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4. Intensifying Multiphase Reactions and Reactors: Strategies and Examples

Author

Utikar, Ranjeet, Ranade, V., Utikar, Ranjeet, and Ranade, V.

Abstract

Intensification is intrinsic to better chemical and process engineering and has always been used in practice. Multiphase reactions and reactors are ubiquitous in chemical and allied industries and are of great economic and ecological importance. There is a great scope for intensifying multiphase reactions and reactors for realizing productivity enhancements, which are crucial for sustainable manufacturing. These enhancements can be in terms of increased throughput; better yield, conversion, and selectivity; smaller environmental footprint; and intrinsically safer operations. The advances in intensified reactors, especially microreactors and microfluidic devices, have created significant awareness about intensification in recent decades. In this article, we discuss different strategies for intensifying multiphase reactions and reactors based on the published information. A variety of tools and examples are presented to showcase the potential of intensification. We have found the efforts toward intensification of multiphase reactions and reactors very rewarding academically as well as professionally. We hope that this article will further stimulate interest in this area and pave the way toward realizing next generation productivity for chemical and allied industries.

Published
2017

8. Hydrogenation of crotonaldehyde over Pt based bimetallic catalysts

Author

Englisch, M., Englisch, Martin, Ranade, Vidyadhar S., Ranade, V., Lercher, J.A., and Catalytic Processes and Materials

Subjects
IR-10200, Process Chemistry and Technology, Inorganic chemistry, chemistry.chemical_element, Heterogeneous catalysis, Catalysis, chemistry.chemical_compound, chemistry, Transition metal, Phase (matter), METIS-105543, Organic chemistry, Physical and Theoretical Chemistry, Crotonaldehyde, Selectivity, Platinum, Bimetallic strip
Abstract

Gas and liquid phase hydrogenation of crotonaldehyde was studied over silica supported promoted Pt catalysts. The influence of reaction temperature and reactant pressure on the activity and selectivity of the catalysts and the role of deactivation was investigated. Addition of Ni, Co and Fe to Pt/SiO2 increased the activity and the selectivity in gas phase hydrogenation. This is attributed to the existence of polar sites in a bimetallic phase favoring the interaction with the carbonyl group and, thus, increasing the rate for the hydrogenation to crotylalcohol. Addition of Ga, Sn and Ge improved the selectivity to crotylalcohol, but decreased the activity of the catalysts. These promoters form catalytically inactive oxides that decorate part of the Pt surface. The electron pair donor¿acceptor interaction of the oxygen of the carbonyl group with the Lewis sites present in such oxide clusters is concluded to cause the enhanced selectivity to crotylalcohol. The addition of La, Bi, Pb and Sb to Pt decreased the activity and the selectivity of the parent catalyst by blocking a part of the active surface. With respect to selectivity, catalyst behavior is independent of the reaction medium. In contrast, the highest activities in gas phase were found for catalysts forming a bimetallic phase, while these catalysts showed the lowest activity in liquid phase due to a fast deactivation.

Published
1997

9. Modeling and simulation of a fluidized bed gasifier.

Author

Jain, A. A., Mehra, A., and Ranade, V. V.

Subjects
COAL dealers, COAL gasification, MATHEMATICAL models, PARTICLES, MATERIALS
Abstract

Abstract: A mathematical model to simulate continuous gasification of coal particles in a bubbling fluidized bed reactor is presented. Material and energy balance equations have been formulated based on the 2‐phase theory. Well‐known correlations have been used to estimate the hydrodynamics. Devolatilization, heterogeneous reactions, and homogenous reactions have been included in the model. The model is used to simulate 29 experimental data sets from the published literature. The model predictions agree very well with the experimental data by adjusting the particle size. After establishing agreement with the data, the model was used to investigate influence of various operating parameters on overall performance (carbon conversion and the gross calorific value of generated gas). Thermodynamic analysis (using the minimization of the Gibbs free energy approach) has also been discussed. The presented model and results provide useful tool and insight on design and operation of fluidized bed gasifier. [ABSTRACT FROM AUTHOR]

Published
2018
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10. CFD Simulation of Annular Centrifugal Extractors

Author

Vedantam, S., Wardle, K. E., Tamhane, T. V., Ranade, V. V., and Joshi, J. B.

Subjects
Article Subject
Abstract

Annular centrifugal extractors (ACE), also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD) has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.

Published
2012
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11. Heat Transfer and Dynamics of Impinging Droplets on Hot Horizontal Surfaces

Author

Utikar, Ranjeet, Pathak, S., Mehra, A., Ranade, V., Utikar, Ranjeet, Pathak, S., Mehra, A., and Ranade, V.

Abstract

In fluidised bed olefin polymerisation reactors, a liquid monomer is added for enhancing heat removal (super-condensed mode). This broadens the operating window and can substantially increase the capacity of a given reactor hardware. Design and location of liquid injection nozzles play a key role in dictating the performance of condensed mode operations. An understanding of the fundamental characteristics of droplet impingement onto solid particles is critical for proper design. In this paper, we study the interactions between liquid droplets and hot solid surfaces across various boiling regimes. High-speed digital imaging is used to capture the droplet vaporisation process. Water droplets impacting on a solid wall with different Weber numbers are investigated. The effect of various parameters such as surface and initial droplet diameter, liquid velocity and surface tension is studied. Experimental data of dynamic drop impact on a flat hot surface are reported. A phenomenological model is developed to describe the droplet vaporisation phenomena in single phase and nucleate boiling regimes. The results from the phenomenological model are compared with the experimental data presented here and the experimental results reported in the literature. The study provides useful clues for understanding the real case when solid particles are much larger than the injected liquid droplets.

Published
2010

14. Liquid phase hydrogenatin of crotonaldehyde over Pt/SiO2 catalysts

Author

Englisch, M., Englisch, Martin, Ranade, V., Lercher, J.A., and Catalytic Processes and Materials

Subjects
chemistry.chemical_classification, METIS-105539, Process Chemistry and Technology, Decarbonylation, Inorganic chemistry, IR-10192, Photochemistry, Aldehyde, Catalysis, chemistry.chemical_compound, Adsorption, chemistry, Thiophene, Crotonaldehyde, Triphenylphosphine, Selectivity
Abstract

The dependence of the catalytic properties of Pt/SiO2 catalysts for the hydrogenation of crotonaldehyde on the hydrogen pressure, the reaction temperature, the nature of the solvent and the presence of several additives were investigated. Strong deactivation of the catalysts mainly caused by decarbonylation of crotonaldehyde and irreversible adsorption of CO was observed. The initial activity of the deactivated catalysts is regained by oxidation of the adsorbed CO to CO2 by purging with air. The selectivity to crotylalcohol increased with increasing number of turnovers per metal site. This is explained with preferential blocking of the nonselective sites on the metal crystallites by CO and by a slow surface modification of the aging catalyst with organic deposits. The overall rate and the selectivity to the saturated aldehyde are markedly enhanced by an increase in hydrogen pressure and by a decrease in reaction temperature. The addition of modifiers such as potassium acetate, triphenylphosphine and thiophene had only little influence on the activity and the selectivity of the catalysts.

Published
1997

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