17 results on '"Thakur, Amit K."'
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2. Slurry-phase ethylene polymerization processes: a review on multiscale modeling and simulations.
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Thakur, Amit K., Gupta, Santosh K., and Chaudhari, Pranava
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MASS transfer coefficients , *MULTISCALE modeling , *BUBBLE column reactors , *POLYMERIZATION , *POLYMERS , *CHROMIUM catalysts , *ETHYLENE , *MOLECULAR weights - Abstract
The exit age distribution, I E i ( I i ), for I N i ideal CSTRs in series using the TIS model is given by HT ht Graph (12) Here, I i is the dimensionless time, defined as HT ht , and I i is the mean residence time of the reactor. The internal age distribution, I I i ( I i ), for I N i - ideal CSTRs in series using the TIS model is given by HT
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- 2022
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3. Multi-objective optimization of an industrial slurry phase ethylene polymerization reactor.
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Thakur, Amit K., Gupta, Santosh K., Kumar, Rahul, Banerjee, Nilanjana, and Chaudhari, Pranava
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POLYMERIZATION reactors , *SLURRY , *ETHYLENE , *PARETO optimum , *OPERATING costs , *POLYMERIZATION - Abstract
Slurry polymerization processes using Zeigler–Natta catalysts are most widely used for the production of polyethylene due to their several advantages over other processes. Optimal operating conditions are required to obtain the maximum productivity of the polymer at minimal cost while ensuring operational safety in the slurry phase ethylene polymerization reactors. The main focus of this multi-objective optimization study is to obtain the optimal operating conditions corresponding to the maximization of productivity and yield at a minimal operating cost. The tuned reactor model has been optimized. The single objective optimization (SOO) and multi-objective optimization (MOO) problems are solved using non-dominating sorting genetic algorithm-II (NSGA-II). A complete range of Pareto optimal solutions are obtained to obtain the maximum productivity and polymer yield at different input costs. [ABSTRACT FROM AUTHOR]
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- 2022
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4. Preface: special issue dedicated to the "International Conference on Energy Sustainability and Advanced Materials – 2022 (ICESAM-2022)" part of the Energy Summit-2022 UPES, Dehradun, India.
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Thakur, Amit K., Gupta, Santosh K., and Ray, Ajay K.
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CONFERENCES & conventions , *CHEMICAL reactors , *CHEMICAL engineers , *CHEMICAL engineering , *ENERGY security - Abstract
This document is a preface to a special issue of the International Journal of Chemical Reactor Engineering (IJCRE) dedicated to the "International Conference on Energy Sustainability and Advanced Materials - 2022 (ICESAM-2022)" held at UPES, Dehradun, India. The conference brought together renowned academicians and industrialists from around the world to discuss topics related to energy security, sustainability, and advanced materials for energy applications. The special issue includes peer-reviewed manuscripts derived from oral presentations at the conference, covering a wide range of topics in energy and chemical engineering. The document expresses appreciation for the contributions of the speakers, reviewers, and authors, and looks forward to future collaborations with IJCRE. [Extracted from the article]
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- 2023
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5. Nanoparticle preparation of pharmaceutical compounds via wet milling: Current status and future prospects.
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Kumar, Rahul, Thakur, Amit K., Chaudhari, Pranava, Arya, Raj Kumar, Gupta, Kaushal Naresh, Thapliyal, Devyani, Bedar, Amita, Krishna, R. Shruti, and Pitchaiah, Kancharlapalli Chinaraga
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NANOPARTICLES , *SPRAY drying , *DRUGS , *DRUG delivery systems , *CRYOGENIC grinding - Abstract
This review discusses the preparation of nanoparticles/nanosuspensions using wet milling processes. It explores wet milling techniques, such as oscillatory bead milling, planetary bead milling, and cryogenic wet milling. The utilization of polymers and surfactants for the preparation of stable nanosuspensions is critically highlighted. One promising approach to enhance the stability of nanoparticle systems includes solidifying nanosuspensions. This review discusses two methods for producing dry nanoparticles: spray drying and spray freeze drying. The influence of these process parameters on particle size is emphasized in this work. Additionally, the review covers the utilization of nanoparticles generated through milling in the study of various drug delivery systems. There are still certain areas within this field that require further investigation of nanoparticle preparation and their application in particle engineering. These unexplored areas are discussed in this review, offering prospective researchers opportunities to gain deeper insights. [Display omitted] [ABSTRACT FROM AUTHOR]
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- 2024
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6. Investigation on crystallization phenomena with supercritical carbon dioxide (CO2) as the antisolvent.
