温度和压力对液态CO2置换开采天然气水合物的分子动力学模拟研究

Molecular dynamics simulations of liquid CO2 replacement extraction of natural gas hydrate by temperature and pressure

中文关键词: CO2置换机理  温度  压力  分子动力学模拟

英文关键词: CO2 replacement mechanism  temperature  pressure  molecular dynamics simulation

中文摘要:

      CO2置换法是天然气水合物具有广阔前景的开采方法之一。然而，其内在的置换机理尚不明晰，没有统一的认识，并且置换时CH4-CO2混合水合物阻碍传质影响了置换速率。考虑不同的CO2置换机理，本文建立了在CH4-CO2混合水合物存在的情况下CO2置换的分子动力学模型，研究了温度与压力条件对CO2置换特性的影响规律。结果表明：在压力为5MPa，温度在261～281K的情况下，温度越高，水合物笼状结构越不稳定，置换反应速率越快，并且温度对水合物笼状结构的影响显著。在温度为281K，压力在5～9MPa的情况下，置换反应对压力变化相对不敏感。对实际置换反应的控制建议考虑改变温度条件来实现。

英文摘要:

      The CO2 replacement method is one of the most promising methods for the exploitation of natural gas hydrate. However, the internal replacement mechanism remains unclear, and there is no consensus on it. Additionally, the mass transfer of CH4-CO2 mixed hydrate during replacement has a significant impact on the replacement rate. Considering the different mechanisms of CO2 replacement, a molecular dynamics model of CO2 replacement in the presence of CH4-CO2 mixed hydrate was established, and the influence of temperature and pressure on the characteristics of CO2 replacement was studied. The findings indicate that at a pressure of 5MPa and temperatures ranging from 261 to 281K, the higher the temperature, the more unstable the hydrate cage structure becomes, leading to a faster replacement reaction rate. Moreover, the influence of temperature on the hydrate cage structure is significant. When the temperature is 281K and the pressure is from 5 to 9MPa, the replacement reaction is relatively insensitive to pressure changes. The control of the actual replacement reaction is recommended to be realized by changing the temperature condition.