US1823897A - Method and apparatus for fractionating hydrocarbon oils - Google Patents

Description

F. W. HALLL Sept. 22, 1931.

METHOD AND APPARATUS FOR FRACTIONATING HYDROCARBON OILS Filed Jan. 27, 1928 wwngn mk TEQRuQQ Mime? a.

swoon doc a) $0M a. 260% elf Soon Patented Sept. 22, 1931 STATE PATENT OFFICE FRANK W. HALL, OF PORT ARTHUR, TEXAS, ASSIGNOR TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE METHOD AND APPARATUS FOR FRACTIONATING HYDROOARBON OILS Application filed January 27, 1928. Serial No. 249,804.

This invention relates to the conversionof higher boiling hydrocarbon oils into lower boiling ones, and has special reference to a cracking process and apparatus of the socalled coil and drum type in which the oil is decomposed or cracked by rapidly raising the temperature thereof in transit through a heating coil and then delivering it into an enlarged drum or chamber in which crack- 1 ing temperatures and" pressures are maintained, and relates more specifically to that part of the apparatus and methodor process called the separators, fractionating towers, dephlegmators orbubble towers, which will i be hereinafter called bubble towers, wherein the vaporous products emerging from the drum or another bubble tower are received and the lighter constituents separated from the heavier constituents, the lighter con- 3 stituents passing off in vapor form, preferably for further processing, and the heavier ones'condensing and dropping to the bottom of the tower, thereafter being withdrawn preferably for recycling through the system.

5 Having in mind the ultimate evolvement of refined hydrocarbon products for commercial distribution, and irnowing that one of the important steps in the processing of said products is the separation, fractionation or rectification of the total constituents, the present invention is intended to accomplish such fractionation in a close and definite manner, thus making available the lighter constituents in vapor form preferably for further process- 3 ing, and the heavier constituents in liquid form which may be further processed or recycled through the system.

There are certain natural drawbacks to be encountered in the removal or separation of J the vaporous lighter constituents from the heavier, such as the tendency of the lighter constituents-to dissolve in the heavier constituents which latter ones continually condense and collect in a body in the bottom of narily maintain a sufficiently high operating or running temperature to effect liberation in the bubble tower of all of the lighter con stituents from the heavier while preventing the heavier constituents from beingcarried the bubble tower, and the inability to ordi-v over in part by the lighter vaporous constituents.

In connection with the coil and drum type of apparatus, I also have in mind that while carrying a pressure of several atmospheres in the heating coil and drum, it may be desirable to carry a lesser pressure in the bubble towers, realizing that by progressively reducing the pressure a readier liberation of the lighter constituents from the heavier constituents may be effected.

One of the objects of the present invention is to provide a method and apparatus ofthe general character of the coil and drum type in which the heat employed for cracking the oil is imparted to the oil in transit through the heating coil, a cracking temperature is inaintainedein the drum, and a desired temperature is maintained on the heavier and lighter condensed constituents reposing in a regulated volume in the bottom of the bubble tower whereby a closer fractionation of the products may be efl'ected. Such lighter constituents as may have mingled with the heavier and become condensed, being continuously subjected to additional heating,

may be vaporized, and rising in the tower,

commingle with the uncondensed lighter vapors, and emerging from near the top of the tower, continue through the system in course of process.

Another object of the invention is to provide an oil cracking process of the general character of the coil and drum type in which part of the heat of combustion of the heating coil furnace may be employed, through the medium of the heated oil in transit through a closed coil submerged in the body of oil in the lower portion of the bubble tower or towers, for maintaining such temperatures of the oil as are desired in effecting a close fractionation or separation of the lighter and heavier constituents.

More specifically it is an object of the present invention to closely divide or fractionate the vaporous hydrocarbon products received into the bubble tower or towers into two distinctly different products, the lighter of which is desired to have an end point substantially equal .to that of the initial boiling point of the heavier constituents.

Still another object of the invention is to provide a process of this general character ln'which the operating pressure of the bubble tower or towers may preferably be pro-- gressively and substantially reduced below that existing in the heatin coil and drum, thereby permitting a readier liberation of the lighter constituents from the heavier in effecting a close fractionation of the produots.

Other objects, together with these, may be better understood from the following description and the accompanying drawing:

Broadly and generall the present invention contemplates sub ecting tho evolve'd vapors from the cracking zone to dephlegmation or fractionation and passing a portion of the hot products from the heating zone or the highly heated oil in transit to the cracking zone, through a heat exchange element positioned in the dephlegmator or fractionating tower to thereby maintain the liquid condensate therein at a vaporizing temperatureto thereby free the said condensate from lower boiling constituents.

