I N 0 USTRIAL A S D ENGINEERISG CHEMISTRY
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VOl. 21, KO.10
Distillation Methods, Ancient and Modern’ G u s t a v Egloff and C. D. Lowry, Jr. UXIVERSAL OIL PRODUCTS COMPASY, CHICAGO, ILL.
H E modern fractionation of liquids in niaiiy respects is age-old. It is interesting to analyze examples of the types of apparatus used in the sixteenth and early seventeenth centuries for the fractional distillation of oil and other liquids, and t o note how advanced were the alchemists of that period, working before the dawn of exact science, in the separation of such materials into their component parts. Many of the principles which are fundamental in the design of present-day distillation apparatus were widely employed in alchemical practice. Among these principles are: (I) taking several streams from a fractionating tower, ( 2 ) re-
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strength of them that are involved and overwhelmed with great bulk, lying hid, as it were, in their chests; and to make them more pure and thin and more noble, as not being content with their common condition, and t o lift them up as high a s heaven. We can by chymical instruments, search out the vertues of plants and better than the ancients could do by tasting them. What therefore could be thought on that is greater? Let one that loves learning and to search nature’s secrets, enter upon this; for a dull fellow will never attain t o this a r t of distilling.
Porta states further: Now we speak of oyls: these require the industry of a most ingenious artificer, for many of the most excellent essences of things do remain in the oyl so close, that without the greatest art, wit, cunning, and pains they cannot be brought to light; so that the whole a r t of distillation dependeth on this.
He adds a further caution: If you distill common oyl, it will hardly run. You must be very careful that the ashes and pot do not wax too hot, for if the oyl within takes fire it will break the vessels and flie up, that it can hardly be quenched, and reach the very ceiling; so that it is best to operate upon oyls in arched rooms.
The economics of distillation were also not overlooked a t this period. Worth (4),writing in 1692 on “The Whole Art of Distillation” stated, “this art is not rightly to be carried on
Figure 1-Tower Taking Off Five Streams (Libavius, Alchymio, Frankfurt, 1606)
fluxing, (3) external regulation of still-head temperature, (4) reboiling of condensates for increased fractionation, ( 5 ) preheating liquid before distillation, (6) feeding liquid into the still while in operation. The alchemical workers had a very high regard for the powers of the distillation process. In the year 1553 Porta (3) mote: Now I a m come to the arts and I shall begin from distillation, a n invention of later times, a wonderful thing to be praised beyond the power of man; not that which the vulgar and unskillful men use, for they do but corrupt and destroy what is good; b u t that which is done by skillful artists. This admirable a r t teacheth how t o make spirits and sublime gross bodies, and how t o condense and make spirits become gross bodies, and t o draw forth of plants, minerals, stones and jewels, the 1
Received February 27, 1929.
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Figure 2-Fractionating Still Head (Donalo d’E7emzla. Dell’ Elixir Vitae, Naples, 1624)
without a considerable large fund, and when so managed will repay the owner or master with considerable interest.” T a k i n g Several S t r e a m s f r o m a F r a c t i o n a t i n g Tower
The ancients in distilling oils and other substances often produced a number of distillates in one operation. A column
October, 1929
INDUSTRIAL AND ENGIiVEERISG CHEMISTRY
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Figure 5-Still with Cooled Head and Preheater (Libavius, Alchymia, Frankfurt, 1606) Figure 3-Still
with Reflux, Dephlegrnator, and Condenser (Lonicer, Kunsiliche Conterfeylunge, Frankfurt, 1.573)
Figure 4-Still
with Large Reflux Area and Fractional Condensation (Donalu d’Eremila, Dell’ Elzzzr Vztae, Naples, 1624)
for doing this, devised about 1606, is shown in Figure 1. I t has outlets for taking off five streams of distillate, of different densities. The form of the distilling vessel inside the furnace is indicated by the dotted outline. Within the tower are four fixed pans or “alembics,” of which only the “rostra” (rostrum, beak) are visible, connected each to its on-n receiver. At the top a fifth alembic runs to a receiver which itself acts as a fractional condenser, the lightest vapors being condensed in a second vessel. At the base of the furnace are attached two small stills receiving gentle heat, which may be used for redistillations. I n describing this apparatus in a book on alchemy, Libavius (2)states that it may be used for the
Figure 6-Still with Cooling System (Ferrara. Chzrurgrae, Frankfurt, 1625)
distillation of wine or spirits, or of spirituous liquids in which aromatic substances have been macerated. By its means “diverse waters and liquors can be elicited at the same time.” The second rostrum provides a liquid, “some\vhat better” than that flowing from the first, the third, a more spirituous liquid, the fourth a fraction of still greater volatility, and the fifth a distillate that is the most volatile of all, or the “quintessence.” The column is called, from the number of its streams, a “pentathlum.” Another fractionating tower (f), which also collects five separate distillates and is of the bulb type, is indicated in Figure 2.
