Solid/Liquid Separation: Scale-up of Industrial Equipment Edited by R. J. Wakeman Professor, Department of Chemical Engineering, Loughborough University, UK E. S. Tarleton Senior Lecturer, Department of Chemical Engineering, Loughborough University, UK ELSEVIER Solid/Liquid Separation: Scale-up of Industrial Equipment Edited by R. J. Wakeman Professor, Department of Chemical Engineering, Loughborough University, UK E. S. Tarleton Senior Lecturer, Department of Chemical Engineering, Loughborough University, UK ELSEVIER UK Elsevier Ltd, The Boulevard, Langford Lane, Kidlington, Oxford 0X5 1GB, UK USA Elsevier Inc, 360 Park Avenue South, New York, NY 10010-1710, USA JAPAN Elsevier Japan, Tsunashima Building Annex, 3-20-12 Yushima, Bunkyo-ku, Tokyo 113, Japan © 2005 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers. First edition 2005 ISBN 1 8561 74204 British Library Cataloguing in Publication Data Solid/liquid separation : scale-up of industrial equipment 1. Separators (Machines) LWakeman, Richard J. ILTarleton, E. S. 666.2'842 ISBN-10: 1856174204 No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Published by Elsevier Advanced Technology, The Boulevard, Langford Lane, Kidlington, Oxford OX5 IGB, UK Tel:+44(0) 1865 843000 Fax:+44(0) 1865 843971 Typeset by Land & Unwin (Data Sciences) Ltd, Towcester, Northants Printed and bound in Great Britain by MPG Books Ltd, Bodmin. Contents Preface xii List of Contributors xv 1 Solid/liquid separation equipment selection 1 1.1 Methods of equipment selection 1 1.2 Test procedures 4 1.2.1 Jar sedimentation tests 4 1.2.1.1 Example calculation of settling rate from jar test 6 1.2.2 Leaf filter tests 7 1.2.2.1 Example calculations from constant pressure test data 9 1.3 Initial selection procedures 11 1.3.1 Specification of duty 11 1.3.2 Specification of settling characteristics 12 1.3.3 Specification of filtration characteristics 12 1.4 Tables of equipment 14 1.5 Computer software for equipment selection 25 1.6 Shortlisting equipment for pilot scale testing 28 1.7 Conclusions 35 References 35 2 Chemical pre-treatment 38 2.1 Basic theory of suspensions 38 2.2 Pre-treatment chemicals 40 2.2.1 pH modification 40 2.2.2 Inorganic coagulants 41 2.2.3 Organic coagulants 42 2.2.4 Bridging flocculants 43 2.2.4.1 The mechanism of bridging flocculation 43 2.2.4.2 Natural products 45 iv Contents 2.2.4.3 Synthetic polyelectrolytes 2.2.4.4 Ionicity 2.2.4.5 Molecular weight and structure 2.2.5 Surfactants 2.3.1 Substrate preparation and characterisation 2.3.1.1 Substrate sampling and preparation 2.3.1.2 Substrate characterisation 2.3.2.1 Example Dose level calculations and definitions 2.3.4.1 Substrate solids concentration 2.3.4.2 Dose level 2.3.5 Qualitative screening tests 2.3.6 Vacuum filtration 2.3 Test protocols 2.3.2 Reagent preparation 2.3.3 Mixing and application techniques 2.3.4 2.3.6.1 Horizontal vacuum filtration 2.3.6.2 Rotary vacuum filtration 2.3.7.1 Calculations 2.3.8.1 Beaker test 2.3.8.2 Sheared CST 2.3.8.3 Free drainage test 2.3.8.4 Centrifugal sedimentometry 2.3.8.5 Piston press test 2.3.7 Pressure filtration 2.3.8 Centrifugation References Acknowledgements 3 Deep bed filters 3.1 Operating characteristics 3.2 Measurement of filterability 3.1.1 Summary of test programme 3.2.1 Definition of filterability number 3.2.2 Apparatus 3.2.3 Experimental procedure 3.2.4 Interpretation of data Small scale filters - filter models 3.3.1 Apparatus 3.3.1.1 Main unit 3.3.1.2 Feed arrangements 3.3.1.3 Outlet arrangements 3.3.1.4 Pressure measurement and sampling 3.3 - 45 46 46 49 49 49 49 51 51 52 53 54 54 54 55 56 56 59 63 66 69 69 71 74 76 78 79 81 82 82 84 85 85 86 86 87 88 89 89 91 91 92 3.4 3.5 3.6 3.7 3.8 3.3.2 3.3.3 Contents v 3.3.1.5 Filling the filter with media Operating procedure Analysis of data 3.3.3.1 Use of particle