US1583973A - Apparatus for cracking oils - Google Patents

Description

May 111 1926. 3,583,973

R. C. HOLMES ET AL APPARATUS FOR CRACKING OIL S Filed June 26. 1919 3 Sheets-Sheet 1 May 11 1926. 1,583,973

R. C. HOLMES ET AL APPARATUS FOR CRACKING OILS Filed June 26, 1919 3 Sheets-Sheet 2 9 V I Ig'VE EOR B W ATTORNEY May 11 1926. 1,583,973

R. c, HOLMES ET AL APPARATUS FOR CRACKING OILS Filed June 2 1919 C5 Sheets-Sheet 5 W Wm Y W ATTORNEY Patented May 11', lQZfi'.

UNITEDf S T-ATESi TENT OFFICE.

RALPH. c. notifies; or nw- YQRKQ Y., AND rnnnnn'rox m. MANLEY, on Houston, TEXASPASSIGNORS TO Tnn'rms COMPANY, OF NEW YoRK, N. Y., 'A'oonrommron OF TEXAS.

. ,ArPARaTus ron. onao xrive :orrs.

' Application filed;Ji1ne'2, 1919. Serial No. 306,936.

Our invention relates to the art of crack ing or decomposing hydro-carbon oils for the purpose of converting heavier products, such as gas oil and fuel oil, into lighter products, such as naptha, gasoline and kerosene. More particularly our invention pertains to apparatus for practicing processesfor the aforesaid purpose, in which the applicatlon of heat andpressure is employed. I

' \Ve are-awarejthat many processes and difierent 'kindsof apparatus have been proposed for the purpose of cracking hydrocarbon oils by means of heat and pressure, but it has been our aim toprovide apparatus suitable ior use on a commercial scale for the quantity roductionof gasoline or the like, by avoic ing the objectionable features and'difliculties which are adherent in the arrangement-s hitherto proposed.-

, \Vhensuflicient heat is applied to a containeror converter to effect decomposition of the petroleum oils therein, the walls of the container .are' very likely to be burned or weakened because the temperature is necessarily high, the vapor contained above the liquid level is a poor conductor of heat and carbon is deposited on the interior walls as a result of the decomposition of the hydro- .carbon oils. This carbon deposit maybe built up to a considerable thickness and is a poor conductor of heat, so that it greatly increases the likelihood of the metal walls being burned or overheated. Furthermore, the heat applied to' the walls at the vapor space and at'the surface of the liquid tends to overheat the oil and to break up the 'vapors into fixed gases.

Any overheating or is particularly undesirable and dangerous when considerable internal pressure exists inthe converter. These difiiculties have in fact materially curtained the. life of the apparatus of this character hitherto, and have limited the feasible pressures and temperatures which couldbe employed, making it impossibleto utilize a relatively high presi sure such as 150 to 200 pounds to the square inch which we have found are productive of a higher yield of" gasoline with the form3.tl.()I1'0f"l6SS unsaturated hydro-carbons which alesser oil therein, so that heat is absorbed by the oil, and neither the oil or the converter are overheated. 1

large'capacity composed of a plurality of units preferably inthe form of vertical stills, tree trom tubes or objectionable joints and so arranged that the heatis distributed over a large area intermediate their ends, instead of being concentrated at any one point.-

3. Bypassing the oil at'a cracking temperature through a series of converters or stills in succession and arranging for withdrawing residue oil from-one or more of the stills near theend of the series where the cracking is most nearly complete and to quantity of external heat is applied.

4:. By utilizing efi'ective means for scrap.-'

ing the carbon from the interiorsurface of a each still.

5. By continuously introducing the fresh oil into the body of oil in the still to which the greatest quantity of heat is applied, and

where, in consequence of the introduction of the cooler charging oil, the rate of heat absorption may be increased with safety.

6. By supplying the highest temperature heat to the'body of the oil in the still where the oil is introduced and where the least burning of the walls cracking has been efifectedby reason of the time element essential to the cracking process and thus insuring that the largest carbon deposit occurs in the stills to which less eX- ternal heat is applied. 1

Another object of the invention is to pro vide an apparatus especially adapted. for continuouscommercial operation on a large scale and-so designed that the oil is passed successively through a series of converters that are severally maintained 'un der-sub stantially uniform operating conditions and which operate concurrently upon the oil in 60 2. By providing apparatus of relatively transit therethrough to effect its conversion, the evolved vapors being taken off of the several converters as fast as they are formed and subsequently condensed and collected to constitute the ultimate product.

