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Injection of carbon dioxide (CO2) into saline aquifers confined by low- permeability cap rock will result in a layer of CO2 overlying the brine. Dissolution of CO2 into the brine increases the brine density, resulting in an unstable situation in which more-dense brine overlies less-dense brine. This gravitational instability could give rise to density-driven convection of the fluid, which is a favorable process of practical interest for CO2 storage security because it accelerates the transfer of buoyant CO2 into the aqueous phase, where it is no longer subject to an upward buoyant drive. Laboratory flow visualization tests in transparent Hele-Shaw cells have been performed to elucidate the processes and rates of this CO2 solute-driven convection (CSC). Upon introduction of CO2 into the system, a layer of CO2-laden brine forms at the CO2-water interface. Subsequently, small convective fingers form, which coalesce, broaden, and penetrate into the test cell. Images and time-series data of finger lengths and wavelengths are presented. Observed CO2 uptake of the convection system indicates that the CO2 dissolution rate is approximately constant for each test and is far greater than expected for a diffusion-only scenario. Numerical simulations of our system show good agreement with the experiments for onset time of convection and advancement of convective fingers. There are differences as well, the most prominent being the absence of cell-scale convection in the numerical simulations. This cell-scale convection observed in the experiments may be an artifact of a small temperature gradient induced by the cell illumination.

The nucleation kinetics of the alpha form of p‐aminobenzoic acid from ethanolic and aqueous solutions is examined through a comparative examination of temperature‐jump and anti‐solvent drown‐out isothermal crystallization methodologies. Analysis of the data reveals the measured induction times, and the calculated effective interfacial tensions as a function of the supersaturation show broadly equivalent behavior for the aqueous‐ethanol mixed‐solvent drown‐out and temperature‐jump ethanol solution systems, confirming the comparability of the two methodologies. The results also demonstrate poorer agreement with the temperature‐jump pure aqueous system, highlighting the importance of the strength of solvation/desolvation as the key rate‐limiting process for the overall nucleation behavior. [ABSTRACT FROM AUTHOR]

Effects of hydrodynamics and surface chemistry properties on attachment interaction between low-rank coal particles and bubbles were investigated. The surfactants such as 2-ethyl hexanol, dodecyl amine hydrochloride, and sodium dodecyl sulfate were added to change the surface chemistry of low-rank coal particles. The relationship between induction time and bubble Reynolds number showed an index relationship. The induction time would become shorter while the energy barriers between particles and air bubbles are easily overcome with bubble Reynolds number increase. Therefore, the hydrodynamics and surface chemistry properties had a significant effect on the attachment interaction between low-rank coal particles and bubbles. [ABSTRACT FROM AUTHOR]

The attachment interaction in a flotation process is critical because it controls the recovery of mineral particles and is dominated by the interaction energy barrier between bubbles and solid particles. In this investigation, the surface properties of coal particles and oily bubbles were evaluated via the X-ray photoelectron spectroscopy (XPS) analysis, zeta potential measurement and induction time tests. The results proved that the classical Derjagin–Landau–Verwey–Overbeek (DLVO) theory did not adequately predict the flotation performances of oily bubble flotation. The attractive interaction or hydrophobic force induced by the hydrophobic force should be considered in the extended DLVO (EDLVO) theory. Throughout this paper, therefore, it is significant to consider the attractive interaction or hydrophobic force between low-rank coal particles and oily bubbles when comparing the advantages of the flotation response using air and oily bubbles. Unlabelled Image • Both DLVO and extended DLVO theory were applied to calculate the energy barrier of oily bubble-coal particle interaction. • Long-flame coal concentrate with 83.33% yield was obtained from oily bubble flotation. • Hydrophobic force is the primary driving force for oily bubble–particle adhesion. [ABSTRACT FROM AUTHOR]

In this paper, the back-calculated induction times of low-rank coal particles on the rising bubble with mobile surfaces were back-calculated from the micro-flotation rate constants. The back-calculated induction times slightly increased with the flotation recovery increase or the surfactant concentration decrease. It is because the drainage time accounting for most of the induction time is affected by the force exerted on the wetting film. Moreover, the force exerted on the wetting film is characterized by the Reynolds number. Furthermore, the Reynolds number increased with increasing bubble rising velocity due to an increase in bubble size as a result of decreasing surfactant concentration. Therefore, the back-calculated induction times could reflect the difference in the flotation recoveries at the same surfactant concentration. Meanwhile, it indicated that the hydrodynamic condition in the flotation process had a significant effect on the back-calculated results of induction times. From this investigation, it can be speculated that the back-calculated induction time of particles sliding on the rising bubble with mobile bubble surfaces is greatly influenced by the Reynolds number. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the retarding effect of a green additive, citric acid, towards calcium carbonate scale deposition is studied. Scale formation is one of the most common causes of malfunctions in process equipment. This is the reason it is crucial to retard scale precipitation, that is, in order to reduce economic damages. With this additive in the solution, experimental runs have been carried out in supersaturation conditions in terms of concentration of calcium carbonate at equilibrium, with a supersaturation ratio ranging from 16 to 280, at 25°C. Three different concentrations of citric acid have been investigated (0.520 × 10−3, 1.041 × 10−3 and 1.561 × 10−3 M) in a laboratory scale plant. Comparing results obtained in terms of induction time with previous experimental runs, performed without additives, citric acid has shown its significant capacity to retard calcium carbonate precipitation, by increasing induction time values. This behaviour is enhanced by raising the additive concentration in solution up to a specific threshold value, beyond which no benefit in terms of calcium scale inhibition is gained. Furthermore, interfacial tension has been computed without and with citric acid at 0.520 × 10−3 and 1.041 × 10−3 M, as a function of the different concentration amounts investigated. The values obtained are in good agreement with data reported in the literature. [ABSTRACT FROM AUTHOR]

