A novel method for producing hydrogen based on the Ca-Br cycle

The Ca-Br cycle is a promising method for efficiently producing hydrogen from water; however, it suffers from limitations inherent to gas-solid reactions. The cycle depends on the repeatable transformation of calcium bromide to calcium oxide and back to calcium bromide. The use of pure solids for these reactions would lead to rapid particle degradation and slow reaction kinetics. To circumvent these problems, a new reactor concept based on molten calcium bromide with dissolved calcium oxide has been proposed and developed. Preliminary experimental results indicate that the solubility of calcium oxide in calcium bromide at 800 °C is at least 1.2 wt%, a level that is expected to be high enough to make the proposed process work as designed. Early attempts to hydrolyze molten calcium bromide indicated that solid calcium oxide formation may inhibit reactivity, and thus injection of the moisture into the salt must be optimized.