细粒砂矿物成分及粒径配比对CO_(2)水合物合成特性影响的实验研究

Experimental study on influence of mineral composition and particle size ratio of fine-grained sand on synthesis characteristics of CO_(2)hydrate

在冻土层中用水合物法封存CO_(2)是一种具有潜力和前景的CO_(2)封存技术。为探究地层性质对CO_(2)封存的影响,在初始压力5.5 MPa、温度1.27℃的条件下,在不同细粒砂矿物成分及粒径配比的影响下进行了CO_(2)水合物合成实验,对实验过程中CO_(2)水合物生成过程的压力-温度变化、CO_(2)水合物平均生成速率、CO_(2)耗气量和相饱和度等进行了分析。结果表明,细粒砂与粗粒砂粒径配比(各组分质量比,下同)为1.0:2.0时的CO_(2)水合物平均生成速率最小(12.60 mmol/min),随着粗粒砂比例的增大,比表面积减少,CO_(2)水合物平均生成速率变慢。蒙脱石黏土不利于CO_(2)水合物生成,粉砂组(含细粒砂与粗粒砂)CO_(2)水合物平均生成速率高于粉砂质黏土组(含细粒砂和蒙脱石黏土),且粉砂组实验更容易实现高的水合物饱和度和CO_(2)耗气量,因此在矿物成分含细粒砂与粗粒砂的区域更适合进行CO_(2)封存。细粒砂与粗粒砂或黏土矿物粒径配比为1.0:0.5时的CO_(2)耗气量分别为0.86 mol、0.77 mol,随着粗粒砂和黏土矿物比例的增大,水合物相饱和度和CO_(2)耗气量均逐渐减小,细粒砂与粗粒砂或黏土矿物粒径配比为1.0:0.5时是适合水合物法封存CO_(2)的比例。

The use of hydrate-based technology for CO_(2) sequestration in permafrost layers is a promising and potential CO_(2) sequestration technique.In order to investigate the influence of formation properties on CO_(2) sequestration,CO_(2) hydrate synthesis experiments were conducted under the conditions of initial pressure of 5.5 MPa and temperature of 1.27℃and the influence of different mineral compositions and particle size ratio of fine-grained.The pressure-temperature changes,CO_(2) hydrate average synthesis rates,CO_(2) consumptions,and phase saturations during the CO_(2) hydrate formation process were analyzed during the experiment.The results show that the CO_(2) hydrate average synthesis rate is the smallest when the ratio of fine-grained sand to coarse-grained sand particle sizes(mass ratio of each component,the same below)is 1.0:2.0,which is 12.60 mmol/min.With the increase of coarse sand proportion,the CO_(2) hydrate average synthesis rate decelerateds due to the reduction of specific surface area.Montmorillonite clay is not conducive to CO_(2) hydrate formation,and the CO_(2) hydrate average synthesis rate of the silty sand group(contains fine-grained sand and coarse-grained sand)is higher than that of the silty clay group(contains fine-grained sand and montmorillonite clay).And the experiments in the silty sand group are more likely to achieve high hydrate saturation and CO_(2) consumption,making it more suitable for CO_(2) sequestration in areas with mineral compositions containing fine-grained sand and coarse-grained sand.The CO_(2) consumption rates for the ratio of finegrained sand to coarse-grained sand or clay mineral particle sizes of 1.0:0.5 are 0.86 mol and 0.77 mol,respectively.With the increase of the proportion of coarse-grained sand and clay minerals,both the hydrate saturation and CO_(2) consumption gradually decrease.The ratio of fine-grained sand to coarse-grained sand or clay mineral particle sizes of 1.0:0.5 is suitable for CO_(2) sequestration using the hydratebased method.