Advances in Industrial Mixing

A Companion to the Handbook of Industrial Mixing

Suzanne M. Kresta, Arthur W. Etchells, David S. Dickey, Victor A. Atiemo-Obeng, Suzanne M. Kresta, Arthur W. Etchells, III, David S. Dickey, Victor A. Atiemo-Obeng

• Publisher: Wiley
• Year: 2015
• Print ISBN: 9780470523827
• eBook ISBN: 9781118944301
• Edition: 1

Advances in Industrial Mixing is a companion volume and update to the Handbook of Industrial Mixing. The second volume fills in gaps for a number of industries that were not covered in the first edition. Significant changes in five of the fundamental areas are covered in entirely updated or new chapters. The original text is provided as a searchable pdf file on the accompanying USB.

• This book explains industrial mixers and mixing problems clearly and concisely.
• Gives practical insights by the top professionals in the field, combining industrial design standards with fundamental insight.
• Details applications in 14 key industries. Six of these are new since the first edition.
• Provides the professional with information he/she did not receive in school.
• Five completely rewritten chapters on mixing fundamentals where significant advances have happened since the first edition and seven concise update chapters which summarize critical technical information.

CHAPTER 10
Solid–Liquid Mixing

lead authors

DAVID A. R. BROWN

BHR Group

ARTHUR W. ETCHELLS III

Rowan University

with sections by

RICHARD K. GRENVILLE

Philadelphia Mixing Solutions

KEVIN J. MYERS

University of Dayton

N. GUL ÖZCAN-TAşKIN

BHR Group

incorporating sections by

VICTOR A. ATIEMO-OBENG

Dow, retired

PIERO H. ARMENANTE

New Jersey Institute of Technology

W. ROY PENNEY

University of Arkansas

10-1 Introduction and Scope

This chapter updates and expands the solid–liquid chapter in the Handbook of Industrial Mixing (Paul et al., ; hereafter referred to as the Handbook). The focus remains on mixing operations involving primarily a particulate solid and a continuous liquid phase carried out in agitated or stirred vessels, although jet mixed systems are briefly discussed in Section 10.6. Fundamental aspects of the hydrodynamics and mass transfer as well as practical design issues for solid–liquid mixing processes involving settling solids, gassed and ungassed, and floating solids are discussed. All of the work applies to turbulent flow and systems that separate over time. Solid–liquid systems where the material forms a pseudohomogeneous fluid are treated as non-Newtonian fluids and are covered in the Handbook under blending (Chapter 9a) and in this volume under Microstructure, Rheology, and Processing of Complex Fluids (Chapter 3b).

The solid–liquid mixing area is one where a lot of new work has been completed since the publication of the Handbook, some old work has been rediscovered, and more work is still needed. At first the sheer size of this chapter may overwhelm those just looking for a simple answer. The user should carefully review the index entries and table of contents. The following gives a little more explanation.

10-1.1 Finding Your Way through This Chapter

This section discusses the role of solid–liquid mixing in the process industries and the problems it causes. If you have not worked with solid–liquid systems before, read this.

Section 10.2 introduces some key solid and liquid and physical properties and characteristics that must be considered before designing a solid–liquid mixing system. If you know the particle properties well and have a relatively standard geometry you can skip this section and plunge into calculating the process results that you find most pertinent. Further details of the effect of physical properties on the prediction of the impeller speed to just suspend solids are presented in Section 10.3.6.

Section 10.3, the largest section in this chapter, discusses the agitation of sinking or settling solids. Two methods are given for calculating the minimum agitator speed to suspend the solids (Section 10.3.4): the more traditional method by Zwietering and a new method based on a more extensive database with somewhat firmer turbulence foundations and similarities to some other methods. The differences in the effect of physical properties appear small, but the implications for scale-up can be significant. This difference is discussed at some length.

The effects of common physical properties on solids suspension are discussed in detail in Section 10.3.6. There is some duplication between this section and Section 10.2. If the user is also interested in the vertical distribution of solids once suspended, the topic is introduced in Section 10.3.5.

