US 2772221 A
Description (OCR text may contain errors)
Nov. 27, 1956 J. STEWART ETAL REACTING HEAVY RESIDUAL FUEL WITH HYDROGEN DONOR DILUENTS Filed July 1, 1953 BZMDJE 20:35 mfi #:EE 1GB EaQmmm 9v A v Bu 2 539%: vv y e 9 hm). 2. A Al. m 0 3 l. mzzom fl w k a J 917- 5 m y .w e n m W O n H I A r J r H r Y O W h WWO TH S M mm y 5 8 OCT JRA United State Patent, 1
REACTING HEAVY RESIDUAL FUEL WITH HYDROGEN DONOR DILUENTS Joseph Stewart, Cranford, Ralph M. Hill, Mountainside, and Arthur W. Langer, Jr., Nixon, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application July 1, 1953, Serial No. 365,424
Claims. (Cl. 196-50) The present invention relates to an improved process for controlling residual fuel quality. It pertains more particularly to a process for reducing undesirable ingredicuts in residual fuels from hydrocarbon oil conversion operations.
In conventional processes for fractionating and refining crude oils, the lower boiling constituents are usually separated first by atmospheric and/or vacuum distillation operations. Depending upon the temperatures .and vacuum conditions employed, the residuum, which may comprise 2 or 3 to 25% or more of the original crude, becomes highly viscous. In order to process the residuum or reduced crude further it is commonly subjected to a relatively mild thermal cracking known as visbreaking. The latter treatment, usually accomplished by heating moderately for a predetermined period of time in a coil or coil and drum type heater, converts a small part of the reduced crude to gas, gasoline and gas oil, and is effective to lower the viscosity of the remainder bottoms fraction to a point where it is suitable for use as a residual fuel.
In the conventional visbreaking process described above, certain insoluble and sedimentary materials often are formed in such quantities that the quality of the residual fuel becomes quite unsatisfactory. This is particularly true with residua of low A. P. I. gravity. The objectionable constituents, as measured by the standard modified naphtha insolubles test and the hot filtration sediment test, increase rapidly with increasing severity of visbreaking in conventional processes. These tests, therefore, become the criteria which limit the extent of visbreaking possible. They appear to be directly related to the extent of stack solids formation when the fuels are burned. Theyrelate quite directly also to the continuing efiicient operation of the burner.
For example, a very mild visbreaking operation on a residuum feed which is already high in the modified naphtha insolubles test, greatly increases the same test results on the bottoms fraction. As low a conversion as 25% may increase the modified naphtha insolubles by as much as 55%. Hence, if a residuum feed already has an 8 to 9 modified naphtha insolubles rating, it is diflicult to reduce the residual fuelvolume' appreciably or at all without exceeding a specification limit of 10% or even 12% of modified naphtha insolubles In a copending application filed-concurrently herewith by Langer, one of the present inventors, Serial No. 365,335, there is described a process by which various heavy oils may be thermally cracked and upgraded, with low and sometimes negligible degradation to coke, 'by the use of a hydrogen donor diluent. The diluent, as therein described, is a high boiling predominantly aromatic hydrocarbon oil fraction which preferably contains a high proportion of condensed ring aromatics. This diluent is partly but not completely hydrogenated and is mixed with the feed prior to thermal cracking so that feed and diluent are heated together.
In the present application, it has been discovered that "ice by blending about 10 to 200% by volume, preferably 20 to based on the residuum feed, of a diluent of the general type mentioned above, the volume of the final residual fuel oil may be very appreciably reduced without degrading it below quality requirements. When the operation is carried out with diluent on a feed already high in modified naphtha insolubles, for example, moderately severe visbreaking may be accomplished without appreciable increase of modified naphtha insolubles in the bottoms. It will be noted that here the object is not to eliminate heavy residual fuel oil but rather to reduce its volume to a moderate degree without substantially impairing its quality as measured by naphtha insolubles and/or sediment, etc. 1
Example I A blend of 50 parts by volume of 900 F.+Bachaquero residuum and 50 parts of partially hydrogenated thermal tar of 700 to 900 F. cut, which contained about 500 s. c. f. of I-Iz/bbl. of tar, was visbroken in a continuous unit at 800 F., 2.4 v./v./hr., and 400 p. s. i. g. pressure. The yield data from the run are tabulated below:
Conversion (wt. percent on resid.) 33.6
Yields (.wt. percent on resid.)
