June 2023
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2 Reads
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1 Citation
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June 2023
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2 Reads
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1 Citation
July 2021
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1 Citation
June 2018
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40 Reads
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14 Citations
Organic Process Research & Development
Continuous manufacturing of pharmaceuticals offers such benefits as production flexibility, reduced drug product costs and improved product quality. Moving towards continuous manufacturing requires suitable small-scale equipment, either by development of new equipment or optimization of existing equipment. In primary manufacturing, particle properties are often altered during crystallization and have to be restored during subsequent processing. Drying a crystallized product is one of the most challenging steps, especially since attrition and agglomeration can occur. To that end, we investigated the drying behavior of a crystalline model compound with moisture levels of up to 10 wt.% in a co-rotating twin screw extruder. The feed mass flows on a piece of small-scale equipment used for pharmaceutical production varied between 0.5 - 2.0 kg/h. Experiments were conducted to evaluate the drying performance in various process settings. Due to a very narrow and consistent residence time distribution, extrusion drying has the potential for pharmaceutical compound drying. In our study, we successfully accomplished drying of a crystalline product with very little agglomeration and/or attrition in some process settings, while preserving a crystal size similar to the raw material. The reduction of particle size occurred due to long residence times (low extruder screw speed) and a decrease in the residual moisture of the product. The aim of our work was to show the potential of extruder drying as a novel continuous manufacturing process for pharmaceuticals and to enable further process development.
November 2014
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19 Reads
In an effort to completely engage students during a semester-long course on “Heat and Mass Transfer”, multiple active learning and peer instruction pedagogical approaches were implemented. Examples of these approaches include: online textbook annotations, reflection activities, and student response systems. By minimizing lectures and encouraging learning through peer instruction, a quasi-flipped classroom environment was achieved. In this talk, I will outline how I transformed my classroom from a passive environment to one that actively engages students through peer-based instruction. Suggestions and recommendations will be provided to those instructors seeking to transform their classrooms into dynamic learning environments.
June 2013
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5 Reads
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1 Citation
February 2013
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75 Reads
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19 Citations
Journal of Nanoparticle Research
Mixing of nanopowders in an environmentally benign magnetically assisted fluidized bed (MAFB) system was studied. Examination of fluidization behavior of agglomerate particulate fluidization (APF; silica R974 or R972) and agglomerate bubbling fluidization (ABF; alumina or titania) nano-powders in un-assisted and MAFB systems confirmed previous results on decreased minimum fluidization velocity and increased bed expansion of APF and ABF powders due to magnetic assistance. APF and ABF powder mixtures behaved like APF powders with the bed expansions in between those of individual constituents. Unlike previous MAFB studies, fluidization as a function of time was studied to examine its influence on nano-mixing. With time, the bed expansion reduced, and reduction was faster as magnet-to-powder ratio increased from 0:1 to 5:1, although fluidization was sustained, confirmed via the pressure drop measurements. Reduction in bed expansion was attributed to change in the nature of nanoagglomerates, which showed increased density as a function of processing time, ruling out electrostatics or elutriation as major factors. Mixtures of silica (APF) and alumina (ABF), processed at various magnet-to-powder ratios, were characterized via statistical analysis from energy dispersive x-ray spectroscopy using field emission scanning electron microscope to compute homogeneity of mixing (HoM). Magnetic assistance improved the HoM as a function of time, and was strongly related to the product of number of magnets and time, similar to previous results in magnetically assisted impaction mixing (MAIM). The best achievable HoM was significantly better than unassisted fluidization and comparable to previous results for rapid expansion of high-pressure suspensions and MAIM.
June 2011
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8 Reads
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3 Citations
November 2010
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6 Reads
Although approximately 60-70% of all chemical engineering processes involve the solid phase in some step, whether as a raw material or a final product, many chemical engineering curriculums do not include a course on solids or particle technology. In this talk, the development of the Particle Technology course at The Cooper Union will be discussed. This course, which consisted of a mixture of undergraduates and graduate students, introduced students to the role of particulates in the petrochemical, pharmaceutical, and other chemical process industries. In doing so, students were able to link previous coursework (fluid mechanics, heat transfer, materials science, numerical methods, mechanics) to problems and situations involving particles, either in processing, or in situations such as handling and storage. In order to further develop this course, computer-based examples using COMSOL, MATLAB, and FLUENT were introduced to provide insight into complex systems involving multiphase flow and equipment. This talk will provide interested instructors with an introduction to the importance of a particle technology course in the chemical engineering curriculum.
