02292nas a2200253 4500008004100000022001400041245009200055210006900147260010600216300001400322490000700336520136000343653001901703653000801722653001301730653002601743653002501769100002401794700002301818700002201841700002701863700002901890856011901919 2007 eng d a0009-250900aModeling of bubble column slurry reactor for reductive alkylation of p-phenylenediamine0 aModeling of bubble column slurry reactor for reductive alkylatio aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcDEC a7290-73040 v623 a

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'-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 `mixing cell approach'. 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.

10abubble columns10aCFD10akinetics10aMathematical modeling10aReductive alkylation1 aChaudhari, Amit, S.1 aRampure, Mohan, R.1 aRanade, Vivek, V.1 aJaganathan, Rengaswamy1 aChaudhari, Raghunath, V. uhttps://library.ncl.res.in/content/modeling-bubble-column-slurry-reactor-reductive-alkylation-p-phenylenediamine-002019nas a2200217 4500008004100000022001400041245009200055210006900147260006800216300001400284490000800298520122500306653001301531653001601544653003301560100002401593700002301617700001801640700002201658856012101680 2008 eng d a0021-899500aModeling of a fluidized bed propylene polymerization reactor operated in condensed mode0 aModeling of a fluidized bed propylene polymerization reactor ope a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY a2067-20760 v1083 a

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.

10aModeling10aPolyolefins10aZiegler-Natta polymerization1 aUtikar, Ranjeet, P.1 aHarshe, Yogesh, M.1 aMehra, Anurag1 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/modeling-fluidized-bed-propylene-polymerization-reactor-operated-condensed-mode-002255nas a2200241 4500008004100000022001400041245005300055210005300108260006900161300001200230490000800242520148400250653002201734653003301756653002101789100002401810700001701834700001901851700001801870700001601888700002201904856008701926 2012 eng d a1385-894700aModeling of liquid propellant combustion chamber0 aModeling of liquid propellant combustion chamber aPO BOX 564, 1001 LAUSANNE, SWITZERLANDbELSEVIER SCIENCE SAcOCT a151-1660 v2073 a

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 `well-mixed reactor'. 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.

10aLiquid propellant10aSingle droplet decomposition10aSpray combustion1 aPandit, Ajinkya, V.1 aKumar, Ashok1 aRao, Srinivasa1 aKedarnath, C.1 aSrihari, R.1 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/modeling-liquid-propellant-combustion-chamber-000510nas a2200133 4500008004100000022001400041245004800055210004800103260010200151300001400253490000700267100002200274856008000296 2013 eng d a0256-249900aMultiphase flows with phase change foreword0 aMultiphase flows with phase change foreword aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScDEC a1065-10660 v381 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/multiphase-flows-phase-change-foreword-002910nas a2200157 4500008004100000022001400041245010800055210006900163260007100232300001600303490000700319520224800326100002402574700002202598856013202620 2015 eng d a0888-588500aModeling hysteresis during crystallization and dissolution: application to a paracetamol-ethanol system0 aModeling hysteresis during crystallization and dissolution appli a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT a10364-103820 v543 a

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.

1 aPandit, Ajinkya, V.1 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/modeling-hysteresis-during-crystallization-and-dissolution-application-paracetamol-ethanol-002178nas a2200229 4500008004100000022001400041245009200055210006900147260009900216300001200315490000700327520132100334653000801655653001601663653003101679653002701710100003001737700001801767700001501785700002201800856012601822 2016 eng d a0955-598600aMixing studies in unbaffled stirred tank reactor using electrical resistance tomography0 aMixing studies in unbaffled stirred tank reactor using electrica aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcMAR a110-1210 v473 a

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.

10aERT10aMixing time10aRadial solid concentration10aUnbaffled stirred tank1 aSardeshpande, Madhavi, V.1 aKumar, Gaurav1 aAditya, T.1 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/mixing-studies-unbaffled-stirred-tank-reactor-using-electrical-resistance-tomography-002308nas a2200157 4500008004100000245007000041210006600111260000800177300001400185490000700199520177300206100002601979700002702005700002202032856009602054 2017 eng d00aModeling G-L-L-S reactor: a case of hydrogenation of nitrobenzene0 aModeling GLLS reactor a case of hydrogenation of nitrobenzene cFEB a1404-14150 v563 aGas-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.1 aSharma, Deepankar, V.1 aPatwardhan, Ashwin, W.1 aRanade, Vivek, V. uhttps://library.ncl.res.in/content/modeling-g-l-l-s-reactor-case-hydrogenation-nitrobenzene