Kdp Nigam - Academia.edu (original) (raw)

Papers by Kdp Nigam

Nanoscale

Significant advances in nanoparticle-related research have been made in the past decade, and amel... more Significant advances in nanoparticle-related research have been made in the past decade, and amelioration of properties is considered of utmost importance for improving nanoparticle bioavailability, specificity, and catalytic performance.

Journal of Environmental Management

Reviews in Chemical Engineering, 2001

... HJ. Pant Isotope Applications Division Bhabha Atomic Research Centre, Trombay, Mumbai 400 085... more ... HJ. Pant Isotope Applications Division Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India Arunabha Kundu and KDP Nigam* Department of Chemical Engineering Indian Institute of Technology, Delhi New Delhi 110 016, India ABSTRACT ...

Catalysis for Clean Energy and Environmental Sustainability, 2021

Journal of Environmental Management, 2021

The large generation of electronic waste (e-waste) is posing a serious threat to society. It is i... more The large generation of electronic waste (e-waste) is posing a serious threat to society. It is important to develop sustainable technology for the effective management of e-waste and the recovery of valuable metals from it. The present study employed hydrometallurgical approach for Cu and Ni extraction from waste printed circuit boards (WPCB) of mobile phones. This study demonstrates the application of ammonia-ammonium sulfate leaching for the maximum recovery of Cu and Ni. Investigations revealed that the most favourable reaction parameters for efficient metal extraction are - ammonia concentration - 90 g/L, ammonium sulfate concentration - 180 g/L, H2O2 concentration - 0.4 M, time - 4 h, liquid to solid ratio - 20 mL/g, temperature - 80 °C and agitation speed - 700 rpm. Under these conditions, 100% Cu and 90% Ni were extracted. Furthermore, the kinetic study was performed using the shrinking core model which revealed that the internal diffusion is the rate-controlling step for Cu and Ni extraction. The activation energies for Cu and Ni extraction were found out to be 4.5 and 5.7 kJ/mol, respectively. Finally, Cu was recovered with 98.38% purity using electrowinning at a constant DC voltage of 2.0 V at Al cathode. The present study provides a solution for concurrent extraction of Cu and Ni from the raw WPCB of mobile phones and selective recovery of Cu from metal leached solution. The process has the potential to recover the resources from WPCB while minimising the pollution caused by mismanagement of WPCB.

The work reported in this investigation involves the determination of the hydrodynamic properties... more The work reported in this investigation involves the determination of the hydrodynamic properties of the Trickle Bed Reactor which has been loaded in various ways to mark the effect of the loading methodologies employed to pack the catalyst pellets. The bed structure of a packed three-phase reactor is critical to study as it provides the essential contact between the phases and provides the catalytic sites where the reaction takes place. Depending on the structural properties of the bed such as local void structure, liquid distribution, two-phase pressure drop, and holdup of fluids gets affected. The study aims to envelop the catalyst bed characteristics such as the local void structure, the length of the catalyst bed, flow characteristics such as liquid and gas flow rate, and liquid distributor at the top of the catalyst bed to gauge and quantify their effect on the hydrodynamics of a trickle bed reactor.

International Journal of Heat and Mass Transfer, 2005

Flatter velocity profiles and more uniform thermal environments are extremely desirous factors fo... more Flatter velocity profiles and more uniform thermal environments are extremely desirous factors for improved performance in flow reactors and heat exchangers. One means of achieving it in laminar flow systems is to use mixers and flow inverters. In the present study a new ...

Chemical Engineering Science, 2006

In the present work attempts were made to investigate the hydrodynamics and heat transfer charact... more In the present work attempts were made to investigate the hydrodynamics and heat transfer characteristics of tube-in-tube helical heat exchanger at the pilot plant scale. The experiments were carried out in counter current mode operation with hot fluid in the tube side and cold fluid in the ...

Chemical Engineering Science, 2001

... Trickle-bed reactors. Chemical Engineering Progress 83, p. 55. View Record in Scopus | Cited ... more ... Trickle-bed reactors. Chemical Engineering Progress 83, p. 55. View Record in Scopus | Cited By in Scopus (34). Pant, HJ, Arunabha Kundu, & Nigam, KDP (2001). Radiotracer applications in chemical process industry. Reviews in Chemical Engineering, 17, 165. ...

Chemical Engineering Science, 2007

In the present work attempts are made to investigate the hydrodynamics and heat-transfer characte... more In the present work attempts are made to investigate the hydrodynamics and heat-transfer characteristics of a coiled flow inverter (CFI) as heat exchanger at the pilot plant scale. The experiments are carried out in counter-current mode operation with hot fluid in the tube side and cold fluid in the shell side. Experimental study is made over a range of Reynolds numbers from 1000 to 16,000 using water in the tube side of the heat exchanger. The shell side fluids used are either cooling water or ambient air. The coiled flow inverter is made up of coils and 90 • bends and inserted in a closed shell. The shell side is fitted with three types of baffles to provide high turbulence and avoid channeling in the shell side. The bulk mean temperatures at various downstream positions are reported for different flow rate on tube side, as well as the heat transfer efficiency of the heat exchanger is also reported. Pressure drop and overall heat-transfer coefficient is calculated at various tube and shell side process conditions. The outer and inner heat-transfer coefficients are determined using Wilson plot technique. The results show that at low Reynolds numbers, heat-transfer is 25% higher as compared to coiled tubes. At high Reynolds numbers, the configuration has less influence on heat transfer. New empirical correlations are developed for hydrodynamic and heat-transfer predictions in the coiled flow inverter.

