Showing papers in "Chemical Engineering & Technology in 2014"
TL;DR: A comprehensive review on the recent progress in preparation and stability of nanofluids is presented in this article, where the settling behavior of nanoparticles in nanoparticles and techniques to stop agglomeration are described.
Abstract: Research on nanofluids has increased significantly in the last decade due to the distinctive potential in many applications such as enhanced heat transfer processes, drug delivery systems, and membrane manufacturing processes. The study of dispersion behavior of nanoparticles in liquids is a topic of keen interest towards the preparation of stable nanofluids. A comprehensive review on the recent progress in preparation and stability of nanofluids is presented. Settling of nanoparticles is the only predicament towards preparation of stable nanofluids which takes place due to formation of agglomerates. The settling behavior of nanoparticles in nanofluids and techniques to stop agglomeration are described. Nanofluid preparation techniques, assessment method of stability, and methods to reduce agglomeration are discussed.
127 citations
TL;DR: In this paper, the total organic carbon (TOC) and selected organic compounds were quantified in the waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks.
Abstract: Process waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks were quantified regarding the total organic carbon (TOC) and selected organic compounds. HTC runs revealed that TOC loads were largely unaffected by process severity or type of feedstock whereas the C2–C6 fatty acids, determined by GC, displayed clear effects of temperature and feedstock. HPLC demonstrated simultaneously the initial increase and subsequent consumption of cellulose-derived furfural and 5-hydroxymethylfurfural as well as the increase of the lignin-derived 2-methoxyphenol. 2-Methylbenzofuran, an example for a substance potentially harmful to aquatic biota, was observed in high concentration in the HTC liquor from wheat straw-based feedstocks.
116 citations
TL;DR: In this paper, different regeneration techniques, reducing costs and minimizing environmental impact, are reported for the reuse of saturated activated carbon (AC) for micro removal of pollutants from the water phase.
Abstract: Activated carbon (AC) is an adsorbent used in most adsorption processes related to micro removal of pollutants from the water phase, but the application is limited due to high costs and environmental issues related to the disposal after saturation. Different regeneration techniques, reducing costs and minimizing environmental impact, are reported for the reuse of saturated AC. These techniques can be performed via two separate strands: regeneration based only on desorption of adsorbed compounds in AC, or based on the decomposition of pollutants adsorbed on AC. Literature on the regeneration of saturated ACs is reviewed and promising techniques are highlighted. One of the most challenging bottlenecks preventing the commercial application of regeneration technologies is the difficulty of scaling-up.
69 citations
67 citations
TL;DR: In this article, a new method for enhancing the mass transfer coefficient in the gas absorption process was reported, which was carried out in a wetted-wall column using different aqueous nanofluids as the solvent.
Abstract: A new method for enhancing the mass transfer coefficient in the gas absorption process is reported. CO2 absorption experiments were carried out in a wetted-wall column using different aqueous nanofluids as the solvent. The mass transfer characteristics were found to increase by applying Al2O3/water nanofluid. The mass transfer coefficient decreased with TiO2/water nanofluid. In the case of Fe3O4/water nanofluid, the mass transfer rate was enhanced by increasing the nanoparticle volume fraction, but the mass transfer coefficient was lower than that obtained with water for all experimental conditions studied. Finally, applying a downward magnetic field resulted in higher mass flux and mass transfer coefficient in comparison with experiments without a magnetic field.
64 citations
TL;DR: A short background of NMR spectroscopy fundamentals and instrumentation is presented along with its potential applications and limitations for real-time analysis in the manufacturing sector in this article, which is expected that soon NMR will be applied to monitor the chemical and physical properties of complex feedstock mixtures and reactions in real time.
Abstract: Although nuclear magnetic resonance (NMR) is one of the most powerful analytical techniques, it has not been widely used as a non-destructive, non-contact inline industrial sensor. A short background of NMR spectroscopy fundamentals and instrumentation is presented along with its potential applications and limitations for real-time analysis in the manufacturing sector. NMR signals are generated in the presence of a magnetic field normally produced by expensive large and heavy magnets which have been the major limiting factor in the use of NMR analysis in factories. However, the last decade has brought substantial advances in the development of cheaper, smaller, and lighter permanent magnets based on rare earth materials that use Halbach and unilateral configurations. Small and light cryogenic-free superconducting magnets are now offered in the market and are opening a new era in manufacturing. It is expected that soon NMR spectroscopy will be applied to monitor the chemical and physical properties of complex feedstock mixtures and reactions in real time which is the ultimate goal of precise process control.
