It really depends on your specifications in order to assess what separation technology will best fit the needs of your specialized application. In the series of credentials listed below, we’ve compared how a nutsche filter dryer would perform versus a centrifuge.
A filter/dryer is totally enclosed and pressure tight (rated to 50 psig/FV at a minimum), a design that eliminates operator exposure and environmental contact with the product (including protection against solvent vaporization). The closed system that is created is especially ideal for high purity, toxic, or flammable materials.
Maintenance and Operational Costs
With no high speed components and a low motor HP when compared to the centrifuge, the filter/dryer scores more points when it comes to maintenance and operational costs. Additionally, the agitator is only used during drying, smoothing, reslurry washing, and discharge, whereas a centrifuge motor is always in operation.
Reduced Moisture Content of Wet Cake
A centrifuge’s typical LOD (limit of detection) difference is 5% to 10% (depending on time and product). This data assumes there is no extended blow through in the filter.
A filter/dryer allows for extended residence time during displacement washing with the added capability of a reslurry washing if the process requires it (with the added benefit of using a reduced amount of wash fluid to effectively complete this step).
Although centrifuges and filter/dryers are available in roughly the same size range, filter/dryers enable possible increased capacity as the units are typically sized to handle the entire batch solids load.
Ability to Handle Extremely Difficult Products
Especially for compressible cakes, centrifuges promise better results than separation in conventional filter/dryers. Centrifuges also prove to be a good solution for cakes not suitable for deep bed filtration.
When it comes to discharging capabilities, both centrifuges and filter/dryers offer their own unique advantages. For complete product discharge, a filter/dryer has some heel associated with agitator to vessel tolerances whereas a centrifuge allows for complete discharge (though this can depend on the centrifuge design). Filter/dryers specialize in flexible discharge which enables the expulsion dry solids, wet solids, slurries, or liquid. In short, depending on your discharge objectives one type of equipment may be more advantageous to you than the other.
With “dryer” as part of its name, it’s no surprise that the filter/dryer takes the lead in this category. Utilizing vacuum or blow through drying, the filter/dryer makes it possible to obtain completely dry material out of the filter, which reduces overall process time.
Live Load Imposed on Filter
There is no live load associated with the filter/dryer thanks to the low RPM agitator (8-20 RPM on average), making the installation cost lower than that of the centrifuge.