The solids flow in the riser of a CFB viewed by Positron Emission Particle Tracking (PEPT)

M. Van De Velden, C. W. Chan, J. P.K. Seville, X. Fan, D. Parker, J. Baeyens

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Circulating Fluidized Beds (CFB) are attracting increasing interest for both gas-solid and gas-catalytic reactions, although operating modes differ completely. To model the reactor, the knowledge of the solids flow in the riser is an important parameter. The design of CFB-riser reactors requires the knowledge of the solids residence time, thus necessitating the study of the particle movement within the riser. Previous studies have mainly focused upon risers operating at lower values of the solids circulation flux, and have distinguished mainly between an S-type and exponential solids hold-up profile in the riser. The present paper used Positron Emission Particle Tracking of a radioactively labelled single particle. The movement of the tracer was monitored in "real time" and determined (i) the particle upwards and downwards velocities; (ii) the population densities of these particles in the cross sectional area of the riser; (iii) the solids flow pattern near the distributor and L-valve; (iv) the existence of 5 different solids hold-up regimes in the riser and the associated (U, G) conditions whereby these different regimes prevail. To operate in a dominant core flow mode, as preferred for reactions where a strict control of the residence time is needed, the superficial gas velocity in the riser should exceed UTR by approx. 1 m/s, whereas G should exceed approximately 100 kg/m2s. To operate in a core-annulus mode, possibly with a BFB at the bottom of the riser, lower G-values need to be applied.

Original languageEnglish
Title of host publicationCFB 2008 - Proceedings of the 9th Int. Conference on Circulating Fluidized Beds, in Conjunction with the 4th International VGB Workshop "Operating Experience with Fluidized Bed Firing Systems"
PublisherTuTech Innovation GmbH
ISBN (Print)9783930400577
Publication statusPublished - 1 Jan 2008
Event9th International Conference on Circulating Fluidized Beds, CFB 2008, in Conjunction with the 4th International VGB Workshop on Operating Experience with Fluidized Bed Firing Systems - Hamburg, Germany
Duration: 13 May 200816 May 2008

Publication series

NameCFB 2008 - Proceedings of the 9th Int. Conference on Circulating Fluidized Beds, in Conjunction with the 4th International VGB Workshop "Operating Experience with Fluidized Bed Firing Systems"

Conference

Conference9th International Conference on Circulating Fluidized Beds, CFB 2008, in Conjunction with the 4th International VGB Workshop on Operating Experience with Fluidized Bed Firing Systems
CountryGermany
CityHamburg
Period13/05/0816/05/08

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