US1688325A

US1688325A - hew yobs

Info

Publication number: US1688325A
Authority: US
Publication date: 1928-10-23
Anticipated expiration: 1945-10-23

Description

J. E. BELL ART 0F CRACKING HYDROCARBONS Filed Jan. 22, 1925 INVENTOR- EIeLDEc. @Mfw QN wmm wth Si ATTORNEYS :a necessa v to effect TRIX, OF BBGEILY?, NEW YORK, AS'

nr here. n. naar., minouccentran?, or

.NEW YORK, N. Y., A CGRPGRATIUN F liti-illu .ART OF CRACKEING HYDROCAHBOTS.

Application filed January This invention re ztes to improvements in processes ior crac fina heavier hydrocarbon oils to produce iydrocarbon oils. rlhis application is l part a continuation of an application tiled l. Y 13, i921, Serial No. 469,127.

More particularly this inventionv relates to improvements in the operation ot pressure stills of the general character described and illustrated in Patent No. 1,285 900, granted to the Sinclair Comp: l November l), 19185 on the application ot Edward il?. vls'om. ln such pressure stills the ain body of oil being cracked confined in a nulli-supply drumprovided with means for the escape oit vapors ot the cracked oil, the body of oil is heated' by circulating oil trom the bull; supply drum through a batteri et externally heated tubes located ina su" le furnace the battery ot heating tubes is ver wily arranged and connected at top and be in to the bulli supply drun'i7 the bottom connection' to the heating tubes includes a pump for forcing circulation of thev oil. trom-the ulk supply drinn to the lower end otthe heating tubes and thence upwardly through theheating tubes and back to the bulk supply drum from the upper end of the Yheating tubes. Y

rlhe cracking ot petroleum hydrocarbon oils erich as gas oil, is accompanied. by a separation oi carbon and tine: gasa the amount ot which is a function ot the'temperature.

and increases very rapidly as the temperature ry the cracking reac on is exceeded. ln the usual practice ot ci aching oils` tc npcraturcs inthe neighborhood ot *l from about 70@ to 8000 lj are employed'. To impart this temperature to the oil in the heating. tubes in the type otl still above referred toga high temperature oit the lieating gases is necessary'. Foreiiiei'ent operation it is desirable to extract from the heating gases the largest possible proportion of theheat contained therein but at the same time it is desirable to avoid excessive temperatures in any region ot the battery of heating tubes in ordei' to minimize separation oi carbon therein. lf carbon separates upon the heating tubes 3 which are subjected to the high temperatures of the heating gases it forms a coating which tends to insulate the surface on 1Which vthe carbon is deposited from the cooling eiiqect The -oil is circulated 22, 1925. Serial No 31.985.

of this particular region to become over- `ed with the development of hot spots d consequent danger of rupture ot the Wall of t ie heating tubes at such point or points. To avoid such dangers, it is necessary to shut doivn the still for the purpose of cleaning the heating tubes trom time to time.

` To promote the economy and etiiciency of the cracking operation it is desirable in carrying out the operation in stills of this character to distribute the heat absorption as equally as possible through the battery of heating tubes, orat least to avoid excessive heating' in any region and to provide 'for effective heat absorption throughout the battery oit heating tubes. The heating gases are at their maximum temperature when they liirst contact with the heating tubes and the temperature oi"- the heating gases declines as they circulate over the heating tubes andas their heat is absorbed by the oil circulating through the heatin0r tubes. If the heat absorptive capacity or' the heating tubes is uniform throughout the battery, considerably the greater part of the heat of the heating gases is absorbed by the tubes, or the parts the tubes, with which the heating gases first contact With the result that this region oit the heating tube battery is subject d to severe .overheating While that part of the battery otv tubes with which the heating gases later contact does not receive as much heat as desirable. li' the front tubes, or those nearncy est the lFirst-bo): of the furnace, are exposed to directradiation from the furnace an additional amount ot heat is imparted to these tubes by direct radiation. As a consequence, the heating tubes with which the heating gases first contact or those exposed to direct radiation from the tire-box ot' the furnace are subjected to such extreme conditions as to require more or less frequent renewal.

