In solvate–solvent systems, the interactions between the constituent functional groups in the component molecular species are important for the fundamental properties, such as the molecular diffusivity and solubility. In this work, in order to evaluate the interactions at the atomic level, the binding strengths of the constituent ketone groups of four vinyl pyrrolidone analogs and methyl methacrylate to the surrounding water molecules are estimated by using the residence times of water obtained from molecular dynamics simulations. To determine the residence times, the residence rates of water are determined as a function of the elapsed time, and the obtained curves are then fitted by exponential polynomial equations. The absolute values of the correlation factors in the fitting are greater than 0.999 regardless of the miscibility of the solvate, demonstrating the validity of the estimated residence times. Additionally, the residence time is strongly correlated with the self-diffusivity of water molecules in these systems. The results indicate that the residence time is an atomic-level criterion to evaluate the affinities between the constituent groups of molecular species.
The prediction of interface shear stress is one of the great challenges of stratified gas–liquid flow in a horizontal pipe. In this work, a new method is proposed to predict interface shear stress, in which the gas–liquid interface is regarded as a flat specified shear wall (SSW). The gas flow is numerically simulated under the same conditions as those in Strand's experiments, the gas-wall and interface shear stress correlations are then modified, and a new Kowalski-type equation of liquid-wall shear stress is presented. Different models are adopted to obtain the gas flow velocity and gas-wall, interface, and liquid-wall shear stresses, and the results are compared with the experimental data and analyzed. The results show that the gas-wall shear stress is well predicted by the SSW k–ω model, the interface shear stress is well predicted by the SSW k–ε model, and the liquid-wall shear stress is well predicted by both the two-fluid model and the Kowalski-type equation. The predictions of liquid holdup and pressure drop of the SSW method improved and agreed better with the experimental data when the gas Reynolds numbers were 9000≤ReG≤50000 and the liquid Reynolds numbers were 15000≤ReL≤30000.
The momentum transfer characteristics of a cone translating in power-law fluids in two different orientations (apex downward and apex upward) with reference to the direction of the mean flow is numerically investigated over wide ranges of conditions: Reynolds number, 1≤Re≤100; power-law index, 0.4≤n≤1.8; and cone angle, 20°≤α≤150°. The governing differential equations (continuity and momentum) are solved numerically. The numerical solution obtained is then postprocessed to infer the effect of orientation for a given cone angle on the wake and drag phenomena. Finally, the present values of the drag coefficient for each orientation are used to develop predictive correlations in terms of Re, n, and α.
The purpose of this study is to examine the possibility of establishing a novel CO2 absorption process with molten alkali carbonate using a bubble column reactor. In our previous study, a hot CO2 recovery process using Li4SiO4 suspended in molten Li2CO3–K2CO3 was developed. In the process, molten alkali carbonate itself showed great potential for CO2 absorption at high temperature. If a hot CO2 absorption process were established using only molten alkali carbonate, it could make the system simpler and the operating temperature range could be extended without the limitation of reaction temperature of solid absorbent. In the study, molten Li2CO3, Na2CO3, K2CO3 and its eutectic mixture were selected as CO2 absorbent. A bubble column was chosen as the device for gas absorption at high temperature. First, the CO2 absorption performance of each single molten alkali carbonate was investigated. The result showed that the molten Li2CO3 had a great ability to absorb CO2 at high temperature. Li2O was thought to be produced by decomposition of Li2CO3 during the melting and purging process and a reaction of CO2 with Li2O occurred during the absorption process. Further, the CO2 absorption performance of eutectic mixture increased exponentially with increasing the ratio of Li2CO3 in composition. Second, the possibility of establishing a CO2 absorption process using molten Li2CO3 was examined. The overall CO2 absorption process in the bubble column was investigated and the experimental results showed that the mass transfer of CO2 into molten Li2CO3 was the rate-controlling step. The operational conditions of the bubble column were optimized. The superficial gas velocity was an important operational parameter that affected both the CO2 absorption rate and total amount of CO2 finally absorbed in the bubble column. The operating temperature also greatly affected the amount of absorbed CO2.
A numerical simulation of incompressible fluid dynamics is developed for computational cells having an aspect ratio larger than 10. In most cases, stability and precision of the existing numerical methods strongly depend on the distortion of cells, although cells with high aspect ratio are required in many situations of water systems such as rivers, lakes and oceans. The proposed method is based on the projection method with Helmholtz–Hodge decomposition of three dimensional Navier–Stokes equations, and is composed of two Poisson’s equations for long and short components of cell size, respectively. To demonstrate the ability of the method, three examples are calculated: (1) flow in a rectangular channel, (2) free surface motion in a shallow channel, and (3) flow in a shallow bay. As a result, it was observed that the proposed method can be easily applied to the prediction of three-dimensional flows using highly distorted computational cells.
