Process intensification is a design strategy aiming to lead benefits in processing, substantially shrinking equipment size, boosting plant efficiency, saving energy, reducing costs, minimizing environmental impact, improving safety, remote control and automation. Membrane processes have potential to replace conventional energy-intensive techniques, to accomplish a selective and efficient transport, to improve the performance of reactive processes, to provide options for a sustainable industrial growth[1]. The design of compact membrane systems performing all the standard unit operations is now reliable[2], and interesting developments are related to the synergic integration of membrane operations(fig. 1). Part of the research activity carried out at ITM-CNR aims, p.es, to develop highly innovative approaches in order to improve the quality of water produced by desalination, to drive down the costs, to solve the brine disposal problem[3]. Present results confirm the ability of Micro- and Ultra - filtration to eliminate suspended solids and colloids. Gas-liquid membrane contactors remove up to 95% of dissolved O2 thus minimizing corrosion; nanofiltration reduces hardness and limits scaling; membrane crystallizers offer the opportunity to recover valuable dissolved salts; evaporative contactors leads to an increase of the water recovery factors up to 90%. Fig. 2 illustrates the sequential connection of all mentioned membrane units. The requirements of process intensification are also well satisfied by membrane engineering in agrofood industry. In ITM-CNR laboratories, the use of integrated membrane processes for the treatment of fruit juices is under investigation (fig. 3). The clarified phase obtained by Ultrafiltration (UF) is concentrated by Reverse Osmosis (RO) and Osmotic Distillation (OD) up to about 60° Brix without significant changes in the Total Antioxidant Activity[4]. The concept of integrated membrane operations is now permeating, with interesting perspectives, also in the petrochemical industry. For ethylene production by thermal cracking[5], membrane are considered for gas separation(GS), production of oxygen enriched air (OEA), hydrocarbons and acid gas removal from waste water and furnaces effluents (MCs), coke elimination from raw water by microfiltration (MF) (fig. 4). Energetic, exergetic and economic analysis confirm the possibility to reach a significant improvement of productivity and costs saving with respect to traditional processes.
References: [1] Drioli E., Romano M. Ind. Eng. Chem. Res. 40 (2001) 1277; [2] Drioli E. Clean Techn Environ. Policy 5 (2003) 3; [3] Drioli E., Criscuoli A., Curcio E. Desalination 147 (2002) 77; [4] Cassano A., Drioli E., Galaverna G., Marchelli R., Di Silvestro G., Cagnasso P. J. Food Eng. 57 (2003) 153; [5] Bernardo P., Criscuoli A., Clarizia G., Barbieri G., Drioli E., Fleres G., Picciotti M. Clean Tech. and Environ. Policy. 6 (2004) 78
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