CA1150478A

CA1150478A - Process for the production of vanadium carbide

Info

Publication number: CA1150478A
Application number: CA000365770A
Authority: CA
Inventors: Harry E. Gardner
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1979-12-26
Filing date: 1980-11-28
Publication date: 1983-07-26
Also published as: DE3046411A1; BE886836A; AU542768B2; NO803905L; JPS6041613B2; DE3046411C2; JPS56100124A; ZA807418B; SE8008940L; BR8008419A; FR2472537A1; IT1128717B; IT8050436A0; FI66334C; LU83026A1; FI66334B; FI803989L; NZ195673A; JPS6042215A; DD202278A5

Abstract

PROCESS FOR THE PRODUCTION OF VANADIUM CARBIDE

ABSTRACT OF THE DISCLOSURE
A process is provided for the production of vanadyl hydrate including solvent extraction and stripping steps. The vanadyl hydrate is then reacted with carbon to produce vanadium carbide.

SPECIFICATION

1.

Description

~ 11061 ~-~,.5~347B

This inventiDn relates to a process for the pro-ductiDn of vanadium carbide V2C. This invention alsb relates to a process fDr the prDductiDn of vanadyl hy-drate, VO(OH)2.xH20, which is used to produce vanadium carbide by the method of this invention. In particular, this invention relates tD a solvent extraction, stripp-ing prDcess for the prDduction Df vanadyl hydrate which is further reacted with carbon by the method Df this in-ventlDn tD produce vanadium carbide. Vanadium carbide is well knDwn in its use in the prDduction of steel.
In accordance with the present invention an iDnic aqueDus vanadium solution, such as a water leach solu-tiDn containing sodium metavanadate, derived from vana-dium ores or cDncentrates, is~provided. To this water leach solution sulfur diDxide, S02, and sulfuric acid, H2S04, are added in amounts described in detail herein-after. The solutiDn which contains vanadyl ion is then solvent ex~racted with an organic sDlvent, described in mDre detail hereinafter. The rich Drganic sDlvent containing the vanadyl ion is then stripped with ammonium hydroxide, NH~OH, causing the vanadyl iDn to precipitate as vanadyl hydrate, VO(OH)2~XH20~ where x is unknown, as the vanadyl ion is rem~ved frDm the solvent-In accordance with the present invention, the vanadyl hydrate is blended with carbon, pelletized, and dried in the absence Df oxygen and then furnaced to form vanadium carbide.
The method Df ~e inventiGn will becDme more clear when cDnsidered together with the accDmpanying drawing which is set fDrth as being merely illustrative of the $~

~- s ~ 11061 47~ --invention and is not intended to be limitative thereof and wherein:
Figure 1 is a simplified flow diagram illustrating an embDdiment of the method of the invention.
The water leach solution used in the practice of this invention is typically derived from the conven-tional processing of vanadium ores Dr concentrates, such as the water leach solution from a roasted vanadium ore.
Typical vanadium processes are described in U. S. Patents 3,132,920; 3,132,390; and 3,320,024. It is preferable that the water leach solution be a true solution to avoid cDntamin~tion Df the prDduct and to ease process-ing. It has been found that the present invention only works for vanadium in an aque~us solution. Typically a water leach solution is an ionic solution of sodium metavanadate, NaV03, with minor amounts of chloride, sulphate, phosphate~ and silicate salts of sodium, calcium, potassium, magnesium,and Dther alkali and alkaline earth metals, and other impurities usually found in water leach solutions derived from the processing of vanadium ores or cDncentrates. For the process of this invention to work satisfactorily the vanadium must be in solution, HDwever9 the vanadium in solution may exist com~ined with other elements as an ionic species such as a vanadate ion in an i~nic solution of sodium metavanadate.
The vanadium in solution may also be derived from alkali, or ~lkaline earth salts ~f pyrovanadate, orthovanadate, decavanadate, Dr any other soluble form of vanadium salts.
Particularly in the practice of this inventiDn, the source of ~anadium is sodium metavanadate. The .. . .

.

