Abstract: The present invention relates to a concentric multi-tube-system nozzle situated beneath the surface of the melt in a refining vessel, especially a refining vessel for converting molten pig iron into steel.The stability and life of the concentric double-tube nozzle is the most crucial factor in carrying out refining in a bottom-blown converter.In accordance with the present invention, there is provided a concentric multi-tube-system nozzle situated beneath the surface of the melt in a refining vessel, comprising:an inner tube;an outer tube positioned concentrically with respect to the inner tube and forming an annular clearance between the inner tube and the outer tube;spacers for circumferentially dividing the annular clearance; anda section defined by two adjacent spacers, the section comprising a contraction portion which is positioned essentially at the upstream side of the section. The contraction portion contributes to a uniform cooling of concentric double-tube nozzle in the circumference thereof.

Abstract: A method of switching bottom blown gases and an apparatus suitable for carrying such method into practice in blowing successively in turn a plurality of gases through piping into molten steel in a steel-making furnace through tuyeres or porous plugs for gas blowing located in a lower portion of the steel-making furnace. The method includes the step of directly releasing into atmosphere at least a portion of the gas flowing in and through the piping in response to a rise in the pressure of the gas when switching the blown gases.

Abstract: A method for classifying wet coal for obtaining coal charges suitable for use in a coke oven comprising classifying the wet coal directly in a cylindrical screen which rotates and revolves around an eccentric rotation shaft while blowing a high pressure gas stream to the screen to eliminate adhesion of the wet coal particles to the screen. The method enables a continuous and consistent classification of wet coals without the clogging of the screen and the dust pollution. The cokes obtained by dry distillation of the coal classified by the present method show high quality.

Abstract: An improved converter steelmaking process that achieves a great increase in the refining capability of top-blown oxygen is provided. The process applies to an oxygen top-blowing converter that also permits bottom blowing of gas and it is characterized by supplying oxygen from a top-blowing lance and a bottom-blowing nozzle substantially throughout the refining operation, with 2 vol. % to less than 17 vol. % of a predetermined total oxygen flow rate being supplied from the bottom-blowing nozzle whereas the remaining part of oxygen is blown onto the surface of the hot metal from the top-blowing lance.