US3179586A - Process for preparing heavy fuel oils - Google Patents

Description

April 20, 1955 HONERKAMP 3,179,586

PROCESS FOR PREPARING HEAVY FUEL OILS Filed Nov. 24, 1959 mp8 F5 51 HBddItLLS I 2 P k 1 EINOZ Ln NOILVZIHQJ'IHSBGI g;

4" I-INOZ NOliVtIVdES o IuJ d 2 5o 3Noz NOUVNBEDOHGAH INVENTOR DONALD L. HONERKAMP add/W 1 44 ATTORNEY United States Patent filice 3,179,586 Patented Apr. 20, 1965 This is a process relating to the hydrogenation of petroleum fuel oils and more particularly to a hydrogenation process for producing heavy fuels with low sulfur content.

Various processes have proved to be of value in the desulfurizing of petroleum hydrocarbons in the past. These processes are of two general types, namely, catalytic hydrodesulfurization and contact hydrodesulfurization. The former encompasses those methods in which the sulfur contained in the charge stock is removed therefrom in the form of a gas such as hydrogen sulfide, by the action of a catalytic material having hydrogenating characteristics such as nickel, nickel oxide, the iron group metal molybdates, sulfides, molybdenum compounds, etc. The contact method on the other hand removes the sulfur by chemically combining it with a contact agent which should i be one possessing hydrogenating characteristics such as an iron group metal, metal oxide or combination thereof deposited on a carrier. The sulfur is removed from the charge stock by being absorbed as metallic sulfide on the contact agent and the process is discontinued when the iron group metal content of the contact has been substantially converted into iron group metal sulfide, and the contact is then regenerated.

Among the major difficulties encountered with these processes is the undue amount of hydrogen consumption resulting in the necessity of abnormally large facilities for the preparation, handling and storage of hydrogen. Therefore, ideally the petroleum industry is desirous of obtaining fuel oils having substantially all of the sulfur content removed while at the same time consuming only relatively small amounts of hydrogen. In the summer months local ordinances in smog prone areas specifically limit the allowable sulfur content in fuel oils burned Within the cities. An example is Los Angeles where a local Rule 62 was passed forbidding the use of fuel oils having a sulfur content greater than 0.5% during the summer smog season. Thus, as the commercially heavy fuels normally utilized today generally contain from about. 1 to 4% sulfur, it has become necessary to devise some method for reducing this sulfur content to satisfy regulations so that a heavy fuel of not greater than 0.5% sulfur is obtained. The method of this invention supplies asolution to these problems by producing heavy fuel with a low sulfur content. In the process of this invention an asphaltic petroleum oil of say at least about 1% sulfur is contacted with free hydrogen in a long-cycle, low-temperature hydrogenation zone and then the resulting constituents are passed into a flash separation zone Where the hydrogencontaining gases are separated from the normally liquid products. The liquid product is then passed into a second separating zone Where gasoline and heavier distillates are separated from the bottoms products. The hydrogen-containing gases separated from the liquid fraction in the first separation or flashing zone are passed. to a hydrodesulfurization zone where the gascontacts cycle oil, for instance, light cycle oil, heavy cycle oil or a mixture of both, at relatively low temperature and pressure conditions and the resulting products are then passed into a separating or flashing zone where the hydrogen-containing gases are separated from the normally liquid products. The separated hydrogen-containing gases may, if desired, be recycled back to the cycle oil hydrodesulfurization zone. The liquid products then pass into a stripping zone Where remaining hydrocarbon gases and hydrogen sulfide are separated and withdrawn. In this zone, small amounts of gasoline and naphtha may also be separated from the heavier constituents. The remaining higher-boiling heavier fraction is then blended with bottoms from the separation zone of the asphalt hydrogenation system. In this manner, a high quality, lowsulfur content fuel oil is produced which meets the requirements of local restrictions such as that of Los Angeles.

The starting materials or feedstocks of the hydrogenation zone of this process are petroleum hydrocarbons which normally have at least 1% sulfur such as reduced crude oil fractions boilingpredominantly above about 850 F. and preferably above about 950 F. Examples of the petroleumfeedstocks of the hydrogenation zone which are liquid at treating conditions, are residuals such as asphalts, tars, vacuum distillate bottoms. materials and the like. The reduced crude oils of this type generally contain along with sulfur other undesirable contaminants such as nitrogen, nickel, vanadium and the like.

