US2119391A - Method for cracking oils in vapor phase - Google Patents

Description

METHOD FOR CRACKING OILS IN VAPOR PHASE Original Filed Dec. 1, 1928 5 Sheets-Sheet 1 m I l H II INVENTOR PERCY C. KEITHJR.

ATTORNEY Sheeta-Sheet 2 P. C. KEITH, JR

Original Filed Dec. 1, 1928 METHOD FOR CRACKING OILS IN VAPOR PHASE May 31, 13..

INVENTOR PERCY C. KEITHq/IP.

max Ao&l W

ATTORNEY P. c. KEITH, JR 2,119,331

METHOD FOR CRACKING OILS IN VAPOR PHASE Original Filed Dec. 1, 1928 5 Skew-Sheet 3 w? A Q Q Q O OO OOYOO INVENTOR PERCY C. lfE/THJR.

ATTORN EY Patented May 31, 1938 METHOD son CRACKINGOILS 1N VAPOR.

PHASE Percy Keith, Jr., Peapack, N. J., assignor to Gasoline Products Company,

Inc., Newark,

N. J., a corporation of Delaware Original application November 9,1933, Serial No.

697,283, which in turn is a divisiono'f Serial" No. 323,005, December 1, 1928. Divided and this application December 6, 1935, Serial No.

This invention relates to the pyrogenesis of petroleum oils and is a division of application Serial No. 697,283, filed November 9, 1933, which is in turn a division of application Serial No. 323,005,

filed December 1, 1928 which'has now'matured as Patent 1,972,149. The invention Will be fully' explained in the following. description and accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a preferred embodiment of apparatus in which my process may be carried out;

Fig. 2 is a diagrammatic representation of an alternative form;

Fig. 3 is a vertical section through a form of apparatus which may be employed in conjunction with my process;

7 Fig. 4 is a cross section taken on the line 4 -4 of Fig. 3; and I v Fig. 5 is a side elevation with parts in section of a form of apparatus employed in conjunction with my process and with the apparatus shown in Figs. 3 and l.

p The pyrogenesis of petroleum oils forproduction of oils of lower boiling point is carried out by heating crude petroleum, or such of its distillates as may economically be utilized in this manner, to cracking temperatures With or without pressure. The fraction intermediate between kerosene and lubricating oils known as gas oil is frequently utilized for this purpose because of its lesser market value, although kerosene, lubricating oil fractions and fuel oils are also employed at times. The fractions so employed are composed of an extended range of compounds as indicated by the range of molecular weights and boiling points. The conglomerate of compounds is subjected to cracking conditions until a certain quantity of material falling within a desired boiling range is produced. Simultaneously with the formation of this product, or products, materials are produced which do not fall within the desired range, for example, when cracking to produce a substantial proportion of gasoline which is a product composed of a large variety of different hydrocarbon compounds, there is simultaneous- 1y produced a quantity of tarry and coky materials. Some elements of a conglomerate stock, for reasons which will be given more fully later, require cracking to a degree less than others, and because of the fact that the stock as a whole is subjected to the same conditions the cracking reaction will be carried too far in the case of some of the constituents of the stock in order to secure the desired quantity of material of a predetermined boiling point range and with the re- 7 Claims. (01. l9649) sultant formation of compounds which do not fall within the said range or which are deleterious to the operatiorigfor reasons which will be more'fully pointed out. The different cracking rates of some of the constituents of the stock tend to accentuate the condition referred to above. I

have discovered that a fundamental increase in the efficiency of the cracking process may be obtained by separating the cracking stock into a conditions have been established by such tests as to yield the same quantity of desired end products from a series'of segregated fractions as is obtainable from cracking conglomerate stock the concomitant loss in gas and/or tarry or coky materials is diminished, or for an equivalent loss the'yield of the desired end products is relatively increase-d.

My process is applicable generally in the pyrogenesis of petroleum oils to produce lower boiling point oils, as, for example, cracking to produce either gas, gasoline, kerosene, gas oil or lubricating oil from stocks of respectively higher boiling point.

