Modelling of krypton-xenon separation by dynamic fixed-bed adsorption on zeolite

International audienceCurrently noble gases are separated by cryogenic distillation, which is an expensive process with safety constraints due to the cryogenic temperatures used. Adsorptive separation, such as temperature/pressure swing adsorption, is studying as it is considered as an energy, safety and cost effective alternative. Different selective materials are described in the literature from inorganic adsorbents based on physical adsorption to new metal-organic frameworks (MOFs) based on size and chemistry. This work focuses on the description of a modelling of Kr-Xe separation by selective adsorption on a chabazite zeolite in a fixed bed column

Gas-liquid mass transfer : a comparison of down-and up-pumping axial flow impellers with radial impellers

The performance of a down- and up-pumping pitched blade turbine and A315 for gas-liquid dispersion and mass transfer was evaluated and then compared with that of Rushton and Scaba turbines in a small laboratory scale vessel. The results show that when the axial flow impellers are operated in the up-pumping mode, the overall performance is largely improved compared with the down-pumping configuration. Compared with the radial turbines, the up-pumping A315 has a high gas handling capacity, equivalent to the Scaba turbine and is economically much more efficient in terms of mass transfer than both turbines. On the other hand, the uppumping pitched blade turbine is not as well adapted to such applications. Finally, the axial flow impellers in the down-pumping mode have the lowest performance of all the impellers studied, although the A315 is preferred of the pitched blade turbine

Modelling and thermodynamic study of krypton separation by dynamic fixed-bed adsorption on zeolite

International audienceThe 85Kr separation from the off-gas of spent nuclear fuel reprocessing is a technical and environmental challenge for the future nuclear industry. The purpose of this document is to present the results of the experimental study and modelling of Kr dynamic adsorption on the commercial zeolite AW500. Continuous experimental acquisitions between 253 K to 293 K have led to the adsorption isotherms of Kr and Xe diluted in nitrogen flow, using the breakthrough curves. The Kr behaviour can be represented by a linear law with an adsorption enthalpy of -7.3 kJ.mol-1, while Xe follows the Freundlich Heller model with an adsorption enthalpy of -18.8 kJ.mol-1. Experimental tests on Xe/Kr mixtures in presence of NO, NO2, CO2 or O2 pointed out the absence of interactions between components. Due to the difference in breakthrough times and desorption kinetics, Kr can be removed from the reprocessing off-gas and concentrated into the desorbed flow. A modelling has been developed using the dynamic simulation software ProSim DAC, based on the mass, energy and momentum balances. The propagation of the gas flow is described by the axially dispersed plug flow and the mass transfer by the Linear Driving Force Model (LDF). The results show that the modelling is in good agreement with experimental results for both Kr and Xe

Modelling of krypton-xenon separation by dynamic fixed-bed adsorption on zeolite

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Temporal and spatial dimension of dissolved oxygen saturation with fluidic oscillator and Mazzei air injector in soil-less irrigation systems

The wider scale use of aerated water for irrigation has been limited by dis-uniformity of aeration in the field, limited longevity of oxygen in irrigation water and lack of knowledge of what oxygen concentration brings optimal growth. Two options are presented for increasing dissolved oxygen (DO) in irrigation water: Venturi (VT) and fluidic oscillator (FO) aeration systems. Sweet corn was grown in pots to evaluate the effect of aerated water. Compared to the control treatment (CK), VT and FO showed an increase in irrigated water DO in the irrigation tank and feeding pots after aeration. Incorporation of surfactant in the irrigation water significantly improved DO level for the VT and FO treatment. Typically the DO levels reached a peak when the pump is turned off and then decline to a minimum after 24 h. The VT and FO systems had a higher magnitude and duration of the DO level in the water in all treatments compared to the CK system. The FO aeration maintained the longest duration of elevated DO in the water by a factor of two compared to the VT aeration. Compared to the CK, the best result on longevity and DO concentration was achieved using 4 ppm of a non-ionic surfactant. The corn biomass was significantly greater for the VT compared to both the FO and CK treatments