Pilot-scale vacuum membrane distillation for decontamination of simulated radioactive wastewater: System design and performance evaluation

Abstract

• Pilot-scale VMD plant with 8.0 m 3 /d production was developed. • Design scheme and schematic of VMD pilot plant were detailed. • High DF of 10 4.85 for Cs and high CF of 110.3 were achieved. • Detailed evaluation of energy efficiency through STEC and GOR was conducted. • Heat loss of pilot-scale membrane module as heat pinch effect was analyzed. A pilot-scale vacuum membrane distillation (VMD) demonstration plant for decontamination of radioactive wastewater with 8.0 m 3 /d water production was developed. The design scheme, main components and functions of VMD pilot plant were detailed. Effects of operational parameters on permeate flux, gain output ratio (GOR) and decontamination factor (DF) of simulated radioactive wastewater were analyzed. As feed temperature increased from 70℃ to 90℃, permeate flux grew exponentially from 1.59 kg/(m 2 ·h) to 6.82 kg/(m 2 ·h). High DF 10 4.85 of Cs + and high concentration factor (CF) 110.3 of simulated radioactive wastewater were reached with stable permeate flux in pilot-plant-scale. DF of Cs + and GOR were relatively stable under various operation conditions. The outlet temperature of membrane modules increased with the growth of flow rate, bringing about 9 °C temperature difference between 2 m 3 /h and 14 m 3 /h at the same inlet temperature of 70 °C. The significant heat loss in radial direction as temperature polarization and in axial direction as the heat pinch effect in hollow fiber membrane modules are the main issues for large-scale MD plant. This study demonstrates a remarkable potential of VMD for decontamination of radioactive wastewater and provides an integrated design of VMD pilot-scale plant.