lV3 NOILLI~H I Rules of Thumb for Chemical Engineers RULES OF THUMB FOR CHEMICAL ENGINEERS A manual of quick, accurate solutions to everyday process engineering problems Third Edition Carl R. Branan, Editor Gulf Professional Publishing an imprint of Elsevier Science Amsterdam London New York Oxford Paris Tokyo Boston San Diego San Francisco Singapore Sydney To my five grandchildren: Katherine, Alex, Richard, Matthew and Joseph Gulf Professional Publishing is an imprint of Elsevier. Copyright by Elsevier (US.4). All rights reserved. Originally published by Gulf Publishing Company, Houston, TX No part of this publication ma!; be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic. mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Permissions may be sought directly from Elsevier's Science & Technology Rights Department in Osford, UK: phone: (+44) 1865 843830, fax: (+44) 1865 853333, e-mail: permissions~,elsei,ier.co.uk. You may also complete your request on-line via the Elsevier Science homepage (http://uww.elsevier.com), by selecting 'Customer Support' and then 'Obtaining Permissions'. ,- E' This book is printed on acid-free paper. Library of Congress Cataloging-in-Publication Data Rules of thumb for chemical engineers: a manual of quick, accurate solutions to eievday process engineering problernsiCar1 R. Branan, editor 3Id ed. p. cm. Includes index. ISBN 0-7506-7567-5 (pbk.: akpaper) 1. Chemical engineering-Handbooks, manuals, etc. I. Branan, Carl. TPl5l.R85 2002 660-dc2 1 2002071157 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British LibrarJ The publisher offers special discounts on bulk orders of this book. For information, please contact: Manager of Special Sales Elsevier Science 200 Wheeler Road Burlington, MA 01803 Tel: 781-3 13-4700 Fax: 781-313-4802 For information on all Gulf publications available, contact our World Wide Web homepage at httD:!'i\nr.lv.bh.com:vuIf 10 9 8 7 6 5 4 3 2 Printed in the United States of America. 3: Fractionators. 49 SECTION ONE Equipment Design 1 1: Fluid Flow. 2 Velocity head 3 Equivalent length 4 Two-phase flow 7 Sonic velocity 12 Metering 12 Control valves 13 Safety relief valves 16 Piping pressure drop Recommended velocities 5 Compressible flow 9 2: Heat Exchangers. 19 TEMA 20 Selection guides 24 Pressure drop shell and tube 27 Temperature difference 29 Shell diameter 30 Shellside velocity maximum 30 Nozzle velocity maximum 3 1 Heat transfer coefficients 3 1 Fouling resistances 38 Metal resistances 40 Vacuuni condensers 42 Air-cooled heat exchangers: forced vs induced draft 42 Air-cooled heat exchangers: psessure drop air side 43 Air-cooled heat exchangers: rough rating 44 Air-cooled heat exchangers: temperature control 46 Miscellaneous rules of thumb 48 Introduction 50 Relative volatility 50 Minimum reflux 51 Minimum stages 52 Actual reflux and actual theoretical stages 52 Actual trays 54 Reflux to feed ratio 53 Graphical methods 54 Tray efficiency Diameter of bubble cap trays 59 Diameter of sieve/valve trays (F factorj 60 Diameter of sievehralve trays (Smith) 61 Diameter of sievehlve trays (Lieberman) 63 Diameter of ballast trays 63 Diameter of fractionators . general 65 Control schemes 65 Optimization techniques 69 Reboilers 72 Packed columns 76 4: Absorbers. 97 Introduction 98 Hydrocarbon absorber design 98 Hydrocarbon absorbers . optimization 100 Inorganic type 101 5: Pumps. 