气体水合物蓄冷技术

通过对气体水合物蓄冷技术基本原理的描述，概括总结了迄今为止对氟里昂气体水合物蓄冷的研究现状和发展概况，揭示在实用空调蓄冷系统中气体水合物作为新的蓄冷技术的节能优势，指明了气体水合物蓄冷技术应用于空调系统中仍需解决或需引起注意的问题。     

不同结构气体水合物稳定性的分子动力学研究

气体水合物是一种包络状晶体,在能源勘探、二氧化碳捕集和封存、海水淡化及空调蓄冷等领域均有潜在的应用价值.稳定性研究能够确定水合物稳定存在的热力学区间,方便水合物在各个领域内应用.然而,通过宏观实验研究很难精确的控制和分析水合物的稳定性及分解特性.本文采用分子动力学模拟,在微观角度研究了构型不同、客体分子不同的情况下,气体水合物稳定性的差异,从径向分布函数、均方位移、F3序参数三个方面进行了探讨.发现对于CO2气体水合物,Ⅰ型结构更加稳定;CO2和环戊烷二元水合物的稳定性优于CO2水合物,为水合物的宏观实验研究和工程应用积累了理论基础.     

水合物储能技术研究现状

水合物为客体分子与主体水分子在一定温度与压力下形成的固体物质。水分子通过氢键形成笼型结构并将气体分子包裹在笼子里。根据其包裹气体的特性,可以通过形成水合物将气体(如C H4、H2等)储存起来,从而实现能量的储存;同时水合物的形成与分解会释放和吸收热量,通过重复形成与分解水合物进行蓄冷也是一种能量储存和利用的方式。本文将介绍水合物储能技术研究的现状,并对水合物储能未来的研究进行展望。     

氨基酸侧链对HCFC-141b水合物形成的影响北大核心CSCD

蓄冷是降低电网峰谷差、实现电网负载侧调峰的一种重要手段,制冷剂水合物作为蓄冷介质具有蓄冷密度大和相变温度高的优点。选用脂肪族和芳香族疏水性氨基酸作为绿色环保型添加剂,研究氨基酸的侧链对HCFC-141b水合物形成过程和蓄冷的影响。研究结果表明,选用的5种氨基酸都可有效缩短HCFC-141b水合物形成诱导时间,显著提高了水合物生成量,增大了HCFC-141b水合物的蓄冷密度。在添加脂肪族氨基酸的3个体系中,氨基酸疏水性越强,水合物生成量越大,蓄冷密度也越高。其中含缬氨酸的体系水合物的平均蓄冷密度最大,约为261.24 kJ/kg,远大于纯水中水合物的平均蓄冷密度(57.83 kJ/kg)。在添加芳香族氨基酸的体系中,含色氨酸的体系水合物的平均蓄冷密度最大,约为222.14 kJ/kg,但低于含缬氨酸体系。氨基酸能够较好地促进水合物的生成,氨基酸的侧链基团及其疏水性是促进水合物形成动力学的主要因素。氨基酸中芳香族侧链基团对降低水合物诱导时间、提高水合物生长速度的作用强于脂肪族侧链基团;而氨基酸的脂肪族侧链基团更有利于水合物生成量和蓄冷密度的提高。氨基酸具有一定的表面活性,促进部分HCFC-141b分散到水相中,增加了水与HCFC-141b接触面积,有利于水合物的形成。     

Current status of energy storage using hydrates

水合物为客体分子与主体水分子在一定温度与压力下形成的固体物质。水分子通过氢键形成笼型结构并将气体分子包裹在笼子里。根据其包裹气体的特性,可以通过形成水合物将气体（如CH₄、H₂等）储存起来,从而实现能量的储存;同时水合物的形成与分解会释放和吸收热量,通过重复形成与分解水合物进行蓄冷也是一种能量储存和利用的方式。本文将介绍水合物储能技术研究的现状,并对水合物储能未来的研究进行展望。     

