Charging Hot Metal in Electric Arc Furnaces (EAF’s): Reducing Cost Structure and Expanding Grade Horizons

Publication Author : Tanmoy Mandal, A. Maity, S. Chatterjee, A. Mukherjee
Publication Year : 2018
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Publication Theme : SQJ Vol 47 No.2
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INTRODUCTION


The latest technology in steel making is to substitute BOF technology with EAF route for steelmaking as raw material flexibility, better quality, higher scrap recycling and increased energy efficiency are realized. With the new advancements in EAF and process technology, in many parts of the world, there is a strong tendency in the mini-mills to improve the quality range to produce flat products that compete strongly with integrated mills.


There are several key opportunities that can be explored by mini-mills and EAF based steel makers to further improve their cost competitiveness, quality and flexibility of operations based on geography, price dynamics and product goals. New charge mix combinations to produce higher quality steels at competitive mini-mill cost structures are possible by converting the conventional EAF operation into a flexible one. Capex and opex lite flexible EAF based mill configurations with optimal combination of scrap, Direct Reduced Iron (DRI), Hot Briquetted Iron (HBI), Hot Metal (HM) can further lower the cost for standard long and flat steels in Asian countries, like India, while enabling the production of higher quality flat steels in North America at mini-mill cost structures. A predictive charge mix model applied to such flexible configurations optimizes production costs taking advantage of the volatility of raw material prices, material compositional constraints and grade goals and can improve profit margins, quality and competitiveness of such hybrid EAF operations substantially.


The current work elucidates a methodology for determining economically attractive and technologically feasible
configurations and dynamically computing the associated charge mix model for different price regimes. An integrated approach encompassing mass and energy balance modeling, flexible design, statistical simulation and economic modelling was used to develop the framework for Charge Mix Optimizer. This optimizes the production cost elements taking into account volatility of raw material prices, operational constraints and grade goals. We substantiate the assertions in our framework using comparative analysis that outlines the selection of the most cost-effective option based on charge mix models, capital investment requirements for flexibility, cost of flexibility and key operational parameters based on data from customers in North America and Asia. We further evaluate the techno-economic feasibility of producing higher quality and auto-grade flats using one such flexible design option, which can be attractive for mini-mills.

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