US2251185A - Distillation apparatus - Google Patents

Description

.July 29,1941. A. s. CARTER HAL I 2,251,185

DI ST ILLATION APPARATUS Filed April 17. 1939 Fl Wiflard 13111-151311 1% iatented July 29, 1941 DISTILLA'IION APPARATUS Albert 8. Carter and Frank Willard Johnson, Wil-- .1 mington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington,- Del., a corporation of Delaware Application April 17, 1939, Serial No. 268,376 I 1 Claim.

This invention relates to improvements in apparatus for fractionally distilling liquids and more particularly is concerned with improved means for reflux control in fractionating columns.

In the past, reflux in fractionating columns has been controlled by such means as controlling the temperature of partial condensers which are arranged to condense and return a portion of the boil-up, and allow the remainder to pass over into second condensers as take-oif; or by means of a total condenser, feeding into weirboxes from which the relative amounts of takeoff and reflux, hereinafter termed reflux ratio, can. be adjusted. These various methods of controlling the reflux ratio are in general not independent of the boil-up, or the physical operation of the column. Thus, if properly set for one rate of distillation, if the rate is changed the reflux ratio will vary unless reset for the new rate. Such arrangements are not satisfactory where it is desired to maintain a constant reflux ratio independent of the rate of distillation.

An object of this invention, therefore, is an improved-design for the head of fractionating columns. A further object is the provision of a reflux control for reflux distillation apparatus. A still further object is a means of reflux control which is completely independent of the behavior of the column and which can easily be adjustedto any predetermined reflux rate. These and other objects will more clearly appear hereinafter.

To accomplish these objects, we have devised a total condenser which preferably condenses all of the vapors from the column and feeds the liquid into a movable distributing vessel, preferably in the shape of a funnel which in turn feeds the column with reflux liquor or the take-off by its movement. Thus the ratio of reflux to take-off is the ratio of the time during which this funnel is in these two feeding positions.

An understanding of our invention is facilitated by reference to theaccompanying drawing which illustrates a preferred embodiment particularly well adapted for reflux control in vacuum distillations, and wherein:

Fig. 1 is a vertical view, partly in section, of a fractionating column modified according to our invention;

Fig. 2 is a vertical view, partly in section, of the essential apparatus of Fig. 1 oriented 90 about the vertical axis;

Fig. 3 is a vertical section in the plane of Fig. 1

and shows the funnel in its second operative position;

Fig. 4 is a diagrammatic illustration of a preferred means for operating the funnel;

Fig. 5 is a top detail of the circuit breaker of Fig. 4.

Referring to Fig. l, a preferred structure embodying our improvement'is mounted on top of any conventional distilling column I which may be of the packed, bubble plate, or any equivalent variety; vapors rise from the column through the side tube 2 and enter the condenser 3 where they are liquefied and returned through the restricted outlet 8 at the bottom of the condenser. 4 feeds into the pivoted funnel 6 which is free to swing as indicated, feeding the liquor stream into either 6, the run-back tothe column i, or 1, the take-oil line. Liquor fed into I is removed from the column as distillate at 8; liquor fed into 5 is returned to the column as reflux. 6 may be a restricted feeding device as shown so ar-' ranged to maintain a continuous flow during the periods when 5 is feeding i, or the liquor may be returned directly to i in an interrupted stream. I1 is the usual pressure equalizer line; The distillation temperature may be measured by a thermometer (not shown) in the vapor line 2.

