Abstract: A process is provided for conditioning fly-ash present in flue gas which also contains sulfur dioxide and steam by subjecting the fly-ash containing flue gas to ultraviolet radiation so as to convert steam present in the flue gas into hydroxyl radicals which oxidizes about 5 to 10 percent of the sulfur dioxide in the flue gas into sulfur trioxide. This photo-produced sulfur trioxide conditions the fly-ash and renders it more easily separated in the electrostatic precipitator.

Abstract: A process for the in-situ transformation of chemical species present in the flue gas to form sulfur trioxide, wherein the fly-ash particles are conditioned by altering their surface electrical properties. More specifically, the subject invention is concerned with fly ash conditioning using plural lamps located at specific positions in a specific arrangements most advantageous to the chemical conversion that would take place. The novel invention conditions flue gas emissions by treating the flue gas with SO.sub.3, where the SO.sub.3 is generated in the flue gas by photocatalytic conversion of SO.sub.2 using selectively spaced and arranged ultra violet light emitting lamps and related automated components.

Abstract: A process for removing SO.sub.2 from a gas mixture including SO.sub.3 and SO.sub.2 having a volume ratio of SO.sub.3 to SO.sub.2 greater than 1. The process includes intimately contacting the gas mixture in a contacting zone, removing a stream of purified gas containing less SO.sub.2 than the gas mixture from an upper portion of the contacting zone, and removing a stream of sulfuric acid from a lower portion of the contacting zone. Also provided are processes for manufacturing sulfuric acid utilizing the process for removing SO.sub.2 which allow increasing the production of concentrated sulfuric acid solutions by producing more sulfur trioxide without an increase of sulfur dioxide emissions.