01678nas a2200181 4500008004100000022001400041245009900055210006900154260007100223300001400294490000700308520097200315100002001287700002101307700001901328700001901347856013001366 2005 eng d a0888-588500aCharacterization of gas-liquid flows in stirred vessels using pressure and torque fluctuations0 aCharacterization of gasliquid flows in stirred vessels using pre a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR a3298-33110 v443 a

Gas-liquid flows in a stirred vessel exhibit different flow regimes and demonstrate complex interaction of transport processes with varying spatio-temporal scales. The knowledge of key space and time scales of fluid dynamics is important for designing and enhancing the performance of gas-liquid stirred reactor. The present study uses simple, robust, and nonintrusive experimental techniques (torque and pressure sensors) to characterize the fluid dynamics in a gas-liquid stirred vessel. Time series obtained from the pressure and torque sensors were analyzed to develop criteria for flow regime identification. Further analyses of torque and pressure time series were done to extract valuable information of different time scales of fluid dynamics. The detailed analysis of torque and wall pressure fluctuations provided not only an insight into the fluid dynamics but also a possible opportunity to on-line monitoring of gas-liquid flows in stirred vessel.

1 aKhopkar, A., R.1 aPanaskar, S., S.1 aPandit, A., B.1 aRanade, V., V. uhttps://library.ncl.res.in/content/characterization-gas-liquid-flows-stirred-vessels-using-pressure-and-torque-fluctuations-002093nas a2200229 4500008004100000022001400041245007300055210006900128260006800197300001200265490000700277520133900284653000801623653000901631653001801640653001501658653002401673100001901697700001901716700002901735856009901764 2005 eng d a0001-154100aComputational study of a single-phase flow in packed beds of spheres0 aComputational study of a singlephase flow in packed beds of sphe a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcFEB a365-3780 v513 a

Packed-bed reactors are widely used in petrochemical, fine chemical, and pharmaceutical industries. Detailed knowledge of interstitial flow in the void space of such packed-bed reactors is essential for understanding the heat and mass transfer characteristics. In this paper, fluid flow through the array of spheres was studied using the unit-cell approach, in which different periodically repeating arrangements of particles such as simple cubical, 1-D rhombohedral, 3-D rhombohedral, and face-centered cubical geometries were considered. Single-phase flow through these geometries was simulated using computational fluid dynamics (CFD). The model was first validated by comparing predicted results with published experimental and computational results. The validated model was further used to study the effect of particle arrangement/orientation on velocity distribution and heat transfer characteristics. The simulated results were also used to understand and to quantify, relative contributions of surface drag and form drag in overall resistance to the flow through packed-bed reactors. The model and the results presented here would be useful in elucidating the role of microscopic flow structure on mixing and other transport processes occurring in packed-bed reactors. (C) 2005 American Institute of Chemical Engineers.

10aCFD10adrag10aheat transfer10apacked bed10apacking arrangement1 aGunjal, P., R.1 aRanade, V., V.1 aChaudhari, Raghunath, V. uhttps://library.ncl.res.in/content/computational-study-single-phase-flow-packed-beds-spheres-002114nas a2200217 4500008004100000022001400041245007900055210006900134260006800203300001400271490000700285520133200292653003901624653001701663653002801680653002001708653001901728100002001747700001901767856011001786 2006 eng d a0001-154100aCFD simulation of gas-liquid stirred vessel: VC, S33, and L33 flow regimes0 aCFD simulation of gasliquid stirred vessel VC S33 and L33 flow r a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY a1654-16720 v523 a

A comprehensive computational model based on the Eulerian-Eulerian approach was developed to simulate gas-liquid flows in a stirred vessel. A separate submodel was developed to quantitatively understand the influence of turbulence and presence of neighboring bubbles on drag acting on bubbles. This submodel was used to identify an appropriate correlation for estimating the interphase drag force. The standard k-epsilon turbulence model was used to simulate turbulent gas-liquid flows in a stirred vessel. A computational snapshot approach was used to simulate motion of the standard Rushton turbine in a fully baffled vessel. The computational model was mapped onto FLUENT4.5, a commercial CFD solver. The model predictions were compared with the previously published experimental data of Bombac and co-workers. The model was used to simulate three distinct flow regimes in gas-liquid stirred vessels: vortex clinging (VC), alternating small cavities (S33), and alternating large cavities (L33). The predicted results show reasonably good agreement with the experimental data for all three regimes. The computational model and results discussed in this work would be useful for understanding and simulating gas holdup distribution and flow regimes in stirred vessels. (c) 2006 American Institute of Chemical Engineers.

