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entirely with water, again shows itself and contaminates the produce, so that only the middle portions of the running are fit for consumption as spirits. Both the first and second feints-the former of which contains a considerable amount of strong spirit--are re-distilled with the low wines produced from the next back of wash.
In the worm, or condensing apparatus, attached to either the wash or the low. wines still, a process goes on the reverse of that which takes place in the still. The vapour, as it circulates through the pipes, parts with its heat to the water that surrounds them, and when sufficiently cooled in this way, condenses into a liquid. Any temperature lower than the boiling point of the wash, effects a partial condensation of its vapour. But as alcohol boils at 39° below the boiling point of water, and as its vapour will not return to the liquid state, until it is cooled to a temperature less than 173°, it follows that the mixed vapours from the wash become, to a certain extent, analysed in the worm, watery and oily vapour condensing in the parts nearest to the still, while the alcohol vapour passes onward unchanged, and only liquifies when cooled below its own boiling point.
Since, however, the condensed vapours flow through the same worm, and unite into one liquid before they reach its extremity, it is manifest that a pure or a strong product cannot be obtained without the expense and trouble of repeated distillations, unless some device be employed to prevent, as far as possible, this admixture from taking place. .
Various expedients have been adopted from time to time, for the purpose of keeping the alcohol vapour separate in the worm, the most efficacious of which consisted in the introduction of pipes from the first rounds of the worm into the body of the still. The watery and oily vapour being chiefly condensed in these, the hottest portions of the worm, is then conveyed, by the pipes in question, back into the still, and subjected to several distillations, while the more alcoholic vapour passes on, and is condensed in a state of comparative purity lower down. In many of the common stills, such as are used for the manufacture of potable whiskey only, a contrivance of this kind is applied, but the result is seldom satisfactory. Indeed, in the case of whiskey intended for consumption as a beverage, it is not desirable to remove the whole of the oil, as it is on the presence of a small portion of this substance, that the flavour and peculiar character of such spirit chiefly depend.
When a highly pure and concentrated spirit is required, devoid of foreign substances, distillers have generally recourse to the apparatus below described :-*
Coffey's Still.—The distilling apparatus known as “ Coffey's Patent Still,” was originally devised by Mr. Æneas Coffey, Inspector General of Excise in Ireland, and was patented by him in the year 1832. Since that time it has undergone several improvements, and is now the form of still generally employed, where the object is the production on the large scale of a rectified spirit of high strength with the greatest attainable economy of time and fuel.
It consists of two oblong upright columns, which are placed side by side and connected, according to the size of the apparatus, by one or two pipes. These columns are termed respectively the Analyzer, and Rectifier-Plate II. Figs. 1 and 3—but it is only for convenience that the apparatus is thus arranged, as the whole might be formed into one continuous column, by placing the rectifier over the analyzer. The column, however, if thus prolonged, would necessarily be about 50 or 60 feet in height, and would be difficult of access in its upper part, and attended with other obvious disadvantages.
* A minuto description of most of the various forms of stills now used in this country or abroad, accompanied by engravings, is given in " Muspratt's Chemistry Applied to the Arts, &c.," under the head of Alcohol.
Each column is composed of a series of wooden frames, which in order to preTent, as much as possible, loss of heat by radiation, have a thickness of from five to six inches ; they are of a rectangular shape (figs. 5 and 6), usually from twelve to fifteen feet in length, and from four to five feet in breadth. The frames of the Analyzer are about fourteen inches, and of the Rectifier about nine inches in depth. Fitting horizontally upon one another they form a column twenty-five or thirty feet high, and are secured together by iron screw ties, which extend from the bottom to the top of the column. The number of frames in the Analyzer is generally about twenty-five, and in the Rectifier about thirty-five, but both the number and dimensions of the frames vary according to the quantity of wash required to be distilled in a given time, and the strength at which it is desired to obtain the spirit.
The frames of the Analyzer (figs. 1 and 2) from the bottom one to about the fourth from the top, are separated by stout copper plates termed diaphragms (figs. 5 and 6) which divide the column into so many distinct compartments. Each diaphragm is pierced to about two-thirds of its length with numerous small holes, the remainder of the sheet being plain. In the plain part are fixed about four simple valves (D"), and one or two short tubes, termed dropping-tubes (D), which project about an inch above the plate, and passing through downwards dip into shallow pans (D'), fixed on the upper side of the next diaphragm, thus forming a steam-trap, and preventing, when in use, the escape of steam or vapour through the tube, the plain part of one diaphragm being placed over the pierced part of the one beneath, and so on, alternately, towards the front and back of the column.
