US2926129A - Deashing of residual fractions - Google Patents

Description

Feb. 23, 1960 c. N. KIMBERLIN, JR., Erm. 2,926,129

DEASHING oF RESIDUAL FRACTIoNs Filed June 13, 1958 DEASG or anemona aimerions' Charles Newton Kimberiin, dr., and Clark Edward Adams, Baton Rouge, La., and Wiiired 0. Tati, Westiield, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Application .lune 13, 1958, Serial No. 74L3'53 TCEairns. (Cl. Zeit- 86) The present `invention relates to the removal of metal- `lic contaminants from petroleum oils and more particu- 'in which such petroleum fractions are burned as fuels. "in operations such as catalytic crocking,-hydrolining and the like, :the presence of very small concentrations 'of these contaminants in thefeed stream leads to the rapid poisoning `of the catalyst, causing va `significant decrease in the product yield, an increase in coke and gas production, and a marked shortening in the life of the catalyst. ln residual -type fuels, such contaminants attack therefractories used to line boilers and combustion chambers; cause slagging and the'build-up of deposits upon boiler tubes, combustion chamber walls and the blades of gas turbines; and severely corrode hightemperature metallic surfaces with which they. come intoicontact.

Although there have been'numerous methods proposed in the past for removingthese contaminants from high boiling petroleum fractions, it has been found that such methods are largely ineffective, generally result in the -loss of substantial quantities of theoil, and in most cases are prohibitively expensive. As a.result,'it hasgenerally been `necessary to restrict `the feed streamsto catalytic `petroleum processing units to those fractions which boil 'below the-range in which the contaminants are'found and to avoid as much as possiblethe use in fuels of fractions which'containthe contaminants in high concentrations.

The present invention provides a new and improved .process forthe removal of iron, nickel, vanadium, and

other metallic contaminants of the porphyrin type from fhigh lboiling petroleum oils, and in .particular Vresidual oils. In accordance with the present invention, such contaminants .are Vremo-ved by subjecting the contaminated oil sequentially to a thermal treatment, treating the heat soakedrmaterial with l to l volumes of a light hydrocarbonpreferably in the presence of an acidic gas. In a preferred embodiment of the invention the solventresidual oil mixture is also subjected to a sludging treatment with an immiscible sludging component `having a high affinity for aromatics, preferably anhydrous liquid The concentration of metallic contaminants and the ratio of volatile to non-volatile contaminants in crude oils vary considerably. The metals content of any distillate fraction will therefore depend upon the type and concentration of contaminants in the crudeoil from which the fraction was distilled, the boiling rangeof the fraction, and the amount of entrainment which-took place during the distillation. Heavygas oil distilled'from typical crudesmay contain from about'l to about 20 pounds feedstock, and the like.

,HCL or BFS, preferably dry hydrogen chloride.

anhydrous .sulfur dioxide.

2,920,129 Patented Feb. 23, i960 HCE of metallic contaminants per 1000 barrels. Residual fracA tions and gas oils derived from crudes which are particu larly high in contaminants may contain as much as 300 pounds of metal per 1000 barrels. Similarly, in some fractions these contaminants may be predominantly of the volatile type and in others they may be essentially of the non-volatile type, depending upon the crude source and the conditions under which the fraction was obtained.

The heat soaking step of the present invention is carried out preferably under conditions of incipient cracking so that no signiiicant amount of lighter components are formed. The conditions required will depend upon a combination of time and temperature, the nature of the The temperature of thermal treatment, however, is below l000 F, and preferably below about 900 F. On the other hand, temperatures above Vabout 600 F. are needed for sufficient reaction rate to maintain times within reasonable limits. Pres- `sures may also be applied to the thermal treating step to maintain the material in a substantially liquid phase.

The solvent precipitation step which follows is carried out in the heat soaked feed stock directly. Preferred are light hydrocarbons boiling in the range of about 55 to 400 F. As a result of the solvent addition, there is precipitated as a light, flocculent precipitate the so-called asphaltene fraction, which is extremely diiiicult to remove from the lsolution phase. A portion of the porphyrins -are precipitated with these asphaltenes, `while a portion remains in solution.

