US1640444A - Process and apparatus for cracking hydrocarbon oils - Google Patents

Description

0 1927. Aug 3 w. F. FARAGHER ET 1.

PROCESS AND APPARATUS FOR CRACKING HYDROCARBON OILS Filed Jan. l5. 1921 4 Sheets-Sheet 1 1,640,444 W. F. FARAGHER ET AL PROCESS AND APPARATUS FOR CRACKING HYDROCARBON OILS Aug. 30, 1927.

Filed Jan. 15, 1921 4 Sheets-Sheet 2 Aug. 30, 1927.

w. F. FARAGHER ET AL PROCESS AND APPARATUS FOR CRACKING HYDROGARBON OILS Filed Jan. 15. 1921 4 sheets-sheet 5 eM/oe/wtoxs 3% eaker/" 5 3 MW W WW Aug. 30, 1927.-

' 1,640,444 w. F. FARAGHER ET AL PROCESS AND APPARATUS FOR CRACKING HYDROCARBON OILS Filed Jan. 15. 1921 4 Sheets-Sheet 4 CRACKED VA PORS HOT GASES Auo v/mons .33 9

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UNITED STATES 1,640,444 PATENT OFFICE.

WARREN F. FARAGHER AND WILLIAM ARTHUR GRUSE, or PITTSBURGH, PENN- SYLVANIA, Assronons To GULF REFINING COMPANY, or PITTSBURGH, TENN- SYLVANIA, A. CORPORATION OF TEXAS.

' PROGESS'AND AIPPARATUS FOR CRACKING HYDROCABBON OILS.

App1ication filed January 15, 1921. Serial No. 437,479.

This invention relates to an improved method and apparatus for making motor fuel or gasoline by cracking hydro-carbon oils, such as the higher boiling fractions and residual oils of petroleum or shale oil distillation.

hen hydrocarbon oils of the character .referred to are subjected to cracking in an externally heated still, serious difliculties are encountered in large-scale operations,

' the deposition of a carbonaceous solid, commonly referred to as carbon, on the heated walls of the still. Such a deposition of carbon interferes with the conduction of heat into the oil, and results in increased cost of gasoline-production owing to the necessity of cleaning the carbon from the still-walls and the loss of operating time during such cleaning operations; while the life of the still-wall is comparatively short due to the rapid burning out of the iron in contact with carbon.

Attempts have been made to overcome the difficulties mentioned by providing stirrers in the still for agitating the oil, but such st-irrers are open to the objection that they require stuffing boxes which must operate against highly heated oil or heated oil vapors at high pressures.

According to the present invention, the difficulties above referred to are overcome or minimized, and an eflicientcirculation of the oil through the heated portion of the still is effected, with avoidance or substantial avoidance of objectionable deposition of carbon onthe still-walls, b providing an upright tubular still, or t e upright tubular portion of a still, with a suitable eductionpipe or tube, and by so introducing a gaseous current or currents, acting on the air-lift principle, that effective circulation of the oil through the heated portion of the still takes place, and the formation of a dead layer of Oll on the hot walls of the still is avoided.

' The gas used in the stirring and circulationof the 011, according to the present inventiOn, may with advantage be the fixed gas formed during the tracking-operation, but

other appropriate gas can be used, such as natural gas or casing-head gas, steam, etc. which has no objectionableefiect upon the cracking operation.

due to In the preferred practice of the invention, only a portion of the still is heated and the oil is circulatedcontinuouslythrough this heatedportion of the still by the provision therein of a suitable eduction-pipe and the introduction of-a current or currents of gas acting, in conjunction with the eductionpipe, on the air-lift principle. The still may itself be a tubular still, vertical or inclined, having the eduction-pipe vertically arranged therein, or, if inclined, having a sufiicient vertical component to provide for the circulation desired; or the'still may be of the boiler type provided with vertical legs extending into the furnace and each having an air-lift circulating device, so that the boiler will act as a reservoir for the. oil which is heated to the cracking-temperature by continuous circulation of a part thereof through the depending legs. The gas may be introduced within the educt-ion-pipe so that it will draw in oil at the bottom and discharge it from the top and so that the oil will then flow down continuously outside the eduction-pipe and be again recirculated; or the gas can be introduced in the space between the eduction-pipe and the still to cause a rapid upward current of oil in this space with the downward return of oil ing constituents resulting from the cracking operation as they are formed, and prevents their remaining in the still to undergo further decomposition. The excess gas, result-.

ing from the' cracking operation, can be. discharged from the still in any of the usual ways, while the gas that is to be recirculated through the still can be freed from, undesired high boiling constituents in a suitable dephlegmator, and from the desired condensable constituents in a suitable condenser, and can then be passed through a pump or gasbooster and sufiicientlyincrea'sed in pressure to be used again.