To these ends, a plurality of converters, preferably of the vertical type, are disposed closely adjacent one another and are preferably arranged to be heated intermediate their ends by means of a single furnace, the structure of which is such that the quantity of heat delivered to the respective converters may be regulated as desired. The several converters are connected above the heating zone by short and direct flow pipes, by means of which the oil which is charged into the bottom of the firstconverter of the series is caused to flow successively through the remaining converters. Above the connecting flow pipes, the vapor spaces of the converters are in open communication through the agency of short and direct vapor line connections. approximately equal oil levels in the converters and the direct vapor line connection function to equalize and distribute the pressure developed in the several converters, which in practice has been found particularly effective in assuring practically constant and equal Oll. levels. The evolved vapors are taken off, as they are formed, from one or more of the converters and are passed through a separator which condenses out the heavier constituents thereof Which are back-trapped to the bottom of the first converter of the series into which the fresh charging oil is introduced. The lighter constituents of the evolved vapors are passed on through a condenser and are subsequently collected.

In operation the furnace structure is so regulated that the several converters are maintained at substantially uniform crack- .ing temperatures, and for this purpose a larger quantity ofheat is applied to the first converter of the series in order to com pensate for the cooling action of the charging oil and back-trapped condensate. Although maintained at the same cracking temperature as the other converters, comparatively little conversion actually takes place in the first converter on account of the short time interval to which the oil is subjected to cracking temperatures therein. Consequently, very little carbon and heavy residue is produced in this converter. The

bulk of the conversion is effected in the remaining converters and the largest amount in the last of the series, in which, therefore, the greatest amount of carbon and heavy residue is deposited. It is from the last con- .verter that the bulk of the carbon and residue is withdrawn and for this purpose a residue draw-off pipe is connected to the bottom thereof where the residue collects in an undisturbed state and may be removed The flow pipes serve to maintain with facility. The bottom of all of the converters are provided with residue draw-oil's, which communicate with a common discharge pipe so that'it is possible to remove residue from any or all of the converters if desired, although in operation it is usually preferable to withdraw the residue from the last one or two converters of the series.

l/Vith the construction and operation thus briefly set forth, it will be understood that all of the converters operate concurrently and under substantially like operating conditions upon the oil in transit through them and that, therefore, the vapors evolved. in the respective converters are substantially alike in characteristics,at least to the extent that they may be co-mingled and collected together to form the ultimate light product resulting from the process.

Other more specific objects of our invention are to provide means for controlling the distribution of heat among the several stills which make up the battery, so as to improve the regulation of the apparatus;

To provide means for establishing and safely maintaining, without leakage, an operative connection between a rotary mechanical scraper inside of each still and suitable driving apparatus outside thereof; and

To provide means for conserving heat by arranging for a heat exchange between the residuum, drawn from the stills at the bottom and the fresh oil prior to the time it is charged into the battery. Other objects and advantages of our invention and features by which they are attained will be set forth hereinafter and we will now describe the same with reference to the illustrative embodiments thereof shown in the drawings and point out the novel features thereof in the appended claims.

Referring to the drawings:

Figure l is a partially diagrammatic elevation of apparatus arranged and constructed in accordance with our invention and constituting an embodiment thereof.

Figure 2 is a sectional elevation of a furnace and a battery of stills which form parts of the apparatus shown in Figure 1.

Figure 3 is a sectional plan view taken on the line 33 of Figure 2 and;

Figure 4 is a sectional elevation on the line of Figure 2, Figures 2,3 and 4 being drawn to a larger scale than the semidiagrammatic view of Figure 1.

Like parts are designated by the same reference characters in all the figures.

The apparatus illustrated, comprises in general abattery of stills designated respectively 1, 2, '3 and 4, a furnace 5, an air condenser or separator 6, a water condenser 7, a pressure regulator 8, a feed pump 9 and a heat exchanger 10.

