US2040064A - Treating hydrocarbon oils - Google Patents

Description

May 5, 1936. A. G. PETERKIN, JR

TREATING HYDROCARBON OILS Filed Aug. 29, 1931 INVENTOR BY La ATTORNEY Patented May 5, 1936 UNITED STATES PATENT OFFICE TREATING HYDROOARBON OILS Application August 29,

3 Claims.

This invention relates to a combined cracking and coking process and contemplates a process in which raw charging stock is subjected to coking and cycle condensate is subjected to crack- 5 ing and distillation to form a fuel oil residue.

When cracked residues, such as the residues withdrawn from pressure cracking stills, are subjected to coking there is a tendency toward the formation of permanent gases instead of gasoline constituents and furthermore the gas oil product formed is highly refractory and diflicult to crack. Therefore, in accordance with my invention I avoid subjecting the cracked bottoms to coking and instead carry on a cracking operation in which a liquid residue is produced while subjecting to coking only the raw or original charging stock. Thus, in the practice of the invention, crude oil or residuum may be subjected to a polymerizing and distilling operation to reduce the oil to an ultimate pitch or coke residue and the evolved vapors may be delivered to a distilling or fractionating zone which may also receive cracked products from a cracking operation and the combined products are distilled to form a liquid residue such as is adapted for fuel oil.

In order to more fully disclose the invention, reference will now be hadto the accompanying drawing which is a flow diagram of a particular embodiment of the invention.

In the system shown in the drawing fresh charging stock is drawn from a suitable source by a pump l0 and passed through a coil ll positioned in a convection heating zone of a furnace l2. This charging stock is preferably a virgin stock, that is, a stock which has not been previously subjected to any material cracking operation and may, for instance, comprise a reduced 40 crude, such as is obtained by straight distillation. The oil is heated in transit through the coil II and is then passed through a transfer line l3 into a coking chamber Hi. The oil is preferably heated in the coil II to a temperature that will sustain coking or pitch-forming conditions in the chamber l4 and cracking may be carried on in the coil H to the extent desired. Steam may be introduced into the coking drum I4 to assist the coking or pitch-forming operation or a stream of a highly heated lighter charging stock may be directed into the coking drum to assist in maintaining therein conditions requisite for coking or pitch-forming.

The evolved vapors are withdrawn from the chamber l4 through a line l5 while the liquid 1931, Serial No. 560,086

is retained therein so that the mass may be converted to a coke residue which may be removed through a manway l6 at the end of a run. A well I1 is indicated for suitable coke boring apparatus. The chamber l4 may be pluralized so that while one of the coke drums is being cleaned another may be utilized in the coke-forming operation. If desired, instead of running to a coke residue, the operation may be carried on so as to remove a pitch through a line l8 which is withdrawn as a liquid and solidifies upon cooling to form a product having a melting point.

The vapors evolved in the coke-forming or pitch-forming operation may be delivered by a line [5 to a distilling and fractionating tower I9. A condensate cut is removed from the tower by line 20 and pump 2| by which the condensate is charged through a line 22 to a heating coil 23 located in a radiant heating zone of the furnace l2. The oil is' subjected to cracking in the coil 23 and is then delivered through a transfer line 24 to the distilling and fractionating tower l9. Thus, the cracked products from the cracking coil 23 and the vapors from the coking drum l4 are subjected to distillation and fractionation to form a cycle condensate for cracking, a vapor fraction which is taken off through the line 25 and a liquid residue withdrawn through a line 26. The vapor fraction is condensed in a condenser coil 21 and collected as a Q final light distillate in the receiving drum 28.

Although the coils II and 23 are illustrated as being disposed in the same furnace, it may be pointed out that these coils may, if desired, be in separately fired furnaces or heated in any suitable manner. If desired, in addition to the cracking coil, such as 23, a reaction chamber may be employed and the cracked products from the reaction chamber directed into the chamber I9.

A valve is indicated in the transfer line l3 so that if desired, the pressure carried in the coking still l4 may be lower than that obtaining in the coil II, and similarly, a valve is shown in the transfer line 24 so that the cracking carried on in the cracking zone 23 may be under a higher pressure than the distilling and fractionating operation conducted in the chamber I 9. The latter chamber may also be at a pressure lower than a pointed out that an advantageous operation is to carry the heating coils II and 23 under several hundred pounds pressure while maintaining the coke drum I4 at a pressure of the order of 100 pounds and the distilling and fractionating chamber l9 at approximately the same pressure as the coking drum or at a lower pressure, for example, pounds or lower.

In practicing the invention, an oil which may preferably be a virgin stock, such as a straightrun reduced crude, is heated in the coil I I sufficiently that when passed into the chamber I4 the desired pitch-forming or coke-forming conditions may be maintained therein with or without the addition of steam or other heated oil as has been explained. In one method of operation contemplated a portion of the hot cracked products from the coil 23 and line 24 maybe passed through a.

branch line 24a into the lower part of chamber Hi. The operation is preferably carried on with cracking in the coil II to such an extent as may be practiced without the formation of injurious coke deposits in the coil, and this Virgin stock is thus reduced to a coke or pitch residue in the chamber 14. The cycle stock which is cracked in the coil 23 is preferably subjected to a high degree of cracking and the cracked products, together with the vapors from the coke-forming or pitch-forming operation are subjected to distillation and fractionation in the tower I9. The residue formed in the tower still I9 is not subjected to coking, but is drawn off as a liquid residue to form a liquid product adapted for fuel oil. The final gasoline or naphtha distillate is collected in the receiver 28.

In case it is desired to charge to the system a crude petroleum or other oil containing a quantity of the lighter petroleum fractions it is advantageous to interpose a stripping or fractionating tower between the coking drum l4 and the distilling and fractionating tower I9. Thus the vapors from the coking drum I4, instead of passing directly to the tower I9, may be introduced into this intermediate tower into which also the crude oil is introduced. The evolved vapors may then pass to the tower I9 and the resultant liquid residue may be drawn off, as by the pump I0, and charged to the heating coil II.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim: 7

1. A combined cracking and coking process comprising passing a crude residuum through a heating zone and continuously applying heat to said crude residuum during its passage therethrough to raise it to a sufficiently high temperature to accomplish coking of the residual constituents thereof, passing said heated crude residuum from said heating zone'directly to a coking zone wherein vaporizable and residual constituents thereof are separated, retaining the separated residual constituents in the coking zone wherein they are reduced to coke by their retained heat,

directing the vaporized constituents from said coking zone into a separate distilling zone and then to a fractionating zone, passing a cycle condensate heavier than gasoline withdrawn from the fractionating zone through a heating zone and continuously applying heat to said cycle condensate during its passage therethrough to raise it to an elevated cracking temperature, passing all of the products resulting from cracking the cycle condensate directly to said distilling zone, subjecting the vapors from the coking zone to fractionation and the products resulting from said cracking to distillation and fractionation in the aforementioned distilling and fractionating zones to form said aforementioned cycle condensate, a final overhead light distillate and a fuel oil residue which comprises the heaviest constituents formed in said distilling zone and separately withdrawing the fueloil residue from the distilling zone without returning same to the process.

2. A process in accordance with claim 1 in which a virgin stock is passed through the first mentioned heating zone.

3. A process in accordance with claim 1 in which the oil passing through each of the heating zones is maintained under superatmospheric pressure during its passage therethrough.

ALBERT G. PETERKIN, JR.

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