US3607724A - Separation of asphaltenes and conversion of black oils - Google Patents

Abstract

Removal of asphaltenes from a hydrocarbonaceous black oil is effected through the use of a foam chamber and a foam breaker. In one application, the asphaltene-free material is thermally cracked and the heavier portion of the cracked effluent is recycled to combine with the fresh feed. The foam is created through the use of high-pressure hydrogen, being intimately admixed with the black oil, followed by depressuring into a foam chamber.

Description

United States Patent [72] Inventors Rog rs, Edward [56] References Cited gi a m k "5 both f m UNITED STATES PATENTS A I No :32 My 2,854,398 9/1958 Knox 208/86 -3,281,350 10/1966 Codetetal. 208/86 F1led Dec. 17, 1969 3,288,703 11/1966 Spars et a1. 208/86 Patented 3 362 901 1/1968 Szepe et al 208/86 Assignee Universal Oil Products Company Des Plaines, Ill. Primary Examiner-Herbert Levine Attorneys.lames R. Hoatson, Jr. and Robert W. Erickson SEPARATION OF ASPHALTENES AND ABSTRACT: Removal of asphaltenes from a hydrocar- VERSION OF BLACK OILS bonaceous black 011 is effected through the use of a foam 1 D i F chamber and a foam breaker. In one application, the asphal- 5 C 8 raw tene-free material is thermally cracked and the heavier por- U.S. Cl 208/86, tion of the cracked effluent is recycled to combine with the 208/309 fresh feed. The foam is created through the use of high-pres- Int. Cl Cl0c 3/00 sure hydrogen, being intimately admixed with the black oil, Field of Search 208/86, 309 followed by depressuring into a foam chamber.

[4 1 Foam Breaker 8 4 Foam Chamber 7?. Hydrogen g /0 7 l f e 2 1 Mixing Zane l5 Thermal Gail Product SeparaI/an SEPARATION OF ASPHALTENES AND CONVERSION OF BLACK OILS The process described herein is adaptable to the removal of asphaltenes from petroleum crude oil residuals having a high metals content. More specifically, our invention is directed toward the removal of asphaltenes from a hydrocarbonaceous black oil and conversion of the asphaltene-free material. This process is applicable to atmospheric tower bottoms, vacuum column bottoms, crude oil residuum, topped and/or reduced crude oils, coal oil extracts, crude oils extracted from tar sands, etc., all of which are commonly referred to in the art as black oils.

Petroleum crude oils, and particularly the heavy residuals obtained therefrom, contain sulfurous compounds in exceedingly large quantities, nitrogenous compounds, high molecular weight organometallic complexes principally comprising nickel and vanadium as the metallic component, and hydrocarboninsoluble asphaltic material. The latter is generally found to be complexed with sulfur, and to a certain extent, with the metallic contaminants. A black oil is generally characterized in petroleum technology as a heavy hydrocarbonaceous material of which more than about 10.0 percent (by volume) boils above a temperature of about 1,050F. (referred to as nondistillables) and which further generally has a gravity less than about 20.0API. Sulfur concentrations are exceedingly high, most often greater than 2.0 percent by weight. Conradson carbon residue factors exceed 1.0 percent by weight and the concentration of metals can range from as low as p.p.m. to as high as about 750 p.p.m.

The process encompassed by the present invention is particularly directed toward the conversion of those black oils contaminated by a high asphaltene content. Specific examples of the charge stocks, to which the present technique is adaptable, include a vacuum tower bottoms product having a gravity of 7.1API, and containing 4.1 percent by weight of sulfur and 23.7 percent by weight of heptaneinsoluble asphalts; a topped Middle East crude oil having a gravity of 110 API and containing about 10.1 percent by weight of asphaltenes and 5.2 percent by weight of sulfur; and, a vacuum residuum having a gravity of 8.8 API, containing 3.0 percent by weight of sulfur and 4,300 p.p.m. of nitrogen.

The utilization of our invention affords the conversion of such material into distillable hydrocarbons, heretofore having been considered virtually impossible to achieve on a continuous basis with an acceptable catalyst life. The principal difficulty, heretofore encountered in a fixed-bed catalytic system, resides in the lack of sufficient stability in the presence of relatively large quantities of metals-Le. from about 150 p.p.m. to as high as 750 p.p.m., computed as the element-and additionally from the presence of large quantities of asphaltic material and other nondistillables. The asphaltic material comprises high molecular weight coke precursors, insoluble in light normally liquid hydrocarbons such as pentane and/or heptane. The asphaltic material is generally found to be dispersed within the black oil, and, when subjected to elevated temperature, has the tendency to flocculate and polymerize whereby the conversion thereof to more valuable oil-soluble products becomes extremely difficult.

