Chemistry of inorganic compounds – Sulfur or compound thereof – Binary compound
Reexamination Certificate
1999-06-02
2001-09-04
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Sulfur or compound thereof
Binary compound
C423S415100, C423S565000, C423S592100, C075S622000
Reexamination Certificate
active
06284214
ABSTRACT:
Many refiners are now forced to process more difficult stocks, which are heavier and more metals contaminated. Many heavy crudes contain significant amounts of vanadium and sulfur and frequently with lesser amounts of Ni, Fe and other metal compounds.
Such heavy crudes are difficult to process catalytically, so an initial stage of thermal processing, usually some form of coking, is typically used to free distillable, relatively metals free products from vanadium containing coke. The coker gas oil and coker naphtha are essentially free of metals and may be processed by conventional catalytic upgrading processes to produce high quality transportation fuels and other hydrocarbon products. Unfortunately, coking of these difficult crudes produces large amount of coke, a solid product with an enhanced concentration of vanadium and sulfur and other metals present in the charge to the coker.
Many cokers produce coke which is so contaminated with metals and sulfur that it has little value as fuel. The sulfur generally precludes use of coke in cement kilns. Such materials usually have enough vanadium to cause processing problems but too low a vanadium concentration to make vanadium recovery economically attractive.
Some coking processes, such as fluid bed cokers, especially those employing gasifiers, can produce large amounts of fine, low density coke particles which is especially difficult to treat using conventional technology.
To illustrate just how difficult it is to process vanadium rich cokes, some representative prior art processes are reviewed below.
U.S. Pat. No. 4,203,759, Metrailer et al, PROCESS FOR THE PREPARATION OF A VANADIUM-CONTAINING METALLIC ASH CONCENTRATE, taught heating partially gasified coke with oxygen containing gas to produce low density ash. Most ash particles produced had a diameter of less than 1 micron. The fine ash was readily processed with sulfuric acid to recover vanadium.
U.S. Pat. No. 4,243,639, Haas et al, METHOD FOR RECOVERING VANADIUM FROM PETROLEUM COKE, taught gasifying the coke with steam in the presence of an alkali metal salt to improve V recovery during subsequent processing steps.
U.S. Pat. No. 4,345,990, Fahlstrom et al, METHOD FOR RECOVERING OIL AND/OR GAS FROM CARBONACEOUS MATERIALS, taught use of two molten baths to process a variety of carbon containing wastes. A lead or zinc first bath operated at 500C. to thermally devolatilize the carbonaceous material, while the second bath of molten iron operated at 1200 C. and operated with oxygen to gasify residual quantities of carbon.
U.S. Pat. No. 4,443,415, Queneau et al, RECOVERY OF V
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AND NICKEL VALUES FROM PETROLEUM COKE, taught slurrying coke in an aqueous solution of sodium carbonate to increase V recovery.
U.S. Pat. No. 4,708,819, Vasconcellos et al, REDUCTION OF VANADIUM IN RECYCLE PETROLEUM COKE, taught the problems of high vanadium levels during partial oxidation (the vanadium forms eutectics with refractory walls, melting them). The vanadium content of recycled, unconverted coke was reduced by froth flotation treatment.
U.S. Pat. No. 4,816,236 Gardner, RECOVERY OF VANADIUM AND NICKEL FROM PETROLEUM RESIDUES, taught recovering vanadium from various Flexicoke residues with varying V contents and particle sizes. The patent reported that Flexicoke from the heater bed had 1-5 wt % vanadium pentoxide, while coke from the cyclone venturi fines had 8-12 wt % vanadium pentoxide. Coke from the wet scrubber had as much as 20 wt % vanadium pentoxide. The patentee taught mixing coke with NaOH, burning and then leaching to recover vanadium. A majority of the Ni was reported to be left in the solids after the leach step.
U.S. Pat. No. 5,259,864, Greenwalt, METHOD OF DISPOSING OF ENVIRONMENTALLY UNDESIRABLE MATERIAL AND PROVIDING FUEL FOR AN IRON MAKE PROCESS E.G., PETROLEUM COKE, taught using a sulfur and heavy metal containing petroleum coke in a melter. The coke was mostly burned to form a fluidized bed of coke which was then reacted with ore and oxygen to make molten iron or steel preproducts. A slag layer contained sulfur freed during combustion of the petroleum coke.
