Session: 08-03: Solar Chemistry: Reforming, Base Chemical & Cement Production

Paper Number: 142261

142261 - The Boudouard Process for High Temperature Heat Capture, Storage, and Delivery to a Distant Location 

Abstract: 

High-quality process heat from clean sources is necessary for decarbonizing the industrial sector.  Because many potential users, including industries and utilities seeking to decarbonize existing thermal-electric generation facilities, often lack the space to co-locate a solar collector field, or possibly a high temperature nuclear heat source, transport of the high temperature heat over long distances may be required.  To avoid the large losses incurred when high temperature heat is transferred as sensible heat, this project aims to convert the heat to thermochemical latent form, transfer it, and regenerate it at the point of use using the Boudouard Reaction (BR) and the Sorption Assisted Boudouard Reaction (SABR) shown in equations (1) and (3) below [1].  

 

BR:  2CO ↔ CO₂ +  C    ΔH = -171 kJ/mol C produced

(1)

 

Metal Carbonation:  MO + CO₂ ↔ MCO₃   ΔH = -180 ~ -270 kJ/mol

(2)

 

SABR:  2CO + MO ↔ MCO₃ + C    ΔH = -350 ~ -440 kJ/mol C produced

(3)

where, in Eqs. (2) and (3), M represents a metal or semi-metal, and usually a Group 2A element.

The Boudouard Reaction shown in (1) is well known, with the reverse reaction being the equally well known dry reforming of carbon [2,3].  This reaction is highly endothermic / exothermic, depending on the direction of the reaction occurring.  The equilibrium favors the C + CO₂ side of the equilibrium in (1) at lower temperatures, but at temperatures above 698 °C the equilibrium reverses because of the large positive entropic term (TΔS) overwhelms the enthalpy term in the Gibbs free energy (i.e., at high temperatures, Δ_RG = Δ_RH – TΔ_RS < 0).  Because CO is kinetically stable at ambient temperature, captured heat can then be stored indefinitely, and transported for use to locations tens to hundreds of kilometers away.  Passing the CO through a suitable catalyst (e.g., Fe or CO) at a suitable temperature, heat can be regenerated with modeled roundtrip exergetic efficiencies as high as 75% or at temperatures over 1000°C.

The sorption assisted BR shown in (3) essentially couples the metal oxide carbonation / decarbonation heat storage process (2) together with the BR process [4], both shifting the BR equilibrium to higher temperatures by sorption of the CO₂ released and boosting the heat content of the process.  Others have employed this approach to shift hydrocarbon reforming to produce CO free Hydrogen [5]. 

In this presentation, the calculated round trip exergy efficiency and reaction kinetics as determined from DSC/TGA data will be shared.

 

References:

[1] See, for example, Yokochi, A. et al. 264c Thermal Energy Transport Using the Sorption-Assisted Boudouard Reaction 2023 AIChE Annual, Nov 5-10 2023, 264c.

[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] See, for example, Roncancio, R. and Jay P. Gore  CO2 char gasification: A systematic review from 2014 to 2020 Energy Conv. Manag.: X 2021, 10, 100060.

[4] Lucie Desage et al.  Thermochemical batteries using metal carbonates: A review of heat storage and extraction J. Energy Stor. 2023, 71, 107901.

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

Presenting Author: Riley Choquette Baylor University

Presenting Author Biography: Name: Riley Choquette

Institution: Baylor University

Email Address: Riley_Choquette@Baylor.edu

Authors:

Ben Phillips Baylor University
Riley Choquette Baylor University
Abigail Joseph Baylor University
Annette Von Jouanne Baylor University
Alexandre Yokochi Baylor University