US2027355A - Cracking process for hydrocarbon oils - Google Patents

Description

Wam 7, 1936. F Hl-,EDSON @27,35

CHACKING PROCESS FOR HYDROCARBON OILS Filed Deo. 14; 1932' Patented Jan. 7, 1936 CRACKING PROCESS FOR HYDROCARBON ILS Frank H. Edson, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware Application December 14, 1932, Serial No. 647,109

features of this invention, and Fig. 2 is a sectional view of the furnace setting.

Referring to the drawing, numeral I designates a source of supply of fresh feed stock, for example, gas oil. The fresh feed in passing from the source of supply through pipe 2 is divided into two or more parts, one fraction being passed through pipe 3 arranged with Valve 3a into a heat insulated conversion chamber or soaking drum 4 and the other part is passed through pipe 5 arranged with valve 5a into the separator l. Pumps 6a and 6b are provided to raise the 5 Claims.

This invention relates to an improved process for cracking hydrocarbon oils with the object of producing lighter hydrocarbons. Its particular object is to more efficiently produce lighter hy- 5 drocarbons as compared with the processes in use at present.

One of the diirculties encountered in the manufacture of naphtha or gasoline by cracking is an accumulation of carbon or coke formed by crack- 10 ing the feed oil under high heat and pressure.

The principal accumulation occurs in the cracking stills to which the feed stock is delivered and to a lesser degree in the towers and pipes.

It is well known that in cracking hydrocarbon l5 oils that the amount of carbon formed is dependent on the gravity, for example, heavier hydrocarbon oils tend to form more carbon than lighter hydrocarbon oils. This formation of carbon in a cracking process of a given hydrocarbon oil is minimized by my process by dividing a charge stock into two parts, passing one part to a soaking drum to contact with an oil maintained at a cracking temperature and pressure, and passing the remaining part to a separator which is maintained at a lower pressure and at an elevated temperature by passing the bottoms from the soaking drum into it. The mixture of loils in the separator is fractionated into four parts, the lowest and highest Vfractions being withdrawn from the system. The two intermediate fractions are passedto a cracking coil, the lower boiling point fraction being first passed into the cracking coil and heated to a cracking temperature at an elevated pressure and the higher boiling fraction being then passed into the heated lower boiling fraction. The mixture is subject to further heat and passed to the soaking drum. By rst heating the lower boiling fraction in the cracking coil, which tends to form less carbon than the higher boiling point fraction, and adding the higher boiling fraction to the hot oil, materially less carbon is formed than by heating the original feed stock or a mixture of the different boiling point fractions.

An object of this invention is to minimize the formation and accumulation of such carbon in the cracking stills and other parts of the system.

Another object of this invention is to subject different parts of feed stock to different degrees 5.0 of heat.

These and other objects are accomplished in accordance with the improved method which is described as follows: l

In the drawing, Fig. l is a diagrammatic pervISIS spective View of an apparatus embodying the pressure.

The soaking drum 4 is fitted with baie plates 8 at the upper part and an outlet vapor pipe 9 which is used for passing the vapors to a bubble tower ID. The bottom of the soaker 4 is provided with an outlet pipe II arranged with valve I2 for passing the higher boiling fractions into the separator l.

The fresh feed supplied to the soaking drum is heated to about a temperature of 750 F. by means of heated oil which is supplied to the soaker from the cracking coil I3 through pipe The pressure maintained in the soaking drum is 250 pounds or more per Square inch. The vapors are removed from the soaking drum through pipe 9 and bubble tower I0 where the same pressurelis maintained and a fraction of the condensatey is returned to the soaking drum by means of pipe I4 and pump I5.

The light vapors separated in the bubble tower I0 are removed by means of pipe I6 to condenser I'I and passed to separator I8 where the gases are separated by means of pipe I9 arranged with valve 2U and a fraction of the condensate is returned to the upper plate of the bubble tower I0 by means of pipe 2l and pump 22.

The remaining fractions of the condensate may be removed from separator I8 through pipe 23 arranged with valve 24 to storage, not shown.

The heavier fractions of the vapors passed from soaking drum 4 to bubble tower I0 and condensed in the bubble tower are withdrawn through pipe 25 arranged with valve 2G which valve is regulated by float 26a in the lower part of the bubble tower IG. The condensate in passing from bubble tower I9 may be cooled in condenser 21 and passed to the upper plate of separator l.l

Bubble tower l0 may be arranged with an accumulation space at the lower part and a plurality of plates such as bellcap plates Z8 in the upper part of the bubble tower.

