US1774291A - Art of cracking hydrocarbon oils - Google Patents

Description

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Aug. ze, i930;

l--l` L. PELZER ART OF CRACKING HYDROCARBON OILS e she'etsrshet Filed June fr. 1927` INVENTOR /a r//f L. Pe/z er y f ATmRNEYs Aug. 2%, 193@ HQ L.. PELZER ART OF CRACKING HYDRCARBON OILS i 6 'sheets-'sheet 2 Filed June '7, 1927 EMM.

Aug. Z, 1930. H. 1 PELZER l ART 0F CRACKING HYDROCARBON OILS Filed June 7, 1927 6 Sheets-Sheet INVENTOR ATTORNEY5 ug. 2y 930 H` L. PELzx-:R

ART OF CRACKING HY'DROCARBON OILS Filed June 7, 1927 6 Sheetsf-Sheet INVENTOR #a ffy/L, Pelzer.

ATTORNEYS Patented Aug. 26,1930

UNITEDk STATES PATENT Price HARRY L. PELZER, OF HIGHLAND, INDIANA, ASSIGNOR TO SINCLAIR RFFINING COMPANY, OF NEW YORK, N. Y., A CORPORATLUN OF MAINE ART OF CRACKIN G HYDROCARBON OIL-S Application filed June 7,

This invention relates to improvements in the cracking of heavier' and higher boiling h vdrowirbon oils, such as gas oil, for the production therefrom of lightervand lower L: boiling hydrocarbrm oils, such as gasoline and gasoline-contanting cracked distlllates. 'lhe invention provides an improved pressure still or pressure still system for cracking hydrocarbon oils and an improved heater for heating oil to a cracking tempera- Iture, both of which have several important advantages.

ln the improved heater of the invention a battery of tubes through which the oil is circulated is arranged in a furnace heating flue through which the heating gases for supplying heat to the oil are passed. This battery of tubes is made up of a succession of banks of vertically arranged tubes` the successive banks of tubes being connected in series by circulating connections connecting the upper end of the first bank with the lower' end of the second bank, the upper end of the second bank with the lower en d of the third bank, aml soon through the series. rlhese circulating connections are arranged externally ol' the heating liuc in which the heating tubes are arranged, although provision may be made to reduce or prevent heat loss from the circulating conmictions. ln operation, oil is supplied to the lower end of the first bank of heating tubes, circulated upwardly therethrough and heatcdtherein by heat exchange with the heating gases,

F then circulated downwardly from the upper end of the first bank to the lower end of the second bank ot' heating tubes, circulated upwardly through the second -bank and further heated therein, and so on, being discharged 40 from the upper end of the last bank of heating tubes in the heater at a cracking.

temperature.

rlhe improved pressure still or pressure still system of the invention comprises a bulk supply drum and an oil heater of the 'type just described with appropriate circulating connections including a suitable forcing means for circulating oil from the `bulk supply drum through the several banks of 5 heating tubes in the heater in a succession 1927. 'Serial No. 197,035.

of passes and then back to the bulk supply drum. In one particularly advantageous forni of the invention, a bed ot' finely divided solid material, such as fullers earth or ground coke, is arranged in the bulk supply drum below the normal liquid level therein, so as to be submerged in the body of oil in the bulk supply7 drum during operation, and between the circulating connections from the battery of heating tubes to the bulk supply drum and the circulating connections.

from the bulk supply drum to the battery of heating tubes, so that oil recirculated through the heating tubes is passed through the bed ot' finely The finely divided solid materialA may be of a character exerting a selective absorbent action with respect to more objectionable constituents of the circulating still charge, in operation, or exerting a desulphurizing action, or it may exert simply a mechanical filtering action. In the combined apparatus of the invention, particularly where it includes a bed of finely divided solid material, the forcing lncans used is advantageously ol' positive displacement type adapted to maintain a. high rate ol' circulation through [he heater. i

ln the heater, the oil circulating therethrough is heated only while flowing upwardly through the vertically arranged heating tubes. 'lhere is thus but a minimum opportunity 'l'or deposit in the heating tubes of pitchy and carbonaceous solids and semisolids formed in the cracking.; operation and uniformity of heat absorption around the entire circumference ofthe heating tubes is promoted. At the same time, the heater of the present invention provides for prolonged travel of the oil in the heating zone. The

oil travels' through the heating zone in a succession of passes in ach of which the relation between the circulation ol the oil and the flow of the heating gases is the same. In the heater of this invention, the circulating oil is thus passedagain and again divided solid 1naterial.

through the heating Zone while the arrangement is such that the heating tubes are afforded a maximum of protection against overheating, general or local.

The improved heater of the invention is of special value and application in connection with operations in which hydrocarbon oils are subjected to relatively severe crackproduction ot fixed gases, gases incondensible at ordinary temperatures and pressures, and pitchy or carbonaceous solids or semisolids accompanies an increase in the severity of the cracking conditions to which an oil is subjected, but in the heater ot' this invention any difficulties due to an .increase in the proportionot fixed gases or pitchy or carbonaceous materials in the oil circulating through the heater, even with prolonged oil travel, are reduced to a minimum. The heater thus has special advantages in the combined pressure still or pressure still tem ot the invention, where unvaporized oil discharged from the heater containing dissolved or suspended pitchy or carbonaceous solids or semi-solids is recirculated through the heater and where it is desirable to subject the oil to prolonged travel through the heating zone or where it is desirable to subject the oil to more severe cracking conditions.

