Classifiers
Air classification
is a process of separating particles into groups or grades at cutpoints ranging from 10 mesh to sub-mesh sizes.
Air classifiers complement screens in applications requiring cutpoints below commercial screen sizes and supplement
sieves and screens for coarser cuts where the special advantages of air classification warrant it.
The applications of air classification are many and varied. Some of the more important uses are:
- Scalping off the coarse end from a pulverized product, usually for further milling. This prevents overgrinding
and saves power.
- The "tailoring" of several size fractions from a heterogeneous mixture of particulate matter. In this
application, each fraction has a different particle size distribution meeting commercial specifications
or requirements of a dry beneficiation process.
- Scalping off the fine end of the product for "de-dusting," "de-fuming" or changing the flow, apparent
density or other physical characteristics of the coarse fraction.
- Beneficiation of a mixture by the removal of impurities contained in a narrow particle size range of
the mixture or the separation of mixed products having substantial difference in settling velocities in
an air stream.
Fisher-Klosterman’s Buell Classifiers are available in a wide range of capacities for sizing, de-dusting or de-fuming
dry particulates at feed rates from a few pounds per hour to 600 tons per hour. Four basic models are available,
each offering cutpoint control in different size ranges.
- The Gravitational-Inertial Classifier utilizes increased air velocities and it is designed for cutpoints
from 50 mesh to 200 mesh.
- The Centrifugal Classifier requires less handling equipment and ranges from 100 microns to 15 microns.
- The Gravitational Classifier is ideally suited for coarser cuts ranging from 10 mesh to 100 mesh.
- The Cyclone Classifier is designed to strip extremely fine particles from a product.
For the classification of dry solids between 10 mesh and 15 microns, pneumatic classifiers have several advantages
over screens: Lower capital cost, lower operating cost, lower maintenance cost, greater on-line dependability, and
less susceptibility to blinding.
Units can be supplied fabricated from carbon or stainless steel as well as with special features such as ceramic
or refractory linings to combat abrasion.
Contact Us today to find out if an aerodynamic
classifier will work for you.
For additional information, please review the following technical papers:
Gravitational
These units are
ideally suited for coarser cuts ranging from 10 mesh to 100 mesh. Feed material is dropped into the top
of the classifier and falls in a continuous feed curtain in front of the vanes through low-velocity air
which enters the side of the classifier. The air flow direction is changed by the vanes from horizontal
to angularly upward, causing separation and classification of the particulate. The coarse particles are
discharged through a valve beneath the classifier. The fines are conveyed by the air to a cyclone for final
recovery.
Please click here to learn more about
the operating principles of this unit.
Gravitational - Inertial
These
units combine gravitational, inertial, centrifugal and aerodynamic forces to classify materials at cut points
ranging from 50 to 200 mesh (300 to 75 microns). The feed material and primary air enter the top of the
classifier in a downward direction. The air makes a 120° change in direction and exits through the vanes
while carrying fine particles with it. The coarse particles, too heavy to make the turn, fall to the bottom
to be discharged through a valve. Secondary air, injected below the vanes, passes through the curtain of
falling particles. Those particles near cutpoint in size are diverted by the secondary air stream into an
eddy current within the heart-shaped chamber. The fines, some captured as they enter the unit and others
drawn from the eddy, are carried by the exiting air to a cyclone for final recovery.
Please click here to learn more
about the operating principles of this unit
Centrifugal
These classifiers
use centrifugal forces, similar to cyclones, to separate particles at cutpoints between 15 and 100 microns.
Internal baffles apply drag forces to the coarse particles while allowing air to pass through them for separation
of the fines. The heaviest particles drop to the bottom of the classifier and are discharged through a valve.
Other particles above the cutpoint soon follow into the coarse particle discharge. The air stream carrying
the fine particles follows a spiral path to the outlets on each side of the unit. The two air streams combine
and enter a cyclone for final recovery of fine particulates.
Please click here to learn more about the operating principles
of this unit:
Cyclone
The
EX Series Cyclone Classifier is designed for the classification of powders where it is necessary to separate
fine particles from large particles. The material to be separated is pneumatically conveyed to the classifier
unit where it is separated into coarse and fine fractions through the use of carefully controlled reverse
air flow. The coarse material is removed at the bottom of the classifier through an airlock device and the
fine materials are transferred pneumatically out of the top of the classifier and collected in a final collection
device such as a high efficiency cyclone or dust collector.
The system is fully adjustable through the modulation of the reverse gas flow and allows the variation
of the "cut point" through a wide range. Testing of material in our lab is recommended prior to equipment
selection and sizing.
The EX Series Cyclone Classifier is available in two basic models:
Features:
- No internal moving parts
- Low maintenance
- Easy adjustment
- Wide range of operation
- Economical initial cost and operation
- Standard sizes to accommodate most applications
- Custom sizes and configurations available
Mobile Classifiers
Buell Mobile Classifers can be rented or purchased to provide a transportable solution to your classification
needs. Units are available to classify up to 150 tons/hr of product.
Highlights of this product include:
- Can meet Superpave specifications
- No water needed (no settling ponds)
- Low maintenance
- Transportable to job sites
- Variable cutpoints
Please take the time to watch the attached video to learn more about this innovative product:
Click Here for Video (3.4MB)
Aggregates "Manufactured Sand"
In
order to produce “manufactured sand”, the stone material used for asphalt, the amount of fine dust (smaller
than 200 mesh) in crushed rock has to be reduced. Laboratory testing using the Buell Gravitational Inertial
Classifier has confirmed that our aerodynamic classifiers can make your product meet specifications without
the use of water or moving parts. The Buell design can operate reliably at product moisture levels up to
2%. Some specific material applications will even allow moisture levels to be as great as 3%. Advantages
of the Buell Classifier:
- No moving parts
- Little or no maintenance
- Low power consumption
- Produces a dry product
- No settling ponds
- Minimal or no adjustment during operation
Click here for detailed case histories showing how we have helped
solve others needs in the Aggregates and Manufactured Sand Industries