Injection of auxiliary reducing agents into the blast furnace - effects on metallurgy and costs

摘要

The injection of different auxiliary reducing agents into the tuyeres of a blast furnace has fundamental effects on the metallurgical reactions and on the total energy and material balance of the process. For a comparison of the different auxiliary reducing agents it is of utmost importance to determine the changes of all balance values and to take all effects on the hot metal costs into consideration with an overall approach. The assessment of the different auxiliary reducing agents is realised by calculations with a blast furnace simulation model. So called "exchange values" and "correction factors" for different process parameters are not input values but results of the calculations. Especially the effects of the injected auxiliary reducing agents on the raceway adiabatic flame temperature (RAFT), additional oxygen need and hot blast amount, shares of direct and indirect reduction, coke consumption, composition and energy content of the top gas and productivity of the furnace cause considerable changes of the balance results and therefore of the hot metal costs. All ideas for injection of auxiliary reducing agents are to be related to the existing or planned infrastructure of the total integrated mill and with the material and energetic circumstances. Considering the prices for all input materials and the estimated prices for the products of the blast furnace different solutions are possible to realise, in dependence on the circumstances, an optimisation in the process and plant technique, a minimisation of the hot metal costs and therefore integrated approaches.