According to the present invention,v the oil is circulated from the bulk supply drum to the loiver end ot the vertically arranged tubes in the furnace, thence upwardly through the heating tubes, and back to the bulk supply drum from the upper end ot the heating tubes; and the heating gases from the firebox are circulated first over the upper end ot the heating tubes and thence downwardly over the heating tubes.

' rlhe oil circulating through the heating tubea and the A alating' over the heating tubes are thus brought into heat 'to heat exchanging relas t "s leavin(r the upare iirst bro ugnt tionuith thc hot a iu is per end oit the heating tubes and the heating 0'ases as they give up their heat are passed downwardly over thc heating tubes the lower end oit the heating tubes Where the oil entering om the bulk supply drum is first brought into heat exchanging relation with the heating gut f-z at the lower temperature at which the' leave the furnace and the oil from the bull( s euply drum lirst brought into heat erch; felation with the heatingr at the imum tenu'ierature 'in the furnace a. .f -i e oil is circulated up,- Wardly tl i tubes it is .finally 'fi vinto hea? nig relation With Q V Xiniuin temperac j upper end olthe heating tune.. t i manunuin temperature. The oil is t heated to the cracking teinperature it lov's pwardly through the heating tubes anu rea :hes the maximum craclr' temperature as it lea-ves the upper end et the heating tuo s, the iinal input of heat tor the cracking i action being. ei'ected in the upper end ot the heating tubes Where the heating gases at maximum tcniperature are brought into heat eirchang g relation with the circulating oil. In the heating tubes there is no resting place for precipitated carbon. and the oil progressively heated in theV direction of its tloiv. The cracking reaction is started in the heating tube-; and the crack- 'ing reaction continues., and thc major part n'iore equally throughout the heating tubes,

and carbon deposit upon the heating surfaces of the tubes is avoided or n'iiniinized, both by the iinproved uniformity o' the heating operation and by bringing the oil to the maximum cracking temperature as it leaves the heating tubes. The circulating oil protects the heating tubes by absorbing heat as it 'lows upwardly therethrough and thev progressive heating ot the oil assists and promotes the upward circulation through the heating tubes.

The unitorn'iity ot the heat absorption in the battery ot heating tubes may be further promoted by progressively increasingthe velocity oi flow oit the heating gases over the heating tubes of the pressure still as the temperature of the heating gases decreases With increased velocities more 'effective heat transfer can be obtained anda certain compensation tor the decreasing. temperature of the heating lgases thus effected. The uniformity of the heat absorption by the heating tubes may also be promoted by shielding the heating tubes from direct radiation from the tire-box supplying the heating gases. Vhere the initial heating surfaces are not so protected, a relatively large proportion ot the heat from the fire-box may be transmitted to the initial heating surfaces by direct radiation from the tire-box with consequent overheating of these surfaces, but by shielding the heating tubes 'from direct radiation the heating tubes are protected and this radiant heat is made available, in large part, as sensible heat in the. heating gases. By reducing the' temperatures to which the initial heating surfaces are exposed where coal is used as fuel, there is also less accumulation thereon of slag which is contained in the products ot cfimbustion trom coal and which at extreme temperatures is in a molten condition.

The process ot the invention may be carried out in a still in which the circulation maintained by thermosiphonic action. The process of the invention, however, is of special value and application in connection With the operation ot pressure stills of the general character referred to in Which the circulation is maintained and promoted by mechanical forcing means suchas a pump. By means of a pump, an increased rapidity ot circulation can be maintained, the increased velocity of flow of the oil through the heating tubes iniproving the heat transfer to the oil and also furtherprotecting the tubes by the more rapid absorption ot' theheat in the rapidly sorption thus ell'ected enable an increased input ot heat to the oil promoting the crack- 1n g reaction and increasing the capacity and deavored to distinguish it from the prior art so far as known to me Without, however, relinquishing or abandoning any portion or feature 1hereof.

