US2063505A - Process for hydrocarbon oil conversion - Google Patents

Description

Dec. 8, 1936. c. HUFF PROCESS FOR HYDROCARBON OU., CONVERSION Original Filed Jan. 30, 192B jmd wim @55 Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE PROCESS FOR HYDROCARBON OIL CONVERSION Application January 30, 1928, Serial No. 250,393 Renewed October 8, 1935 9 Claims.

, The present invention relates to improvements in process for hydrocarbon oil conversion, and refers more particularly to a process especially adapted for vapor phase cracking.

The invention has for its principal object the subjection of hydrocarbons to conditions of vapor phase cracking for the production of maximum yields of desirable lighter hydrocarbons therefrom with a minimum production of coke and non-condensible gas loss. The invention has for another object, the conversion of hydrocarbon oils under conditions of vapor phase cracking in such a manner that the condensed overhead product produced in the process will be suitable for use as motor fuel and will have high anti-knock properties, surpassing in this respect the product of the present day liquid or liquid-vapor phase processes.

I am aware that the art of conversion of hydrocarbons while subjecting the same to conditions of vapor phase cracking is generally old. The principal diiiiculty heretofore encountered when cracking in the vapor phase has been the accumulation of coke in the system which necessitates frequent shutdowns for the removal of the same, the length of the runs in most instances being so short as to render the process unprotable from a commercial standpoint.

It is the purpose and one of the objects of the present invention to obviate this diiculty without substantially decreasing the yield of desirable lighter hydrocarbons, and the manner in which this is done seems to be new and novel to the art.

`I have found that in the conversion of hydrocarbons for the production of low boiling point products certain heavy liquid or semi-liquid ends are produced. When these heavy liquid or semiliquid products of conversion are subjected to further heating they react to form coke and noncondensible gas, forming substantially none of `the desirable low boiling point hydrocarbons during such reaction. Therefore, if the conversion reaction of these heavy ends to sludge and coke can be prevented or checked, the amount of sludge and/or coke will be reduced or even elimij nated, thus permitting the process to operate for greater periods of time, which is, of course, commercially protable and results in aconsequent higher efficiency.

It is a further object of the present invention to provide a method and means for decreasing or preventing the conversion of these heavy ends to sludge and coke, which comprises cooling the heavy ends to a temperature below that at which they react by bringing the same before they have time Ato react to form coke and incondensble gas,

into direct contact with comparatively clean recycled stock produced in the system.

In one of the preferred modes of carrying out the present invention, the hydrocarbon oil vapors released from a concurrently operating distilling or cracking process are subjected to conditions of temperature to cause their conversion into hydrocarbons of low boiling point. Before the heavy ends formed in this reaction have time to react to form coke and non-condensible gas, they are 10 cooled by being brought into direct contact with certain intermediate fractions produced in the system. The vapors are then subjected to a primary fractionation to separate the substantially insufciently converted fractions, the latter being returned to be reheated While the former are subjected to a secondary fractionation for the purpose of condensing the heavier fractions thereof, which for convenience, will be termed hereafter the intermediate fractions of the vapors produced during conversion. In other Words, the light fractions are those which remain uncondensed after passing through the secondary fractionating element, the intermediate fractions are those which condense in the secondary fractionating element, while the heavier fractions of the vapors are those which condense in the primary fractionating element and are returned for further heating and reconversion. In the specific embodiment of the invention, those intermediate fractions are removed from the secondary fractionating element and are brought into direct Contact with the heated vapors in the conversion zone for the p urpose already described.

As a feature of the present invention, the vapors are subjected to conversion conditions in a plurality of separating zones intermediate each of which separation and removal of the heavy ends formed by a previous conversion takes place.

The utility of the invention as well as other features, objects and advantages will be more particularly apparent from the following detailed description.

The single ligure in the drawing is a diagrammatic elevational View of the apparatus by which the objects of the present invention may be carried out.

Referring more in detail to the drawing, oil may be drawn through the line I by the pump 2 and passed into the line 3 controlled by a valve 50 Il. All or any regulated portion of the charge may be diverted into the line 5 controlled by a valve 6, and fed upwardly into the dephlegmator l, or all or any regulated portion may be passed directly through the line 3 to the heating coil 8 55 mounted in the furnace 9. Assume for the purpose of this illustration, that the oil is passed directly to the heating coil 8. While being passed through the latter it is raised to conversion temperature, say 800 degrees F., more or less, passing out through transfer line I controlled by valve I| and discharging into the enlarged drum I2, which may act as a separator and/or conversion drum.

