US1814249A - Cracking still - Google Patents

Description

W. T'. HANCOCK' CRACKING sTILL 2 Sheets-Sheet l Filed Aug. 2l, 1929 July 14, 1931. w. T. HANCOCK CFACKING STILL 2 sheets-smet 2 Filell Aug. 21. 1929 NSN Q mm Z .0 .m :Wt: www o m 4 o m mf, @f Q .Q .l Q\\ Patented .lillyl4, 1931 UNITED STATES PATENT OFFICE WILLIAM T. HANCOCK, OF LONG BEACH, OALIFOR-NKIA cnAexINo STILL Appncation ined August 21, 1929. serial No. 387,380'.

type of still, the cracking stock is passed through one or more heating tubes, during which` time 1t 1s heated to cracking temperasure for a length of time sutiicient t0 complete the cracking reaction. I have'found that by maintainingthe liquid oil under pressure during its ow through the heating tubes, and by agitating the oil during heating and simultaneously scrubbing the tube walls to remove carbonaceous bodies deposited thereon, preferably by the mechanism described in the referred patent, high vyields of cracked roduct are obtained and continuous operation over long periods of time is enabled'by the provision of means for eectively removing from the system heavy residual materials.

The form of heating elements described in the referred patent may be characterized generally as comprising a mechanism Whereby tarry or carbonaceous bodies formed during the crackingl reaction, are prevented from depositing on the heating walls of the apparatusthese materials instead of being'A withdrawn continuously with the residue. The mechanism in its preferred form comprises an externally heated cylindrical tube within which a series of disks are mounted at angles on a longitudinal and rotatable central shaft. A plurality of metallic balls are confined between the disks and are ada ted to be moved upon rotation of the shaft in such a manner that they roll over the lower portion of the tubewall and are elevated and dropped against the wall with hammering effect. The balls simultaneousl are caused to lmove backv and forth longiture, and thereafter conducted to a reaction chamber where it is maintained under presltudinally between the annnlarly arranged plates, andthus have both scrubbing and hammering action on the tube wall with the result that solid matter is prevented from depositing thereon, and instead kept in sus'- pension in the residual liquid. During op'- erations, the oil is ted into one end of the tube and in flowing therethrough is subjected to vaporization and cracking the heavy residual liquid being withdrawn at `the opposite end of the tube.

I have found in accordance with the present invention that materially increased yields and' efficiency in operation maybe gained by the use of one or more ot' the described heating elements in combination with a reaction chamber, initial heating of the oil to high temperature and under pressure takingplaceiu the heating units or.

tubes, and the cracking reaction carried to completion by maintaining the high temper ature oil under pressure within the reaction chamber. rangement ot' the heating units and the re* action chamber, provision is made whereby the heavy carlmnzweous and residual materials prt-,cipitated within heatingun'itsand also in the reaction chamber, may be readily discharged from the system. Maintaining the reaction chamber under pressure serves also to maintain the oil in the heating tubes under pressure. and it may be stated that by heating and agitatiug the oil under pressure, cracking results to a materially greater degree than by merely allowing the oil to flow through the tube at substantially at,- mospherie pressure. As .stated however, cracking to a final und maximum degree occurs upon maintaining the. heated and partially crackful oil tor a period of time in the reaction chamber.

.'lhe above charactcristics and advantages of the invention as well as :nlditional tea.- tures will be understood most readily from t-he follo\\'iiig detailed description. throughout which reference is had'to the accompa nying drawings, in which:

Fig.. l is an elevation, partly in section of a preferred t'orm of apparatus embodying the invention;

By virtue of the particular ar- Fig. 2 is a plan view of the cracking still shown in Fig. l;

Fig. 3 is an end elevation as viewed from the left of Fig. 2;

Fig. 4 is a fragmentary enlarged longitudinal section through one of the heating units andv The oil comprising the cracking stock is delivered to the heating units through inlets 15a by way of header l5, to which oil is delivered from the supply line 1T by a pump 17a. The units 14 preferably are inclined somewhat as indicated, and at the lower ends of the units. outlet pipes 18 lead to a common headerilt). lVithin each of the tubular shells 2l of the heating units is a rotatable and central shaft 2O carried in a bearing at 21 at the upper end of the unit, and at its opposite end by a bearing 22 which may, at the same time, constitute a stuffing box. This stuffing box is carried on the end of a pipe 23 ot reduced diameter which projects beyond the lower end of the tube 524 outside the furnace. thereby enabling the stufling box to be maintained at a comparatively lower temperature than that within the furnace. The feed oil delivered to the heating units through header l5 Hows downwardly through the tubes 24. during which time the oil is heated and subjected to cracking to a considerable degree. The discharge from the heating tubes 24 occurs through outlets 1R, the header 1H, and into the reaction chamber 26 by way of pipe 27.

