US1815050A - Method for treating hydrocarbon oils - Google Patents

Description

July 21, 1931. R. J. DEARBORN ET AL 1,815,050

METHOD FOR TREATING HYDROCARBON OILS Filed Aug. 5, 1927 Patented July 21, 1931 UNITED STATES- PATENT oFFicE RICHARD J. DEARBORN, OF SUMMIT, NEW JERSEY, AND WILL K. HOLMES, OF PORT ARTHUR, TEXAS, ASSIGNORS TO THE TEXAS COMPANY, OF NEW YORK,.N. Y., A.

CORPORATION OF TEXAS I METHOD FOR TREATING HYDROCARBON OILS Application filed August 5, 1927. Serial No. 210,760.

Our invention relates to the conversion of higher boiling hydrocarbons into lower boiling ones for the production of gasoline and the like. i The invention has to do with certain new and useful improvements in the general field of what may be termed the coil and drum or tube and tank methods of treating, and the invention contemplates the heating to crack- 1 ing temperatures of certain oil in a coil or tubular passages or conduits of restricted cross section and the heating of other oil in a converter or battery of converters, preferably of large volume as compared with the tubular heat-er. In one method of carrying on the invention initial or fresh charging stock is admitted to thecracking chamber,

Without having been passed through the tubular conduit or coil, while a distillate produced in the process is introduced into the coil. The process is particularly adapted forthe treatment of reduced crudes, heavy fuel oils and the like, the residuums being charged into the drum or battery of crack- 535 ing stills while distillatesobtained from the cracked or distilled products. are passed into the coil.

One method of operation contemplated by the invention consists in introducing part of the initial charging stock into the drum or stills, and passing another'portion of the initial charge through the coil together with condensate formed in the process.

In present methods of crackingit is common practice to use selected or specially prepared stocks having certain limits as to boiling point range. Our invention obviates the necessity of using specially selected or pre-- pared stocks and contemplates a process wherein a charging stock of wide boiling point range may be satisfactorily treated, since the different conditions as to temperatures and pressure made possible by the practice of the invention are capable of accommodating the different fractions in such a stock. Thus a charging stock having a wide range in boiling point may be introduced into the still wherein the conditions as to temperature and pressure are adapted for the conversion of the heavier constituents into lighter hydrocarbons, while lighter unconverted constituents are directed to the tubular portion of the apparatus wherein they are subjected to higher temperatures and pressures.

7 One method of practicing the invention contemplates the use of different initial charging stocks and in this method of operation an initial charging stock of heavier gravity (lower Baum gravity) or of higher lighter residuum is passed through the coil, or a heavy distillate'may be charged into the drum or still while a lighter distillate is charged into the coil.- In carrying out the invention in accordance with the last named method, a gas 011 or more specifically a heavy gas oil may be charged into the drum or still while a lighter gas oil or kerosene distillate is charged into the coil. The inven tion has a special field of usefulness in connection with the treatment of heavy residuums such as those obtained from Mexican, California and Gulf coast crudes, which may be charged into the still or drum while a fraction obtained in the process by distillation, or a lighter initial charging stock, or a mixture of both, is introduced into the coil.

One method of practicing the invention contemplates a process in which the charge passing through the coil or tubular heater may be raised to a higher cracking temperature under preferably higher pressures than 'the temperatures and pressures maintained in the drum or enlarged chamber. Byreason of the fact that the invention facilitates a variability in cracking conditions obtaining in different parts of the system, it is thus possible to maintain the different constitu ents of the initial charge, or the different initial charging stocks, under conditions lllf) most favorable for the maximum rate of cracking for the different constituents.

One method of the invention contemplates the production, from the evolved vapors of a cracking still, of a condensate which in volume exceeds that of the initial charge and the utilization of this large quantity of condensate in heated condition to maintain or assist in maintaining the required cracking temperature in the still. Thus the condensate is separated out from the evolved vapors, preferably at a temperature not substantially below its boiling point under the pressure employed, and then without substantial loss in heat is passed through a tubular heater, in which it is preferably heated to a high cracking temperature and the highly heated oil then discharged into thestill. By reason of the large volume of hot cycle products the required temperature in the cracking stillis readily maintained even though fresh charge is admitted directly to the still and this resultis accomplished either without the application of any heat to the still, other than the hot entering oil, or by supplying a comparatively small amount of additional heating to the still. The process thus facilitates the treatment of crude oil or crude residuums, since the necessary temperature is maintained in the stills into which the crude or residuum the heavy ends of the charging stock.

In order to more fully disclose the invention, reference will now be had to the accompanying drawing whichillustrates in diagrammatic sectional elevation a particular embodiment and example of the invention.