Inthe production ot' motor fuel gasolines, for example, it is frequently desirable to subject the raw oil to be cracked to quite severe cracking conditions, say to temperatures in excess ot 8O()O l?. and under pressures up to 300 pounds per square inch or more, to secure products having relatively high critical compression or, as it is sometimes expressed, having anti-knock properties. It will be apparent. that the apparatus of the present invention is particularly adaptedior this purpose.

The lire-box for supplying hot products ot' combustion to the heating flue in which the battery ot heating tubes is arranged, in the apparatus ot' the invention, is advantagemisly arranged to eonnminicate with the upper end of the. heating fluel and the stack flue ilor escaping waste heating gases to communicate with the lower end of the. heating flue, so that the heating gases pass generally downwardly through the heating flue. Suitable battles may be arranged in the heat-A ing iue to promote or maintain distribution of {iow of the heating gases therethrough, as by causing them to pass back and forth across the flue as they travel down 'ardly therethrough. In the apparatus ot the present invention, this arrangement provides for the maintenance of generally countercurrent relation between the heating gz ses passing .through the heating flue and the oil circulating through the heating tubes in each ot the successive banks ot heating tubes. It is also advantageous to supply the oil entering the heater first to the bank of heating tubes with which the fresh hot products of combustion, or the fresh heating gases, irst coning conditions. Usually, an increase in the,

tact. The-.several banks ot heating tubes are also advantageously each arranged generally transversely tothe flow ot heating gases through the heating tlue. Further to promote the efficiency of heat trans'tcr through the heating tubes and to increase the capacity ot the apparatus, to permit. realization ot high t'uel etliciencies, to prevent overheating, particularly lo Ial overheating, of the. heating tubes, and to promote uniformity o'l distribution ot heat ubsorption throitlghout the entire battery of heating tubes,.it is :ulvantageous to recirculate through the heating tlue together with fresh hot products oll comluistion, or 'l'resh heating gases ot high teni'.ieraturef` a portion ot the heating gases escaping 'from the heating lue in which the heating tubes are arranged. Such recirculationy ol' a portion ot the escaping heating gases has special advantages in the apparatus ot the present invention where the oil is'cireulated through the same heating zone in a succession ol' passes, particularly with respect to the maintenance of a high average temperature differential between the circulating oil and the heating gases in the heati ng l'urnaee while avoiding overheating ot the oil in any4 part ot the battery ot' heating tubes.

The combined apparatus of the invention, a bulk supply drum wit-h circulating connections to and from an improved heater ot the invention and including a bed ot linely divided solid material arranged in the bulk supply drum below the normal liquid level therein and between the circulating connections to and from the heater, has several further special advantages. ln this general form ot apparatus, it is advantageous to maintain a relatively low rate ol' circulation of the oil through the bed oil solid material and a relatively high rate ot circulation through the heating tubes. ln the apparatus ot this invention, a. much higher ratio between the average velocity through the. heating tubes and the average velocity through the bed ot linely divided solid inaterial can be maintained than, tor example, in apparatus in which an equivalent number ot heating tubes are connected all in parallcl. Increased velocity of oil vliow through the heating tubes, in the apparatus ot the present invention, also further assists in promoting the efiiciency of heat transfer' to the circulating oil and in improving the capacity of the apparatus, 'as well as further protecting the heating tubes against overheating, general or local. The bed ot finely divided solid material acts to remove more objectionable constituents from the circulat ing still charge in the operation ot the ap paratus, suspended pitchy or carbonaceous 'materials by filtering action and dissolved objectionable constituents by absorption or reaction, so that unvaporized oil recirculatlef.,

lllil ills ed through the heating tubes is kept relatively more free from eonstituentswhich are particularly active in formation of deposits in the heating tubes by passage through the bed of finely divided solid material. After passage through thefbed of finely divided solid material, accordingly, the recirculated oil may be subjected tomore severe cracking conditions without danger of objectionable deposition in the heating tubes than would be appropriate if the circulating oil had a higher content of piteliy or carbonaceous solid or semi-solid materials or objectionable constituents promoting deposition. In this respect the combined apparatus of the present invention is particularly advantageous,

l for it provides for removal of such objectionable constituents from the circulating charge before the oil is reeirculated through the heating tubes and for prolonged travel et the oil through the heating tubes after theremoval of such constituents, and is also particularly adapted to the maintenance of relatively more severe cracking conditions in the apparatus. Here again, the increased ratio between the average velocity through the heating tubes and the average velocity through the bed of finely divided solid material which can be maintained in the apparatus of the present invention assists in improving both the effectiveness of the bed of linely divided solid material and the operation of the battery .of heating tubes and of the heating furnace.

The improved pressure still or pressure still system of the invention, particularly including the bed of finely divided material, makes possible improvement both with respect to efiiciency and with respect to capacity, and also is particularly adapted for the production of motor fuel products having relatively high critical compression or having anti-knock properties.