The furnace 5, as clearly shown in Figures 2, 3 and 4, comprises a combustion chamber 11, having a bridge 12, a perforated inclined arch 13, and a secondary arch 14 providing openings into conduits 15; a heat deflecting wall 16, sidewalls 17, a horizontal base 18, raised a few feet above the floor or foundation, a top wall 19, and a plurality of perforated partition walls, 20,

21 and 22, which together withthe heat de-' Ilecting wall 16 provide a plurality of chambers 23, 24, 25 and 26 in which the stills 1, 2, 3 and 4. are respectively disposed.

Each of the stills is vertically arranged and its length is considerably greater than the vertical height of the chamber in which it is located so that it extends materially below the base wall 18 and considerably above the top wall 19. In this way the intermediate portion of each still is disposed within the furnace where it is subjected to high temperatures and both the bottom and top extend outside the heating zone. Conduits 27 and 28 are formed along the sides of the furnace heating chamber at the bottom, and are provided with adjustable L dampers 29, 30, 31 and which regulate the heat supplied to the still chambers from the conduits. Of course, separate furnaces for the respective stills may be used if desired.

lVe prefer to utilize stills of large capacity and as hereinafter explained to keep them filled with oil to a predetermined level above the zone of direct heat application as indicated by gauges 70, so that the cracking process may be continued without interruption,'and the overheating of the stills, and -the production of fixed gases prevented.

The stills are directly interconnected in' series-relation by short lengths of relatively larged sized flow line pipes 33, 34 and 35 and are preferably interconnected by similar vapor line connections 36, 37 and 38. The "apor spaces of the several stills are thus in free and open communication and, therefore, any tendency to effect an unbalance or unequal pressure distribution among the several stills of the battery during their operation is immediately relieved and an' equalization of pressures is at once established. Thus, regardless of any incipient pressure variations, substantially uniform and equalized pressure operating conditions are maintained throughout the battery, and inasmuch as they are also maintained atsubstantially uniform cracking temperatures, all of the stills operate concurrently to produce or evolve substantially the same product. The flow line pipes serve to con duct the, oil fromone still to another successivel'y'and also to assist in establishing As clearly shown in Figure 1 the stills are connected at the bottom through a residue manifold 39 to a tank 40 which forms a part of the exchanger 10, valves 41, 42, 43 .and 44 being arranged to control the respective branches of the several stills.

The exchanger 10, in addition to the tank 40,con'1prises a coil 45 which is disposed within the tank 40 and forms a part of the charging line which is established from the feed pump 9 through pipe 46, coil 45 and a pipe 47, having a control valve 48, to the bottom of the still 1. The tank 40 has a (lraw-olf pipe 42) provided with two branches and 51 connected respectively to the top and bottom of the tank 40 and having valves 52 and 03.

The separator 6 comprises, as illustrated, two sections 54 and 55, but may, of course, consist of one or more sections as desired.

'l lach section comprises a pair of spaced drums 56 connected by vertical tubes or pipes 57. The drums 56 at thebottom of the separator section 54 is connected by a vapor line 58 to the top of the still 4 and top drum of the same section 54 is connected to the bottom drum of the separator section by a pipe 59.

There is a back trap line 60- connected at one end to the bottom drums 56 of the air condenser and atthe opposite end to a point near the bottom of the still 1. The top drum of the separator section 55 is connected by' a vapor line 61 to'a coil 62 of the condenser 7, the opposite end of the coil being connected by a pipe 63, having an outlet valve 64, to the pressure regulator or receiver 8.

This pressure regulator has the form of a drum and is provided with a gauge 65 to indicate the liquid level therein. It'has a condensate outlet 66 controlled by a valve 67 and a. gas outlet 68 controlled by a valve 69.

In order to keep the sides of the walls of the stills free from carbon deposits, each still is provided with a positively operating scraper device comprising a rotatable shaft 71 extending verticallythrough the centre of the still andcarrying a plurality of scrapers 72 which make physical contact with the sides of the still and may be of any suitable construction. 7 bearing 7 3 at the bottom of the still and is driven through worm suitable means.

In order to prevent the vapors around the shaft from the still in which high temperatures and pressures are gearing 74 or other i escape of the The shaft is journaled in a maintained, oil cooled sleeves or pipes 75 extend upwardly from the stills at the top and looselysurround the shafts, a stufling box of suitable construction being located at each end of each sleeve, thus providing 'twoseries related barriers against leakage.

