US1811189A - Oil fractionating apparatus - Google Patents

Description

June 23, 1931. c. SMITH ET AL 1,811,189

OIL FRACTIONATING APPARATUS Filed Feb. 28. 1928 5 Sheets-Sheet 1 14/70/27 level v gmntoz L/d Z.Sm/Z% (o/"126211153. W230):

June 23, 1931. c. SMITH ET AL OIL FRACTIONATING APPARATUS Filed Feb. 2 s, 1928 5 Sheets-Sheet 2 48a gmmtoz 2 6 64/0 6 L 146E021 June 1931. c. L. SMITH ET AL 1,811,189

OIL FRACTIONATING APPARATUS Filed Feb. 28. 1928 5 Sheets-Sheet 4 V gmvitot 'Q/JQZ. 52711177 Corlzchilsfi M2130):

June 23, 1931. c. L. SMITH ET AL 1,811,189

OIL FRACTIONATI NG APPARATUS Filed Feb. 28, 1928 '5 Sheets-Sheet 5 gwuentoz 57722271 CorneZ/usfi. Watson Patented June 23, 1931 CLYDE L. SMITH AND CORNELIUS B. IHA'ISON, C F CHICAGO, ILLINOIS OIL FRACTIONATING APPARATUS Application filed February 28, 1928. Serial No. 257,895.

This invention relates to improvements in fractionating apparatus of the type employed in connection with the refining of petroleum oils or other materials capable of being physically separated orv fractionated in response to varying control temperatures, and one of the outstanding objects of the invention resides in the provision of an improved type of fractionating tower having features of'construction which admit of very close separation between fractions of difi'erent boilingpoints so that when the apparatus is handling hydrocarbon oils in vapor form the gasoline fraction or fractions may be sharplyoseparated from the heavier kerosene fractions or other heavier fractions of higher boiling point, to the end of obtaining the maximum recovery from a given body of stock of a more valuable low boiling point fraction.

Another important object of the invention resides in the provision of means for creating reflux condensation within the fraction; ating tower in a manner which permits ofeffective heat interchange between the arising hot oil vapors and the descending liquid condensate, in order that the descending liquids will be subjected to the higher temperature of the arising vapors for the purpose of depriving the condensate of its low boiling point constituents to a maximum degree, and at the same time to lower the temperature of the arising vapors to condense or liquefy and discharge from such vapors the entrained high boiling point constituents thereof, this action being repeated successively until a final and complete separation of the fractions having different boiling parts is secured with substantially complete recovery of the different fractions which were present in intermingled form when initially heated and vaorized. V

A further object of the invention resides inthe provision of a fractionating tower adapted for the refining of petroleum oils, wherein the upper part of the tower is provided with a heat exchangerin the form of a refluxing coil through which the charging stock or other cooling medium is adapted to be. circulated for the purpose of controlling and accurately regulating theoutlet temperatures of the tower, whereby the vapors taken overhead from the tower may be so controlled as to minimize. the presence thereinof oils having higher boiling points than those desired. Another advantageof the refluxing coil resides in the heat economy effected through its use, in that the heat extracted from the hot oil vapors circulating through the tower by the presence of the refluxing coil, is transferred to the incoming charging stock, so as to effect an initial heating of such charging stock prior to its passage through a heating still or the like.

A further object of the invention resides in providing the lower part of the fractionating tower with a second heat exchanger in the form of a reboiling coil. Through this coil there is adapted to be circulated a hot con densate, obtained from anysuitable source,

which possesses a temperature exceeding. that the fractionating tower which is formed to provide a] plurality of tortuous passages through which the oil vapors are. circulated so as to bring such vapors, into contact with extended heating. surfaces, which serves to prevent liquid entrainment in the oil vapors passing from the tower;

Still, another object of the inventionresides in providing the tower between the reboiling and refluxing sectionslwith a stripping or fractionating section, which comprises a plurality'of trays arra'ngedin spaced order and formed to include narrow metallic stampings of trough formation in crosssection, each of said stampings being, so de-, signed that it contains a liquid level and at the same time presents the maximum amount of surface for vaporcontacts, the troughs or stampings being supported in spaced "horizontal rows within the tower, these troughs or vanes serve to hold a liquid, present a maximum amount of surface for reboiling, and act as baffles to the. rising vapors, causing the latter to follow a weaving course while passing upwardly through the tower and serve to provide effective contacts between the ascending vapors and the descending liquid condensate.

