Determination of the overall heat transfer coefficient in a vacuum pyrolysis moving and stirred bed reactor

Citation
J. Yang et al., Determination of the overall heat transfer coefficient in a vacuum pyrolysis moving and stirred bed reactor, CHEM ENG R, 78(A4), 2000, pp. 633-642
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemical Engineering
Journal title
CHEMICAL ENGINEERING RESEARCH & DESIGN
ISSN journal
0263-8762 → ACNP
Volume
78
Issue
A4
Year of publication
2000
Pages
633 - 642
Database
ISI
SICI code
0263-8762(200005)78:A4<633:DOTOHT>2.0.ZU;2-O
Abstract
A novel moving and stirred bed reactor with a high heat transfer capacity h as been operated to achieve the thermal decomposition of used tyre particle s under vacuum. The overall heat transfer coefficient determined in this re actor reaches 200-250 W m(-2) K-1, a value exceeding the levels obtained in conventional rotary kilns and multiple hearth furnaces. In order to design large scale stirred bed vacuum pyrolysis reactors, both experimental and t heoretical studies were carried out to understand the heat transfer mechani sm and to determine the heat transfer coefficient in the reactor as a funct ion of the operating conditions. In this work, the heat transfer coefficien ts under different agitation speeds up to 22.5 rpm were measured. The heat transfer coefficient was found to increase with the agitation speed, propor tionally to (1/t(mix))(1/2). A Schlunder's modified model was used to descr ibe the correlation between the heat transfer coefficient and the operating conditions. Calculation of the partial heat transfer coefficients during t he three pyrolysis evolution periods revealed the influence of the chemical reactions, the phase change and the feedstock thermal property variation o n the overall heat transfer coefficient during the vacuum pyrolysis of tyre particles.