US1917272A - Analytical fractionating column - Google Patents

Description

July 1.l,A 1933. w. J. PODBIELNIAK ANALYTICAL FRAC'I:IOMTING COLUMN Filed Aug. 15, 19:50 Y' 3 sheets-sheet 1 July 11, 1933. w.I J'. PODBIELNIAK n ANALYTIGAL FRACTIONATING COLUMN V filed Aug. 15, 1930 3 Sheets-.Sheet 2 flag. /a

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w.`.J.l PODBIELNIAK ANALYTICAL FACTIONATING COLUMN July 11, 19343.

, s sheets-sheet s Filed' Aug. ,15 195o r. m a m I Patented July 11, 1933 UNITED STATES WALTER J. PODBIELNIAK, OF TULISA, OKLAHOMA ANALYTICAL FRACTIONATING COLUMN Application filed August 15, 1930. Serial No. 475,585.

This invention has reference to laboratory apparatus for the fractional analysis of volatile liquids and gases or vapors containing condensible liquid fractions. and has to vdo -yparticularly with analytical fractionating columns of the character described in my copending application on Method for analyzing liquid and gas, Serial No. 351,726, tiled April lst, 1929, of which the present application is plished by providing a frartionating column` which is so constructed and proportioned as to obviate the commonly encountered difiiculty in preventing overlapping ofthe vfractionated constituents or cuts, or in other words preventing any one of the fractionated constituents from being contaminated with constituents of higher or lower boiling point.

My improved forni of fractionating column may be characterized as comprisine a distilling or fractionating tube surrounded by an evacuated jacket which provides an effective thermal insulation for the fraetionating tube. The insulation afforded the latter is further increased by plating the jacket with suitable heat reflecting and insulating metal. I may state at this point that one feature of the invention 1es"des in the plating of the jacket in a manner such that the distilling tube will be visible to the analyst through the insulating acket. According to my preferred construction the distilling tube and jacket are made separate, thereby rendering the apparatus less subject to breakage than would be likely in ease these parts were made integral, with-joints that might easily become fractured. Building the column with the distilling tube and jacket as separate parts has the additional advantage of providing a more simple and economical construction, and rendering one or the other of the parts replaceable in case of breakage, without necessitating replacement of the entire column.

By proper dimensioning of the distilling tube, the vapors therein are allowed an extended path of flow in intimate exposure to the reflux liquid, such as is required for eflicient fractionation, yet, however, without necessitating other than a small volume of vapors to be contained Within the column at any one time. I have also provided an improved form of packing within the distilling tube whereby the reflux liquid is caused to have extended and thorough surface exposure to the vapors, without causing but a small amount of the retiux to be held in the column by the packing. Thus by reducing both the quantities of vapor and reflux within the distilling tube, conditions are such as to bring the degree of fractionation of the constituents ofthe fluid being analyzed, to a nicety, and to prevent lagging or overlapping of the constituents due to there being an excessive quan! tity of reiiux held up in the column.

The invention embodies numerous additional features and advantages which however will require no preliminary description and will best be taken up at later points hereinafter.

I describe my invention hereinafter as embodied in aI complete apparatus for analyzin fluids, suitably of the type comprising the su ject matter of my copending application on Apparatus for analyzing liquids and gases, Ser. No. 475,584, tiled of even date herewith, primarily for the purpose of showing one use of the fractionating column under conditions where close fractionation is essential, and where the eliiciency of the column in effecting such separation will be'appreciated. The invention is also described in this connection since it has at present its'most general use in analytical apparatus ofthe character described in my co-pending application. It is to be understood, however, that my improved fractionating column is in no Way limited to use in the particular apparatus hereinafter described, and that it is to be considered as independent and capable of general curve use, either alone or in combination with other apparatus, for the fractional analysis of fluids.

