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In order to enhance the dispersion of desulfurizing agents into hot metal, the injection of nitrogen gas has been used together with the revolutional stirring by an impeller of a gate type. At the both ends of the impeller, a nozzle is embedded and used for the injection of nitrogen gas into hot metal toward the direction opposite to the movement of the impeller.Water model experiments show that the gas injected efficiently breaks up a cone shaped agglomerate of desulfurizing agents at the bottom of the rotational vortex formed around the impeller shaft and makes it disperse homogeneously into the bath. This suggests that the chemical efficiency of desulfurization will be improved to a greater extent than that without the gas injection.The plant scale equipment has been constructed to desulfurize 60t of hot metal in a ladle. Under the condition of 77 rpm in revolution rate and 3 Nm3/min of nitrogen gas, sulfur content of 0.05% is reduced to 0.012% after the treatment of 1 1 min with calcium carbide of 3kg (75% in purity) per ton of hot metal.The observed rate of desulfurization is reasonably interpreted in terms of the rate controlled by sulfur transfer in hot metal.

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D esulfurizatioll equilibria between olle oj Ce, La, T i, Zr alld S in liquid iron are determilled, preventing oxygen cOlltamillatioll oj the iroll melts Jrom crucible material and oxysuifide Jormation ill them. T he results obtained are summarized asJollows .' (1) Equilibrium constallts oj desulfurizillg reactiolls Jor theformatioll q{CeS(s) , LaS(s) , TiS(s), or Z r,S. (s) as tlte equilibrium phase are givell by log K Ce = 20 600/ T + 6.3 9 log K L. = 26 OOO/ T +S.9 8 log K Ti =-S OOO/ T + 4.0, log K zr =-44 100/ T + 19. s ill the temperature range Jrom J 550° to J 650°C, (2) i llteraction parameters betweell tlte desulfurizillg elemellts alld Sll /fur ill liquid iroll are determilled to be e~Ce) =-9.1 , e~L.) =-IS'3(1 6 10°C) e~T!) =-O. IS , e~Z r) =-0.22 at J 600 0 e. (3) Stalldard free ellergy challges for the reactiolls; C e(l) = Ce(%) La(l) = La(%) are derived to be JCS. Co =-24 SOO ca l/ mol , Lle~. La = 12 300 ca l/ mol at J 600 0 e, aod those ofthe forma tioll for T iS (s) alld Z raS, (s) are also determilled at J 600 0 e to be-57 000 all d-227000 cal /mol, respectively.