Hydrate Formation Rate Research Articles

Examination of behavior of lysine on methane (95%)–propane (5%) hydrate formation by the use of different impellers

Hydrate formation characteristics and hydrodynamic behavior have been investigated for mixture of methane–propane hydrate formation with pure water and with the amino acid of lysine 1.5 wt% at 24.5 bars and 2 °C. There were total 12 experiments with full and no baffle estimating the induction time, rate of hydrate formation, hydrate productivity and power consumption. The outcomes showed that radial flow experiments with radial flow have better behavior compared to mixed flow ones due to better interaction between gas and liquid. Furthermore, lysine experiments formed hydrates more quickly compared to pure water experiments showing that lysine functions as promoter and not as inhibitor. RT experiments consume more energy compared to PBT ones, while induction time is always smaller in RT experiments compared to PBT ones.

Probing the effect of various water fractions on methane (CH4) hydrate phase equilibria and hydrate inhibition performance of amino acid L-proline

To develop an effective hydrate risk mitigation strategy for offshore flow assurance its essential to understand the effect of different water fractions on the rate of hydrate formation and study the effect of various water fractions on inhibition effectiveness of eco-friendly gas hydrate inhibitors like amino acids [AA]. This work examines the effect of different water fractions on methane [CH4] hydrate phase equilibria and the effect of various water fractions on the hydrate inhibition strength of AA L-proline at wide operating conditions [40–120 bars]. The experimental results indicate that different water fractions do not have a significant effect on the CH4 hydrate vapor-liquid equilibrium [HLVE] data or hydrate phase equilibria. The 5 wt% L-proline at water fraction 50 vol% shifted the CH4 HLVE by 0.9 ± 0.05 °C (40 bars) and at water fraction 75 vol% it shifted the CH4 HLVE by 1.3 ± 0.05 °C (40 bars). Furthermore, at the same dosage (5 wt%), the THI effect of proline was compared with other amino acids glycine, alanine, and choline based ionic liquids reported in the literature previously. The results indicate that at low dosage [5 wt%], the amino acids glycine and L-alanine tend to slightly more effective thermodynamic hydrate inhibitors compared to the selected choline based ionic liquids. The computer-generated molecular models were used to probe the likely hydrate inhibition mechanism in the presence of amino acids and ionic liquids.

A detailed morphology investigation on the effects of mixed anionic and nonionic surfactants on methane hydrate formation and dissociation

Foam generation from the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter in methane hydrate formation can be potentially reduced by using mixed surfactants. Mixtures of SDS with nonionic surfactants were proposed to solve this problem. Polyoxyethylene (n) lauryl ether (EO3 and EO5) and alkyl poly glycol ether (APG) were chosen to mix with SDS in different concentrations at 8 MPa and 4 °C in the quiescent system for both kinetics and morphology studies. The result showed that the addition of EO3 resulted in the slight increase for the induction time but no change in the formation rate. Adding EO5 showed the stochastic phenomenon on hydrate formation kinetics. In the presence of APG, the induction time increased up to ten times and lowered the hydrate formation rate compared to only 0.25 wt% SDS. The methane uptakes were about the same with all conditions. The morphology showed similar hydrate formation and dissociation patterns with all investigated solutions. Interestingly, the mixture of nonionic surfactants with SDS decreased the foam formation compared with the system with only SDS. The addition EO3 showed the gradual decrease in the foam height with the higher concentration of EO3. Adding the highest EO5 concentration showed the optimum foam reduction compared with all conditions. Moreover, the presence of APG showed the similar effects of foam reduction with EO5.

Mineralogical and structural characterization of the sediments of Krishna Godavari and Mahanadi Basin and their influences on hydrate formation kinetics

Structural and mineralogical characterization of sediment samples of Krishna Godavari (KG) and Mahanadi (MH) basin was performed with the aim of providing in-depth analysis of the effect of mineralogy, grain size and other properties on the hydrate formation. Bulk mineralogy and clay mineralogy of the sediments analyzed through different characterization techniques like X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) that was associated with Energy Dispersive X-Ray (EDX) analysis. Quartz was the main component observed in the sediment samples. A relation between particle size and pore size was also established through particle size (DLS) and pore size characterization (BET) techniques. Finer clay materials were leading in both KG and MH basin samples having slight variation in their quartz content. Illite and smectite were the dominating clay minerals found in the sediments with calcite and albite being the other contributing minerals. Framboids as the pyrites were also observed in sediments and were clearly visible in FESEM observations. Hydrate formation studies were also performed in the sediments to observe the effect of their sedimentology and geology on the occurrence of hydrates in oceanic sediments. Hydrate formation in sediments occurred in less time as compared to pure water system with an accelerated rate of nucleation as per the observations. Kinetic studies were also performed that showed the higher initial rate of hydrate formation in sediments that could be due to the high surface area and additional nucleation sites provided by the sediments as confirmed by BET analysis. Rate constants and other kinetic parameters were also calculated by assuming the first order reaction kinetics of hydrate formation.