The liquid products from the secondary dephlegmator I3 may flow into line |4, controlled by valve |5, from' which they may be forced by means of a pump I6 into a header |1 communicating with the branches I8, I9 and 20, controlled respectively by Valves 22, 23 and 24.

The charge will separate Within the drum I2 into vaporous and non-vaporous products, the latter being withdrawn through the line 2S, controlled by valve 21, communicating with header 28, While the vaporous products may be separately removed through vapor line 29, controlled by valve 30, discharging into the heating coil 3| mounted in a furnace 32.

While passing through the coil 3| the vapors may be raised to a conversion temperature, say 950 degrees F., more or less, passing out through the transfer line 33, controlled by valve 34, and discharging into the enlarged drum 35. While the vapors are passing through line 33 valve 24 in line 20 may be opened to permit a controlled quantity of the liquid products from the dephlegmator I3 to mix with the vapors to cool the heavy end products of conversion, thus checking further reactions of these heavy ends, which latter are separated in the drum 35, being Withdrawn through line 36, controlled by valve 31, communicating with header 28, while the lighter vaporous products may be separately removed through the line 38 controlled by valve 39, discharging into the heating coil 40 mounted in a furnace 4|.

While passing through the coil 40, the vapors may be again raised to a conversion temperature, say 1000 degrees F., more or less, passing out through the transfer line 42 controlled by valve 43, and discharging into the enlarged drum 44. While the vapors are passing through line 42, valve 23 in line I9 may be opened to permit a controlled quantity of the liquid products from the dephlegmator I3 to 'be mixed with the vapors to cool the heavy end products of conversion, thus checking further reaction of these heavy ends. The charge will separate in the drum 44 into vaporous and non-vaporous products, the latter being withdrawn through line 45, controlled by valve 46, communicating with the header 28, While the vaporous products may be separately withdrawn -through line 41, controlled by valve 48, discharging into the heating coil 49 mounted in a furnace 50.

While passing through the coil 49 the vapors may again be raised to a conversion temperature, say 1100 degrees F., more or less, passing out -through the transfer line I, controlled by a valve 52, and discharging into the enlarged drum 53. While the vapors are passing through line 5|, valve 22 in line I8 may be opened to permit a controlled quantity of the liquid products from the dephlegmator I3 to mix with the vapors to cool the heavy end products of conversion, thus checking further reaction of the latter. The charge will separate within the drum 53 into vaporous and non-vaporous products, the latter being Withdrawn through line 54, controlled by valve 55, communicating with the header 28, while the vaporous products may be separately Withdrawn through the line 56, controlled by valve 51, discharging into the bottom of the dephlegmator 1.

While ascending through the dephlegmator 1 the vaporous products of reaction are subjected to the action of a suitable cooling medium whereby the heavier portions of the insufficiently converted fractions condense and ilow to the bottom thereof while the sufliciently converted vapors and the lighter portions of insufficiently converted fractions remaining uncondensed pass out through the line 58 controlled by valve 59, discharging into the secondary dephlegmator I3. The reflux condensate, i. e. heavier fractions, collecting in the bottom of the dephlegmator 1 may be Withdrawn through line 69, and by means of pump passed through line 1|, controlled by valve 12, merging into the line 3 whereby said reflux condensate is returned to the heating coil 8 for retreatment. The vapors passing through dephlegmator 1 may be cooled by diverting a portion of the charging stock form the line 3 through the line 5, controlled by valve 5, and partly or wholly closing valve 4. Or, part or all of the cooling may be accomplished by introducing some of the liquid products from dephlegmator I3 through line 8|, controlled by valve 82, discharging into the upper portion of dephlegmator 1.

While ascending through the secondary dephlegmator I3 the remaining vapors are subjected to the action of a suitable cooling medium whereby the insuiliciently converted fractions condense and flow to the bottom thereof, while the sufficiently converted vapors remain uncondensed, passing out through line 60, controlled by valve 6|, being condensed in the condensing coil 62, the liquid being passed through line 63, into a receiver 64. The receiver 64 may be provided with the usual liquid drawoff line 65, controlled by valve 66, and with the non-condensable gas relief line 61 controlled by Valve 68.

The condensate collecting in the bottom of the secondary dephlegmator I3 may be Withdrawn through the line I4 and passed through the header I1 for the purpose already described. The vapors passing through dephlegmator I3 may be cooled by a portion of the liquid distillate which may be withdrawn from the receiver 64 through line 13, and passed by means of pump 14, through line 15, controlled by valve 16, discharging into the upper part of the dephlegmator I3.