The pivoted funnel 5 may be actuated in any desired manner. If the device is constructed of glass as shown in Fig. 1, it is convenient to swing the funnel by attaching to it a soft iron core 9 which may be glass covered, as shown, and placing this in a changing magnetic field. Referring to Fig. 4 this type of magnetic control is illustrated. Again, the condenser, distributor funnel, etc., are indicated by the same number conventions. The iron core 9, and hence the pivoted funnel" E, are swung by the fleld established by the electromagnet Iii. During the period when the current is applied to ill, the funnel 5 which in its normal or at-rest position is in register with 6 as indicated in'Fig. 1, is directed to feed the take-off 8 as shown in Fig. 3; when the circuit is broken and the electromagnetic field is destroyed, the funnel falls back into the normal position returning the condensate to the column at 6. Current supplied to i maybe from any source Ii of direct current such as dry cells,

storage batteries, a rectifier on an alternating current system, or a direct current generating unit. Electrical current from H is applied on Ill through an interrupting device such as the one illustrated in Figs. 4 and 5. Referring to Fig. 4, the current is conducted to the'center of a rotating disc I! constructed of some non-conducting of the still head through a stufling box which may be actuated in reciprocal motion by means is the ratio of the arc inscribed by I5 on the non-conductor to the arc inscribed on the conductor l3. By suitable design of the conductor l3, this ratio of arc lengths can be made a linear function of the position of IS on the slide l6, so that the reflux ratio can be predetermined by the location of IS on IS.

Any current interrupting device is suitable for the purpose of this magnetic control so long as the periods of open and closed circuit can be predetermined. Operation of the magnetic control is independent of the speed with which the circuit is interrupted (the speed of disc I2) because the ratio of the periods of the cycle remain constant. However, it is desirable to havea speed sufficiently great that the take-off interval is not so great that the equilibrium in the column is disturbed. The restricted feed 6 to the column maintains a more or less constant flow during the take-off interval, provided it is not of great extent. For example, in a typical operation with a predetermined reflux ratio of 9/1, it has been found convenient to rotate the disc i2 at approximately 12 R. P. M., giving a take-off period of 0.5 second and a run-back period of 4.5 seconds. To some extent, the speed with which the funnel can be moved is a function of its inertia. Also, when the take-oil and run-back periods are approximately equal, it is advantageous to operate the interrupter more frequently than when the take-off is a small fraction of the runback. For these reasons, it is desirable to have a variable speed motor drive on disc l2.

Our invention is of course not limited to magnetic operating means illustrated but comprehends rather any equivalent thereof. On large installations, for example, or on constructions where the magnetic principle cannot be applied advantageously, the pivoted distributing funnel 5 can be operated mechanically from the outside by a connecting rod projecting through the side of magnetic device or a motor driven cam. The use of a cam does not permit the .ease of adjustment which can be obtained with a magnetic operation and a controlled electrical circuit; therefore, the latter is preferred. A convenient '-actuating mechanism for the connecting rod consists of a solenoid to which current-is supplied from an interrupter of the design shown in Fig. 4.

The magnetic control is conveniently applied if the still head arrangement is constructed of a non-magnetic material, or it may be used in conjunction with magnetic metals if the magnet I0 is placed inside of the still head in close prox- -imity to 9, but sheathed with a corrosion resistant layer to protect it from the vapors in the still.

V The specific description and drawing above are for purposes of illustration only, it being understood that numerous changes and modifications falling under the definition of our invention as set out in the following claim, are included within the scope thereof.

We claim:

In a reflux distillation apparatus comprising a still and condenser, the improvement which comprises in combination, a funnel located above and in direct communication with the vapor outlet of the still, said funnel being pivoted near its top to swing about a horizontal axis, and having a' stem composed in part at least of ferrous metal, said ferrous metal part being sheathed with a corrosion-resistant material, means for conducting the stream of condensate from the condenser to the funnel, means in register. with the outlet 'of the funnel in its normal at-rest position for conducting reflux condensate to the still, means adjacent the last-named means for conducting condensate to a storage receptacle, an electromagnet adjacent the stem of the funnel and further positioned to bring the outlet of the funnel into register with the means for conducting condensate to the storage receptacle when said magnet is energized, a suitable electric circuit for energizing said magnet and adjustable automatic means operating independently of the operation of the still for periodically main ing and breaking said circuit for predetermined time intervals.

ALBERT S. CARTER.

FRANK WILLARD JOHNSON.

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