WO2016012003A1 - Method for nickel pig iron (npi) decarburization in an aod converter - Google Patents

Abstract

The invention relates to a method for nickel pig iron (NPI) decarburization in an aod converter, wherein a mixture consisting of oxygen and carbon dioxide is guided to the molten mass.

Description

 Process for Nickel Pig Iron (NPI) decarburization in the AOD converter

The invention relates to a process for nickel pig iron (NPI) decarburization

in the AOD converter

Due to the scarcity of suitable raw materials for the production of RST steels, new technologies are increasingly being developed to create inferior alloys of low grade ores. Considering that most technologies run in the blast furnace, their high carbon and silicon content is their consequences.

The quality of these materials usually requires an aftertreatment.

This mainly affects the carbon and silicon content. Both elements are removed by refining with oxygen, but it must be remembered that the elements develop high energy during the oxidation. A burnup of 0.1% carbon heats a melt by approx. 10.5K and a burnup of 0.1% silicon by approx. 28K. As a result of such intense energy development, in the conventional case species-specific material is added, supported by metallurgically neutral slag formers such as lime and dolomite.

In the treatment of steel in the course of steel production, it is known from DE 196 08 530 C2) to blow CO2 as a carrier gas together with solids below the slag surface, wherein the CO 2 almost completely dissociated to CO and O and the formed [O] with additional production of CO reacts with the C from the molten steel.

From DE 690 20 596 T2, DE 2525355 and DE 1964092 it is known to fresh with pure oxygen.

The object of the invention is to improve the economics of decarburization of nickel pig iron (NPI) in the AOD converter. The invention relates to a method for nickel pig Iran decarburization in an AOO converter, wherein a mixture consisting of oxygen and carbon dioxide is fed to the melt.

 In this case, the oxygen is preferably inflated onto the melt, while the carbon dioxide is blown into the melt.

Preferably, the CO 2 is injected through submerged nozzles in the molten metal.

It is a strong reduction of carbon and silicon in the NPI also called HC NPI (High Carbon NPI) to a LC NPI with very low C and Si contents below 0.1%

This is achieved by increasing the decarburization rate and the high

Temperature development is not kept with species-specific material and enormous amounts of slag formers in temperature-friendly range, but with an oxygen / carbon dioxide mixture, which has the property of both conditions.

The following compilation represents a comparison of the characteristics of the conventional and the new inventive technology.

decarburization

The decarburization reaction is explained by the following mechanisms:

Conventional procedure

 {02} = 2 [0] thermal dissociation of oxygen

[Fe] + [0] = (FeO) iron oxidation (FeO) + [C] = [Fe] + {CO} enchooling

[Si] + 2 (0] = (SiO 2) desilication

New method

 {02} = 2 [0] thermal dissociation of oxygen

 [Fe] + 10] = (FeO) iron oxidation

 (FeO) + [C] = (Fe) + {CO} decarburization

 [Si] + 2 (0] = (SiO 2) desilication thermal dissociation of CO 2 {CO 2} = [0] + {CO}

 Decarburization (C] + [0] = {CO}

 Desilication [Si] + 1/2 [0] = (SiO 2)

Oxygen availability in conventional process 2 [0] in the new process

By using C02, thermal dissociation yields another atom of oxygen and increases the reaction rate by 50%.

process cooling

In a high carbon and liquid Raffinattonsprozess remain for cooling after deduction of cooling water Radiattons- and convection losses about 80 kwh energy per t melt. The enthalpy 1t of the typical LC NPI is estimated at about 400 kWh and the enthalpy of a Nm3 from C02 at 2.14 kWh. Accordingly, the following are

Opposite relations

80 kWh / t of melt correspond to: 0.2 1 LC NPI or 37.4 Nm3 C02

The application of C02 thus means a significant increase in production of up to 20%. and a shortening of the refining time by a minimum of 30%.

Claims

claims 1. Process for Nickel Pig Iron Decarburization in an AOD Converter, characterized, that a mixture consisting of oxygen and carbon dioxide is fed to the melt. 2. The method according to claim 1, characterized, that the oxygen is blown onto the melt while the carbon dioxide is blown into the melt. 3. The method according to claim 2, characterized, that the carbon dioxide is injected into the melt by means of submerged nozzles. 4. The method according to any one of the preceding claims, characterized, that the ratio of oxygen / carbon dioxide is between 4/1 and 1/4.