蓄冷空调技术及其发展方向探讨

文章比较了水蓄冷、冰蓄冷、共晶盐蓄冷和气体水合物蓄冷等4种蓄冷空调技术的优缺点，并探讨蓄冷空调技术的发展方向。     

我国气体水合物研究进展

介绍了制冷剂气体水合物作为理想空调蓄冷介质的基础研究结果,并对天然气水合物的研究和前景做了一些阐述。     

天然气水合物开采方法的应用——以Ignik Sikumi天然气水合物现场试验工程为例

天然气水合物已成为世界各国关注的焦点,对天然气水合物开采方法的研究、实践和应用是目前的重点之一.天然气水合物的开采方法主要包括注热法、降压法、注化学试剂法、气体置换法等4种以及这些方法的联用,其中注热法因能耗较大和生产层必须具有良好的孔隙度而使其成本显著提高;降压法无需消耗大量能源,因而被认为是最可行且最具经济价值的天然气水合物生产方法,这一方法可能最适合含水合物盖层以下圈闭有大量气体的矿床;注化学试剂法不是分解天然气水合物的主要方法,不适合长期或大规模使用,且成本较高;气体置换法是通过客气分子的注入来置换天然气水合物中的甲烷,使甲烷释放到孔隙流体中,在被气相包裹的水合物中,气体置换有效率可超过60％,该方法的主要制约因素是水合物储层的低渗透性.2012年5月,在美国阿拉斯加北坡完成了首个用于调查研究天然气水合物藏中CO2-CH4置换潜力的现场试验工程——Ignik Sikumi天然气水合物现场试验,成功注入约6000m3二氧化碳和氮气混合气体,累计生产气体近3× 104m3,未对储层造成压裂破坏.该试验工程为水合物领域的科学研究提供了大量的数据和新的认识,美国能源部也因此宣布了新的研究举措.     

环戊烷纳米乳液水合物蓄冷特性试验研究

为促进静态条件下水合物蓄冷的快速进行,以吐温80、司盘80作表面活性剂,正丁醇作助表面活性剂,通过高速搅拌制备了环戊烷纳米乳液。研究了纳米颗粒粒径和纳米流体浓度对水合物蓄冷过程的影响,结果表明纳米乳液强化了水合物的形成过程,在静态条件下成功实现了环戊烷纳米乳液快速水合蓄冷。     

土壤源热泵系统的土壤蓄冷影响因素研究

以南京为例,运用Trnsys软件的模拟计算方法研究夏热冬冷地区土壤源热泵系统中土壤蓄冷的影响因素。Trnsys系统模型模拟了土壤源热泵系统中土壤在室外干球温度和土壤初始温度影响下,其蓄冷性能的变化。通过对模拟结果进行数据处理与分析,得出土壤初始温度是影响土壤蓄冷性能的主要因素。在土壤温度达到25℃时,建议停止向土壤散热,开启冷却塔蓄冷。     

Entropy generation minimization for charging and discharging processes in a gas-hydrate cool storage system

Thermodynamic optimization models of gas-hydrate cool storage and cool release processes are established in this paper. The optimal temperature configuration at the sensible heat transfer stage and the optimal gas hydrate phase change rate configuration at the phase change stage in the processes of gas hydrate charging and discharging are obtained by taking entropy generation minimization as optimization objective. The optimal control strategies of the cool storage system are determined. The research results indicate that the optimal operating characteristic of the gas-hydrate cool storage system can be achieved by keeping the phase change rates uniform, which are regulated and controlled according to constant heat transfer rates in the charging and discharging processes of gas hydrate. The analysis method and the results presented in this paper can provide important guidelines for optimal design and operation of gas-hydrate cool storage system.     

CO2 sequestration in depleted methane hydrate deposits with excess water

The recent increase in atmospheric CO₂ concentration makes it necessary to investigate new ways to reduce CO₂ emissions. Simultaneously, natural gas hydrate mining technology is developing rapidly. The use of depleted methane hydrate (MH) deposits as potential sites for CO₂ storage is relatively safe and economical. This method can alleviate the shortage of hydrate displacement gas with CO₂. The purpose of this study was to investigate CO₂ hydrate formation characteristics during the seepage process—in reservoirs with excess water—and their effect on CO₂ storage. The experimental process can be divided into 5 parts: MH formation, water injection, MH dissociation, CO₂ hydrate formation, and CO₂ hydrate dissociation. Magnetic resonance imaging was employed to monitor the distribution of liquid water, and the effects of different parameters on the formation and dissociation of CO₂ hydrates were analyzed. It was found that a state of initial water saturation can effectively control hydrate saturation in artificial MH reservoirs for hydrate reservoirs with excess gas. In the process of CO₂ flow, initial water saturation was not the main controlling factor for CO₂ hydrate formation. Increasing the flow pressure and reducing the flow rate were beneficial for CO₂ hydrate formation. This study is of great significance for advancing the science of CO₂ geological storage in the form of deep‐sea hydrates.     

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.     

Development of a hybrid compressed gas engine/PEFC power system using the dissociation expansion characteristics of gas hydrate

The pressure of dissociation and expansion of a gas hydrate can fully power a compression gas engine with a temperature change from 0 °C to 10 °C. The use of green energy (high temperature) and simple refrigeration (low temperature) can easily provide this temperature difference. The dissociation characteristics of a hydrate can be used to develop a clean and efficient hydrate actuator (HA). In this paper, we examine the operation of a hybrid power system consisting of an HA engine and a proton-exchange membrane fuel cell (PEFC), using an example application of an individual house in Sapporo, Japan. A power-generation system that uses the exhaust heat of a PEFC and the cold energy of a heat pump to dissociate and recombine a hydrate is proposed. The results of this analysis indicate that the average electricity production efficiency on a representative day may reach 60.5%. This technique of using the dissociation expansion characteristics of a gas hydrate for power-generation deserves further attention in the search for clean energy.     