The invention will now be explained more fully and in detail in the following detailed description, wherein reference is had to the accompanylng drawings, in which:

Figure 1 is a general illustration, diagrammatic in parts, of the entire apparatus utilized in the analysis of fluids, and embodying preferred form of fractionating column; Fig. 2 is 'a broken longitudinal section through the fractionating column on an enlarged scale; v

Fig. 3 is a section on line 3-3 of Fig. 2;

Fig. 4 illustrates a modified form of construction for the lower end of the fractionating column shown in Fig. 2;

Fig. 5 is a fragmentary View showing a molfified method of plating the insulating jac et;

Fig. 6 is an enlarged fragmentary View showing a section of the distilling tube containing a preferredform of packing;

Fig. 7 is a View similar to Fig. 6; and is included for urposes of illustrating the advantage of t e packing shown in Fig. 6 over an ordinary wire coil;

Fig. 8 is a view similar to Fig. 2 showing a modified form of fractionating column in which the distilling tube is formed integral with the insulating jacket;

Fig. 9 illustrates another modified form of fractionating column wherein the insulating v jacket is formed separate from the distilling tube; and

Fig. 10 `,illustrates a typical distillation plotted from the results obtained during an analysis of a sample of natural gas.

In Fig. 1, illustrating the entire apparatus in connection with which my improved fractionating column is herein described, numeral 10 refers generally to the fractionating column which may be supplied with liquid or gaseous samples to be analyzed, from suitable containers 11 and 12, respectively. For purposes of general description it will suffice to state at this point that the sample taken into the column is subjected to rectification and fractionation therein, and vaporized and uncondenscd constituents of the sample are conducted from the fractionating column through the manifold 13 to suitable containers 14, 14a of known volume. As will later appear, fractionated constituents of the sample being analyzed are maintained in Vapor phase within the containers, and are quantitatively determined by measuring Vapor pressures therein. i

As shown most clearly in Fig. 2, my preferred form of fractionating column comprises an elongated distilling tube 16 which may be of any suitable dimensions, typically of about 1 to 6 feet in length and preferably Y not greatly exceeding about 5 mm. internal diameter. Careful observation and experi mentation have indicated that maximum fractionating efciency is had with a column having an internal diameter of from about 3.4 to 4.0 mm., these limits representing the range in which the capillary action is most suitable for bringing about the most extended and intimate contacting of vapor and refluxed liquid and yet prevent flooding or priming of the column. The distilling tube 16 is surrounded and thermally insulated by an evacuated jacket 17 spaced at 18 from thev tube and.

comprising spaced inner and outer walls 19 and 20 closed at their upper and lower ends. The space 21 between the walls is evacuated as completely as possible to provide an effective thermal insulation throughout substantially the entire length of the distilling tube. The jacket is enlarged at its upper end to provide a reflux or cooling chamber 22 aboutthe upper end of the distilling tube, the cooling chamber being of suflicient size to accommodate a cooling vessel for effecting condensation of the vapors within the distilling tube to provide reflux, as will be more fully described hereinafter. The distillin tube and its surrounding jacket will be pre erably formed of pyrex glass.

The lower end of the distilling tube is enlarged so as to form a distilling bulb 23,l there being a portion 24, which may or may not be enlarged, directly below the distilling bulb, and which forms what may be termed the displacement bulb. The latter is communicable through tube 24a with tubes 25 and 26, leading to the mercury bottle 27, and the liquid and gas sample containers 11 and 12, respectively. Three- Way cocks 28 and 29 are provided for controlling the introduction of mercury and the samples to be analyzed, to the base of the fractionating column in a manner which will hereinafter appear. I may. state that any suitable means may be employed for introducing the samples to the column, the illustrated apparatus, however, being preferred on account of the convenience of manipulation..

Heat is supplied to the contents of bulbs 23 and 24 by means of heating element 30 comprising a high resistance coil of wire 30a wound around a suitable mat 31, for instance a layer of asbestos, placed about the displacement bulb. The current supply wires 30a of the heating element lead from the heating element to the conventionally illustrated rheostat R Which may be controlled to accurately regulate the temperature to which the liquid portion of the sample in the distilling bulb is heated. I, prefer to utilize an'external heating element of the character described instead of an internal heating element contained within the displacement or distilling bulb, due to the fact that an internal heating element may readily be short 'circuited and corroded. An internal heating' element has the additional disadvantage of necessitating substantial enlargement of the distilling bulb and correspondingly greater exposure to the atmosphere, which is unde- 5 lsirable for the most eilicient operation of the column.

