US1765976A - Process of cracking petroleum oils - Google Patents

Description

June 24, 1930. R. A. HALLORAN ET Al- 1,765,976

l PRocEss oF CRACKING PETROLEUM oILs Original Filed Sept. 4, 1925 HEATING ELEMENT composition or tofore been practiced.

Patented June 24, 1930 UNITED STATES PATENT OFFICE RALRH A. HALLORAN AND-ARCHIE I.. STROITT, OF BERKELEY, CALIFORNIA, ASSIGN ORS,

BY MESNE ASSIGNMENTS, TO UNIVERSAL'OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATIONOF SOUTH DAKOTA PROCESS or' CRAOKING PETRQLEUM oILs Application led September 4, 1923, Serial No. 660,828. Renewed December 5, 1927.`

This invention relates to the art of decracking high-boilingpoint petroleum oils by the application' of heat and pressure for the production of relatively low-boiling-point oils.

In nearly alll cracking processes in Which high temperature is employed, development has long been towards the use of relatively small tubes or banks of tubes for the heating element. In the use of such a heating eleinent two methods have been employed to raise the oil to the temperature of the desired cracking reaction: One,--a single or direct passage of the oil through suchheating element in a series flow and thence to a vessel or point where .vaporization takes place, and, the other,-a continuous birculation or cycling of the oil, either thermosiphonic or forced circulation, through a closed circuit, including such heating zone or element, to and from a vessel or chamber Where vaporization takes' place. Cycling with forced circulation, in combination with certain other specified conditions, has here- In 1891 pressure .cracking with forced circulation, in combination with continuous feed, continuous Withdrawal of residuum,` and continuous distillation with condensation under atmosphericpressure, was disclosed by Schuchow and Gavrilow in Russian Patent No. 4782 (No. 175 of 1891). Since then various other combinations with forced circulation have been disclosed in the patent literature.'

In those processes using forced circulation, as employed heretofore, deposition of carbon in the heating element or tubes has seriously interfered With the successful operation of such processes in that it has limited the length of time during Which the process and apparatus can be run before shut-down for carbon removal from the heating element becomes necessary, and has reduced the heat transfer through the element to the oil undergoing heating therein, seriously affecting the efficiency of the heatingelement.. and decreasing the heat absorption rate which must be corrected by increasing the fuel supply to the heating element, thereby rendering control of the operation eX- ceedingly difiicult or impossible and thus affecting not only the chemical reaction butl also the yieldl of the desired low-boilingpoint oils.

It has been found that with many of such processes and the apparatus for'carrying out the same, carbon deposition is a limitation on the yield for any given charging stock beyond which it is not economical tol carry on the operation. Any provision by which the carbon deposition in the tubes is reduced prolongs the length of the run for the same yield and charging rate and for the same length of run produces a higher yield.

It has been customary in the method heretofore utilized in which a cyclic process with continuous withdrawal of tarry residuum is employed, to Withdraw such residuum from the same chamber or compartment in which vaporization takes place and from .which the circulation of the incoming fresh feed starts. As 'a result of this the tarry residuum Withdrawal, instead of being lsubstantially free from loW-boiling-point oils is a representative or average sample of the mixture in the vaporizing chamber or compartment and contains, therefore, in addition to the tarry residuum and fresh stock, unvaporized loW-boiling-point oils. This also results in an undue proportion of the ltarry residuum, resulting after vaporization has taken place, being circulated through v 'heating, thereby affecting the heat control vof such menstruum and tending to create an y undesirable heat differential between the oil as it is circulated and the oil in the vaporizing chamber; This is forthe reason that, if the oil in the vaporizing chamber of the process is to be maintained at substantially uniform temperature by a circulation of oil from said chamber through a heating zone and bak into said chamber, the oil in the heating zone' must be heated to a temperature substantially higher than that of the oil in the chamber to supply the necessary heat of vaporization to the oil in the chamber unless the oil is very rapidly circulated through the heating zone, so that although the oil passing through the heating zone is only heated slightly above that of the vaporizing chamber, such a great volume of oil is circulated therethrough that the total additional heat carried thereby to the vaporizing chamber is sulicient to supply the heat demand in the vaporizing chamber. With a relatively large volume of oil undergoing treatment it -is difficult to maintain this condition without such high rate of circulation as tends to preventl the;