Hydrogen generation via Al‐water reaction promoted by special catalysts has great potential, which can provide hydrogen source for portable fuel cells. In this work, we use wet chemical reduction method to prepare a high‐activity Fe/AlOOH composite with better stability and demonstrate its usage as a catalyst for Al‐water reaction. It is found that Fe/AlOOH composite not only significantly promotes the Al‐water reaction but also shortens the induction time. The catalytic activity of Fe/AlOOH directly correlated with its active area, which, in turn, is closely related to the AlOOH:Fe molar ratio. In addition, increasing the weight content of Fe/AlOOH, reaction temperature, and the Al:water ratio improve the hydrogen generation performance of Al‐water reaction. Mechanism analyses show that water dissociation on AlOOH surface and galvanic microinteractions between Fe and Al promotes the hydration of surface passivating oxide film of Al particle, which improves the Al‐water reaction dynamics. The present work provides a new way to produce hydrogen from Al‐water reaction for portable devices. [ABSTRACT FROM AUTHOR]

The effect of ozone and hydrogen peroxide as dopants on hydrogen-air and ethylene-air detonations was investigated with one-dimensional ZND calculations. Also, the effects of dopants were studied numerically with argon and helium as diluents with an aim to reduce the temperature of detonation products while maintaining a detonation wave of sufficient strength such that its propagation is stable near its propagation limits. The primary goal of the present investigation is to isolate the chemical kinetic effects from fluid and gas dynamic effects by altering the ignition chemistry of an unburned mixture without significantly changing its thermodynamic and physical properties. The ZND calculations demonstrate that the addition of O 3 and H 2 O 2 in small quantities will substantially reduce the induction length (Δ i) and time (τ i), even with higher diluent percentages of argon and helium, making it a viable solution for reducing the operating temperatures of rotating detonation engines (RDEs). The effects of O 3 and H 2 O 2 are also studied numerically at lower equivalence ratios for H 2 /C 2 H 4 -air detonations with an aim to reduce the post-detonation temperatures below 2000 K for its application in practical engine cycles. Also, the efficacy of CF 3 I, as an ignition promoter at small quantities, is studied numerically for hydrogen-air detonations, and its performance is compared with O 3 and H 2 O 2. [ABSTRACT FROM AUTHOR]

This research synthesized polybutadiene nanoparticles and investigated the induction time for their nucleation under different supersaturations and their cross-linking to be utilized in an asymmetric membrane synthesis. Purchased (bulk) polybutadiene was dissolved in toluene and then ethanol was added dropwise to the solution as an antisolvent. The induction time, i.e., the time interval between adding the last drop of ethanol till appearance of a turbidity due to polybutadiene nucleation, was determined. The nucleation mechanism was investigated. Dependence of the induction time on supersaturation suggests that the mechanism of nucleation is primary. The correlation coefficient was obtained as 0.986. After formation, the nanoparticles were cross-linked with sodium persulfate as initiator and divinylbenzene as cross-linking agent. The SEM photos showed the formation of nanoparticles as well as their cross-linking. Such a finely porous layer can act as an effective support for active non-porous layers in applications such as gas separation. Also, based on the practical results, it was determined that for pressure equal 7 bar, temperature of 70 °C, membrane thickness of 1.15 mm and polybutadiene to divinyl benzene ratio of 1.5, the relative separation will be 93.58. [ABSTRACT FROM AUTHOR]

The use of anaesthetics to lower stress in fish farming activities and other routine operations is common in aquaculture. Sodium bicarbonate, also known as baking soda/powder is a recognised and accepted anaesthetic substance commonly used in aquaculture. However, this is not the case in some developing countries such as Zambia, thus limiting the fish farmers' options of using cheaper locally available chemicals as anaesthetic agents in fish culture. Our study aimed at assessing the anaesthetic effects of sodium bicarbonate on greenhead tilapia broodstock. A total of 90 Oreochromis macrochir broodstock (weight 160 ± 10 g and length 169 ± 10 mm) were exposed in triplicates to a sodium bicarbonate bath solution at concentrations of 0.0, 5.0, 10.0, 15.0, 20.0 and 30.0 g/L; and fish per transparent plastic tank (20 L) were used. Induction and recovery time were monitored using a stopwatch. The results of this study revealed a significant effect (P < 0.001) of sodium bicarbonate on both the induction and recovery time for O. macrochir broodstock. Survival rate was 100% and fish resumed normal swimming and feeding soon after the experiment. We therefore recommend sodium bicarbonate to be used as an anaesthetic owing to its availability and affordability. [ABSTRACT FROM AUTHOR]

The efficacy of three common fish anesthetics (clove oil, 2-phenoxyethanol, and tricaine methanesulfonate) was evaluated in the Pacific hagfish (Eptatretus stoutii). The overarching aim of our study was to identify the best anesthetic and concentration for the purposes of routine laboratory use of Pacific hagfish (i.e., short and consistent induction and recovery times and minimized stress and safety risk to hagfish). The objectives of our study were fourfold: (1) identify anesthetic stages of Pacific hagfish using clove oil anesthesia; (2) establish standardized anesthesia preparation procedures; (3) determine the optimal anesthetic and concentration for safely achieving stage V anesthesia; and (4) investigate the effects of repeatedly exposing Pacific hagfish to anesthesia. Experimental concentrations, ranging from 50 to 400 mg/L, of each anesthetic were tested on at least three Pacific hagfish individuals. We found the following: (1) Pacific hagfish exhibited similar stages of anesthesia to those described for bony fishes; (2) sufficient mixing of clove oil with seawater had a considerable effect on the consistency and timing of anesthetic induction; (3) concentration and anesthetic significantly impacted induction and recovery timing, whereas body mass had no impact on anesthetic trends; and (4) repeatedly exposing Pacific hagfish to optimal concentrations of clove oil or MS-222 had no effect on induction or recovery timing, whereas exposure number significantly impacted induction timing when using 2-PE. Due to consistent induction and recovery times, low risk of accidental overdose, and high safety margins for both handler and hagfish, we recommend 175 mg/L of clove oil as the ideal anesthetic and concentration for the routine laboratory use of Pacific hagfish. [ABSTRACT FROM AUTHOR]

