Agglomeration and defluidization in fluidized beds due to thermally induced sintering
Conference
·
OSTI ID:6437407
The surfaces of fluidizable particles often soften at temperatures well below the material's bulk solid melting point. When particles come into contact at elevated temperatures, there is a tendency for material bridges to form resulting in an interparticle adhesive force. This phenomenon, known as sintering, is driven by the reduction of excess surface energy and for each material is dependent on factors such as particle size and morphology, the interparticle compression force and most importantly, temperature. High temperature fluidization of cohesive powders results in agglomeration, thereby increasing the effective diameter and changing the hydrodynamic properties of the particles. If interparticle forces become significantly greater than forces generated by particle motion, defluidization will occur. In industrial practice, agglomeration is usually undesirable and must be avoided, although there are cases where controlled agglomeration is useful as in fluid-bed coal gasification where the mineral matter agglomerates and is removed from the reactor. The experimental work reported here consists of dilatometry to determine the sintering behavior of a powder as a function of temperature and high temperature fluidization in a pilot size unit to measure the minimum fluidization velocity (defluidization limit) and the voidage at minimum fluidization in the cohesive temperature range of the material. A wide variety of particles have been studied ranging from pure substances including polymers, salts and glass beads to ores and cracking catalysts obtained from industrial reactors where problematic agglomeration at high temperature fluidization was encountered.
- OSTI ID:
- 6437407
- Report Number(s):
- CONF-871113-
- Country of Publication:
- United States
- Language:
- English
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