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Kumar, Rahul, Thakur, Amit K., Banerjee, Nilanjana, and Chaudhari, Pranava
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SUPERCRITICAL carbon dioxide , *SUPERSATURATION , *CRYSTALLIZATION , *DISCONTINUOUS precipitation - Abstract
The supercritical antisolvent (SAS) recrystallization process is one of the most promising recrystallization techniques for the particle formation of pharmaceutical compounds. In this process, a solution of active pharmaceutical ingredient (API) is sprayed into the supercritical carbon dioxide (SC CO2) environment. The mass transport of both the solvent and the antisolvent results in supersaturation followed by the crystallization of the API. In this work, a model is developed to estimate the supersaturation profile of solute in a droplet falling in the SC CO2 environment. The droplet consists of paracetamol as a solute and ethanol as a solvent. It moves down in the antisolvent (supercritical CO2) environment. Interestingly, the present model predicts a rise in supersaturation followed by a fall for a while and then a sharp increase. The competing phenomena of nucleation and growth mechanisms are used to justify this variation in the supersaturation. [ABSTRACT FROM AUTHOR]
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- 2021
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7. On the extremum dissipation for steady state incompressible flow past a sphere at low Reynolds number.
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Arya, Raj Kumar, Thapliyal, Devyani, Thakur, Amit K., Kumar, Rahul, and Verros, George D.
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REYNOLDS number , *STOKES flow , *STEADY-state flow , *NONEQUILIBRIUM thermodynamics - Abstract
A methodology based on sound non-equilibrium thermodynamics principles is developed to estimate the extremum dissipation point for steady-state incompressible flow past a sphere at low Reynolds numbers. It is shown, that the extremum dissipation point appears at the point when both the shear stress and the pressure at the surface of the sphere are equal to zero. The Reynolds number and the position of the extremum dissipation flow past a sphere were further estimated with the aid of a mathematical model for pressure distribution on the sphere surface, accounting for both creeping and ideal flow. The parameters of the model were determined by comparison of the calculated pressure distribution at the surface with the available literature data. The conditions at which the separation angle and the extremum dissipation angle coincide were also investigated. It is believed that this work could be used to further elucidate the flow past a sphere. [ABSTRACT FROM AUTHOR]
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- 2023
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8. Oxyanion Removal from Impaired Water by Donnan Dialysis Plug Flow Contactors.
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Fox, Shalom, Stadnik, Kristina, Thakur, Amit K., Farkash, Lior, Ronen, Zeev, Oren, Yoram, and Gilron, Jack
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- 2023
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9. A critical review on thermodynamic and hydrodynamic modeling and simulation of liquid antisolvent crystallization of pharmaceutical compounds.
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Thakur, Amit K., Kumar, Rahul, Vipin Kumar, V.K., Kumar, Amit, Kumar Gaurav, Gajendra, and Naresh Gupta, Kaushal
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SALTING out (Chemistry) , *BINARY mixtures , *SUPERSATURATION , *MASS transfer kinetics , *CRYSTALLIZATION kinetics , *PARTICULATE matter , *DISCONTINUOUS precipitation - Abstract
[Display omitted] • System thermodynamics of the antisolvent crystallization is discussed. • Supersaturation, MSZW, induction time, crystallization kinetics are critically analysed. • Hydrodynamic modeling and CFD-based approach for LASC are critically reviewed. • A complete outlook of LASC is presented. • Modeling based LASC scale-up guidelines and challenges are discussed. Fine particles are in great demand in the pharmaceutical industry due to their versatile applications. Liquid antisolvent crystallization (LASC) is one of the promising approaches to prepare fine particles without requiring high energy. The interdependence of system thermodynamics, mass transfer kinetics, and the multi-phase hydrodynamics in the liquid antisolvent crystallization process is not well understood. In this review, the different modeling aspects of LASC are described from a fundamental perspective. The system thermodynamics of LASC is discussed and several models used in literature to predict the solubility in pure solvents and binary solvent mixtures are summarized. A detailed description of supersaturation, metastable zone width and induction time in antisolvent crystallization are presented and critically analyzed. The nucleation and growth kinetics are discussed and interpreted in terms of process variables. The hydrodynamic aspect of LASC which involves the mixing at different length scales is discussed and analyzed in detail. The CFD simulation-based approach to describe the interaction among different phenomena is critically reviewed. The crystallization scale-up, which is a major challenge in the LASC process, is discussed. A guideline for crystallization scale-up using the CFD-based modeling approach is presented which will be helpful to prospective researchers. [ABSTRACT FROM AUTHOR]
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- 2022
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10. Hydrodynamic modeling of liquid-solid flow in polyolefin slurry reactors using CFD techniques – A critical analysis.