Chemical Engineering Journal, 2008

The present study deals with the numerical simulation of flow patterns and mixing behaviour in Ke... more The present study deals with the numerical simulation of flow patterns and mixing behaviour in Kenics static mixer over a wide range of Reynolds number. Three different sets of Kenics mixer (aspect ratio = 1.5) comprised of 3, 9 and 25 elements each have been characterized. ...

Chemical Engineering and Processing: Process Intensification, 2008

In the present study a tube-in-tube helically coiled (TTHC) heat exchanger has been numerically m... more In the present study a tube-in-tube helically coiled (TTHC) heat exchanger has been numerically modeled for fluid flow and heat transfer characteristics for different fluid flow rates in the inner as well as outer tube. The three-dimensional governing equations for mass, momentum and heat transfer have been solved using a control volume finite difference method (CVFDM). The renormalization group (RNG) k-ε model is used to model the turbulent flow and heat transfer in the TTHC heat exchanger. The fluid considered in the inner tube is compressed air at higher pressure and cooling water in the outer tube at ambient conditions. The inner tube pressure is varied from 10 to 30 bars. The Reynolds numbers for the inner tube ranged from 20,000 to 70,000. The mass flow rate in the outer tube is varied from 200 to 600 kg/h. The outer tube is fitted with semicircular plates to support the inner tube and also to provide high turbulence in the annulus region. The overall heat transfer coefficients are calculated for both parallel and counter flow configurations. The Nusselt number and friction factor values in the inner and outer tubes are compared with the experimental data reported in the literature. New empirical correlations are developed for hydrodynamic and heat-transfer predictions in the outer tube of the TTHC.

Chemical Engineering and Processing: Process Intensification, 2006

Rigorous two-phase flow modeling is one of the great challenges in the classical sciences. As wit... more Rigorous two-phase flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in two-phase flow is due to its extreme importance in various industrial applications. Two-phase computational fluid dynamics (CFD) calculations, using Eulerian–Eulerian model and commercial CFD package FLUENT 6.0, were employed to calculate the gas–liquid flow in pipes. Variables

A two-phase Eulerian model, based on porous media concept, describing the flow domain as porous r... more A two-phase Eulerian model, based on porous media concept, describing the flow domain as porous region is presented to estimate the hydrodynamics of two-phase flow in trickle-bed reactors (TBRs) operating at high pressures. The drag forces between phases have been accounted by employing the relative permeability concept (Sàez and Carbonell, 1985). The model has been validated with the different sets experimental data obtained from different independent sources. All the comparisons lead to the fact that the model functions arguably well in predicting the experimental data for high pressure operations. The developed model is very much flexible unlike the traditional CFD approach, i.e. three-phase Eulerian simulations for different particle size effect incorporation without much complexity. While simulating for high pressure condition, we have applied the recently developed correlations (Nemec and Levec, 2005) for relative permeabilities.

Chemical Engineering Science, 2002

Qualitative changes in the local (pore level) wetting e&ciency of a porous catalyst as a function... more Qualitative changes in the local (pore level) wetting e&ciency of a porous catalyst as a function of catalyst wettability are proposed based on monitoring the 1-D motion of the solid-liquid-gas contact line. As catalyst wettability is increased, the resulting wetting e&ciency is likely to show two distinct transitions viz., (1) a sudden decrease that is inspired by coalescence of neighboring rivulets and, (2) a sudden increase that is inspired by porous nature of the catalyst. As catalyst wettability decreases, the wetting e&ciency is likely to decrease in the beginning but can then be held constant due to pinning or holding of the retracting contact line by liquid-5lled pores. This will result in comparatively much higher wetting efficiencies. It is further proposed that under favorable circumstances this pinning can disappear and will, thus, allow the contact line to retract and wetting e&ciency to decrease. In the end, the e8ect of catalyst geometry on the relation between wetting e&ciency and wettability is presented.

Ionic liquids are well known as green solvents, reaction media and catalysis. Here, three differe... more Ionic liquids are well known as green solvents, reaction media and catalysis. Here, three different sulfonic acid functional ionic liquids prepared in the laboratory are used as catalysts in alkylation of p-cresol with tert-butyl alcohol. The kinetics on each of the catalysts was compared and a kinetic model was developed based on the product distribution over these catalysts. The kinetic parameters were estimated using Marquadt's algorithm to minimize the error function. The Arrhenius plots show a curvature which is best interpreted by the extended Arrhenius equation.

American Journal of Chemical Engineering, 2013

This paper surveyed the most important, well known two-phase mass transfer models, namely film-, ... more This paper surveyed the most important, well known two-phase mass transfer models, namely film-, film-penetration-and surface renewal models, applying them to describe the three-phase mass transfer rates at the gas-liquid interface. These models should enable the user to predict the mass transfer enhancement in the presence of a third, in the mass transport active, dispersed phase. Depending on the particle size of the dispersed phase, the pseudo-homogeneous and/or the heterogeneous model can be recommended for nanometer sized and micrometer sized particles, respectively. The effect of all important mass transport parameters, namely particle size, surface renewal frequency, diffusion depth, solubility coefficient, has been shown by typical figures. It has been analyzed how strongly depends the applicability of the homogeneous-or the heterogeneous models not only on the particle size but on the mass transport parameters. As case study, the measured and the predicted mass transfer rates have been investigated in nanofluids.