OBJECTS AND EMBODIMENTS A principal object of our invention is to remove insoluble asphaltenes from a hydrocarbonaceous charge stock. A corollary objective is to convert an asphaltene-free black oil into lower-boiling hydrocarbon products.

Another object is to provide a combination process for facilitating the conversion of asphaltic charge stocks by l initially removing asphaltenes and (2) thermally cracking the resulting substantially asphaltene-free hydrocarbonaceous material.

Therefore, in one embodiment, our invention provides a process for effecting the removal of asphaltenes from a heavy hydrocarbonaceous charge stock which comprises admixing said charge stock and hydrogen at superatmospheric pressure above about 1,000 p.s.i.g., depressuring the resulting mixture to a level below about 200 p.s.i.g. into an elongated foam chamber, removing an asphaltene-containing foam from the upper portion of said foam chamber and recovering a substantially asphaltene-free hydrocarbon fraction from the lower portion thereof.

In another embodiment, the asphaltene-free fraction is introduced into a thermal cracking reaction zone, or coil, and lower-boiling hydrocarbon products are recovered from the resulting cracked product effluent.

Other embodiments of our invention are primarily directed toward particular operating techniques and preferred ranges of operating variables and conditions. These, as well as other objects will be evident from the following, more detailed description of our invention.

SUMMARY OF INVENTION As hereinbefore set forth, our invention is primarily directed toward the separation, or removal, of asphaltenes from a hydrocarbonaceous black oil. The encompassed process facilitates asphaltene removal by providing a relatively simple and economical operating technique. The charge stock is initially admixed with hydrogen in an amount of from to about 1,000 scf./Bbl., and at a pressure in the range of from 1,000 to about 5,000 p.s.i.g. The minimum hydrogen requirement is about 5.0 cubic feet per pound of asphaltenes. The mixing is effected at a temperature in the range of 250 F to about 700 F.

The high pressure oil/hydrogen mixture is throttled into a foam chamber, entering at a lower locus thereof. The specific design of the foam chamber does not constitute an essential element of our invention. One suitable scheme involves depressuring to a pressure of from 30 to about 200 p.s.i.g. by discharging into the chamber through a sparger assembly. The pressure drop occurring across the sparger nozzles permits the dissolved hydrogen to come out of solution. The released hydrogen forms bubbles which nucleate at the large asphaltene molecules, thereby carrying the same to the upper foam section of the chamber. Nucleation of the hydrogen at the asphaltenes is facilitated when the elongated foam chamber is equipped with a turbine mixture which provides turbulence at the sparger nozzles.

Asphaltene-containing foam is continuously removed from the upper portion of the foam chamber as a result of being displaced by the incoming oil-hydrogen mixture. A substantially asphaltene-free hydrocarbon stream is withdrawn from a lower portion of the chamber. The asphaltic foam is introduced into a suitable foam breaker, such as a rotary vacuum filter. In the filter, for example, the foam is fed directly into the feed pan, and is drawn up against the filter medium. This technique breaks the foam, the hydrogen being released into the drum from which it may be recycled to the mixing zone. Although makeup hydrogen may be introduced at any convenient point of the process, a preferred locus is the hydrogen recycle line prior to the mixing zone. Asphaltenes collected on the drum are removed from the system. Where desired, the filter cake may be washed with a light hydrocarbon capable of dissolving residual, soluble distillables from the asphaltic sludge. Suitable hydrocarbons include heptane, hexane, cyclohexane, etc. This stream may be conveniently admixed with the distillable material emanating from the lower portion of the foam chamber.

In another embodiment, the distillable material from the foam chamber, along with any residual distillables removed from the asphaltic sludge, is introduced into a thermal cracking reaction zone, or coil. The charge, with or without added hydrogen, is heated to a temperature above about 800 F., preferably from about 825 F. to about l,000 F., and raised to a pressure of from 300 to about 3,000 p.s.i.g. The thermally cracked product effluent is separated, for example in a vacuum column to provide a distillable hydrocarbon product stream. Since some condensation of the higher molecular weight is effected in the cracking zone, a heavy fraction is withdrawn from the separation zone and recycled to combine with the fresh feed charge to the initial mixing zone.

