US2185516A - Method of and apparatus for converting oil - Google Patents

Description

Jan. 2, 1 940. P. S NISSON METHOD OF AND APPARATUS FOR CONVERTING 0111 I Filed NOV. 24, 1954 INVENTOR Lm'on ATTORJi;

Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE LIETHOD OF AND APPARATUS FOR CON- VERTING OIL of Ohio Application November 24, 1934, Serial No. 754,646

12 Claims.

This invention relates to a method of and apparatus for converting oils to liquid hydrocarbons of high octane rating, boiling within the gasoline range. More particularly my invention is concerned with a method and apparatus for cracking crude oil in such manner that the lighter fractions are cracked in the vapor phase and the heavy fractions cracked in the liquid phase.

It is well known that vapor phase cracking processes produce gasoline of higher octane rating than liquid phase cracking processes. However, heavy residues are unsuitable for vapor phase cracking. In order to obtain gasoline of high octane rating the prior art has taught to crack heavy oils in the liquid phase and then vaporize the residue from the cracking process and crack the vapors in the vapor phase. It has also been taught to subject liquid phase cracked vapors to secondary cracking in the vapor phase.

My invention distinguishes from these prior processes in that crude oil, either topped or untopped, is heated sufficiently to vaporize the lighter fractions without substantial cracking of the oil, and the vaporized portion cracked in vapor phase, while the unvaporized residue is subjected to liquid phase cracking independently of the vapor phase cracking stage. The cracked vapors from the separate cracking steps are then commingled and fractioned together to produce a blended gasoline of high anti-knock value and recycle stock for the liquid and/or vapor phase cracking stages.

One of the objects of my invention is to provide a method for cracking crude oils containing gasoline having a low octane rating so as to produce motor fuel of high octane rating.

Another object of my invention is to provide a method of cracking oil wherein the products which are vaporized at temperatures below cracking are cracked in the vapor phase while the unvaporized portion is cracked in the liquid phase.

A further object of my invention is to provide a process wherein crude oil is separated into a vaporized and unvaporized fraction and the fractions are simultaneously cracked in separate cracking stages in such manner that the light cracked products from one stage do not pass through the other cracking stage.

Still a further object of my invention is to providea method wherein oil is separated into liquid and vapor portions, the vapor portion cracked in the vapor phase and the heavy cracked residue from the vapor phase stage cracked in the liquid phasetogether with the unvaporized residue of the crude oil,

(c1. 196--60) V l r Another object of my invention is to crack vaporized and unvaporized oil independently of each other in the vapor phase and liquid phase respectively, and fractionate the combined vapors from the two cracking steps to produce a blended fuel 5 of high anti-knock properties.

Another object of my invention is to provide apparatus for independently and simultaneously cracking vaporized and unvaporized oil in order to accomplish the foregoing objects.

Still other objects will be evident from the following detailed description considered in connection with the accompanying drawing of which the single figure is a diagrammatic sketch of one combination of apparatus suitable for carrying out my invention.

Referring to the drawing, I indicates a charging line for the oil to be charged to the cracking unit,

2 is a pump located in the line I to advance the oil through heat exchangers 3 and 4, lines 5 and 20 6, and preheating. coil 1 located in the cooler por tion of a furnace8. The oil leaves the preheating coil 1 through line 9 and passes into the lower portion of vaporizer Ill. The vaporized oil is withdrawn from the top of the vaporizer through line I l. The vapors pass from line H through a set of drying tubes l2 located in the cooler portion of a furnace l3, and from thence to cracking tubes I4 located in the hotter portion of the furnace l3. The furnace is heated by any suitable 30 means, as, for example, burner l5. It will be understood that the furnace and cracking coils as shown in the drawing are purely diagrammatic, and that if desired, additional coils may be placed in the furnace along the side walls and roof or 35 in any other desired manner in order to obtain efficient heat transfer The oil leaves cracking tubes l4 through line l6 and passes into shock chiller I! where the cracked products meet a stream of cooler oil entering the top of the chiller 0 through line IS. A baflie 20 is located in the chiller in order to deflect heavy products of conversion to the bottom of the shock chiller. The vapors with entrained liquid leave the chiller through line 22 and the unvaporized oil leaves the 45 bottom of the chiller through line 24. Vapors pass from line 22 to the bottom of liquid separator 26 from which unvaporized oil is withdrawn through line 28 while the vapors pass overhead through line 30. From line 30 the vapors enter 50 the bottom of a fractionating column 32 from which vapors are withdrawn through the line 34 to a suitable condenser, gas separator, and storage tank, (all of which are not shown on the drawing). The condensate leaves the bottom of 55 the fractionating column through line 36 controlled by valve 38.

