流动状态对甲烷水合物生成速率影响的研究

为了研究流动状态对甲烷在油包水乳液中降压形成水合物过程的影响,在温度为273.35 K,初始压力为6.80 MPa的条件下,进行了一系列不同搅拌速度下甲烷水合物的生成实验。实验结果表明,各组反应的水合物初始形成压力基本一致,诱导时间的长短无规律性。随着搅拌转速的增大,甲烷气体的吸收速度和水合物的生成速度均随之增大。但到达700 r/min后,搅拌转速的继续增加对吸收和水合过程的影响作用并不明显。     

油水体系水合物浆液流动保障研究进展

海洋油气田的高效、安全开采是践行国家深海战略、探索未来战略能源的必要手段。在深海低温、高压环境下运行的多相混输管道的堵塞已成为能源行业安全生产和流动保障的棘手问题,而天然气水合物的快速形成是造成这一问题的主要诱因。明晰油水体系水合物浆液的堵塞机理,开发设计绿色、环保的低剂量水合物抑制剂,掌握浆液的流动特征,将为深水油田多相混输管道的流动保障提供理论基础和技术指导。为此,本文从水合物堵塞过程、化学法防治以及水合物浆液的流动特性等方面总结概括了油水体系水合物浆液的流动保障研究进展。油水体系水合物堵塞主要由水合物的生长、聚集、管壁黏附和着床沉积造成,文章提出：应量化水合物生长、聚集、管壁黏附和着床沉积等因素对流动阻力和管道堵塞的影响,建立科学的工业管道水合物堵塞风险评估理论体系;借助微观尺度实验和分子动力学模拟,厘清不同类型的动力学抑制剂（KHIs）抑制机理和防聚剂（AAs）防聚机理;将实验探索、理论分析和数值模拟相结合,解耦颗粒微观行为与流场宏观物理参数间的关系,定量表征浆液流变性和流动阻力。     

基于PR状态方程的天然气水合物生成温度计算

天然气水合物生成温度的计算在天然气流程工艺设计和生产中经常遇到。然而天然气在开采及管道运输过程中,随着沿程压力、温度的降低,天然气的相态可能发生变化,如果忽略流体相态的变化,在温度计算时就会产生较大的偏差。本文采用PR状态方程来计算相平衡,然后根据DU-GUO88天然气水合物生成条件预测模型计算了天然气水合物生成温度值。结果表明,预测值与实测值相对误差在1%以内,同时对计算方法进行了Visual Basic软件的编程,方便现场推广。     

不同体系中丙烷水合物的生成过程

为了解C3H8水合物的生成特性,加快其生成过程,在可视化实验装置上分别研究了在纯水、十二烷基硫酸钠(SDS,浓度1950′10-6)和十二烷基苯磺酸钠(SDBS,浓度400′10-6)中C3H8水合物的诱导时间、生成速率等. 结果表明,在0.8~1.2℃温度范围内,纯水体系中C3H8水合物的诱导时间最长,SDS体系中C3H8水合物的生成速率最快,达0.0224 mm/h. 与纯水体系相比,表面活性剂明显缩短了C3H8水合物的诱导时间,提高了其生成速率.     

气水体系甲烷水合物生成和分解动力学

为进一步探明搅拌对甲烷水合物生成和分解动力学特性的影响,借助容积约为522mL,最高操作压力21MPa的高压全透明反应釜装置,开展了不同搅拌条件下甲烷水合物的生成、分解和浆液流动实验,得到了搅拌对水合物生成量、生长速率和分解速率的影响规律,基于搅拌电机扭矩值分析了不同搅拌速率下水合物浆液的流动特性。搅拌电机型号ViscoPakt Rheo-57,带有扭矩测量功能,测量最大范围57N·cm,精度±0.04N·cm。结果表明：在水合物开始快速生成的前期,水合物的最大生成量、最大生长速率及平稳生长速率都随搅拌速率的增大而增大,进一步验证了传质是控制水合物生成过程的首要因素;在水合物分解阶段,搅拌能提高水合物颗粒的分散性,促进分解气的运移产出;此外,不同搅拌速率下,水合物浆液的电机扭矩随着水合物体积分数的增大都呈现先保持平稳再逐渐增大最后剧烈波动的规律,由此得到了水合物浆液携带固相颗粒的临界体积分数。研究结论在一定程度上揭示了水合物的生长和分解机理,为动力学预测模型研究提供了参考。     