A still further object of the invention resides in the provision of distributing pans which cooperate with the troughs or vanes for the purpose of insuring an even distribution of the vapors and reflux throughout the tower, preventing channeling of such vapors in any particular portion of the tower. Further, the arrangement of the pans and troughs permits of free vapor passage without unnecessary restriction so that the vapors may flow through the tower at proper velocity to procure the most beneficial results, a feature which enables the tower to operate to advantage when subjected to pressures both above and below normal atmospheric pressures.

With these and other objects in View that will appear as the description proceeds, the invention consists in the novel features of construction, combinations of elements and arrangements of parts hereinafter to be more fully described and pointed out in the appended claims.

In the accompanying drawings;

Figure l is a view in vertical section taken through the lower half of a fractionating tower constructed in accordance with the features of the present invention,

Figure 1a is a similar view showing the upper half of the tower,

Figure 2 is a transverse horizontal sectional view taken on the plane indicated by the line 2-2 of Figure 1,

Figure 3 is a transverse vertical sectional view on the line 3-3 of Figure 1,

Figure 4: is a transverse vertical sectiona view on the line H of Figure 1a,

Figure 5 is a transverse horizontal sectional view on the line 55 of Figure 1,

Figure 6 is a similar View taken on the plane indicated by the line 66 of Figure 1a,

Figure 7 is a plan view on an enlarged scale disclosing more particularly the construction of the vanes used in the drying section of the tower, as set forth in Figure 6,

Figure 8 is a side elevation of such vanes looking in the direction indicated by the arrow X in Figure 6,

Figure 9 is an edge elevation thereof looking in the direction indicated by the arrow Y in Figure 6,

Figure 10 is a transverse sectional view taken on the plane indicated by the line 1010 in Figure 1, showing more particularly the formation of the troughs or vanes employed in the fractionating or stripping section of the tower,

Figure 11 is an enlarged transverse vertical section taken through such troughs or vanes on the line l11l of Figure 10,

Figure 12 is a detail side elevation of one of the troughs or vanes,

Figures 13 and 14 are detail views.

Referring more particularly to the drawings the numeral 1 designates the improved fractionating tower comprising the present invention in its entirety. In the specific form of the invention disclosed in the drawings and hereinafter described in detail, the tower comprises a cylindrical metallic shell which may be approximately feet in height and 8 feet in diameter, there being two horizontally disposed drums provided in connection with the tower each of which is 8 feet in diameter and 16 feet long. It will be understood thatthese dimensions are given merely for purposes of facilitating an understanding of the invention and may be varied from time to time, depending upon the operating conditions in which the tower is situated.

One of these drums is located at the bottom of the tower and is indicated by the numeral :2 and serves to form a reservoir with large vaporizing surface for the oil which is refluxed to the bottom of the tower when the latter is in operation. A substantial liquid level is maintained in the connection 2 when the tower is in operation by means of any suitable type of liquid level controllers. When it is desirable to utilize heat from some hot stream of oil to assist in obtain ing better fractionation, a coil 3 is installed in the section 2 and through which hot oil, obtained from any suitable source, may be passed. The coil 3 has been specifically illustrated in Figures 1 and 3 and, as shown, is supported by means of an angle iron frame work 1, which is first constructed in the bottom of the tower and acts as a support for the various pipes or tubes comprising what is known as the reboiler coil 3. The cross members of the angle iron frame work are bolted together so that they can be easily removed to permit the entire reboiler coil to be taken down for repair or cleaning purposes without interfering with any other portion of the tower.

The coil 3 itself consist in this instance of fifty four inch boiler tubes oined together in series by means of cast steel return bends 5, into which the ends of the tubes comprising the coil 3 are rolled. The return bends have threaded plugs 6 disposed in opposed relation to the tube openings so that access to the tubes is comparatively easy for cleaning or rerolling. The tubes, in this instance, are assembled in seven planes so arranged in a staggered formation that contact between the fluid passing through the sections and the tubes is very uniform. The fluid dropping into this reboiler section is prevented from circulating around the tubes by sealed skirts lUO 7 whichproject from the top of the horizontal just above the top-most coil of the reboiler.