In the apparatus thus illustrated the cracking chamber or drum assumes the form of a still or a plurality or battery of stills 10a 10?), 10c and 1061. A heating coil 11 adapted for heating the oil in transit therethrough to a cracking temperature is disposed in a furnace 12 heated by a burner.13. The stills 10 are mounted in a furnace 14: which is shown as being heated by hot gases from the furnace 12 by means of a flue 15, or heated by burners 16, outlet flues 17 being provided for the removal of the furnace gases. It is to be understoodthat in case it is not desired to heat the stills externally they are suitablv lagged to prevent or retard 1 loss of heat. The stills are shown as being equipped with stirring or scraping apparatus 18 adapted to agitate the oil in the still or to scrape the still walls, particularly those portions of the walls within the furnace 14.

Atransfer line 19 extends from the coil 11 to the stillsand as illustrated this line is the oil passed through the heating coil 11 may be discharged into any one or any num-' ber of the stills, as may be desired; The A stills are shown as being interconnected by liquid level lines 20 and vapor lines 21. The stills are also provided with tar or residue lines 22a, 22?), 22c and 22d which may extend to a suitable exchanger adapted for heating the charging stock, or to suitable tar stripping equipment not shown.

A vapor line 23 conducts vapors from the battery of stills to a condensing, dephlegmating or fractionating apparatus 2t. This apparatus is preferably in the form of a bubble tower or packed column and is in vapor communication through a pipe 25 with a reflux condenser or dephlegmator 26, provided with a reflux pipe 27 for conducting reflux liquid to the fractionating column,

A vapor line 28 conducts vapors from the resired, a part or all of the charge entering the pipe 34 may be introduced into the transfer line 19. The charging line 34 is shown provided with branch lines 35 and 36 communicating with a coil 37 in a reflux condenser 26 and also with branch lines 38 and 39 communicating with a coil 40 positioned in the fractionating column 24. Appropriate valves are shown in these branch lines and in the charging line so that either or both of the coils 37 and 40 may be used or by-passed, as desired.

A hot oil pump 41 is provided for removing the condensate collected in the condenser or dephlegmating device 24 and forcing it into the coil 11. The pump is provided with an intake line 42 adapted to withdraw condensate from the column 24 and with a discharge line 43 provided with branch lines 44, 45, 16 'so that the condensate may be passed through the entire length of the coil 11 or introduced into the coil at an intermediate point, or passed into the stills. The branch line 46 has been shown as extending tostill 100, but if desired, other branch lines may be provided to conduct the condensate into any one or all of the remaining stills. As illustrated, the pipe 43, in its several branches, is equipped with appropriate valves sothat the charge may be passed into any of the branch lines or apportioned or distributed among these several lines.

the coils 37 and 40 so as to preheat the oil and if desired the oil may also be preheated by heat exchange with the tar or residue drawn from the stills. The oil in the stills is held under pressure and maintained at cracking temperatures. The vapors from the stills are passed through the line 23 to the fractionating column 24 wherein higher boiling constituents are separated out and are conducted by the pump 41 through lines 43 and 44 into the heating coil 11. The oil in transit through this coil is raised to a cracking temperature and passes thence through the transfer line 19 and its branches into one or more of the stills, preferably into stills 10a or 10?) or both. ,In this method of operation the pump 47 is not utilized, the entire initial charge being introduced by the pump 33, except that in the beginning of a run the pump 47 may be used to pass charging stock through coil 11 until distilling conditions have been establishedin the stills and a supply of condensate furnished in the dephlegmating apparatus 24. Although this type of operation is adapted for cracking any kind of charging stock, it

is as stated particularly advantageous in the case of charging stocks haying a wide range of boiling point and also in the case when a residuum is used as charging stock. It will be noted that the crude residuum is not circulated through any coil maintained under cracking conditions, but on the contrary, is charged into the stills, the metallic walls of which need not be subjected to as high a temperature as that applied to the heating coil 11. Furthermore, the stills mayfreadily be subjected to agitation or the walls thereof scraped so that the dangers of carbon deposition are minimized. It will furthermore be noted that the residual oil is drawn off from the stills and removed from the system. Vaporization as well as cracking takes place in the stills and the gasoline or naphtha vapors, together with other heavier constituents, pass into the separating or fractionating apparatus 24 from which a condensate is obtained which apparently consists of certain partially converted constituents and may also contain certain products separated out, from the initial charge by mere vaporization. This condensate is of a lower mean boiling point than that of the oil in the stills and it is passed into the coil 11 wherein it is raised to a cracking temperature, preferably to a higher cracking temperature than that obtaining in the stills. The pressure on the oil in transit through the coil 11 is preferably higher than that obtaining in the. stills. 4 This condensate, after being raised to a cracking temperature in the coil 11, and subjected to more or less cracking therein as may be desired, is passed back into the stills wherein the cracking initiated in the coil is continued or completed. In this way the heavier ends of the charging stock are kept entirely away from the high temperature coil 11 and the lighter of the products to be subjected to the cracking operation are continuously segregated to an extent from the heavier or residual products, so that the lighter oil and the heavier oil being converted may each be thus subjected to conditions best suited for its conversion. The fractionated gasoline or naphtha distillate of desired boiling point is taken off and collected in the receiving drum 30 from which it is withdrawn to storage.

