US1547994A - Pressure still - Google Patents

Description

J. E. BELL ET AL July 2s, 192.5.

3 Sheets-Sheet 2 3 Sheets-Sheet 3 PRESSURE STILL J." E. BELL ET AL MN, @mf MNM mw m N N N N NNN NQ QN UNR Filed Apri-1 a, '1921 July 28, 1925.

- deposited upon the heating surfaces of Patented Jalyzs, i925.

UNITED STATES PATENT .OF/FICE'.

JoHN E. BELL, or BROOKLYN, NEW YORK, AND EDWARD W. Isola; or WINNErxA,

- ILLINOIS.

PRESSURE STILL.

Application led April 8, 1921. Serial No. 459,555.

To all whom z't may concern.'

Be it known that we, JOHN E. BELL and EDWARD vW. IsoM, citizens of the vUnited States, residing, respectively, at Brooklyn, county of Kings, and State of New York, and Winnetka, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Pressure Stills, of which the following is a specification.

The pressure stills to which our invention relates are designed to crack petroleum, gas oil and other heavy hydrocarbons and to convert them as far as possible into lighter hydrocarbons Such as those constitutingV the fraction known on the market as gasoline. In cracking such heavy hydrocarbons they are heatedup to very high temperatures, commonly under high pressure, with the result that the heavier oils, or a portion thereof, are broken down forming lighter oils which are vaporized and driven 0H. -The 'vapors are condensed and submitted to furv ther treatment to form the commercial product. In the formation of the lighter oils carbon is freed in considerable quantity remaining behind in the heavy oil and tar in the still and depositing on the heat transmitting surfaces of the latter with which the oil is in contact. The carbon and heavy tar are very poor conductors of heat and whaln t e Still which are exposed to the heating gases insulate the wall from the cooling eect o the oil so that the walls are apt to become overheated, the temperature of the metal increasing over the temperature, of the oil to an extent dependent upon the'thickness of the carbon deposit and the amount of heat externally delivered to the heating surface from the furnace. As a consequence unless the stills are frequently Shut 'down for cleaning or the temperature of the furnacev reduced below that which is most` eiicient, it is diicult to maintain the stills in operation for-a sufficient length of ltime to make l i i fwhichjyield to 'the' cracking operation'and increasesQstepl by Step in the proportion of fcarb'onfand tar contained. The several comsuch operation commercially y practical. There is also considerable hazard to life and propertybecauseofthe possible bursting of the overheated'portions of the stil1,1w hichv isv Tsubjected to the cracking compartments() thatl it 1s, Step by step,

increased because of the pressure'usually maintained in Such stills which may be as much as one hundred pounds per square. inch or more.

The surfaces of the still most exposed to the heat of the furnace are of course most apt to suffer, and in the case of a tubular still, to which our invention more' particularly relates', the tubes with which the products-of combustion from the rebox first come into contact receive the greatest amount of heat from the furnace and consequently suifer the most. It is one of the objects of our invention to provide an improved apparatus for cracking oil in which the heating tubes exposed to the products of combustion from the rebox at the highest temperatures contain oil which is substantially free from carbon and tar, and in which the oil as it accumulates tar and carbon and loses its content of crackable hydrocarbons lowssuccessively through heating tubes exposed to products of combustion from the furnace at successively lower temperatures, and aording greater total surface for deposition of carbonaceous material, thus enabling the `still to be operated for a greater length of time between cleanings than is possible with the constructions heretofore known. f

With this object in view we provide a tank or 'drum containing the main body of f oil to be cracked and connected as'usual to' a condenser in which the vapors constituting the desired fraction are condensed. The drum is provided with transverse. partitions of any desired number which'separate the drum into a series of compartments, and the oil to be cracked is fed tothe first compartment" in-the'series 'andfoverliowsfrom the first compartment'to thesecond and from 90 the"` second to the third, andfsor on, being operation in each prived'f of portions of the hydrocarbons prtrments; `am proyided with heating tubes so connected thereto that the oil in each compartment circulates to the heating tubes which appertain thereto and back to the same compartment, the sets of heating tubes being arranged successively in the flues of the furnace so that those appertaining to the compartment first receiving the oil are subjected to the highest temperaturei and succeeding sets of tubes are subjected to' progressively decreasing temperatures.

