De- and rehydration of Ca(OH)2 in a reactor with direct heat transfer for thermo-chemical heat storage. Part A: Experimental results

Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost the use of the reversible reaction Ca(OH)2 ⇌ CaO + H2O has been suggested. This paper reports on the thermal behavior of a reactor with direct heat transfer between the gaseous reactant and the solid material. Cycling stability is confirmed and the impact of the most significant parameters such as the maximum possible enthalpy difference of the heat transfer fluid between inlet and outlet, the heat transfer, the particle reaction rate and the mass transport is derived. In the test system the particle reaction rate could be identified as the main limiting parameter.

► Test system and reactor with direct heat transfer for the de- and rehydration of Ca(OH)2. ► Cycling stability over 25 cycles in spite of agglomerating particles. ► Significant impact of the gaseous HTF (heat transfer fluid) on the heat output. ► Investigation of the main significant parameters of a thermo-chemical reactor.