US1910048A - Apparatus for cracking hydrocarbons - Google Patents

Description

May 23, 1933- H. L. PELZER Er AL APPARATUS FOR CRACKING HYDROCRBONS Filed Dec. 12, 1928 y ATTORNEYS Patented May 23, 1933 narran stares Param"A ortica HARRY L. PELZER, OF HIGHLAND, INDIANA, AND EUGENE C. HERTHEI, `OIE CHICAGO,

ILLINOIS, .ASSIGNORS TO SINCLAIR REFINING COMPANY, OF NE'W` YORK, N. Y., A

CORPORATION or MAINE APPARATUS non on-AoKrNG iinnooannons Application led December12, 1928. Serial No. 325,413.

This invention relates to the cracking of higher boiling hydrocarbon oils, such as gas oil, for the production of lower boiling oils, such as gasoline or gasoline-containing oils, by distillation under superatmospheric pressure. More particularly the invention relates to improvements in apparatus for carrying out pressure distillation cracking operations.

Pressure distillation cracking operationsr have been well known and widely practiced for many years. In many of such cracking operations itis customary to circulate a high boiling oil through a heating Zone, in which it is heated to a cracking temperature, to a vaporizing zonel from which vapors of the cracked oil, including vapors of the desired lower boiling oil, are taken olf under superatmospheric pressure. In one such known type of operation, only oil free from unvaporized components of oil .which has once passed therethrough is" circulated through the heating zone. In another, unvaporized oil is maintained in circulation through the heating. zone. A process embodying the features of the two types of operation just mentioned is described in an application of Eugene C. Herthel, filed January 12,1928,

Y Serial No. 246,262 now U. S. APatent No.

1,721,779, and the apparatus of the present invention is of special value and application in connection with the improved process described therein. In the process described in the Herthel application, above noted, an initial charge of-oil is brought to cracking conditi ons of temperature and pressure, the higher boiling oil is circulated and recirculated from the vaporizing zone through a heating zone in which it is heated to a cracking temperature and back to the vaporizing Zone, and vapors of the cracked oil yare taken on 'from the vaporizing zone and raw oil is supplied to the higher boiling oil circulating through the heating zone as the operation continues. After a substantial4 amount of cracked oil has been taken oil' and before the oil circulatingthrough the heating zone becomes vsaturated with pitch, recirculation of unvaporized oil from the vaporizing zone to the heating zone is stopped, Vthe circulation of raw oil through the heating zone being con'- tinued and vapors of the cracked oil being vtaken olf from the vaporizing zone until a further substantial amount of cracked oil has been taken off.'l At the same time that the recirculation ofunvazporiaed oil from the vaporn rlhe present yinventiony provides an* im-V proved apparatus which may be used to particular advantagefin connection With a proccss combining certain ofthe featuresof the two knowntypes of operationas above described a nd when employed .in this connection permits the" advantages of' each of these types of operation to be obtained to a maximum degres while eliminating the disadvantages of oth. l ,1` The apparatus of the present invention provides for uniform distribution of the heating effect on the oil heating surfaces and for uniform distribution of the oil being heated over these "heating surfaces, when being operated either with-recirculation of unvaporized oil` through the heating Zone or with recirculation of reflux condensate only, to as great an extent these objectives are accomplished in bulkoil cracking operations wherein a large body of 'oil ismaintained at a' substantially uniform cracking temperature in a bulk supply drum by circulating it from `the bulk supply drum through a battery of heat# ing tubes connected in multiple and back to the bulk supply drum. The apparatus. of the invention also provides for prolonged' eX- posure of the voil being treated to the more severe cracking conditions advantageous to the production of gasoline. or gasoline-like oils of high anti-knock character.4 It is a further advantage of the apparatus of the invention that it is adapted forthe mainteillustration is for the purpose of exemplificaTY tion and that the invention is not limited thereto. The accompanying drawing dia-- grammatically and conventionally represents apressure still system, in elevation and partly in section, embodying the invention.

