Behaviour of trace elements in modern rotary kiln systems - effects on emissions, CO₂ separation systems and the product

During the production of cement clinker, so-called fuel- and raw material-related trace element emissions are generated by combustion and thermal conversion processes. The proportion of trace elements that is not emitted is discharged from the process with the product, the cement clinker, or in the form of process dust. In order to be able to calculate and evaluate this distribution in advance, extensive material balances must be carried out. This makes it possible to estimate in advance what influence the use or replacement of individual fuels and raw materials will have on emissions and product quality.

So far, so-called transfer factors, which were published by the Ministry of Agriculture and Consumer Protection NRW in 2000, have been used for estimation and evaluation. However, the transfer factors are outdated due to the use of modern flue gas cleaning technologies and the increased use of bypass systems and need to be updated. In addition, many plants use other emission reduction processes such as SCR systems for NO_x reduction or the injection of activated carbon to reduce Hg emissions. These emission reduction methods have a significant impact on the trace element behaviour in the process. These emission reduction methods have a significant impact on the trace element behaviour in the process. The use of new substances with higher trace element contents is made more difficult by the use of the old transfer factors. Conversely, due to the recycling and reutilisation rate of waste required by the German Circular Economy Act and the need to use materials with a low CO₂ footprint, there is an urgent need to increase the use of processed fuels and raw materials.

The old transfer factors are to be updated as part of the project. In addition, the trace element content in the raw gas is important for the design of CO₂ capture plants. The SME-rich processing and supply industry as well as the cement industry and a large number of small expert offices and plant manufacturers will benefit in particular from the updating of the transfer factors.