The separator 1 is arranged with two or more bellcap plates 29 in the upper part. Bailie plates 30 are arranged below the bellcap y plates.

The bellcap plate 34 is placed in the lower part of the separator and suitable bailles 35 are arranged below bellcap plate 34. A bottom outlet pipe 36 arranged with valve 31 is used to pass the tar through condenser 38 from separator 1 to storage, not shown. The vapors passing from separator 1 are removed through pipe 39 to bubble tower 40. Bubble tower 40 is provided with a plurality of bellcap plates in the major portion of the tower. An accumulator space 42 is found in the lower part of bubble tower 4U. The vapors from bubble tower 40 are withdrawn through pipe 43, condensed in condenser 44 and passed to separator 45. Separator 45 is provided with a gas outlet pipe 46 arranged with valve 41. A fraction of the condensate is removed from separator 45 through pipe 48 by means of pump 49 and passed to the top of bubble tower 40 as reflux. The remaining fraction of the condensate in separator 45 is passed to pipe 56 arranged with valve 5I to storage, not shown. A portion of the intermediate boiling point condensate on plate 34, separator 1, may be passed through pipe 52 arranged with valve 53 into a small tank 54 which is arranged with baille plates 55 in the upper part and accumulator space 56 in the lower part. The condensed fractions of oil accumulated in the bottom of bubble tower 40 are passed through pipe 51 by means of pump 58 into cracking c`oil I3 arranged in the furnace setting 6D. Coil I3 is arranged in two sections, one section 6I being placed in the convection section of the furnace setting and section 62 is in the radiant heat section of furnace 60, as shown in Fig. 2. The oil accumulated in tank 54 is passed through pipe 63' by means of pump 64 into cracking coil 65 arranged inthe radiant heat section of furnace setting 6D.

For example, the gas oil passing through pipe 2 is divided in two equal parts, one part passing to the soaking drum 4 and the other part passing to the separator 1. The stream of feed oil is described as being divided into two parts; this is for illustration only as it may be divided in a plurality of parts, in which one part is passed to the soaking drum 4 and the other parts to various sections of the separator. The gas oi! passing to the soaking drum is heated by a heat exchange of the vapors coming from the cracking coils and cracked. The lighter fractions are passed off to the bubble tower to be condensed as light naptha. Both soaking drum 4 and bubble tower I0 are maintained at about the same pressure, which is 250 pounds per square inch or more. The fraction of the gas oil passed to the upper part of the separator 1 into which also is passed the liquid fractions present in the soaking drum and the liquid condensate formed in bubble tower I0 is heated by means of oil passed in separator 1 from soaking drum 4. The separator is maintained at about a pressure of 150 pounds per square inch or more and the lower boiling point oils are passed in the form of a vapor into bubble tower 40 where they are fractionated and the condensate formed is withdrawn and passed to the cracking coil I3. The temperature of the bottoms in separator 1 is maintained at about 680 F. The oil accumulating on bell cap plate 34 is removed to tank 54 from which it is passed to the upper section 65 0f the cracking coil I3. Pipe 66 arranged with valve 61 is provided to pass a fraction of the oil from the accumulator 42 of bubble tower 46 to tank 54. The liquid portion, which is mainly tar or fuel oil present in the bottom of separator 1, is removed to storage, not shown.

The lower boiling fractions of the condensate removed from the accumulator of bubble tower 40 are passed rapidly through the cracking coils I3 and 65. Due to the rapid heating and the velocity of this liquid, it is mainly in the vapor phase. As it passes through coil 65, the heavier condensates removed from separator 1 are also introduced into this coil 65 and the mixture of the two oils is then passed from cracking coil 65 to line I3a into an intermediate section of soaking drum 4.

The foregoing description is merely illustrative and alternative arrangements may be made within the scope of the appended claims in which it is my intention to claim all novelty as broadly as the prior art permits.

I claim:

1. Process for the production of light oils from a heavy oil, which comprises passing a stream of the heavy oil from a source of supply, dividing the stream of oil into a plurality of parts, subjecting the parts to pressure, passing one of the parts under pressure into a conversion chamber, heating oil to a cracking temperature in a heating zone under pressure, passing the heated oil into the conversion chamber, separately withdrawing the vapors and liquid from the conversion chamber, condensing the vapors, contacting the liquids with the remaining part of the heavy oil, fractionating the mixture and separately recovering different boiling point fractions of the mixture, subjecting a lower and a higher boiling fraction to pressure, passing the lower boiling fraction of the mixture in a stream through the heating zone, passing the higher boiling fraction into the stream of lower boiling fraction after the stream has been heated to a cracking temperature, subjecting the mixture to heat and passing the mixture into said conversion chamber.

