An ebullated or expanded bed reactor system may be defined as a reactor system having an upflow type single reaction zone reactor containing catalyst in random motion in an expanded catalytic bed state, typically expanded from 10% by volume to about 35% or more by volume above a "slumped" catalyst bed condition (e.g. a non-expanded or non-ebullated state).

ebullating-bed reactor: A type of fluidized bed in which catalyst particles are held in suspension by the upward movement of the liquid reactant and gas flow.
http://www.petro-canada.ca/pdfs/Glossary.pdf
fluidized bed in Al Khateeb dictionary is طبقة مميّعة

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Note added at 5 hrs (2007-07-17 10:30:38 GMT)
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