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A Working Guide to Process Equipment A Working Guide to Process Equipment Norman P. Lieberman Elizabeth T. Lieberman Third Edition New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. 0-07-164096-7 The material in this eBook also appears in the print version of this title: 0-07-149674-2. All trademarks are trademarks of their respective owners. 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If you’d like more information about this book, its author, or related books and websites, please click here. To the union of two people Weathering life's storms together Watching the lightening Waiting for the thunder In friendship, In partnership In love To the Memory of Our Friend and Colleague Gilles de Saint Seine Process Engineer Total-Fina-Elf, France It’s more than losing a friend, it seems as if Liz and I have lost part of ourselves, but we will always remember his gentle determination and insightful work, his love of family and consideration for his colleagues, and not least his marvelous wit. This book is dedicated to our parents: Elizabeth and Tom Holmes, innovative engineers, courageous under fire at war and in peace. Mary and Lou Lieberman whose enduring strength and fortitude have been little noted, but long remembered. For more information about this title, click here Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii Preface to Third Edition . . . . . . . . . . . . . . . . . . . . . . . xix Preface to Second Edition . . . . . . . . . . . . . . . . . . . . . . xxi Preface to First Edition . . . . . . . . . . . . . . . . . . . . . . . . xxiii Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix 1 Process Equipment Fundamentals . . . . . . . . . . . . . . 1.1 Frictional Losses . . . . . . . . . . . . . . . . . . . . . . . 1.2 Density Difference Induces Flow . . . . . . . . . 1.3 Natural Thermosyphon Circulation . . . . . . . 1.4 Reducing Hydrocarbon Partial Pressure . . . 1.5 Corrosion at Home . . . . . . . . . . . . . . . . . . . . . 1.6 What I Know . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Distillation: The First Application . . . . . . . . 1.8 Origin of Reflux . . . . . . . . . . . . . . . . . . . . . . . . 1 3 3 3 4 5 6 8 12 2 Basic Terms and Conditions ................... 13 3 How Trays Work: Flooding Downcomer Backup .................... 23 Tray Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . Downcomer Backup . . . . . . . . . . . . . . . . . . . . Downcomer Clearance . . . . . . . . . . . . . . . . . . Vapor-Flow Pressure Drop . . . . . . . . . . . . . . Jet Flood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Incipient Flood . . . . . . . . . . . . . . . . . . . . . . . . . Tower Pressure Drop and Flooding . . . . . . . 23 25 26 29 31 32 34 How Trays Work: Dumping . . . . . . . . . . . . . . . . . . . . Weeping through Tray Decks 37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 4 4.1 4.2 4.3 4.4 5 Tray Pressure Drop . . . . . . . . . . . . . . . . . . . . . Other Causes of Tray Inefficiency . . . . . . . . . Bubble-Cap Trays . . . . . . . . . . . . . . . . . . . . . . New High Capacity Trays . . . . . . . . . . . . . . . 38 41 43 45 Why Control Tower Pressure . . . . . . . . . . . . . . . . . . Options for Optimizing Tower Operating Pressure 47 5.1 5.2 Selecting an Optimum Tower Pressure . . . . Raising the Tower Pressure Target . . . . . . . . 48 49 vii viii Contents 5.3 5.4 6 ............ ............ 50 54 ............... 57 The Reboiler . . . . . . . . . . . . . . . . . . . . . . . . . . . Heat-Balance Calculations . . . . . . . . . . . . . . . 57 59 How Reboilers Work . . . . . . . . . . . . . . . . . . . . . . . . . . Thermosyphon, Gravity Feed, and Forced 67 What Drives Distillation Towers Reboiler Function 6.1 6.2 7 7.1 7.2 7.3 7.4 8 9 Thermosyphon Reboilers . . . . . . . . . . . . . . . . Forced-Circulation Reboilers . . . . . . . . . . . . . Kettle Reboilers . . . . . . . . . . . . . . . . . . . . . . . . Don’t Forget Fouling . . . . . . . . . . . . . . . . . . . 68 74 75 77 Inspecting Tower Internals . . . . . . . . . . . . . . . . . . . . 8.1 Tray Deck Levelness . . . . . . . . . . . . . . . . . . . . 8.2 Loss of Downcomer Seal Due to Leaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Effect of Missing Caps . . . . . . . . . . . . . . . . . . 8.4 Repairing Loose Tray Panels . . . . . . . . . . . . . 8.5 Improper Downcomer Clearance . . . . . . . . . 8.6 Inlet Weirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Seal Pans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Drain Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Vortex Breakers . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Chimney Tray Leakage . . . . . . . . . . . . . . . . . . 8.11 Shear Clips . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Bubble-Cap Trays . . . . . . . . . . . . . . . . . . . . . . 8.13 Final Inspection . . . . . . . . . . . . . . . . . . . . . . . . 