US2133344A - Process for thermal treatment of hydrocarbons - Google Patents

Description

M. B. COOKE Oct. 18, 1933.

PROCESS FOR THERMAL TREATMENT OF HYDROCARBONS Filed July 6, 1936 I INVENTOR Maur/c e B. C'oake Of: ATTORN Y Patented Oct. 18, 193$ UNITED' STATES PROCESS FOR THERMAL TREATMENT OF I HYDROCARBONS Maurice B. Cooke, Plainfleld, N. J.

Application July 6, 1936, Serial No. 89,089 g 6 Claims.

My invention relates to a process for the treatment of petroleum hydrocarbons to produce therefrom primarily lower molecular weight hydrocarbons by thermal decomposition and synthesis of the hydrocarbons undergoing treatment and, more particularly, so to conduct such treatment as to produce not only lower molecular weight gasoline-like hydrocarbons suitable for use as a motor fuel of high anti-knock qualities, but in addition to secure an increased yield of hydrocarbons of the aromatic series including naphthalene, benzol, xylol and toluol.

When fuel is burned with no excess of air, the temperature of combustion is between 3000 F. and 4000 F.,Such temperatures are too high for the proposed thermal treatment productive oi the desired products and accordingly this temperature must be brought down considerably in order to produce-most efliciently the greatest yield of the desired products.

In my co-pending applications Serial No. 598,- 503 filed March 12, 1932, now-Patent No. 2,046,501,

issued July 7, 1936, to Maurice B. Cooke, and

Serial No. 598,504, filed March 12,1932, now Patent No 2,046,502, issued July 1936, to Maurice B. Cooke, I have disclosed a process for the thermal treatment of petroleum hydrocarbons for the productionof lower molecular weight gasoline-like hydrocarbons by the direct commingling of hot combustion gases with the hydrocarbons being treated. I have, shown therein that the temperature of from 00 F.

to 4000 F. obtained by the generation of these gases may be lowered to a temperature more favorable for the treatment of the hydrocarbons by' tempering or cooling the gases with steam which may be condensed in a preiractionating condensing. zone with considerable advantages being obtain-ed in permitting a reduction in the size of fractionating and recovery equipment over that required where normally incondensible inert tempering gases are employed. In addition, I have shown that the combustion gases may be tempered in part by passing oil to be heated for various ancillary related steps of the process in indirect heat exchange with the hot gases. In particular, I have disclosed; the indirect heatng of a relatively heavy petroleum oil to prepare it for a topping operation; the indirect heating of the topped oil to enable the formation oi. hydrocarbon vapors for subsequent direct thermal treatment with the tempered combustion gases; and the'indirect reheating of a cooled condensate oi the thermally treated vapors to eflect distillation and permit subsequent fractionating or the distillate vapors for ultimate recovery of the desired products.

The character 'of the liquid ultimately produced as a desired product from petroleum hydro-- carbons as disclosed in the processes or the foregoing applications, is essentially dependent upon the time, temperature and pressure conditions employed. 1

It is an object of my invention to produce low molecular weight hydrocarbon products including liquid aromatic products such as naphthalene, benzol, xylol and toluol from heavier petroleum hydrocarbons by the direct thermal treatment of such heavier hydrocarbons with hot combustion gases under closely controlled conditions of time, temperature and pressure.

It is another object of my invention to extract the desired products from the mixture of thermally treated hydrocarbons and combustion gases with fraction'ating and separating equipu ment no greater in size than is normally employed for the extraction of such products from thermally treated petroleum hydrocarbons not admixed with combustion gases.

It is a iurther object of my invention to effect in the same thermal treating zone, a secondary or final conversion into desired products, of such hydrocarbons lower boiling than the desired products as are recovered from the products of the thermal treating operation and recycled to the treating zone.

It is another object of my invention to coordinate the thermal treatment of petroleum hydrocarbons occurring when such hydrocarbons are directly commingled with hot combustion gases, with distillation of the liquid petroleum hydrocarbons for the production of hydrocarbon vapors to be treated, and the tempering or cooling of the combustion gases to the desired treating temperature.