Referring tof the drawing, the pressure still system illustrated comprises'a battery of heating tubes 2L arranged in the heating flue of the furnace 8, the vaporizing drum 4, circulating connections 5,V 6 and 7 including a punnp or other suitable forcing means 8, these connections; and forcing means being arranged for circulating oil.V from the Vaporizing drum upwardly through the heating tubes' back to the vaporizing drum, a valve 9 for closing'the connection between the vaporizing drum 4 and the inlet side of the forcing' means 8, a reflux tower 10` with vapor connection. 11 and reflux returnV connection 12 to the still proper, a connection 13 for introducing raw oil into the reflux tower 10, a condenser 114,. a. receiver 15,. and a connection 16 for discharging unva'porized oil `from the lvaporizing` drum'f4. Y

The batteryy of `heating. tubes 2 are shown as, and mayftoV advantage be, arranged in accordanceI with theimproved heater construction described andi claimed lin anj application i lof Harry L.. Pelzer, filed: Junev 17, 1927, Serial No. 197 ,035, now U. S. Patent No. 1,774,291. This battery of tubes is made upof a series of banksof vertically arranged heating tubes with connections for circulating oil fromthe top` of the first bank to the bottom of the second bank, from the top of the second bank to the bottom of the third bank and so on. These connections joining theupper end of each bank of heating tubes, except the last, with the lower ends of the successive banks, are arranged externally of the heating flue in which the battery of heating tubes is arranged. The' individual banks of heating tubes are composed of a plurality of heating tubes with headers at their upper and lower ends arranged to connect the heating tubes of each separate bank in multiple. The circulating connections and 6 from the bulk supply drum connect with the lower end of thefirst bank of hea-ting tubes in the series, and the circulating connection 7 to the bulk supply drum connects with the upper end of the last bank of heating tubes in the series. The connection 5 for circulating oil :trom the vaporizing drum 4 to the heating tubes 2 opens upwardly into the vaporizing drum below the normal liquid level therein.

The valve 9 proper is arranged at the upper end of this connection. rlhe form of valve illustrated, which is particularly advantageous, comprises a conical closure member arranged to separate the circular opening between the vaporizing drum '4 `and the circulating connection 5. For raising and lowering the conical member 9' an operating extension 24 is attached thereto and carried through the wall of the vaporizing drum through a stung box 25 arranged above the normal liquid level, the operating extension passing upwardly through the vaporizing 'drum and in4 the vapor space therein. The

operating extension 24 is, with advantage, rigidly fixed tothe closure member 9 so that all parts of the valve mechanism exposed to high temperatures and hot oil in the still are of maximum simplicity. The reiiuxv return connections 12 open into circulating connection 5 between valve 9 and the intake sideof theY forcing means 8. With this arrangement the change from circulationi through the heatingv tubes of admiXed reflux condensate and unva-porized oil from the iaporizing drum', to circulation through the heating tubes of reflux condensatewithout admixture of unvapori'zed oilfrom the vaporizing drum, orvice versa, can bemade simply by closing or opening, respectively, valve 9,-.

Connection 17 is provided4 for discharging the distillate product and connection 18 for discharging uncondensed vapors and gases froml the receiver 15. Pressure in the system may bemaintained or regulated by means ofvalve-19 in the vapor line 20 between the reflux tower and the condenser'14 or by means of suitablev valves arranged beyond the kcondenser orl receiver. Connection 21 is pro vided for` initially charging the still at the beginningof the run and: for'pumping outthe still at the end of the run.. To provi-de for completel drainingv of the battery of heating tubes connectiony 26- may be arrangedvwith separate valved connections to. each of the lower headers. Connection 22 is provided for supplying cool oil, foreXample, cool raw r oil tobey supplied to the still system, to or through the bearings of the forcing means 8. Oner form of circulating pump, or forcing means, particularly adaptedY for use in conjunction with the apparatus of the present invention is a positive displacement type of pump such asthat. ill-ustratedin the applications of- Thomas d'e Colon Tifft, Serial No. 197,209, filed J une 7, 1927 now U. S. VPatent No. 1,701,198, and Serial No: 197,2.10,-filed J une 7, 1927, now U.. S. Patent No'..1,701,166, whichY are especially adapted to maintain a high rate of circulation through the oil. heater.

