Influence and Mechanism of Structural Characteristics of Limestone on Quicklime Reaction Activity

Abstract

Quicklime (CaO) is extensively used in metallurgy, chemical engineering, materials science, and greenhouse gas reduction due to its high reactivity, low energy consumption, and environmental benefits. It is considered as one of the most promising raw materials for nanomaterial synthesis and carbon dioxide capture. Previous studies have predominantly focused on the impact of limestone composition and calcination condition. Recent research, however, suggests that the structural characteristics of limestone also play a crucial role in determining the reactivity of quicklime. This study investigates the effect of limestone structure on quicklime reactivity and provides a mechanistic analysis. Three types of limestone with varying structures—clastic-structured, transitional-crystalline-structured, and crystalline-structured—were selected for experiments under different calcination times. The results indicate that quicklime produced from clastic-structured limestone exhibits the highest reactivity. The observed differences in quicklime reactivity can primarily be attributed to the following factors: (1) Clastic-structured limestone possesses larger pore volume and specific surface area, which enhance heat conduction and ensure the uniform decomposition of calcite across various regions. (2) The rock-forming calcite particles are fine and small, allowing for the simultaneous decomposition of the outer shell, middle, and core during heating. This prevents “overburning” of the shell or “underfiring” of the core, thereby improving the overall reactivity. Based on these findings, we propose that fine-grained, high-purity clastic-structured limestone is more favorable for producing high-activity quicklime.