Subclass 1/24: Methods of steam generation characterised by form of heating method (use of solar heat F24J 2/00; jackets or other cooling means in which steam is generated and which serve for cooling other apparatus, see the subclasses for such apparatus) using combustion under pressure substantially exceeding atmospheric pressure Pressure-fired steam boilers, e.g. using turbo air compressors actuated by hot gases from boiler furnace