US2327788A - Distillation process and apparatus - Google Patents

Description

Aug. 24, 1943. K. c. D. HICKMAN DISTILLATION PROCESS \ND APPARATUS Filed June 4, 1941 2 Sheets-5hest IL F QL; 3a FICA.

A TTORNE f5 Aug. 24, 1943.

K. C. D; HlCKMAN DISTILLATION PROCESS AND APPARATUS 2 SheetsSheet 2 Filed June 4, 1941 KENNETH E.D.H|E.KMAN

INVENTOR A TTORNE Y5 Patented Aug. 24, 1943 DISTILLATION PROCESS AND APPARATUS Kenneth C. D. Hickman, Rochester, N. Y., assignor to Distillation Products, Inc., Rochester, N. Y., a corporation of Delaware .Application June 4, 1941, Serial No. 396,569

6 Claims.

This invention relates to an arrangement for ascertaining, or for indicating and controlling the rate of evaporation in high vacuum surface evaporators and molecular stills, as well as similar devices.

In the past, the rate of evaporation in a molecular still has been governed by controlling the temperature of the evaporator. It is difllcult, however, to indicate the temperature with a thermometer or other device inserted in the oil stream on an evaporator in a centrifugal still since friction falsifies the temperature and splashing of the distilland spoils the distillate. In any event, control of temperature in a still does not necessarily control the rate of distillation, since variations in pressure and the composition of the distill and may cause the still to run too slowly or too fast.

Even with the most effective temperature control mechanism, it is ultimately the temperature of the still that is controlled rather than the rate of distillation; while under abnormal circumstances, such as faulty vacuum and in particular when there are many components in the distilland, temperatures alone may be inadequate to control distillation.

In accordance with the main feature of the present invention, it is proposed to indicate or to indicate and to control the rate of distillation by mechanism including one or more elements suspended in the vapor stream and variably deflected by said stream.

Another feature of the invention relates to indicating mechanism including balances having vanes exposed to the stream of distilling vapor in a still, in such a way as to be deflected from their normal positions as distillation commences and increases.

A further feature of the invention relates to the use of a pendulum arrangement for indicating the rate of distillation in a molecular still and employing this indication to control the rate of evaporation. 1

For a further understanding of the invention, reference is made to the detailed description and claims when taken with the drawings in which:

Fig. l is a vertical sectional elevation of a fall ing film still embodying theindicating and controlling arrangement of the present invention;

Fig. 2 is a vertical sectional elevation of a modified form of the invention incorporated in a still wherein the evaporator and condenser are rotatable about a vertical axis;

Fig. 3 is an enlarged elevation of a detail shown in Fig. 2;

Fig. 4 is a diagrammatic representation of the modified control arrangement as used with the still of Fig. 2;

Fig. 5 is a vertical sectional elevation of a further modified form controllin arrangement applied to a still of the type in which the evaporator and condenser disc rotate about a horizontal axis;

Fig. 6 .is a sectional top plan, taken approximately on line E6 of Fig. 5; and

Fig. '7 is a vertical section, taken on line l! of Fig. 5.

In the form of the invention shown in Fig. l, the invention is applied to a falling film molecular still including an upright cylindrical chamber 2 generally annular in cross section, the chamber being defined by an outer casing 3 and a smaller cylindrical casing 4 coaxially positioned therein. The top of the outer casing is sealed by the top plate 3a While the top of the inner casing is sealed by a top plate 5 formed with a reservoir 6 having perforated side walls so that distilland in the reservoir flows through the holes to the outside of the inner casing. A conduit I connected to a source of degassed oil or other distilland discharges into the mentioned reservoir 6. The lower end of the chamber is closed by an annular plate 8 sealed to the lower edges of the inner and outer casings while the lower portion of the inner wall of the casing has secured thereto an annular gutter 9 into which the distillate, condensing on the side wall of the outer casing, can flow. This gutter communicates with a discharge pipe l0 through which the distillate may be drawn from the still. The annular plate 8, likewise, is provided with an outlet pipe ll through which the undistilled residue can be drawn from the still.

Since this still is intended for molecular distillation, a pipe 12 opening through the side wall of the outer casing communicates with the chamber and is connected to a vacuum pump (not shown) whereby extremely low air pressures are developed within the still. The inner casing serves as an evaporating element and is, therefore, internally heated by heating coil sections l3 and M. The construction and operation of this still is similar to that disclosed in the Hickman Patent No. 2,221,691, granted November 12, 1940.

