Influence of blast-furnace process thermal parameters on energy and exergy characteristics and exergy losses

The technology 'blast furnace-converter' dominates at present in the production of steel all over the world. Therefore, the blast-furnace process is continuously being improved, among others, by raising the thermal parameters, such as temperature and oxygen-enrichment of the blast, as well as the addition of auxiliary fuels. The changes in the consumption of coke go together with changes in the consumption of blast, the production of top-gas and its consumption in Cowper stoves, as well as the production of electricity in the recovery turbogenerator utilizing the waste exergy of the top-gas due to raised pressure. Related to a unit of pig iron production, these values are called energy (exergy) characteristics of the blast-furnace plant. They serve as a quantity measure of the thermal improvement of the blast-furnace process. This paper presents an algorithm of the process exergy analysis of simulative investigations of the influence of increased thermal parameters on the thermodynamic perfection of the process and the blast-furnace plant. This algorithm bases on the theoretical empirical balance method of the 'input-output' type. By means of this algorithm the influence of increased thermal parameters of the process not only on the saving of coke but also of the blast can be determined, as well as of the production and composition of top-gas, the consumption of top-gas in the Cowper stoves and the production of electric energy in the recovery turbine. The blast-furnace process displays a high exergy efficiency, whereas the process of compressing and preheating the blast is characterized by rather high exergy losses due to the application of the combustion process. It has been shown that the internal exergy losses in the blast furnace are comparable with the exergy losses in the processes of compressing and preheating of the blast. Calculations were carried out for a modern Polish blast furnace with a volume of 3200 m(3). Copyright (c) 2005 John Wiley & Sons, Ltd.