US1957810A - Hydrocarbon oil conversion - Google Patents

Description

May 8, 1934. J. D.' sEGUY 3,957,810

HYDRocARBoN OIL CONVERSION Filed June 15, 1929 atented v"May 8, 1934 PATENT OFFICE HYDROCARBON OIL CONVERSION JeanDelattre Seglly, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of South Dakota Application June 15, 1929, Serial No. 371,223

3 Claims.

This invention relates to improvements in the conversion of higher boiling point hydrocarbons into products of a more valuable nature, usually of lower boiling points.

5 The operation of cracking processes may result in the formation of an oil fraction heavier than gasoline and possessing characteristics reasonably close to those of kerosene which it may not be desirable to return for further treatment l to the cracking process by which it has been formed.

Reason for such abstention may be because of the refractory character of this fraction called pressure distillate bottoms orrsecondary reflux,

hl and a resulting decrease in the capacity of the cracking unit, when this fraction is mixed with the other materials to be treated therein.

The object of the present invention is to separately treat the secondary reflux or pressure distillate bottoms in such a manner as to obtain a maximum yield of lighter materials at a minimum cost by increasing the rate of conversion and decreasing the cost of the fuel.

I Yhave found that, by effecting the cracking of this material while in direct admixture with a gaseous heating medium, the control of the temperature under which the operation is carried out may be eiected more closely and more evenly throughout the treatment, thereby ,avoiding overcracking of portions of the material and decreasing the formation of gas and coke accompanying the reaction, and increasing the yield of light condensable materials.

In the operation of cracking processes one type Y generally comprises passing an oil through a heating coil and expansion chamber maintained under superatmospheric pressure, separating the vapors and the unvaporized products, withdrawing and isolating the latter, subjecting the vapors to dephlegmation through one or a series of dephlegmators, the heating coil being subjected to direct heat from combustion gases in a suitably designed furnace.

In the operation of such processes particularly where the reflux condensate from the dephlegmator is returned to the heating coil for retreatment'with fresh charging stock, .the temperature of the oil entering the heating coil is in general above 500 F., and in a great many instances 50 around or above 700 F. It follows, therefore,

' that the combustion gases passing over the heating coil may not be cooled to temperatures much below 900 F. and often are at-a temperature between 950 and 1100 F. These gases, therefore, contain considerable residual -heat which may be utilized in a great many ways for preheating or otherwise. f

Another main object of this invention, therefore, is to utilize this residual heat in connection with the conversion of so-called distillate bottoms heretofore described, to produce additional yields of gasoline or light motor fuel.

The combustiongases leaving the furnace as heretofore described, and at a temperature varying between`900 F. to 1100 F. contain suilicient 65 heat to raise hydrocarbon oil to cracking te'mperature where liquid or vapor phase cracking or mixed cracking may occur, depending upon the relative proportions of gas and hydrocarbons in the mixture, which, of course controls the nal temperature of equilibrium of the mixture. Therefore, by regulating the proportion of hydrocarbon oil and gas any desired temperature may be obtained at which said hydrocarbon oil will undergo reaction and produce lighter distillates.

In one preferred embodiment, I preferably control the operation so as to obtain, in the mixture 'of flue gas and hydrocarbon oil, temperatures above 900 F. or temperatures above the critical boiling point of the hydrocarbon oil in order to obtain direct vapor phase cracking which results in a reaction proceeding at a rapid rate, and the production of gasoline or motor. fuel possessing high antiknock properties.

In this manner intermediate products of the high pressure cracking operation, which it may not be desired toreturn thereto for retreatment may be separately retreated at little additional cost by utilizing the waste heat of said high pressure reaction for the production of valuable products. Itmay be desirable, however, depending upon the conditions of the operation, to add to the waste flue gas from the high pressure cracking reaction an additional supply of combustion gases at a/,higher temperature if the heat contained in the waste ue gas may not be sufficient t`o obtain the temperature requiredI for the conversion of said intermediate products.

Other objects and advantages of the inventionwill be brought out more in detail in the following description.

The single ligure in the drawing is a diagrammatic view, partly in section and partly in elevation, of apparatus which may be used to carry out the process of the invention, but it is in no sense a complete drawing or to scale.

Referring to the drawing, raw oil may be treated under so-called liquid, vapor or mixed phase cracking conditions by being drawn from a tank (not shown) through the line 1 and pump 2 into feed line 3, whereby it is directed to a heating coil 4, located in a furnace 5 of any suitable design. The oil is heated in the coil 4 to a suitable cracking temperature, for instance, between 800 and 950 F. under suitable pressure, and is then discharged through a transfer line 6 having valve 6a into reaction chamber 7 where unvaporized products separate from the vapors; the unvaporized products may be withdrawn from chamber 7 through lines 8 controlled by valves 9. vThe rate of withdrawal may be preferably controlled so that the proportion of coke and sludge formed by the reaction and contained in the unvaporized products does not exceed a predetermined limit, for instance, does not exceed 5% as a maximum, and preferably does not exceed 2%.

