The environmentally conscientious disposal of special wastes which cannot be simply dumped, and which are incombustible or poorly combustible, calls for the thermal treatment of these materials at high temperatures.
If the wastes have only a low heat value or are not at all combustible, the addition of fuels is necessary, to make the "combustion" (thermal degradation) of the waste material that is to be treated at all possible.
Usually the waste is put into a rotary kiln and, with the addition of fuel and air, is thermally processed (burned) such that the remaining slag can be safely dumped. The exhaust gases produced by the combustion are cooled in appropriate flue gas units to produce steam. Dust and other impurities (SO.sub.2 etc.) are removed from the flue gas in scrubbers or flue gas washing apparatus connected to the exhaust.
This kind of waste elimination is energy intensive and costly, especially as regards the exhaust gas washing or scrubbing. Furthermore, the known methods depend on the production of steam in order to make economical use of the waste heat from the rotary kiln and the afterburning chamber.