甲烷水合物恒温恒压分解过程研究  

Methane hydrate decomposition at constant temperature and pressure

作　　者：孙长宇[1] 陈光进[1] 郭天民[1] 

机构地区：[1]石油大学油气藏流体相态重点研究室,北京102200

出　　处：《地球化学》2003年第2期112-116,共5页Geochimica

基　　金：国家自然科学基金(29806009)

摘　　要：利用全透明蓝宝石釜及配套系统,采用恒定分解压力方法,在0℃以上和0℃以下两种情况下,测定了CH4水合物分解气量随时间变化数据,并考察了温度/压力推动力对分解速率的影响。实验数据表明,分解速率与推动力有关,推动力越大,分解反应速率越快。并分别建立了两种温度区间情况下的水合物分解动力学模型。当水合物分解温度高于0℃时,水合物的分解可以看作由本征反应速率控制;当温度低于0℃时,分解形成的水会迅速转化为冰,分解气体穿越水合物与冰之间的空隙扩散,分解过程可看作为冰-水合物界面的移动边界问题。采用以上理论的模型计算结果与实验所测的CH4水合物分解动力学数据吻合较好。The kinetics of methane hydrate decomposition is studied using a Sapphire cell apparatus. The kinetic data of methane hydrate decomposition at temperatures from 0.6 to 5.8 ℃ and pressures from 1.0 to 3.0 MPa are measured using constant decomposition pressure method, and at temperature of lower than 0 ℃ . The influence of temperature and pressure on decomposition rate is examined. It is revealed that the decomposition rate of methane hydrate is proportional to difference between gas fugacity at the equilibrium state and that at the actual decomposing state. When temperature is higher than 0 ℃ , the influence of mass transfer could be ignored and hydrate decomposition could be described by intrinsic reaction theory. The average deviation between the experimental gas amount and the calculated value by intrinsic reaction theory is less than 4.8% . When temperature is lower than 0 ℃ , water generated from the hydrate decomposition would transform into ice rapidly at the surface of hydrate crystal. The released gas diffuses from the hydrate and ice mixture layer to the bulk of gas phase. The thickness of hydrate and ice mixture layer would increase with the hydrate decomposition. In this case, the intrinsic reaction rate is very quickly compared with that of diffusion rate, so the hydrate decomposition process is controlled by gas diffusion. The thickness of hydrate layer is reduced correspondingly with the hydrate continuous decomposition and the boundary of ice hydrate moved toward water ice phase. The hydrate decomposition when temperature is lower than 0 ℃ could then be described as a moving boundary phenomenon. When the decomposition time is long, the Fick diffusion coefficient should be revised according to hole size among the ice layer because the ice layer became compact with the increasing of its thickness which resulting in gas diffusion not abide by Fick diffusion law. The results by the model match the experimental data perfectly showing that diffusion theory could be successfully applied to

关 键 词：甲烷水合物 分解速率 动力学 扩散 永久冻土带 温度 压力 深海沉积层 

分 类 号：P744.4[天文地球—海洋科学] P593