The central longitudinal shaft. 2t) carries a plurality of disks 2,50 set in planes making a somewhat acute angle with the shaft as shown in Fig. -l, the disks being of such diameter that their peripheries are spaced slightly from the tube wall. Between adjacent disks a numberof balls 3l is confined, preferably a large enough number to make two rows of balls between adjacent disks. By using balls of say one inch diameter, with three in each row between adjacent disks, the distance between the disks may be slightly more than three inches. The distance between ball centers being thus some.- thing more than one. inch, the disks 3() preferably are set at an angle such that upon rotation, they will impart to the balls resting in a row at the bottom wall of the shell 24,

a longitudinal movement somewhat in ei'J cess of the distance of adjacent ball centers. Between the disks are arranged the radial plates 32 which act during rotation of the shaft, t0 carry the balls around the inside tube. The inner edges 32a of these plates have suitable clearance from the shaft 20,

thereby providing an additional space Jfor passages of liquid or vapor from one side of the plates to the other. Likewise the outer edges B27, do not quite contact with the vtube wall, these edges preferably being inside the peripheries of the disks :lo which in turn are slightly spaced vfrom the tube as indicated at 33.

The longitudinal ball actuating shafts 20 may be rotated by any suitable means, and as a typical form of drive, I have shown the, shafts provided at their lower ends 2o/1 projecting through the stulling boxes 22, with gears 35 meshing with gears it' on shaft 37 which is driven by chains :5S extending over sprockets 39 on shafts 3ST, and sprockets 40 on the main drive shaft ll, the latter in turn being rotated by suitable drive means, for instance a motor M. Thus it will be 'noted that the shafts 20 and disks 250 are simultaneously rotated and at the saine speed by means of the described driving mechanism.

The operation of the parts comprising the individual heating elements will be` readily understood upon inspection of Figs. t and 5. The unvaporixed liquid in fiowing from the upper toward the lower ends of the tubes 2l passes around the edgeof each disk 30 and in a comparatively thin stream directly against the heated tube wall, and thus is periodically and repeatedly subjected to etl'ectivc heating. .\nd also whatever gases and vapors are liberated are likewise caused to repeatedly llow around the edges of the disks and thus come into intimate contact with the heating tube. .\t the same time, both the vapor and liquid are constantly moving in circuitous paths and are constantly intel-mingled, so that these phases collie into repeated contact with each other and also into repeated contact with the tube wall. It. will be apparent that rotation'of the balls likewise is eifective in causing interiningling of the liquid and vapor, as well performing the particular functions which will now be described.

It will be readily seen that upon relativev slow rotation of the shaft 2t), a row of balls that may be temporarily resting on the bottom of the tubey will be picked up by a plate 32 and elevated in contact with the tube wall until they reach a position somewhat. as shown in full lines in the position in Fig. 5.' Upon reaching this position. the balls loll down plate and` usually striking all to the lower-most position D, where the balls remain until picked up bythe next plate. During this operation, the balls are lnoved back and forth longitudinally of the tube by virtue of the disks o0 being set at angles as previously mentioned.'v these combined actions, the balls are caused to scrub the inner surface of the tube thoroughly, and particularly the lower part in which the heavy residual and carbonaceous bodies would otherwise collect, and also to continuously hammer the tube so as to loosen any deposit which may become attached to it. The heavy particles thus are kept free and agitated in the liquid, and are carriedv by the liquid to the lower outlet end of the tube.

The hot liquidvfrom the cracking units delivered to the reaction chamber 2G is maintained at a constant predetermined level L by suitable means, for instance a float controlled valve in the reaction chamber outlet line 46. The residual liquid from the chamber discharged through line 4 6, is conibined with the feed in line 1T and returned to the tubes lat to be subjected to further heating and cracking. The vapors formed during the fiow of oil through the tubes as well as those liberated from the liquid body 47 in the reaction chamber, are conducted through the vapor line i8 to the dephlegm ator 4S), the undesirable heavy fractions in the vapor and entrained particles preferably being absorbed in a portion of the feed oil introduced through line :30 at the ton of the -dephlegmaton and returned through line 51 to the feed in line 17. Provision is made for controllably maintaii'iing a high pressure, preferablybetween l0() and 200 pounds per sq. in., within the reaction chamber and therefore in the cracking tubes, by means of the pressure regulating valve 5:2 in the vapor line 4S. Under certain conditions it may be desirable to provide an additional pressure regulating valve :Bil in the reaction chamber inlet line QT, whereby a comparatively higher pressure may be maintained in the cracking tubes to prevent excessive vaporization tlierein, the reaction chamber pressure being comparatively lower in this case. Generally however it. is preferred to maintain substantially the same pressure in both the cracking' tubes and reaction chamber, and to regulate the pressure by the single valve .32.

