Optimal hot metal desulphurisation slag considering iron loss and sulphur removal capacity part II: evaluation

Abstract

The optimal hot metal desulphurisation (HMD) slag is defined as a slag with a sufficient sulphur removal capacity and a low apparent viscosity (η slag ) which leads to low iron losses. In part I of this study, the fundamentals behind the optimal slag were discussed. In this part these fundamentals are explored by a Monte Carlo simulation, based on FactSage calculations, plant data analysis and melting point and viscosity measurements of the optimal slag. Furthermore, the applicability of knowing the optimal slag composition for an industrial HMD is discussed.

Kinetic Simulation of Hot Metal Pretreatment: Desulfurization Using Powder Injection

“…At the end of the process, the model reveals that the BF slag transforms to a slag rich in dicalcium silicate, which is consistent with the plant data. [54] The -C2S phase is the solid solution of mainly Ca2SiO4 and Mg2SiO4 with small amounts of Fe2SiO4 and Mn2SiO4.…”

“…A common belief at HM desulfurization station is that often more than adequate amounts of Mg and lime are injected at steel plant because penalty to be paid for high final sulfur contents are higher than the costs of extra reagents (the costs associated to increased iron losses due to higher volumes of top slag are often ignored). [54] Therefore, optimization of amount of added flux is important to reduce the process cost. For this purpose, the present model was used at Tata Steel IJmuiden along with many plant campaigns.…”

“…However, it has been reported that entrainment loss is often minimized via increasing the accuracy of the skimmer control, cleaning the skimmer paddle more often, or training the operator. [54] Therefore, scenarios 1 and 5 are preferred to the scenarios 3 and 7 (i.e. less iron loss is estimated for the former ones).…”

Desulfurization of High‐Sulfur HIsarna Hot Metal

“…A slag with a low liquid fraction has a high apparent viscosity, which leads to high iron losses. [6,[26][27][28] Furthermore, a high solid fraction decreases the reaction surface and therefore the reactivity, of the slag, hampering the reaction between MgS and CaO (Reaction 2). As MgS, in contact with oxygen from the air, thermodynamically favors the formation of MgO, the sulfur would return to the hot metal, a phenomenon called resulfurization.…”

“…This will, despite slag modifiers, lead to higher iron losses. [26,27] Apart from the iron losses, the slag skimming time will increase when there is more slag to remove, leading to a longer total process time and higher temperature losses.…”