Power is produced using fuel, preferably with a sulfur content larger than 1% wt, from raw and/or preprocessed oil residues which are burned alone, i.e. without any addition of sorbents, diluents or the like, with a CFB boiler, a pitch boiler or a downshot boiler to generate high pressure steam and/or power and residual emissions. Residual emissions are cleaned to simultaneously remove PM, NO.sub.x and SO.sub.2 therefrom. The sulfur in emissions can be used to produce sulfuric acid. The process uses a low cost fuel, generates steam, and/or power and sulfuric acid and meets all emission requirements for PM, NO.sub.x and SO.sub.2.