Study on thermal regeneration of saturated activated coke coupled with SO2 carbothermal reduction to produce elemental sulfur

The large-scale development of dry flue gas desulfurization technology with carbonaceous adsorbents is limited due to the long process flow, high energy consumption, and narrow application range of sulfuric acid as a by-product. This study focused on the innovative preparation of elemental sulfur from saturated activated coke (SAC) by one step thermal regeneration coupled with SO2 carbothermal reduction. The experimental results showed that the rapid rise in temperature in SAC causes rapid SO2 desorption, resulting in a larger instantaneous SO2 concentration and smaller carbon loss. At temperature higher than 550 °C, most of the adsorbed sulfur converted into gaseous SO2, and a small amount was converted into elemental sulfur with a selectivity of 3.69%. In the temperature range of 650–950 °C, the rapid desorption of SO2 coupled with carbothermal reduction improved the selectivity of elemental sulfur and achieved a near-complete conversion at 950 °C of 93.7%. Furthermore, the re-absorption performance of regenerated AC at 750 °C reached the maximum value of 67.27 mg/g and approached the original AC value of 66.44 mg/g. According to the trade-off between elemental sulfur selectivity and re-adsorption activity, the optimal reaction temperature was determined at 750–850 °C.