In another method of operation, two initial charging stocks are used, one being. introduced by the pump 33 and the other by the pump-47. In this method of operation charging stocks of essentially different boiling points or gravitiesmay be used. Thus a crude residiuum may be charged by the pump 33 into the stills 10 and a distillate oil introduced by the pump 47 into the coil 11;

distillate oils, thus for example, gas oil being introduced by thepump 33 and a kero sene stock or a lighter gas oil stock being introduced by the pump 47. In this method of operation the cycle condensate which is removed from the fractionating column 24 is preferably passed through the branch line 45 and commingled with the initial charge passing through the coil at a point where the temperature of the oil in the coil has been raised to substantially the same temperature as that of the returning condensate.

It will be noted that in this process, a distillate or condensate oil, whether in the form of initial charge or as backtrap or reflux condensate from the fractionating apparatus, or as both condensate and fresh charge, is passed through the heating coil 11, while a heavier charging stock such as crude residuuin is introduced into the stills or enlarged v without having to heat the stills excessively.

Furthermore, the use of the light or clean distillate charging stock in the coil 11 makes it possible to carry on considerable cracking in this coil Without danger of injurious deposition of carbon. Ihe oil charged through the coil is raised to a cracking temperature therein and cracking is initiated and may becarried on in the coil to a greater or less extent; this oil is then discharged into the enlarged converter or battery of converters, the contents of which are maintained under cracking conditions so that the cracking of the oil that has been passed through the coil is, in the large converter or battery of converters, continued While the fresh charge introduced directly into the converter or converters without having been passed through the coil is also subjected to cracking. The oil is preferably forced through the coil 11 at a high velocity and if desired the oil charge may be preheated by heat exchange with hot residue or vapors produced in the system, or otherwise suitexample, be charged into the coil 11 at a ably preheated before being admitted to the coil 11.

By'cycling a large quantity of reflux as compared to the volume of initial charge, such for example as a ratio of backtrap to initial charge of l or 5 to 1, it is possible to maintain the desired cracking temperatures in the stills Without unduly heating the stills, and in some cases even without heatingpthe stills externally at all, the large volume of highly heated oil discharged from the coil 11 into the stills operating largely to maintain the temperatures desired. 4

The particular temperatures or pressures used in the practice of the invention will of course vary within Wide limits, depending upon the characteristics of the charging stocks used, onthe specifications desired for the gasoline or light distillate produced and on various operating conditions. It may be stated, however, that it is preferable to 0perate the system under several hundred pounds pressure with a pressure in the heating coil or cracking coil of 50 or 100 pounds or even more in excess of that in the stills, although it is to be understood that the practice of the invention does not necessarily preclude having substantially the same pressure in the coil and the stills. In general, the oil is heated in transit through the coil to about 800 to 900 F., preferably to about 825 to850 F., and a temperature of about 750 to 775 or higher is maintained in the stills. The reflux condensate Withdrawn from the ffactionating column 24 is removed at as high a temperature as possible consistent with a proper separation in the fractionation column and may, for

temperature of about 600 F. or 700 F. or

. higher.

Obviously, "arious modifications of the invention may be effected without departing from the spirit and scope of the invention. The true scope of the invention is defined in the appended claims.

What we claim is:

1. In the conversion of higher boiling hydrocarbons into lower boiling ones, the process that comprises subjecting hydrocarbon oil in a vaporizing zone to a cracking temperature under superatmospheric pressure, introducing fresh charging stock into said vaporizing zone, passing another fresh charging stock through a heating coil to thereby raise said stock to a cracking temperature in transit through the coil, delivering the oil 'thus heated in the coil to said vaporizing zone, dephlegmating vapors evolved from the vaporizing zone to form a reflux condensate in a heated condition and delivering said reflux condensate to the heating coil to be commingled therein with the fresh charging stock at a point in the coil where the temperature of the fresh charging stock in transit approximates that of the reflux condensate.

2. In the conversion of higher boiling hydrocarbons into lower boiling ones, the process that comprises subjecting hydrocarbon oil in a vaporizing zone to a cracking temperature under superatmospheric pressure, introducing a residual oil as fresh charging stock into said vaporizing zone, passing a condensate oil as fresh charging stock through a heating coil to thereby raise said stock to a cracking temperature in transit through the coil, delivering the oil thus heated in the coil to said vaporizing zone, dephlegmating vapors e"olved from the vaporizing zone to form a reflux condensate in a .heated condition, delivering. said reflux condensate to the-heating coil to be commingled therein with the fresh charging stock at a point in the coil Where the temperature of the fresh charging stock in transit approximates that of the reflux condensate.

In Witness whereof I have hereunto set my hand this 27th day of July, 1927.

. IVILL K. HOLMES.

In witness whereof I have hereunto set my hand this 27th day of July, 1927.

.R. J. DEARBORN.

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