The sleeves are connected inmultiple relatioii to a drum .77 by means of pipes 7 8, and some suitable liquid, preferably a heavy lubricating oil, is circulated from the. drum through the sleeves by means of a pump 76. The quantity of oil in the storage tank 77v is. sufficiently great toinsure that relatively cooloil is supplied to the sleeves.

By this means the stufling boxes at the outer ends of the sleeves, are completely protected from. destructively high temperatures and since pressure is maintained Within the sleeves at least as high, and preferably slightly higher than the pressure in the stills, all possibility of leakeage of vapor which may be varied quite Widely say, from pounds upward. In any case, the pressure is substantially uniform not only in the respectivestills but throughout the system, including the separators and condenser coil 62 by reason of the open pipe connections between these parts and the. stills.

Under the desired equalized pressure conditions the temperatures are increased so that the bodies of oil in the several stills are maintained at substantially uniform temperatures of sufficient intensity to crack or decompose a portion of the oils therein. The amount of heat supplied to the stills 2 and 3, is regulated by properly setting the dampers 29, 30, 31 and 32 and if the furnace is regulated to supply a suitable heat to these stills as Well as to the last still l of the series, it is evident that heat will be supplied 'to still 1 in a greater quantity and at a considerably higher temperature by reason of its close proximity to the combustion chamber. However, since the relatively cool charging oil and back-trapped condensate are introduced into this still the oil therein is maintained at substantially the a same cracking temperature as that in the other stills, the excess of heat inquantity and temperature supplied to the first still serving tocontinuously charging a suitable amount of fresh oil into the first still and consequently apply heat at all times to the stills below the liquid level of the oil therein.

The cracking process is not completely effected When the temperature of the oil reaches a sufliciently high degree, but the cracking temperature must be maintained for a material period of time in order that the oil may be largely converted. In other Words, as soon as the proper ten'iperature 1S reached cracking commences and continues for a considerable length of time before the body of oil is converted. In our apparatus the necessary time element is provided for, in the passing of the oil in succession through the series of stills, which operate concurrently to convert theoil there- 'in into low boiling products. lVhile a certa'in amount of cracking takes place in the first still, the temperature of the oil being substantially uniform throughout all the stills, agreater proportion of the oil is converted in the succeeding. stills, and consequently the deposit of carbon is comparativel y slight in the first still to which fresh oil is supplied and increases to considerable degree in the other stills and is greatest in the last still.

Attention is particularly directed to the fact that according to our arrangement heat is applied at the highest temperature and in the greatest quantities to the first still Where the slightest amount of carbon is deposited. This is a particularly important feature of our invention and enables us to utilize higher pressures relative to the size and capacity of the apparatus, than have been feasible hitherto.

The vapors continuously produced by the cracking of the oils in the several stills conveniently pass over through'the flow lines 33, 34: and 35, or through the vapor lines 36, 37 and 38, or both, thence through the pipe 58 to the separators, the heavier roducts being condensed. and allowed to ow back by gravity through the pipe 60 to the bottom of the still 1. The lighter products which are in the form of vapors or gases pass over through the pipe 61 and are condensed in the coil 62 and are discharged therefrom in the regulator 8. I

Although We find it convenient and eftective to remove the combined evolved vapors from the last still of the series, it is obvious that the common vapor line 58 may be connected to any of the interconnected stills, or in fact that each ofthestills be provided with its own vapor line to carry off the vapors evolved. In any case, however, the intercommunicating vapor pipes willpreferably be employed between the stills to insure an equalization of pressures.

\Ve, prefer to make the process continuous by continuously charging oil from the pump 9 through the exchanger coil 45 and pipe 47 to-the-stillI 1, the liquid level maintained substantially constant in the stills by continuously or frequently withdrawing condensate-from the regulating drum 8, and residual oils from the stills into the exchanger 10 as hereinafter explained.

- In order to prevent the deposit of carbon which is continuously being produced as a Icy-product of. the cracking or decomposing of the oils'inthe stills, the residue which' settles to the bottom of each still may be drawn off at suitable intervals through the residue manifold 39 to the drum 40.

As already explained, the accumulation of residual oil in the first still is slight and very gradual and it is not desirable to with-:

. is undisturbed by the supply of charging product of a desired oil. This residue is, of course, at a high temperature and its heat is given up to the cold oil which is being charged through the pipe 45 and in this way the oils are warmed or preheated to a certain extent before they are charged.

