Phase equilibrium modeling of semi-clathrate hydrates of the CO2+H2/CH4/N2+TBAB aqueous solution system

In this study, the semi-clathrate hydrate dissociation pressure for the CO₂+N₂, CO₂+H₂, CO₂+CH₄, and pure CO₂ systems in the presence of different concentrations of TBAB aqueous solutions is predicted using a strong machine learning technique of multi-layer perceptron neural network (MLP-NN). The developed model, with an overall correlation coefficient (R²) of 0.9961 and mean square error (MSE) of 5.96E?02, presented an excellent accuracy in prognosticating experimental data. A complete statistical evaluation performed to promise the strength and generality of the multi-layer perceptron artificial neural network (MLP-ANN). In addition, the applicability of the proposed network and quality of experimental data was assessed through the Leverage approach.     

Prediction of the conditions for sour gas hydrate formation in the presence of methanol inhibitor

In this work a new thermodynamic model for accurate prediction of H₂S and CO₂ containing sour gas hydrate equilibrium dissociation temperatures in the presence of a gas hydrate thermodynamic inhibitor (methanol) is presented. The average absolute deviation between the predicted and measured sour gas hydrates dissociation temperatures (AADT%) considering pure and mixed acid gases in the presence of methanol inhibitor is about 0.274% which is much lower than those obtained by the other available thermodynamic models. The proposed approach is quite reliable over wide ranges of methanol and acid gases concentrations and can be used for performance evaluation of other gas hydrate inhibitors regarding the design of sour natural gas flow assurance systems in oil and gas industries.     

Model of transient CO2 gas hydrate particle size distribution at its equilibrium condition

Abstract

It is important to comprehend the relationship between temperature and pressure at which different sizes of hydrates with a particular distribution. When hydrate particles are formed at unsteady state condition, the moment and the spreadness of the distribution of the formation of the hydrate particles is changed with time. The change of distribution of hydrate particle is one of the important parameter for the secondary nucleation rate of gas hydrate. In this study, a model is developed and proposed to predict the particle size distribution of carbon dioxide gas hydrate at its equilibrium condition. The distribution model may be useful for further understanding of the nucleation mechanism and its rate of gas hydrate formation.     

Prediction of hydrate equilibrium conditions using k-nearest neighbor algorithm to CO2 capture

Gas or clathrate hydrates are an important issue when they form in the oil and gas pipelines. Since the determination of the hydrate formation temperature and pressure is very difficult experimentally for every gas system and it is impossible in terms of cost and time approximately, mathematical models can be useful tools to overcome these difficulties. In this study, k-nearest neighbor model was used to predict the equilibrium conditions of hydrate formation in absorption and separation of carbon dioxide from flue gas mixture, containing carbon dioxide and nitrogen. At the training phase, temperature and composition data of nitrogen and carbon dioxide in the flue gas mixture at equilibrium conditions and the equilibrium pressures of hydrate formation were used as input and output, respectively. The error percentage less than 0.38% indicates the high accuracy of the proposed model. In this study, 80%, 85%, and 90% of the training data are examined for three numbers of nearest. For three numbers of used nearest (k = 1, k = 2 and k = 3), the value of k = 1 leads to the lowest error; so, it is selected as the best nearest in the presented model.     

复合添加剂对二氧化碳水合物生成条件影响的实验研究及动力学模型建立

基于水合物法储存分离二氧化碳具有较广阔的应用前景,通过实验研究了复合添加剂对二氧化碳水合物生成条件的影响,选用十二烷基硫酸钠(SDS)和十二烷基苯磺酸钠(SDBS)以及两者的混合溶液作为实验用溶液,研究发现当采用浓度为265mg/L的SDS和SDBS质量比为1:1的复合添加剂溶液时,二氧化碳水合物的相平衡点最低,最易生成,此时的溶液体系能很好的促进水合物生成,而且比单一的SDS溶液或者SDBS溶液体系下水合物的生成条件都有所降低。建立了考虑复合添加剂促进作用的新型水合物生成动力学模型。     

高效水合物抑制剂的适应性分析

高效水合物抑制剂通过推迟晶核成核和生长时间,抑制水合物晶粒长大而实现天然气安全集输的目的,注量少是其优点。考察了自主开发的抑制剂YCSY-1的抑制能力、流变性、腐蚀性、发泡性,以及与现有气田水处理工艺的适应性。结果显示,该抑制剂有效作用时间超过1100min,流变性满足注入设备要求,腐蚀性满足行业标准0.076mm/a,发泡率小于6.0%,经处理后水质满足气田回注水技术要求(SY/T6596);完全满足气田集输要求。     

