Elemental mercury occurs naturally in traces in fossil fuels, such as crude oil and natural gas. Knowledge of the mercury solubility in natural gas is critical in order to avoid mercury drop-out, which can cause health, safety, and environmental issues during operation, maintenance, or equipment decommissioning. Moreover, mercury transformation to other forms, such as solid HgS, further complicates the management of mercury levels in a processing plant, as well as the design of mercury removal processes. Therefore, thermodynamic models and algorithms that can accurately describe the chemical and phase equilibria of mercury in natural gas are of paramount importance. In this work, a multiphase flash algorithm is implemented for calculating the solubility of elemental mercury in typical natural gas fluids. The algorithm can handle three- and even four-phase systems (vapor-liquid hydrocarbon-water-mercury), while a free-mercury assumption is proposed to accelerate solution speed. In addition, a simultaneous chemical and phase equilibrium algorithm is employed for studying a theoretical reaction between mercury and H₂S that can lead to solid HgS formation in natural gas. Both algorithms are coupled with the UMR-PRU model, and new interaction parameters are estimated for groups Hg and H₂S with CO₂, N₂, and hydrocarbons, yielding very satisfactory results. Despite the lack of experimental data for comparison, the study of mercury solubility and reaction in natural gas with the proposed algorithms leads to very useful qualitative results, which agree with field observations.

元素汞天然存在于化石燃料中，例如原油和天然气中。为了避免汞掉落，了解汞在天然气中的溶解度至关重要，汞会在运行，维护或设备退役期间引起健康，安全和环境问题。此外，汞向其他形式（例如固体HgS）的转化，使加工厂的汞水平管理以及除汞工艺的设计更加复杂。因此，能够准确描述天然气中汞的化学和相平衡的热力学模型和算法至关重要。在这项工作中，采用了一种多相闪蒸算法来计算元素汞在典型天然气流体中的溶解度。该算法可以处理三相甚至四相系统（汽-液烃-水-汞），而提出了自由汞假设以加快求解速度。另外，采用化学和相平衡的同时算法研究汞与氢之间的理论反应₂ S可导致天然气中形成固态HgS。两种算法都与UMR-PRU模型耦合，并且针对Hg和H ₂ S与CO ₂，N ₂和碳氢化合物的组估计了新的相互作用参数，产生了非常令人满意的结果。尽管缺乏用于比较的实验数据，但使用所提出的算法对汞在天然气中的溶解度和反应的研究仍产生了非常有用的定性结果，与现场观察结果一致。