“CH4-CO2”置换法开采天然气水合物

天然气水合物作为一种储量巨大的清洁能源,其开采价值已引起越来越多的关注。当前天然气水合物开采技术仍不足以商业化应用,还需进一步的实验研究进行理论支撑。二氧化碳置换开采天然气水合物被认为是能同时实现天然气水合物开采与二氧化碳减排、封存的双赢技术,近年来得到了较广泛的研究。置换过程中,混合天然气水合物的热力学和结构性质是预测含水合物沉积物中的热流和水合物解离所需的热量以及评估水合物储层的CO₂储存能力的关键因素。本综述在调研国内外天然气水合物开采技术研究现状的基础上,围绕CO₂置换开采天然气水合物的热力学特性、微观机理与置换效率等,总结了各研究取得的成果,针对置换研究中存在的问题进行了分析,认为当前置换法开采天然气水合物最关键难点在于提高置换效率,而解决该问题的根本在于从热力学和动力学角度弄清楚置换反应的微观机理及控制性因素,明确置换机理,从而在未来的研究有的放矢。     

Adhesion and detachment characteristics of a TBAB hydrate solid on a heat transfer surface (Effect of concentration of TBAB solutions)

In air‐conditioning systems, it is desirable that the liquid–solid phase change temperature of a cool energy storage material be approximately 10^°C, with respect to improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize a large heat capacity of the working fluids. A solid that adheres to the heat transfer surface forms a thermal resistance layer and significantly reduces the rate of cold storage; therefore, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removal of the solid phase from the heat transfer surface was investigated. Tetra‐n‐butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material and the effect of the TBAB solution concentration on the scraping force required to detach the adhered TBAB hydrate solid from the heat transfer surface was experimentally examined. The TBAB hydrate solids were broadly categorized into two types, and the scraping force required for removal of these two types of TBAB hydrate solid was different. The scraping force required for removal of the solid increased due to the effect of increasing the concentration of the TBAB solution. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20254     

三维实验模拟垂直井和水平井降压开采水合物

为了研究降压法在不同井网布置条件下开采天然气水合物的机理,在水合物三维实验模拟平台中进行了垂直井和水平井降压开采实验,获得了两种布井方式的产气、产水、温度变化和三维温度空间分布情况。研究表明,在该实验条件下,利用水平井开采水合物的平均产气速率是垂直井的1.48倍,但水平井开采的产水量较大,垂直井开采的产水量则很小。三维温度分布图表明,开采过程中全釜的温度同步下降,水合物在反应釜内均匀分解,反应釜四周的温度比反应釜中心温度高,热量从边界向釜中心传递。     

天然气水合物导热性能研究现状

天然气水合物导热系数的研究对于模拟自然界天然气水合物的成藏和天然气水合物勘探、开采具有重要意义。本文介绍了获取天然气水合物导热系数的实验测试和模拟计算方法,分析了气体水合物导热特性、导热机理以及水合物复合体系导热。总结了水合物导热规律,即外界温压条件和晶穴占有率对水合物的导热产生影响,且水合物的导热具有相似的温度压力依赖关系,并呈玻璃体的导热特性。水合物玻璃体导热特性由水合物笼型结构决定,而客体分子的存在强化了水合物导热的玻璃体属性。指出非稳态下天然气水合物导热性能变化研究对分析天然气水合物在常压下的稳定性、确定甲烷水合物等最佳储存温度、从导热角度探讨自保护效应机理等具有重要意义。     

Performance simulation of metal hydride hydrogen storage device with embedded filters and heat exchanger tubes

A practical metal hydride based hydrogen storage device would consist of many filters to distribute hydrogen gas and heat exchanger tubes to cool or heat the hydride bed depending on whether hydrogen is being absorbed or desorbed. This paper presents the simulation of such a device with LaNi₅ as the hydriding alloy. A study of the geometric and operating parameters has been carried out to identify their influence in the hydriding performance of the storage device.     

天然气水合物的研究及利用

介绍了水合物的形成和抑制机理，以及多种预测水合物形成条件的模型；分析了用水合物储存和运输天然气面临的问题，各种水合物促进剂的作用机理以及对水合物生成速度、储气密度的影响；叙述了开采、利用天然气水合物资源的研究进展和一种将水合物转化成液体燃料的方法。