Equilibrium Conditions of the Natural Gas Hydrates Formation in the Pore Space of Dispersed Rocks

In this work, the kinetic parameters and equilibrium conditions of the formation of natural gas hydrates in moist fresh and saline sand samples were studied by the method of differential thermal analysis. It was found that, in comparison with the systems "water-natural gas" and "sodium chloride solution-natural gas" in dispersed rocks, the equilibrium curves of hydrate formation are shifted to the region of high pressures and low temperatures. It is shown that the salinity of the pore solution leads to a decrease in the amount of absorbed gas and a decrease in the rate of hydrate formation.

Molecular dynamics simulations on formation of CO2 hydrate in the presence of metal particles

Understanding and controlling the growth of CO2 hydrates is critical for a variety of industrial applications, such as sequestration of greenhouse gases. Due to the excellent physical and chemical properties, metal nanoclusters are widely used as additives in hydrate experiments. However, little is known about the molecular mechanism of this process. In this study, molecular dynamics (MD) simulation was performed at 260 K and 30 MPa by adding different types of metal particles (Cu, Fe and Ag) and different mass fractions (0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt% and 1.3 wt%) to study the growth kinetics of the CO2 hydrate system containing pre-placed hydrate crystal cells. Simulation results showed that the presence of these metal particles has a mixed effect on the growth kinetics, and the extent of the effect seems to varies with different additives and also with the concentration of the metal particles used. It was observed that Cu particles had the most obvious promoting effect on hydrate growth. When the mass fraction of Cu particles was between 0.2 wt% and 1.0 wt%, the rate of hydrate formation increased, especially at the mass fraction of 1.0 wt%. The growth rate of CO2 hydrate was almost 50% higher than that of pure water system at this concentration. In addition, Fe particles had a medium effect on promoting CO2 hydrate growth. Ag particles had no obvious effect on CO2 hydrate growth. Results show that the addition of metal particles with high specific surface areas greatly increases the mass and heat transfer among the gas, liquid and hydrate phases, which is conducive to the growth of CO2 hydrate.

The effect of experimental conditions on methane hydrate formation by the use of single and dual impellers

Natural gas hydrates (NGH) are proposed as gas storage and transportation media owing to their high gas content and long-term stability of hydrate crystal structure at common refrigeration temperatures and atmospheric pressure. Technically feasible, cost efficient hydrate production is one of the crucial items of the whole chain of storage and transportation of gas by means of NGH technology. This study investigates the effects of types and number of impellers and baffles. Single impeller experiments showed that hydrate formation rates of rushton turbine (RT) experiments are always higher than hydrate formation rates of pitched blade turbines upward pumping (PBTU) experiments for all types of baffles but on the other side RT experiments consume more energy. Hydrate yield values are always higher in the RT experiments showing that although the duration of hydrate formation process lasts less compared to PBTU ones, the amount of water that is converted to gas hydrates is more in RT experiments. The same results observed also in dual impeller experiments with the objection that values were closer. In single impeller experiments only PBTU experiments formed hydrates for 3 h while in dual experiments formed PBTU with full baffle and RT with no baffle experiments indicating a serious heat transfer limitations for the other experiments. It should be mentioned that PBT is the same with PBTU since all mixed flow experiments worked in upward pumping.

Influence of THF and THF/SDS on the Kinetics of CO2 Hydrate Formation Under Stirring

Hydrate-based gas separation is a potential technology for CO2 recovery and storage, and its products can be used for fire prevention and control in mines. Promoters are often employed to accelerate or moderate hydrate formation. In this study, experiments were performed to examine the effects of different concentrations of the thermodynamic promoter tetrahydrofuran (THF) and kinetic promoter sodium dodecyl sulphate (SDS) on CO2 hydrate formation under stirring. The results showed that THF significantly shortens the induction time of CO2 hydrates; however, because THF occupies a large cavity in the hydrate structure, it also reduces the gas absorption and hydrate formation rate. SDS has no obvious effect on the induction time of hydrates, but it can increase the gas storage density and hydrate formation rate. Using THF and SDS together consumed more CO2 than using THF alone or pure water. The peak gas consumption rate was 2.3 times that of the THF system. The hydrate formation efficiency was improved by including both THF and SDS, which maximized both the hydrate formation rate and total gas uptake.

