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Determination of the metastable zone and induction time of thiourea for cooling crystallization

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Chinese Journal of Chemical Engineering 2021年第3期34卷 164-168页

作者： Tong Zhou Chunzhao Tu Ya Sun Linan Ji Chuangxian Bian Xiaohua Lu Changsong Wang State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 211816China

The solubility,metastable zone width(MSZW),and induction time of thiourea for cooling crystallization were experimentally determined in the temperature range of 283-323 *** solubility data could be well described by the Apelblat equation model as lnx=-99.55+1071.66/T+16.27 *** determinations of the effects of various stirring and cooling rates indicated that the MSZW increased with increasing and decreasing cooling and stirring rates,***,the induction times at various temperatures and supersaturation ratios were also *** results indicated that homogeneous nucleation could occur at high supersaturation,whereas heterogeneous nucleation was more likely to occur at low *** on the classical nucleation theory and induction period data,the calculated solid-liquid interfacial tensions of thiourea in deionized water at 302.46 and 312.58 K were 2.86 and 2.94 mJ·m^(-2),respectively.

关键词： Thiourea Metastable zone induction time Cooling crystallization

Effect of surfactant Tween on induction time of gas hydrate formation

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Journal of China University of Mining and Technology 2008年第1期18卷 18-21页

作者： ZHANG Bao-yong WU Qiang SUN Deng-lin Safety Engineering College Heilongjiang Institute of Science and Technology Harbin Heilongjiang 150027 China CoUege of Resource and Environment Engineering Liaoning Technical University Fuxin Liaoning 123000 China

Acceleration of gas hydrate formation is important in preventing coal and gas outbursts and is based on a hydration mechanism. It becomes therefore necessary to investigate the effect of surfactants, acting as accelerants for hydrate formation, on induction time. We experimented with three types of a Tween solution with equal concentrations of 0.001 mol/L (T40, T40/T80 (1:1), T40/T80 (4:1)). By means of visual experimental equipment, developed by us, we measured generalized induction time using a Direct Observation Method. The experimental data were analyzed combined with a mass transfer model and a hydrate crystal nuclei growth model. Our major conclusions are as follows: 1) solubilization of surfactants produces supersaturated gas molecules, which promotes the mass transfer from a bulk phase to hydrates and provides the driving force for the complexation between host molecules (water) and guest molecules in a gas hydrate formation process; 2) when the solution of the surfactant concentration exceeds the critical micelle concentration (CMC), the surfactant in an aqueous solution will transform to micelles. Most of the gas molecules are bound to form clusters with water molecules, which promotes the formation of crystal nuclei of gas hydrates; 3) the surfactant T40 proved to have more notable effects on the promotion of crystal nuclei formation and on shortening the induction time, compared with T40/T80 (1:1) and T40/T80 (4:1).

关键词： gas hydrate surfactant induction time coal and gas outburst

Memory effect on the pressure-temperature condition and induction time of gas hydrate nucleation

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Journal of Natural Gas Chemistry 2010年第4期19卷 446-451页

作者： Qiang Wu Baoyong Zhang Safety Engineering College Heilongjiang Institute of Science and Technology Harbin 150027 Heilongjiang China

The focus of this study is to investigate the influence of memory effect and the relation of its existence with the dissociation temperature,using gas hydrate formation and dissociation *** is beneficial because memory effect is considered as an effective approach to promote the thermodynamic and dynamic conditions of gas hydrate *** experimental systems （twenty tests in total） were performed in a 1 L pressure *** types of hydrate morphology,namely massive,whiskery and jelly crystals were present in the *** pressures and temperatures at the time when visual hydrate crystals appeared were ***,the influence of memory effect was quantified in terms of pressure-temperature-time （p-T-t） *** results revealed that memory effect could promote the thermodynamic conditions and shorten the induction time when the dissociation temperature was not higher than 25℃.In this study,the nucleation superpressure and induction time decrease gradually with time of tests,when the earlier and the later tests are *** is assumed that the residual structure of hydrate dissociation,as the source of the memory effect,provides a site for mass transfer between host and guest ***,a driving force is created between the residual structures and its surrounding bulk phase to promote the hydrate ***,when the dissociation temperature was higher than 25 ℃,the memory effect *** findings provide references for the application of memory effect in hydrate-based technology.

关键词： gas hydrate memory effect nucleation thermodynamics induction time

Reaction mechanism between“memory effect”and induction time of gas hydrate formation

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Journal of Coal Science & Engineering(China) 2008年第2期14卷 280-282页

作者：孙登林吴强张保勇 Safety Engineering College Heilongjiang Institute of Science and TechnologyHarbin 150027China College of Resource and Environment Engineering Liaoning Technical UniversityFuxin 123000China

Abstract Using visual experimental apparatus, one system （T40, 1×10^-3 mol/L, nonadded with coal） and another system （T40, 2×10^-3 mol/L, added with coal） were experimented with for three times and two times, respectively. Five groups of P-T experimental parameters were obtained using the data logger system and analyzed combined with the video information of the experiments. Major conclustions show that the induction time is shortened by 10-20 times in the experimental system containing residual pentahedral ring structures; ＂memory effect＂ can accelerate the dynamic progress and improve the thermodynamic conditions of gas hydrate formation.

关键词： memory effect induction time thermodynamic condition gas hydrate

Caffeine Crystallization induction time Measurements Using Laser Scattering Technique and Correlation to Surface Tension in Water and Ethanol

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Chinese Journal of Chemical Engineering 2010年第5期18卷 767-769页

作者：韩佳宾王静康 School of Chemical Engineering & Technology Tianjin University Tianjin 300072 China Earth and Environmental Science Division Los Alarnos National Laboratory Los Alamos New Mexico USA

Caffeine nucleation induction times were measured at 30 °C and 40 °C in water and ethanol solvents employing laser light absorption technique. Supersaturation concentrations and liquid/solid phase surface tensions were calculated from crystallization induction times using classic homogeneous nucleation theory. induction time and surface tension decreased at higher temperature.

