310:
There is a very important distinction between the theoretical plate terminology used in discussing conventional distillation trays and the theoretical plate terminology used in the discussions below of packed bed distillation or absorption or in chromatography or other applications. The theoretical
242:
An example of a very simple tray is a perforated tray. The desired contacting between vapor and liquid occurs as the vapor, flowing upwards through the perforations, comes into contact with the liquid flowing downwards through the perforations. In current modern practice, as shown in the adjacent
230:
The trays or plates used in industrial distillation columns are fabricated of circular steel plates and usually installed inside the column at intervals of about 60 to 75 cm (24 to 30 inches) up the height of the column. That spacing is chosen primarily for ease of installation and ease of
307:, needed in the separating column. The final design choice of the number of trays to be installed in an industrial distillation column is then selected based upon an economic balance between the cost of additional trays and the cost of using a higher reflux rate.
51:. The performance of many separation processes depends on having series of equilibrium stages and is enhanced by providing more such stages. In other words, having more theoretical plates increases the efficiency of the separation process be it either a
349:
arises from the same concept of equilibrium stages as does the theoretical plate and is numerically equal to the absorption bed length divided by the number of theoretical plates in the absorption bed (and in practice is measured in this way).
91:
or laboratory-scale glassware distillation columns constitutes a "plate" or "tray". Since an actual, physical plate can never be a 100% efficient equilibrium stage, the number of actual plates is more than the required theoretical plates.
257:, required in the process should be determined, taking into account a likely range of feedstock composition and the desired degree of separation of the components in the output fractions. In industrial continuous fractionating columns,
311:
plate in conventional distillation trays has no "height". It is simply a hypothetical equilibrium stage. However, the theoretical plate in packed beds, chromatography and other applications is defined as having a height.
222:
So-called bubble-cap or valve-cap trays are examples of the vapor and liquid contact devices used in industrial distillation columns. Another example of vapor and liquid contact devices are the spikes in laboratory
243:
diagram, better contacting is achieved by installing bubble-caps or valve caps at each perforation to promote the formation of vapor bubbles flowing through a thin layer of liquid maintained by a
540:
402:
140:
235:
723:
The concept of the "height equivalent theoretical plate" (H.E.T.P.) was coined in 1922 by
William A. Peters, Jr. of the Dupont Corporation of Wilmington, Delaware, USA. See:
268:
for each of the succession of equilibrium stages until the desired end product composition is achieved. The calculation process requires the availability of a great deal of
87:
processes has been discussed in many reference texts. Any physical device that provides good contact between the vapor and liquid phases present in industrial-scale
432:
197:
170:
217:
286:
used. Using more reflux decreases the number of plates required and using less reflux increases the number of plates required. Hence, the calculation of
250:
To design a distillation unit or a similar chemical process, the number of theoretical trays or plates (that is, hypothetical equilibrium stages),
862:
834:
690:
965:
75:
The concept of theoretical plates and trays or equilibrium stages is used in the design of many different types of separation.
631:
264:
is determined by starting at either the top or bottom of the column and calculating material balances, heat balances and
494:
356:
35:
is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an
855:
699:
667:
474:
17:
1056:
728:
98:
1152:
1142:
1114:
1018:
848:
269:
36:
927:
272:
data for the components present in the distillation feed, and the calculation procedure is very complex.
1034:
300:
is then divided by the tray efficiency, E, to determine the actual number of trays or physical plates,
942:
910:
558:
470:
1147:
1083:
1078:
1039:
599:
453:. Liquids tend to wet the surface of the packing and the vapors contact the wetted surface, where
1157:
837:
by Ivar J. Halvorsen and Sigurd
Skogestad, Norwegian University of Science and Technology, Norway
594:
584:
579:
1102:
992:
488:
The same equation applies in chromatography processes as for the packed bed processes, namely:
331:
315:
56:
1162:
1095:
1090:
1068:
1013:
920:
900:
977:
960:
871:
624:
Chemical
Engineering Design: Principles, Practice and Economics of Plant and Process Design
546:
410:
318:
known as Van Winkle's
Correlation can be used to predict the Murphree plate efficiency for
175:
148:
88:
8:
1073:
1051:
937:
895:
658:
319:
1061:
952:
885:
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The concept of theoretical plates or trays applies to other processes as well, such as
450:
202:
32:
485:
provides a definition of the number of theoretical plates in a chromatography column.
1107:
987:
915:
905:
795:
695:
663:
627:
265:
445:
The material in packed beds can either be random dumped packing (1-3" wide) such as
1046:
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812:
785:
777:
740:
1008:
589:
1119:
828:
466:
224:
60:
338:
for vapor and liquid contacting have an equivalent concept referred to as the
1136:
972:
454:
799:
446:
84:
52:
549:. In capillary column chromatography HETP is given by the Golay equation.
545:
In packed column chromatography, the HETP may also be calculated with the
744:
982:
562:
335:
282:
required to achieve a given separation also depends upon the amount of
64:
39:
with each other. Such equilibrium stages may also be referred to as an
840:
781:
890:
482:
434:
is the number of theoretical plates (also called the "plate count"),
714:
Chemical
Engineering Design, by Gavin Tawler and Ray Sinnott, 2013.