63 citations
55 citations
TL;DR: In this paper, the chemical activation of PET wastes using different chemical agents such as H3PO4, H2SO4, ZnCl2, and KOH was investigated.
Abstract: Due to its high carbon content, low impurities, low cost and easy availability, poly(ethylene terephthalate) (PET) waste is considered as a suitable precursor for the production of activated carbon. The chemical activation of PET wastes using different chemical agents such as H3PO4, H2SO4, ZnCl2, and KOH was investigated. KOH- and ZnCl2-activated PET were found to be the best choices for the adsorption of small and large molecules. The capacities of the adsorbents towards I2, methylene blue, N2, CH4, and CO2 followed the order KOH-PET >H3PO4-PET > ZnCl2-PET > H2SO4-PET; however, in the molasses uptake and selective adsorption of CO2 compared to CH4, ZnCl2-PET performed better than the other adsorbents.
53 citations
TL;DR: Li4SiO4-G sorbent was used for CO2 capture at high temperature in a dual fixed-bed reactor as mentioned in this paper, which was characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption.
Abstract: A convenient water-based sol-gel technique was used to prepare a highly efficient lithium orthosilicate-based sorbent (Li4SiO4-G) for CO2 capture at high temperature. The Li4SiO4-G sorbent was systematically studied and compared with the Li4SiO4-S sorbent prepared by solid-state reaction. Both sorbents were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. The CO2 sorption stability was investigated in a dual fixed-bed reactor. Li4SiO4-G exhibited a special Li4SiO4 structure with smaller crystalline nanoparticles, larger surface area, and higher CO2 adsorption properties as compared with Li4SiO4-S. The Li4SiO4-G sorbent also maintained higher capacities during multiple cycles.
52 citations
TL;DR: In this paper, the reuse of industrial wastes from a coal-fired power plant and a plasma electrolytic oxidation process was attempted to realize a zero discharge by using a singlemode microwave oven equipped with reflux condenser was used for crystallization under atmospheric pressure.
Abstract: The reuse of industrial wastes from a coal-fired power plant and a plasma electrolytic oxidation process was attempted to realize a zero discharge. The batch composition was adjusted by adding sodium hydroxide and sodium aluminate. A single-mode microwave oven equipped with reflux condenser was used for crystallization under atmospheric pressure. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, BET, thermogravimetric analysis, and cation-exchange capacity (CEC) measurement. Analytical results indicated that Na-A zeolite with a defined maximum crystallinity could be successfully synthesized by hydrothermal treatment of fly ash with wastewater. Due to the high CEC, the product can be applied for gas purification and soil remediation processes.
52 citations
TL;DR: An accurate and efficient model based on least-squares support vector machines (LSSVM) is developed for the determination of air specific heat ratios at elevated pressures and comparison with a previously published correlation as well as an intelligent method demonstrates that the performance of the presented model is more satisfactory than that of other methods.
Abstract: An accurate and efficient model based on least-squares support vector machines (LSSVM) is developed for the determination of air specific heat ratios at elevated pressures. Additionally, the coupled simulated annealing optimization strategy is used to calculate the optimal values of the LSSVM parameters. A large dataset of air specific heat ratios as a function of temperature and pressure for about 170 samples is used to develop and validate the model. The leverage approach (Williams plot) is used to determine the applicability domain of the model and to detect probably erroneous data points. Comparison of the obtained results with a previously published correlation as well as an intelligent method demonstrates that the performance of the presented model is more satisfactory than that of other methods.
TL;DR: In this article, the role of various terms, i.e., lift, drag, bubble-induced turbulence, and volume fraction correction terms for drag, is determined for simulation of bubble column bioreactors.
Abstract: The application of computational fluid dynamics (CFD) as a tool to simulate bubble column bioreactors is investigated. A three-dimensional model utilizing the Euler-Euler approach is evaluated. The role of various terms, i.e., lift, drag, bubble-induced turbulence, and volume fraction correction terms for drag, is determined. Good agreement between experimental data and simulation results was obtained by means of a single-bubble size model provided that bubble-induced turbulence and the reduction in drag due to the presence of other bubbles were taken into account.
TL;DR: In this paper, a commercial scale evaluation of three conventional methods of nutrient management and a recently proposed method, which takes into account the availability of nutrients, have been robustly tested and the results show that the application of the newly proposed method opens up the potential for further optimization.
