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Flash crystallization kinetics of methane (sI) hydrate in a thermoelectrically-cooled microreactor
Lab on a Chip ( IF 6.1 ) Pub Date : 2017-08-03 00:00:00 , DOI: 10.1039/c7lc00645d
Weiqi Chen 1, 2, 3, 4 , Bruno Pinho 1, 2, 3, 4 , Ryan L. Hartman 1, 2, 3, 4
Affiliation  

The crystallization kinetics of methane (sI) hydrate were investigated in a thermoelectrically-cooled microreactor with in situ Raman spectroscopy. Step-wise and precise control of the temperature allowed acquisition of reproducible data within minutes, while the nucleation of methane hydrates can take up to 24 h in traditional batch reactors. The propagation rates of methane hydrate (from 3.1–196.3 μm s−1) at the gas–liquid interface were measured for different Reynolds' numbers (0.7–68.9), pressures (30.0–80.9 bar), and sub-cooling temperatures (1.0–4.0 K). The precise measurement of the propagation rates and their subsequent analyses revealed a transition from mixed heat-transfer–crystallization-rate-limited to mixed heat-transfer–mass-transfer–crystallization-rate-limited kinetics. A theoretical model, based on heat transfer, mass transfer, and intrinsic crystallization kinetics, was derived for the first time to understand the non-linear relationship between the propagation rate and sub-cooling temperature. The molecular diffusivity of methane within a stagnant film (ahead of the propagation front) was discovered to follow Stokes–Einstein, while calculated Hatta (0.50–0.68), Lewis (128–207), and beta (0.79–116) numbers also confirmed that the diffusive flux influences crystal growth. Understanding methane hydrate crystal growth is important to the atmospheric, oceanic, and planetary sciences and to energy production, storage, and transportation. Our discoveries could someday advance the science of other multiphase, high-pressure, and sub-cooled crystallizations.

中文翻译:

热电冷却微反应器中甲烷(sI)水合物的快速结晶动力学

甲烷(sI)水合物的结晶动力学是在热电冷却的微型反应器中进行原位拉曼光谱研究的。逐步精确控制温度可以在数分钟内获得可重复的数据,而在传统的间歇式反应器中,甲烷水合物的成核过程可能需要长达24小时。甲烷水合物的传播速率(从3.1–196.3μms -1)在气-液界面处测量了不同的雷诺数(0.7–68.9),压力(30.0–80.9 bar)和过冷温度(1.0–4.0 K)。对传播速率的精确测量及其随后的分析表明,从混合传热,结晶速率受限到混合传热,质量传递,结晶速率受限的动力学过渡。首次建立了基于传热,传质和固有结晶动力学的理论模型,以了解传播速率与过冷温度之间的非线性关系。发现停滞膜(在传播前沿之前)中甲烷的分子扩散率遵循斯托克斯-爱因斯坦,同时计算出哈达(0.50-0.68),刘易斯(128-207)和贝塔(0)。79-116)的数字还证实了扩散通量会影响晶体的生长。了解甲烷水合物晶体的生长对大气,海洋和行星科学以及能源生产,存储和运输都非常重要。我们的发现有一天可能会促进其他多相,高压和过冷结晶的科学发展。
更新日期:2017-08-22
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