US2224570A - Treatment of hydrocarbon oils - Google Patents

Description

Dec. 10, 1940. DIEQERUD 2,224,570

TREATMENT OF HYDROCARBON OILS Original Filed June 17 ,1931

I N VEN TOR. HELGE C. DIESERUD ATTORNEY Patented Dec. 10, 1940 UNITED STATES l ATENT OFFICE The poration of Delaware Original application June Texas Company, New York, N. Y., a cor- 17, 1931, Serial No.

545,010. Divided and this application November 20, 1934, Serial No.

June 2, 1932 2 Claims.

This invention relates to the conversion of hydrocarbon oils and has to do particularly with a vapor phase cracking process having certain features of novelty which will be described and claimed hereinafter.

This application is a division of my co-pending application Serial No. 545,010, filed June 17, 1931.

In the vapor phase cracking of hydrocarbon oils it has been the practice to simultaneously distill a heavy hydrocarbon oil, such as crude oil, in order to obtain a light fraction which may be easily vaporized and cracked Whil in vapor form without excessive deposition of coke. The heavy oil has accordingly been contacted with the vapors from the vapor phase cracker to strip the oil of light constituents and simultaneously shock-cool the vapors to retard undesirable reactions and the resulting unvaporized oil and condensates then redistilled to produce a vapor phase cracking stock. This method has certain disadvantages, particularly in that the heat of the hot vapor phase cracked products often produces undesirable amounts of coke and there is then produced from the redistillation step a resulting fuel oil that is undesirable.

Instead of contacting the hot vapors from the vapor phase cracking operation directly with heavy hydrocarbon oil to be stripped, I provide means for cooling the hot cracked vapors prior to contacting with the fresh oil. Thus a relatively cool, heavy or residual oil may be commingled with the hot vapors and the heat sufiiciently absorbed by the cool oil, or the heat of the vapors may be dissipated by utilizing such heat to reduce the heavy oil to coke. In this way I am able to use more efiiciently the residual oils from the process and at the same time control the reaction so as to retard coke formation at undesirable points in the system and to reduce to coke, in a coking zone, if desired, the heavy oils which cannot be advantageously cracked without harmful deposits of coke in the crack ing zone.

In accordance with the invention, a heavy oil is distilled in a pipe still, which may take the form of a tubular heater and a separator, a vapor fraction is removed and subjected to a vapor phase cracking operation, then the residual liquid fraction from the pipe still commingled with the hot cracked products in the vaporizing zone. If it is desirable to further cool the hot cracked products, I provide means for mixing a portion of the cooler heavy oil from the vaporizer therewith, prior to the mixture reaching the vaporizer.

the liquid phase cracking 753,834. In Canada According to the invention, moreover, the residual liquid from the pipe still may be given a separate heat treatment. Therefore, the liquid may be subjected to a cracking operation substantially in the liquid phase and then the cracked products from both the vapor phase and operation commingled in the vaporizing zone. In this method of operation, however, it is preferable to extensively cool the hot cracked products prior to reaching the vaporizer and for this purpose a heavy oil from the vaporizer may be circulated through-a cooler and the cool oil then mixed with the hot cracked materials transferred to the vaporizer.

Furthermore, according to one method of operation, it is contemplated that the residual liquids from the system may be reduced to coke by the sensible heat of the hot vapors from the vapor phase cracking operation. Accordingly, the heavy oil from the pipe still, either with or without undergoing a cracking treatment, may be commingled with the hot cracked vapors and the mixture reduced to coke in a coke still. The vapors from the coke still may then be dephlegmated with a heavy oil and the resulting unvaporized liquid from the dephlegmating zone con ducted to the coke still or to the pipe still or both.

