Iodine excess separation from hydriodic acid (HI) is one of the most challenging steps of the Sulfur-Iodine thermochemical water splitting cycle. One promising method is the extraction of HI by using phosphoric acid (H3PO4), with the subsequent separation of gaseous hydriodic acid from water and H3PO4by a distillation step. The aim of the present work is to provide new experimental liquid-liquid equilibrium data for the biphasic HI/I2/H2O/H3PO4quaternary system, varying both temperature and solution composition in order to optimize the excess of anhydrous phosphoric acid to be added. Two temperature levels were tested, i.e. 100 °C and 120 °C, and the H3PO4amount was varied in the feed mixture from 7.7% wt to 38% wt while the [I2]/[HI] and [H2O]/[HI] molar ratios were kept constant at, respectively, a value of 3.7 and 5.6. A temperature level of 120 °C, with an H3PO4initial concentration of about 29% wt leads to the lowest amount of water against HI, which minimizes energy costs in the phosphoric acid reconcentration step, the most energy consuming part in this separation process. © 2009 International Association for Hydrogen Energy.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Condensed Matter Physics
- Energy Engineering and Power Technology