It is to be further understood that I have in mind accomplishing within the dephlegma'tor, fractionating tower or rectifier, the complete rectification of the vapors evolved from the cracking zone, on the one hand condensing and withdrawing such heavier constituents as it is desired to remove from the incoming vapors, while on the other hand, and while freeing the total heavier constituents from the said vapors, to conduct the total lighter vaporous constituents throughout,the remainder of the system in the regular course of the process.

The accompanying drawing illustrates an apparatus embodying certain novel features and adapted for carrying out the process disclosed herein, although it will be understood that any form of suitable apparatus may be used in carrying out said process.

Referring to the drawing There is provided an elongated heating coil 1, which might be called a primary heating coil, of restricted cross section, through which oil is assed and heated in transit, deriving heat mm the furnace 2, disposed beneath the coil and fired by the burner 23.

The ho: oil emerging from the coil 1 may be conducted through a heat insulated pipe 5 andthrough the closed coil 15 within the bottom of the bubble tower 16 wherein a body of oil collects, being the condensed heavier constituents, which may have in addition a certain percentage of lighter constitucnts which is is desirable to liberate for commingling and passing on with the other vaporous lighter constituents.

While operating the apparatus it may be desired to direct the flow of hot oil away from the coil 15 so a by-pass has been provided for in the'valve 4, pipe 7, valve 8, and valve 6, whereby the hot oil in continuous circulation may be returned to the secondary heating coil 9 for further heating and disposal as will be hereinafter described.

The hot oil in transit through the closed coil 15, and having a temperature of from 800 F. to 850 F., with an average of approximately 825 F., transmits a part of I its heat through said closed coil to the cooler oil reposing in a body in the bottom of the bubble towerf The cooler oil may have a temperature of slightly less than 750 F. when the coil 15 is not in use.

The hot oil, somewhat cooler upon emerging from the coil 15, may pass through a in the valve 21 pipe 22, valve 23 and the valve 24, whereby the hot oil in continuous circulation ma be returned to the secondary heating" coil 9-t1rough a heat-insulated pipe 26 for further heating and disposal as will be hereinafter described.

It is to be understood that this method and system may comprise one or more bubble tow ers for fractionating the products, and that mainly for descriptive reasons, the apparatus has been drawn, constructed and described, as comprising two such towers numbered 16and 30. o

It is to be further understood that in each successive tower or towers substantially simi lar results may be obtained through the use of the closed heating coil imposed in the bottom of the said tower or towers as may be obtained in the first tower 16, though at varying temperatures and in some instances preferably at lesser pressures.

In regular operation, the process being continuous, the condensed heavier constituents reposing in the bottom of the tower 16 in a regulated volume will normally be continuously withdrawn through a heat-insulated pipe 40 and the valve 39 and may be forced back into the system by the pump 41, preferably re-entering the system through the coi 9.

The hot oil emerging from the heating coil 9 is passed through a heat-insulated pipe 42 and the valve 43, and preferably enters the drum 50 through a pipe 44, and the drum 51 through a pipe 45, although it may be. desired to efiect an entry for the hot oil into the drums 52 and 53 also.

The vaporous products from the hot oil.

undergoing cracking in the drums 50, 51 and the vapor communicating'lines 54, 56 and 58 into the upper portion of drum 53, and the hot oil undergoing cracking overflows from the drum 50 into the drum 51 and from the drum 51 into the drum 52 etc. through the equalizing lines 55, 57 and 59, while the residual products collecting in the drums in regulated volumes may be withdrawn through the pipes 80 82, 84, and 86 ,'and the valves 81, 83, 85, and 8 connecting with the-pipe 88.

The issuingvapors from the drum 53 are conducted through a heat-insulated pipe (0 and discharged nto the bubble tower 16, preferably entering at an intermediate oint above the regulated level of the body 0 liquidreposing in the bottom of the tower; A

pressure regulating valve 71- -is provided in the line whereby the pressure" within the bubble tower 16'may be reduced if desired from that existing in the drums 50, 51, 5 2, and.

53, and the heating coils.

The vaporous products entering the tower 16 at a temperature of approximately'7 50 F. are subjected to fractionation therein, the heavier constituents together with a portion ofthe lighter, condensing and dropping to the bottom of the tower wherein said condensate may be subjected to additional heating applied by the exchange of heat from the oil flowing through the coil 15, the temperature thereby being substantially increased. By such increase in tem rature, a vaporization of the condensed ligh er constituents may be effected, the lighter constituents as vapors will rise, andrising and commingling with the uncondensed lighterconstituents undergo a progressive lowering of temperature until they pass out near the top of the tower 16 through a hcat-insulatedplpe 100 at atemperature of approximatel 450- F. It is thus tobe seen that a jfractionating or bubble tOWBICOIIditlOH is-efiected wherein progressively decreasing temperatures obtain from the bottom to the top of the tower.

. It should be pointed out that the temperatures as given herein are merely for descriptive purposes and are not intended as limitations to the scope of the present invention.