10acomputational fluid dynamics (CFD)10aFlow regimes10agas holdup distribution10aRushton turbine10astirred vessel1 aKhopkar, A., R.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-gas-liquid-stirred-vessel-vc-s33-and-l33-flow-regimes-002393nas a2200241 4500008004100000022001400041245009200055210006900147260010600216300001400322490000700336520152900343653000801872653001701880653001101897653002601908653001901934100002001953700002101973700001901994700001902013856011902032 2006 eng d a0009-250900aCFD simulation of mixing in tall gas-liquid stirred vessel: role of local flow patterns0 aCFD simulation of mixing in tall gasliquid stirred vessel role o aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcMAY a2921-29290 v613 a

In this work, we have used the computational fluid dynamics (CFD)-based models to investigate the gas-liquid flows generated by three down-pumping pitched blade turbines. A two-fluid model along with the standard k-epsilon turbulence model was used to simulate the dispersed gas-liquid flow in a stirred vessel. Appropriate drag corrections to account for bulk turbulence [Khopkar and Ranade, 2005. CFD simulation of gas-liquid flow in a stirred vessel: VC, S33 and L33 flow regimes. A.I.Ch.E. Journal, accepted for publication] were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). The computational model has successfully captured the flow regimes as observed during experiments. The particle trajectory simulations were then carried out to examine the influence of the different flow regimes on the circulation time distribution. The model predictions were verified by comparing the predicted results with the experimental data of [Shewale and Pandit, 2006. Studies in multiple impeller agitated gas-liquid contactors. Chemical Engineering Science 61, 489-504]. The computational model and results discussed in this study would be useful for explaining the implications local flow patterns on the mixing process and extending the applications of CFD models for Simulating large multiphase stirred reactors. (c) 2005 Elsevier Ltd. All rights reserved.

10aCFD10aFlow regimes10amixing10apitched blade turbine10astirred vessel1 aKhopkar, A., R.1 aKasat, Gopal, R.1 aPandit, A., B.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-mixing-tall-gas-liquid-stirred-vessel-role-local-flow-patterns-102910nas a2200241 4500008004100000022001400041245009800055210006900153260009900222300001200321490000700333520203200340653000802372653002902380653001402409653002102423653001802444100002402462700002002486700001902506700001902525856012402544 2006 eng d a0950-423000aCFD simulation of shortstopping runaway reactions in vessels agitated with impellers and jets0 aCFD simulation of shortstopping runaway reactions in vessels agi aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcNOV a570-5810 v193 a

Runaway reactions are continuing to be a problem in the chemical industry. A recent study showed that 26% of our major chemical plant accidents are due to runaways. The consequences of runaway reactions are usually mitigated with (a) reliefs and containment systems or (b) shortstopping (reaction inhibition). This study covers the concept of shortstopping. One of the major reasons for runaways is power failure. In the advent of a power failure, mixing an inhibiting agent with the reactor contents is challenging. However, jets or impellers driven by a small generator can be used for mixing. This study compares shortstopping results in vessels agitated with jets and impellers using computational fluid dynamics (CFD). A commercial CFD code, Fluent is used. For shortstopping systems relying on jet mixing, angle and diameter of jet nozzle and jet velocity are the key design/operating parameters. For the systems with impellers, type, size and RPM of impeller are the key parameters. In this work, mixing with a jet mixer is first investigated for three nozzle diameters and two angles of injection. The best jet mixer configuration on the basis of mixing time is used for shortstopping studies. The simulated shortstopping results with the jet mixer are then compared with those obtained with impeller (Rushton and pitched blade turbine) stirred vessels. Our results identify the conditions for effective shortstopping; i.e., agitation requirements, locations for adding the inhibitor, and the quantity of inhibitor. The distribution of excess inhibitor is shown to be an important and essential design criterion for effective shortstopping when using impeller stirred vessels. The comparative study with a single jet shows that jet mixer is ineffective when used for shortstopping. Efforts such as adding excess inhibitor and inhibition with higher reaction rates at the same power, proved to be ineffective when using jet mixer compared to the results with impellers. (C) 2006 Elsevier Ltd. All rights reserved.