C3 I 1.5 C r/430 F 11.0 430/700" F Q. 9.9 700/900 F 95.3 900/995 F 15.5 995 F.+ 66.4 Coke 0 1 On diluent.
A material balance in modified naphtha insolubles showed that there was actually a decrease of 6.5% of the insolubles in the feed. Within experimental error, it clearly can be said that there was no adverse change in insolubles. With'ordinary visbreaking at the same conversion level there would have been about a 55% increase.
Example II In a batch run at 755-800 F. at -660 p. s. i. g. and 50 minute soaking time, using the same feed and diluent as in Example I, the conversion was somewhat greater as shown in the following tabulation.
In this run an increase of 3.3% in insolubles was found, again within experimental error no appreciable increase is noted.
The process canbe carried out in various ways, one of which is illustrated diagrammatically in the attached drawing. A crude oil may be fed from any suitable source of supply through a line 11 to a distillation unit 13 for taking off gasoline through a line 15, gas oil through line 17 and a bottoms fraction through line 19. The distillation unit may be of either the atmospheric or the vacuum type and other lines, not shown, may be pro= vided for taking off gas and other desired fractions.
The residuum is blended with a partially hydrogenated donor and diluent, as in Examples I and II and described more particularly below. This diluent enters through line 21 and the mixture passes through line 23 to the coil 25 and drum 27 of the visbreaker A. The soaker is best operated under pressure, preferably between 300 and 1000 p. s. i. g. and at a temperature of the range of about 750 to 950 F., preferably 800 to 900" F. The feed rate for diluent plus residuum should be between about 0.5 and 15 v./v./hr. A preferred feed rate is about 2 to 4 v./v./hr. The total visbreaker product is removed through a line 29 to a fractionator B.
In fractionator B, the C4-gases. are taken off through one or more lines 31, a C5 to 430 F. gasoline fraction through line 33, heating oil and gas oil through lines 35, 37 (in some cases these may be combined if desired), a selected diluent cut, boiling above 500 and below 1000 F., preferably boiling above 700 F. and up to 900 F. through line 39-, and a higher boiling residual fuel oil fraction through line 41. The latter may require some cutting back under some specifications c. g. for viscosity control. Hence provision is made to blend small quantities of the fractions from any or all the lines 35, 37, and 39 through lines 42, 43, 44, respectively. Suitable control valves, not shown, are provided as will be obvious.
The diluent fraction from line 39 is led into a hydrogenator C. In order to keep the concentration of condensed ring aromatics high, a thermal tar may be added continuously or intermittently to the diluent fraction through a line 45. Such tar fractions are available in adequate quantities around most modern refineries. It should have more or less the same boiling range as the fraction in line 39 though it may be substantially lower or even a little higher if desired.
The total diluent, including the thermal tar, has an initial boiling point of not less than about 500 F. Its boiling range spread is preferably not too wide, desirably from 50 to 200 F. The diluent is hydrogenated in a conventional manner, preferably using a sulfur insensitive catalyst. Hydrogenation pressure may be from 200 to 2000 p. s. i. g., preferably 500 to 1000. Gaseous hydrogen from any suitable source is fed through a line 47 at a rate sufficient to introduce 200 to 2000 s. c. f.
cracking of clarified oil. The residuum fraction from fractionator B is blended with a suitable flux stock or with any of the continuously boiling fractions from B as shown in the drawing. When the diluent cut is used as one of the blending stocks in the residual fuel it has the additional advantage of producing a low hot filtration sediment in the residual fuel. This is due to the peptizing action of the aromatic components of the diluent stream. It is necessary, of course, in such an operation to add additional thermal tar or other diluent source to maintain. high condensed ring content. This is added to the hydrogenation stage as shown.