Due to the heating ot' the. oil to cracking teml'ieratures in flowing through the tubes ll, heavy carl'ionaceous materials are precipitated as a result. ot' the crac-king reaction,- and as previously mentioned, these bodies are carried in the liquid to the lower eri-ds 24a of the tubes. In order to effectively remove By all i the tarry materials at this point, I provide a purge line in the bottom of the lower ends of each of the tubes, and by periodically opening valves 56 in thepurge line, the undesirable heavy materials are comple-tely forced out of the tubes. Pivef'erablyvdrinn 26a forming the reaction chamber is also inclined to such an extent as to cause carbonaceous bodies precipitated therein to --settle out of the liquid at 2Gb in the lower end bot-tom of the still. As in the previous instance, these materials are periodically discharged from the chamber by opening valve 57 in the blow-ott or purge line 5S.

Preferably the capacity of the reaction chamber is large in comparison with the rate of flow of the stock through the cracking tubes, and consequently the heated liquid is retained in the chamber a considerable length of time in order to enable the cracking reaction' to be carried out to the highest possible degree. As a typical example in the opera-tion of thc still using Diesel as the charging stock, the oil may be heated and delivered into the reaction chamber at a temperature preferably between G00 and 900O F., lthe amount ot product gasoline,

based on the charging stock, obtained upon final rectification and condensation of the vapors, being in the neighborhood of 50%.

I claim:

1. In a` cracking still, a'furnace, a plurality of exteriorly heated inclined tubes in said furnace each tube having a liquid inlet at its upper end and a heated liquid and vapor outlet at its lower end, said tubes being. inclined to cause carbonaceous vsolids therein to settle toward the lower ends of the tubes, a rotatable shaft extending een trally and longitudinally through the tube, a tube of reduced diameter extending ceutrally from one end of the tube, a stumng box at the end of said smaller tube, and the shaft projecting out through said stuffing box, a plurality of ball confining disks set rigidly on said shaft and longitudinally spaced from each other, said disks lying in parallel planes making acute angles with the shaft, pairs of ball carrying plates set between adjacent disks in a radial longitudinal plane, the plates of each pair being at opposite sides of the shaft, the inner edges of the plates being spaced f rom the shaft and the outer edges of thel plates and the peripheries of the disks being` slightly spaced from the tube walls, sets of free balls in the spaces between adjacent disks and at opposite sides oi the pairs of plates; means for simultaiwously driving said shafts at their projecting ends, au inclined reaction chamber above said tubes and into which heated liquid and vapor is discharged from the tubes through said outlets, means for controllably maintaininga high pressure in said tubes and the reaction chamber,

' rality ot' longitudinally spaced ball contining disks mounted on said shaft with their peripheries close to the inner surface of the tube', free balls in the spaces between adjacent disks. and hall arrying plates situated between adjacent disks, said ball Carrying plates being arranged in pairs between each two adjacent disks, the plates of each pair being substantially diametrcally opposite cach other, and there beingT two sets ot said balls, one set at each ot the opposite sidesv of said plates, a carbon residue purge line at the lower end of said heating tube, a reaction chamber above said tube, liquid and vapors being discharged into the chamber from the heating tube through said outlet, said rau-lion chamber being inclined to cause solid carbon precipitate to settle. toward its lower end, a purge lint` at the lower end of said cl'iamber, a line leading from said beating tube inlet into the reaction chamber, and means t'or (.'ontrolling the prossure in said reaction chamber and in the heating tube.

3. In a cracking still, a plurality of inclined heating tubes arranged side'by side, each of said tubes having a liquid inlet and outlet at its upper and lower ends respectively, a rotatable shaft extending longitudinall therethrough, free balls within the tube, and means on said shaft for engaging and agitating the balls; drive means for rotating the shafts. a reaction chamber above sald tubes and into which heated liquid is dischargetfl from thc tubes through said outlets, said reaction.chamber heilig inclined to cause solid carbon precipitate yto settle toward its lower end, a valve controlled purge lin(` at the lower end of the chamber, a manifold communieatiug with said liquid inlets to said beating tubes, a line leading from said manil'old into the reaction chumber at a point above its lower end, and means l'or controllably maintaining pressure in `said tubes and the reaction chamber.

l. In a cracking still, a plurality of inclined heating tubes, eaeli of said tubes having a liquid inlet and,outlet at its upper and lower ends respectively, a rotatable shaft extending longitudinall)Y therethrough, free balls within the tube, and means on said shaft for engaging and agitating the balls; drive means for rotating the shafts, a reaction `chainber above said tubes and into which heated liquid is discharged from the tubes through said outlets, said reaction chamber being inclined cause solid carbon preci itate therein to settle toward one end of t e

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