- It is a further object of my invention to secure an increased yield of desired liquid aromatic and low molecular weight lhydrocarbon products by close control of the character and quantity of the recycle oil returned to the primary thermal treating zone for retreatment with fresh oil.

Other and further objects of my invention will appear from the following description and the appended claims. I

The accompanying drawing-which forms part of the instant specification and is to be read in conjunction therewith is a schematic showing in elevation with parts in section of one form of apparatus capable of carrying out the process or my invention. g

. addition of a cooler inert gas such as steam and partially by passing the gases in indirect heat exchange with cooler liquid petroleum hydro carbons.

- Crude oil is passed in indirect heat exchange with the hot combustion gases whose temperature is thereby lowered while the reduced crude is heated, the heated crude then being subjected to a topping operation in which the depth of the out may vary within wide limits. The topped crude, together with light and heavy recycle oil, forms the charge to a vaporizing coil through which it passes in indirect heat exchange with the gases, the heated" oil then being flashed into vapors. Preferably, the vaporizing coil is located in the hottest portion of the zone through which the combustion gases are being passed. In view of the quantity of oil passing through this coil, it may be necessary to employ external heating means auxiliary to the combustion gases to secure the desired vaporization. The vapors resulting are directly commingled in a mixing zone with the combustion gases which, on entering this zone, have been tempered or cooled to a temperature of from about 1500 F. to about 2500" F., the temperature preferably being from about 1800 F. to about 2000 F. The mixture of hydrocarbon v'apors and combustion gases, which for convenience I shall hereinafter call the reactant, passes through a primary treating zone of a length suflicient to provide the time element necessary to efl'ect decomposition of heavier hydrocarbons of the reactant into lighter hydrocarbons into desired aromatic products. The reactant is preferably subjected to the action "of the hot combustion gases. in this primary zone for a period 01' from about one second to about three seconds, depending upon whether the temperature of these gases is at 2500 F. or a lower temperature of around 1500" F. respectively.

The reactant passes from the primary treating zone into a secondary treating, or soaking zone, wherein the reactant is cooled to a temperature ,0! from about 1050" Fvto about 1800 F. by the spraying into the reactant of a cooler recycle oil substantially completely vaporizableat the re-' sulting temperature, or by indirect heat exchange with a cooler oil. In this secondary treating zone the recomposition and synthesis of hydrocarbons proceeds to form not only lower molecular weight gasoline-like hydrocarbons, but, by reason of the lower temperature, a'substantial quantity of hydrocarbons of the aromatic series including naphthalene, benzol, toluol and xylol. The time oi reaction in this; zone will vary from about one second to about ten seconds, depending upon whether the-temperature o! the re-- actant is about 1800 F, or 1050" F. respectively.

From the. secondary treating zone, the reactant' passes into a combined quenching and separating zone wherein a cooler hydrocarbon oil is sprayed into the reactant whose temperav ture iszquickly reduced to around 600 F. to

"'100-F.- -Atthe..same time and as the result of this quenching operation, the heavy polymers, tars, gums and fuel oil present are condensed and are then withdrawn from the quenching zone and the process. The uncondensed portion of the reactant is then cooled further by passing in, indirect heat exchange with clean water, thus generating steam which is utilized for initially tempering the combustion gases, and as process steam for stripping in the main fractionator. The further cooling of the reactant takes place in a series of separate zones in which the heavier hydrocarbons of the reactant are condensed and from which they may be selectively withdrawn. A portion or all of the heavy condensate formed in these separate condensing zones is returned to the quench zone as reflux for end point control and another portion of this heavy condensate is passed to the main fractionating tower. The uncondensed lower boiling portion of the reactant which may be, for example, a 200 F. to 250 F. end point naphtha plus all lighter hydrocarbons and the combustion gases, is further cooled by indirect heat exchange to condense preferablysubstantially all the normally liquid hydrocarbons. The water resulting from condensation of steam in the mixtur is withdrawn from the separating zone to which the cooled reactant is passed and the liquid hydrocarbons of the reactant are regeneratively reheated by passing in indirect heat exchange with the reactant and then by passing in indirect heat exchange with the hot combustion gases, the liquidreactant being raised thereby in a distillation coil to a temperature suflicient to permit vaporization at the substantially atmospheric'pressure under which the process is conducted. On issuing from this dis-.

main fractionator.