In the practice of the process, the oil is continuously circulated through the heated portion of he still in such 'a way that its temperature is raised into that range in which cracking occurs with the production variety of forms, continuously or still may thus be .of the heating of such a ably high temperatures.

of considerable naphtha and gasoline and relatively little gas and carbon, without local overheating of any portion of the oil to the still higher temperatures at which m'uch gas and carbon are formed. ,The contiuuous and effective circulation of the oil in the heated portion of the still keeps the oil within the desired temperature range throughout and gives a resulting uniform cracking operation, whileavoiding local overheating. The oil which becomes heated by its circulation into contact with the heated walls of the still is continuously swept or scoured off so that the formation oil is prevented, with resulting prevention layer to objection- The apparatus embodying the invention, in whichthe improved process of the. invention can be practiced, may have a great and may be operated either discontinuously. A single provided adapted to operate upon successive charges of oil, or to operate in a continuous manner by the continuous introduction of'oil and the continuous or periodical removal of residue; or'a seriesof stills .can 'be arranged to act successively upon a body of oil which is caused to pass through them under properly regulated conditions of temperature and pressure. The still may with advantage be provided with a tar pot below the furnace and circulating portion'of the still, for the collection of carbon and insoluble substances.

The utilization of the air-lift mechanism and principle for'effecting circulation makes possible eflicient circulation of the oil without the use of moving mechanism and therefore without the use of stufling boxes, so that all connections of the still maybe welded and made gas tight. The gas is also used to much better advantage than is the case when it is allowed merely to bubble through a charge of oil in the still, since the use of the gas in accordance with the airlift principle and mechanism insures a positive flow of oil along the still walls wlth a sufiicient velocity to break up the dead layer of oil which has heretofore been the chief cause of carbon trouble-and deposit.

The invention will be further illustrated and described in connection with the accompanying drawings which show, in a somewhat conventional and diagrammatic manner, different forms of apparatus embodying the invention and adapted for the practice of the process of the invention.

In the accompanying drawings:

Fig. 1 shows one form the gas introduction pipe arranged within the eduction-pipe;

Fig. 2 shows a modified construction with arrangement for introducing the gas into of a dead layer of .with its foot-piece 11 so oil can thus be brought of apparatus with I Fig. 5 is a verticaltransverse section of the apparatus of Fig. 4;

Fig. 6 shows a modified construction in which a series of stills are provided; and

Fig. 7 shows, somewhat diagrammatically, the assembly of a single tube still with condenser, preheaters, etc.

In the different figures of the drawing,

similar parts are referred to by the same numerals, with different letters appended thereto.

In the apparatus of Fig. 1 the still 1 is a vertical tubular still having an oil inlet pipe 2, dephlegmating column 3 with vapor pipe 4 leading therefrom to the condenser, and with a settling chamberor tar pot 5'at the bottom'from which the residue can be withdrawn through the outlet 6. A suitable furnace chamber 7, heated by direct heat or by products of combustion, sur rounds a part of the still, so that only a portion of the still is heated. Within the of the still is arranged an supported by suppipe 9 is arranged that it discharges the gaseous current upwardly within a restricted portion of the eduction tube 8, as shown. -The heated portion eduction tube 8, suitably ports 12, and a gas inle valve 10. In the operation of the apparatus of Fig. 1 the gas, which may. be the fixed gas from the cracking operation, is forced into the pipe 9 and discharged upwardly through the foot-piece 11 into the'central eduction pipe 8, thereby of' the eduction pipe-and causing upward circulation therethrough; This oil is discharged at the top of the eduction; tube, together with the gas, and the oil flows down continuously between the eduction tube and still wall to be again recirculated. A continuous circulation of the oil is thus effected, with resulting uniformity of temperature of the oil body as a whole and resulting avoidance of objectionable overheating of the oil next to the still wall. The entire body of within the range of temperatures most favorable to cracking and maintained within such range without-localoverheating. The gas introduced into the still through the gas inlet pipe escapes, together with the gaseous products of cracking and of distillation. through the dephlegmator 3, where undesired high-boiling constltuents are condensed and returned to the gaseous current can be controlled by means of. a suitable regulatingdrawlng in oil at the bottom i space between still, and then through the condenser (not shown) where condensable constituents are separated. If the condenser is operated under the same pressure as the still, the fixed gas can be withdrawn at this pressure and recirculated, so that no considerable further compression is necessary. Instead of first passing the gas through the condenser and thereby cooling it, the hot gas may be taken off at some point between the final condenser and the still at a correspondingly elevated temperature, and can be recirculated so that its sensible heat is in large part conserved.