However, it is evident that the oils which are back trapped through line 60 to the bottom of still 1 and the oils which are charged through the pipe 47 are at a temperature considerably below that required for crack; ing andconsequently, in order to compensate for cooling action of these oils and to maintain the oil in still 1 at the cracking temperature, a very much greater quantity of heat must be supplied to this still than the others.

Another great advantage of our invention will thus be apparent and arises from the fact that the highest temperture heat is applied to the still where the greatest quantity 1s requlred and where, therefore, the rate of heat absorption may safely be-increasecl.

The pressure and temperature in the ap paratus and the rate of supply and discharge are so regulated that only those vapors which are of desired volatility are allowed to pass out through the vapor line 61 into the water condenser, the. heavier fractions being condensed in the separator and returned .to the bottom of the still 1, so that they maybe cracked or decomposed into hghter products. In this way the apparatus is particularly adapted for the con tlnuous production in large quantities of a gravity distillation or quahty, such as gasoline or naphtha or other lightproducts; Q

apparatus of a preferred form and construction, has been illustrated and de- .scribed for the purpose of showing a way in which this invention may be used, but

the inventive thought upon which this application is based, is broader than this illustrative embodiment thereof, and we therefore intend no. limitations other than those imposed by the appended claims.

What we claims is:

1. Apparatus for cracking oils that comprises a plurality of series connected vertical cracking stills, means for heating the stillsto a uniform. cracking temperature arranged to imparta greater quantity of heat to one of the stills than to the others, relatively high and low temperature condensers arranged to successively receive the evolved vapors as they are formed from the stills and means for'returning the condensate from the high temperature, condenser directly to the still receiving the greater heat quantity.

2. Apparatus for cracking oils that comprises a plurality of series connected vertical cracking stills, means for heating the from the high temperature condenser directv ly to the lower end of the still receiving the greater heat quantity and means for charging fresh oil into said still.

3. Apparatus for cracking oils that comprise a series of vertical stills of large capacity, means for heating the stills intermediate their ends to a cracking temperature, arranged to impart a greater quantity of heat to one of the stills than the others, means for charging oils into the said still and for maintaining the liquid level in the stills above the heated intermediate portions thereof.

4. Apparatus for cracking oils that comprises a series of vertical stills of large ca pacity, means for heating the stills intermediate their ends to a cracking temperature arranged to impart a greater quantity of heat to one'of the .stills than the others, means for charging oils into said still and for maintaining the liquid level in the stills above' the heated thereof evolved vapors under pressure and for separating the heavier condensate and returnlng it to said still receiving the greater heat quantity.

intermediate portions" and means for condensing the of heat to one of the stills than the others,

.means for charging oils into the cooler bottom portion of said still receiving the greater heat quantity and for maintaining the liquid level above the heated intermediate portions of all the stills.

the cooler bottom portion of the still re ceiving the higl'ier temperature heat and for maintaining the liquid level above the heated intermediate portions of all the stills,

and means for condensing the evolved vapors under pressure and-returning the heavier condensate to the cooler bottom of the to the fresh oil still receiving the higher temperature heat.-

7. Apparatus for cracking oils that comprises a series of vertical stills of large capacity, means for heating the stills intermediate their ends arranged to impart a greater quantity of heat to one of the stills than the others, means for charging oil into the cooler bottom portion of said still and for maintaining the liquid level above the heated intermediate portions of all the stills, and means for condensing the evolved vapors under pressure andreturning the heavier condensate to the cooler bottom of said still receiving the greater heat quantity.

8. Apparatus for cracking oils that comprises a series of vertical stills of large capacity, means for heating the stills intermediate their ends to a cracking temperature arranged to impart heat to one of the stills at a higher temperature than the others, a charging line connected to the cooler bottom of the high temperature still, a residuum drum connected to receive residue from the bottom of each of the stills and a coil disposed in the residuum drum and forming a part of the charging line where by the heat of the residue is transferred being charged through the coil.

9. Apparatus for cracking oils that comprises a series of vertical stills of large capacity, means for heating the stills intermediate their ends to a cracking temperature arranged to impart'a greater quantity of heat to one of the stills than the others, a charging line connected to the cooler bottom of said still, a residuum drum connected-to receive residue from the bottom of one or moreof the stills and acoil disposed in the residuum drum and forming a part of the charging line whereby the heat. of the residue is transferred to the fresh oil being charged through the coil.