Cycle oil is utilized as feedstock in the second hydrodesulfurization zone. Cycle oil boils generally in the gas oil range, e.g. primarily in the rangefrom about 370 to 950 F. and is a product of catalytic or thermal cracking or both and this product may contain minor amounts of other components such as aromatic extracts of petroieum oils and light petroleum oils from, for instance,-

atmospheric topping. The cycle oil utilized in this invention is usually produced by the cracking of straight run or recycle gas oils and normally contains an excess of about 0.5 percent of sulfur, preferably from about .5 to 2 percent sulfur. The cycle oil is frequently divided into light and heavy cycle oil. The light cycle oil generally has a boiling range. predominantly below about 700 F., preferably from about 370-650 F. .The heavy cycle oil normally has a boiling range primarily above about 600 F., preferably from about. 600-950 F. These cycle oils may be advantageously mixed, for instance, at least about 20% of each, and preferably the cycle. oil products from the hydrodesulfurization have a sulfur con-. tentof about 0.3 percent sulfur or less. The amount of light or heavy cycle oil used is a matter of economics and thus will vary With the feedstock employed, process utilized and products desired. 1

To more fully understand the nature of my invention, reference should be made to one embodiment of this invention shown in the accompanying diagram in which a crude oil fraction boiling predominantly above 850 P. such as a vacuum asphalt in line 1 is contacted with hydrogen from line 2 in a hydrogenation zone having a reactor 3 at a relatively low temperature and pressure.

amasse as The constituents are then passed through line 4 into a lower pressure flash zone 5 which is normally Within 100 pounds pressure per square inch below that of the hydrogenation zone reactor 3 and also higher than the pressure in the desulfurization zone 15 to avoid the necessity for compressing the off-gases from zone 5 before they enter the cycle oil desulfurization reactor. In the flash zone 5, the hydrogen-containing lighter gases are separated into line 6 and the heavier constituents are passed through line 7 into separation zone 8 where the'gasoline and distillates are separated by lines 9 and 10 respectively and then the heavier bottoms products, for instance, boiling primarily above about 650 F., are passed into line 11. Excess light hydrogen-rich gases are passed by lines 6 and 31 from the separation zone into line 21. The majority of the hydrogen-containing gas from flash zone 5 is passed into line 6 and then into line 114- where the hydrogen-containing gas is contacted with a light cycle oil from line 12 and/or heavy cycle oil from line 13. These constituents in line 14 then pass into the hydrodesulfurization zone 15 which is at low temperature and pressure and then resulting products are passed to lower pressure flash zone 17 where the light hydrogen-containing gases are passed off through line 18. These gases may be recycled into the system by Way of line 14. The

recycle line" 18 can beequipped with gas repressuring apparatus and flash Zone '17 is usually operated at a'pressurenot lower than about 100 p.s.i.g. below the pressure in the desulfurization zone 15 so as to avoid excessive recompression costs. The higher-boiling heavy constituents pass through line 19 into stripper 20 where the light gases such as hydrogen sulfide and hydrocarbon gases are passed through line 22 into line 21 for removal. At this point the lighter-boiling products such as gasoline and naphtha are taken off by line 23 and the heavier gas oil boiling range products remaining, boiling principally in the range of about 400 to 850 F, are passed from line 24 into line 25 and then blended with high-boiling heavy constituents from the hydrogenation zone in line 11. The combined product'can be removed in line 32. If desired, a light gas oil fraction can be taken from zone 8 and passed by line to zone 15 where it serves as part of the feed and to reduce the sulfur content of the final heavy feed blend.