In the ideal embodiment of my process the stock is segregated into a plurality of charging stocks of such character that under the conditions of heat, time, and pressure imposed cracking of the various individual compounds composing the fraction Will take place at substantially the same rate. However, the limitations imposed by practice require segregation into a smaller number of stocks than in the ideal method and I'- therefore segregate into an appropriate number of charging stocks and subject each of such stocks to optimum conditions for the particular segregate.

' I have discovered that in high molecular weight hydrocarbons of straight chain structure the initial scission on cracking frequently occurs adjacent the center of themole'cular chain. In one-application in my process I aim to obtain by cracking the-products of first scission' of the molecule, and I therefore prepare charging stocks which upon their initial scission yield products which fall within the range of physical characteristics of the material desired to be obtained. Thus in the case of gasoline I may proceed by dividing my charging stock into a number of fractions each of which has a molecular weight substantially twice that of a constituent of gasoline, then by cracking the stocks to the extent of one scission I obtain a number of products whose molecular weights fall within the range of molecular weights of the constituents of gasoline. In cases in which the original charging stock contains constituents so heavy that the products of their initial scission will not fall within the range of physical characteristics of the desired products, these constituents may be separated from the remainder of the original charging stock, as by distillation, and treated in one of two ways; i. e. (1) by segregating them from one another as by distillation into individual fractions and then subjecting each segregated fraction to such conditions as will produce from each segregated fraction a product which will yield, upon refractionation, products which may be decomposed as above into gasoline constituents. This procedure enables me to separate unsaturated constituents to a degree and to then subject such fractions to appropriate treatment. (2) In view of the limitations of practice I may subject the entire heavier conglomerate out to cracking conditions best suited to obtain the maximum yield of products which can be segregated into charging stocks of the nature described and cracked in the manner above set forth so as to yield gasoline constituents.

Alternatively, I may prepare a number of fractions of charging stock, including some which cannot be converted by a single scission adjacent the center of the molecule into products falling within the desired range, and subject each such fraction to the degree of time, temperature and pressure necessary to its conversion into products of the desired boiling point range. I may, however, in such cases crack each such fraction to yield a cracked material having a position with respect to the average molecular weight of the series of cracked materials obtained which corresponds to the position held by the parent fraction with respect to the other members of the parent series.

In addition to the foregoing I may make a further separation based on chemical characteristics. Thus, I may separate the original cracking stock into two fractions, one containing a preponderance of saturates and the other containing a preponderance of aromatics and unsaturates, as, for example, by the application of selective treatment with liquid sulphur dioxide. These individual products may thereafter be separated each into products of different boiling point ranges to be separately cracked. as hereinabove described. Alternatively, the fractions of separate boiling point ranges may be first prepared and each thereafter separated into fractions of different chemical characteristics, as, for example, by treatment with liquid sulphur dioxide.

In any event, where several fractions of the original charging stock are prepared, as by distillation, the decomposition products from the several fractions will preferably have average molecular weights whose ratio to each other is approximately the same as the ratio of molecular weights of the parent fractions. For example, in cracking gas oil to produce gasoline the gas oil may be segregated by fractionation into a series of several cuts, each of which has of constituents boiling within a different 50 F. range. The average molecular weights of these fractions are in some ratio to their boiling points, the fraction of relatively high boiling point having the highest molecular weight. In cracking these individual fractions conditions are adjusted to produce a series of cracked products having the same general relationship. Thus, the fractions of lower average molecular weight will have been cracked to produce a cracked material of lower average molecular weight than will have been produced from the parent fractions of relatively higher molecular weight. In this way the lighter constituents of the end product gasoline will have been predominantly produced from those fractions of the cracking stock of lower molecular weight, whereas those fractions of the gasoline of relatively higher molecular weight will have been predominantly produced from the fractions of cracking stock of relatively higher molecular Weight.

