# US 4,395,282 A · Desulfurization mixture and process for making it

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- Number: US 4,395,282 A
- Document ID: US4395282A
- Status: Granted
- Kind: A
- Application number: 06/359,228
- Filed: 1982-03-18
- Granted: 1983-07-26
- Earliest claimed: 1981-03-24
- Assignees: Hoechst Aktiengesellschaft
- Inventors: Albert Braun; Willi Portz; Georg Strauss; Hans-Martin Delhey
- Web page: https://patentgrep.com/patent/US4395282A

## CPC

- C21C 7/0645: {Agents used for dephosphorising or desulfurising}
- C21C 1/025: {Agents used for dephosphorising or desulfurising}
- C21C: PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS

## Abstract

The disclosure provides mixtures for the desulfurization of metal melts, especially steel and crude iron melts, based on CaC.sub.2 --CaO-crystal blends produced in the fused mass. More specifically, the mixtures contain free carbon and carbonate and have a portion of the CaO in the CaC.sub.2 --CaO-crystal blend hydrated to Ca(OH).sub.2. The disclosure also relates to a process for making the mixtures.

## Claims

### Claim 1

A mixture for the desulfurization of steel and crude iron melts comprising
(a) a CaC.sub.2 /CaO-crystalline blend containing 40 to 80 weight % CaO and having crystallized out of a fused mass of CaO and CaC.sub.2,
(b) 1 to 6 weight % of chemically combined water having hydrated CaO in the CaC.sub.2 /CaO-crystalline blend to form Ca(OH).sub.2 ;
(c) 0.5 to 8 weight % free carbon; and
(d) 0.5 to 20 weight % carbonates of a substance selected from calcium, magnesium and sodium.

### Claim 2 (depends on 1)

The mixture of claim 1 comprising 2.5 to 3.5 weight % of chemically combined water.

### Claim 3 (depends on 1)

The mixture of claim 1 having been prepared by introducing finely divided calcium oxide in an excess of 3 to 15 weight %, based on the quantity desired in the CaC.sub.2 /CaO-crystalline blend, into a calcium carbide melt which already has up to 45 weight % calcium oxide contained in it; cooling the mixture to temperatures of 350.degree. to 450.degree. C. to effect solidification; rough-crushing the solidified mixture at these temperatures to particles with a size of less than 150 mm; separating invariably obtained particles with a size smaller than 4 mm from coarser material; admixing the latter with free carbon and carbonate, and comminuting the mixture in the presence of a substance selected from air and nitrogen with a moisture content of 5 to 20 g/m.sup.3, calculated for 1.013 bar and 273.15 K., by crushing and grinding at temperatures lower than 100.degree. C. to particles with a size of less than 10 mm.

### Claim 4 (depends on 1)

A process for the manufacture of a mixture as claimed in claim 1, which comprises introducing finely divided calcium oxide in an excess of 3 to 15 weight %, based on the quantity desired in the CaC.sub.2 /CaO-crystalline blend, into a calcium carbide melt which already has up to 45 weight % calcium oxide contained in it; cooling the mixture to temperatures of 350.degree. to 450.degree. C. to effect solidification; rough-crushing the solidified mixture at these temperatures to particles with a size of less than 150 mm; separating invariably obtained particles with a size smaller than 4 mm from coarser material; admixing the latter with free carbon and carbonate, and comminuting the mixture in the presence of a substance selected from air and nitrogen with a moisture content of 5 to 20 g/m.sup.3 (at 1.013 bar and 273.15 K.) by crushing and grinding at temperatures lower than 100.degree. C. to particles with a size of less than 10 mm.

### Claim 5 (depends on 4)

Process as claimed in claim 4, wherein the calcium oxide which is to be added to the calcium carbide melt is pre-heated to temperatures of up to 2000.degree. C. and is introduced into the melt while hot, the calcium oxide being pre-heated to temperatures which are the higher, the higher the proportion of additionally dissolved calcium oxide desired, within the range 40 to 80 weight %.

### Claim 6 (depends on 4)

Process as claimed in claim 4, wherein a calcium carbide melt containing 20 to 45 weight % calcium oxide is used.

### Claim 7 (depends on 4)

Process as claimed in claim 4, wherein the fraction of particles with a size smaller than 4 mm sieved off after the rough-crushing step, is recycled into the process.

### Claim 8 (depends on 4)

Process as claimed in claim 4, wherein the mixture is comminuted at temperatures of 10.degree. to 50.degree. C. to particles with a size of less than 10 mm.

### Claim 9 (depends on 4)

Process as claimed in claim 4, wherein the mixture is comminuted to particles with a size of less than 0.1 mm.