Direct contact and sweeping gas membrane distillation for process intensification – a comparative study

摘要

Sodium sulphate, a salt commonly found in nature and used in industrial applications, was assessed for process intensification from 40 to 450 g/L with two membrane distillation configurations namely direct contact membrane distillation (DCMD) and sweeping gas membrane distillation (SGMD). The polytetrafluoroethylene (PTFE) membrane with 0.45 mu m pore size, 50% porosity in hollow fiber (HF) configuration was used in the experimental runs. The optimum conditions, based on pure water tests for both configurations were; feed temperature (70 degrees C both configurations), permeate temperature (ambient air for SGMD, 15 degrees C for DCMD), feed flow rate (2.4 L/min for both configurations) and permeate fluid flow rate (25.5 L/min of ambient air for SGMD, 1.32 L/min with water for DCMD). Despite reaching the saturation concentration of Na 2 SO 4, the flux in SGMD and DCMD slightly decreased from 3.1 to 1.9 kg/m(2) h and 1.1 kg/m(2) h, respectively. The average energy consumption of DCMD system at 5.1 kWh/kg was markedly higher as compared with the energy consumption in SGMD system was 1.2 kWh/kg. In addition, at the saturation point, gain output ratio (GOR) for SGMD was three times higher than DCMD which concluded that SGMD system utilized thermal energy more efficiently; noting that SGMD was a favorable configuration in concentrating sodium sulphate solution as compared with DCMD. In terms of resistance analysis, inorganic fouling was overcome after simple cleaning process.