Particle Velocity Fluctuations of Cork Particles in the Riserof a CFB

摘要

Granular theory is the analogous theory for discrete particles as the kinetic theory of gases is forgas molecules. Eulerian- Eulerian simulation codes predict granular temperature and varioustransport and thermodynamic properties based upon granular temperature. Tests were conductedin a cold flow model of a circulating fluidized bed gasifier to gather particle velocity data used incalculating granular temperature and overall mixture fluctuating energy. Similitude analysis wasapplied to to a high pressure transport gasifier to obtain a system operating with air nominally atatmospheric pressure and cork particles approximately 1mm in diameter. Particle velocitymeasurements under various operating conditions were obtained with an LDV system.Measurements were taken in the riser at locations near the wall and at penetrations up to 13mmdepending on the optical visibility. At the wall, the good visibility led to data with enoughcharacter to define clusters and the associated granular temperature within the clusters. Theintracluster granular temperature is about one twentieth the magnitude of the overall mixturefluctuating energy at the wall. The paper also presents mixture fluctuating energy as a function ofthe penetration distance in from the wall. The overall mixture fluctuating energy for the corksystem at these operating conditions ranged between 0.6 and 0.9 m2/s2. A surface map ofgranular overall fluctuating energy as a function of load ratio and penetration from the wall isprovided. Maximum energies appear in the annulus 3 to 5 mm from the wall.