104 Affinity laws 105 Efficienc 105 Minimum fl0.c. 105 General suction system 106 Suction system NPSH available 107 Horsepower 105 Suction system NPSH for studies 108 Suction system NPSH with dissolved gas 109 Larger impeller 109 Construction materials 109 V vi Contents 6: Compressors. 11 2 Ranges of application 11 3 Generalized Z 11 3 Generalized K 114 Horsepower calculation 1 15 Efficiencp 119 Temperature rise 121 Surge controls 12 1 7: Drivers. 122 Motors: efficiency 123 Motors: starter sizes 124 Motors: service factor 124 Motors: useful equations 125 Motors: relative costs 125 Motors: overloading 126 Steam turbines: steam rate 126 Steam turbines: efficiency 126 Gas turbines: fuel rates 127 Gas engines: fuel rates 129 Gas expanders: available energy 129 8: SeparatorslAccumulators. 1 30 Liquid residence time 13 1 Vapor residence time 132 VaporAiquid calculation method 133 LiquidAiquid calculation method 135 Pressure drop 135 Vessel thickness 136 Gas scrubbers 136 Reflux drums 136 General vessel design tips 137 9: Boilers. 138 Power plants 139 Controls 139 Thermal efficiency 140 Impurities in water 145 Conductivity versus dissolved solids 147 Silica in steam 148 Caustic embrittlement 148 Waste heat 150 10: Cooling Towers. 153 System balances 154 Temperature data 154 Performance 156 Performance estimate: a cast history 158 Transfer units 158 SECTION TWO Process Design 161 11: Refrigeration. 162 Types of systems 163 Estimating horsepower per ton 163 Horsepower and condenser duty for specific refrigerants 164 Refrigerant replacements 182 Ethylene/propylene cascaded system 183 Ammonia absorption type utilities Steam jet type utilities requirements 183 requirements 186 12: Gas Treating. 187 Introduction 188 Gas treating processes 188 Reaction type gas treating 190 Physical solvent gas treating 191 Solution batch type 192 Bed batch type 193 PhysicaVchemical type 191 Carbonate type 192 Stack gas enthalpy 141 Stack gas quantity 142 Steam drum stability 143 Deaerator venting 144 Water alkalinity 145 Blowdown control 145 13: ~aCUUm systems. 194 Vacuum jets 195 Typical jet systems 196 Steam supply 197 Contents vii Measuring air leakage 198 Design recommendations 199 Ejector specification sheet 200 Time to evacuate 198 14: Pneumatic Conveying. 202 Types of systems 203 Differential pressures 204 Equipment sizing 204 15: Blending. 206 Single-stage mixers 207 Multistage mixers 207 Gadliquid contacting 208 Liquid/liquid mixing 208 Liquidkolid mixing 208 Mixer applications 209 Shrouded blending nozzle 210 Vapor formation rate for tank filling 210 SECTION THREE Plant Design 21 1 16: Process Evaluation. 21 2 Introduction 2 13 Study definition 2 13 Process definition 2 15 Battery limits specifications 222 Offsite specifications 226 Capital investments 230 Operating costs 237 Economics 240 Financing 244 67: Reliability. 247 18: Metallurgy. 249 Embrittlement 250 Stress-corrosion cracking 256 Hydrogen attack 257 Pitting corrosion 259 Creep and creep-rupture life 260 Metal dusting 262 Naphthenic acid corrosion 264 Fuel ash corrosion 265 Thermal fatigue 267 Abrasive wear 269 Pipeline toughness 270 Common corrosion mistakes 271 19: Safety. 272 Estimating LEL and flash 273 Tank blanketing 273 Equipment purging 275 Static charge from fluid flow 276 Mixture flammability 279 Relief manifolds 282 Natural ventilation 288 20: Controls. 