CO2水合物膜生长过程热质传递规律与分形动力学模型研究

CO2 hydrate technology, to a certain extent, can be applied to seawater desalination, solution concentration, gas separation and seabed sequestration. Gas hydrate film is the main form in hydrate growth process, it will be of great importance in research of gas hydrate film growth，which is leading us to overall understanding of hydrate growth kinetics and development of technologies to promote or inhibit hydrate growth. In this study, nuclear magnetic resonance technique is applied to quantitative analysis of the process of CO2 hydrate film growth, the physical parameter of CO2 solution, the bulk shape and pore microstructure of CO2 hydrate film are obtained; Based on the experimental results and the theories of random fractal geometry, the three-dimensional fractal pore network model for gas hydrate film is developed by the improved simulated annealing alogrith (SAA)，and various phenomena, such as liquid-phase diffusion and flow, temperature gradient, as well as pore microstructure characteristic are considered into the mathematical model，the mechanisms of heat transfer and mass transfer of water or CO2 molecules in hydrate film is explored, besides, the effect on hydrate film growth is analyzed. Moreover, based on considering a series of influences of pressure, temperature, degree of supercooling, salt, and memory effect, the fractal kinetic model of CO2 hydrate film growth is developed accurately, the mechanisms of heat transfer and mass transfer in modeling hydrate film growth are concluded.

CO2水合物技术在一定的程度上可以用于海水淡化、溶液提浓、气体分离及海底封存等。气体水合物膜生长是水合物生长的主要形式，因此研究水合物膜生长规律对于理解水合物生长动力学及进一步开发促进和抑制水合物生长的应用技术具有重要意义。本研究应用核磁共振技术实现CO2水合物膜生长过程的动态检测及量化分析，得到CO2-水溶液物性、水合物膜的整体形态及微观孔隙结构参数变化规律；基于实验数据及随机分形理论，采用改进的模拟退火算法，考虑气液相扩散与流动、温度梯度影响，构建具有真实孔隙空间拓扑结构及几何特征的三维分形孔隙网络模型，探索水分子或CO2分子在水合物膜中的热质传递规律及其对水合物膜生长的影响；并系统地考虑压力、温度、过冷度、盐类、记忆效应等影响因素，建立准确描述CO2水合物膜生长的分形动力学模型，从而揭示水合物膜生长过程的传热传质机理。

CO2水合物技术在一定的程度上可以用于海水淡化、溶液提浓、气体分离及海底封存等。气体水合物膜生长是水合物生长的主要形式，因此研究水合物膜生长规律对于理解水合物生长动力学及进一步开发促进和抑制水合物生长的应用技术具有重要意义。本研究应用核磁共振技术实现了CO2水合物膜生长/分解过程的动态检测及量化分析，发现了气水界面水合物膜增厚的同时会伴随有水中枝晶状水合物呈分形规律生长，量化分析了水合物膜生长形态、生长厚度及增厚速率等变化参数；基于实验数据及分形理论，构建具有真实孔隙空间拓扑结构及几何特征的三维分形孔隙网络模型，探索CO2、水在水合物膜微观孔隙通道中的流动与热质传递规律；并系统地分析了压力、温度、过冷度、记忆效应、表面张力以及填砂多孔介质孔隙结构、初始水饱和度等因素影响，揭示了水合物膜生长/分解过程的传热传质机理。