US2346443A - Fractionating apparatus - Google Patents

Description

April 11, 1944. w. A. McMlLLAN FRACTIONATING APPARATUS Filed Oct. 5, 1940 3am 9.51.5 on

WAL'LACE A. MCMILLAN R A INVENTOR I div fl g H/S ATT RNEYS Patented Apr. 11; 1944 2,346,443 FRACTIONATING APPARATUS Wallace A.

McMillan, Forest Hills, N. Y., assignor,

by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application October 5, 1940, Serial No. 359,853

4 Claims.

This invention relates to distilling and fractionating apparatus of the type adapted for the analysis of mixtures of volatile liquids, gases or vapors containing condensabie liquid fractions, and more particularly to apparatus of this character by means of which efiicient control of the fractionation may be obtained while at the same time the temperatures and pressures of the frac tionation may be accurately recorded.

The principal object of the invention is to provide an apparatus for precise analytical distillation and fractionation in which the fractionation is regulated automatically in accordance with the pressure of the vapors from a fractionating column and in which the temperatures and pressures of the fractionated vapors are also automatically recorded without the necessity of any manual operation. Another object is to provide means for reducing the amount of heat used for the distillation when the pressure of the fractionated vapors increase to a predetermined value. Still another object is to provide means for regulating the passage of fractionated vapors from the fractionating column to a receiver in accordance with the pressure of said vapors.

Apparatus for analytical distillation and fractionation comprising essentially a distilling bulb, an elongated fractionating tube or column surmounting the bulb and a condenser section at the upper end of the fractionating tube with equipment for collecting and measuring the distilled vapors is known; for example, see Podbielniak, Patent No. 1,917,272, granted July 11,-

1933. Apparatus of this type operates on the principle of sharp, relatively adiabatic fractionation to separate constituents of the mixture being analyzed in the order of their boiling points. Apparatus of this type which is available on the market has so far sufllced to provide only a proximate analysis of the mixtures and has proved incapable of giving accurate quantitative results, or even reproducible results with different operators.

An apparatus for accomplishing these results, and by means of which accurate and reproducible results may be obtained, is described in the Mc- Millan Patent No. 2,005,323 granted June 18, 1935. The proper operation of that equipment necessitates the constant attendance of at least one operator since it is necessary to make various manual adjustments to the apparatus during the distilling and fractionation of a given mixture. with the apparatus to be described the operation can be conducted without the frequent attendance of any operator since the fractionation and the recording of the temperatures and pressures are automatic. Apparatus which is now on the market also necessitates several complicated elements which are fragile and very expensive and also involves a complicated measuring and recording system which requires the use of precision equipment which is difficult to obtain. Much of this precision equipment is obtainable only from foreign countries. Moreover, with the apparatus now on the market there is considerable dead space in the pipe connections through the receivers and this, of course, interferes with the accuracy of the determinations.

In accordance with the present invention, an apparatus comprising a distilling bulb, an elongated adiabatic fractionating tube disposed thereabove and surmounted by a condenser section is provided together with means for automatically supplying a cooling liquid to this condenser in accordance with the pressure of the vapors leaving the condenser section. Means are also provided for decreasing the heat applied to the distilling bulb when or if the pressure of the vapors leaving the condenser section reaches a predetermined point. The invention also contemplates the use of a pressure-temperature recorder of the recording potentiometer type, this instrument being operated automatically by and in accordance with variations in pressure in the vapors passing from the condenser section. A pen is adapted to trace a record on a chart roll in accordance with variations in temperature of the vapors in the condenser section while at the same time the chart roll is advanced so that the chart travel is directly proportional to increases in pressure of the vapors leaving the condenser section.

For a further understanding of the invention reference may be had to the accompanying drawing in which:

Figure 1 is an elevational view generally diagrammatic of the apparatus embodying the improvements of the present invention;

Figure 2 is a vertical, sectional elevation through the liquid valve, and

Figure 3 is a vertica1 elevation showing a modified form of valve.