This paper focuses on the assessment of the inclination to self-ignition of various types of wood chips according to the methodology of European standard EN 15188. The study also assesses the effect of heating temperatures on the composition and quantity of gaseous products of heating. Gases were analysed using an infrared spectrometer with Fourier transformation. From the measured results it was found that the inclination to self-ignition differs for various samples of wood chips. The paper discusses certain parameters assumed to affect the inclination of biomass to self-ignite. When assessing the effect of temperature on the composition of gaseous products, a sample of forest wood chips heated at temperatures from 50 to 150 °C resulted in the following gaseous products: carbon dioxide, carbon monoxide, water and aliphatic hydrocarbons; their concentrations increase with the increasing temperature. Carbon oxides have been proposed as indicators of the state of stored materials self-heating. Observations presented in this paper can be used as data for elaborating safety instructions for storage of fuels based on solid biomass. [ABSTRACT FROM AUTHOR]

In this article, five particle size fractions such as +0.500 mm, 0.500–0.250 mm, 0.250–0.125 mm, 0.125–0.074 mm, and −0.074 mm were used to investigate the synergistic effect of particle heterogeneity and size on the hydrophobicity characterization of low rank coal surfaces using induction time and wetting thermodynamic measurements. The high induction time result of +0.500 mm size fraction with low ash content proved that the physical property, especially particle size, has a significant effect on induction time and wetting thermodynamic measurements. Moreover, LHR value and combustible recovery of 0.250–0.125 mm size fraction were higher than that of 0.125–0.074 mm size fraction, which indicated that the induction time measurement was greatly affected by the chemical property, i.e. heterogeneity. Furthermore, wetting thermodynamic measurements can be used as the supplement of induction time measurements while the ash content of the particle size fractions is close. [ABSTRACT FROM AUTHOR]

Summary: The objective of this study was to determine the efficacy of supercritical carbon dioxide turmeric extract (STE) on the oxidative stability of perilla oil (PO), as measured by acid value (AV), peroxide value (PV) and oxidation induction time and compared to control and α‐tocopherol containing PO as a positive control. The antioxidant activity was determined by DPPH, ABTS and FRAPS assays and individual bioactive compounds identified by chromatography. STE demonstrated significantly higher antioxidant activity than the α‐tocopherol. The major components of the STE were identified as ar‐turmerone, turmerone, curlone and bisabolene by GC‐MS and curcumin and demethoxycurcumin by UPLC‐Q‐TOF MS. During thermal treatment at 65 °C for 24 h, the PO containing STE at different concentrations (100, 300, 500 and 1000 μg mL−1) had significantly lower AV and PV, and at least 1.5 times higher induction period than those of the control and α‐tocopherol‐incorporated PO. [ABSTRACT FROM AUTHOR]

• Sucralose shows potential as a green kinetic promoter for gas hydrates. • Sucralose enhances gas uptake: 37% increase at 0.75 wt% in CO 2 hydrate formation. • Sucralose increases the growth rate of carbon dioxide hydrate formation. • Sucralose increases the water to hydrate conversion and storage capacity. Gas hydrates represent a cutting-edge technology for the separation and storage of greenhouse gases, capturing the interest of numerous researchers. Nevertheless, the challenges of low storage capacity and slow hydrate formation can be surmounted through the application of kinetic promoters. This study investigates the kinetic parameters of CO 2 hydrate formation with the influence of sucralose, an eco-friendly additive, at various concentrations. Lab-scale experiments were conducted in a reactor, with initial conditions of 3 MPa pressure and 274.15 K temperature. Among the tested concentrations, the addition of 0.75 wt% sucralose exhibited the highest gas consumption and storage capacity. Compared to pure water at t = 300 min, the inclusion of 0.75 wt% sucralose resulted in a 37 % increase in gas consumption and a corresponding enhancement in storage capacity. Likewise, at t = 20 min, the water-to-hydrate conversion and storage capacity (SC) increased by approximately 35 % compared to pure water. However, as the sucralose concentration in the aqueous solution surpassed 0.75 wt%, the promoting effect on gas consumption declined, showing a diminishing return. Notably, a slight inhibitory behavior was observed during the experiment with a 10 wt% sucralose concentration. Furthermore, the experiments were replicated for certain sucralose concentrations in the aqueous solution under the same initial pressure but at an elevated temperature of 276.15 K. The results demonstrated a reduction in the promoting effect of sucralose, suggesting that raising the cell temperature during the hydrate formation process negatively impacted the kinetic parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Isothermal calorimetry allowed rapid and non-invasive screening of mayonnaise. • Typical workflow was used to transform the heat flow data to oxygen consumption. • Simultaneous determination of antioxidant efficiency, capacity and oxidizability. • Extra virgin olive oil mayonnaise showed highest oxidative stability. This study aimed to introduce a new method based on isothermal calorimetry (IC) for measuring the autoxidation rate in mayonnaise samples. Mayonnaise samples were prepared by homogenizing an aqueous phase, consisting of vinegar and egg yolk, with various oil phases, including sunflower, corn, extra virgin olive, grape seed, and apple seed oils at 60 °C. The rate of free radical formation (R i) was controlled by adding AIBN (R i = 4.4±0.1×10−9 M/s). The autoxidation rate determined by IC was highly correlated with the one measured using the oxygen uptake method (R2 = 0.99). The IC method accurately indicated the antioxidant capacity and rates of both inhibited and uninhibited periods, together with the oxidizability of mayonnaise samples. The mayonnaise made with extra virgin olive oil exhibited the lowest oxidizability, while sunflower oil showed maximum antioxidant efficiency. A significant advantage of the IC method was its ability to simultaneously measure up to 24 samples with minimal effort. [ABSTRACT FROM AUTHOR]

