Abstract
The competitiveness of the South African ferrous foundry industry has been a subject for debate in recent years, mainly driven by a plethora of challenges, import leakages, rapidly rising energy costs exacerbated by low energy efficiency, poor raw material conversion efficiency, lack of skills development and training, costs of quality and availability of steel scrap. A number of ferrous foundries operating in South Africa shrunk by 22% between 2007 and 2014, a trend that signifies the death knell of the local foundry industry. The high cost of electricity among other pertinent issues affecting the foundry industry, has been cited as the main reasons resulting in the closure of many l foundry operations in South Africa. The main aim of this thesis is to increase the energy efficiency of a steel foundry plant through foundry energy mapping and electric arc furnace modelling. The study addresses three important objectives. The first objective of the study is to conduct a pre-assessment of the foundry using the cleaner production Quick- E-Scan methodology which entails a review of the current processes and energy usage patterns within the plant and a detailed analysis of options available for improvement. The second objective of the study is to conduct energy measurements for the purpose of energy accounting of different production area and processes, and last, the approach to the mathematical energy modelling for a three-phase alternating current (AC) electric arc furnace and the overview of the different models applicable in the modelling of energy consumption in the scrap-based electric furnace process. After a careful analysis of a pre-assessment audit, it was found that the foundry has a great potential of energy saving especially looking at the addressed quick win solution and opportunities such as skills development and training which included linking one's key performance indicator (KPI) to energy and the emphasized importance of sub-metering. There was an understanding of Significant Energy Users (SEU’s), but no data existed on the historical consumption, of which measurements were done to clarify and complete the electrical energy balance. This activity found that the furnaces had the highest consumption amounting to 98%. The energy consumption in an EAF was estimated based on the statistical energy consumption and thermodynamic (first law) energy models. Through the results obtained from the model, the thermodynamic model approach was recommended for application at the foundry and therefore it can be concluded that the process modelling incorporated into the melting process is appropriate for use in foundry practice.
M.Tech. (Metallurgy)