~ , ` 11061 7~3 concentration of sodium metavanadate in water is not critical and any concentration is satisf~ctory in the practi~e of this inven~ion 85 long as the sodium metavanadate is in solution. While there is no preferred concentration for the sodium metavanadate in solution it may be desirable at times in order to save processing expenses to use as high a concentratiDn as possible. Sulfur dioxide and sulfuric acid are then added tD the water leach soluti~n. Preferably, the sulfur dioxide is added first and then the sulfuric acid in order to avoid precipitation Df vanadium as ~sodium hexavan~date if the sulfuric acid is added first. The sulfur dioxide is added in a sufficient quantity to reduce the vanad;um ion in solutiDn from V+5 to V
valence. Enough sulfuric acid is then added to obtain a pH in the range frDm about 1.0 to about 3.0, preferably about 1.5 to about 3,0, ~nd more preferably abDut 2.0, to obtain an optimum pH fDr solvent extractiDn whose efficiency is sensitive to the pH. In ~ cDntinuous pro-cess the sulfur di~xide and the sulfuric acid can be added simultaneously tD ~he water leach solutiDn. While sulfuric acid is the preferable acid tD use, other nDn-oxidizing acids such as hydrochloric acid may be used.
Nitric acid should not be used since it is an oxidi~ing acid. Acetic acid shDuld not be used since it is not strong enough. PhDsphoric acid should also nDt be used since it contaminates the product. The V+5 to Vt4 re-ducti~n is measured by e,m,f. potential. ~he V+5 to V~4 reduction is cDnsidered cDmplete when the optlmum e.m.f. pDtential obtained is abDut -200 millivolts at a 4.

, , .

; ; 11061 ~,5i~,r, ~7~3 pH2. An e~m.f. potential in the range of fro~ about -150 to about -300 millivolts is also cDnsidered satisfactDry ln the practice of this inventiDn. V+5 exists in the metavanadate ion, V03, and V~4 exists in the vanadyl ion, V0 2. The concentratiDn of sulfuric acid is not critical and can be added in any concentration but a higher con-centration is desirable in order to avoid dilution of the solution. The sulfur dioxide is preferably added as sulfur diDxide gas but it can also be added in the form Df sulfurDus acid or as a sulphite salt.
The acidified and reduced solution cDntaining vana-dyl ion is now solvent extracted, preferably, in at least a two stage countercurrent solvent extractor. The solvent extraction step will becDme more clear when considered along with the illustration of Figure 1. The acidified and reduced solution containing the vanadyl ion 1 enters stirred mixer tank 14 Df Stage I of the countercurrent extraction step and is mixed with the organic phase stream

2 from settler tank 17 D Stage II. Mixed liquid 3 from mixer tank 14 overflows into settler tank 15 of Stage I
with the organic phase 5 rising to the top and the aqueDus phase 4 to the bottom of settler tank 15. The rich Drganic solvent phase 5 of settler tank 15 is sent as stream 6 to further processing described hereinafter.
The aqueous phase 4 Df settler tank 15 is then transferred as stream 7 tD mixer tank 16 of Stage II wherein it is mixed with lean organic solvent 9 and sulfuric acid 10.
l~e mixed liquid 8 overflows mixer tank 16 i~tD settler ~ank 17 wherein the organic phase 12 rises to the top 3f settler tank 17 and the aqueous phase 11 settles to the ,, ! 11061 bottDm of settler tank 17. The aqueous phase 11 which is the raffinate, also called tails, is discarded as waste 13. The organic phase 12 of settler tank 17 is sent to mixer tank 14 as stream 2. While the two stage countercurrent extract~on step has been shown in Figure 1 in a simplified fashion more sophisticated equipment may be used including more than two stages without departing fr~m the scope of this invention. One stage may be used but this is not deemed to be as effective as at least tWD countercurrent extraction stages. It is conceivable that a cocurrent extraction step may be used but that would also be less effective than a countercurrent extraction stepO The solvent extraction step is a puri-fication step in the process ~f this invention.
Because the solvent extraction step consumes acid, sulfuric acid or other non-oxidizing ~cid is added to the Stage II mixer tank 16 to control the pH at an optimum level of from about 2.5 to about 3, preferably from about 1.5 to about 3.5 in Drder ~o obtain the most efficient extraction of the van~dyl ion by the organic sDlvent.
The preferred organic solvent fDr use in the extrac-tion step is di-2-ethyl hexyl phosphoric acid as a 10%
solution by volume. In addition the solvent solution contains 3% by volume of isodecanol (isodecyl-alcohol), and 87% by -~lume of kerosene as a diluant. The di-2-ethyl hexyl phosphDric acid does the actual extracting of vanadium from the aqueous sDlution by complexing with it. The isodecansl helps keep the vanadium ~omplex in solution. Other sDlvents have n~t been used but it is very conceivable that others will work such as hepta-~ ~ 11061 ~ 47 ~

