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Unformatted text preview: TECHNIQUES A N D INSTRUMENTATION IN ANALYTICAL CHEMISTRY Handbook of Laboratory Distillation With an Introduction to Pilot Plant Distillation - VOLUME 2 TECHNIQUES AND INSTRUMENTATION I N ANALVTICAL CHEMISTRY Volume 1 Evaluation and Optimization of Laboratory Methods and Analytical Procedures. A Survey of Statistical and Mathematical Techniques by D. L. Massart, A. Dijkstra and L. Kaufman Volume 2 Handbook of Laboratory Distillation by E. Krell TECHNIQUES AND INSTRUMENTATION I N ANALYTICAL CHEMISTRY Handbook of Laboratory Distillation With an Introduction to Pilot Plant Distillation Completely revised second edition Erich Krell Akademie der Wissenschaften der DDR Zentralinstitut fur Isotopen- und Strahlenforschung, Leipzig Translation, exclusive of the parts retained from the 1st English edition as prepared by C. G. Verver, Amsterdam, by Dr. phil. Manfred Hecker, Leipzig. E LSEVl E R SCI E NTI F I C P U BLI S H IN G C O M P A N Y 1982 Amsterdam Oxford NewYork - - - VOLUME 2 Publish& in co-edition with VEB Deutmher Verlag der Wissenechaftan, Berlin Dietribntion of thie book is being handled by the following publishers for the E.S.A. and Canada Elsevim North-Holland, Inc. 62 Vanderbilt Avenue NewYwk, NY 10017 for all remaining areas Eleevier Scientific Publishing Company 1 Molenwerf P.O. Box 211, loo0 AE Amsterdam, The Netherlands Lisray ef Congress Cataloging in Publication Data Krell, Erich. Handbook of laboratory distillation. (Techniques and instrumentation in analytical chemistry ; v. 2) Trsnslation of: 3., bearb. und em. A d . Handbuch der Laboratoriumedestille,tion. Bibliography: p. Includes index. 1. D i ~ ~ t ~ ~ 8 t i o n - h b o r a tmanuale. ory I. Title. II. Series. QD63.D8K713 1982 542l.4 82-9855 ISBN 0-444-99523-7 AACR2 @ VEB Deutscher Verlag der Wissenechaften, Berlin, 1982 All rlghts reserved. No part of this publication may be reproduced, stored in a ret,rieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. P r i n t e d in the German Democratic Republic Foreword to the third edition The first edition of 1958 was sold out in a relatively short time. The second edition followed in 1960. The book has become a standard work and has been translated into Russian, English and Hungarian. This edition has again been written with the object of giving an account of the subject of laboratory distillat)ion including recent views and developments. The literature has been reviewed up to the year 1979. The author has adopted the course of dealing only with generally accepted facts ;there are still numerous problems in simple and countercurrent distillation which have not yet been completely clarified and in which there exist differences of opinion among various investigators. Distinct trends in development have nevertheless been mentioned, in order to give an incentive for further work. Owing to the large mass of material, a critical selection has been necessary. An attempt has been made to introduce the mathematical deductions and formulae required in laboratory work in a readily understandable form. Readers with a mathematical turn of mind and those interested in particular problems will find extensive references to the literature for further study. The fundamental scheme of arrangement as applied in the first edition has been retained. Section 5.1.3 has been extended to cover pilot plant distillation. Section 4.2 now deals with fluidand interface dynamics. Chapter 8 could be drastically shortened as there are a variety of components of distillation apparatus and the pertaining measuring and control devices commercially available. The nomograms, which were presented separately, have been inserted in the text. The references for the various chapters have been rearranged and important new items added to them. A great number of review articles serve to provide coinprehensive lists of references for a longer period. The book is intended primarily for physicists, chemists and engineers engaged in chemical industry and in research or development centres, whose work includes distillation on a laboratory or semi-technical scale. It will, however, also be useful t o undergraduates, chemical technologists and laboratory assistants as a source of answers to inany questions in the field of practical distillation and separating processes. It is hoped that it will prove a guide to better and inore economical methods of operation for all these who have to carry out distillation in the laboratory. The author wishes to express his special gratitude to Prof. Dr. habil. K1. Wetzel for his interest in the book, his valuable suggestions and constant support. He also wishes to thank Dr. H. Stage and E. Giebeler for the numerous helpful comments they have made. Further his thanks are due t o the various manufacturers of laboratory apparatus and glassware who have provided him with prospectuses and 6 Foreword to the third edition technical data. Last but not least, he is grateful to the publishers for t,he generous lay-out of the book, in particular to the staff of the chemistry department for their thorough work on the manuscript. It is to be hoped that this third edition will also contribute to the further development of laboratory distillation and that, in laboratories, in industry, in technical schools and universities, it will serve as a textbook and as a guide in the solution of problenls of separation by distillation. Dr.