Design

Design of Horizontal Process Filters

Unlike traditional Horizontal Vacuum Belt Filters, we do not need expensive rubber carrier transporter belts, heavy steel support structures, transporter belt wearing strips, belt tension mechanisms, reciprocating trays, flexible tray connections, tray support rollers, geared motors, cloth travel measurement, varaiable speed drives, electrical control panels, etc.

Materials of Construction

The above is a list of the components that we DO NOT need in our design. Our filter framework structure and index mechanism is inexpensive compared to the HVBF. The materials of construction can be anything which can be fabricated, such as stainless steel or polypropylene. To index the filter we use either compressed air, or hydraulics. The filter has no electrical requirement, making it an ideal selection in flameproof areas. Other than the actual filter cloth, the Polyfilter has no consumable wearing parts. Mechanical components are guaranteed for 3 years.

Feeding and Cake Washing

GENERAL – Unlike the HVBF which must have a continuous supply of feed slurry and cake washing liquid, both carefully regulated to the forward speed of the belt, the filter cloth on the POLYFILTER is stationary, (just like the laboratory Buchner filter), whilst filtration and cake washing are taking place. The benefit of this is that the feed can be applied either continuously, or, if necessary, in small volumes in synchronisation with the filter index. The same applies to the cake wash liquid. The actual decision depends upon the characteristics of the product, not the design of the filter!

Cake Washing

Once the above is understood, it can be seen that the benefits of plug flow washing can be exploited to full advantage, since the cake is stationary. Any wash applied above a compartment, or zone, must exit the filter from that zone, or, if the filter is allowed to index, the next zone(s) along. This is particularly beneficial on liquor recovery applications where an excess of wash liquid would dilute the product. Additionally, by fitting valves or orifice plates in the manifold headers, the rate of liquor flow from the filter can be controlled. On fast filtering, open structured crystaline type products, this ensures a better wash recovery.

Counter Current Cake Washing

From the above it can be seen that the Polyfilters design is ideal for this technique of minimising wash liquor consumption. The cut points are easily identified, and, easily adjusted, without the need of stopping the filter. Any number of stages can be incorporated.

Schematic of Counter Current Cake Washing

 

Cake Drying

On the drying end of the filter, it is possible to fit a cake squeezing plate, which, on some products, can match the cake solids achieved by membrane plate type filter presses. Alternatively, with crystalline structured products, hot air tunnels can be incorporated thus turning the filter into a simple dryer.

Cloth Washing

The indexing design of the Polyfilter permits very small quantities of liquid to be used for cloth washing as the liquid only needs to be applied as the cloth indexes. If the product is the solid, the cloth wash liquor can be pumped back onto the filter, thus eliminating product losses. On cake washing filters, the cloth wash can become part, or all, of the cake wash.

Other Applications

Whilst being a continuous filter, the POLYFILTER vacuum belt filter can also be used for BATCH processes. Here, its performance flexibility has seen it out perform more traditional equipment such as ; basket and decanter centrifuges, nutsche filters, filter presses and enclosed pressure filters.

Batch applications include: –

Aluminium Powder, Copper Oxide, Copper Carbonate, Dental Polymer, PAA, Polyurethane Foam, Guignets Green, Salt