This section of the tower is matte accessible by manholes 8 arranged at each end, these being staggered so that any single tube comprising the coil 3 may be removed from the shell without disturbing any other tubes.

The other drum 9, disposed inthe upper part of the tower, and located about sixteen feet from the top of the tower, contains a heat exchanger or refluxing coil 10 of peculiar design. The coil 10, as herein illustrated, consists of approximately 102 one and onequarter inch D cold drawn seamless steel tubes, each of which is about twelve and onehalf feet long and the tubes are arranged in three groups as shown, in such a manner that the cold oil passing through the coil is forced to travel from one end of the refluxer to the other, the oil travelling through several parallel tubes. These tubes are rolled :into headers 11, which are mounted entirely independently of the supporting structure 12, so that they are free to expand and contract without fracturing any portion of the apparatus. Three groups of tubes are used instead of one large group, so that the tube headers will not be thrown into expansion strains clue to the great difference between the temperature of the oils entering and leav ing the refluxer tubes. The headers 11 are provided with removable plugs 13, which are arranged in registration with the tubes comprising the coil 10, so that each of said tubes may be removed, cleaned or rerolled without affecting any other tube. This facilitates 1' replacement and cleaning.

The vapor passages through the refluxer are so arranged that the vapors weave back and forward through each group of tubes, as indicated by the arrows in Figure 1a, insurllllg contact of the vapors with the tubes throughout the exchanger so that all available surface is efficiently used. Sufficient space is provided throughoutthe vapor portion of this refiuxer section of the tower so that the vapors do not increase in velocity while passing through this section, thereby eliminating the possibility of carrying over excessive amount of entrain-ed liquid. As the maximum amount of condensation takes place in this section of the tower, the fact that the velocity of the vapors is not increased is considered to be a very desirable feature. U shaped drains 1a are provided in all parts of the refluxer where fluid would tend to accumulate, so that the condensates are carried back to the bottom of the refiuxer without coming into further contact with the vapors. At the same time the liquid seal prevents vapors from by-passingthrough this drain. The battle sheets15in the refluxer are electric welded to insure the passage of all the vapors through the tube section of the refluxer. The dead ends of the refiuxer formed by the tube supporting sheets, drain back into the fractionating section of the tower through sealed traps or U shaped bends. It will be understood that cold oil, such as charging stock, may be circulated through the refluxing coil by the inlet and outlet connection 16 and that by regulating thisvolume of cold oil flow the outlet temperatures of the tower may be controlled within exceedingly close limits for the purpose of securing an overhead product of the desired boiling point. At the same time heat economy is present in that the heat extracted from the vapors is transferred to the charging stock, which may be additionally heated in a still or other apparatus for complete vaporization. The section 9 has its ends provided with manholes 17, which provide access to the refluxing section.

The stripping section 18 of the tower is 'lled with trays 19 of a special design. The stripping section 18 is that :portion of the tower between the reboiler section 3 and the vapor inlet conduit 20. The conduit 20 is, of course, connected with a still or other vaporizing apparatus. The fractionating sections 21 of the tower comprise that portion situated between the vapor inlet and the refluxer section 9, the sections 18 and 21 are substantially identical in construction and comprise a plurality of trays 19 and 22 respectively. These trays are made up of narrow steel stampings which, as shown in Figure 11, are substantiah 1y trough shaped in cross section. Each tray may be of any suitable length and its trough shaped upper portion is adapted to receive a suitable quantity of liquid, the sides of the. trays terminating in transversely spaced depending walls 23. The ends of the trays are received within horizontally extending supports 24 fixed within the tower. The upper edges of the supports are notched so as to receive the trays and to maintain the latter-in supported and spaced relationship. As indicated in Figure 11 the trays in adjoining rows are disposed in staggered order so as to secure the most effective contact between the vapors and the trays. In practice, the vanes or-trays are assembled outside of the tower and are then lowered into the tower so as to rest upon the I beams or angle clips 25 secured to the inner walls of the tower. The supports 2% are rigidly secured together in a substantial frame work so as to prevent undue separation or loss in operating positions on the part of the vanes or trays. Filler plates 26 are situated between the outer marginal portions of the trays and the inner walls of the tower and prevent vapor passage upwardly through the tower without proper contact with the vanes or trays.

