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Influence of Hydraulic Pressure on Performance Deterioration of Direct Contact Membrane Distillation (DCMD) Process

1
Environmental Convergence Technology Center, Korea Testing Laboratory 87, Digital-ro 26-gil, Guro-gu, Seoul 08389, Korea
2
School of Civil and Environmental Engineering, Kookmin University, 861-1, Jeongneung-dong, Seongbuk-gu, Seoul 136-702, Korea
*
Author to whom correspondence should be addressed.
Membranes 2019, 9(3), 37; https://doi.org/10.3390/membranes9030037
Received: 13 February 2019 / Revised: 27 February 2019 / Accepted: 1 March 2019 / Published: 6 March 2019
(This article belongs to the Special Issue State-of-the-art Membrane-based Desalination)
Direct contact membrane distillation (DCMD) is a membrane distillation (MD) configuration where feed and distillate directly contact with a hydrophobic membrane. Depending on its operating conditions, the hydraulic pressures of the feed and distillate may be different, leading to adverse effects on the performance of the DCMD process. Nevertheless, little information is available on how hydraulic pressure affects the efficiency of DCMD. Accordingly, this paper investigates the effect of external hydraulic pressure on the process efficiency of DCMD. Gas permeabilities of MD membranes were measured to analyze the effect of membrane compaction by external pressure. Mass transfer coefficients were calculated using experimental data to quantitatively explain the pressure effect. Experiments were also carried out using a laboratory-scale DCMD set-up. After applying the pressure, the cross-sections and surfaces of the membranes were examined using a scanning electron microscope (SEM). Results showed that the membrane structural parameters such as porosity and thickness were changed under relatively high pressure conditions (>30 kPa), leading to reduction in flux. The mass transfer coefficients were also significantly influenced by the hydraulic pressure. Moreover, local wetting of the membranes were observed even below the liquid entry pressure (LEP), which decreased the rejection of salts. These results suggest that the control of hydraulic pressure is important for efficient operation of DCMD process. View Full-Text
Keywords: direct contact membrane distillation (DCMD); hydrophobic membrane; hydraulic pressure; compaction; membrane structure; wetting direct contact membrane distillation (DCMD); hydrophobic membrane; hydraulic pressure; compaction; membrane structure; wetting
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Park, S.-M.; Lee, S. Influence of Hydraulic Pressure on Performance Deterioration of Direct Contact Membrane Distillation (DCMD) Process. Membranes 2019, 9, 37.

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