The non-vaporous products of the reaction withdrawn from drums I2, 35, 44 and 53 and passed into the header 28 may be passed from said header into the drum 53 by opening valve 18 in line 11. Drum 53 may be maintained under a reduced pressure to cause said non-vaporous products to flash. It is obvious of course, that if the drum 53 is operated at a substantially lower pressure than are the other drums, a pump (not shown) may be interposed in the drawoff line 54 to force the liquid to flow against the greater pressure in the header 28. Instead of flashing all or a portion of the non-vaporous products in the header 28, all or a portion of them may be passed through line 19, controlled by valve 80, for retreatment or storage.

It is to be understood that in carrying out the invention, any number of vapor heating elements 3|, 40 and 49 may be used- The vapors may be subjected to cracking temperature and permitted to react to a predetermined extent any number of times, as may be desired, depending, of course, upon the conditions of operation, the products desired, and the charging stock used. rIhe process may be operated at a sub-atmospheric, atmospheric, or superatmospheric pressure.

In using the comparatively clean reflux from the secondary dephlegmator I3, for the purpose described, advantages other than those mentioned in the foregoing description are realized. The' reiiux being comparatively clean and free from heavy ends is especially Well adapted to the vapor phase cracking which it receives upon being recycled into the system to cool the heated `vapors as it will not deposit an undesirable amountl of carbon in the heating elements. By using the condensed distillate from the receiver 64 as a cooling medium for the dephlegmator i3, a portion of said distillate is thus recycled with the reux and subjected to further vapor phase treatment. It is obvious that the heating of the oil and vapors, and consequently the reaction of lthe same, may be controlled by varying the temperature of the heating elements and at the same time varying the velocity of the oW of the oil and vapors through the heating elements.

The process can be operated at temperatures and pressures found most expedient to give the best results. The oil entering the heating coil 8 may be under a pressure of from three to several hundred pounds, the pressure being reduced if desired, by manipulation of the proper valves at the various stages of heating, or it may be allowed to reduce gradually by reason of the friction induced by the system.

It is to be further understood that the vapors are to be ordinarily cooled suiiiciently only to condense and separate the heavy carbon-forming ends from the vapors. The following range of temperatures may be employed in the operation of theprocess. 'Ihe oil may enter coil 8 at a temperature of 500 degrees F. to 800 degrees F., and leave the same at a temperature of '750 degrees F. to 900 degrees F. The vapors may enter coil 3| at a temperature of 700 degrees F. to 900 degrees F., and leave the same at a temperature of 925 degrees F., to 1000 degrees F. The vapors after being cooled may then enter coil 40 at a temperature of 750 degrees F. to 1000 degrees F., and leave the same at a temperature of 850 degrees F. to 1100 degrees F. The cooled vapors may then enter the coil 49 at a temperature of 800 degrees F., to 1050 degrees F., and leave the same at a temperature of from 850 degrees F. to 1200 degrees F.

It is to be understood, of course, that any cooling medium may be used for checking conversion of the heavy ends, other than the reux from the secondary dephlegmator I3.

I claim as my invention:

1. In the vapor phase cracking of hydrocarbon oils, the method which comprises passing hydrocarbon vapors successively through a series of vapor phase cracking zones wherein they are heated to successively higher cracking temperatures, introducing a. cooling o-il into direct contact with the hot vapors promptly upon issuance from each of said zones to precipitate from the vapors heavier coke-forming constituents thereof, dephlegmating the cracked vapors to condense heavier fractions thereof as reflux condensate, and utilizing reflux condensate thus formed as the aforesaid cooling oil.

2. A hydrocarbon oil cracking process which comprises passing the oil through an initial heating zone and heating the same therein suiiiciently to erect substantial vaporization thereof, separating the evolved vapors from unvaporized oil,

subjecting the separated vapors to 'cracking conditions of temperature in a vapor phase cracking zone, introducing a cooling oil into the hot cracked vapors promptly upon issuance from the cracking zone to check further reactio-n of the heavier cokeforming constituents of the vapors, subjecting the vapors to primary and secondary dephlegmation thereby forming primary and secondary reflux condensate, returning said primary reflux condensate to said initial heating zone for retreatment in the process, utilizing said secondary reflux condensate as the aforesaid cooling oil, and condensing the dephlegmated vapors.

