The Disc Filter

The Disc Filters belong to the side feed group of filtering machines. They are generally used in heavy duty applications such as the dewatering of iron ore, hematite, coal, aluminum hydrate, copper concentrate, pyrite flotation concentrates and other beneficiation processes. The filter consists of several discs, up to 15 in the larger machines, each made up from sectors which are clamped together to form the disc. The sectors are ribbed towards the neck and designed for a high capacity drainage rate. One of the main features is that the required floor space taken up by disc filters is minimal and the cost per m2 of filtration area is the lowest when compared to other vacuum filters. During operation each sector enters submergence and a cake is formed on the face of the discs. It then emerges to the drying zone, the liquid drains to a central barrel and from there through a valve to the vacuum receiver. The valve with its bridge setting controls the timing so that once the sector leaves the drying zone it moves over a separating bridge and a snap or low pressure blow is applied to discharge the cake. Scraper blades on the side of each disc guide the cake to discharge chutes which are positioned between adjacent discs and are wide enough to avoid their clogging by the falling cake. A paddle type agitator located at the bottom of the tank maintains the slurry in suspension which in most of the metallurgical applications contains solids with high specific gravity which are fast settling and abrasive.

The main features of this machine include:

• Discs and sectors which may be made in injection molded polypropylene, metal or special redwood.

• A center barrel supported by the main bearings and consisting of piped or trapezoidal filtrate passages. The sectors are attached to the barrel through "o" ring sealed connections in a number equal to the number of disc sectors.

• A valve with bridges and internal compartments for form and dry under vacuum and cake discharge under pressure with 2-2.5 bar snap or 0.2-0.25 bar constant blow. Most disc filters are fitted with one valve only however two valves are often mounted on both drive and nondrive ends with long barreled filters or when the hydraulic loadings are high.

• An agitator with paddles that are positioned between the discs and far enough not to interfere with the forming cake.

• A tank which, on its discharge side, has separated slurry compartments for the discs and discharge chutes for the blown-off cake.

• Two cake discharge blades on both sides of each disc are suspended from a frame mounted on the tank. These serve to deflect and guide the cake to the discharge chutes.

• An overflow trough that spans across the entire tank length and ensures full submergence of the sectors in the cake formation zone (an exposed sector in the 6-o-clock position will cause immediate loss of pressure).

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