US4244925A
Expired / Lapsed
US
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Method for production of alkali metal chromates from chrome ores
Assignee: Honeywell International Inc
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Filing: 1979-07-20
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Granted: 1981-01-13
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Expires: 1999-07-20
Abstract
Abstract A method for producing alkali metal chromates by a single roast of chrome ores without the use of calcium oxide is disclosed. A double roast embodiment is also contemplated for obtainment of enhanced yields. The pollution and hygiene problems associated with the use of lime are substantially eliminated and only negligible amounts of alumina are found in the product chromate liquors without employing steps previously thought necessary. These advantages are achieved by controlling (1) the Bichromate Equivalent: aluminum oxide ratio in the mix, (2) the amount of alkali metal salts added to the mix, (3) the roasting time, (4) the composition and alkalinity of the liquor used for leaching the roast, and (5) the temperature employed. Recovery of vanadium values from the alkali metal chromate liquors is also disclosed.
Inventors
- 👤 Somanahalli N. Subbanna
- 👤 Thomas R. Morgan
- 👤 Douglas G. Frick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:28
CPC Classifications
C; C01; C01G; C01G37/00; C01G37/14; C22; C22B; C22B34/00; C22B34/20; C22B34/22
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
145 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting a mixture comprising chrome ore, a diluent and an alkali metal salt, the amount of alkali metal salt being in the range of from about 30 to 80 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C., for a time period of at least about 30 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range of from about 1.5:1 to 10:1; (b) leaching the roast mixture with a leach liquor having a pH of about 4.5 to 12 to remove the alkali metal chromate values and to form a roast mix residue; and (c) recovering alkali metal chromate values.
Claim 2
Independent Claim
145 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting a mixture comprising chrome ore, a diluent and an alkali metal salt, the amount of alkali metal salt being in the range of from about 30 to 80 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C., for a time period of at least about 30 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range of from about 1.5:1 to 10:1; (b) leaching the roast mixture with a leach liquor having a pH of about 4.5 to 12 to remove the alkali metal chromate values and to form a roast mix residue; and (c) recovering alkali metal chromate values.
Claim 3
Dependent Claim
37 words
A method as described in claim 1 wherein in step (a) the diluent is a member selected from the group consisting of leached residue from a previous roast, iron oxide, pyrites cinder, magnesium oxide, and mixtures thereof.
Claim 4
Dependent Claim
20 words
A method as described in claim 1 wherein in step (a) the diluent is leached residue from a previous roast.
Claim 5
Dependent Claim
20 words
A method as described in claim 1 wherein the temperature in step (a) is from about 1100° to 1200° C.
Claim 6
Dependent Claim
40 words
A method as described in claim 1 wherein the alkali metal salt is a member selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, sodium sulfate, potassium sulfate, potassium carbonate, lithium carbonate, sodium sesquicarbonate and mixtures thereof.
Claim 7
Dependent Claim
21 words
A method as described in claim 1 wherein in step (a) the time period is from about 45 to 360 minutes.
Claim 8
Dependent Claim
49 words
A method as described in claim 1 wherein in step (b) the leach liquor is a member selected from the group consisting of water, an aqueous solution of sodium chromate and mixtures of aqueous solutions of sodium chromate and sodium dichromate and has a pH between 5.0 and 8.0.
Claim 9
Dependent Claim
54 words
A method as described in claim 1 wherein in step (a) the amount of alkali metal salt is in the range of from about 40 to 55 percent of the stoichiometric amount required and the Bichromate Equivalent to aluminum oxide ratio in the mix is maintained in the range of about 3:1 to 4:1.
Claim 10
Dependent Claim
15 words
A method as described in claim 1 wherein the alkali metal salt is sodium carbonate.
Claim 11
Dependent Claim
18 words
A method as described in claim 1 wherein in step (b) the roast mixture is cooled before leaching.
Claim 12
Dependent Claim
22 words
A method as described in claim 10 wherein at least a portion of the roast mix residue is recycled to step (a).
Claim 13
Dependent Claim
201 words
A method as described in claim 1 which further comprises the following steps for recovery of vanadium values from the alkali metal chromate values recovered in step (c): (a) adjusting the pH of the solution of alkali metal chromate values to a value between about 9 and 14; (b) admixing the solution from step (a) with at least 6 but no more than about 10 times the stoichiometric amount of a member selected from the group consisting of CaO, Ca(OH) 2 , CaCl 2 , CaSO 4 and mixtures thereof while maintaining the temperature of the admixture so formed between about 70° and about 90° C. for at least about 10 minutes; (c) separating the admixture into a solid residue containing vanadium values and a solution containing alkali metal chromate values and soluble calcium; (d) recovering the vanadium values from the solid residue; (e) admixing the solution from step (c) with at least about 2.5 times the stoichiometric amount of alkali metal carbonate required to precipitate the soluble calcium; (f) separating the mixture so produced into solid calcium carbonate and a solution containing alkali metal chromate values; and (g) recovering the alkali metal chromate values from the solution in step (f).
Claim 14
Dependent Claim
21 words
A method as described in claim 12 wherein in step (a) the pH is adjusted to between about 11.5 and 13.5.
Claim 15
Dependent Claim
13 words
A method as described in claim 12 wherein the alkali metal is sodium.
Claim 16
Dependent Claim
13 words
A method as described in claim 12 wherein the alkali metal is potassium.
