(224f) Experimental Testing Of A High-Temperature

A high temperature sulfuric acid decomposer suitable for use with a high temperature heat source was designed and fabricated for the Sulfur-Iodine project at Sandia National Laboratories. The design requirements for the decomposer were that the decomposer needed to be resistant to corrosion, thermal creep, and provide a contamination-free product stream. The product stream upon output from the decomposer is O2, SO2 and water vapor. The design and fabrication of the decomposer is the subject of a companion paper; this paper discusses experimental results obtained to date.

The decomposer was placed in a fume hood and surrounded by electrical heating elements. Sulfuric acid is entrained into the decomposer through a ¼? tantalum tube. The stream enters an annular passageway between the outer SiC bayonet and an inner SiC insert. The inner insert contains the product gases, and also transfers usable heat from the product stream into the incoming acid stream. The acid is transported up the bayonet, gaining heat as it rises, passing by a centering land, thence entering a high temperature region ~850C containing 21 g of platinum coated titania catalyst. The acid stream decomposes into O2, SO2 and water vapor. The product stream then enters an annular passageway between the inner SiC insert and an alumina rod that forms a narrow gap between the inner SiC tube and the outer perimeter of the alumina rod. This arrangement provides very good heat transfer characteristics and a large fraction of the process heat is recaptured.

The products exit the decomposer and enter a condensing unit where water is condensed from the process stream, the resultant gas stream enters a drier where any residual water vapor is desiccated, and the gas stream is analyzed with a variety of instruments, including an oxygen monitor, as well as flow rate sensors. Process gases are then exhausted to the atmosphere. Data to date indicate satisfactory operation of the decomposer with no observable corrosion of any of the parts. Heat recovery is excellent, and the process stream to date indicates near theoretical equilibrium sulfur dioxide production rates. Work to fabricate a 48? decomposer bayonet is in progress. Results will be updated as progress continues.