Packed-bed thermal-storage system configurations for shuttle kiln waste-heat recovery

The ceramic industry, which heavily relies on non-renewable energy sources, significantly contributes to carbon dioxide emissions. In particular, periodic or shuttle kilns, used in sanitaryware production, are batch-type furnaces and are predominantly fueled by natural gas. The produced waste heat is often rejected into the environment. This study compares three distinct system configurations for waste heat recovery, which are namely: a standalone heat exchanger (HEX), crossflow or counterflow, a packed-bed thermal storage (PBTS) system for sensible heat storage, and a combination of both. A validated 1-dimensional numerical model, which solves the energy conservation equation for both solid and fluid phases is used for analyzing the PBTS system. The HEX alone recovers up to 16% of total heat input, achieving a 0.93-year payback period and a levelized cost of heat at 0.017€/kWhth. Conversely, an optimally dimensioned PBTS system surpasses HEX efficiency, reclaiming 28.5% of the heat input. It boasts a shorter payback period (0.17-0.32 years) and lower levelized cost (0.003-0.006€/kWhth), demonstrating its superiority in enhancing waste heat recovery in industrial settings.