counting and sizing Full scale filters Filter operation 3.5.1 3.5.2 Flow Control 3.5.1.1 Head loss and permeability 3.5.1.2 Flow controllers Filter washing 3.5.2.1 Fluidised beds and fluidisation theory 3.5.2.2 Calculating head loss 3.5.2.3 Use of air scour 3.5.2.4 Combined air and water wash 3.5.2.5 Cleaning mechanisms 3.5.2.6 Media attrition and loss during backwash 3.5.2.7 Backwashing of dual and triple media filters Filter media 3.6.1 3.6.2 3.6.3 Media types Media testing 3.6.2.1 Size 3.6.2.2 Shape 3.6.2.3 Density 3.6.2.4 Durability 3.6.2.5 Solubility 3.6.2.6 Cleanliness 3.6.2.7 Fall velocity 3.6.2.8 SEM analysis Multilayer filters 3.6.3.1 Depths of filter layers 3.6.3.2 Selectionof filter media Alternative filters 3.7.1 3.7.2 3.7.3 Continuous filters 3.7.1.1 Modelling Pebble matrix filters Slow sand filters Specialized techniques 3.8.1 3.8.2 3.8.3 3.8.4 3.8.5 3.8.6 In-depth sampling Multiple filter operation Radioactive labelling Radial flow filtration Conductivity technique Surface chemical properties 93 94 95 97 98 100 100 100 101 103 103 106 107 107 108 108 108 109 109 109 110 112 115 115 117 118 118 119 119 120 122 123 123 124 126 129 132 132 132 132 132 132 133 vi Contents 3.8.7 Optical fibre endoscopy 3.8.8 Mathematical and computer modelling Nomenclature References 4 Membrane filters - Microflltration and ultrafiltration 4.1 4.2 4.3 4.4 Direct flow filtration (DFF) 4.1.1 Single pass 4.1.2 Approach to media selection 4.1.3 Automated scale-up test devices 4.1.4 Constant pressure test 4.1.4.1 Vcap data calculations 4.1.4.2 Sizing 4.1.4.3 Processing time 4.1.5 Constant flow test (Pcap) 4.1.6 Case study Recirculation systems 4.2.1 Filter selection Tangential flow filtration (TFF) 4.3.1 Biopharmaceutical MF and UF 4.3.1.1 Cassettes 4.3.1.2 Hollow fibre 4.3.1.3 Ceramics 4.3.1.4 Systems 4.3.1.5 Sizing and scale-up for TFF UF 4.3.1.6 Membrane selection 4.3.1.7 System optimisation 4.3.1.8 Determination of the maximum gel concentration (CQ) 4.3.1.9 Diafiltration 4.3.1.10 Cleaning and storage 4.3.1.11 Scale-up 4.3.1.12 Calculation of membrane surface area 4.3.2 Industrial MF 4.3.2.1 System scale-up 4.3.2.2 Laboratory test equipment 4.3.2.3 Test procedure 4.3.2.4 Results and significance of laboratory scale trials 4.3.2.5 Pilot trials 4.3.2.6 Case study TFF/DFF applications 4.4.1 Water processing 133 135 135 136 140 142 142 142 143 144 146 147 148 149 151 153 154 156 156 158 158 160 160 161 164 165 167 170 171 171 172 174 174 175 176 178 179 182 184 184 4.4.1.1 Water quality analysis 4.4.1.2 Pilot testing 4.4.1.3 Test operation, results and discussion 4.4.1.4 Integrity testing 4.4.1.5 Jar testing 4.4.1.6 Data scale up 4.4.1.7 Case study Nomenclature and abbreviations References Acknowledgements 5 Pressure filters 5.1 5.2 5.3 5.4 Equipment introduction and key filters 5.1.1 Plate and frame chamber filters 5.1.2 Recessed plate chamber filters 5.1.3 Membrane filter presses Contents vi 185 188 187 190 191 192 192 194 195 195 196 196 198 199 201 5.1.4 Tower presses, or vertical membrane filter presses 206 5.1.5 Tube presses Filter automation Design considerations 5.3.1 Filter proj ect obj ecti ves 5.3.2 Filter plant philosophy 5.3.3 Filter plant throughput 5.3.4 Filter feed characterisation 5.3.5 Conceptual filter plant design Dimensioning and scale-up 5.4.1 Test methods 5.4.1.1 Sample acquisition and storage 5.4.1.2 Preparation for testing 5.4.2 Test equipment 5.4.2.1 Bench top test equipment 5.4.2.2 Manufacturers test equipment 5.4.2.3 Pilot plant test equipment 5.4.3 Interpreting the test data 5.4.3.1 Cake and medium resistance 209 210 211 212 213 214 214 215 215 215 216 217 218 218 221 222 223 223 5.4.3.2 Mass per unit area from "pressure bomb" tests 226 5.4.3.3 Mass per unit area or volume from manufacturers' test filters and pilot filters 227 5.5 Integrating the filter