Prediction of phase equilibrium of gas hydrates based on different equations of state

doi:10.11949/j.issn.0438-1157.20180794

Abstract

Abstract:

The fugacity calculation results will directly affect the prediction accuracy of the phase equilibria of gas hydrates. Based on the Chen-Guo model, four equations of state (RK, SRK, PR and PT EOS) are used to calculate the fugacity, then to predict the phase equilibria of methane, ethane and carbon dioxide gas hydrates in different temperature ranges, respectively. Results show that for pure water system the model with RK EOS is most suitable for predicting the phase equilibria of methane hydrate, while PR EOS is more suitable for the prediction of ethane and carbon dioxide hydrates. For ice system, SRK EOS is the most suitable for methane hydrate but the prediction below 218.2 K is the main reason for the low prediction accuracy. PR EOS suits the prediction of ethane hydrate and the prediction accuracy for the case below 230.2 K still needs to be improved. And RK EOS is suitable for predicting carbon dioxide hydrate, the prediction accuracy will be improved further if the prediction results below 270.7 K can be much closer to the experimental data.

Key words: gas, hydrate, phase equilibria, equation of state, prediction, fugacity

摘要：

气相逸度的计算结果会直接影响气体水合物相平衡条件的预测精度。基于Chen-Guo模型，选取RK、SRK、PR以及PT四种状态方程计算逸度，分别对甲烷、乙烷以及二氧化碳三种不同气体水合物在不同温度范围内的相平衡条件进行计算。结果表明：纯水条件下，RK方程最适合预测甲烷水合物相平衡条件，而PR方程更适合预测乙烷及二氧化碳水合物相平衡条件；对于冰中，SRK方程适合预测甲烷水合物的相平衡条件，PR方程适合预测乙烷水合物的，而RK方程更适合二氧化碳水合物的；对于甲烷水合物，低于218.2 K的预测是导致模型预测精度偏低的原因；对于乙烷水合物，需要提高低于230.2 K的预测精度；对二氧化碳水合物而言，提高对低于270.7 K的预测可以进一步提高模型预测精度。

关键词: 气体, 水合物, 相平衡, 状态方程, 预测, 逸度

CLC Number:

TQ026

LI Siguang, LI Yanjun, YANG Longbin, SHAO Yazhou, SUN Jianrong, XU Runzhang. Prediction of phase equilibrium of gas hydrates based on different equations of state[J]. CIESC Journal, 2018, 69(S1): 8-14.

李思广, 李彦军, 杨龙滨, 邵亚洲, 孙剑蓉, 徐润章. 基于不同状态方程预测气体水合物相平衡条件[J]. 化工学报, 2018, 69(S1): 8-14.

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