oil in the vaporizing chamber assuming even a substantially quiescent state and thus any carbon formed therein will be mechanically carried into the circulating path and to the heating zone and will not properly settle out from the chamber where it can be removed.

l In United States Patent No. 11,449,227, granted to Richard W. Hanna on March 20, 1923, there is described a cyclic process wherein is employed to material advantage in commercial operation while passing the oil through the heating zone or element at intervals of not substantially more than ten minutes, a pressure andv temperature in excess of that at which thefoil is held at the point at which the 'cycling or circulation either of said, patents.

begins. Y e

In United States Patent No.-l 1,408,698, dated March 7, 1922, granted vto Richard W. Hanna, thereis describeda cyclic process in -which solvent oil is used to material advantage.

Our invention relates to an improvement 1n the respectlve processes of said Letters s Patent Nos. 1,408,698, and 1,449,227, althrough. our invention is not necessarily limited ,to use as an improved process embodying the invention patented or described in We have Adiscovered that by maintaining a relatively small volume of the oil undergoing treatment in the direct path of the circulation and by so conducting the operation that only the heavyde'rivatives produced by the initial vaporization of the circulating menstruum are in the path of circulation, or subject to.being drawn into such circulation, and the reaction is completed in a substantially separate chamber under substantially the same conditions of temperature and pressure so that the further products formed by the completion of the reaction are not subject to being drawn into the circulation, a material reduction in the carbon or coke deposition or formation in the heating tubes is secured and We are able t0 substantially increase the -yield oflow-boiling-point products. Also We effect thereby a saving in fuel. We are also able thus to segregateythe high-boiling-point derivatives of the cracking reaction or tarry residuum from the, menstruum being cycled and withdraw the same substantially without any effect from these heavy derivatives or tarry residuum upon the circulating menstruum. e Y

Our invention will be best understood by reference to the accompanying drawings, which are used merely to illustrate a preferred embodiment of our invention ,and which, it is understood, may be widely varied Without departing from the spirit of the invention, and in which Figure 1 is a diagrammatic View of an apparatus by which my invention may be practiced.

Fig. 2 is an enlarged cross-sectioned View of the evaporator, showing more in detail the Vcycling or initial vaporizing chamber and the-separate final vaporizingl chamber.

In the drawing, 1 indicates a storage vessel for thehigh-boiling-point oil which is to be cracked; l2 is a suitable pump designed to pump such oil from the storage, l, and forcethe same through pipe or conduit 3. 4 indicates a storage vessel for a solvent oil which is tio be mixed with the high-boilingpoint oil to be cracked for the purpose of taking into solution' the heavy bodies produced by cracking such high-boiling-point the preferred form and embodiment of my process. 5 indicates a pump to force solvent oil through line 6finto line 3, where'it is i mixed with the oil to be crackedv Itis obvious, however, that the mixing of the oil to be`fcracked and the solvent oil may take 4place before the same are supplied to the The use of such solvent oil is incident, however, only to through a waste heat exchanger 7, and' thencethrough a continuation of such pipe or conduit 3, into a reflux condenser 8, where such charging stock is subjected to the waste heat of the reflux condenserv and where it joins with the reflux and flows `through pipe 9 into the vaporizing chamber 10 of the druml 11. .The heating coil or element 19 of the cracking system is preferably mounted in a suitable furnace 18, which may be heated in any preferred manner; indicates a pump which takes suction on the'vaporizing chamber 10 through pipe 16, and causes a stream of the liquid therefrom to be circulated through pipe 17, heating coil 19, and pipe 20, back to the vaporizing chamber 10. 21 indicates a suitable valve, by means of which a differential pressure may be maintained on the oil in the vaporizing chamber 10,. and the heating coil 19. 13 represents a Abail-le extending across vthe drum 11,A

