Multipass hollow fiber membrane modules for membrane distillation

Membrane distillation (MD) is an interesting process for desalination; however high thermal energy consumption remains one of the main obstacles in its widespread adoption. The current study presents multipass hollow fiber membrane modules to improve thermal efficiency of MD process. Fundamentally three module designs are considered: conventional one shell and one tube (fiber) pass (A), 1 shell and multiple tube passes (B/C) and equal but multiple shell and tube passes (D). The performance of the proposed designs is analyzed as a function of length of each pass, number of passes and operating conditions by using Aspen Plus simulator. The results demonstrate that the traditional design A yields the highest flux - up to 92 % higher than the multipass design D. On the other hand, the multipass design D is the most energy efficiency and shows up to 35 % less thermal energy consumption than the conventional single pass design of the same length. Single shell and multiple tube pass designs (B/C) show higher flux than D; however, their specific thermal energy consumption remains the highest among all the designs investigated. The pressure drop in multipass modules was marginally (1.5 %) higher than the conventional single pass modules.