Trends in Minimizing and Treating Industrial Wastes for Sustainable Environment

While treating the industrially produced wastes through various processes such as physical, chemical, biological and radiation processes have been implemented on various scales and is the focus of various studies and development, the trend of minimizing and/or eliminating the pollutions at the source via developing and selecting proper catalytic multiphase reactors is worth to be given proper attention and consideration which is the focus of this manuscript beside outlining the processes used for treating the wastes. In order to achieve such goal in minimizing the wastes, these multiphase reactors must be well understood, studied, scaled up and designed. This can be only achieved by developing and implementing advanced measurement and computing techniques which have been developed in our research laboratory and are briefly outlined here with selected results

Liquid Phase Mixing in Trayed Bubble Column Reactors

The Compartmentalization of Conventional Bubble Columns by Perforated Trays Constitutes a Very Effective Method to Reduce the Liquid Back mixing. the Effect of Tray Design and Operating Conditions on the overall Liquid Mixing Was Studied in a Bench-Scale Trayed Bubble Column. the Extent of Liquid Back mixing in the Column Was Investigated in Light of Liquid-Phase Tracer Response Experiments. in Average, a Three-Fold Reduction in the Liquid Back mixing Was Achieved in the Trayed Column as Compared to the Column Without the Trays. Moreover, the Tray Open Area and the Superficial Liquid Velocity Were Found to Have the Strongest Effects on the Liquid Back mixing. the N-CSTR with Back mixing Model Was Found to Match the Experimental Tracer Response Curves Better Than the Axial Dispersion Model. © 2005 Elsevier Ltd. All Rights Reserved

Gas-Liquid Mass Transfer in a High Pressure Bubble Column Reactor with Different Sparger Designs

The Gas-Liquid Mass Transfer in a 0.162 M High-Pressure Stainless-Steel Bubble Column Was Investigated using Three Different Gas Sparger Designs. an Oxygen-Enriched-Air Dynamic Method and an Optical Oxygen Probe Technique Were Implemented to Measure K1 a Values in the Bubble Column Reactor. using the Interfacial Area (A) Values Measured by a Four-Point Optical Probe Technique at Similar Conditions (Xue, 2004), the K1 Values Were Estimated. Axial Dispersion Model (ADM) and Continuous Stirred Tank Reactor (CSTR) Model Were Used to Calculate K1 a as a Fitted Parameter with the Measured Data. the ADM Gave Better Fits to the Experimental Data Than the CSTR Model, Especially at High Axial Locations for the Bubble Column Used with a Large L / Dc Ratio. the Sparger Design Was Found to Have a Noticeable Effect on K1 a in the Low Gas Velocity Range (Ug \u3c 0.15 M / S) But Only a Slight Effect in the High Gas Velocity Range (Ug \u3e 0.20 M / S). the Sparger Design Showed Almost No Effect on the Liquid Side Mass Transfer Coefficient, K1, at High Gas Velocity (Ug = 0.30 M / S), Where No Significant Variations of the Bubble Size Distribution and Hydrodynamics Were Obtained using Different Sparger Designs. Although the K1 a Values Increased with the Operating Pressure, the Pressure Change from 0.1 to 0.4 MPa Yielded Lower K1 Values, as a Result of the Reduced Bubble Size. However, as the Pressure Further Increased to 1.0 MPa, the a and K1 a Values Increased, While the K1 Values Negligibly Decreased. in Addition to the Pressure and Sparger Design Effects, the Superficial Gas Velocity Had Effect of Increasing the K1 Values, While Such Effect Became Small and Flattened Out at High Superficial Gas Velocities. © 2006 Elsevier Ltd. All Rights Reserved

Modeling Catalytic Trickle-Bed and Upflow Packed-Bed Reactors for Wet Air Oxidation of Phenol with Phase Change

In This Study, to Simulate the Steady-State Behavior of Packed-Bed Reactors for Catalytic Wet Oxidation of Phenol, One-Dimensional (1D) Axial Dispersion Model for the Liquid Phase is Coupled with a Cell Stack Model for the Gas Phase, Providing Considerable Phase Change under the Selected Operating Conditions. the Reactor Scale Governing Equations, Reaction Kinetics Involved, and Solution Strategy Are Discussed. the Computational Approach Accounts for the Observed Catalyst Activities, Combined with Local Transport and Catalyst Wetting Effects. the Approach Selected is Shown to Be Suitable and Efficient in Dealing with the Problem in Question. Comparisons of Simulated Model Predictions and Lab Scale Experimental Data Are Presented. Reasonably Simulating the Concentration Profiles in the Reactor at Steady-State Operation, the Model Allows Designers to Determine the Effects of Catalyst Activity and Operating and Feed Conditions on Reactor Performance. the Model Also Clearly Demonstrates the Importance of Including the Phase Change Effect in the Reactor Scale Flow Distribution. © 2005 American Chemical Society

Catalytic Wet Air Oxidation of Phenol in Concurrent Downflow and Upflow Packed-Bed Reactors over Pillared Clay Catalyst