It has been understood through many studies that particle shape is important in terms of particle adhesion to air bubbles in flotation. However, there are many questions yet to be answered. Whether the surface of the particle or its sharp corners is effective is only one of the issues that need to be better understood. Therefore, this study aims to delve deeper into the fundamental studies on the role of particle's geometry (surface, edges, and vertex) in their flotation behavior by investigating the attachment of spherical, cylindrical, triangular prismatic, and cubic particles to air bubbles based on their attachment efficiency, settling velocity, collision efficiency, and induction time. Bubble-particle attachment test results inferred that the attachment efficiency was in the order of cubic > triangular > cylindrical > spherical. In addition, it was found that the induction time of the spherical surface decreased from 37 ms to 15 ms with increasing collector concentration, while the induction time of the edged cubic particle decreased from 8 ms to 2 ms. This was attributed to the fact that the edge facilitates the drainage, thinning, and rupture of the water film between the bubble and the particle, thereby increasing the attachment efficiency. Finally, it has also been observed that the three-phase contact line of the cube particle is larger than that of the spherical particle, which improves the attachment stability and reduces detachment efficiency. The results obtained in this study shed light on the fact that the shape of the particles fed to flotation can be produced by using a suitable mill and thus higher flotation efficiency can be achieved with lower collector concentration. [Display omitted] • Effect of cubic, triangular prismatic, cylindrical, and spherical particles on the attachment behavior were investigated. • The order of the attachment efficiency is: cubic > triangular prismatic > cylindrical > spherical. • Settling orientation and velocity vitally affect bubble-particle attachment. • Edges and vertexes produced higher attachment efficiency than surfaces. [ABSTRACT FROM AUTHOR]

The potential of hydrates formed from R141b (CH3CCl2F), trimethylolethane (TME), and tetra-n-butylammonium bromide/tetra-n-butylammonium chloride (TBAB/TBAC) to be used as working substances for cold storage was investigated to provide a solution for unbalanced energy grids. In this study, the characteristics of hydrate formation, crystal morphology of hydrates, and the stability of hydrate in cyclic formation under 0.1 MPa and at 5 °C were carried out. It found that the ice had a positive effect on the hydrate formation under same conditions. Upon the addition of the ice cube, the induction time of R141b, TME, and TBAB/TBAC hydrates decreased markedly, and significantly high formation rates were obtained. Under magnetic stirring, the rate at which TBAB/TBAC formed hydrates was significantly lower than that when ice was used. In microscopic experiments, it was observed that the TBAB/TBAC mixture formed hydrates with more nucleation sites and compact structures, which may increase the hydrate formation rate. In the multiple cycle formation of TBAB/TBAC hydrates, the induction time gradually decreased with the increasing number of formation cycles and finally stabilized, which indicated the potential of the TBAB/TBAC hydrates for application in cold storage owing to their good durability and short process time for heat absorption and release.

Calcium sulfate is a very important product of precipitation reactions in various branches of industry. The most common applications include building materials, impression materials in dentistry, immobilizing casts and an inactive ingredient of tablet excipients. It is also used as a drying agent and color glaze. In this paper, influence of various conditions, i.e., substrates concentration (supersaturation), temperature and rotational speed on induction time was investigated. The range of investigated parameters was 0.15–0.35 M for concentration with step of 0.05 M, 298–323 K with step of 5 K for temperature, and 1.67–8.33 s−1 for rotational speed with change every 1.67 s−1. The experiments were performed using visual and turbidimetric methods. It was proven that increase in all three investigated parameters resulted in shorter induction time. The turbidimetric method was found to be more precise, but still insufficient for concentrations below 0.15 M. Moreover, as a result of data analysis, a simple method of induction time calculation was proposed when arbitrary measurements in various concentrations are known.

Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction time data, were compared with those obtained from MSZW data. The influences of lag time on the nucleation parameters were examined for the induction time data. The effects of l-arginine impurity concentration on the nucleation parameters based on both the induction time and MSZW data were investigated in detail.

When gas hydrates dissociate into gas and liquid water, many gas bubbles form in the water. The large bubbles disappear after several minutes due to their buoyancy, while a large number of small bubbles (particularly sub-micron-order bubbles known as ultra-fine bubbles (UFBs)) remain in the water for a long time. In our previous studies, we demonstrated that the existence of UFBs is a major factor promoting gas hydrate formation. We then extended our research on this issue to carbon dioxide (CO2) as it forms structure-I hydrates, similar to methane and ethane hydrates explored in previous studies; however, CO2 saturated solutions present severe conditions for the survival of UFBs. The distribution measurements of CO2 UFBs revealed that their average size was larger and number density was smaller than those of other hydrocarbon UFBs. Despite these conditions, the CO2 hydrate formation tests confirmed that CO2 UFBs played important roles in the expression of the promoting effect. The analysis showed that different UFB preparation processes resulted in different promoting effects. These findings can aid in better understanding the mechanism of the promoting (or memory) effect of gas hydrate formation.

