Design and Heat-Insulation Performance of Cenosphere-Based Sound-Absorbing Panels for Converter Stations

A lightweight inorganic sound-absorbing panel was developed using fly ash cenospheres, sintered ceramsite, and aluminum dihydrogen phosphate binder, with particular emphasis on heat-insulation performance under controlled furnace-heating conditions. A sequential formulation design was adopted to investigate the effects of ceramsite content, cenosphere particle size, and binder content. Normal-incidence sound absorption, TG/DTG behavior, thermophysical properties, unexposed-side temperature, and apparent flexural strength were experimentally evaluated, and a three-dimensional transient heat-transfer model was used for macroscopic thermal-response analysis. The A1–A3 cenosphere-based panels exhibited frequency-dependent sound absorption, with peak coefficients approaching 1.0 in the middle- and higher-frequency ranges. The A-series specimens retained more than approximately 98.7% of their mass after heating to 1000 °C. Finer cenospheres and lower binder contents generally reduced thermal conductivity and unexposed-side temperature. B9, containing 30–50 mesh cenospheres, 10 mass parts ceramsite, and 65 mass parts binder, exhibited the lowest measured thermal conductivity of 0.127 W/(m·K) and was identified as the preferred formulation in terms of heat-insulation performance. The apparent flexural strength increased with binder content and reached 2.605 MPa, revealing different effects of binder addition on mechanical and thermal performance. Numerical predictions reproduced the experimental unexposed-side temperature trends, with RMSE values of 4.80–9.66 °C for the representative formulations. The results demonstrated the combined sound-absorption, thermal-insulation, and mechanical characteristics of the developed cenosphere-based panels.