Article ID: ISIJINT-2018-428
Thermochemical energy storage (TcES) system using lithium orthosilicate/carbon dioxide (Li4SiO4/CO2) reaction was developed for recovery and utilization of high temperature thermal energy generated from high temperature industrial process. Li4SiO4/CO2 TcES packed bed reactor (LPR) and zeolite packed bed reactor (ZPR) were developed as thermal energy storage and CO2 reservoir. Both reactors, LPR and ZPR, were connected by flexible tube and thermal driving operation of TcES system was demonstrated. For lithium orthosilicate packed bed reactor, tablet forms of Li4SiO4 named K-tablet was developed and used in this study.
Li4SiO4 carbonation (thermal energy output process) and lithium carbonate (Li2CO3) decarbonation (thermal energy storage process) were conducted sequentially with specific condition. All experimental results showed similar tendency; a middle temperature in the Li4SiO4 packed bed reactor rapidly increased and decreased at the initial time of carbonation and decarbonation respectively. From kinetic analysis, it was confirmed that the developed K-tablet reacted around 80% and a thermal energy output density of LPR was estimated 331–395 kJ/L-packed bed, 759–904 kJ/L-material. The thermal driving demonstration of Li4SiO4/CO2/Zeolite TcES system shows high possibility to utilize surplus heats in low-carbon ironmaking system efficiently.