In accordance with the present invention, means are provided for controlling the amount of heat delivered by said coil sections I3 and it and thereby varying the rate of evaporation effected within the still. The means for determining the rate of evaporation comprises one or more devices responsive to the pressure of the vapor stream as it flows by convection from the inner casing l or evaporating surface, toward the outer casing, 3 or condensing surface. As herein illustrated, two such responsive devices A and B of extremely light weight are employed, one, near the top of the still where the cold distilland is appl1ed to the top portion of the evaporating surface, and the other responsive device is positioned near the lower portion of the evaporating surface. The responsive device comprises a pendulum l5 mounted to swing about a fixed pivot IS. The upper portion of the pendulum is provided with an angular extension I! carrying a switch contact normally engaging the switch spring i8. The lower end of the pendulum carries a very light vane IS in the form of a disc extending generally normal to the vapor stream flowing from the evaporating surface. This pendulum, in its normal position, closes a breakpoint in the circuit of the heating coil section i3 for the upper portion of the evaporating surface. However, when the distilland starts to evaporate, the vapor stream will strike the vane and swing it toward the left as shown in Fig. l. The movement of this vane from its normal vertical position will be a function of the rate of evaporation. Thus, as the evaporation becomes great, the break-point in the mentioned circuit for the heating coil section it will be opened and the upper portion of the evaporating surface will be unheated until the rate of evaporation drops to a point where the vane will resume its normal vertical position, closing the mentioned breakpoint in the heating circuit. The second responsive device B, of like construction and designated by the same characters primed as were used in connection with the first unit, controls the circuit for the heating coil section ill and, therefore, the rate of evaporation in the lower portion of the still. By this arrangement, the rate of evaporation in difierent portions of the still can be regulated at will. It will be appreciated that the invention, is not limited to the use of two vapor pressure responsive devices but a greater or lesser number of such devices can be used as occasion demands.

In the modified form of the invention shown in Figs. 2, 3 and i the invention is applied to a molecular still in which the evaporating element is essentially horizontal and is of particular use with the form of rotating evaporator whereby the distilland advanced over the surface of a heated disc by centrifugal action. This form of still comprises a cylindrical casing 20 closed at its upper and lower ends respectively by the end plates 2! and 22. The end plate 22 is provided at its center with a journal 23 for supporting the lower end of a vertical shaft 25 extending along the axis of the casing and projecting through a stufiing box 2 1 in the upper end plate 2|. This shaft terminates in a pulley 26 or other suitable means by which it can be rotated at any desired speed. Since the device is to be operated as a molecular still, the side wall of the casing is provided with a conduit 21 through which the space within the still can be evacuated by any suitable evacuating means (not shown).

The evaporator disc 28 with its upturned rim 29 and a slightly larger condenser disc 30 also provided with an upturned rim 3| are fixed on the shaft 25 to extend horizontally in spaced parallel relation to each other, the space between the plates being relatively short to effect short path or molecular distillation. The under surface of the evaporator disc 28 is heated by any suitable means such as heating coil sections 32a, 32b and a reflector 33. The upturned rim 29 of the disc 28 holds the undistilled residue until it is collected by a scoop 34 communicating with the discharge pipe 35 sealed in the wall of the still. An inlet pipe 36 sealed in the wall of the casing serves to introduce'distilland to the center of the rotating disc 28. The border of the under surface of the condenser disc 30 has a scoop 31 cooperating therewith to remove the distillate which collects on that surface.

The condenser disc 30 with its upturned edge 3! contains a circulating, refrigerating medium by which this rotating disc is cooled. A convenient way for recirculating the refrigerating medium includes a pipe 39 having one end discharging near the center of the disc 29 and having its other end external of the still connected to a coil 5|. This coil is connected to the outlet of a pump 42, the inlet of which pump is connected by a pipe 53 extending through the wall of the casing and terminating in a scoop 44 projecting into the gutter 3i formed by the upturned edge of the disc. It will be appreciated that in this arrangement, pipe 39 discharges the circulating medium near the center of the evaporator disc and this medium is distributed over the surface of the disc by centrifugal force, gradually reaching the gutter. The medium on reaching the gutter is gathered up by the scoop, being sucked into the external portion of the recirculating system by means of the pump. The construction and operation of the still just described is substantially similar to the still disclosed in the patent to Hickman 2,218,240 granted October 15, 1940.

In accordance with a modified form of the present invention, suitable means are provided for controlling the rate of distillation in this last-described still. In this form of the invention, there is mounted between the evaporator disc 28 and the condenser disc-3U, means for measuring the rate of distillation. This means comprises a scale beam 46 supported at its intermediate point on a flexible suspension 41, the beam being laterally guided by the guide rods 58 (Fig. 3) to extend radially of the disc 28. On the respective ends of the beam, there are mounted cone-shaped cups or vanes 49 and 50 open at their bottoms. The lower edges of these cups are scalloped so that condensate settling thereon will quickly accumulate on the low points of the scallops and drop back to the disc 28. It will be appreciated that the scale beam it and the cups 59 and 50 should be made, of extremely light weight material to provide a sensitive responsive device. 'The scale beam is provided at an intermediate point thereon with a bracket 52 to support a mirror 53 which indicates by the light rays reflected therefrom, the deflection of the scale beam. If it is desired to indicate the rate of evaporation taking place in the still, the portion of the apparatus just described is sufficient for this purpose.