'Ihe invention will be further described in connection with the. aecompanyingl drawings which illustrate, diagrammatically and conventionally, apparatus embodying the invention, but it will be understood that this further description and illustration is intended for exemplification and that the invention is not limited thereto. In the accompanying drawings;

Fig. 1 represents, in elevation and partly in section and with parts broken away, one torni of pressure still or pressure still systeni embodying the invention,

Fig. 2 represents, in elevation and partly in section and with parts broken away, another form of pressure still or pressure still system, including a bed of finely divided solid material, embodying the invention,

Fig. 3 is an elevation, in more detail, of

. the battery ot heating tubes and circulating connections illustrated in the oil heatei shown in Figs. 1 and 2, the heating furnace con- 'P struction being indicated in outlined vertical Fig. 5 is a transverse vertical section through the heating iiue of the heating furnace andthe battery of heating tubes illustrated in Figs. 1 and 2,

Fig. 6 is a fragmentary detail of one of the headers to which the heating tubes are connected, Fig. 7 is a fragmentary section through one of these headers showing a connected heating tube,

Fig. 8 is a horizontal,sectionthrough one forni of circulating pump of special value and application in connection with the apparatus of this invention,

Fig.` 9 is asection on line 9 9 of Fig. S,

Fig. 10 is asection on line 10-10 of Fig. 8,

Fig. 11 is a `simplified diagrammatic showing ofthe oil flow through the iniproved oil heater ofthe invention, and

Fig. 12 is a further siinpliii'ed diagrammatic showing of the relation between the flow of oil and the flow of heating gases in the improved oil heater of' the invention.

The pressure still or pressure still system illustrated in Fig. 1 comprises a bulk supply i drum 15, a battery of heating tubes made up of a series of banks of heating tubes situated in the heating flue of the furnace 1G, and-circulating connections 17, 18 and 1:/ including a circulating pump 20 for circulating oil from the bulk supply drum successively through the series of banks of' heating tubes and back to the bulk supply drum. The battery of heating tubes comprises a series of banks of' vertically arranged heating tubes with connections for circulating oil from thc top of th'ie first bank to theI bottom of the second bank, from the. top of the seeond bank to the bottoni of the third bank. and so on. rlhese connections, connecting the upper ends of the banks 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 circulating connections 17 and 18 from the bulk supply drum connect with the lower end of the first bank of heating tubes in the series and vthe circulating connections 19 to the bulk supply drum connect with the upper end of the last bank of heating tubes in the series.

' In operation, a charge of oil isv maintained in the bulk supply drum 15, oil from this charge is circulated downwardly through. connections 17 and 18 to the lower end of' the rst bank 21 of heating tubes, upwardly through this bank of heating tubes and heated therein, downwardly throug'h the unheated connections to the loo lil-

lil() lower end o't the second bank QQ ot heating tubes, upwardly through this bank of heating tubes and heated therein, downwardly through the unheated connections to the lower end of the third bank Q3 ot heating tubes, upwardly through this bank ot' heating tubes and heated therein, downwardly through the unheated connections to the lower end ot the iourth bank L-'t ot heating tubes,'upwardly through this bank of heating tubes and heated therein, downwardly through the unheated connections to the lower end ot the fil'th and last bank Q5 of' heating tubes, upwardly through this bank ot -heating tubes and heated therein. and thence back to the bulk supply drinn through connections 1S". 'rlhc flow ot oil through the battery ot' oil heating tubes in the heating i'urnace is illustrated, perhaiis more clearly, in Fig. ll. ltelerring to lig. 11,'the successive banks 91, 22, 22,3, Q-t and 25 of heating tubes are arranged in the heating tlue of the furnace and the connections 2G, if?, QS and 29 connecting vthe successive banks of heating tubes in the series are arranged externally ot this heating tlue. Oil supplied through connections 18 passes upwardly through each otl the banks ot'lieat-ing tubes in the series in succession, being heated while flowing upwardly through the vertically arranged heating tubes in the successive banks but being unheated while flowing downwardly from the top ot one bank to the bottom of the next bank, so that the circulating oil is heated only while flowing upwardly through the vertically arranged heating tubes. The oil is then discharged troni the top of the last bank of heating tubes in the series through connections if).

One particularly :ulrantageous torni ot oil harter embodrii they invention. that illustrated in ifi; s. and 2, is illustrated in more detail in lli il to T.

Referring partlcularl)Y to these figures, the heating tui-nare is made up ol` a heating flue 3l), a irebox lV (equipped with suitable means for burning the fuel used to supply heat to the operation) eonlniuuirating with the upper end oi the heating flue. and a stack flue. 32 communicating with the lower end o'l" the heating flue. ln operation,

the hot products ot combustion `l'rom the,

hrebox pass upwardly from the firebox to the upper end ot the heating fine, then downwardly through the heating tine, escaping from the lower end o't theheating flue through the stac i flue. ln the furnace construction illustrated` the bridge wall $23 is arranged to prevent direct radiation 'from the firebox upon the heating tubes arranged in the heating tine. A battery ot heating tubes made up of five lbanks of ten tubes each are arranged in and extend through the heating flue 30. Battles 3l and 35 are arranged in the heating flue to cause the heating gases to pass back and forth across the flue they pass downwardly therethrough. Each ot' the banks of heating tubes is arranged generally transversely to thc low of heating gases to the heating flue. Oil entering the battery ot heating tu es is supplied first to the bank o't heating tubes with which the fresh hot products ot combustion from the tirebox first Contact. Steam jet blowers 3S are arranged, on opposite sides ot the furnace setting, Tor withdrawing through openings 37 a portion ot the heatiiig gases about to enter the Stack tlueland returning it through openings 15S to be recirculated through the heating tine lin adinixture. with tresh hot products o't combustion from the tirebox.

