The second life of ash dumps

Analysis of situation concerned with coal ash TPP utilization demonstrates double nature of existing problem. On the one hand, high-quality ash market is undersaturated, the suppliers are overpricing, but there is still lack of ash. On the other hand, the ecologists tell about vast areas allocated for ash dumps, about millions of tones of needless toxic wastes. How is that possible?

In fact, there is no contradiction; this issue is about different kinds of ash. The one being in demand and in lack of is fly-ash. It is the ash that the smoke coming out of the burners carries away. It is fine, dry, and rather clean. It is easy to work with and to be brought up to the standards requirements. This kind of ash has the only one disadvantage – it is lacking. The smoke carries away at most 10% of ash particles, while the rest of ash goes to the ash dumps. Most often the flow of water is used for this purpose – the so-called “ash removal”. But even if the ash was removing by dry method, it is watered at the ash dump. The result is a different sizes particulate mix, unstable and very wet. It cannot be conditioned – brought up to the standards requirements. And it is very expensive and complicated to dry. So we either have to endure the ash dumps or try to shove this ash and slag mixture somewhere – for example, into the old mines.

But ash and slag can be converted into many interesting products. These are fly-ash aggregate, ash sand, and conditioned ash itself. And also ferrosilicon, magnetite concentrate and coke – as a bonus. The most important is to dry ash and slag correctly.

The technology of ash and slag drying that we use is based upon good old drying drums being significantly modified. Their implementation allows regulating easily the time material stays in the furnace space, the temperature, and the amount of smoke gases. As a result at the output we get average (due to mixing in the drum) dry ash and slag, loosened by air blasts. In such a “fluffed” condition the ash and slag can be easily divided by physical properties: size of particles, their density, magnetic and electrical characteristics. That’s why immediately after drying drum we install block separators, evolving the fractions customers demand from the flow.

Experience of this technology application demonstrates that evolving fractions are characterized by high purity, stability, and homogeneity. And all obtained products find their firm customer. So, our ash recycling technology is completely wasteless – after its application in place of the “lunar landscape” of the ash dump an even area remains. It is suitable for construction, agriculture, recreation, and many other interesting applications. Taking into account high prices of land in the densely populated Northern Europe, increase in cost of the land plot while its transformation from the ash dump into the green loan is one of the most rewarding bonuses in ash recycling.