Department of Chemical Engineering

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IIT Jodhpur

Advanced Heavy Water Reactor (AHWR) is the latest Indian design for a next generation nuclear reactor. It is 300MWe, vertical, pressure tube type, boiling light water cooled natural circulation and heavy water moderated reactor. It burns thorium in its fuel core to meet the objectives of using thorium fuel cycles for commercial power generation. Desalination systems are included in the reactor circuit to produce high quality water from seawater utilizing thermal energy of AHWR to meet the reactor make-up and other process water requirements. Studies have been carried out for various options of using thermal energy of AHWR for desalination. LTE and MED-TVC desalination plants are planned to be coupled with the reactor using Main Heat Transport purification circuit waste heat and using steam from a tapping between the cross-over line of HP and LP turbine respectively. Metallic barriers, intermediate loops and pressure reversal concepts are applied to prevent radioactive ingress to product water of desalination plant. This paper describes the technical feasibility studies of coupling 250m3/day LTE and 2400m3/day MED-TVC seawater desalination plants coupled to AHWR. Coupling of desalination plants, methodologies, loss of reactor power and various safety considerations are discussed in details. © 2013 Elsevier B.V.

World University root node

Desalination

Technical feasibility study for coupling a desalination plant to an Advanced Heavy Water Reactor

Air-cooled fin and tube heat exchangers are used as a condenser in the conventional automotive Heating Ventilation & Air-Conditioning (HVAC) systems. In this study, the use of liquid cooled plate heat exchanger as a condenser in the automotive HVAC systems has been investigated. In the proposed configuration, the cabin heat absorbed by the refrigerant in HVAC system is rejected to the coolant through a liquid cooled condenser and then to the ambient air through a low temperature radiator. Hence, the proposed configuration combines heat rejection from HVAC system with a low temperature radiator circuit of power train cooling. Mixture of Ethylene glycol & Water (coolant), which is used in power train cooling system, is used as secondary fluid in the condenser. Primarily, work done involves design of a liquid cooled condenser, determining boundary conditions for the coolant circuit and evaluation of overall performance of the refrigeration cycle in the HVAC system at various operating conditions. The modified configuration has been evaluated through dynamic simulation of the system in Dymola. Use of a liquid cooled plate heat exchanger as a condenser provides packaging benefits for the system. From the results, conclusions are drawn about the viability of the concept for its integration into a passenger vehicle. Copyright © 2014 SAE International.

SAE Technical Papers

Performance evaluation of automotive HVAC system with the use of liquid cooled condenser

Development of composite membrane using organic polymer and inorganic nanoparticles is an emerging field of water purification process. Here we report the preparation, characterization and performance of a novel composite polymeric membrane prepared using composite of spray dried silica granule and polysulfone. We investigate the structure and performance of the membranes prepared using N-methyl-2-pyrrolidone or N,N-dimethyl formamide as solvent for the composite material. Such polymer-nanocomposite membrane shows significant enhancement of water permeability without sacrificing for the separation performance. In order to establish the structure-function correlation, we probed the mesoscopic structure of polymer casting solution and final membranes using small-angle scattering, atomic force microscopy and contact angle measurements. We put forward a plausible mechanism in support of the enhanced performance of the composite membranes. © 2013 Elsevier B.V. All rights reserved.

Separation and Purification Technology

Novel polysulfone-spray-dried silica composite membrane for water purification: Preparation, characterization and performance evaluation

Numerical simulations to develop an understanding of transport processes inside PBMRs (packed bed membrane reactors) and to evaluate effectiveness of PBMRs in increasing the conversion of HI (hydrogen iodide) decomposition reaction of IS (iodine-sulfur) thermochemical cycle are reported. The computational approach used in the simulations has been validated using the data reported for HI decomposition in a packed bed reactor (PBR). The validated computational approach has been used for parametric studies. Effects of different parameters (temperature, pressure, space velocity, membrane permeability, permselectivity, packed bed porosity and reactor diameter) on HI conversion are reported. The parameters having the maximum impact on the conversion are identified. The findings show that using a PBMR instead of a PBR leads to significant enhancement in conversion and the parameters having high impact on conversion are wall temperature, feed temperature, reactor diameter and packed bed porosity. Based on the findings of parametric studies, ranges of the parameters having maximum impact on conversion are suggested, e.g. The reactor wall temperature is recommended to be in the range of 690-700 K, the bed porosity is recommended to be in the range of 0.2-0.4. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

International Journal of Hydrogen Energy

Numerical simulations of HI decomposition in packed bed membrane reactors

Chain conformations, counter-ion structure, intermolecular hydrogen bonding structure and dynamics of atactic polyethacrylic acid (PEA) in salt-free aqueous dilute solution at 25°C are studied via molecular dynamics (MD) simulations with explicit-solvent and explicit-ion description for the first time. The intermolecular structure was analysed by the radial distribution functions (RDF) for specific atom types between PEA chain, water molecules and Na+ counter-ions, as well as by the hydration near the PEA chain in the solvated system. An increase in f provides an increase in 〈Rg〉 of the chain, consistent with the existence of the compact form of PEA. The simulations show expansion for radius-of-gyration with increase in f, as expected for flexible polyelectrolytes under salt-free condition. The extent of intermolecular hydrogen bonds (H-bonds) between PEA and water is enhanced by increase in f. Chains having a higher counter-ion density show higher values of 〈Rg〉, influenced by intermolecular interactions between PEA and water. The coordination of Na+ counter ions and water molecules to carboxyl oxygens of polyacrylic acid (PAA) increases with charge density of the chain. A comparison of the structure aspects is made with PAA and PMA polyelectrolytes in dilute solution, which brings out the hydrophobic effect of the ethyl side-groups in PEA on conformational properties and counter-ion condensation structure. © 2013 Taylor &amp; Francis.