2. A tube and tank cracking process| which comprises dividing a heavy oil into a plurality of streams, passing one stream under pressure into a cracking zone, heating oil to a cracking temperature under pressure in a heating zone, passing the heated oil into the cracking zone, separately withdrawing vapors and liquids from the cracking zone, condensing the vapors, passing the remaining stream into a fractionating zone, passing the heated liquids from the cracking zone into the fractionating zone, separately withdrawing the fractions of naphtha, fuel oil, and lower and higher boiling point intermediate products from the fractionating zone, subjecting the lower and the higher boiling point intermediate products to pressure, subjecting a stream of the lower boiling intermediate products to cracking by passing through the heating zone, passing into the stream of lower boiling point 1ntermediate products after they have been heated to a cracking temperature a stream of the higher boiling point intermediate products, subjecting the mixture to heat and passing the mixture to the cracking zone where feed oil is added.

3. Process for the production of light oils from a heavy oil, which comprises passing a stream of the heavy oil from a source of supply, dividing the stream of oil into a plurality of streams, subjecting the streams to pressure, subjecting one of the streams to cracking by passing the same into a conversion chamber, heating oil to a cracking temperature under pressure in a heating zone, passing the heated oil into the conversion chamber, separately withdrawing the vapors and liquid from the conversion chamber, condensing the vapors, raising the temperature of the remain-V ing stream of oil by contacting with the hot liquid withdrawn from the conversion chamber in a separating chamber, fractionating the mixture, separately withdrawing vapors and different boiling point fractions of liquids, ractionating the vapors into an overhead distillate and a condensate, subjecting the condensate to pressure,

passing the condensate of the vapors in a stream through the heating zone, passing a higher boiling fraction of the liquids from the separating chamber into the said stream of the condensate after it has been heated to a cracking temperature, heating the mixture and passing the mixture into the said conversion chamber.

4. An improved process for the production of light oils from a heavy oil, which comprises dividing a feed stock of the heavy oil into a plurality of parts, subjecting the parts to pressure, passing one of the parts into a conversion chamber, heating an oil to `a cracking temperature in a heating zone under pressure, passing the heated oil into the conversion chamber, separately withdrawing vapors and liquid from the conversion chamber, ractionating the vapors and separately recovering a liquid and a vapor fraction, passing the remaining stream of feed stock, the hot liquid fraction from' the conversion chamber and the separated liquid fraction of the fractionated vapors from the conversion chamber to a separating zone, fractionating the mixture, separately withdrawing a vapor, a higher and a lower boiling liquid fraction, fractionating the Vapor into an overhead distillate and a condensate, subjecting the condensate to pressure, passing the condensate in a stream through the heating zone to heat it to cracking temperature, subjecting the lower boiling point fraction to pressure, passing the lower boiling fraction into the stream of condensate after the stream has been raised to a cracking pressure, subjecting the mixture to heat and passing the mixture into said conversion chamber.

5. Process for the production of light oils from a heavy oil, which comprises heating an oil in a heating zone under pressure to a temperature of about 950 to 1100 F. and cracking the heated oil under a pressure over 250 pounds per square inch, passing a part of the feed oil at the same pressure into the said oil that is being cracked, separating the vapors and liquid, fractionating the vapors at a pressure of over 250 pounds per square inch, condensing the vapors, passing the bottoms from the fractionated vapors to a zone of lower pressure of over 159 pounds per square inch, passing the liquid into the said Zone of lower pressure, passing the remaining part of the feed oil into the said zone of lower pressure, separately withdrawing from the said zone of lower pressure vapors, bottoms and an intermediate fraction of oil, fractionating the vapors in a fractionating zone, withdrawing and condensing the vapors from' said fraotionating zone, withdrawing the bottoms from said fractionating zone, raising the pressure of said bottoms to more than 250 pounds per square inch, passing said bottoms in a narrow stream through the heating zone to raise the temperature to a cracking temperature, `and passing a stream of the intermeture fraction after raising the pressure to over 250 pounds per square inch into the said stream of bottoms after the bottoms have been heated to a cracking temperature, raising the temperature of the mixture to a cracking temperature of about 950 to 1100 F., and delivering the heated mixture to the body of the oil undergoing cracking.

FRANK I-I. EDSON.

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