US2105526A - Process of hydrocarbon oil conversion - Google Patents

Description

Jam.l 18, 1938. c. P. DuBBs PROCESS OF HYDROCARBON OIL CONVERSION original Filed March 23, 1925 kkuQ hun l l l Patented Jan. 18, 1938 UNITE STATES PATENT OFFICE PRCESS F HYDROCARBON OIL CONVER- SION @riginal application March 23, 1925, Serial No.

17,516. Divided and this application Decemher 3, 1932, Serial No. 645,523.

ternher 17, 1936 Claims.

This application is a division of my application Serial No. 17,516 filed March 23rd, 1925.

This invention relates to .improvements in a method of hydrocarbon oil conversion and refers more particularly to the treatment of hydrocarbon oils under conversion temperature and a substantial super-atmospheric pressure to produce light fractions therefrom suitable for commercial use.

The particular embodiment of the present invention resides in passing a stream of hydrocarbon oil through an elongated passageway, for instance, a continuous coil, mounted in a furnace, where the oil is heated to substantially a conversion temperature while being maintained under a super-atmospheric pressure. This heated oil is then discharged into an enlarged reaction chamber, where substantial separation of the lighter fractions in the form of vapors will take place, said vapors being dephlegmated, condensed and collected in a receiver as distillate. This invention contemplates that regulated portions of said distillate are to be returned from the receiver to the stream of oil heated in the elongated passageway and mixed therewith, either at the point of introduction of said stream of oil to the elongated passageway, or after said stream has passed through the elongated passageway and been heated and while it is being transferred to the reaction chamber.

Various advantages of the invention will appear more fully from the following description.

The single ligure in the drawing is a diagrammatic flow sheet of a commercial form of apparatus in which the process may be carried out.

Referring in detail to the drawing, the raw oil is withdrawn from the supply tank I and passed through the line 2, in which is interposed the raw oil pump 3, this line 2 communicating with the lines 4 and 5. The line 4 has valve 5 interposed therein and discharges the raw oil into the top of the dephlegmator 1. Instead of discharging into the top of the dephlegmator 1, the raw oil may be passed through the line 5, in which latter is interposed the valve 8, said line 5 communicating with the inlet side of elongated passageway 9, which may comprise a continuous coil of say 3 or 4 inch pipe, mounted in a suitable furnace. The feed of raw oil may be split, that is, part may be fed directly to the dephlegmator and part directly to the inlet side of the heating coil 9,

The raw oil, in its passage through the heating coil 9, has its temperature increased and is brought to a conversion temperature, and is dis- Renewed Sepcharged from the upper portion of the reaction chamber I2 through the vapor outlet line I4, in which is interposed valve I5, said line I4 communicating with the lower portion of the dephleginator 1. Superimposed in the interior of the dephlegmator 1 are a plurality of horizontal pans or baffles I6, which need no particular description, as they are standard in commercial practice. The vapors passing upwardly through the dephlegmator are retarded in their travel in order to condense any of the heavier fractions. The raw oil introduced through the line 4 acts partly as a cooling medium for this purpose.

The vapors remaining uncondensed after coursing upwardly through the dephlegmator 1 are discharged into the vapor outlet line I1, in which is interposed valve i8, said line I1 communicating with the condenser coil I9, which, of course, is mounted in the usual condenser box, not shown. The discharge end of the condenser coil has a valve interposed therein and communicates with the receiver 2I, which receiver is, of course, equipped with the usual sight-glass gauges, pressure gauge, and with the incondensable gas outlet 22 controlled by valve 23 and liquid discharge 24 controlled by valve 25.

The unvaporized residue from the reaction chamber I2 is withdrawn through the residue drawoff line 26, in which is interposed valve 21 communicating with the cooling coil 28, and discharging the cooled residue into the line 29, in which is interposed the valve 30, to a residue storage 3l. As the separation of lighter fractions takes place within the reaction chamber I2, carbon will be released and will gradually accumulate on the bottom and build up in the interior of said chamber. It may then be necessary to withdraw the unvaporized residue at various heights from the reaction chamber, and

of course the single line 26 is purely diagrammatic.