llach bank ot heating tubes is made up of a number of tubes connected at opposite 4ends with an upper header 39 and a lower header 40. llxcepting the lower header on the lirst bank of heating tubes in the series and the upper header on the last bank ot heating tubes in the series, these headers are closed at one end and ot the general construction illustrated in Figs. G and T. llugs sil are provided opposite the ends ot each of the heating tubes to permit access for cleaning or to provide for replacement ot heating tubes. Supply connections connect with both ends ot thc lower header l0 on the first bank of' heating tubes and discharge connections connect with both ends of the upper header 39 on the last bank ot heating tubes. This arrangement oi the first and last headers is advantageous in promoting uniform distribution ot flow across the banks ot heating tubes.y Circulating connection 2G, arranged on the .tar side ot the heater as shown in Fig. il, connects the upper header il?) on the first bank ot heating tubes with the lower header lll on the second bank ol' heating tubes. (lirculafing connection 2T, arranged on the near side ol" the furnace as shown in Fig. Il.

connects the'upper header Ch) on the second.

bank ot heating tubes with the lower header -l-O on the third bank ot heating tubes. 'lhe succeeding banks ot heating tubes are. connected in a similar`n1anner by circulating connections QS -and 29. 'lhese circulating connections, as shown particularly in Fig. are arranged entirely outside ot the hcatinel flue 30 in which the heating tubes are nated. These circulating connections, 26. 2T, 2S and 25) are thoroughly lagged or heat insulated to prevent heat loss. The bulk supply drum l5 and the circula-ting connections 17, 18 and 1S), as well as the reflux tower illustrated, are also, with advantage, similarly lagged or heat insulated.

Inv thel Oil heater illustrated, the several banks othcating tubes, the lower headers arid 4,0", and the circulating connections at). Zt. 2E and 29 aie all suspended from the lll) ' provided with a helical v members 102 and 103 are driven upper headers 39 and 39 which in turn are .arried by supports 42 on the furnace setting. Free expansion and contraction of the elements making up the heater with change in temperature is thus provided for. The vertical arrangement of the heating tubes further assists in eliminating any tendency toward sagging of the heating tubes under opcrating'conditions. By arranging all of the heating tubes in the several banks parallel to each other, as in the oil heater illustrated, it is also possible to use a gang cleaner.

One form' of circulating pump, means, particularly adapted for use in conjunction with the apparatus of the invention is illustrated in Figs. 8 to l0. This pump, in so far as it is novel, is the invention of Thomas de Colon Tift a resident of Chicago, county of Cook and State of Illinois. This pump is of positive'displacement type adapted to maintain a high rate of circulationthrough the oil heater.

In the pump illustrated in Figs. S to 10, a stream of oil is drawirin through connec tion 104, divided, and forced out through connections 105 and 106. The forcing means comprise a pair of drivenmembers 102 and 103 arranged in a closely fitting housing 101. Each end of each driven member is flange intermeshing a similar but oppoon the other driven with and closely fitting sitely arranged flange member, each of the helical flanges on opposite ends of the same driven member also being arranged in opposition. The driven in opposite directions and maintained in fixed relation by means of gears 107 and 108.

tion, successive increments of oil are forced v from the central space in the housing 101 between the pairs of intermeshing flanges at'the opposite ends of the driven members to the opposite ends of the housing 101 by rotation, in opposite directions, of the driven members 102 and 103'. From the end spaces in the housing, the oil is discharged through connections 105 and 106.

The housing 101 is closed at its ends by plates 109 and 110 which are bolted between the housing 101 and end covers 111 and 112. The driven members 102 and 103 are arranged on shafts 113 and 114 which extend through bearingsl carried by the plates 109 and 110 inlo the space between these places and the end covers '111 and 112. 'lhese bearings fit the shafts 113 and'114- loosely enough to allow for such expansion as takes place under operating conditions. To prevent the escape of hot oil'from the interior of the housing 101. oil is suppliedto the spaces between the plates 109 and 110 and the end coverslll and 112 through connections 115 and 116 under pressure sufficient to maintain an inflow of oil through the bearings along or forcing are steel forgings.

the, oil heater `line to the condenser lout the still the shafts 113` and 114 into the interior of the housing 101. This inllow ol' oil prevents the escape of hot oil, and also assists in cooling and lubricating the bearings.' Operating extensions of the shaft 113 extend through stuffing boxes 117 and 118 Jfor connection to some suitable driving means, such as an electric motor or steam engine. These stulling boxes also, as well as the gears 107 and 108, are protected against the action of hot oil passing through the pump by the cool oil supplied to the spaces between the plates 109 and 110 and the end covers 111 and 112.

In one advantageous -form of construction, the driven members 102 and 103 are machined from iron castings, the shafts 113 and 114 are of cold rolled steel, and the housing 101 and the end covers 111 and 112 rl`his construction provides for'great safety as the entire pump mechanism is thus enclos'ed within a forged housing. The headers 39, 39', 40 and 40 in illustrated may also with advantage be machined from unitary steel forgings.

Referring again to the apparatus illustrated in Fig. 1, a reflux 'tower 43 is arranged above the bulk supply drum 15, vapors of the cracked oil pass from the bulk supply drum 15 through vapor line 44 to the lower end of the reflux tower 43, and vapors remaining uncondensed escape from the up per end of the reflux tower 43 through vapor 46. The reflux tower 43 is provided interiorly with baffles and a connection 47 is arranged for supplying fresh oilto the upper end l.of the reflux tower 43. The condenser 4G discharges into receiver 47 from which the condensed product is discharged through connectionsl 48 and gases and vapors remaining uncondensed through connection 49. The pressure in the system may be maintained and regulated by means of valve in the vapor line between the reflux tower and the condenser,xor .by means of suitable valves arranged beyond the condenser, for` example in connections 43 and 49. Reflux condensate Vfrom the reflux tower 43, together with the unvaporized portion of fresh oil introduced through connection 47, is returned through connection 51 to the oil flowing through circulating connection 11T. A connection 52 is provided for discharging tar or pitch-laden oil from (he pressure still during operation. rouncrtion 53 is provided for pumping at thel end of a run and forinitially charging the still at the beginning of a run. To provide for complete draining of the battery of heating. tubes, connection is arranged with separate valved connections to each of thev lower headers 40 and 40. As illustrated in Fig. 5, these separate draining lines connecting to the lower headlll) . tubes.