Connections 23, including suitable forcing means, are provided for recirculating over '.IlO

the heating tube'sa portion of the heating Agases whichhave passed thereover, as described in Letters Patent'fNd 1,574,546 and 1,574,547 issued to the Sinclair Refining Company February 23', 1926,011 applications `of John E. Bell.

As an example of onemethod of operating the pressure still or pressure still system `illustrated in the drawing, the still may be initial- `ly charged with about 6000 to 8000 gallons of gasoil with thevalvef) open, the pump 8V started and the furnace 3 fired.y As soon as the' pump 8 is started, raw oil may be forced through connection 29. into Vthe bearings of the pump at a rate of about250 gallons per hour. As the still charge is heated, any water or very light hydrocarbons are vaporized and permitted to escape through the vapor lineQO. After a period of about four to five hours, valve 19 may be closed and the still gradually brought to operating temperature and pressure. .lhen the pressure in the system reaches, for example 100 to 300 pounds per square inclnthe valve 19 may be graduallyopened and regulated to maintain the desir'ed',predetermined pressure `in the system. At about the same time the introduction of raw oil through connection 13 into the upper end of thereflux tower 10 may to advantage bestarted andfther'ate ofuintroduction regulated to maintain the desired-temperature at the top of the reflux tower, for example'550" F. The rateat-which raw oilris introduced into the upper end ofthe refiuxitower 10 may reach 2000 gallons per hour-or incre. Additional raw oil, for example, to' maintain the charge of oil in the vaporizingdrum 4 maybe supplied through connection 22. The total rate at which rawfoil. issupplied may reach 2500 gallons per hour or more. The vapors of the cracked oil escaping uncondensed from the reflux tower 10 through connection 20 will be condensed in the condenser 14 from which the resulting condensate is discharged into the receiver 15. During this rst period of operation in which vapors are taken off from the still, the charge of oil in the still is circulated and recirculated through the heating tubes 2 from and to the vaporizing drum 4. 'The oil travels through the heating Zone in a succession of passes in each of which the rela- Jtion between the circulation of the oil and the flow of the heating gases is the same. The circulating oil is thus passed again and again through the heating Zone while the arrangement is such that the heating tubes are aiforded a maximum of protection against overheating, general or local. The temperature of the oil as it is discharged from the last bank of heating tubes in the heating furnace may be somewhatin excess of the temperature corresponding to the pressure at that point, that is the oil may be somewhat superheated as it is discharged from the battery of heating tubes. Before the circulating still ,charge becomessaturated with pitch orpitch- 'like constituents, for example by the time the distillate taken-olf amounts to 15%-, or somewhat more, of the total raw oil including the initial charge supplied to the operation, the valve 9 should be gradually closed. The first period ofoperation, after the still is brought to operating conditions of temperature and pressure, may approximate two to three hours or. longer. The closing of the valve9`should be very slow Ito permit'gradual. self-adjustment of the operation to the change inoperating conditionsg'for example, complete/closure of "the valve "9 may require an, hour. When the valve 9 is completely closed, but preferably notuntilthen', the discharge of 'unvaporized oil Vfrom they vaporizing; drum 4 should be commencedand regulated, yfor example,.to maintain al constant level within the vaporizing drum.: During thesecond period of operation, after the valve 9 is closed, the oil mixture circulating through the heatf 'ing tubes 2 includes only admixed reflux condensate and vunvaporized raw o1l.4v This second period of'operation may lastvfromQO t'o ,200 hours 'or longer depending upon thekpar- 'ticular stocks under treatment and the particular products desired. c. f

.As the operation terminates, the fires may be first drawn and the valve 9v thenv gradually opened over a period of from one-halftoone hour, .while the introduction of raw' noil 4through connectionygljis ,continued as ydescribed. above. l

We claim-z f 1. A pressure still system comprising a Vaporizing drum, a series of banks 'of heating tubes, said-banks lcomprising a plurality of lheatin g tubes connected in multiple, connections arranged to join said banks of kheating p tubes inseries, a connection opening into the vaporizing drum from below theY normal liquid level therein for circulating oil from the vaporizing drum to theheating tubes, a forcing means in said last mentioned connection, a valve adaptedto close said last mentioned vconnection between the vaporizing drum and the forcing means,a` connection for transfer- Nringoil from the heating .tubes to the vaporizlng drum, 4a reflux tower and a vapor connection between the same andthe vapor space of the'vaporizing'drum,and a refluxv return Iconnection from .the reflux tower, opening minto said, connection for circulating oil from the vaporizing drum lto the' heating` tubes between said. valve andv the` heating tubes.

