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Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle Size Reduction in Pharmaceutical Ma University of Connecticut OpenCommons@UConn Doctoral Dissertations University of Connecticut Graduate School 11-18-2014 Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle Size Reduction in Pharmaceutical Manufacturing Shivangi Naik University of Connecticut - Storrs, [email protected] Follow this and additional works at: https://opencommons.uconn.edu/dissertations Recommended Citation Naik, Shivangi, "Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle Size Reduction in Pharmaceutical Manufacturing" (2014). Doctoral Dissertations. 640. https://opencommons.uconn.edu/dissertations/640 Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle Size Reduction in Pharmaceutical Manufacturing Shivangi Naik, Ph.D. University of Connecticut, 2014 Abstract In the pharmaceutical industry, over 75 percent of all products are in the solid dosage form. Considering their prevalence, the aim of this study was to employ experimental methods and process modeling tools viz. Discrete Element Method (DEM) to ascertain the effect of powder flow and material properties during triboelectrification and particle size reduction. Considering electron exchange to be the dominant mechanism for charge transfer, work function all powders viz. Ibuprofen, theophylline, microcrystalline cellulose and lactose monohydrate was estimated from quantum chemical calculations. Tribocharging of individual powders in a V-blender revealed a higher specific charge for Ibuprofen against all surfaces. Moreover, for mixtures, charge mitigation was observed. To facilitate model development, a hopper-chute assembly was employed to investigate the effect of coefficient of friction (COF) and coefficient of restitution (COR). The specific charge increased with COF due to longer contact time and greater particle- wall collisions. Secondly, the specific charge increased as COR was decreased, suggesting that continuous contacts transfer more charge than bouncing contacts. The model was able to capture the collisional nature of tribocharging although discrepancies were observed between numerical results and experimental observations. Thus, a collective experimental and simulation approach was found to be beneficial in identifying gaps and enabling a comprehensive interpretation of an intricate process. To study the effect of process parameters on milling, dynamic mechanical analyzer was employed to investigate the effect of damage accumulation during breakage. Damage accumulation was found to be low since the change in breakage force upon repeated impacts was insignificant. High feed rates at lower speeds resulted in flood feed conditions, which changed i the mode of breakage from fragmentation to attrition. Additionally, this effect was verified from the velocity profiles obtained from simulations that revealed stagnation of the powder bed, which consequently reduced the breakage rate. Although, the DEM model does not account for any attrition, simulations could qualitatively capture the effect of impeller speed and feed rate on the average particle size. Consequently, a combined experimental and simulations approach can be employed to direct experiment and equipment design thereby providing a better understanding of a process. ii Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle size reduction in Pharmaceutical Manufacturing Shivangi Santosh Naik B. Pharm, University of Mumbai, India, 2007 M. Pharm, University of Mumbai, India, 2009 A Dissertation Submitted in Partial Fulfillment of the Requirements of the Degree of Doctor of Philosophy At the University of Connecticut 2014 iii APPROVAL PAGE Doctor of Philosophy Dissertation Experiment and Discrete Element Based Modeling of Granular Flow: Tribocharging and Particle size reduction in Pharmaceutical Manufacturing Presented by Shivangi Santosh Naik B. Pharm, University of Mumbai, India, 2007 M. Pharm, University of Mumbai, India, 2009 Major Advisor ________________________________________ Bodhisattwa Chaudhuri Associate Advisor _______________________________________ Montgomery Shaw Associate Advisor________________________________________ Ramesh Malla Associate Advisor ________________________________________ Robin Bogner University of Connecticut 2014 iv Dedication To all my grandparents, for their affection and support v Acknowledgements The writing of this dissertation has been one of the most significant academic accomplishments in my life which could not have been achieved by the help and support of family, friends and Almighty. I am deeply indebted to my adviser Dr. Bodhisattwa Chaudhuri for his fundamental role in my doctoral work. Quite simply, his input has been immeasurable. Along