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By-product Management

Burning the coal powder leaves ash as a by-product in the furnaces. The larger particles of coal burn at the bottom of the furnace and their remains form into slag. In the process of desulphurisation of the flue gasses, we separate wet gypsum suspension as the by-product. After removing these by-products from the main process we mix them to produce a material with an earth-like moisture consistency that is used to remedy mining related landscape deformation.

The yearly quantities of produce of the furnaces and desulphurisation that we use to remedy mining related landscape deformation are the following:

  • Ash: 680,000 tonnes
  • Slag: 60,000 tonnes
  • Gypsum suspension: 350,000 tonnes

The ash from the electrostatic filters of generating units one, two, three and four is transported by means of pressurised air and collected in a 2,000 cubic metre silo above the mixing station. The gypsum suspension flows to the mixing station from the produce reservoir of the desulphurisation facility of generating unit four. There are two mixers in the mixing station, one working, and one on standby. They mix the ash and the gypsum suspension at the proper ratio. The dosage of the gypsum suspension is controlled by a regulating valve and depends on the available quantity of ash. In case there is a shortage of ash, the gypsum is dehydrated on the vacuum transport filter to achieve a final product with an earth-like moisture consistency and the stabilized produce that is fit for dry transport. The mixer dumps the produce onto a rubber conveyor belt and ground slag is added from generating unit four. This conveyor belt then transports the produce to temporary deposits, where it is loaded onto trucks. Customised heavy trucks drive the material to its final destinations.

An identical system for preparation and transport of the stabilized produce is in operation on generating unit five. Here we also add finely ground slag on the conveyor belt. The slag and ash from all the generating units mixed with the waste from water preparation can alternatively be transported hydraulically by pipes, or driven by special pumps to the sites needing filling material. Transport of the ground slag from units 1-3 is done exclusively hydraulically. A special, closed water circuit is in operation for this purpose.