Accordingly, there is also employed as a metal coagulatingreagent an acidic material soluble in therpetroleum fractions, a hydrogen'halide such as anhydrous The treating temperature, the volume of hydrogen halide employed and the pressure at which the treatment is carried out `may be varied considerably. It is preferred to treat thevsolvent-residual oil mixture at temperatures between about 70--and 400 -F., although highertemperatures may be employed, and at Vpressures ranging from atmospheric to about `300 p.s.i.g., higher pressures beingalso permissible. The reaction time too may be varied from a rfew minutes to Ias much as a few hours, depending upon theV treating conditions.

Though this combination'gives goed results in demetallizing residual oils, even better results can be obtained by addition of a sludging component, and in particular liquid A sludging action occurs which servesto coagulate the llocculent asphaltene precipitate, enablingits ready separation as a sticky semifluid sludge. :The final .product Vobtained by this combination processingis found to be extremely low in metal .,content, thus enabling the residual oil to be 4used for turbines andthe like.

The exact. nature and process of the present invention, its objects and advantages, will be more fully understood from the following description and drawing show- Aing schematically apreferred embodiment of the invention.

Turning now to ,fthe drawing, reference numeral 1 `designates a crude oil distillation zone which may constitute, for example, an atmospheric pipe still or a combination of atmospheric andl vacuum distillation towers.

vCrude oil may be introduced into distillation zone l step.

Middle distillates may be withdrawn through line 5. These materials, kerosene and light gas oils, may boil4 up to 900 F. and are substantially metal free. A heavy gas oil fraction boiling in the range of between 950 F. and 1300 F. is withdrawn through line 6 and the residual fraction, boiling above the heavy gas oil is taken oif as bottoms product through line 7. Both of these latter streams contain substantial amounts of metallic constitu ents and may be subjected separately to the treating process of the present invention.

The thermal treating zone 8 to which the metal contaminated heavy oil is passed via line 7, is preferably a closed, agitated vessel or drum. The pressure during the heat soaking step is preferably maintained between 200 to 1500 p.s.i.g. As indicated previously, it is advantageous to maintain a temperature of from about 650 to 850 F. in this zione under conditions such that little if any cracking occurs. A residence period of 0.1 to hours is desirable. The effect of the thermal treatment serves to increase markedly the susceptibility of the metallic constituents to later coagulation by the acidic gas treatment, possibly by chang-ing either the character of the porphyrin, the asphaltenes, or the oil.

The solvent precipitation step is carried out on the heat-soaked residua directly, and the latter is passed for this purpose through line 9 to contacting tower 10. This may comprise one or more towers or other vessels adapted to permit the saturation of the oil with gaseous HCl admitted through line 15 under the desired conditions of temperature and pressure. Suitable coils, jacketing, or other Itemperature control means are provided, as are means for agitation.

Solvent, which is preferably an aliphatic or naphthenic hydrocarbon or mixture having 5 to 10 carbon atoms, and which may advantageously be the naphtha fraction withdrawn through line 4 from still 1, s introduced into vessel 10 through line 12, in amounts of. from 0.1 to 10 volumes per volume of oil, preferably 0.3 to 3 volumes per volume of oil. Furthermore, in a preferred embodiment of the invention, 0.1 to 3 volumes of liquid sulfur dioxide per volume of oil are admitted through line 17 to effect sludging of the coagulated metallic components.

