水泥强度诱导提高方法研究

利用物理性能检测、水化放热测定和孔结构测定方法研究了通过掺加微细矿渣、高铝组分和水化硬化浆体诱导提高硅酸盐水泥强度的方法，并对其作用机理进行了探讨，试验表明，适量的微细高铝组分、矿渣组分及水化硬化浆体能够明显提高硅酸盐水泥强度。     

Thermodynamic optimization for crystallization process of gas hydrate

In this paper, thermodynamic optimization is applied to analyze the crystallization process of the gas hydrate related to the gas hydrate cool storage system. Thermodynamic optimization model of the gas hydrate crystallization process is established. By taking the entropy generation minimization as the optimization objective, both the optimal control strategy and the optimal cooling rate of the gas hydrate crystallization process are determined. The minimum entropy generation corresponding to the optimal cooling rate decreases by 7.8% compared with normal situation. The results presented in this paper can provide important guidelines for optimal design and operation of the gas hydrate crystallization process. Copyright © 2010 John Wiley & Sons, Ltd.     

Prediction of carbon dioxide separation from gas mixtures in petroleum industries using the Levenberg–Marquardt algorithm

In this study, two mathematical models for hydrate formation process to separate carbon dioxide by a combination of two different kinds of organic and surfactant promoters are presented. Promoters such as sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and dodecyl trimethyl ammonium chloride as surfactant promoters; also, tetrahydrofuran, cyclopentane, 1,3-dioxolane, and 2-methyl tetrahydrofuran as organic promoters have been used in recent years. The results showed that a combination of 3000 ppm of surfactant promoters and 4 wt% organic promoters had the highest separation rate of carbon dioxide and; consequently, the investigated models were based on this optimum condition. As a matter of fact, by using these simulations the hydrate formation behavior was predicted with high accuracy; moreover, conducting consuming experiments is not essential anymore. To sum up, in the present research both Vandermonde matrix model and Levenberg-Marquardt algorithm were applied to predict the hydrate formation behavior; in addition, their results were precisely considered and validated with experimental data.     

Molecular insights into structural properties around the threshold of gas hydrate formation

Molecular modeling is used to obtain the formation mechanism and stability of structure I methane hydrate. A simple approach is presented to reveal the formation of the characteristic cage of structure I hydrate by water molecules around the methane guest molecules after 1 ns via reducing the temperature from 400 to 275 K under canonical ensemble condition. Then, the stability of methane clathrate hydrate structure is studied during the simulation time of 200 ps. To evaluate the structure of methane hydrate, the radial distribution functions of host–host, host–guest, and guest–guest molecules are obtained. The results prove the methane hydrate formation and its stability.     

Recovering CH4 from natural gas hydrate with CO2 in porous media below the freezing point

The recovery of methane from gas hydrate layers that have been detected in permafrost regions is a promising perspective in the future. In order to study the replacement characteristics of CO₂–CH₄ hydrate in permafrost environments, simulation experiment was carried out in this work. The results indicated that the replacement rate and efficiency increased with the increasing of injection pressure of CO₂ gas. And the replacement rate and efficiency reached up to 0.403?mmol/h and 13.20% during the experiment. Furthermore, the results also showed that the replacement rate of CO₂–CH₄ hydrate was slower below the freezing point.     