In the asphalt hydrogenation zone the pressure may vary from about 700 to 1500 p.s.i.g. with a preferred pressurebeing about 1200 to 1500 p.s.i.g. The temperature range is normally from about 750 to 820 F. with a preferred temperature of from about 780 to 800 F. The space Velocity in the hydrogenation zone may vary from about 0.1 to l WHSV with a preferred WHSV being from about 0.3 to 0.7. Normally pressures above 1500 p.s.i.g. are not economically feasible because of high capitalv costs and hydrogen consumption rate taken in conjunction with the relatively low value of the heavy fuel products. Molecular hydrogen is supplied to the 7 reaction zone at the rate of about 1500 to 7500 standard cubic feet per barrel of asphalt, preferably about 2500 to 5000. A combination of higher temperature with the low space velocity would undesirably produce high I conversion to light products and result in relatively short operating cycles. The off-gas from the hydrogenation is passed into the cycle oil hydrodesulfurization zone which is maintained at a pressure from about 400 to 700 p.s.i.g. with a preferred pressure being from about 400 to '600 p.s.i.g. The temperature in the hydrodesulfurization zone normally varies frornabout 650 to 775 F. and there supplied at the rate'of about 1000 to 5000 standard cubic feet per barrel of cycle oil. When treating light and heavy cycle oils in separate reactions, the preferred conditions include temperatures of about 700 to 775 F., space velocities of about 0.5 to 2 WHSV and hydrogen gas rates of about 2500 to 5000 s.c.f./bbl. for heavy cycle oil and temperatures of about 650 to 770 F., space velocities of about 1 to 3 WHSV and hydrogen gas rate of about 1000 to 4000 s.c.f./bbl. for light cycle oil.

The respective hydrogenation and desulfurization catalysts can be selected from the generally known commercially available solid sulfur-resistant catalysts such as cobalt-molybdenum on alumina, nickel-tungsten on alumina, cobalt-molybdenum on silica stabilized on alu mina and the like and the same or a different catalyst may be utilized in the hydrodesulfurization and/or hydrogenation zones of this invention. Preferably, when a cobalt-molybdenum catalyst is employed there is from 2 to 5% C00 and from 5 to 15% M00 with the remainder being alumina. V

I The following example will serve to illustrate some of the advantages of this invention.

EXAMPLE I commercial -cobalt-molybdena-alumina catalyst A containing 8.5% M00 and 2.5% cobalt. Molecular hydrogen is introduced into the hydrogenating .zone at a rate of 6000 standard cubic feet per barrel of asphalt and this zone is maintained at a temperatureof about 790 F., a pressure of about 1500 p.s.i.g. and a space velocity WHSV of .3. The hydrogen consumption was 900 standard cubic feet per barrel of asphalt. The constituents are then passed into a flash separation zone at a temperature of about 200 F. where the hydrogen-containing gases are separated and then the liquid constituents are passed into an atmospheric topping zone where unflashed gas, 300 barrels per day of gasoline, and 2500, barrels per day of distillates are topped off. The bottom product is 5390 barrels per day boiling above 650 F.

Hydrogen-containing gas from the initial'separating zone of the hydrogenation process is contacted in separate blocked-out operations with 3000 barrels per day of light cycle oil and 1500 barrels per day of heavy cycle oil boiling in a hydrodesulfurization zone in the presence of catalyst A and under the conditions shown in Table I. The products from this zone are then passed into a flash zone where the hydrogen-containing gases are flashed off and the remainder of the products are passed into a stripper where the remaining hydrocarbongases, hydrogen sulfide gas and the like are separated. amounts of gasoline and naphtha are separated from the heavier constituents. The remaining heavier constituents, i.e. 3,070 barrels per day of light cycle oil and 1540 barrels per day of heavy cycle oil analyzing as shown in Table I, are then blended with the higher boiling heavier constituents prepared in the atmospheric topping zone of the asphalt hydrogenation section. Thus, 10,000 barrels per dayof a fuel oil having an API of 19.6 and a sulfur content of .48% is produced. Also produced each day are 1600 barrels of distillate fuel, 900 barrels of naphtha, and 300 barrels of gasoline. The final heavy fuel blend will normally contain at least about 25% of the heavy products from each of the hydrogenation and desulfurization zones.

The following table which shows conditions of the above example and the physical properties of the product obtained will serve to illustrate the advantages of the process of this invention whereby a fuel oil having a sulfur content of less than .5% is obtained.

Also small V Table I Asphalt Light cycle oil Heavy cycle oil Product Total liquid prod.

Feed F.+ Feed Prod.

Prod.

