To
effectively solve the problem of recovery and utilization of
flue gas desulfurized gypsum (FGDG), a new method for preparing SO2 gas by adding a mixture of FGDG and pyrite into a boiling
furnace and utilizing its high-temperature waste heat is proposed.
Using the FactSage 6.1 Reaction module and the Equilib module, the
pyrolysis behavior of FGDG with pyrite and the release characteristics
of SO2 gas were studied. The effects of FeS2 addition, temperature, and ventilation flow rate on the decomposition
of FGDG and the change in gas behavior were studied by thermogravimetric
mass spectrometry and settling furnace (SF) experiments. In addition,
the activation energies of the chemical reactions were determined
by the Kissinger method, the Kissinger–Akahira–Sunose
method, and the Flynn–Wall–Ozawa method. The results
show that between 100 and 200 °C, mainly the loss process of
CaSO4·2H2O crystal water from FGDG occurred.
At 570 °C, FeS2 primarily undergoes self-decomposition.
Between 820 and 1000 °C, the decomposition product of FeS2 reductively decomposes CaSO4. The average activation
energy for the chemical reaction is 298.44 ± 8.83 kJ/mol. A lower
pressure and ventilation and a higher FeS2 addition and
temperature are beneficial for the reduction and decomposition of
FGDG and for the increase in SO2 concentration. Therefore,
in this study, the feasibility of adding FeS2 to reduce
and decompose FGDG to prepare SO2 was preliminarily verified.
The technology proposed in this article may shed some light on the
recovery and high-value utilization of FGDG.