Effects of additives on Ca(OH)2 sorbent for sulfur-and phosphorus-fixing

Premixed combustion of yellow phosphorus tail gas was performed in fluidized bed. ZnO, Fe2O3 and MgO were used as additives of Ca(OH)2 sorbent. The effect of additives on the retention of P2O5 and SO2 in Ca(OH)2 was examined at 960-980 °C, with yellow phosphorus tail gas flowed being controlled at 1 m3/h, and air flowed at 3.6 m3/h. XRD, SEM and EDS techniques were used to analyze and characterize sorbent. The results show that ZnO additive can induce Ca19Zn2(PO4)14 cover sorbent surface and result in the inactivation of sorbent within a short reaction time. Fe2O3 additive can react with CaO to from Ca2Fe2O5, which reduces removal rate of SO2, but improves removal rate of P2O5. MgO additive can promote the spreading of gaseous SO2 and P2O5 in sorbent, accelerate phosphorus crystal particle formation, and consequently improve the removal rate of absorbent toward SO2 and P2O5. When 25% of MgO is presented in sorbent, the removal efficiencies of SO2 and P2O5 increase to about 7.5% and 19.5%, respectively, during 120 min.