Filtration, Simplified

Piece of Cake - When any chemical reaction is complete, a solid liquid separation procedure is usually required. This separation could be to recover a product or intermediate or remove impurities from the batch. In laboratories, Buchner filtration followed by tray or oven drying are usually the preferred options. In the larger scale pilot and process plants, filter dryers are often a common choice. The simplefilter is a simplified alternative to the more complex and costly technology of a filter dryer.

The Technology

The simplefilter is a single-plate pressure filter designed with a contained off-loading via a nitrogen purged glove bag. This technology consists of a main vessel where the slurry enters, a filtration media attached to a swing-out base, a side discharge hatch/plug and a glove bag.

The slurry enters the main vessel via one of the nozzles on the dished head and is filtered by applying gas pressure usually in the form of nitrogen. If necessary, the cloudy filtrate may be pumped back around and re-filtered to ensure that all of the product/intermediate has been collected or impurity removed. The existing cake that now lines the filtration media from the first filtration will also act as a finer secondary filter media to aid the filtration.
At this point during a filter dryer process, the cake would be washed with a displacement or re-slurry wash. While it is still possible to cake wash within the simplefilter, this technology does not include an agitator, making the process of cake washing more basic and less homogeneous. The cake may now be dried or discharged as a wet cake, a reslurry or a dissolved product.

During the drying process, heat transfer is one of the most important factors. The simplefilter incorporates a heated base to complement the traditional jacketed style heating on the main vessel. The solids can be discharged through a plastic glove bag, which provides an ergonomic, contained discharge through the side discharge hatch and can be nitrogen purged and extracted for hazard protection.
The vessel can be cleaned using spray balls or by flooding. It can also be easily inspected as the swing-out heated base has an assisted raise/lower which works on a manual ratchet mechanism and has c-clamps for the sealing of the vessel. This equipment is also fully mobile as a standard so that it can be used anywhere within the plant to make it more flexible.

The simplefilter can also be constructed in various materials, such as 316 Stainless Steel and Alloy 22, but another cost effective option is PFA coated carbon steel, which is approved by the U.S. Food and Drug Administration.

Common Problems with Filtration and Drying Technology

Sustainability is quickly becoming increasingly important to the manufacturing companies today, including those in the pharmaceutical market. There is increased awareness of the need to choose more efficient technology - to not only reduce the carbon footprint, but also to cut costs during these unstable economic times. Having equipment with the capability of carrying out two processes within the one step has its obvious advantages, including installation costs, saving power and saving human resources. Maybe more importantly to a lot of pharmaceutical plants that use highly potent or toxic chemicals is that having one process vessel instead of two reduces the operator exposure possibilities and also reduces the product contamination risk during vessel transfers.

However, while combined filtration and drying equipment provides a more ergonomic and efficient answer to the pharmaceutical market, heel removal is vital, as the intermediate or end product is often very expensive. It is very common to have to dig the cake out, which is not always the easiest of procedures. Keeping the discharge hatch low and level with the filtration media helps give maximum access to the intermediate or end product within the main vessel and avoids the bending while digging out of cake. A heel removal tool is then utilized to aid discharge across this level space, further maximizing product yield.

Simplefilter applications

Some of the common applications that the simplefilter is used for include:

• hydrogenation
• carbon filtration, 
• catalyst recovery
• API filtration
• pre-filter for micro-filtration.

As the list above shows, the simplefilter can be used in many applications as a result of some of its key features. With the easily changed filter cloth that can have a variety of pore sizes, the simplefilter is very versatile in the size of particles it can handle. Because the vessel is rated to six bar (90 psi) of pressure, the filtration can be achieved at many atmospheres of pressure, instead of the one atmosphere achieved with vacuum filtration with a standard Buchner. Also the different materials of construction also lend it to a wide variety of chemistries.