近冰点多孔介质中甲烷水合物生成的温度敏感性

水合物技术是实现天然气储存、气体分离、海水淡化和二氧化碳捕集等的潜在可行途径之一,水合物技术为了降低生产成本同时又保持系统流动性,通常选择冰粉或冰浆等形式使生成反应在冰点附近进行;自然界的天然气水合物多数赋存于天然的多孔介质内,随着全球气温升高,甲烷水合物在临界条件附近的敏感性会导致储层的稳定性下降及潜在的甲烷大量释放,尤其是受气候变化影响较大的冻土带天然气水合物,其储层温度一般也处于冰点附近。本工作研究了硅砂(0.1~0.5 mm)中甲烷水合物在近冰点的形成过程与动力学特征,分别在273.75, 273.85和273.95 K小温差下研究了压力、温度、反应速率和甲烷吸收量变化,分析并计算了硅砂孔隙中水合物、水相和气相的最终体积饱和度。温度与反应速率的变化表明,水合物生成过程呈现出明显的三个阶段,在不同的阶段,温度和反应速率表现出独特的变化特征如峰值、持续时间等,同时对环境温度的敏感性非常强,温度升高后甲烷水合物生长速率及其在孔隙中的饱和度均有所降低,低温下水合物生长点晚及对应诱导期持续更长。     

温度对多孔介质中甲烷水合物生成过程的影响

采用自行设计的实验装置,分别进行了0℃以上(274.7 K)、0℃附近(272.8±0.5 K)和0℃以下(267.4 K)3种不同温度下,在20～40日石英砂中甲烷水合物的生成实验.结果表明甲烷水合物在0℃以上生成比较快;在0℃附近储气量大,水合物在整个砂层中的分布比较均匀.针对实验结果,本文提出了水合物在三种不同温度下的生成机理.     

全可视化反应釜内二氧化碳水合物的生成分解特征

二氧化碳水合物封存技术已成为目前碳封存研究的热点。该技术中对于二氧化碳水合物的生成分解特征及其影响因素的研究是当前的重点和难点。本文设计了高压全透明双反应釜实验平台,以高纯度二氧化碳和去离子水作为研究对象,在17℃、7MPa的初始温压条件下,进行了二氧化碳水合物的初次和二次生成分解实验,并设置对照组对搅拌的影响进行了研究,而后与甲烷在相同条件下的实验进行对比。实验结果表明,搅拌会促进二氧化碳水合物的生成,在400r/min的转速条件下,缩短诱导时间可达40%,增大压降速率可达15%,形成更多且更致密厚实的水合物,并延缓了分解;多次生成可以减少水合物的诱导时间,但对于水合物生成的总量几乎没有影响。与甲烷水合物相比,二氧化碳水合物生成的量大且更难以分解,实验结果有利于二氧化碳的海洋水合物封存技术的开发应用。     

搅拌速率及温度对化学镀镍包石墨的影响

通过化学镀的方法在石墨表面镀覆镍层,使用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分别对复合粉末的表面形貌和物相组成进行表征,研究了镀液的搅拌速率及温度对镍包石墨复合粉末表面形貌的影响。结果表明：搅拌速率和温度过低时,镀液反应不完全,复合粉末包覆不完整;过高的搅拌速率和温度会导致镀液自分解,镀层与基体脱离,镀液中存在团絮状的镍;搅拌速率为400 r/min,温度为85℃时,石墨粉末表面可均匀且完整地镀上一层厚度平均在1μm左右的镍镀层。     

表面活性剂对气体水合物生成过程的定量影响

为确定HCFC?141b水合物生成条件下阴离子表面活性剂十二烷基硫酸钠(SDS)和十二烷基苯磺酸钠(SDBS)的临界胶束浓度(CMC),在0~20℃温度下,通过圆环法实验研究了不同浓度表面活性剂溶液体系的表面张力,考察了表面活性剂对溶液体系表面张力的影响机理并通过C3H8水合物的生成过程实验进行了验证,确定了SDS和SDBS的临界胶束浓度. 结果表明,当SDS和SDBS的质量浓度分别低于500?10?6和100?10?6时,表面活性剂降低水表面张力的效果最明显,二者的CMC分别为1950?10?6和400?10?6,表面活性剂能明显缩短水合反应的诱导时间,提高了其平均生成速率.     