In the main iractionator relatively heavy cracked gas oil is withdrawn as a bottom product, light gas oil'is withdrawn"v as a sidestream, and the overhead product of the fractionator consists of lower molecular weight gasoline-like hydrocarbons and/or hydrocarbons of the arcmatic series including naphthalene, benzol, toluol and xylol which are cooled, condensed and removed from the accumulator-separator as the desired distillate product, The uncondensed portion of the fractionator overhead which will include saturated and unsaturated hydrocarbons of the paraflin series such as propane-propylene, butane-butylene, ethane-ethylene, as well as some hydrogen, methane and entrained gasolinelike hydrocarbons is combined with the uncondensed portion of the reactant, compressed,

cooled and the light condensate resulting sepacompression and cooling operation arepassed to i an absorber wherein they are contacted under pressure with cooled light absorber oil withdrawn as a side stream from the main tractionator, the unabsorbed gases particularly the combustion gases and methane being released to. a fuel gas main and the rich absorption 1011 being recycled to the vaporizing coil as part of the chargeto of a valve 34 in the line 29 thus causing the oil to" flow through a pipe 35 in which valve 36 is pipe II, and discharged through pipe I2 into the fuel gas supply tank I3. The fuel gas is discharged under pressure as needed from the supply tank |3 through the valved pipe |4 into the mixing chamber l5 wherein it is mixed with air fed through a valved pipe l6 in quantities sumcient to produce complete combustion of the gas without excess of oxygen. The combustible mixture formed burns with surface combustion on the granules of refractory material H to form hot combustion gases in the combustion chamber I6; These hot gases will be at a temperature of. from 3000 F. to 4000 F..which'is too high for the eflicient thermal treatment of hydrocarbon vapors in accordance with my process.

The temperature of these gases may be reduced in part by admixing therewith cooler steam fed 'into the gases through the valved pipe I9 at a point 20 inthe combustion chamber l3 where complete combustion of the gas fuel air mixture has taken place. The steam thus'supplied will act as an additional heat carrier medium with the combustion gases, and has the advantage of being condensible and separable from the combustion gases and hydrocarbon vapors at normal atmospheric conditions of temperature and pressure. For this reason I am enabled to reduce the quantity of vapor to be passed through the main fractionating tower. The combustion gases partially cooled by the steam, if such cooling is desired at this time, flow into the chamber 2| and across the tubes forming the heating coil 5. The relatively cool oil passing through the heating coil 5 assists in reducing the temperature of the combustion gas and is at the same time heated to a vaporizing temperature preparatory to fractionation in the fractionating tower 1. Obviously, the heating effected in the coil 5 may be supplementedby an external tube still (not shown) and if no topping operation is necessary or if the cooling effect of the coil 5 on the combustion gases is not deemed necessary, this coil may be dispensed with entirely.

In the fractionating tower I the vapors formed are fractionally separated and the overhead products of desired end point flow through vapor pipe 22, vapor heat exchanger 3 and water cooler 23 into accumulator 24 from which reflux is returned through pipe 25 by pump 26 to the fractionating tower 1 for end point control of the fractionator overhead. Any steam condensed is discharged as water from the accumulator 24 through the valved pipe 21 and the distillate is discharged to storage through the valved pipe 26.

The topped crude accumulating in the base of the tower 1 is withdrawn therefrom through a pipe 29 by means of pump 30 and passes through heat exchanger 4, vapor heat exchanger 3!, and

heat'exchanger 32 into .the vaporizing coil feed tank 33. 'All or part of the oil in the pipe 23 may be diverted therefrom by suitable manipulation opened and through cooler 31'into.a topped oil accumulator 36 from which the oil may be withdrawn through pipe 39 by means of a pump 40 discharging into the feed pipe 29 connecting with feed tank 33 as previously described."