I achieve a number of distinct advantages by this process, for example, the cracking is carried out on each of the individual cuts under conditions which may be predetermined in view of the rate of dissociation of the particular stock to produce the optimum conversion, while the total number of dissociations or the degree of pyrogenesis to produce any given yield of end product is relatively less than would be necessary with the indiscriminate cracking of a conglomerate stock, and thus the concomitant losses in gas and/ or tar or coke are greatly diminished. A further distinct advantage is that polymerization to form products of a greater molecular weight than the parent stock does not occur to the same degree as when cracking a conglomerate stock. It is unnecessary to carry the cracking reaction on some of the constituents of the original stock to the point of forming polymers of a character deleterious to the operation of the process. Thus, in operating upon a conglomerate stock in the manner used at the present time it may be unavoidable to carry the cracking reaction to the point of third, fourth, fifth or higher scission in the case of some of the constituents of the initial charge and to the scission of polymerized prod-' ucts formed therefrom in order to obtain the desired yield of the end product, whereas in my process I prefer to confine the reaction to the formation of the products of scission of a lower order. The scissions of higher order result in an increase in the products of decomposition, or polymerization, which contributes to the formation of the products known as tar and coke.

One of the preferred methods of operating my process is to crack each individual cut of the cracking stock to produce a cracked material having an average molecular weight substantially half of that of the parent out, for example, ranging from 75 to 25% of the average molecular weight of the parent cut. In this way, toan ex- "40 be given to the formation of fixed gas.

View of the particular =stockor in View of the particular characteristics of .theproduct desired, as, for example, to produce a gasoline having a certain definite proportion of material boiling within a certain predetermined range.

The particular method of cracking the individual stocks may be any one of the methods at present employed or hereafter developed. I may, for example, crack these individual cuts in either liquid or vapor phase or in, a combination of the two and under any degree of pressure. In a preferred embodiment of my invention, however, I subject the individual cuts to a vapor phase cracking of relatively short duration ranging, for example, from the order of one second up to times of the order of five minutes, at temperatures which may range between 750 and 1500 F. and at pressures which may range from a few atmospheres to partialvacuum. In this way I am enabled to effect a carefully controlled dissociation of the individual stocks and accurately control the amount of dissociation applied to each of these stocks so that a large proportion of the individual cuts is subjected to a single dissocia- -tion, thereby automatically throwing it into the boiling point range of the desired end product with a minimum production of undesired products. -A further advantage of this procedure that I have discovered is that owing to the relatively short times involved, the temperature range in which cracking is effected and the low specific volume of the gases in the cracking zone, the tendency to polymerization, or reformation of heavier products, is inhibitedthe efficiency of the operation is increased and I am enabled to diminish the formation of tar and/or coke.

In determining the conditions under which individual cuts of the initial conglomerate charging stock are to be cracked consideration must I believe that the theory at present held that fixedgas produced by a cracking operation is substantial- 1y produced by the cracking of tar to coke is mistaken and that in fact such fixed gas is substantially produced by the cracking of constituentsfalling within the gasoline range. I there- 'fore so select the conditions of operation in the preferred form of my process as to prevent the cracking of such gasoline constituents, as, for example, by removing them from the zone of reaction as quickly as possible. In this respect my process is radically different from those at present practiced in which the products falling within the gasoline range, or some of them, are held in the zone of reaction-for considerable periods of time. In the processes in use at the present time these products which are extant in the zone of reaction are either retained there by reason of the nature'of the apparatus which does not permit of their evacuation immediately upon formation, or are retained there by reason of their so lution in liquid since they are in contact with large bodies of heavier liquid content in the system. This eifeot is considerably aggravated in many processes by the use of pressure. It will be noted that in my improved process because of the nature of the apparatus and the charging stock used there is substantially no liquid present in the system at anytime and the apparatus is such that products falling within the gasoline range are removed substantially as quickly as formed.

V The selection of the temperature bears a definite relation to the time element involved in the operationof the apparatus, "the more rapid the boiler sections at intermediate points.

evacuation of the products from the zone'of reaction the higher the temperature whichmay be used, suflicient time being provided to permit the reaction to take place. The effect'of removing the products from the zone of reaction is to arrest the reaction, and it may be desirable to cool immediately the products removed to prevent further reaction by reason of the contained heat.

My process will now be described with specific reference to the apparatus diagrammatically indicated in the drawings. Referring specifically to Fig. 1 a cracking stock such as gas oil is passed through the tubular heater l, surrounded by the refractory setting 2, and heated by means of a burner such as 3 communicating with the setting through the port A. Any alternative means of heating this stock to a temperature of complete or partial vaporization may be employed, such as a heat exchanger or a still. The partly vaporized cracking stock is delivered through the pipe 5 into the fractionating column 6. This column may be suitably insulated and provided with-a number of rectifying devices suchas the customary transverse partitions carrying down flow pipes and vapor contacting devices, not shown.