Above each section of vanes or trays there is p1 ovided a horizontally disposed pan 27 provided, as shown in Figures 1 and 5, with flow openings 28, the walls of which are defined by' upstanding collars 29. The total area of the openings 28 is such as to cause a slight restriction to the passage of the vapors and to thus force the vapors to pass through all of the openings 28. These openings are distributed over the entire cross section of the tower and in this way channeling of the vapors is prevented. Each pan also acts as a distributor for the reflux, there being small dams or reservoirs around each vapor opening 28 produced by the collars 29, the latter being perforated as at 30 slightly below the upper end thereof. The total crosssectional area of these openings or perforations in the pans is worked out to closely conform to the area required for the passage of the material refluxed to the bottom of the tower. Any excess will run over the edges and be distributed on the vanes below. Due to this construction the eliiciency of the fractionating section is greatly increased by insuring distribution of the vapors. and reflux throughout the tower. Each succeeding vane section is turned at right angles to the section below which tends further to effect distribution of vapors uniformly throughout the tower.

The stripping section 18 of the tower con sists in this instance of ten layers of vanes or trays with a distributing pan between the top layer and the vapor inlet. The fractionating section21 consists of three packs, each composed of twenty layers of vanes with a distributing pan above eacii pac I. The trays in the fractionating section of the tower maintain constant fluid levels throughout the tower, the total liquid so retained being in excess of that held on the trays in other towers of this character. This fluid or liquid content of the fractionating section permits of finer control as it is necessary to vaporize or cool a large amount of fluid in order to obtain any great temperature changes in the tower. The vapor to liquid contact is positive, but at the same time, on account of the open character of the tower, the friction caused by the vapors rising through the rain of reflux from the trays is almost negligible. The open nature of the tower makes it ticularly well adapted to low pressure operation and may be adapted with commensurate efliciency to vacuum distillation processes. In this connection it may be stated that the commonly used bub-ble type tower requires a differential pressure through each tray and therefore will probably never be well adapted to high vacuum distillation. This feature also makes the bubble tower undesirable for use with apparatus which is not so designed to withstand high pressures. The present fractions-ting tower, comprising the present invention, has been found to be very flexible as it operates with practically the same eliiciency with a great variation in the amount of oil put through. It is practically impossible to flood the tower or to cause it to prime.

Above the refluxer section 9 there are disposed in this instance twelve trays 31 of the same design as those used in the fractionatvanes are set vertically in rows, with each succeeding row staggered, as shown in Figure 7. This arrangement forms a labyrinth bafile through which the vapors are forced to pass in circuitous course. The velocity is increased somewhat through the drying section so that any fluid entrained in the vapors will be impinged against the vanes 34, and as the vapors must reverse in order to find their way out of the baflle, the liquid is given an opportunity to run down at the corners of these baifles, where it drains into a pan 35 which, in turn, is drained back to the refluxer section. The use of this drying section serves, therefore, to minimize liquid entrainiu 1i; in the vapors which pass off overhead from the tower by way of the outlet 36 provided in the dome 32.

The manufacture of the tower thus described is relatively simple since the parts composing the fractionating and drying sections are stamped from flat strips of steel and can be produced at low cost very quickly. The manner of construction of the various sections permits of very rapid assembly. The fractionating portion of the tower can easily be dismantled for cleaning, should this operation be necessary, and the different parts of the tower are accessible by the manholes provided in the connections 2 and 9.