10aCFD10aimpeller stirred vessels10ajet mixer10arunaway reaction10ashortstopping1 aDakshinamoorthy, D.1 aKhopkar, A., R.1 aLouvar, J., F.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-shortstopping-runaway-reactions-vessels-agitated-impellers-and-jets-001971nas a2200181 4500008004100000022001400041245009600055210006900151260007100220300001400291490000700305520127700312100002001589700002101609700001901630700001901649856012101668 2006 eng d a0888-588500aComputational fluid dynamics simulation of the solid suspension in a stirred slurry reactor0 aComputational fluid dynamics simulation of the solid suspension  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a4416-44280 v453 a

A comprehensive computational fluid dynamics CFD model was developed in the present study to gain insight into the solid suspension in a stirred slurry reactor. The preliminary simulations highlighted the need for the correct modeling of the interphase drag force. A two-dimensional model problem was then developed using CFD to understand the influence of free stream turbulence on the particle drag coefficient. The proposed correlation was then incorporated in a two-fluid model (Euler-Euler) along with the standard k-epsilon turbulence model with mixture properties to simulate the turbulent solid-liquid flow in a stirred reactor. A multiple reference frame approach was used to simulate the impeller rotation in a fully baffled reactor. A computational model was mapped on to a commercial CFD solver FLUENT6.2 (of Fluent Inc., USA). The model predictions were compared with the published experimental data of Yamazaki et al. [Powder Technol. 1986, 48, 205] and Godfrey and Zhu [AIChE Symp. Ser. 1994, 299, 181]. The predicted results show reasonably good agreement with the experimental data. The computational model and results discussed in this work would be useful for extending the applications of CFD models for simulating large stirred slurry reactors.

1 aKhopkar, A., R.1 aKasat, Gopal, R.1 aPandit, A., B.1 aRanade, V., V. uhttps://library.ncl.res.in/content/computational-fluid-dynamics-simulation-solid-suspension-stirred-slurry-reactor-101938nas a2200229 4500008004100000022001400041245008500055210006900140260009100209300002000300490000600320520108100326653003301407653002501440653001701465653002901482653002001511100002101531700002601552700001901578856011101597 2008 eng d a1542-658000aCFD simulation of gas-liquid flows in a reactor stirred by dual rushton turbines0 aCFD simulation of gasliquid flows in a reactor stirred by dual r a2809 TELEGRAPH AVENUE, STE 202, BERKELEY, CA 94705 USAbBERKELEY ELECTRONIC PRESScJAN aArticle No. A600 v63 a

In the present work, we have simulated gas-liquid flows in a tall stirred reactor equipped with dual Rushton turbines. A two fluid model along with the standard k-epsilon turbulence model and modified drag coefficient, (proposed by Khopkar & Ranade, 2006) accounting for the effect of bulk turbulence, was used to simulate the dispersed gas-liquid flow in a stirred reactor. The multiple reference frames (MRF) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc. USA). The model was used to simulate three distinct flow regimes in a gas-liquid stirred reactor: L33-VC (lower impeller-upper impeller), S33-VC and VC-VC. The model predictions were compared with the published experimental data of Bombac & Zun (2000). The predicted results show good agreement with the experimental data for all the three flow regimes. The computational model presented in this work would be useful for simulating different flow regimes in a gas-liquid stirred vessel.

10acomputational fluid dynamics10adual Rushton turbine10aFlow regimes10agas hold-up distribution10astirred reactor1 aKasat, Gopal, R.1 aPandit, Aniruddha, B.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-gas-liquid-flows-reactor-stirred-dual-rushton-turbines-001979nas a2200229 4500008004100000022001400041245007400055210006900129260010600198300001400304490000700318520117900325653000801504653001101512653002101523653002001544100002101564700002001585700001901605700002001624856010501644 2008 eng d a0009-250900aCFD simulation of liquid-phase mixing in solid-liquid stirred reactor0 aCFD simulation of liquidphase mixing in solidliquid stirred reac aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcAUG a3877-38850 v633 a

A comprehensive CFD model was developed to gain an insight into solid suspension and its implications on the liquid-phase mixing process in a solid-liquid stirred reactor. The turbulent solid-liquid flow in a stirred reactor was simulated using a two-fluid model with the standard k-epsilon. turbulence model with mixture properties. The multiple reference frames (MRFs) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model with necessary sub-models was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc., USA). The predicted solid concentration distribution was compared with the experimental data of Yamazaki et al. [ 1986. Concentration profiles of solids suspended in a stirred tank. Powder Technology 48, 205-216]. The computational model was then further extended to simulate and understand the implications of the suspension quality on liquid-phase mixing process. The computational model and the predicted results discussed here will be useful for understanding the liquid-phase mixing process in stirred slurry reactors in various stages of solid suspension. (c) 2008 Elsevier Ltd. All rights reserved.