It is preferred that jacket 17 be silver plated, with the result that the insulation afforded thereby is greatly increased over that 1o due alone to the evacuated space 21. Any

I'suitable heat reflecting material such as silver, platinum, etc., may be utilized for platlng the column, silver being preferred. It is `desirable that during the course of an anal- 5 ysis the operator be enabled to observe at all times the conditions within the distilling tube, and therefore it is desirable that the insulating jacket be transparent at least to a certain degree. In order to permit visio bility of the distilling tube and yet provide additional thermal insulation, there may be deposited a semi-transparent silver film 33 on the inside of the outer wall 20 of the evacuated jacket, the film serving to greatly in- 5 crease the insulation, and yet being suliciently thin that visibility of the distilling tube through the jacket is permitted, a flash-light usually being used to observe conditions in the interior-of the tube. Due tothe thorough thermal insulation of the distilling tube afforded -by the plated jacket, highly volatile liquefied or condensed vapors may be retained in the distilling bulb and in the distilling tube without excessive boiling orV priming. In case a gas sample is being an'- alyzed, a comparatively large quantity of gas may be passed into or through the column in a given period of time, inasmuch as adequate cooling f the gas stream is effected to. C condense and retain in the column thedesired condensible constituents thereof. Since the silver column is practically adiabatic in operation, the efficiency of fractionation within the column is considerably improved over that possible using a non-silvered column.

In Fig. 5, 'I have illustrated a method of platingA the jacket with a comparatively heavy and opaque silver-plate, yet rendering the entire length of the distilling tube below the rellux cooling chamber visible to the opera-tor. According to this variational method, an opaque silver plate 33a may be deposited on the inside of the jacket, leaving narrow unplated strips v34 at opposite sides Q of the jacket and extending longitudinally of the column, through which the distilling tube" may be viewed. Inasmuch as the distilling tubeis of small diameter, the unplated strips 34 may be correspondingly narrowed to such an extent that the effectiveness of the insulation will not be appreciably reduced.

By constructing the jacket separate from.

the distilling tube, additional insulation is provided by the air space 18 between the distilling tube and the inner wall of the jacket.

that should the fractionating column be mounted or constructed in a manner such that the vdistilling tube is stationarily heldl at .both ends, longitudinal expansionof the tube u on being heated may be taken care of by orming the tube with such thin walls that it may be permitted to bend Within,

space 18 in accordance with the degree of expansion. The column shown in Fig. 2 ma also be constructed with the distilling bul outside the vacuum jacket and separately contained in a suitable thermos bottle as shown in Fig. 9, hereinafter described.

YVithin the distilling tube is placed a suitable form f of packing for the purpose of bringing about extended and intimate surface exposure of the downwardly flowing reflux liquid to the rising vapors. Any suitable type of packing may be used which will aid in bringing about thorough lexposure of the reflux liquid to the vapors, but preferably the packing will be of the form shown in Fig.l 6, for reasons that will presently appear. One of .the advantages of this type of packing is that it brings about the desired intimacy of exposure and contacting between the reflux liquid and vapors, and yet retains l only a-minimum amount of liquid in the dis- .tilling tubeat any one time. The result is -that sharp fractionation .between the constituents of the sample is brought about by preventing lagging and overlapping in the The packing 38 comprises a coil of small wire, the normal external diameter of the coilbeing greater than the internal diameter of the distilling. tube, and the exterior surface ofthe coil being ground down as at 39 to the diameter of the distilling tube and to the point at which the coil will lit snugly therein. Preferably the cross section of the coil wire will be substantially semi-circular,

to the end that the tendency forthe reflux liquid 40 flowing downward over the packing to collect in the crevices 41 between the wires e and the Wall of the tube will be minimized fractionation of the various constituents due to liquid being held up in the column.

in comparison with the amount of liquid that would be held up by wires of circular crosssection, due to the greater depth of the crevices formed by the latter. This is clearly illustrated by comparing Fig. 6 with Fig. 7 wherein the coil 42 is comprised of wire of circular cross section which forms comparatively deep crevices 43 with the wall of the tube which results in a much greater quan- 4are established whereby the vapors may be subjected to extremely close fractionation.

