Definition of Spiral Wound Membrane

Spiral-wound filters utilize flat-sheet membranes, feed spacers, and permeate spacers wrapped around a hollow tube called the permeate tube. Spiral wound elements utilize cross flow technology, and because of its construction, can easily be created in different configurations with varying length, diameter, and membrane material.

Construction

Spiral-wound elements consist of membranes, feed spacers, permeate spacers, and a permeate tube. First, a membrane is laid out and folded in half with the membrane facing inward. Feed spacer is then put in between the folded membranes, forming a membrane sandwich. The purpose of the feed spacer is to provide space for water to flow between the membrane surfaces, and to allow for uniform flow between the membrane leaves.

Next, the permeate spacer is attached to the permeate tube, and the membrane sandwich prepared earlier is attached to the permeate spacer using glue. The next permeate layer is laid down and sealed with glue, and the whole process is repeated until all of the required permeate spacers have been attached to the membranes. The finished membrane layers then are wrapped around the tube creating the spiral shape.

How it works

Feed travels through the flow channels tangentially across the length of the element. Filtrate will then pass across the membrane surface into the permeate spacer, where it is carried down the permeate spacer towards the permeate tube. The feed then becomes concentrated at the end of the element body.

Disadvantages

Spiral element fouling is greater than fouling in tubular filtration processes. Spiral elements also cannot handle mechanical cleaning like tubular elements, and contain lower packing density than hollow fiber.

Advantages

Spiral-wound elements come in multiple configurations with different spacers, membrane types, lengths, and diameters that allow it to fit multiple applications. These elements have a very high packing density, surpassing the packing density of plate and frame, tubular, and capillary configurations. Spiral membranes allow for easy cleaning through cleaning in place.

LC23 - Spiral Wound Element Construction GIF