-Ing. Erich Krell Akademie der Wissenschaften der DDR Zentralir~et~itut fur Isotopen- und Strahlenforschung, Leigzig Contents List of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . 11 . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 . A review of the history of laboratory distillation . . . . . . . . . . . . 20 3 . Standardization and data on concentrations. . . . . . . . . . . . . . 32 3.1 Standardization of distillation a p p q a t u s 3.2 Definition of concepts . . . . . . . . . . . . . . . . . . . . . . . . 37 3.3 Symbols and units . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.4 Definitions and conversion of concentrations . . . . . . . . . . . . . . 38 . Physical fundamentals of the separation process . . . . . . . . . . . . 43 1 a 4 . . . . . . . . . . . . . . . 32 4.1 Principles of simple and countercurrent distillation . . . . . . . . . . 43 4.2 4.2.1 4.2.2 4.2.3 Fluid and interface Wetting columns . Film formation . . Column dynamics 4.3 Miscibility of t h e components . . . . . . . . . . . . . . . . . . . . 4.4 4.4.1 4.4.2 Vapour pressure-temperature relationship. p - t . . . . . . . . . . . . 58 Measurement of saturated vapour pressures . . . . . . . . . . . . . . 59 Calculation and representation of saturated vapour pressures . . . . . . . 66 . . . . . . . . . . . . . . . . . . . . . . . . . . . dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 46 54 55 65 . . . . . . . . . . . . . . . . . . 76 4.5 Equation of state and ps-diagrams 4.6 4.6.1 4.6.2 4.6.3 Boiling point diagram, B - 2, equilibrium curve. y* - x . . . . . . . 80 Calculation of vapour-liquid equilibria . . . . . . . . . . . . . . . . 82 Volatility, separation factor oc and activity coefficient y . . . . . . . . . 57 The experimental determination of equilibrium curves . . . . . . . . . 91 4.7 4.7.1 Number of theoretical plates (separat)ingstages) . . . . . . . . . . . . Calculation of separating stages by the McCabe-Thiele method in batch operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calculation of separating stages by the McCabe-Thiele method in continuous distillation . . . . . . . . . . . . . . . . . . . . . . . . . . Determination of separating stages by the McCabe-Thiele method for equilibrium curves with an inflection point or a n azeotropic point . . . . Determination of separating stages for flat equilibrium curves and for equilibrium curves close t o operating line . . . . . . . . . . . . . . . Methods for determining the plate number in batch distillation arithmetically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7.2 4.7.3 4.7.4 4.7.5 102 108 111 115 117 120 8 Contents 4.7.5.1 4.7.5.2 4.7.5.4 Determination of the plate number from difference in boiling point . . . . Calculation of the plate number with the aid of the fractionating factor and the Rose formulae . . . . . . . . . . . . . . . . . . . . . . . Calculation of the minimum plate number by the Fenske equation for ideal mixtures and w = ca . . . . . . . . . . . . . . . . . . . . . Other methods and comparieon . . . . . . . . . . . . . . . . . . . 4.8 4.8.1 4.8.2 4.8.3 Theory of packed columns . . . . . . . . . . . . . Process of separation in a packed column . . . . . Determination of the transfer unit. TU . . . . . . Intensity of countercurrent exchange; time required 4.9 Determination of t.he number of plates and transfer units in the batch and continuous separation of multicomponent mixtures . . . . . . . . . 140 4.10 4.10.1 4.10.2 4.10.3 4.10.4 4.10.5 4.10.6 4.10.7 4.10.8 4.10.9 Testing plate columns and packed columns . . . . . . . . . . . . . . 144 Column diameter . . . . . . . . . . . . . . . . . . . . . . . . . 146 Effective separating length; the introduction of column packing . . . . . 146 Test mixtures end the composition of the charge . . . . . . . . . . . . 150 Reflux ratio and quantity of reflux . . . . . . . . . . . . . . . . . . 162 Total. static and operating hold-up . . . . . . . . . . . . . . . . . . 167 Operating presaure . . . . . . . . . . . . . . . . . . . . . . . . . 159 Load and vapour velocity . . . . . . . . . . . . . . . . . . . . . . 160 Method of column calibration . . . . . . . . . . . . . . . . . . . . 162 Data for packed and plate columns . . . . . . . . . . . . . . . . . . 