decyl-phosphoric acid in mixture with lsodecanol and kerosene. The volume percentages of the compDnents of the organic solvent can be varied by those skilled in the art withDut departing from the scope or purpose of the J
invention.
The rich organic solvent phase 5 cDntaining the vanadyl ion is then sDlvent stripped and thickened. This is ~ccomplished by first sending the rich organic solvent phase as stream 6 to mixer tank 20 wherein it is mlxed with ammDnium hydroxide 21 and a recycle stream 22 con-taining recycled aqueous solution 23 from settler-thickener tank 24 and aqueous filtrate 25 from filter 26.
It is deemed novel to use ammonium hydroxide tD strip vanadium from the solvent by chemically reacting with the solvent to form the ammonium salt Df di-2-ethyl hexyl phosphoric acid, thus regenerating the solven~.
Sufficient excess ammonium hydroxide is added to mixer tank 20 to strip the vanadium from the solven~. In the previsus extraction step ammonium iDn is exchanged for vanadyl ion, while in the stripping step the vanadyl ion is replaced with the ammDnium ion. In the stripping step the vanadyl iDn precipitates as vanadyl hydrate, VO(OH)2.xH20, where x is unknown, as vanadyl iDn is remDved from the solventO
The stripped mixture 27 fr~m mixer tank 20 overflows into se~ler-thickener tank 24, wherein three phases fDrm, an organic phase 28 on top CQmprising lean sslvent which is sent to extraction Stage II as stream 9, below the organic phase 28 an aqueous solution phase 29 which contains excess ammonium hydroxide which is then combined ~50~7~

with aqueous filtrate 25 frDm filter 26 and sent as stream 22 to mixer tank 20 combined with ammonium hy-droxide 21; and a solid phase 30 comprising vanadyl hy-drate which settles to the bottom Df settler thickener tank 24, which is sent as stream 31 to filter 26. It is novel and unexpected that three phases form in settler thickener tank 24 and alsD that vanadyl hydrate separates out gs a third phase rather than as an emulsion.
The filtrate 25 from filter 26 is cDmbined with the aqueDus solution stream 23 from settler-thickener tank 24 and recycled as descr~bed above.
Filtered wet solid vanadyl hydrate 32 is blended in blender 33 with carbon 34 and ~hen pelletized in pelletizer 35, dried in dryer 36 in the absence Df oxygen Dr air, and then furnaced in furnace 37 under vacuum Dr inert atmosphere t~ furm vanadium carbide, V2C sh~wn as stream 38 in Figure 1. It is deemed novel to reduce vanadyl hydrate with carbon to prDduce vanzdium carbide.
In the past, vanadium carbide was produced from carbon and vanadium trioxide, V203.
The invention will become more clear when considered together with the follDwing example which is set forth as being merely illustrative of the inventi~n and which is not intended9 in any ~anner, tD be limitative thereof.
Unless utherwise indicated, all parts and percentages are by weight~

5~7 8 EXAMPLE

The sample treated consisted Df 2097 liters of water leach solution prDduced frDm a vanadium ore that had been roasted with salt (NaCl). The solution assayed 4.05 grams V205 per liter, 27 grams Cl per liter and 7.8 grams S0~ per liter. The solution was acidified and reduced using ~.91 grams S02 per gram V25 and 0.90 gram HCl per gram V205. The variations in the pH and emf were 1.8 to 2.4 and ~190 to -160 mv. respectively.
This solution was processed by solvent extraction ir. a two stage mixer-settler apparatus at a nominal flow-rate Df one liter per minute. The raffinate averaged 0.04g V205/L resulting in a recovery of 99 percent of the vanadium. The s~lvent was composed of 8% di-2 ethyl-hexyl phosphoric acid, 3% Isodecanol, and 89% kerosene by volume. The vandium enriched sDlvent contained 7.1 g V20s/L. The rich solvent was stripped by contacting with 120 g NH40H per liter solution in a mixer then separated intD three phases in a settler-thickener tank.
The barren solvent was recycled to the extraction circuit. The aqueous solution phase was recDnstituted with concentrated ~40H to provide stripping solution.
The solid vanadyl hydrate slurry was removed from the the settler-thickener tank as a slurry, filtered and collected as a wet filter cake. A sample of this product (dried at 130 C) assayed 91.0% V205, 0.53~/0 S, .