In the apparatus of Figs. 2 and 3, the gas is introduced or liberated into the annular the still walls 1 and the central tube 8 so that the oil is caused to flow upwardly through the heated annular zone around the central tube and then down-- wardly through the central tube. The diameter of the central pipe is increased in this case so that the velocity of the oil through this annularjspace is very considerably increased. It is of course obvious that in whatever form used, the eduction tube must be of such size and so placed with reference 'to the heated still wall as to give a vigorous circulation of oil along and against the heated still wall.

In the apparatus of Figs; 4 14 is a boiler type still having three depending legs 1", each exposed to the furnace for a portion of its length, and each provided with a circulating device similar to that of Fig. 1 or Fig. 2. The boiler 14 in this case acts as a reservoir for the oil which is heated to the cracking temperature range by continuous circulation of a portion of the oil through the depending legs, each of which is provided with an air-lift circulating device. The boiler 14 is provided with a separate outlet 15 for the residue, in addition to the outlets 6 at the bottom of the depending legs. The lower part of the boiler is also surrounded by a flue construction 17 "(shown only in Fig. 5) by means of'which it is heated by the waste gases from the furnace 7 the boiler portion of the apparatus thus acting as a reservoir in which entering oil is preheated.

In the apparatus of Fig. 6 a series offour tubular stills 1, 14, 1 and 1, is arranged so that the oil can be introduced into the first still and passed through each of the others in succession. The oil may thus be introduced into the still 1, through the inlet pipe 4 2, and the oil from this still then passed into the still 1, and so on. Connecting pipes 18, 19 and 20 are arranged between the stills and provided with both hand operated and adjustable. automatically operating regulat ing valves. The flow from one stillto the next may be by gravity, in which case the hand operated valves are opened and the pumps are not employed, or thepumps 21,

and 5 the an 22 and 23 may be used so that the oil can be pumped from one still into the next. The Iour stills, in this case, mayv have separate and separately controlled outlet pipes which may lead to a common vapor line 19 and a common condenser. In such case, the outlet pipes 4', 4, 4 and 4 are provided with suitable regulating valves, such'as the automaticadjustable relief valves 40, 40*, 40 and 40 so that "the different unit stills may operate at different temperatures and pressures. It is to be' understood that the temperatures and pressuremay be regulated independently in each still. The bottoms may be withdrawn continuously from the last still of the series, or from any one of the series, as the character of the oil treated and the conditions of operation may require.

In Fig. 7 there is represented diagrammatically the assembly of a single tube still of a construction such as is shown in Fig. 2, with appropriate condenser, preheaters,

heat exchangers, pumps, etc. The condenser is illustrated conventionally at 25 and the receiver for the condensate at 26, this receiver'having an outlet pipe 27 with an automatic relief valve 28 therein, and also having an outlet pipe 29 for the fixed gases leading to the vapor pipe 30 which supplies the gas blower 31 with the gas-or vapor introduced into the still through the pipe 32 and the gas or vapor inlet pipe 9. The vapor pipe 30 is also connected withthe main vapor pipe 4, so that the gases introduced into the still may be either the fixed gases from the receiver 26, or admixed gases and vapors obtained through the pipe 30, .or a mixture of both in varying proportions.

