Scrap and slag-forming materials are smelted in a liquid bath of molten metal formed upon starting the smelting unit MAGMA.
For refining of the molten metal from phosphorus and partially from sulphur, oxidised basic slag (slag ratio 0.05-0.06) is put over the molten metal which is from time to time renewed.
The heat required for metal heating and smelting is fed into the working space of the smelting chamber by fuel-oxygen burner and by oxidation of coal by gaseous oxygen fed into the bath by special lances.
Temperature of molten slag is 1600-1650оС and temperature of metal is 1500-1580оС.
The generated metal semi-product is non-continuously released from the smelting chamber into the ladle transported further to the heating facility of the ladle-furnace unit.
Processed slag is released from the smelting chamber non-continuously. At a later stage it can be used for production of Portland cement clinker.
Production capacity of the standard model of MAGMA for scrap reaches 60-65 tons per hour.
The smelting unit can also operate with extra-furnace heating of scrap by off-gases. Above the smelting chamber, a hermetically sealed shaft heater of scrap in this case is installed, the shaft heater being equipped with holding and dozing devices and lances for afterburning of CO in the off-gases.Production capacity of MAGMA in this case increases up to 80 tonnes per hour.
Use of MAGMA for continuous smelting of ferrous metals scrap and production of metal semi-product allows to significantly reduce the aggregate consumption of fuel as compared with conventional arc steel furnaces due to more rational use of the energy of primary fuel.
The proposed technology of scrap processing has a number of technical and economic advantages over the conventional combination used in electric-smelting of steel: steel electric arc furnace - ladle-furnace unit.
First of all, this means an increase of output of proper liquid metal in smelting. Whereas conventional smelting of scrap in an arc furnace with the use of smelting intensifiers provides an output of proper product in the range of 91-92%, the proposed technology provides an output of proper product after scrap smelting in the range of 94-95%.
Increase of output of the proper product is achieved through:
- lesser oxidation of iron when smelting in a liquid bath (immersion of a piece of scrap into the molten mass)
- lesser development of iron oxidation in the presence of coal carbon
- recuperation of iron-containing dust captured by the gas treatment system and injected back to the molten slag
- small losses of iron in the form of prills in cast slag due to the use of small volume of slag in the process of re-smelting of scrap and application of original siphon design of release of slag from MAGMA
- exclusion of slag pumping from MAGMA due to application for metal of a tap hole equipped with a siphon channel
The proposed technology of smelting of ferrous scrap, as compared with the technology conventionally used, decreases capital costs because of absence of heavy-duty electric arc furnace and respective costly power infrastructure for its operation.