水合物存在条件下CH4和CO2在溶液中溶解度计算

实验测定了在不同温度、压力条件下,水合物存在时CO2和CH4在水溶液中的溶解度。将Chen-Guo水合物模型和拓展的P-T状态方程应用到水合物存在条件下CH4和CO2在溶液中的溶解度计算,对于V-Lw-H三相条件下CH4和CO2在液相中的溶解度取得了较高的计算精度。本文将vander Waals-Platteeuw模型和拓展的P-T状态方程结合,建立了用于计算高于三相平衡压力条件下CH4和CO2在液相中溶解度的模型。考察了系统压力对CH4和CO2在液相中溶解度的影响。结果表明,压力增加会显著影响CH4和CO2在其溶液中的溶解度。模型基于两点假设经过改进后具有较高的计算精度,能够用于水合物存在条件下CH4和CO2在液相中溶解度的计算。     

CO2置换CH4水合物的相平衡研究进展

总结了近年来国内外CO2置换CH4水合物的相平衡研究成果,包括置换机理、相平衡实验、混合水合物相平衡的影响因素及相平衡研究的应用。研究表明,电解质溶液、微波等体现了电场对水合物形成的作用力;表面活性剂、多孔介质需要考虑界面张力、吸附等作用对相平衡条件的影响;气体组分对水合物形成的影响与各自的水合物相平衡条件、组分之间的相互作用有一定关系。目前的相平衡实验研究多采用观察法,有一定的误差,并且无法研究多孔介质内的水合物形成情况,因此需要结合一些微观成像技术、色谱分析技术满足实验要求;液态或乳化液形式的CO2由于其运输、注入、分离、置换效果的优势受到了重视,但是相关的相平衡研究尚处于起步阶段;CO2置换的工程实际条件不同于实验室,注热或降压措施的影响范围较大,所以考虑多孔介质沉积层的多个物理场变化的相平衡研究将是今后研究的重要课题。     

CH4/CO2混合气置换强化含氮低品质甲烷的浓缩

针对CO₂置换吸附分离CH₄/N₂过程中CO₂再生困难的问题,采用少量产品气CH₄真空吹扫以提高CO₂的解吸效果,并以解吸得到的CH₄/CO₂混合气为置换步骤的置换气,通过置换来强化含氮低品质甲烷的浓缩过程。以自制椰壳活性炭为吸附剂,对CH₄/CO₂混合气置换强化吸附回收含氮低品质甲烷工艺过程进行了实验与模拟研究。在gPROMS软件中建立并求解固定床吸附分离模型方程,预测了CH₄、N₂ 和CO₂在自制椰壳活性炭上的竞争吸附穿透曲线,通过预测结果和实验的对比,验证了数学模型方程的准确性。对比了不同置换气强化吸附分离低品质甲烷的效果,结果表明CH₄/CO₂混合气置换强化相对于CO₂置换强化可获得更高纯度产品。进行了CH₄/CO₂混合气置换强化真空变压吸附循环实验,可以将14%的CH₄/N₂和53%的CH₄/CO₂联合富集到98.8%,同时获得77.8%的回收率。     

CH4+C2H4气体混合物的水合物相平衡

实验考察了CH_4 C_2H_4 THF 水混合体系在一定温度(276.15～282.15K)、压力(2.0～3.0MPa)和THF水溶液浓度(THF摩尔分数60％～12.0％)范围内的气体-水合物相平衡情况。结果表明:富水相中THF的加入大大地阻碍了水合物孔穴中C_2H_4的进入,使得乙烯在气、固两相中的分配发生了逆转,乙烯在气相中被提浓,而无THF存在时乙烯则是在水合物相中得到富集。     

CO2置换水合物过程中CH4-CO2-H2O体系多相平衡模型

通过将水合物相引入传统多相闪蒸模型中,提出了基于传统水合物闪蒸结果初始化水合物相分率和组成的新方法,同时提出了含水合物相的多相闪蒸模型求解步骤.根据实验测试的CO2+ CH4+ H2O和CO2+ N2+ H2O体系的相平衡数据,验证了文中模型的准确性,同时将计算结果与PVTsim和CSMGEM软件比较.结果 表明:文中...     

