Bunsen reaction in the iodine-sulfur thermochemical cycle represents a key process step, seeing that it implies the direct contact of iodine with sulfur-containing recycling components, being interfaced to both the sulfuric acid and hydrogen iodide decomposition sections. Therefore, although being less critical in terms of coupling with the high-temperature heat source (nuclear or solar), and despite the relatively low operating temperatures and pressures, other fundamental issues must be regarded. First, the best match with the other sections is to be identified. Second, since iodine and water removal from the produced acids prior decomposition are operations responsible of the major heat losses, in order to minimize the energy consumption in the downstream units, the two produced acid solutions must be as pure and concentrated as possible. Third, side reaction occurrence must be avoided.

A laboratory-scale glass-made Bunsen reactor with SO2 feed flow rates the order of 10-50 L/h has been assembled and its performances are currently investigated. The main general objective is to assess the most favorable operative conditions to enhance downstream purification and concentration of the produced acid solutions. Particularly, the effect of temperature on one hand, and the water and iodine excess in the feed on the other hand, are investigated.

Both semi-continuous and continuous tests are carried out, and potential side products (sulfur or hydrogen sulfide) formation is determined at the end of each experiment.

The preliminary reactor design basically consists of a packed column operating at 1 atm, without mechanical mixing device, and with iodine conveniently fed either as a pure melt (at temperatures above 113°C), or using a hydrogen iodide water solution as carrier.

Our preliminary experimental results on the performances of this system will be discussed.