Referring now to the important features of the present invention, portions of the distillate collected in the receiver 2 I are withdrawn into the line 32, in which is interposed valve 33, by means of the suction imposed by the pump 34, the `discharge side of said discharge pump 34 discharging the distillate into the line 35. Said line 35 communicates with the receiving end of the transfer line il! by means of the connection 36, in which is interposed valve 3l, or said distillate may be by-passed through the line 38 in which is interposed the valve 39, introducing said distillate into the stream of raw oil and reflux being passed into the inlet side of the heating coil 9.. A drain dll, having a valve 4I, may be provided adjacent the inlet to the coil 9.

The reflux condensate produced in the dephlegmator 'l and the unvaporized raW oil are Withdrawn from the dephlegmator l through the reflux line 42, in Which is interposed Valve 43, and passed to the hot oil pump 44. The discharge side of the hot oil pump 44 discharges the mixture of reflux condensate and unvaporized ravv oil into the line 45, in Which is interposed the valve 4t, said line 45 communicating With the line 46 going to the heating coil 9. In case it is not desirable to impose an applied pressure on the mixture of raw oil and reflux condensate being withdrawn through the line 42, a by-pass 4l is provided, controlled by valve 48, it being understood that when the mixture is passed through the line 4l, valve 48 is opened and valves 43 and 46 closed, and vice versa.

The particular utility and reasons for returning regulated portions of the distillate from the receiver 2I and mixing said portions with the oil being heated before it is discharged into the reaction chamber, will be noW set forth. For illustration, a 24 Baum gravity fuel oil made from Mid-Continent Crude is treated in the plant and produces 30% Navy initial and end point gasoline. The capacity of the plant will be 700 barrels without the hot oil pump 44 and say 1000 barrels of raw charging stock per day with the reflux pump 44. The entire plant may be operated at 170 pounds pressure per square inch and the oil as it leaves the heating coil 9 Will be at a temperature of say about 860 F.

Sixty percent of the raw oil fed into the plant Will be converted into pressure distillate, 501% of Which pressure distillate will be gasoline and the remainder will be pressure distillate bottoms or gas oil. The unvaporized portion in the reaction chamber I2 Will be a residue representing about 35% of the raw oil treated and will have a gravity of say 18 Baume. This unvaporized residue Will contain in suspension considerable pitchy matter and only part of this pitchy matter held in suspension will settle out upon standing. This pitchy material seems to be in a more or less colloidal condition in the residue.

From my experience, I believe that this pitchy matter is made up of carbon in a very nely divided state, Which carbon mechanically combines With the heavy ends of the oil, and the combination is so strong as to resist the oil attracted to the carbon from becoming dissolved in the remainder of the oil, floating in the oil as a scum which seriously interferes With the oil being used as fuel on account of the fact this scum Will clog the pipes and burners of the fuel system.

Operating the plant so as to increase the yield of gasoline increases the amount of this pitchy matter, which stays in suspension in the residue, and as the residue to be marketable as fuel oil cannot lcontain over a certain amount of sediment, this suspended pitchy matter renders the hours.

residue unmarketable for fuel. I have discovered that by increasing the percentage of gasoline or light gravity cracked oil to the uncracked oil as it passes through the heating coil 9, and before discharging into the reactionV chamber, that this increased percentage of gasoline or light gravity cracked oil prevents the formation of an excessive amount of this pitchy matter in the residue. At the present time, I do not fully understand how this formation of an excessive amount of pitchy matter is prevented, but it is my opinion that part of the carbon produced from cracking unites mechanically with the heavy ends of the oil and forms a pitchy matter Which remains suspended in the oil. Therefore, that oil in which the pitchy matter is suspended does not have the power to break down the attraction of the carbon to the heavy ends and cause the heavy ends to go into solution and thus precipitate the carbon.

