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Gregory T. Benz. Agitator Design for Gas-Liquid Fermenters and Bioreactors
Table of Contents
List of Tables
List of Illustrations
Guide
Pages
Agitator Design for Gas–Liquid Fermenters and Bioreactors
Preface
Foreword
Foreword for Greg Benz
1 Purpose of Agitator Design
References
2 Major Steps in Successful Agitator Design
Define Process Results
Define Process Conditions
Choose Tank Geometry
Calculate Equivalent Power/Airflow Combinations for Equal Mass Transfer Rate
Choose Minimum Combined Power
Choose Shaft Speed; Size Impeller System to Draw Required Gassed Power
Decision Point: D/T and Gassing Factors OK?
Mechanical Design
Decision Point: Is the Mechanical Design Feasible?
Repeat to Find Lowest Cost
Repeat for Different Aspect Ratios
Repeat for Different Process Conditions
Finish
Summary of Chapter
List of Symbols
References
3 Agitator Fundamentals
Agitated Tank Terminology
Prime Mover
Reducer
Shaft Seal
Wetted Parts
Tank Dimensions
How Agitation Parameters Are Calculated
Reynolds Number
Power Number
Pumping Number
Dimensionless Blend Time
Aeration Number
Gassing Factor
Nusselt Number
Froude Number
Prandtl Number
Geometric Ratios
Baffle Number
Dimensionless Hydraulic Force
Thrust Number
Typical Dimensionless Number Curves
Example 1: Power Draw Calculation
Answer
Example 2: Pumping Calculation
Answer
Example 3: Blend Time Calculation
Answer
A Primer on Rheology
Newtonian Model
Pseudoplastic or Shear Thinning, Model (Aka Power Law Fluid)
Bingham Plastic
Herschel–Bulkley
Impeller Apparent Viscosity
A Bit of Impeller Physics
Summary of Chapter
List of Symbols
Greek letters
References
4 Agitator Behavior under Gassed Conditions
Flooding
kla Method
Power Draw Method
Visual Flow Pattern Method
Effect on Power Draw
Holdup
Example of Holdup Calculation
Holdup “War Story”
Variable Gas Flow Operation
Mechanical Effects
Summary of Chapter
List of Symbols
References
5 Impeller Types Used in Fermenters
Impeller Flow Patterns
Axial Flow
Radial Flow
Mixed Flow
Chaos Flow
Examples of Axial Flow Impellers. Low Solidity
High Solidity
Example
Up‐pumping vs. Down Pumping
Examples of Radial Flow Impellers
Straight Blade Impeller
Disc, aka Rushton, Turbines
Example
Smith Turbines
CD‐6 Turbine by Chemineer; aka Smith Turbine by Many Manufacturers
Example
Deeply Concave Turbines
Deep Asymmetric Concave Turbine with Overhang (BT‐6)
Examples of Mixed Flow Impellers
Examples of Chaos Impellers
Shear Effects
Specialty Impellers
Summary of Chapter
List of Symbols
References
6 Impeller Systems
Why Do We Need a System?