Referring to the drawing, an elongated, jacketed, fractionating tube or column [0 is provided at its lower end with a distillation vessel or bulb l2 and a jacketed condenser section I at its upper end. The distillation bulb is provided with a suitable heating element such as the electrical resistance coil IS. A conduit l8 comprising a from certain foreign countries. with the present invention, a somewhat diflerent vapor passage leads from the condenser section to one or more receivers in which a reduced pressure is normally maintained as by means of a suitable vacuum pump 2l.- A container 22 of a cooling medium such as liquid nitrogen is connected to the condenser section l4 by means 'of pipe 24 and a pipe 26 leading from a source of compressed air, not shown, is connected to the top of the vessel 22, the arrangement being such, as.will be described hereinafter, that the compressed air forcs the liquid nitrogen into the condenser section l4 at the proper time, thereby reducing the pressure of the vapors taken oil through the conduit I 8 andthus regulating the fractionation by control of reflux and distillation rate. Disposed in the conduit I 8 is a valve device 28 comprising a pair of porous discs 38 preferably formed of sintered glass filter plates and extending across the vapor passage. One leg of a mercury manometer 32 is connected to the conduit l8 between the discs 30 and the other leg of the manometer is open to atmosphere as usual. A flexible tube 34 connects the lower end of the manometer 32 with a mercury bulb or reservoir 36 which can be adjusted up or down to vary the height of the mercury in the manometer. The porous discs 30 may be formed of glass ground to a powder, burned to a sintering point and formed into discs or plates of a convenient size and are of such construction that they are pervious to the passage of gas or vapor whil impervious to the passage of mercury therethrough. Thus, when the pressure in the olftake l8 drops below a certain value the mercury will rise in the manometer leg connected to the offtake and will fill the space between the two sintered discs 30, thus preventing vapor from the fractionator ID from passing to the receivers 20. When the pressure in the oiltake I8 rises above the predetermined value or norm-a1 the mercury is depressed within the manometer leg so as to open the gas passage through the sintered discs 30.

The general construction of the valve device 28 comprising the pair of sintered glass discs 30, is described inthe aforementioned McMillan Patent 2,005,323. The glass discs have formerly been sealed in parallel in opposite sides of a glass T and this construction has been obtainable only In accordance mounting of the discs has been provided as shown in Figures 2 and 3 and has proved to be very satisfactory. As shown in Figure 2, the discs 30 are sealed in the ends of pipes I8A, these pipes comprising a portion of the ofitake l8 previously described. The ends of the pipes [8A containing the discs 30 are placed in a T 3| which may be of metal or other suitable material and the ends of the pipes are preferably seated against suitable gaskets 33. A sealing material is placed so as to seal the space around the ends of the pipes |8A and between the pipes and the T 3|. It has been found that this construction is simple to efiect and it renders unnecessary the importing of expensive equipment. Although the T 3! is shown as constructed of metal, this member may, of course, be made of glass which will provide suitable insulating means for the electrical contacts to be placed within the valve and which will be described hereinafter. Another method of mounting the glass discs 30 is shown in Figure 3 in which the discs are sealed in opposite legs of a T 35 formed of a plastic, preferably of acrylic or styrene resin types. The ends of the pipes IBA can be sealed into the opposite legs of the T after the T has been constriicted. or the entire T may be cast around the end of the pipes and the discs 30. In either case a construction is provided which is transparent so that mercury within the valve can be observed and which will provide an insulating medium in which electric-a1 contacts and wires may be mounted.

Within the valve 28 are arranged upper and lower electrical contacts 38 and 40, respectively, and at a lower point in the manometer 32 is disposed a third contact 42. Disposed in the pipe 26 leading to the vessel of cooling medium 22 is a valve 44 normally held in an open position by means of a compression spring 46. The valve 44 is provided with a solenoid 48 and the solenoid winding is connected in circuit with a suitable source of electricity 50, the upper contact 38 and the third contact 42 in the manometer 32. In the operation of this portion of the apparatus when the mercury within the manometer 32 fills the space between the discs 30 so as to shut oil the gas or vapor passage, the electrical circuit will be completed between contacts 38 and 42 and the solenoid 48 will be actuated to hold the valve 44 in its closed position against the compression of the spring 46. When the pressure increases in the oiftake I8, the mercury will be depressed in the manometer leg and the electrical circuit will be broken between contacts 38 and 42, whereupon the solenoid 48 will be de-energized and the spring 46 will open the valve 44 allowing compressed'aiito pass into the vessel 22 and force part of the liquid nitrogen into the condenser I 4 to cool the vapors and thus reduce the pressure. When the pressure has been sufficiently reduced, the mercury will rise in the manometer leg, thus again closing the electrical circuit just described, so that the valve 44 will be closed to stop the flow of cooling medium into the condenser, thereby allowing the pressure to increase again. It will be seen that an apparatus has thus been provided whereby the fractionation will be controlled automatically in accordance with the pressure of the fractionated vapors.

The electrical contact 48 is connected in another circuit with the coil 52 of a break relay 54, the source of electricity 60 and contact 42. The armature 56 of the relay 54 is adapted to close a circuit containing a source of electricity 58 and a suitable alarm device such as a buzzer 60. Thus, should the pressure in the ofltake l8 rise to an abnormal degree, the circuit between the contacts 40 and 42 will be broken, thus deenergizing the coil 52 and permitting a spring 62 to pull the armature 56 to the right to close the circuit to energize the alarm 68. In addition the circuit containing the electrical source 58 is preferably connected to the coil 64 of a relay 66 and a suitable switch 68 through wires 69. The relay 66 is connected in circuit with the electrical heating coi1 "5 of the distillation vessel l2 so that in the event of an abnormal increase in the pressure of the vapors in oiftake l8, the relay 64 will be closed ing the heating element l6 of the distillation vessel l2. The reduction of heat in the vessel I: will, of course, slow up the distillation to reduce the pressure of the vapors in conduit l8.