Reaction conditions within tower 10, which is preferably maintained as a-countercurrent reaction zone, are temperatures of 30 to 300 F. and pressures of 25 to 500 p.s.i.g. The residence time of the oil may range from 5 to 100 minutes or more. The deashed oil-solvent mixture, along with gaseous HC1 or other acidic metal coagulating gas is passed overhead via line 14 and passed through heater 16 to ash tower 18, where the hydrocarbon solvent along with HCl and any dissolved SO2 is lashed 01T overhead through line 20, while oil of exceptionally low metal content is recovered from flash zone 18 through line 19. The iiashed solvent and gases are passed to cooler 24 via lines 20 and 22, and thence to settler 26, which is maintained under conditions of decreased temperature and increased pressure to liquefy the SO2 Returning now to tower 10, the semi-duid sludge is withdrawn downwardly through line 34 and is, in a preferred embodiment of the present invention, further processed to recover the sulfur dioxide. This may be done by passing it through heating zone 36 into a fluidized solids ash zone 3S. Here `a bed of finely divided solids, preferably derived from previously treated asphaltene, is maintained `as a dense, uidized bed of solids maintained by an upward owing gas stream admitted through line 41. This bed of solids may be at a temperature of about 100 to l000 F., and the sludge is deposited thereon,l whereby it is decomposed to a solid carbonaceous material and gaseous SO2 and hydrocarbon. These gases are Withdrawn through cyclone 40 equipped with dipleg 42 for return of fines to the uidized bed, and are passed via lines 43 and 22 to settler 26. A portion is recycled via line 41 to reactor 38 to maintain the bed in uidized condition. Solid carbonaceous residue may be withdrawn through line 4S and he used as solid fuel.

In the settling zone, which is adapted to settle out and separate liquid SO2 from solvent hydrocarbon, HC1 may be withdrawn overhead as uncondensed gas via line 28 for recycle to the system or may be recycled dissolved in liquid streams. Similarly, the hydrocarbon solvent forms an upper layer and is passed, in whole or in part, via line 32 to tower 10. Sulfur dioxide `is likewise recycled vifa line 30 to tower 10.

The process of the present invention may be subjected to many variations without departing from its spirit. Thus, instead of separately heat treating the oil prior to addition of solvent, it may be desirable, under certain circumstances, to thermally treat the oil-solvent mixture preferably after saturation with the coagulating gas. IIn still another modification, total crude, from which fixed gases have been stripped, may be fed to the heat soaking vessel 8 and then to the countercurrent contacting tower l10. Naphtha recycle is fed to the top of the tower equivalent to about 0.1 to l0 volumes on feed. The naphtha cut may be of various boiling ranges or the total fraction boiling up to about 400 F. The naphtha-deashed oil solution is taken overhead from the contacting tower to a distillation tower where the naphtha recycle stream is cut out and excess naphtha from the crude taken oi as make naphtha. The SO2-residue stream is taken from the bottom of the tower and decomposed as described hitherto. The SO2- HC1 fraction is taken overhead from the still and compressed for recycling. Operating in this manner integrates the distillation step after the solvent precipitation process, and produces both the precipitant for the demetallizing process as well as any other cut desired in the "crude distillation step.

The process of the present invention yields an oil with very, low metal content from a highly contaminated stream, as shown below.

The following experiments were carried out with Bachaquero crude topped at 400 F. in order to illustrate the effects of the variables involved. The Bachaquero topped crude is representative of the Venezuelan heavy lake crudes containing large amounts of vanadium and nickel components. The sample used had a gravity of 14.1 API, a Furol viscosity of 187 SSF at 122 F., and contained 450 p.p.m. vanadium, 50 p.p.m. nickel, 2.3 wt. percent sulfur and 0.38 wt. percent nitrogen with a Connadson carbon content of 11.3 Wt. percent.

The data below show the superior selectivity obtained by treatment with heavier hydrocarbons as compared with conventional deasphalting using propane. The propane deasphalting results are taken from correlations to show data at both the same yield and at the same degree of metals removal. Results were obtained with the Bachaquero topped crude which had not been subjected to heat treatment.

