Thermophysical properties of lime as a function of origin (Part 3): Emissivity
(2nd from left), 1300 °C (3rd from left) and 1380 °C (right)
Significant temperature homogenisation takes place in the cross-section of shaft kilns due to radiation. This heat transport is proportional to the emissivity of the lime. It is shown that the emissivities are in the 0.35 to 0.70 range, depending on the origin of the limestone. Heat fluxes can therefore differ by up to a factor of 2, depending on the origin.
The limestone burning process is determined by a lot of material properties. These thermophysical properties depend on the origin of the limestone. The first two parts of this series [1, 2] investigated the specific heat capacity, enthalpy of reaction and decomposition pressure of various limestones.
This third part focuses on the emissivity. This, to a significant extent, determines the temperature homogeneity in the cross-section of shaft kilns. In parallel-flow regenerative (PFR) and in single-shaft counterflow kilns, the fuel is injected via lances. There is thus a discrete...