The magnetic stirred reactor has been widely used because of its good sealing performance. Particle image velocimetry experiments are performed in the square cross-section of a magnetic stirred reactor. The flow structure and time evolution law at specific frequencies are obtained by a dynamic mode decomposition method. The results show that the turbulence at the stirring-bar outlet is fully developed, but there is an attenuation structure at other locations. The flow is in an unstable equilibrium state, and the Reynolds number can only reflect the local characteristics. The high-energy flow structures are the vortex structures formed by periodic rotating flow, free surface vortices, and cyclic shear flow. Because of the coupling between the fluid and stirring bar, vibration of the stirring bar is generated. This paper provides a new solution for the analysis of the mixing process as well as a basis for understanding the flow mechanism of the magnetic stirred reactor.
The recovery of scarce metals from secondary resources is desirable from an economic and ecological perspective. The limitations of natural resources and the continuous growth of advanced metal materials increase the importance of securing metal resources. The purpose of this study was to utilize a newly synthesized ionic liquid (IL), trioctyldodecylphosphonium bromide (P8,8,8,12Br), as a novel extractant for Cd(II) and Zn(II) from a chloride medium. An investigation into the extraction parameters, including the acid concentration, extractant type, and equilibration time, for both metals was performed. Two IL molecules were involved in the extraction reaction for both metals. The selective stripping of Cd(II) and Zn(II) from the loaded IL phase was achieved with 1 M oxalic acid and 3 M HNO3, respectively. The presence of other metals did not affect the extraction efficiencies of Cd(II) and Zn(II). The extraction efficiencies of Cd(II) and Zn(II) were maintained at 94% and 95%, respectively, with an equilibration time of 2 h. Although Fe(III) and Cu(II) were extracted into the IL phase in significant amounts, the removal of Fe(III) and Cu(II) could be achieved by scrubbing using 1 M Na2SO3 and 3 M H2SO4, respectively. P8,8,8,12Br exhibited excellent recyclability through consecutive extraction–stripping cycles. A recovery scheme for Cd(II) and Zn(II) from a wasted battery-model solution was developed based on the extraction data. P8,8,8,12Br could recover Cd(II) and Zn(II) from a mixed metal solution in high purity. This study highlights the future potential of P8,8,8,12Br in metal recycling.
To optimize operating conditions for separation and recovery method with a porous type anion-exchange resin, a competitive adsorption model was developed by considering mass transfer and ion-exchange reactions of each component. The model well described the concentration profiles adsorbed in the axial direction of the column packed with the resin, which are difficult to determine experimentally, in addition to the concentration profiles in the effluent from the column. The model was also able to predict optimum operating conditions to maximize the recovery yield of the target material and is effective for the process design of the recovery method with the resin.
A novel molecular imprinting technology was developed to prepare highly selective sorbents, composed of adhesive peptides and microporous silica particles, for the adsorption of target metal ions from aqueous environments. Using solid-phase peptide-synthesis, tyrosine-, lysine-, and histidine-containing peptides were tailored to contain tyrosine-, lysine- and histidine-rich regions. The tyrosine residues of the peptide were converted to 3,4-dihydroxy-L-phenylalanine (DOPA) residues to give the peptides adhesive properties mimicking the adhesion of mussel-foot proteins to wet surfaces. The resulting DOPA-peptides were incubated with target metal ions Ni(II), Cu(II), Co(II), or Zn(II), and subsequently with microporous silica particles, at pH 8.0 and 25°C. Almost all the DOPA-peptides, with the metal ions, strongly attached to the particles within 24 h and were not detached from them upon washing with an aqueous solution of pH 1–12. However, the metal ions were easily released from the particles at a pH below 7.0, implying that imprinted cavities from the target metal ions, created on the peptide-immobilized silica particles, remained after the removal of the template metal ions. The metal adsorption characteristics of the resulting particles, which were termed metal-imprinted peptide–silica particles (metal-iPSPs), were investigated. The target metal ions were adsorbed to metal-iPSPs at a pH of 8.0. The adsorption kinetics fit a pseudo-second-order model well. The adsorption isotherm was well approximated using the Langmuir model, indicating that the metal-iPSP surface was homogeneous, adsorption sites were equivalent, and the coverage formed a monolayer. The metal-iPSPs exhibited a significant and high selectivity for the imprinted target metal ions in the presence of an equimolar quantity of competitive metal ions.
