The residence time distribution of the gas phase in the riser of a circulating fluidised bed
Advancing the chemical engineering fundamentals
Multifase Flows (T2-5P)
Keywords: riser, circulating fluidised bed, gas mixing
An increasing interest arises in new applications of the circulating fluidised bed for gas catalytic reactions, in addition to the well-established catalytic cracking (FCC). Gas mixing in the riser of the CFB becomes an important parameter. The present paper focuses on the riser of the reactor, where reactions take place. A literature review on gas mixing is presented, together with experimental results obtained in a 0.1 m I.D. riser. The behaviour is different when the bed material is inactive, such as sand, or active, such as catalyst. In the inactive case, tests at different working conditions of gas velocity and solids circulating rate showed that only a minor amount of gas mixing is detected in the in the riser and that the residence time can be calculated assuming plug flow.
When adsorption of the gas on the catalyst takes place, there is a significant amount of gas back mixing (adsorbed on the reflux particles near the wall), and the plug flow approach no longer holds.
Experimental results will prove this different behaviour and will be transformed in a model for gas mixing in the riser of a CFB.
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 13:30 to 15:00, in session Multifase Flows (T2-5P).
