Solid-liquid filtration is defined as the separation of solids from slurries (solid-liquid mixture) using a filter medium. In this process either the solid, the liquid or both could be the product of interest and can be recovered or removed accordingly. At the industrial scale, various conventional systems are employed for solid-liquid separation such as Centrifuge, Plate and Frame Filter Press, Nutsche Filter, Agitated Nutsche Filter and many more. Centrifuges use centrifugal force as the driving force for filtration. They are generally regarded as a low-cost solution and offer higher degree of dryness for solid products. However, it has several challenges such as requirement of higher power rating, intensive labour and larger space.  The limitation of centrifuge’s cake holding capacity demands an increase in the number of centrifuges and other resources for large volume filtration within the required timeframe. Moreover, there is an increase in the degree of risk when filtering products containing solvents. Catering to few of the above challenges is the Agitated Nutsche Filter (ANF). These are largely employed in the process industries. ANFs are designed to contain solvents in a closed system. This eliminates the environmental and safety associated risks. On the other hand, during filtration in ANF, an increase in the cake thickness occurs which adds resistance to its filtration rate. This increases the filtration time or necessitates addition of filtration area, leading to requirement of multiple ANFs. Another prevalent technology in the industry is the Plate and Frame Filter Press. It is one of the oldest techniques having several limitations. This reduces its applications in the modern industry. Elucidating on the old technologies, the Rotary Vacuum Drum Filters (RVDF) is an established technology for solids recovery from liquid suspension. The RVDF consists of a drum covered with suitable filter media immersed in a slurry. Differential Pressure is applied across the membrane using vacuum that causes cake formation, which is easily washable. A knife or blade scrapes the product from the surface thus maintaining the cake thickness. This technique is suited for slurries, suspensions and liquids with solid content – which in general clogs other types of traditional filters and helps in maintaining a constant filtration rate. Though the technology is recognised for few applications, the new and improved design of the Filtech RVDF has extended its applications beyond the traditional scope. It offers several technological advantages that provides solutions for various challenges the industries face. RVDFs have proved to increase the productivity and ensure consistency of product quality that complies with pharmaceutical regulatory standards. RVDF offers the flexibility of Pre-coat and Direct Media Filtration. Direct media filtration can be used for solid filtration wherein solids as desired products can be separated from slurries/suspensions. This is largely applied in the final and intermediate filtration in API, Chemicals, F&B, and other process industries. For fine Liquid Filtration, Pre-coat filtration is applied – e.g. charcoal filtration, fermentation broth filtration, juice clarification, wineries, distilleries, etc. As the operation is continuous and automatic – the operating cost is low. Trials using the RVDF has shown a 90%* reduction in filtration time contributing to an equal reduction in CAPEX and up to 85%* reduction in OPEX compared to traditional filtration techniques. The RVDF-GT (gas tight) model is the closed-hood design of RVDF capable of processing volatile and/or toxic solvents and products under inert atmosphere (N₂).  Handling sensitive or potent ingredients where contamination must be avoided can be achieved using the RVDF-GT. The flexibility of the RVDF to function in both batch and continuous mode is a boon for the pharmaceutical industry as it shifts from batch to continuous mode of production. Along with this, several tools related to automation and controls can be embedded in the RVDF further saving process time and operation costs.

*indicative figures based on pilot trials and actual commissioning. Subject to change depending on the product and process.