8.14 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 79 How Instruments Work . . . . . . . . . . . . . . . . . . . . . . . Levels, Pressures, Flows, and Temperatures 9.1 9.2 9.3 9.4 9.5 10 Lowering the Tower Pressure The Phase Rule in Distillation 80 81 81 81 82 82 83 84 84 84 85 86 86 89 Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Foam Affects Levels . . . . . . . . . . . . . . . . . . . . Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 94 97 98 101 Packed Towers: Better than Trays? . . . . . . . . . . . . . . Packed-Bed Vapor and Liquid Distribution 105 10.1 10.2 How Packed Towers Work . . . . . . . . . . . . . . Maintaining Functional and Structural Efficiency in Packed Towers . . . . . . . . . . . . . 10.3 Advantages of Packing vs. Trays . . . . . . . . . 105 111 117 Contents 11 Steam and Condensate Systems . . . . . . . . . . . . . . . . Water Hammer and Condensate Backup Steam-Side Reboiler Control 11.1 11.2 11.3 11.4 11.5 11.6 11.7 12 Steam Reboilers . . . . . . . . . . . . . . . . . . . . . . . . Condensing Heat-Transfer Rates . . . . . . . . . Maintaining System Efficiency . . . . . . . . . . . Carbonic Acid Corrosion . . . . . . . . . . . . . . . . Condensate Collection Systems . . . . . . . . . . Deaerators . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surface Condensers . . . . . . . . . . . . . . . . . . . . . 119 121 124 127 128 131 133 Bubble Point and Dew Point . . . . . . . . . . . . . . . . . . . Equilibrium Concepts in Vapor-Liquid Mixtures 137 12.1 12.2 13 Bubble Point . . . . . . . . . . . . . . . . . . . . . . . . . . . Dew Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 141 144 Steam Strippers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Source of Latent Heat of Vaporization 145 13.1 13.2 14 Heat of Evaporation . . . . . . . . . . . . . . . . . . . . Stripper Efficiency . . . . . . . . . . . . . . . . . . . . . . 145 147 Draw-Off Nozzle Hydraulics . . . . . . . . . . . . . . . . . . Nozzle Cavitation Due to Lack of Hydrostatic Head 155 14.1 14.2 14.3 14.4 15 Nozzle Exit Loss . . . . . . . . . . . . . . . . . . . . . . . Critical Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . Maintaining Nozzle Efficiency . . . . . . . . . . . Overcoming Nozzle Exit Loss Limits . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pumparounds and Tower Heat Flows Closing the Tower Enthalpy Balance 15.1 15.2 15.3 16 119 155 158 159 163 165 ........... 167 The Pumparound . . . . . . . . . . . . . . . . . . . . . . Vapor Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fractionation . . . . . . . . . . . . . . . . . . . . . . . . . . 167 171 175 Condensers and Tower Pressure Control Hot-Vapor Bypass: Flooded Condenser Control ........ 177 Subcooling, Vapor Binding, and Condensation . . . . . . . . . . . . . . . . . . . . . . 16.2 Pressure Control . . . . . . . . . . . . . . . . . . . . . . . 178 184 16.1 ix x Contents 17 18 Air Coolers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fin-Fan Coolers 193 17.1 Fin Fouling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Fan Discharge Pressure . . . . . . . . . . . . . . . . . 17.3 Effect of Reduced Airflow . . . . . . . . . . . . . . . 17.4 Adjustments and Corrections to Improve Cooling . . . . . . . . . . . . . . . . . . . . . 17.5 Designing for Efficiency . . . . . . . . . . . . . . . . . 193 195 196 Deaerators and Steam Systems . . . . . . . . . . . . . . . . . Generating Steam in Boilers and BFW Preparation 18.1 18.2 18.3 19 Boiler Feedwater . . . . . . . . . . . . . . . . . . . . . . . Boilers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Convective Section Waste-Heat Steam Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vacuum Systems: Steam Jet Ejectors Steam Jet Ejectors 215 216 Theory of Operation . . . . . . . . . . . . . . . . . . . . Converging and Diverging Compression . . Calculations, Performance Curves, and Other Measurements in Jet Systems . . . . . . . 19.4 Optimum Vacuum Tower-Top Temperature 19.5 Measurement of a Deep Vacuum without Mercury . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 219 220 232 233 234 Steam Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Use of Horsepower Valves and Correct Speed Control Principle of Operation and Calculations . . . Selecting Optimum Turbine Speed . . . . . . . . 235 241 Surface Condensers . . . . . . . . . . . . . . . . . . . . . . . . . . . The Condensing Steam Turbine 247 21.1 21.2 21.3 22 206 211 217 20.1 20.2 21 205 ............ 19.1 19.2 19.3 20 197 198 The Second Law of Thermodynamics . . . . . Surface Condenser Problems . . . . . . . . . . . . . Surface Condenser Heat-Transfer Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shell-and-Tube Heat Exchangers Heat-Transfer Fouling Resistance 248 253 258 258 ............... 259 22.1 Allowing for Thermal Expansion . . . . . . . . . 22.2 Heat-Transfer Efficiency . . . . . . . . . . . . . . . . . 259 268