The effect of olfactory bulb lesions on the induction time of sevoflurane has never been studied. We aimed to investigate this issue. In this study, we found that the volume of olfactory bulbs and the pore of the fila olfactoria were significantly lower with the fibrosis of olfactory bulbs in animals subjected to olfactory bulbectomy. Volatile anesthetics induction times were measured in all groups. Prolonged induction was observed in olfactory bulbectomy group. It was concluded that increased induction times of sevoflurane may be due to the olfactory bulb lesion.

• Solid concentration was a determinant for comparing wet and dry grinding kinetics. • Both abrasion and disintegrative fracture behaviors made particles rounded. • Differences in shape and roughness between dry and wet grinding were evaluated. • Particles with irregular shape and smooth surfaces presented shorter induction times. This study explored the influence of wet and dry grinding conditions on breakage rate, shape factor and surface roughness of ground particles, induction time (the threshold for particle–bubble attachment to occur), and flotation recovery. The experimental results indicated that the dry grinding breakage rate was much higher than the wet grinding one. The first-order region was limited to a relatively short grinding time, where it was considered that little or no secondary breakage occurred. With the increasing time, the dry grinding breakage rate increased, while it decreased for wet grinding (solid concentration of 70 vol.%). The differences in shape factor and surface roughness of the wet- and dry-ground samples were attributed to different breakage mechanisms and grinding energy amounts generated by those two types of procedures. The wet-ground particles were characterized by more irregular shape factors and smoother surfaces, and thus presented shorter induction times and higher floatation recoveries compared to the dry-ground ones. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Formation of gas hydrates is a first-order phase transition that starts with nucleation. Nucleation rate is central to nucleation phenomena of any system as it defines the rate at which critical nuclei form in a unit volume or other measures of system size. For gas hydrates, a primary difficulty in the investigation of gas hydrate nucleation has been the inability of researchers to compare nucleation rates of gas hydrates across various systems of different scales and complexity, as it is not even clear which measure(s) of system size is most appropriate to use in a given circumstance. This inadequacy in turn has been limiting the capacity of researchers to investigate the nucleation process itself. Here we first derived general scaling laws of nucleation rates of gas hydrate systems and then applied it to compare the nucleation rate of methane hydrate determined by a High Pressure Automated Lag Time Apparatus (HP-ALTA) to that of a flow loop. The ratio of the nucleation rates of two systems (of the same guest gas and at the same driving force) scales linearly with the ratio of the system sizes (i.e., the ratio of most probable induction times scales linearly with the inverse of the ratio of the system sizes). Comparison of five conceivable measures of the system size for the scaling suggests that the total length of the three-phase-lines in the system is the most appropriate measure for scaling of the nucleation rate of methane hydrate. [ABSTRACT FROM AUTHOR]

• SDS, CTAB and water-based nanofluids of SiO 2 , Al 2 O 3 , and CuO are used as kinetic promoters in hydrate formation process. • Englezos - Bishnoi model is utilized for calculating the apparent rate constant of hydrate growth. • SDS and CTAB are the most effective promoters in increasing the average apparent rate constant and water to hydrate conversion. • SiO 2 nanofluid shows the most promising promotion effects by reducing the induction times of CO 2 and CH 4 hydrates formation. • SDS Aqueous solution is the most effective promoter that can enhance the average apparent rate constant of CO 2 and CH 4. Sodium dodecyl sulfate (SDS) with concentrations of 300 ppm and 500 ppm; cetyl trimethylammonium bromide (CTAB) with concentrations of 220 ppm and 700 ppm; and water-based nanofluids of SiO 2 , Al 2 O 3 , and CuO with concentrations of 0.1, 0.3, and 0.5 wt% were used as kinetic promoters in methane hydrate formation process at initial conditions of 274.15 K and 5.5 MPa and carbon dioxide hydrate formation process at initial conditions of 274.15 K and 3 MPa. Englezos and Bishnoi model was utilized for calculating the apparent rate constant of hydrate growth and van der Waals-platteeuw model coupled with CPA equation of state was used to model hydrate phase equilibrium conditions. SDS with a concentration of 500 ppm and CTAB with a concentration of 700 ppm are the most effective promoters in increasing the average apparent rate constant and water to hydrate conversion. SiO 2 nanofluid with a concentration of 0.3 wt% shows the most promising promotion effects by reducing the induction times of CO 2 and CH 4 hydrates formation by 70 and 74%, respectively. Aqueous solution of SDS with a concentration of 500 ppm is the most effective promoter that can enhance the average apparent rate constant of CO 2 and CH 4 by 350 and 200%, respectively. [ABSTRACT FROM AUTHOR]

A series of experiments on CO2 hydrate formation were carried out in the presence of titanium dioxide (TiO2), silicon dioxide (SiO2), multi-walled carbon nanotubes (MWNTs) nanoparticles. The effects of these nanoparticles on induction time, final gas consumption, and gas storage capacity have been investigated at the temperature of 274.15 K and the initial pressure of 5.0 MPa.g. The induction time of CO2 hydrate formation was remarkably shortened to 12.5 min in the presence of 0.005 wt% MWNTs nanoparticles. The high thermal conductivity and heat capacity of MWNTs nanoparticles presented better heat transfer, and large surface area provided more suitable sites for heterogeneous nucleation of CO2 hydrate. [ABSTRACT FROM AUTHOR]