In any method of operation, according to the invention, it is preferable to preheat the fresh oil charged to the system. Such preheating may be conveniently accomplished in the dephlegmating zone which may comprise a single zone wherein the fresh oil is stripped, the vapors fractionated and the liquids accumulating therein passed all, or in part, to the pipe still or the coking zone; or, the dephlegmating zone may comprise two separate zones, one zone constituting a stripper, wherein the fresh oil is stripped by the hot vapors passed thereto and the resulting unvaporized oil passed to the coking still, and the other zone comprising a fractionating tower where the vapors are subjected to reflux condensation by heat exchange with the charging stock and the liquids collecting therein passed to the pipe still.

The invention may be more clearly understood by reference to the accompanying drawing wherein is shown, for purposes of illustration, one form of apparatus for carrying out the invention.

In the drawing, the reference character 2 represents a furnace in which is located heating coils 4, 6 and 8 for heating the oil. The heating coil 4 and separator l0, comprise a pipe still for distilling the hydrocarbon oil, charged to the coil 4 through the lines [2 and I4. A vapor line 15 connects the top of the separator ID with a vapor phase cracking coil 8. A line l8 serves to conduct the products from the coil 8 to the coke stills 20 and 22 through the connecting branches 24 and 26 respectively. A vapor line 28 connects the vapor space of the coke stills to the bottom of the dephlegmator 38. The line 32, branching from the pipe l8, serves as a by-pass to conduct the products from the coil 8 around the coke stills and directly to the dephlegmator 30 via pipe 34 and the line 28. By suitable regulation of valves 36 and 38, in lines 32 and 34 respectively, the products in line 32 may be directed into the line 40, mentioned hereinafter, whereby the vapor phase cracked products may be commingled with the liquid phase cracked products therein and the mixture conducted to the dephlegmator 30.

Referring again to the separator ID, a line 42, in which is interposed a pump 44 and a valve 46, serves to conduct residual liquid from the bottom thereof into line l8 to commingle with the vapor phase cracked products fromcoil 8. A branch line 48, controlled by valve 50, serves to convey, if desired, the residual liquid, withdrawn through line 42 to the cracking coil 6. The coil 6 in turn is connected by the line 40 with the dephlegmator 30 to conduct oil from the coil to the dephlegmator so as to enter thereto at a point slightly higher than the entrance of the products through vapor pipe 28.

The dephlegmator 30 is shown as an enlarged tower which is divided into two sections by a partition 54 having a vapor riser 56 therein. The lower section of the tower, below the partition or pan 54, constitutes a stripping section wherein oil introduced through pipes 58 and 40 may be stripped of the lighter constituents by contact with the vapors introduced through line 28 while running down over the baffles 68. A line 62, controlled by valve 66, serves to withdraw from the bottom of the tower residual liquid which may be pumped to storage by a pump 84. A branch line 68, communicating with line 18, serves to by-pass the residual liquid to the coke stills 20 and 22. A by-pass line 10, in which is interposed a cooling coil 12, serves to by-pass the oil from the line 68 to the line 48 by suitable regulation of valves 14 and 16 in the lines 68 and 10 respectively.

The upper section of the dephlegmator, above the partition 54, serves as a fractionating or dephlegmating column. A cooling coil '88, lo cated in the top thereof, serves to cool the vapors by conducting therethrough fresh oil from the line 88 through which charged oil is pumped by the pump 82. A branch line 58, referred to hereinbefore, serves to conduct a portion of the charging oil to the stripping section by suitable regulation of valves 84 and 86 in the lines 88 and 58 respectively. A branch'pipe 88, controlled by valve 90, serves to introduce fresh oil directly into the fractionator, if desired. A pipe 92, communicating with the bottom of the fractionating section, serves to conduct unvaporized charge and reflux liquid collecting on the pan 54 to the pump 94 which in turn forces the oil through pipe [4 to the pipe still. A vapor line 96 conects the top of the tower 38 to a cooling coil 98 which in turn is connected by line I with a receiver I82, the latter having the usual gas release pipe I84 and liquid draw-01f line I06. A line 108, connecting with the pipe I05, serves to convey condensate from the receiver I02 to the fractionator to act as a reflux medium.