234:
238:
Typical bubble cap trays used in industrial distillation columns
283:
687:
478:
244:
325:
766:"A new form of chromatogram employing two liquid phases"
621:
813:
Definition of the number of plates (in chromatography)
729:"The efficiency and capacity of fractionating columns"
497:
413:
359:
205:
178:
151:
101:
733:
The
Journal of Industrial and Engineering Chemistry
465:The theoretical plate concept was also adapted for
172:is the number of actual, physical plates or trays,
535:{\displaystyle N_{t}={\frac {H}{\mathrm {HETP} }}}
534:
426:
397:{\displaystyle N_{t}={\frac {H}{\mathrm {HETP} }}}
396:
211:
191:
164:
134:
442:is the height equivalent to a theoretical plate.
199:is the number of theoretical plates or trays and
1134:
344:height equivalent to a theoretical plate (HETP).
83:The concept of theoretical plates in designing
293:is usually repeated at various reflux rates.
856:
688:Perry, Robert H. & Green, Don W. (1984).
655:
460:
763:
863:
849:
275:In an industrial distillation column, the
231:access for future repair or maintenance.
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651:
649:
647:
645:
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617:
615:
233:
135:{\displaystyle N_{a}={\frac {N_{t}}{E}}}
870:
683:
681:
679:
622:Gavin Towler & R K Sinnott (2007).
326:Distillation and absorption packed beds
78:
14:
1135:
831:by Ming Tham, Newcastle University, UK
764:Martin, A.J.P.; Synge, R.L.M. (1941).
726:
844:
640:
612:
552:
752:(Martin & Synge, 1941), p. 1359.
691:Perry's Chemical Engineers' Handbook
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24:
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520:
517:
388:
385:
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379:
25:
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219:is the plate or tray efficiency.
266:equilibrium flash vaporizations
70:
806:
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708:
13:
1:
829:Distillation, An Introduction
694:(6th ed.). McGraw-Hill.
662:(1st ed.). McGraw-Hill.
605:
225:Vigreux fractionating columns
438:is the total bed height and
7:
568:
334:separation processes using
322:separating binary systems.
10:
1179:
1027:
1001:
951:
943:Thermodynamic equilibrium
878:
727:Peters, W.A. Jr. (1922).
626:. Butterworth-Heinemann.
559:capillary electrophoresis
461:Chromatographic processes
1096:Distribution coefficient
1040:Hammett acidity function
1019:Liquid–liquid extraction
928:Le Chatelier's principle
270:vapor–liquid equilibrium
595:Fractional distillation
585:Extractive distillation
580:Continuous distillation
1057:Coordination complexes
993:Thermodynamic activity
536:
451:structured sheet metal
428:
398:
239:
213:
193:
166:
136:
1069:Dissociation constant
1014:Equilibrium unfolding
901:Equilibrium chemistry
656:Kister, H.Z. (1992).
537:
429:
427:{\displaystyle N_{t}}
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237:
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194:
192:{\displaystyle N_{t}}
167:
165:{\displaystyle N_{a}}
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1153:Chemical engineering
1143:Separation processes
978:Predominance diagram
961:Equilibrium constant
600:McCabe–Thiele method
547:Van Deemter equation
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411:
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320:distillation columns
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89:distillation columns
79:Distillation columns
67:or similar process.
33:separation processes
1052:Binding selectivity
1028:Specific equilibria
938:Reversible reaction
896:Dynamic equilibrium
872:Chemical equilibria
835:Distillation Theory
770:Biochemical Journal
745:10.1021/ie50150a002
659:Distillation Design
1062:Macrocyclic effect
886:Chemical stability
575:Batch distillation
561:and some types of
553:Other applications
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330:Distillation and
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1129:
1108:Common-ion effect
1035:Acid dissociation
988:Reaction quotient
906:Equilibrium stage
782:10.1042/bj0351358
776:(12): 1358–1368.
633:978-0-7506-8423-1
530:
392:
316:empirical formula
212:{\displaystyle E}
130:
41:equilibrium stage
29:theoretical plate
18:Equilibrium stage
16:(Redirected from
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1047:Binding constant
933:Phase separation
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1163:Distillation
1115:Vapor–liquid
1002:Applications
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340:plate height
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85:distillation
82:
74:
71:Applications
53:distillation
48:
44:
40:
28:
26:
1120:Henry's law
911:Free energy
749:See p. 476.
336:packed beds
45:ideal stage
37:equilibrium
1137:Categories
1103:Solubility
1074:Hydrolysis
983:Phase rule
606:References
563:adsorption
332:absorption
65:adsorption
57:absorption
1091:Partition
921:Helmholtz
891:Chelation
483:Gold Book
1084:of water
879:Concepts
800:16747422
569:See also
457:occurs.
31:in many
791:1265645
342:or the
47:, or a
953:Models
798:
788:
698:
666:
630:
477:. The
471:Martin
407:where
284:reflux
145:where
916:Gibbs
479:IUPAC
475:Synge
796:PMID
696:ISBN
664:ISBN
628:ISBN
473:and
440:HETP
347:HETP
314:The
245:weir
786:PMC
778:doi
741:doi
481:'s
449:or
1139::
794:.
784:.
774:35
772:.
768:.
737:14
735:.
731:.
678:^
642:^
614:^
565:.
227:.
63:,
59:,
55:,
43:,
27:A
864:e
857:t
850:v
802:.
780::
747:.
743::
704:.
672:.
636:.
527:P
524:T
521:E
518:H
514:H
509:=
504:t
500:N
436:H
420:t
416:N
389:P
386:T
383:E
380:H
376:H
371:=
366:t
362:N
304:a
302:N
297:t
295:N
290:t
288:N
279:t
277:N
261:t
259:N
254:t
252:N
207:E
185:t
181:N
158:a
154:N
128:E
123:t
119:N
113:=
108:a
104:N
20:)
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