Experimental investigation and model validation of a CaO/Ca(OH)2 fluidized bed reactor for thermochemical energy storage applications

Abstract

The CaO/Ca(OH) 2 hydration/dehydration chemical loop has long been recognized as a potential candidate for application in energy storage systems for concentrated solar plants. However, the technology still remains at a conceptual level because little information has been published on the performance of the key reactors in the system. In this work, we experimentally investigate the hydration and dehydration reactors in a 5.5 kW th batch fluidized bed reactor, in conditions relevant to larger systems (superficial gas velocities of up to 0.53 m/s, temperatures of up to 500ºC for dehydration, input H 2 O (v) fractions between 0 and 0.8 etc.). Furthermore, to assist in the interpretation of the experimental results, a standard 1D bubbling reactor model has been formulated and fitted to the experimental results by including kinetic information at particle level independently measured in a thermogravimetric apparatus. The results indicate that the hydration reaction is mainly controlled by the slow kinetics of the CaO material tested while significant emulsion-bubble mass-transfer resistances were identified during dehydration due to the much faster dehydration kinetics.

Gas–solid thermochemical heat storage reactors for high-temperature applications

“…X factor =1.5 fitted the experimental results for both hydration and dehydration reaction in a 5.5 kW th batch fluidized bed reactor [78]. Actually, any X factor >1.5 can also be used because the relatively slower reaction kinetics is controlling the overall process of the reaction in the bed and that the bubble-emulsion mass transfer resistances can be ignored.…”

“… Figure 12 Simulation of the loading of a MgH 2 reactor with and without solving the flow [70].  Figure 13 Schematic representation of a CaO/Ca(OH) 2 fluidized bed reactor model during hydration (left) and dehydration (right) [78].  Figure 14 Working principle of gas-solid reaction systems.…”

“…On the contrary, if the powdered materials flow and mix inside the reactors, different assumptions should be made in the modeling of these reactors. Criado et al [78] described a fluidized bed reactor by a 1D classic bubbling bed model (Fig. 13) assuming perfect mixing of the powdered solids and the gas.…”

“…Schematic representation of a CaO/Ca(OH) 2 fluidized bed reactor model during hydration (left) and dehydration (right)[78].…”

Mixed Metal Oxide Systems Applied to Thermochemical Storage of Solar Energy: Benefits of Secondary Metal Addition in Co and Mn Oxides and Contribution of Thermodynamics

“…Various systems can be considered, other than metal oxides [3,7]. For example, hydroxides, and especially calcium hydroxide [8][9][10][11][12][13][14] shows promising results for TCES. The systems based on carbonates are also relevant for TCES application.…”