水合物形成促进剂研究进展

添加促进剂是高效制备水合物的研究热点,促进剂及其添加量对水合物生成效果至关重要。本文主要从热力学促进剂和动力学促进剂两大类型进行分析：总结了可溶水相热力学促进剂和不可溶水相热力学促进剂的浓度对水合物形成相平衡的影响;从表面活性剂、纳米粒子和相变材料等添加剂,阐述了动力学促进剂添加量对水合物生成诱导时间、储气量和生成速率等方面的影响。促进剂都存在最佳浓度的添加量,并且不同类型促进剂复配更有利于水合物生成。目前添加促进剂后水合物形成机理的研究大多从宏观现象推测,部分学者通过拉曼光谱、X射线衍射和显微观察探索分析促进剂对水合物形成的微观影响,这方面研究有待于进一步开展。添加量作为水合物形成促进剂的重要指标,研究者应得到水合物形成促进剂的最佳浓度与所研究对象的关联性。     

纳米SiO2反相泡沫法固化天然气技术研究

天然气水合物（NGH）是天然气与水在低温高压条件下形成的笼形物,亦称可燃冰。本文根据天然气水合物的生成机制,在实验室模拟天然气水合物的生成环境。实验主要通过将95％的水与5％的纳米SiO：制成泡沫,并在1．3℃条件下,将纯度为99．9999％的天然气充人到装有泡沫的密闭反应釜中,观察反应釜中压力的变化情况,并探究不同的充气压力对储气密度的影响。     

TBAB和CP双添加剂水合物法分离烟气中的CO2

在四正丁基溴化铵（TBAB）和环戊烷（CP）双添加剂体系下进行了一级水合物法分离烟气中CO2的研究。对比了纯体系和双添加剂体系对水合物生成过程及分离效果的影响。获得了合适的操作条件（温度276.15 K,压力2.0～3.3 MPa）、初始液气比（0.78）、添加剂浓度（CP体积分数为0.6%）。在合适条件下,双添加剂体系相比纯TBAB体系水合过程的载气量达至1.5～2.0倍,剩余气相中CO2摩尔分数由17%降至7%,去除率由40%～50%上升到60%～70%。实验表明,双添加剂体系在水合物法CO2分离技术的分离效果及节能方面存在潜力,为工业化水合物法净化烟气提供了参考和标准。     

2,6-二氯-4-氨基苯酚的合成

[目的]制备新型农药氟啶脲和氟铃脲的高纯度中间体2,6-二氯-4-氨基苯酚。[方法]采用2,6-二氯苯酚为原料,在溶剂中硝化合成2,6-二氯-4-硝基苯酚,再在自制的催化剂存在下水合肼催化还原合成2,6-二氯-4-氨基苯酚,探讨合成过程的影响因素。[结果]实验确定了最佳反应条件,得到了纯度大于99.0%的目标产物。[结论]该工艺具有收率高、操作简单、安全可靠的特点,可为工业化生产提供参考。     

Modeling of CO2‐Hydrate Formation at the Gas‐Water Interface in Sand Sediment

Sub‐seabed geological storage of CO₂ in the form of gas hydrate is attractive because clathrate hydrate stably exists at low temperature and high pressure, even if a fault occurs by diastrophism like a big earthquake. For the effective design of the storage system it is necessary to model the formation of CO₂‐hydrate. Here, it is assumed that the formation of gas hydrate on the interface between gas and water consists of two stages: gas diffusion through the CO₂‐hydrate film and consequent CO₂‐hydrate formation on the interface, between film and water. Also proposed is the presence of a fresh reaction interface, which is part of the interface between the gas and aqueous phases and not covered with CO₂‐hydrate. Parameters necessary to model the hydrate formation in sand sediment are derived by comparing the results of the present numerical simulations and the measurements in the literature.     