Abstract: Energy production from phytomass residues such as harvest
leftovers is generally accepted as a sustainable way. Excellent
results may be reviewed in papers based on laboratory
observations. However, trials performed on a commercial scale
show that without proper disintegration long retention times,
huge fermenters, or various chemicals are required. The results
obtained in a commercial scale suggest that intensive
disintegration makes subsequent processes less manageable. Two
conventional methods of nutrient management and the recently
proposed method, which takes into account the availability of
nutrients, have been robustly tested. The data from all three
methods and the technological and cost assessment that followed
demonstrated that the application of the newly proposed method
opens up the potential for further optimization, which may lead
up to significant reductions in energy price.
TL;DR: In this paper, a porous nano-CaO/MgO-based adsorbent was prepared using MgO as a support in order to increase the sorption capacity and durability.
Abstract: A porous nano-CaO/MgO-based adsorbent was prepared using MgO as a support in order to increase the sorption capacity and durability. The magnesium sol prepared by reacting MgO slurry with citric acid was added to nano-CaCO3 slurry and the mixture was calcinated to obtain the nano-CaO/MgO-based adsorbent. The influence of MgO content on the structure and sorption performance of the resulting adsorbent was studied in detail. The pore radius and specific surface area of the adsorbent increased with higher MgO content. The adsorbent exhibited superior sorption performance during calcium looping and maintained a good durability at the calcination temperature, thus being an interesting candidate for future work.
TL;DR: A particle pre-weakening characterization method by single-particle/single-pulse test has been developed in this paper, and the emerging challenges for the mining industry to realize the benefits of this novel comminution technology include scale-up for industrial application, hybrid circuit design, maximization of pulse-induced cracks, and study of the downstream processing effects.
Abstract: The recent progress in electrical comminution using high-voltage pulses and the technical challenges in order to bring this technology to the mining industry are outlined. Pre-weakening ore particles and preferential liberation of minerals at coarse sizes are the two major research outcomes that may have potential benefits for the industry. A particle pre-weakening characterization method by single-particle/single-pulse test has been developed. The emerging challenges for the mining industry to realize the benefits of this novel comminution technology include scale-up for industrial application, hybrid circuit design, maximization of pulse-induced cracks, and study of the downstream processing effects.
TL;DR: Impaired optimization approaches like particle swarm optimization (PSO) and hybrid approach focused on pinpointing accurate interconnection weights through the proposed ANN model can lead to more reliable in situ combustion quality predictions, simulation design, and further plans of heavy-oil recovery methods.
Abstract: Enormous efforts have been made to facilitate produced-gas analyses by in situ combustion implication in heavy-oil recovery processes. Robust intelligencebased approaches such as artificial neural network (ANN) and hybrid methods were accomplished to monitor CO2/O2/CO. Implemented optimization approaches like particle swarm optimization (PSO) and hybrid approach focused on pinpointing accurate interconnection weights through the proposed ANN model. Solutions acquired from the developed approaches were compared with the pertinent experimental in situ combustion data samples. Implication of hybrid genetic algorithm and PSO in gas analysis estimation can lead to more reliable in situ combustion quality predictions, simulation design, and further plans of heavy-oil recovery methods.
TL;DR: A comprehensive overview of coal oxidation methods under mild conditions is provided, including oxidation with oxygen, ozone, ruthenium ion catalysis, oxidizing acid, electrolysis, sodium hypochlorite, and hydrogen peroxide.
Abstract: A comprehensive overview of coal oxidation methods under mild conditions is provided, including oxidation with oxygen, ozone, ruthenium ion catalysis, oxidizing acid, electrolysis, sodium hypochlorite, and hydrogen peroxide. The changes in chemical structure of coal during oxidation, the mechanism of different types of oxidation methods, and the possible applications of oxidation products are summarized. Comparison of these oxidation methods demonstrated that hydrogen peroxide and sodium hypochlorite oxidation of coal under mild conditions are the most suitable methods to study the molecular structure of coal and to obtain high-value organic chemicals. Applications of different analytical techniques for determination and quantification of products and coal structures are also reviewed.
TL;DR: In this article, the influence of several process parameters like milling time, ball-to-beaker volume ratio, diameter of milling balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary ball mills was investigated.
Abstract: The influence of several process parameters like milling time, ball-to-beaker volume ratio, diameter of milling balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary ball mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations.
TL;DR: In this paper, the authors explored the minimization of energy consumption for countercurrent switched cryogenic packed beds in which separation of CO2 and other components of natural gas can be achieved based on differences in freezing or desublimation points.
