Method and device for washing/cleaning granular material from slag and washing/cleaning bottom/boiler ash from a thermal waste treatment, and mineral residue and recycling material

A method for washing/cleaning granular material from slag as well as bottom/boiler ash from a thermal waste treatment as well as mineral residue and recycling material, wherein in such method the granular material is added to a process liquid and is subjected to ultrasound therein, wherein said process liquid is located in an upright or vertical cleaning channel with an upper feeding end and a lower extraction end, in which method the granular material is classified within tight grain size limits into a plurality of screened fractions and only one of the plurality of screened fractions is delivered from the upper feeding end into the cleaning channel at a time and moves freely downwards in the process liquid towards the lower extraction end due to the force of gravity and is subjected to ultrasound during the sinking movement, such that the cleaning channel is flown through by the process liquid from the bottom to the top at a flow rate to slow down sinking speed of the granular material which flow rate is attributed to each screened fraction such that various particles of the screened fraction selected for treatment have a desired retention time in the cleaning channel, and the liquid escaping from the upper feeding end is extracted via an overflow.