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Gas Hydrate Formation Probability and Growth Rate as a Function of Kinetic Hydrate Inhibitor (KHI) Concentration
Chemical Engineering Journal ( IF 15.1 ) Pub Date : 2020-01-22 , DOI: 10.1016/j.cej.2020.124177
Vincent W.S. Lim , Peter J. Metaxas , Paul L. Stanwix , Michael L. Johns , Gert Haandrikman , Daniel Crosby , Zachary M. Aman , Eric F. May

Kinetic hydrate inhibitors (KHIs) are polymeric based chemicals that delay the nucleation and/or suppress the growth rate of gas hydrate crystals. While KHIs have been used successfully to mitigate hydrate blockage risk during oil and gas production, the mechanisms by which they function remain unclear. In this work, multiple high-pressure stirred automated lag time apparatus (HPS-ALTA) were used to investigate the impact of a KHI on the subcooling formation probability distributions of methane hydrates and the subsequent initial growth rates. Over 3000 hydrate formation events were measured around 12 MPa using seven independent HPS-ALTA cells with KHI concentrations of up to 3 wt% in water. The addition of KHI made hydrate formation much less stochastic: significant reductions occurred in both the width of the formation probability distribution for a given cell, and in the offsets between distributions measured with different cells. Average initial hydrate growth rates were reduced by approximately by a factor of 5 as KHI concentration increased, even though the average driving force (subcooling) increased by a factor of up to 3. However, above a KHI concentration of 0.3 wt%, a diminishing return was observed in both the nucleation delay and growth rate suppression. A Classical Nucleation Theory (CNT) framework was applied to investigate whether polymer adsorption onto active nucleation sites could explain the observed delay in formation onset. However, the CNT kinetic parameter extracted from the measured formation probability data increased with concentration, which is opposite to the dependence predicted by the polymer-adsorption model of nucleation suppression by KHIs.



中文翻译:

气体水合物形成概率和生长速率作为动力学水合物抑制剂(KHI)浓度的函数

动力学水合物抑制剂(KHI)是基于聚合物的化学物质,可延迟成核和/或抑制气体水合物晶体的生长速率。尽管KHI已成功用于减轻油气生产过程中水合物堵塞的风险,但其作用机理仍不清楚。在这项工作中,使用多个高压搅拌自动滞后时间设备(HPS-ALTA)来研究KHI对甲烷水合物过冷形成概率分布和随后的初始增长率的影响。使用七个独立的HPS-ALTA池(在水中的KHI浓度高达3 wt%),在12 MPa左右测量了3000多个水合物形成事件。KHI的添加使水合物的形成变得随机性降低:对于给定像元,形成概率分布的宽度以及使用不同像元测得的分布之间的偏移都显着减少。即使平均驱动力(过冷)增加了多达3倍,但随着KHI浓度的增加,平均初始水合物生长速率也降低了约5倍。但是,当KHI浓度超过0.3 wt%时,其降低了在成核延迟和生长速率抑制方面都观察到返回。应用经典成核理论(CNT)框架研究聚合物是否吸附到活性成核位点上可以解释观察到的形成开始延迟。但是,从测得的形成概率数据中提取的CNT动力学参数随浓度的增加而增加,

更新日期:2020-01-22
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