289 Introduction 290 Extra capacity for process control 290 Controller limitations 291 False economy 292 Definitions of control modes 292 Control mode comparisons 292 Control mode vs application 292 Pneumatic vs electronic controls 293 Process chromatographs 294 SECTION FOUR Operations 285 21 : Troubleshooting. 296 Introduction 297 Fractionation: initial checklists 297 Fractionation: Troubleshooting checklist 299 Fractionation: operating problems 301 Fractionation: mechanical problems 307 troubleshooting 311 Fractionation: “Normal” parameters 312 Fractionation: Getting ready for viii Contents Fluid flow 313 Firetube heaters 317 Gas treating 319 Measurement 325 Refrigeration 316 Safety relief valves 318 Compressors 323 22: Startup. 326 Introduction 327 Probable causes of trouble in controls 328 Checklists 330 Settings for controls 327 Autoignition temperature 371 Gibbs free energy of formation 376 New refrigerants 386 26: Approximate Conversion Factors. 387 Approximate conversion factors 388 Appendixes 389 Appendix 1: Shortcut Equipment Design Methods.0verview. 390 23: Energy Conservation. 334 Appendix 2: Geographic Information Systems. 392 Target excess oxygen 335 Stack heat loss 336 Stack gas dew point 336 Equivalent fuel values 338 Heat recovery systems 339 Process efficiency 340 Steam traps 341 Gas expanders 343 Fractionation 344 Insulating materials 344 24: Process Modeling Using Linear Programming. 345 Process modeling using linear programming 346 25: Properties. 351 Introduction 352 Approximate physical properties 352 Viscosity 353 Surface tension 358 Gas diffusion coefficients 358 Water and hydrocar~ons 360 Natural gas hydrate temperature 364 Inorganic gases in petroleum 366 Relative humidity 357 Appendix 3: Internet Ideas. 394 Appendix 4: Process Safety Management. 397 Appendix 5: Do-It-Yourself Shortcut Methods. 399 Appendix 6: Overview for Engineering Students. 406 Appendix 7: Modern Management Initiatives. 409 Appendix 8: Process Specification Sheets. 41 0 Vessel data sheet 411 Shell and tube exchanger data sheet 412 Double pipe (G-fin) exchanger data sheet 413 Air-cooled (fin-fan) exchanger data sheet 414 Direct fired heater data sheet 415 Centrifugal pump (horizontal or vertical) data sheet 416 Pump (vertical turbine-can or propellor) data sheet 417 Tank data sheet 418 Cooling tower data sheet 419 Foam density 368 EquiITalent diameter 369 Index. 423 SECTION ONE Equipment Design [...]... a, - np $ E ne $5 s 5 $5 g 5 $5 ;z c - a , c E 4 - E N E m a, d - ~ 28 32 38 42 46 52 56 7c 84 9 E 112 12E 19c - 21 24 27 30 33 36 39 51 60 69 81 90 99 20 22 24 28 32 34 36 44 52 64 72 80 92 - Sudden Equiv L in terms of small d - - - x 3 x x x II II II II II II n 0 - - ~ E: Sudden 2 s 0 U - 5 7 8 10 12 18 25 31 37 42 47 53 60 65 70 3 4 5 6 8 12 16 20 24 26 30 35 38 42 46 - - - 1 1 2 2 3 4 5 - n -0 -a... 20 Vacuum Condensers Air-cooled Heat Exchangers: Forced vs Induced Draft Air-cooled Heat Exchangers: Pressure Drop Air Side Air-cooled Heat Exchangers: Rough Rating Air-cooled Heat Exchangers: Temperature Control Miscellaneous Rules of Thumb 24 27 29 30 30 31 31 38 40 19 42 42 43 44 46 48 20 Rules of Thumb for Chemical Engineers TEMA Figures 1-4 and Table 1 from the Standards of Tubular Exchanger Manufacturers... flows 4-6 .5 1-5 0. 5-3 4-8 1. 5-4 2-7 1 5-3 0 1 5-8 0 0. 