US1971244A - Process for converting petroleum hydrocarbons - Google Patents

Description

Aug. 21, 1934. H. E. wlDDELL PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS Filed May 2l, 1924 mvv www.'

INVENTOR.

ATTv RNEY.

Patented Aug. 21, 1934 PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS Henry E. Widdell, Kansas City, Mo., assignor, by mesne assignments, to Gasoline Products Company, Inc., Wilmington, Del., a corporation of Delaware Application May 21, 1924, Serial No. 714,845

Claims. (Cl. 196-51) This invention relates to improvements in a process for converting. petroleum hydrocarbons, and refers more particularly to a process in which relatively heavy oils are converted to oils of a 5 lighter character having substantially the qualities of commercial gasoline.

Among the objects of the invention are, to provide a process combining c ertain advantages among which are the utilization of the charging stock as a refluxing medium circulated through a closed coil in a dephlegmating tower without being brought into intimate contact with the light vapors passing therethrough; to provide a process in which the charging stock, after being preheated and converted in a reacting stage is directed and circulated through a body of reux condensate collected in the bottom of the dephlegmating tower whereby a portion of the heat contained in the converted oil is transmitted to the condensate, driving off additional vapors therefrom and simultaneously therewith the synthetic crude or converted product is relieved of excess heat which permits of the more accurate control in the subsequent vaporizing stage; to provide a process in which two charging stocks of a relatively different nature are simultaneously treated in separate portions of a unit and blended in an evaporator, producing an improved distillate on condensation and a better quality bottom; to provide a process which preferably is operated continuously and one in which alarge amount of oil may be treated over a relatively short period of time, and in general, to provide an apparatus for carrying out this process.

The single figure is a diagrammatic view showing the separate units and their connections. The placing of the different stages has been varied in order to produce a more compact ligure.

Referring to the drawing, at 1 is shown a furnace in which is mounted an upper bank of coils 2 and a lower bank of coils 3 connected by a transfer line 4. 5 is a reaction chamber preferably made of a steel forging and adapted to withstand high pressures ranging up to 1,000 to 1,500 pounds per square inch. At 6 is shown an evaporator connected by a vapor line 'I to the condensing tower 8 which in turn is connected by a pipe 9 to the refluxing or dephlegmating tower 10 whose interior is preferably of a bubble tower construction. At ll is shown a gasoline At 16 is shown a separate furnace in which is mounted a continuous coil or pipevstill 1'7. Both of the furnaces 1 and 16 are preferably heated by means of gas burners not shown.

Describing now more in detail the manner in which the oil is circulated through the system, charging stock from any convenient sourd`- prf erably having the characteristics of lacroseiiie, gas oil or the like is introduced through the line 17. This charging stock is forced by means ci high pressure pump 18 either directly through the by-pass line 19 'controlled by a valve 20 ro the upper coil 2 mounted in the furnace l or may be charged through the line 21 controlled n by a valve 22 and circulated through a preheating coil 23 positioned in the upper portion of the relluxing tower 10. This relatively cool oil, while being preheated by the hot vapors rising through the tower, also serves as a refluxing agent condensing out the relatively higher boiling point fractions from the vapors and knocking them back into the tower through which they gravitate against the flow of the vaporous hydrocar bon fractions. This preheated charging stock is returned through the line 23' and is introduced into the upper bank of tubes 2 in the furnace 1 where it is further heated and passed, through the transfer line 4 into the lower baril: of l tubes 3 while therein being rapidly brought to a conversion temperature. While in a condi tion of incipient conversion, that is, while the oil is at a cracking temperature but before any substantial decomposition has taken place, the highly heated stock is directed through the transfer line 24 to the reaction chamber 5 in which it is collected in a substantial body" moving slowly to the outlet end and to the discharge line 25,

4This reaction chamber permits not only the collection of the oil in a substantial body where digestion may take place, but introduces a time element in the oils conversion. It is in this reaction chamber that the cracking reaction is consummated. The temperature and pressure conditions are controlled in order to prevent any substantial vaporization, that is, the conversion or cracking conditions are so regulated that the conversion takes place substantially in the liquid phase. This digestion, or rearrangement of the molecular bodies in the oil, results in what is termed as a synthetic crude which is drawn off through the valve 26 and discharge line 25. This synthetic crude is of a relatively different nature than the charging stock in that the oil body now contains a relatively larger percent of lighter or lower boiler point fractions which may be readily driven off by subsequent distillation.

