More than 95% of cast-iron in the world is still produced in blast furnaces. Modern blast furnaces are powerful units that produce tons of cast-iron daily, but they require prepared, high-quality raw materials like agglomerate cakes, steel pellets, and iron. Recycling industrial waste that contains iron (of which Russian enterprises alone produce more than 5 million tons of annually) is economically and technologically irresponsible and next-to-impossible in blast furnaces.
„A NUST MISIS research group led by Gennady Podgorodetskyi, a Candidate of Technical Sciences and the head of the NUST MISIS Research & Education Center IMT, jointly with Vtoraluminumproduct, one of the University`s industrial partners, have created and launched a unique pilot unit of airlift reactor (based on a gas purging approach) for the effective and environmentally-friendly production of iron and non-ferrous metal concentrates from waste sludge”, said Alevtina Chernikova, Rector of NUST MISIS.
Hundreds of millions of tons of waste in the form of sludge, dust, cinder, etc. accumulates annually as a result of the chemical industry’s metallurgy work with ferrous and non-ferrous metals. This waste contains large amounts of metal that isn’t currently extracted because of a lack of effective industrial technologies capable of separating its useful components out.
The new innovative blast developed at NUST MISIS is built on an airlift approach and the technological processes are carried out in a liquid slag bath blown by gas. The bubbles formed greatly speed up the chemical processes in the bath, and aggressively mix the iron liquid and slag.
Gennady Podgorodetskyi, head of the group, said: „We have improved the ROMELT technology created at NUST MISIS in the 80s, and have separated the reactor into two zones: melting and recovery. Our calculations showed that in such a furnace configuration, it is possible to reduce the consumption of coal and oxygen per 1 ton of the resulting cast by
20-30%.The slag bath and ferrous melt are blown by a stream of gas with an oxygen containment of 50-99%.The temperature is kept at 1400–1500 оС.Iron-containing materials, power plant coal, and fluxing additives are put on the surface of the molten bath. Coal, falling on the melt surface, gets involved with the slag flows in the bottom zone of the bath where through oxygen flow, its combustion takes place into carbon dioxide and water vapor. Then, the melt flows into the recovery area, where the final restoration to cast iron takes place. A number of non-ferrous metals are also recovered to metal and removed with waste gas from the furnace. Then they are collected in dust and form another commercial product — a concentrate of non-ferrous metals.”
The specific low rate of energy carries—20-30% lower than the world`s best analogues—is a major advantage of the developed blast. The research may even qualify for the European BAT (Best Available Techniques) nomination. This development is for now, technologically oriented, but emissions are significantly lower compared to world analogues and the blast also suppresses the generation of especially dangerous ecotoxicants.
„On a customer`s demand, the slag composition can be picked for further processing into slag stone products or heat-insulating slag wool, and can serve as a basis for cement clinker productions, among other things. Due to the unique design of the unit, energy carriers` costs can be increased to 500 kg of coal and 500 nm3 per 1 ton of resulting cast iron. As a result, we recycle unusable industrial waste, and receive cast, commercial slag, and concentrate of non-ferrous metals. There is no waste in our technology. We also intend to test the pilot sample on the non-waste technology of the gasification of numerous carbon-containing wastes, including municipal solid waste”, — noted Gennady Podgorodetskyi.
The unique pilot unit developed in Mtsensk (Oryol Oblast, Russia) at the premises of STALKRON is designed for the recycling of industrial waste, slags, and sludge from the production of cast-iron, as well as for the production of gas carbon from carbon-containing waste including municipal solid waste. The reactor has already attracted the attention of domestic power engineers and producers of ferrous metals.
The successful testing of the developed technologies and the further replication of units is a step toward the creation of non-waste production of ferrous and non-ferrous metallurgy, as well as a positive and powerful future environmental factor.