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Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Al-water reaction promoted by catalysts is a promising hydrogen generation technology. In this work, a high-activity M-B/γ-Al 2 O 3 (M = Co, Ni) catalyst is prepared by wet chemical reduction method. It is found that M-B/γ-Al 2 O 3 catalyst significantly promotes the Al-water reaction and decreases the induction time. When the molar ratio of γ-Al 2 O 3 to Co-M in Co–B/γ-Al 2 O 3 catalyst is 1:1, the induction time is only 0.43 h. The catalytic activity of M-B/γ-Al 2 O 3 is proportional to its active area. SEM analyses show that M-B particles are dispersed on γ-Al 2 O 3 surface, which reduces the agglomeration of M-B and increases the active surface of M-B/γ-Al 2 O 3 , leading to a high catalytic activity. A possible mechanism is proposed, which shows that the dissociation of water molecules on γ-Al 2 O 3 surface and the microgalvanic interaction between M-B and Al can promote the hydration process of passive oxide film on Al particle surface, speeding up the Al-water reaction. Image 1 • High-activity M-B/γ-Al 2 O 3 catalyst was prepared by wet chemical reduction method. • M-B/γ-Al 2 O 3 greatly promotes the Al-water reaction and decreases the induction time. • The catalytic activity of M-B/γ-Al 2 O 3 is proportional to its active area. • A possible mechanism for Al-water reaction promoted by M-B/γ-Al 2 O 3 was proposed. [ABSTRACT FROM AUTHOR]

An improved, high pressure, stirred automated lag time apparatus (HPS-ALTA) was used to determine gas hydrate nucleation and growth rates from induction time measurements at fixed subcooling. The improved HPS-ALTA uses multiple thermoelectric elements to allow rapid, radially symmetric heating and cooling, which together with the automatic detection of hydrate formation, makes feasible the measurement of statistically significant induction time distributions. Four induction time probability distributions, with between 83 and 312 points, were measured at subcoolings ranging from (6 to 9.7) K for water with a synthetic natural gas mixture at pressures around 12 MPa. The induction time data measured at each subcooling were exponentially distributed and were fit using a model derived from Classical Nucleation Theory based on the mononuclear nucleation mechanism. The nucleation rates obtained in this work were consistent within a factor of three or better with recent literature measurements made using a completely different apparatus. Hydrate growth rates measured at fixed subcooling using the improved HPS-ALTA were also found to be stochastic but consistent with previous measurements of the kinetic growth rate in a binary gas mixture. The results obtained here establish the need to improve theoretical models of hydrate formation to reconcile predicted nucleation rates with the much slower ones observed experimentally. [ABSTRACT FROM AUTHOR]

Gas hydrate technology is a promising approach for carbon capture. However, due to the multi-physics and multi-scale complexity of the process, this technology is not sufficiently understood for real-life scale applications. In particular, further fundamental studies of the hydrate formation mechanisms and rate are needed to achieve relevant insights into the process design and intensification. High-fidelity numerical models are crucial to capture and explain the dominant physicochemical mechanisms involved in the process. This paper presents a new variation of the shrinking core model (SCM) that can capture the practically observed features of the carbon dioxide (CO 2) hydration process, including the nucleation phase behavior and induction time, which have not been exploited previously. Accordingly, the most significant contribution of the current work to the literature is the proposal and demonstration of an efficient and rapid predictive tool for the CO 2 hydrate nucleation process. Moreover, a model-based estimation of the induction time, as a critical parameter in CO 2 hydrate rate estimation and control, is presented. Additionally, the temperature history profile over the nucleation and growth phases is simulated and compared against experimental data from the literature. The proposed model offers an in-depth and rationale analysis tool compared to the primary forms of the SCM and other models in which the nucleation stage has been compromised for the sake of mathematical modeling and numerical solution simplicity. The proposed concept is generic enough to be used for CH 4 hydration process too. Image 10481 • A kinetic model is presented to observe features of the hydrate-based CO 2 capture. • The model is able to predict the nucleation phase behavior and induction time. • Temperature history profile over the nucleation and growth phases is simulated. • The numerical estimation of the internal concentration profiles for a hydrating particle is demonstrated. • A model-based criterion was proposed to estimate the nucleation number. [ABSTRACT FROM AUTHOR]

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• Initial coating preferentially formed on defects and scratches, and around bubbles on the surface. • Induction time was influenced by initial deposition, and not just by local composition, as demonstrated experimentally. • Coating deposition was favored for areas with a high local current density. The purpose of this study was to develop a detailed understanding of the initial stages of coating electrodeposition. Of particular interest were the changes that take place during the induction period before a steep change in the voltage at constant current is observed. Experiments designed to elucidate the role of concentration buildup clearly showed that a local change in concentration was not solely responsible for the observed induction period. This conclusion is further supported by experiments where the induction time at a specified current was observed to vary with the type of substrate used for deposition. Consequently, scanning electron microscopy was used to study the morphology of the initial deposit on different substrate surfaces including bare steel, galvanized steel, and phosphated steel. It was found that the initial film formed preferentially at specific locations on the metal surfaces, such as on defects or scratches, where the local current density was likely to be higher. The initial film also appeared to form around gas bubbles that were present on the substrate surface. Preferential film deposition at areas of high local current density was observed directly in experiments with intentionally scratched surfaces. The additional insight provided by this study will help to improve our ability to model accurately the early stages of E-coat deposition and, eventually, the accuracy of large-scale simulations for process performance prediction and optimization. [ABSTRACT FROM AUTHOR]

Abstract Natural gas + water-in-diesel emulsion + AA systems with and without wax were used to investigate the influence of wax crystals and their heat- and mass-transfer effect on hydrate formation from macroscopic and microscopic aspect in a flow system. Hydrate nucleation and initial growth were found to be a partially occurred phenomenon. Wax was found to prolong the hydrate induction time through two significant effects: one was the macroscopic heat-transfer effect produced by wax deposition with insulating effect, and the other was the microscopic mass-transfer resistance originating from the wax crystals that were adsorbed at or adjacent to the oil-water interface. Hydrate induction time shortened and became less scattered with the increasing initial pressure. Based on the heat-transfer theory of a flow system and the hydrate nucleation theory, an improved model for hydrate induction time prediction was developed by coupling calculation of hydraulics and heat-transfer and by introducing mass-transfer effect of adsorption of wax crystals. The findings of this work are meaningful for providing essential information and supports for the ongoing deep-sea oil and gas production and the application of hydrate-management strategies in the presence of wax crystals in a flow system. [ABSTRACT FROM AUTHOR]

