The testing of the environmental compatibility in the use of different secondary fuels and raw materials is in the forefront of many studies. The inputs of trace elements into the kiln system via secondary materials can increase or decline depending on the origin of the wastes. The trace elements are predominantly bound into the clinker. Only the highly volatile element mercury is relevant for emissions, and the input of this into the kiln system is limited by restricting the content in the materials used.
So that secondary raw materials can be used in an environmentally safe way in the cement industry, the effect of the raw materials and the mode of operation of the kiln on the emissions of individual organic compounds was investigated. The studies were performed inter alia with a continuously measuring mass spectrometer on kiln installations. They show that no marked changes in the quantity of individual organic compounds released occur as a result of the substitution of natural raw materials by secondary ones. Raw materials which contain a high proportion of volatile organic components can be added at higher temperatures such as in the region of the calciner or kiln inlet. In this temperature range, the organic compounds are fully converted.