Recovered Oil Treatment Vol. P.p.m. Percent Ni-l-V Yield 3 Vol. Pantano/1 Vol. Feed 94. 4 137 Propane Deasphalting:

Same Yield 94. 4 340 Same Metals Removal 79. 4 137 3Vol. Hexane/l V01. Feed 97.0 122 erogare@ content. These treatments were lcarriedout with Bah` aquero topped crude after the indicated heat treatment by adding 3 volumes of nepentane, saturatingthe mixture with anhydrous HC1 Igas and adding about one-half volume of liquid sulfur dioxide. Under these conditions the precipitate immediately separated as a semi-iluid sludge at the bottom of the reaction vessel.

Heat treatment for shorter periods of time at higher temperatures does not appear as lgood for metals removal as longer heating at low temperatures.

Data obtained with Bachaquero topped crude heat soaked for 4 hours at 725 F. show the effect of the vari- The combination of both treatment with HC1 gas and sludging with liquid sulfur dioxide gives much better metals removal than either treatment alone. The above data also show that a CS/Cq light naphtha boiling from about 110 to 180 F. is a satisfactory diluent. This material gives somewhat poorer metals removal than the light n-paraflins because of the enhanced solvent power of the benzene contained therein. The ready availability of such naphtha fractions, however, oisets this slight disadvantage. Data obtained with the naphtha also show that the degree of metals removal can be controlled by the amount of diluent added, larger amounts removing more metals, although equivolume naphtha is still very eifective.

The following data show that in addition to metals removal there are other quality improvements for the oil product such as increased gravity, decreased Conradson carbon, decreased viscosity and decreased nitrogen content. All of these improvements increase the value of the feed for catalytic cracking and other general uses.

Severe solvent precipitation treatment gives product approaching catalytic cracking feed quality Product- 3/1 Pentane-l-HCl--Soz Baeha- Sludging Feed Heat Treatment quero Topped Crude 4 His. 4 Hrs. 4 Hrs.

N one 700 725 75 Vol. Percent Oil 100 89 86 85 89 Oil Inspections:

Gravity, API 14.1 19.8 21. 3 23.1 27. 3 Con, C., Wt. Percent.-. 11.3 4 0 3.1 2.5 1.4 P.p.m. Nickel 50 5 2 l. 5 1. 5 P.p.rn. Vanadium 450 84 10 2. 5 2 Wt. Percent Sulfun 2 3 2. 2 1. 7 1. 8 1.7 Wt. Percent Nitrrgen... 0 58 0 23 0.14 0.07 0.04 Viso., SSF 122 F. 187 37 20 12 i6 Theffollowing' data .showthat the 700.F.l bottoms of -Bahaquero cmde'representing-the bottom 76% of the topped crudeis similarly improved by this treatment. Also data vare included which show that a domestic crude, 400 'F. Hawkinstopped crude,of much lower metals vcontent isimproved `by this treatment. lThese feeds i were heatsoaked for 4 hours at 700 F. before being treated with 3 volumes of n-pentane, saturated with HC1 and sludged ,with 0.5 'volume of liquid sulfur dioxide.

' Wt. SSF Vol. P.p.rn. API Percent 122 Percent Ni-I-V Gravity Cn., F.

700 F.|Bachaquero:

Feed 580 9. 8 14. 8 5, 300 80.5 23 19.0 4.0 42

In an -additional experiment a mixture of Bachaquelro topped crude and three volumes of n-pen-tane saturated with HC1 gas was heat-soaked for 4 hours at 700 F. The product oil was recovered in 89 vol. percent yield on feed land had a nickel plus vanadium content of 20 ppm. These results are similar to those expected for treatment of the feed heat-soaked under the same condi tions with 3 volumes of n-pentane and saturated with HCl gas.

What is claimed is:

1. An improved process for upgrading a metallic contarninated petroleum fraction including constituents boiling above about 950 F. which comprises subjecting said fraction to an initial thermal treatment at a temperature between about 600 to 900 F. for a period of 0.1 to 5 hours, thereafter contacting said fraction in a precipitation zone with 0.1 to l0 volumes of a light hydrocarbon per volume of oil, an acid gas and about 0.1 to 3.0 volumes of liquid SO2 per volume of oil, thereby precipitating and coagulating metallic contaminants and separating a heavy oil substantially free from the precipitated and coagulated metallic contaminants.

