Use of briquets of highly dispersed metallic wastes for the conversion of vanadium-bearing conversion pig iron

Abstract

The oxidant usually used in the blowing of vanadium-bearing conversion pig irons in converters is a special agglomerate which ensures that the process of the removal of vanadium from the pig proceeds to completion. However, for several reasons, the composition and structure of the converter slag formed in this process does not always meet the requirements of the customers for this product.In particular, the slags formed at the Chusovoi Metallurgical Plant have a relatively high content of metal (in the form of inclusions, scrap, and dispersed iron), which increases the physical losses of the slag during separation and complicates the slag's chemical treatment during roasting and leaching. In addition, there are restrictions on the allowable concentrations of Cat, dispersed iron, and other components.In light of this situation, the plant has resorted to the use of briquets of a special composition to convert vanadium-bearing conversion pig iron. The briquets ensure that the main conditions required for the removal of vanadium from the pig will be created during the steelmaking operation. The briquets were prepared by pressing the raw material with a force of up to 200 kgf/cm 2. The strength of the finished briquets is sufficient to allow them to be transported, stored, and charged into the converter. They have a density of 2.3-2.6 tons/m 3 and a moisture content of 3.4-4.8%. Table 1 shows their chemical composition compared to sinter.The main difference between the composition of the briquets and the composition of the sinter is that the briquets contain alkalis (up to 2% Na20 ) and carbon (up to 5% crushed coke). We should also point out the relatively low content of iron oxides and the high content of Fe203 among the oxides in the briquets. The total content of oxides (Cr203 + V205 + Tit2) is more than twice as great as the content of oxides in the sinter.The process of removing vanadium from pig iron with the use of briquets having the composition shown in Table 1 was studied under production conditions at the Chusovoi plant by gradually replacing sinter with briquets until just briquets were being used in the conversion of vanadium-beating conversion pig iron (Table 2).Silicon, titanium, manganese, and chromium are oxidized in the same way as in the conventional process, regardless of the type of oxidant that is used. However, we should note that the relative concentrations of manganese and chromium present during the blow were somewhat higher -0.04--0.06% -when a high percentage of briquets was used. This trend is clearer when viewed from the standpoint of vanadium content -the degree of vanadium removal from the pig iron decreased from 92.1 to 79.1%. The oxidation loss of carbon also decreased: from 18-20 to 6-7%. Thus, the decarbonization reaction was slowed as expected, but so was the rate at which vanadium was removed from the pig iron.This raises the question of whether the result just described was related to the process of oxidation of the vanadium or to the V205 capacity of the converter slag. It is a...