In Fig. 4 I show a form of construction for the lower portion of the fractionating column whereby the distilling tube may be formed integral with the jacket, the upper portion of the column, however, being substantially as shown in Fig. 2. In Fig. 4, the

inner wall 19 of the jacket is shown to be joined at 45 to the tube immediately above the bulb 23, there being a bulge 19a in the inner jacket wall at the point of juncture with the distilling tube in order to avoid sharp angles between the joined parts which would likely cause the joint to be fractured under, comparatively slight shock or strain. The distilling tube is joined to the outer wall 2O of the jacket immediately below the bulb 23 as at 46, the wall .of the tube being curved sharply toward'the jacketto increase the angularity therebetween and thereby strengthen the joint as mentioned with reference to the upper joint 45.

Condensation of the vapors in the upper portion of the distilling tube within the cooling chamber 22 is accomplishedby passing a suitable refrigerantthrough a cooling vessel 48, of cross sectional shape as illustrated in Fig. 3 and extending around the distilling tube. The cooling vessel will preferably be made of high thermal conductivity metal. A suitable insulating material 49 maybe placed between the cooling vessel and the evacuated jacket, and also above the cooling vessel to the top of the jacket. The cooling chamber may be sealed against the admission of moisture by depositing a suitable moisture proof material 50 on top of the asbestos packing 49. The cooling vessel is spaced, for ex-v ample, as at 51 from the distilling tube, and the space filled with a material of high heat conductivity, for example finely divided or powdered copper. The upper end of the distilling tube projecting above the cooling vessel may be protected against breakage by a sleeve52 joined to the top of the cooling vessel and extending more or less closely about .the tube. In order to insure ample protection for the distilling tube, sleeve 52 will preferably be of metal, and in order to reduce its heat conductivity to a minimum, the sleeve will be provided with closely spaced perforations 53 throughout its length.

Vessel 48 is cooled, for example, lby circulatingor blowing a suitable refrigerant there- Lemma of the vessel as the vapors are condensed in the distilling tube, there is placed within the cooling vessel suitable material, such as glass Vbeads 59, having a high specific heat, and

which when once cooled to low temperature, will remain near such temperature for a considerable length of time because of their high degree of heat conductivity. 'The analyst is thereby enabled to admit comparatively larger quantities of refrigerant to the cooling `vessel at longer intervals than would otherwise be permissible in the absence of the material, so that a fairly constant reflux temperature is maintained. And of course the quantity of the beads 59 in the vessel may be increased or decreased accordancewith the operating conditions' desired.

In Fig. 8 I show a form of fractionating column similar in certain respects to the type shownin Fig. 2, butdiffering mainly in that the distilling tube, :throughout the greater portion of its length, forms the inner wall.

surrounding the cooling chamber 22a. rIlhe l upper section 166 of the distilling tube eX- tends upward from the joint 61 through the reflux chamber as in the previously described form. Cooling vessel 48a may be similar to that shown in Fig. 2, and is immersed in a suitable low freezing point liquid 62 contained within the cooling chamber, the cooling vessel being spaced from the tube as at 51a to allow the latter to be in contact with the liquid throughout its length. I may state that the use of a volatile liquid within the cooling chamber, instead of the provision of the insulating packing such as shown in Fig. 2, may be preferable in certain instances'. The liquid used in the cooling chamber may convemently be comprised of, for example, certain of the more volatile low freezing point fractions'of casing head gasoline, or other liquids of similar volatility. As in the previously described design, the column will be insulated by a silver plating 64 deposited on the inner surface of the wall 20a of the jacket.

In Fig. 9 I show anotherform of column of somewhat simpler construction, and illusnecessary to insulate the distilling vessel or bulb and the refiux chamber, since the liquids being analyzed-would undergo no vaporization at atmospheric temperatures, and the vapors Iwould be readily condensibleat atlnospheric temperature or at temperatures not greatly below atmospheric.

'.The apparatus shown in Fig. 9 comprises a distilling tube 65 having'on its lower end an enlarged distilling bulb 66, around the lower end of which is wrapped the heating element 91. Fluid to be distilled is introduced to the distilling' bulb through tube -92 extending f sample inthe distilling through the wall of the bulb and terminating at a point spaced slightly above the bottom thereof. After the sample has beencom'- pletelypassed .into the distilling bulb, mer-` cury may .be introduced throu h tube 91 for the purpose heretofore descri d of sealing the 4sample within the column. At the end of the distillation, the mercury may be drawn out of the distilling bulb through tube 92, substantially all the mercury belng re movable since the tube terminates at the bottom of the bulb. The vapors at the upper end of the tube are subjected to partial condensation to provide the reflux, by a suitable .condenser 67 through which a cooling fluid is passed. The vapors are finally liquefied in condenser 68 and the liquid fractions Ineasured in graduate 69. The distilling tube is thermally insulated between the distilling bulb and' the reflux separate evacuated character described condenser by means of a jacket 7 0 of the general with reference to Fig.

