Manganese Dioxide Calcination (2D)

Furnace Conditions

Temperature 480 °C

Oxygen level 18%

Feed moisture 8.0%

Time acceleration 6×

Live Readout

Process time

0 s

Moisture left

100.0%

Mn2O3 overburn

0.0%

Activity index

0.0%

How it works

Two competing thermally-activated reactions run on every grain in the charge, each following Arrhenius kinetics k = A·e^-Ea/RT:

Drying:        H2O(ads) -> H2O(g)          Ea ≈ 55 kJ/mol
Decomposition: 2 MnO2 -> Mn2O3 + 0.5 O2    Ea ≈ 180 kJ/mol
dM/dt = -k_dry * M
da/dt = k_dec * (1-a) / (1 + [O2]/[O2]_ref)

Decomposition's activation energy is more than 3× the drying step's, so it stays negligible below roughly 500 °C even as moisture clears out fast — then turns on sharply above it (a textbook illustration of why activation energy, not temperature alone, decides which reaction dominates). Extra oxygen partial pressure pushes the equilibrium 2MnO2 ⇌ Mn2O3 + 0.5O2 back toward MnO2 (Le Chatelier), suppressing the decomposition rate in the denominator term above.

Moisture (blue tint) — adsorbed water still clinging to a grain; too much left over causes gassing in the finished cell.
Overburn (rust-red tint) — grains that converted to electrochemically inactive Mn2O3; too little heat/time leaves moisture, too much destroys activity.
Activity index — an illustrative combined score, 100×(1−a)×(1−0.5×moisture/100); it is not a literal voltammetric measurement, just a way to see the sweet spot.

Moist grain Active MnO2 Overburnt Mn2O3