Long used in the food and beverage industry, lenticular filters offer optimal and cost-effective solutions for processing foods and drinks. They are particularly used in applications involving small-batch production or moderate flow rates. Each module consists of stacked filter “lenses”. What are the advantages, the limitations, and the latest developments of these filters?
Conventional lenticular filters
Standard lenticular filters are made up of cells, each consisting of two filter-media discs separated by a polypropylene spacer. This drainage system is located at the center of the cell, on the downstream side of both plates, with flow occurring from the outer surface of the plates toward the inside. A polypropylene gasket running along the outer edge of the two discs forms a complete cell. The filter media used are of the same nature as those employed for filter sheets: cellulose, synthetic fibers, diatomaceous earth, silica, activated carbon, etc. Depending on the configuration, filtration is carried out either at the surface or in depth.
The cells are stacked on top of one another to obtain a lenticular module of the required height. Adapters fixed to the central shaft keep each cell in position. This geometry maximizes the filtration surface area within a given volume. The assembly is placed inside a sealed filter housing, whose dimensions depend on the diameter of the cells and their number.
Lenticular modules provide all the advantages of traditional filter sheets, but within a closed and sterile environment, preventing external contamination and product loss. Several modules may also be stacked within a single filter vessel.
Expert advice
Lenticular filters are often used in wine filtration, and at various stages (clarifying filtration, microfiltration, sterilizing filtration).
Limitations of conventional devices
Conventional lenticular modules have limitations inherent to their design.
Because the filter media is not protected, its integrity can be compromised during shipping, handling, installation, or maintenance. After use, and for the same reasons, lenticular modules may disintegrate when removed from the filter housing.
Since the cells are very close to one another, they can deform or shift slightly until they come into contact in certain areas during sterilization, rinsing, or filtration. This ultimately reduces the effective filtration surface.
These devices cannot withstand backpressure: the unfixed cell media can rupture very easily, with backpressure as low as 0.05 bar. This leads to tears that divert the fluid and compromise the quality of the filtrate.
Finally, traditional lenticular modules have low mechanical strength and deform under high temperatures. This sensitivity becomes problematic during hot-water disinfection, steam sterilization, or hot filtration operations.
Next-generation lenticular filters
To optimize the capacity, reliability, and robustness of lenticular filters, some manufacturers now offer innovative designs based on the use of double separators placed on either side of the filter cells. The filter media is thus protected from mechanical stress, effectively “caged” between these two polypropylene separators, which are either snap-fitted or joined by ultrasonic welding. The outer separators, the filter-media discs, and the inner separators are all mounted on a rigid central polypropylene core. The result is an extremely robust structure.
This arrangement prevents any risk of blockage. Thanks to the separators, the device maintains a maximum filtration surface area throughout its service life. Cell deformation or collapse is no longer possible, and the risk of disc damage is minimized. Backflushing becomes feasible for module regeneration.
These next-generation lenticular devices offer numerous advantages. Their service life is longer than that of conventional filters, due to better utilization of the filtration surface, the absence of clogged filtration areas, and optimized distribution of the incoming fluid and drainage. The modules can be regenerated by backflushing and reused.
Device reliability is also improved, thanks to resistance to vacuum conditions or shocks related to backpressure, and to the absence of cell deformation during operation, disinfection, or hot sterilization. Filtration quality is enhanced, with no risk of bypass. Handling and installation are easier due to the strength of the structure and the fact that the filter discs are now protected.
Expert advice
These filters are available in a wide range of retention ratings, enabling coarse to fine filtration as well as microbiological reduction.
An example: glucose syrup filtration
Certain fluids used in the food industry, such as glucose syrup, contain fine suspended particles that must be removed. The objective is multifold: improving product clarity, reducing contamination levels, and protecting downstream systems.
This solid contamination (heat-resistant spores, for example) is often too high for implementing a traditional filtration system using filter cartridges, whose dirt-holding capacity is limited by the available filtration surface and void volume. Glucose syrup also has a high viscosity, which would require oversized cartridge filters.
Rather than investing in expensive equipment designed to remove solid particles (centrifuges, plate filters, etc.), it is recommended to use lenticular modules, which offer a quick-to-implement, economical solution perfectly suited to this type of fluid.
In the field of edible oils, these lenticular filters can also be used for final filtration to remove organic particles, colloids, and triglycerides, helping prevent flocculation inside bottles.
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