A low-temperature spray-cyclone system for zero-liquid discharge treatment of RO brine using extended two-phase CFD modeling and experimental validation

A novel approach for zero-liquid discharge (ZLD) treatment of reverse osmosis brine has been developed using a low-temperature spray-cyclone system. This innovative method employs hot air flow at a low temperature to evaporate micron-sized brine droplets continuously. By utilizing 3D modeling via computational fluid dynamics (CFD) with the Euler-Lagrange multiphase approach, including Extended Two-Phase CFD Modeling, the design of the cyclone and spray nozzle was optimized.

The system demonstrated exceptional evaporation efficiency of 96.5% under optimal operating conditions of 70 °C inlet air temperature and 0.03 kg/s air mass flow rate. Energy assessment revealed a specific evaporation energy requirement of 2.5–3.8 kWh/m³, with heat recovery via a shell-and-tube heat exchanger reducing the net energy demand by roughly 28%.

The compact design, high efficiency, and energy recovery features make this system a promising solution for meeting ZLD requirements in reverse osmosis brine management. The authors acknowledge the University of Tehran and Technical University of Denmark for their support and facilities during the research.