@article { ISI:000251763600036, title = {Modeling of bubble column slurry reactor for reductive alkylation of p-phenylenediamine}, journal = {Chemical Engineering Science}, volume = {62}, number = {24, SI}, year = {2007}, note = {8th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, Indian Inst Technol Delhi, New Delhi, INDIA, DEC 16-19, 2007}, month = {DEC}, pages = {7290-7304}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

A bubble column slurry reactor (BCSR) model has been developed for the reductive alkylation of p-phenylenediamine (PPDA) with methyl ethyl ketone (MEK) to N, N{\textquoteright}-di-secondary-alkyl-p-phenylenediamine (Di-amine). This particular reaction system is commercially relevant and involves a combination of parallel and consecutive reactions comprising equilibrium non-catalytic (homogeneous) and catalytic (heterogeneous) steps. The proposed model is based on the {\textquoteleft}mixing cell approach{\textquoteright}. In this work the mixing cell approach has been extended by including a liquid backflow stream from all but the bottommost mixing cell. The model incorporates the contributions of gas-liquid and liquid-solid mass transfer, heat effects, and complex multistep reaction kinetics. CFD model is used to estimate the extent of backflow among mixing cells and its dependence on operating parameters. The effect of gas and liquid velocities, catalyst loading, inlet PPDA concentration, and temperature on the conversion, selectivity, global rate of hydrogenation, and temperature rise is discussed. The comparison of the current approach with the traditional mixing cell model is discussed. The BCSR model presented here will be useful to provide guidelines for designing and improving overall performance of bubble column reactors. (C) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {bubble columns, CFD, kinetics, Mathematical modeling, Reductive alkylation}, issn = {0009-2509}, doi = {10.1016/j.ces.2007.08.065}, author = {Chaudhari, Amit S. and Rampure, Mohan R. and Ranade, Vivek V. and Jaganathan, Rengaswamy and Chaudhari, Raghunath V.} } @article { ISI:000254672800002, title = {Modeling of a fluidized bed propylene polymerization reactor operated in condensed mode}, journal = {Journal of Applied Polymer Science}, volume = {108}, number = {4}, year = {2008}, month = {MAY}, pages = {2067-2076}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

The gas-phase polymerization of propylene is one of the most widely accepted and commercially used processes for the manufacture of polypropylene (PP). Because of the highly exothermic nature of polymerization reactions, temperature runaway and subsequent polymer melting and agglomeration may occur, and the reactor has to be operated in a small operating window for safety. The addition of liquid monomer for heat removal (condensed mode) broadens the operating window and can substantially increase (by 50-100\%) the capacity of given reactor hardware. This article describes the extension of a comprehensive mathematical model for the simulation of fluidized bed PP reactors to include the condensed mode of operations. The model is used to determine the influence of the operating parameters on the polymer properties and particle size distribution. The model is also used to determine the effects of two active sites and the reaction kinetics on macroscopic variables. The developed framework is useful for simulating multimonomer, multisite Ziegler-Natta-type olefin fluidized bed polymerization reactors operated under condensed mode. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108: 2067-2076, 2008.

}, keywords = {Modeling, Polyolefins, Ziegler-Natta polymerization}, issn = {0021-8995}, doi = {10.1002/app.27748}, author = {Utikar, Ranjeet P. and Harshe, Yogesh M. and Mehra, Anurag and Ranade, Vivek V.} } @article { ISI:000311184500020, title = {Modeling of liquid propellant combustion chamber}, journal = {Chemical Engineering Journal}, volume = {207}, number = {SI}, year = {2012}, note = {22nd International Symposium on Chemical Reaction Engineering (ISCRE), Maastricht, NETHERLANDS, SEP 02-05, 2012}, month = {OCT}, pages = {151-166}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Liquid propellants are fuels which do not require external supply of oxygen for combustion. These fuels are widely used for propulsion applications in oxygen rare environments (underwater, space). We had previously presented a model for solid propellant decomposition in a combustion chamber. In this study we extend the model for the case of combined solid and liquid propellant combustion. Sub-models relating to solid propellant combustion and outlet flow-rate in the present study are borrowed from the previous study. The combustion chamber is assumed to be a {\textquoteleft}well-mixed reactor{\textquoteright}. A model is developed to characterize the liquid propellant spray assuming the spray is a collection of individually burning droplets. A single droplet decomposition model was developed and used along-with the spray model to solve for the liquid propellant burning rate. Appropriate numerical methods and computer programs were developed to solve the model equations. The model predictions were compared with the experimental data obtained in earlier studies. Appropriate methodology for calibrating the model parameters was developed and its usefulness was demonstrated by comparing the simulated pressure profiles with the experimental pressure profiles. The presented model and results will be useful for selecting appropriate liquid propellants for propulsion systems and for the development of a system level model of propulsion systems. (C) 2012 Elsevier B.V. All rights reserved.