The feed tank 33 contains the oil which is to beheated in a vaporizing coil and after vaporization thermally treated by direct contact with combustion gases of proper temperature, and in the case where the initial charge oil has been subjected to an initial topping operation as previously described, consists of this topped oil such as heavy gas oil, and cracked recycle gas oil recovered in the operation of the process as will be more fully described hereinafter.

The oil to be treated is.withdrawn from the feed tank 33 through the pipe 4| by means 01' the pump 42 which forces the oil through the pipe 43, through the valves 44 and 45 in the pipe 43, through the vaporizing heating coil 46in the chamber 2| from which the heated oil is transferred through the pipe 41 into the flash tower 46. The oil circulating through the coil 46 is heated during transit to a vaporizing temperatureand at the same time the combustion gases are partially cooled by indirect heat exchange with the colder oil. In view of the relatively large quantity of oil passing through this heating coil, I may deem itnecessary to provide additional means for heating the oil such as a tube still (not shown) externally of the chamber 2|,

connected into the pipe 43. By such means, I can obtain a very close control of the temperature change of the combustion gases by the coil 46. A pipe 43 controlled by a valve 50 connects the pipes 43 and 41 in order that all or part of the oil from pipe 43 may be passed directly into the flash tower 43 as operating conditions with respect to temperature may dictate.

The coil 46 is preferably placed in the chamber 2| in such position as to come in contact with the combustiorigases attheir highest temperature, although the exact positioning and arrangement of the tubes forming the coil '46 will be governed by the furnace design and by the amount of tempering of the combustion gases con emplated.

In the flash tower 48, the heated oil from pipe 41 is flashed into vapors and unvaporized ,oil, which latter forms a fuel oil and is withdrawn through the pipe 5|, valve 52, heat exchanger 53 and cooler 54 by the pump 55 which discharges 'the fuel oil to storage.

- The hydrocarbon vapors formed in the flash tower 48 discharge therefrom at substantially atmospheric pressure through the pipe 56 into the mixing chamber 5'! wherein they are mixed with the combustion gases issuing from the' chamber 2|.

The combustion gases entering the mixing chamber 51 will have been reduced in temperature by the steam and indirect heat exchange to a temperature between about 1500 F. to about .2500 F. and preferably to a temperature such that the mixture of hydrocarbon vapors and combustion gases will be at a temperature of from'about 1800 F. to about 2000" F. which I have found is most favorable for the primary thermal decomposition or cracking of the heavier hydrocarbons of the mixture to produce lower,

ing zone 51 into the primary treating or cracking zone 58, the time of passage of the reactant through which varies from between about one second at 2500 F. to about three seconds at 1500 F.

The reactant leaves the primary thermal treating zone 58 after the proper time interval and enters the secondary thermal treating or polymerizing zone 59 wherein the reactant is cooled to a temperature between about 1050" F. to about the reactant through the secondary treating zone will vary from about one second at 2000 F., to about five seconds at 1400 F., to aboutten seconds at 1200 F. V

The reactant on leaving the secondary treating zone 59 enters a separator 6| wherein the temperature is quickly lowered to around 600 F. to 700 F. to substantially terminate further reaction by spraying into the reactant a cooler oil through a suitable quench nozzle 62. The heavy polymers, tars and gums of the nature or fuel oil which are condensed in the separator 6| are discharged through the valved'pipe 53 into the pipe 5i and sent to storage with the fuel oil from flash tower 48.

Theuncendensed portion of. the reactant rises upwardly through a plurality of fractionating trays 84 countercurrent' to downflowing cooler reflux oil. The reactant of desired end point discharges from the separaior 6i through the pipe 65 into condensing vessel 65.

The condensing vessel 66 is provided with a cooling coil 61 into which clean cool water is passed by pump 68 through pipe 69 and cooler l0. The water is heated in the coil 61 by exchange with the hot reactant and the steam formed is discharged through the pipe II into the steam supply tank I2 from which tempering steam is withdrawn at will through the pipe I9.

