US2489628A

US2489628A - Cracking process for the production of olefins from hydrocarbons

Info

Publication number: US2489628A
Application number: US640704A
Authority: US
Inventors: Louis P Evans
Original assignee: Socony Vacuum Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1946-01-12
Filing date: 1946-01-12
Publication date: 1949-11-29
Anticipated expiration: 1966-11-29

Description

Nov. 29, 1949 EVANS 2,489,628

CRACKING PROCESS FOR THE PRODUCTION OF OLEFINS FROM HYDROCARBONS Filed Jan. 12, 1946 FLUE GAS BURNING zone AIR

qusucn I8 zJ man TEMP. CRACKING ZONE LOW TEMP. VAPORIZING AND CRACK- 4 ING ZONE LOUIS P EVANS INVENTOR.

ATTORNEY Patented Nov. 29, 1949 CRACKING PROCESS FOR THE PRODUC- TION OF OLEFINS FROM HYDROCARBONS Louis P. Evans, Woodbury, N. J., assignor to Socony-Vacuum Oil Company, Incorporated, a

corporation of New York Application January 12, 1946, Serial No. 640,704

6 Claims.

This invention relates to a process for high temperature short time cracking of petroleum hydrocarbons in a continuous system adapted to utilize by-products of the reaction to maintain the system in thermal balance at the desired high temperatures.

It is known that various petroleum hydrocarbons may be cracked under conditions of high temperature, say greater than 1200 F. and for short reaction times on the order of a few seconds and preferably less than one second to give good yields of lower olefins. Such reactions give large yields of tarry and coke-like by-products, particularly from high boiling stocks and it has been customary to use distillate stocks for this purpose to reduce the deposition of solid materials which may block up the apparatus in a relatively short time.

According to the present invention, high yields of lower olefins are produced by contacting residual stocks, crude oil and the like in liquid phase with a solid granular refractory materia1 at a sufllciently high temperature to induce thermal cracking at temperatures which will give the desired products. Since the stock is supplied in liquid phase, it need not be a distillate and my invention contemplates the use of residua, crude oils, solvent tars and other stocks which contain components incapable of distillation at'atmospheric pressure without substantial decomposition. As used hereinafter, the term heavy stock is to be understood as referring to crudes and other petroleum mixtures which contain components boiling above decomposition temperatures under pressures on the order of atmospheric.

The purposes of the invention are achieved by establishing a downwardly moving bed of inert granular refractory at a temperature sufficiently high to insure cracking at temperatures in excess of 1200" F. of the hydrocarbon vapors formed in the moving bed as hereinafter described. A heavy stock is introduced to the moving bed at an intermediate point. This results in immediate vaporization of the light ends of the stock which pass upwardly through the bed and are thereby rapidly heated to thev desired conversion temperature. The space velocity is so adjusted that the vapors remain in contact with the refractor for a very short time, preferably less than a second after reaching conversion temperature and are then withdrawn and promptly quenched to a temperature below that at which the conversion reaction takes place. The portion of the charge which is not immediately vaporized passes downwardly with the moving bed and is further vaporized and. thermally cracked to yield additional vapors which 2 rise to mingle with the original vapors for high temperature cracking in-the upper part of the bed.

Due to the presence of heavy components, a substantial portion of the charge undergoes a coking step producing hydrocarbon vapors and a fairly large amount of carbonaceous deposit which remains on the refractory. The refractory granules, carrying carbonaceous deposit are transferred to a burner above the reaction chamber wherein they are contacted with combustion air, burning all the carbonaceous material and raising the temperature of the inert granules to the level desired in the reactor.

The objects and advantages of the invention will be further understood by reference to the annexed drawing wherein the single figure is a diagrammatic representation of apparatus for conducting the process. In this figure the reaction chamber 1 is adapted for downward flow of a substantially compact bed of granular material supplied through feed pipes 2. The granular material is at an extremely high temperature as it moves downwardly through reactor l and it therefore rapidly heats hydrocarbon vapors rising through the upper portion of reactor l to the temperature for the desired reaction. An oil in liquid phase is supplied from a pipe 3 to a series of spray nozzles 4 which distribute the liquid charge across the reactor at an intermediate point. The granular material is still at a high temperature as it passes the sprays l and it causes vaporization of a portion of the charge thus separating the charge into a heavy and a light fraction. The light fraction in vapor phase passes immediately upward to be rapidly heated to the desired conversion temperature while the heavy fraction remains as liquid on the refractory passing downwardly through the reactor.