Investigating hydrate formation rate and the viscosity of hydrate slurries in water-dominant flow: Flowloop experiments and modelling

Water dominated flow is typically encountered in mature oil and gas fields after water breakthrough has occurred; gas hydrate formation in these systems is generally associated with a high risk of flowline blockage. With the move towards production of natural hydrate deposits as an abundant source of gas, understanding water dominated flow will become increasingly important, particularly as these systems inherently operate near or within the hydrate equilibrium region. In this work, we present an improved mass-transfer limited hydrate growth rate model, which includes the effect of hydrate slurry viscosification on formation. This is validated through several methane hydrate formation experiments employing a 10 mm ID flowloop operating at high water cut (100 vol% water).The model is based on understanding mass transfer limitations for hydrate slurry systems; the mass transfer coefficient itself was estimated by the small eddy cell model and considers changes in the viscosity and diffusion coefficient due to an increase in hydrate volume fraction. Further, differential effective medium theory was employed to predict the viscosity of the hydrate slurry. The gas-water interfacial area was directly estimated (without any correlations) by employing high quality images captured through an in-line camera instrumented on the flowloop. Experimental results obtained from the flowloop were used to validate the overall growth rate predictions of our model. Overall, this work offers a pathway to improve predictive capabilities for the coming generation of natural gas hydrate production, and to increase confidence in our ability to actively manage hydrate formation for water dominant systems.

Influence of pressure on the formation process of CH4 hydrate in porous media below the freezing point

AbstractNatural gas hydrates are mainly stored in the pores of the sedimentary layer in permafrost regions, and the formation characters in porous media were particularly important for the exploitation and utilization of natural gas hydrates. So, it is essential to understand the formation process of methane hydrate in porous media below freezing point. In this study, the formation process of methane hydrate was studied in a closed system in porous media below freezing point. The results indicated that the initial pressure played an important role in the formation characteristics of methane hydrate in porous media below freezing point. The higher the initial pressure was, the larger the formation rate of methane hydrate. And the maximum formation rate attained 6.46 × 10−4 mol/h when the initial pressure was 9.0 MPa under the same temperature and particle size conditions. Furthermore, the final conversion rate was larger at higher initial pressure and the final conversion rate attained 56.5% at an initial pressure of 9.0 MPa. Furthermore, the pressure disturbance could improve the formation process of methane hydrate and the final conversion rate was larger to some extent. The relevant results will provide a theoretical reference for natural gas hydrates exploitation.

Kinetic analysis of dual impellers on methane hydrate formation

Abstract This study investigates the effects of types of impellers and baffles on methane hydrate formation. Induction time, water conversion to hydrates (hydrate yield), hydrate formation rate and hydrate productivity are components that were estimated. The initial hydrate formation rate is generally higher with the use of Ruston turbine (RT) with higher values 28.93 × 10−8 mol/s in RT/RT with full baffle (FB) experiment, but the decline rate of hydrate formation was also high compared to up-pumping pitched blade turbine (PBTU). Power consumption is higher also in RT/RT and PBT/RT with higher value 392,000 W in PBT/RT with no baffle (NB) experiment compared to PBT/PBT and RT/PBT experiments respectively. Induction time values are higher in RT/RT experiments compared to PBT/PBT ones. Hydrate yield is always smaller when there is no baffle in all four groups of experiments while the higher values exist in experiments with full baffle. It should be noticed that PBT is the same with PBTU, since all experiments with mixed flow have upward trending.

Experimental Investigation toward the Kinetic Study of Methane Hydrate Formation in the Presence of THF+SDS

In this study, the effect of the mixture of two types of promoters including THF and SDS as well as the effect of temperature and pressure was studied on the methane hydrate formation. In order to investigate the effect of promoters, the induction time, as well as the amount of water, converted to the hydrate was reported; moreover, the percent of methane hydrate was calculated as results. According to the results obtained from experimentation, by adding SDS as surfactant the induction time decreases significantly in the presence of 0.243 mL THF. The results showed that for the condition where initial pressure was 40 bar and SDS concentration was chosen to be 1500 ppm the induction time decreases 59.5%. Also, the results declared that with the increase in the initial pressure the values of the induction time decline. For those that the initial pressure was set at 50 bar and the aqueous solution contains 250 ppm SDS the rate of hydrate formation was observed to be higher than those lower SDS concentrations were used. Furthermore for the condition where the initial pressure was set on 40 bars and the concentration of SDS was chosen to be 1500 ppm the rate of hydrate formation was found to be the maximum value. Finally, the results of experimentation and modeling showed that for the condition where initial pressure was chosen 50 bar the apparent rate constant of hydrate formation was maximum, for the solution with 250 ppm SDS. Also, this parameter would be 80% much higher than those of pure water was used at beginning of the hydrate crystals growth.

