天然气水合物温度压力盐浓度三维相平衡曲面方程

3-D phase equilibrium surface equation of methane hydrate considering the effect of temperature, pressure and salt concentration

关键词:  水合物  三维  相平衡方程  统计热力学理论  Clausius-Clapeyron线性行为

Key words:  hydrate  3-D  phase equilibrium equation  statistical thermodynamics theory  Clausius-Clapeyron linear behavior

摘要:

天然气水合物相平衡关系在与水合物生成/分解相关的工程问题中具有重要意义。基于天然气水合物相平衡的统计热力学理论和CSMHYD软件,得到水合物相平衡点大范围的温度、压力、NaCl盐浓度数据,拟合得到精度高(拟合优度达0.99)、物理意义合理、表达简洁的天然气水合物温度-压力-盐浓度三维相平衡曲面方程。方程适用的压力和NaCl溶液浓度区间几乎涵盖了目前工程中可能遇到的所有情况。方程曲面与来自多篇文献试验数据的吻合度相当高,相平衡曲面方程的拟合函数选取更为合理,高盐度、高压区域的预测值比现有曲面精确。最后根据方程验证了曲线的Clausius-Clapeyron线性行为。 

Abstract:

Methane hydrate phase equilibrium is of great significance in engineering problems related to hydrate formation/decomposition. According to the theory of statistical thermodynamics and CSMHYD software for gas hydrate phase equilibrium, a large number of hydrate phase equilibrium data of temperature, pressure and concentration of NaCl are obtained within the scope of engineering, by which the three dimensional phase equilibrium surface equation is fitted with high precision, reasonable physical meaning and simple expression. The applicable pressure and NaCl solution concentration of the phase equilibrium equation cover almost all the situations possibly encountered in the engineering. The results of the surface equation are in good agreement with the experimental data from a lot of literature. Furthermore, the predicted values of phase equilibrium by the fitted function are more reasonable and accurate in high salinity and high pressure area than that in the literature. Based on the equation, the law of T-p equilibrium line caused by the variation of salt concentration is studied, and Clausius-Clapeyron linear behavior is verified.