Extractant-impregnated resins (EIRs) prepared from 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name PC-88A), neodecanoic acid (Versatic 10), and XAD-7HP polymeric beads have been developed for separation and pre-concentration of scandium (Sc). The separation factors between Sc and other metal ions are very high, allowing for selective recovery of Sc from a complex metal-mixture solution. Furthermore, desorption of Sc is quantitatively achieved using 2 M sulfuric acid, which is difficult for single-extractant-impregnated resins. The adsorption behavior, kinetics, and loading capacity of the binary EIR were investigated. The good reusability of the resin was confirmed by five times repeated use in recycling operation. This binary-extractant-impregnated concept could provide a new way to develop novel ion-exchange resins for metal separation.
The HPA (High Pressure Absorber) process was studied in detail using three sets of typical high-pressure condensate field gas. The CECUP (Comprehensive Energy Consumption for Unit Production) served as the basis for evaluating energy consumption, and by using ASPEN HYSYS software to simulate and analyze the three HPA processes, and process III was considered better. The method for obtaining the best HPA process under certain conditions was determined by analyzing the operating variables such as inlet split ratio, de-ethanizer pressure and absorber pressure. The adaptability of the HPA process was analyzed using three feed gases with different richness, compared with the DHX process, and obtaining the adaptability range of HPA process to feed gas pressure and richness.
A high performance ZSM-5 zeolite membrane is applied to remove H2O from the esterification of acetic acid and isopentanol by pervaporation. The influences of reaction conditions on the isoamyl acetate yield are studied in detail. Compared with the traditional esterification of acetic acid and isopentanol, the esterification with “membrane extractor” has a well isoamyl acetate yield at low reaction temperature. With the reaction temperature, acetic acid/isopentanol molar ratio and effective membrane surface area to esterification mixture ratio volume of 100°C, 3.0/1.0, 2.0 wt% NaHSO4, and 0.26 cm2/cm3, respectively, the isoamyl acetate yields was 98.39%, the membrane flux and separation factor (H2O to organic) were 0.21 kg·m−2·h−1 and 1040, respectively. Further, the ZSM-5 zeolite membrane shows good long–term stability and reproducibility for the pervaporation-esterification, the isoamyl acetate yields of the esterification-pervaporation for intermittent 8 times or continuous 160 h still remained at 97.73% and 98.30%, respectively. In addition, the ZSM-5 zeolite membrane still retained the typical MFI diffraction peaks and morphology by XRD and SEM characterization after long-term PV–esterification .
Poly(L-lactic acid) (PLLA) membranes prepared via a nonsolvent-induced phase separation method with a nonionic surfactant (Tween 80) have been applied as depth filters in the filtration of bacterial cell suspensions and mammalian cell broths. Finger-like pores captured the cells inside the membrane, avoiding the formation of a dense cell cake on the membrane surface. The filtration rate of lactic acid bacterial cell suspensions increased 4–5 times during depth filtration compared to that observed during screen filtration with a smooth surface. During depth filtration, the connected cellular structure as well as the finger-like pores captured the bacterial cells. The plots of the reciprocal of permeation flux vs. the permeate volume per unit filtration area suggest that capturing the bacterial cells in the pores resulted in reduced blocking constants during depth filtration compared to screen filtration. During the filtration of CHO cell broths, the cells were captured in the finger-like pores of the PLLA depth filter and on the screen filter membranes of cellulose acetate. The permeation flux was sustained at high levels for longer durations during depth filtration compared to screen filtration, although the initial flux was lower than that in screen filtration. The PLLA depth filter will be useful as a prefilter in the filtration of suspensions of compressible bacterial and mammalian cells.
The present study applies supercritical water oxidation (SCWO) as a pretreatment method for the stable carbon isotope ratio analysis of rice. In this study, three kinds of polished rice with different locations of production were treated by SCWO using a batch-type reactor. At a temperature of 500°C, pressure of 25 MPa, and reaction time of 120 min with an excessive amount of oxygen, more than 99% of the rice-derived organic carbon was converted into carbon dioxide without generating any other C-containing gases. Utilizing TiO2 as a catalyst, 99.5% of rice-derived organic carbon was selectively converted into CO2 within 15 min. In each case, the stable carbon isotope ratio of generated CO2 was successfully obtained using isotope ratio mass spectrometry. The δ13C value of CO2 from the SCWO treatment of rice was compared with that of CO2 from the catalytic combustion of rice.
