Filtration and drying are essential steps in many industrial processes that involve the separation of solids from liquids. Solids can be discharged directly into a dryer, or, in the case of a filter/dryer, the drying function is done by the same machine. The agitated vacuum dryer manufacturer follows the overall process.
Filtration can be divided into two types of operations: continuous and discontinuous. Nutsche filtration, on which we’ll concentrate, is a batch filtration method that employs vacuum and/or pressure in a closed vessel. Product isolation, less operator exposure, reduced product handling, and environmental protection against solvent evaporation are just a few of the advantages of employing this technology.
Furthermore, the level of confinement provided can meet GMP and other health and safety regulations that businesses frequently encounter. Nutsche filter dryers are widely employed in pharmaceutical, fine chemical, dye and paint manufacturing, and wastewater treatment applications for these reasons.
Here’s a glance at the basic phases of a nutsche filter usual dryer’s filtration and drying procedure.
The product to be filtered, usually an aqueous or solvent-based solid/liquid slurry, is transferred from the primary location to the filter dryer in the first stage. The filter should be large enough to handle the volume of solids being charged. The maximum solids height should be equal to or less than the agitator stroke, according to a conventional rule of thumb.
The liquid is forced through the solid bed and filter material in the second phase by applying pressure and/or suction. When solids become visible, the procedure can be stopped or continued until all of the liquid has been pushed out. In nutsche filters, you can choose from cloth, single layer metal screen, or multi-layer sintered metal as a filter material.
- Washing by Displacement
Fresh wash liquid is sprayed on top of the solid cake, with care taken not to disturb the cake’s surface. Pressure or vacuum are used to drive the liquid through. Displacement washing accomplishes two goals: it eliminates the liquid and its contaminants while keeping the cake intact, and it replaces the old liquid with a new liquid. Before this step, you can use smoothing to try to close any gaps in the cake.
- Washing with Reslurry
If more impurity extraction or dissolving is required, re-slurry washing is a supplementary washing method. This is accomplished by mixing fresh wash liquid with the solids. Before filtering the wash liquid, the agitator is stopped and lifted. When a long contact time between the wash fluid and the solids is necessary, or when the displacement wash does not achieve the requisite wash quality, the re-slurry process is utilised.
After any filter or wash, especially after the last wash, when gas is blown through the cake, utilise this next procedure. To remove residual moisture, the agitator is utilised to close cracks and compress the cake. This function will aid in the uniform flow of liquid or gas through the filter cake, as well as the elimination of liquid and gas channelling, which reduces displacement washing and gas blow through efficiency.
- Cooling/ Drying
To complete the drying and subsequent cooling operation, the solid must be evacuated through a second dryer in most filter types. Both functions are merged in nutsche filter dryers, and drying can take place in the same vessel. The vessel surfaces are heated to accomplish this. Vacuum drying and convection drying are the two forms of drying available. The method employed is determined by the product’s characteristics. The most popular method, vacuum drying, uses a vacuum source, agitation, and a dust filter.
The valve/port on the vessel’s sidewall is used to complete this final stage. As the agitator turns, the product is moved to the side-discharge valve. When the desired product to be discharged is not a dry solid, there are some applications where this is the case. Nutsche filter dryers are built with flexible discharge in mind, allowing for the discharge of wet solids, slurries, and even liquids.
Understanding the phases in the nutsche filtering and drying process might help you tell this machine apart from other types of separation technologies. Promas Engineers are pharmaceutical equipment manufacturers based in India.