Phase behavior and kinetics properties of gas hydrates in confinement and its application

AbstractMassive amounts of gas hydrates occur naturally in the pores of sediments or fractures in permafrost regions and beneath the oceans. For hydrate formation in confinement, the equilibrium condition can shift to harsher conditions, lowering the water activity and subsequently depressing the hydrate freezing temperature at a given pressure. Conversely, the nucleation and rate of hydrate formation, as well as hydrate conversion can be increased in confinement. Therefore, reliable assessment of the hydrate distribution in nature requires accurate thermodynamic and kinetic models of hydrate formation; however, these models tend to be based upon the properties of bulk hydrates. Hydrate formation and growth promotion in confinement are also potentially interesting for hydrate technological applications, such as gas separation, energy storage, and flow assurance. This paper reviews the thermodynamic and kinetic properties and their interrelations of gas hydrates in confined spaces.

Different pathways for methane hydrate nucleation and crystallization at high supercooling: Insights from molecular dynamics simulations

Natural gas hydrates are potential energy sources in the future, and thus it is important to understand its microscopic formation process. In this study, fourteen molecular dynamics (MD)trajectories were performed using the all-atom models by direct molecular dynamics simulations to investigate the nucleation and crystallization of methane hydrate from two-phase system of methane and water at T = 250 K and P = 50 MPa. Due to the strong interaction parameters used between water and methane in this study, methane molecules from gas phase can quickly enter the water phase to form supersaturated solution in the initial stage, increasing the probability of nucleation and the formation rate of hydrates. It was found that the hydrate nucleation and growth rate were slow in the initial configurations with the low-content methane, which is more conducive to the formation of crystalline hydrate. In configurations with low-content methane, sI crystal domains, sII crystal domains and polycrystalline structures with the coexistence of sI-like and sII were observed obviously in three trajectories. Our simulated results show that, at high supercooling, methane and water can still directly form crystalline methane hydrate.

Combination of Silica Gel and Surfactin Promoting Methane Hydrate Formation

Abstract Recently, gas hydrates based technologies have been exploited for few novel applications such as storage and transpiration of natural gas, gas mixtures separation, CO2 capture, and seawater desalination. Most of these applications are currently facing a challenge of low rate of gas hydrate formation. Chemical additives like surfactants can play a role of a good kinetic promoter for gas hydrate formation. The present study reports the application of biosurfactant for enhancing gas hydrate formation. Biosurfactant was produced by Bacillus subtilis strain A21. These types of microbes show their presence in the real gas hydrate sites also. The surfactin was characterized using many sophisticated techniques, conforming the formation of surfactin. It was used in the presence of fixed bed media of silica gel, and it was observed that surfactin in the presence of silica gel increased the consumption of moles of methane as well as reduced the induction time also as well as the conversion was also increased up to 27.9% for 390 min for 1000 ppm surfactin hence indicating it to be a clean and novel promoter of methane hydrate formation in combination with silica gel which can replace its synthetic counterparts which have environmental concerns.

Multiple methane hydrate formation in powder poly(vinyl alcohol) cryogel for natural gas storage and transportation

The aim of this work is to investigate the possibility of using a new water-containing material for multicycle gas hydrate formation with a high rate and water-to-hydrate conversion ratio in relation to natural gas storage and transportation. Recently, we developed a powdered water-containing material formed by grinding a frozen poly(vinyl alcohol) (PVA) water solution in the presence of silica nanoparticles and further thawing the prepared system. The obtained material is called powder PVA cryogel (PPVACG). In this work multiple methane hydrate formation/dissociation cycles in PPVACG were investigated for the first time. It was found that the equilibrium conditions for methane hydrate formation in PPVACG (7 wt% PVA and 5 wt% nanoparticles) were the same as those for pure bulk water. The methane hydrate formation rate as well as the water-to-hydrate conversion for PPVACGs were no less than those for the known dispersed “dry water” and “gelatinous dry solution” systems. However, PPVACGs showed a higher stability and higher methane uptake capacity in comparison with “dry water” and “gelatinous dry solution” in repeated gas hydrate formation/dissociation cycles starting from the third cycle. The results may be useful for the development of hydrate-based technologies for the storage, transportation, and utilization of natural and anthropogenic gases.

Kinetic Analysis of Methane-Propane Hydrate Formation by the Use of Different Impellers.