10. Apparatus for cracking oils that com-' prises a furnace having an elevated horitheir ends, a combustion chamber supplying heat to the compartments in succession, and

conduits conducting heat directly from the combustion chamber and adjustable dampers for regulating the discharge of heat from the conduits to the intermediate still compartments.

11. Apparatus for cracking oils that comprises a furnace having an elevated horizontally extending heating chamber, vertical stills disposed in said chamber and extending through the walls thereof above and below, so that heat is applied to the stills intermediate their ends, a combustion chamber supplying heat to the heating chamber at one end,-and separate and independent conduits for regulating the heat supplied'to the several stills.

12. In an apparatus for cracking oils, a plurality of vertically disposed retorts communicating with each other by means of liquid level lines and; vapor equalizer lines, a vapor outlet from one or more of the retort-s for conductingall of the evolved vapors, a separator connected to said vapor outlet having a condensate outlet extending to the lower portion of one of the retorts and also having a vapor out-let, a condenser con-\ nected to said separator vapor outlet, means for charging oil into the retorts, means. for removing residuum from the retorts, and means for regulating pressure in the apparatus.

13. In an apparatus for cracking oils, a plurality of vertical retorts, vapor communications between said retorts, means whereby the oil flows from one retort to the others in succession, a vapor outlet from one or more of the retorts for conducting all of the evolved vapors, a separator connected to said vapor outlet, means for conducting condensate fromthe separator to the lower portion of one of the retorts, means for removing the vapors from the separator and condensing them, means disposed within each retort for removing carbon from the torts below said overflow pipes adapted to impart most heat to the first retort of the pipe connections between the vapor spaces,"

- of said retorts, means for heatingsaid reseries, means. for suzpplying oil under pressure to the first retort of the series and causin it to pass progressively through the plurality of vertically disposed retort-s, overflow pipes connecting said retorts in'series,

pipe connections between the vapor spaces of said retorts, means for heating said retorts below said overflow pipes adapted to impart most 'heat to the first retort of the series, means for supplying oil under pressure to the first retort of the series and causing it to pass progressively through the other retorts, means for drawin they are evolved from the retorts, means for separating out the unconverted portions of said vapors and means for condensing the remainder.

16. In an apparatus for cracking oils, a

plurality of vertically disposed retorts, overflow pipes connecting said retorts in series, pipe connections between the vapor spaces of said retorts, means for heating said retorts below said overflow pipes adapted to impart most heat to the first retort of the series, means for supplying oil under pressure to the first retort of the series and cansing it to pass progressively through the other retorts, means for drawing off the vapors as they are evolved from theretorts, means for separating outthe unconverted portions of said vapors and returning them to the ,bottom of the first retort, for treatment, and means for condensing the remaining vapors under. pressure.

17. In an apparatus for cracking oils, a

series of vertical retorts, oil pipe connec tions between said'retorts, means for heating said retorts adapted to impart most heat to th first retort of the series, means for supplying oil under pressure to the first retort of the series, means for drawing oft the vapors produced, means for separatingout th inuconverted portion of said ,vapors, means for returning said unconverted portion to one of said retort-s and means for condensing the remainderof the vapors.

l -18. -In an apparatus for cracking oils, a

. series of vertical retorts, oil pipe connections b'etweensaid retorts, means for heating said retorts adapted to impart most heat to the first retort of the series, means for supplying oil under pressure to the first retort, means for drawing off the vapors ,produced from the-retort at the other end of the series, meansforseparating out the unconverted portion of said vapors, means for condensing the off the vapors as.

for returning said unconverted portion to one of said retorts and means for condensing the remainder of the-vapors.

1%). In an apparatus for cracking oils, a plurality of retorts each adapted to'lcontain a considerable volume of Oil, liquid ipe connections between said retorts, m ans for imparting most heat to the first. retort in the. series, means for supplying oil under pressure continuously to the first retort, means for drawing off the vapors from said retorts and separating the unconverted portion from the converted portion, means for returning the unconverted portion to one of said retorts, means for condensing the converted vapors and means for maintaining substantially uniform vaporv pressure throughout the system.

