(281g) Experimental Evaluation of Thermal Energy Storage Using the Sorption-Assisted Boudouard Process

The ability to supply high temperature carbon free heat to power generation and industrial processes is key to the decrease of the carbon footprint of our current technology-intensive civilization [1]. Recently, our lab has focused on the capture, storage, and delivery of very high temperature (in the order of 1000^oC) heat to remote locations using the sorption-assisted Boudouard reaction, shown in the equation below

2CO + MO ↔ MCO₃ + C ΔH = -350 kJ/mol

where M represents a Group 2A element for this process [2 - 6]. This reaction is reversible, with the left hand side preferred at high temperatures, whereas the right hand side is preferred at lower temperatures. A brief thermodynamic analysis of the system for various M species as well as when no sorption is employed shows the equilibria in Figure 1. As can be seen, the equilibrium temperature increases as you move down the periodic table (i.e., the equilibrium temperatures go as T_Mg < T_Ca < T_Sr < T_Ba).

In this process, heat is captured and regenerated at high temperatures, up to ~1275K (~1550°C), while energy storage and transfer occurs at ambient temperature. This approach allows for very long-term heat storage and transfer of the heat to remote locations without degradation, a particularly useful aspect to processes that may lack ready access to nearby land on which to capture the heat.

A conceptual implementation of the process is shown in Figure 2. In this concept, heat is captured at the Heat Absorption Reactor which we have implemented as a directly heated fluidized bed reactor, and in which the reverse sorption assisted Boudouard reaction is carried out. The reactants consist of carbon black and metal carbonate formed as a product of the heat regeneration step. As necessary several heat absorption reactors can be implemented in parallel to scale the process to the energy load required. Heat is released at a second Heat Release Reactor, also currently implemented as a fluidized bed reactor. The heat is transferred between the collector and releaser as chemical latent energy at room temperature, avoiding degradation regardless of storage duration and distance between the collector and the process.

This presentation will share initial results of the process kinetics and experimental heat-collected to heat-delivered exergetic efficiency of the process.

References:

[1] See, for example, https://www.energy.gov/eere/solar/articles/funding-notice-concentrating-solar-thermal-power-fiscal-year-2022-research. Accessed 3/1/2022.

[2] Boudouard, O. Influence De La Vapeur D’eau Sur La Réduction De L’anhydride Carbonique Par Le Charbon C. R. Hebd. Acad. Sci. 1905, 141, 252– 253.

[3] Rout, K.R. et al. Highly Selective CO Removal by Sorption Enhanced Boudouard Reaction for Hydrogen Production Catal. Sci. Technol. 2019, 9, 4100–4107.

[4] Miao, Y. et al. Thermal Energy Storage Using the Boudouard Reaction 2019 AIChE Solar Technol, December 2019, Waco, TX.

[5] Miao, Y. et al. A Thermal Energy Storage Using the Boudouard Reaction 2020 AIChE Annual, Virtual, Nov 16-20 2020, 559f.

[6] See, for example, Yokochi, A. et al. Thermal Energy Storage Using Sorption-Assisted Boudouard Processes 2021 AIChE Annual, Nov 7-19 2021, 737e.