The gas‐adsorption mechanism of kinetic hydrate inhibitors

Li, Zhi; Liao, Kai; He, Qingyou; Chen, Junli; Ren, Liang-Liang; Li, Fengguang; Zhang, Xuehua; Liu, Bei; Chen, Guangjin

doi:10.1002/aic.16681

Cited by 26 publications

(27 citation statements)

References 21 publications

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“…This is mainly due to the steric hindrance effect of the PVP. To be more specific, as shown in Figure , the oxygen atom on the five-numbered lactam ring of the PVP could form two hydrogen bonds with the hydrogen atoms of the water molecule and thereby absorb on the surface of the hydrate crystal . Consequently, the growth of the hydrate crystal is inhibited.…”

Section: Results and Discussionmentioning

confidence: 99%

“…In recent years, hydrate management using low-dosage hydrate inhibitors (LDHIs) has been widely investigated. As a kind of LDHIs, kinetic hydrate inhibitors (KHIs), which are mainly vinyl lactam polymers containing five-membered or/and seven-membered lactam rings, can work very well in preventing hydrate nucleation and growth by absorbing to the nucleation sites and growth sites of the hydrate crystals . Up to now, the effectiveness of KHIs in hydrate prevention has been verified by many researchers. − However, the effectiveness of KHIs in hydrate and wax coexisting systems is seldom investigated.…”

Section: Introductionmentioning

confidence: 99%

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Investigation on Hydrate Growth at the Oil–Water Interface: In the Presence of Wax and Kinetic Hydrate Inhibitor

Song

Ning

et al. 2020

Langmuir

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In oil industry, the coexistence of hydrate and wax can result in a severe challenge to subsea flow assurance. In order to study the effects of wax on hydrate growth at the oil–water interface, a series of microexperiments were conducted in a self-made reactor, where hydrates gradually nucleated and grew on the surface of a water droplet immersed in wax-containing oil. According to the micro-observations, hydrate shells formed at the oil–water interface in the absence of kinetic hydrate inhibitor (KHI). The roughness and growth rate of hydrate shells were analyzed, and the effects of wax were investigated. In addition, vertical growth of the hydrate shell was observed in the presence of wax, and a mechanism was proposed for illustration. In the presence of KHI, small hydrate crystals formed separately at the oil–water interface instead of hydrate shells. The presence of KHI reduced the growth rate of hydrates and changed the wettability of hydrates. Moreover, the presence of wax showed no obvious effect on the effectiveness of KHI under experimental conditions.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation on Hydrate Growth at the Oil–Water Interface: In the Presence of Wax and Kinetic Hydrate Inhibitor

Song

Ning

et al. 2020

Langmuir

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“…We conjecture a similar mechanism is at work in this study, where three distinct KHIs (two commercial PVP and PVCap and one natural KHI, Pectin) synergize with a THI (MEG). A few more studies describe a similar inhibition mechanism based on the adsorption capacity of KHIs with gas molecules (to delay nucleation) and hydrate crystals (to slow down growth). − The detailed mechanism for synergy is discussed below, as well as visually explained in a schematic provided in Figure .…”

Section: Mechanism Of Synergy Between Khi and Thi (Meg)mentioning

confidence: 99%

Synergistic Kinetic Hydrate Inhibition of Pectin, PVP, and PVCap with Monoethylene Glycol

