Pyrite transformation and sulfur dioxide release during calcination of coal gangue

Abstract

Calcination is a typical process associated with the utilization of coal gangue. A concern associated with this procedure is the emission of sulfur dioxide (SO₂). In this work, the behavior of SO₂ release during coal gangue calcination under an air atmosphere were systematically investigated and compared to the characteristics of SO₂ evolution from pure pyrite calcination. Results show that although sulfur in coal gangue mainly exists in the form of pyrite, it represents different transformation behaviors from that in pure mineral pyrite. At 500 °C, the release rate of SO₂ is significantly higher in coal gangue than in mineral pyrite due to the fact that coal gangue combustion can occur at low temperatures, which favors the SO₂ release, while at 600 and 700 °C they become almost the same. The shrinking core model cannot describe the SO₂ emission profiles in coal gangue and, instead, a hybrid 3D diffusion, i.e. the Jander model, is successfully developed in this study.