The reactant in the condensing vessel is cooled to an extent sufllcient to condense the heavier hydrocarbons which accumulating as fractional condensate in the condensate basins I3, I4 and 15 may be withdrawn therefromthrough the pipes I6, 'I I and 18, respectively, and returned in suita ble proportions through the pipe I9 to the separator 6| as reflux by suitable manipulation'ot the valves 80, BI and 82.'

The uncondensed portion of the cooled reactant inthe condensing vessel 60 will preferably have as its heaviest constituent a hydrocarbon distillate having about a 200 F. to a 250 F. end

point and discharges from the condensing vessel 66 through a pipe 83, through coolers I0, 84 and 85, and through pipe 85 into separator 81.

In the separator 81, the condensate resulting from the cooling of the reactant will preferably consist primarily of hydrocarbons boiling above the pentane or C5 hydrocarbons. The water resulting from condensation of the tempering steam is withdrawn from the separator 81 I through the valved pipe 00.

desirable-tor the production of the desired aromatic products. The uncondensed portion 01 the reactant in the separator 81 will therefore consist of a mixture of those saturated and unsaturated hydrocarbons which are normally gaseous at normal atmospheric conditions of tempera ture and pressure and the combustion gases such as hydrogen, nitrogen, carbon dioxide and carbon monoxide. Obviously there will also be in heat exchanger 94, pipe 95, heat exchanger 53' and pipe 96 to the distillation coil 91 in the chamoer 2i. If desired, the heat exchanger 84 may be lay-passed to the pipe 95 through the valved pipe 98 and, likewise, a portion of the condensate in the pipe 93 may be by-passed through the valved pipe 99 into the pipe 43 leading to the vaporizing coil 46 by suitable manipulation of the valves shown. A valved pipe I connecting the pipes 95 and 43 permits the by-passing of a portion of the condensate issuing from the heat exchanger 94 into the oil flowing through the pipe 42 to the vaporizing coil 40.

The reactant condensate flowing through the distillation coil 91 is heated therein to a temperature sufllcient to permit vaporization of the heated oil at low or substantially atmospheric pressure and is discharged through the transfer pipe IM to the main tractionator I02.

The heavy condensate separated from the reactant in,the condensing chamber 65 may be transferred in whole or in part through the pipe I03 controlled by the valve I04 by suitable manipulation of the valves 8|, 82 and I04. In thus returning the heavy condensate from the pipe I03 to the iractionating tower I02, I am enabled to eflect sharp separation of suitable recycle stock such as heavy cracked gas oil for recycling to the vaporizing coil. Steam from the supply tank I2 may be injected into the tractionator I02 through the pipe I by opening the valve 200.

From the tractionator I02 there is withdrawn a relatively heavy recycle oil such as cracked gas 32, and cooler I08. Aportionot the oil in the.

pipe I06 passes through the pipe I09 controlled by the valve IIO into the pipe 02 of the separator 0| for use as quench oil. Another portion of the oil in the pipe I00 is passed through the pipe III controlled by the valve II2 into the spray nozzle 00 from which it is discharged to control the temperature of the reactant in the secondary treating zone 50.

The relatively heavy oil withdrawn from the Iractionator I02 through the pipe I06 is most suitable as recycle oil andflthe greater quantity or this oil passes through the pipe I06 and from thence through the pipe I12 controlled by the valve II4 into the Ieed'itank 33 from which a vapor return line I I5 leads to the main fraction ator I02. I have found; that for most satisfactory operation of my process, the'ratio of heavy recycle oil to fresh oil in the feed tank 33 should be from about one to one, to three to one.

A light gas oil is withdrawn as a sidestream from the fractionator I02 through the pipe II6 by means of a pump III and passes through a cooler lit to an absorber II8 for use as cooled lean absorption oil as will be more fully described hereinafter.

