US1353316A - Apparatus for cracking hydrocarbons - Google Patents

Description

J. W. COAST, JR.-

APPARATUS FOR CRACKING HYDROCARBONS.

APPLICATION FILED sEPT.27,1911.

1,353,31 6. PatentedSept 21, 1920.

i115 jfinmeys.

UNITED STATES PATENT OFFICE.

JOHN COAST, JR., OF TULSA, OKLAHOMA, ASSIGNOR TO THE PROCESS COMPANY, OF

TULSA, OKLAHOMA, A CORPORATION or .MABYLAND.

APPARATUS FOR CRACKING HYDROCARBONS.

Specification of Letters Patent. Patented Sept. 21, 1920.

Application filed September 27, 1917. Serial No. 193,457. 1

following is a full, clear, and exact description, reference being had to the accompanying drawing, forming a part of this specifiapparatus for cracking hydrocarbons, the.

cation.

, This lnventlon relates to lmprovements 1n main object being to generally improve this art by providing a safe, economical and highly eflicient means for treating high boiling point hydrocarbons to obtain a more volatile product known as gasolene, or crude gasolene.

More specifically stated, an object of the invention is to protect cracking stills from.

the injurious effects of fre carbon and tarry substances known in the art as coke and coke-forming matter. By positively eliminating the danger and minimizing the labor and trouble usually due to the formation of coke in cracking stills, the cracking operations can be carried on continuously for a much longer period of time, without cooling the stills and without removing the residues. A great saving of time and fuel is effected by operating the stills in this manner. The method of circulating and collecting the coke-forming matter overcomes the danger of overheating and rupturing the stills, thereby very materially increasing the life of the stills and reducing the cost of repairs.

to a minimum. This coke-forming matter 1s not a good conductor of heat, and 1n the ordinary cracking stills it accumulates between the fire and the oil, thus preventing the free transmission of heat to the oil. Un: der these conditions, the still becomes overheated, and fuel is dissipated or wasted in heating the coke, instead of being utilized as an efiicient heating medium for the oil.

Another object of the invention is-to facilitate the cleaning of the still by causing coke-forming matter to accumulate in receptacles from which it. can be easily removed. Another object is to generally increase the efficiency of the apparatus by forcibly circulating the oil from a still through a heat ing coil, thereby further economizmg' in the large cylindrical still.

- coke forming use of fuel, maintaining all of the oil at a desirable high temperature, and enabling the temperature of all of-the oil to be raised quickly at the beginning of the operation.

A further object is to increase the yield of 'low boiling point hydrocarbons by subjecting the oil to treatment under two different conditions, as will be hereinafter pointed out. The pressure and temperature of the contents of a still are preferably different from; the pressure and temperature of the heating coil hereinafter pointed out, and a stream of the oil undergoing distillation is circulated back and forth, from the heating coil to the still. In the preferred form of the invention, all of the foregoing advantages are obtained by continually circulating a stream of oil from. a large cylindrical cracking still, through a pipe known as'a heating coil, or cracking coil and then back to the cylindrical cracking still, at the same time separating cokeforming matter from the circulating oil. The contents of the pipe may be maintained at a higher temperature and under a higher pressure than the cylindrical still. It may be noted that the relatively small pipe will withstand a higher pressure than a oils, the pipe is maintained at a relatively high temperature and the pressure is regulated soas to prevent vaporization therein. The heavy hydrocarbons are thus subjected to the desired degree of heat, and thereafter permitted to vaporize at a lower temperature in the largestill, where the pressure is low enough to obtain this result. However, both the still and the pipe forming a cracking coil' are preferably I maintained under pressure, and at a. cracking temperature. If desired, a substantially uniform temperature and pressure may be maintained throughout the apparatus. v V

' Figure I is a diagrammatical view of a cracking apparatus constructed in accordance with the invention. I 1

Fig. IIis an enlarged vertical section of one of the strainers, or filters, whereby matter is separated from the circulating oil. In the apparatus shown to illustrate the invention, a large cylindrical cracking still 1 is arran ed above a heating chamber 2 and con- In treating some necte by means of a vapor pipe 3 to an air cooled reflux condenser 4. 5 desifgnates a vapor pipe leading from the re u condenser 4 to a main condensing coll 6 from which the low boilingpoint product. is re:

.covered. The condensing coil 6 is preferably arranged in a water tank 7.