Reaction Engineering
Fermenter History
Steps to Impeller System Design
Choose Number of Impellers
Choose Placement of Impellers
Choose Type(s) of Impellers
Choose Power Split or Distribution Among Impellers
Choose D/T and/or Shaft Speed
D/T Effects with Variable Gas Flowrates
Example 6.1
Example 6.2
Conclusions on D/T Ratio
Design to Minimize Shear Damage
Sparger Design
Ring Sparger
Pre‐dispersion
Fine Bubble Diffuser
Summary of Chapter
List of Symbols
References
7 Piloting for Mass Transfer
Why Pilot for Mass Transfer
Methods for Determining kla
Sulfite Method
Dynamic Method; aka Dynamic Gassing/Degassing Method
Steady‐State Method; aka Mass Balance Method
Combined Dynamic and Steady‐State Method
Equipment Needed for Scalable Data
Data Gathering Needs
Experimental Protocol
Example Problem: Experimental Protocol for Steady‐State Analysis
Summary of Chapter
List of Symbols
References
8 Power and Gas Flow Design and Optimization. What This Chapter Is about
Where We Are in Terms of Design
Design with no Data
Example of Procedure
Design with Limited Pilot Data
Design with Full Data
Choose Minimum Combined Power
Example Problem
State of Design Completion
Additional Considerations
Summary of Chapter
List of Symbols
References
9 Optimizing Operation for Minimum Energy Consumption per Batch. Purpose of This Chapter
Prerequisite
Conceptual Overview
Detailed Procedure
Example Problem
Minimizing Total Energy Usage
Practical Design
Additional Considerations
Summary of Chapter
List of Symbols
References
10 Heat Transfer Surfaces and Calculations. Purpose of This Chapter
Design Philosophy
Overview of the Problem
Heat Sources
Cooling Sources
Heat Exchange Surface Overview
Principle of Heat Transfer Calculation
Calculations By Type of Surface. Vessel Jacket, Agitated Side
Simple Unbaffled Jacket, Jacket Side
Dimple Jacket, Jacket Side
Half‐Pipe Coil, Jacket Side
Helical Coil, Inside
Helical Coil, Process Side
Vertical Tube Bundle, Inside
Vertical Tube Bundle, Process Side
Plate Coil, Inside
Plate Coil, Process Side
Example Problem: Vertical Tube Bundle. Problem Statement
Problem Solution
Additional Consideration: Effect on Power Draw
Additional Consideration: Forces on Heat Exchange Surfaces Used as Baffles
Additional Consideration: Wall Viscosity
Additional Consideration: Effect of Gas
External Heat Exchange Loops
Summary of Chapter
List of Symbols
References
Further Readings
11 Gasses Other Than Air and Liquids Other Than Water
General Principle
Comments on Some Specific Gasses. Ammonia
Carbon Dioxide
Carbon Monoxide
Hydrogen
Methane
Oxygen
Economic Factors
Disposal Factors
Effects of Different Gasses on kla
Effects of Different Gasses on Driving Force
Operating Condition Effects
Constraints on Outlet Concentration
Safety
Liquids Other Than Water
Summary of Chapter
List of Symbols
References
12 Viscous Fermentation. General Background
Sources of Viscosity
Viscosity Models for Broths
Effect of Viscosity on Power Draw
Example Problem
Example Problem Answer
Effect of Viscosity on kla
Effect of Viscosity on Holdup
Effect of Viscosity on Blend Time
Effect of Viscosity on Flooding
Caverns
Estimating Cavern Size
Xanthan and Gellan Gums
Viscosity Models for Gums
Installation Survey
Effect of D/T and No. and Type of Impellers on Results in Xanthan Gum
Production Curve
Heat Transfer
All‐Axial Impeller Design
Invisible Draft Tube vs. Axial/Radial Combination
Mycelial Broths
Typical Viscosity Model
Morphology Effects
Recommendations
Summary of Chapter
List of Symbols
References
13 Three Phase Fermentation
General Problem
Effect on Mass Transfer
Effect on Foam
Emulsion vs. Suspension
Complexity: How to Optimize Operation
Summary of Chapter
List of Symbols
References
14 Use of CFD in Fermenter Design. Purpose of This Chapter
Basic Theory
Methods of Presenting Data
Velocity Distribution
Cavern Formation
Blending Progress
Flow Around Coils
Bubble Size, kla, Holdup
DO Distribution
Summary of Chapter
List of Symbols
References
15 Agitator Seal Design Considerations. Introduction
Terminology
Main Functions of Fermenter Shaft Seals
Common Types of Shaft Seals
Material Considerations
Methods of Lubricating Seals
Seal Environmental Control and Seal Support System
Seal Life Expectations
Special Process Considerations
Summary of Chapter
Reference
16 Fermenter Agitator Mounting Methods. Introduction
Top Entering Methods
Direct Nozzle Mount
Beam Gear Drive Mount with Auxiliary Packing or Lip Seal; Beams Tied into Vessel Sidewall
Beam Gear Drive Mount with Auxiliary Mechanical Seal; Beams Tied into Vessel Sidewall
Beam Gear Drive Mount with Auxiliary Mechanical Seal; Beams Tied into Building Structure
Complete Drive and Seal Mount to Beams Tied into Vessel Sidewall, with Bellows Connector
Complete Drive and Seal Mount to Beams Tied into Building Structure, with Bellows Connector
Bottom Entering Methods
Direct Nozzle Mount
Floor Gear Drive Mount with Auxiliary Packing or Lip Seal
Floor Gear Drive Mount with Auxiliary Mechanical Seal
Floor Integrated Drive and Seal Mount with Bellows Connector
Summary of Chapter
References
17 Mechanical Design of Fermenter Agitators. Introduction
Impeller Design Philosophy
Discussion on Hydraulic Force
Shaft Design Philosophy
Shaft Design Based on Stress
Simple Example Problem
Sample Problem with Steady Bearing
Shaft Design Based On Critical Speed
Cantilevered Designs
Example Problem
Units with Steady Bearings
Solid Shaft vs. Hollow Shaft
Role of FEA in Overall Shaft Design‐Simplified Discussion
Agitator Gear Drive Selection Concepts
Early History
Loads Imposed
Handle or Isolate Loads?
