A sulfur-iodine flowsheet using precipitation, electrodialysis, and membrane separation to produce hydrogen

The preliminary flowsheet of an electrodialysis cell (EDC) and membrane reactor (MR)-embedded SI cycle has been developed. The key components consisting of the preliminary flowsheet are as follows: a Bunsen reactor having a mutual separation function of sulfuric acid and hydriodic acid phases, a sulfuric acid refined column for the purification of the sulfuric acid solution, a HIx-refined column for the purification of the hydriodic acid solution, an isothermal drum coupled to a multi-stage distillation column to concentrate the sulfuric acid solution, a sulfuric acid vaporizer, a sulfuric acid decomposer, a sulfur trioxide decomposer, a sulfuric acid recombination reactor, a condensed sulfuric acid solution and sulfur dioxide/oxygen gas mixture separator, a precipitator to recover excess iodine dissolved in the hydriodic acid solution, an electrodialysis cell to break through the azeotrope of the HI/I2/H2O ternary solution, a multi-stage distillation column to generate highly concentrated hydriodic acid vapor as a top product of the column, a membrane reactor to decompose hydrogen iodide and preferentially separate the hydrogen, and a hydrogen scrubber. The material and energy balance of each component was established based on a computer code simulation using Aspen Plus™. The thermal efficiency of the EDC and MR-embedded SI process has also been evaluated and predicted as 39.4%.

► A SI process to adopt precipitation, electrodialysis, and membrane technologies.
► A modified SI flowsheet to prevent a tube clogging problem due to excess iodine.
► Operating condition to minimize energy demand at a HI–I2–H2O distillation column.
► A thermal network to achieve a hydrogen production efficiency of 39.4%.