US4298379A — Production of high purity and high surface area m…

Claim 1

Independent Claim 121 words

A process for the preparation of high surface area, high purity MgO from a solution of: sulfates of Mg, Ca, and other metals selected from the group consisting of Fe, Ni, Co, and Al; and impurities including B and Si, comprising the steps of: (a) precipitating from the solution said other metals as hydroxides; (b) separating the solution from the precipitate; (c) concentrating the separated solution to a specific gravity of from about 1.35 to 1.5, whereby Ca, B, Si and residual impurities are precipitated; (d) separating the concentrated solution from the precipitate; (e) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (f) decomposing the dehydrated MgSO 4 crystals to form high purity MgO suitable for producing refractory materials.

Claim 2

Dependent Claim 121 words

A process for the preparation of high surface area, high purity MgO from a solution of: sulfates of Mg, Ca, and other metals selected from the group consisting of Fe, Ni, Co, and Al; and impurities including B and Si, comprising the steps of: (a) precipitating from the solution said other metals as hydroxides; (b) separating the solution from the precipitate; (c) concentrating the separated solution to a specific gravity of from about 1.35 to 1.5, whereby Ca, B, Si and residual impurities are precipitated; (d) separating the concentrated solution from the precipitate; (e) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (f) decomposing the dehydrated MgSO 4 crystals to form high purity MgO suitable for producing refractory materials.

Claim 3

Dependent Claim 23 words

The process as defined by claim 1, wherein the precipitation of the metal hydroxides comprises adding Mg(OH) 2 to the metal sulfates solution.

Claim 4

Dependent Claim 30 words

The process as defined by claim 2 or 1, further comprising adjusting the pH of the metal sulfate during said precipitation step to a value between about 6.5 and 8.5.

Claim 5

Dependent Claim 25 words

The process as defined by claim 3, wherein said pH of the metal sulfates solution is adjusted to a value between about 7 and 7.5.

Claim 6

Dependent Claim 24 words

The process as defined by claim 4, further comprising exposing the metal sulfates solution to air oxidation while the metal hydroxides are being precipitated.

Claim 7

Dependent Claim 22 words

The process as defined by claim 1, comprising concentrating the separated solution at a temperature between about 40° C. and 90° C.

Claim 8

Dependent Claim 20 words

The process as defined by claim 6, wherein the separated solution is concentrated to a specific gravity of about 1.42.

Claim 9

Dependent Claim 34 words

The process as defined by claim 1, wherein the step of recovering the dehydrated MgSO 4 from the concentrated solution comprises first crystallizing hydrated MgSO 4 and then dehydrating the crystallized MgSO 4 .

Claim 10

Dependent Claim 138 words

A process for the preparation of high purity, high surface area MgO suitable for producing refractory materials, from a solution of: sulfates of Mg, Ca, and other metals selected from the group consisting of Fe, Ni, Co, and Al; and impurities including B and Si, comprising the steps of: (a) precipitating from the solution said other metals as hydroxides; (b) separating the solution from the precipitate; (c) concentrating the separated solution sufficiently to precipitate CaSO 4 ; (d) separating the concentrated solution from the precipitate; (e) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (f) decomposing the dehydrated MgSO 4 crystals to form high purity MgO having a controlled surface area of between about 7 and 50 m 2 /g, by heating at a temperature between about 800° C. and 1000° C. in a reducing atmosphere.

Claim 11

Dependent Claim 138 words

A process for the preparation of high purity, high surface area MgO suitable for producing refractory materials, from a solution of: sulfates of Mg, Ca, and other metals selected from the group consisting of Fe, Ni, Co, and Al; and impurities including B and Si, comprising the steps of: (a) precipitating from the solution said other metals as hydroxides; (b) separating the solution from the precipitate; (c) concentrating the separated solution sufficiently to precipitate CaSO 4 ; (d) separating the concentrated solution from the precipitate; (e) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (f) decomposing the dehydrated MgSO 4 crystals to form high purity MgO having a controlled surface area of between about 7 and 50 m 2 /g, by heating at a temperature between about 800° C. and 1000° C. in a reducing atmosphere.

Claim 12

Dependent Claim 28 words

The process as defined by claim 9, wherein the decomposition step also produces sulfur-containing gases, further comprising the step of burning the sulfur-containing gases to SO 2 gas.