The fractionating tower thus described is particularly well adapted for petroleum refining processes and may be used in straight still distillation processes or in connection i h petroleum cracking processes where relatively high temperatures and pressures are utilized, also, in connection with both liquid and vapor phase methods of petroleum conversion. It will be understood that in the operation of the tower the heated vapors, obtained from any suitable source, enter the tower by way of the inlet conduit 20 and ascend through the tower, coming first into contact with the baflies. or vanes of the fractionating sections 21, wherein the constituents of high boiling point condense by coming into contact with the cooler metallic surfaces of the trays 22 arranged within said fractionating section and also with descending reflux condensate. The vapors of lower boiling points after passing through the fractionating section come into contact with the reflux coil wherein a greater temperature difl'erential obtains, the passing of cold oil through the refluxing, coil serving to absorb the heat cooling coil soas to conduct the vapors and to permit of their use for any suitable purfrom .the ascending vapors and to reduce their temperature sufiiciently to liquefy the'heavier and oui'vvardl i from the tower by way of the tra s 31 andthe drvin sections33 the va Jors plSS1I15 O-Vll16&d from the tower oy the outlet 36. This outlet may lead'toadditional ractionatlng towers or may pass through a ose. The passage 01" the first charging stock throiwh the refluxin coil is nreferabl under b h i i automatic control so that the temperature of the out-going vapors *may be' very carefully regulated to procure a'maximum recovery of petroleum fractions of specified boiling points. In other words by carefully regulating this temperature the tower is capable of sharply separating gasoline and kerosene fractions. TillS islikewise true as regards gasoline and naphtha, or kerosene and gas oil, 50lgtls'Oll-ZIIIClWZIX'Cl'IStIllZItG. In this connectionit should be observed that one or more of the i-ractionating towers may be used in connection' with a distillation or fractionating system to obtainany desired number of cuts or fractions froma given body of oil. Preferably, the towers are arranged in series with the heavier products removed'trom the bottom ofeach tower and the lighter products from the top thereof. Thus the liquefied and heavy bottoms of one tower may be circulated through the reboiling coil 3 in the next adjacent tower, thereby procuring high heat economy and an efiiciently operating system. The reflux liquid gradually descends within the tower passing, for example, from the refluxing coil into the fractionating section, wherein all of its lighter constituents are released by the upwardly moving vapors. The reflux condensate then settles into the stripping section arranged below the vapor inlet, and finally this reflux condensate collects in the bottom of the tower around the surfaces of the reboiling coil 3, where the oil is additionally heated by the hot oil circulating through the reboiling coil for the purpose of insuring the maximum recovery of all of the low boiling compounds which may be present in the reflux condensate by the time the latter reaches the bottom of the tower. As previously stated, this reflux condensate which accumulates in the bottom of the tower may be removed for storage purposes or in the course of its removal may be circulated through the reboiling coil of an adjacent and complimental tower for the purpose of utilizing to the fullest extent the heat which may be present therein.

What is claimed is:

1. In liquid and vapor contacting apparatus, a plurality of relative superposed rows of horizontally disposed open topped liquid retaining trays, a vertically disposed shell havinga vapor inlet-and a vapor outlet formed therein between which inlet-and outlet said Y trays are mounted, the trays of each row being disposed in parallel relatively spaced re- 7 ,lationship and laterally-offset with respect to and spaced from .thetrays in the next adj oining-upperand lower rows, notched spacbars forpositively maintaining the trays in such spaced relationship, anda supporting -3 frame formed for the removal and unitar support of said trays and bars.

in liquid and vapor-contacting apparatus, a plurality of relativesuperposedrows vvoi horizontally disposed open toppedkliqui'dc retaining trays,:a vertically disposed shell vhaving a vapor inlet and a .vapor outlet formed therein between which inlet andoutlet said trays are mounted, the trays-ofeach row being disposed in'parallel relatively 15 spaced relationship and laterallyofliset with respect to and spaced from the trays in the next adjoining upper and lower rows, and notched spacing bars extending at right angles to. said trays formaintaining the lat- 55,

terrin such spaced -relationships, the lower edges of said bars resting upon the upper edgesof thevnextlower row of trays, the notches in said barsserving to maintain the trays supported thereby secure against move- 35 mentiongitudinally of the bars. 7 3. In liquid and vapor contacting apparatus, a pluralityof relative superposed rows of horizontally disposed open topped liquid retaining trays, a vertically. disposed shell r1 having ia vapor inlet and a vapor outlet formed therein between which inlet and outlet said trays are mounted, the trays of each row being disposed in parallel relatively spaced relationship and laterally offset with T1 respectto and spaced from the trays in the next adjoining upper and lower rows, and spacingdevices extending substantially at rightangles to said trays for positively maintaining the latterin the spaced relation- "7 ship specified, said devices being supported by the .upper portions of the trays provided in the next adjacent lower row.

