CHAPTER IV.

MODERN DISTILLING APPARATUS.

In the previous chapter we have given a description of small, simple stills, such as were used until late years, and which are yet used in many localities where distilling is carried on on a small scale. We will now describe the principle features of more complicated and elaborate apparatus.

All modern distilling apparatus for the production of a high grade of alcohol is based upon the principle set forth in the description of the Coffey still; that is, upon using a distilling column and a concentrating column, wherein the "wash" or mash fermented as described, passes over a series of plates or other obstructions in contact with an ascending column of heated vapor. This heated vapor extracts the alcohol from the wash, or from the low wines of the concentrator, and is continually strengthened during its journey until it passes off to a condenser as a vapor very rich in alcohol. The converse of this is true with the wash, which in its downward course is gradually deprived of its alcohol until it finally passes off at the bottom of the column.

Fig. 22 is illustrative of the general form and arrangement of such a column and its adjuncts; the details, however, will vary with each make of still. In this the "column" consists of a casing really continuous but divided into two portions--the distilling portion _A_ and the rectifying portion _B_. The operation is alike, however, in principle in both portions.

The wash by means of a suitable pump is forced into an overhead tank or concentrator _G_ where it is warmed by the hot vapors as will be later described. It passes around the interior of the concentrator in a coil _c_ and then passes off by a pipe _a_ to the uppermost plate of the distilling portion _A_ of the column.

The plates, as before explained on page 55, are each formed with a dropping tube _O_ (see Fig. 23), which extends above the plate to an extent slightly less than the desired thickness of the layer of liquid on each plate, and with perforations each having an upwardly projecting rim, and each covered with a cap _A_. This rim and cap form a trap. The ascending vapors pass up through the perforations, down between the rim and the edge of the cap and thus out through the layer of wash contained on the cap. The wash remains constantly level with the top of the tube _O_, the excess running off through the tube _O_ to the compartment or plate beneath.

To return to Fig. 22, the wash by the pipe _a_ enters the distilling portion of the column at the uppermost plate thereof and, as described above, drops down from plate to plate. A steam pipe _S_ enters the bottom compartment of the distilling portion of the column and the steam as it rises through the little traps, bubbles out through the layer of wash and in each compartment enriches itself with alcohol. Thus the rising column of vapor is constantly becoming richer and the downward current of wash constantly weaker until at last it passes away as spent wash at the very bottom of the column by the pipe _D_.

The hot vapors, as before described, pass upward and enter the rectifying portion of the column _B_. This consists of a series of compartments having perforated bottoms and dropping tubes. The vapor passes upward through these perforations of the plates,--the condensed portion of it dropping back again on to the lower plates or on to the distilling plates to be again vaporized and concentrated and the more highly vaporized portion passing out at the top of the column through the pipe _E_ to the concentrator _G_.

The concentrator consists of a tank containing water within which is supported a vessel _F_ having double walls. The interior of this vessel is likewise filled with water. Between the double walls and surrounding the coiled pipe _c_ passes the vapors from pipe _E_.

At the bottom of the vessel _F_ is a compartment _f_ connected by a pipe _F¥_ with the upper compartment of the rectifying column. The less highly heated vapors will be condensed by the passage through the double walls of the vessel and the condensation will collect in the compartment _f_, and from there pass off by pipe _F¥_ back to the rectifying column, to be again vaporized and strengthened by the descent from plate to plate of _B_.

The rich and highly vaporized vapors which have passed the test of this preliminary concentration, pass out of the compartment _f_ by a pipe _M_. Here again the water surrounding the pipe tends to condense all but the most highly charged vapor and send it back to compartment _f_ but the vapor which succeeds in passing over through pipe _G_ is carried downward to a condenser _H_ where it is finally condensed and drawn off as at _g_. It is necessary that the rate of mash feed be regulated so that neither too much mash shall be pumped into the mash heater _G_, or too little, and the pipe leading from the pump to the heater is therefore provided with a tap and an indicating dial.

In these modern stills the following are particularly important points to be especially brought to the consideration of the distiller.

It cannot be too strongly impressed that effectiveness of the distilling column depends on the plates dividing it,--that is, upon the horizontality of the plates and the form of the traps or perforations. If the plates are not horizontal the wash is not maintained at a uniform level across the entire extent of the plate and hence some of the ascending vapor will pass out without contacting with the wash through uncovered traps, while others of the traps will be so deeply submerged in wash that the vapor cannot bubble through.

Again the caps should be so made as to divide the vapor into fine streams and bring it into contact with each part of the wash. Plates simply perforated and uncapped give excellent results for they molecularize the vapor ascending through the liquid contained on the plates, but they require a constant pressure of vapor, and any variations of pressure tends to discharge them. In addition these perforations gradually enlarge by the action of acids in the wash or clog up, and the apparatus soon works badly.

Good forms of capped traps are those shown in Figs. 24, 25 devised by Barbet. These are provided with an interior upwardly projecting rim. Extending over the rim and down around it is a copper cap having its margin slitted.

