A unique technology of recycling reclaimed waste capable of solving a number of environmental problems has been invented by scientists from the Faculty of Geology of Voronezh State University.
The project of VSU geologists under the leadership of Viktor Nenakhov, the Dean of the Faculty of Geology and the Head of the Department of General Geology and Geodynamics, "The technology of recycling screenings at the Pavlovsk mining and processing works aimed at increasing their market demand and reducing environmental damage" has taken second prize in the contest of Innovation projects of Voronezh State University in 2014–15. The project's author is Dmitry Shevtsov, a postgraduate student at the Department of General Geology and Geodynamics.
The scientists have focused their research on waste material consisting of stone screening dust that has formed as a result of the Pavlovsk mining and processing works. VSU geologists studied its mineral composition and used the data to develop a new innovative technology for its recycling.
'At present the amount of accumulated stone screening dust is about 30 million tonnes. It is made up of granite crush less than 5 millimetres in size. What's more, about one million tonne of stone screening dust is produced annually which has an enormous environmental impact. We started our recycling project to mitigate such impact,' said Dmitry Shevtsov.
The recycling technology developed by the VSU scientists is based on distributing the screenings into 3 fractions depending on the size of particles: the first fraction is from 5 to 2.5 mm in size, the second – from 2.5 to 0.2 mm and the third – 0.2 and smaller. The first and the second fractions can be used as the final product.
The first fraction is mainly used as a filler in asphalt. Considering the amount of road works in the region and the country as a whole this product has an extensive market. Additionally, the demand for the product increases considerably between October and April as it is used in dealing with icy conditions. One of the advanced applications of the fraction is in roofing, which can be explained by the development of wooden house building. Another application of the fraction is man-made stone production.
'The second fraction is of interest to producers of reinforced concrete products which traditionally use glass sand as a filler. The experts believe that the sand manufactured using the second fraction has better physical and mechanical properties (with 40% increase in rigidity), it also has a better hardening rate,' says the project's author. 'Vibropress product manufacturers (paving slabs, road kerbs, etc.) and dry building mix manufacturers (sand-cement plaster facade mixes, poured flooring, tile grouts, and tile adhesives) have also have shown a lot of interest in this type of fraction.
The third fraction is the most valuable component of the screening. It includes such minerals as black iron ore, titanic iron ore, rutile and zircon. Titanic iron ore and rutile are materials that are in high demand by manufacturers of titanium sponge and titanium white. Titanium sponge is used in the chemical and metallurgy industries and is a strategic material. Titanium white is mainly used in paint production. Today it is mostly imported. For example, titanium white for the Semiluki varnish and lacquer plant is imported from China. Many plants receive ilmenite concentrate from Ukraine and Australia. Zircon concentrate is of very high value; its price on the world market is about 2–3 thousand dollars per tonne. The Nuclear industry and rocket and missile engineering are based on zircon processing end products. The third component of the fraction is the highly prized black iron ore which is used in iron metallurgy and the electrochemical industry. To ensure waste free production the remains of the third fraction can be used to produce slag wool.
At a rough estimate, the value of screening supplies stored by the company is about 50 billion roubles.'
'Heavy minerals are strategically important materials,' says Dmitry Shevtsov. 'For example, zircon mining in Russia amounts to about 5 thousand tonnes annually. However, there is a much larger demand for it – about 150 thousand tonnes annually and by 2020 it will have reached about 600 thousand tonnes annually. The lack of material has to be compensated for by imports.
This means that the project has great potential in the context of the present foreign trade difficulties. Full-scale introduction of this innovative technology will contribute to solving a number of environmental problems by means of reducing waste production, and reduce the shortage of strategically important materials requiring import. High-level processing of each screening component ensures very high profitability of the developed innovative technology. The fact that the technology can be used not only at the Pavlovsk mining and processing works but at other production facilities is also of great importance.