US2105467A - Treatment of hydrocarbons - Google Patents

Description

Jan. 18, 1938. P. MED. BIDDISON ET AL 2,105,467'

TREATMENT OF HYDROC ARBONS Filed Feb. 20, 1935 6,45 OIL Patented Jan. 18, 1938 TREATBIENT F HYDROCARBONS Pascal McDonald Biddison, Dallas, Tex., and Max R. Ryan and Charles R. Burke, Tulsa, Okla., assignors to Danciger Oil & Refineries, Inc.,

Tulsa, Okla.

Application February 20, 1935, Serial No. 7,438

1 Claim.

Our invention consists in new and useful improvements in the method of producing low boiling point hydrocarbon products such as gasoline, naphtha and benzol, suitable for use as motor fuels, from high boiling point hydrocarbons, and is in the nature of an improvement on the invention disclosed in U. S. Letters Patent to Pascal McDonald Biddison and Hugh T. Boyd, #1,345,740, issued July 6, 192,0.

The primary object of the invention is to greatly increase the productionof low boiling point hydrocarbon products suitable for use as motor fuels and to improve their quality, and also to eliminate many of the difculties of operation heretofore experienced in conversion processes.

Another object of our invention is to provide means for carefully regulating and controlling the operation in order that low boiling point hydrocarbons may be simultaneously produced from several higher boiling point hydrocarbons as de- 0 sired by the operator. This we accomplish among other means, by the injection of a suitable gas which is mingled with the high boiling point hydrocarbon oil to be converted into low boiling point hydrocarbon products suitable for motor fuel, while both are being heated to a temperature sufficiently high to accomplish the desired conversion.

'Ihe use of a gaseous medium in a process of this character as described in the U. S. Patent No. 1,345,740, above referred to, involves the law of partial pressures, and is of great value in producing the desired results, and We have found that a further reason for the advantages of such process is that under a temperature and pressure relationship peculiar to each grade and class of oil, prior to the occurrence of the vaporization of the hydrocarbon oil, a condition of molecular instability of several of the constituents of the oil is produced and therefore certain constituents of the gas combine with those of the hydrocarbon oil.

In our process, the mixture of hydrocarbon oils and gas in the cracking zone is raised to such a pressure and temperature that on at least a portion of the oils, a state of molecular instability is produced with the result that conversion of some of the oil into lower boiling point hydrocarbons occurs, and simultaneously there may be molecular readjustment between oil constituents and gas constituents whereby certain gas constituents become components of some of the lower boiling point liquid hydrocarbon components resulting from the process.

A still further object of our invention is to combine with this gas injection feature an eicient system of refluxing, heat exchange, cleansing, quenching and mixing at various steps of the operation to produce a motor fuel of the desired quality, with a minimum loss and maximum efficienCy.

With the above and other objects in view which will appear as the description proceeds, our invention consists in the novel features hereini set forth, illustrated in the accompanying drawing and more particularly pointed out in the appended claim.

In the accompanying drawing, we have shown a flow diagram which illustrates one form of apparatus by means of which our invention may be carried out.

Referring to the drawing, I represents a line leading from a suitable source of raw charging stock (not shown) to the inlet end of a vapor heat exchanger 2 located in the upper end of a vapor separator 3. The outlet end of the heat exchanger 2 is connected to a line 4 provided with a valve 5 and terminating in communication with line 6 leading into the lower portion of the separator 3.

. 1 and 8 represent cracking zones preferably of the type comprising a bank or banks of tubes which also discharge into line 6, the former through line 9 and valve l0, and the latter being directly connected to line 6 through valved connecton Il.

The lower extremity of the vapor separator 3 is provided with a liquid draw-olf connected into line l2 provided with a valve I3 and terminating in communication with a stripping tower lli, the latter being provided with a vapor discharge line l5 leading to condenser I6, and a liquid drawoff at its lower extremity connected into line Il. The discharge end of the condenser I5 is connected by line i8 to line I9 which leads in one direction to a suitable storage tank (not shown) and is provided with a valve 2D and pump 2l, While in the opposite direction the line I9 leads to substantially the central portion of a fractionating column 22, a suitable pump 23 and valve 24 being provided between the pipe I8 and the fractionating column 22. Thus, by manipulation of the valves 2D and 24, the condensate from l5 may pass to a storage receptacle or may be returned to the system through`the fractionating column 22 as will hereinafter appear.