As is well known, the thermal cracking reaction is a function of both time and temperature and the unvaporized portion of the stock is subjected to a liquid phase cracking reaction at fairly high temperature resulting in its conversion to cracked vapors and coke as it passes downwardly through the reactor. An inert gas such as steam is supplied at 5 to a number of inverted angles 6 near the bottom of the reactor. This inert gas serves to strip vaporizable material from the inert gran! ules and carry the vapors upwardly into the high temperature cracking zone. It has been found that reactions of the type conducted in the high temperature cracking zone are often aided by the presence of steam and for this reason it is preferred that steam be used as the stripping medium in the bottom of the reactor. The coke-covered granules are withdrawn from the bottom of the reactor at a desired rate regulated by valve I and pass to the bottom of an elevator 8 which discharges through pipe 9 into the top of a burner Ill. The granules are fed by feed pipes l I to the high temperature burning zone to which air is supplied by pipe 12 and inverted angles l3. Th burning air causes rapid combustion of the carbonaceous material deposited on the granules in the lower portion of the reactor l and large amounts of heat are liberated, thus raising the temperature of the refractory granules to a level suitable for heating and cracking the charge in reactor I. The highly heated granules pass through a feed leg [4 into which a small amount of steam may be introduced by line l5 in order to purge flue gas and air from the highly heated granules. It will be recognized of course that the temperature of the steam admitted at i 5 can be used to aid in control of the temperature of the granules but I prefer that such control be exercized by the degree of preheat of the air supplied at I 2. Thus, if a higher temperature is desired for the granules, it is preferred to obtain this result by preheating the combustion air either by heat exchange with the flue gas removed at l 6 or by burning oil or other fuel therein before passing the air to the burning zone.

Returning now to the reactor, the products of the reaction are withdrawn at line I! and promptly quenched. to a temperature at which the reaction ceases as by the addition of cold oil through pipe l8. Alternatively, the hot products may be quenched by any other suitable means, as by passing through a bed of cold granular material which may be similar in nature to that circulated through the reactor l.

The granular material circulated in the system is preferably non-porous to give a high heatcarrying capacity and must be highly refractory since it is subjected to extremely high average temperatures and may reach even higher temper atures at localized zones of rapid burning in the burner ID; A typical example of use of the apparatus shown is in the manufacture of ethylene, which requires a temperature of 1400 to 1500 F. with a reaction time of about 0.1 second. A typical charge is a topped crude such as Michigan crude which is supplied at 3 at a temperature of about 200 F. A granular aluminum oxide refractory known as Corhart was supplied to the reactor at 1565 F. at a rate to provide about 90 lbs. of hot granules per gallon of liquid oil. Steam at 250 F. and a rate of 40 volumes per volume of liquid oil charge was supplied at 6. The withdrawn vapors were quenched to about 900 F. and passed to a fractionator for separation of lower olefins, the heavy stock from the bottom of the fractionating system being recycled in part to the charge and utilized in part as quench oil to be supplied at I8. The temperature of air supplied to the burner was controlled to maintain the granules withdrawn therefrom at about 1600 F. I claim:

1 A process for the manufacture of valuable products from petroleum mixtures containing substantial proportions of components which decompose at temperatures below their atmospheric bolling points which comprises moving a substantially compact mass of highly heated refrac- Y anu es ca ying carbonaceous deposits thereon downwardly through a confined burning zone, passing a combustion supporting gas through said granules in said burning zone to thereby burn 01f the carbonaceous material and raise the temperature of said granules, causing the temperature of said granules to rise by retaining therein substantially all the heat released by such burning in excess of that absorbed as sensible heat by the said gas, passing the highly heated granules from said burning zone to confined reaction space therebelow, passing said granules downwardly through said reaction space as a compact substantially continuous bed introducing said mixture in liquid phase and at a temperature substantially below its reaction temperature and below that of said bed into said bed at only a single intermediate level spaced a substantial distance from the upper and lower ends of said bed to effect a quenching of the bed temperature below said level of introduction to a temperature level substantially below that in the portion of said bed above said level of introduction and to effect a partial vaporization of said mixture yielding vapors which move upwardly through the high temperature upper portion of said bed to be cracked and a liquid residue which moves downwardly with the refractory granules to undergo low temperature vaporization and cracking in the low temperature portion of said bed below said level of introduction, introducing an inert gas into the bottom of said bed to move upwardly therethrough, withdrawing vaporous products of the reaction from the top of said space, separately withdrawing granules containing coke deposit from the bottom of said space and transferring the granules so removed to said burning zone above said space, the temperature of said heated granules so passed to said reaction space being sufliciently high to raise the temperature of the vapors in the said upper portion of said space to a level at which the desired cracking reaction takes place, not substantially below about 1200" R; whereby heat for vaporizing charge components and heating vapors to the desired reaction temperature is derived from combustion of large amounts of carbonaceous matter deposited on said granules by reason of the nature of the charge.

2. A process for the manufacture of valuable products from petroleum mixtures containing a ature of said granules, causing the temperature of said granules to rise by retaining therein substantially all the heat released by such burning in excess of that absorbed as sensible heat by the said gas, passing the highly heated granules from said burning zone to a confined reaction space therebelow, passing said granules downwardly through said reaction space as a compact substantially continuous bed, introducing said mixture in liquid phase into said bed at only a'single intermediate level spaced a substantial distance from the upper and lower ends of said bed at a temperature substantially below that required for its reaction and below the average temperature of said bed to effect a quenching of the bed tem perature below said level of introduction to a temperature range substantially below that in said bed above said level of introduction and to efiect a partial vaporization of said mixture yielding vapors which move upwardly through the high temperature upper portion of said bed wherein they are cracked and a liquid residuewhlch moves downwardly with the refractory granules to .undergo low temperature vaporization and cracking in the low temperature portion of said bed lying below said level of introduction, introducing an inert gas into the bottom of said bed to move upwardly therethrough, withdrawing vaporous products of reaction from the upper end of said reaction space, separately withdrawing granules bearing a carbonaceous deposit from the bottom o'i' sai'd reaction space and transferring the granules so removed to said burning zone above said reaction space, the temperature of said heated granules so passed to said reaction space being :sufiioiently high to raise the temperature of the vapors in the said upper portion of said space to a level at which the desired cracking reaction takes place; whereby heat .for vaporizing charge components and heating vapors to the desired reaction temperature :is derived from combustion of large amounts of carbonaceous matter deposviited onsaid granules by reason of the nature of the charge.

