PROCESS REGENERATING REAR-EARTH-METALS-WITH DIGESTING COMBUSTION RESIDUES OF REAR-EARTH-METAL-CONTAINING STONE COALS, FIRST OF ALL BROWN COALS

The invention relates to a method for recovering rare metals from the combustion residues of various coals, in particular brown coals. The recovery is performed by digestion, more particularly by aqueous and/or dilute alkaline and/or dilute acidic digestion, where two or three of these steps can be combined in any desired order or they may be carried out separately. During digestion the concentration of the solution is monitored and the subsequent digestion steps are terminated at a desired concentration. The solid and liquid phase are then separated and the rare metals are isolated from the liquid phase while the solid phase, optionally after neutralization and/or washing can be utilized for example as a source of energy.