3. In the art of vapor phase cracking, the method which comprises initially separating hydrocarbo-n oil into vapors and unvaporized oil maintaining a continuous flow of said vapors through a series of units each of which includes a heating zone and a separating zone, subjecting the vapors to a vapor phase cracking temperature in each of said heating zones, separating heavier constituents of the heated vapors in each of said separating zones, preventing passage of such separated heavier constituents through said heating zones,

combining said heavier constituents and said unvaporized oil in the last separating zone of the series and ash distilling the mixture therein by pressure reduction, and dephlegmating the vapors issuing from the last of said separating zones.

4. A process as defined in claim 3 further characterized in that said heating zones are maintainedat temperatures which increase progressively in the order of the passage of vapors therethrough.

5. A hydrocarbon oil cracking process which comprises passing the oil through an initial heating zone and heating the same therein suflicient- 1y to effect substantial vaporization thereof, separating the evolved vapors from unvaporized oil, subjecting the separated vapors to cracking conditions of temperature in a vapor phase cracking zone, introducing a secondary reflux condensate formed in the process into the hot cracked vapors promptly upon issuance from the cracking zone to separate heavier coke-forming constituents from the vapors and to evolve vapors from said secondary reflux condensate, passing the resultant vaporous mixture through a second vapor phase cracking zone and heating the same therein to higher temperature than is maintained in the first-mentioned cracking zone, subjecting the cracked vapors from said second cracking zone to primary dephlegmation and returning resultant primary reflux condensate to said initial heating zone for revaporization and recycling through the f vapor phase cracking zones, subjecting the primary dephlegmated vapors to secondary dephlegmation to condense therefrom insufficiently cracked fractions lighter than said primary reflux condensate, utilizing such lighter insufciently cracked fractions as said secondary reflux condensate, and condensing as a product of the process the vapors uncondensed by the secondary dephlegmation.

6. A `hydrocarbon oil cracking process which comprises passing the oil through an initial heating zone and heating the same therein suiciently to effect substantial vaporization thereof, separating the evolved vapors from unvaporized oil, subjecting the separated vapors to cracking conditions of temperature in a vapor phase cracking zone, cooling the cracked vapors to condense heavier coke-forming constituents thereof, combining said constituents with said unvaporized oil and ash distilling the resultant mixture by pressure reduction, dephlegmating the flashed vapors to condense heavier fractions thereof and returning resultant reilux condensate to the process for retreatment, and condensing the dephlegmated vapors.

7. In the art of Vapor phase cracking, the method which comprises initially separating hydrocarbon oil into vapors and unvaporized oil in a distilling Zone maintained under pressure, maintaining a continuous ow of said vapors through a series of units each of which includes a heating zone and a separating zone, subjecting the vapors to a vapor phase cracking temperature in each of said heating zones, separating heavier constituents of the heated vapors in each of said separating zones, preventing passage of such separated heavier constituents through said heating zones, introducing said heavier constituents from preceding separating zones of the series and said unvaporized oil into the last separating zone of the series, maintaining said last zone under lower pressure than the preceding zones and effecting substantial distillation therein, and dephlegmating the vapors issuing from the last of said separating zones.

8.. A hydrocarbon oil cracking process which comprises passing the oil through an initial heating zone and heating the same therein sufficiently to eiect substantial vaporization thereof, separating the evolved vapors from unvaporized oil, subjecting the separated vapors to cracking conditions of temperature in a vapor phase cracking zone, introducing a cooling oil into the hot cracked vapors to check further reaction of the heavier coke-forming constituents of the vapors, flash distilling said unvaporized oil by pressure reduction dephlegmating the flashed vapors and the vapor phase cracked vapors and utilizing resultant reflux condensate as said cooling oil, and condensing the dephlegmated vapors.

9. A hydrocarbon oil cracking process which comprises passing the oil through an initial heating zone and heating the same therein sulciently to effect substantial vaporization thereof, separating the evolved vapors from unvaporized oil, subjecting the separated vapors to cracking conditions of temperature in a vapor phase cracking zone, introducing a condensate formed in the process into the hot cracked vapors to separate coke-forming constituents from the vapors and to evolve vapors from said condensate, subjecting the resultant vaporous mixture to vapor phase cracking in a second cracking zone, ilash distilling said unvaporized oil by pressure reduction and condensing the flashed vapors, and utilizing a portion of the condensed ilashed vapors as said condensate.

LYMAN C. HUFF.

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