Vienna University of Technology (Vienna, Austria):

Steinparzer T., Mag. Eng., Project Assistant, thomas.steinparzer@tuwien.ac.at

Haider M., Univ. Prof., Mag. Eng., Dr. Tech., Head of Research Area of Thermodynamics and Thermal Engineering
Gröbl T., Mag. Eng., Project Assistant, Institute for Energy Systems and Thermodynamics

Siemens VAI Metals Technologies GmbH (Linz, Austria):
Fleischanderl A., Mag. Eng. Dr. Tech., Vice President Technology Steelmaking, Minimill and Environmental Technology
Enickl G., Mag. Eng. Head of Energy Technology 
Hampel A., Mag. Eng. Senior Expert
Zauner F., Mag. Eng. R&D Project Manager

This paper deals with the possibilities of heat recovery systems for electric arc furnaces (EAF). Due to the lack of steam demand in mini mills the main target is electric power generation. Heat recovery plants based on saturated or superheated steam were considered. Therefore thermal energy storage systems are necessary. Different systems were compared to each other based on transient simulations using the commercial process simulation software APROS (Advanced PROcess Simulator).The use of thermal energy storage systems for heat recovery at steelmaking is feasible and reasonable from a technical point of view. Molten salt and concrete seem to be the most promising technologies for the generation of superheated steam in combination with a Ruths steam accumulator system. The energy recovery system using molten salt both as a heat transfer fluid and as thermal storage medium is very attractive. But this system is strongly affected by potential high-temperature corrosion phenomena. All in all heat recovery solutions for EAF have to be tailor-made and appropriate to the operation of each furnace. Next project step is the evaluation of different heat exchanger materials with regard to high-temperature corrosion on the off-gas side. Therefore an onsite pilot plant based on molten salt has been built. In addition, appropriate components for molten salt processing (e. g. pumps, valves, etc.) are evaluated in this pilot plant. The commissioning of the pilot plant was in April 2012. Screening of suitable thermal energy storage systems and media indicated even more sensible heat storage media. Options for heat storage are sand or carbon dioxide. For latent heat storage media the screening of phase change materials is being enforced.

1. Hampel, A.; Fleischanderl, A.; Enickl, G.; Zauner, F.; Steinparzer, T.; Haider, M.: Innovative approach to the use of offgas heat for highefficiency green power generation, Proc. AISTech 2011, 3 May 2011, Indianapolis, USA, p. 1017/61
2. Brandt, C.; Griebel, C.; Schneegans, J.; Gaderer, M.: Power generation from waste heat of an electric arc furnace at a steel plant — preliminary results, METEC InSteelCon, 30 June 2011, Düsseldorf, Germany.
3. Haider, M.; Eisl, R.; Schwaiger, K.; Holzleithner, F.: SandTES — a novel thermal energy storage system based on sand, Eurotherm Seminar No. 93, 18 November 2011, Bordeaux, France.
4. Raade, J.; Padowitz, D.: Development of molten salt heat transfer fluid with low melting point and high thermal stability, Halotechnics Inc., 2010, Perpignon, France.
5. Hänninen, M.; Ylijoki, J.: The one-dimensional separate two phase flow model of APROS, VTT Research Notes 2443, 2008. 
6. Laing, D.; Steinmann, W.; Tamme, R.; Richter, C.: Solar Energ. 80 (2006) No. 10, p. 1283/89.