The vapors emerging from the bubble tower 16 through the heat-insulated pipe 100, enter the bubble tower 30'preferably at some intermediate point above" the regulated level of liquid reposing in the bottom of the latter tower. A pressure regulatin valve 101 is provided in the line 100 where y the pressure within the bubble tower 30 may be reduced if desired from that existing in the bubble tower 16.

The vaporous products upon entering the for tower 30 may be fractionated or separated, the lighter from the heavier constituents, in substantially the same manner as in the tower 16, exce t that the temperatures and pressures may be ower', thereby causing a difference in the resulting. products. The heavier constituents in repose as residual condensate in the bottom of the tower 30 may be withdrawn through the pipe 103 and the valve 104, while the lighter constituents as a vapor may emerge from near the top of the tower.

The vapors issuing from near the top of the tower 30 pass through a pipe 105 and through the water condenser coil 106, the condensate and fixedvapor's or gases emerging from said condenser coil passing through a pipe 107 into the collecting tank 108, which is provided with a gas outlet 110 and a valve 109 and a liquid discharge outlet 112 and a valve 111.

Although this invention as set forth does embody more or less specific details of construction and operation, it should be understood that many variations may be efiected without departing from the spirit and scope of the invention.

What I claim is:

1. The process of converting higher boiling hydrocarbon oil's into lower boiling ones that comprises passing the oil under superatmospheric pressure through a primary and a secondary heating coil wherein the oil is heated to a cracking temperature, delivering the heated oil into an enlarged chamber wherein a body of oil is maintained under cracking temperature and pressure, passing the evolved vapors to a fractionating tower and subjecting said vapors to fractionation therein'to form an overhead vapor fraction and a liquid condensate, assing highly heated oil from the primary eating coil through a closed coil in contact with the liquid condensate collected in the bottom of the fractionating tower to thereby maintain the condensate at a vaporizing temperature.

2. The process of converting higher boiling hydrocarbon oils'into lower bolling ones which comprises passing the oil through a. heating coil to raise it to a cracking temperature under superatmospheric pressure, dischargin the highly heated oil into an enlarged c amber in which cracking and vaporization takes place, conducting evolved vapors to a fractionating tower and subjecting them to fractionation therein to form an overhead vapor fraction and a. final liquid condensate, collecting the final liquid condensate in the lower portion of the fractionating tower, passing a 'portion of the highly heated oil from the heating coil, before it has been discharged into the enlarged chamber, through a coil in contact with the liquid condensate collected in the lower portion of the fractionating tower and returning this ortion of heated oil to the heating coil fiirther heating.

3. The process of converting higher boiling hydrocarbon oils into lower boiling ones which comprises heating the oil to a cracking temperature under superatmospheric pressure in a series of coils, delivering the highly heated oil into a series of drums wherein cracking temperature and pressure is maintained, conducting evolved vapors to l a fractionating tower wherein the pressure is reduced and subjecting the said vapors to fractionation therein, conducting a portion of the highly heated oil that has been raised to a cracking temperature through a heating coil submerged in the liquid condensate col lected in the fractionating tower and returning this portion of heated oil to the series of oils for further heating.

4. The process of converting higher boilin; hydrocarbon oils into lower boilin ones that comprises passing the oil raise to a cracking temperature through cracking drums, conducting the vapors to a fractionating tower, taking off an overhead vapor, holding in transit a regulated quantity'of liquid condensate, introducing fresh charging stock into a primary heating coil, highly heating the oil therein, passing the heated oil through a coil submerged in the liquid condensate in the tower. conducting the oil upon emerging from said coil through a secondary heating coil wherein the oil is further heated to a cracking temperature and delivered to the cracking drums.

5. Apparatus for cracking hydrocarbon oils comprising a secondary heating coil, a cracking chamber incommunication therewith, a fractionating tower in vapor communication with the cracking chamber, and having space for retaining a regulated quantity of liquid condensate therein, a closed heating coil in contact with the liquid condensate, means for conducting hot oil from a primary heating coil to the said closed coil in contact with the liquid condensate, means for returning the oil from the closed heating coil to the secondary heating coil wherein the oil is heated to a cracking temperature.

6. Apparatus of coil and drum type for cracking higher boiling hydrocarbon oils under superatmospheric pressure, comprising a primary and a secondary heating coil in series, a series of crackin drums, a pipe having branches establishlng communication from the secondary heating coil to several drums of the series, a fractionating tower in vapor communication with the series of cracking drums, means for regulating the pressure within the fractionating tower, means for heating a body of liquid condensate collecting within the fractionating tower and means for returning the liquid condensate to the secondary heating coil.

In witness whereof I have hereunto set my hand this 11th day of January, 1928.

FRANK V. HALL.

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