I do find that When I increase the percentage of gasoline or light gravity cracked oils to the total oil flowing from the coil 9 to reaction chamber I2, that I decrease the amount of this pitchy matter held in suspension in the oil with the carbon and by regulating the increase, I can practically prevent any substantial amount of carbon mechanically combining with the heavy ends of the oil to form a pitchy suspended matter in the residuum. I have also discovered that the amount of free carbon accumulating in the reaction chamber per barrel of gasoline produced is decreased by increasing the amount of gasoline or light gravity oil Contained in the oil as it is transferred to the reaction chamber. For example, an oil producing normally about 40 pounds of carbon per barrel of gasoline produced 'can be so treated as to produce only about 30 pounds of carbon per barrel of gasoline produced.

As a further illustration of my invention, in operating the plant there is fed 500 barrels of raw oil through the elongated heating tube 9, and at the same time there is fed 2000 barrels of reflux tothe heating tube 9, making a total of 2,500 barrels of oil passing through the tubes and discharging into the reaction chamber every 24 Of this total, 2,300 barrels Will be vaporized in the reaction chamber, passing into the dephlegmator through the vapor line Iii. Ap-

proximately 2,000 barrels are condensed in the dephlegmator and returned to the heating coil 9 mixed With a fresh supply of oil, as heretofore described. The remaining 300 barreis will dis-J charge as vapor from the top of the dephlegmator and will be collected in the pressure distillate receiving tank 2l, after being condensed in the condenser coil I9. This 300 barrels of pressure distillate contains approximately barrels of gasoline, which is 30% of the 500 barrels of raw charging stock used, but is only 6% of the 2,500 barrels of oil passed through the heating tube 9.

In order to enrich the amount of gasoline or cracked oil to the total amount of oil passed through the heating tube 9, there are passed 500 barrels of raw charging stock and 500 barrels of reflux through the heating tube 9, making a total of 1000 barrels going through the heating tube and into the reaction chamber. Approximately 800 barrels of this amount pass to the dephlegmatcr l as vapor through the line I4, 500 barrels of which are condensed in the dephlegrnator and returned to the heating tube 9, mixing with another 500 barrels of fresh charging stock. The remaining 300 barrels pass out of the top of the dephlegmator in the form of vapor and are even- CII 2,105,526 tually collected in the pressure distillate receiver and come out in the form of distillate, this 300 barrels containing approximately 150 barrels of gasoline. The 200 barrels remaining unvaporized in the reaction chamber may be withdrawn; as residue.

In the above illustration, the 150 barrels of .gasoline produced comprises 30% of the raw oil treated, but is of the 1000 barrels of oil passing through the heating tube 9 and into the reaction chamber i2. By comparison with the run set forth above, it will be seen that I have doubled the percentage of gasoline produced in the oil passing through the heating tube.

Now I can still further increase these relative percentages by passing 500 barrels of oil directly through the heating tube 9 and discharge same into the reaction chamber I2, withdrawing from said reaction chamber 200 barrels as residue and 300 barrels as vapors, which pass through the dephlegmator, all of said 300 barrels going over into the pressure distillate receiver tank, and therefore, no reux being furnished to the oil flowing through the heating tube 9. In this case, it will be seen that the gasoline produced is not only of the raw oil treated, but is 30% of the amount of the oil passed through the heating tube 9, or lve times the amount of gasoline compared with the first operation above described. This latter operation, however, will cause the heating tube 9 to become seriously congested with carbon unless the pressure is increased in proportion, which of course, makes the pressure extremely high.

Another method oi accomplishing the same result is to feed 300 barrels of raw oil into the plant and have 700 barrels of reux, making a total of 1,000 barrels passing through the heating tube 9 and discharging into the reaction chamber. One hundred barrels of unvaporized residue may be withdrawn from the reaction chamber and 900 barrels of vapors passed to the dephlegmator, of which 900 barrels '700 barrels are condensed and refiuxed back' to the heating tube 9, as heretofore described, the remaining 200 barrels discharging from the top of the dephlegmator as vapors and condensed and collected in the pressure distillate receiver 2l, this 200 barrels containing approximately 150 barrels of gasoline, which comprises 50% of the raw oil passed into the plant, but 15% of the total oil passed through the heating tube 9. It will be noted that this 15% is more than twice the amount produced on the basis of oil cracked, as compared with the first operation above described.