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Thakur, Amit K., Kumar, Rahul, Banerjee, Nilanjana, Chaudhari, Pranava, and Gaurav, Gajendra Kumar
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SLURRY , *CRITICAL analysis , *FLUIDIZATION , *SENSITIVITY analysis , *HYDRODYNAMICS - Abstract
This first-of-its-kind review discusses the hydrodynamics for polyolefin productions in slurry reactors using CFD. Past reviews in this field are specifically focused on the CFD simulations of gas-phase reactors. This paper critically discusses the multi-scale behavior of liquid-solid hydrodynamics in polyolefin slurry reactors. The multifarious aspects of liquid-solid and solid-solid interactions and their impact on reactor performance are discussed. The review also discusses the possible methods to avoid the reactor operational difficulty due to various interactions such as slug formation, particle swelling, and aggregation. The in-depth analysis presented in this work can serve as a prerequisite for the design, scale-up, and optimization of any liquid-solid fluidization system. The CFD tools with their framework, simulation parameters, and the importance of parameter sensitivity analysis have been critically analysed. The article stems to provide a roadmap for future research work and proposes the challenges of future research that will help the prospective researchers. [Display omitted] • Hydrodynamic modeling approaches for the slurry polyolefin reactors are discussed. • The multifarious interactions and their impact on reactor performance are analyzed. • Particle swelling, agglomeration and slug formation impact reactor operation. • CFD framework and parameter sensitivity analysis are critically reviewed. • A roadmap for future research opportunities and challenges are discussed. [ABSTRACT FROM AUTHOR]
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- 2022
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11. A critical review on the particle generation and other applications of rapid expansion of supercritical solution.
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Kumar, Rahul, Thakur, Amit K., Banerjee, Nilanjana, and Chaudhari, Pranava
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SUPERCRITICAL carbon dioxide , *SUPERSATURATION , *NANOCARRIERS , *PARTICLE size distribution , *PARTICULATE matter , *CARBON dioxide , *SOLUBILITY , *SIZE reduction of materials - Abstract
[Display omitted] The novel particle generation processes of Active Pharmaceutical Ingredient (API)/drug have been extensively explored in recent decades due to their wide-range applications in the pharmaceutical industry. The Rapid Expansion of Supercritical Solutions (RESS) is one of the promising techniques to obtain the fine particles (micro to nano-size) of APIs with narrow particle size distribution (PSD). In RESS, supercritical carbon dioxide (SC CO 2) and API are used as solvent and solute respectively. In this literature survey, the application of RESS in the formation of fine particles is critically reviewed. Solubility of API in SC CO 2 and supersaturation are the key factors in tuning the particle size. The different approaches to model and predict the solubility of API in SC CO 2 are discussed. Then, the effect of process parameters on mean particle size and the particle size distribution are interpreted in the context of solubility and supersaturation. Furthermore, the less-explored applications of RESS in preparation of solid-lipid nanoparticles, liposome, polymorphic conversion, cocrystallization and inclusion complexation are compared with traditional processes. The solubility enhancement of API in SC CO 2 using co-solvent and its applications in particle generation are explored in published literature. The development and modifications in the conventional RESS process to overcome the limitations of RESS are presented. Finally, the perspective on RESS with special attention to its commercial operation is highlighted. [ABSTRACT FROM AUTHOR]
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- 2021
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12. Comparative analysis of various pretreatments to mitigate fouling and scaling in membrane distillation.
