Use of filter discs in metallurgical industries

The disc filters have common applications in heavy duty processes for example dewatering of iron, copper concentration, floats concentration and other industrial processes. The filter discs were extensively used in 60s in the metallurgical plants.

The filter is made of many discs about 15 in the large size equipments, each part consists of sectors that are joined together to build the disc. The benefit is that disc filters cover nominal floor space and cost per operation is much lower as compare to vacuum filters.

Filter disc in operation

During the operation, every sector enters submergence and a cake is developed on the face of discs. It then emerges to the drying region, the liquid drains to the middle barrel from there via a valve to the vacuum receiver. The valve monitors the timing so that as soon as sector exits the drying region, it goes over a separation bridge and a snap or low pressure blow is applied to cake discharge. Scraper blades on every disc side direct the cake to discharge chutes that are located between adjacent discs and are sufficiently wide to prevent clogged by dropping cake. An agitator positioned at the end of tank collect slurry in suspension that in other metallurgical processes collects solids with high specific gravity that are abrasive.

Other disc filter types

Disc filters can serve as vacuum disc filters or pressurized disc filters. Due to differential pressure application on both sides of Hastelloy mesh filter discs, the effective filter area is significantly larger than drum filter for the same floor area.

Pressurized disc filters:

a.       Pressurized disc filter involves the application of lower pressure gas to the slurry side

b.      The compressed gas develops the essential pressure differential for filtration

c.       The filter is configured in an air-tight housing.

d.      Filtration starts when the disc quits the slurry

e.      Internal valves and piping channel the filtrate far from all discs and towards a receiver.

f.        The filter housing is created to comprise of a redistributed process gases. It can be developed from different materials.

Vacuum Disc Filters

a.       Cake development: An internal valve opens that allows vacuum creation inside the filter screen. The cake develops on a part of the submerged drum

b.      Cake drying: With the rotation out of slurry by the slurry, the drying process starts. Vacuum is applied to develop a pressure differential essential to discard the filtrate.

c.       Cake Discharge: An internal valve locks the vacuum at this level. The discharge processes can be a scraper belt, belt or roll. The compressed air is used to eradicate the cake from the filter screen.

Precoat disc filters

A Precoat disc filter performs as vacuum disc or a pressurized disc filter.

Capillary Action disc filters: These filters are used to dewater mineral concentrates and pelletize the feed slurries.  The porous disc replace the traditional filter cloth. The capillary action draws liquid through pores and a small size vacuum pump is needed that significantly lowers the energy consumption.