Technology of Milk & Milk Products

Arranging the sequence correctly for Classification of membrane processes:

The correct chronological order is Option 1: (C), (B), (D), (A)..

Correct option: (1) (C), (B), (D), (A).

• Back-Flushing (Back-Washing) in Membrane Modules:
• Hollow Fiber Modules: Consist of thousands of open capillary fibers bundled in a cylindrical shell. Permeate flow can be momentarily reversed from the outside-in or inside-out under pressure (back-flushing) without causing mechanical rupture or delamination. This periodic reverse pulse dislodges fouling cake layers accumulated on the membrane surface.
• Spiral Wound Modules: Cannot tolerate back-flushing because reverse transmembrane pressure causes membrane leaves to delaminate, balloon, and rupture.
• Plate and Frame / Tubular: Have limited or specialized back-pulsing capabilities compared to hollow fibers.
• Correct Option: Option 1 (Hollow fiber).

• Anti-Telescoping Devices (ATD):
• In spiral wound membrane modules, multiple membrane leaves and feed spacer meshes are wrapped spirally around a central perforated permeate collection tube.
• During high-velocity crossflow operation, axial pressure drop creates substantial drag and shear stress along the feed channel. This force tends to push the inner spirals forward relative to the outer wraps, causing a cone-like deformation known as telescoping.
• Anti-Telescoping Devices (ATD): Rigid end-plates (spiders) fitted at both ends of each spiral wound element to mechanically constrain the rolls and prevent telescoping deformation.
• Correct Option: Option 4 (Spiral wound).