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.