Top Feed Filter
The Swenson Top Feed Filter excels at dewatering and drying crystallizne materials.
- 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 the feed hopper where suspended solids settle to bottom while excess liquor overflows and returns to process. Solids are carried through nozzles by injecting saturated liquor, generally filtrate. The magma, formed of solids and liquor, strikes the spreader apron and flows over the feed dam. Baffles focus the feed stream onto the surface of the drum. As the drum rotates, the liquor enters the internal sections after being sucked through the filter medium, on which the solids are continuously deposited as a uniform, porous cake. The cake is washed to displace mother liquor, then into the heat zone, where much of the wash 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 the intermediate scraper blade, allowing the thinner, partly dried cake to travel through the final part of the drying cycle. The cake is then completely removed by the final scraper. Sprays clean the filter medium and the cycle is repeated.
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.