ers may open into each of the lower headers through the openingopposite the end tube in each bank of heating tubes. To permit removal of the connections when so made for cleaning, a fianged fitting is provided as shown at 55. Additional fresh oil, in excess of that suppliedA through connection 4:7 and in excess of that supplied through con nections 115 and 116 for preventing the escape of hot oil and for cooling and lubricating the pump bearings, may be supplied, during operation, through connections 115 and 116 and forced into the pressure still through the pump bearings.

The pressure still or pressure still system, illustrated in Fig. 2, includes a bed 56 of nely divided solid material arranged in the bulksupply drum 15y below the normal liquid leveltherein and between the circulating connections 19 from the battery of heating tubes to the bulk supply drum and the circulating connections 17 from the bulk supply drum to the battery of heating In this form of the invention, the unvaporized oil circulating in the pressure still or pressure still system is passed through the bed of finely divided solid material after each passage through the battery of heating tubes and before it is recirculated through the battery of heating tubes. The bed may, for exa .,iple, be made up of from four to seven tons of fullers earth of 15-30 mesh or of from two to five tous of coke ground to 15-30 mesh. This form of apparatus has the special advantage of pro-- vviding for the maintenance of a high ratio between the average velocity through the heating tubes and the average velocity through the bed of finely divided solidv material. Likewise, it provides for prolonged" or more severe heating of the oil in passage through the battery of heating tubes bef tween successive passes through the bed of finely divided solid material. In the apparatus illustrated in Fig. i2, the same partsdescribed in connection with the apparatus illustrated in Fig. 1 are designated with the same reference characters. lt will be noted that, in the apparatus illustrated in Fig.. 2, the connection 52 for discharging tar or pitch-laden 'oil is arranged for discharge of oil from abo've the bed 56 of finely divided solid material. The bed of finely divided solid material maybesupported on any suitable supporting means adapted to 'permit free passage of'theoil and to retain the. finely divided solidfmatcrial. This support, for example, may be made up of a number of screens of graduated ineness supported between perforatedplates.

As an 'example of operation of the pressure still or pressure still system illustrated in Fig. 2, the still Ais charged With say 8,000 gallons of cold gas oil, and this still charge gradually brought to vthe desired cracking vconditions of temperature and pressure.

`oil as it is discharged from the last bank of 300 pounds persquareinch,

heating tubes in the heating furnace may be somewhat in excess of the temperature corresponding to the pressure at that point, that is the oi(l may be somewhat super* heated as it is discharged from the battery of heating tubes. After the, still is brought to operating conditions, fresh oil may'be supplied through connection 47 to maintain the desired headtemperature at the top of the reflux tower 43, and additional fresh oil may be supplied through connections 1.15 and 116. The total amount of freshf oil so supplied'may amount to as much 1,500 gallons to 2,500 gallons per hour or more. Likewise, during operation, as much as 500 gallonsito.1,500 gallons per hour or more of tar or pitch-laden oil may be discharged through connection 52. The rate ofeirculation through the circulating pump 20 may be maintained in the neighborhood of L1,000 gallons per minute. The bed of finely divided solid material is replaced with fresh or regenerated material when it becomes saturated with pitchy or carbonaceous material;

1t will be apparent-that the improved oil heater of the invention has several advantages for heating oil to a cracking temperature independently of its particularly advantageous application in the combined pressure still or pressurestill system of the invention. It is, for example, useful in connection with so-called once through operations in which the oil circulated through the oil heater and heated therein to a crack? ing temperature comprises only fresh oil or fresh oil admixed with reflux condensate. The oil heater of the invention is, however, particularly advantageous in connection with pressure stills or pressure still systems in which unvaporized oil discharged from the heater` is again `rccirculateal therethrough.

In one aspect, the present invention includes or provides animproved method of' heating hydrocarbon oils to 'a cracking temperature in which the oil is circulatedin aY series'trv of successive passes upwardly through a heating zone, downwardly outside of the heating Zone, upwardly through the heating Zone, and so on, so that the oil is heated only While circulating upwardly through the heating zone, and the total stream of oil' finally discharged fromthe heatingoperation at a cracking temperature. In this operation, the direction of .circulation of the oil in each of the succes- .drinn through the battery in such first bank of saine, and the samerclation is maintained between the tlow of heating gases through the hating zone and the circulation ot' oil therethrough in each 'of the successive passes. ln this aspect, the improved method also includes passing the heating gases through the heating Zone so that heat eX- change between the heating gases and the oil occurs lirst between the heating gases and the oil on its lirst passage through the heating Zone, then betweenthc heating gases and th'c oil on its second passage through the heating-zone, and so on; the maintenance ot generally counter-current relation between the flow of heating gases and the circulating oil by passing the heating gases through the heating zone in a generally downward direction; and tempering ot the heating gases passing through the heating Zone by rccirculating through the heating Zone a portion of the escaping heating gases. This aspect of the invention, an improved method of heating oil to a cracking temperature, is illustrated diagrainmatically in Fig. 12.