CO2置换开采天然气水合物研究进展

介绍了近年来CO2置换开采天然气水合物技术的研究进展;论述了CO2与天然气水合物中CH4置换反应在热力学上的可能性;认为正确理解置换反应机理、探索新的反应技术并提高反应速率是置换开采技术走向产业化的关键。     

二氧化碳置换法模拟开采天然气水合物的研究进展

目前实验室模拟开采天然气水合物(NGH)的最主要的方法为外激法,通过注热、降压等方式使水合物分解释放出甲烷(CH₄),外激法最大的问题在于水合物的分解容易造成地层结构变化,导致地质斜坡灾害。利用二氧化碳(CO₂)在水合物相中置换开采CH₄,由于置换过程发生在水合物相中,不改变水合物相结构,因此可以降低地质灾害风险。本文全面介绍了利用CO₂在水合物相从NGH中置换CH₄的研究进展,从置换可行性、动力学模型、模拟研究、实验研究等方面对当前的研究进行了综述,并为进一步发展置换法开采CH₄技术指出了方向。     

CH4和CO2转化催化剂的研究

分别用弛放气和ＣＯ２以及纯ＣＨ４和ＣＯ２作气源,研究了ＴｉＯ２的加入对传统Ｎｉ系转化催化剂性能的影响。     

水合物法分离烟气(CO2/N2)中CO2的实验研究

利用四丁基溴化铵(TBAB)作为促进剂进行了水合物法分离烟气(CO2/N2)的实验研究.结果表明较高TBAB浓度下生成的水合物较多,其中包含更多的未填充气体的纯TBAB水合物;解析气中的CO2含量受到气体消耗率及实验初始压力的影响;TBAB浓度、实验温度在实验条件范围内对解析气中的CO2含量影响并不明显.CO2摩尔分数为17.4%的CO2/N2混合气通过_二级水合物/膜分离流程可回收到CO2摩尔分数为95.0%的解析气.     

CO2-N2-TBAB和CO2-N2-THF体系的水合物平衡生成条件

利用等温压力搜索法测定了CO2-N2-TBAB与CO2-N2-THF体系的水合物平衡生成压力. 实验的压力范围为0.69~14.55 MPa,温度范围为275.75~288.15 K. 结果表明,TBAB与THF均可作为添加剂有效降低气体水合物的平衡生成压力. 在较低的药剂浓度下,CO2-N2-TBAB的水合物平衡生成压力低于CO2-N2-THF体系. 在较高的浓度下,两种体系的水合物平衡生成压力没有明显差别.     

Kinetic investigation of CO2 and N2 clathrate hydrate formation using cyclopentane: Application in desalination

Hydrate-based desalination could be a promising technique for producing fresh water from saline water, as it is an eco-friendly process and suitable for large-scale implementation. To make the hydrate-based desalination technology easily scalable, we looked at using air (or N₂) or CO₂ as a hydrate former, along with cyclopentane (CP). Hydrate former CP helps to reduce the operating conditions, as CP forms hydrate at ambient pressure. However, hydrate formation kinetics due to water-insoluble CP is slow. In this work, the kinetics of hydrate formation in saline water were investigated and compared to identify the utility of CO₂ and N₂ as hydrate formers for desalination work. The addition of CP as a hydrate former should transform the structure of CO₂ hydrate from structure I (sI) to structure II (sII), as CP occupies the large cages (5¹²6⁴) in the gas hydrate. A set of three similar reactors were used for this study to collect data quickly. Furthermore, the triple reactor setup is a unique reactor design mounted on a shaker, and a set of SS-316 balls present inside the horizontal reactor imparts the mixing. Experiments with the CO₂-CP mixture and N₂-CP mixture have been studied in the presence or absence of 3 wt.% NaCl at 274 K and 3 MPa pressure. The gas uptake kinetics, water recovery, and separation efficiency have been investigated.     

