Why do you insist on oxygen? It's required for the oxidation but what you need now is only to remove sulfur dioxide .
SO2 + O2 --> SO3 (this process DOES take place industrially - e.g: contact process)
Ca(OH)2 + SO3 --> CaSO4 + H2O?
Correct, but in industry, people don't release SO
3 outside since it's very toxic, most of the SO
3 is used for making sulfuric acid, and the amount of releasing is very small, the byproduct of industry usually SO
2 and so the equation must be the reaction between Ca(OH)
2 and SO
2.
@skyjumper: wikipedia is correct but SO
2 is the precursor of SO
3, and the gas in industrial exhausted gas that you found is SO
2 not SO
3.