Abstract This study was aimed at the synthesis of pure phase zeolite 4A from coal fly ash sourced from Nishat power plant in the Punjab province of Pakistan. Analysis of fly ash (FA) demonstrated that it can be used to produce low silicate type zeolites specifically zeolite 4A due to its Si/Al molar ratio of ∼2. The current investigation emphasized on the addition of induction time (before and after crystallization) to the fly ash extract of Si-Al-Na species that was extracted from fly ash. The induction time helped in catalysing primary and secondary gel formation during the synthesis leading to controlled formation of single phase with high crystallinity and small crystallite size. The physiochemical investigations of synthetic zeolite 4A by using various analytical techniques made the proposed process justified on comparison with commercial zeolite 4A. The X-Ray Diffraction (XRD) analysis for synthesize zeolite 4A confirmed only one crystallographic phase and small crystallite size with 82% crystallinity compared to reference zeolite with 75% crystallinity. Fourier-Transform Infrared spectroscopy (FTIR) spectra revealed the structural aspects of synthesis and reference zeolite by indicating the presence of identical structural units with same height and width of peaks. Morphological analysis by Scanning Electron Microscope (SEM) showed a well-defined cubic shape of synthesis zeolitic crystals. Surface area analyses by Brunauer–Emmett–Teller (BET) showed that synthesized zeolite possessed 122 m2/g surface area that is 3 times higher than reference zeolite of 36.3 m2/g. The synthesized zeolite was also found to have smaller particle size than reference zeolite. Thermal stability comparison of both zeolites was studied by non-isothermal Thermo Gravimetric Analysis-Differential Thermal Analysis (TGA-DTA) thermograms from 25 to 800 °C temperature and both the samples were found to be stable at 800 °C. Highlights • Pakistani Coal Fly ash for synthesis of zeolite 4A and waste into useful material. • New step of induction time in the conventional two-step hydrothermal synthesis. • Pure, single-phase crystals with high crystallinity and small crystallite size. • Comparative physiochemical analysis of the synthesized and reference zeolite 4A. • Analytical techniques employed were XRD, SEM, BET, FTIR, PSA, EDX and TGA. [ABSTRACT FROM AUTHOR]

In this work, the impact of functional group on the thermodynamics and kinetics of CO 2 hydrates are investigated experimentally. The hydroxylated multi-wall carbon nanotubes (OH-MWCNT) and carboxylated carbon nanotubes (COOH-MWCNT) along with pristine carbon nanotubes (MWCNT) are selected for this study. The carbon nanotubes are suspended in a 0.03 wt% sodium dodecyl sulfate (SDS) aqueous solution and the results are compared with SDS aqueous solution at the same concentration of 0.03 wt% and deionized water. The CO 2 hydrate phase boundary and kinetic parameters of CO 2 hydrate formation including induction time, the initial rate and amount of gas consumed, gas uptake, storage capacity, and water to hydrates conversion are studied. The results show that the nanofluids studied do not affect the equilibrium conditions of CO 2 hydrates. In addition, 0.01 and 0.05 wt% of COOH-MWCNT mixed with 0.03 wt% SDS showed highest initial hydrate formation rate and gas uptake. Furthermore, a comparison between SDS and COOH-MWCNT (without stabilizer SDS) at 0.03 wt% revealed that addition of COOH-MWCNT to the water enhance the initial hydrates formation rate compared to SDS. • Carbon nanotube does not change CO 2 phase equilibrium. • The kinetic of CO 2 hydrates formation in the presence of SDS and carbon nanotube are discussed. • Nanofluid contain 0.05 wt% COOH-MWCNT+0.03 wt% SDS is the most efficient promoter. • Surfactant-free of COOH-MWCNT nanofluid show higher initial CO 2 hydrate formation rate compared to SDS. • Amount of gas consumption, storage capacity, and water to hydrates conversion rate are discussed. [ABSTRACT FROM AUTHOR]

In hospitals, operating rooms (ORs) are very demanding in terms of the indoor air quality (IAQ) and require systems that minimize the concentrations of pollutants (microorganisms, chemical and particulate matter). Air treatment devices that use photocatalytic oxidation (PCO) could potentially be used in the OR to improve IAQ. In this work, the fate of two OR pollutants acrylonitrile (chemical found in surgical smoke) and isoflurane (anesthetic gas) when they go through a PCO device was investigated. The experiments were conducted in a laboratory closed loop multi-pass reactor. A mathematical model was utilized to enable the calculation of one indicator (single-pass removal efficiency) for acrylonitrile and two indicators (induction period and single-pass removal efficiency) for isoflurane. The degradation efficiency was then accessed by studying the influence of environmental parameters on these indicators. The parameters that were studied are the relative humidity, presence of co-pollutants and presence of particles. The parameters were observed to have similar effects on the degradation of both compounds. Increasing relative humidity inhibited the degradation probably due to competitive adsorption. The presence of co-pollutants like nitrous oxide and acetic acid caused a possible competition for adsorption unto active sites thus decreased the degradation efficiency of acrylonitrile and isoflurane. The increase in the concentration of the co-pollutants enhances the competitive effect and further decreases the degradation efficiency of the target pollutants. Finally the presence of particles on the photocatalytic media could block active sites thereby inhibiting the degradation of acrylonitrile and isoflurane. Image 1 • The influence of relative humidity, co-pollutants and particles on PCO of isoflurane and acrylonitrile is studied for first time. • RH inhibits the degradation of compounds probably due to competitive adsorption between water and pollutant molecules. • The presence of co-pollutants decreases the removal efficiency of the target pollutants probably due to competitive adsorption. • The presence of particles on media may block the active sites and thus decrease the removal of acrylonitrile and isoflurane. [ABSTRACT FROM AUTHOR]

