An apparatus and method of burning trash containing aluminum in a furnace having a moving grate and inclined trays. The grate has an upper and lower part. The inclined trays are provided with one or more inclined plates. The inclined plates are supported on the trays below the upper part of the grate and above the lower part of the grate. Ash and molten aluminum falls through the upper part of the grate, onto the inclined plates, the ash slides off the plates and the aluminum remains on the plates. The plates have holes therethrough to allow air flow for combustion. Some blockage of the holes by aluminum will result over time, but not enough to significantly restrict the flow of combustion air to the combustion area. The trays are removed through the side walls of the furnace for removal of the aluminum when necessary.