The design of this column is not a feature of the invention and any column or corresponding device which is appropriately designed to separate petroleum oil into a number of fractions by rectification may be alternatively employed. Provision is made for taking off an overhead cut in vapor phase from the column by means of the vapor outlet 1 and a number of side cuts (ordinarily in liquid phase, but which may be in the vapor phase) from the side outlets 8, 9, ill, I I, I2,

to the top or intermediate points and with aheatingcoil adjacent to the bottom or withremodifications will be incorporated to the degree necessary to obtain the desired separation of the individual fractions. outlets l to l5, inclusive, are, in View of the necessities of practice, relatively close out fractions having, for example, 90% of constituents boiling within a 50 F. range, and while these ranges to some extent overlap, the cuts repre-' sent a complete series of charging stocks, each of which approaches, within the limits of commercial practicability, an ideal charging stock as above defined. This series of cuts has a range of boiling points and corresponding molecular weights which increases throughout the series. These various cuts are passed to individual crackers through control apparatuses Hi to 23 inclusive which will be hereinafter more fully described, and from the control apparatuses the cuts pass respectively to the individual cracking apparatuses which have been diagrammatically indicated by the numerals 24 to 3|, inclusive. I may employ any form of cracking apparatus, such as stills which may be adapted to operate under pressure or tubular crackers with or without reaction chambers or tubular stills operated in the vapor phase. In any event, the cracking is carried out under conditions which may be ,ascertained in advance by tests to besuited to the The cuts taken off through All such individual out. Preferably, when operating to make gasoline the individual cuts are cracked to such an extent that the average molecular weight of the cracked material produced from an individual cut ranges from 25 to of that of the parent fraction. I obtain in this way a series of cracked products with serially larger molecular weights corresponding in order to the molecular weights of the original fractions of cracking stock. The desired end product is therefore obtained by the selective cracking of preferred stocks and with less actual molecular disruptions and recombinations than would be incidental to handling a cracking stock as a conglomerate. For convenience all of the cracked materials discharged from the crackers 24 to 3|, inclusive, through outlets 32 to 39, inclusive, may be conducted by means of the manifold 40 into the rectifying column 4| which is of suitable construction to permit the separation thereof into the desired end product, as, for example, gasoline which may be taken off in vapor phase, if desired, through the outlet 42, and a number of side cuts taken off through the side outlets 43 to 50, inclusive. These side cuts taken off through the outlets 43 to 59, inclusive, are preferably fractionated so that of the constituents of each cut boil within a range of 50 F. and will be hereinafter more fully considered. The column 6 may be operated under any pressure at which appropriate fractionation may be secured, and for purposes of heat economy, is preferably operated under a pressure in excess of atmospheric, say, for example, a pressure not exceeding pounds per square inch. I achieve in this way the additional advantage that the cuts taken off from the outlets 8 to l5, inclusive, may, in this manner, be supplied by virtue of their initial pressure to the respective cracking apparatuses 24 to 3|, inclusive. The column 4| may be operated under pressure preferably less than that obtaining in column 6 so that the progress of material through the entire system is effected by virtue of the initial pressure obtaining in column 6. The side cuts from column 5 fall within the gas oil range and are such as may, to a large extent, be converted into constituents boiling within the gasoline range, particularly where the cracking is so controlled as to produce molecular disruptions occurring at or near the mid-point of the molecule.

The plant illustrated is only an approach to the ideal and some polymerization may occur to products whose molecular weight is higher than those taken off through the side outlets B to l5, inclusive, of column 6. Such polymerized products are preferably separately processed as outlined in the preferred manner of processing the cut withdrawn through l5a, but for commercial reasons may be removed from column 4| through the side outlets 5| and diverted through pipe |5a to pipe |5b to be combined with and processed with the products withdrawn from column 6 through outlet l5a.