and so located that the vaporizing chamber 10, is relatively small as compared with the compartment 12. This baffle completely closes ofl" the vaporizing chamber 10, from the compartment 12,'except for a small opening about six inches in diameter next to the lowest point onthe periphery of the drum 11 14 represents a bank of tubes arranged in a horizontal plane and extending through the l baffle 13. These tubes are closed on the end located in compartment 12. .The other end is open and is upturned, so as to extend above the level of the liquid kept in the vaporizing chamber 10. Within the final reaction and vaporizing chamber 12 .the

4.bottoms of these tubes 14 are provided with suitably spaced small openings through which the vapor, evolved in the initial vaporizing and cycling chamber 10, is forced to flow into the body of reacting oil in the chamber 12. These tubes'14 are to be' tightly welded to the bathe-13 to insure the forcing of the passage of all such vapor Ifrom chamber 10 through tubes 14 into chamber 12. Themaximum level of oilin the chamber( 10 is determined by the level of the discharge openings from4 the tubes 14 into the chamber 12. The level of reacting oil in the chamber 12 is regulated by the withdrawal of residual oil therefrom and the maximum level of oil in chamber 10 is not dependent upon the level of oil in chamber 12., Baffles 22 are for the purpose of breaking up convection or eddy currents in compartment 12. s

A' vapor line 23, extends from compartment 12 tothe reflux condenser or column 8,

and thence through heat exchanger 7 to condenser 24. The condensate flows into a receiving'drum 25, Where the fixed or uncondensable gases are` released through conduit 28 and valve 29. The condensate is released through valve 26 and passes to storage 27.

31 represents a 'discharge pipe through which tarry residuum is withdrawn continuously from the system and passed through the cooler 32 to storage 33. The withdrawal of this tarry residuum is controlled by valve 3.0. f

With such an'organized apparatus or system as thus illustrated and described, we

'the cracking operation desired. 'When my process is performed in such a system, we preferably maintain in the final evaporating chamber a relatively large volume of the v re-acting oil undergoing vaporizatlon. Preferably we conduct the vapors from the cycling chamber 10 into the final evaporating chamber in such manner as to discharge them into this body of oil as, for instance, by means vof the vapor conduit pipes 14.. By thus discharging these hot vapors into vand causing them to rise throughk this body of re-act-ing oil vaporization-thereofis assisted and an economy of the heat demand effected. Thus a further reduction in the potential formation of carbony or heavy derivatives in the heating element. is secured and an increased' yield for the same charging rate is thus secured. The final withdrawal of the low-boiling-point vapors is from this final evaporating chamber12. The withdrawal ofthe heavy derivatives of the cracking operation is also 'from such chamber 12 and preferably as far removed as possible from the actual cycling menstruum of the systeml The reacting oil is maintained for an appreciable time in this chamber 12 and the main precipitation or settling out of the carbon, tarry bodies or heavy derivatives orl cracking takes place therein. The period vof re-action is thus prolonged by the reaction of the oil in the final evaporatinfr chamber 12, as described, without permittingV this prolonged reaction, and the consequent precipitation and settling out of the oil of the heaviest derivatives, to effect the operation of the cyclic system, which includes, as before described, a heating zone or coil and a -cycling chamber, in which latter material vaporization is effected.l

However, our invention is not necessarily limited to conducting the vapors from the cycling or initial vaporizing chamber into the re-actin oil in the final vaporizing chamber. I desired such vapors may be permitted to flow from the cycling chamber over into the vaporizing space above the reacting oil in the final chamber 12, as by providing a suitable opening (not shown) at or near the" top ofthe baffle 13, orthey may be separately discharged, as through a Itwill be apparent in the practice of this process that a very considerable amount of vaporization will take place in the Vaporizing chamber 10. The vapors here formed include the lighter or desirable fractions, and, in addition, a large proportion of heavier products, which will later be returned to the system as reflux from the tower 8, all kof which vapors mustof necessity pass through the tubes 14 and into the oil in compartment 12 of the system.

