A STRUCTURAL PORE DEVELOPMENT MODEL FOR CALCINATION

Abstract

A structural pore development model has been developed to describe microscopic pore evolution from the thermal decomposition reaction of a single calcium carbonate sphere, this model depicts a uniform distribution of equal sized pores growing from the surface of the sphere toward its center while CO₂ is evolved from the pore bottom. The chemical reaction at the interface, as well as heat transfer from the surroundings to the decomposing sphere and transport of CO₂ from the pore bottom to the bulk gas, are included in the model. The model shows good agreement with experimental data for CaCO₃, and limestone particles of size ranging from 10 μm to 1.1 cm in diameter at various background CO₂, pressures and temperatures

The simulation of the calcination reaction confirms the experimental observations indicating slower calcination rates at higher background CO₂ pressures, mainly due to internal unsteady-state buildup of CO₂ in the pore. The effect of the background₂ pressure is significantly more prominent in the smaller particles. The activation energy derived from the model is equal to 38.0 kcal/g-mol which is in the range of those reported by other investigators and is noticeably close to the heat of the calcination reaction.

KEYWORDS:

• Pore model
• Calcination
• Pore development