In order that the vapors of the desired composition may be developed approximately in equal quantities in the several compartments and the temperature of the oil itself maintained, the number or total length of heating tubes is increased successively7 from the first to the last compartment. This arrangement also provides a large extent of surface on which carbon can be deposited in the coolest part of the still where it is least likely to be baked to a hard crust.

The circulation through the heating tubes may be natural or forced. Ina companion application 437 ,662, filed January 17, 1921, we have described and claimed a construction such as outlined above in which the circulation of the oil is independent of any mechanical or other forcing means, being due to convective action caused by the heating of the oil and the evolution of vapors and gases thereby.

1n the construction of the present application, however, we employ a forced circulation, pumps being provided for the several compartments which receive the oil therefrom and pump it through the .respective sets `of heating tubes and back to the compartments. Other features of novelty will appear from the drawing taken in connection with the following description. It is to be understood, however, that the speciic disclosure is for the purpose of exempliiication only and` that the scope of the invention is defined in the following claims in which we have endeavored to distinguish it from the prior art so far as known to us, without, however, relinquishing or abandoning any portion or feature thereof.

In the drawing, Fig. 1 is a vertical longitudinal sectional view of a preferred form V of still embodying our invention, parts being shown in elevation; Fig. 2l is va. vertical transverse section therethrough on line 2 2 Vof Fig. 1 looking in the `direction of the arrows; and Fig. 3 a plan partly in horizontal section on the line 3-3 of Fig. 1.

Each partis identiied by thefrsame referl ence character wherever it occurs in the several views.

Inv-the preferred construction'shown the drum 6 which contains the bulk of thestill charge is of the cylindrical, boiler type and is supported on I-beams 7 upon the furnace structure 8. The drum is divided by partitions 9 into a number of approximatelyl here indicated as four in number.` The oil to be cracked is lirst fed into the front vcompartment 10 from which, after it reaches the desired level, it voverflows through pipe 11 into the second compartment and thence by overflow pipe 11a into the third compartment and so on. The tar finally is drawn 0E from the last compartment. 1f desired the oil may be fed directly from a su ply tank to said first compartment throng inlet B, or it may be introduced through the reflux tower C, a supply pipe D being provided for this purpose. E is the vapor line.

The furnace is provided with a fire-box 12, which may be of any usual or suitable character, and a series of vertical flues 13, 13, 13b, .130, the first of which connects with the fire-box through the throat 14, the second .with the first at the top of the furnace structure through passage 15, the third with the second through passage 16 at the bottom of the furnace structure and the fourth with the third through passage 17 at the top of the 'furnace structure. The )products of combustion from the fire-box thus circulate up the first heating flue, down the second, up the third, and downthe fourth and pass to the stack through stack ilue 18. rl"he heating units 20of the first compartment of the drum are ycontained in the first heating flue; the heating units 20a of the second compartment in the second heating flue, and `so on, so that there is a substantial drop in temperature between each unit and the following unit due to the cooling of the gases from the fire-box. The temperature may also be regulated or adjusted in the successive flues by valves V and V in the supplemental passages P and P.