It will further be apparent that the oil passing from compartment 10 through the opening in the baille 13 into theicompartment 12 will beheld at a cracking temperature. This oil is withdrawn at the .chamber 10 from the circulating menstruum of the system. The rate of withdrawal is determined by the rate of withdrawal of the heavy derivatives of cracking from the chamber 12 plus the rate of withdrawal of vapor formed in the chamber 12, from the chamber 12, less all condensation in the chamber 12 of vapor entering thereinto through the conduits 14. y v,

There will be a sli4 ht fall in temperature due to small radiation losses and toheat absorbed by additional vaporization andl reaction in this compartmente12f Itis this additional reaction and vaporization which so greatly adds to' the increase in yield of the process and makes it possiblel to withdraw a residuum substantially free from constituents desired as distillates. The construction of drum 11 is but diagrammatically indicated, it being understood that in practice the drum must of course be supported upon a suitable foundation and in accordance with ordinary refinery practice would be suitably insulated against dissipation of heat by radiation or convection.

Very satisfactory results have been obtained by the use of this process including the use of baffle 13 but without the use of the tubes 14 in which case a vapor opening is arranged at the top ofbaiile 13 as before referred to. It has been found, however, that the fall of temperature in lthe oil in compartment 12 is greater and the increase in yield less than with the use of the vapor tubes 14. f

While we have shown in the drawings the cycling and initial vaporizing chamber 1.0 and the final reacting and vaporizing chamber 12 as parts of a single element,'

indicated in the drawing as. an'fvaporator, it is obvious that the functions and mode ol operation of these would not be 'changed nor would the process be materially altered if the initial vaporizing and cycling chamber 10 and the final reaction and vaporizing chamber 12 were constructed as totally independent units and merely so connected as to` have the described functions and funcrocess and system as a whole. We, thereore, wishit understood that in so far as the drawings illustrate or we have herein described these two chambers as parts of a single element, such has been done conventionally and lfor convenience and we do not thereby limit our invention thereto.

` Preferably condensation of the vapors in the condenser 24 is under pressure maintained on the system by regulation of the valve 26. The crackingoperation may be performed at any required temperature and under such pressure above atmospheric as may be best suited to the particular con- -ditions and oils to be treated.

In the preferred embodiment as stated above, the reflux is joined with the feed and is introduced into and becomes a part of the circulating menstruum. The menstruum is thus maintained substantially free from heavy and tarry-bodies and the diculties resulting from carbon deposition substan` tially reduced. Itis apparent, however,

that the feed and reflux may be introduced into other parts than those indicated.

We claim Y 1. The cycli'jj'rocessofi-Cracking petroleum oils under'` 'a5'"substfintiall ,v constant temperature andpres'sure, both-'o A which are substantially unifol'mthroughout the crack-f ing system,.. which includes forcibly'circulat-g ing the oilf'iindergoing treatmentin a relatlvely small stream from an initial vaporizing and cycling chamber through a heatf ing zone and back into said chamber, passing a portion of the oil in circulation from said cycling chamber to a non-cycling chamber, in .such manner as to maintain iny said cycling chamber a relatively small volume of oil and in said non-cycling chamber a relatively vlarge volume of said oil in order that heavy derivatives are formed mainly in said non-cycling chamber, effecting thgcompletion of the desired cracking reaction 1n said non-cycling chamber, withdrawing the vapors, and withdrawing residual oil.