8 desi ates a heating coil, or cracking coil, pre erably consisting of a long coil of relatively small pipe arranged in a heating chamber or.furnace 9. An intake pipe 10, leading from the lower end of the pipe 8, passes through an end wall of the cylindrical still 1 and is connected to a filter A. designates a pipe section arranged in the lower portion of the cylindrical still 1 and connected to a rotary pump 12. A pipe section 13 leads fromthe pump to the filter A.

. A power shaft 14, passing through a stuffing box 15 at one end of the cylindrical still, may be rotated to actuate the pump 12. A pinion 16 fixed to the inner end of shaft 14, meshes withan operating wheel 17 on the pump, and this shaft 14 may be rotated by transmitting power to a wheel 18 at the exterior of the still.

The cracking coil 8 is provided with a discharge pipe 19 passing through an end of the cylindrical still and connected to a filter A, the latter being provided with a disby adjusting a valve 22 adjacent to,the

burner 21. The bottom of the large cylindrical still may be heated by a flame dis-' charged from an oil burner 23, and the temperature may be regulated by adjusting a valve 24. To avoid the heat losses usually 7 .incurred by discharging hot gases and products of combustion from a heating chamber, a flue 25 leads from the heating chamber 9 to the heating chamber 2. The hot fluid passing from the chamber 9, flows over a baffle 26, then downwardly through the flue 25 to the heating chamber 21 below the" still 1. A flue 27 leads from the heating chamber 2. 28 designates a by-pass formed below the heating chamber 2 to place the flue 25 in communication with the flue 27. A damper 29 may. occupy the position sho-wn by full lines in Fig. I to close communication between the flue 25 and the by-pass 28, and said damper may be adjusted to the position shown by dotted lines, so as to prevent the hot gases from flowing through the heating chamber 2. The filters or strainers, A and A may be made exactly alike, each preferably compris- "lIlg a screen 30 (Fig. 11) arranged. in a housing iii wherein the coke-forming matter the oil is again filtered in the filter is separated from the oil. Each filter, or strainer, may also include a layer of mineral wool 32 arranged above the screen 30, and a'layer of fullers earth'33 between the mineral wool and the top wall of the housing 31. This top wall may be easily 'removed'for the purpose of removing accumulations of coke-forming matter from the filter.

While the oil is undergoing distillation, the rotary pump 12 is operated continually, thereby drawing oil and coke-forming matter through the perforations in the intake pipe 11 near the hotstill bottom, the stream of oil and coke-forming matter being drawn to the pump 12, and forced through the' pipe 13 to the filter A.- The free carbon, or cokeforming matter, accumulates in the filter A,

and the filtered oil is constantly discharged through the ipe 10 to the intake end of the coil 8. i stl'eam of oil is thus taken from the relatively large body in the cylindrical still 1, and forced through the coil 8 from which it is discharged through the pipe 19, filter A and discharge pipe 20. The stream of oil is forced through the coil at a high velocity, so as to carry coke-forming matter to the filter A, the filtered oil being discharged through the pipe 20 to the main body of oil in the large still. By circulating and filtering a stream of oil as herein shown, coke-forming matter is constantly drawn from the lower portion of the large still 1 and deposited in the filter A, where it will not in any way interfere with the transmission of heat to the oil.

It is also an advantage to filter the oil before discharging it into'the coil. The usual method of cracking hydrocarbons in coils, consists in forcing a fresh charge of unheated oil into the hot coil of pipe, without in any way removing coke-forming matter from the oil. As a result, the coke or carbon accumulates in the small pipe, and at some point or points the coil soon becomes clogged by the-coke or carbon, and it is then usually necessary to discontinue the cracking operation for the purpose of removing the coke from the pipe. There is also danger of overheating the pipe at the coke deposits. Thereforc, o.ne of the desirable features of a the present invention consists in subjecting the oil to a cracking operation in the large cylindrical still, forcing a stream of the hot oil through the coil, and at the same time separating free carbon or coke-forming matter from the oil before it reaches the coil.

' This, of course, will not entirely prevent the formation of coke or carbon in the pi e, so be fore it is returned to the main body in the large still.

