Sulfur dissolves in molten oxide slag as a sulfide (S\(^{2-}\)) under many high-temperature metallurgical processing environments. O\(^{2-}\) and S\(^{2-}\) exchange reaction in the molten oxide has been well known. Traditionally, a sulfide capacity (\(C_{\text{S}}\)) was used to characterize the S-holding ability of molten slags under given sulfurizing potential (\(p_{{\text{S}}_2}/p_{{\text{O}}_2}\))—dilute dissolution behavior of sulfide in the molten slags. A number of sulfide capacity models have been reported. Those were reviewed with an emphasis on their core idea regarding the formulation of \(C_{\text{S}}\) models. It was pointed out that two issues should be explicitly taken into account in the modeling of sulfide dissolution in molten oxide: “oxygen distribution” in the slag (free, non-bridging, and bridging oxygens) and “sulfide stability.” These two issues are the core facts that control the sulfide dissolution in the molten oxide. The \(C_{\text{S}}\) models taking into account these issues resulted in improved results for the sulfide capacity calculation. In addition to this, some additional issues which were often neglected were raised: (1) sulfide dissolution in acidic slag, (2) sulfide dissolution at high S content, and (3) sulfide dissolution in multi-component slag where more than one basic oxide exist. These issues were interpreted by “cooperative phenomena” using the Modified Quasichemical Model (MQM) in the quadruplet approximation. This approach treats the \(C_{\text{S}}\) as the real S content under a given sulfurizing potential by formulating the Gibbs energy of the “oxysulfide” solution. The model explicitly distinguishes two distinct sublattices for cations and anions. A Second-Nearest-Neighbor (SNN) Short-Range Ordering (SRO) between two different cations over O anion was considered, which accounts for the distribution of free, bridging, and non-bridging oxygens in the slag. A First-Nearest-Neighbor (FNN) SRO between cation and anion (O and S) was taken into account, which represents the chemical stability of sulfide of different cations. By simultaneously taking into account the FNN- and SNN-SRO using the quadruplets, a configurational entropy of the mixing in the solution was described. Therefore, the approach takes into account the actual sulfide dissolution mechanism in the molten oxide more realistically, thereby resulting in superior prediction ability for the sulfide capacity calculation. In addition, the application of the MQM was extended in a highly concentrated region of sulfide, thereby describing molten “oxysulfide.” Recent experimental works on oxysulfide phase diagrams and the model calculations are discussed to show the wider model applicability. Sulfide dissolution in slags with more than one basic oxide component results in the sulfur association with the various cations. A quantitative description of the different cation-sulfur associations is described in terms of the FNN SRO. By considering the FNN SRO, it is possible to find which cation is more associated with sulfur than other cations. The application of the model is also useful not only in understanding the dissolution behavior of sulfide in slags but also in designing slag/flux in various metallurgical processes.

在许多高温冶金加工环境下，硫以硫化物 (S \(^{2-}\) ) 的形式溶解在熔融氧化物炉渣中。O \(^{2-}\)和 S \(^{2-}\)在熔融氧化物中的交换反应已经众所周知。传统上，硫化物容量（\(C_{\text{S}}\)）用于表征给定硫化电位下熔渣的 S 保持能力（\(p_{{\text{S}}_2}/ p_{{\text{O}}_2}\) )——硫化物在熔渣中的稀释溶解行为。已经报道了许多硫化物容量模型。那些被审查的重点是他们关于\(C_{\text{S}}\)公式的核心思想楷模。有人指出，在熔融氧化物中硫化物溶解的建模中应明确考虑两个问题：炉渣中的“氧分布”（游离、非桥连和桥连氧）和“硫化物稳定性”。这两个问题是控制熔融氧化物中硫化物溶解的核心事实。的\（C _ {\文本{S}} \）考虑到这些问题的模型改进了硫化物容量计算的结果。除此之外，还提出了一些经常被忽视的其他问题：(1) 酸性炉渣中的硫化物溶解，(2) 高 S 含量下的硫化物溶解，以及 (3) 多组分炉渣中的硫化物溶解，其中超过一种碱性氧化物存在。这些问题通过使用四元组近似中的修正准化学模型 (MQM) 的“合作现象”来解释。这种方法处理\(C_{\text{S}}\)通过公式化“氧硫化物”溶液的吉布斯能，作为给定硫化电位下的真实 S 含量。该模型明确区分了阳离子和阴离子的两个不同亚晶格。考虑了 O 阴离子上的两个不同阳离子之间的第二最近邻 (SNN) 短程排序 (SRO)，它解释了渣中游离、桥连和非桥连氧的分布。考虑了阳离子和阴离子（O 和 S）之间的第一最近邻 (FNN) SRO，它代表了不同阳离子硫化物的化学稳定性。通过同时考虑使用四元组的 FNN-和 SNN-SRO，描述了溶液中混合的构型熵。因此，该方法更真实地考虑了熔融氧化物中实际硫化物的溶解机制，从而为硫化物容量计算提供了优越的预测能力。此外，MQM 的应用扩展到了硫化物高度集中的区域，从而描述了熔融的“氧硫化物”。讨论了最近关于硫氧化物相图的实验工作和模型计算，以显示更广泛的模型适用性。含有一种以上碱性氧化物成分的熔渣中的硫化物溶解导致硫与各种阳离子缔合。FNN SRO 描述了不同阳离子-硫缔合的定量描述。通过考虑 FNN SRO，可以找到哪个阳离子比其他阳离子与硫更相关。