# US 4,394,454 A · Method for making sintered dolomite with a low porosity and a good hydration stability

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- Number: US 4,394,454 A
- Document ID: US4394454A
- Status: Granted
- Kind: A
- Application number: 06/342,449
- Filed: 1982-01-25
- Granted: 1983-07-19
- Earliest claimed: 1981-05-09
- Assignees: Dolomitwerke GmbH
- Inventors: Karlheinz Rosener; Alfred Roeder; Wolfgang Munchberg; Herbert Richrath; Max Chmiel
- Web page: https://patentgrep.com/patent/US4394454A

## CPC

- C04B 35/06: based on oxide mixtures derived from dolomite
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

To produce a dolomite sinter with a low porosity and a good hydration stability made of difficult-to-sinter raw dolomite, the dolomite is milled and caustic burnt dolomite, dolomite hydrate or semi-burnt dolomite in quantities between 3 and 20% by weight relative to the total mixture is added to the raw dolomite powder and is calculated as oxide, as well as foreign oxide, such as Fe.sub.2 O.sub.3, Al.sub.2 O.sub.3 or SiO.sub.2, in such quantities that the total content of the foreign oxide mixture is 1 to 3% by weight.

## Claims

### Claim 1

In a method for making a dolomite sinter with a low porosity and a good hydration stability made of milled raw dolomite comprising the steps of adding foreign oxides to milled pure raw dolomite powder having a low content of foreign oxides, pressing the milled raw dolomite powder-foreign oxide admixture into briquets, and heating the briquets to a sintering temperature, the improvement comprising:
adding a member selected from the group consisting of burnt dolomite, dolomite hydrate, semi-burnt dolomite and combinations thereof in quantities of between 3 and 20% by weight, relative to the total mixture, to said raw dolomite powder and wherein said foreign oxides are added in such quantities such that the total content of foreign oxides is 1 to 3% by weight calculated on the ignition loss free mixture.

### Claim 2 (depends on 1)

The method according to claim 1, wherein said foreign oxide added includes Fe.sub.2 O.sub.3, Al.sub.2 O.sub.3 and SiO.sub.2.

### Claim 3 (depends on 1)

The method according to claim 1, wherein said member selected from the group consisting of caustic burnt dolomite, dolomite hydrate, semi-burnt dolomite and combinations thereof is admixed with raw dolomite powder in quantities of between 5-10% by weight.

### Claim 4 (depends on 1, 2)

The method according to claim 1 or 2, wherein said foreign oxides are added to the admixture in such quantities that the total content of the foreign oxides in the mixture is 1.5 to 2.5% by weight.

### Claim 5 (depends on 2)

The method according to claim 2, wherein the content of Fe.sub.2 O.sub.3 is 0.8% by weight, Al.sub.2 O.sub.3 is 0.5% by weight and SiO.sub.2 is 0.8% by weight in the admixture.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said admixture to be pressed consists of granular sizes of less than 0.1 mm.

### Claim 7 (depends on 1)

The method according to claim 1, wherein said mixture to be pressed consists of granular sizes of more than 1 mm.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the sintering temperature is 1600.degree. to 2000.degree. C.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the pressing of the mixture is carried out with pressures of more than 2 t/cm.sup.2.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the sintering of the molded article is carried out by using solid combustion material for sintering.

### Claim 11 (depends on 10)

The method according to claim 10, wherein said solid combustion material is coal dust.