Abstract: Isothermal pressure search method was used to measure the phase equilibrium conditions of cyclopentane (CP)-methane hydrates in the temperature range from 84.4 to 303.8 K and the NaCl mass concentration range from 0 to 10%. The results indicate that the equilibrium pressures of structure II hydrates of CP-methane are lower than that of methane hydrate. The phase equilibrium pressures of CP-methane hydrates increase with the increase of temperature, and increase linearly with the increase of NaCl concentration in solutions. Moreover, the effects of temperature and NaCl concentration are enlarged at a high temperature. A calculation and prediction model for equilibrium conditions of CP-methane (structure II) hydrates has been developed based on Van der Waals-Platteeuw isothermal adsorption theory and Pitzer activity coefficient model. The prediction results show that the model can depict the equilibrium conditions of CP-methane (structure II) hydrates well (average relative error at 4.07%).

Key words: cyclopentane-methane hydrate, phase equilibrium, model, brine system

摘要： 利用恒温搜索法测定了温度284.4~303.8 K、NaCl质量浓度0~9.978%水溶液中环戊烷-甲烷水合物(II型)的相平衡条件. 结果表明，该体系水合物相平衡压力远低于纯甲烷水合物，且随温度升高和盐度增大逐渐升高. 在Van der Waals-Platteeuw等温吸附模型和Pitzer活度模型的基础上建立了环戊烷-甲烷水合物在盐水体系中的相平衡理论模型，模拟预测值与实验测定值的吻合度较好，平均相对误差为4.07%，能较好地预测盐水体系中环戊烷-甲烷水合物(II型)的相平衡条件.

关键词: 环戊烷-甲烷水合物, 相平衡, 模型, 盐水体系