| The slag processing and using is an important requirement about the development of circular economy for iron and steel industry.In the First Steel Plant of Xinyu Iron and Steel Group the industrial test of LF hot slag recycling has been carried out. By scanning electron microscopy, the molten steel is analyzed about inclusions contained sulphur element in LF slag recycling; the slag is studied by thermodynamic calculation in the cycling and the change of desulfurization performance of the slag is analyzed; By using scanning electron microscopy, XRD and mineralogical microscopes, the phase composition and morphology of the slag are analyzed.The steel samples which are analyzed in the industrial test cycling shows that: (1)In cycling, the end of [S] in the refining have achieved the goal of controlling components and met the production requirements for non-aluminum steel and aluminum steel;(2) Inclusions contained sulfur element are for 3μm,30μm,40μm in size, the shape of the inclusions are roughly spherical; The inclusions contained sulfur element present in the Inclusion of CaO·Al2O3·MgO·FeO,Al2O3·MgO·ZrO2·FeO. CaO·ZrO2·FeO.The thermodynamic results show that:(1) The alkalinity of slag in cycling is similar to the alkalinity of initial slag, the average alkalinity of initial slag are 3.2, the alkalinity of majority salgs in cycling are in the level of 2.8 to 3.3; The (FeO+MnO) content of slag in cycling are less than 1.5%, the reductibility of slag is better;(2) Adding lime are for 2 kg/t,2.2 kg/t,2.7 kg/t,3.4 kg/t,4 kg/t,4.3kg/t to hot slags can maintain a high desulfurization rate,the 84% of average desulfurization rate can be obtained, corresponding the sulfur distribution ratio is at 170～420 and the sulfur capacity is 0.02～0.037. At no-adding lime conditions, the tapping temperature is about 1600℃, the 84% of average desulfurization rate are available; Corresponding the sulfur distribution ratio is 230～403 and the sulfur capacity is 0.038～0.06. LF slag phase analysis shows that: (1) The slag of aluminum steel has a relatively larger degree of superheat than non-aluminum steel, the degree of superheat of aluminum steel are higher than 100℃, the degree of superheat of non-aluminum steel is between 68℃and 124℃. Aluminum steel and non-aluminum steel slag are influenced by the alkalinity largely, but the change of slag phase have not a big difference. Figure from the mineral phase microscope and scanning electron microscopy can be seen that the slag phase is in the uniform distribution and the melting of slag is in a good condition.(2) The phase of LF slag mainly compose of calcium silicate mineral,calcium aluminate composition and contains a small amount of no-melting magnesium oxide, calcium oxide, alumina oxide. The dicalcium silicate contains C2S,C3S, The calcium aluminate contains CA,C2A,C3A and C12A7, there is also a small amount of composition phase of calcium and magnesium system,calcium and aluminum system,magnesia and aluminum system.(3) The salg phase contained sulfur element is failed to find its existence in aluminum steel and non-aluminum steel. |
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