How are powders and bulk solids discharged from the Circle Feeder (Mass Flow Feeder)?
A simple experiment will explain the principle. Place a cylindrical container with an open bottom on a flat surface. Fill the cylinder with a powder. Next, lift the container a few millimeters from the flat surface. A small amount of powder will flow from the cylinder between the edge of the cylinder and the flat surface. A larger gap between the cylinder and the flat surface will allow for more powder flow. Next, insert a wire on the flat surface lengthwise across the cylinder opening. As the wire is rotated, powder is moved to the periphery and the cylinder can be completely emptied. This is the concept behind the Circle Feeder.
How can the Circle Feeder prevent bridging?
The Circle Feeder opening can be increased until it exceeds the critical arching diameter of the feed material (the diameter at which it will bridge). The maximum inlet diameter of the Circle Feeder is 4.0 meters (13.1 ft).
How uniform is the feed-rate from the Circle Feeder?
Generally, the Circle Feeder offers a uniform rate, with 1 to 3 % accuracy in volumetric mode, although this depends on the specific properties of the material being fed. Operating in gravimetric mode, with load cells, greatly improves the metering accuracy.
Is mass flow (first-in/first-out) possible with the Circle Feeder?
Yes-The Circle Feeder’s patented discharge system makes mass flow possible.
Can the Circle Feeder be used with materials that tend to fluidize and flow freely?
Yes, the Circle Feeder can be used with materials that flood easily when aerated, but have lower mobility when degassed. The initial Circle Feeder charge must be made with the discharge gate valve closed and the material allowed to degas before it is discharged. Subsequent charges must be made with a heel of degassed material in the bottom of the hopper to "seal the discharge" and prevent flooding.
Can the Circle Feeder feed materials with a large particle size?
The Circle Feeder has been successfully used to feed coal, gypsum, and other larger particle size materials. For some applications, testing may be necessary to ensure feeding success.
Can the Circle Feeder feed wet materials?
Yes, the Circle Feeder has been successfully used with centrifuge cakes, pigments, sewage sludge, and other "difficult-to-process" materials.
Can the Circle Feeder feed fibrous materials?
The Circle Feeder has successfully been used to feed glass fibers, Polypropylene, vinyl, nylon, cellulose, cement reinforcement, and many other fibrous materials. Specially designed scrapers need to be evaluated in a test program.
Will abrasive materials cause excessive wear on the rotary vane?
Because of the large volume of material that is moved in the Circle Feeder's outer ring, a slow rotational speed gives high volumetric through puts. Typical rotation speeds range from 0.5 to 4.0 rpm. For very abrasive materials, some wear will occur, but the degree of wear is typically less than traditional feeders because of the slow rotational speed. Under normal operating conditions, a Circle Feeder that is processing iron ore requires replacement of the rotary vane every seven years. A hardened surface can be applied to the surface of the rotary vane if desired.
Will the Circle Feeder crush fragile materials particles?
It depends on many factors, such as the properties of the material, shape of the hopper, etc. If crushing is a concern, it is best evaluated through testing. The Circle Feeder offers many different designs and the specific design required for your material can be determined during testing.
Will the Circle Feeder cause product melting?
The peripheral velocity of the Circle Feeder vane is so slow that its rotation generates negligible heat. Many Circle Feeder installations are successfully operating with materials that melt between 40 and 60 degrees C.
What is the maximum product temperature the Circle Feeder can handle?
With standard models, the product temperature must be 80&Mac176;C or less and the ambient temperature between 0 to 40&Mac176;C. Heat-resistant models have been successfully operated with 500&Mac176;C material.
