Electrodialysis treatment of secondary steam condensate obtained during production of ammonium nitrate. Technical and economic analysis

The process of electrodialysis desalination of secondary steam condensate produced during ammonium nitrate production using various anion-exchange membranes is studied in the laboratory and on pilot scale electrodialysis modules. The main parameters of the process: current efficiency, salt flux and power consumption, are studied. The membranes studied include three commercial heterogeneous anion exchange membranes: Ralex AMH produced by Mega a.s.; MA-40 and MA-41 produced by JSC Szchekinoazot; and the homemade profiled membrane MA-41P. It is shown that the profiled membrane possesses the best mass transfer characteristics this is explained by the combined effects of several factors. These factors include a significant increase of the active membrane area available for mass transfer, intensive fluid mixing and a decrease in the water splitting rate. Among the smooth membranes the Ralex AMH shows the best performance due to its larger active area. The mass transfer properties of the membranes are explained with the help of scanning electron microscopy and voltammetry. The reason behind their behavior in the electrodialysis process is explained by the properties and morphology of their surfaces. An analysis of the economics of the desalination process is made. It is shown that from an economical point of view, MA-41 membranes can be successfully applied in the electrodialysis demineralization process despite their lower mass transfer characteristics compared to the Ralex AMH membranes. Due to their lower mass transfer rates, a larger number of modules is required to achieve the same goals. However, this is compensated for by their lower price. (C) 2015 Elsevier B.V. All rights reserved.