Melting - pre-study of models and mapping: physical
modeling of scrap melting

Abstract: A lot can be won by better use of the steel. For example the higher
strength the less material is needed and less material gives easier
transportation, less discharge and energy and need less resource. Scrap has
been used in steel industry for over a century.

This master thesis is a part of a European commission project
called “Control and optimisation of scrap charging strategies and melting
operations to increase steel recycling ratio”. Mefos is a partner of that
project and this master thesis contains the parts “Pre-study of models and
mapping” and “Physical modelling of scrap melting”.

Melting of scrap metal is of increasing interest to the metallurgical
industry since it allows the recycling of metals at a fraction of the
original production cost. This is in some way a new area, which is seen by
the results in the study. But in some areas this has been looked on, for
example in Japan and Canada there has been some interesting work on this
field. Some theories of melting are commented, and examples are given on
the enthalpy-porosity method, the conservation element/solution element
method and the homogenization theory.

This master thesis is presenting melting of scrap steel in an EAF, electric
arc furnace. The melting process is depending on the heat transfer from the
arc and the convective heat transfer in the liquid metal. Scrap metal
refers to either metal chopped from the end of ingots or compressed blocks
of used beverage containers. This means that the scrap is of various
shapes. The heat and mass transfer between liquid and solid phases results
in a complex problem. As soon as the melting begins the molten liquid drips
down toward the bottom of the furnace. Thereafter, the molten liquid level
rises while the height of the scrap metal decreases. The scrap is heated
both from the arc and the molten liquid at the bottom.

In the physical model the electric arc is simulated by a hot-air gun,
melting ice instead of iron scrap. The experiments in the physical model
are to be used as input in a CFD-analysis. CFD stands for Computational
Fluid Dynamics, and is a form of computer simulation.