The plant described in the flow chart is based on the principle that at a given pressure, the maximum of the cracking of oil passing through the heating tube 9 is limited below that amount of cracking that will cause a substantial deposit of carbon in the heating tube 9. This maximum can be increased to a certain extent by increasing the pressure under which the plant is operating and also the velocity at which the oil passes through the tube. Having established this principle, I increase the yield of low boiling point products by keeping at or below the maximum percentage of cracking in each pass of the oil through the heating tube 9 and then separate from this oil the uncracked portion, returning same to the tube for further heating, this operating cycle being repeated until the desired percentage of the total oil has been converted into gasoline and thus avoid excessive deposits of carbon in the heating tube 9.

I now seek to increase the percent of gasoline o-r similar cracked products and at the same time prevent excessive formation of pitchy matter in the residue and produce less coke per barrel of gasoline produced. I have already described how this percentage of gasoline can be increased by increasing the pressure, but the amount of pressure increase is, of course, limited, and there may be objections to high pressures. Therefore, in order not to violate any of the principles involved in a successful operation of the cracking plant as above dened, I have discovered that by increasing the percent of gasoline or light gravity cracked oil in the oil passing through the heating tube, these results .can be accomplished. Therefore, I add distillate or light gravity cracked oil to the stream of heated oil which is to be discharged into the reaction chamber, either before it is passed through the heating tube 9 or after it is passed through the heating tube 9 and before discharge into the reaction chamber. Said distillate or light gravity oil is added in such proportion as to substantially prevent the formation of pitchy matter in the residue, and these proportions will, of course, vary, not only with the character of oil being treated, but with the manner in which the regular operation is carried out.

A by-pass 49 controlled by valve 50 is provided in the line 32 in case it is not necessary to use the pump 34, valves 5| and 52 being closed in this event. By my invention, I nd I am able to obtain high yields of gasoline, even when cracking fuel oil, and at the same time produce therefrom a residue containing only a very low percentage of pitchy matter in suspension, which residue is marketable for fuel. In addition, I find that there is produced less solid matter per gallon of gasoline produced.

It is of course, understood that the stream of distillate may be split and part introduced through the line 35 into the mixture flowing through the transfer line l0, and part being introduced through the line 38 into the mixture feeding toward the heating tube 9 through the pipe 46.

I have disclosed the idea of returning portions of the pressure distillate from the receiver 2|. It is, of course, obvious that the gasoline or other lighter gravity oil may be introduced from any source of supply and need not be the distillate produced in the operation.

A preheater 53 having valves 54 introduced therein may be connected into the line 35, the valve 55 in line 35 being closed. The use of the preheater is, of course, optional. The operator of the plant may nd it desirable when treating certain oils under certain conditions to preheat the lighter gravity oil. Ihe degree of heating will be governed by conditions surrounding the operation. In other Words, it may be advisable to preheat the lighter gravity oil only slightly, that is, below the temperature of the oil discharging from the outlet end of the coil 9, or it may be advantageous to heat same to or just below the temperature at which the oil passing through the coil 9 is discharged, in order that no appreciable cooling of the oil heated in the coil 9 will take place in the transfer line I0, and yet preventing any substantial decomposition of the lighter gravity oil such as the distillate heretofore referred to into xed gas. When the distillate is introduced the oil is preferably not preheated.

Regulated portions of the lighter gravity oil may be introduced to the reaction chamber through the connecting line. 5S, valve 51 controlling said introduction. This pipe 56 may discharge at any height into the reaction chamber.