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Hsieh, I-Min, Thakur, Amit K., and Malmali, Mahdi
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MEMBRANE distillation , *FOULING , *OIL field brines , *SURFACE preparation , *FERRIC oxide , *ULTRAFILTRATION , *PERVAPORATION - Abstract
Membrane distillation (MD) has shown strong promise for treating hypersaline produced water (PW) streams. Scaling and fouling on the membrane surface, however, have been identified as major challenges for commercialization and widespread application. The focus of this study was to first identify the nature of foulants and scalants on the membrane surface and then investigate the pretreatment strategies that mitigate the extent of fouling and scaling on the membrane surface. Vacuum MD (VMD) was selected for this study because of its higher flux at more moderate feed temperatures that eventually leads better assessment of fouling and scaling on the membrane surface. VMD flux tests were carried out with three different real PW samples at total dissolved solids concentrations in the range of 120–160 g/L. It was found that an efficient pretreatment prior to MD is required to mitigate the fouling potential of the organic matter, mostly suspended constituents, in PW samples. Suspended organics fouled and quickly wetted the MD membrane. Major conventional treatments, including filtration, oxidation, coagulation, air floatation, and aeration were investigated to pretreat the PW before VMD tests. A comprehensive comparative analysis is presented showing that the ultrafiltration and coagulation pretreatments displayed the best performance in mitigating the fouling and scaling, while oxidative pretreatment was found to be effective in reducing the iron concentration to less than 5 ppm. The surface of scaled membranes was carefully characterized to further evaluate the performance of each pretreatment. The components that had the highest tendency to precipitate on the membrane surface were identified as strontium sulfate, calcium carbonate, sodium chloride, iron oxide, and silica. These findings are supported by thermodynamic estimation of the saturation index. • Membrane distillation proposed for desalinating hypersaline produced water • Suspended organic matter fouls the membrane, leading to immediate membrane wetting. • Pretreatment of produced water required for long-term performance • Fouling and scaling characterized; sulfate and carbonates found as major scalants • Produced water concentrated to 290 g/L and +50% water recovery achieved [ABSTRACT FROM AUTHOR]
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- 2021
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13. Solar assisted CaCl2 desiccant wheel rotor system for simultaneous cooling and dehumidification operation: experimental and modelling approach.
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Prasad, Amarjeet Kumar, Singh, Dhirendra Kumar, Shankar, Ravi, Thakur, Amit K., and Singh, Dheerandra
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DRYING agents , *HUMIDITY control , *COOLING systems , *COOLING , *AIR flow , *CALCIUM chloride , *HUMIDITY - Abstract
High temperature and humidity of many reason of India in the summer season is the major challenge for human comfort also in the drying. In the present work, experiments have been performed to examine the cooling and dehumidification process in the summer season for human comfort and industrial application with the help of calcium chloride (CaCl2) based desiccant material solid desiccant wheel integrated with solar heating arrangements. In this study experimental findings are also evaluated by the mathematical model. During the dehumidification of air in the process unit humidity changes from 17.75 to 29.03 g H2O/kg dry air to 2.8–3.9, 6.8–8.15, 8.92–10.9 & 9.79–11.87 g H2O/kg dry air for flow rate at 1, 2, 3 & 4 m/s, respectively. The process air outlet temperature is increased in the range of 2.58–3.53 K for all air flow rates. After humidification of process outlet air, human comfort condition (HCC) is produced with temperature and humidity in the range of 30–33 °C and 7.77–12.47 g H2O/kg dry air for different air flow rates. Overall airflow for velocity 2–4 m/s can be recommended for the HCC condition. The proposed modelled expression indicates less than 10 % error between the actual and modelled value for different sections. [ABSTRACT FROM AUTHOR]
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- 2024
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14. Numerical simulation of fluid flow in microchannels with induced irregularities.
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Chaudhari, Pranava, Kapoor, Ashish, Awasthi, Yashraj, Thakur, Amit K., and Kumar, Rahul
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FLUID flow , *FLOW simulations , *COMPUTATIONAL fluid dynamics , *PRESSURE drop (Fluid dynamics) , *REYNOLDS number , *MICROCHANNEL flow - Abstract
Microchannels are small-scale channels with unique properties that make them useful in various fields, such as electronics, biomedical engineering, and chemical engineering. This research paper investigates the effect of microchannel geometry on fluid flow behavior at different values of the Reynolds number. A rectangular microchannel with a pattern of obstructions and water as the working fluid was used in this study. Computational fluid dynamics (CFD) simulations were used to investigate the impact of different channel geometrical configurations and different values of the Reynolds number on fluid flow behavior. The results showed that the channel geometrical configuration and the Reynolds number significantly affect fluid flow behavior. A geometry with increasing obstruction heights led to higher values of pressure drop than the geometry with decreasing obstruction heights. This study provides valuable insights into microchannel flow behavior and can be used for the development of optimized microchannel designs for diverse applications. [ABSTRACT FROM AUTHOR]
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- 2023
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15. Gas-liquid downward flow through narrow vertical conduits: effect of angle of entry and tube-diameter on flow patterns.