' In accordance with the invention, means are also provided for automatically recording the pressures and temperatures of the vapors leaving "re condenser section I4 and passing through the conduit I8 to the receivers 20. To this end a second mercury manometer I4 has one leg I6 communicating with the conduit I8 through a valve I8. The other leg of the manometer is open to the atmosphere as usual and a flexible tube 80 connects the lower end of the manometer with a mercury bulb or reservoir 82. The reservoir 82 is mounted in a bracket member 84 slidable vertically on a guide rod 86 and having threaded connection with a rotatable threaded rod 88, the latter supported in suitable bearings 90. As the rod 88 is rotated the bracket 84 and thus the mercury reservoir 82 will be moved up or down so as to control the level of the mercury in the manometer leg 14. A recording instrument 92, preferably of the recording potentiometer type, is provided with a chart roll 94 over which a chart 96 passes as the roll is rotated. The instrument is also provided with a recording pen 98 which is moved laterally of, the chart 96 in accordance with variations in temperature in the fractionating column l0, which temperature variations actuate a thermocouple I connected to the instrument 92 by means of suitable wires I02. The instrument 92 may be of any' suitable type as long as it includes the elements so far mentioned. A reversible electric motor I04 is arranged to drive the chart roll 94 through suitable gearing I06 and this motor is also connected through suitable reduction gearing which may comprise a worm and wheel I08, to drive the threaded rod 88. Thus, when the motor I04 is energized it will rotate the chart roll 94 to advance the chart 96 while at the same time the rod 88 will be rotated to raise the bracket 84 and thereby the mercury reservoir 82.

In order to control automatically the motor I04, an electrical circuit is provided comprising a contact I I0 mounted within and near the upper end of the manometer leg I6, and another contact II 2 located within and adjacent the bottom of the manometer I4. In addition to the contacts III] and H2 this circuit also includesa source of electricity H4 and a break relay H6. The contacts, not shown, of the relay H6 are connected in another circuit with the motor I04 and a source of electricity IIB. As the receiver pressure rises during distillation the mercury level in the manometer leg I6 will fall below the contact IIO, which comprises a fixed reference point, and the circuit to the relay II6 will thereby be broken and the actuation of the relay will,

then complete the circuit to energize the motor I04. As stated herein-before, when the motor I04 is energized it will drive the chart roll 94 to advance the chart 96 and simultaneously therewith it will rotate the threaded rod 88 so as to lift the mercury reservoir 82 to bring the mercury level in the manometer leg I6 back until electrical contact is remade at 0. The completing of the circuit between contacts H0 and H2 will thus actuate the relay II6 to stop the motor I04 and the chart 96 and the mercury reservoir 82 will remain in the positions then obtained until the receiver pressure again depresses the mercury in the manometer leg I6 I sufllciently to open the circuit to the relay IIB when the cycle will be repeated.

As long as a certain component of a gaseous mixture is being distilled from the column I0 the temperature will, of course, remain substantially constant. The pressure in the receiver 20 and the offtake I8 will, however, increase during this period and the pen 98 will, therefore, draw a straight, vertical line such as I20 on the chart 88. When the distillation of one component of the gaseous mixture has been completed the temperature will, of course, rise until the boiling point of the next component or the next constant boiling mixture is reached. The pen 98 will thereupon move horizontally a certain distance across the chart 96 as indicated at I22 with very little vertical movement of the chart during this time so that the distillation curve will be a series of slopes and plateaus in the usual manner. The proportion of any ingredient in a gaseous mixture can be readily computed from the chart by calculation of the ratio of the length of the vertical line representing the distillation of that component, to the total vertical length of the chart during the entire distillation. When the mercury reservoir 82 has been lifted to the top of the rod 88, or whenever it is desired to change a chart, to adjust the amount of mercury in the reservoir or to change distillate receivers it is merely necessary to close the valve 18 and to energize the motor I04 so that it will be operated in the reverse direction. The rod 88 will then rotate to lower the bracket 84 and the reservoir 82 to a point near the bottom of the rod after which the valve I8 can be opened and a new recording started.