Singh

Suri

2023

Energy Fuels

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Before injecting any kinetic hydrate inhibitor (KHI) into a flow line, the standard procedure is to dissolve the chemical, which is mostly a polymer, in a solvent such as water, methanol, or glycol. It is ideal if the solvent synergizes with the KHI in hydrate inhibition. In this paper, the synergy of three KHIs, poly(vinylpyrrolidone) (PVP), poly(vinyl caprolactam) (PVCap), and a natural biodegradable polymer Pectin at 0.25 wt %, is investigated with one of the common solvents monoethylene glycol at concentrations (0.5–20 wt %). The hydrate-inhibiting performance of the KHIs and their solvent blends is evaluated using an autoclave to measure the induction time (IT) and the molar hydrate growth rate, which is approximately taken equal to the molar gas consumption rate (HGR/GCR) in constant cooling rate tests and isothermal tests. The individual hydrate inhibition testing results showed that MEG alone at high dosages (up to 20 wt %) is a very poor KHI, while Pectin is a moderate KHI with performance lower than the commercial KHIs (PVP and PVCap) at similar concentrations. The hydrate growth rate of Pectin is however, lower compared to that of both PVP and PVCap. The blends of the KHIs with MEG, showed significant hydrate inhibition synergy in all of the KHI–MEG blends with increasing MEG concentration from 0.5 to 20 wt %. The synergy was maximum at 5 wt % of MEG for all the KHIs with IT enhancement of around 50% for PVP and PVCap and 200% for Pectin. Almost 30–60% reduction in HGR was observed in the blends compared to that of their individual KHI polymer HGRs. Isothermal experiments at 1.5, 6, and 8 °C were done using KHI–MEG blends to simulate possible field/subsea conditions. Among the three KHIs at 0.25 wt % blended with 5 wt % of MEG at 6 °C, PVP–MEG and Pectin–MEG blends gave an almost equal IT of 3.5 h, while the PVCap–MEG blend gave a slightly higher IT of 4.55 h. The HGR of the Pectin–MEG blend was however, the lowest (0.055 m/h) when compared to the PVP–MEG blend HGR (0.08 m/h) and the PVCap–MEG blend HGR (0.075 m/h). Similar IT but lower HGR values were found at 1.5 °C when 20 wt % of MEG with 0.25 wt % of Pectin was used. No hydrates were formed up to 6 days with 0.25 wt % of Pectin and 5 wt % of MEG at 8 °C due to a low subcooling of 1.3 °C. In summary, adding MEG to commercial KHIs such as PVP, PVCap and natural KHI Pectin increases their IT tremendously due to synergy and at the same time lowers their HGRs. As the blends of Pectin–MEG are highly biodegradable, they can be used at locations that have relatively low subcooling requirements and where biodegradability and lower hydrate growth rate are essential as they have similar ITs as that of PVP–MEG blends while lower HGRs than both PVP–MEG and PVCap–MEG blends.

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“…Chen et al and his group − studied the inhibitive mechanism of self-made KHIs using molecular dynamics simulation, as shown in Figure . A superior inhibitive effect was achieved by enhancing the binding interactions between well-organized inhibitors with stretched skeletons and water molecules, strengthening the gas-adsorption ability of the inhibitors, as well as placing the inhibitors at the gas–liquid interface or hydrate surface.…”

Section: Ldhi Research In Chinamentioning

confidence: 99%

“…Typical snapshots of PVP-A (a) in an aqueous solution and (b) on the hydrate nucleus surface. Reproduced from Li et al Copyright (2019) John Wiley and Sons.…”

Section: Ldhi Research In Chinamentioning

confidence: 99%

Status of Natural Gas Hydrate Flow Assurance Research in China: A Review

Shi¹,

Song²,

Duan³

et al. 2021

Energy Fuels

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Natural gas hydrates (NGH) are prone to causing pipeline blockage in flow assurance, attracting considerable attention in the petroleum industry. This work reviews the significant progress in hydrate flow assurance research in China. Gas hydrate structures are briefly introduced to provide a basic understanding, while the application and development of hydrate management strategies in China are summarized. Subsequently, the development and improvement of hydrate phase equilibrium models are presented, which have been widely applied to the practical challenges of flow assurance. Moreover, kinetics research involving hydrate nucleation, growth, and decomposition are summarized, including nucleation mechanisms, induction time, memory effect, hydrate growth at different interfaces, hydrate growth at a microscopic level, and hydrate decomposition under different systems. The current research status of hydrate slurry flow is also analyzed in detail, covering the viscosity and flow resistance of hydrate slurry and the mechanisms of hydrate particle aggregation, deposition, and blockage. In addition, even though the numerical models of hydrate slurry multiphase flow have been sorted out, the accurate quantitative calculations and risk assessments are still in the initial stage, presenting significant room for improvement. Although substantial research progress has been made in China regarding gas hydrate flow assurance, considerable effort should be devoted to further understanding the intrinsic mechanism work to improve the applicability of various models. This review discusses the current developments, existing problems, and future prospects in the various basic hydrate flow assurance fields in China. It aims to provide readers with an overview of hydrate flow assurance research in China, hoping to provide a reference for developing this field.

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The gas‐adsorption mechanism of kinetic hydrate inhibitors

Cited by 26 publications

References 21 publications

Investigation on Hydrate Growth at the Oil–Water Interface: In the Presence of Wax and Kinetic Hydrate Inhibitor

Investigation on Hydrate Growth at the Oil–Water Interface: In the Presence of Wax and Kinetic Hydrate Inhibitor

Synergistic Kinetic Hydrate Inhibition of Pectin, PVP, and PVCap with Monoethylene Glycol

Status of Natural Gas Hydrate Flow Assurance Research in China: A Review

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