A constant level can be maintained in the still in any suitable manner. for example, by feeding the oil to the still, in the appargtus of Fig. 7, through the pipe 35, from t e oil supply vessel 34 in which a-constant levelis maintained by any suitable means (not shown). The oil 'to be, supplied to the still enters through the pipe 36 and is pumped by the pump 37 through the preheater 39, where it is preheated by the residue from. the bottom of the still, then through the preheater 40 where it is further preheated in any suitablemanner, and it enters the constant-level supply vessel 34 ina preheated condition and is supplied 1n this condition to the still. The operation of the. pump 37 is automatically controlled (by .condensable constituents.

improved oil cracking process therein, the oil is maintained at a suitable level, for example, at the level indicated at 16 in Fig. 1 or 16 in Fig. 5 or 42 in Fig. 7, and this level can be automatically maintained by the introduction of further amounts of oil through a suitably regulated oil supply pipe. The residuum can be drawn off through the bottom outlet of the still either continuously or intermittently, and its heat utilized in the preheater 39 ofFig. 7 for assisting-in preheating the oilsupplied to the still. The gaseous and vapor products resulting from the cracking and distilling operation together with the gas'introduced through the gas inlet pipe or pipes, are taken ofi through the dephlegmator and vapor pipe to the condenser 25\,of Fig. 7 or other suitable condenser. If the condenser is to be operated under the same pressure as the still,.which is the'preferred practice, the regulating valve may be beyond the condenser, as indicated at 28 in Fig. 7, and the pipe leading from the still will: then require no regulating valve. If the condenser is to be operated under a lower pressure than the still, suitable regulating valves (not shown) can be provided in the vapor pipe 45 leading from the still to the condenser and in line 29.

The necessary gas for recirculation can be withdrawn either at the still pressure and temperature and reintroduced into the still, or the gas can be used after ithas passed through the condenser and been freed from The diagrammatic arrangementof Fig. 7 provides either for using the hot compressed gases from the still and recirculating them, or for recirculating the fixed-gases after the condensable constituents have been removed. This arrangement for making use of the gases, or

gases and vapors, produced by the process,

is a particularly advantageous method of procedure. Other suitable gas than that resulting from the cracking operation can, however, be usedin the practice of the invention, as well as other gaseous materials such as steam, although it will usually be more advantageous to make use of the gas or vapors produced by the cracking operation and to return and reuse such gases repeatedly. By drawing ofl" the hot compressed gases or vapors from the still, they can be used with conservation of their tem= perature and pressure, so that only a small increase in pressure is required for recirculation, and so that the recirculated gas does not exert any-considerable cooling action on the oil.

p still may be preheated to a greater or less extent, as above noted. A part of the necessary heat can be supplied by means of a heat interchanger 39 through which the still bottoms are discharged; while a part of the preheating may be The oil feed to the from the still.

.densing such vapors.

cracking operation may thus be carried eflected by bringing the oil feed into heat interchanging relation with the hot vapors The oil feed can thus be passed through the condenser for the vapors from the still, or through one or'more of the series of such condensers, where such a series is used for fractionally cooling and con- The preheating effect thus secured may be supplemented, if desired, by further preheating of the oil feed in any suitable manner, and the oil feed can advantageously be preheated to such a degree as to vaporize and remove any water present therei In illustrating the various forms of appau ratus in the accompanying drawings, we

have omitted the heat insulation or lagging of the still, connecting pipes, etc., but it will be understood that, in practice, suitable heat insulation will be provided to avoid objectionable losses from all exposed parts of the still and of the system which become heated. It will be understood that the stills of Figs. 1 to 6 are provided withsuitable pressure, temperature and level indicating devices (not shown) as well as with means for producing and-maintaining within the still the necessary temperature and pressure conditions for I the cracking operation. The

under a regulated pressure, for example, of between 60'and 500pounds per square inch, and preferably in the neighborhood of to out 150 pounds per square inch, depending upon the nature of the oil to be cracked and the products desired. The continuous rapid circulation of the oil through the heated zone of the still promotes the uniformity of heat ing and enables substantially all the entire body of oil to be maintained at the desired temperature for the particular oil treated.