DESCRIPTION OF DRAWING The accompanying drawing illustrates an embodiment of our invention wherein the asphaltene-free distillables are subjected to thermal cracking. The embodiment is presented by way of a simplified flow diagram in which valves, pumps, heaters, compressors, startup lines, heat-recovery circuits, and other miscellaneous appurtenances have been omitted. The use of these, and other standard hardware, are well within the purview of one skilled in the art of petroleum refining techniques.

The drawing will be described in connection with the deasphalting and conversion of 40,000 BbL/day of a vacuum column bottoms product having a gravity of about 100 AP! and containing about 10.0 percent by weight of heptane-insoluble asphaltenes. The charge stock enters the process by way of line 1, and is admixed with a heavy recycle stream in line 3, the mixture continuing through line 1 into mixing zone 5. Hydrogen, including makeup and recycled hydrogen from line 4, enters mixing zone 5 through line 2. The temperature of the mixture is about 400 F and the pressure is about 1,000 p.s.i.g. The hydrogen circulation is about 5.0 cubic feet per pound of asphaltenes, or about 440,000 scf./hr.

The mixture is introduced into foam chamber 7 via line 6, and is depressured therein, through sparger nozzles, to a pressure slightly less than about 100 p.s.i.g. Asphaltene-containing foam is withdrawn through line 8 into foam breaker 9, the latter being a rotary vacuum filter. The asphaltic cake is removed by way of line 10, and hydrogen is recirculated through line 4 by compressive means not illustrated. Asphalt is removed in an amount of 2,112,362 lbs/day, or slightly more than 1,000 tons/day.

An asphaltene-free hydrocarbon stream is withdrawn from foam chamber 7 through line 11 and, following heating to a temperature of about 900 F., is introduced into thermal coil 12 at a pressure of 100 p.s.i.g. The thermally cracked product effluent in line 13 is introduced into product separation means 14. Distillable hydrocarbons, having an end boiling point of about l,050 F. are removed by way of line 15, in an amount of about 39,770 BbL/day. About 40,000 BbL/day of nonvacuum distillable tower bottoms is withdrawn by way of line 3, and recycled therethrough to mixing zone 5. In effect, this recycle provides a combined liquid feed ratio to thermal coil 12 of 2.0, which value is within the preferred range of 1.1 to 6.0.

The foregoing specification indicates the method by which our invention is effected, and, with respect to one embodiment, the benefits afforded through the utilization thereof.

We claim as our invention:

1. A process for the removal of asphaltenes from a heavy hydrocarbonaceous charge stock which comprises admixing said charge stock and hydrogen at superatmospheric pressure above about 1,000 p.s.i.g., depressuring the resulting mixture to a level below about p.s.i.g., into an elongated foam chamber, removing an asphaltene-containing foam from the upper portion of said foam chamber and recovering a substantially asphaltene-free hydrocarbon fraction from the lower portion thereof.

2. The process of claim 1 further characterized in that said charge stock and hydrogen are admixed at a pressure in the range of 1,000 p.s.i.g., to about 5,000 p.s.i.g., and at a temperature of 250 F. to about 700 F.

3. The process of claim 1 further characterized in that said asphaltene-containing foam is introduced into a foam breaker, said foam is separated into an asphaltic residuum and a hydrogen-rich gaseous phase, and said gaseous phase is recycled to combine with said charge stock.

4. The process of claim 1 further characterized in that said asphaltene-free fraction is introduced into a thermal cracking reaction zone, or coil, and lower-boiling hydrocarbon products are recovered from the resulting cracked product effluent.

S. The process of claim 4 further characterized in that said product effluent is separated to recover lower-boiling hydrocarbon products and to provide a higher-boiling stream, the latter being recycled to combine with said charge stock.

Claims (4)

1. 2. The process of claim 1 further characterized in that said charge stock and hydrogen are admixed at a pressure in the range of 1,000 p.s.i.g., to about 5,000 p.s.i.g., and at a temperature of 250* F. to about 700* F.
2. 3. The process of claim 1 further characterized in that said asphaltene-containing foam is introduced into a foam breaker, said foam is separated into an asphaltic residuum and a hydrogen-rich gaseous phase, and said gaseous phase is recycled to combine with said charge stock.
3. 4. The process of claim 1 further characterized in that said asphaltene-free fraction is introduced into a thermal cracking reaction zone, or coil, and lower-boiling hydrocarbon products are recovered from the resulting cracked product effluent.
4. 5. The process of claim 4 further characterized in that said product effluent is separated to recover lower-boiling hydrocarbon products and to provide a higher-boiling stream, the latter being recycled to combine with said charge stock.

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