922
INDUSTRIAL AND ENGINEERING CHEMISTRY Refluxing
The principle of refluxing was recognized rather early in development of the distillation art. Lonicer in the sixteenth century pictured the ingenious apparatus shown in Figure 3.
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zone. Above that is a dome around which a cooling liquid is placed. This cooling medium increases the refluxing action and also provides for the collection of a distillate fraction in the small receiver attached to the dome. The uncondensed vapors then pass through a cooling coil and another portion is collected in a chamber K . Part of the vapors is condensed, owing to the air-cooling of chamber K . The final fraction of the vapors is condensed in dome L and collected in receiver M. The apparatus thus recovers three liquids from the starting material. External Regulation of Still-Head Temperature
Temperature control of the vapors leaving the top of a still or dephlegmator is of the greatest importance in fractionation.
Figure 7-Still with Reboilers (Philiatrus, Remediis Secretis, Lyons, 1555)
The still is provided with a large air-cooled dome with a zigzag pipe leading from it, to provide a greater cooling area and in this way increase the reflux ratio. A secondary fractionation of the vapors leaving the top of the air-cooled pipe takes place through their contacting with the large cooling surface of a receiver, dome, and second bent pipe. The lightest vapors then pass through a water-cooled condenser
Figure 9-Distilling System with Reboiling and Fractional Condensation (Libavius, Alchymia. Frankfurt, 1606)
The ancients devised external cooling arrangements so as to regulate the temperature of these vapors as desired. Libavius in the year 1606 (Figure 5 ) showed a column whose top was surrounded by a liquid bath into which controlled quantities of cooling material could be passed. I n 1625 Ferrara pictured a device reproduced in Figure 6, which included a cooling liquid flowing around a stillhead in order t o regulate the temperature of the vapors leaving the still. The cooling agent also functioned to increase or decrease the refluxing action upon the vapors. Reboiling of Condensates for Increased Fractionation
A. is the Fornace. B. the Retort. C. the ReciDient. D. the Aperture with a Pipe of a Moderate bigness, on which may be set the Alembeck E. The other Fornace is F which containing a moderate Fire, sublimes what falls idto the receiving Vessel up into the Alembeck E. And so the Matter which is distilled from the Retort B by the Fire of the Fornace F , is presently sublimed; which may not only be useful in this Case, but also in every Sublimation of other Matters. Figure 8-Reboiler and Still (Valentine, “Triumphal Chariot of Antimony,” London, 1655)
and are collected as a liquid product in a second receiver. The fractionating and refluxing system thus collects two liquid condensates. Another refluxing device is shown in Figure 4. The form of the still provides a large air-cooling area above the heated
I n the distillation of liquids, particularly when using the bubble tower, reboiling of the reflux condensate is necessary if close fractionation is desired. The ancients recognized the principle of reboiling condensates as early as 1555, when Philiatrus showed stills with reboilers connected thereto. His distillation layout is shown in Figure 7 . Valentine also indicated reboiling, in the apparatus shown in Figure 8. Libavius presents the series of reboilers and fractional condensers pictured in Figure 9. The body of the still and the first receiver extend into the furnace. Their construction is shown in the small figure. The three subsequent receivers are enclosed in a compartment which receives heat from the firebox through a damper. According t o Libavius, the first of the receivers is subjected to the most intense, and the latter ones to milder heating, so that the first condensates are “material” and the latter ones “spiritual,” while the most volatile portion collects in the final receiver.
October, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
P r e h e a t i n g L i q u i d before Distillation a n d Feeding Liquid i n t o Still while i n O p e r a t i o n
The preheating of a liquid prior to its passing into distillation apparatus, and the principle of feeding in liquid while distillation is going on are shown in Figure 5. The products of combustion from the furnace serve to heat the distilling vessel, and also to preheat the feed-in stock placed in a vessel set within the lower compartment in the wall of the stack. The preheated liquid is run into the still so as t o prolong the operation, its flow being regulated by a stopcock in the pipe connection. The stillhead is surrounded by water, which flows from a vessel in the upper compartment of the back wall (an arrangement called a Moorshead). This water cooling condenses the vapor in the upper dome, which is then collected in the receiver. In other pieces of apparatus of a similar sort outlets are provided to allow residual material to be withdrawn from the still during the distillation, thus making continuous operation possible.
923 AUTOMATIC TEMPERATURE CONTROLLER
FRACTIONAT, SECT’oN
PREHEATED CRUDE 0
Modern Application of T h e s e Principles
The application of these alchemical principles of distillation in modern practice is shown in Figure 10. This plate is the flow chart of a typical crude oil distillation unit operating a t atmospheric pressure. Every one of the six processes which have been exemplified by the drawings of alchemical apparatus is utilized in this still; in fact, the parts embodying these ideas are among its most important features. Outlets are shown for taking off four streams of distillate. The number of
Figure 10-Modern
Crude Oil Distillation Unit
the flow of liquid through it, a practice corresponding to the external regulation of stillhead temperatures shown in Figures 4 and 6. Three reboilers are shown at the side and bottom of the tower. The crude oil is fed into the pipe still in a preheated condition in a continuous manner. Figure 11 is a view of a petroleum distilling unit, whose design resembles Figure 10. Where the stills of the alchemists had a t most a capacity of a few gallons, the modern stills can handle more than 200,000 gallons of oil per day. The pipe still and tower in Figure 11 are used in running Ohio crude oil to heavy flux bottoms, taking six fractions from the tower: (1) gasoline, (2) naphtha, (3) kerosene, (4) gas oil, (5) wax distillate, and (6) cylinder stock. Models of the alchemical distillation apparatus which have been pictured are exhibited in the Deutsches Museum in hlunich, Germany. The collections of this museum show in great detail the methods and achievements of science, and exemplify all important industrial processes. The Deutsches Museum was the inspiration for the Julius Rosenwald Industrial Museum which is being built in Chicago. I n this institution a section is to be devoted,to ancient and modern distillation apparatus. L i t e r a t u r e Cited (1) Donafo d ’ e r e m i t a , Dell’ Elizir V i f a e , Naples, 1624. (2) Libavius, Alchymia, Frankfurt, 1606. (3) Porta, “Natural Magic,” Naples, 1553 and 1589: English tranalation, London, 1658. (4) Worth, “The Whole Art of Distillation,” London, 1692.
Wild Orange Leaf Distillation Figure 11-Modern
Petroleum Distilling Unit
streams could be increased if desired. Refluxing is accomplished by controlling the amount of crude oil passing into the heat exchanger a t the top of the bubble tower. This exchanger has an automatic temperature Control regulating
About 80 tons of oil of petit-grain, distilled from the leaves of the wild orange tree, are annually exported from Paraguay. The leaves are collected from all over Paraguay, but more particularly in the region that lies from 50 to 100 miles east of Ascuncion. The oil is distilled bv the natives in small Drimitive stills, and finds a ready market as a basis for perfumes and flavorings. France, the Netherlands, and the United States rank first, second, and third as purchasers of the oil.