The downhole hydrocyclone separator for purifying natural gas hydrate:structure design,optimization, and performance

ABSTRACT

The exploitation efficiency of natural gas hydrate is highly affected by sand production. In this paper, hydrocyclone purification separator was designed. A combination of single factor with computational fluid dynamics (CFD) was used to optimize the structure parameters. The performance of optimized hydrocyclone was also investigated. It shows that the sand separation efficiency increases from 90.4% to 98.7%, and the natural gas hydrate separation efficiency increases from 89.5% to 97.8%. Furthermore, the cut size of sand and natural gas hydrate are as low as 3 and 2 µm, respectively, and separation efficiency remains above 80% under inlet parameters. It can provide some reference for the design and manufacture of the in situ purification separator for gas hydrate mixture slurry.     

国内多孔介质中天然气水合物成藏机理研究现状

南中国海的沉积物和青藏高原等冻土带中富含大量的天然气水合物,其成藏机理是开采天然气水合物的关键之一。本文介绍了中国近年来对多孔介质中模拟天然气水合物成藏的研究现状,包括主要的研究单位、研究者、研究方法与仪器设备以及近年来国内期刊上多孔介质中天然气水合物成藏机理的文献情况。     

Quantitative analysis of CO2 hydrate formation in porous media by proton NMR

Gas hydrate is a nonstoichiometric crystal compound formed from water and gas. Most nonvisual studies on gas hydrate are unable to detect how much water is converted to hydrates, and thus, the hydrate stoichiometry calculations are inaccurate. This study investigated the CO₂ hydrate formation process in porous media directly and quantitatively. The characteristics of the time-variable consumption of hydrate formation indicated a two-stage formation, hydrate enclathration and continuous occupancy. The enclathration stage occurred in the first 20 min of the formation when considerable heat is released. The continuous occupancy stage lasted longer than the hydrate enclathration because the empty cages in previously formed hydrates would also be occupied. The higher formation pressures can accelerate water consumption and increase cage occupancy. The compositions of completely formed CO₂ hydrates at 2.7, 3.0, and 3.3 MPa and 275.15 K were determined as CO₂·6.90H₂O, CO₂·6.70H₂O, and CO₂·6.49H₂O, respectively.     

Quantitative determination of pore-structure change and permeability estimation under hydrate phase transition by NMR

Quantitatively characterizing the seepage features is critical important for multi-fluid flow in gas hydrate accumulations; however, limited researches concern water permeability during hydrate phase transition. In this work, nuclear magnetic resonance (NMR) measurement is employed to observe the in situ formation and dissociation of tetrahydrofuran (THF) hydrate in porous media. Results indicate that the relative free water and bound water consumption during hydrate phase transition can affect the seepage features of sediments. In addition, we investigate the growth habits of THF hydrate in quartz glass sand and find the growth pattern of the hydrate transforms from suspension to cementation when its saturation exceeds approximately 35%. The Tokyo model shows that the hydrate are heterogeneous distribution of pore-filling and likely to evolve in larger pores; The findings clearly show that NMR is an efficient and direct technique for investigating the seepage characteristics during hydrate phase transition as well as pore fluid distribution in sediments.     

全透明高压反应釜甲烷水合物动力学实验

水合物的生长和分解规律对开发海洋天然气水合物资源,实现深水天然气水合物气液固多相管道输送都具有重要意义。为了进一步揭示水合物的生长和分解特性,本文采用高压全透明反应釜装置,进行了温度0～30℃、压力3.35～8.16MPa和搅拌速率200～1000r/min范围内的16组甲烷水合物生长和分解动力学实验研究。结果表明：实验过程可分为水合物诱导期、快速生长期、缓慢生长期以及分解期这4个阶段。在水合物快速生长阶段,获得了温度、压力、搅拌电机扭矩和水合物生长速率随时间的变化规律,观察到了水合物颗粒的均相和非均相分布状态。通过加热促使水合物分解,揭示了分解阶段温度、压力和分解速率等关键参数的变化规律以及水合物块的分解形态。分析表明,水合物颗粒的分布状态与水合物浆液的流动性直接相关;水合物块的静态分解过程受到分解气传质控制。