Discrete Element Method (DEM) proved to be an essential tool to optimize the industrial auger dosing process for pharmaceutical powders. During the DEM parameter calibration process of a certain powder, several parameter combinations might lead to a similar bulk response, which could also vary for other bulk responses. Therefore, a methodology is needed in order to narrow down the number of combinations and be at once close to reality representation. In this study, a vertical auger dosing setup is used as a standard calibration device to extract three different bulk responses, i.e., angle of repose, bulk density, and mass flow rate. Simulations using LIGGGHTS software package are performed based on Design of Experiments (DoE) by varying four input factors, i.e., auger speed, particle-particle and particle-wall static friction coefficients, and particle-particle rolling friction coefficient. The successful application of multivariate regression analysis (MVRA) results in predicting the bulk behavior within the studied ranges of parameters. In this regard, clustering the different predicted behaviors of the three responses together allows to dramatically reduce the admissible parameter combinations. Consequently, an optimized set of calibrated DEM parameters is chosen, where the simulation results accurately match the experimental reference data. This simple dynamic calibration tool proves to strongly verify and predict the flowability of free-flowing bulk materials.
Advanced functional materials require sophisticated control of particle characteristics. The bottom-up process has been extensively used to produce functional materials for controlling the particle properties of composite particles. We propose crystallization at liquid-liquid interfaces as an advanced particle formation method. This review introduces crystallization at a liquid-liquid interface based on several case studies used in various applications. Conventional crystallization has been generally used to produce crystals and particles with homogeneous particle properties. Liquid-liquid interfacial crystallization makes it possible to create composite particles with hetero-phase structures and interfaces. Liquid-liquid interfacial crystallization with an inkjet technique can control the droplet size accurately, and the shape and particle size distribution are successfully controlled in inorganic-organic composite particles. In addition, we succeed in creating organic-organic composite particles using the interfacial crystallization by an ultrasonic spray nozzle. The coating efficiency of organic particles on the particles is enhanced using the ultrasonic spray nozzle in comparison with anti-solvent crystallization. In this study, the fabrication of inorganic-organic composite particles using a coaxial tube reactor on the liquid-liquid interfacial crystallization is proven successful. These findings suggest that liquid-liquid interfacial crystallization is a promising means of efficiently producing composite particles because of their applicability to infusion in various processes.
Consistency and reliable flow are of great concern during the handling and processing of flour. In this study, wheat flour was consolidated by normal stress and vibration, and rheological factors including bulk solid compressibility, Warren-Spring cohesion strength, permeability, and wall friction were evaluated. Soft red winter (SRW) and hard red spring (HRS) wheat flours were vibrated for 5 and 10 minutes and compressed under 10 and 20 kPa for 12 and 24 h. After vibration, wall friction increased from 10.87° to 14.13° for SRW flour and decreased from 11.00° to 7.10° for HRS flour, and the permeability decreased for both the flours. Consolidation time and stress had a significant effect (P < 0.05) on wall friction and compressibility. The HRS Carr index increased from 25.77 to 38.48 when consolidated under 20 kPa for 24 hours, but the SRW Carr index decreased slightly from 46.60 to 44.24. The SRW flour permeability decreased significantly (P < 0.05) when compression pressure was increased from 10 to 20 kPa. while HRS permeability was less affected by consolidation. The consolidation and vibration effects on bulk flour properties differed likely due to inherent differences in the composition and hardness of HRS and SRW.
Intermetallic compounds are becoming hot materials as catalysts because they show unique catalytic properties that originate from a unique electronic structure and an atomic ordered surface. Ternary intermetallic catalysts have rarely been reported, which is likely due to the difficulty in synthesizing their supported nanoparticles, the typical form for catalysis research; however, there could be novel catalysts in ternary systems because they have much more elemental combinations than binary systems. They are expected to exhibit novel properties due to the synergy between three elements. Metallurgical methods, such as arc-melting, can easily synthesize intermetallic compounds even in ternary (or more) systems if they are thermodynamically stable. Thus, only metallurgical synthesis enables screening for ternary intermetallic catalysts. The catalyst screening of Heusler alloys, which are a group of ternary intermetallic compounds popular in other research fields, such as magnetics, has been conducted using metallurgical synthesis. The screening revealed fundamental catalytic properties of Heusler alloys for several reactions and identified good catalysts for the selective hydrogenation of alkynes. The systematic control of catalysis was also demonstrated by the substitution of fourth elements using a feature of Heusler alloys. This paper describes the importance of ternary intermetallic catalysts with practical examples of Heusler alloy catalysts and discusses future prospects.
This article provides a review of the recent progress in understanding and predicting additives-induced drag reduction (DR) in turbulent wall-bounded shear flows. We focus on the reduction in friction losses by the dilute addition of high-molecular weight polymers and/or fibers to flowing liquids. Although it has long been reasoned that the dynamical interactions between polymers/fibers and turbulence are responsible for DR, it was not until recently that progress was made in elucidating these interactions in detail. Advancements come largely from numerical simulations of viscoelastic turbulence and detailed measurements in turbulent flows of polymer/fiber solutions. Their impact on current understanding of the mechanics and prediction of DR is discussed, and perspectives for further advancement of knowledge are provided.