The effect of variations from “standard” mixer geometry, both on the suspension and distribution of solids, is covered in Section 10.3.7. This variation includes the use of multiple impellers, the impact of vessel base shape, poorly baffled systems, and angled shaft agitators for smaller tanks. The significant impact of liquid fill height is also discussed.

Continuous and semibatch (including tank draining) operations are discussed in Section 10.3.9. Section 10.3.8 discusses the situation where solids are suspended while a gas is also sparged. Design recommendations and scale-up advice are summarized in Section 10.3.10.

Solids that float without agitation, including solids that are less dense than the liquid, dense solids, or flocs containing trapped gas, and solids that are difficult to wet are a common cause of industrial problem. Section 10.4 discusses the drawdown and incorporation of floating solids.

Section 10.5 discusses problems that sometimes occur due to particle attrition; Section 10.6 discusses the suspension and mixing of solids using jets; Section 10.7 discusses solid–liquid mass transfer; and the chapter concludes with Section 10.8, a short discussion of lab and pilot-scale testing approaches and objectives.

Not included in this chapter are several solid–liquid contacting operations such as liquid or gas-fluidized beds, or liquid–solid contacting in fixed-bed systems. Froment and Bischoff (1990) discu...

Table of contents

• Cover
• Title page
• Copyright
• Contributors List
• Editors’ Introduction
• Contents of the DVD, Including Instructional Videos
• Introduction: A Technical Definition of Mixing
• Chapter 1a Residence Time Distributions
• Chapter 1b Mean Age Theory for Quantitative Mixing Analysis
• Chapter 2a Turbulence in Mixing Applications
• Chapter 2b Update to Turbulence in Mixing Applications
• Chapter 3a Laminar Mixing: A Dynamical Systems Approach
• Chapter 3b Microstructure, Rheology, and Processing of Complex Fluids
• Chapter 4 Experimental Methods:
• Chapter 5a Computational Fluid Mixing
• Chapter 5b CFD Modeling of Stirred Tank Reactors
• Chapter 6a Mechanically Stirred Vessels
• Chapter 6b Flow Patterns and Mixing
• Chapter 6c Vessel Heads: Depths, Volumes, and Areas
• Chapter 7a Mixing in Pipelines
• Chapter 7b Update to Mixing in Pipelines
• Chapter 7c Introduction to Micromixers
• Chapter 8 Rotor–Stator Mixing Devices
• Chapter 9a Blending of Miscible Liquids
• Chapter 9b Laminar Mixing Processes in Stirred Vessels
• Chapter 10 Solid–Liquid Mixing
• Chapter 11 Gas—Liquid Mixing in Turbulent Systems
• Chapter 12 Immiscible Liquid–Liquid Systems
• Chapter 13a Mixing and Chemical Reactions
• Chapter 13b Scale-up Using the Bourne Protocol: Reactive Crystallization and Mixing Example
• Chapter 14a Heat Transfer
• Chapter 14b Heat Transfer In Stirred Tanks—Update
• Chapter 15 Solids Mixing
• Chapter 16 Mixing of Highly Viscous Fluids, Polymers, and Pastes
• Chapter 17 Mixing in the Fine Chemicals and Pharmaceutical Industries
• Chapter 18 Mixing in the Fermentation and Cell Culture Industries
• Chapter 19 Fluid Mixing Technology in the Petroleum Industry
• Chapter 20 Mixing in the Pulp and Paper Industry
• Chapter 21a Mechanical Design of Mixing Equipment
• Chapter 21b Magnetic Drives for Mixers
• Chapter 22 Role of the Mixing Equipment Supplier
• Chapter 23 Commissioning Mixing Equipment
• Chapter 24 Mixing Safety
• Chapter 25 Mixing Issues in Crystallization and Precipitation Operations
• Chapter 26 Mixing in the Water and Wastewater Industry
• Chapter 27 Mixing in the Food Industry
• Chapter 28 Mixing and Processes Validation in the Pharmaceutical Industry
• Index
• EULA