10aCFD10amixing10asolid suspension10astirred reactor1 aKasat, Gopal, R.1 aKhopkar, A., R.1 aRanade, V., V.1 aPandita, A., B. uhttps://library.ncl.res.in/content/cfd-simulation-liquid-phase-mixing-solid-liquid-stirred-reactor-001442nas a2200169 4500008004100000022001400041245008900055210006900144260007100213300001400284490000700298520079100305100002001096700002101116700001901137856011601156 2009 eng d a0888-588500aCFD Simulation of bubble columns: modeling of nonuniform gas distribution at sparger0 aCFD Simulation of bubble columns modeling of nonuniform gas dist a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP a8186-81920 v483 a

Most laboratory bubble columns are equipped with sieve plate spargers. The sieve plate spargers are known to lead to nonuniform gas distribution. It is important to account for such nonuniform gas distribution at the sparger in the computational model before experimental data collected from such columns are used to fit the model parameters. In this article, such an attempt is made. A detailed, 3D CFD model was developed to simulate unsteady gas-liquid flows in bubble Columns with sieve plate spargers. The sensitivity of the nonuniformity of gas distribution at the sparger with sparger resistance was examined. The model predictions were compared with the experimental data. The developed model and presented results will be useful for Simulating industrial bubble columns.

1 aRampure, M., R.1 aMahajani, S., M.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-bubble-columns-modeling-nonuniform-gas-distribution-sparger-000936nas a2200133 4500008004100000245003800041210003800079260001800117300000900135520054800144100001900692700001800711856007300729 2016 eng d00aCatalysis and catalytic processes0 aCatalysis and catalytic processes bElsevier Inc. a1-143 aCatalytic reactions are ubiquitous in chemical and allied industries. A homogeneous or heterogeneous catalyst that provides an alternative route of reaction with lower activation energy and better control of selectivity can make a substantial impact on process viability and economics. In this chapter, the basics of catalysis and catalytic processes are introduced. Some aspects of reaction and reactor engineering required to realize catalytic processes in practice are also discussed. In addition, the organization of the book is outlined. 1 aRanade, V., V.1 aJoshi, S., S. uhttps://library.ncl.res.in/content/catalysis-and-catalytic-processes01354nas a2200145 4500008004100000245004700041210004700088260001800135300001200153520091000165100001801075700001801093700001901111856007801130 2016 eng d00aCatalysis for fine and specialty chemicals0 aCatalysis for fine and specialty chemicals bElsevier Inc. a317-3923 aThe fine and specialty chemical industry is extremely diverse, encompassing pharmaceuticals, dyestuffs, food additives, agrochemicals, polymer additives, flavors and fragrances, various chemical intermediates, etc. Fine and specialty chemicals have been around for more than 100 years and they are produced with the aim of either being used as is or in the form of additives/formulations. These organic chemicals are generally manufactured in batch or semibatch processes. Most of these generally involve multistep processes and often generate significant by-products/effluents per kg of useful products. Catalysis can be effectively used to reduce such waste generation and to minimize consumption of raw materials. In this chapter, we present various applications of homogeneous, as well as heterogeneous catalysis and catalytic processes, which are particularly relevant to fine and specialty chemicals1 aJoshi, S., S.1 aBhatnagar, A.1 aRanade, V., V. uhttps://library.ncl.res.in/content/catalysis-fine-and-specialty-chemicals01140nas a2200133 4500008004100000245003500041210003500076260001800111300001200129520075700141100001900898700001900917856007000936 2016 eng d00aCatalytic reaction engineering0 aCatalytic reaction engineering bElsevier Inc. a263-3143 ahemical reaction engineering has contributed remarkably in bringing laboratory-developed chemistry into commercial practice. Reaction engineering is useful for analysis of reactions, identifying rate-limiting steps, determining overall rates, selection of reactor configuration and design and scale-up of reactors. Reaction engineering also provides useful insights into catalytic cycles and provides clues for improving catalyst systems. It essentially includes all the activities necessary to evolve best possible hardware and operating protocol for the reactor to carry out the desired transformation of raw materials (or reactants) into value-added products. This chapter provides an overview of reaction engineering aspects of catalytic processes.1 aGunjal, P., R.1 aRanade, V., V. uhttps://library.ncl.res.in/content/catalytic-reaction-engineering00599nas a2200145 4500008004100000020002000041245008400061210006900145260004500214100002100259700001500280700001700295700001900312856012200331 2016 eng d a978-151083442-200aCharacterizing flow and solid suspension in optimax crystallization workstation0 aCharacterizing flow and solid suspension in optimax crystallizat aSan Francisco; United StatesbAIChEcNOV1 aSardeshpande, M.1 aPandit, A.1 aVedantam, S.1 aRanade, V., V. uhttps://www.scopus.com/record/display.uri?eid=2-s2.0-85019102692&origin=inward&txGid=820eae9eac7a8eac5ea31078647c0e4f