An Experimental Study is Presented for Comparing the Behavior of a Packed Bed Reactor in the Catalytic Liquid-Phase Oxidation of Aqueous Phenol with Two Modes of Operation, Downflow and Upflow. the Operating Parameters Investigated Included Temperature, Reactor Pressure, Gas Flowrate, Liquid Hourly Space Velocity and Feed Concentration. Because of the Completely Wetted Catalyst, the Upflow Reactor Generally Performs Better for High Pressures and Low Feed Concentrations When the Liquid Reactant Limitation Controls the Rate. the Interaction between the Reactor Hydrodynamics, Mass Transfer, and Reaction Kinetics is Discussed. for Both Operation Modes, Complete Phenol Removal and Significant Total Organic Carbon (TOC) Reduction Can Be Achieved at Rather Mild Conditions of Temperature (150-170°C) and Total Pressure (1.5-3.2 MPa). the Results Show that the Phenol and TOC Conversion Are Considerably Affected by the Temperature, While the Air Pressure Only Has Minor Influence. Total Elimination of TOC is Difficult Since Acetic Acid, as the Main Intermediate, is Resistant to Catalytic Wet Oxidation. All Tests Were Conducted over Extrudates of Fe-Al Pillared Clay Catalyst, Which is Stable and Maintains its Activity during the Long-Term Experimental Process. No Significant Catalyst Deactivation Due to Metal Ion Leaching and Polymer Deposition Was Detected. © 2004 Elsevier Ltd. All Rights Reserved

Catalytic Wet Oxidation of Phenol by Hydrogen Peroxide over Pillared Clay Catalyst

Extrudates of Al-Fe Pillared Clay Catalyst Suitable for Packed-Bed Operations Are Evaluated for Wastewater Treatment Via a Wet Oxidation Process Employing Hydrogen Peroxide as the Oxidant. the Reaction Was Carried Out in a Semibatch Basket Reactor under Rather Mild Conditions. Operational Parameters Were Studied under the Following Conditions: Temperature from 25 to 90 °C, Atmospheric Pressure, Initial Phenol Concentration from 100 to 2000 Ppm of the Liquid Phase, Catalyst Loading from 0 to 10 G/L, and Input H2O2 Concentration from 0.15 to 0.6 Mol/L. under These Conditions, the Al-Fe Pillared Clay Catalyst Achieves a Total Elimination of Phenol and Significant Total Organic Carbon (TOC) Removal. This Catalyst Can Be Used Several Times Without Any Change in its Catalytic Properties, and Hence, It Would Be a Promising Catalyst for Industrial Wastewater Treatment. the Reaction Takes Place to a Significant Extent Both in the Liquid Phase and on the Catalyst Surface. Hence, Apparent Kinetic Models Were Developed by Formulating the Reaction Rate in Two Kinetic Expressions that Separately Consider the Homogeneous and Heterogeneous Contributions. using the Second-Order Approach for the Homogeneous Reaction and the Langmuir-Hinshelwood Approach for the Heterogeneous Reaction, the Developed Kinetic Models Describe Well the Removal of Phenol and the Formed Intermediate Carbon over the Entire Range of the Variables Studied

Local Time-Averaged Gas Holdup in Fluidized Bed Reactor using Gamma Ray Computed Tomography Technique (CT)

Many Invasive and Non-Invasive Techniques Have Been Used to Analyze the Hydrodynamics of Fluidized Beds. in This Study, the Effect of Superficial Gas Velocity and Bed Particle Density on the Hydrodynamics of Gas–solid Fluidized Beds Was Investigated by using a Cylindrical Plexiglas Fluidized Bed Column, 14 Cm in Diameter. Air at Room Temperature Was Used as the Fluidizing Gas and Two Different Geldart Type-B Particles Were Used: Glass Beads and Copper Particles with Material Densities of 2.5 and 5.3 G/cm3, Respectively, with the Same Size Particle, 210 µm. to Measure the Time-Averaged Cross-Sectional Gas and Solid Holdup Distribution, Gamma Ray Computed Tomography Was Used for the First Time as a Non-Invasive Technique Instead of using X-Rays (Due to the Height Attenuation of the Copper Particles). the Results Show that Gas Holdup Increases by Increasing the Superficial Gas Velocity, and Decreasing the Particle Density Increases the Gas Holdup in the Bed

Liquid Holdup Measurement Techniques in Laboratory High Pressure Trickle Bed Reactors

Three Different Techniques, Which Are Tracer, Drainage and Weighing Methods, Are Used to Measure Liquid Holdup in a Laboratory Trickle-Bed Reactor Operated under High Pressure. the Holdup Measurements Are Compared to Determine the Applicability of These Methods at High Pressure Operation. It Was Found that Tracer and Drainage Techniques Give Comparable Values for the Total Liquid Holdup. Although Several Investigators Recommended the Weighing Method over the Others based on their Experiments Performed at Atmospheric Conditions, It Was Found that the Weighing Method Failed to Measure Liquid Holdup Properly at High Pressure Operation

Liquid Holdup and Pressure Drop in the Gas-Liquid Cocurrent Downflow Packed-Bed Reactor under Elevated Pressures

An Experimental Investigation of the Residence Time Distribution, Liquid Holdup, and Pressure Drop in a Gas-Liquid Downflow Packed Bed Reactor with Porous Particles Operated under Elevated Pressures is Presented. the Effects of the Two-Phase Flow Rates and Reactor Pressures on the External Liquid Holdup and Pressure Drop Are Discussed. a Mechanistic Model, Which Accounts for the Interaction between the Gas and Liquid Phases by Incorporating the Shear and Velocity Slip Factors between Phases, is Employed to Predict the External Liquid Holdup and Pressure Drop for the Experimentally Covered Flow Regime. the Involved Parameters, Such as Shear and Velocity Slip Factors and Ergun Single-Phase Flow Bed Constants, Are Calculated from the Correlations Developed Via Neural Network Regression. the Model\u27s Predictions and the Experimental Observations at Elevated Pressure Are Compared. © 2004 Elsevier Ltd. All Rights Reserved