In the preferred construction shown a conduit 40 containing a venturi or blower leads from the bottom of the last heating iue 13c and connectsl with the first heating lflue 13 at a point 18 behind the bridge wall 19 by which construction any desired proportion of the cooled products of combustion may be returned to iue 13 and mixed with the fresh products of combustion. rising from the fire-box to modify the temperature thereof to prevent overheating of the first set of oil heating tubes. Furthermore, by the ,return of the cooled products of combustion the total volume or mass of products of combustion brought into contact per unit of time with the oil heating units and the velocity thereof are increased, the total amount of heat extracted from the fuel augxmented, and the heat absorption'more evenly distributed among the several'sets of heating tubes.

tration of our invention, comprises threel distnct elements or circulation systems,"by

llao

' which oil is withdrawn from the compartof the still.

menti'and circulated through the corresponding heating flue of the furnace and back to the same compartment. Each of these elements .comprises a short header 21 connected into the bottom of the still compartment and a .long header 25. These headers are arranged immediately outside of one wall of the furnace, as seen in Figs. 2 and 3, the headers 21 being connected into thebottom The headers 25, as shown in Figs. 1 and 2, are arranged intermediate of and below headers21. In the form of the invention shown a group of tubes connect each header 21 with the corresponding header 25, each group of tubes comprising` pipes 22 connected into headers 21 and eX- tending downwardly therefrom and across the flue, cross headers 23 arranged on the side of the furnace structure opposite headers 21 and 25, and pipes 24 extending downthe cross headers 23 to the.

headers 25.` Preferably the walls of the furnace are out away or recessed as at 80 and 81 to receive said headers. rThe headers are formed with opening 26, normally closed by screw plugs 26V as shown in Fig. 3, in order to permit the insertion of a tool for cleaning the pipes 22 and 24. The threeV headers 25y in each group are closed at their fupperends, as best seen in Fig. 3, and are connected at their' lower ends to common manifolds 27, which communicate by pipes 28 with the outlets of pump 30. The inlets of said pump are connected by pipes 32 `to the same compartment of the drum to which the heating tubes and headers supplied byy said pump are joined. It will now be understood that when the pump is in operation it receives oil to be cracked through the pipes 32 from the corresponding compartment of the drum and forces it through the headers and heating tubes back to the same compartment of the drum.

A separate pump may be employed for effecting the circulation 1n each of the compartments. It is convenient, however, that the pumps be arranged in a common casing and driven by common means and the construction is so shown in the drawings. We have chosen for the purpose of illustration what we have found to be the pump best adapted for the' purpose,to wit: a rotary pump of the double piston type sometimes known as a Connersville pump. As indicated in the drawings, the series of pumps is driven by asuitable motor 33 and the casing is divided by partitions 34 into a series of independent chambers 35, 35, etc., each containing a pair of pistons 36. These pumps are connected to their respective compartments 10, 10a, etc., of the drum on the `inlet side by pipes 32 and tothe corresponding manifolds 27 by its.' pipe 28, ythe pumps being independent except in so far as they are enclosed in tlr same housing and operated by the same mechanism.

A T 36 is inserted in the connection 28 between the last heating unit and the corment, eight in each series connected to the second and so on. It follows that though the temperature of the products of combustion declines progressively from the first pass or heating flue tothe last, the heat absorption and therefore the cracking effect is approximately equalized.

From the foregoing the operation of the still Will be apparent. The drum is lled to the desired level, preferably through the inlet B and the overiow pipes y11, 11, etc. Preferably, the subsequent supply is continuously introduced through the reflux tower, vwhere it is preheated and assists in condensing and returning'to the drum the insufficiently cracked hydrocarbons. The pumps, being set in operation, continuously circulate the oil upwardly through the respective heating units, the circulation being assisted by convective effect due to heating. The oil in the iirst compartment and its heating unit will first reach cracking temperature and the other compartments and heating units will reach crackingI temperature in order. As cracking and vaporization takes place, oil is continuously supplied to the rst compartment, preferably through the reflux tower and, in the preferred operation, tar is continuously drawn oif through the manifold 27c andv outlet pipe 28 connected to the last heating unit. A branch pipe, provided with a valve, may be connected to pipe 28 for this purpose. The pumps are continuously operating during the run to maintain a rapid circulation of the oil in the respective compartments and heating units. The vapors rising from the several compartments all flow into the reflux tower, from which those of sufficiently low l which obviously any ment and heating unit, which is subjected to the highest temperature, is provided with a flux of light oil.

