Untersuchungen zum Verhalten des Feinstaubes und dessen Rückführung bei der Wirbelschichtverbrennung im Head-End für HTR-Brennelemente
Staib, K. G. (Corresponding author)
Publikationen vor 2000; PRE-2000; Retrocat
Jülich Kernforschungsanlage Jülich GmbH, Zentralbiliothek, Verlag 1986
137 p.
Report
Book
Addenda
Berichte der Kernforschungsanlage Jülich 2059
OpenAccess
Please use the identifier: http://hdl.handle.net/2128/12469 in citations.


Fluidized bed burning, favoured for removal of HTGR-fuel element matrix graphite, is equipped with a fines recycling system, designedeither as "external recycling" or "in-bed-filter cartridge assembly" in order to keep steady state conditions. Due to the introduction of the LEU-fuel element concept higher demands are placed on fines handling, as low enriched uranium oxide in the fluidized bed is converted to the mechanically fairly unstable component of U$_{3}$O$_{8}$ and this causes considerably increased fines generation.The present study is concerned with investigations about the occurrence and behaviour of fines with regard to both recycling systems.In flow experiments (at room temperature) elutriation and residence time of fines are studied using radioactively labelled fines fractions. The efficiency of in-bed-filter recycling can thus be shown. The relationships between mean residence time of fines and flow velocity, fluidized bed mass and injection height are defined. In real fluidized bed combustion experiments (at c . 900-950 °C) fines elutriation and graphite conversion - correlated to CO-content - are found to be greater in external than in integrated recycling and generally show an increase with higher gas velocities, all other parameters being kept constant. From a process engineering point of view fluidized beds with their intensive mixing can be regarded as a continuous stirred tank reactor, while their chemical reaction mechanism is that of a plug flow reactor. It is particularly noteworthy that a main reaction zone is formed in the lower parts of the fluidized bed, comprising of only about 10% of total bed height. With respect to special requirements in nuclear application the external recycling is marked by its greater inherent flexibility in addition to process engineering advantages.