In the practice of the invention, the rapid circulation of the oil with respect to the heated iron surfaces of the tubular still will effectively prevent the" formation of objectionable carbon deposits and tend to remove any carbon that may incidentally be formed.

most effective cracking of too Such carbon as is formed in the circulating acter and results in a higher yield of gasolene and lower gas and coke losses, and hence an increased capacity or improved yields for a given sized still, while the effective life of the still is at the same time increased, and

the still can be run for long periods of time esses,

herein we refer to the same without the necessity for discontinuing operations for cleaning purposes. The provision of a tubular form of still, with continuous operation, large volume of highly heated oil under pressure subjected to furtherheating effect, as in the usual boiler type stills heated by direct heat. So also, the keeping of the still walls of the heated zone free from carbon deposit and from a layer of dead oil permits the use of a greater heat influx to theoil and consequently a greater capacity for a still ofdefinite size.

It will thus be seen that the improved process and apparatus of the present invention enable the cracking of oils and the production of motor fuel .or naphtha to be effected in an advantageous manner, with in creased eflicienoy and uniformity of operation, and with substantial avoidance of the usual difficulties met with in cracking procthe improved results are obtained in a simple and advantageous manner.

In referring to the cracking of oil in the present specification and claims, we intend to include the treatment of various hydrocarbon oils, and more particularly the treatment of higher boiling fractions and residual oils of petroleum or shale oil distillation, for the production of motor fuel or gasolene; but other oils, such as lignite or coal tar, or tar oils, etc., can be similarly treated; and we include all such materials within the term oil, as used in the accompanying claims.

It will, of course, be understood that the passages governing the circulation in the still are not restricted to any particular shape or location, provided only that they serve as a means for constantly sweeping away the dead oil from the highly heated-cracking surfaces. They may have, therefore, any shape or disposition that will effect that purpose.

In referring to the air-lift principle principle that is applied in pumping water where air is pumped into. .and mixed with water in one of two balanced columns so that flow is set up due to the reduction of density in the column into which the air is introduced. In the present application of this principle flow is caused by the reduction of density of the oil body into which the gas streams are introduced and the kinetic energy of injected gas streams is not relied upon for maintaining the circulation. In. carrying out the process and in the operation of the apparatus of the present invention, circulation is efiected without reference to the velocity of introduction of the gas streams and the simavoids thedanger of having a free or substantially due to carbon deposition; and that 1 ple liberation of the gas in the oil at zero velocity is sufiicient to-maintain clrculation in accordance with the present invention.

WVe claim:

1. The method of cracking oils, which comprises subjecting a body of oil in a still to the action of heated surfaces and thereby heating the oil to a' cracking temperature under pressure and introducing a current or currents of gas, acting on the air-lift principle, in upwardly directed jets in an upwardly directed passage within the body of oil, the gaseous current or currents belng made up of gases produced during the cracking operation.

2. The method of cracking oils, which comprises subjecting a body of oil in a still to the action of heated surfaces andthereby heating the oil to a crackingtemperatureunder pressure, withdrawing gases and vapors from the still, and introducing gases and vaaors withdrawn from the still at substantially the still temperature in upwardly directed jets, acting on the air-lift principle, in an upwardly directed passage within the body of oil, thereby effectively circulating the oil with respect to the heated surfaces.

3. An apparatus for cracking oils, comprising a still provided with heating means for heating the oil therein to a cracking temperature under pressure, means for withdrawing gases from the still, and means for reintroducing a gaseous current or currents comprising a portion of the same into the still in upwardly directed jets, acting on the air-lift principle, near the lower end of an upwardly directed circulation pipe arranged in the still and adapted for coactin with the gaseous current or currents for e fecting circulation of the oil over the heat ing'surfaces of the still.

4. An apparatus for cracking oils, comprising a still provided with heating means for heating the oil therein to cracking temperature under pressure, means for Withrawing gases and vapors from the still, and means for reintroducing, at substantially the still temperature, a current or currents comprising a portion of the withdrawn gases and yapors into the still in upwardly directed ets near the lower end of an upwardly directed; circulation pipe therein adapted for co-actmgwith the gaseous current or currents and for effecting circulation of the oil with respect to the. heating surfaces 'by the air-lift principle.

In testimony whereof we afiix our signatures.

WARREN F. FARAGHER. WILLIAM ARTHUR GRUSE.

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