It will now be understoodthat the present invention overcomes. or materially reduces,

the danger and expense due to the presence of carbon or coke in the still, at the same time avoiding the loss of heat usually due to accumulations of coke between the fire and the oil. The circulation of the oil also increases the efficiency of the heating elements. Another important feature consists in the treatment of the same body of oil in alarge cracking still and also in a cracking coil. Someoils, or some constituents of the heavy hydrocarbon oil, will not respond readily to the cracking operation which takes place in only one still. By repeatedly subjecting the oil to the conditions existing in both the cracking coil and cylindrical still, a more effective cracking operation is obtained, and the yield of low boiling point liquid is greatly increased.

Owing to the manner in which the oil is circulated, also to the removal of coke from the walls of the stills, the apparatus can be operated continuously for a considerable period of time, and a fresh charge of oil can be occasionally introducel into the system, by means of a pump 30 and a pipe 31 leading from the pump to the pipe 10.

The apparatus herein shown is particularly adapted for use in cracking high boiling point products of distillation, such, for

example, as distillates, or residues, resulting from the. distillation of crude petroleum.

By regulating a valve 32, in the vapor pipe 5, any desired pressure may be obtained in the large cylindrical still 1. The pressure in the cracking coil may be regulated by adjusting a valve 33 in the'discharge pipe 19. The pressure in the large still is preferably greater than 50 pounds per square inch, for example, about 80 pounds per square inch, and the temperature of the contents of the large still preferably ranges from about 600? F. to 800 F. The low boiling point vapors passing from the liquid, flow through the vapor pipe 3 and reflux condenser 4 to the pipe 5 leading to the main condenser 6 from which the low boiling point product is recovered.

The two different cracking elements herein shown are preferably maintained at different temperatures and under different pressures, the pressure and temperature in the cracking coil being preferably higher than the pressure and temperature in the larger still. The small pipe will withstand a relatively high pressure and a relatively high temperature.- By regulating the valve 33',

any desired relatively high pressure, for exe ample, 150 pounds per square inch, can be maintained in the pipe still, while the valve 32' in the vapor pipe 5 is regulated to maintain a lower pressure, for example, 80 pounds per square. inch, in the large cylindrical still. Although the temperature of the cracking coil is relatively high, vaporization of the oil therein can be prevented by the relatively high pressure, and when the oil is discharged lighter constituents are permitted to vaporize under the lower degree of pressure in the large still. which do not respond to the ordinary cracking treatment may be successfully cracked when subjected to the high pressure and the high temperature existing in the cracking coil. Obviously, such treatment increases the yield of low boiling point fractions.

Since the large body of oil in the cylindrical still 1 is heated internally by the relatively hotstream of oil passing from the cracking coil, it is not necessary to subject the bottom of the large still to the high temperature usually employed when all of the heat is transmitted directly to the still bottom.

The cracking coil is preferably provided with an intake pipe 40 having branches 41 and 4:2 for the admission of steam and natural gas. Valves 43and 44 may be regulated Many of the heavy fractions to control the flow of steam and natural gas,

and when necessary or desirable these valves can be closed, or only one of the valves can be opened to admit only one of the fluids to the intake pipe 40. The velocity of the oil in the coil is increased by introducing the steam and gas at a relativelyhigh pressure. It is important to note that the circulating stream of oil is confined under pressure and cracked in the presence of steam and gas, preferably .natural gas. By mixin the steam and gas with the circulating 011, the yield is increased, and a sweeter and better product having a more desirable initial boiling' point is obtained. This seems to indicate that only a very small percentage of the i oil is converted into a fixed gas, or that the natural gas is absorbed in the oil by the action of steam and a high degree of heat.

The process herein disclosed is claimed in an application for patent filed byme Sep L I tember 27, 1917, Serial Number 193,456.

I claim 1. In an apparatus for cracking petroleum hydrocarbons, two cracking elements comprising a pipe and a relatively large still,

hydrocarbons, a large cylindrical cracking still, a cracking coil, oil conductors whereby a stream of oil may be circulated back and forth from said still and through the crack ing coil, apump for forcing the stream of a i 1,353,31e

oil through said conductors and through cracking still, said valves being adjustable the cracking coil, a vapor line leading from independently of each other so as to regu- 10 said cylindrical cracking still, a pressure late thepressure of the stream of oil inderegulating valve for regulating the pressure pendently of the pressure in the cylindrical in said vapor line and cylindrical cracking cracking still. still, and a pressure regulating valve ar- In testimony that I claim the foregoing ranged in the course of the fluid flowing I hereunto afiix my si nature. from the cracking coil to the cylindrical J O' W, COAST, JR.

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