Abstract: A fuel-conveying incineration grate has grate beams (1) for extending in a longitudinal direction obliquely downward in the longitudinal direction. The grate beams (1) have first surfaces (4) on first sides of the grate beams (1) stepped downwardly in said direction for receiving fuel, opposite surfaces on opposite sides of the grate beams (1), and lateral surfaces (3) sealingly closely adjacent to each other across widths of the grate beams (1) substantially along full lengths of the grate beams (1) in the longitudinal direction. The grate beams (1)relatively reciprocate in the longitudinal direction for conveyting the fuel thereon. At least two longitudinally extending ducts (6, 7) are in thermal communication with the opposite sides of the grate beams (1) for a heat-transmission medium. Connecting points (12, 13) at least at one end of the grate beams (1) provide for flow of the heat-transmission medium at least one of towards and away form the ducts (6, 7).

Abstract: Waste material is incinerated by a partial combustion in a furnace on step grates and the heated combusted product is supplied in a rotary kiln in which the waste is liquified. Solid waste material passing through the grate is collected with ash products, separated from flue gases, including boiler ash, fly ash and residue from flue gas cleaning. The collected products are returned to the inlet of the rotary kiln where these products are introduced along with he combusted waste. In this manner, the slag, boiler ash, flue ash and other harmful residual products from the combustion process are fused into the liquified waste to form a glass-like mass from which salts and heavy metal cannot be leached out.