The main economically affordable and promising energy source, extracted in the EU, is coal. Therefore, the largest thermal power plants and GRES power plants are coal-fired. At the same time, the coal power is among the most environmentally hazardous, because coal has the maximum quantity of wastes per unit of produced energy. In particular, after coal is burned ash and slag wastes (hereinafter – ASW) remain in the quantity which exceeds 1/5 of the amount of source coal and in absolute figures for the EU reaches 1 million tons per year. Except the problem of land allocation for ash dumps, ASW represent serious environmental hazard because they contain soluble substances (including the salts of heavy metals), which are washed away by rain and penetrate into the groundwater aquifers, poisoning them. Hence, ash dumps are the permanent source of water and soil pollution, leading to inefficient use of land resources and reducing market value of land, buildings and structures around. This proves the relevance of the problem of ASW disposal and the need to find new areas of their use.


The main consumer of ASW is traditionally the construction industry, but the interest of builders is mainly limited by fly ash obtained by dry disposal scheme, as it is characterized by relatively stable properties, delivered in dry form, and contains a little coal which is highly undesirable impurity in concretes and mortars. ASW obtained by wet disposal scheme is hardly used because of an unstable granulometric composition, high humidity (200%) and a significant (up to 25%) coal content. Considering that the volume of such ASW 10-15 times exceeds the volume of fly ash, we can conclude that at the most 7-10% of produced ASW are utilized. Tightening of environmental regulations on the content in building materials such elements as chromium, mercury, cadmium and other toxic substances contained in the ash, generally endangers the very opportunity of applying unprocessed ash in the construction.

At the same time, the concentration of coal, ferrosilicon, aluminum oxide, and some other elements and compounds in the ASW is sufficient to consider them as raw materials for production of valuable industrial and energy products. One tone of ASW on an average contains 500-550 kg of silicon oxide, 200-250 kg of aluminum oxide, 100-200 kg of high quality coal, 50-70 kg of ferrosilicon. Some ashes have industrial concentrations of titanium, vanadium, chromium, germanium, rare earth elements.

Our company develops and implements in industry recycling technologies for ash and ASW of energy and metallurgical industry. The main feature of the proposed ASW-processing technologies is complex extraction of a wide range of products. This distinguishes our proposal from other general solutions focused on getting only 1-2 target products that is unprofitable for such complex row materials as ASW.

During the processing of ASW according to the proposed scheme marketable products are refined from impurities of heavy and rare metals. The latter are transformed into insoluble (environmentally friendly) compounds and can be further utilized.

Conceptually, the recycling process we offer can be divided into 3 stages:

  1. Conditioning of disposed ash and slag. The technology includes ash and slag drying and classification based on fractions size (broken slag, slag sand, ash). The resulting materials are delivered to customers in the construction industry.
  2. Separation of ash and slag. In addition to drying and fractionation the process includes separation of associated valuable components by physical methods (magnetic, gravity and flotation separation). Technology allows getting additionally carbon, iron oxide, ferrosilicon and micro-sphere.
  1. Deep processing of ash. The technology implies the complete decomposition of ash and slag or some of its components by pyro- and hydrometallurgical methods with division into basic oxides and separation of associated valuable impurities. Most operations are performed in the water medium, which eliminates dusting and aerosol emissions. The technology is essentially waste-free as all the final products have market value and target consumers.

The transition from the lowest stage to the highest allows increasing significantly the value of producing products as well as the processing efficiency (see table).

Marketable products produced at every stage of ASW processing



Output, mass %

Range of application

Price, €/t

First stage(investments about 1 000 000 €)

  broken slag 20…30 aggregate for concrete 15
  slag sand 20…30 aggregate for concrete 20
  fly ash 40…60 active admixture to concrete/cement 40
Selling price of processing products of 1 ton of ash 30

second stage (investments about 5 000 000 €)

  broken slag 20…30 aggregate for concrete 15
  slag sand 20…30 aggregate for concrete 20
  fly ash 40…60 active admixture to concrete/cement 40
  coal (graphite, coke) 5…15 return to TPP 50
  ferromagnetic particles 5…10 metallurgy, cement production, 70
  ferrosilicon 5…7 metallurgy 350
  micro-sphere 0,01…0,05 special fields 300
Selling price of processing products of 1 ton of ash 70

third stage (investments about 10 000 000 €)

  coal (graphite, coke) 5…15 return to TPP 50
  ferrosilicon 5…7 metallurgy 350
  micro-sphere 0,01…0,05 special fields 300
Fe2O3 iron oxide (III); (hematite) 7…10 red pigment production 1000
Fe3O4 iron spinel; (magnetite) 7…15 black pigment production 1000
SiO2 amorphous silicon oxide ; (microsilica; silicafume;
precipitated silica)
50…70 admixture to mortars/concretes, adsorbent, silicate block component 2000
Al2O3 amorphous aluminum oxide; (alumina) 10…25 concrete hardening accelerator, aluminum and corundum production 2500
TiO2 titanium oxide (titania, titanium white) 1…5 catalyst, white pigment, titanium production 3000
  minority oxides: CuO, NiO, V2O5, Cr2O3, WO3, rare earth elements до 5 raw material for nonferrous metallurgy; contain valuable and rare elements  
Selling price of processing products of 1 ton of ash 1800

To date, our company has built 3 ash processing plants under the first stage that operate successfully, 1 plant operating under the second stage technologies, and the plant using the third stage technology is being designed.