Abstract: Minimization of energy consumption was explored for countercurrent switched cryogenic packed beds in which separation of CO2 and other components of natural gas can be achieved based on differences in freezing or desublimation points. Highly pure CO2 and methane were obtained after separation. An experimental setup for CO2 removal from natural gas was constructed and a detailed experimental study was conducted by changing different operating parameters. Compared to other cocurrent or jacket-cooled constant-temperature configurations, countercurrent switched beds provided optimal separation and energy efficiencies. The effects of important process parameters like initial temperature profiles of the cryogenic bed, feed composition, and feed flow rate on energy requirement, bed saturation, bed pressure, and cycling times were investigated. The energy requirement for cryogenic packed beds was compared with the conventional cryogenic distillation process.
TL;DR: In this article, two simple models were proposed and tested for the mechanism of ripening of a conglomerate suspension to a single enantiomorph by temperature cycles in both models, the initial crystal size distributions and masses of the two enantiomorphics are equal, but either the crystal growth rate or the growth rate distribution is varied.
Abstract: Two simple models are proposed and tested for the mechanism of ripening of a conglomerate suspension to a single enantiomorph by temperature cycles In both models, the initial crystal size distributions and masses of the two enantiomorphs are equal, but either the crystal growth rate or the growth rate distribution is varied The difference in the crystal growth kinetics of the two enantiomorphs may be caused by the intrinsic thermodynamic stability of the crystals occurring in the initial suspension The initial nucleation of one of the two enantiomers will occur earlier than that of the counter-enantiomer This results in the formation of two populations occurring under different conditions, leading to different internal crystalline perfection and therefore different thermodynamic stability
Abstract: Mechanochemistry, a branch of solid-state chemistry, analyzes processes which can occur in solids due to the application of mechanical energy. This energy is supplied by high-energy milling. The mechanochemical approach belongs to the group of procedures that intensify the course of processes by producing various surface and bulk defects in treated solids. The accumulated energy acquired by milling is utilized in subsequent processes. In principle, the potential of mechanochemistry can be applied in cases, where the economic demand, the high temperatures as well as wet processes are under consideration. Several applications of mechanochemistry will be illustrated to demonstrate its potential in such apparently distinct fields like extractive metallurgy, materials engineering, and medicine.
TL;DR: In this article, the kinetics of FTS on a commercial cobalt catalyst were studied with syngas containing CO, CO 2, H 2, and H 2 O. The intrinsic kinetic parameters as well as the influence of pore diffusion (technical particles) were determined.
Abstract: The production of liquid hydrocarbons based on CO2 and renewable H2 is a multi-step process consisting of water electrolysis, reverse water-gas shift, and Fischer-Tropsch synthesis (FTS). The syngas will then also contain CO2 and probably sometimes H2O, too. Therefore, the kinetics of FTS on a commercial cobalt catalyst was studied with syngas containing CO, CO2 ,H 2, and H2O. The intrinsic kinetic parameters as well as the influence of pore diffusion (technical particles) were determined. CO2 and H2O showed only negligible or minor influence on the reaction rate. The intrinsic kinetic parameters of the rate of CO consumption were evaluated using a Langmuir-Hinshelwood (LH) approach. The effectiveness factor describing diffusion limitations was calculated by two different Thiele moduli. The first one was derived by a simplified pseudo first-order approach, the second one by the LH approach. Only the latter, more complex model is in good agreement with the experimental results.
TL;DR: In this article, a comparison of the ability of Raman, UV, NIR, and IR spectroscopy techniques to detect polymorphic transformation in the same system has been performed.
Abstract: Raman, UV, NIR, and IR spectroscopy are commonly used techniques to monitor solute concentration and solid composition during crystallization processes of polymorphic compounds. Since a comprehensive study and comparison of the ability of these techniques to detect polymorphic transformation in the same system has not been performed yet, this work aimed at developing a complete quantitative calibration model that describes the process in terms of solute concentration and solid composition for each technique. A comparison between the different process analytical technology tools was conducted using various physical and mathematical approaches. Chemometrics techniques, multivariate and univariate approaches, and different regression techniques were tested and an integrated calibration model is proposed.
TL;DR: In this article, the hydrodynamics of single-phase liquid flow with relatively high fluid viscosities in a microchannel was investigated experimentally and a modified capillary number representing the mutual effects of the viscosity of the continuous phase and the dispersed phase was proposed for predicting the slug sizes in microchannels.
Abstract: The hydrodynamics of single-phase liquid flow with relatively high fluid viscosities in a microchannel was investigated experimentally. The results showed that the conventional theory could predict the single-phase flow with high fluid viscosities in microchannels. Furthermore, the effect of viscosity on the slug flow of two immiscible liquid phases in a microchannel was studied with high-speed imaging techniques. It was found that a higher dispersed-phase viscosity quickened the flow pattern transition from slug flow to parallel flow and resulted in smaller slugs. A modified capillary number representing the mutual effects of the viscosities of the continuous phase and the dispersed phase was proposed for predicting the slug sizes in microchannels.