3. .A process for the manufacture of valuable products from petroleum mixtures containing substantial proportions of components which decompose at temperatures below their atmospheric boiling points which comprise moving a substantially compact mass of highly heated ire- ;tractory granules carrying carbonaceous deposits thereon downwardly through a confined burning .zone, passing a combustion supporting gas through said granules in said burning zone to thereby burn UK the carbonaceous material and raise the temperature of said granules, causing the temperature of said granules to rise by retaining therein substantially all the heat released by such burning in excess of that absorbed as sensible heat by the said gas, passing the highly heated granules from said burning zone to a confined reaction zone therebelow, passing :s-aid granules downwardly through said reaction zone as a substantially compact column of gravitatin-g granules, introducing said petroleum mixture in the liquid phase into said column at only a single intermediate level spaced :a substantial distance from the upper and lower ends of said column at a temperature below its reaction temperature and below that of said column to efiect a partial vaporization of said liquid mixture at the level .of introduction, controlling the temperature and rate of introduction of said liquid mixture to effect a substantial quenching of the granules below said level of introduction to a temperature level substantiall below that in said column above said level of introduction and substantially below 1200" F., passing vapors resulting from the partial vaporization of said liquid mixture upwardly through a high temperature portion of said column lying above the level of liquid introduction to oiiect cracking of said vapors to lower boiling products, passing the nonvaporized portion of the liquid mixture downwardly with the granules to undergo low temperature vaporization and cracking in the lower portion of said column, introducing steam into the lower "end of said column and passing it upward- .ly therethrough to aid in vaporization of said non-vaporized portion, passing the steam and vapors formed inthe column below the level o'flliquid introduction upwardly through the high temperature portion of said column along with "the initially formed "vapors, controlling the period of contact between vapors and heated granules in said high temperature portion of said column below about one second and withdrawing the lower boiling products 'iirom the upper end of said reaction zone, separately withdrawing granules :bearing .a carbonaceous deposit from the bottom of said reaction zone and transferring the granules so removed to said burning zone above said reaction zone, the temperature of said heated granules so passed to said reaction zone being sufllciently high to raise the temperature of the vapors in the upper portion of said reaction zone to :a level at which the desired reaction takes place, not substantially below about .1200 11; whereby 'heat for vaporizing charge components and heating vapors to the desired reaction temperature is derived from combustion of large amounts of carbonaceous matter deposited on said granules by reason of the nature of the charge.

4. process for the manufacture of valuable products from petroleum mixtures containing substantial proportions of components which decompose at temperatures below their atmospheric boiling points which comprise moving a substantially compact mass of highly heated refractory granules carrying carbonaceous deposits thereon downwardly through a confined I urning zone, passing a combustion supporting gas through said granules in said burning zone to thereby burn off the carbonaceous material and raise the temperature of said granules, causing the temperature of said granules to rise by retaining therein substantially all the heat released by such burning in excess of that absorbed as sensible heat by the said gas, passing the highly heated granules from said burning :zone to a confined reaction zone therebelow, passing said granules downwardly through said reaction zone as a substantially compact column of graNitating granules, introducing said petroileum mixture in the liquid phase into said column at only a single intermediate level spaced a substantial distance from the upper and lower ends of said column at a temperature below its reaction temperature and below that of said column toeffe'ct a partial vaporization of said liquid mixture at the level of introduction, controlling the temperature and rate of introduction of said liquid mixture to effect a substantial quenching of the granules below said level of introduction to a temperature level substantially below that of said column above said level of introduction and substantially below 1200 F., passing vapors resulting from the partial vaporization of said liqui'd mixture upwardly through a high temperature portion of said column lying above the level of liquid introduction to efiect cracking of said vapors to lower boiling products, passing the nonvaporized portion of the liquid mixture downwardly with the granules to undergolow temperature vaporization and cracking in the lower portion o said column, introducing steam into the lower end of said column and passing it upwardrly therethrough to aid in vaporization of said non-vaporized portion, passing the steam and yaipors formed in the column below the level of liquid introduction upwardly through the high tem- :perature portion of said column along with the initially termed vapors, controlling the period or contact between vapors and heated granules in said high temperature portion of said column below about one second and withdrawing the lower boiling products from the upper end of said reaction zone, immediately quenching said .products so withdrawn to reduce the temperature thereof and thereby halt the conversion reaction,

separately withdrawing granules bearing a carbonaceous deposit from the bottom of said reaction zone and transferring the granules so re moved to said burning zone above said reaction zone, the temperature of said heated granules so passed to said reaction zone being sufiiciently high to raise the temperature of the vapors in the upper portion of said reaction zone to a level at which the desired reaction takes place, not substantiall below about 1200 F.; whereby heat for vaporizing charge components and heating vapors to the desired reaction temperature is derived from combustion of large amounts of carbonaceous matter deposited on said granules by reason of the nature of the charge.

