(737a) Experimental Evaluation of a Solar Carbonation-Calcination Reactor Under Simulated High-Flux Solar Irradiation

Two-step calcium oxide carbonation–calcination chemical looping is studied for carbon dioxide (CO₂) capture and high-temperature thermochemical energy storage applications [1]. The process involves solar-driven endothermic calcination reaction of calcium carbonate (CaCO₃)and non-solar exothermic carbonation reaction of calcium oxide (CaO) with CO₂:

Calcination (endothermic): CaCO₃ → CaO + CO₂

Carbonation (exothermic): CaO + CO₂ → CaCO₃

Previous pertinent studies of the process include investigations of reaction chemistry, transport phenomena, solar reactor design, and process integration [1–4].

In this work, we experimentally evaluate the thermochemical performance of a sorbent material and a solar thermochemical reactor. The reaction kinetics are investigated using non-isothermal thermogravimetric analysis (TGA) with raw CaCO₃ pellets of size in the range of 2–5 mm. Calcination and carbonation reaction rates and extents are measured as a function of temperature, CO₂ flow rate and sample heating rate. Under a heating rate of 10 K min^-1 and the atmosphere of 100 mL min^-1 CO₂ and 20 mL min^-1 Ar, the calcination is found to occur at about 910°C and is completed in about 18 min. For the same conditions, the carbonation occurs at about 860°C and its extent reaches 47.3% after 34 min.

The solar reactor experimental setup consists of a high-flux solar simulator as a source of concentrated solar radiation [5], a 1 kW dual-cavity solar-driven packed-bed reactor [4], and auxiliary equipment. The reactor consists of two concentric cylindrical cavities, an irradiated inner cavity surrounded by a packed bed of reacting particles, as previously described in [4]. The reactor has an easy-to-assemble and modular design, allowing for future upgrades and studies of other processes. In a typical experiment, the inlet gas is preheated to an intermediate temperature for simulating heat recuperation, and the product gas composition is monitored using a mass spectrometer. The composition and internal morphology of the sorbent particles are analyzed using XRD and SEM techniques before and after the reactor experiments. The effects of calcination and carbonation temperatures, reactor heating rate, inlet gas temperature, CO₂ flow rate, and duration of the calcination and carbonation steps on the reactor solar-to-chemical conversion efficiency are investigated. The experimental results will be used to validate a transient heat transfer model of the reactor and to optimize the solar reactor and process design.

References:

[1] Reich, L., Yue, L., Bader, R. and Lipiński, W., 2014. Towards solar thermochemical carbon dioxide capture via calcium oxide looping: A review. Aerosol and Air Quality Research, 14(2), pp.500–514.

[2] Yue, L., Reich, L., Simon, T., Bader, R. and Lipiński, W., 2017. Progress in thermal transport modelling of carbonate-based reacting systems. International Journal of Numerical Methods for Heat, 27(5), pp.1098–1107.

[3] Bayon, A., Bader, R., Jafarian, M., Fedunik-Hofman, L., Sun, Y., Hinkley, J., Miller, S. and Lipiński, W., 2018. Techno-economic assessment of solid–gas thermochemical energy storage systems for solar thermal power applications. Energy, 149, pp.473–484.

[4] Reich, L., Melmoth, L., Yue, L., Bader, R., Gresham, R., Simon, T. and Lipiński, W., 2017. A solar reactor design for research on calcium oxide-based carbon dioxide capture. Journal of Solar Energy Engineering, 139(5).

[5] Bader, R., Haussener, S. and Lipiński, W., 2015. Optical design of multisource high-flux solar simulators. Journal of Solar Energy Engineering, 137(2).