tion in the capital cost may result from improved catalytic materials and higher hydrogen production capacity in each facility.
Calcium-Bromine-Iron Cycle The calcium-bromine-iron (Ca-Br, or UT-3) cycle involves solid-gas interactions that may facilitate the reagent-product separations, as opposed to the all-fluid interactions in the SI cycle, but it will introduce the problems of solids handling, support, and attrition. This process is formed of the following reactions (Doctor et al., 2002):
The thermodynamics of these reactions have been found favorable. However, the hydrogen production efficiency of the process is limited to about 40 percent, owing to the melting point of Ca-Br2 at 760°C (Schultz et al., 2002).
Other Cycles Argonne National Laboratory’s Chemical Engineering Division is studying other cycles like the copper-chlorine thermochemical cycle. The energy efficiency of the process is projected to be 40 to 45 percent (ANL, 2003). This work is currently being investigated only by ANL, at a bench-scale R&D level, and no pilot demonstra-