Danieli's Green Steel Vision: an environmentally sustainable approach for steel industry development

摘要

The current economic crisis and growing environmental issues have led the steel industry to face the simultaneous effects of low demand and production overcapacity in a globalized steel market, whilst confronting high energy prices and the need to comply with the green economy. In this context, energy efficiency becomes a key objective to gain both cost savings and the reduction of greenhouse gas emission.In particular, heat recovery from waste gas of the electric arc furnace (EAF) represents one of the greatest opportunity to reduce the consumption of primary energy and C02 emissions in steel industry. It has been estimated that 25% - 30% of the total energy provided to the steelmaking processes by means electric arc furnace is lost by exhaust gas, named also off-gas or primary fumes. The most common heat recovery systems from off-gas are those that involve the pre-heating of scrap. However, the diffusion of scrap pre-heating systems is limited by economic reasons (i.e. higher scrap cost, additional investment and maintenance cost) and environmental issues (dioxins formation due to contamination of the scrap by organic materials). The modern steel plants can overcome these issues adopting a new design approach, based on the integration between fumes cleaning and heat recovery functions, of the fumes treatment plant (FTP). The heat of the off-gas, if recovered and converted into electrical power, can make the whole fumes treatment plant autonomous from the electric point of view, thus making it a "Zero-Energy FTP". This means that it is possible to avoid the operational costs of the FTP, thus increasing the steelmaking competitiveness and its environmental performance. In order to achieve the "Zero-Energy FTP", it is necessary to overcome the challenging difficulties given by the high variability of off-gas temperature. In the following, the solution developed by Danieli&C. Spa and University of Udine will be explained and its first realization in the ABS Spa steel plant will be shown.