The efficiency of the operation is shown by the reduced volume of good quality residual fuel made by this process. In visbreaking 'a certain Bachaquero 900 F.+ residuum 94 barrelsof specification residual fuel (modified naphtha insolubles limiting) is produced from every I00 barrels of crude. In contrast, by this process only 61 barrels of fuel are produced with a consequent increase in the yield of the more valuable distillate fractions.
, What is claimed is:
1. A process for reducing substantially the volume of a heavy fuel oil residuum having a measured content of naphtha insoluble and/or sediment components without substantially increasing said content, which comprises blending said residuum with 10 to 200% by volume of a hydrogen donor diluent obtained as stated thereinafter, passing said blend through a visbreaker under pressure in the range of 300 to 1000 p. s. i. g. and non-catalytically at a feed rate of 0.5 to 15 v./v./hr. and a temperature range of about 750 to 950 F., fractionating the visbroken blend to separate more volatile products, a predominantly aromatic condensed ring fraction boiling in a range with- 1' in the limits of 500 F. to 1000 F., and a heavy fuel (cubic feet under standard conditions) per barrel of corn- I bined diluent entering the hydrogenator C. Hydrogen rich gas leaving the hydrogenator through line 49 is recycled to line 47.
The diluent which has taken up enough hydrogen to be an effective donor, but is not nearly saturated, passes through line 51 from the hydrogenator C to line 21 where it blends with the residuum to be visbroken.
While the most important object in the present invention is the reduction of the volume of total heavy fuel oil without impairing its quality the gain in production of more volatile products is also considerable. When specification limits for insolubles in fuel oil are exceeded and the fuel must be cut back considerably any economic gains from the visbreaking are reduced or wiped out. By the present process, the content of asphaltenes and coke in the final bottoms is kept low-sometimes even below the content of the feed, while substantial visbreaking and conversion to more valuable products take place.
It will be obvious that some variations may be made in the process without departing from the spirit thereof. For example, the hydrogen for the process may be produced by reforming of natural gas, by the water gas reaction, or by hydroforming, etc. The original source of hydrogen donor diluent may be any refinery or coal tar fraction which has a boiling range and initial boiling point corresponding to or near that which is cut from fractionator B and which contains a relatively high concentration of fused ring aromatic compounds such as anthracenes, phenanthrenes, pyrenes and the like. A suitable diluent can be obtained, for example, from the 700900 F. fraction of the tar produced by thermal oil product, partially hydrogenating said condensed ring fraction by adding thereto 200 to 2000 s. c. f. of hydrogen per barrel, and recycling the hydrogenated fraction as diluent to blend with said original residuum.
2. Process according to claim 1 wherein a part of said condensed ring, fraction is blended with the heavy fuel oil product.
3. Process according to claim 1 wherein part of a more volatile fraction is blended with the heavy fuel oil product.
4. The process of claim 1 in which the residuum is utilized in an amount of 20 to volume percent, the visbreakingtemperature is in the range of 800 to 900 F., the feed rate is 2.to 4 v./v./hr. and the condensed ring fraction boils within the range of 700 to 900 F.
5. The process of claim 4 in which a minor proportion of a thermal tar prepared by the thermal cracking of a clarified oil is added to the recycled fraction.
References Cited in the file of this patent UNITED STATES PATENTS 2,197,460 Adams Apr. 16, 1940 2,381,522 Stewart Aug. 7, 1945 2,426,929 Greensfelder Sept. 2, 1947 2,436,257 Hansford Feb. 17, 1948 2,502,958 Johnson Apr. 4, 1950 2,620,293 Blue Dec. 2, 1952 2,670,322 Krebs Feb. 23, 1954 OTHER REFERENCES Sachanen: Chemical Constituents of Petroleum, page 274 (1945), Reinhold Publishing Corp., New York, N. Y.
Sachanen: Conversion of Petroleum, 2nd edition revised and enlarged, page 2 (1948), Reinhold Publishing Corp, New York, N. Y.