Reaction Kinetics In A Novel Low-temperature Limestone Calcination Approach Examined Via Numerical Simulations And Isoconversional Methods

Abstract

The calcination of limestone at ∼900°C produces lime (CaO), a critical precursor in the manufacturing of societally important materials such as cement and steel. The chemical decomposition of CaCO3 to CaO, along with the thermal loads necessary for this reaction supplied by fossil fuels, results in 1.33 tons of CO2 emitted per ton of lime. In light of the above, a novel calcination process based on self-propagating high-temperature synthesis (SHS) has been recently proposed. SHS utilizes exothermic heat generated by the combustion of fuel (e.g., lignin) mixed with the reactants to drive the reaction, thereby enabling calcination at ∼450°C, and thereby significant reductions in emissions and energy consumption. SHS-based calcination pathway is different from that of conventional calcination, requiring an understanding of the underlying kinetics, which this paper aims to accomplish. Numerical heat-transfer simulations are carried out on pellets with varying fuel contents, sizes, and porosity, and validated using experimentally determined surface temperature profiles. The use of enthalpy of the limestone domain in the simulated pellets as an indicator of the extent of SHS reaction is a unique attribute of this work. The activation energies, determined through isoconversional methods—without the assumption of a specific reaction model—are observed to be 60–80% lower for SHS-based limestone calcination compared to conventional calcination. This reduction, which depends on the fuel content (higher fuel content leads to lower activation energy), underscores the ultrafast nature of the SHS process. Both SHS-based and conventional calcination routes are determined to follow the contracting geometry model, albeit with lower interface shrinkage dimension for the SHS pathway. Reaction product characterization indicates an enhanced sintering effect due to the ultrafast nature of SHS. A fundamental understanding of the kinetics of SHS-based calcination allows for optimization of the process, enabling further carbon- and energy-efficiency for the process.

Department(s)

Materials Science and Engineering

Second Department

Civil, Architectural and Environmental Engineering

Comments

Arizona State University, Grant DMR 2228782

Keywords and Phrases

Activation energy; Calcination; Heat transfer models; Isoconversional kinetics; Limestone; Self-propagating high-temperature synthesis (SHS)

International Standard Serial Number (ISSN)

0040-6031

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Elsevier, All rights reserved.

Publication Date

01 Aug 2025

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