US1915681A - Apparatus for fractionating cracked products - Google Patents

Description

June 27, 1933. E, w LUSTER APPARATUS FOR FRACTIONATING CRACKED PRODUCTS Filed March 29, 1950 narvlrlviii v lu INVENTOR ATTORNEY Patented June 27, 1933 t UNITED "STATES PATENT oFFicE ERIC w. DUSTER, or w sTrIELnnEw JERSEY, Assreivonro STANDARD orn DEVELOPMENT COMPANY, A CORPORATION or DELAWARE "AIVPVPARATU'S non FRAC'IIQNATING 'oRAoxEnrRoDUo'rs V 7 Application filed March 29, 1930. Serial No. 439,953.

This invention relates to an apparatusfor separating cracked products into their constituents. Itmay beused in connectionwith liquid and vapor phase cracking processes although usually it can be employed with more advantage inr'connection with liquid phase cracking processes. I A main object of the present invention is toallowtthe simultaneoussupply of fresh 10 feed oil to the bubble tower ofjthe cracking system and the withdrawal of heavy uncracked products unmixed with fresh-feed from the same bubbletowerm Another object is to allow the withdrawal of heavy residual products from. the bubble tower into which fresh I gas .oil or' other charging stock,,is fed, without drawing off charging stock and thereby losing part of the conversionduring the. cracking operation. 1

Another object is to provide an apparatus for carrying out such aprocess.

I Other objects and advantages will become apparent during the following description 2 read in conjunction with the drawing, which is a vertical diagrammatic section through the bubble tower constructed according to the invention.

V It is common practice in cracking operations, to discharge the feed oil into direct contact with hot cracked vapors, so that it finally collects atthe bottom of a tower freed from lower boiling fractions and is pumped therefrom, together with the heavy residual products, to the cracking equipment. I

The direct contact has the disadvantage that in the case where it is desired to remove from the system part of the heavy residual products, it has not been possible to do this without simultaneously removing a certainv portion of the fresh gas oil or other charg- .ing stock, which is mixed with the heavy products. This, however, is not desired be- 7 cause the fresh gas oil is a better cracking stock thanthe heavy products which have already gone through the cracking coil and soaking drum and therefore consist of hydrocarbons more resistant to decomposition than fresh gas oil. I have discovered a method and devised an apparatus which will cracking coil.

be described jointly and which eliminate the disadvantage just discussed.

In the figure, the numeral 'l'designates a bubble tower into which the cracked hydrow carbon oil largely in vapor form, from which the tar has been eliminated, isvdischarged through line .2. The bubble tower, comprises a shell which is divided into several compartments by means of a number of perforated plates 3 on which bell caps and reflux lines are arranged. A partition wall 4 is-provided in'the middle sectionof the bubs bletower', running through several compartmentsand dividing them into passageways. The partition wall may be flat, in which case 05 each compartment is divided into two half: cylindrical sections, or it may be circular, in

which case each'compartment is divided into a cylindric alj and an annular section. The partition wall may, however, have any other '7 suitable shape. It divides the shellinto upwardly extending inlet and outlet passage:

ways opening at top and .bottom into the shell. V

' The fresh gas oil may be fed through line 5 to cooling coils 6 arranged in the upper part of the'bubble tower and then discharged through line 7 into theuppermost compartment of the inlet-passage which has been formed by the partition wall. The gas oil comes here into direct contact with the stream of vapors passing upward and causes the condensation of the heavier products and at the same time becomes itself further preheated. After leaving the last compartment which is provided with a partition wall the gas oil commingles with the heavyresidual products returned to the lowest plates through the reflux lines. The mixture of fresh gas oil andheavy residual'products finally accumulates at'the bottom ofthe tower and is passed therefrom through line 8 to the I The light products leave the A tower through line 9 and are introduced either into a final condenser or into a secondary '95 bubble tower, forthe purpose of further frac- I tionation.

From the compartment which is just above the partition wall the refluxed liquid is returned by reflux line 11 to the uppermost compartment of the outlet passage and which does not come in contact with fresh gas oil. This reflux, which consists of heavy residual products, is finally returned to the lower compartments without partition walls. One of the compartments of the outlet passage, for example the lowest one, is provided with a valved line 12 through which part of the heavy residual products may be eliminated from the system. It is obvious that such products will not be mixed with fresh gas oil. The product eliminated throughline 12 may be used for various purposes such as for instance, Diesel oil, or it may be mixed with the tar to control the gravity thereof and the mixture used as fuel oil.

It will be obvious that the fresh gas oil may be discharged into the secondary bubble tower instead of being discharged into the primary bubble tower. The operation of the secondarybubble tower is in this case similar to the one just described but the product removed through line 12 is lighter. It is usually passed through another vessel in which it is stripped from the light products by m'eans of open steam and isused, after cooling, as furnace oil.

In. a unit charging 10,000 gals. of gas oil per hour of total feed, the fresh feed may var from 25 to 100% of the total feed, but is usually to The temperature of the oil at the outlet end of the heating coil may be for example 880 F. I The amount of heavy gas oil or Diesel Oll'WlilllClliLV/D F0111 the tower may vary from 10 to 30% of the total feed. The temperature of the stocks so withdrawn will be from 600 to700 E, being higherfor the lowest percentage of fresh feed The pressure on the tower will be from atmospheric to 175#, but in general will be between and per square inch.

Having thus described my invention what I claim is the following:

1. A fractionating tower comprising a shell, means dividing an intermediate portion of the shell into upwardly extending non-communicating inlet and outlet passageways opening at top and bottom into the shell, the tower including perforated plates with bell caps and reflux lines, the plates extending transversely of the shell above and below the passageways and through the passageways, means for introducing hydrocarbons into the tower below the passageways, means for introducing fresh feed oil into the inlet passageway, means for withdrawing reflux condensate from the outlet passageway of the shell, and an outlet at the top and bottom of the tower. a

- 2. A fractionatingtower according to claim 1, in which the means for introducing fresh feed oil into the inlet passagewayopens into the upper portion of the inlet passageway and in which the means for withdrawing reflux condensate from the outlet passageway of the shell leads from the lower portion of theoutlet passageway. r r

3-. A fractionating tower according to claim 1, in which the means for dividing the intermediate portion of the shell is a substantially vertically disposed partition extending transversely of the shell.

4. A fractionating tower according, to

claim 1, in which the means for introducing fresh feed oil into the inlet passage leads 3 through the upper portion of the tower whereby indirect heat exchange of the fresh feed oil and the tower contents is effected.

ERIC W. LUSTER;

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