A second charging line 25 leads from a suitable source of a lighter charging stock and has interposed therein a pump 26, said line leading to the inlet end of a second vapor heat exchanger 2'! arranged adjacent heat exchanger 2 in the upper end of the vapor separator1 3. The outlet end of this heat exchanger 2'! is connected into a line 28 which leads to the inlet pipe 29 of the cracking zone The bottom of the fractionating column 22 is provided with a liquid draw-01T in communication With line 30, having a suitable pump 3| interposed therein and terminating in communication with the inlet pipe 32 of the cracking zone 8.

The top of the vapor separator 3 is providedwith a vapor outlet connected into vapor line 33 which terminates in communication with the lower portion of the ractionating column 22. At a suitable point in the upper portion of the vapor separator 3 below the heat exchangers 2 and 2'!, We provide a condensate accumulator 34 which may be of any suitable type, that shown in the drawing consisting of an annular tray extending entirely across the separator shell. and having a central opening bounded by a vertically extending circular wall 35, and an overiiow pipe 34 equipped with a liquid seal at its lower end. The side of the tray 34 opposite the liquid seal is provided with an opening leading into line 36 which extends through the shell of the separator and terminates at its opposite end in communication with the fractionating column 22 at a point preferably above the connection of the vapor line 33, said line 36 being provided with a Valve 3'! at a point intermediate its ends.

38 represents a charging line leading from a third source of charging stock such as gas oil (not shown) and terminating in communication with the line i9 leading to the fractionating column 22, said line 38 having interposed therein a pump 39. Thus, by manipulation of the valve 24 in line I9, this gas oil charging stock may be fed to the fractionating column 22 either alone or combined with the condensate from condenser i3.

At a suitable point in the upper portion oi the fractionating column 22, we provide a line-4U which leads to a point below the top of an accumulator 4l, the lower end of the latter being provided with a liquid draw-off connected into line 42 provided with pump 43 and valve 44, and terminating in communication with line 25 leading to heat exchanger 2'! in the vapor separator 3.

The top of the accumulator is arranged in communication with a vapor line 45 which leads into theupper portion of the fractionating column 22 at a point above the connection of line 4Q just described. Thus the liquid in the accumulator 3l may be intermingled with the light distillate ied through line 25, heat exchanger 2'! and line 28 to the cracking .Zone l, and the vapors from said accumulator carried back to the upper portion of the fractionating column 2'2.

The top of the fractionating column 22 is equipped with a vapor outlet arranged in communication with a line i3 which terminates in communication with a gas separator and has interposed therein a suitable condenser 613. The bottom of the gas separator 4'! has a liquid drawoff line e9 connected to a branch line 50 which leads back to the upper portion of the fractionating column 22, a pump 5I being provided at a suitable point ingsaid branch line whereby a portion of the condensate kfrom the gas separator 4'! is returned to the top of the fractionating column. The remainder of said condensate is conveyed from the system through line 49 to a suitable point not shown. 52 represents agas line leading from the topof the gasseparator 4'! through Which the separated gases leave the system.

Adjacent the inlet ends of the cracking zones and 8, We provide gas lines 53 and 5ft leading into inlet lines` 29 and 32, respectively, for the purpose and in the manner hereinafter described more in detail. l y

Having thus described one form of apparatus by means of which our improved method ci' treating high boiling point hydrocarbons may be carried out, its operation is as follows:

Raw oil charging stock, which may comprise any constituents of petroleum crude, is supplied through line l, heat exchanger 2, line valve 5 into line 6 Where it mingles with the gases, vapors and liquids from the cracking Zones 'l and 8. This mixture enters vapor separator 3 through line E and substantial vaporization takes place in said separator. The unvaporized portion of the mixture has the general characteristics oi" fuel oil and is withdrawn from the bottom of the vapor separator through line l2, and if desired, this residual oil may be further treated in the tar stripper hi.

