New design and sustainability assessment of industrial plant for continuous supercritical hydrothermal synthesis of zirconia

Supercritical hydrothermal synthesis is a green and environmental-friendly technology of nanomaterial synthesis. China's first industrial-scale plant for supercritical hydrothermal synthesis of zirconia has been successfully built, and the new design concepts of reactor, anti-corrosion evaluation, heat recovery, control systems, safety requirements, as well as process integration in this plant were reported in this article. The particle size tends to increase from 5.08 nm to 9.92 nm as the reaction concentration rises in industrial-scale, which demonstrates the feasibility of scaling up supercritical hydrothermal synthesis. Economic benefits and environmental impacts of the plant were comprehensively evaluated. The operation cost of the whole industrial plant is approximately $340 per hour, and more than 90 % of the running cost results from depreciation and the purchase of raw materials. Compared with other plasma technologies and ball milling processes, the GWPs of the SCFRS technology is 23–60 % lower than that of other competing methods. Moreover, the results of Cumulative Energy Demand (CED) and Global Warming Potential (GWP) shows that CO₂ emissions and energy in the precursor along with heating and cooling stages have the most significant impact on total GWPs and CEDs. The basic information at industrial level was of great value for further scale-up and development of zirconia application.