.2, excepting its difference in shape.

The distilling bulb 66 may be lowered into a wide mouth evacuated thermos jacket or bottle 93, plated either transparently or opaquely with a transparent area through which the 'distilling bulb is visible, theplat ing of the vessel 93 beingr similar to the plating of the distilling tube insulatingjacket. The insulating vessel 93 has a dual purpose in that it provides a means for precooling the bulb and within tube 92 as the sample is passed thereinto, and also in that it provides an effective thermal insulation to the atmosphere for the distilling bulb during the distillation. For purposes of precooling the sample in the distillingbulb prior to starting of the distillation, 1iquid air or other suitable refrigerant may be passed into the thermos vessel through tube 94. lAfter the distillationis started the refrigerant will It may be stated that utilized parts, should-one become broken,

design resides initscial elamps forl supporting the apparatus, and

also 1n that the thermos vessel serves both for the ur ose of roviding a recovolin bath, and Ian gfi'ectivepthermal inslilation frgom the atmosphere.

The form of fractionatingcolumn shown in Fig. 2 may be considered oas preferred mainly for two reasons. Inthe first place by constructing the distilling tube and jacket separately, replacement of either one of these may be made without the necessity for rebuilding or replacing the entire column, and in this regard it may be stated that the probability of breakage is gradually reducedA by the elimination of such joints ,as shown at 6() and 61 in theintegral design of Fig. 8, which may become fractured when subjected to severe strains or shocks. Again by providing a separate, sin'- gle'and continuous distilling tube, the possvbility of liquid becomingr held up within the column at the joints, with the resultant introduction of error in the results due to lagging, as heretofore explained, is prevented. For instance, in F ig. 8 it will be noted that the joint 61'forms a pocket at 71 within vwhich the reflux liquid would have a tendency to collect, with resultant lowering of reduction in the closeness of fractionation ofthe sample, as will be readily apparent.

I shall now describe briefly Ithe remainder of the apparatus, and the operation of'the System in conducting analysis of liquid and gaseous samples. Manometers 72 and 7 3 are provided for measuring the pressures within the fractionating column and receiving bottles respectively, three- way cocks 74 and 75 being provided at the junctures of the 'manometer tubes with the manifold. Receivers 14 and 14a communicate with the manifold through tubes 7 6 and 77, three-way cocks 78 and 79 being provided at the junctures of said tubes with the manifold. A regulating 'cock S0 is placed in the manifold between cocks 74 and 75, cock Sil-being` adjustable to control-- ling the rate of distillation from lthe fractionating column, as will hereinafter appear. Beyond cock 78 is an exhaust line 81 leading to the' vacuum pump 82 by means of which the distilling tube, manifold connections and the receiving vessels may be evacuated before starting the analysis. As will later be explained, the amount of vapor collected in tle receiversA is calculatedfrom the known capacity ofthe receiver and from the pressure and temperatures of the vapors therein, and in order that the temperatures in the re ceivers may remainv as nearly constant as possible, toprevent errors or necessitate troublesomecorrections in the calculations, the receivers are immersedin liquid -contained in . tanks 83, 83a, the liquid temperature being measured by thermometers Accurate reading of the temperature of va- 11 to .be surrounded by a jacket 86 through which a suitable cooling agent, such as carbon dioxide, may be expanded. BeforeI introducing the sample to the column, theapparatus is evacuated and the reflux chamber cooled by blowin liquid air through the cooling vessel. top-cock 80 being then closed, stop- cocks 28 and 29 are turned to admit thev desired quantity of liquid to the distilling bulb 23, both cocks being closed when a sample of the desired size has been put into the column. Stop-cock 28 is then turned to admit mercury from bottle 27 to tube 24, and by elevating bottle 27, mercury is caused to rise within -the column and into bulb 24, thereby displacingthe sample into the distilling bul.b`.2 3'. The mercury may be considered as standing at a level L-L, although it may be'. maintained atother levels, and the entire sample trapped within bulb 23, by the mercury seal. The heat supplied to the sample for. distillation from the heating element 30 is conducted throu h the body of mercury in the displacement c amber 24. Since the bulbv 23 is thoroughly insulated by the evacuated jacket so as to insure the sampleagainst atmospheric heating by cooling of the reflux to a low tem erature, as previously described, the disti lation may be started at a temperature below atmospheric.