Vapors separated in reaction chamber 7 may be withdrawn therefrom through line 10 having valve 1l, and passed to a primary dephlegmator 12. Therefractionation may be obtained by the injection. of a cooling agent (which may be one of the products of the system or raw oil) introduced through line 13 having Valve 14. Reflux condensate formed by this fractionation may be withdrawn from dephlegmator 12 through line 15 and it fmay be removed from the system through line 16 having valve 17, or preferably it is returned to the feed line 3 through line 18 and hot oil pump 19, whereby said reiiux condensate from the primary dephlegfnator is retreated by the mixed phase reaction.

Vapors not condensed in primary dephlegmator 1,2 may be removed from the top thereof through line 20, having valve 21, and directed to a secondary dephlegmator 22 wherein through additional cooling provided by the injection of cold Aoil through line 23 having valve 24 or otherwise, the vapors entering dephlegmator 22 maybe separated into vapors having the characteristics of motor fuel, and secondary reflux condensate or distillate bottoms.

The uncondensed vapors and uncondensable gases removed from the top of dephlegmator 22 pass through line 25, controlled by valve 26, and through condenser 27 into receiver 28, provided with the usual valve-controlled distillate drawof line 29 and Valve-controlled gas release line 30.

The secondary reflux formed in dephlegmator 22 may be Withdrawn from the bottom -thereof through line 31 having valve 3l and Inay be withdrawn from the system through line 32 having valve 33, or as a feature of my invention, it may be preferably directed through line 34 (controlled by valve 34') and pump 35 to a further cracking zone as will be presently described.

Any'suitable pressure may be maintained on the mixed phase cracking zone, for instance, pressure from to 800 pounds to the square inch may be maintained on the heating coil 4.

"i The chamber 7 and dephlegmator 12 may be maintained under equalized pressure or under different pressures controlled by the various' valves shown.

An illustrative operat'on which is not to be taken as a limitation of the scope of the invention may be given; the following conditions may be maintained on the mixed phase cracking zone: The oil may be charged to the heating coil4 and heated therein to a temperature of about 900 F. and passed to the chamber 7,

both chamber and coil being maintained under a pressure of approximately 225 pounds.

Dephlegmation of the vapors in dephlegmator l2 forms a reflux condensate which is retreated in the heating coil 4, the mixture of raw o l and reflux condensate entering heating coil 4 being at a temperature of, say 700 F., more or less. 4

By controlling the temperature of the vapor leaving the dephlegmator 12 at about 550 F. under a pressure of about 200 pounds, a pressure distillate containing approximately to of material boiling below 410 F. may be produced.

This material boiling below 410 F. may go into the manufacture of gasoline. 'Ihe balance of the pressure distillate which may be called pressure distillate bottoms, is separated from the lower boiling point material by proper control of the dephlegmation in dephlegmator 22, and condensed and directed through lines 31 and 34 to the further treatment which will hereafter be descnbed. These pressure distillate bottoms generally have a boiling point range between about 400 and about 550600 F. at

atmospheric pressure. *Y

In the operation of the process under the above given conditions the combustion gases after passing over coil 4 in furnace 5 may be at a temperature varying between 950 and 1100 F., more or less.

These nue gases may be directed from the furnace 5 through flue 36 and, in part or in toto, they may be directed to flue 37 controlled by damper 38 leading to suitable stack (not shown) or, preferably, the flue gases from flue 3 6 maybe passed to flue 39 controlled by damper 40, then to a hot gas blower 41, into the injectionue 42.

By proper manipulation of dampers 38 and 40, the quantity of gas returned to the injection flue 42 may be properly controlled.

The condensate from the dephlegmator-22 may be caused to physically commingle with the flue gas in injection flue 42. This condensate is returned thereto through lines 31, 34 and pump 35 as heretofore described and through line 43 entering injection flue 42 in any suitable manner which would provide for complete and rapid mixing of the secondary condensate with the flue gas. The control of the nal temperature of the mixture is effected by suitable control of the respective proportions of flue gas and secondary condensate in the mixture. An additional control of the temperature of the mixture may be effected by providing means for injecting in the spent flue gas leaving furnace 5 a proportion f combustion gases at a higher temperature. The process may be provided, for instance, with a by-pass flue 44, having a damper 45 connecting flue 36 with the combustion chamber of furnace 5 hear the point at which fuel is subjected to combustion at its discharge from the burner, and is, therefore, near its maximum temperature. In this manner, the temperature of the flue gas directed to the injection flue 42 may be raised above the temperature of the spent flue gas leaving furnace 5.

