Abstract: An energy conversion, conveyance and utilisation system, particularly for providing process heat in industrial plants, which makes use of a source of heat such as a nuclear reactor to dissociate sulfur trioxide according to the reaction:2SO.sub.3 .revreaction.2SO.sub.2 + O.sub.2,the dissociation products being conveyed through a pipeline to a remote utilization station where the heat of recombination is utilized, the resulting sulfur trioxide being returned through the pipeline to the reactor site. The pipeline incorporates separate pipes in which the sulfur dioxide and sulfur trioxide are conducted in liquefied form, surrounded by a duct in which the gaseous oxygen flows.