DE1184364B - Process for the production of agglomerates containing metallic iron which serve as a substitute for scrap iron in steel production - Google Patents

Description

Process for the production of as a replacement for scrap iron in steel production Serving, metallic iron-containing agglomerates The invention relates to a Process for the production of as a replacement for scrap iron in steel production serving, metallic iron-containing agglomerates by reducing up to iron ore dust containing about 8% gangue in a fluidized bed, without that a reduction of the gangue occurs, and subsequent agglomeration of the reaction product.

It has been shown that there is considerable Difficulties in obtaining agglomerates free of reoxidation phenomena. When reducing iron ores to pure iron powder or from higher to lower It is iron oxides in a fluidized bed by means of a reducing gas known to coat the reduced reaction product with lime after agglomeration, thus not only caking, but also reoxidation of the agglomerates to avoid. However, this cannot prevent that after the reduction in In the hot state, finely divided iron, which is pyrophoric, is reoxidized.

The aim of the invention is to overcome these difficulties and to provide a process for the production of metal iron-containing agglomerates serving as a substitute for scrap iron, in which no reoxidation occurs either in the reduction stage or in the hot or cooled agglomerates. According to the invention, this aim is achieved in that the iron ore dust is "added to such a partial amount of lime" before its at least partial reduction and the agglomerates produced are coated with so much lime that the agglomerates have a content of - Lime, from about 1 to 30 percent by weight, furthermore> have a gangue content of not 'more than 10 percent by weight and the remainder of dust containing metallic iron.

The iron ore dust and that added to it are expediently in this case Share of lime initially preheated together to around 870 to 1050 ° C and then in introduced the reduction zone.

The iron contained in the agglomerates produced according to the invention is in contrast to the agglomerates according to previous processes, in which always at least part of the iron is reoxidized, in a completely pure state, so that the agglomerates obtained are more excellent in steel production Suitable as a substitute for scrap iron.

Further features, advantages and details of the invention emerge from the description and the claims. According to the invention, in d # Reaktznnsl product introduces lime in an amount that is so measure is, d4- the contained therein al: 'an Silicic acid, phosphorus, and so- like a gathering bakieri-, tuid'`ie - * W 4dation ver is prevented. Calibrated in the agglomerate excess,. Lime can .r: slag formation other @; materials,;, .. x3x, ° `tahlofencharge used. will. The obtained agglomerates have the following composition: Lime. . . . ... . . . . . . . . . ,approximately. 1 to 30.oJb Gangga @ -rten @ iserib4tigei.StaA kest '. ' The lime: can _eritpaeler -;: - inFn: @ on` @ Calcium.> carbonate, calcium oxide or other alkaline earth metals bonds, for example dolomite, can be used the. Hence the term "lime" should refer to this Extending materials in general. Part of the lime is mixed with the ore dust before reduction and the rest as a coating on the surface of the Agglomerates applied. The one with the ore dust in Lime mixed in the reduction stage prevents a Caking and reoxidation of the iron part Chen and remain intimate with these and the gaits mixed in the agglomerates, while the lime coating on the agglomerates which prevents surface reoxidation.

The actual reduction process can follow any process, d. H. continuously or in individual batches, one or two stages, whole or are partially carried out. The ore can contain up to about 8% gangue, and it is preheated to about 870-1050 ° C before entering the reduction zone. Limestone is expediently fed to the preheater together with the ore. at Limestone is calcined at the above preheating temperature, but the resulting Carbon oxide is not used in the actual reduction system and the heat of calcination fed from the outside. The reducing reactions are endothermic and the lime serves as an additional heat transfer medium. The amount of added lime varies between 1 and 20 percent by weight of charged ore. The temperature of the reduction zone is in the range of about 650 to 870 ° C, and the lime enables the implementation of the Reduction at these temperatures without caking occurring. The lime can also be added directly to the reduction zone, d. H. without closing the preheater run through.

After the reduction process, the ferrous dust becomes the accompanying Gaits and the lime agglomerated and cooled in the usual way, taking care too wear is that there is no contact with air. To this end, additional Lime in finely divided form is applied to the surface of the agglomerates. Appropriate the limestone and agglomerates are shaken together. The lime can do something moistened with water or heating oil to improve its adhesion. The resulting coating prevents the agglomerates from coming into direct contact with air and thus prevents reoxidation of their surfaces.

As a specific example of the invention, scrap replacement according to the invention was produced by reducing a typical ore from Venezuela of the following composition: Fe (as Fe.Od .. .. .. ... 58.0% Free water. . . . . . . . . . 8.0% Ignition losses 6.5 0 / a Gaits Silica. . . . ... 1.0% Phosphorus ......... 0.050 / 0 Others. . . . . . . . . . 1.65% 2.70% A 95% -reduced product from this ore contains 4.361 per cent of the gangue, of which 1.62% consists of silica and 0.081% of phosphorus. The weight of the limestone to be used, which is supposed to make this product self-slagging in the Siemens-Martin furnace, was calculated on the assumption that the requirement is 2 moles of CaO per mole of silica and 1.5 moles of CaO per mole of phosphorus. On this basis, the ore requires 32.9 kg of limestone per ton or 3.65% limestone. This quantity. Limestone plus an appropriate excess will be divided between the ore fed to the reduction zone and the agglomerate coating. The composition of the end agglomerates was: Dust containing iron ... 92.58% Gaits. . . . . . . . . . . 4.220 / 0 Lime as Ca0. . . . . . . . 3,201 / 0 100,000 / 0 Ferrous dust ... 90,320 / 0 Gaits. . . . . . . . . . . 4.12% Lime as CaCOa. . . . . . 5.56% 100.001 / 0 If the risk of caking is insignificant, most of the lime is applied as a coating on the agglomerates, otherwise a large part of the lime must be added to the reduction zone.

Claims (2)

Claims: 1. A method for producing as a replacement for scrap iron agglomerates containing metallic iron used in steel production, in the case of iron ore dust containing up to about 8% gangue in a fluidized Bed is at least partially reduced by means of a reducing gas, without that a reduction of the gangue occurs, then the reaction product agglomerates is, and the agglomerates are coated with lime, characterized in that the iron ore dust already before its at least partial reduction Partial amount of lime is added and the agglomerates produced still contain as much lime are coated so that the agglomerates have a lime content of about 1 to 30 percent by weight, also a gait content of; no more than 10 percent by weight and the remainder metallic Dust containing iron. 2. The method of claim 1, characterized indicates overall that the iron ore dust and the addition amount of lime is first preheated together at about 870 ° to 1050 ° C and then introduced into the reduction zone him. Documents considered: German Patent No. 822 402; Italian patents Nos. 459 543, 482 232; U.S. Patent No. 2,450,343.