The residue withdrawn from chiller l'i through line 24 may be sent by a pump 40 either to line ll or through by-pass 42 controlled by valve 43, then through line 45 and pumped into vaporizer lit by means of pump 41. From line 4| the residue may be sent to the shock chiller IT through line 48, in which is located pump 49, heat exchanger 3, and line 50; or it may be sent to mixing tank 5! through line 52 controlled by valve 53. Excess residue may be withdrawn from the system through line 54 controlled by valve 55. The liquid residue from liquid separator 20 may be sent by pump 58 through lines 60 to El, or is withdrawn from line 60 by pump 4'! through line 45 controlled by valve 62 and sent to vaporizer 40. From line 6| the oil may be sent to line 48 and returned to the shock chiller IT, or to line 03 controlled by valve B t and then through line 52 to mixing tank 51-. The condensate from the fractionating column 32 may pass through lines 36 and 66 either to shock chiller H by way of lines 43,50, and E8, or to line 48 by way of line 68 controlled by valve 10 through line 52 to mixing tank 5!; or the condensate may be by-passed through line ll controlled by valve l2 and sent by pump 13 through line 6 and heating coil 1 to vaporizer ID. The lines M, 6!, and 06 are controlled by valves M, and 16 respectively.

The residue from the vaporizer i0 is withdrawn through the line and sent into the mixing tank 55 where it is joined by the fractions which may be collected from the chiller H, liquid separator 25 and fractionating column 32. The hot oil collected in the mixing tank 5i is withdrawn therefrom through line 88' by pump 90 and passed through cracking coils 92 located in the hotter portion of the heating chamber of the furnace 8 which may be heated in any suitable manner, as, for example, burner 96. The oil leaves the cracking coils 92 through line 98 controlled by valve Hi0 and passes into the bottom of vaporizing chamber 46. The vapors leave the top of the vaporizer 46 through line Hi4 controlled by valve Hi6 and join the vapors l aving the top of the liquid separator 20 through line 30. The combined vapors then pass into the bottom of the fractionating tower 32. It will be evident that the vaporsv from the vaporizer 40 can pass directly into the fractionating column 32 prior to joining the vapors from the liquid separator 26. The unvaporized residue is withdrawn from vaporizer 46 through line E08 con trolled by valve H0 and passes through heat exchanger t in heat interchange with the fresh oil being charged to the system. The residue is then withdrawn to storage through line H 2.

The process operates'in the following manner. Liquid oil, preferably an oil such as Mt. Pleasant, Michigan crude which contains a considerable amount of hydrocarbons boiling within the gasoline range but which have a low anti-knock rating, is charged through the line I into heat interchangers 3 and 4 where the temperature is raised somewhat, and thence through lines 5 and 6 into the preheating coil where the temperature is raised to about 700 F. in order to vaporize the lighter boiling fractions without cracking the oil. The oil heated to this temperature then passes into the vaporizer l0 where the light fractions up to and including gas oil, pass ofi as vapors through line i l and thence through the coils I2 where any entrained liquid is vaporized. The

temperature of the furnace gases passing over the coils I2 is insuflicient to raise the vapors to a cracking temperature but is suficient to completely dry the vapors in order to lessen deposition of coke in the cracking coils. The dry vapors then pass into the bank of cracking tubes 54 where they are cracked into lighter hy-- drocarbons at a temperature of approximately 1-000 to 1200 F; and under a pressure ranging from 0' to approximately 50 pounds per square inch. The'cracked products then pass into the shock chiller ill where they are contacted with cool oil in order to suddenly reduce them to a temperature below conversion temperature. This temperature may be between 550 to 650 F. and preferably about 600 F. From the shock chiller the vapors pass into the liquid separator 20 where entrained oil and high boiling vapors are separated, and the vapors, including a major portion of the gas oil, pass overhead into iractionating column 32'. The fractionating column 32 may be of the Well known bubble plate type so that the vapors are separated boiling substantially within the gasoline range and withdrawn from the top through line i'-'. The condensate withdrawn through the line 30 may then pass through heat interchanger 3 where it is cooled vaporizer i0 and the shock chiller ll or a por-' tion passed to the mixing tank 5i and a portion to the shock chiller H. The residues Withdrawn from the shock chiller I! and liquid separator 20 may be cooled and returned to the shock chiller ll or united with the unvaporized crude oil in the mixing tank 5|, and the mixture which is in a highly heated state of the order of 400 to 600 F., sent to the liquid phase cracking coils 02 where the oil is cracked under a pressure ranging from to 1000 pounds per square inch and at a temperature from 800 to 925 F., more or less. If desired, the residues from chiller H and separator .20 may be divided and part .sent to the chiller and part to the mixing tank. The pressure of the cracked products leaving the coil 92 is reduced by means of valve I00. to a pressure sufficient to enable the lighter fractions up to and including gas oil to pass overhead as vapors and enter the fractionating column 32. heavy residue which collects in the vaporizer 46 is withdrawn through heat exchanger 4 to preheat the crude charging stock and then passed to storage as fuel oil. At times it may be necessary to withdraw heavy residue collecting in the chiller from the system and thismay be done through line 5% controlled by valve 55.

