Investigation on the Nucleation and Crystallization Performance of Ammonium Chloride in an Oil–Gas Multicomponent Environment Using Molecular Dynamics

In the petroleum refining unit, the deposition of ammonium chloride (NH 4 Cl) crystals often leads to severe equipment corrosion. Understanding the nucleation mechanism and key influencing factors is crucial to effective corrosion prevention. In this paper, molecular dynamics simulation was performed to explore the nucleation process of NH 4 Cl and the role of multicomponent environments (containing H 2, CH 4, C 2 H 6, H 2 O, and NH 4 Cl) under realistic operational conditions. During the dynamic evolution process, NH 4 Cl molecules continuously aggregate to form a cluster structure. Water molecules exhibit the strongest interaction with these clusters due to their strong polarity and hydrogen bonding, with this interaction energy significantly intensifying as their concentration increases. This directly impacts the molecular diffusivity and the structural orderliness of the ammonium chloride clusters. Further studies demonstrate that water molecules form a strong hydrogen-bonding interaction with NH 4 + and Cl – ions. As the number of water molecules increases, the quantity of ion–water hydrogen bonds in the system increases. This promotes the formation of a solvation layer around NH 4 Cl clusters, resulting in looser structures, reduced orderliness, and significantly increased nucleation difficulty.