Three reasons for a furnace electrical model

Nicole Sweeten


Many furnaces in the pyrometallurgical industry are heated by resistive heating. Electrodes are immersed in the slag bath and current is passed between them. The slag bath acts as a resistor in the electrical circuit and energy is released in the slag bath by Joule heating. This has proven to be a very successful way of operating furnaces for many years.

I thought I would start this series on electrical modelling by explaining why I think an electrical model can be so useful:

  1. Estimating the resistance of a new furnace is a key step in furnace design, and is used to size the required transformer. Transformers are expensive, and an incorrectly sized transformer can severely impede the furnace operation for its entire life. I have seen furnace designers still using empirical models for this purpose, even though modern tools and computing make it so simple to build a model of the electrics that I believe this should be standard practice.
  2. An improved understanding of an operating furnace could be of value to the operational team. Once you have an operating furnace, the measurements of current, voltage, resistance and power are available. It is difficult, however, to know parameters such as electrode immersion, arc length and electrode length because the electrodes are constantly worn away. Dip tests can be conducted to measure the length, but an electrical model could also provide insights and improved real-time estimates.
  3. Multiphysics modelling requires an electrical sub-model to estimate the location and rate of energy released in the furnace. A multiphysics model can be used to estimate several parameters, such as bath velocities and temperature distributions. A model could also be used to simulate the effect of changing furnace design or operating parameters such as slag bath depth, electrode immersion, furnace diameter, taphole location etc.

If you have questions electrical modelling of furnaces, please contact us. Also keep an eye out for follow-up blog posts, and the paper on modelling of the electrics in a 3-electrode AC furnace we will be publishing soon. You can comment below, contact us on the social media links, fill in a contact form or send us an email. We would love to hear from you.

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Johan Zietsman


We are looking forward to exploring, discovering, and learning together as part of our drive to empower teams in our industry. In the past, we hosted Thermo Week, during which we focused on thermochemistry. Pyro Week has a broader scope, to address more of the needs that we have identified in our pyrometallurgy community.

Johan Zietsman


We are grateful to welcome Charlotte Hollenbach to our management team from 1 February 2022. You are already making a difference since you have joined, Charlotte, and it is great to have you in our team. We look forward to making a real difference together into the future. A warm welcome to Ex Mente.