By means of my invention it is possible to take crude oil with low octane gasoline content and without topping it, pass the gasoline vapors together with other light fractions of the crude oil through a vapor phase cracking process. In this manner the gasoline is reformed simultaneously with the cracking of the heavier fractions so that the resulting product is all of desirable antiknock rating.

It will be further seen that my process is flexible so that instead of taking off gas oil from The fractionating'column 32 and cracking it in the vapor phase, substantially only the light fractions of the crude oil may be taken overhead and passed through the vapor phase cracking step while the recycle stock is cracked in the liquid phase cracking stage.

My process may be applied to crude untopped 0115 containing gasoline of low octane rating, or to other topped crudes. By adding a fractionating tower to the crude oil vaporizer, Pennsylvania base oils can similarly be separated into 'a vapor and liquid charging stock to be cracked in accordance with my invention. When treating Pennsylvania oils it will be necessary to separate the wax distillate and cylinder stock from the cracking stock, and this may be done by taking off vapor phase cracking stock as vapors and liquid phase cracking stock as a side stream from the fractionating tower. The cylinder stock may be withdrawn as a residue and the wax distillate as a separate side stream.

What I claim is:

1. The method of converting crude oil into motor fuel of high octane rating which comprises separating crude oil into a vapor and a liquid fraction without cracking the oil, simultaneously cracking the vapors in a vapor phase cracking stage and the unvaporized liquid in a liquid phase cracking stage, separating cracked vapors from unvaporized residue in both cracking stages, commingling and fractionating the vapors, separately withdrawing the unvaporized oil produced in the liquid phase cracking step from the system without further cracking, withdrawing unvaporized residue from the vapor phase cracking and recycling it to the liquid phase cracking stage, withdrawing and cooling condensate formed in the fractionating stage, and contacting the products issuing from the vapor phase cracking stage with the cooled condensate.

2. The method of converting crude oil into motor fuel of high octane number which comprises passing the oil in a restricted stream through a heating coil where the oil is heated to a temperature sufiicient to vaporize the lighter fractions but insufficient to produce any substantial cracking, vaporizing the vaporizable constituents, heating the vapors at a temperature below cracking in order to dry them, passing the dry vapors through cracking coils wherein the vapors are heated to a temperature between 1000 and 1200" F. at low super-atmospheric pressure, passing the hot unvaporized residue from the initial vaporizing step through a zone of restricted cross-sectional area wherein the oil is subjected to cracking temperature of 800 to 925 F. and pressure of from to 1000 pounds per square inch, separating vapors from residue in the vapor phase and liquid phase cracking stages, separately withdrawing the unvaporized oil produced in the liquid phase cracking step from the system without further cracking, recycling the unvaporized residue from the vapor phase stage to the liquid phase stage, fractionating the combined vapors, cooling the condensate resulting from said fractionation, and contacting the condensate with the vapors issuing from the vapor phase cracking stage.

3. Apparatus of the character described comprising a furnace, a heating coil located in the convection heating zone adjacent the combustion gas outlet of said furnace, a second heating coil located in the convection heating zone of said furnace ahead of said first mentioned coil, a vaporizer, means for passing oil through said first mentioned coil to said vaporizer, a second jointly fractionating vapors leaving said separator and said second vaporizer, means for recycling residue from said separator to said second mentioned coil, and means for recycling condensate free from cracked residue from said fractionating means to said first mentioned vaporizer.

l. The method of converting crude oil into motor fuel of high anti-knock value which comprises heating the oil to a temperature suflicient to vaporize the lighter fractions thereof without substantial cracking, directly subjecting the vapors to vapor phase cracking conditions of temperature and pressure, partially cooling the products issuing from the vapor phase cracking zone to a temperature sufficient to inhibit further conversion, separating the vapors from the unvaporized residue in the partially cooled products, fractionating and condensing the vapors, commingling the residue from the vapor phase cracked products with the residue from the initial vaporizing zone, without substantial cooling, and subjecting the commingled residues to cracking in the liquid phase under relatively higher superatmospheric pressure and lower temperatures than those maintained in the vapor phase cracking stage and fractionating and condensing the vapors from the liquid phase cracking step with out further cracking thereof.