The drawing diagrammatically illustrates, in elevation and partly in section, a pressure still adapted for carrying out the processl of the invention, the furnace structure being lil() shown in vertical section and the remainder` of the still being` shown, somewhat conventionally, in elevation.

T he pressure still illustrated is of the general character described and illustrated in nectingsuccessively the bulk supply drum,the

circulating punlp. the lower end oftheheating tubes, the upper end of the heating tubes and the bulk supply drum. rlhe vapors escaping from the bulk supply drum to the vapor line 2 may be passed through a reflux tower 8 in Awhich they may be subjected to direct contact with fresh oil chargedto the still. The vapors from the reflui; tower escape through vapor line 9 to condenser and receiver. The pressure may be regulated between the reflux tower and the condenser or beyond the con denser. From the reflux tower, reflux., and admired fresh oil if fresh oil is introduced into the reflux tower, are returned to the still through connection 10. Fresh oil may be introduced into the upper end of tlie reflui: tower through connection 11. Cool fresh oil may be supplied to the bearings of the circulating pump through connection 12 to cool and protect the same. A connection 13 is provided for pumping out and initially charging the still. A connection` 14 is arranged for withdrawing tar from the still during the operation thereof.

The furnace structure comprises a fire-box 15 which be of any usual orvapproved construction furnishing the required amount ofvheat, an uptalre 16, a downtalie heating flue 17 and a stack flue 18. The battery of oil heating tubesv 3 is suspended vertically in the heatingfllue 17,v the upper' header 19 thereof being supported upon I beams 2O and 21 on top of the furnace. The heated products of combustion descending vthe heating flue 17 are causedto circulate back and forth over the heating tubes by means of

baffles

22 and 23. rlhese baffles are supported by the tubes and cooperate with partitions 24; and 25 respectively to cause the heating gases to circula-te bach and forth over the heating tubes. The lower end of the heating lue is Closed by a partition or floor 26 arranged somewhat above the lower end of the heating tubes and supported thereby, this partition or'floorcooperating withpartitions 27 and 28 to close the lower end of the heating flue completely. rl"he upper end of the heating flue is closed by partition 29 arrangedl in the opening in the top of the furnace through which the heating tubes depend, this partition being supported by the heating tubes. The heating tubes 3 of the battery are thus suspended from their upper end and a e free to expand and con'- tract with changes of temperature. rlhe battery of heating tubes may likewise be removed as a unit through the opening in the top of the furnace for the purpose of inspectioii or repair. f

'lhe distance between the top of the heating liuc is gre tance between the bn` r.` latter distance in turn i tance between the battle id the the heating flue so thedA the veloci heating gases is progre, through the successive passe" 22 and the than the disflue as the temperature of the heating gases falls, thereb r compensating' to a ircV` ss extent for the decreased heatingl effect of the heating as their temper: 'ies. The front tubes of the battery of heat tubes are prevented from receiving an undu 85 amount of heat by direct radiation from the lire-box 15 by provision of the bridge wall 30 and the elongated throat or uptake 16, the bridge wall acting as a .scr-een to cut off d'rert radiation from the lire-box to 1 ig tubes. fllhe term lirebox is used in the usual nanner in this application to include the part of the furnace Asetting in which the fuel and gaseous products generated therefrom a o burned. rl"he heating tubes of the battery may also be provided with he-i sorbing elements of suitable chars eter, sho conventionally at Such het elements present a materiaincreased sur` ce of contact and enable materially increased amount of heat to be transferred to the oil with result that the oil can be circulated at a more rapid rate wit-hout decrease of the heat absorption, further assisting in protecting the tubes and increasing the capacity of the pressure still.