'Ihe continuous supply of fresh oil to the first compartment, combined with the vaporization throughout the several compartments and the withdrawal of tar from the heating unit connected to the last compartment, causes a continuous movement of the oil through the successive compartments, which yis accompanied by a successive diminution in the content of crackable 'hydrocarbons and an increase in the amount of tar and free carbon in the successive compartments and heating units. In a still constructed according to this invention, the oil is exposed to the highesttemperature during that phase in the cracking thereof in which it contains the least carbon and the largest amount of lighter and convertible hydro-v carbons, and consequently there is no serious deposition of carbon where it would be most objectionable. As the carbon increases and the content of crackable hydrocarbons diminishes in the successive compartments and corresponding heating units, this is -odset in the successive heating units by the successive reductions in temperature and increases in the heating surface exposed to the hot gases and on which the carbon may deposit.

Furthermore, in the construction shown and described, the temperature and heat absorption in the several heating units may be controlled as desired by means of the venturi, returning a proportion of the products of combustion, and the valves V, V', of

employed, controlling direct communication between the heating flues. Thus, by returning a greater proportion of the products of combustion from the nal heating flue to t the first heating flue, the temperature of the gases to which the heating unit in the latter is exposed is lowered without, however, a corresponding diminution in the heat absorption because of the increased volume of gases circulating through and about the heating tubes. rlhis effect is also received by the successive heating units though in lessmarked degree, the tendency being in the direction of equalizing the heating effeet. A still further equalizing effect may be obtained by opening to a greater or less extent the valves V, V.y

We claim:

1. In an oil still, a drum, aseries of partitions dividing the drum into successive compartments, titions through which the compartments communicate, means for supplying oil to the compartment at one end of said drum, a furnace having a heatingl fine, a series of sep-- arate heating units corresponding to the successive compartments in the drum each p being connected to one of the compartments desired number may be` compartments,

there being openings in said parseries, a furnace havingy a heating iue, a

series of heating units corresponding to the compartments inthe drum each heating unit being connected to one of the compartments and being located in the heating flue, the

heating unit connected to the feed corn-y partment being arranged in the heating flue nearest the furnace, and a corresponding series of pumps for forcing oil from said compartments through the heating units and back to the same compartment.

8. In a oil still, a drum having a series of communicating compartments, means for feeding oil to the first of said compartments and exhausting tar from the last of said compartments whereby a continuous flow -may be had through said compartments,

means for conducting away the vapors generated, a furnace having a heating flue, a corresponding series of separate heating units each being connected to one of said compartments only and extending into the heating flue of the furnace, and a corresponding series of pumpsconnected to the compartments and to the heating units connected thereto` and adapted to receive oil from' said compartments vand force it through the heating units and back to the same compartment.

4. In an oilstill, a drum, a series of communicating compartments in the drum, means for feeding oil into the first of said compartments and exhausting tar from the last of said compartments, and means for leading away vapors from compartments, a corresponding series of separate heating units connected to each of said said compartments and to the heatingunits connected thereto to cause the oil to circulate from the compartments through said heating units and back to the same compartment, and means common to the pumps toV drive same.

a pump connected to each of.

said

" 5. In an oil still, a drum, partitions in the drum dividing same into a' series of com-- municating compartments, means for feeding oil into the first of said compartments, means for withdrawing tar from the last of said compartments, a furnace,'a corresonding series of separate heating units connected to the respective compartments and located in the furnace, each of said heating units comprising a header connected to the l drum, a series of pipes connected to the tons-of the respective pumps being mounted on common shafts, means for driving said shafts, connections from the inlets of the re spective pumps to the respectiveV compartments of the drums, and connections from the respective outlets of the pumps to the respective second said headers of the heating units.