166 4.11 Pressure drop. limiting velocity and calculation of column dimensions . 4.13 Heat calculations 4.13 Distillate properties and distillation diagrams . . . . . . . . . . . . . 187 4.14 4.14.1 4.14.2 4.14.3 h t r u c t i o n s for the oalculation of distillation conditions . . . . . . . . . 193 Batch distillation a t atmospheric pressure . . . . . . . . . . . . . . . 193 Continuous distillation . . . . . . . . . . . . . . . . . . . . . . . 197 Vacuum distillation . . . . . . . . . . . . . . . . . . . . . . . . 198 4.16 Diatillation calculations by computer . . . . . . . . . . . . . . . . . 198 4.7.5.3 . (i . . . . 120 121 125 127 . . . . . . . . 128 . . . . . . . . . 128 . . . . . . . . . 132 . . . . . . . . . 136 . . . . . . . . . . . . . . . . . . . . . . . . . . . Separating processes . . . . . . . . . . . . . . . . . . . . . . . . 167 182 203 5.1.4.3 The scale of operation . . . . . . . . . . . . . . . . . . . . . . . . 203 Nicro- and semi-micro-distillation . . . . . . . . . . . . . . . . . . 203 Analytical distillation . . . . . . . . . . . . . . . . . . . . . . . 210 Preparative and production distillation . . . . . . . . . . . . . . . . 214 Semi-technical columns . . . . . . . . . . . . . . . . . . . . . . . 215 Pilotplants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 The preparation of distilled water . . . . . . . . . . . . . . . . . . 225 The separation of isotopes . . . . . . . . . . . . . . . . . . . . . . 228 Isotope separation by low-temperature countercurrent distillation . . . . 231 The preparation of D, and lSO, by countercurrent distillation of water 232 The preparation of various isotopes . . . . . . . . . . . . . . . . . 242 5.2 5.2.1 5.2.2 5.2.2.1 6.2.2.2 Methods of operation . . . . . . . . . . . . . . . . . . . . . . . . 244 Batch and semi-continuous distillation . . . . . . . . . . . . . . . . 245 Continuous distillation . . . . . . . . . . . . . . . . . . . . . . . 246 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 6.1 6.1.1 5.1.2 5.1.3 5.1.3.1 6.1.3.2 5.1.3.3 5.1.4 5.1.4.1 5.1.4.2 Contents 9 5.2.2.3 5.2.2.4 5.2.2.3 5.2.3 Apparatus for continuous column distillation . . . . . . . . . . . . . . 250 Examples of application from laboratory practice . . . . . . . . . . . . 254 Starting up continuous distillations . . . . . . . . . . . . . . . . . . 255 Separation by partial condensation . . . . . . . . . . . . . . . . . . 256 5.3 5.3.1 5.3.2 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 Low-temperature distillation . . . . . . . . . . . . . . . . . . . . . 260 High-temperature and isothermal distillation . . . . . . . . . . . . . . 269 5.4 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 Distillation pressure . . . . . . . . . . . . . . . . . . . Simple and countercurrent distiHction under reduced pressure Continuous equilibrium vaporisation (flash distillation) . . . Thin-film distillation . . . . . . . . . . . . . . . . . . . Molecular distillation . . . . . . . . . . . . . . . . . . . Pressure distillation . . . . . . . . . . . . . . . . . . . . . . . . . 274 . . . . . . 274 . . . . . . 280 . . . . . 283 . . . . . 292 . . . . . 305 6 . Selective separating processes . . . . . . . . . . . . . . . . . . . . 307 6.1 Carrier vapour distillation . . . . . . . . . . . . . . . . . . . . . . 307 6.2 6.2.1 6.2.2 Szeotropic and extractive distillation . . . . . . . . . . . . . . . . . 312 dzeotropic distillation . . . . . . . . . . . . . . . . . . . . . . . . 317 Extractive distillation . . . . . . . . . . . . . . . . . . . . . . . . 327 6.3 Solution distillation and special methods . . . . . . . . . . . . . . . 334 . Constructional materials and apparatus . . . . . . . . . . . . . . . . 336 7.1 Const.ructional materials for distillation apparatus . . . . . . . . . . . 336 7.2 7.2.1 Standard apparatus and unit parts . . . . . . . . . . . . . . . . . . 337 Taps and valves . . . . . . . . . . . . . . . . . . . . . . . . . . 344 7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 Columns . . . . . . . . . . . . . . . . . . E m p t y columns . . . . . . . . . . . . . . . Packed columns . . . . . . . . . . . . . . . Plate columns . . . . . . . . . . . . . . . . Columns with stationary elements . . . . . . Columns with rotating elements . . . . . . . 7.4 Condensers and dephlegmators . . . . . . . . . . . . . . . . . . . . 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 347 366 358 365 373 382 \ 7.5 7.5.1 7.5.2 7.5.3 Adapters; still and column heads . . . . . . . . . . . . . . . . . . 387 Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 Still heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 Column heads . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 7.6 7.6.1 7.6.2 Still pots. receivers and fraction collectors . . . . . . . . . . . . . . . 398 Still pots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 Receivers and fraction collectors . . . . . . . . . . . . . . . . . . . 