The materials delivered through the pipe |5b represent materials which cannot be converted into constituents of the gasoline series by a single disruption adjacent the center of the molecule and, while I may segregate these bottoms by fractionation in the manner described and thereafter crack selectively the individual components and then refractionate and then recrack the individual components falling within the gas oil range to gasoline range, I find it suflicient to subject these components to a mild cracking by forcing the same through the tubular heater 52 surrounded, for example, by the refractory setting 53 heated through the port 54 by means of the burner 55. The cracking effected in the heater 52 is not intended to convert the stock treated therein predominantly to gasoline, but rather to convert a substantial proportion of the stock into stocks having molecular weights approximating those removed from column 6 through the side outlets 8 to l5, inclusive. There is, of course, the incidental production of a small quantity of gasoline where the operation is not accurately controlled. The stock cracked in this manner is delivered through the outlet 56 into the rectifying column 51, which may be of any suitable construction, in which it is fractionated to form an overhead distillate, for example, taken off through the outlet 58 which may consist of gasoline and a series of intermediate cuts taken off through the side outlets 59 to 66, inclusive, which are preferably cut to have 90% constituents boiling within a range of 50 F. These constituents boiling within the kerosene and gas oil ranges are such as may to a large extent be converted into constituents of gasoline by a single disruption occurring at or adjacent the mid-point of the individual molecule. Any heavy ends may be taken off through the side outlet 68, and, while they are preferably handled by separation and cracking of the individual segregates, as above outlined, I find it suflicient in commercial practice to carry these compounds by means of the pipe 69 back into the inlet side of the tubular heater 50 for a second cracking operation. Any tarry products collecting in the base of the towers 4|, 5'! and 9| are withdrawn by means of bottom outlets 50a, 10 and Illa, and diverted from the system. The products obtained from the side outlets 59 and 66 inclusive, represent products which have been cracked and separated into products having .a molecular weight approximating those removed from the side outlets on column 6. As segregates they are passed through the control apparatuses diagrammatically indicated by the numerals H to 18, inclusive, discharging into cracking apparatuses fll to 88,inclusive, which may be of any suitable construction, although they are preferably of the type hereinafter described. The cuts obtained from tower 4| from the side outlets 43 to 50, inclusive, are cuts which have been subjected to cracking and subsequent fractionation. These preferably will be cracked in the same manner as cuts 8 to I5, inclusive, derived from tower 6, but for commercial reasons they may be blended with cuts 59 to 66, inclusive, and passed through the crackers 8| to 88, inclusive. In the ideal embodiment of my process all polymerized cuts, even of the same molecular weight as the cuts 8 to l5, inclusive, will be treated separately. This is desirable for two reasons, the first being that the dissociation speed of these polymers may be different than those of 8 to l5, inclusive, and further, because I have discovered that the presence of polymerized cuts in contact with undecomposed cuts will enhance the formation of tar.

The cracking accomplished in these cracking apparatuses is conducted under conditions ascertained by test or experience to be best for the particular cuts and may be so adjusted as to produce cracked material having an average molecular weight ranging from 25 to 75% of the average molecular weight of the cut from which the cracked material is derived. In this way a series of cracked materials of serially larger average terial. The cuts which have been cracked through apparatuses 8| to 88, inclusive, may be diverted through the common flow line 98 into the rectifying column -9I which may be of any suitable design. From this rectifying column gasolinejmay'be removed through outlet 92.

Fromthe side of column 9| a series of cuts, shown ,as 93 to 88a, inclusive, may be withdrawn and because of their small quantity may be diverted through crackers 8| to 88, inclusive. It will be understood that if the pressure in, or the location of, the tower 9I is not such as to cause liquid to flow through the lines 93 to 99a, inclusive, into the lines leading to the crackers 8I to 88, inclusive, suitable pumps and check valves or other well-known apparatus may be employed for effecting this purpose.

- The cut I08 may be diverted back to the tubular heater as in the case of cut 5| as is the case likewise with cut 68 from column 51. Thecut 68 differs from cuts I 00 and 5| in that it represents to a large extent products which have not been converted into those ofthe desired molecular weight, whereas cuts 5I and I00 are substantially products which have been formed by polymerization since the plant shown is only an approach to the ideal. For the same reason: as before outlined, tarry matter may be removed through line lIlUa.

