Pneumatic Conveying

Fluidization in Pneumatic Conveying and Cooling of Fly Ash

powered by: bulk solids handling / Redaktion BSH (BulkSolidHandling)

Due to its properties fly ash is a difficult to handle material. However systems have been designed utilizing the fluidizing property of fly ash with great success.

Fly ash is generated as result of combustion of coal in a boiler. Presently two types of utility boilers are commercially used for power generation namely pulverized coal fire (PCF) and fluidized bed combustion (FBC). Ash generated in a boiler is conventionally divided under two classes. A portion of the ash in the coarser particles is collected at the bottom of the furnace. This is known as bottom ash for PCF and bed ash in FBC. Another portion of the ash (80-90 per cent) , comprising of fine particles generally below 300 micron are carried away by the flue gas and collected in many places along the flue gas path namely economizer area,  air heated area, electrostatic precipitators or bag filters etc. This ash is known as fly ash.

The fly ash is pneumatically conveyed from the storage hoppers below economizer, air heater and ESPs to a station silo generally located near plant boundary. From the station silos fly ash is taken away by tankers or disposed off to ash pond areas. These conveying should be done in an eco friendly manner and as far as possible at a lower velocity. Ash is highly erosive. Therefore lower the velocity of conveying lower is the wear and tear of the components used for conveying. Also power consumption of conveying should be low in good conveying systems. Further ash being stored in powdered form in silos or bins and have a caking tendency under stored condition, systems are designed to make sure smooth flow of ash from these bins and silos.In all the above areas systems have been designed utilizing the fluidizing property of powdered material with great success.

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Published: 03/01/2012 | bulk solids handling / Redaktion BSH (BulkSolidHandling)

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