Technological Aspects of Primorskaya Thermal Power Plant’s Ash and Slag Wastes Preparation for REE Removal

Complete elemental analysis of ash and slag wastes (ASW) of Primorskaya thermal power plant (TPP) Primorsky Krai, Russia was carried out. As a result of the research, it was found that among the rare and rare earth elements (REE). The highest content is noted for: Sc (20.9 ppm), Y (36.93 ppm), La (38.97 ppm), Ce (82.51 ppm), Nd (34.41 ppm). That fact correlates with data on the average world content of such components in industrial waste from coal combustion. Various methods for extracting REE from the ASW were tested including fusion with alkali and treatment with various mineral acids. The highest degree of REE extraction (more than 70%) from ash melt is observed for a mixture of concentrated nitric, hydrochloric and hydrofluoric acids and a solution of boric acid. In order to preliminary reveal the distribution of REE in the ASW, samples were subjected to flotation, magnetic separation and gravity separation. The possibility of preliminary concentration REE from ASW was shown. For In, La, Nd, Pr, Sm concentration occurs more than 2 times. The possibility of obtaining 4 types of marketable by-products (slag sand; unburned coal; iron oxides concentrate; pure silicon dioxide) at preliminary REE separation stage was shown.