Developing an evaluation model for cost saving initiatives on sinter plants

Abstract

Ever-rising operating costs are placing the South African steel industry under significant financial pressure. Energy costs are increasing at a rate higher than inflation which makes it extremely difficult for local steel producers to remain competitive in a market which is flooded by cheaper imported steel. Energy cost savings initiatives such as improved efficiencies, load shifting and peak clip projects have already proved to reduce the operating costs of mines in South Africa. The implementation of similar energy cost savings projects in the steel industry can assist to alleviate the operating costs of steel plants. With their main focus on production, plant personnel seldom have the time and opportunity to concentrate on the reduction of energy costs. Steelmaking is a complex process with several concurrent and integrated systems. Numerous studies focussed on the larger downstream energy consumers in the steel production process and very limited consideration has been given to the raw material preparation processes. Amongst the many raw material preparation processes, literature has indicated that the most significant energy cost savings opportunities exist on sinter plants. The main objective of this study is to investigate the potential for energy cost savings opportunities on sinter plants in South Africa. Literature on existing energy savings opportunities were thoroughly investigated. An evaluation process was developed to identify those that are most feasible for the South African environment. A specific South African sinter plant was selected as a case study. A list of all potential cost saving opportunities was compiled for evaluation against a set of predefined criteria as defined in the various evaluation matrices contained throughout this study. The evaluation matrices provided inputs to a defined initiative rating function and all potential alternatives were rated. The most feasible cost saving opportunity was found to be the alignment of the sinter production schedule with that of the Eskom time-of-use (TOU) periods. Large fans driven by energy intensive electrical motors are used during the sintering process. A developed simulation indicated that it is possible to schedule production away from peak TOU periods thereby reducing the overall electricity cost. Pilot studies were conducted to investigate the possibility of performing a load shift. An electrical consumption load shift between 9 MW and 14 MW was achieved during these studies. A load shift of 9 MW is equivalent to an annual cost saving of R10 million. The pilot studies therefore proved that electricity costs on sinter plants can be reduced by optimising production schedules.