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Kumar, Amit, Das, Gargi, Ray, Subhabrata, Jha, Jay Mant, Thakur, Amit K., and Panda, Swapna Rekha
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STRATIFIED flow , *TRANSITION flow , *TWO-phase flow , *GLASS tubes - Abstract
The present study investigates the flow pattern characteristics of air-water co-current down-flow in millichannels. The experiments have been performed in glass tube of diameter 0.0042 and 0.008 m. The fluids are injected through Y entry the included angle between the Y arms being 45°, 90°, 135°, and 180° (T Entry). The investigation reveals that the flow patterns are function of tube-diameter, and angle of fluid entry. Interestingly, stratified flow has been observed for steeper Y entry section at low liquid flow rates. [ABSTRACT FROM AUTHOR]
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- 2021
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16. Liquid antisolvent recrystallization and solid dispersion of flufenamic acid with polyvinylpyrrolidone K-30.
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Kumar, Rahul, Kumar, Sanjay, Chaudhari, Pranava, and Thakur, Amit K.
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SIZE reduction of materials , *POVIDONE , *DISPERSION (Chemistry) , *DRUG bioavailability , *PARTICULATE matter , *RECRYSTALLIZATION (Chemistry) - Abstract
Flufenamic acid (FFA) is a Biopharmaceutical Classification System- II (BCS-II) class drug with poor bioavailability and a lower dissolution rate. Particle size reduction is one of the conventional approaches to increase the dissolution rate and subsequently the bioavailability. The use of the liquid antisolvent method for particle size reduction of FFA was studied in this work. Ethanol and water were used as solvent and antisolvent, respectively. Experimental parameters such as solution concentration (10–40 mg/ml), flow rate (120–480 ml/h), temperature (298–328 K) and stirring speed (200–800 rpm) were investigated. Furthermore, the solid dispersion of FFA was prepared with polyvinylpyrrolidone K-30 (PVP K-30) with different weight ratios (1:1, 1:2, 1:3 and 1:4) and samples were characterized using SEM, FTIR and XRD techniques. The experimental investigation revealed that higher values of concentration, injection rate, stirring speed, along with lower temperature favored the formation of fine particles. SEM analysis revealed that the morphology of raw FFA changed from rock-like to rectangular-like after liquid antisolvent recrystallization. FTIR analysis validated the presence of hydrogen bonding between FFA and PVP in solid dispersion. XRD analysis showed no significant change in the crystallinity of the processed FFA. [ABSTRACT FROM AUTHOR]
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- 2021
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17. Molecular thermodynamics for scaling prediction: Case of membrane distillation.
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Islam, Md Rashedul, Hsieh, I-Min, Lin, Bosong, Thakur, Amit K., Chen, Chau-Chyun, and Malmali, Mahdi
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MEMBRANE distillation , *THERMODYNAMICS , *PHASE equilibrium , *SOLUTION (Chemistry) , *PRECIPITATION forecasting - Abstract
[Display omitted] • A parametrized thermodynamic model proposed to predict phase equilibria. • Performance of the MD simulated in a subroutine custom model. • Scaling of salts are predicted during MD operation. • Scaling prediction is validated via experimental results. • Complex interaction among molecular and ionic species are highlighted. Membrane distillation (MD) for water treatment is significantly impaired by the scaling of dissolved minerals. The type and content of minerals generally measured as total dissolved solids (TDS) in hypersaline brines not only reduce the MD flux but also control the scaling behavior on the membrane surface. The scaling-induced pore blockage further reduces water flux and eventually leads to membrane wetting. The scaling problem is even more pronounced in the treatment of produced water (PW) as it contains 3–7 times higher TDS concentrations, compared to seawater. Theoretically, the necessary conditions for a salt to precipitate can be traced from its solubility product constant and activity of the constituents within the solution. Therefore, a comprehensive thermodynamic model is necessary to represent the electrolyte behavior and to predict the precipitation of different salts in a complex solution like PW. We pursued electrolyte Nonrandom Two Liquid Theory (eNRTL), a state-of-the-art electrolyte model, to address the PW fluid phase equilibria. With a fully parameterized eNRTL model, we predicted salt precipitations in two different PW samples and compared the results against the experimental findings. Furthermore, we forecast the precipitation of salts in response to the change in PW concentration and temperature in the MD operation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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