石英砂粒径大小对甲烷水合物形成及分布的影响

为了研究不同粒径多孔介质体系中甲烷水合物的形成，本文采用粒径分别为0.075~0.5mm、0.5~1mm、1~2mm和2~3mm的石英砂作为多孔介质，在初始压力7.0MPa、温度0.5℃条件下进行水合物形成实验并进行取样观察、分层分解，得出不同粒径大小石英砂中甲烷水合物形成及分布的特征。结果表明：随着石英砂粒径的增大，石英砂砂体中的水合物形成量和初始水合物形成速率在逐渐减小；在粒径为0.075~0.5mm、1~2mm和2~3mm石英砂中，充气过程中水合物便开始形成，且并未出现明显的水合物大量形成阶段，而在粒径为0.5~1mm石英砂体系中出现了水合物大量形成的阶段；通过计算发现，0.5~1mm石英砂体系的气体消耗量最大，为0.47mol，2~3mm石英砂体系的气体消耗量最小，仅为0.05mol；在这4种粒径的石英砂体表面的甲烷水合物主要以分散状均匀分布于颗粒之间或胶结成块，但这一观察结果与通过分解的方法所得到的石英砂上部水合物形成量大于下部的结果存在差异；重复实验也发现，仅在粒径为0.5~1mm石英砂顶部出现了水合物大量富集的现象，因此推断认为在一定粒径的介质体系同时上部存在较大空隙时，水合物有可能会在空隙中大量富集存在。这一实验结果对自然环境中水合物的赋存区域及形态的预测具有一定的参考价值。     

海洋天然气水合物储层拉削开采新方法及可行性分析

针对深水浅层非成岩天然气水合物借鉴刨煤机刨削采煤过程提出一种新的拉削开采方法，参照拉刀结构特点设计了一种集开采、收集和输送为一体的拉削管。建立了拉削开采三维模型，对其工作原理和工作步骤进行了说明。用有限元仿真对采空区和拉削管受力进行了分析。结果表明，岩土力学仿真下采空区开采半径和开采角度的增大都会引起剪切应力的增加，最大剪切应力发生在采空区上部的起始位置和终止位置；在不发生剪切破坏的采空区中选择体积较大者作为理想采空区，估算出拉削开采方法的日产气量为142000 m3，具有应用潜力；开采工况下，拉削管的最大等效应力小于管材的屈服极限，表明开采过程中拉削管处于弹性形变，满足方法需求。     

Determination of atomistic deformation of tricalcium silicate paste with high-volume fly ash

We examined the effect of incorporating high-volume fly ash on the atomic arrangement and interatomic deformation behavior of calcium silicate hydrates in tricalcium silicate paste upon exposure to external forces. The interatomic structural changes and strains under compressive load were assessed using synchrotron in situ high-energy X-ray scattering-based atomic pair distribution function analysis. Three different types of strains, which were (a) macroscopic strains from gauges on the surfaces of specimen, (b) strains in a reciprocal space (Bragg peak shift), and (c) strains in real space (PDF peak shift), were compared to each other. All monitored and calculated strains for tricalcium silicate-fly ash (50 wt% fly ash) paste were compared with the counterparts of the pure tricalcium silicate paste. Pair distribution function analysis in the range of r < 10 Å indicated that the atomic arrangement of tricalcium silicate-fly ash was similar to that of synthetic calcium silicate hydrates followed by that of pure tricalcium silicate paste. Moreover, the pair distribution function refinement results revealed that the calcium silicate hydrate structure in tricalcium silicate-fly ash paste was similar to tobermorite 11 Å, unlike that in pure tricalcium silicate paste. The interatomic strain of tricalcium silicate-fly ash in the real space (r < 20 Å) was smaller than that of tricalcium silicate under compression, which suggested that the incompressibility of calcium silicate hydrates at atomistic scale was enhanced by the incorporation of fly ash into it. This was likely to be caused by the increased silicate polymerization of calcium silicate hydrates, which was attributed to the increase in the amount of silicate in their structure via the addition of fly ash.     

Thermodynamic Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylammonium Propionate

The phase equilibrium temperature and dissociation heat of tetrabutylammonium propionate (TBAPr) hydrate are reported. TBAPr hydrate is a type of ionic semiclathrate hydrates and also could potentially be used as thermal energy storage material. The temperature‐composition phase diagram of the TBAPr hydrate was determined in a defined range of mass fractions. Considering the dissociation heat of differential scanning calorimetry (DSC) measurements, multiple peaks of heat flow were observed in the TBAPr‐water system at the TBAPr mass fraction lower than 0.35, and there was a single peak at the mass fraction higher than 0.37.