5-1 .5 *To be used as guide, pressure drop and system environment govern final selection of pipe size For heavy and viscous fluids, velocities should be reduced to about values shown Fluids not to contain suspended solid particles Suggested Steam Pipe Velocities in Pipe Connecting to Steam Turbines Service-Steam Typical range, Wsec 10 0-1 50 17 5-2 00 40 0-5 00... of line, ft h1 = elevation at origin of line ft Pa,g= average line pressure, psia E = efficiency factor E = 1 for new pipe with no bends, fittings, or pipe diameter changes Qb 10 Rules of Thumb for Chemical Engineers E = 0.95 for very good operating conditions, typically through first 1 2-1 8 months E = 0.92 for average operating conditions E = 0.85 for unfavorable operating conditions Nomenclature for. .. Fluid Saturated Vapor 0 to 50 psig Gas or Superheated Vapor 0 to 10 psig 11 to 100 psig 101 to 900 psig Typical Design* Velocities for Process System Applications 56’’ Line Sizes 8’ -1 2’’ 3 0-1 15 5 0-1 25 6 0-1 45 5 0-1 40 4 0-1 15 3 0-8 5 9 0-1 90 7 5-1 65 6 0-1 50 11 0-2 50 9 5-2 25 8 5-1 65 214 *Values listed are guides, and final line sizes and flow velocities must be determined by appropriate calculations to suit... YLand YG curves in Perry’s4 for both phases in turbulent flow (the most common case): YL = 4.6X-1.78 12.5X”.68+ 0.65 + Y G = X’YL 8 Rules of Thumb for Chemical Engineers 10.0 8.0 6.0 4.0 2.0 L c z ‘2 0 6 2 P 1.0 0.8 0.6 0.4 m : 0.2 0.1 0.08 0.06 O.OE ,/ - 7 - \ x 10 x 100 x 1,000 Flowrate, Ib/h ’ \ x 10,000 x 100,000 Sizing Lines for Flashing Steam-Condensate The X range for Lockhart and Martinelli... mechanically can do chemically yes, mechanically or chemically yes, mechanically or chemically yes, mechanically or chemically yes, mechanically or chemically Tube exteriors with triangular pitch cleanable chemically only chemically only chemically only chemically only chemically only Tube exteriors with square pitch cleanable yes, mechanically or chemically chemically only yes, mechanically or chemically yes,... Diameter) in 7 Failure of Automatic Controls 8 Loss of Reflux 9 Chemical R-eaction (this heat can sometimes exceed the heat of an external fire) Consider bottom venting for reactive liquids.' Plants, situations, and causes of overpressure tend to be dissimilar enough to discourage preparation of generalized calculation procedures for the rate of discharge In lieu of a set procedure most of these problems... table gives equivalent lengths of pipe for various fittings Table 1 Equivalent Length of Valves and Fittings in Feet Enlargement e - - w m E E 'Z L a 02 gF Fg -Y a , m a, > m a,c 0) O 0) 0- 3 h - 17/2 2 27h 3 4 6 8 10 12 14 16 18 20 22 24 30 36 42 48 54 60 450 500 550 650 688 750 26 33 40 50 65 100 125 160 190 21 0 240 280 300 335 370 - - ~ 55 70 80 100 130 200 260 330 400 - - ~ ~ 7 14 11 17 30 70 120... L3 & L, = length of various looped sections d,, d2 d3 & d, =internal diameter of individual line corresponding to lengths L1, L , L3 & Ln r 2.6182 d22.6182 +d3 2.6182 then: when dE= dl = d2 = d3 then LE = Ll + 0.27664 L2 + 0.1305 L3 Example A multiple system consisting of a 15 mile section of 3-8 %-in OD lines and l-l03/,-in OD line, and a 30 mile section of 2-8 x411 lines and l-l@h-in OD line Find . lV3 NOILLI~H I Rules of Thumb for Chemical Engineers RULES OF THUMB FOR CHEMICAL ENGINEERS A manual of quick, accurate solutions to everyday process. - - - - - - Sudden Std. red. Sudden Std. red. La 02 gF Fg "2 -Y a,c DO 0- ~ 55 70 80 100 130 200 260 330 400 450 500 550 650 688 750 - - - - -. Permissions'. ,- E' This book is printed on acid-free paper. Library of Congress Cataloging-in-Publication Data Rules of thumb for chemical engineers: a manual of quick, accurate