It maybe stated at this point that the amount of sample is calculated from the determined amount of vapor distilled during the run and from the amount of residue removed from the column at the end of the distillation.

After introducing the sample to the column, the pressure therein is somewhat below atmospheric, and, in starting the distillation, the column pressure is preferably brought to approximately atmospheric by applyingliet Y In building up the pressure in the fraetionating column to the desired amount,

stop-cock is closed at first and the vapors rising `within the distilling tube are condensed in the upper part of the distilling tube. If the sample is of such volatility as to vaporize or boil excessively at room temperature or to such an extent that it becomes difficult to avoid flooding the column, the pressure may be allowed to ri'se somewhat Leraars above atmospheric. Again, should the vapor temperature rise above room temperature before the pressure in the column builds up to the amount desired, -it may be necessary to start the distillation at a lower pressure, since otherwise the vapor delivered from the column would condense in the manifold connections.

When conditions are satisfactory within the column, distillation is started by cracking the regulating cock 8() to allow the fractionated vapors to pass slowly into receiver 14, cocks 74 and 7 5 being open and cock 79 closed. Frequent simultaneous readings of the milli-volmeter V, indicating the fractionated vapor temperatures at the point of outlet from the column, and of the manometers 72 and 73, indicating the pressures in the column and receiving bottle, respective-4 ly,are recorded, from which data the analyst later constructs a' graph plotting vapor temperatures (corrected to a standard pressure) against the amount of vapor' distilled.

As the distillation proceeds, it will be noted that the vapor temperature remains almost constant for a relatively long period, assuming of course that the pressure is maintained constant. This indicates that`one of the volatile hydrocarbon constituents is being fractionated from the sample with but slight contamination. After most of this particular hydrocarbon has been distilled, the vapor temperature tends to rise, and this rise in temperature should be prevented by adjusting cock 80 to retard the rate of distillation, thereby increasing the reflux ratio to improve the fractionation at the end point 'of that particular fraction. In controlling the operation of the system, it may be stated that the rate of regulatiny cock, and that the pressure and degree o fractionation in the column are controlled by the regulating cock, amount of heat input, and cooling of the reflux. The same general procedure is followed as described, during the fraction of each of the individual constituents of the fluid being analyzed.

The fractions are thus distilled off one'by one until the volatility of the residue left in the distilling bulb is such as to render further distillation tedious and impractical, due

distillation is controlled by the 'ured quantityof residue. from the column inj dicates the slze of sample originally distilled. It will be understood that at no time during the analysis does the vapor pressure in the container 14 exceed what may be termed the condensation pressure of the gas rat the temperature inthe container, that is, the pressure above which condensation of any ofthe vapor fractions could take place. y

In, the analysis of a natural gas sample receiver 14a is used'. The apparatus isirst evacuated, preliminary to the introduction` of the sample. In order to gain accuracy in the analysis of a gas sample, it is desirable that thesample be of considerable volume, and especially in case the gas is dry. In the testing of samples containing comparatively small amounts ofheavierhydrocarbons such as pentane and hexane in natural gas, it may Vbe necessary to-handle a fairly large sample in order to retain inthe columnl a sufficient volume of condensate for distillation; The

gas Sample may be taken from any desired source, for instance, a measured sample of gas is held in the container 12, the latter being of smaller capacity than the receiver 14a,

and the gas pressure preferably being at or above atmospheric. After purging line 26, having opened cock'28, evacuationof the apparatus is discontinued, cock 7 5 is turned to connect the receiver with manometer 71.V

and regulating cock 50 is turned to cut off the fractionating column from the remainder of the apparatus. A mercury seal is then formed in the column immediately below the beating element by permitting mercury to rise from the leveling bottle.l