When turbulent combustion simulations are performed using the flamelet approach, which indirectly considers the detailed chemical reaction mechanism, the probability density function (PDF) gets applied to statistical distributions for turbulent fluctuations in the mixture fraction that are modeled using the Reynolds-averaged Navier–Stokes or the large eddy simulation. In this case, the so-called “presumed PDF”—i.e., one in which the PDF is assumed and the flamelet table is constructed in advance—is generally employed, and the β-function is widely used for the PDF. This study investigated numerical integration for the equation with the β-function and examined the appropriate method. We succeeded in establishing the optimum value of the parameter for the integration interval and determining the appropriate numerical integration method.
We proposed a novel ammonia synthesis process in which the pressure of a N2–H2 nonthermal plasma system swung between low and high values to improve energy efficiency of the ammonia synthesis. We compared the energy efficiency, calculated by the amount of ammonia produced and plasma input power between constant-pressure system and pressure-swing one. In the constant pressure system, the highest ammonia formation rate and energy efficiency were obtained at the lowest pressure. On the other hand, the pressure swing system provided a higher ammonia formation rate and energy efficiency than the constant pressure system even though the pressure-swing range is within that of the constant pressure system. Consequently, the highest ammonia formation rate and energy efficiency were obtained by the pressure-swing system. Additionally, the dependence of ammonia formation efficiency on the plasma input power was investigated. In the constant pressure system, the amount of ammonia produced increased linearly with plasma input power. Interestingly, however, in the pressure swing system, the amount of ammonia produced saturated with increasing plasma input power. Therefore, the amount of ammonia produced did not decrease significantly even when the plasma input power was reduced, and the highest energy efficiency of 2.0 g-NH3/kWh was obtained under the minimum plasma input power condition tested for the pressure swing system.
Encapsulation of both 3,4-ethylenedioxythiophene (EDOT) and terthiophene (TTh) into a cyclodextrin-based metal–organic framework (CD-MOF) was successfully achieved upon use of an adsorption technique. The average amount of EDOT introduced into the CD-MOF was calculated to be 4.3 molecules per hydrophilic nanopore. On the other hand, from the relationship between the molecular size of TTh and the nanopore volume, TTh was evaluated and found to be mostly isolated in each hydrophobic nanopore of the CD-MOF. Co-oligomerization of EDOT and TTh in a CD-MOF was initiated by exposure to I2 vapor and subsequent heating at 80°C for 6 h. A trace amount of the co-oligomers consisting of two TTh molecules and four or five EDOT molecules was detected by using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The chemical structure of the co-oligomer was considered to be TTh bound at both ends of the EDOT tetramer or pentamer.
Effects of electrode and phase configurations on arc behavior and temperature distribution in a multiphase AC arc were successfully clarified. A high-speed video camera with band-pass filters were addressed to measure the arc. A multiphase AC arc is promising material processing technology owing to the characteristics of large high-temperature volume and high energy efficiency. The arc behavior was observed by imaging arc discharge with a high-speed camera in millisecond time scale. The temperature was conducted by Boltzmann plot method using two types of argon line emissions filtered by the band-pass filters. The obtained excitation temperature is high with a range of 7.0×103 to 1.3×104 K. The arc swing in front of electrode becomes wider and the temperature uniformity improves as the number of electrodes and phases increase. The characteristic time due to fluctuation of 12-phase AC arc was 1.4 ms, which was sufficiently shorter than the residence time of raw material in the arc. The 12-phase AC arc is useful for material processing in terms of temperature uniformity and fluctuation time.