Referring specifically to Fig. 2 which is the diagrammatic elevation of apparatus'adapted to processing crude oil or other petroleum oils containing constituents of higher boiling point than gasoline. The charging stock is passed through the tubular heater I surrounded by the suitable refractory setting 2, heated by means of the burner diagrammatically indicated at 3, communicating with the setting through the port 4. The crude oil may be heated in heater I to a temperature of substantially complete or partial vaporization and is thereafter discharged through pipe 5 into the rectifying column 6. In the event that it is desired to produce a quantity of gas oil or cracking material in addition to that normally occurring from the crude, conditions in the tubular heater I may be adjusted toproduce a cracking effect, preferably of a moderate char a'cter, to convert heavier materials to a considerable extent into-,,products such as kerosene and gas oil, which products are in turn susceptible to being converted into gasoline by a minimum number ofmolecular disruptions. This operation is not, of course, conducted under the ideal cracking conditions which I havehereinabove described, but is utilized :only as a matter of expediency. The rectifyingcolumn 6 maybe of any suitable type. Provision may, for example, be made-to take an overhead cut of gasoline by means of the vapor outlet I and a series of side cuts from the outlets 8 to I5, inclusive, and H5, to H8, inclusive. It wi1l,.of course, be understood that any alternativenumbercof side cuts may be employed, the design in any case being determined by the character of the stock .to be treated and the number of. side cuts which it is desired to make. vAssuming that cuts such as kerosene and gas oil are taken off from the side outlets 8 to I5, inclusive, these are preferably fairly closely fractionated so that 90% of the total constituents of each cut will boil Within a range of say 50 F. Products evolved from the tower 6 which are heavier than gas oil, or so heavy that they cannot be converted into gasoline to a large extent by a single disrup tion adjacent the mid-portion of the molecule, may be takenoff from the column 6 by means of the side outlets II5. to H8, inclusive, combined in the manifold 5a and thereafter. treated in the same manner as the products obtained from the outlet 55a of Fig. 1. Any heavy residue resulting during the operation may be diverted from the system by means of the outlet I20.

The several side cuts taken from column 8 through the side outlets 8 to I5, inclusive, may be handled in the identical manner as the side cuts taken from column 6 of Fig. 1 through the side outlets 8 to I 5, inclusive, and inasmuch as the product taken from column 6 through the side outlets H5 to H6, inclusive, is handled in the identical manner as the products taken from the column 5 in Fig. 1 through the pipe I5a, the subsequent progress of these materials may be ascertained by reference to the previous description relating to Fig. l and need not be more fully illustrated or described. Referring specifically to Figs. 3 and 4, the form of cracking apparatus which I prefer to employ for cracking the individual closely fractionated cuts which have been described from, time to time is detailed, which apparatus has been designated for example by numerals 24 to 3I, inclusive, and 8| to 88, inclusive. This apparatus consists of a refractory setting I56 andmay be heated through the port I5I by means of. the burner diagrammatically indicated as I52. A baffle wall such as I53 may be provided and a down draft section I54 communicating with a stack I55. The tubular heaters I56 and I51 in the down draft section may comprise a number of tubes through which oil may circulate by means of inlets and outlets I58, I59, I68,

IBI, respectively, and sections of this character may be utilized for heating or cracking the cuts of relatively wide boiling point corresponding to the operations which have been previously described as conducted in tubular heaters I. and 52. The walls of the setting I50 are preferably lined with a number of relatively short tubular heaters I62 to I'll, inclusive, each of which is adapted to the circulation of hydrocarbon materials by means of inlets and outlets such as Ififia and I65b, etc. These sections are relatively short being composed of only a few lengths of tubing adapted to be heated to a large extent by the radiant products of combustion evolved. In operation I prefer to maintain these heaters I62 to III, inelusive, at temperatures intermediate between 750 and 1500 F. and to conduct cracking operations therein at relatively low pressures ranging from a few atmospheres to subatmospheric. The total time of heating of the hydrocarbon gases at these temperatures is preferably limited to a period ranging from one second up to the order of five minutes, which conditions I find to favor a symmetrical dissociation which isamenable to control with a simultaneous formation of a relatively small quantity of the products of re-association or polymerization. In vapor phase cracking apparatus, such as that shown, I may admix with the petroleum oil undergoing cracking in the vapor phase a material to limit the formation of polymers. I have discovered the formation of deleteriously affect the cracking reaction, will be hereinafter referred to as diluent gases. The cracked and heated hydrocarbons delivered through the respective outlets of coils 862 to ill, inclusive, are preferably quenched by cooling them immediately either by contact with a liquid or a vapor at temperature below cracking, for example, by contact with steam or by conducting them against relatively cool metal surfaces, for example, through a relatively cool large eX- changer. I am thus enabled to control the extent to which the reaction is permitted to proceed and thus determine the constitution of the product. The combination, rectification and subsequent disposition of these products has been hereinabove described.

