scholarly journals A Graphical Alternating Conditional Expectation to Predict Hydrate Phase Equilibrium Conditions for Sweet and Sour Natural Gases

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Hai-Quan Zhong ◽  
Qi-Long Yao ◽  
Yu Wang ◽  
Yu-Fa He ◽  
Zi-Han Li
Keyword(s):  
Phase Equilibrium ◽  
Natural Gas ◽  
Hydrate Formation ◽  
Equilibrium Conditions ◽  
Natural Gases ◽  
Alternating Conditional Expectation ◽  
Hydrate Phase ◽  
Ace Model ◽  
Data Points ◽  
Formation Phase

Natural gas hydrate has been widely of concern due to its great potential in application to address problems including gas storage, transmission, separation techniques, and also as energy resource. Accurate prediction of hydrate formation phase equilibrium conditions is essential for the optimized design during natural gas production, processing, and transportation. In this study, a novel graphical alternating conditional expectation (ACE) algorithm was proposed to predict hydrate formation phase equilibrium conditions for sweet and sour natural gases. The accuracy and performance of the presented ACE model were evaluated using 1055 data points (688, 249, and 118 data points for sweet natural gas, CO2-CH4, and H2S-CO2-CH4 systems, respectively) collected from literature. Meanwhile, a comparative study was conducted between the ACE model and commonly used correlations, including thirteen models for sweet natural gases, three models for CO2-CH4 binary system, and seven thermodynamic models for H2S-CO2-CH4 ternary system. The obtained results indicated that the proposed ACE model produces the best results in prediction of hydrate phase equilibrium temperature for sweet natural gases and pressure for CO2-CH4 system with average absolute relative deviation (AARD) of 0.134% and 2.75%, respectively. The proposed quick and explicit ACE model also provides a better performance in prediction of hydrate phase equilibrium pressure for H2S-CO2-CH4 ternary systems with AARD=5.20% compared with seven thermodynamic methods considered in this work, except for CPA/Electrolyte/Chen–Guo combined model (AARD=4.45%).

scholarly journals Integrating Support Vector Regression with Genetic Algorithm for Hydrate Formation Condition Prediction

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 519
Author(s):  
Jie Cao ◽  
Shijie Zhu ◽  
Chao Li ◽  
Bing Han
Keyword(s):  
Genetic Algorithm ◽  
Natural Gas ◽  
Gas Hydrate ◽  
Hydrate Formation ◽  
Support Vector ◽  
Gas Hydrate Formation ◽  
Svm Model ◽  
Data Points ◽  
Formation Conditions ◽  
Relative Molecular Weight

To predict the natural gas hydrate formation conditions quickly and accurately, a novel hybrid genetic algorithm–support vector machine (GA-SVM) model was developed. The input variables of the model are the relative molecular weight of the natural gas (M) and the hydrate formation pressure (P). The output variable is the hydrate formation temperature (T). Among 10 gas samples, 457 of 688 data points were used for training to identify the optimal support vector machine (SVM) model structure. The remaining 231 data points were used to evaluate the generalisation capability of the best trained SVM model. Comparisons with nine other models and analysis of the outlier detection revealed that the GA-SVM model had the smallest average absolute relative deviation (0.04%). Additionally, the proposed GA-SVM model had the smallest amount of outlier data and the best stability in predicting the gas hydrate formation conditions in the gas relative molecular weight range of 15.64–28.97 g/mol and the natural gas pressure range of 367.65–33,948.90 kPa. The present study provides a new approach for accurately predicting the gas hydrate formation conditions.

scholarly journals Why Should We Use Residual Thermodynamics for Calculation of Hydrate Phase Transitions?

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4135
Author(s):  
Bjørn Kvamme ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Wantong Sun ◽  
Mojdeh Zarifi ◽  
...  
Keyword(s):  
Natural Gas ◽  
Hydrate Formation ◽  
Reference Method ◽  
Temperature Stability ◽  
Heat Pumps ◽  
Ideal Gas ◽  
Thermodynamic Method ◽  
Hydrate Phase ◽  
Model Scheme ◽  
Non Equilibrium

The formation of natural gas hydrates during processing and transport of natural has historically been one of the motivations for research on hydrates. In recent years, there has been much focus on the use of hydrate as a phase for compact transport of natural gas, as well as many other applications such as desalination of seawater and the use of hydrate phase in heat pumps. The huge amounts of energy in the form of hydrates distributed in various ways in sediments is a hot topic many places around the world. Common to all these situations of hydrates in nature or industry is that temperature and pressure are both defined. Mathematically, this does not balance the number of independent variables minus conservation of mass and minus equilibrium conditions. There is a need for thermodynamic models for hydrates that can be used for non-equilibrium systems and hydrate formation from different phase, as well as different routes for hydrate dissociation. In this work we first discuss a residual thermodynamic model scheme with the more commonly used reference method for pressure temperature stability limits. However, the residual thermodynamic method stretches far beyond that to other routes for hydrate formation, such as hydrate formation from dissolved hydrate formers. More important, the residual thermodynamic method can be utilized for many thermodynamic properties involved in real hydrate systems. Consistent free energies and enthalpies are only two of these properties. In non-equilibrium systems, a consistent thermodynamic reference system (ideal gas) makes it easier to evaluate most likely distribution of phases and compositions.

Phase equilibrium modelling of natural gas hydrate formation conditions using LSSVM approach

2016 ◽  
Vol 34 (16) ◽  
pp. 1431-1438 ◽  
Author(s):  
Alireza Baghban ◽  
Saman Namvarrechi ◽  
Le Thi Kim Phung ◽  
Moonyong Lee ◽  
Alireza Bahadori ◽  
...  
Keyword(s):  
Phase Equilibrium ◽  
Natural Gas ◽  
Gas Hydrate ◽  
Hydrate Formation ◽  
Natural Gas Hydrate ◽  
Gas Hydrate Formation ◽  
Formation Conditions

scholarly journals Hydrate Phase Transition Kinetic Modeling for Nature and Industry–Where Are We and Where Do We Go?