9.

~ 7 8 0-21% Fe2~ 0.01% SiO2 and 0.022% P.
A portion of the wet filter cake was mixed with powdered carbon and pDwdered iron using a ratio of 3.27 parts V20s to one part carbon and sufficient iron powder to result in about 2% Fe in the final product. Iron is commonly added as a densifying agent in the production of vanadium carbide but is not necessary in the practice of this invention. This mixture was formed into pellets about Dne centimeter in dianleter which were then dried and reduced to vanadium carbide in an induction furnace under an argon atmosphere at 1700 C. The product assayed 85.45% V, 9.99% C, 0.57% 0 and 0.002% N. This product is vanadium carbide ~V2C).

Although the present invention has been described and set forth in some detail, it should be further understood that the same is susceptable Df changes, msdifications and variations with~ut departing from the scope and spirit of the invention.

10 .

.,

Claims

WHAT IS CLAIMED IS:

1. A method for the manufacture of vanadyl hydrate comprising the steps of:
(a) providing an aqueous solution of vanadate ion;
(b) adding sulfur dioxide and a non-oxidizing acid to said aqueous solution to obtain a pH of about 1 to 3.0 to reduce said vanadate ion to the vanadyl ion and reduce the vanadium ion in solu-tion from V+5 to V+4;
(c) solvent extracting said vanadyl ion with an organic solvent from said aqueous solution;
(d) stripping said vanadyl ion from said organic solvent with ammonium hydroxide to form a preci-pitate of vanadyl hydrate; and (e) separating the solid vanadyl hydrate from said solvent.

2. The method of claim 1 further including the steps of:
(a) blending the vanadyl hydrate with carbon;
(b) pelletizing the blended mixture;
(c) drying the pelletized blended mixture in the absence of oxygen; and (d) furnacing the dried, blended mixture of vanadyl hydrate and carbon to form vanadium carbide.

3. The method of claim 1 wherein said aqueous solution of step (a) is a water leach solution.

4. The method of claim 1 wherein said aqueous solution of step (a) is a solution of metavandate ion.

5. The method of claims 3 or 4 wherein said sulfur dioxide is added to said aqueous solution before said non-oxidizing acid is added to said aqueous solution.

6. The method of claims 3 or 4 wherein said sulfur dioxide and said non-oxidizing acid are simultaneously added to said aqueous solution.

7. The method of claims 3 or 4 wherein said non-oxidizing acid is sulfuric acid.

8. The method of claims 3 or 4 wherein said non-oxidizing acid is hydrochloric acid.

9. The method of claims 3 or 4 wherein said sulfur dioxide is added to reduce said vanadate ion to the vanadyl ion as measured by an e.m.f. potential at a pH of about 2 in the range of from about - 150 to about - 300 millivolts.

10. The method of claims 3 or 4 wherein said sulfur dioxide is added in the form selected from the group con-sisting of sulfur dioxide gas, sulfurous acid and a sulfite salt.

11. The method of claims 3 or 4 wherein said vanadyl ion is extracted with said organic solvent in a counter-current extractor having at least two stages.

12. The method of claims 3 or 4 wherein the pH during extraction is maintained in the range of from about 1.5 to about 3.5 by the addition of a non-oxidizing acid.

13. The method of claims 3 or 4 wherein said organic solvent comprises a mixture of di-2-ethylhexyl phosphoric acid, isodecanol, and kerosene.

14. The method of claims 3 or 4 wherein said organic solvent comprises a mixture of heptadecyl phosphoric acid, isodecanol, and kerosene.

15. The method of claims 3 or 4 wherein the solid vanadyl hydrate is separated from said solvent by settling in a settler-thickener and then filtering excess liquid from said solid vanadyl hydrate.