with his help in DEM coding, he has kept me focused on the task at hand and provided advice and guidance at all hours. He gave me the freedom for research and at the same time continued to provide valuable feedback, and encouragement. In addition to our academic collaboration, I greatly value the close personal rapport that Dr. Chaudhuri and I have forged over the years. I am also grateful to my associate advisors, Dr. Montgomery Shaw, Dr. Ramesh Malla and Dr. Robin Bogner for their careful appraisal and direction throughout the project. The good advice, support and friendship of my committee members have been invaluable on both an academic and a personal level, for which I am extremely grateful. I sincerely appreciate their constant motivation and thank them for their belief in me as student. They always encouraged me to “Stay Hungry and Stay Foolish”. I would also like to thank Dr. Bruno Hancock, Dr. Yu Weili and Dr. Yuri Abramov for their critical comments and valuable inputs during my research. Their constant involvement has helped me to gain a better understanding of this subject. A sincere thanks to Dr. Martin Rowland for his suggestions and practical remarks during my research. I am extremely thankful to the Pharmaceutics faculty for providing a comprehensive graduate curriculum. The graduate seminars, courses and symposiums provided ample training and experience to grow as scientist. I would also like to thank Dr. Burgess, Dr. Xiuling, Dr. Kalonia and Dr. Pikal for useful comments and suggestions throughout my graduate study. vi I personally thank Leslie Lebel and Mark Armati for their prompt assistance and special care for international students. I am indebted to my friends including Shweta, Bindu, Raj, Saurabh, Japneet, Masha, Liz, Bruna, Ekneet, Xiaoming, Chaitra, Deepthi, Meera, Sangeetha, Sandhya, Rima, Kinjal, Ruchita, Eric, Dave, Joe, Johanna, Janet and Yan for their support. I would also like to thank Mark Drobney from Depot Campus. Mark has been a great friend who is always ready to help. I have never heard Mark say the word “Impossible”. In fact, his dedication and enthusiasm for his work has been a great inspiration. I am deeply thankful to my family for their love, support, and sacrifices. Without them, this thesis would never have been written. No measure of gratitude is sufficient for their patience, love and understanding. vii Table of contents Approval Page iv Dedication v Acknowledgements vi Table of Contents viii Chapter 1 1-7 Introduction and Organization of this thesis Chapter 2 8-42 Triboelectrification: A review of experimental and mechanistic modelling approaches with a special focus on pharmaceutical powder Chapter 3 43-80 An experimental and numerical based study of tribocharging during granular flow Chapter 4 81-123 Triboelectrification of pharmaceutical blenders in a V-blender: An experimental and model based study Chapter 5 124-151 An experimental and numerical based study of tribocharging of pharmaceutical mixtures Chapter 6 152-188 Quantifying dry milling in pharmaceutical processing: A review on experimental and modeling approaches Chapter 7 Chapter 7 189-226 Investigation of Comminution in a Wiley Mill: Experiments and DEM Simulations viii Chapter 8 227 - 230 Summary and Future studies ix Chapter 1 Introduction and Organization of Thesis Processes involving particulate matter are prevalent throughout the pharmaceutical industry where close to 75 percent of pharmaceutical products are formulated as tablets and capsules. These processes often consist of series of unit operations, each intended to alter the properties of material to facilitate processing and imparting desired attributes to the final product. Hence, the need for understanding the behavior of such complex particulate systems is of critical importance. To allow acceptable variations, the importance of mechanistic and parametric factors of the processes should be studied. These aspects of different unit operations pose a challenge owing to the complexities of the process involved [1-4]. For instance, electrostatic charges are known to develop upon interaction between dissimilar surfaces depend. The process of tribocharging is complex and is dependent on many factors such as shape, humidity, contact surface and mechanical factors. It is reported that flow of granular material in a typical unit operation like pneumatic conveying, fluidization, spray deposition, blending can generate 10−7 – 10−4 C/kg of static charges. Discharge of these charges in the presence of volatile liquid can also lead to explosion hazard [5-6]. Hence, myriads of industries including pharmaceutical expend significantly on safety measures and hazard detection techniques in their processing facilities. Other processes
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