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4149
Author(s):  
Bjørn Kvamme ◽  
Matthew Clarke
Keyword(s):  
Phase Transition ◽  
Natural Gas ◽  
Kinetic Modeling ◽  
Hydrate Formation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Massive Growth ◽  
Hydrate Phase ◽  
Induction Times ◽  
Classical Thermodynamics

Hydrate problems in industry have historically motivated modeling of hydrates and hydrate phase transition dynamics, and much knowledge has been gained during the last fifty years of research. The interest in natural gas hydrate as energy source is increasing rapidly. Parallel to this, there is also a high focus on fluxes of methane from the oceans. A limited portion of the fluxes of methane comes directly from natural gas hydrates but a much larger portion of the fluxes involves hydrate mounds as a dynamic seal that slows down leakage fluxes. In this work we review some of the historical trends in kinetic modeling of hydrate formation and discussion. We also discuss a possible future development over to classical thermodynamics and residual thermodynamics as a platform for all phases, including water phases. This opens up for consistent thermodynamics in which Gibbs free energy for all phases are comparable in terms of stability, and also consistent calculation of enthalpies and entropies. Examples are used to demonstrate various stability limits and how various routes to hydrate formation lead to different hydrates. A reworked Classical Nucleation Theory (CNT) is utilized to illustrate that nucleation of hydrate is, as expected from physics, a nano-scale process in time and space. Induction times, or time for onset of massive growth, on the other hand, are frequently delayed by hydrate film transport barriers that slow down contact between gas and liquid water. It is actually demonstrated that the reworked CNT model is able to predict experimental induction times.

Assessing Hydrate Formation in Natural Gas Pipelines Under Transient Operation / Ocena zjawiska tworzenia się hydratów w warunkach nieustalonego przepływu gazu w gazociągach

2013 ◽  
Vol 58 (1) ◽  
pp. 131-144
Author(s):  
Andrzej Osiadacz
Keyword(s):  
Natural Gas ◽  
Gas Flow ◽  
Hydrate Formation ◽  
Operating Conditions ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Hydrate Phase ◽  
Real Gas Effects ◽  
Classical Thermodynamics

This work presents a transient, non-isothermal compressible gas flow model that is combined with a hydrate phase equilibrium model. It enables, to determine whether hydrates could form under existing operating conditions in natural gas pipelines. In particular, to determine the time and location at which the natural gas enters the hydrate formation region. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. Real gas effects are determined by the predictive Soave-Redlich-Kwong group contribution method. By means of statistical mechanics, the hydrate model is formulated combined with classical thermodynamics of phase equilibria for systems that contain water and both hydrate forming and non-hydrate forming gases as function of pressure, temperature, and gas composition. To demonstrate the applicability a case study is conducted.

Influence of tetramethylammonium hydroxide on methane and carbon dioxide gas hydrate phase equilibrium conditions

2017 ◽  
Vol 440 ◽  
pp. 1-8 ◽  
Author(s):  
Muhammad Saad Khan ◽  
Behzad Partoon ◽  
Cornelius B. Bavoh ◽  
Bhajan Lal ◽  
Nurhayati Bt Mellon
Keyword(s):  
Carbon Dioxide ◽  
Phase Equilibrium ◽  
Gas Hydrate ◽  
Tetramethylammonium Hydroxide ◽  
Equilibrium Conditions ◽  
Carbon Dioxide Gas ◽  
Hydrate Phase

scholarly journals An Experimental Study on the Formation of Natural Gas Hydrate With Thermodynamic Inhibitors

2021 ◽  
Vol 9 ◽  
Author(s):  
Na Wei ◽  
Cuiying Xie ◽  
Wantong Sun ◽  
Haitao Li ◽  
Lin Jiang ◽  
...  
Keyword(s):  
Phase Equilibrium ◽  
Natural Gas ◽  
Gas Hydrate ◽  
Oil And Gas ◽  
Volume Concentration ◽  
Hydrate Formation ◽  
Natural Gas Hydrate ◽  
Gas Hydrate Formation ◽  
Supercooling Degree ◽  
Cavity Structure

Gas hydrates formed in the conditions of high pressure and low temperature in deep sea and in the process of oil and gas transportation, natural gas hydrate (NGH), will seriously affect the safety of drilling and completion operations and marine equipment and threaten the safety of drilling platform. How to prevent the hydrate formation in the process of oil and gas production and transportation has become an urgent problem for the oil and gas industry. For this reason, in view of the formation of NGH in the process of drilling and producing marine NGH, the phase equilibrium calculation research of NGH formation was carried out, the mathematical model of gas hydrate formation phase equilibrium condition was established, and the experimental research on NGH formation was carried out through adding different thermodynamic inhibitors. The experimental phenomena show that, first, the stirring speed has little effect on the inhibition of hydrate formation. Second, when the pressure is 10 MPa and the volume concentration of inhibitor is 1, 3, 5, and 7%, the supercooling degree of hydrate formation is 1.81, 8.89, 11.09, and 9.39°C, respectively. Third, when the volume concentration of inhibitor is 1, 3, 5, and 7%, the induction time of hydrate formation is 10328, 14231, 19576, and 24900 s, respectively. As the polymer molecules in the inhibitor reduce the activity of water in the system and fill the cavity structure of the hydrate, they reduce the generation conditions of NGH and break the original phase equilibrium conditions when NGH is generated, thus forming NGH at a lower temperature or higher pressure.

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