Cock 29 is then cracked to allow gas from the sample vessel 12 to fiow into the apparatus through tube 90 containing a suitable drying reagent, the gas thence passing through the mercury seal into the fractionating tube.`

During the introduction of gas to the column,

the pressure therein mayA build up to atmos-.

pheric or greater, and the heavier fractions are condensed as refluxin the upper part of the column, the .reflux bath being kept-at the lowest temperature possible, in casethe gas sample contains highly volatile fractions such as methane. Condensation in the reiiux section of the distilling tube is continued throughout the period of feeding gas into .the column, and vthe condensible fractions of the gas are continuously condensed so that the 'column pressure does not build up to an excessive degree. In case the pressure should tend to build up abnormally, fixed gases may lbe taken off to the receiver until the entire gas sample is lput into the column. After feeding the gas sample tothe column, cock 29 is closed and the condensed fractions of the gas contained in the distilling bulb 23 are subjected to fractional distillation according to the previously described VVprocedure followed in the analysis of gasoline.

In case the gas sample contains but a low percentage of condensible vapors, it may be necessary to put through the column a large sample of the gas and to analyze the heavy hydrocarbon liquid condensate. To avoid filling the distilling bulb and fractionating tube with condensate, most of the methane and lighter gases may be allowed to pass from the top of the column while only the comparatively heavy fractions are condensed as reflux. However, it is readily possible to condense the methane and other liquid fractions at the top of the column, and todistill and fractionate them in the same manner as the heavier fractions. It may be added that should a large gas sample be available, and

'after the column is once primed with reflux,

it is possible thereafter to conduct the distillation in a manner such that not only the heavier fractions but also a considerable proportion of the lighter fractions present in the sample may be retained in the column, while the non-condensible portions of the gas are distilled off' during the entry of the sample. Calculations forithe conversion of vapor in the receiver to liquid volume are based upon the ideal gas laws. The vapor .analyze these gases when having available a refrigerant not capable of condensing the more volatile fractions by themselves. before entering the gas sample to the fractionating column, the latter may rst be primed with a liquid, the vapors from which at the temperature of the particular refrigerant being used in the reiuxchamber are capable of'condensing. It may be assumed, for instance, that the distillation tube isiirst primed with a suitable quantity of propane, carbon dioxide being used as a refrigerant in the cooling vessel. 'Ihen upon introducing the sample to the column, volatile fractions in the gas are dissolved in the priming' liquid. After being dissolved in the propane, the partial pressures of the volatile fractions are lowered to such an extent that the vapors will condense at the temperature in the reflux chamber. The heavier fractions in the gas samples, such as propane, hexane, etc., of courseare readily condensible in the reflux tube. In this manner the volatile constituents in this sample maybe condensed as the latter is fed into the column; and either dur-I loo Thus,

ing the entry ofsample, or after the entire sample has been condensed and retained in the column, separation of the `successive constituents for delivery to the receivers may t-ake place in the manner heretofore described. `When the fractions of higher volatility than propane have been separated, a propane constituent containing that utilized as the priming liquid and also the propane contained in the gas sample, is separated, and having previously noted the amount of propane used' as priming liquid, the propane content of the gas may be calculated from a distillation curveas shown in Figure l0.

In Fig. 10 there is shown a typical graphv a particular fraction, for instance methane, has been distilled oil', the curve rises almostl vertically' to the vaporizing temperature of the next heavier compound ethane, in the series, the rise of the curve between the methane and the ethane plateaus' indicating sharp fractionation between these compounds. Also the fact that the various -plateaus extend substantially lhorizontally,

indicating constant temperature during their respective vaporizati'on, serves to show thatI these fractions are produced in substantially a pure state.

I claim:

1. Apparatus for precise analytical fractionation comprising an elongated distilling column, means for supplying vapors to the lower portion thereof, means for cooling the upper portion thereof, and an evacuated insulating jacket surrounding the column and having" its inner wall spaced therefrom to provide an air space between the column and the jacket.

2. Apparatus as described in claim 1, wherein the space between the insulating jacket and thedistilling column is closed at a point near the lower portion of the column and at a point near the upper portion of the column, to provide a relatively stagnant air space between the column and the jacket.

