Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group vb metal
Reexamination Certificate
2001-06-05
2003-11-25
Bell, Bruce F. (Department: 1746)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group vb metal
C423S063000, C423S067000, C423S511000, C423S544000, C423S549000, C429S101000, C429S105000, C429S204000, C429S205000, C252S062200, C252S506000, C252S520400, C205S496000, C205S554000
Reexamination Certificate
active
06652819
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the production of a high purity vanadium compound from vanadium-containing carbonaceous residues containing at least about 20% by weight of carbon and at least about 1% by weight of vanadium, each on dry basis, by combined dry and wet treatments.
Various processes have been hitherto proposed to recover vanadium from vanadium-containing carbonaceous residues. Generally adopted are wet treatment methods in which a mixture of the carbonaceous residues and water is subjected to multi-stage leaching and precipitation treatments through pH adjustment and oxidation/reduction (JP-A-H08-325651 and H10-251025). Wet treatment methods require complicated troublesome repetition of steps for isolating vanadium from other metals. Further, since vanadium content in the carbonaceous residues is low, leaching of vanadium therefrom cannot be efficiently performed.
To cope with the above problems, dry treatment methods have been proposed (U.S. Pat. Nos. 3,661,543, 3,702,516, 3,759,676, 4,203,759, 4,420,464, 4,816,236, 5,277,795, 5,466,383 and 5,670,061) in which vanadium-containing carbonaceous residues are combusted to remove carbon to form vanadium-concentrated ash from which vanadium is subsequently recovered by leaching with a strong alkali or acid. However, the dry treatment methods in which the carbonaceous residues are mixed with alkali metal hydroxides or carbonates and the mixture is combusted in an oxygen-containing atmosphere to remove carbon with the simultaneous conversion of vanadium into water-soluble fused mixture still have problems. In particular, the dry treatment methods require a relatively large amount of expensive alkali metal compounds in the combustion stage and a relatively large amount of strong alkali or acid in the leaching stage.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an economical process which can efficiently produce a high purity vanadium compound from vanadium-containing carbonaceous residues.
It is a special object of the present invention to provide a vanadium sulfate electrolyte solution.
In accomplishing the above objects, the present invention provides a process for the production of a vanadium compound from carbonaceous residues containing at least about 20% by weight of carbon and at least about 1% by weight of vanadium, which comprises the steps of:
(a) combusting the carbonaceous residues at a temperature of 500-690° C. using an oxygen-containing gas to form vanadium-containing combustion residues;
(b) heating the vanadium-containing combustion residues at a temperature T in ° C. under an oxygen partial pressure of at most T in kPa wherein T and P meet with the following conditions:
log
10
(
P
)=−3.45×10
−3
×T+
2.21
500
≦T≦
1300
to obtain a solid product containing less than 5% by weight of carbon and vanadium at least 80% of which is tetravalent vanadium oxide;
(c) mixing the solid product with water and sulfuric acid to form a mixture and to selectively leach tetravalent vanadium ion while maintaining the pH of the mixture in the range of 1.5-4;
(d) separating a liquid phase from the mixture;
(e) adding an alkaline substance to the liquid phase to adjust the pH thereof in the range of 4.5-7.5 and to selectively precipitate vanadium ion as a tetravalent vanadium compound; and
(f) separating the precipitates obtained in step (e).
In another aspect, the present invention provides a method of preparing a vanadium sulfate electrolyte for a redox flow battery, which comprises subjecting a vanadium sulfate solution containing nickel ion to electrolytic reduction in a cathode chamber in the presence of tin ion to decrease the oxidation-reduction potential of the solution to −0.2 V or below on the basis of the standard hydrogen electrode, and to precipitate and remove nickel ion from the solution.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
Carbonaceous residues containing at least about 20% by weight, generally at least about 50% by weight, of carbon and at least about 1% by weight of vanadium are used as a raw material for the production of a vanadium compound according to the present invention. Such residues are generally comprised of inorganic substances containing vanadium and a carbonaceous material containing heavy hydrocarbons. Examples of such carbonaceous residues include carbon sludge from a heavy oil gasification reactor, fly ash from a heavy oil combustion boiler and petroleum pitch or coke from a heavy oil thermal cracking reactor.
As used herein, “carbon sludge from a heavy oil gasification reactor” refer to a wet solid containing carbon and ash and obtained in gasifying heavy hydrocarbon oil, such as vacuum residue of petroleum crude, by partial oxidation. The gas product from the gasification reactor is washed and purified with water. The used washing water which is obtained as a by-product in the purification of the gas product is in the form of a soot-containing water slurry (soot water). The soot water is filtered to give the wet solid containing carbon and ash.
As used herein, “fly ash from a heavy oil combustion boiler” refer to a solid containing (a) carbon produced in combustion of heavy oil in a boiler, (b) ash derived from heavy metals, such as vanadium, nickel and iron, contained in the heavy oil and optionally (c) ammonium sulfate formed when ammonia is fed for the purpose of preventing corrosion of a duct and a dust collector by sulfuric anhydride (SO
3
).
As used herein, “petroleum pitch or coke from a heavy oil thermal cracking reactor” refer to pitch or coke produced as by-product by cracking petroleum heavy oil in a reactor such as a delayed coker, flexicoker or visbraker and containing carbon as a major ingredient and heavy metals such as vanadium and nickel derived from the heavy oil.
As used herein, “at least about 20% by weight of carbon” refer to an amount of carbon element of at least about 20% by weight on dry basis when measured in accordance with the analytical method defined in Japanese Industrial Standards JIS M 8813.
The carbonaceous residues used as a raw material in the present invention may contain water in an amount of 10-90% by weight. When the water content is high, it is preferred that the carbonaceous residues be dried at a temperature of about 400° C. or lower. Too high a drying temperature above about 400° C. is disadvantageous because of significant dust formation. When a combustion step, which will be described hereinafter, is carried out using a fluidized bed system, it is desired that the dried carbonaceous residues be ground to a weight average particle diameter of 400 &mgr;m or less, more preferably 200 &mgr;m or less, for reasons of fluidizability and easiness in handling of the carbonaceous residues.
In the process of the present invention, the carbonaceous residues are subjected to a combined dry and wet treatment.
In the dry treatment, the carbonaceous residues are combusted at a temperature of 500-690° C. using an oxygen-containing gas to form vanadium-containing combustion residues (step (a)). A combustion temperature below 500° C. is insufficient to reduce the amount of carbon within an acceptable period of time. Too high a combustion temperature above 690° C. causes fusion of vanadium oxide (e.g. V
2
O
5
) and agglomeration of the combustion residues so that difficulties are caused for handling thereof. Further, such a high temperature will cause vaporization of vanadium compounds which then deposit on inside walls of the combustion furnace and its associated pipes. Generally, the combustion is performed so that the carbon content is reduced to less than 10 weight.
The vanadium-containing combustion residues are then heated at a temperature T in ° C. (degrees centigrade) under an oxygen partial pressure of at most P in kPa wherein T and
Shiroto Yoshimi
Wakabayashi Ataru
Bell Bruce F.
Chiyoda Corporation
Lorusso, Loud & Kelly
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