In order to utilize the contained heat in the oil to distill off these lighter fractions, thereby reducing materially the heat loss in the system, the oil is directed through the line 25 either directly through a .by-pass 27 controlled by a valve 28 and through the line 29 to the evaporator 6 or, under certain conditions, it is circulated through the line 30 and coil 31 positioned in the tower 10, thence through the line 32 back into the line 29 to the evaporator i5. This latter course through the coil 31 is adopted when the cil contains excessive heat, that is, under conditions where there would be an excessive vaporization if the oil were introduced directly to the evaporating tower. Such conditions arise when a relatively light oil is treated, such as kerosene oil. With certain of the heavier oils, such as heavy gas oil, the temperature as it is withdrawn from the reaction chamber is not excessive and does not produce excessive vaporization in the evaporator. This difference is primarily due to the heat necessary to distill ofthe lighter oils of different characters. vIf circulated through the coil 31 in the tower 10, the oil is surrounded by a cooler medium or reflux condensate which has been separated out in the tower and to which heat is transmitted, serving to reboil this reflux condensate and drive off additional vaporcus fractions while the synthetic crude circulated through the coil is relieved of its excessive temperature and reduced to a condition where more suited to proper vaporizing conditions when released in the evaporator 6. The function of the valve 26 is to relieve the pressure on the synthetic crude v'hich results in the drawing off of the lighter fractions in the evaporator tower 6.

Simultaneously with this treatment in the cracking portion of the apparatus, there is introduced through the line 33 a charging stock of relatively heavier oil, preferably an oil having the characteristics of commercial fuel oil,-a product from which the lighter fractions including benzine, kerosene and gas, oil cuts have been removed. This charging stock is charged by means of the pump 34 either directly through the by-pass line 35 to the line 36 communicating with the pipe still 171, or it may be circulated through the line 37 in which is interposed the heating coils 38 positioned in the condenser tower 8. If circulated through the pipe 37, after preheating, it is returned and directed through the line 36 to the pipe still 171 where it is heated to a temperature sufficient to vaporize off a substantial portion of the oil bodies contained therein. The fluid oil products from the pipe still pass through the line 39 and are introduced in an evaporator vsimultaneously with the syntheticl crude from the cracking unit.

This blending of the highly heated oils in the evaporator' serves not only to promote the evolution of vapors but also has the advantage of producing a blended bottom which is drawn off through the pipe 40 in which is interposed a valve 4l controlled by an automatic liquid level regulating device 42. Normally, when the lighter fractions are distilled from the synthetic crude with the contained heat in the oil and a large percentage of the oil passed overhead as vapor, the resulting bottom is objectionable due to the presence of considerable quantities of free carbon which makes the product objectionable when utilized as fuel oil. Likewise, when fuel oil is treated in a pipe still, and considerable quantities of the oil driven overhead, the resulting residual material is of a relatively viscous nature and only uid at high temperature. When the products are combined or blended in the manner described there results a bottom which is a free flowing oil with a relatively high degree of fluidity at 32 F. or 0" C. This bottom can be readily circulated through pipe lines even at low temperatures. Free carbon is contained in this bottom to an amount not materially in excess of three pounds per barrel, and when operating on some types of oil the carbon cont-ent runs materially below one pound per barrel. In some cases, it is scarcely discernible. The residual material or bottom which collects in the evaporator as described is drawn off through the line 40, passed through a cooling coil 43 and is directed through the line 44 to a fuel oil storage.

The overhead material distilled off from the oil body rises and passes through the packing material diagrainmatically shown at 45. These vapors are directed through a line 7 to a condenser tower wherein partial condensation is effected due to loss of heat through radiation and the circulation of the cool fuel oil charging stock through coils 38 positioned in the tower.

The reiiux condensate separated out in the tower 8 is automatically withdrawn through the line 45 controlled by the liquid level regulating device diagrammatically shown at 46, This reflux material passes from the line 45 through the line 46 to a recharging stock cooler 47, thence to a recharging stock storage through the line 48.

The overhead material from the partial condenser tower 8 is directed through the line 49 to the refluxing or dephlegmating tower 10 which is preferably of bubble type construction. The vapors rising through this tower are subjected therein to the refluxing action of a plurality of pools of relatively cooler oil which serve to separate out the higher boiling point fractions and gravitate these fractions downwardly to a pool maintained in the bottom of the tower by means of a liquid level regulating device 50. This condensate maintained inthe bottom of the tower is subjected to the reheating action of the synthetic crude when the same is circulated through the coil 31. It is drawn off after collection by the liquid level regulating device through the discharge line 51 in which is interposed a valve 52 and is directed with the condensate from the partial condensing tower 8 through the line 46 and recharging stock cooler 47 The final vapors or gasoline fractions pass over from the top of the tower through the line 12 to the gasoline condenser 1l from which the distillate is discharged through the cooling coil 13 and through the line 14 to the gas separator 15. The incondensible gas is withdrawn through the pipe 53 controlled by a valve 54, while the liquid drawoif through the line 55 is similarly controlled by a liquid level regulating device 56.

The process permits of continuously treating oils of a relatively different character and uti lizes as recharging stock the bottoms recovered from the separate stages whereby a more-com plete treatment is effected and the heat loss materially reduced. Furthermore, wherever possible it will be noted that the contained heat of the oil is utilized to preheat incoming cooler oil or the cooler oil utilized to reux or separate out objectionable higher boiling point fractions. The

such as fuel oil, in combination with a cracking system while eliminating the objectionable features of cracking fuel oil direct.