2. -A pressure, still .systemv f comprising a .vaporizing drum, a seriesofbanks ofheating tubes, said banks comprising aplurality of `heating tubes connected in multiple, connections arranged tojoin said banks of heating tubes inV series, aconnection opening into the vaporizing drum from below `thefnormal liquid level therein for circulating oil fromthe vaporizing drum to the heating tubes, a forcvaporizing drum, a series of banks of heating Vtubes arranged 1n a heating flue, said banks "'Valverand the heating tubes. Y

-ing'mean'sin said last mentioned connection,

a Valve adapted to close said, last mentioned 'connect-ion between the vaporizing drum and theforcingmeans, a connection for transferring oilffrom the heating tubes to the Vaporiz- `ing drum, a reflux towerl and a vapor connection between the same and the vapor space of the Vaporizing drum, and a reflux return Yconnection from the reflux tower opening into said 'connection for circulating oil from. the vaporizing drum to the heating tubes between said-valve and said forcing means. 3. .A pressure still system comprising a va- -porizing drum, a series ofbanks. of heating tubes, said kbanks comprising a vplurality of heatingtubes connected'in multiple, connections arranged to )om said banks of heating tubes in series, a connection opening upwardly into the vaporizing drumbelow the normal liquid level'therein for circulating oil from the vaporizing drum to the heating tubes, a forcing means in said last mentioned connectioina valve arranged .at the upper end of said last named connection'an-d an operating extension therefor extending upwardly through'the vaporizing drum and through thevapor space within the same and passing through the walls of the vaporizingrdrum above the normal liquid level therein, a connection for transferring oil from thel heating `tubes to the vaporizing drum, a reflux tower and Vapor connection between the vsame and the vapor space of the vaporizmg drum, and

a reflux return connection opening into said connection for circulating oil from the vaporizing drum to the heating tubes between said 4. A pressure still system comprising a comprising a plurality of heating tubes connected in multiple, connections between the upper ends ofthe banks of heating tubes, except the last, in such series .and the lower end-s of the successive banks, said connections being Yarranged externally of the heating flue in which the heating tubes are arranged, a connection opening into the vaporizing drum below the normal liquid level therein for circulating oil from the lvaporizing drum to the 'vaporizing drum, a series ofbanks of heating ltubes arranged in ya rheating flue, said banks comprising a plurality of heating tubes connected in multiple, connections between the upperends of the banks of heating tubes, ex-

cept the last, in such series and lthe lower ends 'of' successive banks, said connections being arranged externally of the heating flue in 'which' the heating tubes are arranged, a con-v nectionbetween the lower en-d` of the first bank of heating tubes-in the series and the vaporizing drum opening into the vaporizing drum below the normal liquid level therein,

a forcing Vmeans in said last named connection arranged to circulate oil from the vaporizing drum to the heating tubes, a valve adapted to close said last named connection between the flue with the other end thereof, said heating tubes being sopositioned in said heating flue with-'respi-ict to the firebox and with respect tothe heating tube connections that the first bank-of heatingtubes in said series will contact firstwith'lieating gases passingthrough the heating flue.

' In testimony whereof-:wel aflix our signatures; HARRY L, PELZER.

EUGENE C, HERTHEL.

lower'end of the first bank of ,heatingtubes in said series, a forcing means in said last said last named connection between'the forcing means and the vaporizing drum, a connection from'the upper end of the last bank of heating tubes in said series to the vaporizing drum, a reflux tower and vapor connections between the same and thevapor space of the Vaporizing drum, and ya reflux return vconnection from the reflux tower opening into said connection for ycirculating oil from the Vaporizing drum to the heating tubes between said valve and the heating tube-s.

'5.` A pressure still system comprising a namedconnect'iom a valve adaptedto close

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