2. The cyclic process of cracklng petroleum oils under constant temperature and pressure, both of which are substantially `uniform throughout the cracking system,

which includes forcibly circulating the oil undergoing treatment in a relatively small stream from an initial vaporizing and -cy-l cling chamber through a heating zoneand back into said chamber, feeding the oil to be treated to said circulation in suficient quantity to maintain a substantially uniform volume of oil in circulation, withdrawing a portion of the partially converted oil from the circulL'iing menstruum at said cycling chamber and passing it to a second reacting and vaporizing chamber, maintaining such oil in said second chamber for a time suflicient to permit the comple.- tion of the desired reaction and under the required conditions of ressure and temperature without recirc ation, withdrawing the vapor, and withdrawing residual oil.

3. The cyclic process of cracking petroleum oils under constant temperature and pressure, both of which are substantially uniform throughout the cracking system, which includes forcibly circulating the oil undergoing treatment in a relatively small stream from an initial vaporizing andcycling chamber throu h a heating zone and back into said chamber, feeding the oil to be treated to said circulation in a sufficient quantity to maintain a substantially uniform volume of oil in circulation, withdrawing aportion of the partially converted oil from the circulating menstruum-l at Said chamber and passing it to a second reacting and vaporizing chamber, maintaining liquid communication between said chambers, maintaining a closed condition against the withdrawal of vapor from said cycling chamber except through the second chamber kand through the reacting oil therein, withdrawing the vapor fromsaid second chamber, and withdrawing residual oil from said second chamber.

4. A process ofv cracking petroleum oils under a substantially constant temperature and pressure, both of which are substantially uniform throughout the cracking system, which includes first forcibly circulating the oil undergoing treatment from a vaporization and cycling chamber through a heating zone and back into said chamber, continually withdrawing a portion of the oil from such circulating system and passing it to a cracking chamber in which a relatively larger volume of oil is maintained than in said vaporization and cycling chamber, the oil in said second chamber being maintained in a quiescent state to permit removal of residuals, the vapor lformed in the first chamber being passed through the oil in the second chamber', feeding the oil to be'treated to said circulation in suicient quantity to maintainsubstantially a uniform volume of oil in circulation, withdrawing the vapors formed, and withdrawing residual oil from said second chamber so as to remove heavy derivatives therefrom. l 5.' A cyclic process of cracking petroleum oils which 'includes heating the oils undergoing cracking by circulating the oils from an evaporating lchamber to and through a chamber to said second chamber, and withl drawing the vapors.

6. In the pressure distillation -of oils heavier than gasoline '.for the production of gasoline-like products, maintaining a plu-y body to maintain all said oil bodies at cracking temperature, the later oil bodies deriving heat solely from said oil passed through the heating zone.

7. In the pressure distillation of oils heavier than gasoline for the production of gasoline-like products, maintaining a` plurality of bodies of oil and causing oil to flow successively therethrough, withdrawing oil from the first of said oil bodies, passing it together with fresh oil through a heating Zone and returning such oil in heated state to said first oil body to maintain all said oil bodies at cracking temperature, the later oil bodies deriving heat solely from said oil passed through the heating zone.

8. In the pressure distillation of oils heavier than gasoline for the production of gasoline-'like products, maintaining a plurality of bodies of oil and causing oil to flow successively therethrough, said oil bodies being at conversion temperatures, removing vapors therefrom, cooling said vapors to condense therefrom products heavier than the desired gasoline-like products, withdrawy ing zone and returning .such oil in heated lstate to said first oil body to maintain all said oil bodies at cracking temperature, the later oil bodies deriving heat solely from said oil passed through the heating zone.

Signed at Richmond, California, this 28th day of August, 1923.

4 RALPH A. HALLORAN.

ARCI-IIE L. STROUT.

heating zone and back into the evaporating chamber, passing a portion of the heated oil to a second chamber in which the cracln'ng reaction is continued while maintaining the 'goil quiescent and withdrawing residual oil

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