The objective of the CaBr2 hydrolysis study at Argonne National Laboratory is to experimentally demonstrate that a sparging contactor can be used to develop an economical process for hydrogen production. The first step in Ca-Br cycle consists of reacting one mole of steam with CaBr2 to form two moles of HBr. This is an endothermic reaction with an optimal range of reaction temperature between 1000 and 1050 K (730 — 780ºC). Analysis of the experimental hydrolysis reaction indicates that a second order hydrolysis reaction in CaBr2 may be possible because of the formation of a complex involving CaBr2 and CaO. Analyzing the reaction using second order kinetics finds kf (a/Vb) falling between 2.03-4.06 (l/min cm) where the overall reaction system is represented by the equation below:

3 CaBr2 + H2O >> (CaBr2)2•CaO + 2 HBr

This reaction is highly endothermic and appears to form a complex. At a design temperature of 1050 K (777°C), the heat of reaction is 181.5 kJ/mol (43.38 kcal/mol), and the Gibbs free energy change is positive at 99.6 kJ/mol (23.81 kcal/mol). This reaction system behavior is critical for understanding and evaluating the scale-up of the Ca-Br cycle.