Chloridizing processing of accumulated ash and slag waste of the Kazakhstan CHP plants has been studied. The possibility of separating iron from ash by magnetic separation to obtain a commercial iron-containing product (≈50% Fe) is demonstrated. It is shown that the residual iron content in the non-magnetic ash fraction is minimal (1.2%), while the aluminum content is about 98%. In the mullite composition, silica is mainly present in the non-magnetic ash fraction (≈97%). The silicon content in the non-magnetic fraction obtained after wet separation increased from 27.7 to 29.5 wt.%. It has been established that the complete decomposition of mullite occurs when the non-magnetic ash fraction is roasted at 1,100°C for 60 minutes, and the CaCl2 consumption is twice the stoichiometric value required for the decomposition of mullite. An increase in the degree of aluminum extraction into a cinder is caused by a change in the phase composition of ash during roasting, which occurs as a result of dehydration of low-solubility compounds. The resulting cinder contains the gelenite and anorthite phases, which are highly soluble in HCl. It has been found that the quantitative gelenite-to-anorthite ratio in the cinder, obtained under the optimal roasting conditions, is 5:1. For practical purposes, it is essential to provide for the charge mixing conditions during the ash roasting process in the presence of CaCl2, for example, by using a tubular rotary furnace. This will improve the contact between the ash particles and calcium chloride, while creating favorable conditions for the complete breakdown of mullite and formation of highly soluble aluminum compounds in the form of anorthite and gelenite.