In the present study, the effect of different kinds of impellers with different baffles or no baffle was investigated. Up-pumping pitched blade turbine (PBTU) and Rushton turbine (RT) were the two types of impellers tested. The reactor was equipped with different designs of baffles: full, half and surface baffles, or no baffles. Single (PBTU or RT) and dual (PBTU/PBTU or RT/RT) use of impellers with full (FB), half (HB), surface (SB), and no baffle (NB) combinations formed two sets of 16 experiments. The first group of experiments was close to the equilibrium line (P = 26.5 bars and T = 8.5 °C), and the second group was deep in the equilibrium line (P = 24.5 bars and T = 2 °C). There was estimation of rate of hydrate formation, induction time, hydrate productivity, overall power consumption, split fraction, and separation factor. In both single and dual impellers, the results showed that RT experiments are better compared to PBTU in the rate of hydrate formation. The induction time is almost the same because we are deep in the equilibrium line while, hydrate productivity values are higher in PBTU compared to RT experiments. As a general view, RT experiments consume more energy compared to PBTU experiments.

Transport of water and methane particles in a reactor to produce natural gas hydrates

Energy storage is an interesting phenomenon today that has the potential to move forward. Accumulation of energy in the form of a hydrate is important in terms of transport options to the site of coverage of unexpected energy peaks in the technology industry. Natural gas hydrate is in the solid state, which makes up about 85% of the water and 15% of the gas bound in the clathrate lattice. Insufficient research and development of hydrates has caused that the real application in convection systems of natural gas accumulation is in the phase of theoretical studies. This unconventional energy source is currently destined for the distant path to energy efficiency. The main aim of the article is to describe the parameters that affect the rate of hydrate formation. The article presents a basic analysis of the phase equilibrium criteria of methane hydrate. Storing energy in a form suitable for safe storage and further release is a current efficiency in processes that use the need to store energy.

Methane hydrate formation behaviors in high water-cut oil-in-water systems with hydrate promoters.

Hydrate slurry transport technology has become a focal point among worldwide researches, due to its high economic efficiency. However, the mechanism and law of hydrate growth kinetics in flow systems were still unclear, especially in high water-cut oil–water systems with hydrate promoters. On this basis, this paper conducted a series of growth kinetic experiments using a high-pressure transparent sapphire cell, and investigated systematically several influencing factors (such as initial pressure, the concentration of emulsifier, hydrate promoter, and the concentration of hydrate promoter) of growth kinetics, and obtained the quantitative relationship between these factors and gas consumption as well as the hydrate growth rate (gas consumption rate). It could be seen from the analysis of these influencing factors that the presence of hydrate promoters can promote hydrate nucleation rapidly and shorten the hydrate induction time, as compared with the (diesel oil + water) system. The concentration of emulsifier is positively correlated with the induction period of hydrate formation, whether it was sodium dodecyl sulfate (SDS) or l-leucine (l-l) systems. The SDS and l-l system could significantly improve the formation kinetics of methane hydrate in the emulsion system, while tetrabutylammonium bromide (TBAB) and polysorbate 80 (Tween80) significantly inhibited the nucleation and growth of methane hydrate in the emulsion. The kinetic curves of hydrate formation showed a trend of first increasing and then gradually decreasing, with the increase of SDS concentrations. However, the hydrate formation kinetics tended to increase gradually and reach equilibrium in the l-l system, with an increase in the concentration of l-l.

The experimental study and molecular dynamic simulation of THF hydrate growth kinetics in the presence of Arabic and Guar gum: New approaches in promotion of THF hydrate formation

The effect of two natural polymers, Guar gum and Arabic gum, on tetrahydrofuran hydrate formation kinetics was examined and simulated in the present investigations. The experiments were conducted under atmospheric pressure in a batch reactor. The induction time and growth rate of the hydrate formation were measured and the results of two gums were compared together. Both of the gums dramatically promoted the hydrate formation nucleation and growth rate at very low concentrations; overally Guar gum was better and at best it decreased the induction time (delay time) of the hydrate formation by 11 times. This is most likely the first report of edible molecules that promote the rate of THF/H2O hydrate formation. The molecular dynamic simulation showed that the presence of gums causes a greater tendency to order the water molecules around the THF molecules for forming the hydrate cages. Although there is a greater probability of hydrogen bonding between Arabic gum and water molecules, Guar gum has a better effect on the hydrate growth rate compared to the Arabic gum. After all, in addition to promote the THF hydrate formation rate, the most important property of these natural polymers is that they are edible and environmentally-friendly, so they can be considered as a novel candidate for the future of clathrate hydrate science and storage of H2 and He through the THF hydrate.