This study aims to determine the ratio of turmeric rhizome extract (TE) and tamarind leaf extract (TLE), which is suitable for the time of induction and the highest antioxidant synergism. The TE:TLE ratio examined was 10:1; 10:1.5 and 10:2. The chosen variable was the amount of peroxide. Observations carried out for 7 hours at one-hour intervals using ferric thiocyanate (FTC) method and thiobarbituric acid (TBA) method. Relationship between the time and absorbance were depicted to show the induction time and synergism in antioxidants. The results showed that all TE and TLE ratios had antioxidants that inhibited lipid oxidation reactions at the stage of initiation and propagation. TE and TLE ratios 10:1, 10:1.5 and 10:2 had induction time, respectively 2.9577; 3.0206 and 3.1882 hours with FTC method, 3.6116; 3.706 and 3.8722 h with the TBA method. Synergism in antioxidants was 103.534; 106.924 and 110.705 % with the FTC method, and 102.9393; 109.522 and 115.969 % with TBA. The highest antioxidant synergism in both methods was shown by the ratio of TE:TLE = 10:2. [ABSTRACT FROM AUTHOR]

Abstract Flotation strongly depends on bubble–particle attachment interactions. However, modelling of bubble–particle attachment interactions is challenging particularly due to the difficulties in quantifying the hydrophobic interactions between an air bubble and a non-spherical particle using a well-advanced technique such as atomic force microscopy; the reason is that these measurements are not reproducible when particles are non-spherical. This paper proposes a methodology to determine the hydrophobic interaction constants between air bubbles and coal particles in the presence of a surfactant. The bubble–particle hydrophobic constants were determined from first principles using the Navier-Stokes equation and the Glembotsky experimental technique. It was found that the higher the surfactant concentration, the higher the hydrophobic constants. The results showed that the calculated critical film rupture thickness is inversely related to the induction time measurements, and the maximum critical film rupture thickness matched the minimum induction time. The decrease in the electrostatic double layer repulsive energies resulted in the decrease in the induction times. Highlights • Thin liquid film drainage mechanism was studied. • The hydrophobic constants between bubbles and coal particles were determined. • The induction time is inversely related with the critical film thickness. • The electrostatic force affected more film rupture than the hydrophobic forces. [ABSTRACT FROM AUTHOR]

A stirred-kettle hydrate production experimental device was used to study effects of dynamic accelerator SDS (twelve sodium dodecyl sulfate) and thermodynamic accelerator THF (tetrahydrofuran) on CO2 capture from simulated flue gas by hydrate based gas separation (HGBS). Mixed gas contained CO2 with a mole fraction of 25% and N2 with a mole fraction of 75% was used to simulate flue gas. The effects of different concentrations of SDS and THF on the separation effect were studied. On this basis, the effects of different initial pressures and different reaction temperatures on the separation efficiency were studied. The results showed that both SDS and THF can increase the CO2 recovery, but simultaneously reduce the separation factor. When the temperature was 3.5°C and the initial pressure was 9.2 MPa, adding 0.01wt% SDS, the CO2 recovery increased by 4.3% compared with pure water, and the separation factor decreased by 44.8%. When the temperature was 6.5°C and the initial pressure was 3.7 MPa, adding 0.5mol% THF, the CO2 recovery increased by 30.4% compared with pure water, and the separation factor decreased by 72.8%. Under experimental conditions, more appropriate concentrations of SDS and THF were 0.01wt% ~ 0.05wt% and 0.5mol%~ 2mol%, respectively. The initial pressure increase can effectively shorten the hydration reaction induction time, increase the gas storage density, CO2 recovery and separation factor. Reducing the temperature can effectively improve the separation efficiency. [ABSTRACT FROM AUTHOR]

Abstract Particle-bubble interactions play a vital role in froth flotation that is widely used for the recovery of valuable minerals from gangue minerals. In this study the effects of nanobubbles on particle-bubble interactions were visualized using a specially designed apparatus to show the trajectory of solid particles of different degrees of hydrophobicity moving around a regular sized flotation bubble. It has been shown that particle hydrophobicity and the nanobubbles generated on particle surface enhance the particle-bubble interaction process by affecting the balance between the hydrodynamic and surface chemistry forces that control the trajectory of a particle moving around a bubble surface. Increased particle surface hydrophobicity in terms of contact angle from 50o to 85o and 110o enhanced the particle-bubble interaction by reducing the induction time from 75 ms to 52 ms and 48 ms, respectively. In the presence of nanobubbles on particle surface, the thin film between the particle and the bubble ruptures up to 50% faster. It has also been observed that nanobubbles are capable of producing fine particle aggregates that facilitate the particle-bubble interaction process. Graphical abstract Nanobubble Effects on Hydrodynamic Interactions between Particles and Bubbles Unlabelled Image Highlights • A specially designed apparatus developed for visualizing particle-bubble interactions • Shorter induction time visualized with increased particle hydrophobicity. • Faster attachment observed in presence of nanobubbles on particle surfaces. • Fine particle aggregates enhanced collision and attachment probabilities. • Larger detachment monitored with increased particles size. [ABSTRACT FROM AUTHOR]