Feed

Prod. Heavy fuel blend Operating conditions:

Pressure, p.s.i.g Temperature, "F Space velocity,

I-Iz-containing gas rate, s.c.f.[b.

Stream time, B. 011/ #Cat.

Hydrogen cons,

Bromine N Carbon residue Aniline Pt F 0 insolubles Percent C Percent H Percent S-..

1(SUS).

I claim:

1. A process for manufacturing a heavy fuel comprising contacting a residual, asphaltic petroleum hydrocarbon boiling predominantly above about 950 F. and having at least about 1% sulfur with hydrogen gas and a hydrogenation catalyst in a hydrogenation zone at a pressure of from about 1200 to 1500 p.s.i.g., a space velocity of from about 0.3 to 0.7 WHSV and a temperature of from about 780 to 820 F., separating hydrogen gas from the liquid product, separating lower-boiling distillate from the higher-boiling bottoms product, contacting said separated hydrogen gas with a petroleum cycle gas oil boiling in the range of about 370 to 950 F. and having at least about .5% sulfur, in a hydrodesulfurization zone containing a hydrodesulfurization catalyst and at a pressure of from about 400 to 700 p.s.i.g., a space velocity of from about .5 to 3 WHSV and a temperature of from about 650 to 775 F., separating gas oil boiling range hydrocarbon from the resulting liquid product, and blending said bottoms product from the hydrogenation 2 (SFS).

5390 B/D 650+ product.

3070 B/D desultun'zed li ht cycle oil.

1640 B/D desulfurized heavy cycle oil.

zone and said gas oil boiling range hydrocarbon from said desul-furization zone to provide a low sulfur-containing heavy fuel.

2. The method of claim 1 in which the catalyst in both reaction zones is cobalt-molybdena-alumina.

References Cited by the Examiner UNITED STATES PATENTS 2,773,008 12/56 Hengestebeck 208-89 2,844,517 7/58 Inwood 208-210 2,878,179 3/59 Hennig 208-210 2,892,774 6/59 Porter et a1. 208-218 2,951,032 8/60 Inwood 208-210 2,983,676 5/61 Howland 208-254 3,011,971 12/61 Styngstad et a1 208-216 ALPHONSO D. SULLIVAN, Primary Examiner.

ALLAN BQEI'ICHER, MILTON STERMAN,

' Examiners.

Claims (1)

1. A PROCESS FOR MANUFACTURING A HEAVY FUEL COMPRISING CONTACTING A RESIDUAL, ASPHATIC PETROLEUM HYDROCARBON BOILING PERDOMINATNTLY ABOVE ABOUT 950*F. AND HAVING AT LEAST ABOUT 1% SULFUR WITH HYDROGEN GAS AND A HYDROGENATION CATALYST INA HYDROGENATION ZONE AT A PRESSURE OF FROM ABOUT 1200 TO 1500 P.S.I.G., A SPACE VELOCITY OF FROM ABOUT 0.3 TO 0.7 WHSV AND A TEMPERATURE OF FROM ABOUT 780 TO 820*F., SEPARATING HYDROGEN GAS FROM THE LIQUID PRODUCT, SEPARATING LOWER-BOILING DISTILLATE FROM THE HIGHER-BOILING BOTTOMS PRODUCT, CONTACTING SAID SEPARATED HYDROGEN GAS WITH A PETROLEUM CYCLE GAS OIL BOILING IN THE RANGE OF ABOUT 370 TO 950*F. AND HAVING AT LEAST ABOUT .5% SULFUR IN A HYDRODSULFURIZATION ZONE CONTAINING A HYDRODESULFURIZATION CATALYST AND AT A PRESSURE OF FORM ABOUT 400 TO 700 P.S.I.G., A SPACE VELOCITY OF FROM ABOUT .5 TO 3 WHSV AND A TEMPERATURE OF FROM ABOUT 650 TO 775*F., SEPARATING GAS OIL BOILING RANGE HYDROCARBON FROM THE RESULTING LIQUID PRODUCT, AND BLENDING SAID BOTTOMS PRODUCT FROM THE HDROGENATION ZONE AND SAID GAS OIL BOILING RANGE HYDROCARBON FROM SAID DESULFURIZATION ZONE TO PROVIDE A LOW SULFUR-CONTAINING HEAVY FUEL.

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