Refining control of top- and bottom-blowing converter by manipulating bottom-blown gas flow rate.

Abstract

SynopsisThe effect of gas bottom-blowing condition on the refining characteristics of a top-and bottom-blowing converter in comparison with that of topblowing condition has been studied, on the basis of the amount of accumulated oxygen in the converter (Os), which represents the change in oxidation/reduction reactions between hot metal and slag.It is possible to express quantitatively the relationships between hard blow/soft blow by the manipulation of top-blowing jets and strong agitation/weak agitation by that of bottom-blown gas. The manipulation of the flow rate of bottom-blown gas permits to control the blowing reaction more effectively than that o f the top-blowing jet.In connection with the above fact, dynamic control of blowing reaction in the top-and bottom-blowing converter has been done, with the flow rate of bottom-blown gas as a manipulated variable and the variation of Os as a controlled variable. By the application of the multistep optimum control theory to the blowing reaction model, the stability of blowing operation and metallurgical characteristics, i.e., the ranges of changes in (T.Fe) of slag, phosphorus and manganese concentration of molten steel at blow end, were narrowed appreciably.

Model study on mixing and mass transfer in ferroalloy refining processes

“…The estimated n values are in very good agreement with the emprical constants reported by several research workers, [1,6,[23][24][25][26][27][28][29][30] which were in the range 0.13 to 0.50.…”

“…Despite the several studies done, a question still exists concerning the optimum stirring conditions to achieve optimum liquid-phase mass transfer, since the various process and technological parameters such as metallurgical characteristics at turndown, the process of slag formation during gas injection, and the rates of carbon and phosphorus removal, as well as sulfur elimination, are controlled mostly by the extent of liquid-phase mixing. [24][25][26][27] Cold model studies of this nature are required in order to investigate the effect of gas flow rate, bath height, and location and number of tuyeres on the mass transfer rates of liquid/liquid as well as gas/liquid systems.…”

Study on metallurgical characteristics of the bottom-blown O2–CaO converter

“…At present, converter steelmaking usually adopts the smelting method of top-blowing supersonic oxygen jet and bottom blowing an inert gas to mix [1][2][3][4], and slagging lime is added in batches from the furnace mouth in lump form. However, there are some problems in the conventional steelmaking converter, such as insufficient stirring of the molten pool, slag melting slowly, and the relatively small contact area between the slag and the molten metal, which limits the dephosphorization and desulphurization ability of the slag, affects the uniformity of composition and temperature of molten steel, and slag foaming is so serious and easy to cause spills or spatter that the smelting state is not stable enough [5][6][7][8][9][10].…”