Hydrate formation in oil–water systems: Investigations of the influences of water cut and anti-agglomerant

To investigate the characteristics of hydrate formation in oil–water systems, a high-pressure cell equipped with visual windows was used where a series of hydrate formation experiments were performed from natural gas + diesel oil + water systems at different water cuts and anti-agglomerant concentrations. According to the temperature and pressure profiles in test experiments, the processes of hydrate formation under two kinds of experimental procedures were analyzed first. Then, based on the experimental phenomena observed through the visual windows, the influences of water cut and anti-agglomerant on the places of hydrate formation and distribution, hydrate morphologies and hydrate morphological evolvements were investigated. Hydrate agglomeration, hydrate deposition and hydrate film growth on the wall were observed in experiments. Furthermore, three different mechanisms for hydrate film growth on the wall were identified. In addition, the influences of water cut and anti-agglomerant on the induction time of hydrate formation were also studied.     

Experimental study of hydrate formation in oil–water systems using a high-pressure visual autoclave

To investigate the characteristics of hydrate formation in oil–water systems, a high-pressure visual autoclave equipped with visual windows was used where a series of hydrate formation experiments were performed from natural gas + diesel oil + water systems at different water cuts (30 and 70%), rotation rates (100, 200, 300 r/min) and thermodynamic conditions (temperature, pressure). According to the temperature and pressure profiles in test experiments, the processes of hydrate formation under two kinds of experimental procedures were analyzed first. Then, based on the experimental phenomenon observed through the visual windows, hydrate morphologies and hydrate morphological evolvements throughout the experiments were mainly investigated. In experiments, the growth and annealing of hydrate films on the wall, the agglomeration and deposition of hydrate coated water droplets, flocculent-like hydrate deposition with water trapped in and the Pickering effect of hydrates were identified. Simultaneously, based on the experimental data of thermodynamic parameters, the kinetics of hydrate formation was studied by calculating the variations of hydrate film area and gas consumption in different experiments. In addition, the influences of temperature, pressure, and rotation rate on hydrate morphologies, hydrate morphological evolvements, and hydrate formation kinetics were also focused on.     

Inhibition of hydrogasification of brown coals by moisture: Influence of heating rate, temperature and pressure

Two types of Rheinische Braunkohle with different mineral matter contents, each with two different moisture contents plus a coke produced from the coal with the lower ash content, were gasified at total pressures between 0.2 and 5 MPa with pure or dry hydrogen, hydrogen/water vapour and argon/water vapour mixtures. In studies with controlled heating (4 K min⁻¹ up to 850 °C) it was found that: 1. methane formation rates and methane yields during gasification in dry hydrogen are drastically lowered with increased moisture of the coals but only at high pressures which reduce evaporation of water; 2. methane formation rates and methane yields during gasification with wet hydrogen (x_H2o = 0.02) are generally lowered with all materials; 3. increasing the water content does not further lower the yields or lead to water vapour gasification. Studies at constant temperature (after rapid heating, 100 K s⁻¹) confirmed these results. It was found that increasing the temperature to 950 °C does not eliminate the inhibiting effect of moisture (in hydrogen) if hydrogen pressure is low ≈ ≤ 1 MPa. It was also determined that raising the temperature above 850 °C with a simultaneous increase in pressure up to 5 MPa hydrogen effectively prevented the inhibition by moisture. It was concluded that extremely stable ether bridges are blocking the active sites at the carbon suface and are therefore responsible for the inhibitory effect of moisture in hydrogasification.     

