Top Feed Filter 1

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TOP FEED FILTER

Page 1

CRYSTALLINE MATERIALS

can be Dewatered and Dried On the Swenson Top-Feed Filter

Advantages:

Two units in One (Filter and Dryer) - Reduces initial cost of equipment and installation.

Bone-Dry Product - Thoroughly dried by hot air under closely controlled conditions.

High Capacity - Hot air comes in intimate contact with each grain, resulting in quick drying

High Thermal Efficiency - Mechanical removal of much of the liquor reduces heat consumption per unit output

No Dust - As hot air is filtered through the cake, floating particles attach themselves to coarse particles and are removed from the system

Low Operating Cost - Automatic control reduces amount of attention required. Cost is further decreased by high capacity and high thermal efficiency

Long Service Life - All parts move at low speed and are built of high-grade materials

Clean Filter Stations - Operates under vacuum and under controlled conditions, minimizing spillage and waste

Flexible - Can dry salts which normally form hydrated crystals to the anhydrous phase without special method of operation

The feed, at low density, is pumped into feed hopper A, where suspended solids settle to bottom while excess liquor overflows and returns to process. Solids are carried through nozzles B by injecting saturated liquor, generally filtrate. The magma, formed of solids and liquor, strikes spreader apron C and flows over feed dam D. Baffle E focuses feed stream onto point on surface of drum P. As drum P rotates, the liquor enters sections 0, being sucked through filter medium H, on which the solids are continuously deposited as a uniform, porous cake.

The cake passes under wash J. where the impure mother liquor is replaced by water, then into the heat zone, where much of this water is removed mechanically, the remainder being heated to the boiling point. Drying now takes place, followed by removal of the outer dry crust by intermediate scraper K, allowing the thinner, partly dried cake to travel through final part of drying cycle. Cake is then completely removed by final scraper L. Spray M cleans filter medium, and the cycle is repeated.

Hot air is forced into filter hood N through duct P by booster fan, thereby preventing leakage of cold air. Dried product drops to bottom of hood and is picked up by screw conveyor R and discharged through pipe S onto conveyor T.

Liquor and air pass from sections G through ports U into receiver, where separation takes place. Air goes to exhauster to be removed to atmosphere. Liquor enters seal tank and is pumped back to the process.

APPLICATION

The process of separating solids from liquids embraces a wide variety of problems and materials, from colloidal suspensions to magmas containing coarse crystals which settle so rapidly that it becomes difficult to maintain a uniform suspension of the solids by means of mechanical agitation.

In general, any suspension in which the solids settle readily can be filtered on top-feed filters and, hence, they are limited to the coarse, rapid-settling crystalline solids especially where the solids are to be dried on the filter and where washing is not especially important. Top-feed filters should not be used if a turbid filtrate is objectionable.

FILTER MEDIUM

Wire cloth or perforated plate is usually used as the filter medium with top-feed filters. The metal should be selected with a view to avoiding erosion and corrosion. The size of openings in the filter medium depends to some extent on the size of particles in the magma.