Drying in the Process Industry E-Book

C. M. van't Land

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 528

Veröffentlichungsjahr: 2011

Beschreibung

A comprehensive approach to selecting and understanding drying equipment for chemical and mechanical engineers A detailed reference of interest for engineers and energy specialists working in the process industry field, Drying in the Process Industry investigates the current state of the art of today's industrial drying practices, examines the factors influencing drying's high costs in both equipment and energy consumption, and summarizes key elements for keeping drying operations under budget and performing at peak capacity safely while respecting the environment. Extensive coverage of dryer basics as well as essential procedures concerning the selection of industrial dryers--such as how to gather results of relevant laboratory measurements, carry out small-scale tests, and correctly size equipment--help to inform readers on criteria for generating scalable specifications that greatly assist buying decisions. Drying in the Process Industry: * Takes a practical approach to drying equipment, from an author with four decades in the industry * Describes a diverse array of drying equipment (convective, like flash, spray, fluid-bed, and rotary; contact, like paddle and steam; radiation) from an engineer's perspective * Provides quick and ready access to drying technologies with references to more detailed literature * Treats drying in the context of the entire production process True of all process facilities where drying plays an important role, such as those in the chemical, pharmaceutical, plastics, and food industries, the purchase of improper industrial drying equipment can significantly affect a manufacturer's economic bottom line. With the guidance offered in this book, engineers will be able to confidently choose industrial drying equipment that increases profits, runs efficiently, and optimally suits their needs.

Leseprobe

Contents

Cover

Title Page

Copyright

Preface

Chapter 1: Introduction

Chapter 2: Drying as Part of the Overall Process

2.1 RESIDUAL MOISTURE

2.2 OPTIMIZATION OF THE DEWATERING STEP

2.3 PROCESS CHANGES TO SIMPLIFY DRYING

2.4 COMBINATION OF DRYING AND OTHER PROCESS STEPS

2.5 NONTHERMAL DRYING

2.6 PROCESS CHANGES TO AVOID DRYING

2.7 NO DRYING

Chapter 3: Procedures for Choosing a Dryer

3.1 SELECTION SCHEMES

3.2 PROCESSING LIQUIDS, SLURRIES, AND PASTES

3.3 SPECIAL DRYING TECHNIQUES

3.4 SOME ADDITIONAL COMMENTS

3.5 TESTING ON SMALL-SCALE DRYERS

3.6 EXAMPLES OF DRYER SELECTION

Chapter 4: Convective Drying

4.1 COMMON ASPECTS OF CONTINUOUS CONVECTIVE DRYERS

4.2 SATURATED WATER VAPOR PRESSURE

4.3 WET-BULB TEMPERATURE

4.4 ADIABATIC SATURATION TEMPERATURE

4.5 HUMIDITY CHART

4.6 WATER–MATERIAL INTERACTIONS

4.7 DRYING WITH AN AUXILIARY MATERIAL

4.8 GAS VELOCITIES

4.9 HEAT LOSSES

4.10 ELECTRICAL ENERGY CONSUMPTION

4.11 MISCELLANEOUS ASPECTS

4.12 MATERIAL BALANCE (kg·h−1)

4.13 HEAT BALANCE (kJ·h−1)

4.14 SPECIFIC HEAT OF SOLIDS

4.15 GAS FLOWS AND FAN POWER

4.16 DIRECT HEATING OF DRYING AIR

Chapter 5: Continuous Fluid-Bed Drying

5.1 GENERAL DESCRIPTION

5.2 FLUIDIZATION THEORY

5.3 DRYING THEORY FOR RECTANGULAR DRYERS

5.4 REMOVAL OF BOUND MOISTURE FROM A PRODUCT IN A RECTANGULAR DRYER

5.5 CIRCULAR FLUID-BED DRYERS

5.6 APPENDIX: CALCULATION OF THE BIOT NUMBER OF A CAN PARTICLE IN A FLUID-BED COOLER

Chapter 6: Continuous Direct-Heat Rotary Drying

6.1 GENERAL DESCRIPTION

6.2 DESIGN METHODS

Chapter 7: Flash Drying

7.1 GENERAL DESCRIPTION

7.2 DESIGN METHODS

7.3 DRYING IN SECONDS

7.4 APPLICATION OF THE DESIGN METHODS

Chapter 8: Spray Drying

8.1 GENERAL DESCRIPTION

8.2 SINGLE-FLUID NOZZLE

8.3 ROTARY ATOMIZER

8.4 PNEUMATIC NOZZLE

8.5 PRODUCT QUALITY

8.6 HEAT OF CRYSTALLIZATION

8.7 PRODUCT RECOVERY

8.8 PRODUCT TRANSPORTATION

8.9 DESIGN METHODS

Chapter 9: Miscellaneous Continuous Convective Dryers and Convective Batch Dryers