I claim:

l. In apparatus for cracking hydrocarbon oils, a bulk supply drum, a batteryot haiting tubes, and circulating connections between tlie bulk supply drum and the battery of heating tubes'including aforcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back'to the bulk supply drum, said battery of heating tubes being arranged in a heating flue and comprising a series of banks of vertically arranged heating tubes and connections between the upper ends of the banks of heating tubes, except the last, in such series and the lower ends of the successive banks, the last mentioned connections being arranged externally of the heating flue in which the heating tubes are arranged.

2. ln apparatus tor cracking hydrocarbon oils, a bulk supply drum, a battery ot heating tubes. and circulatingconnections between the. bull; supply drinn and the. battery ot' heating tubes including a forcing means lor circulating oil from thc bulksupply ot heating tubes and back tot-he bulk supply drinn, said battery ot healing tubes being arranged in a heating tluc and comprising 'a series 'ot banks ot' \ertically arranged heating tubes and connections between thc upper ends ol` the banks ol' heating tubes` except the last., series and the lower endsl oi' the successive banks, the last mentioned connections being arranged externally ot thedieating tlue in which the heating tubes are arranged, the circulating connections from the bulk supply drum to the battery of heating tubes connecting with the lower end of the heating tubes in such series and the. circulating .connections from thel battery ot heating tubes to'the-bulk supplyV upper end ot' the tery of heating tubes being arranged in ay heating flue and comprising ya series of banks of vertically arranged heating tubes and connections between the upper ends et the banks ot heating tubes, except the last, in such series and the lower ends ot the successive banks, the last mentioned 'connections being arranged externally of the heating tine in which the heating tubes are arranged, the circulating connections trom the bulk supply drun'rto the battery of heating` tubes connecting with the lower end of the rst bank of heating tubes in such series and the circulating connections from the. battery of heating tubes to the bulk .supply drum connecting with the upper end 'of the last bank of suchseries, the first bank ot heating tubes in such series being arranged to contact lirst with heating gases passing through the heating Hue in which the battery of heating tubes is arranged.

4. In apparatus for cracking hydrocarbon oils, a bulk supply drum, a batteryot heating tubes, and circulating connections between the bulk supply drum and the battery of heating tubes includingV a forcing means for circulating oilfrom the bulk supply 'drum through the battery of heating tubes and back to the bulk supply drinn, said bat-- tery of heating tubes being arranged in a heating tlue and comprising a series ot banks of vertically arranged heating tubes Yand connections between the upper ends ol' the banks ot heating tubes, except the last, in such series and the lower ends ol the successive banks, the last mei'itioncd conneci tionsbeing arranged externally ot the heat-A ing flue in which the heating tubes are arranged. a lircbox communieating with the upper end ot said hailing tlu` and a. stack' flue, communicating with the lower end ot' said li ating liuc. y

5. ln apparatus tor cracking hydrocarbon oils` a hulk supply drinn. a battery ol heating tubes. and circulating connections bctii'een the ,bulk supply drinn and the battery ot heatingtubcsl including i forcing means' for-circulating oil from the bulk supply drum through the battery otheating tubes and back to the bulk supply drum. said battery of heating tubes being arranged in a heating' flue and comprising a series of banks of vertically arranged heating tubes and being arranged externally of the heating` iiue in which'the heating tubes are arranged,

` a iirebox communicating with one end oi' .said heating fiueand a stack flue communicating with the other end, and means for recirculating through the heating flue with fresh hot products of combustion from the iirebox a portion of heating gases escaping from the heating flue in which the heating tubes are'arranged. Y

6. In apparatus for cracking hydrocarbon oils, a bulk supply drum, a battery of heat- -ing tubes, and circulating connections between thel bulk. supply drum and the battery of heating tubes including a forcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back to the bulk supply drum,

said battery of heating tubes being` arranged in a heating iue and comprising a series of banks of vertically arranged heating tubes and connections between the upper ends of the banks of heating tubes, except the last, in such series and the lower ends of the successive banks, the last mentioned connections being arranged externally of the heating flue inwhich the heating tubes are arranged, each of said banks of heating tubes being arranged. transversely to flow of heating gases through. said heating lue.

7 In apparatus for cracking hydrocarbon oils, a bulksupply drum, a battery of heating tubes, and circulating connections between the bulk supply drum and the bat- I tery of heating tubes including a forcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back.to the bulk supply drum, said battery of heating tubes being arranged in a heating iiue and comprising a series of banks of vertically arranged heating tubes and connections between the upper ends of the banks of heating tubes, except the last, in such series and the lower ends ot the successive banks, the last mentioned connections being arranged externally ot the lfcating Hue `in which the heating tubes are arranged, and a bed of iinely divided solid material arranged in the bulk supply drum below the normal liquid level therein and between the circulating connections from the battery of heating tubes to the bulk supply drum and from the bulk supply drum to the battery of heating tubes.

8.y Inapparatus for cracking hydrocarbon oils, a' bulk supply drum, a battery of heating tubes, and circulating connections between :the bulk supply drum and thebattery of heating tubes including a forcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back to the bulk supply drum, said battery of heating tubes being arranged in a heating flue and comprising a series oi banks of vertically arranged heating tubes and connections between the upper ends of the banks of heating tubes, except the last, in such seriesand the lower ends of the successive banks, the last mentioned connections being arranged externally of the heating flue in which the heating tubes are arranged, and a bed of finely divided solid material arranged in the bulk supply drum belowl the normal liquid level therein and between the circulating connections from the battery of heating tubes tothe bulk supply drum and from the bulk supply drum tothe battery of heating tubes, the circulating connections from the bulk supply drum to the battery of heating tubes connecting with the lower end of the first bank of heating tubes in such series and the circulating connections from the battery o'f heating tubes to the bulk supply drum connecting with the upper end of the last bank of such series.