Ordinarily, it is desirable to control the rate of evaporation in the still and to this end additional apparatus is provided. Photoelectric cells 56 and 5? are mounted outside of the still in a vertical plane so that when the scale beam 36 is in its normal horizontal position, light from the light source 56 is directed by the lens 55 to the mirror 53. From this mirror, the light is reflected through the window W in the wall of the still, along the path indicated by the broke line 59, between the photoelectric cells 56 and 51. The

amplifier 60 amplifies any output currents of these photoelectric cells as a result of light falling thereon, to selectively operate the relays 62 and B3. The relays 62 and 63, when operated respectively, open the circuits for the heating coils 32a and 32b of the evaporator disc 28. With this arrangement, if the inner portion of the evaporator disc 28, heated by coil 32b, is evaporating at a faster rate than the outer portion of this disc which is heated by the coil 32a, then the inverted cup 56 will rise higher than the cup 49, moving the scale beam 46 counter-clockwise. This causes the mirror 53 to deflect the rays of light 59 from its position between the photoelectric cells 56 and 51 until these rays strike the photoelectric cell 56. The photoelectric cell 56 passes current which is amplified by the amplifier 60 causing the relay 63 to operate. Relay 63 at its armature and back contact opens the heating circuit for the coil 321) until such time as the scale beam 46 returns to its horizontal position. At this time, the light rays 59 will no longer strike the photoelectric cell 56 but instead will pass between the cells 56 and 51. Under this condition, the photoelectric cell 56 passes no current and consequently its related relay 63 will deenergize to close again the heating circuit for the coil 32b.

In the event that the portion of the evaporator disc 28 which is'heated by the coil 32a evaporates the distilland at a rate higher than the inner portion of the disc, then the inverted cup 49 will be elevated above the cup 50 to swing the scale beam 46 in a clockwise direction. In this instance, the mirror 53 will refiect light on the photoelectric cell 51. This cell will then pass current which is amplified by the amplifier 69 to energize the relay 62. Relay 62 at its armature and back contact interrupts the circuit for the heating coil 32a. Of course, when the desired rate of evaporation for the outer portion of the evaporating disc 26 prevails the scale beam 46 will resume its normal horizontal position so that the light rays 59 will again be reflected between the two photoelectric cells. As a result of this, relay 62 deenergizes to close again the circuit for coil 32a.

Provision is also made in this modified arrangement to control the overall rate of evaporation from the evaporator disc 28. In the event that this disc is evaporating the distilland at too fast a rate, then both of the cups 49 and 59 will be elevated displacing the scale beam 46 vertically and with it the mirror 53. Thus, the rays of light 49 reflected by the mirror 53 will be elevated to fall on a third photoelectric cell 65. The current now flowing through this cell is amplified by amplifier 66, the output of which includes a relay 61. Relay 61 when energized interrupts the power leads 68 to the heating coils 32a and 32b. Thus, when the overall rate of evaporation is too great, the relay 61, when thus energized by the photoelectric cell 65 and the amplifier 66, interrupts the heating circuits for the heating coils 32a and 321).

It will be understood that the photoelectric cell arrangement for detecting the deflection of the scale beam and for controlling the rate of evaporation in the still as a result thereof, is merely typical of various arrangements that can be used. This modified form of the invention is, therefore, not limited to the specific arrangement just described.

