Abstract: Densified fly ash pellets are produced by the steps comprising:A. Sizing the fly ash to produce a fraction substantially finer than -200 mesh (U.S. Standard);B. Moistening the sized fraction with sufficient water to form green pellets;C. Sizing the green pellets;D. Tumbling the sized green pellets to effect particle packing until excess water has been squeezed out, said pellets being kept dusted during tumbling with sized fly ash from step (a) to absorb the squeezed out water and thereby prevent agglomeration;E. Drying the packed green pellets to remove the free water therefrom;F. Heating the dried pellets from about 1000.degree. F to within about 70 - 90% of the absolute softening temperature of the ash and;G. Sintering the pellets from (f) at a temperature of 70 to 90% of the absolute softening temperature of the ash.The densified fly ash pellets constitute a low cost particulate heat exchange material for supplying heat to a fluidized bed carbon gasification zone.