Handle Loads Option 1: Oversized Commercial Gear Drive
Handle Loads Option 2: Purpose‐Built Agitator Drive
Isolate Loads Option 1: Hollow Quill Integrated Drive with Flexibly Coupled Extension Shaft
Isolate Loads Option 2: Outboard Support Bearing Module
Bearing Life Considerations
Noise Considerations
Torsional Natural Frequency
Important or Useful Mechanical Design Features
Summary of Chapter
List of Symbols
Greek Letters
References
18 Sanitary Design. Introduction
Definitions
Construction Principles
Wetted Parts Construction Methods. Welded Construction
In‐Tank Couplings
Mounting Flange Area
Axial Impellers
Radial Impellers
Bolts and Nuts
Steady Bearings
Use of Castings, 3‐D Printing
Polishing Methods and Measures1: Polishing vs. Burnishing
Polishing Methods and Measures2: Lay
Polishing Methods and Measures3: Roughness Average
Electropolish
Passivating
Effect on Mechanical Design
Summary of Chapter
Additional Sources of Information
List of Symbols
References
19 Aspect Ratio
Acknowledgment
Definition and Illustration of Aspect Ratio
What Is the Optimum Aspect Ratio?
Effects of Z/T on Cost and Performance at a Given Working Volume. Vessel Cost
Agitator Shaft Design Difficulty
Power Required for Mass Transfer
Agitator Cost
Airflow Requirements
Compressor Power
DO Uniformity
Heat Transfer Capability
Real Estate/Land Usage Issues
Building Codes; Noise
Illustrative Problem Number 1
Vessel Dimensions
Airflow and Power
Heat Transfer Data and Assumptions
Heat Transfer Results
Blend Time, DO Uniformity
Capital Cost (Agitator Plus Vessel Only)
Other Operating Costs
So What Is the Optimum Aspect Ratio for This Problem?
Illustrative Problem Number 2
Illustrative Problem Number 3
Summary of Chapter
List of Symbols
References
20 Vendor Evaluation
Product Considerations
Gear Drive Ruggedness
Design Technology
Impeller Selection
Shaft Design
Company Considerations
Reputation with Customers
Company Size
Years in Business
Years Under New Ownership
Employee Turnover
Vertical Integration
R&D Program and Publications
Depth of Application Engineering
Testing Laboratory
ISO Certification (Necessary vs Sufficient)
Quality Control Program (Not Lot Sample; 100%)
Rep vs Direct Sales (a Good Rep Annoys the Manufacturer)
Service Capability
Typical Delivery Times and Performance
Parts Availability
Price (Least Important)
Willingness to Work with Consultants
Vendor Audit Checklist
Use of an Outside Consultant
Summary of Chapter
List of Symbols
References
A.Appendix to Chapter 20
21 International Practices. Introduction
North America. Vendors
Design Practices
Selling/Buying Practices
Degree of Vertical Integration
Role of Design Firms
R&D
Culture
EU. Vendors
Design Practices
Selling/Buying Practices
Degree of Vertical Integration
Role of Design Firms
R&D
Culture
Japan
Vendors
Design Practices
Selling/Buying Practices
Degree of Vertical Integration
Role of Design Firms
R&D
Culture
China
Vendors
Design Practices
Selling/Buying Practices
Degree of Vertical Integration
Role of Design Firms
R&D
Culture
Summary of Chapter
Cultural Resources
Afterword
Index. a
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