The mechanism of solids mixing is considered as a vital factor to the metal smelting, catalytic cracking and combustion performance in the multi-particle field. In this paper, the computational fluid dynamics coupling discrete element method (CFD-DEM) approach was employed to simulate the binary particles movement and mixing within a baffle type internal circulating fluidized bed (ICFB). Moreover, the mixing behaviors of binary particles were experimentally validated in the macroscopic scale. Polyethylene particles were used as bed material, and glass beads and rubber particles were chosen as tracers. The above two research methods are to add tracer particles after achieving the circulating movement of polyethylene particles around the vertical plate. The mixing behaviors were investigated in terms of flow patterns, solid circulating mass flux, and mixing index. Moreover, the effect of inlet gas velocity ratio on mixing also conducted in the current research. The results indicate that there is an optimal velocity value of fast and low inlet gas velocity to achieve the solid circulation mass flux. The particle density has a significant influence on the mixing degree and rate of the binary particles. Besides, from the simulation of the effect of four groups of inlet gas velocity on mixing index with glass beads as tracer particles, it is found that more particles can be entrained into the cycle mixing movement with the increasing gas velocity. These findings could be helpful for the design and optimization of the novel fluidized reactors.
The catalytic performance of MCM-48 was greatly improved by the introduction of a small amount of chromium during the oxidative dehydrogenation of isobutane. Various characterization procedures such as XRD, N2 adsorption–desorption isotherms, TEM, NH3-TPD, XPS, and XAFS were used to identify the role that chromium played in the improvement, and XPS and XAFS results provided the most valuable information. Both measurements revealed that the chromium species existed as Cr6+ inside the framework of MCM-48 before oxidative dehydrogenation, but was reduced to Cr3+ during the reaction. The characteristic pore nature of MCM-48 also contributed to an enhancement of the selectivity to isobutene via the suppression of consecutive oxidation reactions.
Solid circulation characteristics of an inclined-type lower loop seal and a vertical-type lower loop seal were investigated in a circulating fluidized bed system that consists of two bubbling fluidized beds and one fast fluidized bed with oxygen carrier particles (OCN-A, Geldart group B) as bed materials. The results were compared with those of a previous experiment that used a CO2 absorbent (P-78, Geldart group A). Stable and continuous solid circulation was achieved at a lower gas flow rate with the inclined-type lower loop seal than the vertical-type lower loop seal, and the volume based solid circulation rate showed similar values at a given riser flow rate regardless of the lower loop seal types and particles used in this study.
This study evaluates the costs and carbon dioxide emissions associated with the production of various lithium ion batteries using current and more advanced materials. We constructed an evaluation system which enables the user to quantitatively clarify the effect of each elemental technology on battery performance and production costs. This method allows the evaluation of production costs and CO2 emissions of present and future batteries in terms of future technology development, production scale-up effects, and the use of high-performance new materials. As an example, a battery using innovative cathode and anode materials was evaluated by the process design approach. The future production cost and CO2 emissions for this battery are reduced from 17.5 to 4.6 JPY W h−1 and 161 to 37 g-CO2 W h−1, compared to the present batteries, indicating significant impacts on energy use. Finally, the important areas in battery research and development are highlighted, and a roadmap for battery technology is proposed.
In petrochemical process plants, there are many heat exchangers using industrial water as coolant. Further, water treatment systems usually recycle the water in order to minimize the environmental loads. Optimization of maintenance management of the heat exchangers and treatment of industrial water is needed since the quality of industrial water strongly affects the corrosion rate of tubes in heat exchangers and the decrease of their heat transfer coefficients. In this paper, a method is proposed to obtain the optimum conditions utilizing multivariate analysis based on data collected in the daily works of maintenance and water treatment. A concrete example of applying this method to 31 existing plants and optimizing PDCA management of maintenance by improving the sum of maintenance cost and water treatment cost is shown.
LNG process optimization using Genetic Algorithms was investigated and compared with knowledge-based search algorithm implemented on the same process with the same objective function. The aim was to investigate the effectiveness of such algorithm in contrast to Genetic Algorithms. Scrupulous attention was given to simulating the same process as previous research using HYSYS®. The simulation software was connected to the C++ GA library (GALib) via Component Object Model (COM) Technology. Steady State, Incremental and Deme Genetic Algorithm implementations were tried out and the Deme Genetic Algorithm was found to be superior to other implementations. Mutation and crossover operators were changed exponentially throughout the GA run. The results show 27% reduction in specific power consumption when compared to the optimum case obtained by earlier research. This proves the superiority of Genetic Algorithms over Knowledge based search algorithms suggested by earlier research.