Claim 13

Dependent Claim 21 words

The process as defined by claim 10, further comprising recycling the SO 2 gas to form H 2 SO 4 .

Claim 14

Dependent Claim 33 words

The process as defined by claim 9, wherein the concentrating step comprises concentrating the separated solution to a specific gravity of from about 1.35 to 1.5, whereby impurities including calcium sulfate are precipitated.

Claim 15

Dependent Claim 23 words

The process as defined by claim 12, further comprising concentrating the separated solution at a temperature between about 40° C. and 90° C.

Claim 16

Dependent Claim 17 words

The process as defined by claim 9, wherein the reducing atmosphere comprises CO and H 2 .

Claim 17

Dependent Claim 20 words

The process as defined by claim 9, wherein the separated solution is concentrated to a specific gravity of about 1.42.

Claim 18

Dependent Claim 35 words

The process as defined by claim 9, further comprising the steps of: (g) briquetting the MgO; and (h) dead burning the briquetted MgO at temperatures greater than about 2000° C., whereby refractory MgO is produced.

Claim 19

Dependent Claim 45 words

The process as defined by claim 9, further comprising the steps of: (g) briquetting the MgO combined with carbon; (h) heating the briquetted MgO in a kiln in an atmosphere of chlorine; and (i) electrolyzing the resulting MgCl 2 , whereby Mg metal is produced.

Claim 20

Dependent Claim 173 words

A process for refining a magnesium, calcium, iron and nickel containing ore, comprising the steps of: (a) grinding the ore; (b) preparing a slurry of the ground ore in sulfuric acid containing less than ten percent of water; (c) adding water to the acid-ore slurry in an amount which is effective to initiate a sulfation reaction; (d) allowing the sulfation reaction to continue, utilizing the heat of the sulfation reaction to heat the acid-ore slurry, whereby water-soluble metal sulfates and insoluble residue are formed; (e) leaching the sulfation product with water to extract the water-soluble metal sulfates in solution; (f) separating the metal sulfates solution from the insoluble residue; (g) precipitating from the solution iron and nickel as hydroxides; (h) separating the solution from iron and nickel hydroxide precipitate; (i) concentrating the solution sufficiently to precipitate CaSO 4 ; (j) separating the concentrated solution from the precipitate; (k) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (l) decomposing the dehydrated MgSO 4 crystals to form high purity, high surface area MgO.

Claim 21

Dependent Claim 173 words

A process for refining a magnesium, calcium, iron and nickel containing ore, comprising the steps of: (a) grinding the ore; (b) preparing a slurry of the ground ore in sulfuric acid containing less than ten percent of water; (c) adding water to the acid-ore slurry in an amount which is effective to initiate a sulfation reaction; (d) allowing the sulfation reaction to continue, utilizing the heat of the sulfation reaction to heat the acid-ore slurry, whereby water-soluble metal sulfates and insoluble residue are formed; (e) leaching the sulfation product with water to extract the water-soluble metal sulfates in solution; (f) separating the metal sulfates solution from the insoluble residue; (g) precipitating from the solution iron and nickel as hydroxides; (h) separating the solution from iron and nickel hydroxide precipitate; (i) concentrating the solution sufficiently to precipitate CaSO 4 ; (j) separating the concentrated solution from the precipitate; (k) recovering dehydrated MgSO 4 crystals from the concentrated solution; and (l) decomposing the dehydrated MgSO 4 crystals to form high purity, high surface area MgO.

Claim 22

Dependent Claim 38 words

The process as defined by claim 18, further comprising the steps of: neutralizing the unreacted sulfuric acid in the metal sulfates solution; and selectively precipitating iron from the neutralized solution by autoclaving said solution under an oxygen atmosphere.

Claim 23

Dependent Claim 21 words

The process as defined by claim 19, wherein the neutralization is effected by adding ground ore to the metal sulfates solution.

Claim 24

Dependent Claim 17 words

The process as defined by claim 18, further comprising smelting the metal hydroxide precipitate to form ferronickel.

Claim 25

Dependent Claim 19 words

The process as defined by claim 18, further comprising hydrometallurgically separating nickel from the iron and nickel hydroxide precipitate.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1984-11-02	1985-05-04	1985-11-03	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1988-11-02	1989-05-04	1989-11-03	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1992-11-02	1993-05-04	1993-11-03	$7700.00	Window Closed / Lapsed

Production of high purity and high surface area magnesium oxide

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