It will thus be seen that by a comparatively simple construction the apparatus of the present invention accomplishes the following operations entirely automatically: controls the supply of cooling medium to the condenser jacket of the distillation column, in accordance with the distillation pressure at the outlet of the column; controls the supply of heating fluid to the still, in accordance with the distillation pressure, and actuates the chart of the recording instrument so that the travel of the chart is made proportional to the pressure increase within the vapor receiver.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

I. Distillation apparatus comprising in combination a fractionating column, a vapor offtake from said fractionating column, a mercury manometer having one leg communicating at its upper end with said vapor offtake and responsive to pressure therein, means for adjusting the height of mercury in said manometer comprising a reservoir adapted to contain mercury and a flexible tube connecting said reservoir with the bottom of said manometer, means for recording the pressure of fractionation in said column, a vertically disposed rotatable screw, a member threaded on said screw and attached to said reservoir so as to support said reservoir, an electric motor connected to drive said pressure recording means and to rotate said screw, an electrical contact in the lower end of said manometer, a second electrical contact in the upper end of said manometer leg, and an electric circuit including said contacts, a relay, a source of electricity and said motor, the arrangement being such that as the pressure increases in said ofitake the mercury will be depressed in said manometer leg to a point below said second electrical contact whereupon said electric circuit will be broken to said relay, said relay being arranged to start the electric motor when the manometer circuit is broken to cause said motor to drive said pressure recording means and simultaneously therewith to rotate said screw to elevate said reservoir.

2. Distillation apparatus comprising in combination a tractionating column, a vapor oiitake from said fractionating column, a mercury manometer having one leg communicating at its upper end with said vapor ofl'take and responsive to pressure therein, means for adjusting the height of mercury in said manometer comprising a reservoir adapted to contain mercury and a flexible tube connecting said reservoir with the bottom of said manometer, means for recording the pressure and the temperature of fractionation in said column comprising a recording instrument having a chart roll and a pen adapted to trace a record on said chart, means for elevating said reservoir, an electric motor connected to drive said chart roll and to operate said elevating means, a thermocouple disposed in said fractionating column and connected to said instrument to actuate said pen, an electrical contact in the lower end of said manometer, a second electrical contact in the upper end of said manometer leg, a relay, a source of electricity and an electric circuit including said contacts, relay, source of electricity and motor, the arrangement being such that as the pressure increases in said ofltake the mercury will be depressed in said manometer leg whereupon said electric circuit will be broken to said relay, said relay being arranged to start the electric motor when the manometer circuit is broken to cause said motor to advance said chart and simultaneously therewith to operate said elevating means.

3. Distillation apparatus comprising in combination a fractionating column, a vapor oiftake from said fractionating column, a mercury manometer having one leg communicating at its upper end with said vapor ofitake and responsive to pressure therein, means for adjusting the height of mercury in said manometer comprising a bulb adapted to contain mercury and a flexible tube connecting said bulb with the bottom of said manometer, means for recording the pressure and the temperature of fractionation in said column comprising a recording instrument having a chart roll and a pen adapted to trace a record on said chart, a vertically disposed rotatable screw, a member threaded on said screw and attached to said bulb so as to support said bulb, an electric motor connected to drive said chart roll and to rotate said screw, a thermocouple disposed in said fractionatlng column and connected to said instrument to actuate said pen, an electricalcontact in the lower end or said manometer, a second electrical contact in the upper end of said manometer leg, a relay and a source of electricity, and an electric circuit including said contacts, relay, source of electricity and motor, the ar rangement being such that as the pressure increases in said ofitake the mercury will be depressed in said manometer leg whereupon said electric circuit will be broken to said relay. said relay being arranged to start the electric motor when the manometer circuit is broken to cause said motor to rotate to advance said chart and simultaneously therewith to rotate said screw to elevate said bulb.

4. Distillation apparatus comprising in combination a fractionating column, a vapor ofitake from said fractionating column, a mercury ma nometer having one leg communicating at its upper end with said vapor ofitake and responsive to pressure therein, means for adjusting the height of mercury in said manometer comprising a bulb adapted to contain mercury and a flexible tube connecting said bulb with the bottom of said manometer, a pressure and temperature recording instrument having a chart roll and a pen adapted to trace a record on said chart, a thermocouple disposed in said fractionating column and connected to said instrument to actuate said pen, a vertically disposed rotatable screw, a member threaded on said screw and attached to said bulb so as to support said bulb, an electric motor connected to advance said chart roll and to rotate said screw in proportion to increase in pressure in said ofitake, an electrical contact in the lower end of said manometer, a second electrical contact in the upper end of said manometer leg, and an electric circuit including said contacts and said motor, the arrangement being such that as the pressure increases in said ofitake the mercury will be depressed in said manometer leg to a point below said second electrical contact whereupon said electric circuit will be broken to cause said motor to rotate to advance said chart and simultaneously therewith torotate said screw to elevate said bulb while said pen records on said chart variations in temperature in said column.

WALLACE A. MCMILLAN.

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