2. The process of claim 1 wherein said acid gas is hydrogen chloride.

3. An improved process for upgrading a metal contaminated petroleum fraction containing constituents boiling above 950 P. which comprises heat-soaking said fraction at a temperature of from about 650 to 850 F. for a period of about 0.1 to about 5 hours, in a heat soaking zone, thereafter mixing said heat soaked oil with 0.1 to l0 volumes of a hydrocarbon having from 5 to 10 carbon atoms in a precipitation zone, saturating said mixture with 4gaseous HC1, maintaining precipitation conditions of 30 to 300 F. and 25 to 500 p.s.i.g. in said Zone, sludging said mixture with 0.1 to 3 volumes per volume oil of liquid anhydrous SO2, and recovering a heavy oil greatly depleted in metallic impurities.

4. The process of claim 3 wherein said oil is heat soaked for about 4 hours at abou-t 750 F.

5. The process of claim 3 wherein topped crude is passed sequentially to said heat soaking zone and said precipitation zone, a naphtha fraction passed to said zone, a mixture of naphtha and deashed oil withdrawn from the upper portion of said zone and passed to a distillation zone.

6. The process of claim 3 wherein a sludge formed in said processris decomposed into solid carbouaceous material and gaseous SO2 and hydrocarbons by directly contacting said sludge in a coking zone with a bed of iluidized solid carbonaceous material heated to a temperature in the range of about 100 F. to about 1000 F. and maintaining said bed in a lluidized state by recycling a portion of the gaseous S02 and hydrocarbon liberated in said ooking zone.

7. The process of claim 6 wherein said heavy oil is recovered by passing a liquid mixture separated from the sludge to a ashing zone, withdrawing from said ashing zone a gaseous mixture of said hydrocarbon, HC1 and SO2, combining said gaseous mixture with a portion of the gases withdrawn from the coking zone, passing said gases to a settling zone maintained at conditions of decreased temperature and increased pressure to condense the gaseous SO2 and hydrocarbon while maintaining the HC1 in a gaseous state and separately withdrawing from said settling zone a liquid SO2 stream, a liquid hydrocarbon solvent stream and a gaseous HC1 stream and recycling said streams to the precipitation zone.

References Cited in the le of this patent UNITED STATES PATENTS 2,130,147 Milmore Sept. 13, 1938 2,188,012 Pilat et al. Ian. 23, 1940 2,650,898 Case Sept. 1, 1953 2,685,561 Whiteley et a1. Aug. 3, 1954 2,727,853 Hennig Dec. 20, 1955 2,780,587 Watkins Feb. 5, 1957 2,834,715 Pratt May 13, 1958

Claims (1)

1. AN IMPROVED PROCESS FOR UPGRADING A METALLIC CONTAMINATED PETROLEUM FRACTION INCLUDING CONSTITUENTS BOILING ABOVE ABOUT 950*F. WHICH COMPRISES SUBJECTING SAID FRACTION TO AN INITIAL THERMAL TREATMENT AT A TEMPERATURE BETWEEN ABOUT 600* TO 900*F. FOR A PERIOD OF 0.1 5 HOURS, THEREAFTER CONTACTING SAID FRACTION IN A PRECIPITATION ZONE WITH 0.1 TO 10 VALUMES OF A LIGHT HYDROCARBON PER VOLUME OF OIL, AN ACID GAS AND ABOUT 0.1 TO 3.0 VOLUMES OF LIQUID SO2 PER VOLUME OF OIL, THEREBY PERCIPITATING AND COAGULATING METALLIC CONTAMINANTS AND SEPARATING A HEAVY OIL SUBSTANTIALLY FREE FROM THE PRECIPITATED AND COAGULATED METALLIC CONTAMINANTS.

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