In the modified form of the invention shown in Figures 5, 6 and '7 a bifilar pendulum is utilized in detecting the varying rate of evaporation along different portions of an evaporator. This form of the invention may be utilized in the still disclosed in the Hickman Patent No. 2,180,053 granted November 14, 1939, which still comprises a sealed receptacle 18 arranged to be evacuated through the pipe 1|. Opposing vertical walls of the receptacle are respectively provided with a journal 12 and a stufiing box 13 in which a shaft 14 is supported horizontally One end of this shaft projects through the stuffing box to the outside of the receptacle, terminating thereat in a pulley 15 by which it can be driven. On this shaft, there are fixed in parallel short path relation, an evaporator disc 11 provided with a peripheral gutter 18 and a condenser disc 19, likewise provided with a peripheral gutter 80. An inlet pipe 8| passing through the wall of the receptacle discharges distilland near the center portion of the evaporator disc 11. As the evaporator disc 11 rotates, the distilland supplied to the center of the disc is distributed over the surface thereof by centrifugal action, the undistilled residue accumulating in the gutter 18 for removal through the scoop 82 and a discharge pipe 83, all as more fully disclosed in the mentioned Patent No. 2,180,053. The evaporator disc 11 is heated by heating coils 84a and 84b positioned adjacent the outer surface of this disc. A scoop 81 for the removal of distillate, cooperates with the margin of that surface of the condenser disc which is adjacent the evaporator disc. The surface of the condenser disc 19 remote from the evaporator disc 11 is arranged to be supplied with a layer of cooling medium. This cooling medium is supplied in a recirculating system having a cooling coil 85 located outside of the receptacle 16. The lower end of this coil is connected to an inlet pipe 86 sealed in the wall of the receptacle and discharging near the center of the condenser disc 19. As the condenser disc 18 rotates, the cooling medium supplied thereto through pipe 86 spreads as a layer over the surface of this disc by centrifugal action. The spreading medium collects in the gutter 80 where it is gathered up by a scoop 89 and conveyed by a pipe 90, sealed in the wall of the receptacle, to the upper end of the cooling coil 85, as fully disclosed in the last mentioned Hickman patent.

In order to indicate the rate of evaporation from the surface of the evaporator disc 11, a bifilar pendulum is employed. This pendulum comprises two threads 92 having their upper ends secured in spaced relation to the top of the receptacle. The lower ends ofthese threads are connected in spaced relation to a very light rigid support 93 on the ends of which there are secured the vanes 94 and 95. provided with drip points 94a and 95a so that the condensate settling thereon will quickly accumulate as drops on these points and fall off of the vanes. The threads 92 support a mirror 91 on which light rays from a source of light such as the electric light bulb 98, is directed by the lens 99. This mirror cooperates with the photoelectric cells such as 56 and 51 previously described as well as the amplifier 60 to sele tively operate the relays 62 and 63 to control the heating coils 84a and 84b.

In the operation of this still, the receptacle is evacuated and the shaft 14 with the evaporator disc 11 and the condenser disc 19 mounted thereon are rotated at a relatively high rate of speed. The evaporator plate 11 is heated by the heating coils 84a and 84b and the surface of the con- These vanes are denser disc 19 is cooled by the recirculating medium as mentioned. When now the distilland is introduced through the pipe 8| to the center of the evaporator disc 11, this distilland is distributed by a centrifugal force over the inner surface of the evaporator disc. In passing over this heated disc some of the distilland is evap orated and the vapor flows by convection to the adjacent surface of the condenser disc '19 where it condenses as a distillate which is removed and discharged by the scoop 81. The residue of the distilland is collected in the gutter 78 from which it is'gathered by the scoop 82 and discharged outside of the still through the pipe 83. It will be understood that as the rate of evaporation from the evaporator plate increases, the pressure of the flowing vapor will increase. If the rate of evaporation is faster near the center of the evaporator disc, the pendulum will tend to rotate clockwise (Fig. 6) whereas if the rate of evaporation is greater at the outside portion of the disc, the pendulum will tend to rotate counter-clockwise. The mirror 91 mounted on the supporting threads -92;"thus= wings to apply light through window W selectively to'the photoelectric cells 55 and '57. These cells together with the amplifier 6D selectively operate the relays 62 and 63 to control the circuits of the heating coils 84a and 84 in the manner already described.

What I claim is:

1. In an arrangement of the clas described, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said heating element, displaceable vane-like means suspended between said elements in the path of the vapor flowing therebetween, and means responsive to the displacement of said displaceable means for controlling said heating means.

2. In an arrangement of the class described, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said evaporating element, means including a pendulum suspended between said elements in the path of the vapor flowing therebetween, and means responsive to the action of said pendulum for controlling said heating means,

3. In an arrangement of the class described, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said evaporating element, means including a bifiliar pendulum suspended between said elements in the path of the vapor flowing therebetween, and means responsive to the action of said bifiliar pendulum for controlling said heating means.

4. In an arrangement of the class described, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said evaporating element, means including a pair of balances suspended between said elements in the path of the vapor flowing therebetween, and means responsive to the action of said balances for controlling said heating means.

5. In an arrangement of the classdescribed, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said evaporating element, and means including a biflliar pendulum suspended between said elements in the path of the vapor flowing therebetween to indicate the force of progression of said vapor.

6. In an arrangement of the class described, a still comprising an evaporating element, means for heating said element, a condensing element in cooperative distilling relation to said evaporating element, and means including a pair of balances suspended between said elements in the path of the vapor flowing therebetween to indicate the force of progression of said vapor.

KENNETH C. D. HICKMAN.

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