The mixture of secondary condensate and flue gas obtained at the discharge of line 43 is then passed through a contact vapor cracking chamber 46, which maybe of any desirable construction provided at the bottom with a cleaning manhole 46' and with a draw-off line 47 having valve 48 through which heavy products formed by the reaction may be withdrawn.

The size of the chamber and rates of input are4 suitably .controlled to allow for the proper time for the cracking reaction to proceed at the temperature maintained, and one or more chambers may be used in series, if desired.

'I'he pressure maintained on the mixture undergoing conversion in chamber 46 may be atmospheric or higher, but it is preferably such that vapor phase cracking conditions are established.

The resultant vap'orous products of reaction are withdrawn from chamber 46 through pipe 49 on which may be interposed valve 50, and directed to scrubber or separator 51 wherein condensation of the heavier hydrocarbons may take place in such a manner that the mixture of vapors and gas leaving the scrubber 51 contains the desired motor fuel product.

'Ihe uncondensed vapors may be Withdrawn from the scrubber or fractionating apparatus 51 through line 52, having valve 53, thence passed to condenser 54 and to separating apparatus 55 where the liquid hydrocarbons may be withdrawn through line 56 having valve 57 and from which the gases may be withdrawn through line 58 having valve 59. These gases may be returned to the process in part or in toto to help regulate temperature of the mixture in chamber 46 with many accompanying useful results.

The condensate formed in scrubber or fractionating apparatus 51 may be withdrawn from the process through line 60, having valve 61, or it may be returned to the process for further treatment through line 62 having valve 63 on which is interposed a pump 64 whereby said condensate is returned throughline 65 to any suitable part of the system such as, for instance, line 43. In this manner this condensate is subjected to additional any desired pressure on the scrubbing, fractionating, condensing and receiving parts of the vapor cracking zone. If desirable, the vapors or condensate leaving dephlegmator 22 may be combined with those leaving fractionator 51 for condensation or collection of both' in admixture.

It is to be understood that the specific temperature and pressure conditions which I have used.

in describing a specific embodiment of the invention are not to be taken in any way as limiting the scope of the invention. The pressure in the high pressure cracking zone may vary from 25 pounds to several thousand pounds, more or less. Those temperature conditions will be maintained in the high pressure zone which will result in the maximum conversion of a given charging stock consistent with economical operation.

'Ihe temperature and pressure conditions, as well as the relative proportions used to illustrate the invention will suiiice 'to indicate its scope without limiting the invention to these specific conditions.

I claim as my invention:

1. A process of hydrocarbon oil conversion which comprises subjecting a charging stock to cracking conditions of temperature at superatmospheric pressure to vaporize a substantial portion thereof, separating the vapors from the non-vaporous residue, separating, by condensation, a fraction of said vapors corresponding to pressure distillate bottoms and having a boiling point range between 400 F. and 600 F., and subjecting this latter fraction to vapor phase cracking conditions by vphysically co-mingling same with highly heated gas, characterized in that said highly heated gas comprises the residual combustion gas from the cracking ofthe original charging stock.

2. A hydrocarbon oil cracking process which comprises heating charging oil to cracking temperature under pressure in a heating zone by indirect heat exchange with hot combustion gases, separating the vapors from the unvaporized oil, subjecting the separated vapors to primary dephlegmation thereby forming a primary reiiux condensate, subjecting the remaining vapors to controlled secondary dephlegmation to form a secondary reflux condensate corresponding to pressure distillate bottoms and having a boiling point between 400 F and 600 F. and which is lighter and more refractory to cracking than said primary reux condensate, returning said primary reflux condensate to said heating zone for retreatment therein, subjecting said more refractory secondary reflux condensate to vapor phase cracking independently of and at higher temperature than said charging oil and primary reux condensate and utilizing in such vapor phase cracking residual heat contained in the combustion gases which have passed in heat exchange relation with the charging oil, and condensing as products of the process the resultant vapor phase cracked vapors and the vapors uncondensed by said primary and secondary dephlegmations.

3. A hydrocarbon oil cracking process which comprises heating charging oil to 'cracking temperature under pressure in a heating zone by indirect heat exchange with hot combustion gases, separating the vapors from the unvaporized oil, subjecting the separated vapors to primary dephlegmation thereby forming a primary reflux condensate, subjecting the remaining vapors to controlled secondary dephlegmation to form a secondary reflux condensate corresponding to pressure distillate bottoms and having a boiling point between 400 F. and 600 F. and which is lighter and more refractory to cracking than said primary reflux condensate, returning said primary reflux condensate to said heating zone for retreatment therein,.subjecting said more refractory secondary reflux condensate to vapor phase cracking independently of and at higher temperature than said charging oil and primary reflux condensate by mixing the same with the combustion gas after its use in heating the charging oil and condensing as products of the process the resultant vapor phase cracked vapors and the vapors uncondensed by said primary and secondary dephlegmations.

JEAN DELA'ITRE SEGUY.

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