into the flow sheet 229 5.5.1 Filter elevation 230 5.5.2 Feed preparation 230 viii Contents 5.5.3 Trash removal 5.5.4 Surge capacity 5.5.5 Filter feed pump 5.5.6 5.5.7 Cake compression or “pressing” 5.5.8 5.5.9 Filtrate handling 5.5.10 Filter cake handling 5.5.11 Cloth washing 5.6 Plant operating considerations References Appendix Feed manifold flushing and core blowing Cake drying by air blowing 6 Vacuum filters 6.1 Advantages and limitations of vacuum filters 6.1.1 Vacuum filters - limitations 6.1.2 Vacuum filters - advantages 6.2.1 Batch discharge filters 6.2.2 Continuous discharge filters 6.2 Descriptions of full-scale filters 6.2.1.1 Single tipping pan filters 6.2.2.1 Rotary drum vacuum filters 6.2.2.2 Rotary disc filters 6.2.2.3 Horizontal belt filters 6.2.2.4 Multiple tipping pan filters 6.2.2.5 Table filters 6.2.3.1 Rotary valve assembly 6.2.3.2 Filtrate receiver 6.2.3.3 Filter medium 6.2.3.4 Cake discharge techniques 6.2.3 Common components 6.3 Basic process design considerations 6.3.1 Initial equipment selection 6.3.2 Filter cloth selection 6.3.3 Test suspensions 6.3.4 Chemicals pretreatment - flocculants and coagulants 6.3.5 Solids concentration effects 6.4 Experimental test procedure 6.4.1 Filter test leaf 6.4.2 Filter test leaf procedures 6.4.2.1 Bottom feed filters 6.4.2.2 Top feed filters 230 230 23 1 232 233 233 234 234 235 235 236 238 239 240 240 242 242 242 242 244 244 253 254 257 258 258 259 26 1 263 2 64 265 265 268 269 27 1 272 273 273 275 278 280 6.5 6.6 6.7 6.8 6.9 Cor 6.4.2.3 Precoat filters 6.4.2.4 Cake washing Interpretation of test data 6.5.1 Filtration theory and applicable equations 6.5.2 Filtration flux 6.5.3 Filter cake properties 6.5.4 Filter cake washing 6.5.5 Time and mechanical degradation of agglomerated particles 6.5.6 Air flow rate and applied vacuum Laboratory and pilot-scale test units 6.6.1 Laboratory scale trials 6.6.2 Pilot scale trials Test results scale-up 6.7.1 Scale-up factor on measured rate 6.7.2 Scale-up on test area 6.7.3 Scale-up on filter cake discharge 6.7.4 Cumulative scale-up factor on filtration rate 6.7.5 Air flow requirement Full-scale filtration equipment Worked examples 6.9.1 Drum filter - filtration troubleshooting 6.9.1.1 Investigation and discussion 6.9.2 Drum filter - sizing 6.9.2.1 Investigation and discussion Nomenclature References 7 Filtering centrifuges 7.1 7.2 The basic filtering centrifiige 7.1.1 Basic filtering batch centrifuge 7.1.1.1 Feeding 7.1.1.2 Washing 7.1.1.3 Spinning 7.1.1.4 Discharging 7.1.1.5 Filtrate clarity 7.1.2 Basic filtering continuous centrifiige 7.1.2.1 Feeding 7.1.2.2 Washing and drying 7.1.2.3 Discharging 7.1.2.4 Filtrate clarity Filtering centrifuge types 7.2.1 Batch filtering centrifuge types 7.2.1.1 Vertical plough discharge itents ix 281 283 283 283 287 289 291 293 293 295 295 296 297 297 298 299 299 300 300 302 303 303 307 307 311 312 314 314 315 317 319 319 320 320 321 323 323 323 323 324 325 325 [...]... amount of data about the process and some preliminary knowledge of the separability of the feed together with a form of inference mechanism such as a selection chart or table This combination allows the identification of a range of equipment that could be expected to carry out the required duty If necessary, the equipment list can be shortened 2 Solid/Liquid Separation: Scale-up of Industrial Equipment. .. calculate the ratio of the mass of wet cake to the mass of wet cake 1.2.2.1 Example calculations from constant pressure test data The following data were obtained from a leaf filter with an area of 45 cm^ using a pressure difference of 70 kPa (data taken from Wakeman and Tarleton, 2005) The ratio of the mass of wet cake to mass of dry 10 Solid/Liquid Separation: Scale-up of Industrial Equipment cake was... of the separation characteristics of the slurry (e.g