Referring specifically to Fig. 5, this is a diagrammatic representation of control apparatus which has been indicated by the numerals IE to 23, inclusive, and H to '18, inclusive. This apparatus comprises the side outlet, such as 8, carrying a fraction from any one of the rectifying columns hereinabove described, discharging into cracking apparatus such as diagrammatically indicated by the numeral 26. A cooling coil such as 200 is connected into the outlet 8, preferably adjacent the under side thereof. This coil, controlled by the valve 29 I, discharges into the pipe 8 at a point below its origin. The coil 2% may be surrounded by a receptacle, such as 262, through which a cooling fluid is circulated by means of inlets and outlets, such as 203 and 264, respectively, so that any petroleum oil, either in liquid or vapor form, passing through the coil 200 is automatically cooled and discharged in cooled condition back into pipe 8. By manipulation of the valve 21!! the amount of cooled material which is reintroduced into the pipe 8 may be carefully controlled, and in this way the temperature of the products passing into the cracking apparatus 24 may be controlled, and hence the temperature of the products discharged from the cracking apparatus 24 may be correspondingly controlled. The form of apparatus which I have just described is particularly adapted to the close control of vapor phase cracking, which I prefer to conduct in apparatus such as 24 and to which I prefer to subject the various fractions into which I separate my original cracking stock.

I claim:

1. The process of treating hydrocarbon oil which comprises introducing highly heated oil into a separating zone wherein separation of the oil into vapors and liquid residue occurs as a result of its contained heat, fractionating in a first fractionating zone vapors separated in said first separating zone to form an intermediate condensate, removing fractionated vapors from said first fractionating zone and condensing them as a desired product, subjecting such intermediate condensate to cracking temperature to effect conversion into lower boiling products, fractionating resultant products of said cracking in a second fractionating zone to form an intermediate condensate, withdrawing said liquid residue from said separating zone and passing it through a heating zone in a stream of restricted crosssectional area, whereby said oil is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a second separating zone wherein vapors separate from residue, fractionating in a third fractionating zone vapors separated in said second separating zone to form an intermediate condensate, removing the fractionated vapors and condensing them as a desired product, mixing intermediate condensate removed from said second fractionating zone with intermediate condensate removed from said third fractionating zone and passing the mixture so obtained through a second heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a separating zone wherein vapors separate from residue, and fractionating vapors so obtained to form an additional quantity of final desired products.

2. The process of treating hydrocarbon oil which comprises introducing highly heated oil into a first separating zone to cause separation thereof into vapors and a liquid residue, fractionating in a first fractionating zone vapors separated in said first separating zone to form an intermediate condensate, removing vapors from said first fractionating zone and condensing them as a final desired product, removing said liquid residue and passing it through a first heating zone wherein it is raised to a cracking tempera ture and subjected to conversion, introducing the resulting cracked products into a second separating zone wherein separation thereof into vapors and a liquid residue occurs, removing said liquid residue last mentioned, fractionating said vapors in a second fractionating zone to form an intermediate condensate, passing the last named in termediate condensate through a second heating zone wherein it is raised to a cracking tem perature and subjected to conversion, introducing the resulting cracked products into a third separating zone wherein vapors separate from liquid residue, fractionating said vapors lastmentioned in a third fractionating zone to form an intermediate condensate and a relativeiy heavy condensate, combining said heavy condensate with the liquid residue removed from said first separating zone for passage through said first heating zone, and removing fractionated vapors from said third fractionating zone and condensing them to form an additional quantity of final desired products.

