Pervaporation (PV) has shown great promise in water desalination technology. In this work, laponite XLG-Poly (vinyl alcohol) (PVA-Lap) mixed matrix membranes (MMMs) were fabricated to investigate the elaboration of desalination of high-salinity water by pervaporation. The influence of laponite content on the morphology, chemical structure and hydrophilicity of the membranes was investigated. In addition, salt transport properties in the membranes were observed. Moreover, the effect of different laponite content in the PVA matrix on the desalination performance was observed at temperatures from 40°C to 70 °C and feed solutions with up to 10 wt% NaCl. The prepared MMMs showed higher hydrophilicity and roughness of the surface and higher mechanical stability. The higher water flux of 58.6 kg/m 2 .h with a salt rejection over 99.9 % was achieved using 2 wt% laponite XLG MMMs desalinating 3 wt% aqueous NaCl solution at 70 °C. The salt permeability in the membrane was lower by two orders of magnitude than that of water. The water/salt selectivity increased, while the water permeability decreased, with increasing of laponite content in the membrane.
The controllability
study is an integral part of chemical process
design. In this work, the controllability of two special distillation
techniques, extractive distillation and pressure swing distillation,
designed for the separation of azeotropic mixtures is investigated
with dynamic tools. The control design interface of Aspen Plus and
Matlab are applied for the modeling and evaluation of the two systems.
Dynamic controllability indices are determined and aggregated in a
desirability function. The results are compared to obtain efficient
help for process design activity. The pressure swing distillation
shows significantly better controllability features than the extractive
distillation. The reason can be the fact that in the case of the extractive
distillation, a third compound, the extractive agent, is added to
the system to carry out the separation, therefore making the system
more complex. As far as the selection of manipulated variables is
concerned, in the case of the extractive distillation, the reflux
flows should be preferred to the reflux ratios but in the case of
the pressure swing distillation, the reboiler heat loads are preferred
to the reflux ratios since those are closer to the controlled compositions.
Both separation systems show worse controllability features if the
product purity requirement is approaching to the pure products, that
is, close to 100%. Although the energy consumption of the pressure
swing distillation is higher than that of the extractive distillation,
it has the inherent feature that it can be automatically heat integrated
due to a column operated at high pressure and, as a consequence, higher
temperatures.
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