组合型水合物抑制剂评价及应用

针对陕北地区冬季气温较低,天然气采气管线生产过程中容易形成水合物堵塞管道及设备的问题,为了替代甲醇,开展了新型水合物抑制剂的筛选评价室内研究,筛选出了一种用于防止采气管线水合物形成的组合型水合物抑制剂,并在此基础上进行了现场试验应用。试验结果表明,该型抑制剂加注量在2.0%(w)时,抑制时间超过1400 min;采出水处理后悬浮物(SS)的质量浓度降至4.8 mg/L,油质量浓度小于15 mg/L,pH值小于8,该抑制剂有助于水处理过程,处理后水质完全满足SY/T 6596-2016《气田水注入技术要求》。     

An Experimental Study on the Synergetic Effects of Kinetic and Thermodynamic Gas Hydrate Inhibitors

Gas hydrate can be inhibited by using hydrate inhibitors, such as thermodynamic inhibitors (e.g., methanol and salts) and kinetic inhibitors (KHIs; polymer based). The study of kinetic hydrate inhibitors is paid growing attention in recent years because of its low dosage and environment friendly features, but its application is restricted at high sub-cooling conditions. In this study, the combination of kinetic hydrate inhibitor (polyvinylcaprolactam based) and thermodynamic inhibitors (methanol and NaCl) was investigated in terms of the synergetic effect of the two types of hydrate inhibitors and the effects of pressure and sub-cooling time on the kinetic inhibition effect. The results show that the combined system has a good synergetic effect, which can make the KHIs to stand at higher sub-cooling conditions. The performance of polyvinylcaprolactam and methanol is better than that of polyvinylcaprolactam and NaCl, and the combined system can be also greatly affected by high pressure and long sub-cooling time.     

Exploitation of methane in the hydrate by use of carbon dioxide in the presence of sodium chloride

The replacement process of CH4 from CH4 hydrate formed in NaCl solution by using pressurized CO2 was investigated with a self-designed device at temperatures of 271.05,273.15 and 275.05 K and a constant pressure of 3.30 MPa.The mass fraction of the NaCl solution was either 0.5 wt% or 1.0 wt%.The effects of temperature and concentration of NaCl solution on the replacement process were investigated.Experimental results showed that high temperature was favorable to the replacement reaction but high NaCl concentration had a negative effect on the replacement process.Based on the experimental data,kinetic models of CH4 hydrate decomposition and CO2 hydrate formation in NaCl solution were established.The calculated activation energies suggested that both CH4 hydrate decomposition and CO2 hydrate formation are dominated by diffusion in the hydrate phase.     

Vapor-hydrate phases equilibrium of (CH4+C2H6) and (CH4+C2H4) systems

Separation of the(C1 C2)hydrocarbon system is of importance in natural gas processing and ethylene production.However it is the bottleneck because of its high refrigeration energy consumption, and needs to be urgently addressed.The technology of separating gas mixtures by forming hydrate could be used to separate(C 1 C 2 )gas mixtures at around 0°C and has attracted increasing attention worldwide.In this paper,investigation of vapor-hydrate two-phase equilibrium was carried out for(C 1 C 2 )systems with and without tetrahydrofuran(THF).The compositions of vapor and hydrate phases under phase equilibrium were studied with model algorithm when structure I and structure II hydrates coexisted for the(methane ethane)system.The average deviation between the modeled and actual mole fractions of ethane in hydrate and vapor phases was 0.55%,and that of ethylene was 5.7%when THF was not added.The average deviation of the mole fraction of ethane in vapor phase was 11.46%and ethylene was 7.38%when THF was added.The test results showed that the proposed algorithm is practicable.     