BEG, K) If the proposed duty is simply to thicken a slurry then it is not necessary to carry out a filtration test However, for a total separation of the solid from the liquid (as obtained in a filter, for example) both settling and filtration tests need to be performed 14 Solid/Liquid Separation: Scale-up of Industrial Equipment 1,4 Tables of equipment. .. selection of equipment The basis for the selection and ranking of potentially suitable equipment for a particular separation is described through knowledge of experimental data, selection charts and an expert system approach Additional tables indicate how ranked equipment can be further short-listed for further investigation 1.1 Methods of equipment selection Although a number of different approaches to equipment. .. the feed and economic factors (Tables 1.5 and 1.6) yes 1r Shortlist of equipment for pilot testing or further simulation Figure 1.1 Flowchart for the selection of solid/liquid separation equipment by performing further small scale test work more germane to the identified equipment The final shortlist of equipment contains those items of equipment that are worth further evaluation through pilot testing... computer software has been developed to commercial standards and this led to the release of FDS The underlying philosophies used within the selection module of FDS are described in this chapter 4 Solid/Liquid Separation: Scale-up of Industrial Equipment 1,2 Test procedures The general procedure developed by Purchas provides a valuable, nonspecialist, guide through the complex and confusing area of equipment. .. determined by industrial practice The style of the book has a strong practical emphasis and is intended to act as a reference text for engineers concerned with applications evaluation of equipment or its scale-up Solid/liquid separation has many features in common with solid/gas (or air) separation, but also certain clear points of difference One of these remains the virtual total absence of any standardized... development The enormous choice of solid/liquid separation equipment is bewildering to the non-expert and selection of appropriate equipment is thus problematic to the design engineer It is often difficult to identify the most appropriate separator without extensive previous knowledge of a similar separation problem The purpose of this chapter is to provide guidance on what form of small scale tests and results... volume of the settled solids after 24 hours (or some shorter time if the settling has completed), expressed as a percentage of the original volume, should also be recorded 6 Solid/Liquid Separation: Scale-up of Industrial Equipment (a) I (b) 1 Clear liquid (c) Uniform concentration (d) Sediment in compression Figure 1.2 Sedimentation of a suspension in a jar test 1.2.1.1 Example calculation of settling... volume of sludge at the bottom of the measuring cylinder after the slurry has finished settling, and check the acceptability of the supernatant liquid 5 The settling rate is determined by plotting a graph of suspensionsupernatant interface height v^* time, identifying the set of points which comprise the initial linear portion and calculating the gradient of a line of best fit The proportion of sludge . identification of a range of equipment that could be expected to carry out the required duty. If necessary, the equipment list can be shortened 2 Solid/Liquid Separation: Scale-up of Industrial Equipment. Integration of equipment in flow sheet 8.5.1 8.5.2 8.5.3 8.5.4 Separation of polyvinyl chloride Classification of kaolin slurries Separation in calcium carbonate plant Separation of yeast. Department of Chemical Engineering, Loughborough University, UK ELSEVIER Solid/Liquid Separation: Scale-up of Industrial Equipment Edited by R. J. Wakeman Professor, Department of Chemical