5. The method of converting crude oil into motor fuel which comprises heating the oil to a temperature sufficient to separate it into a vapor fraction and an unvaporized fraction without substantial cracking, directly subjecting the vapors to vapor phase cracking conditions of temperature and pressure, directly contacting the cracked vapors with cooling oil and lowering the temperature of the cracked products below conversion temperature, separating the tarry residue and withdrawing it from the system, separating heavy ends from the remaining products, fractionating the remaining products into a condensate heavier than gasoline and a gasoline fraction, commingling said unvaporized fraction and said heavy ends and subjecting them to cracking temperatures lower than and pressures higher than those to which the vapors are subjected, separating the cracked products into vapors and residue, commingling the latter vapors with those resulting from the vapor phase cracking step and fractionating the commingled vapors, and independently withdrawing the residue from the high pressure cracking step from the system without further cracking.

6. Method in accordance with claim 5 in which the condensate heavier than gasoline is recycled to the vapor phase cracking step.

7. Method in accordance with claim 2 in which the condensate is cooled by indirect heat exchange with the crude oil.

8. A process of converting hydrocarbon oils into motor fuels boiling within the gasoline range which comprises heating the oil sufficiently to vaporize the lighter fractions but insufiiciently to produce any substantial amount of cracking,

vaporizing the lighter fractionsgsubjecting the vapors to vapor phase cracking conditions under high temperatures and low super-atmospheric pressures, simultaneously cracking the unvaporized residue in a liquid phase cracking stage at relatively lower temperature and higher superatmospheric pressure, separate from the vapor phase cracking stage, separating vapors from both cracking stages, separately withdrawing the unvaporized oil produced in the liquid phase cracking stage from the system without further cracking, combining and fractionating the combined vapors, recycling condensate formed in the fractionating stage to the vapor phase cracking stage, and recycling unvaporized residue from the vapor phase cracking stage to the liquid phase cracking stage.

9. Method in accordance with claim 8 in which vapors from the liquid phase cracking stage are fractionated and those portions thereof boiling Within the gasoline range are condensed without further cracking.

10. Apparatus of the character described comprising a heating coil and a vaporizer connected thereto, vapor phase and liquid phase cracking means connected to the upper and lower portions respectively of the vaporizer, means for contacting a fluid with the products leaving the vapor phase cracking means, separate means for separating vaporized from unvaporized products issuing from each cracking means, means for independently withdrawing unvaporized residue produced in the liquid phase cracking means from the system, means for conjointly fractionating the vapors, means for recycling the unvaporized products from the vapor phase cracking means to the liquid phase cracking means, and means for recycling liquid condensate free from cracked residue from the fractionating means to said contacting means and to said heating coil.

11. The method of converting crude oil into motor fuel of high octane number which comprises passing the oil in a restricted stream through a heating coil wherein the oil is heated to a temperature sufiicient to vaporize the lighter fractions but insufficient to produce any substantial cracking, vaporizing the vaporizable constituents, heating the vapors at a temperature below cracking in order to dry them, passing the dry vapors through a cracking zone wherein they are cracked at high temperature and low superatmospheric pressure, passing the hot unvaporized residue from the initial vaporizing step through a separate. cracking zone wherein the oil is cracked at relatively low temperature and high pressure, separating vapors from residue in the two cracking stages, separately withdrawing the unvaporized residue, produced in the residue cracking stage, from the system without furthersuperatmospheric pressure, separating cracked unvaporized residue from the cracked vapors,

mixing said cracked unvaporized residue with unvaporized oil from the initial separating stage; cracking the mixture in the liquid phase independently of the cracked Vapors at relatively low temperature and high pressure,'separating vapors from the liquid phase cracked oil,separately withdrawing the unvaporized oil produced-in the liquid phase cracking stage from thesystem without further cracking, ccmmingli-ngvapors from said liquid phase cracking stage Withvapors from said vapor phase cracking stage and fractionating the commingled vapors.

PHILIP S. NISSON,

Patent No. 2,185,516.

CERTIFICATE OF CORRECTION.

January 2, 19LLO. PHILIP S. NISSON. It is hereby certified that error appears in the printed s oecification of the above numbered patent requiring correction as follows: Page l sec 0nd column, line 29, claim 12, for the word "lower" read low; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of January, A. D. 19M).

. Henry Van Arsdale, (Seal) Acting Commissioner-of Patents.

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