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Investment Evaluation of an Integrated Steel Mill using Multiple Criteria

A conventional steel manufacturing process generates considerable amounts of reject streams and secondary raw material. These streams are either recycled back to the process or treated as waste. Recycling affects negatively on the production yield and on the controllability of unit operations. Waste represents considerable cost unless utilized in another production process as raw material. In these streams, there exists a potential to use the chemical elements more effectively. Therefore, it might be interesting to find an economical technical solution to collect the streams and increase steel production. Investments on process equipment are typically evaluated using conventional economic figures, like payback time, Net Present Value (NPV) etc. The problem with these practices is, that they consider only numerical aspects. Non-numerical and non-economical criteria are hard to cater to the evaluation. Still, they may affect on the investment profitability in the long run. Such criteria include environmental friendliness or the aspects of process integration. The article presents a comparison of a conventional steel manufacturing process with one reject stream processing alternative. A target in the process modification is to optimize the use of material and energy within the site. The comparison is based on a balanced set of criteria that affect on the efficiency of an investment. The use of these criteria is a part of the new methodology that has been developed to evaluate investments on integrated process sites. In addition to the criteria, the complete methodology includes: 1) connection of company’s strategic issues into technical design and decision making, 2) optimization of the process and calculation of process potentials (differences in the performance values between the existing process and the modified process) through the use of process integration methodologies and 3) use of decision-making aids. The research is a part of Finnish National Technology Program, “Process-Integration 2000–2004”.