Technical and economic analysis of an advanced multi-stage flash crystallizer for the treatment of concentrated brine

In this study, we present an advanced multi-stage flash crystallizer and analyze its potential for the treatment of concentrated brine. The proposed system was evaluated with raw seawater at the lab scale and through ASPEN Plus simulation of reverse osmosis (RO) and membrane distillation (MD) condensates at a larger scale. Lab scale XRD result revealed the proposed crystallizer can separate Na₂SO₄ crystals from solution. A variety of configurations were then simulated, including number of stages, flow rates, and temperatures, to determine impacts on the recovery rate of distillate and salts. Based on the simulation data, the gained output ratio increased with the number of stages from 2.77 to 4.0, stabilizing at a flow rate of 700 L/h at 70 °C for 40 stages. A recovery rate of 4% for water and 25.05 kg/h for Glauber's Salt (Na₂SO₄·10H₂O) was observed. Based on the technoeconomic analysis, the optimal configuration was a 7-stage module operated at 60 °C and a flow rate of 700 L/h. Treatment cost were $1.17 per m³ of feed, which reduced to $0.35 per m³ when the sale of beneficial resources was considered. When the MD pretreatment was considered, the total combined treatment costs were $2.01 per m³, without the sale of beneficial resources, which was highly competitive with other treatment methods.