9.1 CONVEYOR DRYERS

9.2 WYSSMONT TURBO-DRYER

9.3 NARA MEDIA SLURRY DRYER

9.4 ANHYDRO SPIN FLASH DRYER

9.5 HAZEMAG RAPID DRYER

9.6 COMBINED MILLING AND DRYING SYSTEM

9.7 BATCH FLUID-BED DRYER

9.8 ATMOSPHERIC TRAY DRYER

9.9 CENTRIFUGE–DRYER

Chapter 10: Atmospheric Contact Dryers

10.1 PLATE DRYERS

10.2 MILDLY AGITATED CONTACT DRYERS (PADDLE DRYERS)

10.3 VIGOROUSLY AGITATED CONTACT DRYERS

10.4 VERTICAL THIN-FILM DRYERS

10.5 DRUM DRYERS

10.6 STEAM-TUBE DRYERS

10.7 SPIRAL CONVEYOR DRYERS

10.8 AGITATED ATMOSPHERIC BATCH DRYERS

Chapter 11: Vacuum Drying

11.1 VACUUM DRYING

11.2 FREEZE-DRYING

11.3 VACUUM PUMPS

Chapter 12: Steam Drying

12.1 SUGAR BEET PULP DRYER

12.2 GEA EXERGY BARR–ROSIN DRYER

12.3 ADVANTAGES OF CONTINUOUS STEAM DRYING

12.4 DISADVANTAGES OF CONTINUOUS STEAM DRYING

12.5 ADDITIONAL REMARKS CONCERNING CONTINUOUS STEAM DRYING

12.6 EIRICH EVACTHERM DRYER

Chapter 13: Radiation Drying

13.1 DIELECTRIC DRYING

13.2 INFRARED DRYING

Chapter 14: Product Quality and Safeguarding Drying

14.1 PRODUCT QUALITY

14.2 SAFEGUARDING DRYING

Chapter 15: Continuous Moisture-Measurement Methods, Dryer Process Control, and Energy Recovery

15.1 CONTINUOUS MOISTURE-MEASUREMENT METHODS FOR SOLIDS

15.2 CONTINUOUS MOISTURE-MEASUREMENT METHODS FOR GASES

15.3 DRYER PROCESS CONTROL

15.4 ENERGY RECOVERY

Chapter 16: Gas–Solid Separation Methods

16.1 CYCLONES

16.2 FABRIC FILTERS

16.3 SCRUBBERS

16.4 ELECTROSTATIC PRECIPITATORS

Chapter 17: Dryer Feeding Equipment

17.1 FLUID-BED DRYERS

17.2 DIRECT-HEAT ROTARY DRYERS

17.3 FLASH DRYERS

17.4 SPRAY DRYERS

17.5 CONVEYOR DRYERS

17.6 HAZEMAG RAPID DRYER

17.7 ANHYDRO SPIN FLASH DRYER

17.8 PLATE DRYERS

17.9 VIGOROUSLY AGITATED CONTACT DRYERS

17.10 VERTICAL THIN-FILM AND DRUM DRYERS

Notation

Index

Copyright © 2012 by John Wiley & Sons. All rights reserved.

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Library of Congress Cataloging-in-Publication Data

Land, C.M. van’t, 1937– Drying in the process industry / C.M. van’t Land. p. cm. Includes bibliographical references and index. ISBN 978-0-470-13117-6 (hardback) 1. Drying. 2. Drying apparatus. 3. Chemical processes. I. Title. TP363.L229 2011 660′.28426–dc22 2011012195

PREFACE

Drying is an important operation in the process industry. This book treats drying as a method for accomplishing liquid–solid separation by other than mechanical means. Usually, heat is supplied, leading to evaporation of a liquid (usually water), and this leaves a solid behind. Drying accomplishes the transformation of a process stream and, as such, often produces a salable product. As drying is an energy-intensive activity and dryers are expensive pieces of equipment, drying must be carried out as economically as possible.

