An investigation into the laboratory method for the evaluation of the performance of kinetic hydrate inhibitors using superheated gas hydrates

Villano, Luca Del; Kelland, Malcolm A.

doi:10.1016/j.ces.2011.01.057

Cited by 51 publications

(33 citation statements)

References 24 publications

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“…The superheating test method was used in earlier studies from our research group to increase the reproducibility of T o values or induction times in standard constant cooling and isothermal tests, respectively. 8 The ranking of KHIs using the superheating constant cooling test method is consistent with those from the standard constant cooling method, provided that the correct test conditions and test methods are used. Dependent upon the chosen hydrate dissociation temperature and duration, some systems (especially those of different KHI classes) might contain different amounts of non-melted hydrates.…”

Section: ■ Results and Discussionmentioning

confidence: 88%

Kinetic Hydrate Inhibition of Poly(N-isopropylacrylamide)s with Different Tacticities

et al. 2012

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Poly(N-isopropylacrylamide)s (PNIPAMs) and poly(N-isopropylmethacrylamide)s have been investigated recently as kinetic hydrate inhibitors (KHIs). Now, poly(N-isopropylmethacrylamide) is commercialized. These are usually made by standard radical polymerization methods, which do not allow for control over the polymer tacticity. For this study, PNIPAMs were synthesized using new polymerization methods, giving a fairly high degree of tacticity control. We report here results on the performance of different tacticities of PNIPAMs with similar molecular weights in KHI tests with natural gas in stirred autoclaves and on tetrahydrofuran (THF) structure II hydrate crystal growth. From the results, we can conclude that the polymer tacticity does affect the KHI performance of PNIPAMs. PNIPAM with a higher syndiotactic percentage performed better than PNIPAM with a lower syndiotactic percentage. Both polymers demonstrated some kind of crystal surface adsorption by affecting the morphology of the THF hydrate crystals. ■ INTRODUCTIONNatural gas hydrates are crystalline solids, in which gas molecules (guest molecules) are trapped inside hydrogenbonded water cavities. Typical guest molecules include carbon dioxide and small hydrocarbons, such as methane, ethane, and propane. In the mid-1930s, it was discovered that thermodynamic conditions (elevated pressure and low temperature) favoring hydrate formation occur in pipelines and that natural gas hydrates were blocking gas transmission lines. 1 Natural gas hydrate plugging is one of the costly and challenging problems for the oil and gas industry, especially for deepwater fields. The prevention of gas hydrate formation can be accomplished in a few methods. Among them is the chemical treatment, which includes the usage of kinetic hydrate inhibitors (KHIs). They are generally water-soluble polymers. The mechanism is to delay the nucleation and crystal growth. The main classes of KHIs that have been in commercial use are polymers based on homo-polymers and co-polymers of vinyl caprolactam (VCap) as well as hyperbranched polyesteramides. 2 A group of KHIs based on the polymer of alkylacrylamide was developed. It was also pointed out that poly(N-monoalkyl(meth)acrylamide)s are also known to perform well as KHIs, especially when isopropyl serves as the alkyl group. 3 Therefore, we are interested in studying the KHI performance of this new KHI class.One of the important properties of polymers are their tacticity, which describes the relative stereochemistry of adjacent chiral centers within a macromolecule. 4 As shown in Figure 1, there are three types of tacticities, namely, isotactic with all pendant groups located on one side of the backbone, syndiotactic with alternating orientated pendant groups, and atactic with randomly orientated pendant groups. In a previous work, the KHI performance of poly(N,N-dialkylacrylamide)s was studied to determine the effect of polymer tacticity of this KHI class. 5 The results show that syndiotactic poly(N,Ndialkylacrylamide)s perform better than other...

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Section: ■ Results and Discussionmentioning

confidence: 88%

Kinetic Hydrate Inhibition of Poly(N-isopropylacrylamide)s with Different Tacticities

et al. 2012

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“…As a more accurate alternative, subcooling temperatures at the onset of hydrate nucleation were measured in order to evaluate the KHIs. Previous studies have established that measurements of subcooling temperatures are less variable than those of induction times1047.…”

Section: Resultsmentioning

confidence: 99%

“…S5). These methods have been frequently used to assess the performance of KHIs on a laboratory scale47.…”

Section: Methodsmentioning

confidence: 99%

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

Kwak

Lee

et al. 2013

Sci Rep

211

137

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As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

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“…The autoclave which is made of stainless steel, is cylindrical with a volume of 750 mL. The relative large volume of autoclave could reduce the stochastic effect for hydrate nucleation (Villano and Kelland, 2011), thus ensuring experimental repeatability. The working temperature range is between À20 and 90 C, and the temperature is controlled by a circulator bath and is measured with two temperature sensors to an accuracy of ±0.05 C. The pressure in the autoclave is measured with a pressure sensor to an accuracy of ±0.01 MPa, ranging from 0 to 40 MPa.…”

Section: Apparatus and Proceduresmentioning

confidence: 99%

Synergism of thermodynamic hydrate inhibitors on the performance of poly (vinyl pyrrolidone) in deepwater drilling fluid

Zhao

Qiu

Zhou

et al. 2015

Journal of Natural Gas Science and Engineering

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An investigation into the laboratory method for the evaluation of the performance of kinetic hydrate inhibitors using superheated gas hydrates

Cited by 51 publications

References 24 publications

Kinetic Hydrate Inhibition of Poly(N-isopropylacrylamide)s with Different Tacticities

Kinetic Hydrate Inhibition of Poly(N-isopropylacrylamide)s with Different Tacticities

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

Synergism of thermodynamic hydrate inhibitors on the performance of poly (vinyl pyrrolidone) in deepwater drilling fluid

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