Otimização da reciclagem de resíduos siderúrgicos por redução carbotérmica
Reis, Walter Luiz da Costa
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The evolution of the world-wide production of steel in rates superior to 7% per year in the last five years, strongly driven by China, which got off 222,4 millions in 2003 for 489,0 million tons in 20071, leads to a strong increase in the demand of iron ore. Therefore, fine ore price of Carajás for Asia went out from 28,14 in 2003 for 73,20 US$ cents for unity of iron in 2007. An increase of 160%. These facts, when related to the layer exhaustion and the growing environmental pressures on Iron and Steel Plants of the whole world, have been taking to a series of studies to the use of the residues bearers from iron produced in these factories. Up to that time, there has not been consolidated any technology which is technically and economically viable for the recycling of these residues so far. The present work is about the usage of the blast furnace mud, the mill scale and the iron oxide produced in the pickling lines of Companhia Siderúrgica Nacional (CSN) in self reduction pellets shape. It starts the productions in scale laboratorial and industrial after the chemical and physical characterizations from these raw materials. As soon as the most appropriated formulation was defined, the production in experimental scale began. These tests were carried out in the residues palletizing pilot plant, developed by CSN. There were also tests of self reduction and of meltreduction. In the first one, the formation of a metal drop inside a hallow sphere was obtained, and in the second one a metal profit of 99,1%. In sequence, the alternatives were valued for internal recycling of these pellets. The use of the heat contained in the empty hot-metal torpedo-cars for self-reduction showed the most economical route. This technology of recycling was introduced industrially in CSN. Thus, in the present work of doctorate, it was developed an unpublished route for industrial recycling for iron and steel residues, which was technically and economically feasible.