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Precipitator particulate disposal
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After the particulate has been charged, collected on the collecting electrodes and rapped off, the final step in precipitator operation is the removal of collected material. For most applications, the material is collected below the collecting and discharge electrodes in hoppers which are shaped like inverted pyramids. From the hoppers, material is either removed in a batch process via a pneumatic conveying system or by mechanical chain conveyors.
For wood or bark fired units, because of the possibility of fires due to high levels of unburned carbon, large trough type hoppers are used with continuous mechanical evacuation.
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One unique requirement for particulate disposal is the recovery boiler in the pulp and paper industry.
Originally, dust removal was accomplished with pyramidal hoppers, however because of the hydroscopic
nature of salt cake, extensive heat tracing and insulation of the hoppers were necessary for satisfactory
dust removal. To overcome these problems, a drag conveyor or scraper system was designed to remove collected
salt cake. Early systems had frequent maintenance due to the many moving mechanical components on the system.
In an effort to overcome some of the drawbacks of drag conveyors, the wet bottom system evolved. Although
this system did overcome the frequent maintenance problems associated with the scraper systems, wet bottom
systems have their own problem namely corrosion at the wet-dry interface point.
Quick links to:
Collecting electrodes
Discharge electrodes
Rappers
Particulate disposal
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