In this paper, recent developments of the devolatilization model and soot-formation model for the numerical simulations of pulverized-coal combustion fields, and the technology used to measure soot particles in pulverized-coal combustion fields are reviewed. For the development of new models, the validation of the developed models using measurement is necessary to check the accuracy of the models because new models without validation have a possibility to make large errors in simulations. We have developed the tabulated devolatilization process model (TDP model) that can take into account the effect of particle heating rate on the volatile matter amount and the devolatilization-rate parameters. The accuracy of the developed TDP model was validated by using the laser Doppler velocimetry data for the bench-scale coal combustion test furnace. The soot-formation model combined with TDP model for the large eddy simulation (LES) has been also developed. The spatial distributions of both the soot-volume fraction and the polycyclic aromatic hydrocarbons were measured by virtue of laser-induced incandescence (LII) and laser-induced chemiluminescence (PAHs-LIF). The accuracy of the developed soot-formation model was validated by using the measured data.
Inertial impactors are applied widely to classify particulate matters (PMs) and nanoparticles (NPs) with desired aerodynamic diameters for further analyses due to their sharp cutoff characteristics, simple design, easy operation, and high collection ability. A few hundred papers have been published since the 1860s that addressed the characteristics and applications of the inertial impactors. In the last 30 years, our group has also carried out lots of studies to contribute to the design and the improvement of inertial impactors. With our understanding of inertial impactors, this article reviews previous studies of some typical types of the inertial impactors including conventional impactors, cascade impactors, and virtual impactors and the parameters for design consideration of these devices. The article also reviews some applications of the inertial impactors, which are mass concentration measurement, mass and number distribution measurement, personal exposure measurement, particulate matter control, and powder classification. The synthesized knowledge of the inertial impactor in this study can help researchers to design an inertial impactor with an accurate cutoff diameter, a sharp collection efficiency curve, and no particle bounce and particle overloading effects for long-term use for PM classification and control purposes.
The Calcium-Looping (CaL) process has emerged in the last years as a promising technology to face two key challenges within the future energy scenario: energy storage in renewable energy-based plants and CO2 capture from fossil fuel combustion. Based on the multicycle calcination-carbonation reaction of CaCO3 for both thermochemical energy storage and post-combustion CO2 capture applications, the operating conditions for each application may involve remarkably different characteristics regarding kinetics, heat transfer and material multicycle activity performance. The novelty and urgency of developing these applications demand an important effort to overcome serious issues, most of them related to gas-solids reactions and material handling. This work reviews the latest results from international research projects including a critical assessment of the technology needed to scale up the process. A set of equipment and methods already proved as well as those requiring further demonstration are discussed. An emphasis is put on critical equipment such as gas-solids reactors for both calcination and carbonation, power block integration, gas and solids conveying systems and auxiliary equipment for both energy storage and CO2 capture CaL applications.
Circulating fluidized beds (CFB)s are important technical equipment to treat gas–solid systems for fluid catalytic cracking, combustion, gasification, and high-temperature heat receiving because their mass and heat transfer rates are large. Cyclones are important devices to control the performance of CFBs and ensure their stable operation; heat-carrying and/or solid catalyst particles being circulated in a CFB should be efficiently separated from gas at a reduced pressure loss during separation. In commercial CFBs, a large amount of solids (> 1 kg-solid (m3-gas)–1 or > 1 kg-solid (kg-gas)–1) is circulated and should be treated. Thus, gas–solid cyclones with a high solids loading should be developed. A large number of reports have been published on gas–solid separators, including cyclones. In addition, computational fluid dynamics (CFD) technology has rapidly developed in the past decade. Based on these observations, in this review, we summarize the recent progress in experimental and CFD studies on gas–solid cyclones. The modified pressure drop model, scale-up methodology, and criteria for a single large cyclone vs. multiple cyclones are explained. Future research perspectives are also discussed.
It has been well known that mineral samples from different locations and origins can exhibit a significant shift in their properties and behavior. The present study of three samples of kaolin from a wide set of origin of deposits, composition, and ceramic properties, provided an important and perhaps a unique opportunity for investigating the interdependence of mineralogy, chemical composition, particle morphology, and surface property with their rheological behavior in ceramic applications such as casting rate. The X-ray diffraction patterns of kaolin samples #2 and #3 suggested low crystallinity with Hinckley Index (HI) ranging between 0.78 and 0.8. On the other hand, kaolin sample #1 was highly ordered with HI of about 1.21, and it had higher quartz content. This free quartz could enhance the permeability and hence increase the casting rate. The abundance of divalent ions (Ca2+ and Mg2+) in samples #2 & #3 could result in the collapse of the electrical double layer and reduction of zeta potential, consequently, coagulation of the particles leading to an increase of viscosity and dispersant demands. The morphology study suggested the platelet particles in sample #2 & #3 would lead to slower dewatering, thus, lower casting rate than that of blocky (lower aspect ratio and narrower size distribution) particles in sample #1.