This tar stripper tower is maintained at a lower pressure than the vapor separator 3 whereby further vaporizatio-n occurs when the oil enters this zone of lower pressure. In some instances, it may be desirable to increase the stripping action in the tower iii by the use of steam, cr vacuum, or both. The vapors evolved in the stripping tower l are discharged through line i5 and condensed in 3, and the condensate may pass from line I8 through valve 23 and pump 2i to a suitable storage receptacle not shown, or by closing the valve 20, it may be conveyed in whole or in part through line i9, valve 213 and pump 23 and discharged into the fractionating column 22. The stripped residuum is withdrawn from the stripping tower I3 by means of line H.

The gases and vapors formed in the vapor separator 3 flow upwardly past the vapor. heat exchangers 2 and 2'! where they are partially cooled and the highest boiling point fractions arecondensed, the condensate dropping back into the accumulator 3d. From the accumulator Sil, this condensate passes through line 36 and valve 3l into the ractionating column 22. If desired, the valve 3'! may be closed or regulated to permit the condensate or a portion thereof to overilow `from the accumulator 34 through the overflow pipe 34 and drop back into the vapor separator, thus acting as a cooling medium for the separator.

The uncondensed portions` of the gases, and vapors leave the separator 3 at its upper end through line 33 and are introduced into the lower portion of the fractionating column 22 at a point below the connection of vline 36, and as they pass upwardly through the fractionating column, they come into contact with the cooler down-flowing reflux which cools the gas vapor stream and condenses the heaviest constituents of the vapors.

During this operation, a second stream of-cool charging stock which preferably comprises 'a clean oil such as gas oil, may be supplied through line 38 and pumped by pump 39 and line i9 either alone or admixed with the condensate from-NH3, into the ractionating column 22 at a point above the entrance of the vapor line 33. A portion of this charging stock or mixture, as the case may be,v is vaporized and passes upwardly with the rising vapors in the fractionating column. The remaining portion of said charging stock will iiow downwardly as reflux and together with the normal condensate in the fractionating column, is 75 withdrawn from the bottom of the column i through line 30 and pumped by pump 3l into the Ycracking conditions in zone 8 and discharged through valve II and line 6 into the separator 3, commingled with the preheated charge of raw oil fed through lines I and 4 as hereinbefore described.

'I'he presence of this hydrocarbon gas admixed with the materials entering the cracking zone 8 creates a partial pressure effect which is of great Value in producing the desired results, and furthermore, under suitable temperature and pressure conditions, produces a condition of molecular instability of several ofthe constituents of the oil prior to the'occurrence of the vaporization of such oil, whereby certain constituents of the gas combine with those of the hydrocarbon oil.

A portion of the down-flowing reflux in the fractionating column 22 having the general characteristics of naphtha, is removed from the fractionating column through line 40 and is conveyed to the accumulator 4I from whence it is pumped by pump 43 through line 42, valve 44 and line 25, through the heat exchanger 21 in the vapor separator 3, through line 28 and into the inlet 29 of the cracking zone l. This material may be joined by a stream of fresh charging stock which consists of a light distillate such as naphtha,

'kerosene or a light gas oil fed through line 25 and pumped by pump 26 through the system.

As in the case of the material entering the cracking zone 8, a stream of suitable hydrocarbon gas is continuously introduced through line 53 into the inlet line 29 of the cracking zone I and comes into direct contact with the material fed through line 28, thus producing a charging mixture for the cracking zone 'l composed of hydrocarbon gas, a portion of the reux from the accumulator 4I and a portion of the fresh charge fed through line 25, which mixture is subjected to cracking conditions in Zone 'I and discharged through line 9, valve I and line 6 into the vapor separator 3 commingled with the cracked mixture discharged from zone 8 and the preheated charge of raw oil fed through lines I and 4. It will be noted that this commingling may take place either prior to or during the vaporization of the mixtures.

As in the case of cracking zone 8, thepresence of the hydrocarbon gas in zone 'I creates a partial pressure eect and a condition of molecular instability whereby certain constituents of the gas combine with those of the oil. The temperature maintained in the cracking zone 1 is preferably sufficiently high to partially crack the intermediate boiling point hydrocarbons, but lower than the temperature in the cracking zone 8.

A typical example of the conditions of operation in a run of our improved process is as follows:

'I'he unit was operated fty hours and twenty minutes at an average cracking coil temperature of 924 F. The last twenty hours and fortyve minutes of operation Was at a temperature of 928 F. The temperature in the outlet of the gas furnace feeding to the cracking coils during these periods averaged 1027 F. The average pressure on the cracking coil was 438 lbs. during the entire run.

