The effect of temperature and formulation (relative volumes of the gas phase) on phase and chemical transformations in the MgO – C – H2O – air system at 298 – 2400 K is considered using methods of thermodynamic and physicochemical simulation with a view to using carbonized periclase refractories under industrial conditions. Temperature ranges for stable existence of refractory phases and formulation ranges (for the gas phase) with allowance for different chemical homo- and heterophase interactions are determined. Effects of temperature, concentration, and pressure of pore gases (CO2, CO, CH4, H2O, H2, etc.) on the bulk material and effects of the carbon component, porosity, intrinsic and atmospheric moisture on gasification processes are considered in terms of a theoretical simulation model.