Heat transfer characteristics are complex, specifically in the dense phase region of fluidized beds. In this paper, the flow characteristics and the heat transfer coefficients of an immersed horizontal tube in a pressurized fluidized bed were examined. The digital image analysis technique was used to determine the emulsion phase fraction, contact time, the bubble frequency, and the fluidization number at different pressure. The bubble phase fraction and the contact time of the emulsion phase decreased with increasing pressure while the emulsion phase fraction and the bubble frequency increased. The fraction and the contact time of the emulsion phase decreased with increasing gas velocity while the bubble phase fraction and the bubble frequency increased. The average heat transfer coefficient increased with pressure and reached a maximum at the optimal fluidized gas velocity. At the same pressure and gas velocity, the smaller particle size led to a higher average heat transfer coefficient for Geldart B particles. A model of the average heat transfer coefficient was derived based on the emulsion phase fraction, contact time, and the Froude number.
In this study, carbon black (CB) and carbon (coal-tar pitch-based spherical activated carbon (SAC)) were used to successfully fabricate composite-type SAC (CB/coal-tar-pitch-SAC), and its surface was coated with TiO2 to produce the composite material TiO2/CB/coal-tar-pitch-SAC. CB helps in decreasing the pore size of CB/coal-tar-pitch-SAC and increasing its specific surface area and total pore volume, which can be verified by the Brunauer–Emmett–Teller (BET) method. Practically, TiO2/CB/coal-tar-pitch-SAC can sterilize the bacteria present in the water. This study intensively verifies the high reusing sterilization capacity of TiO2/CB/coal-tar-pitch-SAC. The results indicate that TiO2/CB/coal-tar-pitch-SAC can effectively improve the water environment.
A steel plant is a complex system that is composed of interacting components. Iron-making uses a large amount of energy and emits a large amount of CO2. A strategy to decrease the energy cost and CO2 emission must consider all ways that a change in technology can affect other aspects of SP operation. To do this, a mathematical model of plants can be used for optimization. Electric arc furnace (EAF) is a process to make liquid steel (LS). An EAF makes LS by reprocessing scrap metal, direct-reduced iron, and pig iron. EAF steelmaking is an energy-intensive process, so methods to decrease energy cost are being sought. Also, the EAF sometimes uses additional carbon-based fuel and emits some CO2. A mathematical model based on material flow and energy flow is developed to simulate the EAF steelmaking and optimize the energy usage, CO2 emission or total cost. This optimization is a mixed integer linear program, and is solved by a commercial optimization tool, GAMS. Sensitivity analysis that considers the costs of electricity and natural gas is added to anticipate how optimization results can change with as variables change. The effects of carbon tax are also considered. Using this mathematical model, case studies are conducted, and optimization results are evaluated. The results of this study give an optimized strategy for steelmaking, while maintaining steel grade; the strategy can increase the efficiency of the steelmaking process.
Blast Furnace (BF) iron making process is an extremely complex industrial process. The molten iron silicon content is considered as an important indicator of the thermal status of the blast furnace. The stabilization control of blast furnace depends on the molten iron silicon content. Three classic subspace identification methods including MOESP (Multivariable Output-Error State sPace), CVA (Canonical Variate Analysis) and SSARX (Subspace identification method ARX) are considered to establish the state space model of blast furnace ironmaking process. The inputs to the model are the most responsible and easily measured variables for the fluctuation of thermal state in blast furnace while the output to the model is the molten iron silicon content. The identified state space models are then tested on datasets obtained from No.1 BF in LiuGang Iron and Steel Group Co. of China. Experiment results show that the blast furnace ironmaking process can be reliably modeled by these subspace identification methods. Further, the SSARX method outperforms over the other two subspace identification methods with closed loop data.
A stochastic multi-objective mathematical model based on material and energy flows under the system uncertainty of specific electricity demand-related scraps characteristics and operation conditions was developed to simulate the electric arc furnace steelmaking process and optimize carbon dioxide emission and cost. Considering several energy-saving technologies based on stochastic thermodynamic energy efficiency and electricity price, this paper suggests an optimal cost-saving and carbon-dioxide-emission-reducing strategy. The suggested model provides a trade-off relationship between cost and CO2 emission. To minimize CO2 emissions, a tunnel preheater without additional fuel consumption was suggest In contrast, to minimize the cost of utilizing cost-effective fossil fuels instead of electricity as the system energy requirement, an oxy-fuel burner and shaft furnace type of preheater were proposed. This problem was formulated as a mixed-integer linear programming model.