As another method of operation, regulated portions of the vapors discharging from the top of the dephlegmator may be diverted through the line 5S, lcontrolled by valve 59, and forced by means of pump 60 interposed in said line 58 to the transfer line I, or to any point in the heating tube 9 which may be found desirable. Vapors may be. diverted in this manner either with or without the return of any liquid distillate and with or Without the introduction of any other lighter gravity oil in case the distillate is not utilized for this purpose.

I claim as my invention:

l. A cracking process which comprises passing hydrocarbon oil in a restricted stream through a heating zone and heating the same therein to cracking temperature under pressure, discharging the hot oil stream into an enlarged reaction zone maintained under cracking conditions of temperature and pressure, removing vapors from the reaction zone and dephlegrnating the same to condense insufficiently cracked fractions thereof, returning resultant reflux condensate to the heating zone, combining a gasoline-containing portion of the dephlegmated vapors with the hot oil stream discharging from the heating Zone to the reaction Zone, finally condensing the remaining portion of the dephlegrnated vapors and introducing a portion of the resultant distillate into the reaction zone at a point remote from the point of discharge of the hot oil stream thereinto.

2. A cracking process which comprises passing hydrocarbon oil in a restricted stream through a heating zone and heating the saine therein to cracking temperature under pressure, discharging the hot oil stream into the upper portion of an enlarged reaction zone maintained under cracking conditions of temperature and pressure., removing vapors from the reaction Zone and dephlegmating the same to condense insuinciently cracked fractions thereof, returning resultant reflux condensate to the heating Zone, combining a portion of the dephlegmated vapors with the hot oil stream discharging from the heating zone to the reaction zone, finally condensing the remaining portion of the dephlegmated vapors and introducing a gasoline-containing portion of the' resultant distillate into the lower portion of the reaction zone.

3. A cracking process which comprises passing hydrocarbon oil in a restricted stream through a heating zone and heating the same therein to Vthrough-the pipe 38, the valve 3l being closed,

cracking temperature under pressure, discharging the hot oil stream into an enlarged vertical reaction vzone maintainedv under cracking conditions of temperature and pressure, passing the unvaporized oil downwardly through the enlarged zone and removing the same. from the lower portion thereof, removing vapors from the reaction zone and dephlegmating the same to condense insufficiently cracked fractions thereof, subjecting the dephlegmated vapors to further condensation to form a gasoline-containing distillate, passing a gasoline-containing portion of said distillate through a second heating zone and heating the same therein sufficiently to prevent cooling of said hot oil discharged from the first-mentioned heating Zone upon commingling therewith, and then discharging the thus heated distillate directly into the lower portion of the reaction Zone to commingle with the unvaporized oil therein.

4. A cracking process which comprises heating hydrocarbon oil to cracking temperature under pressure while flowing in a restricted stream through a heating zone, subsequently discharging the heated oil into the upper portion of an enlarged separating zone and separating the same therein into vapors and unvaporized oil, fractionating the vapors to condense heavier fractions thereof and to form a gasoline-containing distillate, passing a gasoline-containing portion of said distillate through a second heating zone and heating the same therein sufficiently to prevent cooling of said heated oil upon commingling therewith, and then discharging the thus heated distillate directly into the lower portion of the separating zone to commingle with the unvaporized oil therein.

5. A method of hydrocarbon oil conversion, consisting in passing a stream of hydrocarbon oil through a continuous elongated passageway, Where it is heated to a conversion temperature, maintaining a substantial super-atmospheric pressure on the oil, discharging said heated oil into an enlarged zone where substantial separation of lighter fractions in the form of vapors will take place, separately withdrawing the vapors and subjecting them to dephlegmation, in condensing portions of the uncondensed vapors after dephlegmation and collecting them as liquid distillate, returning regulated portions of the vapors without substantial condensation and mixing them with the heated oil prior to discharge into the enlarged zone, also returning and mixing regulated portions of the liquid distillate with the heated oil prior to discharge into the enlarged zone for the purpose of increasing the percentage of lighter fractions in said oil.

CARBON P. DUBBS.

Images