Yields y Percent Gravity Gallons of charge Fresh oil charged 36. 2 976. 64 100. 00 Pressure distillate 57. 4 432.10 44. 24 Pentane and higher in residue gas. 89. 85 9. 20 Gasoline in recycle stock at nd of run. 57.6 11.14 1,14 Residuum 17. 6 143. 99 14. 74 Recycle stock after removal of gasoline at cnd of run 27. 7 156. 05 l5. 98 Lnss 14. 70

Av. rate Total per hn Cu. ft. 0u. ft. Volume of gas charged to unit l2, 958 60 Volume of gas from unit 32, 520 152 Volume of gas from u uit pcntano, free 30, 249 141 Oil rates (average for entire run) Fresh oil charged per hour gallons 4.55 Recycle oil charged per hour do 22.13

Combined feed charged per hour do 26.68 Ratio recycle to fresh oil 4.86 Soaking time average for entire run seconds 25.5

'Ihe total gasoline produced was 54.58% of the fresh oil charged to the unit. Of this, approximately '7.69% is attributable to the gas charged to the unit. This was calculated by a comparison of an identical run without the introduction of gas, which resulted in a production of gasoline at the rate of 46.89% of the total fresh oil charged.

It is understood that the foregoing is merely given as an example and that we do not intend to limit ourselves in any way by these figures.

Any vapors contained in the reflux fed through line 4D to accumulator 4| and any vapors evolved in said accumulator are returned to the fractionator 22 through line 45 leading from the top of the accumulator 4 I.

The uncondensed gases and vapors from the fractionating column 22, which comprise the motor fuel constituents, pass from the top of the fractionator through line 4B and ow through the condenser 48 from whence the condensate and nOn-condensable gases enter gas separator 41. There, a separation takes place, the gases leaving the system through line 52 and the condensate being withdrawn through line 49. If desired, a portion of this condensate may be directed from line 49 through line 50 where it is pumped' by pump I into the top of the fractionating column 22 to act as a reflux and control the top temperature of the fractionator.

It will thus be seen that we have provided a highly improved method of producing low boiling point hydrocarbon products suitable for use as motor fuels from high :boiling point hydrocarbons, which method is capable of a maximum flexibility of operation and regulation to control from various points in the system the quantity and quality of the desired products.

Naturally the temperature and pressure conditions under which this operation is conducted will vary in accordance with the grade of oil employed as charging stock and the quality of the desired product. It has therefore seemed unnecessary to specifically mention pressures and temperatures in the foregoing description as we feel that any `one skilled in the art would, from this disclosure, be enabled to carry out the process to the ends desired. v

From the foregoing it is believed that the operation and advantages of our improved method may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details of apparatus and the steps disclosed Without departing from the spirit of the invention as set out in the following claim.

What we claim and desire to secure by' Letters Patent isz A process of treating hydrocarbon oils which consists in passing a stream of oil through a re- Aiiuxing zone in direct contact with a stream of previously heated hydrocarbon gases and vapors from a vaporizng zone, vaporizing the lower boiling fractions of said stream of oil in said reuxing Zone while heating the higher boiling fractions of said stream, condensing in said reuXing zone the higher boiling fractions of vapors, withdrawing from said refluxing zone a mixture of higher boiling point liquid hydrocarbons and conducting the same to a cracking zone admixed with a stream of hydrocarbon gas, preheating a second stream of oil by indirect contact with hot vapors in said vaporizing zone, and passing the same through a separate cracking zone admiXed with a stream of hydrocarbon gas, preheating a third stream of oil by indirect contact with hot vapors in said vaporizing zone and commingling the same with the streams flowing from said cracking zones, the temperature of said third stream of oil being substantially lower than that of the streams from said cracking zones, conducting the commingled mixture to said vaporizing zoney where substantial vaporization takes place, conducting the evolved vapors and gases Vfrom said vaporizing zone to said reiiuxing zone, continuously removing the vapors and gases from the refluxing zone, and subjecting'the same to condensation and separation to formthe desired product,` and withdrawing the liquid residuum1v from said separating zone.

PASCAL MCDONALD BIDDISON. MAX R. RYAN.

CHARLES R. BURKE. v Y

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