Red mud-molten salt composites for medium-high temperature thermal energy storage and waste heat recovery applications

Argyrios Anagnostopoulos; Maria Elena Navarro; Maria Stefanidou; Yulong Ding; Georgios Gaidajis

doi:10.1016/j.jhazmat.2021.125407

Red mud-molten salt composites for medium-high temperature thermal energy storage and waste heat recovery applications

J Hazard Mater. 2021 Jul 5:413:125407. doi: 10.1016/j.jhazmat.2021.125407. Epub 2021 Feb 17.

Authors

Argyrios Anagnostopoulos¹, Maria Elena Navarro², Maria Stefanidou³, Yulong Ding², Georgios Gaidajis⁴

Affiliations

¹ Birmingham Centre for Energy Storage & School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, United Kingdom; Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, Poland. Electronic address: a.anagnostopoulos@bham.ac.uk.
² Birmingham Centre for Energy Storage & School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, United Kingdom.
³ Laboratory of Building Materials, School of Civil Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
⁴ Laboratory of Environmental Management and Industrial Ecology, Department of Production and Management, Engineering, Democritus University of Thrace, GR-67100 Xanthi, Greece.

PMID: 33930958
DOI: 10.1016/j.jhazmat.2021.125407

Abstract

Red mud (RM) is an industrial waste of the aluminum industry with presently estimated worldwide legacy-site stockpiles of 4 billion tones. RM is typically disposed in the sea, dams or dykes, posing a significant environmental hazard due to its high alkalinity and traces of heavy metals. Despite recent valorization efforts, only 15% of RM deposits are currently utilized. In this work, a novel use of RM to formulate composite phase change materials (CPCMs) is proposed. The CPCM is formulated by milling nitrate salts with RM, compressing and subsequent sintering of the two. Overall good performance over the temperature range of 25-400 ℃ is observed. Maximum latent heat of the CPCMs is 58 J/g, while average thermal conductivity and C_p are in the range of 0.77-0.83 W/mK and 1.03-1.31 J/g ℃, respectively. No variations in the melting point or latent heat are observed after 48 cycles. Energy storage density is calculated to be up to 1396 MJ/m³. The working temperature of this novel CPCM make it ideal for waste heat recovery of medium-high temperature waste heat streams providing a valorization pathway and valorization for RM as a by-product for energy-related applications.

Keywords: Composite; Molten salt; Phase change; Red mud; Thermal energy storage; Waste heat recovery; Waste management; Waste valorization.