US1810574A - Method of manufacturing high compression automotive distillate - Google Patents

Description

C. J. PRATT Filed June 14, 1928 METHOD OF MANUFACTURING HIGH COMPRESSION AUTOMOTIVE DISTILLATE June 16, 1931.

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Patented June 16, 1931 ALTENT OFFICE CLIFTON JOHN PRATT, OF ST. LOUIS, MISSOURI, ASSIGNOR TO THE AUTOMOTIVE DIS- TILLATE CORPORATION, OF INDEPENDENCE, KANSAS, A CORPORATION OF KANSAS METHOD OF MANUFACTURING HIGH COMPRESSION AUTOMOTIVE DISTILLATE Application filed June 14,

This invention relates to a process of, and apparatus for distilling oils and with re-. gard to certain more specific features to the method of and apparatus for improvedly converting crude petroleum oil into high compression automotive distillate.

Among the several objects of the invention may be noted the provision of improved means for carrying on a plurality of cracking processes on a given oil'in such manner that coking in the furnace tubes is eliminated and a better product produced but at the same time carrying on one of said cracking processes directly in the tubes of a heating furnace, whereby the requirements for an expansion chamber is eliminatedpthe provision of means for effecting an improved blend of the products due to said cracking processes; the provision of apparatus for the purposeset forth having a minimum number of elements and requiring the minimum amount of heat; and the provision of means of the class described in which accurate control may be had with less difliculty. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprsies the elements and combinations of elements, steps and sequence of steps, features of construction, and arrangements of parts which will be exemplified in the structure hereinafter described, and the scope of the ap-plicatlon of which will be indicated in the following claims.

In the accompanying drawing, in which is illustrated one of various possible embodiments of the invention, the figure illustrates diagrammatically the relationship between the elements of the system.

1 Similar reference characters indicate corresponding parts throughout the single view of the drawing.

Referring now more particularly to the drawing, numeral 1 indicates a supply tank for crude oil, numeral 3 indicates a residuum tank, numeral 5 a tank for precracked or recycled stock and numeral 7 a gasoline tank. It isto be understood that the term gasoline \valves 39the heat exchanger 35 can be bypassed by the hot residuum passing toward 1928. Serial No. 285,407.

sion automotive distillate obtained by the present process.

Numerals 9 and 11 indicate cooling boxes for the purpose of cooling materials passed to the tanks 3 and 5 respectively and 13 is a condenser box for material passing to tank 7. Numerals 15 and 17 indicate outlets for tanks land 5 respectivelywhich outlets pass to pumps 19 and 21 respectively.

The crude oil pump 19 has an outlet 23 from which branches one line 25 to a furnace connection 27 and another line 29 which passes to an evaporating chamber 31 of a bubble tower 33. The line 29 passes through a heat exchanger 35 the latter being heated by the hot residuum which passes from said evaporating chamber 31 to residuum tank 3, provided that valve 37 is closed and valves 39 are open. By opening valve 37 and closing the tank 3. Valves 41 and 43 permit of control of lines 25 and 29 in such a way that the pump 7 19 may be caused to pump through either of the lines 25 or 29 separatel or through both in any desired proportion, ependingupon the relative valve openings. Suitable meters and gauges are used in connection with the pumps.

The pump 21 is equipped withan outlet line 45, also leading to said furnace connec'- tion 27 by wa offpreheating or reflux coils 47 and 49. Viilve's 51 and 53 on each side of the furnace connection 27 permit of such control that either of the pumps may be cut into or out of action for pumping liquid into the cracking furnace F through the connection 27. Or said valves 51, 53 may be set to permit passage to the furnace from both pumps 19 and 21. i

The single cracking furnace. F is equipped with heating tubes 55 which are in communication with the connection 27 and in communication' with an outlet line 57 leading to the evaporating chamber 31 of the bubble tower 33. A suitable burner 59 is used to heat" the furnace.

It will be noted that one preheating or reflux coil 49 is in the evaporating chamber 31, and the other preheating or reflux coil 47 is herein. refers to the improved high compresin the fractionating or dephlegmating chamber 61, of the bubble tower 33, the chamber 61 being in communication with the chamber 31 by way of the stand pipe 63. A vapor outlet line is provided from the top of the fractionating chamber and passes to the gasoline tank 7 by way of condenser box 13.

