A case study on raw material blending for the recycling of ferrous wastes in a blast furnace

The utilisation of ferrous wastes in a blast furnace is a well established recycling process to cope with the enormous amounts of ferrous residues in the iron and steel industry. The further input flows of this process, that is especially coke and fluxes, as well as its output flows, that is pig iron and by-products, are highly dependent on the blending of the ferrous wastes while they differ highly in the revenues gained for the treatment and their chemical composition. So far, no planning approach exists for the blending of the residues on the operational planning level that models the dependency of the costs and revenues on the raw material blend and the thermodynamic reactions in the recycling processes adequately. Therefore we present an approach for this operational production planning problem focusing on an integration of such a sufficiently detailed modelling of the underlying metallurgical processes into the planning model. The basis of our approach is a thermodynamic simulation of the processes. From this simulation we derive linear input-output functions for the relevant material and energy flows by using multiple linear regression. These input–output functions form the core of our blending model developed for the planning task. The model is implemented as an integrated decision support system. Exemplary application results are given. These results validate the approach and show that ecological the economic optimisation leads also to results which are advantageous in terms of resource efficiency and emission reduction. Though developed for a specific recycling process, the methodology can be transferred to other metallurgical (recycling) processes, as well as other parts of the process industries, and is therefore of high relevance.