3. The process of treating hydrocarbon oil which comprises passing relatively heavy oil through a first heating zone, introducing resulting highly heated oil into a first separating zone wherein vapors separate from liquid residue, fractionating vapors so obtained in a first fractionating zone to form an intermediate condensate, removing the fractionated vapors and condensing them as a final desired product, removing liquid residue from said first separating zone and passing it through a second heating zone in a stream of restricted cross-sectional area, wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a second separating zone wherein vapors separate from residue, fractionating resulting vapors in a second fractionating zone, removing the fractionated vapors and condensing them as a desired pro-duct, removing intermediate condensate collected in said first fractionating zone and passing it through a third heating zone in a stream of restricted crosssectional area wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a third separating zone wherein vapors separate from residue, fractionating vapors so obtained in a third fractionating zone to form a relatively heavy condensate, removing fractionated vapors from said third fractionating zone and condensing them as a desired product, and removing heavy condensate from said third fractionating zone and combining it with liquid residue removed from said first separating zone for passage through said second heating zone.

l. A process in accordance with claim 3 wherein an intermediate condensate is formed in both the said second fractionating zone and said third fractionating zone, said condensates are removed and passed as a mixture through a fourth heating zone wherein the mixture is raised to a cracking temperature and subjected to conversion, the resulting cracked products are introduced into a fourth separating zone wherein vapors separate from residue, and vapors so obtained are fractionated to form an additional quantity of final desired products.

5. The process of treating hydrocarbon oil which comprises passing crude oil through a first heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a first separating zone wherein vapors separate from liquid residue, fractionating vapors so obtained in said first fractionating zone to forman intermediate condensate, removing the fractionated vapors and condensing them to form a final desired product, removing liquid residue from said first separating zone and passing it through a second heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a second separating zone wherein vapors separate from residue, fractionating vapors so obtained in a second fractionating zone to form an intermediate condensate and a heavier condensate, removing the fractionated vapors from said second fractionating zone and condensing them to form an additional quality of final desired products, removing said heavier condensate and combining it with the liquid residue removed from said first separating zone for passage through said second heating zone, removing intermediate condensate from said first fractionating zone and passing it through a third heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the re sulting cracked products into a third separating zone wherein vapors separate from residue, fractionating vapors so obtained in a third fractionating zone to form intermediate condensate, removing fractionated vapors from said third fractionating zone and condensing them to form an additional quantity of final desired products, re-

moving intermediate condensate from said second and from said third fractionating zones and passing them as a mixture through a fourth heating zone wherein the mixture is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a fourth separating zone wherein vapors separate from residue, and fractionating vapors so obtained to form an additional quantity of final desired products.

6. The process of treating hydrocarbon oil which comprises introducing highly heated oil into a first separating zone to cause separation thereof into vapors and a liquid residue, fractionating in a first fractionating zone vapors separated in said first separating zone to form a final desired product, removing said liquid residue and passing it through a first heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a second separating zone wherein separation thereof into vapors and a liquid residue occurs, fractionating said vapors in a second fractionating zone to form an intermediate condensate, passing the last named intermediate condensate through a second heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a third separating zone wherein vapors separate from residue, fractionating said vapors last-mentioned in a third fractionating zone to form an intermediate condensate and a relatively heavy condensate, combining said intermediate condensate with said intermediate condensate from the second fractionating zone for passage through said second heating zone, combining said heavy condensate with the liquid residue removed from said first separating zone for passage through said first heating zone, and removing fractionated vapors from said third fractionating zone and condensing them to form an additional quantity of final desired products.

'7. The process of treating hydrocarbon oil which comprises introducing heated oil into a first separating zone wherein separation of the oil into vapors and liquid residue occurs, fractionating in a first fractionating zone vapors separated in said first separating zone to form a condensate, passing said liquid residue and said condensate through separate cracking zones wherein they are heated at cracking temperature and subjected to conversion, subjecting the resulting productsof the cracking of both said liquid residue and said condensate to fractionation, separate and apart from said first separating and fractionating zones, passing a resultant condensate through a separate cracking zone wherein it is heated at a cracking temperature and subjected to conversion, separately subjecting the resulting cracked products to fractionation to form a final desired light distillate and a heavy reflux condensate and combining said heavy reflux condensate with said liquid residue for cracking therewith.

PERCY C. KEITH, JR.

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