The distribution of residence-times in an industrial fluidised reactor

✍ Scribed by P.V. Danckwerts; J.W. Jenkins; G. Place

• Publisher: Elsevier Science
• Year: 1954
• Tongue: English
• Weight: 947 KB
• Volume: 3
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(54)80004-2

✦ Synopsis

The distribution of residence-times of the gas flowing through a fluidised catalyst regenerator has been determined by using helium as a tracer. Only about 5 y0 of the gas spends less than half, and about 5 y0 more than twice, the mean residence-time in the regenerator. It appears that the flow through the fluidised bed itself is much closer to piston-flow than to complete mixing, the hold-back being less than 0.1. R&+um&--En utiliiant l'helium comme indicateur, !es auteurs ont etudie la distribution des u dur6es de sejour " d'un gas qui s'ecoule au travers d'un r&&&ateur de catalyseur fluidisd. Tandis que 5 y0 de la masse totale du gaz pr6sente une " d&e de sejour " inferieure ir la moitid de la valeur moyenne, il y en a aussi 5 y0 dont la " durte de sejour " depasse le double de cette valeur. 11 semble qu'au travers d'un lit fluidiie, l'ecoulement gazeux se rapproche beaucoup plus d'une veine cylindrique rigide que d'un regime turbulent, la " r&tension " reste inferieure ir 0.1.

When

gas flows through a lluidised bed of solid particles, there is a considerable spread of residence-times ; different molecules of entering gas spend different lengths of time in passage, so that part of the gas spends less, and part more than the average length of time in the bed. This 'spread of residence-times, which is caused by back-mixing, or departure from piston-flow, is one of the most important characteristics of a fluidised reactor, as it will influence the nature and rate of the reaction. As yet, however, there is very little published information on the subject.