It is appreciated that the different stages may be redesigned and changed as to construction and connections altered without departing from the spirit of the invention. Broadly, the invention covers the simultaneous treatment of oils of a relatively different character to produce an increased and improved quality distillate and at the same time improving the character of the residual material or bottoms may be considered by-products of the process.

I claim as my invention:

1. A process of converting oil comprising separately and simultaneously treating charging stocks of a relatively different character, one in a coil and enlarged chamber under such conditions of temperature and pressure as to crack the oil while maintaining it in substantially liquid phase, the other in a tube still wherein it is treated under temperatures sufficient to distill off a major portion thereof, combining the heated oils in a separate evaporating stage maintained at reduced pressure to vaporize the lighter fractions of the combined oils, dephlegmating the vapors in separate successive stages, passing one charging stock through one of the dephlegmating stages, passing the other charging stock through the other dephlegmating stage before their admission to the heating stages, recycling unvaporized residues from the evaporating stage and reux condensate from the dephlegmating stages to the heating stages for retreatment.

2. A process of converting hydrocarbons comprising heating an oil to conversion temperatures and under a high pressure, passing the heated oil before any substantial decomposition takes place, to a reaction stage wherein the oil is maintained for a time sufcient for conversion to take place, controlling the temperature and pressure on said oil to prevent any substantial distillation of the oil, heating a charging stock of relatively different character in a heat distillation stage to a temperature sufficient to distill off a portion thereof, combining the oils in an evaporating stage maintained at a pressure materially below that in the conversion stage whereby the lighter fractions of the combined oils are evaporated, and to produce a fuel oii residue having a high degree of fluidity at low temperatures and a low content of free carbon, dephlegmating the vapors in a series of stages, condensing the dephlegmated vapors and recycling fuel oil residue from the evaporating stage to the heat distillation stage, and passing. each of the charging stocks through different ones of the said dephlegmating stages to preheat each stock before its admission to the heating stage to which it is charged.

3. A process of converting hydrocarbons comprising heating an oil to conversion temperatures and under a high pressure, passing the heated oil before any substantial decomposition takes place to a reaction stage wherein the oil is maintained for a time sufficient for conversion to take place, controlling the temperature and pressure on said oil to prevent any substantial distillation of the oil, heating a charging stock of relatively different character in a heat distillation stage to a temperature sufficient to distill off a major portion thereof, combining the oils in an evaporating stage maintained at a reduced pressure to vaporize the lighter fractions of the oils and to produce a fuel oil residue having a high fluidity at low temperatures and a low content of free carbon, dephlegmating the vapors in a series of stages, preheating the stock charged to the heat distillation stage by passing it in heat exchange relation with the vapors in one of the dephlegmating stages, and recycling a portion of the fuel oil residue to said heat distillation stage.

4. The method of continuously skimming and cracking hydrocarbons which comprises skimming but not substantially cracking a stream of crude oil by heating the stream under pressure to a temperature high enough to vaporize gas oil and lighter fractions, transmitting the resultant mixture to an expansion chamber, depositing the carbonaceous residual oil in said chamber and maintaining the pressure therein low enough to release said gas oil and lighter fractions in the form of vapors, removing said residual oil from the system, subjecting said vapors to reflux condensation under a pressure lower than the rst mentioned pressure and thereby condensing the gas oil fraction of the crude oil, cracking the condensed gas oil by pumping it through a cracking coil under a higher pressure, transmitting the cracked mixture from said coil to a chamber and separating the vapors from the carbonaceous residuum therein, removing said residuum from the system, subjecting the cracked vapors to reflux condensation, and mixing the resultant reflux condensate with said gas oil fraction of the crude oil passing to said cracking coil, so as to subject the mixture to the cracking operation, and transmitting heat from said cracked vapors to said stream of crude oil before said stream is heated to vaporize the gas oil.

5. The method of continuously skimming and cracking hydrocarbons which comprises skimming but notl substantially cracking a stream of crude oil by heating the stream" under pressure to a temperature high enough to vaporize the gas oil and lighter fractions, transferring the resultant mixture to an expansion chamber, depositing the carbonaceousresidual oil in said chamber and maintaining the pressure therein low enough to release said gas oil and lighter fractions in the form of vapors, removing said residual oil from the system, subjecting said vapors to reflux condensation under a pressure lower than the first mentioned pressure and thereby condensing the gas oil fraction of the crude oil, cracking the con densed gas oil by forcing it through a cracking coil under a higher pressure, passing the cracked mixture from said coil to a vaporizing chamber and separating the vapors from the carbonaceous residuum therein, removing said residuumfrom the system, subjecting the cracked vapors to re-y flux condensation, mixing the resultant reflux condensate with said gas oil fraction of the crude oil passing to said cracking coil so as to subject the mixture to the cracking operation, and subjecting the stream of crude oil to heat exchange with the blended vapors of both the skimming and cracking operations before said stream is discharged into said expansion chamber.

HENRY E. WIDDELL.

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