Bulk Removal-Cyclones

Lime-Kiln Operation. Gases containing up to 40% carbon dioxide from the lime kiln pass through a cyclone separator, which removes the bulk of entrained dust. The gas is then blown through the two scmbbers, which remove the finer dust, cooled, and passes iato an absorption tower. Here carbon dioxide may be recovered by the sodium carbonate or Girbotol process. 

Cyclonic filters are a primary means of removing bulk particulates from gas streams. They rely on centrifugal force to separate solids from the gas by directing the gas flow into a circular path. Because of inertia, the particulates are unable to follow the same path and are separated from the gas... 

Char acts as a vapour cracking catalyst so rapid and effective separation from the pyrolysis product vapours is essential. Cyclones are the usual method of char removal and two are usually provided - the first to remove the bulk of the material and the second to remove as much of the residual fines as possible. However, some fines always pass through the cyclones and collect in the liquid product where they accelerate aging and exacerbate the instability problem, which is described below. 

The proper operation of a spray dryer-scrubber also requires that a dry product be formed and subsequently removed from the gas stream. Pilot tests have shown that the product salts will be dry and collectable if the gas temperature at the dryer outlet is maintained about 20 °F above its dewpoint. This also tends to minimize plume formation. The cyclone collectors used in the pilot tests removed 89-99% of the product. Although this was excellent performance by mechanical collectors, particulate emission standards will require either replacement of the cyclones or additional collection devices in series with the cyclones. The system design presently favored involves using cyclones to remove the bulk of the product and adding a small electrostatic precipitator for final particulate removal. The sodium salts produced in the spray dryer-scrubber... 

It was observed during the Mohave tests that the fine fly ash particles entering the spray dryer were often trapped in the cyclone along with the bulk of the product salt, apparently because of agglomeration with the atomized droplets in the spray dryer. Thus, the dryer itself helps to minimize emission of fine ash particles which are normally difficult to remove even with an electrostatic precipitator. Numerous samples have been taken and extensive data have been accumulated on the physical... 

Attempts have been made to integrate a cyclone in front of the gas outlet removing the bulk of the dust discharging to lower areas of the bed. The complex structure and operational problems due to high thermal and mechanical stress to the equipment resulted in rejection of this solution [196]. 

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