9.- In apparatus for cracking hydrocarbon oils, a bulk supply drum, a battery of heating tubes, and circulating connections between the bulk supply drum and the battery of heating tubes including a forcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back to the bulk supply drum, said battery of heating tubes being arranged in a heating iiue and comprising a series of banks Vof vertically arranged heating tubes and connections between the upper ends of the banks of heatingr tubes, except the last, in such series and the lower ends of the successive banks, the last mentioned connections being arranged externally of the heating i'lue in which the heating tubes are arranged, and a bed of finely divided solid material arranged in the bulk supply drum below the normal liquid level therein and between the circulating connections from the battery of heating tubes to the bulk supply drum and from the bulk supply drum to the battery of heating tubes, the circulating connections from thebulk supply drum to the battery of heating tubes connecting with the lower end of the first bank of heating tubes in such series and the circulating connections 'from the battery ot heating tubes to the heating tubes, and circulating connectionsbetween the bulk supplyidrum and the battery of heating tubes including a forcing means for circulating oil from the bulk supply drum through a battery of heatin tubes and back to the bulk supply drum, said battery of heating tubes being arranged. in a heating liue and comprising a series of 'banks of vertically arranged heating tubes .material arranged in the bulkI supply drum below the normal liquid level therein and between the circulating connections from the battery of heating tubes to the bulk supply drum and from the bulk supply drum to Vthe battery of heating tubes, a irebox communicating with the upper end of said heating lue and a stack flue communicating withthe lower end of said heating flue.

ll. In apparatus forcracking hydrocarbon oils, a bulk supply drum, abattery of heating tubes, and circulating connections between the bulk supply drum and the bat` tery Aof heating tubes including a forcing means for circulating oil from the bulk supply drum through the battery of heating tubes and back to the bulk supply drum, said battery of heating tubes being arranged in a heating flue and comprising a series of banks of vertically arranged heating tubes and connections between the upperends of the banks of heating tubes, 4except the last, in such series and the lower ends of the successive banks, the last mentioned connections being arranged externally of the hea-ting flue in which the heating tubes are arranged, and a bed of finely-divided solid material arranged in the bulk supply drum below the normal liquid level therein and between the circulating connections from the battery of heating tubes to the bulk supply drum and from the bulk supply drum to the battery of heating-tubes, a lIirebox communicating with one end of said heating flue and a stack flue communicating with the other end, .and means for recirculating through the heating flue with fresh hot products of combustion from the tirebox a portion of heating gases escaping from the heating flue in which the heating tubes are arranged.

12. In apparatus for cracking hydrocarbon oils, `a bulk supply drum,la battery of heating'tubes, 'and circulating connections between the bulk supply drum and the bat-` tery of heating tubes including a forcing means forA circulating oil from the bulk supply drum through the `battery of heating tubes and back to the bulk supply drum, said` battery of heating4 tubes Abeingv arrangedin a' heating Hue and comprising a series of banks of vertically arranged heating ltubes and connections between the upper ends of the banks of heating tubes, ex-

cept the last, in such series and the lower ends of the successive banks, the last mentioned connections being arranged externally of the heating flue in which the heating tubes are arranged, and a bed of inel supply drum below the normal liquid level therein and between the circulating connections from the battery of heating tubes to the bulk supply drum and from the bulk supply drum to the battery of heating tubes, each of said banks of heating tubes being arranged transversely to iow of heating gases through said heating flue.

13. In apparatus for cracking hydrocarbon oils, an improved oil heater comprising a furnacehaving a heating iiue and a battery of heating tubes arranged in and extending transversely through said heating flue, said battery of heatingtubes comprising a closed series of banks of vertically arranged heating tubes and direct connections between the upper endsof the banks of heating tubes, except the last, in suoli series and the lower ends of the successive banks, the said connections being arranged externally of the heating flue in which the heating tubes are arranged.

14. In apparatus for cracking hydrocarbon oils, an improved oil heater comprising a furnace having a heating Hue and a battery of heating tubes arrangedA in and eX- tending transversely through said heating iue, said battery of heating tubes comprising a closed series of banks of vertically arranged heating tubes and direct connections between the upper 'ends of the banks of heating tubes, except the last, in such series and Y divided solid material arranged in the bulk m the lower ends of the successive banks, the

flue, said battery of heating tubes compris-` ing a closed series of banks of vertically arranged heating tubes and direct connections between the upper ends of the banks of heating tubes, except the last, in such series and the lower ends of the successive banks, the said connections being arranged externally of the heating ilue in which the heating tubes are arranged, a firebox communieating with the upper end of said heating fine and a stack iue communicating with the lower end of said heating flue.