Molecular Simulation

Conformations and hydration structure of hydrophobic polyelectrolyte atactic poly(ethacrylic acid) in dilute aqueous solution as a function of neutralisation

Grand canonical Monte Carlo simulations are used to study the behaviour of triangle-well (TW) fluids with variable well widths confined inside slit pores. The effect of individual factors influencing the properties of confined fluids such as fluid-fluid interactions, pore size and pore wall-fluid interactions are obtained using simulations as it is difficult to experimentally determine the same. An interesting observation of this study is that inside the narrow pore of slit height h* = 5 at the high-pressure condition of P* = 0.8, for the TW fluid with long-range attraction or for the fluid at a low temperature for even a short-range attraction, the density profiles show layering such that there is a sticking tendency of the particles at centre, while there is a depletion of particles near the wall (as the layers at the centre have higher density peak heights than near the walls). © 2014 Taylor & Francis.

Molecular Physics

Molecular simulation study of triangle-well fluids confined in slit pores

In this study, both reverse osmosis (RO) and forward osmosis (FO) experiments are conducted to concentrate simulated inactive ammonium diuranate (ADU) filtered effluent solution (by mixing uranyl nitrate and ammonium nitrate) using indigenously developed cellulose acetate blend (CAB) and thin-film composite polyamide (TFCP) membranes. Both the membranes are prepared and characterized in terms of pure water permeability and solute rejection for 2000 ppm NaCl feed, water contact angle and surface average roughness. Subsequently, testing of volume reduction and concentration of simulated ADU effluent solution are carried out using custom made RO and FO testing systems. It is found that in RO process, the performance in terms of volume reduction factor and concentration factor with respect to uranium for both CAB and TFCP membranes are comparable but the CAB membranes show better performance than the TFCP membranes in FO modes. The concentration of ammonium nitrate is less in RO concentrate than in the FO concentrates. Similar experiments with the feed solution having different concentration of uranium (1-20 ppm) with same concentration of ammonium nitrate show that in FO, almost no leaching of uranium is found to the draw solution side but in RO, some of the uranium starts passing to the permeate side, particularly at lower concentration of uranium in the feed. © 2013 © 2013 Balaban Desalination Publications. All rights reserved.

Desalination and Water Treatment

Concentration of ammonium diuranate effluent by reverse osmosis and forward osmosis membrane processes

Ultrafiltration (UF) membranes in capillary configuration are deployed in domestic water purification with respect to removal of contaminants. Fouling is an inherent phenomenon in UF process and has been reported to cause decline in flux, reduces membrane life, etc. So, it has to be thoroughly studied in order to optimise the logistics of process operation. Considering the concentration of contaminants in different parts of India, the fouling studies investigations were carried out in the range of 5-15 ppm of various constitutes such as Iron, Manganese, and the organic foulants-sodium alginate and humic acid. Out of various parameters affecting fouling like feed pressure, feed temperature, feed pH, the effort was directed towards studying the effect of various foulants (and at different loadings) on the membrane. Results obtained from experiments suggest that the fouling caused by the organics (sodium alginate and humic acid) is higher than that of inorganics (iron and manganese). Iron caused higher fouling than manganese. Sodium alginate caused higher fouling than humic acid. It is observed that humic acid caused more irreversible fouling than sodium alginate. Attempts have been made to develop a mathematical model to represent the fouling phenomena. The effect of fouling for different loadings of various foulants was seen in terms of change in transmembrane pressure (TMP), under conditions of constant permeate flow. TMP in the proposed model is expressed as the function of feed flow rate, intrinsic membrane porosity, permeability of the membrane, and the plugging constant. The values of plugging constant represent the interactions between the feed and the membrane and thus suggest the degree of fouling, both reversible and irreversible fouling, caused by different foulants and at different loadings. Irreversible pore constriction fraction is a measure of irreversible fouling and it has also been determined for different foulants and at different loadings. © 2013 © 2013 Balaban Desalination Publications. All rights reserved.

Fouling studies of capillary ultrafiltration membrane

An all silica DDR (deca dodecasil rhombohedral) zeolite membrane with dense, interlocked structure has been developed for separation of H2 from HI/I2 mixture of HI decomposition reaction. In this work, the DDR zeolite membrane was synthesized on the seeded clay-alumina substrate within 5 days. The seeds were synthesized by sonication mediated hydrothermal process within short crystallization time which enhanced the nucleation for the membrane growth. The synthesized membranes along with seed crystals were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy (EDAX). The selectivity of hydrogen with respect to CO2 and Ar was evaluated by single gas permeation studies at room temperature. The tests for corrosion resistance were carried out upto 120 h with both support and DDR membrane at 130 °C which confirmed the stability of membrane under the harsh HI/I2 environment. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Synthesis, characterization and corrosion performance evaluation of DDR membrane for H2 separation from HI decomposition reaction

Molecular mechanisms regulating human trophoblast differentiation remain poorly understood due to difficulties in obtaining primary tissues from very early developmental stages in humans. Therefore, the use of human embryonic stem cells (hESCs) as a source for generating trophoblast tissues is of significant interest. Trophoblast-like cells have been obtained through treatment of hESCs with bone morphogenetic protein (BMP) or inhibitors of activin/nodal/transforming growth factor-β signaling, or through protocols involving formation of embryoid bodies (EBs); however, there is controversy over whether hESC-derived cells are indeed analogous to true trophoblasts found in vivo. In this review, we provide an overview of previously described efforts to obtain trophoblasts from hESCs. We also discuss the merits and limitations of hESCs as a source of trophoblast derivatives. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.