U.S. Pat. No. 5,277,795, Thornhill et al, PROCESS AND APPARATUS FOR RECOVERING HEAVY METAL FROM CARBONACEOUS MATERIAL, taught burning petroleum coke to produce ash then processing the ash to extract metallic compounds.
U.S. Pat. No. 5,324,341, Nagel et al, METHOD FOR CHEMICALLY REDUCING METALS IN WASTE COMPOSITIONS, taught molten metal processing of metal containing wastes. Multiple reducing agents reduced oxygen-containing metals compounds in a metal-containing waste composition. Claim
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mentioned use of an oxide of V as an oxidizing agent.
U.S. Pat. No. 5,427,603, Samant et al, METHOD OF TREATING A VANADIUM-CONTAINING RESIDUE, taught processing petroleum coke with air at 850C. in a fluidized bed with an inert bed of granular iron oxide with an oxygen partial pressure between 10-4 bar and 10-6 bar to produce ash. The ash was then processed over a magnetic separator to recover the inert iron oxide for recycle.
U.S. Pat. No. 5,484,554 Vuoung et al, OXIDANT INJECTION FOR IMPROVED CONTROLLED OXIDATION, taught processing of coke in a partial oxidation reactor. The V in the coke forms a V rich slag in the reactor.
While not related directly to processing coke, U.S. Pat. No. 4,071,355, Staggers, RECOVERY OF VANADIUM FROM PIG IRON, taught removal of vanadium from pig iron to produce a vanadium rich slag by oxidizing molten pig iron at 2600-2900 F.
The teachings of these patents, which are incorporated by reference, could be summarized as follows.
Vanadium in petroleum containing coke is difficult to recover directly, that is, from the coke, because it is in a form which does not lend itself to conventional leaching approaches. The carbon, probably present in the form of condensed chelating structures, effectively shields significant portions of the metal from conventional leaching solutions.
Vanadium in coke can be recovered much more readily after combustion, because the vanadium in the ash produced is more susceptible to leaching, though even here some treatment, such as with sodium carbonate or sodium hydroxide was needed to improve metal recovery during leaching.
Vanadium in coke is always found with sulfur. The conventional way to deal with sulfur in steel making is to make slag with the sulfur.
We discovered that a molten metal process, originally developed to produce high purity hydrogen or synthesis gas from various waste streams, could be modified to process vanadium containing coke, dissolve the vanadium in its metallic state into the iron bath and reject much, but not all of the sulfur in the coke as H2S which could be processed in a Claus unit to recover elemental sulfur. We also discovered a way to enhance sulfur removal, by adding various agents which created a reducing atmosphere in the bath and promoted removal of dissolved sulfur as H2S. It was even possible to reduce or eliminate the need for sulfur capture agents and an accompanying sulfur rich slag, while processing V and S containing coke.
Details of the basics or a preferred molten metal process are disclosed in one or more of the following patents, which are incorporated by reference.
U.S. Pat. No. 5,755,839, MOLTEN METAL REACTOR SWING SYSTEM AND PROCESS.
U.S. Pat. No. 5,645,615, MOLTEN DECOMPOSITION APPARATUS AND PROCESS.
U.S. Pat. No. 5,577,346 MULTI-ZONE MOLTEN-METAL HYDROGEN AND FUEL GAS GENERATION PROCESS.
U.S. Pat. No. 5,435,814, MOLTEN METAL DECOMPOSITION APPARATUS.
The process defined by the above four patents could tolerate a great many feeds, including coal and trash, but was primarily directed to production of relatively pure hydrogen gas at superatmospheric pressure. This work was not directed toward vanadium recovery from petroleum coke, ignored the problem of S/V containing coke, and did not suggest use of reducing conditions in the bath during V capture, nor use of gaseous reducing agents to continuously, or at the end of a cycle, strip sulfur from the molten metal bath as H2S.
Our process used a special form of molten metal processing to d
Holcombe Thomas C.
Malone Donald P.
Griffin Steven P.
Hobbes Laurence P.
Marathon Ashland Petroleum LLC
Stone Richard D.
Vanoy Timothy C
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