A bilinear constitutive response for polyureas as a function of temperature,strain rate and pressure

Polyurea is widely applied as a coating material to increase the survivability of structures under impact loading. In this study, a systematic experimental program about the stress–strain behaviors of two polyaspartic esters polyureas is conducted over the temperature range of 233 K–293 K and strain rate range of 0.001/s–15,000/s, including the high‐pressure effects on the response of the polyureas. Based on the experimental results, the effects of temperature, strain rate, and pressure on the stress–strain behaviors are analyzed, the mechanical properties of the two polyureas are compared. The temperature and strain rate dependences of the Young's modulus, yield stress, and strain hardening slope are modeled. Finally, a bilinear constitutive model is proposed to describe the temperature, strain rate, and pressure dependences of the stress–strain behaviors. The model predictions, which agree well with the experimental results, provide basis for the application of the two polyureas. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45256.     

环戊烷-甲烷水合物生成过程的温度特性

研究了环戊烷-甲烷水合物生成过程中的温度变化,分析了体系的热量损失。在不同初始温度(4℃、8℃和12℃)、压力(2MPa、4MPa、6MPa、8MPa和10MPa)和进气方式(一次性进气、连续进气和间歇进气)的条件下,测定了釜内温度,对比了以上各因素对釜内最高温度(T_max)与釜内最大温升(ΔT_max)的影响。实验表明,T_max主要受压力和进气方式影响,初始温度对其影响不明显;ΔT_max受初始温度、压力和进气方式影响显著。在间歇进气方式下,初始温度越低、压力越高,ΔT_max越大。其中,在初始温度为4℃、压力为10MPa、进气时间间隔为30min的间歇进气方式下,ΔT_max可达16.5℃。此外,由热量分析发现,体系的主要热量损耗表现为体系向环境中的散热。因此,提高保温层的绝热性能,有利于提高水合物生成热的热量有效利用率。     

聚酯切粒机转速控制方案优化概述

介绍并分析了聚酯某生产线6台切粒机原转速控制方案及其缺点,重点介绍了新控制方案的设计思路及编程过程中的主要步骤及注意事项。     

Induction time,storage capacity,and rate of methane hydrate formation in the presence of SDS and silver nanoparticles

In this communication, the kinetic parameters of methane hydrate formation (induction time, quantity and rate of gas uptake, storage capacity (SC), and apparent rate constant) in the presence of sodium dodecyl sulfate (SDS), synthetized silver nanoparticles (SNPs), and mixture of SDS?+?SNPs have been studied. Experimental measurements were performed at temperature of 273.65?K and initial pressure of 7?MPa in a 460?cm³ stirred batch reactor. Our results show that adding SDS, SNPs and their mixture increases the quantity of gas uptake, water to hydrate conversion, and SC of methane hydrate formation, noticeably. Using 300?ppm SDS increases the SC and the quantity of methane uptake 615, and 770%, respectively, compared with pure water. Investigating the hydrate growth rate at the start of hydrate formation process shows that, using SNPs, SDS, and their mixture increases the initial apparent rate constant of hydrate rate, considerably. Our results show that the system of methane?+?water?+?SDS 500?ppm?+?SNPs 45?µM represents the maximum value of initial apparent rate constant, compared with other tested systems.     

温度与压力对单孔气泡形成过程的影响

温度压力对进气管孔口气泡的生成具有重要影响。以氮气-水、氦气-水、氮气-十四烷为研究体系,采用高速摄像法,观察了恒速流下孔口气泡的形成过程,考察了孔口气速（0~1500 cm/s）、温度(293~393 K)、压力（0~6 MPa）、孔径（1.12, 2.5 mm）、气体类型（N₂、He）对气泡生长过程的影响。实验表明：随着压力增加,气泡直径减小,纵横比增加;温度升高一方面导致黏度、密度和表面张力降低,使气泡直径减小,另一方面加剧了液体汽化,使得气泡直径增大。根据实验结果修正了Gaddis提出的气泡直径模型,引入饱和蒸气压贡献项,得出新的适用于高温高压条件下气泡直径的估算式。