16. In apparatus for cracking hydrocar- 460 oil upwardly through a heating zone, then of oil through the heatin e i l 1,774,291

- bon oils, an improved oil heater comprising cracking temperature in said heating zone a furnace having a heating flue and a batby indirect heat exchange with heating tery of heating tubes' arran ed in and exgases passed transversely to theseveral paths tending transversel throng said heating of said stream of oil through the heating v 5, fiue, said battery o heating tubes compris#v zone, .heat being transferred to said stream 71: ing a closed series of banks of vertically arof oil only while circulating upwardly ranged heating tubes and direct connections through saidheating zone, and discharging f between the upper ends of the banks of heatthe total stream of oil from the heating o'ping tubes, except the last, in such series and eration after the several successive passes 1L() the 'lower ends of the successive banks, the through said heating zone and at a cracking 7k said connections being arranged externally temperature. of the heating flue in which the heating' 20. A method of heating hydrocarbon oils tubes are arranged, a irebox communicating to a cracking temperature, which comprises with one -end of said heating fiuc and a supplying a stream of the oil to the heating il?, stackl flue communicating with the other operation, circulating this stream of oil in As0 end, and means for 'recirculating through a succession of passes -through a heating the heating ue with fresh hot products of zone, the direction of circulation of the oil combustion from the firebox a portion of in each of the successive passes through said heating gases escaping from the heating liue heating zone being the same, heating the in which the heating tubes are arranged. stream' of oil'to acracking temperature in 35 c 17. In apparatus for cracking hydrocarsaid heating zone by indirect heat exchange bon oils, an im roved oil heater comprising with heating gases passed transversely to a furnace having a heating flue and a battery the several paths of said stream of oil of heating tubesarranged in and extending through the heating zone, and discharging transversely through said heating flue, said the total stream' of oil from the heating 90 battery of heating tubes comprising a closed operation after the succession of passes series of banks of vertically arranged heatthrough said heating zone and lat a cracking ing tubes and ldirect connections between temperature. t i the upper ends of the banks of heating tubes, 21. A method of heating hydrocarbon oils except the last, in such series and the lower to a cracking temperature, `which comprises 95 ends of the successive banks, the said consupplying a stream of the oil to the heating nections being arranged externally of the operation,'circulating this stream of oil in heating flue in which the heating tubes are a succession of passes through a heating arranged, supply connections connecting zone, the direction of circulation of the oil with the lower end of the rst bank of heatin each of the successivepasses through said 100 ing tubes in such series, the first bank of heating zone being the same, heating the heating tubes in such series being arranged stream of oil to a cracking temperature in to contact first with heating ases passing said heating zone by indirect heat exchange through the heating flue in said furnace. with heating gases passed therethrou h, the 40 18. In apparatus for cracking hydrocarheating gases being passed throug said 105 bon oils, an improved oil heater comprising l heating zone generally countercurrent to the a furnace having a heating flue and a battery circulation of the oil therethrough and of heating tubes arranged in and extending transversely to the several paths of said through said heating flue, said battery of stream of oil through the heating zone, and t5 heating tubes comprising a closed series of discharging the total stream of oil from 110 banksof vertically arranged heating tubes the heating operation after the succession and direct connections between the upper of passes through said lheating zone and at ends of the banks of heating tubes, except a cracking. temperature. the last, in such series and the lower ends 22. A method of heating hydrocarbon oils of the successive banks, the said connections to a cracking temperature, which comprises 115 being arranged externally of the heating flue supplying a stream of the oil to the heating in which the heating tub'es are arranged, operation, circulating this stream of oil upeach of said banks of heating tubes being wardly through a heatin` zone, then downarranged transversely to flow of ,heating wardly outside of said heating zone,then gases through said heating iiue. upwardly through said heating zone, and so 12o 19. A method of heating hydrocarbon on in' a plurality of successive passes oils to a craclng temperature, which comthrough said heating zone in the heating prises supplying a stream of the oil to the operation, passing heating gases transheating operation, circulating this stream of versely to the several paths of said stream downwardly outside of said heating zone, indirect heat exchanging relation with the then upwardly through said heating zone, oil. stream on its rst pass through said ,I and so 1n a plurality of successive passes heating zone, then in indirect heat ex-r .through vsaid h eating zone in the heating changing relation with the oil stream on its operation, heatlng the stream of oil to a second pass through said heating zone, and 130 0* zone first in 125 A so on, and thereby heating the stream of oil to a cracking temperature in said heating zone, heat being transferred to said stream of oil only while circulating upwardly through said heating zone, and discharging.

the total stream of oil from the heating operation after the several successive passes through said heating zone and at a cracking temperature.

23. A method of .heating hydrocarbon oils to a cracking temperature, which comprises supplying a stream of the oil to the heating operation, circulating this stream of oil upwardly through a heating zone, then downwardly outside Osaid heating Zone,'then upwardly through said heating Zone," and so on in a plurality of successive passes through said heating zonetin the heating operation, passing heating gases. downwardly through said heating Zone'and transoperation, circulating this stream of oil upwardly through a heating zone, then downwardly outside ofA said heating zone, then upwardly through said heating zone,and so on in a plurality of vsuccessive passes through said heating zone inthe heating operation, passing heating gases downwardly through said heating zone and transversely to the several paths of said stream of oil through the heating zone in indirect heat exchanging relation with the oil circulating therethrough and thereby heating the stream of oil to a cracking temperature in said heating zone, recirculating through said heating Zone a lportion of the heating gases escaping therefrom, heat being transferred to said stream of oil only while circulating upwardly the heating operation after the several successive passes through said heatingzone and at a cracking temperature.I

25. In apparatus for' cracking hydrocarbon oils, an improved oil heater comprising a furnace having a heating ue and a battery of heating tubes arranged in and .extending throughv said heating lue, said battery of heating tubes comprising a series of banks of vertically through said heating zone, and discharging the total stream of oil from.

arranged heating' tubesfand'connectons between `the upper ends of the banks of heatingtubes, except the last, in such series and the lower ends of the successive banks,y the said connections being arranged externally of the lheating flue in which the heating tubes are arranged, each of the said connections having a cross sectional area less than the aggregate cross sectional area of the preceding bank of heating tubes.

In testimony whereof, Ihave subscribed my name.

HARRY L. PELZER.

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