20. In an apparatus for cracking oi's, a plurality of tubular vertically disposed retorts connected in series at theirupper ends, a single furnace for heating said retorts to a. cracking temperature'abov'e the extreme lower ends thereof and for supplying the most heat to the retort at one end of the series, mechanical means insaid retorts for preventing the accumulation of carbon on the interior surfaces and permitting it to be precipitated, means for collecting and drawing ofi residuum including the precipitated carbon below the heating. zone, means for suppiying oil under. pressure to the retort receiving the most heat and, for causing the oil to flow from one retort to another and means for drawing off and condensing thevapors produced. 21. In an apparatus for cracking oils, a plurality of vertically disposed retorts, overflow pipes connecting said retorts in series, pipe connections between the vapor spaces of said retorts, means for heating said retorts below said overflow pipes adapted to impart most heat to the first retort of the series, means for supplying oil under pressure to the first retort of the series and causing it to pass. progressively through the'other retort, means for drawing oil the. vapors as they are formed from theretorts, means for separating out the unconverted portions ofsaid vapors, means for returning said unconverted portions to the first retort, v

and means'for condensing the remainder.

22. In an apparatus for cracking oils, a

ranged to impart a greater quantityof heat I -nieans i'or withdrawing residue from a still or stills in which the greater conversion takes place, said still or stills being removed from the one into which the oil is charged, means for heating the oil in the several stills to a substantially uniform cracking temperature arranged to impart a greater quantity of heat to the stillbeing charged to compensate for the cooling action of the charg ing'oil, and means for'withdrawing the evolved vapors from the stills.

24. In an apparatus for cracking oils, a series of stills means for charging oil under pressure into one of the st'ills and causing it .to flow from one still to another to maintain substantially constant levels therein,

means for heating the oil in the several stills to a substantially uniform cracking temperature, means for withdrawing the evolved vapors from each of the stills, and means for separating out the unconverted portions of the vapors fronr'each still and returning them to the still being charged, said heating means being arranged to impart a greater quantity of heat to the still receiving the charging oil and condensate to compensate for the cooling action thereof.

25. In apparatus for cracking oils under pressure, a pluralityof vertically disposed tubular stills, located in side-by-side proximity, short" horizontal flow line pipesdirectly connecting the .several adjacent stills "to-permit the oil to pass from one still to another and maintain uniform oil levels therein, means for charging oil into one of the end stills of the series and causing it to flow successively through said stills, means for heating-the several stills below' the oil level to severally maintain the stills at a substantially uniform cracking temperature, and short horizontal vapor linepipes directly connecting the vapor spaces'ot the ad- ]acent stills at points above the flow line 'pipes for equalizing the vapor pressures and assisting in maintaining constant oil levels in the several stills.

26. In apparatus for cracking oils under pressure, a plurality of vertically disposed stills located in side by side proximity, short horizontal flow line pipes directly connecting the severa adjacent stills in series to permit the oil to flow from one still to another and maintain uniform oil levels therein, means for charging oil into one of the end stills of the series and causing it to flow successively through said stills, means for maintaining the several stills at a substantially uniform cracking ten'iperature, short horizontal vapor line pipes directly connecting the vapor spaces of the adjacent stills at points above the [low line pipes for equalizing the vapor pressures and assisting in maintaining constant oil levels in the several stills, means for preliu'iinarily condensing the heavier constituents of-the vapors evolved in the several stills and means for returning all of the condensate to the still being charged.

27. Inapparatus for cracking oils under pressure, a plurality of vertically disposed stills locatedin side by side proximity, short horizontal flow line pipes directly connecting the several adjacent stills in series to permit the oil to flow from one still to another and maintain uniform oil levels therein, means for charging oil into one of the end stills of the series and'causiug it to flow successively through said stills. means {or maintaining the several stills at. a substantially uniform cracking temperature, short horizontal vapor line pipes directly connecting the vapor spaces of the adjacent stills at points above the flow line pipes tor equalizing'the vapor pressures and assisting, in maintaining constant oil levels in the several stills,'and heat exchange means sociated with the charging line and bottom of the last still of the series for preheating the charging-oil by means of the residual oil from the last still.

In Witness whereof, I have hereunto set my hand this 25th day of June. 1919.

a RALPH C. HOLMES. In Witness whereof, I'have hereunto set my hand this 19th day of June, 1919.

FREDERICK T. MANLEY.

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