Abstract: An improved gas turbine combined cycle system having a diffuser duct between the gas turbine and steam generator. The diffuser duct has boundary layer suction to prevent gas jet separation, thereby reducing pressure loss and improving gas velocity profiles in the duct, while eliminating the need for internal flow controls. The gas turbine combined cycle system can be vertically oriented to reduce the plan area of the system and provide for convenient use of a symmetrical diffuser duct and the use of forced circulation on the water side of the steam generator.

Abstract: Gases containing SO.sub.2 from a furnace are contacted in the scrubbing zone of a scrubber with an aqueous scrubbing medium containing solid alkaline earth metal carbonate, seed crystals of alkaline earth metal sulfate and dissolved alkaline earth metal carbonate and sulfate and having a pH of from 6.0 to 6.5. The SO.sub.2 reacts to form sulfites and bisulfites. The scrubbing medium is then withdrawn from the scrubbing zone and discharged to a reaction tank. Air is blown through the scrubbing medium in the reaction tank and then up into and through the scrubber and scrubbing zone. The oxygen reacts with sulfite to form sulfate in both the reaction tank and the scrubbing zone. The amount of oxygen is controlled so that the pH in the scrubber will not drop below about 4.5 and so as to oxidize not more than about 30 to 50% of the sulfite.