This book is a follow-up to my earlier book, Industrial Drying Equipment:Selection and Application. In comparison to that book, the theoretical basis has been strengthened and the contents have been updated and extended.

The objective of this book is to assist the process development engineer, the process engineer, and the plant engineer in their selection of drying equipment. The theoretical background of drying and criteria to be observed when selecting drying equipment are discussed. Dryer descriptions and procedures for sizing them are treated. The subjects of product quality, process safety, process control, gas cleaning, and dryer feeding complete the book.

Acknowledgments

The writing of the earlier book was made possible by permission of Akzo Nobel Chemicals B.V., to whose management I am still grateful. The invaluable experience gained while in their employ was an important element in the design of that book.

Thanks are due a former colleague, Dave Buckland, who for the earlier book helped to convert my “Dutch English” into proper English and suggested a number of improvements to the contents. For the present book, the linguistic aspects of the modifications of and extensions to the earlier text were checked by the publisher, to whom I am grateful. Thanks are also due my former manager, Hans Postma, who read the manuscript of the earlier book on behalf of Akzo Nobel Chemicals B.V. and, in doing so, made useful suggestions.

Shortly after the earlier book appeared, I began to give seminars on drying in the process industry, mainly in Germany and The Netherlands. I am grateful for the information and suggestions given to me by participants in these seminars. The seminar interaction made clear in which direction industrial drying is going and provided useful contacts and material for the present book.

I began work as a consultant after my retirement. Thanks are due to the companies that I worked for, which thus helped me to extend my knowledge of industrial drying and keep it up to date. Particular appreciation is extended for the assistance given by:

M. Andreae-Jäckering, Altenburger Maschinen Jäckering GmbH

A. Bouwmeester, GMF-Gouda Processing Solutions

D.W. Dahlstrom, Alstom Power, Inc.

S. Gerl, Maschinenfabrik Gustav Eirich GmbH & Co. KG

A. Glockner, Glatt GmbH

A.K.E. Greune, Hazemag & EPR GmbH

W. Hinz, Buss-SMS-Canzler GmbH

W.J.L. Janssen, Deconsult

J. Schmid, FIMA Maschinenbau GmbH

H. Schneider, GoGaS Goch GmbH & Co. KG

I also thank the following companies, which most kindly provided data, drawings, and/or photographs:

Adolf Kühner AG, Birsfelden, Switzerland

Alstom Power, Inc., Warrenville, IL

Altenburger Maschinen Jäckering GmbH, Hamm, Germany

Andritz Fliessbettsysteme GmbH, Ravensburg, Germany

Andritz KMPT GmbH, Vierkirchen, Germany

Anhydro A/S, Søborg, Denmark

Bartec GmbH, Gotteszell, Germany

Bepex International LLC, Minneapolis, MN

Berthold Technologies GmbH & Co. KG, Bad Wildbad, Germany

Braunschweigische Maschinenbauanstalt AG, Braunschweig, Germany

Bucher Processtech AG, Niederweningen, Switzerland

Buss-SMS-Canzler GmbH, Butzbach, Germany

Carrier Vibrating Equipment, Inc., Louisville, KY

CPM Wolverine Proctor LLC, Horsham, PA

CPM Wolverine Proctor Ltd, Glasgow, UK

Deconsult, Heelsum, The Netherlands

FIMA Maschinenbau GmbH, Obersontheim, Germany

FLSmidth A/S, Valby, Denmark

Gala Industries, Inc., Eagle Rock, VA

GEA Barr-Rosin Ltd, Maidenhead, UK

GEA Pharma Systems nv, Wommelgem, Belgium

GEA Process Engineering A/S, Søborg, Denmark

GE General Eastern Instruments, Wilmington, MA

Glatt GmbH, Binzen, Germany

GMF-Gouda Processing Solutions, Waddinxveen, The Netherlands

GoGaS Goch GmbH & Co. KG, Dortmund, Germany

Grenzebach BSH GmbH, Bad Hersfeld, Germany

Hazemag & EPR GmbH, Dülmen, Germany

HERMETIC-Pumpen GmbH, Gundelfingen, Germany

Hosokawa Micron B.V., Doetinchem, The Netherlands

IMA Edwards Freeze Drying Solutions, Dongen, The Netherlands

Kidde Fenwal Inc., Ashland, MA

Kidde Products Limited, Colnbrook, UK

Komline-Sanderson Engineering Corporation, Peapack, NJ

Maschinenfabrik Gustav Eirich GmbH & Co. KG, Hardheim, Germany

Microdry Inc., Crestwood, KY

Mikropul GmbH, Cologne, Germany

Mitchell Dryers Ltd, Carlisle, UK

Nara Machinery Co., Ltd, Frechen, Germany

Oerlikon-Leybold Vacuum GmbH, Cologne, Germany

Patterson-Kelley/Harsco, East Stroudsburg, PA

Process Sensors Corp., Milford, MA

Rembe GmbH Safety + Control, Brilon, Germany

Rosenmund VTA AG, Liestal, Switzerland

SPX Flow Technology Danmark A/S, Søborg, Denmark

STALAM S.p.A., Nove, Italy

Strayfield Limited, Reading, UK

Streekmuseum voor Tholen en Sint-Philipsland “De Meestoof,” Sint-Annaland, The Netherlands

Surface Measurement Systems Ltd, London, UK

Swenson Technology, Inc., Monee, IL

TREMA Verfahrenstechnik GmbH, Kemnath, Germany

Vaisala Oyj, Helsinki, Finland

3V Cogeim SRL, Dalmine, Italy

Vibra Maschinenfabrik Schultheis GmbH & Co., Offenbach am Main, Germany

Wyssmont Company, Inc., Fort Lee, NJ

I also wish to thank the following publishers, who most kindly provided permission to use material:

Access Intelligence, New York

Informations Chimie, Paris, France

The McGraw-Hill Companies, New York

Wiley-Blackwell, Oxford, UK

I am greatly indebted to my wife, Annechien, for her constant encouragement and patience.

C.M. VAN'T LAND

2

DRYING AS PART OF THE OVERALL PROCESS

In the early stages of investigating a drying problem, attention should be given to the entire manufacturing process. This holistic approach may yield one of the following conclusions:

1. The dried product can have a certain residual moisture content.

2. The dewatering step can be optimized.

3. It is possible to simplify the drying step via a process change.

4. The drying step can be combined with one or more other process steps.

5. It is possible to remove the water by a nonthermal method.

6. The drying step can be avoided by changing the process.

7. The product is not dried, whereas the process is not changed.

These seven options are examined below in greater detail.

2.1 RESIDUAL MOISTURE

To dry a product to a very low moisture content often requires a great deal of energy; however, it is sometimes sufficient to dry a product to a specific moisture content before selling it. This would reduce energy costs, and it would be advantageous that more product be sold at the same raw material cost. This option can be useful in combination with a reliable in-plant continuous moisture-monitoring system.

2.2 OPTIMIZATION OF THE DEWATERING STEP

Before drying, it is generally advantageous to remove as much water as possible by filtration or centrifugation. Centrifugation is in this respect in principle more effective than filtration, but it cannot always be used. Due to the centrifugal force, centrifuge cakes may become impermeable.

Example 2.1 The strong fiber Twaron (trade name of Teijin Twaron) is obtained by spinning a solution of the p-aramid polymer poly(p-phenyleneterephtaloylamide) (PPTA) in concentrated sulfuric acid. On spinning, the aramid molecules are arranged in parallel, which confers strength to the yarn through hydrogen bridges. The polymerization of terephtaloyldichloride and p-phenylenediamine to PPTA precedes this step. Prior to the dissolution in concentrated sulfuric acid, the polymer crumb is recovered from an aqueous slurry and dried. Initially, dewatering was carried out using a belt filter to produce an intermediate product containing 6.5 kg of water per kilogram of PPTA. In the 1990s the belt filter was replaced by a filter press, producing an intermediate product containing 2 kg of water per kilogram of PPTA.