Integrated chlorination technology for producing alumina and silica from ash-slag waste of the TPP of Kazakhstan

Abstract

The paper proposes a technology for the disposal of accumulated ash-slag waste in Kazakhstan using chlorinated ash roasting with further leaching of the cinder with hydrochloric acid. The possibility of preliminary separation of iron (Fe3+) from ash by magnetic separation with the production of a commercial iron-containing product (∼50% Fe) and a non-magnetic fraction with a high content of aluminum is shown.It has been established that the preliminary roasting of the non-magnetic fraction of ash at: 1100°С, the consumption of CaCl2 2 times exceeding its stoichiometric consumption required for the decomposition of mullite, holding for 60 min, and leaching in HCl, leads to an increase in the aluminum content in the solution up to 16.09 g/l. As a result of dehydration of hardly soluble compounds an increase in the degree of extraction of aluminum is caused by a change in the phase composition of ash during roasting. In the obtained cinder the gehlenite and anorthite phases are formed which are well soluble in HCl.The influence of HCl consumption, temperature and duration of the process on the degree of dissolution of the main aluminum compounds - gehlenite and anorthite - has been studied. It has been established that at: S:L = 1:3 ratio, HCl concentration = 30%, temperature 60°С and leaching time of 1 h, a high extraction of silica into a solid commercial product is achieved - 99.8% due to the maximum transfer of impurities to solution. The aluminum content in the solution is 16.09 g/l.