401 7.7 7.7.1 7.7.2 7.7.3 Insulation and heating devices . . . . . . . . . . . . . . . . . . . . 405 The heating of still pots and flasks . . . . . . . . . . . . . . . . . . 405 The heating of feed-stock and bottom . . . . . . . . . . . . . . . . . 410 Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 7.8 7.8.1 7.8.2 Packings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 Shape of packing units . . . . . . . . . . . . . . . . . . . . . . . 420 Constructional material of pnckings . . . . . . . . . . . . . . . . . . 427 10 Contents . A n t o d o devices. measuring and control equipment . . . . . . . . . . 430 8.1 8.1.1 8.1.2 Automatic equipment . . . . . . . . . . . . . . . . . . . . . . . . 430 Fully automatic equipment for standardized boiling point analysis . . . . 431 Fully automatic equipment for fractionation . . . . . . . . . . . . . -134 8.2 8.2.1 8.2.2 Temperature measurement and control . . . . Temperature measurement . . . . . . . . . . Temperature control . . . . . . . . . . . . . 440 440 446 8.3 8.3.1 8.3.1.1 8.3.2 8.3.2.1 8.3.2.2 Pressure measurement and control Pressure measurement and control above 760 mm and from 760 to 1 mm Hg The method of controlled evacuation . . . . . . . . . . . . . . . . . Pressure measurement and control from 1 to Hg . . . . . . . . . . The MeLeod compreaion manometer . . . . . . . . . . . . . . . . . Vacuum control to pressures of mm Hg . . . . . . . . . . . . . . 448 449 8.4 8.4.1 8.4.2 Reflux and rate of evaporation . . . . . . . . . . . . . . . . . . . -163 Time-operated devices for reflux control . . . . . . . . . . . . . . . 463 Control of boil-up rate . . . . . . . . . . . . . . . . . . . . . . . 465 8.5 8.6.1 8.5.2 8.6.3 8.5.4 Measurement of physical data during distillation . . . . . . . . . . . . 467 Melting point . . . . . . . . . . . . . . . . . . . . . . . . . . . 468 Refractive index . . . . . . . . . . . . . . . . . . . . . . . . . . 468 Dielectric constant . . . . . . . . . . . . . . . . . . . . . . . . . 470 Various determinations . . . . . . . . . . . . . . . . . . . . . . . 471 8.6 Measurement and metering of gases and liquids 9. Arrangement of a distillation laboratory. starting up dietillation apparatus 479 9.1 479 9.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frameworks and services . . . . . . . . . . . . . . . . . . . . . . Building u p the apparatus . . . . . . . . . . . . . . . . . . . . . . Sealing ground joints . . . . . . . . . . . . . . . . . . . . . . . . Starting up distillation apparatus . . . . . . . . . . . . . . . . . . . 9.6 Safety measures . . . . . . . . . . . . . . . . . . . . . . . . . . 491 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 . . . . . . . . . . . . . . . . . . . . . . . . . . . 512 8 9.2 9.3 9.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lay-out Relerenoes Subject index 453 457 459 162 472 482 184 488 490 List of symbols 9 B, BP c CI, cv u n Di d E F F. FP Fr f 9 !7u H LG L E bottom product rate in continuous distillation effective surface area quantity of charge t o a batch distillation degree of wetting boiling point specific heat specific heat at constant pressure specific heat at constant volume quantity of vapour diffusion coefficient degree of air-tightness diamet,er product rate volatility melting point solidification point fractionating factor cross-sectional area acceleration due t o gravity standard value of y quantity of operating hold-up column height (separating length) height equivalent t o a theoretical plate intensity heat content heat content of vaporized distillate heat content of vaporized reflux Kelvin equilibrium constant boiling point heat transfer coefficient velocity constant molar heat of vaporization mean liquid flow density over column cross-section liquid flow density a t a given point length (also, maldistribution = uneven distribution) mean free path inner diameter molecular weight mole fraction number of moles mass mixing number column efficiency refractive index for the sodium D line 12 na "J %h 0 P P P* Q VB QKO Qv QZ R R T s 8 8, T Tb t li V Vb VIllOi V 'Jgew "min W WS 2u 100 ICk x t 2\ ZZ Xt3 ZE XO Xe Y ?/* z 1 P -I I 6 & 17 e 6 x 1 Liet of symbols number of transfer units specific stage number number of theoretical plates or stages surface area total pressure pressure (partial preasure, distillation pressure) vapour preesure of a pure substance quantity of heat he& supplied to still pot heat removed by condenser heat loss heat supplied to preheater in continuous distillation universal gas constant reflus rate heat of vaporization gas flow rate stage efficiency mean stage efficiency thermodynamic temperature equilibration time time voltage volume fraction by volume molecubr volume reflux ratio selected reflux ratio minimum reflux ratio work constructiona...
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