Shungite, unique in composition, structure and properties, is a very promising raw material for replacing coke in metallurgy:
In the metallurgical industry, coke consumption makes up 37% of the total consumption of fuel and energy resources. For example, in blast-furnace production, the share of coke in the cost of cast iron is about 30%. And in the production of ferroalloys, the share of coke is up to 15%, and electricity is up to 40%. So, for this industry, it is practical to expand the raw material base of carbonaceous reducing agents by including shungite from Karelia, Russia.
Shungite, which is mined in the Zazhoginsky deposit in Karelia, Russia, is a rock that has unique composition, structure and properties. Karelian shungite is a high-potential raw material in both ferrous and non-ferrous metallurgy.
Due to the exceptionally developed contact between active carbon and silicates, when the shungite rock is heated, silica is reduced to metallic silicon and silicon carbide. That is why shungite is an effective raw material in the production of foundry iron, ferroalloys, and silicon carbide, and also in the process of removing liquid slag from heating wells and in the smelting of elemental phosphorus.
Shungite carbon is very active in oxidation-reduction reactions. Shungite consists of both solid carbon and a significant amount of silicon oxide; both of these components are in chemically active forms. Therefore, shungite can be used in metallurgy as a reducing agent, and simultaneously as SiO2-containing flux and a source of silicon (for example, in the production of ferrochrome or ferrosilicochrome).
The ratio of the main components of the rock is carbon (30%), which does not contain volatiles, and silicon (55%) is close to the stoichiometry, which is necessary for reduction processes in the Si-C-O system. Shungite carbon is non-crystalline, so it is resistant to graphitization, and it maintains high reactivity within the entire temperature range of metallurgical processes. The ash (mineral) part (70%) consists of silicates, in which SiO2 is 85%.
Shungite has a uniform distribution of silicate minerals with a particle size of fewer than 10 microns in the carbon matrix. Thus, there is a close and developed (up to 20 m2/g) contact between silicate and carbon. As a result, this increases the role of solid-phase reactions in the reduction process, so shungite application has a number of technological advantages, which enables to replace coke and siliceous raw materials (quartzite) in metallurgy: in silicon carbide production, in silicon cast-iron smelting and ferroalloys smelting. In terms of reactivity, it is not inferior to coke.
Shungite has high mechanical strength (800-1200 kg / cm2) and low abrasion index.
Shungite has a high density (2.2-2.4 t/m3), which enables to use the volume of the furnace unit more economically when it replaces the traditional carbon-silica mixture.
These properties show opportunities in the application of shungite:
- In grooves and floaters as a strengthening additive instead of coke and quartzite in metallurgy;
- In blast-furnace smelting in order to increase the silicon content in cast iron by loading shungite in a blast furnace instead of ferrosilicon;
- In ferroalloys smelting in blast furnace;
- In ferroalloys smelting in electric furnaces;
- In SiC production in order to process SiC into fire-resistant and chemically resistant construction materials, and additionally to use as a refractory mass filler and as a reducing agent.
For example, in ferromanganese smelting, primary slag contains an increased amount of manganese oxide. Provided that shungite is used in the mixture, the forming silicon carbide reduces manganese from slag as in two possible reactions:
3 MnO + SiC ---> 3Mn + SiO2 + CO
3 MnO + SiC + C ---> Mn3C + CO.
Silicon carbide from shungite is involved in the process of manganese reduction, which leads to a decrease in heat loss by lowering the level of the smelting zone.
In industrial ferromanganese smelting, the percentage of shungite application reaches more than 50% (instead of coke)
Shungite application in the technological process does not affect the chemical composition of alloys.
In blast furnace smelting of ferroalloys, the percentage of shungite application (instead of coke) is 100% on average.
Shungite, unique in composition, structure and properties, is a very promising raw material for replacing coke in metallurgy
Conversion pig-iron and cast-iron production