Claim 17
Independent Claim
193 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting a mixture comprising chrome ore, roast mix residue and alkali metal salt, the amount of alkali metal salt being in the range of from 40 to 55 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature from about 1100° to 1200° C. for a time period of about 45 to 360 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range from about 3:1 to 4:1; (b) cooling the roast mixture and leaching said cooled mixture with a leach liquor having a pH between about 5.0 and 8.0 to remove the alkali metal chromate values and to form a roast mix residue, said leach liquor being a member selected from the group consisting of water, an aqueous solution of sodium chromate and mixtures of aqueous solutions of sodium chromate and sodium dichromate; (c) recovering the alkali metal chromate values; and (d) recycling at least a portion of said residue from step (b) to step (a).
Claim 18
Independent Claim
193 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting a mixture comprising chrome ore, roast mix residue and alkali metal salt, the amount of alkali metal salt being in the range of from 40 to 55 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature from about 1100° to 1200° C. for a time period of about 45 to 360 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range from about 3:1 to 4:1; (b) cooling the roast mixture and leaching said cooled mixture with a leach liquor having a pH between about 5.0 and 8.0 to remove the alkali metal chromate values and to form a roast mix residue, said leach liquor being a member selected from the group consisting of water, an aqueous solution of sodium chromate and mixtures of aqueous solutions of sodium chromate and sodium dichromate; (c) recovering the alkali metal chromate values; and (d) recycling at least a portion of said residue from step (b) to step (a).
Claim 19
Independent Claim
285 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting in a first roasting step a mixture comprising chrome ore, a diluent and an alkali metal salt, the amount of alkali metal salt being in the range of from about 35 to 80 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C. for a time period of at least about 30 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range of from about 3.0:1 to 10:1; (b) leaching the first roast mixture with a leach liquor having a pH between 4.5 to 12 to remove the alkali metal chromate values and to form a first roast mix residue; (c) reacting in a second roasting step a second mixture comprising at least a portion of said residue and an additional amount of alkali metal salt, the amount being about 30 to 60 percent of the stoichiometric amount of alkali metal salt required to react with the chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C. for a time period of at least about 45 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in the second reaction mixture in the range of from about 1.5:1 to 4:1; (d) leaching the resulting second roast mixture with a leach liquor having a pH between 4.5 to 12 to remove said alkali metal chromate values; and (e) recovering the alkali metal chromate values from the leach liquor removed in steps (b) and (d).
Claim 20
Independent Claim
285 words
A method for the manufacture of alkali metal chromates having a low alumina content, which comprises the following steps: (a) reacting in a first roasting step a mixture comprising chrome ore, a diluent and an alkali metal salt, the amount of alkali metal salt being in the range of from about 35 to 80 percent of the stoichiometric amount required to react with chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C. for a time period of at least about 30 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in said mixture in the range of from about 3.0:1 to 10:1; (b) leaching the first roast mixture with a leach liquor having a pH between 4.5 to 12 to remove the alkali metal chromate values and to form a first roast mix residue; (c) reacting in a second roasting step a second mixture comprising at least a portion of said residue and an additional amount of alkali metal salt, the amount being about 30 to 60 percent of the stoichiometric amount of alkali metal salt required to react with the chrome in said mixture, in an oxygen-containing atmosphere at a temperature of from about 900° to 1200° C. for a time period of at least about 45 minutes while maintaining a Bichromate Equivalent to aluminum oxide ratio in the second reaction mixture in the range of from about 1.5:1 to 4:1; (d) leaching the resulting second roast mixture with a leach liquor having a pH between 4.5 to 12 to remove said alkali metal chromate values; and (e) recovering the alkali metal chromate values from the leach liquor removed in steps (b) and (d).
Claim 21
Dependent Claim
22 words
A method as described in claim 17 wherein the reaction in step (c) is effected in the presence of additional chrome ore.
Claim 22
Dependent Claim
36 words
A method as described in claim 17 wherein step (a) the diluent is a member selected from the group consisting of leached residue from a previous roast, iron oxide, pyrites cinder, magnesium oxide and mixtures thereof.
Claim 23
Dependent Claim
201 words
A method as described in claim 17 which further comprises the following steps for recovery of vanadium values from the alkali metal chromate values recovered in step (e): (a) adjusting the pH of the solution of alkali metal chromate values to a value between about 9 and 14; (b) admixing the solution from step (a) with at least about 6 but no more than about 10 times the stoichiometric amount of a member selected from the group consisting of CaO, Ca(OH) 2 , CaCl 2 , CaSo 4 and mixtures thereof while maintaining the temperature of the admixture so formed between about 70° and about 90° C. for at least about 10 minutes; (c) separating the admixture into a solid residue containing vanadium values and a solution containing alkali metal chromate values and soluble calcium; (d) recovering the vanadium values from the solid residue; (e) admixing the solution from step (c) with at least about 2.5 times the stoichiometric amount of alkali metal carbonate required to precipitate the soluble calcium; (f) separating the mixture so produced into solid calcium and a solution containing alkali metal chromate values; and (g) recovering the alkali metal chromate values from the solution in step (f).
Claim 24
Dependent Claim
21 words
A method as described in claim 20 wherein in step (a) the pH is adjusted to between about 11.5 and 13.5.
Claim 25
Dependent Claim
13 words
A method as described in claim 20 wherein the alkali metal is sodium.
Claim 26
Dependent Claim
13 words
A method as described in claim 20 wherein the akali metal is potassium.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-13 | 1984-07-14 | 1985-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-13 | 1988-07-14 | 1989-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-13 | 1992-07-14 | 1993-01-13 | $7700.00 | Window Closed / Lapsed |