Dynamics adsorption of the enhanced CH4 recovery by CO2 injection

The dynamic adsorption isotherms of CO₂-EGR were measured by using an Intelligent Gravimetric Analysis system. In the initial CO₂ injecting stage, all the injected CO₂ enters into the adsorbent and the mole fraction of CH₄ in the gas phase () is maintained at 1.0. The CH₄ recovery factor () increases. The duration of this stage (t_CD) depends on the selectivity of CO₂ over CH₄ (). An adsorbent with large has long t_CD. In the second stage, the injected CO₂ competes with CH₄ for adsorption. The cumulative of the second stage is much larger than that of the initial stage. However, decreases sharply. in the whole CO₂ injection is always larger than that before CO₂ injection, suggesting that CH₄ desorption results from the displacement of CO₂ rather than from pressure depletion.     

Replacement of CH4 in Hydrate in Porous Sediments with Liquid CO2 Injection

The dynamics of the replacement of CH₄ in hydrate in porous sediments with liquid CO₂ was investigated using a self‐developed experimental apparatus at different temperatures and initial pressures. The pressure increases steadily as the replacement reaction processes. The amount of the replaced CH₄ is almost the same as that of the CO₂ forming hydrate in the early stage and gradually becomes somewhat less in the later stage. The initial pressure has minor effects on the replacement rate, and temperature reduction causes a lower replacement rate. The experimental results suggest that the replacement rate is not related to the region of the temperature‐pressure conditions but is mainly affected by the fugacity differences of CH₄ hydrate decomposition and CO₂ hydrate formation.     

水合物法模拟海底封存CO2气体的实验

向海底地层和枯竭油气藏中注入CO₂气体形成稳定的CO₂水合物是一种极具前景的CO₂封存技术。为了进一步探究这一技术,本文利用水合物法进行了多组3MPa、5℃天然湿砂的CO₂封存实验模拟。初始水饱和度设置为10%、40%、70%,分别进行了纯水封存实验和3.5%（质量分数）NaCl溶液的封存实验,还利用自主研发的反应釜系统探索了3种不同进气方向（顶部进气、横置进气、底部进气）下的CO₂封存效果。结果发现横置进气的封存量普遍大于顶部进气的封存量,底部进气的封存量最小,而且横置进气的封存速度最快;初始水饱和度越高,水合物饱和度就越高,但水合物转化率越低,CO₂固态封存比例也越低;与纯水实验相比,盐的存在降低了CO₂的封存量,固态封存比例也会低于纯水实验,但封存速度更快。本文为实际工程操作时合理控制封存地层水饱和度、盐度以及合适的进气方向提供了依据。     

One‐dimensional productivity assessment for on‐field methane hydrate production using CO2/N2 mixture gas

The direct recovery of methane from gas hydrate‐bearing sediments is demonstrated, where a gaseous mixture of CO₂ + N₂ is used to trigger a replacement reaction in complex phase surroundings. A one‐dimensional high‐pressure reactor (8 m) was designed to test the actual aspects of the replacement reaction occurring in natural gas hydrate (NGH) reservoir conditions. NGH can be converted into CO₂ hydrate by a “replacement mechanism,” which serves double duty as a means of both sustainable energy source extraction and greenhouse gas sequestration. The replacement efficiency controlling totally recovered CH₄ amount is inversely proportional to CO₂ + N₂ injection rate which directly affecting solid ‐ gas contact time. Qualitative/quantitative analysis on compositional profiles at each port reveals that the length more than 5.6 m is required to show noticeable recovery rate for NGH production. These outcomes are expected to establish the optimized key process variables for near future field production tests. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1004–1014, 2015     

Separation of CO2 and CH4 on CaX zeolite for use in Landfill gas separation

In this study, adsorption separation of main components of landfill gas, methane (CH₄) and carbon dioxide (CO₂) was carried out. Henry's law constants, limiting heat of adsorption values, pure and binary isotherms for CO₂ and CH₄ were determined for CaX zeolite adsorbent. Pure isotherm data were compared to those for NaX zeolite from previous studies. The CO₂ adsorption capacity of CaX was greater than that of NaX; however, NaX's separation factor was higher. The heat of adsorption for CO₂ for CaX was higher than those for NaX. © 2013 Canadian Society for Chemical Engineering