Electrodialysis versus chromatography for desalting silage juice: Comparison of both processes with regard to energy consumption

Abstract

In many cases, desalination is an important step during the separation of valuable substances from solutions. In this study, grass silage juice, a renewable resource for the production of lactic acid as well as amino acids, was processed. Electrodialysis and process chromatography were investigated as methods for the above task. The main aim of this work is an estimation of the energy demand of both processes in connection with sustainable development. Scale up and calculations for industrial plants were done on the basis of the laboratory results. The energy consumption for desalting step was 134 and 54.76 kWh m-3 of silage juice in electrodialysis and chromatography process, respectively. However, since the commercial products are normally required, the energy consumption for concentration step (evaporation) was taken in consideration. With this regard, the energy demand for lactic acid production was 5.05 kWh kg-1 (in electrodialysis process) and 3.42 kWh kg -1 (in chromatography process). In chromatography, the evaporation took a great part (77.95%) of the total energy whereas in electrodialysis process, this part was only 22.0%. In the present application, it seemed that chromatography could be preferred. However, it must be noted that in present case the salt content is quite high (35 g L-1). Based on the preliminary obtained data, it was assumed that, if the salt content were approximately 15 g L-1, the total energy consumption for ED process would equal to that of chromatography process. © 2005 Elsevier B.V. All rights reserved.