The Hampering Effect of Precipitated Carbon on Hot Metal Desulfurization with Magnesium

Abstract

Carbon may precipitate during the hot metal desulfurization (HMD) process as a result of carbon oversaturation because of temperature decrease. The precipitated carbon flakes form a layer between hot metal and slag. It is postulated that this carbon layer hampers desulfurization with magnesium by preventing MgS particles from reaching the slag phase. At Tata Steel in IJmuiden, the Netherlands, carbon in hot metal is measured in 657 heats after reagent injection. With this data, it can be determined whether the hampering effect of precipitated carbon on MgS flotation has a significant effect on the performance of the industrial HMD process. Plant data show a correlation between the precipitated carbon and the specific magnesium consumption for hot metal with a low initial sulfur concentration (below 225 ppm). This correlation cannot be found for hot metal with a higher initial sulfur concentration (above 275 ppm). Furthermore, a sulfur mass balance is made over the converter process, that shows no effect of carbon precipitation during HMD on resulfurization in the converter. The limited experimental accuracy of the plant data prevents a quantitative description of the hampering effect. The measurements do suggest that the effect is small.

Optimal hot metal desulphurisation slag considering iron loss and sulphur removal capacity part I: fundamentals

“…These differences in a O are caused by different process conditions, the large error for EMF measurements at low ranges and typical HMD temperatures (up to 50% [29]) and the different measurement depth. It is expected that a O at 50 cm below the metal-slag interface, where industrial EMF measurements are typically done, is higher than at the metal-slag interface itself, where carbon oversaturation and precipitation locally lowers a O [14,33]. As for C S the a O value at the metal-slag interface is relevant, a O = 5•10 −7 (0.5 ppm) is used in this study.…”

Desulfurization of High‐Sulfur HIsarna Hot Metal

“…In industrial HMD stations, ṁMg values between 1.0 and 2.5 are observed. [9,10,13,14] This wide range is caused by differences in process conditions and reagent quality. However, to have a fair measure for desulfurization efficiency of industrial HMD stations, ṁMg needs to be corrected for part of the magnesium remaining dissolved in the hot metal without reacting with the dissolved sulfur.…”

“…This leads to the following adjusted specific magnesium consumption ( ṁ ’ Mg ). [ 6,13 ] …”

“…This means that for an industrial HMD process, the desulfurization efficiency can be expressed by the specific magnesium consumption ( ṁ Mg ). [ 6,13 ] …”