Optimizing lime and cement production with an electrochemical reactor: investigating the impact of the feedstock

Details

Supervisors

Joris Proost

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux, à finalité spécialisée

Abstract

This thesis investigates the optimization of lime production using an electrochemical reactor, with a particular focus on the impact of feedstock purity (99, 95 and 58 wt% of CaCO3) on the efficiency of the decarbonation process and on the final precipitates. Cement production is a major contributor to global CO2 emissions, primarily due to the calcination of limestone (CaCO3) to produce clinker. The research, conducted within the framework of the Faraday project, aims to decarbonize this process through the development of a novel hybrid electrolyzer. The results demonstrate that the purity of CaCO3 significantly affects the efficiency of hydrogen ion (H+) consumption during the decarbonation process. Purity-Adjusted Hydrogen Ion Consumption Efficiency (PA-HICE) was proposed as performance indicator. High-purity limestones (L-99, L-95) exhibited PA-HICE above 90%, whereas a lower-purity limestone (L-58) showed a reduced efficiency of 80.58%. This drop was caused by the presence of MgCO3 in L-58. As an impurity, it was found to compete with CaCO3 for H+, thereby decreasing overall process efficiency. On the other hand impurities like Fe2O3 and SiO2 remain mostly undissolved. The study also highlighted the impact of particle size distribution (PSD) on the anodic pH during the process, further influencing the efficiency of impurity removal and the quality of the final product. The final products, primarily composed of calcium hydroxide (Ca(OH)2), varied in quality based on the initial feedstock purity. High-purity feedstocks resulted in products with over 90% Ca(OH)2, while the lower-purity L-58 produced a significantly less pure product with only 43.83% Ca(OH)2. Conversion ratio (from CaCO3 to Ca(OH)2) were computed, for the high-grade limestone they are similar to synthetic CaCO3 (i.e. over 90%) . For L-58, it was only 75.66 %, demonstrating the impact of magnesium over the entirety of the process. The fineness improved for all the precipitated material and the PSDs became homogeneous.