}, keywords = {Liquid propellant, Single droplet decomposition, Spray combustion}, issn = {1385-8947}, doi = {10.1016/j.cej.2012.06.033}, author = {Pandit, Ajinkya V. and Kumar, Ashok and Rao, G. Srinivasa and Kedarnath, C. and Srihari, R. and Ranade, Vivek V.} } @article { ISI:000330613400001, title = {Multiphase flows with phase change foreword}, journal = {Sadhana-Academy Proceedings in Engineering Sciences}, volume = {38}, number = {6}, year = {2013}, month = {DEC}, pages = {1065-1066}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, issn = {0256-2499}, author = {Ranade, Vivek V.} } @article { ISI:000363917000023, title = {Modeling hysteresis during crystallization and dissolution: application to a paracetamol-ethanol system}, journal = {Industrial \& Engineering Chemistry Research}, volume = {54}, number = {42}, year = {2015}, month = {OCT}, pages = {10364-10382}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Crystallization and dissolution processes are of great scientific and commercial interest. Significant efforts have been made in the past to develop mathematical models to describe these processes. In this work, observed hysteresis in particle counts during the crystallization and dissolution processes was used to develop and to test the mathematical models of crystallization and dissolution. Crystallization and dissolution experiments were performed with a system of paracetamol and ethanol. An undersaturated solution was first cooled at a particular rate causing crystallization and crystal growth. The solution was then reheated at the same rate to completely dissolve the generated particles. The particle counts and particle size distribution were measured online using a focus beam reflectance measurement (FBRM) probe. A hysteresis was observed in particle counts with respect to the solution temperature. It was also observed that this hysteresis was affected by the applied heating/cooling rates (0.3, 0.5, and 0.7 K/min) for of the solution. A systematic modeling framework based on the population balance equation (PBE) is developed for quantitatively capturing this hysteresis and the influence of cooling/heating rate on the hysteresis curve. A two-level approach was developed to simulate hysteresis: (a) PBE was solved using computationally efficient method of moments for the crystallization stage. This step was used to efficiently estimate values of parameters appearing in the model equations. (b) PBEs describing crystallization and dissolution were then solved using high resolution finite volume (HRFV) scheme coupled with the moving pivot method. The simulated hysteresis curve showed good agreement with the experimental data. Though simulated results over predicted the average particle (by,similar to 131\%), the models were successful in qualitatively explaining the counterintuitive trends observed as the average particle size was tracked with time. The framework was thus shown to be a reliable and robust framework to model crystallization and dissolution processes. The developed approach, models, and results will be useful for simulating industrially relevant crystallization dissolution processes.

}, issn = {0888-5885}, doi = {10.1021/acs.iecr.5b01088}, author = {Pandit, Ajinkya V. and Ranade, Vivek V.} } @article { ISI:000370101800013, title = {Mixing studies in unbaffled stirred tank reactor using electrical resistance tomography}, journal = {Flow Measurement and Instrumentation}, volume = {47}, year = {2016}, month = {MAR}, pages = {110-121}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Unbaffled stirred tanks are extensively used in chemical process industries for variety of applications including semi-batch reactions. In un-baffled stirred tanks, impeller rotation generates a vortex and reactants are added into this vortex. There is a growing interest towards understanding the mixing performance of such unbaffled stirred vessels. The present work is aimed at providing experimental results on mixing time and solid particle distribution inside an unbaffled vessel using electrical resistance tomography (ERT). A methodology for using ERT for characterizing vortex and mixing in unbaffled stirred vessel was established. The ERT was used to measure the mixing time with and without solid particles (glass beads, 250 mu m) in a stirred reactor. In this study, ERT technique was effectively applied for imaging solid-liquid flow and developed suitable data processing methodologies. It observed that estimated liquid phase mixing time for Un-baffled vessel was more as compared to baffled vessel. Radial solid concentration profiles showed Gaussian distribution inside the vessel. The presented methodology of using ERT and experimental results will be useful for designing and estimating mixing and solid distribution in unbaffled stirred tanks. (C) 2016 Elsevier Ltd. All rights reserved.

}, keywords = {ERT, Mixing time, Radial solid concentration, Unbaffled stirred tank}, issn = {0955-5986}, doi = {10.1016/j.flowmeasinst.2016.01.003}, author = {Sardeshpande, Madhavi V. and Kumar, Gaurav and Aditya, T. and Ranade, Vivek V.} } @article {43468, title = {Modeling G-L-L-S reactor: a case of hydrogenation of nitrobenzene}, journal = {Industrial \& Engineering Chemistry Research}, volume = {56}, year = {2017}, month = {FEB}, pages = {1404-1415}, abstract = {Gas-liquid liquid solid (GLLS) reaction systems are often encountered in manufacturing of fine and specialty chemicals. More often than not, such reaction systems involve multiple reactions, and selectivity toward the desired component always poses challenges. An adequate understanding of various parameters affecting GLLS reactor performance is essential to develop strategies for realizing desired selectivity. In this work, a comprehensive reaction engineering model for simulating four phase hydrogenation reactions has been developed. A generalized mixing cell based framework for a reaction system with four interacting phases (gas [G], aqueous [L], organic [L], and solid catalyst [S]) was developed. The model is written in a general way so as to specify one of the liquid phases as a continuous phase, and the other three phases are dispersed into it. In each cell, vapor space is included. The model includes the possibility of evaporation of solvent and internal condensation (in vapor space). The model can also be applied for a dead end (from a perspective of reacting gas) reactor. Model equations were solved using MATLAB. The equations and solution methodology were verified by comparing numerical solutions with available solutions of various limiting cases. A case of four phase hydrogenation of nitrobenzene to para amino phenol and aniline was considered to illustrate the application of the developed model. Key findings from the model were validated by comparing with laboratory scale experimental data. The model was then used to develop insights and guidelines for enhancing selectivity toward desired product. The developed model and presented results will be useful to develop general guidelines for design and optimization of GLLS reactors.}, doi = {10.1021/acs.iecr.6b03744}, author = {Sharma, Deepankar V. and Patwardhan, Ashwin W. and Ranade, Vivek V.} }