天然气水合物热力学抑制剂作用机制及优化设计

基于2种典型天然气水合物生成预测理论模型,结合水合物热力学抑制剂评价实验数据以及水活度测试结果,分析了水合物热力学抑制剂影响天然气水合物生成条件的作用机制,建立了水合物生成温度降低值与水活度的关系式。结果表明,水合物热力学抑制剂降低水合物生成温度,或提高水合物生成压力的作用机制是降低溶液的水活度,其抑制水合物生成效果随水活度的降低线性增加。通过模拟深水钻井环境,对 典型的水合物热力学抑制剂氯化钠,以及钻井液常用的有机盐甲酸钠进行了水活度测试以及水合物抑制效果评价实验,探讨了可降低钻井液水活度的有机盐加重剂Weigh作为水合物抑制剂的可能性。结果表明,加入氯化钠或甲酸钠降低水活度至0.84,钻井液可在1 500 m水深条件下循环16 h无水合物生成 ;Weigh可大幅降低溶液水活度,水合物抑制效果优于氯化钠、甲酸钠以及由氯化钠和乙二醇组成的复合抑制剂。针对深水钻完井作业中遇到的必须使用低密度钻井液或完井液的情况,初步优化设计了低密度水合物抑制剂,可保证钻井液和完井液在低密度条件下(1.05~1.07 g/cm³)有效抑制水合物生成。     

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.     

Computation of equilibrium hydrate formation temperature for CO2 and hydrocarbon gases containing CO2 in the presence of an alcohol, electrolytes and their mixtures

This work presents the applicability of a unified model to predict the CO₂-rich gas and pure CO₂ hydrate formation conditions in aqueous solutions containing glycerol, methanol, ethylene glycol, electrolytes and their mixtures. A water activity model is introduced that combines the effect of the soluble gases, an alcohol and electrolytes. Then this model is used together with the model of Holder et al. [Holder, G.D., Corbin, G., Papadopoulos, K.D., 1980. Thermodynamic and molecular properties of gas hydrates from mixtures containing methane, argon and krypton. Ind. Eng. Chem. Fundam. 19 (3) 282] to predict CO₂-rich gas and CO₂ hydrate formation conditions. The predictions are in excellent agreement with experimental data.     

静态超重力水合反应器中二氧化碳水合物生成过程热量分析

通过对二氧化碳水合物在静态超重力反应器中生成过程分析发现,其生成过程可以分为成核诱导生成和稳定快速生成两个阶段。第一个阶段内生成量很少,同时存在着气体积累过程。第二个阶段内水合物的生成与冰粒的融化和气体积累过程逐渐达到平衡,二氧化碳水合物的生成速率为249.8mol/h。同时对该生成过程的热量进行了分析,结果表明实验范围内水合反应器热量利用效率与超重力因子成线性增长关系,其最大值为87.39%。     

模板法多孔炭的制备及CH_4/N_2/CO_2吸附分离

以糠醇为碳源,模板法两次浸渍制备多孔炭,采用XRD、SEM、FTIR、N_2吸附-脱附等方法对其进行表征,利用磁悬浮天平测量了CH_4,N_2,CO_2的吸附等温线,并对吸附等温数据进行Langmuir拟合,由Henry常数预测多孔炭对混合体系的平衡选择性。表征结果显示,多孔炭孔分布较窄,具有丰富的孔结构,在一定程度上复制了分子筛的孔道结构,且表面呈现一定的极性,有利于CH_4,N_2,CO_2的吸附和分离。实验结果表明,CH_4,N_2,CO_2的平衡吸附量大小的顺序为:CO_2>CH_4>N_2,Langmuir模型拟合相关系数均大于0.993,拟合效果较好,可用Langmuir理论解释气体在多孔炭孔结构及表面的吸附行为,制备的多孔炭适用于烟道气中CO_2的吸附与分离及煤层气等非常规天然气的提纯,但对垃圾填埋气的分离效果不显著。     

顺式对位环己二甲酸异构化的化学平衡和动力学的研究

在高压搅拌釜中，研究了顺式对位环己二甲酸（顺ＨＴＰ）钠盐在水溶液中异构化成反ＨＴＰ钠盐，在２２０～２８０℃的化学平衡和在８０～２２０℃的反应动力学。结果表明，这一反应是放热的一级可逆反应。其化学平衡常数与温度的关系为：１ｎＫ＝　－０．７４７２；反应热为：ΔＨ０＝－８．４９２（ｋＪ／ｍｏｌ）；反应速率常数为：ｋ＝３．５１０×１０（１１）ｅｘｐ（　）（ｈ（－１））；活化能为：Ｅ＝１１０．０（ｋＪ／ｍｏｌ）。     

