Methods and systems for the removal of SO2 from waste combustion flue gas are described herein. One such system for removing SO2 from waste combustion flue gas containing SO2 uses a semi-dry desulfurization system for contacting the flue gas with a solvent moistened absorption material. Thereafter, a recirculated water quench is used for contacting the flue gas with recirculated water at a relatively low pH, followed by a condenser used for contacting the flue gas with a water spray. Additionally, a NaOH supply for supplying NaOH to the condenser and an oxidizing catalyst supply for supplying an oxidizing catalyst to the condenser, are likewise used to produce cleaned flue gas for release to the atmosphere.