TL;DR: In this article, an enhanced stress energy model is used to predict the optimum process parameters for inorganic materials in wet stirred media milling based on results for a different grinding material.
Abstract: Wet grinding processes, especially in terms of nanoparticle production, are extremely energy intensive, and for hard and abrasive product materials, high grinding media wear is produced. In order to minimize energy consumption, the choice of the process parameters is crucial. The decision on the process parameters often depends on experience or a certain number of laboratory- or pilot-scale experiments. Here, an enhanced stress energy model is used, which enables the prediction of optimum process parameters for inorganic materials in wet stirred media milling based on results for a different grinding material. The use of this model to select the process parameters is also valid with regard to grinding media wear: The grinding media wear reaches minimum values if the optimum parameters pertaining to the minimum specific energy are chosen based on this enhanced stress energy model, especially if soft products are ground.
TL;DR: In this article, a dual-plane high-speed ERT system is proposed to map two-phase distributions with varying operational parameters, and a volume-of-fluid-based CFD model is adopted to determine the air-core size.
Abstract: Electrical resistance tomography (ERT) allows to measure hydrocyclone internal flow dynamics in situ. A dual-plane high-speed ERT system is proposed to map two-phase distributions with varying operational parameters. Experimental results are presented in terms of air-core diameter and its size variation for various feed flow rates and design variables. The total variation algorithm provides the best results compared to Tikhonov and Gauss-Newton algorithms. The influence of finite element method mesh size on air-core resolution is evaluated. High-speed video imaging and a volume-of-fluid-based two-phase computational fluid dynamics (CFD) model are adopted to determine the air-core size. Cross validation of air-core size and shape is performed by ERT measurements with CFD simulations and high-speed video imaging.
TL;DR: Ceria-promoted nickel catalysts supported on nanocrystalline MgO were prepared and employed in methane reforming with CO2 Their characterization was accomplished by X-ray diffraction, BET, temperatureprogrammed oxidation, and temperature-programmed reduction (TPR) techniques as mentioned in this paper.
Abstract: Ceria-promoted nickel catalysts supported on nanocrystalline MgO were prepared and employed in methane reforming with CO2 Their characterization was accomplished by X-ray diffraction, BET, temperature-programmed oxidation, and temperature-programmed reduction (TPR) techniques Cerium oxide (CeO2) proved to have a positive effect on catalytic activity, stability, and carbon suppression in methane reforming with CO2 A higher CeO2 content increased the catalyst activity and decreased the amount of deposited carbon over the spent catalysts The suppression of carbon was related to the high oxygen storage capacity of CeO2 In addition, TPR analysis revealed that the CeO2 promoter reduced the chemical interaction between nickel and support, resulting in an increase in reducibility and higher dispersion of nickel
TL;DR: In this article, the authors proposed a new application of AcILs, which is to use AcIL as drying material, based on their hygroscopicity and their properties and structures.
Abstract: Acetate-based ionic liquids (AcILs) are green and designable solvents applied in many fields. However, AcILs are found to be highly hygroscopic. On the one hand, the high hygroscopicity of AcILs influences their properties and structures. On the other hand, this hygroscopic property renders AcILs, and especially [EMIM][Ac], potentially useful as drying materials, a new application of AcILs proposed in this paper. These two traits could be interconnected, interdependent, and interconvertible, which implies that a shortcoming of AcILs, i.e., their hygroscopicity, leading to changes in their physical properties, could be turned into a useful feature, e.g., the potential usage as drying material, if it is dealt with properly.
TL;DR: In this article, a nanostructure bimetallic Ni-Co-MgO catalysts were used for dry reforming of Methane using coprecipitation with different NiCo contents and characterized by XRD, BET, N2 adsorption/desorption, temperature-programmed reduction (TPR), SEM, and temperature programmable oxidation (TPO).
Abstract: Methane dry reforming was studied over nanostructure bimetallic Ni-Co-MgO catalysts. The catalysts were prepared by coprecipitation with different Ni-Co contents and characterized by XRD, BET, N2 adsorption/desorption, temperature-programmed reduction (TPR), SEM, and temperature-programmed oxidation (TPO) techniques. XRD results let conclude that all samples contained MgO crystallite phases. With a higher Ni content the intensity of the diffraction peaks became stronger, indicating growth of the crystallite size of the prepared solid solutions. BET analysis demonstrated that a higher Ni-Co content decreased the surface area. The optimal catalyst could be determined which had the highest activity and a good stability in dry reforming reaction.