ln carrying out the process of the pre 'fit invention in the apparatus illustrated, the oil is circulated from the bull; supply drum i Y means of the circulating pump L1- to t end of the heating tubes o and thence y therethrough and back to the bu drum from 'the upper end of the heatM f The circulation is assisted by the pro ssiye heating of the oil as it flows upwardly through the heating tubes. rl`he het products of combustion rising from.' the fire-boit 15 are rst brought in contact with the upper end of the heating tubes and. then circulate bach and forth over the heating tubes downwardly to the stack ilue 18. The heat in the hot products of combustion is thus effectively utilized, the cooler oil entering the lower end of the heating tubes from the bulk supply drum being first brought into heat exchanging relation with the products of combustion which have been cooled by their passage through the heating flue and the oil circulatuir upwardly through the heating tubes is veits ul nate temperature by heat exchange with the prodv tubes also assists in proi'noting uniform distribution of the heat absorptieni. The bridge wall. cuts oli' dn'ect radiation from the firebor: to the heating tub avoidi c orein Ling of the front tubes the b; this cause, and the velocity oi the products of combustion as they downwardly through the heating .tlue and as their temperature decreases c le to absorption of heat of the circulating oil As inc `sed by the progressive decrease in the area ot tl e passage through which the heating e' 4u'eulate.

l/Vhat claimed -iew and desired to be scoured by Letters :Patent of the United States is:

1. The improvement in the operation oi' externally heated pressure stills Yter cracking hydrocarbon oils, which comprises circulating oil trom a bulk supply drum to the lower end of verticallyr arranged heating tubes and thence upwardly through the heating tubes and back to the bulk supply drum trom the upper end of the heating tubes, heating the oil to the cracking temperature in the heating tubes by passing heating gases first in contact with the upper end ot the heating tubes and then downwardly over the heating tubes and progressively increasing the velocity of flow olf the heating gases as their temperature declines, whereby uniform distribution of the heat absorption is promoted and the oil is brought to the maximum cracking temperature as it leaves the heating` tubes and is discharged to the bulk supply drum.

2. The improvement in the operation of Xternally heated pressure stills for cracking hydrocarbon oils, which comprises circulating oil from a bulk supply drum to the lower end of vertically arranged heating tubes and thence upwardly through the heating tubes and back` to the bulk supply drum from the upper end of the heating tubes, heating the oil to the cracking temperature in the heating tubesoypassing hot products of combustion from a tire-box tirst in conta ct with the upper end of the heating tubes and thence downwardly over the heating tubes, and preventing direct radiation trom the fireboX to all parts of the heating tubes, whereby uniform distribution of the heat absorption is promoted and the oil is brought to the mairimum cracking temperature as it leaves the upper end of the heating tubes and is discharged to the bulk supply drum.V y

3. The improvement in the operation of externally heated pressure stills for cracking hydrocarbon oils which comprises mechanically circulating oil, from a bulk supply drum to the lower end of vertically arranged heating tribes and thence upwardly through the heating tubes and back to the bulk supply drinn from the upper end of the heating tubes, heating thc oil to the cracking temperature in the heating tubes by passing heating gases in Contact with the upper end or" the heating tubes and thence downwardly over the heating tubes and progressively increasing the velocity of flow of the heating gases as their tei'nperature declines, whereby uniform distribution of the heat absorption isl promoted and the oil is brought to a maximum cracking temperature as it leaves the heating tubes and is discharged to the bulk supply drum. Y

il. The improvement in the operation of externally heated pressure stills for cracking hydrocarbon oils, which comprises circulating oil from a bulk supply drum to the lower end of vertically arranged heating tubes and back to the bulk supply drum from the upper end of the heating tubes, heating the koil toA the cracking temperature in the heating tubes by passing heating gases first in contact with the upper end of the heating tubes and then downwardly over the heating tubes, progressively increasing the velocity of i'low of the heating gases as their temperature declines, and preventing direct radiation from the fireboX to all parts of the heating tubes, whereby uniform distribution oi the heat absorption is promoted and the oill is brought to the maximum cracking temperature as it leaves the upper end of the heating tubes and is discharged to the bulk supply drum.

In testimony whereof I affix my signaature.`

y LOLA R. BELL,

Emeeam'ai of the Last WzZZ amtTestamea of J'om'E'. Bell, Deceased.