Suitable pyrometers P are used for checking temperatures throughout the system.

' The operation may be divided into two stages, namely, (A) starting operation, and (B) continuous operation.

(A) To start, valves 43, 39 and 53 are shut, while valves 41, 37 and 51 are open. Pump 19 is started but pump 21 is not. The burner 59 is operated at a relatively low rate. Hence the pump 19 withdraws crude oil from the tank 1 and delivers it by way of valve 41, line 25, valve 51, connection 27, tubes 55 and line 57 to the evaporating chamber 31. Inasmuch as crude oil has a great tendency to coke in the furnace tubes when too high a heat is used, the heat of the furnace is kept down so that coking of the crude oil is prevented in the tubes 55. The temperature at this stage of the operation in line 57 is of the order of 800 degrees F: but this may be somewhat varied with the particular crude stock being used. The point is that the temperature should under starting conditions be kept down so that coking of the crude oil in the tubes 55 is prevented.

Under the starting conditions recited above the rate of distillation is low. Hot

residuum and unevaporated crudes collect in the chamber 31 and flow to the residuum tank 3 through valve 37. Somevapors pass into the fractionating chamber 61, where fractionating takes place, at least to the extent of forming a liquid level 67 of intermediate fraction or recycling stock which flows into the tank 5.

(B) After a period of operation such as above described, the pump 21 is started for continuous operation and the crude oil pump 19 is permitted to continue running. However, all valves are reversed in position so that valves 43,39 and 53 are open, while valves 41, 37 and 51 are closed. This results in the, pump 21 delivering recycling stock from the bulk supply in the tank 5 through line 45 (including preheating coils 47 and 49) through the furnace connection 27, furnace coils 55 and line 57 to the evaporating chamber 31. Thus it will be seen that instead of crude stock being pumped through the cracking furnace F, that the clear and beter quality of intermediate, recycling stock from tank 5 is pumped through said furnace. The recyclingstock better resists coking at higher tem eratures than the crude stock, so that the urner 59 is now causedto increase the furnace temperature. During continuous operation the ter'npearture in line 57 is of the order of 1250 degrees F., depending upon 65 the particular oil being treated, It will be seen that the furnace temperature is some v four to five hundred degrees higher under continuous operating conditions as compared with starting operating conditions. The clear recycling stock enters the furnace at a temperature of the order of 550 degrees 13]., due to the action of the preheating coils 4 ,49.

It is to be understood that the change over from operation A to B may be made graduallyby' slowly opening valves 43, 39 and 53 and proportionally slowly closing valves 41, 37 and 51. At the same time the temperature of the furnace gradually increases.

Under ultimate continuous operating conditions, the pump 19 pumps all of the crude oil through line 29 and heat exchanger 35 to the evaporating chamber 31 where it meets the high temperature cracked vapors from the cracking furnace. The residuum from chamber 31 flows through the heat exchanger 35 to preheat the crude oil and in efi'ect said heat exchanger takes the place of the furnace F in regard to heating the crude oil. The temperature of the oil due to the action of the preheater is not'such as to cause coking but it does effect an incipient distillation.

Under the continuous operating conditions full distillation is had and the vapors from both the crude and recycling stockspass into the fractionating chamber 61 and are separated therein to provide both intermediate fractions for further carrying on the recycling process and also to provide light vapors which pass out through line 65 to the condenser 13, and are condensed to distillate or gasoline which passes to the tank 7. Hence with one furnace the advantages are had of segregating the means for heating crude stock and recycled stock and also the advantage of obtaining a blending action in the bubble tower 33. The blending can be controlled by controlling temperatures and pressures throughout the system, that is, Within the limits for proper heating of the oil in View of this invention.

One of the features of the present invention I comprises the operation of the system such that the recycled, intermediate stock passing through the coils 55 will reach a cracking temperature in said tubes, the tubes being long enough to permit this action. Hence,

stock from the cracking furnace F. In the present invention, the intimate contacting is achieved by maintaining a liqud level of the preheated crude stock in the vaporizing chamber 31, and introducing the said superheated cracked vapors below this liquid level. The bubble tower 33 also provides a fractionating or dephlegmating chamber 61. Said bubble in the cracking tower 33 is not maintained at high pressures, but on the contrary is maintained atsubstantially atmospheric pressure.

