Optimizing lime and cement production with electrochemical reactors : investigating the impact of applied current and limestone granulometry

Details

Supervisors

Proost, Joris

Faculty

Ecole polytechnique de Louvain

Degree label

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

Abstract

Lime and hydrogen are two critical chemical compounds for various sectors in expansion. Lime is the main precursor of cement, extensively used in construction, while hydrogen serves as energy carrier or reducing agent. Both of their conventional production processes are carbon-intensive, creating major issues for the humanity as a consequence. The hybrid electrolyzer aims to produce these two chemicals while minimizing the carbon dioxide emissions by powering it with low-carbon electricity sources. This thesis takes part in the Faraday's project that develops this advanced electrochemical reactor. Here, the calcium carbonate dissolution and the calcium hydroxide precipitation are experimentally analysed as a function particle size with diameters up to 2 mm, and current with values up to 1.5 A. A mathematical model based on the Hixson-Crowell equation is suggested to describe the particle size impact and its subsequent mass-transport limitation. The model relies on assumptions that turn out to be too far from reality. The crucial ones being the perfect sink and the spherical hypothesis. The current influences linearly the dissolution on the range tested. The classical nucleation theory is used to describe the difference between the thermodynamic equilibrium and the actual concentrations during precipitation. The precipitation starts at a calcium ion concentration of about 1 g/L, independently of the current level. After latency zone, the calcium ion concentration evolves in order to reach the thermodynamic equilibrium, at the independent rate of -134 mg/(h·L).