Method for Desulfurizing

Abstract

The method employs a desulfurization agent that is introduced into a smelt of one of molten pig iron and molten steel. The desulfurization agent contains calcium oxide, bitumen and at least one flux agent, with the agent containing 1 to 10% by weight bitumen.

Claims

1. A method for slag treatment comprising the step of adding a desulphurization agent to a melt of at least one of a molten pig iron and a molten steel, said agent containing calcium oxide, bitumen as well as between 0.01 and 10% by weight of at least one flux agent, wherein the at least one flux agent is selected from the group of members consisting of multivalent alcohols, bituminous coal, silicone oils and mixtures thereof, and wherein the agent does not contain any calcium carbide, any magnesium or any magnesium alloy.

2. A method in accordance with claim 1, wherein the agent is introduced into the molten pig iron or into the molten steel by an immersion lance process using a transport gas or by a stirring-in process.

3. A method in accordance with claim 1, wherein the agent is provided in the form of one or more briquettes and is added into the molten pig iron or into the molten steel for pre-sulfurizing and/or for the slag treatment of molten pig iron or of molten steel.

4. A method for treating pig iron comprising the steps of obtaining a smelt of one of molten pig iron and molten steel; introducing a desulfurization agent into said smelt composed of calcium oxide or a mixture which contains at least 20% by weight of calcium oxide and one or more compounds selected from the group consisting of calcium hydroxide, calcium carbonate, and any desired mixtures of the aforesaid compounds; 1 to 10% by weight bitumen; 0.01 to 10% by weight of a flux agent to increase the flow behavior of said calcium oxide, said flux agent being selected from the group consisting of multivalent alcohols, bituminous coals, silicone oils glycols, organopolysiloxanes, any desired mixtures thereof, and polymethylhydrogensiloxane; and up to 10% by weight of an additive selected from the group consisting of cryolite, sodium borate, fluorite, and any desired mixtures thereof.

5. A method for treating pig iron comprising the steps of obtaining a smelt of one of molten pig iron and molten steel; introducing a desulfurization agent into said smelt composed of calcium oxide or a mixture which contains at least 20% by weight of calcium oxide and one or more compounds selected from the group consisting of calcium hydroxide, calcium carbonate, and any desired mixtures of the aforesaid compounds; 2 to 6% by weight bitumen; 0.01 to 10% by weight of a flux agent to increase the flow behavior of said calcium oxide, said flux agent being selected from the group consisting of multivalent alcohols, bituminous coals, silicone oils glycols, organopolysiloxanes, any desired mixtures thereof, and polymethylhydrogensiloxane; and up to 10% by weight of an additive selected from the group consisting of cryolite, sodium borate, fluorite, and any desired mixtures thereof.

6. The method of claim 5 wherein said agent contains 80 to 99.9% by weight of calcium oxide.

7. The method of claim 6 wherein at least 80% by weight of the calcium oxide has a grain size of less than 32 μm.

8. The method of claim 6 wherein said agent is in the form of at least one briquette of a size (length×width) viewed in cross-section of from 10×5 to 200×100 mm.

9. The method of claim 5 wherein the bitumen is selected from the group of members consisting of road construction bitumen, hard road construction bitumen, soft bitumen, modified bitumen, distillation bitumen, high-vacuum bitumen, polymer-modified bitumen, special bitumen, industrial bitumen, oxidation bitumen, hard bitumen, blended bitumen, cold bitumen, fluxed bitumen, flux bitumen, natural asphalt and any desired mixtures of two or more of the aforesaid compounds.

10. The method of claim 5 wherein said agent contains between 0.05 and 0.5% by weight of said flux agent.

11. The method of claim 5 wherein the calcium oxide is soft burnt lime.

12. The method of claim 11 wherein said agent contains between 0.05 and 0.5% by weight of said flux agent.

Description

EXAMPLE

[0073] A mixture was manufactured by mixing:

[0074] 93.9% by weight of calcium oxide;

[0075] 6% by weight hard bitumen; and

[0076] 0.1% by weight silicone oil (flux agent).

[0077] This mixture was mixed homogeneously in a mixer and ground to a powder having a distribution of a range of grain sizes in which 84.30% by weight of the powder has a grain size of less than 32 μm, 87.9% by weight of the powder has a grain size of less than 45 μm, 90.1% by weight of the powder has a grain size of less than 63 μm, and at least 95.12% by weight of the powder has a grain size of less than 90 μm.

[0078] The desulfurization agent thus obtained was injected into an amount of 1.1 kg/t pig iron by an immersion lance process in multiinjection with respect to the mixture involved containing lime and bitumen. In this respect, at pig iron temperatures around 1300° C. with unchanging injection amounts of the other substances involved in the multiinjection, 350 ppm sulfur was removed from the molten pig iron.

[0079] Pig iron having a sulfur content of 26 ppm on average was obtained.

COMPARISON EXAMPLE

[0080] A desulfurization agent was manufactured as described in the example, with the exception that it does not contain any bitumen.

[0081] A mixture was rather manufactured by mixing:

[0082] 97.9% by weight technical calcium carbide;

[0083] 2.0% by weight cryolite (additive); and

[0084] 0.1% by weight silicone oil (flux agent).

[0085] This mixture was ground as described in the example and was introduced into molten pig iron by an immersion lance process in multiinjection while taking account of the same technological conditions at the same plane with 1.1 kg/t pig iron.

[0086] Pig iron having a sulfur content of 25 ppm was obtained.