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Autofluidization: The fluidization of solid particles by gases evolving from the particles
Author(s) -
Lawrence A. David,
Gogolek Peter E.,
Kuang James
Publication year - 1998
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450760206
Subject(s) - fluidization , fluidized bed , coke , slugging , quartz , mechanics , materials science , mineralogy , chemistry , waste management , composite material , metallurgy , flow (mathematics) , engineering , physics
An experimental procedure was developed to study the autofluidization (i.e. the fluidization of solid particles by gases evolving from the particles) of green coke. It was found that the best method was to heat a 30 cm deep bed of 178 μm quartz sand to 800°C while fluidizing it with air and then adding a small batch of ˜1 mm coke particles to the surface of the bed. After allowing the coke to mix with the sand for 20 s, the fluidizing air was reduced to a lower rate. Pressure is then measured as a function of height in the bed and time. The result is a series of pressure measurements which decay smoothly from the fluidized state to a new steady state once all the coke's volatiles have been released. From these measurements it is possible to calculate gas velocities in the bed as well as bed voidage and apparent density. It was found that the upper sections of the bed would remain fluidized for up to nearly 2 min after the coke was added to the sand while the lower parts of the bed were never fluidized. Simple theory, in the form of the Blake‐Kozeny equation, does a good job of predicting when autofluidization will occur and what the changes in bed height and pressure are within the bed.