Abstract: A heat recuperator having a triple pass cross-flow ceramic core comprising ribbed layers bonded together has divider ribs thicker than other supporting ribs in order to provide greater seal area to adjoining layer.

Abstract: A heat recuperator having a triple pass cross-flow ceramic core comprising ribbed layers bonded together has divider ribs thicker than other supporting ribs in order to provide greater seal area to adjoining layer.

Abstract: A process is disclosed for recovering tungsten and rhenium from a tungsten and rhenium source. The process involves firing the source in an oxidizing atmosphere at a sufficient temperature for a sufficient time to convert the tungsten and rhenium to their respective oxides, to remove a portion of the rhenium as volatilized oxide, and to form a first fired material containing essentially all of the tungsten and the remaining portion of the rhenium, increasing the surface area of the resulting oxidized tungsten, and firing the first fired material in an oxidizing atmosphere at a sufficient temperature for a sufficient time to remove essentially all of the remaining portion of the rhenium as volatilized oxidized rhenium and to form an essentially rhenium-free oxidized tungsten.