August 2009
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188 Reads
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56 Citations
We show experimental results on a proposed technique to enhance the fluidization of nanoparticle beds. This technique consists of the application of an alternating electric field to the nanofluidized bed. Three different field configurations have been tested: co-flow field, cross-flow field, and variable field configurations. Nanoparticle agglomerates are naturally charged by contact and tribo charging mechanisms and therefore are agitated by the action of the externally applied field, which enhance fluidization. According to our observations, the best results are obtained for the variable field configuration. In this configuration, the electric field strength is higher at the bottom of the bed, whereas it is almost negligible at the free surface. Thus, the larger agglomerates, which tend to sink at the bottom of the bed due to stratification, and usually impede uniform fluidization, are strongly agitated. It is thought that the strong agitation of the bigger agglomerates that usually sink to the bottom of the bed contributes to further homogenize the distribution of the gas flow within the bed by destabilizing the development of gas channels close to the gas distributor. On the other hand, the smaller agglomerates at the vicinity of the free surface are just weakly excited. Consequently, fluidization is greatly enhanced, whereas at the same time excessive elutriation is avoided. It is demonstrated that this technique is even suitable to achieve highly expanded fluidization of unsieved nanopowder samples even though the fluidization state returns to be heterogeneous upon the electric field being turned off. © 2009 American Institute of Chemical Engineers AIChE J, 2010
November 2008
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34 Reads
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37 Citations
Chemical Engineering Science
In this paper we investigate the behavior of a fluidized bed of silica nanoparticles under the influence of externally applied vibrations and an electrostatic field. We have observed that the application of these fields separately has opposite effects on bed expansion. On one hand, vertical vibrations enhance bed expansion as the vibration intensity is increased up to a critical value. On the other hand, an electrostatic field applied in the horizontal direction, hinders bed expansion. In previous research papers, it has been suggested that the size of nanoparticle agglomerates could be affected either by vibration or by the action of the electric field. Using the modified Richardson–Zaki method to analyze our experimental data we find that vertical vibration tends to decrease the average agglomerate size in agreement with previous research. However, in this work we look further into the physical mechanisms which affect the response of the fluidized bed. Our results suggest that both vibration and the electric field produce a significant perturbation to the flow of agglomerates within the fluidized bed. Vibration transmits a vertical motion to the agglomerates that enhances bed expansion until the vibration velocity becomes of the order of the expected rising velocity of macroscopic bubbles. At this critical point, bubble growth is stimulated by vibration. A horizontal electrostatic field produces a drift of the charged agglomerates toward the walls that gives rise to fluidization heterogeneity and bed collapse. When both fields are simultaneous applied, these opposed effects can be practically compensated.
... While the ECX program was initiated out of an acute need to share ideas for effective online teaching practices in the midst of a pandemic, the CFD envisioned ECX to serve as a long term virtual program to connect the broad and geographically dispersed community of civil engineering educators and to facilitate discussions around important civil engineering education topics, such as those outlined in the ASCE Civil Engineering Education Summit report [12], well beyond online teaching. Like other learning communities and communities of practice [13,14], including those developed in response to the COVID-19 pandemic [15], ECX aims to engage and connect community members in discussions around shared interests; however, unlike traditional learning communities that require participation over extended periods of time, community members can select which ECX sessions to join based on topical interest and availability. Additionally, ECX could serve as a mechanism for ASCE to continue to engage the over one thousand ETW graduates worldwide and grow the community of people impacted by ExCEEd programs. ...
July 2021
... Using their mobile phone, participants earned points by completing challenges including taking selfies with attendees that met specified criteria, recording teaching tips, scanning QR codes at plenaries, taking short quizzes, and responding to reflection prompts. [1] Scavenger hunt apps help introduce participants to new scenarios and help build a sense of community and belonging. [2][3][4] They can be used to support classes and synergistic extracurricular activities. ...
June 2023
... In addition to the benefits presented above, by learning and practicing other modes of technical communication, engineering students develop a foundational skill that is key to their future success (Prausnitz and Bradley, 2000;Kmiec, 2004). Writing emails, preparing budgets and justifying them, and taking meeting minutes are examples of routine tasks for engineers (Tranquillo and Cavanagh, 2007;Lepek and Stock, 2011). Nonetheless, engineering curricula do not often specifically target these skills (Pinelli et al., 1996). ...
June 2011
... The authors demonstrated that it is feasible to combine API crystallization and drying (primary manufacturing) with wet granulation and drying (secondary manufacturing), performing several operation units in one step [13]. Kreimer et al. (2018) employed a twin-screw extruder to dry a crystallized product during primary manufacturing with a similar purpose because improper drying can lead to changes in particle size distribution and morphologic changes that can negatively impact further manufacturing of an API [17]. ...
June 2018
Organic Process Research & Development
... This results in uneven fluidization characterized by bubbles and channels in the fluidized bed. External forces exerted by mechanical stirrers, pulsed gas flow, admix of large magnetic particles, centrifugation, acoustic waves, microjets, impactor plates and vibration can be used to enhance the fluidization behavior of nanoparticles [6][7][8][9][10][11][12][13][14]. ...
February 2013
Journal of Nanoparticle Research
... [31,70,71] On the contrary, the ultrafine particles follow agglomerate particulate fluidization (APF). [31,72,73] During this process, the particle bed can attain remarkably high expansion and maintain stable fluidization without bubbles. [73] Moreover, the airflow velocity as a function of voidage around the fluidized agglomerates follows the Richardson-Zaki equation. ...
January 2008
... These methods very rarely exploit their potential for control. Most examples [36] (a) and vibration [49] (c); Acoustic fluidization of fine powders: limestone [43] (b); Magnetic stabilization [44] (d) and electro-fluidized beds [50] (e); Centrifugal fields: a vortex chamber [74] (f); Reproduced with permission from the given references. focus on simply enabling fluidization (e.g. ...
August 2009
... Studies have been conducted to characterize the improvement induced by vibration, and shown the impacts of effective disruption on agglomerates [16] as well as gas channels [7,17,18], leading to a more homogeneous flow, bed expansion [19], reduced bubble size [20], reduced minimum fluidization velocity [21], and mitigated powder stratification [22]. Similar impacts are also witnessed for the fluidization of ultra-fine cohesive powders [23,24]. With several successful attempts, vibration assistance has been piloted in industrially relevant applications, such as aeration drying and conveying of cohesive powders [25][26][27]. ...
November 2008
Chemical Engineering Science