The wash carried on the plate circulates about the caps and the alcoholic vapors bubble out through the slits and up through the wash, the vapor thus being finely divided and coming into intimate contact with each portion of the wash and thus more thoroughly depriving it of its alcohol.

Besides this there is another advantage resident in these caps, namely, that distillation may be stopped for several hours and then re-started without trouble for the reason that the wash has been retained on the plates, whereas were the plates simply perforated the wash would ooze through and the plates have to be recharged. This form of plate may be easily repaired and does not necessitate the removal or replacement of the plate itself. The caps alone need be removed.

For thick washes, which tends to obstruct the slits of the cap, Barbet has devised the cap shown at the right in Fig. 25. This cap extends down to the plate itself, and has very narrow slits in its periphery. With such a cap as shown in Fig. 24, the bran, sediments, etc., would tend to settle upon the top of the cap, enter beneath it and through the slits. The cone-shape of the top of this cap prevents the deposit of dregs thereon and the very narrow slits oppose the entrance of bran or sediment.

While, for the sake of clearness, an old form of concentrator, _G_, has been shown, the concentrator, preheater for the wash, and condensers, to-day, are usually composed of bundles of tubes through which the vapors pass surrounded by water or the cool wash. These should be of bronze or copper and made without solder. The tubes should be capable of being taken out for cleaning or repairing.

In many distilling apparatuses the distilling column and the rectifying column are in two parts, one beside the other. This overcomes the objection of having a very high column and also prevents the low wines, _i.e._, the weak alcoholic liquor after its first concentration, from passing into the wash as it would do with the continuous column.

In order that the amount of steam entering the column may be regulated, the column is usually provided with a steam regulator (Fig. 26); whose principle of operation may be easily under stood by referring to Fig. 22. It comprises an upper and a lower chamber _Z Z¥_ connected by a central tube _K_ which projects down nearly to the bottom of the lower chamber. A pipe _W_ communicates with the steam chamber _R_ of the column and enters the chamber _Z_ above the level of the water contained therein. In the upper chamber _Z¥_, is a float _X_, connected to the differential lever _T_ of a steam valve _T¥_ which controls the inlet of steam passing through pipe _S_ to the steam chest _R_. The principle of operation is very simple. When the pressure in the steam chest _R_ becomes too great, steam in the pipe _W_ and chamber _Z_ forces the water therein up in tube _K_, thus lifting the float _X_ and closing the steam entrance valve _T¥_. When the pressure of steam is low, the level of the liquid in _Z_ rises and liquid in _Z¥_ runs into _Z_, the float _X_ falls opening valve _T¥_ and allowing a greater flow of steam.

As it is often desirable to change the pressure of steam in the column at various points in the operation, the best regulators are usually provided with means to that end.

In order to measure the output of the still, there is attached thereto a gauge glass (_J_ in Fig. 22), a diagram of which is shown in Fig. 27. This consists of a jar _A_ connected at its lower end at _b_ by an annular passage _B_ to a chamber _E_ from which proceed the taps _F_. Centrally through the passage _B_ passes a tube _c_ connected at its lower end to the pipe _C_ leading from the condenser. The tube _C c_ projects upward into the jar _A_ and is open at its upper end.

Now the opening _b_ is of a certain size and it is obvious that it will carry off a certain amount of liquid when running full or the amount allowed to flow out by the exit tap _F_. If now, more than that quantity of alcohol is produced, the alcohol will rise in the jar _A_ until the rate of inflow and outflow is equal. If, however, the still is producing less than that quantity then the level of liquid in _A_ will gradually drop. Hence, by observing the level of the liquid in _A_ and its constancy or variation in level, it is possible to tell precisely how much alcohol is running per hour and if the rate is steady. The jar _A_ is provided with a cap _G_ whereby an alcoholometer may be inserted into tube _c_ for the purpose of testing the strength of the liquor. The taps _F_ are for the purpose of collecting the first runnings, the pure alcohol and the last runnings or "feints."

These principles are also embodied in the apparatus designed by the Vulcan Copper Works Co., of Cincinnati, and illustrated in Fig. 28. The apparatus comprises the still, a wash heater and a condenser. The still is composed of a series of chambers from 12 to 24, the internal construction of which is shown in Fig. 29. Each chamber consists of a peculiarly perforated plate _A_, a drop pipe _B_, a seal _C_, into which the drop pipe from the plate above projects, and a central standard _D_.

Returning now to Fig. 28, at the bottom of the column is a manifold _E_, with pipes _F_ and _G_ whereby either exhaust or live steam may be admitted. _H_ designates the discharge or slop valve, controlled by a float _I_ whereby a constant level of slop or spent wash is kept in the bottom chamber.

To the right of the column is seen the slop tester _J_ and hydrometer _L_, whereby the spent wash may be tested to see if the spirit is being properly extracted. The steam pressure is indicated by means of a float _N_ contained within a vessel _M_, a tally weight moving against a scale _K_, showing the pressure of steam entering through pipe _O_ and acting against water contained in vessel _M_. Each chamber is provided with a manhole plate _P_, and a try-cock _Q_, whereby the operation of each chamber may be tested. _R_ is a gage glass to show the level of the slop in the bottom chamber.

