Methods for identifying the material-recyclable share of SRF during co-processing in the cement industry

Solid Recovered Fuels (SRF) include non-combustible mineral components (e.g. CaCO3, SiO2, Al2O3) that are required as raw materials for producing clinker and are completely incorporated into the clinker during the thermal recovery of SRF. This paper discusses simple and practicable ways of finding the relative amount of SRF that may be utilised as raw material (given as the recycling index). For this purpose, the entire mineral content of SRF was determined as the ash content and its main components were identified using different analytical methods. • A fusion melt of the previously incinerated sample with subsequent measuring using ICP-OES and XRF as well as a total digestion of the incinerated and non-incinerated sample with subsequent measuring using ICP-OES/ICP-MS were applied. • The results showed a good agreement of all four analytical methods for the elementary oxides Al2O3, CaO, Fe2O3, SiO2, TiO2, P2O5 and MgO (relative deviation from 6.6 to 38.9%) and slightly higher deviations for K2O, Na2O and SO3 (14.2–96.0%). • It was also shown that different incineration temperatures (550 °C, 815 °C and 950 °C) have no effect on the result of the recycling index unless it is assumed that the recycling index equals the ash content.