mm  r ~ 7.5 mm   < 15 mm   < 13 (18) mm  z ~ 10 (30) mm  z < 5 mm G-L Ug=30cm/s

CHEMICAL REACTION ENGINEERING LABORATORY Calibration Curve - G-L Beta-Spline Fitting Beta-Spline Fitting Ong: G-L Ug=30cm/s Detector #30 (X) Distance, cm Counts

CHEMICAL REACTION ENGINEERING LABORATORY Position Reconstruction - G-L off center < 6 mm off center < 2 mm  r ~ 6 mm  r < 5 mm   < 9 mm   < 5 mm  z ~ 10 mm  z < 3 (5) mm Ong: G-L Ug=30cm/s

CHEMICAL REACTION ENGINEERING LABORATORY Calibration Curve - Slurry ring 3: r = 7.62 cm ring 0, 1, 2: r = 0, 2.54, 5.08 cm Arches are caused by the wall and solids (wall path) (medium) G-L-S Ug=45cm/s Detector #30 (X)

CHEMICAL REACTION ENGINEERING LABORATORY Position Reconstruction - Slurry off center ~ 6 (20) mm off center < 3.5 (6) mm  r < 10 (20) mm  r < 7 mm   ~ 10 mm   < 7 (10) mm  z ~ 10 (30) mm  z ~ 3 (10) mm G-L-S Ug=45cm/s

CHEMICAL REACTION ENGINEERING LABORATORY CARPT Slurry Experiments Modifications 1. Tripoid redesigned 2. Det. changed 3. Plate redesigned 4. Det. moved closer 5. Gear box added 6. Rod guides added

CHEMICAL REACTION ENGINEERING LABORATORY CARPT Slurry Experiments

CHEMICAL REACTION ENGINEERING LABORATORY Conclusion and Future Work Developed automated CARPT calibration device, detector alignment, photo peak scanning procedures and position reconstruction algorithm enable acquisition of CARPT experiments even in thick wall high pressure metal vessels. Process the acquired experimental data. - reconstruct the tracer particle (x,y,z) positions - filter the positions - process the velocities - process the “turbulent parameters” (stresses & TKE) - process the eddy diffusivites Finish the DP experiments and finish processing holdup profiles.