The overhead products of the fractionator I02 are discharged therefrom through the pipe I20 and pass through the heat exchanger 3| and cooler I2I to the separator I22 from which con densate is returnedthrough pipe I23 by means of pump I24 to the fractionator I02 as reflux for end point control of the fractionator overhead. Water is withdrawn from the accumulator I22 through the pipe I25 controlled by the valve I26 and the distillate, which I shall refer to as heavy distillate to distinguish it from the light distillate recovered from the uncondensed gases in the. accumulator I22 and separator 81, is discharged through the pipe I21 by the pump I23 as the desired aromatic liquid product.

The gases remaining uncondensed in the accumulator I22 will consist of hydrocarbons both saturated and unsaturated, uncondensible at substantiallyatmos'pheric pressure and at the temperature of the cooling water employed. These gases will contain entrained low molecular weight gasoline-like hydrocarbons and are discharged through the pipe I23 adjoining the pipe 89 feeding the suction side of the compressor I30. The mixture of combustion gases and hydrocarbon vapors is compressed and discharged through pipe I3I and cooler I32 into separator I33 from which the light distillate previously referred to is discharged through the pipe I34 controlled by the valve I35 into the pipe I36 through which flows rich absorption 011 being delivered from the absorber II3 to the pipe II for recycling to the" vaporizing coil l6. V

The uncondensed ,gases in the separator I33 are discharged through the pipe I31 into the absorber I I9 wherein residual hydrocarbons suitable for recycling to produce the desired aromatics are absorbed in the lean oil fed to the absorber through the pipe H0 and returned with the rich oil through the pipe I 36 to the vaporizing coil.

The unabsorbed gases are discharged through the pipe I33 and pressure relief valve I33'into the fuel gas main I0 from which they may be discharged to the atmosphere by opening the valve "I40, or picked up by the compressor 8 by opening the valve I.

It will be observed that I .have accomplished the objects of my invention and have provided a process for thermal treatment of petroleum hydrocarbons by the direct commingling of such hydrocarbons with combustion gases under carefully controlled conditions of time and temperature. I have provided a process by which the conversion and synthesis :of the hydrocarbons is effected by the thermal treatment of the combustion gases so as to produce an increased yield of liquid aromatic products such as naphthalene,

benzol, toluol, and xylol, together with liquid low molecular weight gasoline-like hydrocarbons suitable for use as motor fuel of high anti-knock rating. I have provided a process in which the yield of the desired liquid aromatic products is increased through the recovery and recycling of unsaturated hydrocarbons formedin the reactant by' the" thermal treatment. I have also provided a unitary process in which the temperature of .the combustion gases is controlled by indirect heat exchange with 011 being passed to various stages of the process and by the admixture with the combustion gases of a cool inert gas such as steam which is readily condensible and may be employed as a heat carrying medium withoutrequiring an increased size of the fractionating ap- I paratus.

It willbe observed that certain features and sub-combinations are of utility and may be em-' ployed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims. This is contemplated by and is ,withinthe scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. A process for thermally treating petroleum hydrocarbons including the steps of generating combustion gases having a substantially complete absence of oxygen, cooling the hot gases to a temperature of from about 1500 F. to about 2500 F., admixing dry hydrocarbon vapors with the cooled gases to form a reactant at cracking temperature, soaking the reactant at substantially cracking temperature for from about one to about three seconds to form normally gaseous, unsaturated hydrocarbons, cooling the reactant to a lower and polymerizing temperature of from about 1050 F. to about 1800 F., maintaining the reactant at the lower temperature for from about one to about twelve seconds to polymerize nor,- mally gaseous, unsaturated hydrocarbons to higher molecular weight, aromatic hydrocarbons,

a lower and polymerizing temperature of from about 1200 F. to about 1800 F., maintaining the reactant at the lower temperature for from about one to about twelve seconds to polymerize said normally gaseous, unsaturated hydrocarbons to higher molecular weight, aromatic hydrocarbons,

quenching the reactant to a temperature below 700 F. to substantially terminate further reaction and recovering aromatic hydrocarbons from the quenched reactant.

