Waste heat transportation system, using phase change material (PCM) from steelworks to chemical plant

This paper describes the feasibility of a latent heat transportation (LHT) system that uses phase change material (PCM) to recover waste heat at temperatures over 300 °C in steelworks and supplies it to a distillation tower of benzene, toluene, and xylene (BTX). The operating data in the proposed system – as well as in a conventional heat supply system and a sensible heat transportation (SHT) system – were calculated based on heat and material balances in order to evaluate energy requirements, exergy loss, and CO2 emissions. The results showed that an LHT system using NaOH with a solid–solid transformation temperature of 293 °C and a melting point of 320 °C as PCM has 2.76 times the amount of heat-storage density of an SHT system; additionally, it has only 8.6% of the energy requirements, 37.9% of the exergy loss, and 17.5% of the CO2 emissions of a conventional system that lack heat-recovery capabilities. The results suggest the possibility of transporting heat via high-temperature PCM from steelworks to chemical plants. Such infrastructure would offer many benefits such as energy savings, reductions in exergy loss and CO2 emissions, and the benefits associated with coproduction.