关键词： caffeine induction time crystallization surface tension

Experimental study of hydrogen sulfide hydrate formation: induction time in the presence and absence of kinetic inhibitor

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Journal of Energy Chemistry 2013年第1期22卷 114-118页

作者： Yousef Salamat Abdolreza Moghadassi Mohammad Illbeigi Ali Eslamimanesh Amir H. Mohammadi Department of Chemical Engineering Faculty of Engineering Arak University Chemical Engineering Department Faculty of Engineering Isfahan University Department of Chemical & Biomolecular Engineering Clarkson University Institut de Recherche en Gnie Chimique et Ptrolier (IRGCP) Paris Cedex France Thermodynamics Research Unit School of Chemical Engineering University of KwaZulu-Natal Howard College Campus

In this paper, the effect of adding different concentrations of kinetic inhibitors on the induction time of hydrogen sulfide hydrate formation in a reactor equipped with automatic adjustable temperature controller is studied. A novel method namely ＂sudden cooling＂ is used for performing the relevant measurements, in which the induction time of H2S hydrate in the presence/absence of PVP and L-tyrosine with different concentrations （100, 500, and 1000 ppm） is determined. As a result, PVP with the concentration of 1000 ppm in aqueous solution is detected as a more suitable material for increasing the induction time of H2S hydrate formation among the investigated kinetic hydrate inhibitors.

关键词： hy^ogen sulfide gas hydrates clathrate hydrates kinetic inhibitor induction time sudden cooling

Glutamatergic neurons of piriform cortex delay induction of inhalational general anesthesia

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Fundamental Research 2024年第4期4卷 829-840页

作者： Liang Zhou Qipeng Ran Rulan Yi Huanyao Tang Yu Zhang Tian Yu Key Laboratory of Brain Science Zunyi Medical UniversityZunyi 563003China Department of Anesthesiology Affiliated Hospital of Zunyi Medical UniversityZunyi 563003China Guizhou Key Laboratory of Anesthesia and Organ Protection Zunyi Medical UniversityZunyi 563003China

Since their clinical application in the 1840s,the greatest mystery surrounding general anesthesia(GA)is how different kinds of general anesthetics cause reversible unconsciousness,and the precise neural mechanisms underlying the *** past years,although many studies revealed the roles of cortex,thalamus,brainstem,especially the sleep-wake circuits in GA-induced loss of consciousness(LOC),the full picture of the neural circuit mechanism of GA is still largely *** studies have focused on the importance of other brain ***,we report that the activity of glutamatergic(Glu)neurons in the piriform cortex(PC),a critical brain region for odor encoding,began to increase during the LOC of GA and gradually recovered after recovery of *** lesions of the anterior PC(APC)neurons accelerated the induction time of isoflurane *** and optogenetic activation of APcGlu neurons prolonged isoflurane and sevoflurane anesthesia induction,whereas APcclu neuron inhibition displayed the opposite ***,the modification of APcclu neurons did not affect the induction or emergence time of propofol *** addition,odor processing may be partially involved in the induction of isoflurane and sevofurane GA regulated by APCclu *** conclusion,our findings reveal a critical role of APCGlu neurons in inhalational GA induction.

关键词： Piriform cortex Inhalationalgeneral anesthesia Glutamatergic induction time odor

Methane hydrate formation and dissociation in synthetic seawater

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Journal of Natural Gas Chemistry 2012年第6期21卷 625-632页

作者： Vikash Kumar Saw Iqbal Ahmad Ajay Mandal G.Udayabhanu Sukumar Laik Gas Hydrate Laboratory Department of Petroleum Engineering Department of Applied Chemistry Indian School of Mines

The formation and dissociation of methane gas hydrate at an interface between synthetic seawater （SSW） and methane gas have been experimentally investigated in the present work. The amount of gas consumed during hydrate formation has been calculated using the real gas equation. induction time for the formation of hydrate is found to depend on the degree of subcooling. All the experiments were conducted in quiescent system with initial cell pressure of 11.14 MPa. Salinity effects on the onset pressure and temperature of hydrate formation are also observed. The dissociation enthalpies of methane hydrate in synthetic seawater were determined by Clausius-Clapeyron equation based on the measured phase equilibrium data. The dissociation data have been analyzed by existing models and compared with the reported data.

关键词： methane hydrate formation and dissociation total dissolved salt induction time subcooling

Accelerated nucleation of tetrahydrofuran(THF)hydrate in presence of ZIF-61

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Journal of Natural Gas Chemistry 2012年第3期21卷 299-301页

作者： Yanhong Wang Xuemei Lang Shuanshi Fan School of Chemistry and Chemical Engineering Key Lab of Enhanced Heat Transfer and Energy ConservationMinistry of EducationSouth China University of TechnologyGuangzhou 510640GuangdongChina

Clathrate hydrate can be used in energy gas storage and transportation, CO2 capture and cool storage etc. However, these technologies are difficult to be used due to the low formation rate and long induction time of hydrate formation. In this paper, ZIF-61 （zeolite imidazolate framework, ZIF） was first used in hydrate formation to stimulate hydrate nucleation. As an additive of clathrate hydrate, ZIF-61 promoted obviously the acceleration of tetrahydrofuran （THF） hydrate nucleation. It shortened the induction time of THF hydrate formation from 2-5 h to 0.3-1 h mainly due to the template function of ZIF-61 by which the nucleation of THF hydrate has been promoted.

关键词： tetrahydrofuran hydrate hydrate promoter ZIF-61 nucleation induction time