Experimental Investigation of the Hydrodynamics in a Liquid-Solid Riser

Liquid-Solid Fluid Dynamics Has Been Investigated in a 6-In. (0.15 M) Cold-Flow Circulating Fluidized Bed Riser using Non-Invasive Flow Monitoring Methods. Gamma-Ray Computed Tomography (CT) Was Used to Measure the Time-Averaged Cross-Sectional Solids Volume Fraction Distributions at Several Elevations. the Time-Averaged Mean and Fluctuating Solids Velocity Fields Were Quantified using the Computer-Automated Radioactive Particle Tracking (CARPT) Technique. the Experimental Equipment, Protocol of Implementation, and Data Analysis Have Been Discussed Briefly, with Particular Emphasis on the Specific Features in the Use of These Techniques for Studying High-Density Turbulent Flows as in a Liquid-Solid Riser. the Experimental Study Examines Nine Operating Conditions, that Is, Three Liquid Superficial Velocities and Three Solids Flow Rates. the Solids Holdup Profile is Found to Be Relatively Uniform Across the Cross Section of the Riser, with Marginal Segregation Near the Walls. the Time-Averaged Solids Velocity Profiles Are Found to Have a Negative Component at the Walls, Indicating Significant Solids Backmixing. Detailed Characterization of the Solids Velocity Fields in Terms of RMS Velocities, Kinetic Energies, Hurst Exponents, Residence Time Distributions, Trajectory Length Distributions, Dispersion Coefficients, and So Forth Are Presented. Comparative and Symbiotic Analyses of the Results Were Used to Develop a Coherent Picture of the Solids Flow Field. in Addition, the Work Also Serves to Demonstrate the Power and Versatility of These Flow-Imaging Techniques in Studying Highly Turbulent and Opaque Multiphase Systems. © 2005 American Institute of Chemical Engineers

Comparative Hydrodynamics Study in a Bubble Column using Computer-Automated Radioactive Particle Tracking (CARPT)/computed Tomography (CT) and Particle Image Velocimetry (PIV)

The Hydrodynamics of a 10-Cm-Diameter Cylindrical Bubble Column at the Superficial Gas Velocity of 2, 4, and 8 Cm/s Are Investigated by Computer-Automated Radioactive Particle Tracking (CARPT), Particle Image Velocimetry (PIV), and Computed Tomography (CT). These Experimental Techniques Are Capable of Providing the Knowledge of Velocity and Holdup Fields in a Bubble Column System, Which Are Essential as the Experimental Benchmark for Modeling of Such Systems. the Flow Field of Liquid Phase, as Well as the Reynolds Stresses, Obtained by CARPT and PIV in an Air-Water System Are Compared in Detail. the Results Indicate that CARPT and PIV Complement Each Other Well. Further, the Profile of Gas Holdup Obtained by Gamma Ray based on CT Compares Favorably to the Independently Determined Holdup

Analysis of Photobioreactors for Culturing High-Value Microalgae and Cyanobacteria Via an Advanced Diagnostic Technique: CARPT

Photosynthetic Algal Cultures Are a Potential Source of Many High-Value Products. in Photobioreactors (PBR), the Availability and the Intensity of the Light, Which Are Affected by the Cells\u27 Movement, Are the Major Factors Controlling the Biomass Productivity. Hydrodynamics, Hence, Play a Significant Role in the Reactor\u27s Performance, as They Determine Not Only the Flow Field, I.e. Liquid Flow and Mixing, Shear Stresses, Etc., But Also the Movements of the Cells. in This Work, Computer-Automated Radioactive Particle Tracking (CARPT) Technique Was Employed to Evaluate its Feasibility for Characterizing PBRs. Liquid Velocity Profiles, Cells\u27 Movement, and the Temporal Irradiance Patterns Obtained by Coupling the Cells\u27 Trajectories and the Irradiance Distribution Model Have Been Determined. the Effects of the Biomass Concentration, Reactor Geometry, and the Aeration Rate on the Irradiance Patterns Are Discussed. the Results Demonstrate that the CARPT Technique is Promising for PBR Analysis. It Provides Fundamental Information Needed to Advance the Cells\u27 Growth Prediction and Modeling, and the Design, Scale-Up and Operation of PBRs. © 2003 Elsevier Science Ltd. All Rights Reserved

A Method for Estimating the Solids Circulation Rate in a Closed-Loop Circulating Fluidized Bed

We Propose a Simple Method for Accurately Estimating the Solids Circulation Rate in a Closed-Loop Liquid-Solid Circulating Fluidized Bed. the Technique is based on the Use of Radioactive Isotopes for Estimating the Solids Velocity and Volume Fraction Distribution in a Chosen Section of the Circulating Fluidized Bed Loop. the Method is Demonstrated for a Liquid-Solid Circulating Fluidized Bed, and is Readily Applicable in Other Systems Such as Gas-Solids Circulating Fluidized Beds or Closed-Loop Pneumatic and Hydraulic Transport Lines. with Minor Modifications, the Method May Be Used for Industrial Systems as Well. © 2001 Elsevier Science B.V. All Rights Reserved

Experimental validation of computational fluid dynamic codes (CFD) for liquid-solid risers in clean alkylation processes

This manuscript, based on the presentation given by one of the authors (M.P. Dudukovic) at the Technological and Engineering Forum in Pančevo, May 21 2002, summarizes the use of the computer automated radioactive particle tracking (CARPT) and gamma computed tomography (CT) in obtaining the data needed to validate the Euler-Euler based CFD simulations for solids distribution, flow pattern and mixing in a liquid-solid riser. The riser is one of the reactors considered for acid solid catalyst promoted alkylation. It is shown that CFD calculations, validated by CARPT-CT data, show promise for scale-up and design of this novel reactor type

Gas Holdup in Bubble Columns at Elevated Pressure Via Computed Tomography

Gas Holdup in a Pressurized Bubble Column (Pressure from 0.1 to 0.7 MPa) Was Studied in a Laboratory Scale Vessel (Diameter 0.162m) with Air-Water System over a Range of Superficial Gas Velocities (0.02-0.18 M/s) using Non-Invasive Γ-Ray based Computed Tomography (CT). It Was Found that the Cross-Sectional Average Gas Holdup Increases with Pressure, as Well as with Superficial Gas Velocity. at All Operating Conditions, the Azimuthally Averaged Radial Gas Holdup Profiles Exhibit a Characteristic Shape with Greater Gas Holdup in the Column Center Than by the Walls. It is Also Observed that with an Increase in Pressure, the Transition to Churn-Turbulent Regime Characterized by the Change of the Radial Gas Holdup Profile from Relatively Flat to Almost Parabolic, is Delayed to Higher Superficial Gas Velocities. the Average Cross-Sectional Gas Holdup at Each Operating Condition Was Compared with Predictions of Existing Correlations and Large Discrepancies in Predictions (As High as 300%) Were Found. © 2001 Elsevier Science Ltd. All Rights Reserved