At the top of the column are three rectifying chambers fitted with boiling pipes and traps _T_, which distribute the ascending vapor and boil out the low wines returned from the wash-heater or fore-warmer.

The heater consists of a shell enclosing a series of tubes extending into an upper and lower chamber. The wash or "beer," is pumped into the lower chamber of the heater, and passes upward through the tubes to the upper chamber from which is it carried by a pipe to the plate _A_ next below the rectifying plates.

The vapor from the column passes into the middle compartment of the heater and surrounds the beer tubes. The vapors give their heat to the beer and are thus cooled, the low wines being condensed and flowing back onto the uppermost rectifying plate, while the highly vaporized portions pass out to the condenser. This is of the same general construction as the heater, the vapor being cooled and condensed to liquid by the tubes through which a constant current of cool water is passed. This enters at _U_ and passes out at _V_. These tubular condensers are particularly good as they may be easily cleaned. From the condenser the spirit passes to a discharge box _W_. A portion of the flow passes into a test tube _X_, provided with a hydrometer. A trap _Y_ and an air pipe _Z_ provide means for the escape of gas.

As before stated, the form of perforations in the plates of a column through which the vapor pass upward through the beer or wash is particularly important. The steam must be thoroughly diffused through the beer, or else particles of mash are carried up, accumulate around the perforations, baking there and clogging them up. The clogging and eventual stoppage of the perforations prevent the agitation of the mash carried on the plate, and a layer of mash accumulates and bakes on the head, or plate, above. Thus the operating capacity of the still is reduced and a larger quantity and greater pressure of steam is necessary with consequent waste of fuel.

It is necessary then that the form of perforation or trap through which the vapor ascends should be such that agitation of the beer shall be enforced in its movement across the plate, and that the steam shall be thoroughly diffused through the beer. In the Vulcan still above referred to, these results are accomplished by forming each perforation with a tongue, as shown in the fragmentary view of a plate, Figs. 30 and 31, the tongues of all the holes being directed towards the periphery of the plate. It is claimed that by this construction the steam is diverted forward and injected into the beer, throwing the beer into vigorous motion, completely diffusing the steam and accelerating the motion of the beer from the seal _C_ to the drop pipe _B_.

Fig. 32 illustrates another form of distilling apparatus manufactured by the same company, which is practically the same as the apparatus previously described except that it is provided with a "goose-necked" separator, interposed between the wash-heater and the enclosure. This consists of a series of convoluted tubes contained in a tank of cold water. The vapor from the heater passes into these convolutions. The heavier vapors are condensed therein and returned to the heater from which they descend into the column while the more volatilized vapors pass over into the final condenser. The _U_-bends at the bottoms of each convolution act like so many low wine chambers in the still shown in Fig. 9 the highly heated vapor continually bubbling through the condensed vapor in the _U_ bend and there becoming greatly enriched and concentrated.

This apparatus, it is claimed, is applicable to the distillation of grain, molasses or cane juice and will yield 170 or 180 per cent., or the equivalent to 85-90 G. L. or 34-36 Cartier.

A distinctly modern type of still, though akin to the still shown in Figs. 19 and 20, is the inclined column of Gillaume, shown in section in Fig. 33 and in full view in Fig. 34. Gillaume in devising this form of apparatus had particularly in mind the distillation of thick washes, and the necessity of compelling a circulation of the wash.

The bottom of the inclined column _A_ is divided by lateral extending, upwardly projecting plates or partitions _a_ forming a continuous channel through which the wash passes from side to side and from top to bottom and then out through a regulator. The upper plate of the column has downwardly projecting partitions _b_ which with the partitions _a_ form a series of traps. The steam enters at the bottom of the column into a reservoir, and in order to pass upward is forced beneath each partition _b_ and through the washer contained in the channels of the bottom. When it reaches the upper end of the column it has passed through a continuous series of wash-filled compartments containing a constantly moving current of wash.

The vapors from the top of the column pass off to the wash heater or to a concentrator.

In Fig. 34 is shown a form of Gillaume still designed to distill all sorts of liquids whether thin or thick. The wash is supplied from an overhead tank to a regulating tank _K_ from which a pipe _k_ leads to a regulating tap _m_. The wash re-ascends into the wash heater _B_ and when heated descends by pipe _F_ into the uppermost compartments of the column _A_. The vapor passes to the condenser _B_, by a pipe _H_, and the spent wash is discharged by a siphon _C_. In addition to the parts above referred to, _a_ designates entrance of wash into heater, _b_ exhaust test tube, _d_ steam entrance tap _G_ alcohol test glass, _G¥_ exhaust test glass, _o_ valve for regulating strength of spirit, _O_ steam regulator, _p_ water entrance tap, _r_ exit tap, and _D_ the spent wash extractor.

The Gillaume apparatus is particularly valuable for the production of industrial or agricultural alcohol. It is claimed that it is easily understood and operated even by unskilled labor, while it produces a large proportion of alcohol of a high strength.

A view of a complete apparatus on a large scale is shown in the Fig. 40 in the chapter on rectification.