DD275705A1 - PROCESS FOR PREPARING LIQUID RAW IRON - Google Patents

Abstract

The invention relates to a process for the pretreatment of liquid pig iron, which is intended for use in a steelmaking plant. The aim and object of the invention is to achieve an effective pre-desulfurization of the pig iron by a simple method and using cost-effective waste products while increasing the silicon content in order to increase the chemical heat of use in steelmaking. According to the invention, the object is achieved in that mixtures of calcium carbide and ferrosilicon are added to the pig iron before or during refilling.

Description

Characteristic of the known technical solutions The quality requirements of the steels to be produced mean that the molten pig iron is the main feedstock

The modern steelmaking process such as the oxygen-steel process is subjected to pretreatment, which mainly serves desulphurization. This pre-treatment relieves both the blast furnace of expensive and coking intensive driving to protect low sulfur levels in pig iron and the steelmaking plant from excessive desulphurisation work.

It is known that the desulfurization treatment is carried out by means of immersion lance injection methods in special plants,

in which fine-grained desulfurizing agents, such as powder mixtures of calcium carbide and certain gas-releasing

Additives are blown into the pig iron (BRD-OS 2709062). With the immersion lance method is a high Accuracy of desulfurization treatment and a good degree of utilization of the desulfurization achieved. It is for

However, these methods required that in addition to the establishment of special treatment facilities used

Desulphurising must undergo a special treatment and thus a not inconsiderable cost factor

of steelmaking. In addition, in the injection process with a certain treatment time can be expected, which can lead to disruptions in the exact time to be observed production flow especially at high Ausgangsschwefelgehalten.

It is known that in steelworks practice under certain conditions a pre-desulfurization of the pig iron before

actual injection treatment is made. This is usually done with simple desulfurization methods that do not have to meet stringent requirements for accuracy, but in a short tent lead to high sulfur degradation. Simple and fast-acting desulfurization processes are pouring jet mixing processes according to the article by Ulrich KaIIe et al. in the journal Stahl and Eisen 97 (1977) No. 8 pp. 382-393 using soda. The disadvantages of

Soda desulphurisation and low-viscosity slag which acts aggressively on refractory lining and their disposal

also causes significant environmental problems. In the case of soda desulphurisation, excessive heat and smoke develop- ments occur above the treatment vessel, necessitating appropriate dedusting systems.

According to OE C21C 2349156 soda presses are used to increase the dust during the desulfurization process

to reduce.

A pig iron desulfurization by means of special moldings is described in AS C 21C 2042934. Have difise procedures

the disadvantage that the dust nuisance is only partially solved and the remaining disadvantages of soda desulfurization can not be solved. In addition, that due to the low specific gravity of the desulfurizing a part through

Floating and dusting remains ineffective. In AT186193916 is a desulfurizing additive in briquet form, consisting of a ferroalloy, cement and

calcium fluoride-containing materials described. Besides the disadvantage of high expenses for the production of the

Formlinges are not achieved sufficient desulfurization effects. Object of the invention

OBJECT OF THE INVENTION It is to carry out an effective and environmentally friendly pre-desulfurization of the pig iron before its use in a desulfurization plant by a simple process using inexpensive waste products.

Presentation of the invention

Surprisingly, it has been found that a more effective use of solid desulfurizing agents in the jet blending process becomes possible when added in admixture with a feedstock which has a high specific gravity and dissolves in the liquid crude clay.

Eriungungegomäß the task is golöst that vorgologt a mixture brossehend from ferrosilicon and calcium carbide prior to transferring the Roholeone In the Aufschlagberolch the Gloßstrahls in Aufnahmogofäß. A waste product is used which contains 60-90% forrosilizlum with silicon contents of 8-30% and 10-50% calcium carbide. The waste product is used in such an amount that 1-20 kg of this product is used per ton of pig iron.

The addition of the mixture takes place in closed metal drums. This will both the safety issues

dissolved in handling calcium carbide and increased the effectiveness of the desulfurizing agent.

By adding the mixture of ferrosilicon and calcium carbide, the duration of the subsequent fine desulfurization becomes

reduced.

The use of the mixture at the same time has the advantage that an increase in the silicon content and thus the

chemical heat of the pig iron. As a result, higher scrapings can be processed in steel production.

Aujführungsbelspiele Before transferring a quantity of pig iron of 190 tons from the pig iron transport ladle to the charging ladle, 12 drums are used

a 200kg mixture of 70% ferrosilicon (Si content 12.5%) and 30% calcium carbide presented in the impingement of Umfüllstrahls.

Initial values of the pig iron before transfer:

Temperature 1379 "C silicon content 0.71% S-content 0.043%

Pig iron values after transfer:

Temperature 1349 ⁰ C Silicon content 0.76% S content 0.032%

Claims (1)

Process for the pretreatment of molten pig iron, characterized in that a mixture consisting of a proportion of 50-90% ferrosilicon with silicon contents of 8-30% and 10-50% calcium carbide in an amount of 1-20 kg per tonne of pig iron in closed drums the transfer of the pig iron is presented in the impact area of Umfüllstrahls. Field of application of the invention The invention relates to an ancestor for the pretreatment of liquid iron melts, preferably pig iron melts intended for use in a steelmaking plant. The process is used for the pre-desulfurization of the iron melts before they are used in special desulphurisation plants or before their use in a steelmaking plant.