This thesis is built on the remarkable achievement of my predecessor Mag. Dr.mont Lytvynyuk, who has developed the fundament of the current converter model. The focal point of this dissertation is the verification of all previously established functions. The thermodynamic and kinetic reaction model was confirmed with respect to the different implemented melting- and dissolution models of the charged materials as well as to the used mass and energy balance. Furthermore, validation was carried out using industrial data provided by voestalpine steel Donawitz GmbH. The outcome led to two further converter campaigns where a defined scrap sort was taken to eliminate one key factor for end values of phosphorus and manganese in crude steel. In addition, the model’s behaviour was monitored at different converter practices (lance height, scrap sorts, etc.) and geometry (diameter of the bath, number of purging plugs). For that purpose, data supplied by voestalpine steel Linz GmbH was utilized. The outcome of the validation revealed certain weaknesses of the model. The major development is the semi-empirical mathematical formulation of the reaction area between slag/metal/gas phases. The following influencing factors are included in the improved model: the pressure after the control valve, nozzle geometry, surface tension, densities, and viscosities of metal and slag phase, diameter of droplets, residence time as well as many more. Additionally, 4500 pseudo-ternary phase diagrams were calculated in FactSageTM with the components SiO2-FeO-CaO-(0-40wt.%)MgO-(0-40)wt.%MnO-Fe. They are applied to determine the saturation concentration of CaO and MgO in the slag, which is important for the calculation of the driving force of the dissolution process. Although the precisely data bases is the choise of stable phases crucial for the calculation results of the saturation lines. Based on this uncertainness further experiments has to be done to verify the calculated diagrams. To assess the dynamic mass transfer coefficient of CaO a new examination method was established. Furthermore, a pre-processor model was programmed to simulate the time before the blowing process starts. Whereas the focus lays on the reaction of the slag from the last charge and on the behaviour of scrap during hot metal charging.