Study on chemical-looping combustion of coal with CaSO₄ oxygen carrier assisted by CaO addition

The reactivity between the CaSO₄ oxygen carrier with CaO additive and coal under steam atmosphere was studied in a fluidized bed reactor. The experimental results show that the addition of CaO can improve the performance of both coal gasification and CaSO₄ reduction, and increase the reaction rate of coal gasification and CaSO₄ reduction and the CO₂ generating rate. However, the catalysis of CaO drops as the reaction temperature rises. And the optimum reaction temperature is 900 ℃, at which the releases of gaseous sulfides are remarkably decreased by 63.19% and 27.37% for SO₂ and H₂S, respectively, as the molar ratio of CaO to CaSO₄ is 1.18. Meanwhile, the amount of CO₂ absorbed by CaO can be controlled to less than 2%.