天然气水合物抑制剂研究与应用进展

天然气开采及储运过程中,天然气水合物常常造成管道、阀门和设备等的堵塞,虽然防治天然气水合物的工业方法很多,但是最有效的方法还是添加化学抑制剂。为此,介绍了防治天然气水合物所采用的物理和化学等工业方法、天然气水合物抑制剂的最新研究现状、作用机理及应用范围,比较了几种天然气水合物抑制剂的优缺点,明确了天然气水合物抑制剂的选择原则：以技术和经济因素为基础,通过工业实践寻求一种抑制效果好、用量小、环境友好、操作简单、便于储存运输、成本低廉的天然气水合物抑制剂;列举了国内外工业现场试验的成功案例,指出了天然气水合物抑制剂的发展趋势是低剂量天然气水合物抑制剂和复合型天然气水合物抑制剂将逐渐替代热力学天然气水合物抑制剂,其中低剂量天然气水合物抑制剂需要不断改进自身的缺点才能更具有竞争力。     

N-甲基二乙醇胺溶液中CO2气体吸收与水合物生成特性实验研究

目的酸性气田开发气流中往往含有二氧化碳(CO₂)和硫化氢(H₂S)等酸性组分,易形成天然气水合物(简称水合物),引起管道堵塞。解决酸性组分吸收剂对水合物作用机制不明确问题,为脱除酸性气体组分并防治水合物生成提供理论依据。 方法 采用恒温恒容法研究了N-甲基二乙醇胺(MDEA)溶液质量分数、搅拌状态及初始压力对CO₂气体吸收规律的影响、MDEA溶液对CO₂水合物生长速率和宏观晶体形态的影响,并与传统热力学抑制剂乙二醇(EG)效果进行对比。 结果CO₂气体吸收量随MDEA溶液质量分数的增加表现为先增后减的趋势。开启搅拌和降低压力可加快CO₂气体的吸收速率,增加气体吸收量。在气液界面,水合物晶体以二维模式生长,并且MDEA可改变CO₂水合物的宏观形貌,增加其质量分数可显著增加CO₂水合物覆盖溶液表面的时间、降低CO₂水合物的生长速率。与EG相比,MDEA水合物的动力学抑制效果较差,但水合物膜覆盖时间较长,生长速率较慢。 结论MDEA可与溶液中水分子形成氢键,与水合物竞争水分子,减少水的活性,同时,MDEA分子可与CO₂分子结合,与水合物竞争CO₂,显著降低水合物生长速率。研究结果对酸性气体的分离捕获和天然气流动的安全保障具有理论指导意义。      

Experimental study and modeling of the kinetics of gas hydrate formation for acetylene,ethylene, propane and propylene in the presence and absence of SDS

The kinetics of hydrate formation of the hydrocarbons acetylene, ethylene, propane, and propylene were investigated using a fully stirred batch reactor. In relation to hydrate formation, a kinetic model was used to determine the induction time, the rate of hydrate formation, the apparent hydration rate constant, water-to-hydrate conversion associated with hydrate growth as well the storage capacity. This was done for all gases investigated in this study. Experiments were performed in the temperature and pressure ranges of (273.7–280.0) K and (0.5–4.12) MPa, respectively. Furthermore, the effect of sodium dodecyl sulfate (SDS) on the gas hydrate formation rate was examined. A substantial growth in the hydrate nucleation rate was observed in the presence of SDS.     

Prediction of hydrate formation conditions to separate carbon dioxide from fuel gas mixture in the presence of various promoters

In this study estimation of hydrate formation conditions to separate carbon dioxide (CO₂) from fuel gas mixture (CO₂+H₂) was investigated in the presence of promoters such as tetra-n-butylammonium bromide (TBAB), tetra-n-butylammonium fluoride (TBAF), and tetra-n-butyl ammonium nitrate (TBANO₃). The emission of CO₂ from the combustion of fuels has been considered as the dominant contributor to global warming and environmental problems. Separation of CO₂ from fuel gas can be an effective factor to prevent many of environmental impacts. Gas hydrate process is a novel method to separate and storage some gasses. In this communication, a feed-forward artificial neural network algorithm has been developed. To develop this algorithm, the experimental data reported in the literature for hydrate formation conditions in the fuel gas system with different concentrations of promoters in aqueous phase have been used. Finally, experimental data compared with estimated data and with calculation of efficiency coefficient, mean squared error, and mean absolute error show that the experimental data and predicted data are in acceptable agreement which demonstrate the reliability of this algorithm as a predictive tool.