6. In an oil still, a drum, transverse 'partitions in the same dividing the lower .portion thereof into successive communicating compartments, means for feeding-oil 'into the first of said compartments at one end of the drum, means for withdrawing residue at the far end of the drum, means for leading away vapors, a furnace having a Hre boX adjacent the first mentioned end of the drum, an outlet Hue adjacentthe drawoifV end of the drum, Hues connecting the firebox ,and outlet Hue, heating units communicating with the respective compartments and extending into the heating Hue, and v'pumps connected on the outlet side to each said heating unit and on the inlet side to the corresponding compartment of the drum.

7. In an oil still, a drum, transverse partitions in the drum dividing the lower portion thereof linto successiver communicating compartments, means for `supplying. oil to the compartment at one end of the drum,

means for permitting theescape of residues from the compartment at the opposite end of the drum, a line for' leading off vapors, a furnace having a heating Hue extending along with the end of the Hue beneath the first mentioned end of the drum, and a stack Hue.

at the other end of the heating Hue, heating units for each compartment' each comprising headers communicating therewith, pipes connected to the headers at one end, headers to which the pipes are connected at their other ends, a manifold to VWhich the last named headers of each unit are connected, a pump the outletl side of which v1s connected to said manifold and a connection from the inlet side of the pump to the corresponding compartment. c.

8. In an oil still, a drum, transverse partitions in the drum dividing the lower part thereof into successive communicating compartments, means for feeding oil into the first of said compartments at one end of the drum, means for withdrawing residue from the last of said compartments at the other end of the drum, a vapor line, a furnace comprising heating Hues extending beneath the drum, a fire box for said furnacel at the end ofthe heating Hues corresponding tol the first compartment of the drum, an outthe drum, a Hrebox communicating` l heating Hue,

including a' pump let Hue connected to the exhaust end of the heatlng Hues, independent heating units communicating with tlierespective compartments, the heating areas of which increase progressively from 'the Hrst to the last unit,'pumps Aconnectedon their outletv sides to the respective heating units, and l I Acommunicating with the drum-arranged in the heating Hue between the Hrst mentioned heating means-and the furnace,- connections for supplying fresh oil to the still and means'for inltially' circulating the fresh oil 4throughfthe last mentioned separate heating means.- i

l0. In. an oil still, a furnace having a vheating Hue, a drum adapted to `contain a charge of oil, heating `means arranged in the heating Hue and connections including a pump for circulating oil from and to the drum therethrough, Vaseparate heating means communicating with the drum arranged in the heating Hue between the first mentioned heating means and the. furnace, connections for supplying fresh A.oil to the still `and means including a pumpfor initially circulating the fresh oil through the last mentioned separate heating means.

11. In an oil still, a furnace having -a heating Hue, a drum adapted vto contain a charge of oil, a reflux tower communicating, with the drum, heating means arranged in the heating Hue and connections including a pump for circulating oil from and to the drum f therethrough, 'a separate heating means communicating with the drum arranged in the heating Hue between-the first mentioned heating meansl and the furnace,

connections for supplying freshjoil to the still and connectionsv for returning refiux'x from the reHux tower to the still, an'dimeans for initially clrculating thefresh o il andv rel flux through the last mentioned'separate heating means, Y Y

12. In an oil still, a furnace .havlngg'a charge of-,o1l, a reHux tower' communicata drum adaptedv to conta-in av ing-with the drum,rmeans forintrod'ucing fresh oil into -the refluxV tower, heating means arranged in the heating Hue .and connections forl circulating o-ilf-l-f-rom and to thev drum therethrough, a separate heating v means communicating with the drum arranged in the heating Hue between. f the first mentioned heating means *and the furnace, they fresh and means for initially circulating Oil and. admfixed refiuxf from the heating niue, a drum adapted to contain a chargeof oil, a refluxftower communicating' with `the` drum, heating means arranged in the heating flue `and connections including a pump for Vcirculating oil from and to the drum therethrough, a separate heating means communicating with the 'drum ar- 10 ranged in the heating flue between the first mentioned heating means and the furnace, and means for initially circulating the reflux from the reflux tower through the last mentioned separate `heating means.

JOHN E. BELL. EDWARD W. isoM.

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