3. A process for thermally treating petroleum hydrocarbons including the steps of generating combustion gases having a substantially complete absence of oxygen, cooling the hot gases to a temperature of from about 1500 F. to about 2500 F., admixing dry hydrocarbon vapors with the cooled gases to form a reactant at cracking temperature, soaking the reactant at substantially the cracking temperature for from about one to about three seconds to form normally gaseous. unsaturated hydrocarbons, cooling the re- "unsaturated hydrocarbons, cooling the reactant to I actant to a polymerizing temperature of from about 1050" F. to about 1800 F., maintaining the reactant at the polymerizing temperature for from about one to about twelve seconds to polymerize the normally gaseous, unsaturated hydrocarbons to higher molecular weight aromatic hydrocarbons, quenching the reactant to a temperature below 700 F. and cooling the quenched reactant and separating therefrom a light condensate comprising mainly normally liquid hydrocarbons of gasoline boiling range and a heavy condensate comprising mainly hydrocarbons boiling above the gasoline boiling range, fractionating the condensates to obtain a plurality of successively higher boiling hydrocarbon fractions,

recovering from one 01 said fractions desired aromatic hydrocarbons, vaporizing another of said fractions and admixing the vapors formed with said first mentioned cooled gases as dry hydrocarbon vapors.

4. A process for thermally treating petroleum hydrocarbons including the steps 02 generating combustion gases having a substantially complete absence of oxygen, cooling the hot gases to a temperature or from about 1500 F. to about 2500 F., admixing dry hydrocarbon vapors with the cooled gases to form a reactant at cracking temperature, soaking the reactant at substantially the mixing temperature for from about one to about three seconds to form lower molecular weight hydrocarbons including normally gaseous, unsaturated hydrocarbons, cooling the reactant to a lower and polymerizing temperature of from about 1050 F. to about 1800 F., maintaining the reactant at the lower temperature for irom about one to about twelve seconds to polymerize said normally gaseous, unsaturated hydrocarbons to normally liquid aromatic hydrocarbons, quenching the reactant to a temperature below 700 F. and recovering liquid aromatic hydrocarbons from the quenched reactant.

5. A process for thermally treating petroleum hydrocarbons including the steps of generating combustion gases having a substantially complete:

absence of oxygen, cooling the hot gases to a temperature of from about 1800 F. to about 2000 F., admixing dry hydrocarbon vapors with the cooled gases to form a reactant at cracking temperature, maintaining the reactant at substantially the mixing temperature for from about one to about three seconds to form lower molecu-.

lar weight hydrocarbons, including normally gaseous, unsaturated hydrocarbons, cooling the reactant to a lower temperature of from about 1200 F. to about 1800 F., polymerizing the reactant at lower temperature for from about one to about twelve seconds to form normally liquid aromatic hydrocarbons from said normally gaseous,

unsaturated hydrocarbons, quenching the reactant to a temperature below 700 F. to substantially terminate further reaction and recovering liquid aromatic hydrocarbons from the quenched reactant.

6. A process for thermally treating petroleum hydrocarbons including the steps of generating combustion gases having a substantiallycomplete absence of oxygen, cooling the hot gases to a temperature of from about 1500 F. to about 2500 F., admixing dry hydrocarbon vapors with the cooled gases to form a reactant at cracking temperature, maintaining the reactant at substantially the mixing temperature for from about one to about three seconds to form lower boiling hydrocarbons including normally gaseous, unsaturated hydrocarbons, cooling the reactant to a lower temperature of from about 1050 F. to about 1800 F., maintaining the reactant at the lower temperature for from about one to about twelve seconds to polymerize said normally gaseous unsaturated hydrocarbons to normally liquid aromatic hydrocarbons, quenching the reactant to a temperature below 700 F. and cooling the quenched reactant and separating therefrom a light condensate comprising mainly normally liquid hydrocarbons of gasoline boiling range and a heavy condensate comprising mainly hydrocarbons boiling above the gasoline boiling range, fractionating the condensates to obtain a plurality of successively higher boiling hydrocarbon 1 fractions, recovering from one or said fractions desired liquid aromatic hydrocarbons, vaporizing another of said fractions and admixing the vapors formed with said first mentioned cooled gases as dry hydrocarbon vapors.

MAURICE B. COOKE.

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