Dephosphorization method for molten iron

Abstract

The invention provides a dephosphorization method for molten iron, which mainly aims at the dephosphorization of the molten iron of a large converter. The method comprises the following steps of: (1) supplying oxygen to the surface of the molten iron from the top through an oxygen lance, wherein the oxygen supply strength is changed in a range of 0.8 to 1.1 Nm<3> / t / min; (2) adding slag forming materials mainly comprising lime, light burned dolomite and ore into the molten iron through a hopper arranged above the converter to perform slag formation, wherein the binary alkalinity (CaO / SiO2) of the formed slag is 1.6 to 2.0; and (3) supplying stirring gas to the interior of the molten iron through a gas supply system at the bottom of the converter, wherein the gas supply strength is 0.25 to 0.40Nm<3> / t / min. The method promotes slag formation and oxygen supply by using low melting point of the low-alkalinity slag, easy slag forming property due to low temperature of the molten iron and large amount of the ore, prolongs the blowing time by using low oxygen supply strength, realizes full mix between slag and metal by using high bottom blowing strength, realizes dephosphorization, and has the advantages of good dephosphorization effect, low lime using amount, low consumption of accessories for dephosphorization and little slag discharge.

Description

technical field [0001] The invention relates to a method for dephosphorizing molten iron, in particular to a method for dephosphorizing molten iron using a large-scale top-bottom combined blowing converter. Background technique [0002] In recent years, the requirements for phosphorus content in iron and steel products have become increasingly stringent. In order to meet the requirements of steel quality, phosphorus in molten iron needs to be removed as efficiently as possible during the pretreatment stage of molten iron. Dephosphorization of molten iron is generally carried out in molten iron transport containers (such as torpedo tanks) or converters. In the process of dephosphorizing molten iron using a transport container, due to the small space above the transport container, in order to avoid splashing, the refining slag is selected from the top slag with high alkalinity and low total iron content, which limits the need for desiliconization before dephosphorization, res...

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Problems solved by technology

However, the solid oxygen sources in this method are mainly sintered ore, rolled steel scale, iron-containing dust, iron ore, iron ore, etc. These solid oxygen sources need to be processed into a particle size of less than 1mm, which needs to be dried and spraying equipment is added. Therefore This method requires large production investment and high equipment maintenance requirements, so it is difficult to popularize and apply it in most steel mills

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