Assessment of ash and slag waste as a source of environmental pollution and as a source of secondary raw materials
Authors:   Kazakh National Research Technical University named after K.I. Satpayev, Nurpeisova Marzhan , Zhumagulov Temirbek ,   OP “Engineering Technologies”, Fedotenko Natalia ,   Institute of Problems of Integrated Development of Mineral Resources named after Academician N.V. Melnikov of the Russian Academy of Sciences, Kurmanbayev Olzhas ,   Kazakh National Research Technical University named after K.I. Satpayev
Published: May 2024

Introduction. Currently, more than 500 million tons of fly ash have been accumulated on the territory of the Republic of Kazakhstan, the volume of which will increase to one billion tons by 2030. Such accumulation of fly ash in storages creates a powerful anthropogenic impact on the biogeocenosis. A significant proportion of these man-made materials are formed during the burning of Ekibastuz coals. There is practically no processing of ash and slag waste on an industrial scale. For various reasons, ash dumps are not used in Kazakhstan, because the physico-chemical properties have been very poorly studied, in addition, during their processing, other wastes or ash dumps unsuitable for use are obtained from these wastes, because they contain a lot of unburned coal. As of 01.01.2020, the share of recycled, reused, burnt ash and slag waste in Kazakhstan amounted to 0.7%. The relevance and significance of this problem is due to the fact that man-made waste from CHP plants is not sufficiently processed, and current ash waste accumulates and occupies huge areas, which removes them from land use. Knowledge of the chemical composition of the ash will allow it to be used to obtain building materials. The purpose of this work is to study the properties of ash and slag waste during the burning of coal from the Ekibastuz deposit in Kazakhstan, to assess them as a source of environmental pollution, to determine the possibility of obtaining demanded building materials from them. Research methods. To determine the phase composition of the studied material, an upgraded diffractometer DRON-3M on CuKa radiation with software was used. Radiographs of the sample were obtained in the range of 2° (angles) from 10 to 70°. The chemical composition was determined using an energy dispersion spectrometer “EDX-8000”. Micrography of fly ash was taken on a scanning electron microscope Superprob-733. Research materials. Ash and slag waste from the burning of coal from the Ekibastuz deposit in Kazakhstan. Research results and discussion. The physical characteristics of ash have been established: specific surface area – ~200 m2/kg, true density – 2.1 g/cm3, bulk density – ~780 kg/m3. Fractional composition: the highest content of particles with a size of 100 microns (25.8%), 80 microns (12.12%), 50 microns (21.46%) and 45 microns (21.38%); at the same time, unburned carbon is concentrated in large fractions, glass phase – in small ones. Analysis of the chemical composition of Ekibastuzky ash allowed to find out the composition of coal minerals. The main components are silicon and aluminum oxides, and there is also a large amount of iron oxide. Knowledge of the chemical composition of ash allows it to be used in the production of building materials. Conclusion. The results of the conducted studies have shown the possibility of using ash and slag waste as secondary raw materials in the construction of road materials in order to reduce the anthropogenic load on the environment.