The four or five upper frames are not furnished with diaphragms, but together form a chamber into which the wash and hot feints are thrown—the wash by a pipe (F) from the rectifier, which, in some stills, enters at the top and passes down to a pan on the first diaphragm, similarly to the dropping tubes ; in other stills the pipe after passing through the centre of the top terminates in a large rose, which scatters the wash in thin streams through all parts of the chamber; whilst the hot-feints are discharged on the first diaphragm by a pipe (H) leading from the hot-feints pumps and receiver.
From the top of the Analyzer a copper pipe, or line-arm (A) of about twelve or fourteen inches in diameter, ascends a short distance, then turns and descends to, and enters the lowest frame of the rectifying column, forming the connection between the two columns. Stills of large dimensions are generally provided with two line-arms which are constructed with loose or slip joints as security against accident. Each of the diaphragm frames is furnished with a man-door (E), for the more effectual cleansing of the plate from the thick deposit left by the wash,
From the bottom of the Analyzer a discharge pipe in the form of a syphon (C), communicates with the spent wash reservoir ; this pipe is surrounded by a second pipe (C") forming a jacket. The space between the jacket and spent wash pipe is filled with water which is kept constantly flowing while the still is at work; the water is supplied by a pipe (N) that passes through the upper frames of the rectifying column from a cistern, and proceeds by (O) from the jacket to the steam boilers. In lieu of a jacket, the discharge-pipe is sometimes carried in a
continuous coil through a vessel containing water, to the spent wash reservoir. The water when thus heated is used to feed the steam boilers.
The apparatus is worked by high-pressure steam, the communication with the boilers being by a pipe (B), furnished with a stop-cock, which enters the bottom frame of the Analyzer. From this frame a small pipe (I) ascends outside, fitted at the top with a glass syphon tube containing mercury, which forms a gauge to indicate the pressure of the steam. A similarly constructed pipe and gauge (Q) are also attached to the line-arm, in order to show the pressure of the low-wines as they pass to the rectifier.
The Rectifier (Fig. 3 and 4), is like the Analyzer, divided into compartments by diaphragms (P) between the frames ; those from the bottom up to the spirit-sheet (fig. 7) being pierced, whilst those from the spirit-sheet to the top are, generally, plain, the spirit-sheet itself being the first without holes : they are also fitted with valves (D”) and dropping tubes (D) as in the Analyzer. The plain diaphragms do not extend the full length of the frame, a vacancy of a few inches being left at each end alternately, between the diaphragm and the frame, to allow of the passage of the spirituous vapour. Where plain diaphragms are not employed there is no difference in the construction of the plates, above or below the spirit-sheet : in either case the spirit-sbeet is provided with a sunken recess, or well, to collect the spirit, which is then conveyed by a pipe passing through the front of the frame, to the refrigerator.
A copper pipe (8), about four inches in diameter, attached to the wash reservoir, and furnished with a cock to regulate the supply of wash, enters the column at the fourth frame from the top, and (as G) traverses the space in each frame between the diaphragins four times from the back to the front in a serpentine course. This serpentine pipe (G) is formed of a number of U shaped tubes—the length of the tube being nearly the entire length of the frame ; two are fixed in each frame, the open ends projecting through to the exterior of the front (fig. 6) the two inner arms, or lengths of the tubes are then connected together by an elbow or bend with flanch joints (G), and the outside arms by similar bends with the tubes in the next frames above and beneath. This is the construction of the pipe in each frame except that at the spirit-sheet, in which only one U tube is fixed, the whole forming a continuous serpentine pipe of great length-usually from 1000 to 1200 feet.
Leaving the Rectifier at the frame next to the bottom one, this wash pipe (as F) rises on the outside to the top of the column, and passes over to, and enters the top of the Analyzer, as previously stated. The pipes marked S, G, and F, form in fact one continuous pipe.
A pipe (U), leading from the water cistern, is connected with the serpentino wash pipe a short distance from the point at which it enters the rectifying column, a cock being placed near the junction : this is known as the tempering pipe : by it the attendant is enabled to reduce the gravity of the wash with water if requisite, as it flows througb the rectifier-to continue to work off the still when the charge of wash from the reservoir has passed into the Analyzer-to regulate the temperature of the interior of the Rectifier-and, by lowering the temperature, to increase the rectifying power of the apparatus. The three upper frames have also a similarly constructed course of serpentine pipes, but of smaller diameter, connected with the water cistern at the top by the pipe V, and, by N with the jacket of the spent wash pipe at the bottom of the Analyzer.