The recovery of waste heat from the absorber vent gases of a CO 2 capture unit by using membrane distillation technology for freshwater production

Abstract

In this study, direct contact membrane distillation (DCMD) technology was proposed to produce freshwater by utilizing the low-grade waste heat from the gases purged from the absorber of a CO2 capture unit. A Rate-based model has been used to simulate a monoethanolamine (MEA)-based CO2 capture process in Aspen Plus® V.10, and DCMD unit was simulated with the MATLAB software. The regeneration energy requirement in the CO2 capture process and freshwater production in DCMD unit were analyzed by varying the operating parameters. Cold seawater and purged gas were allowed to pass through the additional heat exchanger; as a result, the temperature of seawater increased. Then the warmed seawater was injected into the DCMD unit to produce freshwater. The freshwater production was 88,599 L/day at the feed temperature of 52.2 °C, which reduced to 85,050 L/day when the feed temperature declined to 50.3 °C. The freshwater production was 88,950 L/day at the permeate temperature of 10 °C, which declined to 78,450 L/day when the permeate temperature increased to 20 °C. Since adequate amount of freshwater was produced by the proposed system, the proposed integration method could help to mitigate environmental pollution and freshwater crises.