Tantalum is an important metal in many different industrial fields. The refractory metal finds its main applications in electronics, semiconductor technology, is used in capacitors and as an alloying element. The mining of tantalum ore (coltan) takes place for example in Central Africa. However, the extraction of metal from conflict-affected countries is not acceptable. To guarantee a conflict-free supply chain, certification systems have been established. Furthermore, an alternative route of winning Tantalum is needed, to ensure the metal supply and reduce price fluctuation. As a secondary source of refractory metals, recycling processes have to be increased. However, in some ways it is not that easy, for economic or technological terms some problems have to be solved. In Laufenburg (Germany), H.C. Starck established a recycling process that produces a synthetic tantalum concentrate (SynCon). The aim of this master thesis is to optimize the SynCon production process, due to improving the metal/slag separation by the use of additives. This tantalum concentrate is obtained from the following raw materilas: tin slags, sludges and powdered production waste. Finally, after three thermal process steps the SynCon emerges. In order to increase the tantalum yield and to reduce the energy consumption, the melting behavior of slags considering various additives is examined. Those substances are tested by adding them to a synthetically slag based on industrial composition and compare the results with a processrelated one. By using additives, the melting behavior of the slags should be improved in relation to melting temperatures. For the slag analyses a hot stage microscope is used to test the flow behaviour. The additives considered in the experiments are CaF2, Na2O, K2O and LiO2.The results of the microscope show a clear influence of at least one component. This additive (LiO2) is used in further smelting experiments. Three melts are tested according to their settling behaviour. Two are synthetic melts, one includes the additive, and the third is a special mixture, similar to the process one. The comparison of those melts shows that there is a better settling behaviour by using the LiO2 in the smelting process.