3. Apparatus for precise analytical fractionation comprising an elongated distilling tube, means for supplying vapors to the lower portion thereof, means for cooling the vapors at the upper portion thereof, and beata-'1nsulating means surrounding said tube, the

tube being of a diameter to secure capillaryactionon reflux fluid to bring` about extended v contacting of vapor and reflux fluid therein without flooding the column and not substantially. exceeding 5 mm., said column having an open core.4

4. Apparatus as described in claim 2, wherein the heat insulating means is an evacuated jacket surrounding said distilling tube.

5. Apparatus as described in claim 2, wherein said heat Ainsulating means is an evacuated jacket surrounding the distilling tube, said jacket having therein means providing a reflecting surface and extending longitudinally of the tube for substantially the length thereof.

6. Apparatus for precise analytical fractionation comprising an elongated distilling tube, means for supplying vapors to the lower portion thereof, means for cooling the vapors at the upper portion thereof, heat insulating means surrounding said tube, the tube being of a diameter to secure capillary action on reflux fluid to bring about extended Contactin of vapor and reflex fluid therein without ooding thezcolumn, and a helical wire coil within the tube and having its turns in'contact with the wall thereof, there being an open core within said column and coil.

j 7. Apparatus as .described in claim 6, wherein the exterior surface of the turns of saidl coil are formed flat to contact with the wall of the tube:

' 8. Apparatus for precise analytical fractionation comprising an elongated distilling tube, a distilling bulbformed in the lower portion of said tube, ,means for applying dry, radiant cooling to-an upper portion of said tube and insulating means surrounding said tube, bulb and cooling means.

j, 9. Apparatus for precise analytical distillation comprising an elongated distilling tube, means for supplying vapors to the lower portion thereof, heat insulating means surrounding the tube for substantially the entire length thereof, said insulating means being spaced from the tube at the upper portionvthereof to provide a reflux chamber, and means within said reflux chamber for applying dry radiant cooling to the tube to form i reflux therein.

10. Apparatus for precise analytical distillation comprising an elongated distilling tube, means for supplying vapors to the lower portion thereof, heat insulating means surrounding the tube for substantially the entire length thereof, said insulating means being spaced from the-tube at the upper portion thereof to provide a reflux Chamber, a cooling vessel within said chamber embracing the upper portion of the tube and spaced therefrom, and means for supplying a refrigerant fluid in said cooling vessel whereby dry, radiant cooling is applied to the tube to form reflux therein.

11. Apparatus as described in claim 10,

wherein a dry, heat conductive material in finely divided form -is interposed between said cooling chamber and said column.

12. Apparatus for precise analytical distillation comprising an elongated distilling tube, means for supplying vapors to the W- erx portion thereof, an'evacuated jacket surrounding the tube for substantially the entire length thereof, said jacket being spaced from the tube at the upper portion thereof to f provide a reflux chamber, a cooling vessel for supplying vapors to the lower portion aving heat-conductive walls withln said chamber embracing the tube land spaced therefrom,'means fory supplying a refrigerant lluid in said cooling vessel, and dry, finely-divided heat conductive material interposed between the inner wall of`the cooling vessel and the tube whereby dryradiant cooling is applied to the tube to form reflux therein. p

13. Apparatus as described in claim 12, wherein the cooling vessel is partly lled with small particles of high heat capacity, such as glass beads. i

14. Apparatus for precise analytical dis# tillation, an elongated distilling tube, means thereof, and cooling means at the upper portion thereof, sald coo ing means comprising a vessel having heat-conductive walls embracing said tube and spaced therefrom, means for supplying a cooli fluid to said vessel and dry, fine divide t1onation com heat conducvessel and the tube.

15. Apparatus for precise analytical frac- I `tionation comprising an elongated distilling tube, a distilling bulb at the lower' end of said tube and communicating therewith, said bulb having a downwardly projecting extension for applyin heat to said extension, and aheat conductlve fluid .within said extension to seal a fluid to be distilled in the bulb and convey heat thereto.

16. Apparatus for precise analyticalfrae prising an elongated distilling tube, a distilllng bulb at thelower end of said tube and communicating therewith, said bulb having a downwardly projecting eX-` tension, an electrical heating coil surroundtive material interposed between the cooling ing said extension and a heat conductive Huid within said extension to seal a fluid to be distilled in the bulb and convey heat theref ne i lao

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