酸性天然气与水体系内超临界-气-液-水合物多相平衡模型

Supercritical-gas-liquid-hydrate multiphase equilibrium model in the sour natural gas and water system

针对酸性天然气与水体系内超临界-气-液-水合物多相平衡,构建了基于Gibbs自由能最小化原理的多组分流体多相平衡模型。为了提高其鲁棒性和计算精度,提出了相态稳定性判别的热力学判据和相组成分析的约束优化模型;考虑分子间非对称相互作用,建立了改进的Peng-Robinson状态方程,提出了统一的气体多参数平衡常数关系式,构建了不同相态中的逸度模型;建立了CH_(4)+CO_(2)+H_(2)S+H_(2)O体系的相平衡实验数据库,提出了对相平衡模型参数进行同步确定的多参数非线性拟合算法。与传统模型对比结果表明,新模型的收敛性更好、计算误差更小。

As for the supercritical-gas-liquid-hydrate multiphase equilibrium in the sour natural gas and water system, a multi-component fluid multiphase equilibrium model is established based on the minimization principle of Gibbs free energy. To improve the robustness and calculation accuracy of the above model, this paper proposes a thermodynamic criterion for phase stability judgment and a constrained optimization model for phase composition analysis. Considering the asymmetric interaction between molecules, the paper establishes an improved Peng-Robinson equation of state, puts forward a unified multi-parameter equilibrium constant relation of gas, and sets up a fugacity model under different phase states. Moreover, the paper establishes an experiment database of phase equilibrium of the CH_(4)+CO_(2)+H_(2)S+H_(2)O system, and proposes a multi-parameter nonlinear fitting algorithm for the simultaneous determination of parameters of the phase equilibrium model. Compared with the traditional model, the proposed model has better convergence and smaller calculation errors.