In this work a C++ based fast calculation model, named ¿FastCalc, for a metallurgical process with the metal recycling and a detailed OpenFOAM based Computational Fluid Dynamics (CFD) model for the converter heat up step considering structural mechanics has been developed. Modeling of the metal recycling using standard CFD methodology for the required reactive multi-phase system with the turbulent combustion and the characteristic process time is computationally extremely expensive. Development of the digital twin with the possibility to control and variate influential process parameters in the real time needed a combined approach using numerical solutions in conjunction with statistical approach and empirical models for the relevant physical phenomena occurring in the system. In the fast calculation concept energy input due to combustion and the flue gas composition in the system are determined from the minimum principle of the total Gibbs energy in the equilibrium state. Energy transport to the solid and the liquid phase are modeled using experimentally approximated transfer coefficients taking into account temperature dependency of the relevant physical properties. Contribution of the radiative heat transfer for the participating gases is considered using empirical, concentration, pressure and temperature dependent model, with the surface to surface model for the radiative heat exchange between the walls and the metal/alloy phase. Furthermore, implemented model incorporates the heat loss during the charging, heat conduction in the refractory material and the heat source and the chemical composition influence from the organic contaminate. Converter preheat treatment step in the real time processing scale is generally still challenging for the detailed geometrically resolved industrial scale CFD modeling, which is of necessity for the identification of the temperature profile in the refractory material and corresponding flow induced local maximum for mechanical and thermal stresses. A multi-region approach with a turbulent combustion in the fluid phase and a heat transfer combined with the structural mechanics for the complex arbitrary real scale geometry with the chemically limited prevailing time steps needed an innovative conceptual approach. For that purpose numerically efficient flamelet model with the tabulated chemistry, decoupling complex chemistry structures from the dynamics of the turbulent flow through the pre-processing step has been combined with the multi-region conjugate heat transfer. Multiphysics with structural mechanics and fluid dynamics interaction are solved within the Finite Volume (FV) approach with adequate coupling of the relevant physical properties on the region interfaces. Stress-strain relation with additional thermal stresses, assuming linear elastic continuum mechanics, is modeled using isotropic Hookes law.