In this study, to synthesize dolomite (CaMg(CO3)2) with desired crystal properties, the minute gas–liquid interfaces of CO2 fine bubbles were utilized as new crystallization regions where crystal nucleation is dominant. Furthermore, the synthesized CaMg(CO3)2 crystals were converted to inorganic phosphor by doping emission center ions and sensitizing ions. To improve the emission characteristics of the inorganic phosphor based on CaMg(CO3)2, an effective method to achieve a high Mg/Ca ratio and particle size reduction is indispensable for the crystallization process. In the regions near the minute gas–liquid interfaces, local supersaturation is generated because of the accumulation of Ca2+ and Mg2+ and acceleration of CO2 gas absorption due to minimized bubble formation. Hence, CaMg(CO3)2 fine particles with a higher Mg/Ca ratio can be expected to crystallize. At a solution pH of 6.8 and a reaction temperature of 298 K, CO2 fine bubbles with an average diameter (dbbl) of 40 µm were continuously supplied to removed-K brine from the salt manufacture discharge using a self-supporting bubble generator, and CaMg(CO3)2 was crystallized within 120 min. The CO2 flow rate (FCO2) was maintained between 5.96 and 23.8 mmol/(L·min). For comparison, reactive crystallization with CO2 bubbles at a dbbl of 2,000 µm was also conducted using a dispersing-type generator. Moreover, the obtained CaMg(CO3)2 with different Mg/Ca ratios and average particle sizes (dp) was converted to inorganic phosphor by immersion for 60 min into a TbCl3/CeCl3 aqueous solution of 0.10 mol/L Tb3+ and Ce3+ each. Consequently, during reactive crystallization of CaMg(CO3)2 from removed-K brine, CO2 fine bubble injection at a high FCO2 helped to achieve a higher Mg/Ca ratio and micronization of CaMg(CO3)2 owing to the generation of numerous local regions with higher supersaturation around the minute gas–liquid interfaces. Additionally, when CaMg(CO3)2 obtained from removed-K brine was converted to the inorganic phosphor, CaMg(CO3)2 fine particles with dp less than 10 µm and a Mg/Ca ratio of approximately 0.5 were found to be suitable for the synthesis of green inorganic phosphor with a high emission intensity under the experimental conditions employed in this study.
It is challenging to prepare intermetallic Ni–Al nanopowders via chemical processes due to the difficulty in reducing Al-based oxides. Previously, we successfully obtained the single phase porous nanopowders of Ni3Al and NiAl from the low porosity oxide precursors in molten LiCl–CaH2 at 600°C. In this study, we examined the effects of porosity and the Ni/Al molar ratio of the oxide precursors on the BET surface areas and phases of the final Ni–Al nanopowders. The results showed that the porosity was not reflected in the final products, but the Ni/Al molar ratio defined the crystal structures. The intermetallic Ni5Al3 phase was not obtained at all, possibly due to the low rate of formation, whereas pure intermetallic Ni3Al and NiAl phases were obtained separately without any impurity phases.
A cross-linked poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) fibrous web supported composite ionomer (Aquivion) membrane was fabricated and evaluated for high-temperature and low-humidity proton exchange membrane fuel cell operations. PVA/PAA fibrous webs were initially prepared by the electrospinning method, followed by heat-treatment for cross-linking the polymers in order to increase mechanical strength. The successful formation of cross-linking bonds between PVA and PAA was confirmed by Fourier transform infrared spectroscopy analysis. For electrolyte membrane preparation in single cell tests, the fibrous webs were further impregnated with an Aquivion ionomer phase, which could be observed in scanning electron microscopy images. The prepared composite membrane had considerably improved mechanical strength compared to Aquivion-only membranes, as was evident by a 1.78-fold increase in tensile strength. Single cell and proton conductivity tests were also performed. The Aquivion-impregnated PVA/PAA fibrous composite membranes showed approximately 1.4-, 1.6-, and 1.2-fold higher maximum power densities than did the Aquivion-only membranes at 75°C/100% relative humidity (RH), 75°C/40% RH, and 120°C/40% RH, respectively. These results demonstrate the strong potential of the cross-linked PVA/PAA fibrous composite membranes impregnated with Aquivion for application to PEMFC operation at high temperatures and in low-humidity (>40% RH) regions.