Bahco classifier

Respirable coal mine dust samples from three different US mines were classified into four fractions using a Bahco classifier [34]. Shape factors were determined as ratios of the following mean diameters. From microscopy ... 

Figure 5.18. The BAHCO classifier uses centrifugal action, by rapidly spinning the entire instrument, and air flow, induced by vanes on the bottom of the rotor, to bring about separation of a powder into coarse and fine fraction. Fines are carried with the air flow out of the fractionation chamber then centrifuged at the large radius of the disc. Coarse fineparticles undergo sufficient centrifugal action to overcome the air flow and are deposited immediately to the wall of the disc.

Mineral standards were hand crushed to -1/4 inch, then ground to a fine powder in a ball mill (alumina elements) or Bleuler Model 526/LFS678 puck mill. The resultant powder was aerodynamically classified in a Bahco Model 6000 micro particle classifier and the finest fraction ( 18 throttle) was collected. A size criterion of 90% or more by weight of particles 5 micron and smaller in diameter was used for the mineral standards. Sizes were verified by Coulter Counter. Duplicate 13 mm KBr pellets were prepared and the spectra were weight-scaled by techniques similar to those reported by Painter (3) and Elliot (4). With one exception, all the mineral standard spectra were averages of spectra from duplicate pellets. The one exception was the iron sulfate spectrum, which was obtained as the difference spectrum by subtracting the spectrum of HCl-washed weathered pyrite from that of the weathered pyrite. A weight correction was applied to the difference spectrum. 

Fig. 5.4 Simplified schematic diagram of the Bahco microparticle classifier showing its major components I, electric motor 2, threaded spindle 3, symmetrical disc 4, sifting chamber 5, container 6, housing 7, top edge 8, radial vanes 9, feed point 10, feed hole 11, rotor 12, rotary duct 13, feed slot 14, fanwheel outlet 15, grading member 16, throttle.

---