While the dephlegmating tower 30 is shown in the drawing as a single unit it is to be understood that the lower stripping section and upper fractionating section may comprise separate towers. In some cases it is contemplated that the lower stripping section may be eliminated entirely. Such may well be done when the coking units are in use and in such event, vapors from the coking still would pass directly to the fractionator'or, as an alternative, the partition 54 might be eliminated. The lower stripping section is particularly useful when the coking stills are not used and the products from coils 6 and 8 are passed directly to the stripper. The liquids may then be withdrawn from the bottom of the tower and by-passed through line I Hi to the pipe still or through line 68 to the cooler 12.

In practicing the invention with an apparatus such as that shown in the drawing, a charging stock such as crude oil or reduced crude is charged by pump 82 through the line 80. In case the oil is reduced crude it may be desirable to pass the oil through coil 18 in indirect heat exchange relation with the vapors in the tower. However, when crude oil containing gasoline constituents is used it is preferable to charge the oil, entirely or in part, directly into the tower through line 88. If the oil is charged directly into the tower it is stripped largely of its gasoline content and the unvaporized portion and condensates collect on the pan 54. 'The oil, according to the method of operation, is then conducted through line l2 or from the bottom of the fractionator through line 92 to the pipe still. The oil is heated in coil 4 toa temperature insufiicient to cause appreciable cracking but sufficient to cause substantial vaporization, say BOO-750 F. The oil is separated in separator l0 into a vapor fraction and a residual liquid fraction. The vapor fraction, comprising a wide cut consisting largely of naphtha and gas oil, is subjected to a vapor phase cracking operation. For this purpose. the vapors are conducted through heating coil 8 in which the oil is subjected to the highest temperature in the furnace, for example, about 9001l50 F. The hot vapor phase cracked products are then transferred through line l8 to the coke stills, wherein coking of the heavy oil charged thereto takes place as will be more fully explained hereinafter.

The residual liquid fraction from separator I0 is withdraw through line 42 and may be passed directly into line l8 where it commingles with the hot cracked vapors therein and then the mixture is' transferred to the coke stills. As an alternative, the valve 46 in the line 42 may be closed and the valve 50 in line 48 opened and the residual liquid forced through the heating coil 6. It is proferable that cracking, substantially in the liquid phase, takes place in coil 6 and therefore the oil is heated therein to a temperature of about 750-950 F. under a pressure of 200-600 pounds per square'inch applied by the pump 44. The cracked products are transferred through line 40 and the by-pass line 32 into line 18 to mix with the vapor phase cracked products and the mixture then transferred to the coke stills. The pressure is preferably reduced at valve 36 to approximately equal to the pressure maintained in the vapor phase cracking opera tion which may be from atmospheric to 200' pounds per square inch. In the coke stills all volatile products are vaporized and the unvaporizable material reduced to coke. A plurality of coke stills is available so that one may be cleaned of the coke deposited therein while the other is in use. The vapors from the coke still are passed through vapor line 23 to the lower portion of the stripping section of tower 30. Since the vapors are at a relatively high temperature a heavy oil is usually introduced through line 58 into direct contact with the vapors whereby the heavy oil is partially distilled and the less volatile constituents of the vapors condensed. The liquids collecting in the bottom of the stripper are withdrawn through line 62 and may be passed to storage. It is preferable, however, to by-pass these liquids through line 68 back to line H! where they commingle with the vapor phasecracked products and pass with the mixture to the coke stills.

