Electrically Heated Multilayer Ceramic Composite Tubes for High-Temperature Endothermic Reactions

A high-temperature reactor concept using electrically heated oxide ceramic tubes is investigated with the aim of replacing fossil fuels with renewable electricity and reducing CO₂ emissions in the chemical industry. The multilayer ceramic composite tubes are resistant to thermal stress and consist of an inner monolithic oxide ceramic, a thin metallic heating element, and an outer Al₂O₃/Al₂O₃ ceramic matrix composite (OCMC) layer. Dry reforming of methane was tested up to 1150 °C, with and without catalyst. Due to the non-gas-tight OCMC layer, process conditions had to be adjusted to prevent soot formation on the heater. A tube-in-tube design allows for heat recovery and reduces the outlet temperatures. Conversion rates of up to 80 % have been achieved, but temperature drops due to the endothermic reaction can lead to secondary soot forming conditions.