5. A'process for manufacture of gaseous olefin products from high boiling petroleum fractions which comprises: moving a substantially compact mass of highly heated refractory granules carrying carbonaceous deposits thereon downwardly through a confined burning zone, passing a combustion supporting gas through said granules in said burning zone to thereby burn off the carbonaceous material and raise the temperature of said granules substantially above 200 F., gravitating the heated granules from said burning zone to a confined reaction zone therebelow, passing said granules downwardly through said reaction zone as a substantially compact gravitating column, introducing the high boiling petroleum fraction at a temperature substantially below that of said column and below its vaporization and reaction temperature into said column at only one level which is spaced a substantial distance -from the upper and lower ends of said column to efifect a partial vaporization of said fraction and to efiect a quenching of said granules to atemperature substantially below that of said column above said level of introduction and below 1200 F. but not below a suitable liquid phase cracking temperature, passing vapors resulting from the partial vaporization of said liquid mixture upwardly through a high temperature portion of said column lying above the level of liquid introduction to eifect cracking of said vapors to gaseous olefin containing products, passing the non-vaporized portion of the liquid mixture downwardly with the granules to undergo low temperature vaporization and cracking in the lower portion of said column, introducing steam into the lower end of said column and passing it upwardly therethrough to aid in vaporization of said non-vaporized portion, passing the steam and vapors formed in the column below the level of liquid introduction upwardly through the high temperature portion of said column along with the initially formed vapors, controlling the period of contact between vapors and heated granules in said high temperature portion of said column below about one second and withdrawing the lower boiling products from the upper end of said reaction zone, separately withdrawing granules bearing a carbonaceous deposit from the bottom of said reaction zone and conveying the granules so removed upwardly to said burning zone above said reaction zone.

6. A process for manufacture of ethylene from high boiling petroleum fractions which comprises: moving a substantially compact mass of highly heated refractory granules carrying carbonaceous deposits thereon downwardly through a confined burning zone, passing a combustion supporting gas through said granules in said burning zone to thereby burn ofi the carbonaceous material and raise the temperature of said granules, causing the temperature of said granules to rise by retaining therein substantially all the heat released by such burning in excess of that absorbed as sensible heat by the said gas, passing the highly heated granules from said burning zone to a confined reaction zone therebelow, passing said granules downwardly through said reaction zone as a substantially compact column, introducing said petroleum fraction as a liquid existing below its reaction temperature and below the temperature of said column into said column at only one level, which level lies intermediate the upper and lower ends of said column and is spaced a substantial distance therefrom, to efiect a partial vaporization of said fraction and to eifect a quenching of said granules to a temperature which is below that in said column above said level of liquid introduction and substantially below 1200 F. but not below a suitable liquid phase cracking temperature passing vapors resulting from the partial vaporization of said liquid mixture upwardly through a high temperature portion of said column lying above the level of liquid introduction to effect cracking of said vapors to gasiform ethylene containing products, passing the non-vaporized portion of the liquid mixture downwardly with the granules to undergo low temperature vaporization and cracking in the lower portion of said column, introducing steam into the lower end of said column and passing it upwardly therethrough to aid in vaporization of said non-vaporized portion, passing the steam and vapor-s formed in the column below the level of liquid introduction upwardly through the high temperature portion of said column along with the initially formed vapors, controlling the period of contact between vapors and heated granules in said high temperature portion of said column below about one second and withdrawing the gasiform prodnote from the upper end of said reaction zone, immediately quenching said products to a level not above about 900 F., separately withdrawing granules containing coke deposit from the bottom of said reaction zone and transferring the granules so removed to said burning zone above said reaction zone, the temperature of said heated granules so passed to said reaction zon being sufliciently high to raise the temperature of the vapors in the upper portion of said reaction zone to a level at which the desired cracking reaction takes place, between about 1400 F. and about 1500 F.; whereby heat for vaporizing charge components and heating vapors to the desired reaction temperature is derived from combustion of large amounts of carbonaceous matter deposited on said granules by reason of the nature of the charge.

LOUIS P. EVANS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,601,786 Weaver Oct. 5, 1926 2,239,801 Voorhees Apr. 29, 1941 2340,814 Lidov Feb. 1, 1944 2 348,699 Tuttle May 9, 1944 2,390,031 Schutte et al. Nov. 27, 1945 2,403,608 Payne et a1. July 9, 1946 2,405,395 Bahlke et a1. Aug. 6, 1946