Green steel refers to the strategy aimed at making the steelmaking process greener and more sustainable. But the trend towards increased sustainability within the steelmaking process is not without its difficulties, especially in understanding its thermophysical basics starting with sintering the iron ore or its sinter fines. Heat flow is controlled by convection, conduction and radiation. The most important material properties controlling heat flow in solids and between gases and solids are: Thermal diffusivity or thermal conductivity, specific heat and total hemispherical emissivity. These properties change with temperature.

There exist various customary measuring methods for heat conduction: either stationary methods, which provide thermal conductivity, or transient methods, which provide thermal diffusivity [1]. However, most customary methods cannot be used, because iron ores are very coarse and require a large sample volume for representative measurements. A simple measuring method has been tested that can be expanded to very large samples. The bulk material is deposited in a rotationally symmetric crucible. Thermocouples are placed in protection tubes at different heights, so that the measuring point is on the central axis. Further thermocouples are placed above the sample and in the middle of the crucible base. The set-up is placed in a furnace surrounded by a muffle of a refractory material and heated to the maximum temperature required. Different atmospheres could be applied for natural gas combustion, H2 combustion or pure Hydrogen atmospheres.

The heating of the fill is simulated in an FE model using the COMSOL software. The heat transfer between the crucible and the environment is taken into account by a Taylor expansion of the heat radiation. Good agreement is achieved. [2] The heat transport under natural gas combustion atmosphere in the bulk material is dominated by the heat radiation between the particles and therefore increases almost to the third power of the temperature.