4. In liquid and vapor contacting apparatus, a plurality of vertically superposed 1515 horizontal rows of longitudinally extending relatively spaced liquid retaining trays, the trays ofeach row being disposed in parallel relatively spaced relationship and offset laterally with respect to andspaced from the 1'20 trays in the next-adjoining upperand lower tray-rows whereby'tortuous passagesar provided between :said trays, supporting and spacing devices for maintaining said trays in unitary assembly and spacedrelationship,and :125

an inc-perforate jacket surrounding the trayassembly and operatingto confine fluids to substantially vertical travel through the tray assembly.

.5. lniliquidand vaporcontacting appatrays of each row being disposed in parallel relatively spaced relationship and offset laterally with respect to and spaced from the trays in the next adjoining upper and lower tray rows whereby tortuous passages are provided between said trays, supporting and spacing devices for maintaining said trays in unitary assembly and spaced relationship, an imperforate jacket surrounding the tray assembly and operating to confine fluids to substantially vertical travel through the tray assembly, and a distributing pan arranged over the tray assembly in a horizontal plane, said pan being provided in the bottom thereof with a plurality of outlets formed to retain a liquid level in the bottom of said tray.

6. In fractionating apparatus. a shell. a vapor inlet in the lower part of said shell and a vapor outlet in the upper part of said shell, a frame mounted stationarily within said shell between the vapor inlet and outlet, said frame including a plurality of cross members having registering notches provided therein, and a plurality of horizontally extending trays arranged in vertically superposed rows, the ends of said trays being receivable within the notches provided in said cross members, the notches in said cross members being so disposed that the trays of adjoining rows are arranged in staggered relationship.

7 In a fractionating tower, a shell, a vapor inlet in the bottom of said shell and a vapor outlet near the top of the shell, a fractionating section between the vapor inlet and outlet consisting of a plurality of superposed groups of nested trays, each group comprising a plurality of horizontally arranged rows of trays arranged in relatively spaced offset order to produce tortuous vapor passages through and between the trays, each of said trays being formed to include a troughfor the reception of liquid condensate. apertured distributing pans arranged immediately over each group of trays and a structural frame work for supporting the trays stationarily within said shell.

8. A fractionating tower comprising a shell of substantially closed hollow form, a vapor inlet in the lower part of said shell. and a vapor outlet in the upper part of said ;hell, a heating coil situated in the bottom of said shell, a cooling coil'in the upper part of vapors to travel laterally and upwardly through said drying baffles.

9. A fractionating tower comprising a substantially hollow and closed body, a vapor inlet in the lower part of said bodyand a vapor outlet in the upper part thereof, said body having the lower portion thereof formed to include a liquid receiving reservoir, a heating coil suspended within said reservoir, inlet and outlet connections formed with said coil and leading exteriorly of said body to permit of the circulation of a heating medium through said coil, means for withdrawing liquid from said reservoir, a cooling coil situated in said body between said vapor inlet and outlet, inlet and outlet connections connected with said cooling coil for admitting of the circulation of a cooling medium through said cooling coil, a group of stripping bailles arranged within said body between the heating coil and the vapor inlet, vertically superposed groups of tractionating battles between said vapor inlet and said cooling coil, a group of vertically arranged drying bafies between said cooling coil and said vapor outlet and means for causing the vapors to travel laterally and upwardly through said drying baflies.

In testimony whereof we aflix our signatures.

CLYDE L. SMITH. CORNELIUS B. IVATSON.

said shell, stripping bafiies stationarily mounted in said shell between said vapor inlet and said heating coil, stationary groups of fractionating bafiies mounted within said shell between said vapor inlet and said cool-- ing coil, a plurality of vertically arranged drying baffles situated in the upper part of said shell between said cooling coil and said vapor outlet and means for causing the

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