Curcumin (Cur), a hydrophobic polyphenol compound, holds promising potential as an anticancer agent. However, the poor solubility in water and the low bioavailability of curcumin have limited its therapeutic applications. In this regard, we reported the formulation of curcumin using a solid-in-water (S/W) nanodispersion technique to enhance the water solubility and therapeutic activity of curcumin. This new aqueous formulation comprises simple preparation protocols: emulsification and freeze-drying for encapsulating hydrophobic biomolecules with a hydrophilic surfactant, followed by redispersion of the resultant solid complexes in an aqueous solution. Pluronics F68 and F127 were used here for the encapsulation of curcumin. Enhanced aqueous solubility of curcumin was achieved by encapsulating curcumin with a hydrophilic surfactant using the S/W nanodispersion technique. The resultant nanosized formulation had a narrow size distribution and high entrapment efficiency of curcumin. The highest loading capacity of curcumin in S/W nanodispersion was obtained with a weight ratio of curcumin to pluronic of 1 : 10 for both surfactants. The release profile of the complexes was found to depend on the type of surfactant, suggesting that the selection of a proper surfactant is crucial for controlling curcumin delivery. The anticancer activity of the S/W formulation of curcumin was correlated with the drug release profiles and cellular uptake, which in turn was influenced by the hydrophobicity and chemical structure of the surfactant.
Carbon-supported Ni catalysts were prepared and used to convert an ethanol/water mixture to CH4. When using 5 wt% ethanol, successful conversion to CH4 and CO2 was achieved at a temperature as low as 250°C. Marginal amounts of undesired by-products such as acetaldehyde were produced even at a low conversion of ethanol. The composition of the product gas was similar to that in the equilibrium state. The rate of ethanol conversion was independent of ethanol concentration, and the activation energy was assumed to be 105 kJ/mol. Our carbon-supported Ni catalysts were found to show high activity for ethanol conversion from the comparison with literature data. The energy balance shows that this process needs little thermal energy to convert the ethanol/water mixture when heat of the outlet stream of the reactor is recovered by heat exchange with the inlet stream since the reaction is a slightly exothermic reaction. CH4 produced in the reactor can be purified by physical absorption of CO2 in water; however, CH4 can be also absorbed in the water at high operating pressure. CH4 can be recovered at 94% when the operating pressure of the absorber is 3 MPa from equilibrium consideration.
The dehydration behavior of LiOH-modified Mg(OH)2 (LiOH/Mg(OH)2), as a new chemical heat storage material, was investigated. Structural analysis of LiOH/Mg(OH)2 was carried out using an X-ray diffraction (XRD) meter. The profile of the dehydration reaction of LiOH/Mg(OH)2 was observed to analyze the dehydration kinetics of the LiOH/Mg(OH)2 samples. The XRD patterns of the LiOH/Mg(OH)2 samples shifted toward higher angles than that of Mg(OH)2. This indicated that the lattice parameter might have changed and lattice defects such as oxygen vacancies might have been generated on the surface of Mg(OH)2. The rate of the dehydration reaction increased as the amount of added LiOH increased; therefore, LiOH/Mg(OH)2 could be a potential chemical heat storage material. We concluded that LO20 (Mg(OH)2 containing 20 mol% LiOH) was the combination with the most optical mixing mole ratio. This result was determined by analyzing the dehydration activation energy values. When the dehydration reactions of the LiOH/Mg(OH)2 samples were considered to be first-order reactions, the calculated mole fraction of Mg(OH)2 could not be reproduced. However, the calculated mole fractions of Mg(OH)2 were in agreement with those measured considering the reactions to be zero- and first-order reactions. Therefore, the kinetics of the dehydration reaction of the LiOH/Mg(OH)2 samples included both zero- and first-order reactions.
This study investigated the mechanical properties of a packed bed of hydrogen storage alloy before and after hydrogen absorption/desorption. As a result, it was found that the initial packing ratio decreases with an increase in the number of absorption/desorption cycles. During the loading process, the packing structure changed more for a packed bed with lower packing ratio, and the tangent modulus increased, whereas the structure changed little during the unloading process. Further, the compression behavior was almost elastic when the packed bed was loaded again.