It will be seen that the recycled stock collecting in the bottom of the fractionating chamber 61 comprises an intermediate fraction, from whichthe residuums and higher boiling-point coke-forming constituents have already'been removed. This stock has already been subjected'to at least one crackin operation (in the evaporating chamber 31 and may, therefore, be termed a precracked stock,

By using the recracked or recycled stock Furnace F for high temperature operation, the formation of carbon is minimized. The'small amount of free carbon that may be produced in tubes is carried forwardly in the tubes by the velocity of the vapors due to cracking in the tubes, said carbon being held in suspension be: cause of the turbulence had at bends and the like. Thus instead of carbon deposits building up in tubes 55, the carbon is carried over to the bubble tower.

Some carbon is also directly formed in the bubble tower due to the cracking action of the cracked vapors on the preheated crude oil. However, the formation and agglomeration of carbon in the bubble tower is not a serious result, inasmuch as the carbon formed is of a porous and spongy nature through which operations may be continued without interruption of the plant. Even excessive deposits are easily cleaned out. Onthe other hand, if these deposits were permitted to occur in the tubes 55, much more dificulty would be had. The tubes might burn out and at best they would clog up sooner and prevent operation altogether.

In the present process the crude oil itself is cracked so as to obtain the greatest percentage of lowest boiling point h drocarbons. This is done by breaking up t e highest boiling point hydrocarbons in the crude oil. In the case of the precracked or recycled stock there are produced by cracking hydrocarbons coming in the gasoline series but with a boiling point range substantially higher, so that a maximum percentage of higher boiling point hydrocarbons is had. By blending these hydrocarbons from both the crudes and the cracked recycled stock in the bubble tower the advantages of both results are bad in the final condensed product passing to tank 7.

Under starting conditions the head pressure for pump 19 is about five pounds gauge. Under running conditions it is about two pounds gauge and whenever the puinp 21 is running its head pressure is about seventyfive pounds gauge. It is to be noted that these pressures are for the purpose of overcoming frictional resistance in the piping, coils, and the like, only, and do not constitute superimposed pressures requiring expansion valves at subsequent points in the apparatus. It is intended that pressure and temperature be so controlled within the requirements for the improved operations set out that the pressure in the bubble tower 33 will remain at about that of the atmosphere, that is, zero pounds gauge.

lln view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

( 1. The process of treating hydrocarbons which comprises preheating said hydrocarvapors to form recycling hydrocarbons, sep- 7,

arately removing and cooling said recycling hydrocarbons, maintaining an independent bulk supply of said cooled recycling hydrocarbons, whereby the optimum treating conditions for said recycling hydrocarbons may be continuously controlled, withdrawing recycled hydrocarbons from said bulk supply, and substantially completely cracking said recycled hydrocarbons without dilution in the vapor phase ata temperature of the order of 1250 F. at substantially no superimposed pressure, bringing the hot cracked vapors thus formed into contact with said preheated hydrocarbons, and removing light cracked hydrocarbon vapors and condensing the same.

2. The process of treating hydrocarbons which comprises preheating said hydrocarbons, subjecting said "preheated hydrocarbons to a preliminary cracking operation at substantially atmospheric pressure by establishing a liquid level of said preheated hydrocarbons and introducing cracked hydrocarbon vapors beneath said liquid level, whereby the preheated hydrocarbons are cracked and mixed vapors and liquid residuums are formed,-removing said liquid residuums, partially condensing said mixed vapors removing and cooling said recycling hydrocarbons by indirect heat exchange, maintain- I ing an independent bulk supply of said cooled recycling hydrocarbons, whereby the 0 timum treating conditions for said recyc mg hydrocarbons may be continuously controlled, withdrawing recycled h drocarbons from said bulk supply, preheatmg the withdrawn recycling hydrocarbons by indirect heat exchange with said mixed vapors, and substantially completely cracking said recycled hydrocarbons without dilution in the vapor phase at a temperature of the order of 1250" F. at substantially no superimposed pressure,

bringing the hot cracked vapors thus formed a into contact With said preheated hydrocarbons, and removing light cracked hydrocarbon vapors and condensing the same.

In testimony whereof, I have signed my name to this specification this 11th day of June, 1928. V

p CLIFTON JOHN PRATT.

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