According to one method of operation, the coke stills are not used but instead the cracked products are passed directly to the tower 30. In this method of operation it is necessary to cool the vapor phase cracked products in order to prevent coking in the tower 30 so that the liquid fuel may be withdrawn from the bottom thereof. This cooling may be done partially by contacting the cooler liquid from the separator it directly with the vapor in line 18 by passing the residual liquid therefrom through line 42 instead of to the craclnng coil 6. The mixture is then passed through lines 32, 34 and 28 or through lines 32 and 48 directly to the tower 30. Another method of cooling is to contact residual liquid from the bottom of tower 30 with the hot products and to do this residual oil, withdrawn through line 62, may be lay-passed through line E9 to the line id and in this case the hot materials from line 32 are passed to line 80 instead of pipe 35. The degree of cooling may be regulated, according to this latter method, by controlling the temperature of the liquid in line 10 by use of the cooling coil 72, around which a cooling medium may be circulated. When using the cooler 12 the degree of cooling can be controlled to such an extent that it is possible to crack the residual liquid from separator Ill in the coil 6 and yet have no unduly high temperature in the tower 38. When by-passing the coke stills as just described it is often desirable to eliminate the partition lit and collect all the liquids from the bottom of tower 3i] and for this purpose I have shown by-pass line I It, through which a portion of the liquids not used for cooling may be returned to the pipe still.

The vapors rising in the tower 3!! are dephlegmated or fractionated preferably in the presence of charging stock; the unvaporized portion of which collects in the lower portion of the tower together with condensates and the mixture returned to the pipe still. Vapors of substantially gasoline boiling range are removed from the top of the tower. These are condensed to produce the desired gasoline distillate. A portion of the distillate may then be returned, if desired, to the top of the tower through line M8 to serve as a reflux medium for controlling the end point of the final distillate.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of treating hydrocarbon oils to convert higher boiling hydrocarbons into lower boiling hydrocarbons which comprises introducing fresh charging stock into a fractionating zone to dephlegmate vapors therein to thereby cause partial vaporization of the fresh charging stock and partial condensation of vapors therein, directing the resultant admixture of reflux condensate and unvaporized portion of the fresh charging stock directly to a coking zone wherein coking is carried on by the aid of hot cracked products introduced thereinto, passing evolved vapors from said coking zone to said fractionating zone, subjecting the vapors from said fractionating zone to further fractionation to separate a reflux condensate from a desired light distillate, conducting said reflux condensate to a heating coil wherein it is heated to a temperature adequate to effect substantial vaporization and discharging the heated oil into a separating zone wherein separation of vapors from unvaporized oil takes place entirely separately from said fractionating and coking zones, subjecting the vapor fraction thus separated to cracking temperature by passage thereof through a separate heating zone in a stream of restricted cross sectional area to cause conversion thereof, subjecting the unvaporized oil thus separated to cracking temperature by passage thereof through a separate heating zone in a stream of restricted cross-sectional area to cause conversion thereof, and passing the resulting products from said streams at cracking temperature to said coking zone.

2. The method of treating hydrocarbon oils to convert higher boiling hydrocarbons into lower boiling hydrocarbons which comprises introducing fresh charging stock into a fractionating zone to dephlegmate vapors therein to thereby cause partial vaporization of the fresh charging stock and partial condensation of vapors therein, directing the resultant admixture of reflux condensate and unvaporized portion of the fresh charging stock directly to an enlarged reaction zone wherein separation of vapors from'residue takes place, passing resultant separated vapors from said reaction zone to said fractionating zone, subjecting the vapors from said fractionating zone to further fractionation to separate a reflux condensate from a desired light distillate, conducting said reflux condensate to a heating coil wherein it is heated to a temperature adequate to effect substantial vaporization and discharging the heated oil into a separating zone wherein separation of vapors from unvaporized oil takes place entirelyseparately from said fractionating and reaction zones, subjecting the vapor fraction thus separated to cracking temperature by passage thereof through a separate heating zone in a stream of restricted cross sectional area to cause conversion thereof, subjecting the unvaporizedoil thus separated to cracking temperature by passage thereof through a separate heating zone in a stream of restricted cross-sectional area to cause conversion thereof, and passing the resulting products from said streams at cracking temperature to said enlarged reaction zone.

HELGE C. DIESERUD.

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