Preliminary processing method for molten iron

Abstract

In the present invention, when using one converter-type smelting furnace to continuously carry out molten iron desiliconization processing and dephosphorization processing with a midway slag discharge step therebetween, in the slag discharge step a sufficient amount of slag is promptly discharged to the outside of the furnace, and sufficient dephosphorization processing in terms of cost and quality is carried out. Provided is a preliminary processing method having the following: a desiliconization step for desiliconizing molten iron (5) by supplying a gaseous oxygen source from a top blowing lance (2) to the molten iron (5) in a converter-type smelting furnace; a slag discharge step for discharging from the converter-type smelting furnace at least a portion of the slag generated by the desiliconization step; a dephosphorization processing step for, after the slag discharge step, dephosphorizing the remaining molten iron by adding a CaO solvent into the converter-type smelting furnace and supplying the gaseous oxygen source from the top blowing lance. During the desiliconization, the slag height in the furnace is measured, and in a state where the measured slag height is in a predetermined range of proportion to a free board in the furnace defined by the distance from the molten iron bath surface to the furnace throat, the desiliconization processing is stopped.

Description

technical field [0001] The present invention relates to a pretreatment method of molten iron in which desiliconization and dephosphorization of molten iron are continuously performed using a converter type refining furnace, and an intermediate slagging process is interposed between the desiliconization and dephosphorization. Background technique [0002] In recent years, the development of pretreatment technology for molten iron using a converter-type refining furnace has progressed, and the following pretreatment methods have been developed. That is, a refining method has been developed in which, after desiliconization of molten iron in a converter-type refining furnace, the converter-type refining furnace is tilted and the slag in the furnace (the slag generated by the desiliconization process is referred to as "desiliconization slag") has been developed. ") at least part of it is discharged, and then CaO-based flux is thrown into the furnace to dephosphorize the remaining...

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Problems solved by technology

However, for desiliconization slag with low electrical conductivity, the reflectivity of microwaves is very small and most of them pass through, so there are also reflected waves from the molten iron bath surface and multiple reflected waves on the molten iron bath surface and the slag surface, so The method of Patent Document 4 cannot detect the slag level

[0013] In addition, in Patent Document 5, an antenna for transmission and reception is inserted into a furnace, and in a refining furnace exposed to high-temperature slag and molten iron droplets, these droplets adhere to and solidify on the On the antenna, it is difficult to measure continuously during the refining period

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