AREA TECNICO SCIENTIFICA

29° cicloCorso di dottorato in Scienze dell’ingegneria energetica e ambientale

Waste heat recovery in steel industry: Using aluminium alloys as Phase Change Material

(PCM) to overcome temperature fluctuation issues

Problem Statement Steel industry is an energy intensive sector representing amajor consumer of electricity and one of the largest producersof greenhouse gas (GHG) emissions. 30% of the world steelproduction is made by through Electric Arc Furnace whichloses 15÷35% of the used energy in the form of waste gas.Heat recovery from the waste gas of the Electric Arc Furnacerepresents a huge opportunity to reduce GHG emissions ofsteel industry. Nevertheless, the diffusion of heat recoverysystems is hindered by large fluctuations in thermal powerwhich characterize waste gas of steel industry processes.

Proposed SolutionThe research project proposes to develop a heat recoverysystem based on phase change materials (PCMs) in order toovercome thermal power fluctuation issues. The innovativesystem intends to exploit aluminum alloys as PCMs because oftheir suitable melting temperature, high latent heat of fusionand high thermal conductivity.

Research AimsThe main objectives of the research project are to develop anddesign the innovative heat recovery system based on PCMsminimizing capital cost of the waste heat recovery system andminimizing average load factor of the downstream energyconversion technology. The research project has to accomplishthe following specific aims:• Identify most suitable material and design criteria for the

PCM containers• Define the best configuration in terms of PCM container size

and layout• Select the most suitable heat transfer fluid and its operative

condition• Perform a detailed techno-economic analysis of the PCM-

based technology• Optimize the whole heat recovery system to maximize

performance and minimize costs

Research approach

Such a complex problem requires an interdisciplinaryapproach. In particular, the following research analyses havebeen performed:

• Thermo-mechanical analysis• Thermo-fluid dynamic analysis• Energy system modelling

In addition, in-depth knowledge on corrosion of moltenaluminium alloys is required to develop an affordable and cost-effective system

ResultsThe application of aluminium alloys as PCM can reduce ofabout 70% the temperature fluctuation of the waste gas. Theimpact of the reduction of temperature fluctuation leads to:• +30% average load factor of the turbine• -25% capital cost of the whole waste heat recovery system

Future ResearchImplement a physical control system in the PCM container bymeans detailed 3D computational fluid dynamic simulationsand perform tests on resistance of anti-corrosive coatingsunder thermal cycling conditions

dott. Fabio Dal Magro

prof. Gioacchino Nardin

dott. Stefano Savino

Info:

Tel. +39 0432 558011

Fax. +39 0432 558027

dalmagro.fabio@spes.uniud.it

Riferimenti bibliograficiPCM-based energy recovery from electric arc furnaces. G. Nardin, A. Meneghetti F. DalMagro, N. Benedetti. Applied Energy 2014 (Awarded as Best Paper of Excellence ICAE 2013)

Enhancing energy recovery in the steel industry: Matching continuous charge with off-gasvariability smoothing. F. Dal Magro, A. Meneghetti, G. Nardin, S. Savino. Energy Conversionand Management 2015

Thermal stress analysis of PCM containers for temperature smoothing of waste gas. F. DalMagro, D. Benasciutti, G. Nardin. Applied Thermal Engineering (paper under review)