超临界水中硫酸钠结晶动力学的分子动力学模拟

在超临界水反应器中,硫酸钠是易造成堵塞的一种常见无机盐,研究其结晶动力学对于防盐沉积反应器的设计具有重要意义.本文采用LAMMPS分子动力学模拟软件研究硫酸钠在超临界水中的微观结晶过程,其中水分子采用SPC/E模型,离子-离子、离子-水分子相互作用采用Coulumb和Lennard-Jones联合势能函数.结果表明:水对离子的静电屏蔽作用随温度升高而增强、随密度减小而减弱;增大超临界水的温度和密度有利于离子扩散,进而促进离子相互碰撞、成核;在模拟的超临界水参数范围内,其成核速率的数量级为1029cm^-3·s^-1,生长速率为(19.8~25.8) m·s^-1.

Molecular Dynamics Simulation on Crystallization Kinetics of Sodium Sulfate in Supercritical Water

Sodium sulfate is a common inorganic salt that causes blockage in supercritical water (SCW) reactors. An investigation of its crystallization kinetics is important for the design of deposition-preventing reactors. Microscopic crystallization process of sodium sulfate in SCW was studied with LAMMPS molecular dynamics simulation. Water molecule was calculated with SPC/E model, and ion-ion and ion-water interactions were calculated with Coulumb and Lennard-Jones combined potential energy functions. It shows that the impact of water on electrostatic shielding effect of ion charges decreases at higher temperatures and lower densities. Increasing temperature and density is advantageous to diffusion of ions, which helps ions to collide and form nuclei. Magnitude of nucleation rate is generally in the order of 10²⁹ cm^-3s^-1 in simulated parameters range of SCW.